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
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
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
48 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
49 Free Software Foundation, Inc.
51 Permission is granted to copy, distribute and/or modify this document
52 under the terms of the GNU Free Documentation License, Version 1.1 or
53 any later version published by the Free Software Foundation; with the
54 Invariant Sections being ``Free Software'' and ``Free Software Needs
55 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
56 and with the Back-Cover Texts as in (a) below.
58 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
59 this GNU Manual. Buying copies from GNU Press supports the FSF in
60 developing GNU and promoting software freedom.''
64 This file documents the @sc{gnu} debugger @value{GDBN}.
66 This is the @value{EDITION} Edition, of @cite{Debugging with
67 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
68 @ifset VERSION_PACKAGE
69 @value{VERSION_PACKAGE}
71 Version @value{GDBVN}.
77 @title Debugging with @value{GDBN}
78 @subtitle The @sc{gnu} Source-Level Debugger
80 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
81 @ifset VERSION_PACKAGE
83 @subtitle @value{VERSION_PACKAGE}
85 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
89 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
90 \hfill {\it Debugging with @value{GDBN}}\par
91 \hfill \TeX{}info \texinfoversion\par
95 @vskip 0pt plus 1filll
96 Published by the Free Software Foundation @*
97 51 Franklin Street, Fifth Floor,
98 Boston, MA 02110-1301, USA@*
103 This edition of the GDB manual is dedicated to the memory of Fred
104 Fish. Fred was a long-standing contributor to GDB and to Free
105 software in general. We will miss him.
110 @node Top, Summary, (dir), (dir)
112 @top Debugging with @value{GDBN}
114 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
116 This is the @value{EDITION} Edition, for @value{GDBN}
117 @ifset VERSION_PACKAGE
118 @value{VERSION_PACKAGE}
120 Version @value{GDBVN}.
122 Copyright (C) 1988-2009 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Reverse Execution:: Running programs backward
137 * Stack:: Examining the stack
138 * Source:: Examining source files
139 * Data:: Examining data
140 * Macros:: Preprocessor Macros
141 * Tracepoints:: Debugging remote targets non-intrusively
142 * Overlays:: Debugging programs that use overlays
144 * Languages:: Using @value{GDBN} with different languages
146 * Symbols:: Examining the symbol table
147 * Altering:: Altering execution
148 * GDB Files:: @value{GDBN} files
149 * Targets:: Specifying a debugging target
150 * Remote Debugging:: Debugging remote programs
151 * Configurations:: Configuration-specific information
152 * Controlling GDB:: Controlling @value{GDBN}
153 * Extending GDB:: Extending @value{GDBN}
154 * Interpreters:: Command Interpreters
155 * TUI:: @value{GDBN} Text User Interface
156 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
157 * GDB/MI:: @value{GDBN}'s Machine Interface.
158 * Annotations:: @value{GDBN}'s annotation interface.
160 * GDB Bugs:: Reporting bugs in @value{GDBN}
162 * Command Line Editing:: Command Line Editing
163 * Using History Interactively:: Using History Interactively
164 * Formatting Documentation:: How to format and print @value{GDBN} documentation
165 * Installing GDB:: Installing GDB
166 * Maintenance Commands:: Maintenance Commands
167 * Remote Protocol:: GDB Remote Serial Protocol
168 * Agent Expressions:: The GDB Agent Expression Mechanism
169 * Target Descriptions:: How targets can describe themselves to
171 * Operating System Information:: Getting additional information from
173 * Copying:: GNU General Public License says
174 how you can copy and share GDB
175 * GNU Free Documentation License:: The license for this documentation
184 @unnumbered Summary of @value{GDBN}
186 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
187 going on ``inside'' another program while it executes---or what another
188 program was doing at the moment it crashed.
190 @value{GDBN} can do four main kinds of things (plus other things in support of
191 these) to help you catch bugs in the act:
195 Start your program, specifying anything that might affect its behavior.
198 Make your program stop on specified conditions.
201 Examine what has happened, when your program has stopped.
204 Change things in your program, so you can experiment with correcting the
205 effects of one bug and go on to learn about another.
208 You can use @value{GDBN} to debug programs written in C and C@t{++}.
209 For more information, see @ref{Supported Languages,,Supported Languages}.
210 For more information, see @ref{C,,C and C++}.
213 Support for Modula-2 is partial. For information on Modula-2, see
214 @ref{Modula-2,,Modula-2}.
217 Debugging Pascal programs which use sets, subranges, file variables, or
218 nested functions does not currently work. @value{GDBN} does not support
219 entering expressions, printing values, or similar features using Pascal
223 @value{GDBN} can be used to debug programs written in Fortran, although
224 it may be necessary to refer to some variables with a trailing
227 @value{GDBN} can be used to debug programs written in Objective-C,
228 using either the Apple/NeXT or the GNU Objective-C runtime.
231 * Free Software:: Freely redistributable software
232 * Contributors:: Contributors to GDB
236 @unnumberedsec Free Software
238 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
239 General Public License
240 (GPL). The GPL gives you the freedom to copy or adapt a licensed
241 program---but every person getting a copy also gets with it the
242 freedom to modify that copy (which means that they must get access to
243 the source code), and the freedom to distribute further copies.
244 Typical software companies use copyrights to limit your freedoms; the
245 Free Software Foundation uses the GPL to preserve these freedoms.
247 Fundamentally, the General Public License is a license which says that
248 you have these freedoms and that you cannot take these freedoms away
251 @unnumberedsec Free Software Needs Free Documentation
253 The biggest deficiency in the free software community today is not in
254 the software---it is the lack of good free documentation that we can
255 include with the free software. Many of our most important
256 programs do not come with free reference manuals and free introductory
257 texts. Documentation is an essential part of any software package;
258 when an important free software package does not come with a free
259 manual and a free tutorial, that is a major gap. We have many such
262 Consider Perl, for instance. The tutorial manuals that people
263 normally use are non-free. How did this come about? Because the
264 authors of those manuals published them with restrictive terms---no
265 copying, no modification, source files not available---which exclude
266 them from the free software world.
268 That wasn't the first time this sort of thing happened, and it was far
269 from the last. Many times we have heard a GNU user eagerly describe a
270 manual that he is writing, his intended contribution to the community,
271 only to learn that he had ruined everything by signing a publication
272 contract to make it non-free.
274 Free documentation, like free software, is a matter of freedom, not
275 price. The problem with the non-free manual is not that publishers
276 charge a price for printed copies---that in itself is fine. (The Free
277 Software Foundation sells printed copies of manuals, too.) The
278 problem is the restrictions on the use of the manual. Free manuals
279 are available in source code form, and give you permission to copy and
280 modify. Non-free manuals do not allow this.
282 The criteria of freedom for a free manual are roughly the same as for
283 free software. Redistribution (including the normal kinds of
284 commercial redistribution) must be permitted, so that the manual can
285 accompany every copy of the program, both on-line and on paper.
287 Permission for modification of the technical content is crucial too.
288 When people modify the software, adding or changing features, if they
289 are conscientious they will change the manual too---so they can
290 provide accurate and clear documentation for the modified program. A
291 manual that leaves you no choice but to write a new manual to document
292 a changed version of the program is not really available to our
295 Some kinds of limits on the way modification is handled are
296 acceptable. For example, requirements to preserve the original
297 author's copyright notice, the distribution terms, or the list of
298 authors, are ok. It is also no problem to require modified versions
299 to include notice that they were modified. Even entire sections that
300 may not be deleted or changed are acceptable, as long as they deal
301 with nontechnical topics (like this one). These kinds of restrictions
302 are acceptable because they don't obstruct the community's normal use
305 However, it must be possible to modify all the @emph{technical}
306 content of the manual, and then distribute the result in all the usual
307 media, through all the usual channels. Otherwise, the restrictions
308 obstruct the use of the manual, it is not free, and we need another
309 manual to replace it.
311 Please spread the word about this issue. Our community continues to
312 lose manuals to proprietary publishing. If we spread the word that
313 free software needs free reference manuals and free tutorials, perhaps
314 the next person who wants to contribute by writing documentation will
315 realize, before it is too late, that only free manuals contribute to
316 the free software community.
318 If you are writing documentation, please insist on publishing it under
319 the GNU Free Documentation License or another free documentation
320 license. Remember that this decision requires your approval---you
321 don't have to let the publisher decide. Some commercial publishers
322 will use a free license if you insist, but they will not propose the
323 option; it is up to you to raise the issue and say firmly that this is
324 what you want. If the publisher you are dealing with refuses, please
325 try other publishers. If you're not sure whether a proposed license
326 is free, write to @email{licensing@@gnu.org}.
328 You can encourage commercial publishers to sell more free, copylefted
329 manuals and tutorials by buying them, and particularly by buying
330 copies from the publishers that paid for their writing or for major
331 improvements. Meanwhile, try to avoid buying non-free documentation
332 at all. Check the distribution terms of a manual before you buy it,
333 and insist that whoever seeks your business must respect your freedom.
334 Check the history of the book, and try to reward the publishers that
335 have paid or pay the authors to work on it.
337 The Free Software Foundation maintains a list of free documentation
338 published by other publishers, at
339 @url{http://www.fsf.org/doc/other-free-books.html}.
342 @unnumberedsec Contributors to @value{GDBN}
344 Richard Stallman was the original author of @value{GDBN}, and of many
345 other @sc{gnu} programs. Many others have contributed to its
346 development. This section attempts to credit major contributors. One
347 of the virtues of free software is that everyone is free to contribute
348 to it; with regret, we cannot actually acknowledge everyone here. The
349 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
350 blow-by-blow account.
352 Changes much prior to version 2.0 are lost in the mists of time.
355 @emph{Plea:} Additions to this section are particularly welcome. If you
356 or your friends (or enemies, to be evenhanded) have been unfairly
357 omitted from this list, we would like to add your names!
360 So that they may not regard their many labors as thankless, we
361 particularly thank those who shepherded @value{GDBN} through major
363 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
364 Jim Blandy (release 4.18);
365 Jason Molenda (release 4.17);
366 Stan Shebs (release 4.14);
367 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
368 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
369 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
370 Jim Kingdon (releases 3.5, 3.4, and 3.3);
371 and Randy Smith (releases 3.2, 3.1, and 3.0).
373 Richard Stallman, assisted at various times by Peter TerMaat, Chris
374 Hanson, and Richard Mlynarik, handled releases through 2.8.
376 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
377 in @value{GDBN}, with significant additional contributions from Per
378 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
379 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
380 much general update work leading to release 3.0).
382 @value{GDBN} uses the BFD subroutine library to examine multiple
383 object-file formats; BFD was a joint project of David V.
384 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
386 David Johnson wrote the original COFF support; Pace Willison did
387 the original support for encapsulated COFF.
389 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
391 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
392 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
394 Jean-Daniel Fekete contributed Sun 386i support.
395 Chris Hanson improved the HP9000 support.
396 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
397 David Johnson contributed Encore Umax support.
398 Jyrki Kuoppala contributed Altos 3068 support.
399 Jeff Law contributed HP PA and SOM support.
400 Keith Packard contributed NS32K support.
401 Doug Rabson contributed Acorn Risc Machine support.
402 Bob Rusk contributed Harris Nighthawk CX-UX support.
403 Chris Smith contributed Convex support (and Fortran debugging).
404 Jonathan Stone contributed Pyramid support.
405 Michael Tiemann contributed SPARC support.
406 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
407 Pace Willison contributed Intel 386 support.
408 Jay Vosburgh contributed Symmetry support.
409 Marko Mlinar contributed OpenRISC 1000 support.
411 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
413 Rich Schaefer and Peter Schauer helped with support of SunOS shared
416 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
417 about several machine instruction sets.
419 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
420 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
421 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
422 and RDI targets, respectively.
424 Brian Fox is the author of the readline libraries providing
425 command-line editing and command history.
427 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
428 Modula-2 support, and contributed the Languages chapter of this manual.
430 Fred Fish wrote most of the support for Unix System Vr4.
431 He also enhanced the command-completion support to cover C@t{++} overloaded
434 Hitachi America (now Renesas America), Ltd. sponsored the support for
435 H8/300, H8/500, and Super-H processors.
437 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
439 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
442 Toshiba sponsored the support for the TX39 Mips processor.
444 Matsushita sponsored the support for the MN10200 and MN10300 processors.
446 Fujitsu sponsored the support for SPARClite and FR30 processors.
448 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
451 Michael Snyder added support for tracepoints.
453 Stu Grossman wrote gdbserver.
455 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
456 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
458 The following people at the Hewlett-Packard Company contributed
459 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
460 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
461 compiler, and the Text User Interface (nee Terminal User Interface):
462 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
463 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
464 provided HP-specific information in this manual.
466 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
467 Robert Hoehne made significant contributions to the DJGPP port.
469 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
470 development since 1991. Cygnus engineers who have worked on @value{GDBN}
471 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
472 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
473 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
474 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
475 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
476 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
477 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
478 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
479 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
480 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
481 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
482 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
483 Zuhn have made contributions both large and small.
485 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
486 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
488 Jim Blandy added support for preprocessor macros, while working for Red
491 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
492 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
493 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
494 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
495 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
496 with the migration of old architectures to this new framework.
498 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
499 unwinder framework, this consisting of a fresh new design featuring
500 frame IDs, independent frame sniffers, and the sentinel frame. Mark
501 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
502 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
503 trad unwinders. The architecture-specific changes, each involving a
504 complete rewrite of the architecture's frame code, were carried out by
505 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
506 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
507 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
508 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
511 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
512 Tensilica, Inc.@: contributed support for Xtensa processors. Others
513 who have worked on the Xtensa port of @value{GDBN} in the past include
514 Steve Tjiang, John Newlin, and Scott Foehner.
517 @chapter A Sample @value{GDBN} Session
519 You can use this manual at your leisure to read all about @value{GDBN}.
520 However, a handful of commands are enough to get started using the
521 debugger. This chapter illustrates those commands.
524 In this sample session, we emphasize user input like this: @b{input},
525 to make it easier to pick out from the surrounding output.
528 @c FIXME: this example may not be appropriate for some configs, where
529 @c FIXME...primary interest is in remote use.
531 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
532 processor) exhibits the following bug: sometimes, when we change its
533 quote strings from the default, the commands used to capture one macro
534 definition within another stop working. In the following short @code{m4}
535 session, we define a macro @code{foo} which expands to @code{0000}; we
536 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
537 same thing. However, when we change the open quote string to
538 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
539 procedure fails to define a new synonym @code{baz}:
548 @b{define(bar,defn(`foo'))}
552 @b{changequote(<QUOTE>,<UNQUOTE>)}
554 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
557 m4: End of input: 0: fatal error: EOF in string
561 Let us use @value{GDBN} to try to see what is going on.
564 $ @b{@value{GDBP} m4}
565 @c FIXME: this falsifies the exact text played out, to permit smallbook
566 @c FIXME... format to come out better.
567 @value{GDBN} is free software and you are welcome to distribute copies
568 of it under certain conditions; type "show copying" to see
570 There is absolutely no warranty for @value{GDBN}; type "show warranty"
573 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
578 @value{GDBN} reads only enough symbol data to know where to find the
579 rest when needed; as a result, the first prompt comes up very quickly.
580 We now tell @value{GDBN} to use a narrower display width than usual, so
581 that examples fit in this manual.
584 (@value{GDBP}) @b{set width 70}
588 We need to see how the @code{m4} built-in @code{changequote} works.
589 Having looked at the source, we know the relevant subroutine is
590 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
591 @code{break} command.
594 (@value{GDBP}) @b{break m4_changequote}
595 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
599 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
600 control; as long as control does not reach the @code{m4_changequote}
601 subroutine, the program runs as usual:
604 (@value{GDBP}) @b{run}
605 Starting program: /work/Editorial/gdb/gnu/m4/m4
613 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
614 suspends execution of @code{m4}, displaying information about the
615 context where it stops.
618 @b{changequote(<QUOTE>,<UNQUOTE>)}
620 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
622 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
626 Now we use the command @code{n} (@code{next}) to advance execution to
627 the next line of the current function.
631 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
636 @code{set_quotes} looks like a promising subroutine. We can go into it
637 by using the command @code{s} (@code{step}) instead of @code{next}.
638 @code{step} goes to the next line to be executed in @emph{any}
639 subroutine, so it steps into @code{set_quotes}.
643 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
645 530 if (lquote != def_lquote)
649 The display that shows the subroutine where @code{m4} is now
650 suspended (and its arguments) is called a stack frame display. It
651 shows a summary of the stack. We can use the @code{backtrace}
652 command (which can also be spelled @code{bt}), to see where we are
653 in the stack as a whole: the @code{backtrace} command displays a
654 stack frame for each active subroutine.
657 (@value{GDBP}) @b{bt}
658 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
660 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
662 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
663 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
665 #4 0x79dc in expand_input () at macro.c:40
666 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
670 We step through a few more lines to see what happens. The first two
671 times, we can use @samp{s}; the next two times we use @code{n} to avoid
672 falling into the @code{xstrdup} subroutine.
676 0x3b5c 532 if (rquote != def_rquote)
678 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
679 def_lquote : xstrdup(lq);
681 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
684 538 len_lquote = strlen(rquote);
688 The last line displayed looks a little odd; we can examine the variables
689 @code{lquote} and @code{rquote} to see if they are in fact the new left
690 and right quotes we specified. We use the command @code{p}
691 (@code{print}) to see their values.
694 (@value{GDBP}) @b{p lquote}
695 $1 = 0x35d40 "<QUOTE>"
696 (@value{GDBP}) @b{p rquote}
697 $2 = 0x35d50 "<UNQUOTE>"
701 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
702 To look at some context, we can display ten lines of source
703 surrounding the current line with the @code{l} (@code{list}) command.
709 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
711 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
714 538 len_lquote = strlen(rquote);
715 539 len_rquote = strlen(lquote);
722 Let us step past the two lines that set @code{len_lquote} and
723 @code{len_rquote}, and then examine the values of those variables.
727 539 len_rquote = strlen(lquote);
730 (@value{GDBP}) @b{p len_lquote}
732 (@value{GDBP}) @b{p len_rquote}
737 That certainly looks wrong, assuming @code{len_lquote} and
738 @code{len_rquote} are meant to be the lengths of @code{lquote} and
739 @code{rquote} respectively. We can set them to better values using
740 the @code{p} command, since it can print the value of
741 any expression---and that expression can include subroutine calls and
745 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
747 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
752 Is that enough to fix the problem of using the new quotes with the
753 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
754 executing with the @code{c} (@code{continue}) command, and then try the
755 example that caused trouble initially:
761 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
768 Success! The new quotes now work just as well as the default ones. The
769 problem seems to have been just the two typos defining the wrong
770 lengths. We allow @code{m4} exit by giving it an EOF as input:
774 Program exited normally.
778 The message @samp{Program exited normally.} is from @value{GDBN}; it
779 indicates @code{m4} has finished executing. We can end our @value{GDBN}
780 session with the @value{GDBN} @code{quit} command.
783 (@value{GDBP}) @b{quit}
787 @chapter Getting In and Out of @value{GDBN}
789 This chapter discusses how to start @value{GDBN}, and how to get out of it.
793 type @samp{@value{GDBP}} to start @value{GDBN}.
795 type @kbd{quit} or @kbd{Ctrl-d} to exit.
799 * Invoking GDB:: How to start @value{GDBN}
800 * Quitting GDB:: How to quit @value{GDBN}
801 * Shell Commands:: How to use shell commands inside @value{GDBN}
802 * Logging Output:: How to log @value{GDBN}'s output to a file
806 @section Invoking @value{GDBN}
808 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
809 @value{GDBN} reads commands from the terminal until you tell it to exit.
811 You can also run @code{@value{GDBP}} with a variety of arguments and options,
812 to specify more of your debugging environment at the outset.
814 The command-line options described here are designed
815 to cover a variety of situations; in some environments, some of these
816 options may effectively be unavailable.
818 The most usual way to start @value{GDBN} is with one argument,
819 specifying an executable program:
822 @value{GDBP} @var{program}
826 You can also start with both an executable program and a core file
830 @value{GDBP} @var{program} @var{core}
833 You can, instead, specify a process ID as a second argument, if you want
834 to debug a running process:
837 @value{GDBP} @var{program} 1234
841 would attach @value{GDBN} to process @code{1234} (unless you also have a file
842 named @file{1234}; @value{GDBN} does check for a core file first).
844 Taking advantage of the second command-line argument requires a fairly
845 complete operating system; when you use @value{GDBN} as a remote
846 debugger attached to a bare board, there may not be any notion of
847 ``process'', and there is often no way to get a core dump. @value{GDBN}
848 will warn you if it is unable to attach or to read core dumps.
850 You can optionally have @code{@value{GDBP}} pass any arguments after the
851 executable file to the inferior using @code{--args}. This option stops
854 @value{GDBP} --args gcc -O2 -c foo.c
856 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
857 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
859 You can run @code{@value{GDBP}} without printing the front material, which describes
860 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
867 You can further control how @value{GDBN} starts up by using command-line
868 options. @value{GDBN} itself can remind you of the options available.
878 to display all available options and briefly describe their use
879 (@samp{@value{GDBP} -h} is a shorter equivalent).
881 All options and command line arguments you give are processed
882 in sequential order. The order makes a difference when the
883 @samp{-x} option is used.
887 * File Options:: Choosing files
888 * Mode Options:: Choosing modes
889 * Startup:: What @value{GDBN} does during startup
893 @subsection Choosing Files
895 When @value{GDBN} starts, it reads any arguments other than options as
896 specifying an executable file and core file (or process ID). This is
897 the same as if the arguments were specified by the @samp{-se} and
898 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
899 first argument that does not have an associated option flag as
900 equivalent to the @samp{-se} option followed by that argument; and the
901 second argument that does not have an associated option flag, if any, as
902 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
903 If the second argument begins with a decimal digit, @value{GDBN} will
904 first attempt to attach to it as a process, and if that fails, attempt
905 to open it as a corefile. If you have a corefile whose name begins with
906 a digit, you can prevent @value{GDBN} from treating it as a pid by
907 prefixing it with @file{./}, e.g.@: @file{./12345}.
909 If @value{GDBN} has not been configured to included core file support,
910 such as for most embedded targets, then it will complain about a second
911 argument and ignore it.
913 Many options have both long and short forms; both are shown in the
914 following list. @value{GDBN} also recognizes the long forms if you truncate
915 them, so long as enough of the option is present to be unambiguous.
916 (If you prefer, you can flag option arguments with @samp{--} rather
917 than @samp{-}, though we illustrate the more usual convention.)
919 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
920 @c way, both those who look for -foo and --foo in the index, will find
924 @item -symbols @var{file}
926 @cindex @code{--symbols}
928 Read symbol table from file @var{file}.
930 @item -exec @var{file}
932 @cindex @code{--exec}
934 Use file @var{file} as the executable file to execute when appropriate,
935 and for examining pure data in conjunction with a core dump.
939 Read symbol table from file @var{file} and use it as the executable
942 @item -core @var{file}
944 @cindex @code{--core}
946 Use file @var{file} as a core dump to examine.
948 @item -pid @var{number}
949 @itemx -p @var{number}
952 Connect to process ID @var{number}, as with the @code{attach} command.
954 @item -command @var{file}
956 @cindex @code{--command}
958 Execute @value{GDBN} commands from file @var{file}. @xref{Command
959 Files,, Command files}.
961 @item -eval-command @var{command}
962 @itemx -ex @var{command}
963 @cindex @code{--eval-command}
965 Execute a single @value{GDBN} command.
967 This option may be used multiple times to call multiple commands. It may
968 also be interleaved with @samp{-command} as required.
971 @value{GDBP} -ex 'target sim' -ex 'load' \
972 -x setbreakpoints -ex 'run' a.out
975 @item -directory @var{directory}
976 @itemx -d @var{directory}
977 @cindex @code{--directory}
979 Add @var{directory} to the path to search for source and script files.
983 @cindex @code{--readnow}
985 Read each symbol file's entire symbol table immediately, rather than
986 the default, which is to read it incrementally as it is needed.
987 This makes startup slower, but makes future operations faster.
992 @subsection Choosing Modes
994 You can run @value{GDBN} in various alternative modes---for example, in
995 batch mode or quiet mode.
1002 Do not execute commands found in any initialization files. Normally,
1003 @value{GDBN} executes the commands in these files after all the command
1004 options and arguments have been processed. @xref{Command Files,,Command
1010 @cindex @code{--quiet}
1011 @cindex @code{--silent}
1013 ``Quiet''. Do not print the introductory and copyright messages. These
1014 messages are also suppressed in batch mode.
1017 @cindex @code{--batch}
1018 Run in batch mode. Exit with status @code{0} after processing all the
1019 command files specified with @samp{-x} (and all commands from
1020 initialization files, if not inhibited with @samp{-n}). Exit with
1021 nonzero status if an error occurs in executing the @value{GDBN} commands
1022 in the command files.
1024 Batch mode may be useful for running @value{GDBN} as a filter, for
1025 example to download and run a program on another computer; in order to
1026 make this more useful, the message
1029 Program exited normally.
1033 (which is ordinarily issued whenever a program running under
1034 @value{GDBN} control terminates) is not issued when running in batch
1038 @cindex @code{--batch-silent}
1039 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1040 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1041 unaffected). This is much quieter than @samp{-silent} and would be useless
1042 for an interactive session.
1044 This is particularly useful when using targets that give @samp{Loading section}
1045 messages, for example.
1047 Note that targets that give their output via @value{GDBN}, as opposed to
1048 writing directly to @code{stdout}, will also be made silent.
1050 @item -return-child-result
1051 @cindex @code{--return-child-result}
1052 The return code from @value{GDBN} will be the return code from the child
1053 process (the process being debugged), with the following exceptions:
1057 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1058 internal error. In this case the exit code is the same as it would have been
1059 without @samp{-return-child-result}.
1061 The user quits with an explicit value. E.g., @samp{quit 1}.
1063 The child process never runs, or is not allowed to terminate, in which case
1064 the exit code will be -1.
1067 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1068 when @value{GDBN} is being used as a remote program loader or simulator
1073 @cindex @code{--nowindows}
1075 ``No windows''. If @value{GDBN} comes with a graphical user interface
1076 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1077 interface. If no GUI is available, this option has no effect.
1081 @cindex @code{--windows}
1083 If @value{GDBN} includes a GUI, then this option requires it to be
1086 @item -cd @var{directory}
1088 Run @value{GDBN} using @var{directory} as its working directory,
1089 instead of the current directory.
1093 @cindex @code{--fullname}
1095 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1096 subprocess. It tells @value{GDBN} to output the full file name and line
1097 number in a standard, recognizable fashion each time a stack frame is
1098 displayed (which includes each time your program stops). This
1099 recognizable format looks like two @samp{\032} characters, followed by
1100 the file name, line number and character position separated by colons,
1101 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1102 @samp{\032} characters as a signal to display the source code for the
1106 @cindex @code{--epoch}
1107 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1108 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1109 routines so as to allow Epoch to display values of expressions in a
1112 @item -annotate @var{level}
1113 @cindex @code{--annotate}
1114 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1115 effect is identical to using @samp{set annotate @var{level}}
1116 (@pxref{Annotations}). The annotation @var{level} controls how much
1117 information @value{GDBN} prints together with its prompt, values of
1118 expressions, source lines, and other types of output. Level 0 is the
1119 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1120 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1121 that control @value{GDBN}, and level 2 has been deprecated.
1123 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1127 @cindex @code{--args}
1128 Change interpretation of command line so that arguments following the
1129 executable file are passed as command line arguments to the inferior.
1130 This option stops option processing.
1132 @item -baud @var{bps}
1134 @cindex @code{--baud}
1136 Set the line speed (baud rate or bits per second) of any serial
1137 interface used by @value{GDBN} for remote debugging.
1139 @item -l @var{timeout}
1141 Set the timeout (in seconds) of any communication used by @value{GDBN}
1142 for remote debugging.
1144 @item -tty @var{device}
1145 @itemx -t @var{device}
1146 @cindex @code{--tty}
1148 Run using @var{device} for your program's standard input and output.
1149 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1151 @c resolve the situation of these eventually
1153 @cindex @code{--tui}
1154 Activate the @dfn{Text User Interface} when starting. The Text User
1155 Interface manages several text windows on the terminal, showing
1156 source, assembly, registers and @value{GDBN} command outputs
1157 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1158 Text User Interface can be enabled by invoking the program
1159 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1160 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1163 @c @cindex @code{--xdb}
1164 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1165 @c For information, see the file @file{xdb_trans.html}, which is usually
1166 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1169 @item -interpreter @var{interp}
1170 @cindex @code{--interpreter}
1171 Use the interpreter @var{interp} for interface with the controlling
1172 program or device. This option is meant to be set by programs which
1173 communicate with @value{GDBN} using it as a back end.
1174 @xref{Interpreters, , Command Interpreters}.
1176 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1177 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1178 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1179 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1180 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1181 @sc{gdb/mi} interfaces are no longer supported.
1184 @cindex @code{--write}
1185 Open the executable and core files for both reading and writing. This
1186 is equivalent to the @samp{set write on} command inside @value{GDBN}
1190 @cindex @code{--statistics}
1191 This option causes @value{GDBN} to print statistics about time and
1192 memory usage after it completes each command and returns to the prompt.
1195 @cindex @code{--version}
1196 This option causes @value{GDBN} to print its version number and
1197 no-warranty blurb, and exit.
1202 @subsection What @value{GDBN} Does During Startup
1203 @cindex @value{GDBN} startup
1205 Here's the description of what @value{GDBN} does during session startup:
1209 Sets up the command interpreter as specified by the command line
1210 (@pxref{Mode Options, interpreter}).
1214 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1215 used when building @value{GDBN}; @pxref{System-wide configuration,
1216 ,System-wide configuration and settings}) and executes all the commands in
1220 Reads the init file (if any) in your home directory@footnote{On
1221 DOS/Windows systems, the home directory is the one pointed to by the
1222 @code{HOME} environment variable.} and executes all the commands in
1226 Processes command line options and operands.
1229 Reads and executes the commands from init file (if any) in the current
1230 working directory. This is only done if the current directory is
1231 different from your home directory. Thus, you can have more than one
1232 init file, one generic in your home directory, and another, specific
1233 to the program you are debugging, in the directory where you invoke
1237 Reads command files specified by the @samp{-x} option. @xref{Command
1238 Files}, for more details about @value{GDBN} command files.
1241 Reads the command history recorded in the @dfn{history file}.
1242 @xref{Command History}, for more details about the command history and the
1243 files where @value{GDBN} records it.
1246 Init files use the same syntax as @dfn{command files} (@pxref{Command
1247 Files}) and are processed by @value{GDBN} in the same way. The init
1248 file in your home directory can set options (such as @samp{set
1249 complaints}) that affect subsequent processing of command line options
1250 and operands. Init files are not executed if you use the @samp{-nx}
1251 option (@pxref{Mode Options, ,Choosing Modes}).
1253 To display the list of init files loaded by gdb at startup, you
1254 can use @kbd{gdb --help}.
1256 @cindex init file name
1257 @cindex @file{.gdbinit}
1258 @cindex @file{gdb.ini}
1259 The @value{GDBN} init files are normally called @file{.gdbinit}.
1260 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1261 the limitations of file names imposed by DOS filesystems. The Windows
1262 ports of @value{GDBN} use the standard name, but if they find a
1263 @file{gdb.ini} file, they warn you about that and suggest to rename
1264 the file to the standard name.
1268 @section Quitting @value{GDBN}
1269 @cindex exiting @value{GDBN}
1270 @cindex leaving @value{GDBN}
1273 @kindex quit @r{[}@var{expression}@r{]}
1274 @kindex q @r{(@code{quit})}
1275 @item quit @r{[}@var{expression}@r{]}
1277 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1278 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1279 do not supply @var{expression}, @value{GDBN} will terminate normally;
1280 otherwise it will terminate using the result of @var{expression} as the
1285 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1286 terminates the action of any @value{GDBN} command that is in progress and
1287 returns to @value{GDBN} command level. It is safe to type the interrupt
1288 character at any time because @value{GDBN} does not allow it to take effect
1289 until a time when it is safe.
1291 If you have been using @value{GDBN} to control an attached process or
1292 device, you can release it with the @code{detach} command
1293 (@pxref{Attach, ,Debugging an Already-running Process}).
1295 @node Shell Commands
1296 @section Shell Commands
1298 If you need to execute occasional shell commands during your
1299 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1300 just use the @code{shell} command.
1304 @cindex shell escape
1305 @item shell @var{command string}
1306 Invoke a standard shell to execute @var{command string}.
1307 If it exists, the environment variable @code{SHELL} determines which
1308 shell to run. Otherwise @value{GDBN} uses the default shell
1309 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1312 The utility @code{make} is often needed in development environments.
1313 You do not have to use the @code{shell} command for this purpose in
1318 @cindex calling make
1319 @item make @var{make-args}
1320 Execute the @code{make} program with the specified
1321 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1324 @node Logging Output
1325 @section Logging Output
1326 @cindex logging @value{GDBN} output
1327 @cindex save @value{GDBN} output to a file
1329 You may want to save the output of @value{GDBN} commands to a file.
1330 There are several commands to control @value{GDBN}'s logging.
1334 @item set logging on
1336 @item set logging off
1338 @cindex logging file name
1339 @item set logging file @var{file}
1340 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1341 @item set logging overwrite [on|off]
1342 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1343 you want @code{set logging on} to overwrite the logfile instead.
1344 @item set logging redirect [on|off]
1345 By default, @value{GDBN} output will go to both the terminal and the logfile.
1346 Set @code{redirect} if you want output to go only to the log file.
1347 @kindex show logging
1349 Show the current values of the logging settings.
1353 @chapter @value{GDBN} Commands
1355 You can abbreviate a @value{GDBN} command to the first few letters of the command
1356 name, if that abbreviation is unambiguous; and you can repeat certain
1357 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1358 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1359 show you the alternatives available, if there is more than one possibility).
1362 * Command Syntax:: How to give commands to @value{GDBN}
1363 * Completion:: Command completion
1364 * Help:: How to ask @value{GDBN} for help
1367 @node Command Syntax
1368 @section Command Syntax
1370 A @value{GDBN} command is a single line of input. There is no limit on
1371 how long it can be. It starts with a command name, which is followed by
1372 arguments whose meaning depends on the command name. For example, the
1373 command @code{step} accepts an argument which is the number of times to
1374 step, as in @samp{step 5}. You can also use the @code{step} command
1375 with no arguments. Some commands do not allow any arguments.
1377 @cindex abbreviation
1378 @value{GDBN} command names may always be truncated if that abbreviation is
1379 unambiguous. Other possible command abbreviations are listed in the
1380 documentation for individual commands. In some cases, even ambiguous
1381 abbreviations are allowed; for example, @code{s} is specially defined as
1382 equivalent to @code{step} even though there are other commands whose
1383 names start with @code{s}. You can test abbreviations by using them as
1384 arguments to the @code{help} command.
1386 @cindex repeating commands
1387 @kindex RET @r{(repeat last command)}
1388 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1389 repeat the previous command. Certain commands (for example, @code{run})
1390 will not repeat this way; these are commands whose unintentional
1391 repetition might cause trouble and which you are unlikely to want to
1392 repeat. User-defined commands can disable this feature; see
1393 @ref{Define, dont-repeat}.
1395 The @code{list} and @code{x} commands, when you repeat them with
1396 @key{RET}, construct new arguments rather than repeating
1397 exactly as typed. This permits easy scanning of source or memory.
1399 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1400 output, in a way similar to the common utility @code{more}
1401 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1402 @key{RET} too many in this situation, @value{GDBN} disables command
1403 repetition after any command that generates this sort of display.
1405 @kindex # @r{(a comment)}
1407 Any text from a @kbd{#} to the end of the line is a comment; it does
1408 nothing. This is useful mainly in command files (@pxref{Command
1409 Files,,Command Files}).
1411 @cindex repeating command sequences
1412 @kindex Ctrl-o @r{(operate-and-get-next)}
1413 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1414 commands. This command accepts the current line, like @key{RET}, and
1415 then fetches the next line relative to the current line from the history
1419 @section Command Completion
1422 @cindex word completion
1423 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1424 only one possibility; it can also show you what the valid possibilities
1425 are for the next word in a command, at any time. This works for @value{GDBN}
1426 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1428 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1429 of a word. If there is only one possibility, @value{GDBN} fills in the
1430 word, and waits for you to finish the command (or press @key{RET} to
1431 enter it). For example, if you type
1433 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1434 @c complete accuracy in these examples; space introduced for clarity.
1435 @c If texinfo enhancements make it unnecessary, it would be nice to
1436 @c replace " @key" by "@key" in the following...
1438 (@value{GDBP}) info bre @key{TAB}
1442 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1443 the only @code{info} subcommand beginning with @samp{bre}:
1446 (@value{GDBP}) info breakpoints
1450 You can either press @key{RET} at this point, to run the @code{info
1451 breakpoints} command, or backspace and enter something else, if
1452 @samp{breakpoints} does not look like the command you expected. (If you
1453 were sure you wanted @code{info breakpoints} in the first place, you
1454 might as well just type @key{RET} immediately after @samp{info bre},
1455 to exploit command abbreviations rather than command completion).
1457 If there is more than one possibility for the next word when you press
1458 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1459 characters and try again, or just press @key{TAB} a second time;
1460 @value{GDBN} displays all the possible completions for that word. For
1461 example, you might want to set a breakpoint on a subroutine whose name
1462 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1463 just sounds the bell. Typing @key{TAB} again displays all the
1464 function names in your program that begin with those characters, for
1468 (@value{GDBP}) b make_ @key{TAB}
1469 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1470 make_a_section_from_file make_environ
1471 make_abs_section make_function_type
1472 make_blockvector make_pointer_type
1473 make_cleanup make_reference_type
1474 make_command make_symbol_completion_list
1475 (@value{GDBP}) b make_
1479 After displaying the available possibilities, @value{GDBN} copies your
1480 partial input (@samp{b make_} in the example) so you can finish the
1483 If you just want to see the list of alternatives in the first place, you
1484 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1485 means @kbd{@key{META} ?}. You can type this either by holding down a
1486 key designated as the @key{META} shift on your keyboard (if there is
1487 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1489 @cindex quotes in commands
1490 @cindex completion of quoted strings
1491 Sometimes the string you need, while logically a ``word'', may contain
1492 parentheses or other characters that @value{GDBN} normally excludes from
1493 its notion of a word. To permit word completion to work in this
1494 situation, you may enclose words in @code{'} (single quote marks) in
1495 @value{GDBN} commands.
1497 The most likely situation where you might need this is in typing the
1498 name of a C@t{++} function. This is because C@t{++} allows function
1499 overloading (multiple definitions of the same function, distinguished
1500 by argument type). For example, when you want to set a breakpoint you
1501 may need to distinguish whether you mean the version of @code{name}
1502 that takes an @code{int} parameter, @code{name(int)}, or the version
1503 that takes a @code{float} parameter, @code{name(float)}. To use the
1504 word-completion facilities in this situation, type a single quote
1505 @code{'} at the beginning of the function name. This alerts
1506 @value{GDBN} that it may need to consider more information than usual
1507 when you press @key{TAB} or @kbd{M-?} to request word completion:
1510 (@value{GDBP}) b 'bubble( @kbd{M-?}
1511 bubble(double,double) bubble(int,int)
1512 (@value{GDBP}) b 'bubble(
1515 In some cases, @value{GDBN} can tell that completing a name requires using
1516 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1517 completing as much as it can) if you do not type the quote in the first
1521 (@value{GDBP}) b bub @key{TAB}
1522 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1523 (@value{GDBP}) b 'bubble(
1527 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1528 you have not yet started typing the argument list when you ask for
1529 completion on an overloaded symbol.
1531 For more information about overloaded functions, see @ref{C Plus Plus
1532 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1533 overload-resolution off} to disable overload resolution;
1534 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1536 @cindex completion of structure field names
1537 @cindex structure field name completion
1538 @cindex completion of union field names
1539 @cindex union field name completion
1540 When completing in an expression which looks up a field in a
1541 structure, @value{GDBN} also tries@footnote{The completer can be
1542 confused by certain kinds of invalid expressions. Also, it only
1543 examines the static type of the expression, not the dynamic type.} to
1544 limit completions to the field names available in the type of the
1548 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1549 magic to_delete to_fputs to_put to_rewind
1550 to_data to_flush to_isatty to_read to_write
1554 This is because the @code{gdb_stdout} is a variable of the type
1555 @code{struct ui_file} that is defined in @value{GDBN} sources as
1562 ui_file_flush_ftype *to_flush;
1563 ui_file_write_ftype *to_write;
1564 ui_file_fputs_ftype *to_fputs;
1565 ui_file_read_ftype *to_read;
1566 ui_file_delete_ftype *to_delete;
1567 ui_file_isatty_ftype *to_isatty;
1568 ui_file_rewind_ftype *to_rewind;
1569 ui_file_put_ftype *to_put;
1576 @section Getting Help
1577 @cindex online documentation
1580 You can always ask @value{GDBN} itself for information on its commands,
1581 using the command @code{help}.
1584 @kindex h @r{(@code{help})}
1587 You can use @code{help} (abbreviated @code{h}) with no arguments to
1588 display a short list of named classes of commands:
1592 List of classes of commands:
1594 aliases -- Aliases of other commands
1595 breakpoints -- Making program stop at certain points
1596 data -- Examining data
1597 files -- Specifying and examining files
1598 internals -- Maintenance commands
1599 obscure -- Obscure features
1600 running -- Running the program
1601 stack -- Examining the stack
1602 status -- Status inquiries
1603 support -- Support facilities
1604 tracepoints -- Tracing of program execution without
1605 stopping the program
1606 user-defined -- User-defined commands
1608 Type "help" followed by a class name for a list of
1609 commands in that class.
1610 Type "help" followed by command name for full
1612 Command name abbreviations are allowed if unambiguous.
1615 @c the above line break eliminates huge line overfull...
1617 @item help @var{class}
1618 Using one of the general help classes as an argument, you can get a
1619 list of the individual commands in that class. For example, here is the
1620 help display for the class @code{status}:
1623 (@value{GDBP}) help status
1628 @c Line break in "show" line falsifies real output, but needed
1629 @c to fit in smallbook page size.
1630 info -- Generic command for showing things
1631 about the program being debugged
1632 show -- Generic command for showing things
1635 Type "help" followed by command name for full
1637 Command name abbreviations are allowed if unambiguous.
1641 @item help @var{command}
1642 With a command name as @code{help} argument, @value{GDBN} displays a
1643 short paragraph on how to use that command.
1646 @item apropos @var{args}
1647 The @code{apropos} command searches through all of the @value{GDBN}
1648 commands, and their documentation, for the regular expression specified in
1649 @var{args}. It prints out all matches found. For example:
1660 set symbol-reloading -- Set dynamic symbol table reloading
1661 multiple times in one run
1662 show symbol-reloading -- Show dynamic symbol table reloading
1663 multiple times in one run
1668 @item complete @var{args}
1669 The @code{complete @var{args}} command lists all the possible completions
1670 for the beginning of a command. Use @var{args} to specify the beginning of the
1671 command you want completed. For example:
1677 @noindent results in:
1688 @noindent This is intended for use by @sc{gnu} Emacs.
1691 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1692 and @code{show} to inquire about the state of your program, or the state
1693 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1694 manual introduces each of them in the appropriate context. The listings
1695 under @code{info} and under @code{show} in the Index point to
1696 all the sub-commands. @xref{Index}.
1701 @kindex i @r{(@code{info})}
1703 This command (abbreviated @code{i}) is for describing the state of your
1704 program. For example, you can show the arguments passed to a function
1705 with @code{info args}, list the registers currently in use with @code{info
1706 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1707 You can get a complete list of the @code{info} sub-commands with
1708 @w{@code{help info}}.
1712 You can assign the result of an expression to an environment variable with
1713 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1714 @code{set prompt $}.
1718 In contrast to @code{info}, @code{show} is for describing the state of
1719 @value{GDBN} itself.
1720 You can change most of the things you can @code{show}, by using the
1721 related command @code{set}; for example, you can control what number
1722 system is used for displays with @code{set radix}, or simply inquire
1723 which is currently in use with @code{show radix}.
1726 To display all the settable parameters and their current
1727 values, you can use @code{show} with no arguments; you may also use
1728 @code{info set}. Both commands produce the same display.
1729 @c FIXME: "info set" violates the rule that "info" is for state of
1730 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1731 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1735 Here are three miscellaneous @code{show} subcommands, all of which are
1736 exceptional in lacking corresponding @code{set} commands:
1739 @kindex show version
1740 @cindex @value{GDBN} version number
1742 Show what version of @value{GDBN} is running. You should include this
1743 information in @value{GDBN} bug-reports. If multiple versions of
1744 @value{GDBN} are in use at your site, you may need to determine which
1745 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1746 commands are introduced, and old ones may wither away. Also, many
1747 system vendors ship variant versions of @value{GDBN}, and there are
1748 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1749 The version number is the same as the one announced when you start
1752 @kindex show copying
1753 @kindex info copying
1754 @cindex display @value{GDBN} copyright
1757 Display information about permission for copying @value{GDBN}.
1759 @kindex show warranty
1760 @kindex info warranty
1762 @itemx info warranty
1763 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1764 if your version of @value{GDBN} comes with one.
1769 @chapter Running Programs Under @value{GDBN}
1771 When you run a program under @value{GDBN}, you must first generate
1772 debugging information when you compile it.
1774 You may start @value{GDBN} with its arguments, if any, in an environment
1775 of your choice. If you are doing native debugging, you may redirect
1776 your program's input and output, debug an already running process, or
1777 kill a child process.
1780 * Compilation:: Compiling for debugging
1781 * Starting:: Starting your program
1782 * Arguments:: Your program's arguments
1783 * Environment:: Your program's environment
1785 * Working Directory:: Your program's working directory
1786 * Input/Output:: Your program's input and output
1787 * Attach:: Debugging an already-running process
1788 * Kill Process:: Killing the child process
1790 * Inferiors:: Debugging multiple inferiors
1791 * Threads:: Debugging programs with multiple threads
1792 * Processes:: Debugging programs with multiple processes
1793 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1797 @section Compiling for Debugging
1799 In order to debug a program effectively, you need to generate
1800 debugging information when you compile it. This debugging information
1801 is stored in the object file; it describes the data type of each
1802 variable or function and the correspondence between source line numbers
1803 and addresses in the executable code.
1805 To request debugging information, specify the @samp{-g} option when you run
1808 Programs that are to be shipped to your customers are compiled with
1809 optimizations, using the @samp{-O} compiler option. However, many
1810 compilers are unable to handle the @samp{-g} and @samp{-O} options
1811 together. Using those compilers, you cannot generate optimized
1812 executables containing debugging information.
1814 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1815 without @samp{-O}, making it possible to debug optimized code. We
1816 recommend that you @emph{always} use @samp{-g} whenever you compile a
1817 program. You may think your program is correct, but there is no sense
1818 in pushing your luck.
1820 @cindex optimized code, debugging
1821 @cindex debugging optimized code
1822 When you debug a program compiled with @samp{-g -O}, remember that the
1823 optimizer is rearranging your code; the debugger shows you what is
1824 really there. Do not be too surprised when the execution path does not
1825 exactly match your source file! An extreme example: if you define a
1826 variable, but never use it, @value{GDBN} never sees that
1827 variable---because the compiler optimizes it out of existence.
1829 Some things do not work as well with @samp{-g -O} as with just
1830 @samp{-g}, particularly on machines with instruction scheduling. If in
1831 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1832 please report it to us as a bug (including a test case!).
1833 @xref{Variables}, for more information about debugging optimized code.
1835 Older versions of the @sc{gnu} C compiler permitted a variant option
1836 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1837 format; if your @sc{gnu} C compiler has this option, do not use it.
1839 @value{GDBN} knows about preprocessor macros and can show you their
1840 expansion (@pxref{Macros}). Most compilers do not include information
1841 about preprocessor macros in the debugging information if you specify
1842 the @option{-g} flag alone, because this information is rather large.
1843 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1844 provides macro information if you specify the options
1845 @option{-gdwarf-2} and @option{-g3}; the former option requests
1846 debugging information in the Dwarf 2 format, and the latter requests
1847 ``extra information''. In the future, we hope to find more compact
1848 ways to represent macro information, so that it can be included with
1853 @section Starting your Program
1859 @kindex r @r{(@code{run})}
1862 Use the @code{run} command to start your program under @value{GDBN}.
1863 You must first specify the program name (except on VxWorks) with an
1864 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1865 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1866 (@pxref{Files, ,Commands to Specify Files}).
1870 If you are running your program in an execution environment that
1871 supports processes, @code{run} creates an inferior process and makes
1872 that process run your program. In some environments without processes,
1873 @code{run} jumps to the start of your program. Other targets,
1874 like @samp{remote}, are always running. If you get an error
1875 message like this one:
1878 The "remote" target does not support "run".
1879 Try "help target" or "continue".
1883 then use @code{continue} to run your program. You may need @code{load}
1884 first (@pxref{load}).
1886 The execution of a program is affected by certain information it
1887 receives from its superior. @value{GDBN} provides ways to specify this
1888 information, which you must do @emph{before} starting your program. (You
1889 can change it after starting your program, but such changes only affect
1890 your program the next time you start it.) This information may be
1891 divided into four categories:
1894 @item The @emph{arguments.}
1895 Specify the arguments to give your program as the arguments of the
1896 @code{run} command. If a shell is available on your target, the shell
1897 is used to pass the arguments, so that you may use normal conventions
1898 (such as wildcard expansion or variable substitution) in describing
1900 In Unix systems, you can control which shell is used with the
1901 @code{SHELL} environment variable.
1902 @xref{Arguments, ,Your Program's Arguments}.
1904 @item The @emph{environment.}
1905 Your program normally inherits its environment from @value{GDBN}, but you can
1906 use the @value{GDBN} commands @code{set environment} and @code{unset
1907 environment} to change parts of the environment that affect
1908 your program. @xref{Environment, ,Your Program's Environment}.
1910 @item The @emph{working directory.}
1911 Your program inherits its working directory from @value{GDBN}. You can set
1912 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1913 @xref{Working Directory, ,Your Program's Working Directory}.
1915 @item The @emph{standard input and output.}
1916 Your program normally uses the same device for standard input and
1917 standard output as @value{GDBN} is using. You can redirect input and output
1918 in the @code{run} command line, or you can use the @code{tty} command to
1919 set a different device for your program.
1920 @xref{Input/Output, ,Your Program's Input and Output}.
1923 @emph{Warning:} While input and output redirection work, you cannot use
1924 pipes to pass the output of the program you are debugging to another
1925 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1929 When you issue the @code{run} command, your program begins to execute
1930 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1931 of how to arrange for your program to stop. Once your program has
1932 stopped, you may call functions in your program, using the @code{print}
1933 or @code{call} commands. @xref{Data, ,Examining Data}.
1935 If the modification time of your symbol file has changed since the last
1936 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1937 table, and reads it again. When it does this, @value{GDBN} tries to retain
1938 your current breakpoints.
1943 @cindex run to main procedure
1944 The name of the main procedure can vary from language to language.
1945 With C or C@t{++}, the main procedure name is always @code{main}, but
1946 other languages such as Ada do not require a specific name for their
1947 main procedure. The debugger provides a convenient way to start the
1948 execution of the program and to stop at the beginning of the main
1949 procedure, depending on the language used.
1951 The @samp{start} command does the equivalent of setting a temporary
1952 breakpoint at the beginning of the main procedure and then invoking
1953 the @samp{run} command.
1955 @cindex elaboration phase
1956 Some programs contain an @dfn{elaboration} phase where some startup code is
1957 executed before the main procedure is called. This depends on the
1958 languages used to write your program. In C@t{++}, for instance,
1959 constructors for static and global objects are executed before
1960 @code{main} is called. It is therefore possible that the debugger stops
1961 before reaching the main procedure. However, the temporary breakpoint
1962 will remain to halt execution.
1964 Specify the arguments to give to your program as arguments to the
1965 @samp{start} command. These arguments will be given verbatim to the
1966 underlying @samp{run} command. Note that the same arguments will be
1967 reused if no argument is provided during subsequent calls to
1968 @samp{start} or @samp{run}.
1970 It is sometimes necessary to debug the program during elaboration. In
1971 these cases, using the @code{start} command would stop the execution of
1972 your program too late, as the program would have already completed the
1973 elaboration phase. Under these circumstances, insert breakpoints in your
1974 elaboration code before running your program.
1976 @kindex set exec-wrapper
1977 @item set exec-wrapper @var{wrapper}
1978 @itemx show exec-wrapper
1979 @itemx unset exec-wrapper
1980 When @samp{exec-wrapper} is set, the specified wrapper is used to
1981 launch programs for debugging. @value{GDBN} starts your program
1982 with a shell command of the form @kbd{exec @var{wrapper}
1983 @var{program}}. Quoting is added to @var{program} and its
1984 arguments, but not to @var{wrapper}, so you should add quotes if
1985 appropriate for your shell. The wrapper runs until it executes
1986 your program, and then @value{GDBN} takes control.
1988 You can use any program that eventually calls @code{execve} with
1989 its arguments as a wrapper. Several standard Unix utilities do
1990 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1991 with @code{exec "$@@"} will also work.
1993 For example, you can use @code{env} to pass an environment variable to
1994 the debugged program, without setting the variable in your shell's
1998 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2002 This command is available when debugging locally on most targets, excluding
2003 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2005 @kindex set disable-randomization
2006 @item set disable-randomization
2007 @itemx set disable-randomization on
2008 This option (enabled by default in @value{GDBN}) will turn off the native
2009 randomization of the virtual address space of the started program. This option
2010 is useful for multiple debugging sessions to make the execution better
2011 reproducible and memory addresses reusable across debugging sessions.
2013 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2017 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2020 @item set disable-randomization off
2021 Leave the behavior of the started executable unchanged. Some bugs rear their
2022 ugly heads only when the program is loaded at certain addresses. If your bug
2023 disappears when you run the program under @value{GDBN}, that might be because
2024 @value{GDBN} by default disables the address randomization on platforms, such
2025 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2026 disable-randomization off} to try to reproduce such elusive bugs.
2028 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2029 It protects the programs against some kinds of security attacks. In these
2030 cases the attacker needs to know the exact location of a concrete executable
2031 code. Randomizing its location makes it impossible to inject jumps misusing
2032 a code at its expected addresses.
2034 Prelinking shared libraries provides a startup performance advantage but it
2035 makes addresses in these libraries predictable for privileged processes by
2036 having just unprivileged access at the target system. Reading the shared
2037 library binary gives enough information for assembling the malicious code
2038 misusing it. Still even a prelinked shared library can get loaded at a new
2039 random address just requiring the regular relocation process during the
2040 startup. Shared libraries not already prelinked are always loaded at
2041 a randomly chosen address.
2043 Position independent executables (PIE) contain position independent code
2044 similar to the shared libraries and therefore such executables get loaded at
2045 a randomly chosen address upon startup. PIE executables always load even
2046 already prelinked shared libraries at a random address. You can build such
2047 executable using @command{gcc -fPIE -pie}.
2049 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2050 (as long as the randomization is enabled).
2052 @item show disable-randomization
2053 Show the current setting of the explicit disable of the native randomization of
2054 the virtual address space of the started program.
2059 @section Your Program's Arguments
2061 @cindex arguments (to your program)
2062 The arguments to your program can be specified by the arguments of the
2064 They are passed to a shell, which expands wildcard characters and
2065 performs redirection of I/O, and thence to your program. Your
2066 @code{SHELL} environment variable (if it exists) specifies what shell
2067 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2068 the default shell (@file{/bin/sh} on Unix).
2070 On non-Unix systems, the program is usually invoked directly by
2071 @value{GDBN}, which emulates I/O redirection via the appropriate system
2072 calls, and the wildcard characters are expanded by the startup code of
2073 the program, not by the shell.
2075 @code{run} with no arguments uses the same arguments used by the previous
2076 @code{run}, or those set by the @code{set args} command.
2081 Specify the arguments to be used the next time your program is run. If
2082 @code{set args} has no arguments, @code{run} executes your program
2083 with no arguments. Once you have run your program with arguments,
2084 using @code{set args} before the next @code{run} is the only way to run
2085 it again without arguments.
2089 Show the arguments to give your program when it is started.
2093 @section Your Program's Environment
2095 @cindex environment (of your program)
2096 The @dfn{environment} consists of a set of environment variables and
2097 their values. Environment variables conventionally record such things as
2098 your user name, your home directory, your terminal type, and your search
2099 path for programs to run. Usually you set up environment variables with
2100 the shell and they are inherited by all the other programs you run. When
2101 debugging, it can be useful to try running your program with a modified
2102 environment without having to start @value{GDBN} over again.
2106 @item path @var{directory}
2107 Add @var{directory} to the front of the @code{PATH} environment variable
2108 (the search path for executables) that will be passed to your program.
2109 The value of @code{PATH} used by @value{GDBN} does not change.
2110 You may specify several directory names, separated by whitespace or by a
2111 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2112 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2113 is moved to the front, so it is searched sooner.
2115 You can use the string @samp{$cwd} to refer to whatever is the current
2116 working directory at the time @value{GDBN} searches the path. If you
2117 use @samp{.} instead, it refers to the directory where you executed the
2118 @code{path} command. @value{GDBN} replaces @samp{.} in the
2119 @var{directory} argument (with the current path) before adding
2120 @var{directory} to the search path.
2121 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2122 @c document that, since repeating it would be a no-op.
2126 Display the list of search paths for executables (the @code{PATH}
2127 environment variable).
2129 @kindex show environment
2130 @item show environment @r{[}@var{varname}@r{]}
2131 Print the value of environment variable @var{varname} to be given to
2132 your program when it starts. If you do not supply @var{varname},
2133 print the names and values of all environment variables to be given to
2134 your program. You can abbreviate @code{environment} as @code{env}.
2136 @kindex set environment
2137 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2138 Set environment variable @var{varname} to @var{value}. The value
2139 changes for your program only, not for @value{GDBN} itself. @var{value} may
2140 be any string; the values of environment variables are just strings, and
2141 any interpretation is supplied by your program itself. The @var{value}
2142 parameter is optional; if it is eliminated, the variable is set to a
2144 @c "any string" here does not include leading, trailing
2145 @c blanks. Gnu asks: does anyone care?
2147 For example, this command:
2154 tells the debugged program, when subsequently run, that its user is named
2155 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2156 are not actually required.)
2158 @kindex unset environment
2159 @item unset environment @var{varname}
2160 Remove variable @var{varname} from the environment to be passed to your
2161 program. This is different from @samp{set env @var{varname} =};
2162 @code{unset environment} removes the variable from the environment,
2163 rather than assigning it an empty value.
2166 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2168 by your @code{SHELL} environment variable if it exists (or
2169 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2170 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2171 @file{.bashrc} for BASH---any variables you set in that file affect
2172 your program. You may wish to move setting of environment variables to
2173 files that are only run when you sign on, such as @file{.login} or
2176 @node Working Directory
2177 @section Your Program's Working Directory
2179 @cindex working directory (of your program)
2180 Each time you start your program with @code{run}, it inherits its
2181 working directory from the current working directory of @value{GDBN}.
2182 The @value{GDBN} working directory is initially whatever it inherited
2183 from its parent process (typically the shell), but you can specify a new
2184 working directory in @value{GDBN} with the @code{cd} command.
2186 The @value{GDBN} working directory also serves as a default for the commands
2187 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2192 @cindex change working directory
2193 @item cd @var{directory}
2194 Set the @value{GDBN} working directory to @var{directory}.
2198 Print the @value{GDBN} working directory.
2201 It is generally impossible to find the current working directory of
2202 the process being debugged (since a program can change its directory
2203 during its run). If you work on a system where @value{GDBN} is
2204 configured with the @file{/proc} support, you can use the @code{info
2205 proc} command (@pxref{SVR4 Process Information}) to find out the
2206 current working directory of the debuggee.
2209 @section Your Program's Input and Output
2214 By default, the program you run under @value{GDBN} does input and output to
2215 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2216 to its own terminal modes to interact with you, but it records the terminal
2217 modes your program was using and switches back to them when you continue
2218 running your program.
2221 @kindex info terminal
2223 Displays information recorded by @value{GDBN} about the terminal modes your
2227 You can redirect your program's input and/or output using shell
2228 redirection with the @code{run} command. For example,
2235 starts your program, diverting its output to the file @file{outfile}.
2238 @cindex controlling terminal
2239 Another way to specify where your program should do input and output is
2240 with the @code{tty} command. This command accepts a file name as
2241 argument, and causes this file to be the default for future @code{run}
2242 commands. It also resets the controlling terminal for the child
2243 process, for future @code{run} commands. For example,
2250 directs that processes started with subsequent @code{run} commands
2251 default to do input and output on the terminal @file{/dev/ttyb} and have
2252 that as their controlling terminal.
2254 An explicit redirection in @code{run} overrides the @code{tty} command's
2255 effect on the input/output device, but not its effect on the controlling
2258 When you use the @code{tty} command or redirect input in the @code{run}
2259 command, only the input @emph{for your program} is affected. The input
2260 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2261 for @code{set inferior-tty}.
2263 @cindex inferior tty
2264 @cindex set inferior controlling terminal
2265 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2266 display the name of the terminal that will be used for future runs of your
2270 @item set inferior-tty /dev/ttyb
2271 @kindex set inferior-tty
2272 Set the tty for the program being debugged to /dev/ttyb.
2274 @item show inferior-tty
2275 @kindex show inferior-tty
2276 Show the current tty for the program being debugged.
2280 @section Debugging an Already-running Process
2285 @item attach @var{process-id}
2286 This command attaches to a running process---one that was started
2287 outside @value{GDBN}. (@code{info files} shows your active
2288 targets.) The command takes as argument a process ID. The usual way to
2289 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2290 or with the @samp{jobs -l} shell command.
2292 @code{attach} does not repeat if you press @key{RET} a second time after
2293 executing the command.
2296 To use @code{attach}, your program must be running in an environment
2297 which supports processes; for example, @code{attach} does not work for
2298 programs on bare-board targets that lack an operating system. You must
2299 also have permission to send the process a signal.
2301 When you use @code{attach}, the debugger finds the program running in
2302 the process first by looking in the current working directory, then (if
2303 the program is not found) by using the source file search path
2304 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2305 the @code{file} command to load the program. @xref{Files, ,Commands to
2308 The first thing @value{GDBN} does after arranging to debug the specified
2309 process is to stop it. You can examine and modify an attached process
2310 with all the @value{GDBN} commands that are ordinarily available when
2311 you start processes with @code{run}. You can insert breakpoints; you
2312 can step and continue; you can modify storage. If you would rather the
2313 process continue running, you may use the @code{continue} command after
2314 attaching @value{GDBN} to the process.
2319 When you have finished debugging the attached process, you can use the
2320 @code{detach} command to release it from @value{GDBN} control. Detaching
2321 the process continues its execution. After the @code{detach} command,
2322 that process and @value{GDBN} become completely independent once more, and you
2323 are ready to @code{attach} another process or start one with @code{run}.
2324 @code{detach} does not repeat if you press @key{RET} again after
2325 executing the command.
2328 If you exit @value{GDBN} while you have an attached process, you detach
2329 that process. If you use the @code{run} command, you kill that process.
2330 By default, @value{GDBN} asks for confirmation if you try to do either of these
2331 things; you can control whether or not you need to confirm by using the
2332 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2336 @section Killing the Child Process
2341 Kill the child process in which your program is running under @value{GDBN}.
2344 This command is useful if you wish to debug a core dump instead of a
2345 running process. @value{GDBN} ignores any core dump file while your program
2348 On some operating systems, a program cannot be executed outside @value{GDBN}
2349 while you have breakpoints set on it inside @value{GDBN}. You can use the
2350 @code{kill} command in this situation to permit running your program
2351 outside the debugger.
2353 The @code{kill} command is also useful if you wish to recompile and
2354 relink your program, since on many systems it is impossible to modify an
2355 executable file while it is running in a process. In this case, when you
2356 next type @code{run}, @value{GDBN} notices that the file has changed, and
2357 reads the symbol table again (while trying to preserve your current
2358 breakpoint settings).
2361 @section Debugging Multiple Inferiors
2363 Some @value{GDBN} targets are able to run multiple processes created
2364 from a single executable. This can happen, for instance, with an
2365 embedded system reporting back several processes via the remote
2369 @value{GDBN} represents the state of each program execution with an
2370 object called an @dfn{inferior}. An inferior typically corresponds to
2371 a process, but is more general and applies also to targets that do not
2372 have processes. Inferiors may be created before a process runs, and
2373 may (in future) be retained after a process exits. Each run of an
2374 executable creates a new inferior, as does each attachment to an
2375 existing process. Inferiors have unique identifiers that are
2376 different from process ids, and may optionally be named as well.
2377 Usually each inferior will also have its own distinct address space,
2378 although some embedded targets may have several inferiors running in
2379 different parts of a single space.
2381 Each inferior may in turn have multiple threads running in it.
2383 To find out what inferiors exist at any moment, use @code{info inferiors}:
2386 @kindex info inferiors
2387 @item info inferiors
2388 Print a list of all inferiors currently being managed by @value{GDBN}.
2390 @kindex set print inferior-events
2391 @cindex print messages on inferior start and exit
2392 @item set print inferior-events
2393 @itemx set print inferior-events on
2394 @itemx set print inferior-events off
2395 The @code{set print inferior-events} command allows you to enable or
2396 disable printing of messages when @value{GDBN} notices that new
2397 inferiors have started or that inferiors have exited or have been
2398 detached. By default, these messages will not be printed.
2400 @kindex show print inferior-events
2401 @item show print inferior-events
2402 Show whether messages will be printed when @value{GDBN} detects that
2403 inferiors have started, exited or have been detached.
2407 @section Debugging Programs with Multiple Threads
2409 @cindex threads of execution
2410 @cindex multiple threads
2411 @cindex switching threads
2412 In some operating systems, such as HP-UX and Solaris, a single program
2413 may have more than one @dfn{thread} of execution. The precise semantics
2414 of threads differ from one operating system to another, but in general
2415 the threads of a single program are akin to multiple processes---except
2416 that they share one address space (that is, they can all examine and
2417 modify the same variables). On the other hand, each thread has its own
2418 registers and execution stack, and perhaps private memory.
2420 @value{GDBN} provides these facilities for debugging multi-thread
2424 @item automatic notification of new threads
2425 @item @samp{thread @var{threadno}}, a command to switch among threads
2426 @item @samp{info threads}, a command to inquire about existing threads
2427 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2428 a command to apply a command to a list of threads
2429 @item thread-specific breakpoints
2430 @item @samp{set print thread-events}, which controls printing of
2431 messages on thread start and exit.
2435 @emph{Warning:} These facilities are not yet available on every
2436 @value{GDBN} configuration where the operating system supports threads.
2437 If your @value{GDBN} does not support threads, these commands have no
2438 effect. For example, a system without thread support shows no output
2439 from @samp{info threads}, and always rejects the @code{thread} command,
2443 (@value{GDBP}) info threads
2444 (@value{GDBP}) thread 1
2445 Thread ID 1 not known. Use the "info threads" command to
2446 see the IDs of currently known threads.
2448 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2449 @c doesn't support threads"?
2452 @cindex focus of debugging
2453 @cindex current thread
2454 The @value{GDBN} thread debugging facility allows you to observe all
2455 threads while your program runs---but whenever @value{GDBN} takes
2456 control, one thread in particular is always the focus of debugging.
2457 This thread is called the @dfn{current thread}. Debugging commands show
2458 program information from the perspective of the current thread.
2460 @cindex @code{New} @var{systag} message
2461 @cindex thread identifier (system)
2462 @c FIXME-implementors!! It would be more helpful if the [New...] message
2463 @c included GDB's numeric thread handle, so you could just go to that
2464 @c thread without first checking `info threads'.
2465 Whenever @value{GDBN} detects a new thread in your program, it displays
2466 the target system's identification for the thread with a message in the
2467 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2468 whose form varies depending on the particular system. For example, on
2469 @sc{gnu}/Linux, you might see
2472 [New Thread 46912507313328 (LWP 25582)]
2476 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2477 the @var{systag} is simply something like @samp{process 368}, with no
2480 @c FIXME!! (1) Does the [New...] message appear even for the very first
2481 @c thread of a program, or does it only appear for the
2482 @c second---i.e.@: when it becomes obvious we have a multithread
2484 @c (2) *Is* there necessarily a first thread always? Or do some
2485 @c multithread systems permit starting a program with multiple
2486 @c threads ab initio?
2488 @cindex thread number
2489 @cindex thread identifier (GDB)
2490 For debugging purposes, @value{GDBN} associates its own thread
2491 number---always a single integer---with each thread in your program.
2494 @kindex info threads
2496 Display a summary of all threads currently in your
2497 program. @value{GDBN} displays for each thread (in this order):
2501 the thread number assigned by @value{GDBN}
2504 the target system's thread identifier (@var{systag})
2507 the current stack frame summary for that thread
2511 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2512 indicates the current thread.
2516 @c end table here to get a little more width for example
2519 (@value{GDBP}) info threads
2520 3 process 35 thread 27 0x34e5 in sigpause ()
2521 2 process 35 thread 23 0x34e5 in sigpause ()
2522 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2528 @cindex debugging multithreaded programs (on HP-UX)
2529 @cindex thread identifier (GDB), on HP-UX
2530 For debugging purposes, @value{GDBN} associates its own thread
2531 number---a small integer assigned in thread-creation order---with each
2532 thread in your program.
2534 @cindex @code{New} @var{systag} message, on HP-UX
2535 @cindex thread identifier (system), on HP-UX
2536 @c FIXME-implementors!! It would be more helpful if the [New...] message
2537 @c included GDB's numeric thread handle, so you could just go to that
2538 @c thread without first checking `info threads'.
2539 Whenever @value{GDBN} detects a new thread in your program, it displays
2540 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2541 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2542 whose form varies depending on the particular system. For example, on
2546 [New thread 2 (system thread 26594)]
2550 when @value{GDBN} notices a new thread.
2553 @kindex info threads (HP-UX)
2555 Display a summary of all threads currently in your
2556 program. @value{GDBN} displays for each thread (in this order):
2559 @item the thread number assigned by @value{GDBN}
2561 @item the target system's thread identifier (@var{systag})
2563 @item the current stack frame summary for that thread
2567 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2568 indicates the current thread.
2572 @c end table here to get a little more width for example
2575 (@value{GDBP}) info threads
2576 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2578 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2579 from /usr/lib/libc.2
2580 1 system thread 27905 0x7b003498 in _brk () \@*
2581 from /usr/lib/libc.2
2584 On Solaris, you can display more information about user threads with a
2585 Solaris-specific command:
2588 @item maint info sol-threads
2589 @kindex maint info sol-threads
2590 @cindex thread info (Solaris)
2591 Display info on Solaris user threads.
2595 @kindex thread @var{threadno}
2596 @item thread @var{threadno}
2597 Make thread number @var{threadno} the current thread. The command
2598 argument @var{threadno} is the internal @value{GDBN} thread number, as
2599 shown in the first field of the @samp{info threads} display.
2600 @value{GDBN} responds by displaying the system identifier of the thread
2601 you selected, and its current stack frame summary:
2604 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2605 (@value{GDBP}) thread 2
2606 [Switching to process 35 thread 23]
2607 0x34e5 in sigpause ()
2611 As with the @samp{[New @dots{}]} message, the form of the text after
2612 @samp{Switching to} depends on your system's conventions for identifying
2615 @kindex thread apply
2616 @cindex apply command to several threads
2617 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2618 The @code{thread apply} command allows you to apply the named
2619 @var{command} to one or more threads. Specify the numbers of the
2620 threads that you want affected with the command argument
2621 @var{threadno}. It can be a single thread number, one of the numbers
2622 shown in the first field of the @samp{info threads} display; or it
2623 could be a range of thread numbers, as in @code{2-4}. To apply a
2624 command to all threads, type @kbd{thread apply all @var{command}}.
2626 @kindex set print thread-events
2627 @cindex print messages on thread start and exit
2628 @item set print thread-events
2629 @itemx set print thread-events on
2630 @itemx set print thread-events off
2631 The @code{set print thread-events} command allows you to enable or
2632 disable printing of messages when @value{GDBN} notices that new threads have
2633 started or that threads have exited. By default, these messages will
2634 be printed if detection of these events is supported by the target.
2635 Note that these messages cannot be disabled on all targets.
2637 @kindex show print thread-events
2638 @item show print thread-events
2639 Show whether messages will be printed when @value{GDBN} detects that threads
2640 have started and exited.
2643 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2644 more information about how @value{GDBN} behaves when you stop and start
2645 programs with multiple threads.
2647 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2648 watchpoints in programs with multiple threads.
2651 @section Debugging Programs with Multiple Processes
2653 @cindex fork, debugging programs which call
2654 @cindex multiple processes
2655 @cindex processes, multiple
2656 On most systems, @value{GDBN} has no special support for debugging
2657 programs which create additional processes using the @code{fork}
2658 function. When a program forks, @value{GDBN} will continue to debug the
2659 parent process and the child process will run unimpeded. If you have
2660 set a breakpoint in any code which the child then executes, the child
2661 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2662 will cause it to terminate.
2664 However, if you want to debug the child process there is a workaround
2665 which isn't too painful. Put a call to @code{sleep} in the code which
2666 the child process executes after the fork. It may be useful to sleep
2667 only if a certain environment variable is set, or a certain file exists,
2668 so that the delay need not occur when you don't want to run @value{GDBN}
2669 on the child. While the child is sleeping, use the @code{ps} program to
2670 get its process ID. Then tell @value{GDBN} (a new invocation of
2671 @value{GDBN} if you are also debugging the parent process) to attach to
2672 the child process (@pxref{Attach}). From that point on you can debug
2673 the child process just like any other process which you attached to.
2675 On some systems, @value{GDBN} provides support for debugging programs that
2676 create additional processes using the @code{fork} or @code{vfork} functions.
2677 Currently, the only platforms with this feature are HP-UX (11.x and later
2678 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2680 By default, when a program forks, @value{GDBN} will continue to debug
2681 the parent process and the child process will run unimpeded.
2683 If you want to follow the child process instead of the parent process,
2684 use the command @w{@code{set follow-fork-mode}}.
2687 @kindex set follow-fork-mode
2688 @item set follow-fork-mode @var{mode}
2689 Set the debugger response to a program call of @code{fork} or
2690 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2691 process. The @var{mode} argument can be:
2695 The original process is debugged after a fork. The child process runs
2696 unimpeded. This is the default.
2699 The new process is debugged after a fork. The parent process runs
2704 @kindex show follow-fork-mode
2705 @item show follow-fork-mode
2706 Display the current debugger response to a @code{fork} or @code{vfork} call.
2709 @cindex debugging multiple processes
2710 On Linux, if you want to debug both the parent and child processes, use the
2711 command @w{@code{set detach-on-fork}}.
2714 @kindex set detach-on-fork
2715 @item set detach-on-fork @var{mode}
2716 Tells gdb whether to detach one of the processes after a fork, or
2717 retain debugger control over them both.
2721 The child process (or parent process, depending on the value of
2722 @code{follow-fork-mode}) will be detached and allowed to run
2723 independently. This is the default.
2726 Both processes will be held under the control of @value{GDBN}.
2727 One process (child or parent, depending on the value of
2728 @code{follow-fork-mode}) is debugged as usual, while the other
2733 @kindex show detach-on-fork
2734 @item show detach-on-fork
2735 Show whether detach-on-fork mode is on/off.
2738 If you choose to set @samp{detach-on-fork} mode off, then
2739 @value{GDBN} will retain control of all forked processes (including
2740 nested forks). You can list the forked processes under the control of
2741 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2742 from one fork to another by using the @w{@code{fork}} command.
2747 Print a list of all forked processes under the control of @value{GDBN}.
2748 The listing will include a fork id, a process id, and the current
2749 position (program counter) of the process.
2751 @kindex fork @var{fork-id}
2752 @item fork @var{fork-id}
2753 Make fork number @var{fork-id} the current process. The argument
2754 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2755 as shown in the first field of the @samp{info forks} display.
2757 @kindex process @var{process-id}
2758 @item process @var{process-id}
2759 Make process number @var{process-id} the current process. The
2760 argument @var{process-id} must be one that is listed in the output of
2765 To quit debugging one of the forked processes, you can either detach
2766 from it by using the @w{@code{detach fork}} command (allowing it to
2767 run independently), or delete (and kill) it using the
2768 @w{@code{delete fork}} command.
2771 @kindex detach fork @var{fork-id}
2772 @item detach fork @var{fork-id}
2773 Detach from the process identified by @value{GDBN} fork number
2774 @var{fork-id}, and remove it from the fork list. The process will be
2775 allowed to run independently.
2777 @kindex delete fork @var{fork-id}
2778 @item delete fork @var{fork-id}
2779 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2780 and remove it from the fork list.
2784 If you ask to debug a child process and a @code{vfork} is followed by an
2785 @code{exec}, @value{GDBN} executes the new target up to the first
2786 breakpoint in the new target. If you have a breakpoint set on
2787 @code{main} in your original program, the breakpoint will also be set on
2788 the child process's @code{main}.
2790 When a child process is spawned by @code{vfork}, you cannot debug the
2791 child or parent until an @code{exec} call completes.
2793 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2794 call executes, the new target restarts. To restart the parent process,
2795 use the @code{file} command with the parent executable name as its
2798 You can use the @code{catch} command to make @value{GDBN} stop whenever
2799 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2800 Catchpoints, ,Setting Catchpoints}.
2802 @node Checkpoint/Restart
2803 @section Setting a @emph{Bookmark} to Return to Later
2808 @cindex snapshot of a process
2809 @cindex rewind program state
2811 On certain operating systems@footnote{Currently, only
2812 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2813 program's state, called a @dfn{checkpoint}, and come back to it
2816 Returning to a checkpoint effectively undoes everything that has
2817 happened in the program since the @code{checkpoint} was saved. This
2818 includes changes in memory, registers, and even (within some limits)
2819 system state. Effectively, it is like going back in time to the
2820 moment when the checkpoint was saved.
2822 Thus, if you're stepping thru a program and you think you're
2823 getting close to the point where things go wrong, you can save
2824 a checkpoint. Then, if you accidentally go too far and miss
2825 the critical statement, instead of having to restart your program
2826 from the beginning, you can just go back to the checkpoint and
2827 start again from there.
2829 This can be especially useful if it takes a lot of time or
2830 steps to reach the point where you think the bug occurs.
2832 To use the @code{checkpoint}/@code{restart} method of debugging:
2837 Save a snapshot of the debugged program's current execution state.
2838 The @code{checkpoint} command takes no arguments, but each checkpoint
2839 is assigned a small integer id, similar to a breakpoint id.
2841 @kindex info checkpoints
2842 @item info checkpoints
2843 List the checkpoints that have been saved in the current debugging
2844 session. For each checkpoint, the following information will be
2851 @item Source line, or label
2854 @kindex restart @var{checkpoint-id}
2855 @item restart @var{checkpoint-id}
2856 Restore the program state that was saved as checkpoint number
2857 @var{checkpoint-id}. All program variables, registers, stack frames
2858 etc.@: will be returned to the values that they had when the checkpoint
2859 was saved. In essence, gdb will ``wind back the clock'' to the point
2860 in time when the checkpoint was saved.
2862 Note that breakpoints, @value{GDBN} variables, command history etc.
2863 are not affected by restoring a checkpoint. In general, a checkpoint
2864 only restores things that reside in the program being debugged, not in
2867 @kindex delete checkpoint @var{checkpoint-id}
2868 @item delete checkpoint @var{checkpoint-id}
2869 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2873 Returning to a previously saved checkpoint will restore the user state
2874 of the program being debugged, plus a significant subset of the system
2875 (OS) state, including file pointers. It won't ``un-write'' data from
2876 a file, but it will rewind the file pointer to the previous location,
2877 so that the previously written data can be overwritten. For files
2878 opened in read mode, the pointer will also be restored so that the
2879 previously read data can be read again.
2881 Of course, characters that have been sent to a printer (or other
2882 external device) cannot be ``snatched back'', and characters received
2883 from eg.@: a serial device can be removed from internal program buffers,
2884 but they cannot be ``pushed back'' into the serial pipeline, ready to
2885 be received again. Similarly, the actual contents of files that have
2886 been changed cannot be restored (at this time).
2888 However, within those constraints, you actually can ``rewind'' your
2889 program to a previously saved point in time, and begin debugging it
2890 again --- and you can change the course of events so as to debug a
2891 different execution path this time.
2893 @cindex checkpoints and process id
2894 Finally, there is one bit of internal program state that will be
2895 different when you return to a checkpoint --- the program's process
2896 id. Each checkpoint will have a unique process id (or @var{pid}),
2897 and each will be different from the program's original @var{pid}.
2898 If your program has saved a local copy of its process id, this could
2899 potentially pose a problem.
2901 @subsection A Non-obvious Benefit of Using Checkpoints
2903 On some systems such as @sc{gnu}/Linux, address space randomization
2904 is performed on new processes for security reasons. This makes it
2905 difficult or impossible to set a breakpoint, or watchpoint, on an
2906 absolute address if you have to restart the program, since the
2907 absolute location of a symbol will change from one execution to the
2910 A checkpoint, however, is an @emph{identical} copy of a process.
2911 Therefore if you create a checkpoint at (eg.@:) the start of main,
2912 and simply return to that checkpoint instead of restarting the
2913 process, you can avoid the effects of address randomization and
2914 your symbols will all stay in the same place.
2917 @chapter Stopping and Continuing
2919 The principal purposes of using a debugger are so that you can stop your
2920 program before it terminates; or so that, if your program runs into
2921 trouble, you can investigate and find out why.
2923 Inside @value{GDBN}, your program may stop for any of several reasons,
2924 such as a signal, a breakpoint, or reaching a new line after a
2925 @value{GDBN} command such as @code{step}. You may then examine and
2926 change variables, set new breakpoints or remove old ones, and then
2927 continue execution. Usually, the messages shown by @value{GDBN} provide
2928 ample explanation of the status of your program---but you can also
2929 explicitly request this information at any time.
2932 @kindex info program
2934 Display information about the status of your program: whether it is
2935 running or not, what process it is, and why it stopped.
2939 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2940 * Continuing and Stepping:: Resuming execution
2942 * Thread Stops:: Stopping and starting multi-thread programs
2946 @section Breakpoints, Watchpoints, and Catchpoints
2949 A @dfn{breakpoint} makes your program stop whenever a certain point in
2950 the program is reached. For each breakpoint, you can add conditions to
2951 control in finer detail whether your program stops. You can set
2952 breakpoints with the @code{break} command and its variants (@pxref{Set
2953 Breaks, ,Setting Breakpoints}), to specify the place where your program
2954 should stop by line number, function name or exact address in the
2957 On some systems, you can set breakpoints in shared libraries before
2958 the executable is run. There is a minor limitation on HP-UX systems:
2959 you must wait until the executable is run in order to set breakpoints
2960 in shared library routines that are not called directly by the program
2961 (for example, routines that are arguments in a @code{pthread_create}
2965 @cindex data breakpoints
2966 @cindex memory tracing
2967 @cindex breakpoint on memory address
2968 @cindex breakpoint on variable modification
2969 A @dfn{watchpoint} is a special breakpoint that stops your program
2970 when the value of an expression changes. The expression may be a value
2971 of a variable, or it could involve values of one or more variables
2972 combined by operators, such as @samp{a + b}. This is sometimes called
2973 @dfn{data breakpoints}. You must use a different command to set
2974 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2975 from that, you can manage a watchpoint like any other breakpoint: you
2976 enable, disable, and delete both breakpoints and watchpoints using the
2979 You can arrange to have values from your program displayed automatically
2980 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2984 @cindex breakpoint on events
2985 A @dfn{catchpoint} is another special breakpoint that stops your program
2986 when a certain kind of event occurs, such as the throwing of a C@t{++}
2987 exception or the loading of a library. As with watchpoints, you use a
2988 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2989 Catchpoints}), but aside from that, you can manage a catchpoint like any
2990 other breakpoint. (To stop when your program receives a signal, use the
2991 @code{handle} command; see @ref{Signals, ,Signals}.)
2993 @cindex breakpoint numbers
2994 @cindex numbers for breakpoints
2995 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2996 catchpoint when you create it; these numbers are successive integers
2997 starting with one. In many of the commands for controlling various
2998 features of breakpoints you use the breakpoint number to say which
2999 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3000 @dfn{disabled}; if disabled, it has no effect on your program until you
3003 @cindex breakpoint ranges
3004 @cindex ranges of breakpoints
3005 Some @value{GDBN} commands accept a range of breakpoints on which to
3006 operate. A breakpoint range is either a single breakpoint number, like
3007 @samp{5}, or two such numbers, in increasing order, separated by a
3008 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3009 all breakpoints in that range are operated on.
3012 * Set Breaks:: Setting breakpoints
3013 * Set Watchpoints:: Setting watchpoints
3014 * Set Catchpoints:: Setting catchpoints
3015 * Delete Breaks:: Deleting breakpoints
3016 * Disabling:: Disabling breakpoints
3017 * Conditions:: Break conditions
3018 * Break Commands:: Breakpoint command lists
3019 * Error in Breakpoints:: ``Cannot insert breakpoints''
3020 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3024 @subsection Setting Breakpoints
3026 @c FIXME LMB what does GDB do if no code on line of breakpt?
3027 @c consider in particular declaration with/without initialization.
3029 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3032 @kindex b @r{(@code{break})}
3033 @vindex $bpnum@r{, convenience variable}
3034 @cindex latest breakpoint
3035 Breakpoints are set with the @code{break} command (abbreviated
3036 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3037 number of the breakpoint you've set most recently; see @ref{Convenience
3038 Vars,, Convenience Variables}, for a discussion of what you can do with
3039 convenience variables.
3042 @item break @var{location}
3043 Set a breakpoint at the given @var{location}, which can specify a
3044 function name, a line number, or an address of an instruction.
3045 (@xref{Specify Location}, for a list of all the possible ways to
3046 specify a @var{location}.) The breakpoint will stop your program just
3047 before it executes any of the code in the specified @var{location}.
3049 When using source languages that permit overloading of symbols, such as
3050 C@t{++}, a function name may refer to more than one possible place to break.
3051 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3054 It is also possible to insert a breakpoint that will stop the program
3055 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3056 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3059 When called without any arguments, @code{break} sets a breakpoint at
3060 the next instruction to be executed in the selected stack frame
3061 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3062 innermost, this makes your program stop as soon as control
3063 returns to that frame. This is similar to the effect of a
3064 @code{finish} command in the frame inside the selected frame---except
3065 that @code{finish} does not leave an active breakpoint. If you use
3066 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3067 the next time it reaches the current location; this may be useful
3070 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3071 least one instruction has been executed. If it did not do this, you
3072 would be unable to proceed past a breakpoint without first disabling the
3073 breakpoint. This rule applies whether or not the breakpoint already
3074 existed when your program stopped.
3076 @item break @dots{} if @var{cond}
3077 Set a breakpoint with condition @var{cond}; evaluate the expression
3078 @var{cond} each time the breakpoint is reached, and stop only if the
3079 value is nonzero---that is, if @var{cond} evaluates as true.
3080 @samp{@dots{}} stands for one of the possible arguments described
3081 above (or no argument) specifying where to break. @xref{Conditions,
3082 ,Break Conditions}, for more information on breakpoint conditions.
3085 @item tbreak @var{args}
3086 Set a breakpoint enabled only for one stop. @var{args} are the
3087 same as for the @code{break} command, and the breakpoint is set in the same
3088 way, but the breakpoint is automatically deleted after the first time your
3089 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3092 @cindex hardware breakpoints
3093 @item hbreak @var{args}
3094 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3095 @code{break} command and the breakpoint is set in the same way, but the
3096 breakpoint requires hardware support and some target hardware may not
3097 have this support. The main purpose of this is EPROM/ROM code
3098 debugging, so you can set a breakpoint at an instruction without
3099 changing the instruction. This can be used with the new trap-generation
3100 provided by SPARClite DSU and most x86-based targets. These targets
3101 will generate traps when a program accesses some data or instruction
3102 address that is assigned to the debug registers. However the hardware
3103 breakpoint registers can take a limited number of breakpoints. For
3104 example, on the DSU, only two data breakpoints can be set at a time, and
3105 @value{GDBN} will reject this command if more than two are used. Delete
3106 or disable unused hardware breakpoints before setting new ones
3107 (@pxref{Disabling, ,Disabling Breakpoints}).
3108 @xref{Conditions, ,Break Conditions}.
3109 For remote targets, you can restrict the number of hardware
3110 breakpoints @value{GDBN} will use, see @ref{set remote
3111 hardware-breakpoint-limit}.
3114 @item thbreak @var{args}
3115 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3116 are the same as for the @code{hbreak} command and the breakpoint is set in
3117 the same way. However, like the @code{tbreak} command,
3118 the breakpoint is automatically deleted after the
3119 first time your program stops there. Also, like the @code{hbreak}
3120 command, the breakpoint requires hardware support and some target hardware
3121 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3122 See also @ref{Conditions, ,Break Conditions}.
3125 @cindex regular expression
3126 @cindex breakpoints in functions matching a regexp
3127 @cindex set breakpoints in many functions
3128 @item rbreak @var{regex}
3129 Set breakpoints on all functions matching the regular expression
3130 @var{regex}. This command sets an unconditional breakpoint on all
3131 matches, printing a list of all breakpoints it set. Once these
3132 breakpoints are set, they are treated just like the breakpoints set with
3133 the @code{break} command. You can delete them, disable them, or make
3134 them conditional the same way as any other breakpoint.
3136 The syntax of the regular expression is the standard one used with tools
3137 like @file{grep}. Note that this is different from the syntax used by
3138 shells, so for instance @code{foo*} matches all functions that include
3139 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3140 @code{.*} leading and trailing the regular expression you supply, so to
3141 match only functions that begin with @code{foo}, use @code{^foo}.
3143 @cindex non-member C@t{++} functions, set breakpoint in
3144 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3145 breakpoints on overloaded functions that are not members of any special
3148 @cindex set breakpoints on all functions
3149 The @code{rbreak} command can be used to set breakpoints in
3150 @strong{all} the functions in a program, like this:
3153 (@value{GDBP}) rbreak .
3156 @kindex info breakpoints
3157 @cindex @code{$_} and @code{info breakpoints}
3158 @item info breakpoints @r{[}@var{n}@r{]}
3159 @itemx info break @r{[}@var{n}@r{]}
3160 @itemx info watchpoints @r{[}@var{n}@r{]}
3161 Print a table of all breakpoints, watchpoints, and catchpoints set and
3162 not deleted. Optional argument @var{n} means print information only
3163 about the specified breakpoint (or watchpoint or catchpoint). For
3164 each breakpoint, following columns are printed:
3167 @item Breakpoint Numbers
3169 Breakpoint, watchpoint, or catchpoint.
3171 Whether the breakpoint is marked to be disabled or deleted when hit.
3172 @item Enabled or Disabled
3173 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3174 that are not enabled.
3176 Where the breakpoint is in your program, as a memory address. For a
3177 pending breakpoint whose address is not yet known, this field will
3178 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3179 library that has the symbol or line referred by breakpoint is loaded.
3180 See below for details. A breakpoint with several locations will
3181 have @samp{<MULTIPLE>} in this field---see below for details.
3183 Where the breakpoint is in the source for your program, as a file and
3184 line number. For a pending breakpoint, the original string passed to
3185 the breakpoint command will be listed as it cannot be resolved until
3186 the appropriate shared library is loaded in the future.
3190 If a breakpoint is conditional, @code{info break} shows the condition on
3191 the line following the affected breakpoint; breakpoint commands, if any,
3192 are listed after that. A pending breakpoint is allowed to have a condition
3193 specified for it. The condition is not parsed for validity until a shared
3194 library is loaded that allows the pending breakpoint to resolve to a
3198 @code{info break} with a breakpoint
3199 number @var{n} as argument lists only that breakpoint. The
3200 convenience variable @code{$_} and the default examining-address for
3201 the @code{x} command are set to the address of the last breakpoint
3202 listed (@pxref{Memory, ,Examining Memory}).
3205 @code{info break} displays a count of the number of times the breakpoint
3206 has been hit. This is especially useful in conjunction with the
3207 @code{ignore} command. You can ignore a large number of breakpoint
3208 hits, look at the breakpoint info to see how many times the breakpoint
3209 was hit, and then run again, ignoring one less than that number. This
3210 will get you quickly to the last hit of that breakpoint.
3213 @value{GDBN} allows you to set any number of breakpoints at the same place in
3214 your program. There is nothing silly or meaningless about this. When
3215 the breakpoints are conditional, this is even useful
3216 (@pxref{Conditions, ,Break Conditions}).
3218 @cindex multiple locations, breakpoints
3219 @cindex breakpoints, multiple locations
3220 It is possible that a breakpoint corresponds to several locations
3221 in your program. Examples of this situation are:
3225 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3226 instances of the function body, used in different cases.
3229 For a C@t{++} template function, a given line in the function can
3230 correspond to any number of instantiations.
3233 For an inlined function, a given source line can correspond to
3234 several places where that function is inlined.
3237 In all those cases, @value{GDBN} will insert a breakpoint at all
3238 the relevant locations@footnote{
3239 As of this writing, multiple-location breakpoints work only if there's
3240 line number information for all the locations. This means that they
3241 will generally not work in system libraries, unless you have debug
3242 info with line numbers for them.}.
3244 A breakpoint with multiple locations is displayed in the breakpoint
3245 table using several rows---one header row, followed by one row for
3246 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3247 address column. The rows for individual locations contain the actual
3248 addresses for locations, and show the functions to which those
3249 locations belong. The number column for a location is of the form
3250 @var{breakpoint-number}.@var{location-number}.
3255 Num Type Disp Enb Address What
3256 1 breakpoint keep y <MULTIPLE>
3258 breakpoint already hit 1 time
3259 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3260 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3263 Each location can be individually enabled or disabled by passing
3264 @var{breakpoint-number}.@var{location-number} as argument to the
3265 @code{enable} and @code{disable} commands. Note that you cannot
3266 delete the individual locations from the list, you can only delete the
3267 entire list of locations that belong to their parent breakpoint (with
3268 the @kbd{delete @var{num}} command, where @var{num} is the number of
3269 the parent breakpoint, 1 in the above example). Disabling or enabling
3270 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3271 that belong to that breakpoint.
3273 @cindex pending breakpoints
3274 It's quite common to have a breakpoint inside a shared library.
3275 Shared libraries can be loaded and unloaded explicitly,
3276 and possibly repeatedly, as the program is executed. To support
3277 this use case, @value{GDBN} updates breakpoint locations whenever
3278 any shared library is loaded or unloaded. Typically, you would
3279 set a breakpoint in a shared library at the beginning of your
3280 debugging session, when the library is not loaded, and when the
3281 symbols from the library are not available. When you try to set
3282 breakpoint, @value{GDBN} will ask you if you want to set
3283 a so called @dfn{pending breakpoint}---breakpoint whose address
3284 is not yet resolved.
3286 After the program is run, whenever a new shared library is loaded,
3287 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3288 shared library contains the symbol or line referred to by some
3289 pending breakpoint, that breakpoint is resolved and becomes an
3290 ordinary breakpoint. When a library is unloaded, all breakpoints
3291 that refer to its symbols or source lines become pending again.
3293 This logic works for breakpoints with multiple locations, too. For
3294 example, if you have a breakpoint in a C@t{++} template function, and
3295 a newly loaded shared library has an instantiation of that template,
3296 a new location is added to the list of locations for the breakpoint.
3298 Except for having unresolved address, pending breakpoints do not
3299 differ from regular breakpoints. You can set conditions or commands,
3300 enable and disable them and perform other breakpoint operations.
3302 @value{GDBN} provides some additional commands for controlling what
3303 happens when the @samp{break} command cannot resolve breakpoint
3304 address specification to an address:
3306 @kindex set breakpoint pending
3307 @kindex show breakpoint pending
3309 @item set breakpoint pending auto
3310 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3311 location, it queries you whether a pending breakpoint should be created.
3313 @item set breakpoint pending on
3314 This indicates that an unrecognized breakpoint location should automatically
3315 result in a pending breakpoint being created.
3317 @item set breakpoint pending off
3318 This indicates that pending breakpoints are not to be created. Any
3319 unrecognized breakpoint location results in an error. This setting does
3320 not affect any pending breakpoints previously created.
3322 @item show breakpoint pending
3323 Show the current behavior setting for creating pending breakpoints.
3326 The settings above only affect the @code{break} command and its
3327 variants. Once breakpoint is set, it will be automatically updated
3328 as shared libraries are loaded and unloaded.
3330 @cindex automatic hardware breakpoints
3331 For some targets, @value{GDBN} can automatically decide if hardware or
3332 software breakpoints should be used, depending on whether the
3333 breakpoint address is read-only or read-write. This applies to
3334 breakpoints set with the @code{break} command as well as to internal
3335 breakpoints set by commands like @code{next} and @code{finish}. For
3336 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3339 You can control this automatic behaviour with the following commands::
3341 @kindex set breakpoint auto-hw
3342 @kindex show breakpoint auto-hw
3344 @item set breakpoint auto-hw on
3345 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3346 will try to use the target memory map to decide if software or hardware
3347 breakpoint must be used.
3349 @item set breakpoint auto-hw off
3350 This indicates @value{GDBN} should not automatically select breakpoint
3351 type. If the target provides a memory map, @value{GDBN} will warn when
3352 trying to set software breakpoint at a read-only address.
3355 @value{GDBN} normally implements breakpoints by replacing the program code
3356 at the breakpoint address with a special instruction, which, when
3357 executed, given control to the debugger. By default, the program
3358 code is so modified only when the program is resumed. As soon as
3359 the program stops, @value{GDBN} restores the original instructions. This
3360 behaviour guards against leaving breakpoints inserted in the
3361 target should gdb abrubptly disconnect. However, with slow remote
3362 targets, inserting and removing breakpoint can reduce the performance.
3363 This behavior can be controlled with the following commands::
3365 @kindex set breakpoint always-inserted
3366 @kindex show breakpoint always-inserted
3368 @item set breakpoint always-inserted off
3369 All breakpoints, including newly added by the user, are inserted in
3370 the target only when the target is resumed. All breakpoints are
3371 removed from the target when it stops.
3373 @item set breakpoint always-inserted on
3374 Causes all breakpoints to be inserted in the target at all times. If
3375 the user adds a new breakpoint, or changes an existing breakpoint, the
3376 breakpoints in the target are updated immediately. A breakpoint is
3377 removed from the target only when breakpoint itself is removed.
3379 @cindex non-stop mode, and @code{breakpoint always-inserted}
3380 @item set breakpoint always-inserted auto
3381 This is the default mode. If @value{GDBN} is controlling the inferior
3382 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3383 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3384 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3385 @code{breakpoint always-inserted} mode is off.
3388 @cindex negative breakpoint numbers
3389 @cindex internal @value{GDBN} breakpoints
3390 @value{GDBN} itself sometimes sets breakpoints in your program for
3391 special purposes, such as proper handling of @code{longjmp} (in C
3392 programs). These internal breakpoints are assigned negative numbers,
3393 starting with @code{-1}; @samp{info breakpoints} does not display them.
3394 You can see these breakpoints with the @value{GDBN} maintenance command
3395 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3398 @node Set Watchpoints
3399 @subsection Setting Watchpoints
3401 @cindex setting watchpoints
3402 You can use a watchpoint to stop execution whenever the value of an
3403 expression changes, without having to predict a particular place where
3404 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3405 The expression may be as simple as the value of a single variable, or
3406 as complex as many variables combined by operators. Examples include:
3410 A reference to the value of a single variable.
3413 An address cast to an appropriate data type. For example,
3414 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3415 address (assuming an @code{int} occupies 4 bytes).
3418 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3419 expression can use any operators valid in the program's native
3420 language (@pxref{Languages}).
3423 You can set a watchpoint on an expression even if the expression can
3424 not be evaluated yet. For instance, you can set a watchpoint on
3425 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3426 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3427 the expression produces a valid value. If the expression becomes
3428 valid in some other way than changing a variable (e.g.@: if the memory
3429 pointed to by @samp{*global_ptr} becomes readable as the result of a
3430 @code{malloc} call), @value{GDBN} may not stop until the next time
3431 the expression changes.
3433 @cindex software watchpoints
3434 @cindex hardware watchpoints
3435 Depending on your system, watchpoints may be implemented in software or
3436 hardware. @value{GDBN} does software watchpointing by single-stepping your
3437 program and testing the variable's value each time, which is hundreds of
3438 times slower than normal execution. (But this may still be worth it, to
3439 catch errors where you have no clue what part of your program is the
3442 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3443 x86-based targets, @value{GDBN} includes support for hardware
3444 watchpoints, which do not slow down the running of your program.
3448 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3449 Set a watchpoint for an expression. @value{GDBN} will break when the
3450 expression @var{expr} is written into by the program and its value
3451 changes. The simplest (and the most popular) use of this command is
3452 to watch the value of a single variable:
3455 (@value{GDBP}) watch foo
3458 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3459 clause, @value{GDBN} breaks only when the thread identified by
3460 @var{threadnum} changes the value of @var{expr}. If any other threads
3461 change the value of @var{expr}, @value{GDBN} will not break. Note
3462 that watchpoints restricted to a single thread in this way only work
3463 with Hardware Watchpoints.
3466 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3467 Set a watchpoint that will break when the value of @var{expr} is read
3471 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3472 Set a watchpoint that will break when @var{expr} is either read from
3473 or written into by the program.
3475 @kindex info watchpoints @r{[}@var{n}@r{]}
3476 @item info watchpoints
3477 This command prints a list of watchpoints, breakpoints, and catchpoints;
3478 it is the same as @code{info break} (@pxref{Set Breaks}).
3481 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3482 watchpoints execute very quickly, and the debugger reports a change in
3483 value at the exact instruction where the change occurs. If @value{GDBN}
3484 cannot set a hardware watchpoint, it sets a software watchpoint, which
3485 executes more slowly and reports the change in value at the next
3486 @emph{statement}, not the instruction, after the change occurs.
3488 @cindex use only software watchpoints
3489 You can force @value{GDBN} to use only software watchpoints with the
3490 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3491 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3492 the underlying system supports them. (Note that hardware-assisted
3493 watchpoints that were set @emph{before} setting
3494 @code{can-use-hw-watchpoints} to zero will still use the hardware
3495 mechanism of watching expression values.)
3498 @item set can-use-hw-watchpoints
3499 @kindex set can-use-hw-watchpoints
3500 Set whether or not to use hardware watchpoints.
3502 @item show can-use-hw-watchpoints
3503 @kindex show can-use-hw-watchpoints
3504 Show the current mode of using hardware watchpoints.
3507 For remote targets, you can restrict the number of hardware
3508 watchpoints @value{GDBN} will use, see @ref{set remote
3509 hardware-breakpoint-limit}.
3511 When you issue the @code{watch} command, @value{GDBN} reports
3514 Hardware watchpoint @var{num}: @var{expr}
3518 if it was able to set a hardware watchpoint.
3520 Currently, the @code{awatch} and @code{rwatch} commands can only set
3521 hardware watchpoints, because accesses to data that don't change the
3522 value of the watched expression cannot be detected without examining
3523 every instruction as it is being executed, and @value{GDBN} does not do
3524 that currently. If @value{GDBN} finds that it is unable to set a
3525 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3526 will print a message like this:
3529 Expression cannot be implemented with read/access watchpoint.
3532 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3533 data type of the watched expression is wider than what a hardware
3534 watchpoint on the target machine can handle. For example, some systems
3535 can only watch regions that are up to 4 bytes wide; on such systems you
3536 cannot set hardware watchpoints for an expression that yields a
3537 double-precision floating-point number (which is typically 8 bytes
3538 wide). As a work-around, it might be possible to break the large region
3539 into a series of smaller ones and watch them with separate watchpoints.
3541 If you set too many hardware watchpoints, @value{GDBN} might be unable
3542 to insert all of them when you resume the execution of your program.
3543 Since the precise number of active watchpoints is unknown until such
3544 time as the program is about to be resumed, @value{GDBN} might not be
3545 able to warn you about this when you set the watchpoints, and the
3546 warning will be printed only when the program is resumed:
3549 Hardware watchpoint @var{num}: Could not insert watchpoint
3553 If this happens, delete or disable some of the watchpoints.
3555 Watching complex expressions that reference many variables can also
3556 exhaust the resources available for hardware-assisted watchpoints.
3557 That's because @value{GDBN} needs to watch every variable in the
3558 expression with separately allocated resources.
3560 If you call a function interactively using @code{print} or @code{call},
3561 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3562 kind of breakpoint or the call completes.
3564 @value{GDBN} automatically deletes watchpoints that watch local
3565 (automatic) variables, or expressions that involve such variables, when
3566 they go out of scope, that is, when the execution leaves the block in
3567 which these variables were defined. In particular, when the program
3568 being debugged terminates, @emph{all} local variables go out of scope,
3569 and so only watchpoints that watch global variables remain set. If you
3570 rerun the program, you will need to set all such watchpoints again. One
3571 way of doing that would be to set a code breakpoint at the entry to the
3572 @code{main} function and when it breaks, set all the watchpoints.
3574 @cindex watchpoints and threads
3575 @cindex threads and watchpoints
3576 In multi-threaded programs, watchpoints will detect changes to the
3577 watched expression from every thread.
3580 @emph{Warning:} In multi-threaded programs, software watchpoints
3581 have only limited usefulness. If @value{GDBN} creates a software
3582 watchpoint, it can only watch the value of an expression @emph{in a
3583 single thread}. If you are confident that the expression can only
3584 change due to the current thread's activity (and if you are also
3585 confident that no other thread can become current), then you can use
3586 software watchpoints as usual. However, @value{GDBN} may not notice
3587 when a non-current thread's activity changes the expression. (Hardware
3588 watchpoints, in contrast, watch an expression in all threads.)
3591 @xref{set remote hardware-watchpoint-limit}.
3593 @node Set Catchpoints
3594 @subsection Setting Catchpoints
3595 @cindex catchpoints, setting
3596 @cindex exception handlers
3597 @cindex event handling
3599 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3600 kinds of program events, such as C@t{++} exceptions or the loading of a
3601 shared library. Use the @code{catch} command to set a catchpoint.
3605 @item catch @var{event}
3606 Stop when @var{event} occurs. @var{event} can be any of the following:
3609 @cindex stop on C@t{++} exceptions
3610 The throwing of a C@t{++} exception.
3613 The catching of a C@t{++} exception.
3616 @cindex Ada exception catching
3617 @cindex catch Ada exceptions
3618 An Ada exception being raised. If an exception name is specified
3619 at the end of the command (eg @code{catch exception Program_Error}),
3620 the debugger will stop only when this specific exception is raised.
3621 Otherwise, the debugger stops execution when any Ada exception is raised.
3623 When inserting an exception catchpoint on a user-defined exception whose
3624 name is identical to one of the exceptions defined by the language, the
3625 fully qualified name must be used as the exception name. Otherwise,
3626 @value{GDBN} will assume that it should stop on the pre-defined exception
3627 rather than the user-defined one. For instance, assuming an exception
3628 called @code{Constraint_Error} is defined in package @code{Pck}, then
3629 the command to use to catch such exceptions is @kbd{catch exception
3630 Pck.Constraint_Error}.
3632 @item exception unhandled
3633 An exception that was raised but is not handled by the program.
3636 A failed Ada assertion.
3639 @cindex break on fork/exec
3640 A call to @code{exec}. This is currently only available for HP-UX
3644 A call to @code{fork}. This is currently only available for HP-UX
3648 A call to @code{vfork}. This is currently only available for HP-UX
3653 @item tcatch @var{event}
3654 Set a catchpoint that is enabled only for one stop. The catchpoint is
3655 automatically deleted after the first time the event is caught.
3659 Use the @code{info break} command to list the current catchpoints.
3661 There are currently some limitations to C@t{++} exception handling
3662 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3666 If you call a function interactively, @value{GDBN} normally returns
3667 control to you when the function has finished executing. If the call
3668 raises an exception, however, the call may bypass the mechanism that
3669 returns control to you and cause your program either to abort or to
3670 simply continue running until it hits a breakpoint, catches a signal
3671 that @value{GDBN} is listening for, or exits. This is the case even if
3672 you set a catchpoint for the exception; catchpoints on exceptions are
3673 disabled within interactive calls.
3676 You cannot raise an exception interactively.
3679 You cannot install an exception handler interactively.
3682 @cindex raise exceptions
3683 Sometimes @code{catch} is not the best way to debug exception handling:
3684 if you need to know exactly where an exception is raised, it is better to
3685 stop @emph{before} the exception handler is called, since that way you
3686 can see the stack before any unwinding takes place. If you set a
3687 breakpoint in an exception handler instead, it may not be easy to find
3688 out where the exception was raised.
3690 To stop just before an exception handler is called, you need some
3691 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3692 raised by calling a library function named @code{__raise_exception}
3693 which has the following ANSI C interface:
3696 /* @var{addr} is where the exception identifier is stored.
3697 @var{id} is the exception identifier. */
3698 void __raise_exception (void **addr, void *id);
3702 To make the debugger catch all exceptions before any stack
3703 unwinding takes place, set a breakpoint on @code{__raise_exception}
3704 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3706 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3707 that depends on the value of @var{id}, you can stop your program when
3708 a specific exception is raised. You can use multiple conditional
3709 breakpoints to stop your program when any of a number of exceptions are
3714 @subsection Deleting Breakpoints
3716 @cindex clearing breakpoints, watchpoints, catchpoints
3717 @cindex deleting breakpoints, watchpoints, catchpoints
3718 It is often necessary to eliminate a breakpoint, watchpoint, or
3719 catchpoint once it has done its job and you no longer want your program
3720 to stop there. This is called @dfn{deleting} the breakpoint. A
3721 breakpoint that has been deleted no longer exists; it is forgotten.
3723 With the @code{clear} command you can delete breakpoints according to
3724 where they are in your program. With the @code{delete} command you can
3725 delete individual breakpoints, watchpoints, or catchpoints by specifying
3726 their breakpoint numbers.
3728 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3729 automatically ignores breakpoints on the first instruction to be executed
3730 when you continue execution without changing the execution address.
3735 Delete any breakpoints at the next instruction to be executed in the
3736 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3737 the innermost frame is selected, this is a good way to delete a
3738 breakpoint where your program just stopped.
3740 @item clear @var{location}
3741 Delete any breakpoints set at the specified @var{location}.
3742 @xref{Specify Location}, for the various forms of @var{location}; the
3743 most useful ones are listed below:
3746 @item clear @var{function}
3747 @itemx clear @var{filename}:@var{function}
3748 Delete any breakpoints set at entry to the named @var{function}.
3750 @item clear @var{linenum}
3751 @itemx clear @var{filename}:@var{linenum}
3752 Delete any breakpoints set at or within the code of the specified
3753 @var{linenum} of the specified @var{filename}.
3756 @cindex delete breakpoints
3758 @kindex d @r{(@code{delete})}
3759 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3760 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3761 ranges specified as arguments. If no argument is specified, delete all
3762 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3763 confirm off}). You can abbreviate this command as @code{d}.
3767 @subsection Disabling Breakpoints
3769 @cindex enable/disable a breakpoint
3770 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3771 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3772 it had been deleted, but remembers the information on the breakpoint so
3773 that you can @dfn{enable} it again later.
3775 You disable and enable breakpoints, watchpoints, and catchpoints with
3776 the @code{enable} and @code{disable} commands, optionally specifying one
3777 or more breakpoint numbers as arguments. Use @code{info break} or
3778 @code{info watch} to print a list of breakpoints, watchpoints, and
3779 catchpoints if you do not know which numbers to use.
3781 Disabling and enabling a breakpoint that has multiple locations
3782 affects all of its locations.
3784 A breakpoint, watchpoint, or catchpoint can have any of four different
3785 states of enablement:
3789 Enabled. The breakpoint stops your program. A breakpoint set
3790 with the @code{break} command starts out in this state.
3792 Disabled. The breakpoint has no effect on your program.
3794 Enabled once. The breakpoint stops your program, but then becomes
3797 Enabled for deletion. The breakpoint stops your program, but
3798 immediately after it does so it is deleted permanently. A breakpoint
3799 set with the @code{tbreak} command starts out in this state.
3802 You can use the following commands to enable or disable breakpoints,
3803 watchpoints, and catchpoints:
3807 @kindex dis @r{(@code{disable})}
3808 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3809 Disable the specified breakpoints---or all breakpoints, if none are
3810 listed. A disabled breakpoint has no effect but is not forgotten. All
3811 options such as ignore-counts, conditions and commands are remembered in
3812 case the breakpoint is enabled again later. You may abbreviate
3813 @code{disable} as @code{dis}.
3816 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3817 Enable the specified breakpoints (or all defined breakpoints). They
3818 become effective once again in stopping your program.
3820 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3821 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3822 of these breakpoints immediately after stopping your program.
3824 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3825 Enable the specified breakpoints to work once, then die. @value{GDBN}
3826 deletes any of these breakpoints as soon as your program stops there.
3827 Breakpoints set by the @code{tbreak} command start out in this state.
3830 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3831 @c confusing: tbreak is also initially enabled.
3832 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3833 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3834 subsequently, they become disabled or enabled only when you use one of
3835 the commands above. (The command @code{until} can set and delete a
3836 breakpoint of its own, but it does not change the state of your other
3837 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3841 @subsection Break Conditions
3842 @cindex conditional breakpoints
3843 @cindex breakpoint conditions
3845 @c FIXME what is scope of break condition expr? Context where wanted?
3846 @c in particular for a watchpoint?
3847 The simplest sort of breakpoint breaks every time your program reaches a
3848 specified place. You can also specify a @dfn{condition} for a
3849 breakpoint. A condition is just a Boolean expression in your
3850 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3851 a condition evaluates the expression each time your program reaches it,
3852 and your program stops only if the condition is @emph{true}.
3854 This is the converse of using assertions for program validation; in that
3855 situation, you want to stop when the assertion is violated---that is,
3856 when the condition is false. In C, if you want to test an assertion expressed
3857 by the condition @var{assert}, you should set the condition
3858 @samp{! @var{assert}} on the appropriate breakpoint.
3860 Conditions are also accepted for watchpoints; you may not need them,
3861 since a watchpoint is inspecting the value of an expression anyhow---but
3862 it might be simpler, say, to just set a watchpoint on a variable name,
3863 and specify a condition that tests whether the new value is an interesting
3866 Break conditions can have side effects, and may even call functions in
3867 your program. This can be useful, for example, to activate functions
3868 that log program progress, or to use your own print functions to
3869 format special data structures. The effects are completely predictable
3870 unless there is another enabled breakpoint at the same address. (In
3871 that case, @value{GDBN} might see the other breakpoint first and stop your
3872 program without checking the condition of this one.) Note that
3873 breakpoint commands are usually more convenient and flexible than break
3875 purpose of performing side effects when a breakpoint is reached
3876 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3878 Break conditions can be specified when a breakpoint is set, by using
3879 @samp{if} in the arguments to the @code{break} command. @xref{Set
3880 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3881 with the @code{condition} command.
3883 You can also use the @code{if} keyword with the @code{watch} command.
3884 The @code{catch} command does not recognize the @code{if} keyword;
3885 @code{condition} is the only way to impose a further condition on a
3890 @item condition @var{bnum} @var{expression}
3891 Specify @var{expression} as the break condition for breakpoint,
3892 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3893 breakpoint @var{bnum} stops your program only if the value of
3894 @var{expression} is true (nonzero, in C). When you use
3895 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3896 syntactic correctness, and to determine whether symbols in it have
3897 referents in the context of your breakpoint. If @var{expression} uses
3898 symbols not referenced in the context of the breakpoint, @value{GDBN}
3899 prints an error message:
3902 No symbol "foo" in current context.
3907 not actually evaluate @var{expression} at the time the @code{condition}
3908 command (or a command that sets a breakpoint with a condition, like
3909 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3911 @item condition @var{bnum}
3912 Remove the condition from breakpoint number @var{bnum}. It becomes
3913 an ordinary unconditional breakpoint.
3916 @cindex ignore count (of breakpoint)
3917 A special case of a breakpoint condition is to stop only when the
3918 breakpoint has been reached a certain number of times. This is so
3919 useful that there is a special way to do it, using the @dfn{ignore
3920 count} of the breakpoint. Every breakpoint has an ignore count, which
3921 is an integer. Most of the time, the ignore count is zero, and
3922 therefore has no effect. But if your program reaches a breakpoint whose
3923 ignore count is positive, then instead of stopping, it just decrements
3924 the ignore count by one and continues. As a result, if the ignore count
3925 value is @var{n}, the breakpoint does not stop the next @var{n} times
3926 your program reaches it.
3930 @item ignore @var{bnum} @var{count}
3931 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3932 The next @var{count} times the breakpoint is reached, your program's
3933 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3936 To make the breakpoint stop the next time it is reached, specify
3939 When you use @code{continue} to resume execution of your program from a
3940 breakpoint, you can specify an ignore count directly as an argument to
3941 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3942 Stepping,,Continuing and Stepping}.
3944 If a breakpoint has a positive ignore count and a condition, the
3945 condition is not checked. Once the ignore count reaches zero,
3946 @value{GDBN} resumes checking the condition.
3948 You could achieve the effect of the ignore count with a condition such
3949 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3950 is decremented each time. @xref{Convenience Vars, ,Convenience
3954 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3957 @node Break Commands
3958 @subsection Breakpoint Command Lists
3960 @cindex breakpoint commands
3961 You can give any breakpoint (or watchpoint or catchpoint) a series of
3962 commands to execute when your program stops due to that breakpoint. For
3963 example, you might want to print the values of certain expressions, or
3964 enable other breakpoints.
3968 @kindex end@r{ (breakpoint commands)}
3969 @item commands @r{[}@var{bnum}@r{]}
3970 @itemx @dots{} @var{command-list} @dots{}
3972 Specify a list of commands for breakpoint number @var{bnum}. The commands
3973 themselves appear on the following lines. Type a line containing just
3974 @code{end} to terminate the commands.
3976 To remove all commands from a breakpoint, type @code{commands} and
3977 follow it immediately with @code{end}; that is, give no commands.
3979 With no @var{bnum} argument, @code{commands} refers to the last
3980 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3981 recently encountered).
3984 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3985 disabled within a @var{command-list}.
3987 You can use breakpoint commands to start your program up again. Simply
3988 use the @code{continue} command, or @code{step}, or any other command
3989 that resumes execution.
3991 Any other commands in the command list, after a command that resumes
3992 execution, are ignored. This is because any time you resume execution
3993 (even with a simple @code{next} or @code{step}), you may encounter
3994 another breakpoint---which could have its own command list, leading to
3995 ambiguities about which list to execute.
3998 If the first command you specify in a command list is @code{silent}, the
3999 usual message about stopping at a breakpoint is not printed. This may
4000 be desirable for breakpoints that are to print a specific message and
4001 then continue. If none of the remaining commands print anything, you
4002 see no sign that the breakpoint was reached. @code{silent} is
4003 meaningful only at the beginning of a breakpoint command list.
4005 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4006 print precisely controlled output, and are often useful in silent
4007 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4009 For example, here is how you could use breakpoint commands to print the
4010 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4016 printf "x is %d\n",x
4021 One application for breakpoint commands is to compensate for one bug so
4022 you can test for another. Put a breakpoint just after the erroneous line
4023 of code, give it a condition to detect the case in which something
4024 erroneous has been done, and give it commands to assign correct values
4025 to any variables that need them. End with the @code{continue} command
4026 so that your program does not stop, and start with the @code{silent}
4027 command so that no output is produced. Here is an example:
4038 @c @ifclear BARETARGET
4039 @node Error in Breakpoints
4040 @subsection ``Cannot insert breakpoints''
4042 If you request too many active hardware-assisted breakpoints and
4043 watchpoints, you will see this error message:
4045 @c FIXME: the precise wording of this message may change; the relevant
4046 @c source change is not committed yet (Sep 3, 1999).
4048 Stopped; cannot insert breakpoints.
4049 You may have requested too many hardware breakpoints and watchpoints.
4053 This message is printed when you attempt to resume the program, since
4054 only then @value{GDBN} knows exactly how many hardware breakpoints and
4055 watchpoints it needs to insert.
4057 When this message is printed, you need to disable or remove some of the
4058 hardware-assisted breakpoints and watchpoints, and then continue.
4060 @node Breakpoint-related Warnings
4061 @subsection ``Breakpoint address adjusted...''
4062 @cindex breakpoint address adjusted
4064 Some processor architectures place constraints on the addresses at
4065 which breakpoints may be placed. For architectures thus constrained,
4066 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4067 with the constraints dictated by the architecture.
4069 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4070 a VLIW architecture in which a number of RISC-like instructions may be
4071 bundled together for parallel execution. The FR-V architecture
4072 constrains the location of a breakpoint instruction within such a
4073 bundle to the instruction with the lowest address. @value{GDBN}
4074 honors this constraint by adjusting a breakpoint's address to the
4075 first in the bundle.
4077 It is not uncommon for optimized code to have bundles which contain
4078 instructions from different source statements, thus it may happen that
4079 a breakpoint's address will be adjusted from one source statement to
4080 another. Since this adjustment may significantly alter @value{GDBN}'s
4081 breakpoint related behavior from what the user expects, a warning is
4082 printed when the breakpoint is first set and also when the breakpoint
4085 A warning like the one below is printed when setting a breakpoint
4086 that's been subject to address adjustment:
4089 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4092 Such warnings are printed both for user settable and @value{GDBN}'s
4093 internal breakpoints. If you see one of these warnings, you should
4094 verify that a breakpoint set at the adjusted address will have the
4095 desired affect. If not, the breakpoint in question may be removed and
4096 other breakpoints may be set which will have the desired behavior.
4097 E.g., it may be sufficient to place the breakpoint at a later
4098 instruction. A conditional breakpoint may also be useful in some
4099 cases to prevent the breakpoint from triggering too often.
4101 @value{GDBN} will also issue a warning when stopping at one of these
4102 adjusted breakpoints:
4105 warning: Breakpoint 1 address previously adjusted from 0x00010414
4109 When this warning is encountered, it may be too late to take remedial
4110 action except in cases where the breakpoint is hit earlier or more
4111 frequently than expected.
4113 @node Continuing and Stepping
4114 @section Continuing and Stepping
4118 @cindex resuming execution
4119 @dfn{Continuing} means resuming program execution until your program
4120 completes normally. In contrast, @dfn{stepping} means executing just
4121 one more ``step'' of your program, where ``step'' may mean either one
4122 line of source code, or one machine instruction (depending on what
4123 particular command you use). Either when continuing or when stepping,
4124 your program may stop even sooner, due to a breakpoint or a signal. (If
4125 it stops due to a signal, you may want to use @code{handle}, or use
4126 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4130 @kindex c @r{(@code{continue})}
4131 @kindex fg @r{(resume foreground execution)}
4132 @item continue @r{[}@var{ignore-count}@r{]}
4133 @itemx c @r{[}@var{ignore-count}@r{]}
4134 @itemx fg @r{[}@var{ignore-count}@r{]}
4135 Resume program execution, at the address where your program last stopped;
4136 any breakpoints set at that address are bypassed. The optional argument
4137 @var{ignore-count} allows you to specify a further number of times to
4138 ignore a breakpoint at this location; its effect is like that of
4139 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4141 The argument @var{ignore-count} is meaningful only when your program
4142 stopped due to a breakpoint. At other times, the argument to
4143 @code{continue} is ignored.
4145 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4146 debugged program is deemed to be the foreground program) are provided
4147 purely for convenience, and have exactly the same behavior as
4151 To resume execution at a different place, you can use @code{return}
4152 (@pxref{Returning, ,Returning from a Function}) to go back to the
4153 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4154 Different Address}) to go to an arbitrary location in your program.
4156 A typical technique for using stepping is to set a breakpoint
4157 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4158 beginning of the function or the section of your program where a problem
4159 is believed to lie, run your program until it stops at that breakpoint,
4160 and then step through the suspect area, examining the variables that are
4161 interesting, until you see the problem happen.
4165 @kindex s @r{(@code{step})}
4167 Continue running your program until control reaches a different source
4168 line, then stop it and return control to @value{GDBN}. This command is
4169 abbreviated @code{s}.
4172 @c "without debugging information" is imprecise; actually "without line
4173 @c numbers in the debugging information". (gcc -g1 has debugging info but
4174 @c not line numbers). But it seems complex to try to make that
4175 @c distinction here.
4176 @emph{Warning:} If you use the @code{step} command while control is
4177 within a function that was compiled without debugging information,
4178 execution proceeds until control reaches a function that does have
4179 debugging information. Likewise, it will not step into a function which
4180 is compiled without debugging information. To step through functions
4181 without debugging information, use the @code{stepi} command, described
4185 The @code{step} command only stops at the first instruction of a source
4186 line. This prevents the multiple stops that could otherwise occur in
4187 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4188 to stop if a function that has debugging information is called within
4189 the line. In other words, @code{step} @emph{steps inside} any functions
4190 called within the line.
4192 Also, the @code{step} command only enters a function if there is line
4193 number information for the function. Otherwise it acts like the
4194 @code{next} command. This avoids problems when using @code{cc -gl}
4195 on MIPS machines. Previously, @code{step} entered subroutines if there
4196 was any debugging information about the routine.
4198 @item step @var{count}
4199 Continue running as in @code{step}, but do so @var{count} times. If a
4200 breakpoint is reached, or a signal not related to stepping occurs before
4201 @var{count} steps, stepping stops right away.
4204 @kindex n @r{(@code{next})}
4205 @item next @r{[}@var{count}@r{]}
4206 Continue to the next source line in the current (innermost) stack frame.
4207 This is similar to @code{step}, but function calls that appear within
4208 the line of code are executed without stopping. Execution stops when
4209 control reaches a different line of code at the original stack level
4210 that was executing when you gave the @code{next} command. This command
4211 is abbreviated @code{n}.
4213 An argument @var{count} is a repeat count, as for @code{step}.
4216 @c FIX ME!! Do we delete this, or is there a way it fits in with
4217 @c the following paragraph? --- Vctoria
4219 @c @code{next} within a function that lacks debugging information acts like
4220 @c @code{step}, but any function calls appearing within the code of the
4221 @c function are executed without stopping.
4223 The @code{next} command only stops at the first instruction of a
4224 source line. This prevents multiple stops that could otherwise occur in
4225 @code{switch} statements, @code{for} loops, etc.
4227 @kindex set step-mode
4229 @cindex functions without line info, and stepping
4230 @cindex stepping into functions with no line info
4231 @itemx set step-mode on
4232 The @code{set step-mode on} command causes the @code{step} command to
4233 stop at the first instruction of a function which contains no debug line
4234 information rather than stepping over it.
4236 This is useful in cases where you may be interested in inspecting the
4237 machine instructions of a function which has no symbolic info and do not
4238 want @value{GDBN} to automatically skip over this function.
4240 @item set step-mode off
4241 Causes the @code{step} command to step over any functions which contains no
4242 debug information. This is the default.
4244 @item show step-mode
4245 Show whether @value{GDBN} will stop in or step over functions without
4246 source line debug information.
4249 @kindex fin @r{(@code{finish})}
4251 Continue running until just after function in the selected stack frame
4252 returns. Print the returned value (if any). This command can be
4253 abbreviated as @code{fin}.
4255 Contrast this with the @code{return} command (@pxref{Returning,
4256 ,Returning from a Function}).
4259 @kindex u @r{(@code{until})}
4260 @cindex run until specified location
4263 Continue running until a source line past the current line, in the
4264 current stack frame, is reached. This command is used to avoid single
4265 stepping through a loop more than once. It is like the @code{next}
4266 command, except that when @code{until} encounters a jump, it
4267 automatically continues execution until the program counter is greater
4268 than the address of the jump.
4270 This means that when you reach the end of a loop after single stepping
4271 though it, @code{until} makes your program continue execution until it
4272 exits the loop. In contrast, a @code{next} command at the end of a loop
4273 simply steps back to the beginning of the loop, which forces you to step
4274 through the next iteration.
4276 @code{until} always stops your program if it attempts to exit the current
4279 @code{until} may produce somewhat counterintuitive results if the order
4280 of machine code does not match the order of the source lines. For
4281 example, in the following excerpt from a debugging session, the @code{f}
4282 (@code{frame}) command shows that execution is stopped at line
4283 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4287 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4289 (@value{GDBP}) until
4290 195 for ( ; argc > 0; NEXTARG) @{
4293 This happened because, for execution efficiency, the compiler had
4294 generated code for the loop closure test at the end, rather than the
4295 start, of the loop---even though the test in a C @code{for}-loop is
4296 written before the body of the loop. The @code{until} command appeared
4297 to step back to the beginning of the loop when it advanced to this
4298 expression; however, it has not really gone to an earlier
4299 statement---not in terms of the actual machine code.
4301 @code{until} with no argument works by means of single
4302 instruction stepping, and hence is slower than @code{until} with an
4305 @item until @var{location}
4306 @itemx u @var{location}
4307 Continue running your program until either the specified location is
4308 reached, or the current stack frame returns. @var{location} is any of
4309 the forms described in @ref{Specify Location}.
4310 This form of the command uses temporary breakpoints, and
4311 hence is quicker than @code{until} without an argument. The specified
4312 location is actually reached only if it is in the current frame. This
4313 implies that @code{until} can be used to skip over recursive function
4314 invocations. For instance in the code below, if the current location is
4315 line @code{96}, issuing @code{until 99} will execute the program up to
4316 line @code{99} in the same invocation of factorial, i.e., after the inner
4317 invocations have returned.
4320 94 int factorial (int value)
4322 96 if (value > 1) @{
4323 97 value *= factorial (value - 1);
4330 @kindex advance @var{location}
4331 @itemx advance @var{location}
4332 Continue running the program up to the given @var{location}. An argument is
4333 required, which should be of one of the forms described in
4334 @ref{Specify Location}.
4335 Execution will also stop upon exit from the current stack
4336 frame. This command is similar to @code{until}, but @code{advance} will
4337 not skip over recursive function calls, and the target location doesn't
4338 have to be in the same frame as the current one.
4342 @kindex si @r{(@code{stepi})}
4344 @itemx stepi @var{arg}
4346 Execute one machine instruction, then stop and return to the debugger.
4348 It is often useful to do @samp{display/i $pc} when stepping by machine
4349 instructions. This makes @value{GDBN} automatically display the next
4350 instruction to be executed, each time your program stops. @xref{Auto
4351 Display,, Automatic Display}.
4353 An argument is a repeat count, as in @code{step}.
4357 @kindex ni @r{(@code{nexti})}
4359 @itemx nexti @var{arg}
4361 Execute one machine instruction, but if it is a function call,
4362 proceed until the function returns.
4364 An argument is a repeat count, as in @code{next}.
4371 A signal is an asynchronous event that can happen in a program. The
4372 operating system defines the possible kinds of signals, and gives each
4373 kind a name and a number. For example, in Unix @code{SIGINT} is the
4374 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4375 @code{SIGSEGV} is the signal a program gets from referencing a place in
4376 memory far away from all the areas in use; @code{SIGALRM} occurs when
4377 the alarm clock timer goes off (which happens only if your program has
4378 requested an alarm).
4380 @cindex fatal signals
4381 Some signals, including @code{SIGALRM}, are a normal part of the
4382 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4383 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4384 program has not specified in advance some other way to handle the signal.
4385 @code{SIGINT} does not indicate an error in your program, but it is normally
4386 fatal so it can carry out the purpose of the interrupt: to kill the program.
4388 @value{GDBN} has the ability to detect any occurrence of a signal in your
4389 program. You can tell @value{GDBN} in advance what to do for each kind of
4392 @cindex handling signals
4393 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4394 @code{SIGALRM} be silently passed to your program
4395 (so as not to interfere with their role in the program's functioning)
4396 but to stop your program immediately whenever an error signal happens.
4397 You can change these settings with the @code{handle} command.
4400 @kindex info signals
4404 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4405 handle each one. You can use this to see the signal numbers of all
4406 the defined types of signals.
4408 @item info signals @var{sig}
4409 Similar, but print information only about the specified signal number.
4411 @code{info handle} is an alias for @code{info signals}.
4414 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4415 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4416 can be the number of a signal or its name (with or without the
4417 @samp{SIG} at the beginning); a list of signal numbers of the form
4418 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4419 known signals. Optional arguments @var{keywords}, described below,
4420 say what change to make.
4424 The keywords allowed by the @code{handle} command can be abbreviated.
4425 Their full names are:
4429 @value{GDBN} should not stop your program when this signal happens. It may
4430 still print a message telling you that the signal has come in.
4433 @value{GDBN} should stop your program when this signal happens. This implies
4434 the @code{print} keyword as well.
4437 @value{GDBN} should print a message when this signal happens.
4440 @value{GDBN} should not mention the occurrence of the signal at all. This
4441 implies the @code{nostop} keyword as well.
4445 @value{GDBN} should allow your program to see this signal; your program
4446 can handle the signal, or else it may terminate if the signal is fatal
4447 and not handled. @code{pass} and @code{noignore} are synonyms.
4451 @value{GDBN} should not allow your program to see this signal.
4452 @code{nopass} and @code{ignore} are synonyms.
4456 When a signal stops your program, the signal is not visible to the
4458 continue. Your program sees the signal then, if @code{pass} is in
4459 effect for the signal in question @emph{at that time}. In other words,
4460 after @value{GDBN} reports a signal, you can use the @code{handle}
4461 command with @code{pass} or @code{nopass} to control whether your
4462 program sees that signal when you continue.
4464 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4465 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4466 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4469 You can also use the @code{signal} command to prevent your program from
4470 seeing a signal, or cause it to see a signal it normally would not see,
4471 or to give it any signal at any time. For example, if your program stopped
4472 due to some sort of memory reference error, you might store correct
4473 values into the erroneous variables and continue, hoping to see more
4474 execution; but your program would probably terminate immediately as
4475 a result of the fatal signal once it saw the signal. To prevent this,
4476 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4479 @cindex extra signal information
4480 @anchor{extra signal information}
4482 On some targets, @value{GDBN} can inspect extra signal information
4483 associated with the intercepted signal, before it is actually
4484 delivered to the program being debugged. This information is exported
4485 by the convenience variable @code{$_siginfo}, and consists of data
4486 that is passed by the kernel to the signal handler at the time of the
4487 receipt of a signal. The data type of the information itself is
4488 target dependent. You can see the data type using the @code{ptype
4489 $_siginfo} command. On Unix systems, it typically corresponds to the
4490 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4493 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4494 referenced address that raised a segmentation fault.
4498 (@value{GDBP}) continue
4499 Program received signal SIGSEGV, Segmentation fault.
4500 0x0000000000400766 in main ()
4502 (@value{GDBP}) ptype $_siginfo
4509 struct @{...@} _kill;
4510 struct @{...@} _timer;
4512 struct @{...@} _sigchld;
4513 struct @{...@} _sigfault;
4514 struct @{...@} _sigpoll;
4517 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4521 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4522 $1 = (void *) 0x7ffff7ff7000
4526 Depending on target support, @code{$_siginfo} may also be writable.
4529 @section Stopping and Starting Multi-thread Programs
4531 @cindex stopped threads
4532 @cindex threads, stopped
4534 @cindex continuing threads
4535 @cindex threads, continuing
4537 @value{GDBN} supports debugging programs with multiple threads
4538 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4539 are two modes of controlling execution of your program within the
4540 debugger. In the default mode, referred to as @dfn{all-stop mode},
4541 when any thread in your program stops (for example, at a breakpoint
4542 or while being stepped), all other threads in the program are also stopped by
4543 @value{GDBN}. On some targets, @value{GDBN} also supports
4544 @dfn{non-stop mode}, in which other threads can continue to run freely while
4545 you examine the stopped thread in the debugger.
4548 * All-Stop Mode:: All threads stop when GDB takes control
4549 * Non-Stop Mode:: Other threads continue to execute
4550 * Background Execution:: Running your program asynchronously
4551 * Thread-Specific Breakpoints:: Controlling breakpoints
4552 * Interrupted System Calls:: GDB may interfere with system calls
4556 @subsection All-Stop Mode
4558 @cindex all-stop mode
4560 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4561 @emph{all} threads of execution stop, not just the current thread. This
4562 allows you to examine the overall state of the program, including
4563 switching between threads, without worrying that things may change
4566 Conversely, whenever you restart the program, @emph{all} threads start
4567 executing. @emph{This is true even when single-stepping} with commands
4568 like @code{step} or @code{next}.
4570 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4571 Since thread scheduling is up to your debugging target's operating
4572 system (not controlled by @value{GDBN}), other threads may
4573 execute more than one statement while the current thread completes a
4574 single step. Moreover, in general other threads stop in the middle of a
4575 statement, rather than at a clean statement boundary, when the program
4578 You might even find your program stopped in another thread after
4579 continuing or even single-stepping. This happens whenever some other
4580 thread runs into a breakpoint, a signal, or an exception before the
4581 first thread completes whatever you requested.
4583 @cindex automatic thread selection
4584 @cindex switching threads automatically
4585 @cindex threads, automatic switching
4586 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4587 signal, it automatically selects the thread where that breakpoint or
4588 signal happened. @value{GDBN} alerts you to the context switch with a
4589 message such as @samp{[Switching to Thread @var{n}]} to identify the
4592 On some OSes, you can modify @value{GDBN}'s default behavior by
4593 locking the OS scheduler to allow only a single thread to run.
4596 @item set scheduler-locking @var{mode}
4597 @cindex scheduler locking mode
4598 @cindex lock scheduler
4599 Set the scheduler locking mode. If it is @code{off}, then there is no
4600 locking and any thread may run at any time. If @code{on}, then only the
4601 current thread may run when the inferior is resumed. The @code{step}
4602 mode optimizes for single-stepping; it prevents other threads
4603 from preempting the current thread while you are stepping, so that
4604 the focus of debugging does not change unexpectedly.
4605 Other threads only rarely (or never) get a chance to run
4606 when you step. They are more likely to run when you @samp{next} over a
4607 function call, and they are completely free to run when you use commands
4608 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4609 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4610 the current thread away from the thread that you are debugging.
4612 @item show scheduler-locking
4613 Display the current scheduler locking mode.
4617 @subsection Non-Stop Mode
4619 @cindex non-stop mode
4621 @c This section is really only a place-holder, and needs to be expanded
4622 @c with more details.
4624 For some multi-threaded targets, @value{GDBN} supports an optional
4625 mode of operation in which you can examine stopped program threads in
4626 the debugger while other threads continue to execute freely. This
4627 minimizes intrusion when debugging live systems, such as programs
4628 where some threads have real-time constraints or must continue to
4629 respond to external events. This is referred to as @dfn{non-stop} mode.
4631 In non-stop mode, when a thread stops to report a debugging event,
4632 @emph{only} that thread is stopped; @value{GDBN} does not stop other
4633 threads as well, in contrast to the all-stop mode behavior. Additionally,
4634 execution commands such as @code{continue} and @code{step} apply by default
4635 only to the current thread in non-stop mode, rather than all threads as
4636 in all-stop mode. This allows you to control threads explicitly in
4637 ways that are not possible in all-stop mode --- for example, stepping
4638 one thread while allowing others to run freely, stepping
4639 one thread while holding all others stopped, or stepping several threads
4640 independently and simultaneously.
4642 To enter non-stop mode, use this sequence of commands before you run
4643 or attach to your program:
4646 # Enable the async interface.
4649 # If using the CLI, pagination breaks non-stop.
4652 # Finally, turn it on!
4656 You can use these commands to manipulate the non-stop mode setting:
4659 @kindex set non-stop
4660 @item set non-stop on
4661 Enable selection of non-stop mode.
4662 @item set non-stop off
4663 Disable selection of non-stop mode.
4664 @kindex show non-stop
4666 Show the current non-stop enablement setting.
4669 Note these commands only reflect whether non-stop mode is enabled,
4670 not whether the currently-executing program is being run in non-stop mode.
4671 In particular, the @code{set non-stop} preference is only consulted when
4672 @value{GDBN} starts or connects to the target program, and it is generally
4673 not possible to switch modes once debugging has started. Furthermore,
4674 since not all targets support non-stop mode, even when you have enabled
4675 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
4678 In non-stop mode, all execution commands apply only to the current thread
4679 by default. That is, @code{continue} only continues one thread.
4680 To continue all threads, issue @code{continue -a} or @code{c -a}.
4682 You can use @value{GDBN}'s background execution commands
4683 (@pxref{Background Execution}) to run some threads in the background
4684 while you continue to examine or step others from @value{GDBN}.
4685 The MI execution commands (@pxref{GDB/MI Program Execution}) are
4686 always executed asynchronously in non-stop mode.
4688 Suspending execution is done with the @code{interrupt} command when
4689 running in the background, or @kbd{Ctrl-c} during foreground execution.
4690 In all-stop mode, this stops the whole process;
4691 but in non-stop mode the interrupt applies only to the current thread.
4692 To stop the whole program, use @code{interrupt -a}.
4694 Other execution commands do not currently support the @code{-a} option.
4696 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
4697 that thread current, as it does in all-stop mode. This is because the
4698 thread stop notifications are asynchronous with respect to @value{GDBN}'s
4699 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
4700 changed to a different thread just as you entered a command to operate on the
4701 previously current thread.
4703 @node Background Execution
4704 @subsection Background Execution
4706 @cindex foreground execution
4707 @cindex background execution
4708 @cindex asynchronous execution
4709 @cindex execution, foreground, background and asynchronous
4711 @value{GDBN}'s execution commands have two variants: the normal
4712 foreground (synchronous) behavior, and a background
4713 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
4714 the program to report that some thread has stopped before prompting for
4715 another command. In background execution, @value{GDBN} immediately gives
4716 a command prompt so that you can issue other commands while your program runs.
4718 You need to explicitly enable asynchronous mode before you can use
4719 background execution commands. You can use these commands to
4720 manipulate the asynchronous mode setting:
4723 @kindex set target-async
4724 @item set target-async on
4725 Enable asynchronous mode.
4726 @item set target-async off
4727 Disable asynchronous mode.
4728 @kindex show target-async
4729 @item show target-async
4730 Show the current target-async setting.
4733 If the target doesn't support async mode, @value{GDBN} issues an error
4734 message if you attempt to use the background execution commands.
4736 To specify background execution, add a @code{&} to the command. For example,
4737 the background form of the @code{continue} command is @code{continue&}, or
4738 just @code{c&}. The execution commands that accept background execution
4744 @xref{Starting, , Starting your Program}.
4748 @xref{Attach, , Debugging an Already-running Process}.
4752 @xref{Continuing and Stepping, step}.
4756 @xref{Continuing and Stepping, stepi}.
4760 @xref{Continuing and Stepping, next}.
4764 @xref{Continuing and Stepping, nexti}.
4768 @xref{Continuing and Stepping, continue}.
4772 @xref{Continuing and Stepping, finish}.
4776 @xref{Continuing and Stepping, until}.
4780 Background execution is especially useful in conjunction with non-stop
4781 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
4782 However, you can also use these commands in the normal all-stop mode with
4783 the restriction that you cannot issue another execution command until the
4784 previous one finishes. Examples of commands that are valid in all-stop
4785 mode while the program is running include @code{help} and @code{info break}.
4787 You can interrupt your program while it is running in the background by
4788 using the @code{interrupt} command.
4795 Suspend execution of the running program. In all-stop mode,
4796 @code{interrupt} stops the whole process, but in non-stop mode, it stops
4797 only the current thread. To stop the whole program in non-stop mode,
4798 use @code{interrupt -a}.
4801 @node Thread-Specific Breakpoints
4802 @subsection Thread-Specific Breakpoints
4804 When your program has multiple threads (@pxref{Threads,, Debugging
4805 Programs with Multiple Threads}), you can choose whether to set
4806 breakpoints on all threads, or on a particular thread.
4809 @cindex breakpoints and threads
4810 @cindex thread breakpoints
4811 @kindex break @dots{} thread @var{threadno}
4812 @item break @var{linespec} thread @var{threadno}
4813 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4814 @var{linespec} specifies source lines; there are several ways of
4815 writing them (@pxref{Specify Location}), but the effect is always to
4816 specify some source line.
4818 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4819 to specify that you only want @value{GDBN} to stop the program when a
4820 particular thread reaches this breakpoint. @var{threadno} is one of the
4821 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4822 column of the @samp{info threads} display.
4824 If you do not specify @samp{thread @var{threadno}} when you set a
4825 breakpoint, the breakpoint applies to @emph{all} threads of your
4828 You can use the @code{thread} qualifier on conditional breakpoints as
4829 well; in this case, place @samp{thread @var{threadno}} before the
4830 breakpoint condition, like this:
4833 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4838 @node Interrupted System Calls
4839 @subsection Interrupted System Calls
4841 @cindex thread breakpoints and system calls
4842 @cindex system calls and thread breakpoints
4843 @cindex premature return from system calls
4844 There is an unfortunate side effect when using @value{GDBN} to debug
4845 multi-threaded programs. If one thread stops for a
4846 breakpoint, or for some other reason, and another thread is blocked in a
4847 system call, then the system call may return prematurely. This is a
4848 consequence of the interaction between multiple threads and the signals
4849 that @value{GDBN} uses to implement breakpoints and other events that
4852 To handle this problem, your program should check the return value of
4853 each system call and react appropriately. This is good programming
4856 For example, do not write code like this:
4862 The call to @code{sleep} will return early if a different thread stops
4863 at a breakpoint or for some other reason.
4865 Instead, write this:
4870 unslept = sleep (unslept);
4873 A system call is allowed to return early, so the system is still
4874 conforming to its specification. But @value{GDBN} does cause your
4875 multi-threaded program to behave differently than it would without
4878 Also, @value{GDBN} uses internal breakpoints in the thread library to
4879 monitor certain events such as thread creation and thread destruction.
4880 When such an event happens, a system call in another thread may return
4881 prematurely, even though your program does not appear to stop.
4884 @node Reverse Execution
4885 @chapter Running programs backward
4886 @cindex reverse execution
4887 @cindex running programs backward
4889 When you are debugging a program, it is not unusual to realize that
4890 you have gone too far, and some event of interest has already happened.
4891 If the target environment supports it, @value{GDBN} can allow you to
4892 ``rewind'' the program by running it backward.
4894 A target environment that supports reverse execution should be able
4895 to ``undo'' the changes in machine state that have taken place as the
4896 program was executing normally. Variables, registers etc.@: should
4897 revert to their previous values. Obviously this requires a great
4898 deal of sophistication on the part of the target environment; not
4899 all target environments can support reverse execution.
4901 When a program is executed in reverse, the instructions that
4902 have most recently been executed are ``un-executed'', in reverse
4903 order. The program counter runs backward, following the previous
4904 thread of execution in reverse. As each instruction is ``un-executed'',
4905 the values of memory and/or registers that were changed by that
4906 instruction are reverted to their previous states. After executing
4907 a piece of source code in reverse, all side effects of that code
4908 should be ``undone'', and all variables should be returned to their
4909 prior values@footnote{
4910 Note that some side effects are easier to undo than others. For instance,
4911 memory and registers are relatively easy, but device I/O is hard. Some
4912 targets may be able undo things like device I/O, and some may not.
4914 The contract between @value{GDBN} and the reverse executing target
4915 requires only that the target do something reasonable when
4916 @value{GDBN} tells it to execute backwards, and then report the
4917 results back to @value{GDBN}. Whatever the target reports back to
4918 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
4919 assumes that the memory and registers that the target reports are in a
4920 consistant state, but @value{GDBN} accepts whatever it is given.
4923 If you are debugging in a target environment that supports
4924 reverse execution, @value{GDBN} provides the following commands.
4927 @kindex reverse-continue
4928 @kindex rc @r{(@code{reverse-continue})}
4929 @item reverse-continue @r{[}@var{ignore-count}@r{]}
4930 @itemx rc @r{[}@var{ignore-count}@r{]}
4931 Beginning at the point where your program last stopped, start executing
4932 in reverse. Reverse execution will stop for breakpoints and synchronous
4933 exceptions (signals), just like normal execution. Behavior of
4934 asynchronous signals depends on the target environment.
4936 @kindex reverse-step
4937 @kindex rs @r{(@code{step})}
4938 @item reverse-step @r{[}@var{count}@r{]}
4939 Run the program backward until control reaches the start of a
4940 different source line; then stop it, and return control to @value{GDBN}.
4942 Like the @code{step} command, @code{reverse-step} will only stop
4943 at the beginning of a source line. It ``un-executes'' the previously
4944 executed source line. If the previous source line included calls to
4945 debuggable functions, @code{reverse-step} will step (backward) into
4946 the called function, stopping at the beginning of the @emph{last}
4947 statement in the called function (typically a return statement).
4949 Also, as with the @code{step} command, if non-debuggable functions are
4950 called, @code{reverse-step} will run thru them backward without stopping.
4952 @kindex reverse-stepi
4953 @kindex rsi @r{(@code{reverse-stepi})}
4954 @item reverse-stepi @r{[}@var{count}@r{]}
4955 Reverse-execute one machine instruction. Note that the instruction
4956 to be reverse-executed is @emph{not} the one pointed to by the program
4957 counter, but the instruction executed prior to that one. For instance,
4958 if the last instruction was a jump, @code{reverse-stepi} will take you
4959 back from the destination of the jump to the jump instruction itself.
4961 @kindex reverse-next
4962 @kindex rn @r{(@code{reverse-next})}
4963 @item reverse-next @r{[}@var{count}@r{]}
4964 Run backward to the beginning of the previous line executed in
4965 the current (innermost) stack frame. If the line contains function
4966 calls, they will be ``un-executed'' without stopping. Starting from
4967 the first line of a function, @code{reverse-next} will take you back
4968 to the caller of that function, @emph{before} the function was called,
4969 just as the normal @code{next} command would take you from the last
4970 line of a function back to its return to its caller
4971 @footnote{Unles the code is too heavily optimized.}.
4973 @kindex reverse-nexti
4974 @kindex rni @r{(@code{reverse-nexti})}
4975 @item reverse-nexti @r{[}@var{count}@r{]}
4976 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
4977 in reverse, except that called functions are ``un-executed'' atomically.
4978 That is, if the previously executed instruction was a return from
4979 another instruction, @code{reverse-nexti} will continue to execute
4980 in reverse until the call to that function (from the current stack
4983 @kindex reverse-finish
4984 @item reverse-finish
4985 Just as the @code{finish} command takes you to the point where the
4986 current function returns, @code{reverse-finish} takes you to the point
4987 where it was called. Instead of ending up at the end of the current
4988 function invocation, you end up at the beginning.
4990 @kindex set exec-direction
4991 @item set exec-direction
4992 Set the direction of target execution.
4993 @itemx set exec-direction reverse
4994 @cindex execute forward or backward in time
4995 @value{GDBN} will perform all execution commands in reverse, until the
4996 exec-direction mode is changed to ``forward''. Affected commands include
4997 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
4998 command cannot be used in reverse mode.
4999 @item set exec-direction forward
5000 @value{GDBN} will perform all execution commands in the normal fashion.
5001 This is the default.
5006 @chapter Examining the Stack
5008 When your program has stopped, the first thing you need to know is where it
5009 stopped and how it got there.
5012 Each time your program performs a function call, information about the call
5014 That information includes the location of the call in your program,
5015 the arguments of the call,
5016 and the local variables of the function being called.
5017 The information is saved in a block of data called a @dfn{stack frame}.
5018 The stack frames are allocated in a region of memory called the @dfn{call
5021 When your program stops, the @value{GDBN} commands for examining the
5022 stack allow you to see all of this information.
5024 @cindex selected frame
5025 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5026 @value{GDBN} commands refer implicitly to the selected frame. In
5027 particular, whenever you ask @value{GDBN} for the value of a variable in
5028 your program, the value is found in the selected frame. There are
5029 special @value{GDBN} commands to select whichever frame you are
5030 interested in. @xref{Selection, ,Selecting a Frame}.
5032 When your program stops, @value{GDBN} automatically selects the
5033 currently executing frame and describes it briefly, similar to the
5034 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5037 * Frames:: Stack frames
5038 * Backtrace:: Backtraces
5039 * Selection:: Selecting a frame
5040 * Frame Info:: Information on a frame
5045 @section Stack Frames
5047 @cindex frame, definition
5049 The call stack is divided up into contiguous pieces called @dfn{stack
5050 frames}, or @dfn{frames} for short; each frame is the data associated
5051 with one call to one function. The frame contains the arguments given
5052 to the function, the function's local variables, and the address at
5053 which the function is executing.
5055 @cindex initial frame
5056 @cindex outermost frame
5057 @cindex innermost frame
5058 When your program is started, the stack has only one frame, that of the
5059 function @code{main}. This is called the @dfn{initial} frame or the
5060 @dfn{outermost} frame. Each time a function is called, a new frame is
5061 made. Each time a function returns, the frame for that function invocation
5062 is eliminated. If a function is recursive, there can be many frames for
5063 the same function. The frame for the function in which execution is
5064 actually occurring is called the @dfn{innermost} frame. This is the most
5065 recently created of all the stack frames that still exist.
5067 @cindex frame pointer
5068 Inside your program, stack frames are identified by their addresses. A
5069 stack frame consists of many bytes, each of which has its own address; each
5070 kind of computer has a convention for choosing one byte whose
5071 address serves as the address of the frame. Usually this address is kept
5072 in a register called the @dfn{frame pointer register}
5073 (@pxref{Registers, $fp}) while execution is going on in that frame.
5075 @cindex frame number
5076 @value{GDBN} assigns numbers to all existing stack frames, starting with
5077 zero for the innermost frame, one for the frame that called it,
5078 and so on upward. These numbers do not really exist in your program;
5079 they are assigned by @value{GDBN} to give you a way of designating stack
5080 frames in @value{GDBN} commands.
5082 @c The -fomit-frame-pointer below perennially causes hbox overflow
5083 @c underflow problems.
5084 @cindex frameless execution
5085 Some compilers provide a way to compile functions so that they operate
5086 without stack frames. (For example, the @value{NGCC} option
5088 @samp{-fomit-frame-pointer}
5090 generates functions without a frame.)
5091 This is occasionally done with heavily used library functions to save
5092 the frame setup time. @value{GDBN} has limited facilities for dealing
5093 with these function invocations. If the innermost function invocation
5094 has no stack frame, @value{GDBN} nevertheless regards it as though
5095 it had a separate frame, which is numbered zero as usual, allowing
5096 correct tracing of the function call chain. However, @value{GDBN} has
5097 no provision for frameless functions elsewhere in the stack.
5100 @kindex frame@r{, command}
5101 @cindex current stack frame
5102 @item frame @var{args}
5103 The @code{frame} command allows you to move from one stack frame to another,
5104 and to print the stack frame you select. @var{args} may be either the
5105 address of the frame or the stack frame number. Without an argument,
5106 @code{frame} prints the current stack frame.
5108 @kindex select-frame
5109 @cindex selecting frame silently
5111 The @code{select-frame} command allows you to move from one stack frame
5112 to another without printing the frame. This is the silent version of
5120 @cindex call stack traces
5121 A backtrace is a summary of how your program got where it is. It shows one
5122 line per frame, for many frames, starting with the currently executing
5123 frame (frame zero), followed by its caller (frame one), and on up the
5128 @kindex bt @r{(@code{backtrace})}
5131 Print a backtrace of the entire stack: one line per frame for all
5132 frames in the stack.
5134 You can stop the backtrace at any time by typing the system interrupt
5135 character, normally @kbd{Ctrl-c}.
5137 @item backtrace @var{n}
5139 Similar, but print only the innermost @var{n} frames.
5141 @item backtrace -@var{n}
5143 Similar, but print only the outermost @var{n} frames.
5145 @item backtrace full
5147 @itemx bt full @var{n}
5148 @itemx bt full -@var{n}
5149 Print the values of the local variables also. @var{n} specifies the
5150 number of frames to print, as described above.
5155 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5156 are additional aliases for @code{backtrace}.
5158 @cindex multiple threads, backtrace
5159 In a multi-threaded program, @value{GDBN} by default shows the
5160 backtrace only for the current thread. To display the backtrace for
5161 several or all of the threads, use the command @code{thread apply}
5162 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5163 apply all backtrace}, @value{GDBN} will display the backtrace for all
5164 the threads; this is handy when you debug a core dump of a
5165 multi-threaded program.
5167 Each line in the backtrace shows the frame number and the function name.
5168 The program counter value is also shown---unless you use @code{set
5169 print address off}. The backtrace also shows the source file name and
5170 line number, as well as the arguments to the function. The program
5171 counter value is omitted if it is at the beginning of the code for that
5174 Here is an example of a backtrace. It was made with the command
5175 @samp{bt 3}, so it shows the innermost three frames.
5179 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5181 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5182 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5184 (More stack frames follow...)
5189 The display for frame zero does not begin with a program counter
5190 value, indicating that your program has stopped at the beginning of the
5191 code for line @code{993} of @code{builtin.c}.
5194 The value of parameter @code{data} in frame 1 has been replaced by
5195 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5196 only if it is a scalar (integer, pointer, enumeration, etc). See command
5197 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5198 on how to configure the way function parameter values are printed.
5200 @cindex value optimized out, in backtrace
5201 @cindex function call arguments, optimized out
5202 If your program was compiled with optimizations, some compilers will
5203 optimize away arguments passed to functions if those arguments are
5204 never used after the call. Such optimizations generate code that
5205 passes arguments through registers, but doesn't store those arguments
5206 in the stack frame. @value{GDBN} has no way of displaying such
5207 arguments in stack frames other than the innermost one. Here's what
5208 such a backtrace might look like:
5212 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5214 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5215 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5217 (More stack frames follow...)
5222 The values of arguments that were not saved in their stack frames are
5223 shown as @samp{<value optimized out>}.
5225 If you need to display the values of such optimized-out arguments,
5226 either deduce that from other variables whose values depend on the one
5227 you are interested in, or recompile without optimizations.
5229 @cindex backtrace beyond @code{main} function
5230 @cindex program entry point
5231 @cindex startup code, and backtrace
5232 Most programs have a standard user entry point---a place where system
5233 libraries and startup code transition into user code. For C this is
5234 @code{main}@footnote{
5235 Note that embedded programs (the so-called ``free-standing''
5236 environment) are not required to have a @code{main} function as the
5237 entry point. They could even have multiple entry points.}.
5238 When @value{GDBN} finds the entry function in a backtrace
5239 it will terminate the backtrace, to avoid tracing into highly
5240 system-specific (and generally uninteresting) code.
5242 If you need to examine the startup code, or limit the number of levels
5243 in a backtrace, you can change this behavior:
5246 @item set backtrace past-main
5247 @itemx set backtrace past-main on
5248 @kindex set backtrace
5249 Backtraces will continue past the user entry point.
5251 @item set backtrace past-main off
5252 Backtraces will stop when they encounter the user entry point. This is the
5255 @item show backtrace past-main
5256 @kindex show backtrace
5257 Display the current user entry point backtrace policy.
5259 @item set backtrace past-entry
5260 @itemx set backtrace past-entry on
5261 Backtraces will continue past the internal entry point of an application.
5262 This entry point is encoded by the linker when the application is built,
5263 and is likely before the user entry point @code{main} (or equivalent) is called.
5265 @item set backtrace past-entry off
5266 Backtraces will stop when they encounter the internal entry point of an
5267 application. This is the default.
5269 @item show backtrace past-entry
5270 Display the current internal entry point backtrace policy.
5272 @item set backtrace limit @var{n}
5273 @itemx set backtrace limit 0
5274 @cindex backtrace limit
5275 Limit the backtrace to @var{n} levels. A value of zero means
5278 @item show backtrace limit
5279 Display the current limit on backtrace levels.
5283 @section Selecting a Frame
5285 Most commands for examining the stack and other data in your program work on
5286 whichever stack frame is selected at the moment. Here are the commands for
5287 selecting a stack frame; all of them finish by printing a brief description
5288 of the stack frame just selected.
5291 @kindex frame@r{, selecting}
5292 @kindex f @r{(@code{frame})}
5295 Select frame number @var{n}. Recall that frame zero is the innermost
5296 (currently executing) frame, frame one is the frame that called the
5297 innermost one, and so on. The highest-numbered frame is the one for
5300 @item frame @var{addr}
5302 Select the frame at address @var{addr}. This is useful mainly if the
5303 chaining of stack frames has been damaged by a bug, making it
5304 impossible for @value{GDBN} to assign numbers properly to all frames. In
5305 addition, this can be useful when your program has multiple stacks and
5306 switches between them.
5308 On the SPARC architecture, @code{frame} needs two addresses to
5309 select an arbitrary frame: a frame pointer and a stack pointer.
5311 On the MIPS and Alpha architecture, it needs two addresses: a stack
5312 pointer and a program counter.
5314 On the 29k architecture, it needs three addresses: a register stack
5315 pointer, a program counter, and a memory stack pointer.
5319 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5320 advances toward the outermost frame, to higher frame numbers, to frames
5321 that have existed longer. @var{n} defaults to one.
5324 @kindex do @r{(@code{down})}
5326 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5327 advances toward the innermost frame, to lower frame numbers, to frames
5328 that were created more recently. @var{n} defaults to one. You may
5329 abbreviate @code{down} as @code{do}.
5332 All of these commands end by printing two lines of output describing the
5333 frame. The first line shows the frame number, the function name, the
5334 arguments, and the source file and line number of execution in that
5335 frame. The second line shows the text of that source line.
5343 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5345 10 read_input_file (argv[i]);
5349 After such a printout, the @code{list} command with no arguments
5350 prints ten lines centered on the point of execution in the frame.
5351 You can also edit the program at the point of execution with your favorite
5352 editing program by typing @code{edit}.
5353 @xref{List, ,Printing Source Lines},
5357 @kindex down-silently
5359 @item up-silently @var{n}
5360 @itemx down-silently @var{n}
5361 These two commands are variants of @code{up} and @code{down},
5362 respectively; they differ in that they do their work silently, without
5363 causing display of the new frame. They are intended primarily for use
5364 in @value{GDBN} command scripts, where the output might be unnecessary and
5369 @section Information About a Frame
5371 There are several other commands to print information about the selected
5377 When used without any argument, this command does not change which
5378 frame is selected, but prints a brief description of the currently
5379 selected stack frame. It can be abbreviated @code{f}. With an
5380 argument, this command is used to select a stack frame.
5381 @xref{Selection, ,Selecting a Frame}.
5384 @kindex info f @r{(@code{info frame})}
5387 This command prints a verbose description of the selected stack frame,
5392 the address of the frame
5394 the address of the next frame down (called by this frame)
5396 the address of the next frame up (caller of this frame)
5398 the language in which the source code corresponding to this frame is written
5400 the address of the frame's arguments
5402 the address of the frame's local variables
5404 the program counter saved in it (the address of execution in the caller frame)
5406 which registers were saved in the frame
5409 @noindent The verbose description is useful when
5410 something has gone wrong that has made the stack format fail to fit
5411 the usual conventions.
5413 @item info frame @var{addr}
5414 @itemx info f @var{addr}
5415 Print a verbose description of the frame at address @var{addr}, without
5416 selecting that frame. The selected frame remains unchanged by this
5417 command. This requires the same kind of address (more than one for some
5418 architectures) that you specify in the @code{frame} command.
5419 @xref{Selection, ,Selecting a Frame}.
5423 Print the arguments of the selected frame, each on a separate line.
5427 Print the local variables of the selected frame, each on a separate
5428 line. These are all variables (declared either static or automatic)
5429 accessible at the point of execution of the selected frame.
5432 @cindex catch exceptions, list active handlers
5433 @cindex exception handlers, how to list
5435 Print a list of all the exception handlers that are active in the
5436 current stack frame at the current point of execution. To see other
5437 exception handlers, visit the associated frame (using the @code{up},
5438 @code{down}, or @code{frame} commands); then type @code{info catch}.
5439 @xref{Set Catchpoints, , Setting Catchpoints}.
5445 @chapter Examining Source Files
5447 @value{GDBN} can print parts of your program's source, since the debugging
5448 information recorded in the program tells @value{GDBN} what source files were
5449 used to build it. When your program stops, @value{GDBN} spontaneously prints
5450 the line where it stopped. Likewise, when you select a stack frame
5451 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5452 execution in that frame has stopped. You can print other portions of
5453 source files by explicit command.
5455 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5456 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5457 @value{GDBN} under @sc{gnu} Emacs}.
5460 * List:: Printing source lines
5461 * Specify Location:: How to specify code locations
5462 * Edit:: Editing source files
5463 * Search:: Searching source files
5464 * Source Path:: Specifying source directories
5465 * Machine Code:: Source and machine code
5469 @section Printing Source Lines
5472 @kindex l @r{(@code{list})}
5473 To print lines from a source file, use the @code{list} command
5474 (abbreviated @code{l}). By default, ten lines are printed.
5475 There are several ways to specify what part of the file you want to
5476 print; see @ref{Specify Location}, for the full list.
5478 Here are the forms of the @code{list} command most commonly used:
5481 @item list @var{linenum}
5482 Print lines centered around line number @var{linenum} in the
5483 current source file.
5485 @item list @var{function}
5486 Print lines centered around the beginning of function
5490 Print more lines. If the last lines printed were printed with a
5491 @code{list} command, this prints lines following the last lines
5492 printed; however, if the last line printed was a solitary line printed
5493 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5494 Stack}), this prints lines centered around that line.
5497 Print lines just before the lines last printed.
5500 @cindex @code{list}, how many lines to display
5501 By default, @value{GDBN} prints ten source lines with any of these forms of
5502 the @code{list} command. You can change this using @code{set listsize}:
5505 @kindex set listsize
5506 @item set listsize @var{count}
5507 Make the @code{list} command display @var{count} source lines (unless
5508 the @code{list} argument explicitly specifies some other number).
5510 @kindex show listsize
5512 Display the number of lines that @code{list} prints.
5515 Repeating a @code{list} command with @key{RET} discards the argument,
5516 so it is equivalent to typing just @code{list}. This is more useful
5517 than listing the same lines again. An exception is made for an
5518 argument of @samp{-}; that argument is preserved in repetition so that
5519 each repetition moves up in the source file.
5521 In general, the @code{list} command expects you to supply zero, one or two
5522 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5523 of writing them (@pxref{Specify Location}), but the effect is always
5524 to specify some source line.
5526 Here is a complete description of the possible arguments for @code{list}:
5529 @item list @var{linespec}
5530 Print lines centered around the line specified by @var{linespec}.
5532 @item list @var{first},@var{last}
5533 Print lines from @var{first} to @var{last}. Both arguments are
5534 linespecs. When a @code{list} command has two linespecs, and the
5535 source file of the second linespec is omitted, this refers to
5536 the same source file as the first linespec.
5538 @item list ,@var{last}
5539 Print lines ending with @var{last}.
5541 @item list @var{first},
5542 Print lines starting with @var{first}.
5545 Print lines just after the lines last printed.
5548 Print lines just before the lines last printed.
5551 As described in the preceding table.
5554 @node Specify Location
5555 @section Specifying a Location
5556 @cindex specifying location
5559 Several @value{GDBN} commands accept arguments that specify a location
5560 of your program's code. Since @value{GDBN} is a source-level
5561 debugger, a location usually specifies some line in the source code;
5562 for that reason, locations are also known as @dfn{linespecs}.
5564 Here are all the different ways of specifying a code location that
5565 @value{GDBN} understands:
5569 Specifies the line number @var{linenum} of the current source file.
5572 @itemx +@var{offset}
5573 Specifies the line @var{offset} lines before or after the @dfn{current
5574 line}. For the @code{list} command, the current line is the last one
5575 printed; for the breakpoint commands, this is the line at which
5576 execution stopped in the currently selected @dfn{stack frame}
5577 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5578 used as the second of the two linespecs in a @code{list} command,
5579 this specifies the line @var{offset} lines up or down from the first
5582 @item @var{filename}:@var{linenum}
5583 Specifies the line @var{linenum} in the source file @var{filename}.
5585 @item @var{function}
5586 Specifies the line that begins the body of the function @var{function}.
5587 For example, in C, this is the line with the open brace.
5589 @item @var{filename}:@var{function}
5590 Specifies the line that begins the body of the function @var{function}
5591 in the file @var{filename}. You only need the file name with a
5592 function name to avoid ambiguity when there are identically named
5593 functions in different source files.
5595 @item *@var{address}
5596 Specifies the program address @var{address}. For line-oriented
5597 commands, such as @code{list} and @code{edit}, this specifies a source
5598 line that contains @var{address}. For @code{break} and other
5599 breakpoint oriented commands, this can be used to set breakpoints in
5600 parts of your program which do not have debugging information or
5603 Here @var{address} may be any expression valid in the current working
5604 language (@pxref{Languages, working language}) that specifies a code
5605 address. In addition, as a convenience, @value{GDBN} extends the
5606 semantics of expressions used in locations to cover the situations
5607 that frequently happen during debugging. Here are the various forms
5611 @item @var{expression}
5612 Any expression valid in the current working language.
5614 @item @var{funcaddr}
5615 An address of a function or procedure derived from its name. In C,
5616 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5617 simply the function's name @var{function} (and actually a special case
5618 of a valid expression). In Pascal and Modula-2, this is
5619 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5620 (although the Pascal form also works).
5622 This form specifies the address of the function's first instruction,
5623 before the stack frame and arguments have been set up.
5625 @item '@var{filename}'::@var{funcaddr}
5626 Like @var{funcaddr} above, but also specifies the name of the source
5627 file explicitly. This is useful if the name of the function does not
5628 specify the function unambiguously, e.g., if there are several
5629 functions with identical names in different source files.
5636 @section Editing Source Files
5637 @cindex editing source files
5640 @kindex e @r{(@code{edit})}
5641 To edit the lines in a source file, use the @code{edit} command.
5642 The editing program of your choice
5643 is invoked with the current line set to
5644 the active line in the program.
5645 Alternatively, there are several ways to specify what part of the file you
5646 want to print if you want to see other parts of the program:
5649 @item edit @var{location}
5650 Edit the source file specified by @code{location}. Editing starts at
5651 that @var{location}, e.g., at the specified source line of the
5652 specified file. @xref{Specify Location}, for all the possible forms
5653 of the @var{location} argument; here are the forms of the @code{edit}
5654 command most commonly used:
5657 @item edit @var{number}
5658 Edit the current source file with @var{number} as the active line number.
5660 @item edit @var{function}
5661 Edit the file containing @var{function} at the beginning of its definition.
5666 @subsection Choosing your Editor
5667 You can customize @value{GDBN} to use any editor you want
5669 The only restriction is that your editor (say @code{ex}), recognizes the
5670 following command-line syntax:
5672 ex +@var{number} file
5674 The optional numeric value +@var{number} specifies the number of the line in
5675 the file where to start editing.}.
5676 By default, it is @file{@value{EDITOR}}, but you can change this
5677 by setting the environment variable @code{EDITOR} before using
5678 @value{GDBN}. For example, to configure @value{GDBN} to use the
5679 @code{vi} editor, you could use these commands with the @code{sh} shell:
5685 or in the @code{csh} shell,
5687 setenv EDITOR /usr/bin/vi
5692 @section Searching Source Files
5693 @cindex searching source files
5695 There are two commands for searching through the current source file for a
5700 @kindex forward-search
5701 @item forward-search @var{regexp}
5702 @itemx search @var{regexp}
5703 The command @samp{forward-search @var{regexp}} checks each line,
5704 starting with the one following the last line listed, for a match for
5705 @var{regexp}. It lists the line that is found. You can use the
5706 synonym @samp{search @var{regexp}} or abbreviate the command name as
5709 @kindex reverse-search
5710 @item reverse-search @var{regexp}
5711 The command @samp{reverse-search @var{regexp}} checks each line, starting
5712 with the one before the last line listed and going backward, for a match
5713 for @var{regexp}. It lists the line that is found. You can abbreviate
5714 this command as @code{rev}.
5718 @section Specifying Source Directories
5721 @cindex directories for source files
5722 Executable programs sometimes do not record the directories of the source
5723 files from which they were compiled, just the names. Even when they do,
5724 the directories could be moved between the compilation and your debugging
5725 session. @value{GDBN} has a list of directories to search for source files;
5726 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5727 it tries all the directories in the list, in the order they are present
5728 in the list, until it finds a file with the desired name.
5730 For example, suppose an executable references the file
5731 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5732 @file{/mnt/cross}. The file is first looked up literally; if this
5733 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5734 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5735 message is printed. @value{GDBN} does not look up the parts of the
5736 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5737 Likewise, the subdirectories of the source path are not searched: if
5738 the source path is @file{/mnt/cross}, and the binary refers to
5739 @file{foo.c}, @value{GDBN} would not find it under
5740 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5742 Plain file names, relative file names with leading directories, file
5743 names containing dots, etc.@: are all treated as described above; for
5744 instance, if the source path is @file{/mnt/cross}, and the source file
5745 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5746 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5747 that---@file{/mnt/cross/foo.c}.
5749 Note that the executable search path is @emph{not} used to locate the
5752 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5753 any information it has cached about where source files are found and where
5754 each line is in the file.
5758 When you start @value{GDBN}, its source path includes only @samp{cdir}
5759 and @samp{cwd}, in that order.
5760 To add other directories, use the @code{directory} command.
5762 The search path is used to find both program source files and @value{GDBN}
5763 script files (read using the @samp{-command} option and @samp{source} command).
5765 In addition to the source path, @value{GDBN} provides a set of commands
5766 that manage a list of source path substitution rules. A @dfn{substitution
5767 rule} specifies how to rewrite source directories stored in the program's
5768 debug information in case the sources were moved to a different
5769 directory between compilation and debugging. A rule is made of
5770 two strings, the first specifying what needs to be rewritten in
5771 the path, and the second specifying how it should be rewritten.
5772 In @ref{set substitute-path}, we name these two parts @var{from} and
5773 @var{to} respectively. @value{GDBN} does a simple string replacement
5774 of @var{from} with @var{to} at the start of the directory part of the
5775 source file name, and uses that result instead of the original file
5776 name to look up the sources.
5778 Using the previous example, suppose the @file{foo-1.0} tree has been
5779 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5780 @value{GDBN} to replace @file{/usr/src} in all source path names with
5781 @file{/mnt/cross}. The first lookup will then be
5782 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5783 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5784 substitution rule, use the @code{set substitute-path} command
5785 (@pxref{set substitute-path}).
5787 To avoid unexpected substitution results, a rule is applied only if the
5788 @var{from} part of the directory name ends at a directory separator.
5789 For instance, a rule substituting @file{/usr/source} into
5790 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5791 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5792 is applied only at the beginning of the directory name, this rule will
5793 not be applied to @file{/root/usr/source/baz.c} either.
5795 In many cases, you can achieve the same result using the @code{directory}
5796 command. However, @code{set substitute-path} can be more efficient in
5797 the case where the sources are organized in a complex tree with multiple
5798 subdirectories. With the @code{directory} command, you need to add each
5799 subdirectory of your project. If you moved the entire tree while
5800 preserving its internal organization, then @code{set substitute-path}
5801 allows you to direct the debugger to all the sources with one single
5804 @code{set substitute-path} is also more than just a shortcut command.
5805 The source path is only used if the file at the original location no
5806 longer exists. On the other hand, @code{set substitute-path} modifies
5807 the debugger behavior to look at the rewritten location instead. So, if
5808 for any reason a source file that is not relevant to your executable is
5809 located at the original location, a substitution rule is the only
5810 method available to point @value{GDBN} at the new location.
5812 @cindex @samp{--with-relocated-sources}
5813 @cindex default source path substitution
5814 You can configure a default source path substitution rule by
5815 configuring @value{GDBN} with the
5816 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
5817 should be the name of a directory under @value{GDBN}'s configured
5818 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
5819 directory names in debug information under @var{dir} will be adjusted
5820 automatically if the installed @value{GDBN} is moved to a new
5821 location. This is useful if @value{GDBN}, libraries or executables
5822 with debug information and corresponding source code are being moved
5826 @item directory @var{dirname} @dots{}
5827 @item dir @var{dirname} @dots{}
5828 Add directory @var{dirname} to the front of the source path. Several
5829 directory names may be given to this command, separated by @samp{:}
5830 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5831 part of absolute file names) or
5832 whitespace. You may specify a directory that is already in the source
5833 path; this moves it forward, so @value{GDBN} searches it sooner.
5837 @vindex $cdir@r{, convenience variable}
5838 @vindex $cwd@r{, convenience variable}
5839 @cindex compilation directory
5840 @cindex current directory
5841 @cindex working directory
5842 @cindex directory, current
5843 @cindex directory, compilation
5844 You can use the string @samp{$cdir} to refer to the compilation
5845 directory (if one is recorded), and @samp{$cwd} to refer to the current
5846 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5847 tracks the current working directory as it changes during your @value{GDBN}
5848 session, while the latter is immediately expanded to the current
5849 directory at the time you add an entry to the source path.
5852 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5854 @c RET-repeat for @code{directory} is explicitly disabled, but since
5855 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5857 @item show directories
5858 @kindex show directories
5859 Print the source path: show which directories it contains.
5861 @anchor{set substitute-path}
5862 @item set substitute-path @var{from} @var{to}
5863 @kindex set substitute-path
5864 Define a source path substitution rule, and add it at the end of the
5865 current list of existing substitution rules. If a rule with the same
5866 @var{from} was already defined, then the old rule is also deleted.
5868 For example, if the file @file{/foo/bar/baz.c} was moved to
5869 @file{/mnt/cross/baz.c}, then the command
5872 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5876 will tell @value{GDBN} to replace @samp{/usr/src} with
5877 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5878 @file{baz.c} even though it was moved.
5880 In the case when more than one substitution rule have been defined,
5881 the rules are evaluated one by one in the order where they have been
5882 defined. The first one matching, if any, is selected to perform
5885 For instance, if we had entered the following commands:
5888 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5889 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5893 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5894 @file{/mnt/include/defs.h} by using the first rule. However, it would
5895 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5896 @file{/mnt/src/lib/foo.c}.
5899 @item unset substitute-path [path]
5900 @kindex unset substitute-path
5901 If a path is specified, search the current list of substitution rules
5902 for a rule that would rewrite that path. Delete that rule if found.
5903 A warning is emitted by the debugger if no rule could be found.
5905 If no path is specified, then all substitution rules are deleted.
5907 @item show substitute-path [path]
5908 @kindex show substitute-path
5909 If a path is specified, then print the source path substitution rule
5910 which would rewrite that path, if any.
5912 If no path is specified, then print all existing source path substitution
5917 If your source path is cluttered with directories that are no longer of
5918 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5919 versions of source. You can correct the situation as follows:
5923 Use @code{directory} with no argument to reset the source path to its default value.
5926 Use @code{directory} with suitable arguments to reinstall the
5927 directories you want in the source path. You can add all the
5928 directories in one command.
5932 @section Source and Machine Code
5933 @cindex source line and its code address
5935 You can use the command @code{info line} to map source lines to program
5936 addresses (and vice versa), and the command @code{disassemble} to display
5937 a range of addresses as machine instructions. You can use the command
5938 @code{set disassemble-next-line} to set whether to disassemble next
5939 source line when execution stops. When run under @sc{gnu} Emacs
5940 mode, the @code{info line} command causes the arrow to point to the
5941 line specified. Also, @code{info line} prints addresses in symbolic form as
5946 @item info line @var{linespec}
5947 Print the starting and ending addresses of the compiled code for
5948 source line @var{linespec}. You can specify source lines in any of
5949 the ways documented in @ref{Specify Location}.
5952 For example, we can use @code{info line} to discover the location of
5953 the object code for the first line of function
5954 @code{m4_changequote}:
5956 @c FIXME: I think this example should also show the addresses in
5957 @c symbolic form, as they usually would be displayed.
5959 (@value{GDBP}) info line m4_changequote
5960 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5964 @cindex code address and its source line
5965 We can also inquire (using @code{*@var{addr}} as the form for
5966 @var{linespec}) what source line covers a particular address:
5968 (@value{GDBP}) info line *0x63ff
5969 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5972 @cindex @code{$_} and @code{info line}
5973 @cindex @code{x} command, default address
5974 @kindex x@r{(examine), and} info line
5975 After @code{info line}, the default address for the @code{x} command
5976 is changed to the starting address of the line, so that @samp{x/i} is
5977 sufficient to begin examining the machine code (@pxref{Memory,
5978 ,Examining Memory}). Also, this address is saved as the value of the
5979 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5984 @cindex assembly instructions
5985 @cindex instructions, assembly
5986 @cindex machine instructions
5987 @cindex listing machine instructions
5989 @itemx disassemble /m
5990 This specialized command dumps a range of memory as machine
5991 instructions. It can also print mixed source+disassembly by specifying
5992 the @code{/m} modifier.
5993 The default memory range is the function surrounding the
5994 program counter of the selected frame. A single argument to this
5995 command is a program counter value; @value{GDBN} dumps the function
5996 surrounding this value. Two arguments specify a range of addresses
5997 (first inclusive, second exclusive) to dump.
6000 The following example shows the disassembly of a range of addresses of
6001 HP PA-RISC 2.0 code:
6004 (@value{GDBP}) disas 0x32c4 0x32e4
6005 Dump of assembler code from 0x32c4 to 0x32e4:
6006 0x32c4 <main+204>: addil 0,dp
6007 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6008 0x32cc <main+212>: ldil 0x3000,r31
6009 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6010 0x32d4 <main+220>: ldo 0(r31),rp
6011 0x32d8 <main+224>: addil -0x800,dp
6012 0x32dc <main+228>: ldo 0x588(r1),r26
6013 0x32e0 <main+232>: ldil 0x3000,r31
6014 End of assembler dump.
6017 Here is an example showing mixed source+assembly for Intel x86:
6020 (@value{GDBP}) disas /m main
6021 Dump of assembler code for function main:
6023 0x08048330 <main+0>: push %ebp
6024 0x08048331 <main+1>: mov %esp,%ebp
6025 0x08048333 <main+3>: sub $0x8,%esp
6026 0x08048336 <main+6>: and $0xfffffff0,%esp
6027 0x08048339 <main+9>: sub $0x10,%esp
6029 6 printf ("Hello.\n");
6030 0x0804833c <main+12>: movl $0x8048440,(%esp)
6031 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
6035 0x08048348 <main+24>: mov $0x0,%eax
6036 0x0804834d <main+29>: leave
6037 0x0804834e <main+30>: ret
6039 End of assembler dump.
6042 Some architectures have more than one commonly-used set of instruction
6043 mnemonics or other syntax.
6045 For programs that were dynamically linked and use shared libraries,
6046 instructions that call functions or branch to locations in the shared
6047 libraries might show a seemingly bogus location---it's actually a
6048 location of the relocation table. On some architectures, @value{GDBN}
6049 might be able to resolve these to actual function names.
6052 @kindex set disassembly-flavor
6053 @cindex Intel disassembly flavor
6054 @cindex AT&T disassembly flavor
6055 @item set disassembly-flavor @var{instruction-set}
6056 Select the instruction set to use when disassembling the
6057 program via the @code{disassemble} or @code{x/i} commands.
6059 Currently this command is only defined for the Intel x86 family. You
6060 can set @var{instruction-set} to either @code{intel} or @code{att}.
6061 The default is @code{att}, the AT&T flavor used by default by Unix
6062 assemblers for x86-based targets.
6064 @kindex show disassembly-flavor
6065 @item show disassembly-flavor
6066 Show the current setting of the disassembly flavor.
6070 @kindex set disassemble-next-line
6071 @kindex show disassemble-next-line
6072 @item set disassemble-next-line
6073 @itemx show disassemble-next-line
6074 Control whether or not @value{GDBN} will disassemble the next source
6075 line or instruction when execution stops. If ON, @value{GDBN} will
6076 display disassembly of the next source line when execution of the
6077 program being debugged stops. This is @emph{in addition} to
6078 displaying the source line itself, which @value{GDBN} always does if
6079 possible. If the next source line cannot be displayed for some reason
6080 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6081 info in the debug info), @value{GDBN} will display disassembly of the
6082 next @emph{instruction} instead of showing the next source line. If
6083 AUTO, @value{GDBN} will display disassembly of next instruction only
6084 if the source line cannot be displayed. This setting causes
6085 @value{GDBN} to display some feedback when you step through a function
6086 with no line info or whose source file is unavailable. The default is
6087 OFF, which means never display the disassembly of the next line or
6093 @chapter Examining Data
6095 @cindex printing data
6096 @cindex examining data
6099 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6100 @c document because it is nonstandard... Under Epoch it displays in a
6101 @c different window or something like that.
6102 The usual way to examine data in your program is with the @code{print}
6103 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6104 evaluates and prints the value of an expression of the language your
6105 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6106 Different Languages}).
6109 @item print @var{expr}
6110 @itemx print /@var{f} @var{expr}
6111 @var{expr} is an expression (in the source language). By default the
6112 value of @var{expr} is printed in a format appropriate to its data type;
6113 you can choose a different format by specifying @samp{/@var{f}}, where
6114 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6118 @itemx print /@var{f}
6119 @cindex reprint the last value
6120 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6121 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6122 conveniently inspect the same value in an alternative format.
6125 A more low-level way of examining data is with the @code{x} command.
6126 It examines data in memory at a specified address and prints it in a
6127 specified format. @xref{Memory, ,Examining Memory}.
6129 If you are interested in information about types, or about how the
6130 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6131 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6135 * Expressions:: Expressions
6136 * Ambiguous Expressions:: Ambiguous Expressions
6137 * Variables:: Program variables
6138 * Arrays:: Artificial arrays
6139 * Output Formats:: Output formats
6140 * Memory:: Examining memory
6141 * Auto Display:: Automatic display
6142 * Print Settings:: Print settings
6143 * Value History:: Value history
6144 * Convenience Vars:: Convenience variables
6145 * Registers:: Registers
6146 * Floating Point Hardware:: Floating point hardware
6147 * Vector Unit:: Vector Unit
6148 * OS Information:: Auxiliary data provided by operating system
6149 * Memory Region Attributes:: Memory region attributes
6150 * Dump/Restore Files:: Copy between memory and a file
6151 * Core File Generation:: Cause a program dump its core
6152 * Character Sets:: Debugging programs that use a different
6153 character set than GDB does
6154 * Caching Remote Data:: Data caching for remote targets
6155 * Searching Memory:: Searching memory for a sequence of bytes
6159 @section Expressions
6162 @code{print} and many other @value{GDBN} commands accept an expression and
6163 compute its value. Any kind of constant, variable or operator defined
6164 by the programming language you are using is valid in an expression in
6165 @value{GDBN}. This includes conditional expressions, function calls,
6166 casts, and string constants. It also includes preprocessor macros, if
6167 you compiled your program to include this information; see
6170 @cindex arrays in expressions
6171 @value{GDBN} supports array constants in expressions input by
6172 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6173 you can use the command @code{print @{1, 2, 3@}} to create an array
6174 of three integers. If you pass an array to a function or assign it
6175 to a program variable, @value{GDBN} copies the array to memory that
6176 is @code{malloc}ed in the target program.
6178 Because C is so widespread, most of the expressions shown in examples in
6179 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6180 Languages}, for information on how to use expressions in other
6183 In this section, we discuss operators that you can use in @value{GDBN}
6184 expressions regardless of your programming language.
6186 @cindex casts, in expressions
6187 Casts are supported in all languages, not just in C, because it is so
6188 useful to cast a number into a pointer in order to examine a structure
6189 at that address in memory.
6190 @c FIXME: casts supported---Mod2 true?
6192 @value{GDBN} supports these operators, in addition to those common
6193 to programming languages:
6197 @samp{@@} is a binary operator for treating parts of memory as arrays.
6198 @xref{Arrays, ,Artificial Arrays}, for more information.
6201 @samp{::} allows you to specify a variable in terms of the file or
6202 function where it is defined. @xref{Variables, ,Program Variables}.
6204 @cindex @{@var{type}@}
6205 @cindex type casting memory
6206 @cindex memory, viewing as typed object
6207 @cindex casts, to view memory
6208 @item @{@var{type}@} @var{addr}
6209 Refers to an object of type @var{type} stored at address @var{addr} in
6210 memory. @var{addr} may be any expression whose value is an integer or
6211 pointer (but parentheses are required around binary operators, just as in
6212 a cast). This construct is allowed regardless of what kind of data is
6213 normally supposed to reside at @var{addr}.
6216 @node Ambiguous Expressions
6217 @section Ambiguous Expressions
6218 @cindex ambiguous expressions
6220 Expressions can sometimes contain some ambiguous elements. For instance,
6221 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6222 a single function name to be defined several times, for application in
6223 different contexts. This is called @dfn{overloading}. Another example
6224 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6225 templates and is typically instantiated several times, resulting in
6226 the same function name being defined in different contexts.
6228 In some cases and depending on the language, it is possible to adjust
6229 the expression to remove the ambiguity. For instance in C@t{++}, you
6230 can specify the signature of the function you want to break on, as in
6231 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6232 qualified name of your function often makes the expression unambiguous
6235 When an ambiguity that needs to be resolved is detected, the debugger
6236 has the capability to display a menu of numbered choices for each
6237 possibility, and then waits for the selection with the prompt @samp{>}.
6238 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6239 aborts the current command. If the command in which the expression was
6240 used allows more than one choice to be selected, the next option in the
6241 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6244 For example, the following session excerpt shows an attempt to set a
6245 breakpoint at the overloaded symbol @code{String::after}.
6246 We choose three particular definitions of that function name:
6248 @c FIXME! This is likely to change to show arg type lists, at least
6251 (@value{GDBP}) b String::after
6254 [2] file:String.cc; line number:867
6255 [3] file:String.cc; line number:860
6256 [4] file:String.cc; line number:875
6257 [5] file:String.cc; line number:853
6258 [6] file:String.cc; line number:846
6259 [7] file:String.cc; line number:735
6261 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6262 Breakpoint 2 at 0xb344: file String.cc, line 875.
6263 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6264 Multiple breakpoints were set.
6265 Use the "delete" command to delete unwanted
6272 @kindex set multiple-symbols
6273 @item set multiple-symbols @var{mode}
6274 @cindex multiple-symbols menu
6276 This option allows you to adjust the debugger behavior when an expression
6279 By default, @var{mode} is set to @code{all}. If the command with which
6280 the expression is used allows more than one choice, then @value{GDBN}
6281 automatically selects all possible choices. For instance, inserting
6282 a breakpoint on a function using an ambiguous name results in a breakpoint
6283 inserted on each possible match. However, if a unique choice must be made,
6284 then @value{GDBN} uses the menu to help you disambiguate the expression.
6285 For instance, printing the address of an overloaded function will result
6286 in the use of the menu.
6288 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6289 when an ambiguity is detected.
6291 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6292 an error due to the ambiguity and the command is aborted.
6294 @kindex show multiple-symbols
6295 @item show multiple-symbols
6296 Show the current value of the @code{multiple-symbols} setting.
6300 @section Program Variables
6302 The most common kind of expression to use is the name of a variable
6305 Variables in expressions are understood in the selected stack frame
6306 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6310 global (or file-static)
6317 visible according to the scope rules of the
6318 programming language from the point of execution in that frame
6321 @noindent This means that in the function
6336 you can examine and use the variable @code{a} whenever your program is
6337 executing within the function @code{foo}, but you can only use or
6338 examine the variable @code{b} while your program is executing inside
6339 the block where @code{b} is declared.
6341 @cindex variable name conflict
6342 There is an exception: you can refer to a variable or function whose
6343 scope is a single source file even if the current execution point is not
6344 in this file. But it is possible to have more than one such variable or
6345 function with the same name (in different source files). If that
6346 happens, referring to that name has unpredictable effects. If you wish,
6347 you can specify a static variable in a particular function or file,
6348 using the colon-colon (@code{::}) notation:
6350 @cindex colon-colon, context for variables/functions
6352 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6353 @cindex @code{::}, context for variables/functions
6356 @var{file}::@var{variable}
6357 @var{function}::@var{variable}
6361 Here @var{file} or @var{function} is the name of the context for the
6362 static @var{variable}. In the case of file names, you can use quotes to
6363 make sure @value{GDBN} parses the file name as a single word---for example,
6364 to print a global value of @code{x} defined in @file{f2.c}:
6367 (@value{GDBP}) p 'f2.c'::x
6370 @cindex C@t{++} scope resolution
6371 This use of @samp{::} is very rarely in conflict with the very similar
6372 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6373 scope resolution operator in @value{GDBN} expressions.
6374 @c FIXME: Um, so what happens in one of those rare cases where it's in
6377 @cindex wrong values
6378 @cindex variable values, wrong
6379 @cindex function entry/exit, wrong values of variables
6380 @cindex optimized code, wrong values of variables
6382 @emph{Warning:} Occasionally, a local variable may appear to have the
6383 wrong value at certain points in a function---just after entry to a new
6384 scope, and just before exit.
6386 You may see this problem when you are stepping by machine instructions.
6387 This is because, on most machines, it takes more than one instruction to
6388 set up a stack frame (including local variable definitions); if you are
6389 stepping by machine instructions, variables may appear to have the wrong
6390 values until the stack frame is completely built. On exit, it usually
6391 also takes more than one machine instruction to destroy a stack frame;
6392 after you begin stepping through that group of instructions, local
6393 variable definitions may be gone.
6395 This may also happen when the compiler does significant optimizations.
6396 To be sure of always seeing accurate values, turn off all optimization
6399 @cindex ``No symbol "foo" in current context''
6400 Another possible effect of compiler optimizations is to optimize
6401 unused variables out of existence, or assign variables to registers (as
6402 opposed to memory addresses). Depending on the support for such cases
6403 offered by the debug info format used by the compiler, @value{GDBN}
6404 might not be able to display values for such local variables. If that
6405 happens, @value{GDBN} will print a message like this:
6408 No symbol "foo" in current context.
6411 To solve such problems, either recompile without optimizations, or use a
6412 different debug info format, if the compiler supports several such
6413 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6414 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6415 produces debug info in a format that is superior to formats such as
6416 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6417 an effective form for debug info. @xref{Debugging Options,,Options
6418 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6419 Compiler Collection (GCC)}.
6420 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6421 that are best suited to C@t{++} programs.
6423 If you ask to print an object whose contents are unknown to
6424 @value{GDBN}, e.g., because its data type is not completely specified
6425 by the debug information, @value{GDBN} will say @samp{<incomplete
6426 type>}. @xref{Symbols, incomplete type}, for more about this.
6428 Strings are identified as arrays of @code{char} values without specified
6429 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6430 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6431 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6432 defines literal string type @code{"char"} as @code{char} without a sign.
6437 signed char var1[] = "A";
6440 You get during debugging
6445 $2 = @{65 'A', 0 '\0'@}
6449 @section Artificial Arrays
6451 @cindex artificial array
6453 @kindex @@@r{, referencing memory as an array}
6454 It is often useful to print out several successive objects of the
6455 same type in memory; a section of an array, or an array of
6456 dynamically determined size for which only a pointer exists in the
6459 You can do this by referring to a contiguous span of memory as an
6460 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6461 operand of @samp{@@} should be the first element of the desired array
6462 and be an individual object. The right operand should be the desired length
6463 of the array. The result is an array value whose elements are all of
6464 the type of the left argument. The first element is actually the left
6465 argument; the second element comes from bytes of memory immediately
6466 following those that hold the first element, and so on. Here is an
6467 example. If a program says
6470 int *array = (int *) malloc (len * sizeof (int));
6474 you can print the contents of @code{array} with
6480 The left operand of @samp{@@} must reside in memory. Array values made
6481 with @samp{@@} in this way behave just like other arrays in terms of
6482 subscripting, and are coerced to pointers when used in expressions.
6483 Artificial arrays most often appear in expressions via the value history
6484 (@pxref{Value History, ,Value History}), after printing one out.
6486 Another way to create an artificial array is to use a cast.
6487 This re-interprets a value as if it were an array.
6488 The value need not be in memory:
6490 (@value{GDBP}) p/x (short[2])0x12345678
6491 $1 = @{0x1234, 0x5678@}
6494 As a convenience, if you leave the array length out (as in
6495 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6496 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6498 (@value{GDBP}) p/x (short[])0x12345678
6499 $2 = @{0x1234, 0x5678@}
6502 Sometimes the artificial array mechanism is not quite enough; in
6503 moderately complex data structures, the elements of interest may not
6504 actually be adjacent---for example, if you are interested in the values
6505 of pointers in an array. One useful work-around in this situation is
6506 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6507 Variables}) as a counter in an expression that prints the first
6508 interesting value, and then repeat that expression via @key{RET}. For
6509 instance, suppose you have an array @code{dtab} of pointers to
6510 structures, and you are interested in the values of a field @code{fv}
6511 in each structure. Here is an example of what you might type:
6521 @node Output Formats
6522 @section Output Formats
6524 @cindex formatted output
6525 @cindex output formats
6526 By default, @value{GDBN} prints a value according to its data type. Sometimes
6527 this is not what you want. For example, you might want to print a number
6528 in hex, or a pointer in decimal. Or you might want to view data in memory
6529 at a certain address as a character string or as an instruction. To do
6530 these things, specify an @dfn{output format} when you print a value.
6532 The simplest use of output formats is to say how to print a value
6533 already computed. This is done by starting the arguments of the
6534 @code{print} command with a slash and a format letter. The format
6535 letters supported are:
6539 Regard the bits of the value as an integer, and print the integer in
6543 Print as integer in signed decimal.
6546 Print as integer in unsigned decimal.
6549 Print as integer in octal.
6552 Print as integer in binary. The letter @samp{t} stands for ``two''.
6553 @footnote{@samp{b} cannot be used because these format letters are also
6554 used with the @code{x} command, where @samp{b} stands for ``byte'';
6555 see @ref{Memory,,Examining Memory}.}
6558 @cindex unknown address, locating
6559 @cindex locate address
6560 Print as an address, both absolute in hexadecimal and as an offset from
6561 the nearest preceding symbol. You can use this format used to discover
6562 where (in what function) an unknown address is located:
6565 (@value{GDBP}) p/a 0x54320
6566 $3 = 0x54320 <_initialize_vx+396>
6570 The command @code{info symbol 0x54320} yields similar results.
6571 @xref{Symbols, info symbol}.
6574 Regard as an integer and print it as a character constant. This
6575 prints both the numerical value and its character representation. The
6576 character representation is replaced with the octal escape @samp{\nnn}
6577 for characters outside the 7-bit @sc{ascii} range.
6579 Without this format, @value{GDBN} displays @code{char},
6580 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6581 constants. Single-byte members of vectors are displayed as integer
6585 Regard the bits of the value as a floating point number and print
6586 using typical floating point syntax.
6589 @cindex printing strings
6590 @cindex printing byte arrays
6591 Regard as a string, if possible. With this format, pointers to single-byte
6592 data are displayed as null-terminated strings and arrays of single-byte data
6593 are displayed as fixed-length strings. Other values are displayed in their
6596 Without this format, @value{GDBN} displays pointers to and arrays of
6597 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6598 strings. Single-byte members of a vector are displayed as an integer
6602 For example, to print the program counter in hex (@pxref{Registers}), type
6609 Note that no space is required before the slash; this is because command
6610 names in @value{GDBN} cannot contain a slash.
6612 To reprint the last value in the value history with a different format,
6613 you can use the @code{print} command with just a format and no
6614 expression. For example, @samp{p/x} reprints the last value in hex.
6617 @section Examining Memory
6619 You can use the command @code{x} (for ``examine'') to examine memory in
6620 any of several formats, independently of your program's data types.
6622 @cindex examining memory
6624 @kindex x @r{(examine memory)}
6625 @item x/@var{nfu} @var{addr}
6628 Use the @code{x} command to examine memory.
6631 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6632 much memory to display and how to format it; @var{addr} is an
6633 expression giving the address where you want to start displaying memory.
6634 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6635 Several commands set convenient defaults for @var{addr}.
6638 @item @var{n}, the repeat count
6639 The repeat count is a decimal integer; the default is 1. It specifies
6640 how much memory (counting by units @var{u}) to display.
6641 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6644 @item @var{f}, the display format
6645 The display format is one of the formats used by @code{print}
6646 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6647 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6648 The default is @samp{x} (hexadecimal) initially. The default changes
6649 each time you use either @code{x} or @code{print}.
6651 @item @var{u}, the unit size
6652 The unit size is any of
6658 Halfwords (two bytes).
6660 Words (four bytes). This is the initial default.
6662 Giant words (eight bytes).
6665 Each time you specify a unit size with @code{x}, that size becomes the
6666 default unit the next time you use @code{x}. (For the @samp{s} and
6667 @samp{i} formats, the unit size is ignored and is normally not written.)
6669 @item @var{addr}, starting display address
6670 @var{addr} is the address where you want @value{GDBN} to begin displaying
6671 memory. The expression need not have a pointer value (though it may);
6672 it is always interpreted as an integer address of a byte of memory.
6673 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6674 @var{addr} is usually just after the last address examined---but several
6675 other commands also set the default address: @code{info breakpoints} (to
6676 the address of the last breakpoint listed), @code{info line} (to the
6677 starting address of a line), and @code{print} (if you use it to display
6678 a value from memory).
6681 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6682 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6683 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6684 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6685 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6687 Since the letters indicating unit sizes are all distinct from the
6688 letters specifying output formats, you do not have to remember whether
6689 unit size or format comes first; either order works. The output
6690 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6691 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6693 Even though the unit size @var{u} is ignored for the formats @samp{s}
6694 and @samp{i}, you might still want to use a count @var{n}; for example,
6695 @samp{3i} specifies that you want to see three machine instructions,
6696 including any operands. For convenience, especially when used with
6697 the @code{display} command, the @samp{i} format also prints branch delay
6698 slot instructions, if any, beyond the count specified, which immediately
6699 follow the last instruction that is within the count. The command
6700 @code{disassemble} gives an alternative way of inspecting machine
6701 instructions; see @ref{Machine Code,,Source and Machine Code}.
6703 All the defaults for the arguments to @code{x} are designed to make it
6704 easy to continue scanning memory with minimal specifications each time
6705 you use @code{x}. For example, after you have inspected three machine
6706 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6707 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6708 the repeat count @var{n} is used again; the other arguments default as
6709 for successive uses of @code{x}.
6711 @cindex @code{$_}, @code{$__}, and value history
6712 The addresses and contents printed by the @code{x} command are not saved
6713 in the value history because there is often too much of them and they
6714 would get in the way. Instead, @value{GDBN} makes these values available for
6715 subsequent use in expressions as values of the convenience variables
6716 @code{$_} and @code{$__}. After an @code{x} command, the last address
6717 examined is available for use in expressions in the convenience variable
6718 @code{$_}. The contents of that address, as examined, are available in
6719 the convenience variable @code{$__}.
6721 If the @code{x} command has a repeat count, the address and contents saved
6722 are from the last memory unit printed; this is not the same as the last
6723 address printed if several units were printed on the last line of output.
6725 @cindex remote memory comparison
6726 @cindex verify remote memory image
6727 When you are debugging a program running on a remote target machine
6728 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6729 remote machine's memory against the executable file you downloaded to
6730 the target. The @code{compare-sections} command is provided for such
6734 @kindex compare-sections
6735 @item compare-sections @r{[}@var{section-name}@r{]}
6736 Compare the data of a loadable section @var{section-name} in the
6737 executable file of the program being debugged with the same section in
6738 the remote machine's memory, and report any mismatches. With no
6739 arguments, compares all loadable sections. This command's
6740 availability depends on the target's support for the @code{"qCRC"}
6745 @section Automatic Display
6746 @cindex automatic display
6747 @cindex display of expressions
6749 If you find that you want to print the value of an expression frequently
6750 (to see how it changes), you might want to add it to the @dfn{automatic
6751 display list} so that @value{GDBN} prints its value each time your program stops.
6752 Each expression added to the list is given a number to identify it;
6753 to remove an expression from the list, you specify that number.
6754 The automatic display looks like this:
6758 3: bar[5] = (struct hack *) 0x3804
6762 This display shows item numbers, expressions and their current values. As with
6763 displays you request manually using @code{x} or @code{print}, you can
6764 specify the output format you prefer; in fact, @code{display} decides
6765 whether to use @code{print} or @code{x} depending your format
6766 specification---it uses @code{x} if you specify either the @samp{i}
6767 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6771 @item display @var{expr}
6772 Add the expression @var{expr} to the list of expressions to display
6773 each time your program stops. @xref{Expressions, ,Expressions}.
6775 @code{display} does not repeat if you press @key{RET} again after using it.
6777 @item display/@var{fmt} @var{expr}
6778 For @var{fmt} specifying only a display format and not a size or
6779 count, add the expression @var{expr} to the auto-display list but
6780 arrange to display it each time in the specified format @var{fmt}.
6781 @xref{Output Formats,,Output Formats}.
6783 @item display/@var{fmt} @var{addr}
6784 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6785 number of units, add the expression @var{addr} as a memory address to
6786 be examined each time your program stops. Examining means in effect
6787 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6790 For example, @samp{display/i $pc} can be helpful, to see the machine
6791 instruction about to be executed each time execution stops (@samp{$pc}
6792 is a common name for the program counter; @pxref{Registers, ,Registers}).
6795 @kindex delete display
6797 @item undisplay @var{dnums}@dots{}
6798 @itemx delete display @var{dnums}@dots{}
6799 Remove item numbers @var{dnums} from the list of expressions to display.
6801 @code{undisplay} does not repeat if you press @key{RET} after using it.
6802 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6804 @kindex disable display
6805 @item disable display @var{dnums}@dots{}
6806 Disable the display of item numbers @var{dnums}. A disabled display
6807 item is not printed automatically, but is not forgotten. It may be
6808 enabled again later.
6810 @kindex enable display
6811 @item enable display @var{dnums}@dots{}
6812 Enable display of item numbers @var{dnums}. It becomes effective once
6813 again in auto display of its expression, until you specify otherwise.
6816 Display the current values of the expressions on the list, just as is
6817 done when your program stops.
6819 @kindex info display
6821 Print the list of expressions previously set up to display
6822 automatically, each one with its item number, but without showing the
6823 values. This includes disabled expressions, which are marked as such.
6824 It also includes expressions which would not be displayed right now
6825 because they refer to automatic variables not currently available.
6828 @cindex display disabled out of scope
6829 If a display expression refers to local variables, then it does not make
6830 sense outside the lexical context for which it was set up. Such an
6831 expression is disabled when execution enters a context where one of its
6832 variables is not defined. For example, if you give the command
6833 @code{display last_char} while inside a function with an argument
6834 @code{last_char}, @value{GDBN} displays this argument while your program
6835 continues to stop inside that function. When it stops elsewhere---where
6836 there is no variable @code{last_char}---the display is disabled
6837 automatically. The next time your program stops where @code{last_char}
6838 is meaningful, you can enable the display expression once again.
6840 @node Print Settings
6841 @section Print Settings
6843 @cindex format options
6844 @cindex print settings
6845 @value{GDBN} provides the following ways to control how arrays, structures,
6846 and symbols are printed.
6849 These settings are useful for debugging programs in any language:
6853 @item set print address
6854 @itemx set print address on
6855 @cindex print/don't print memory addresses
6856 @value{GDBN} prints memory addresses showing the location of stack
6857 traces, structure values, pointer values, breakpoints, and so forth,
6858 even when it also displays the contents of those addresses. The default
6859 is @code{on}. For example, this is what a stack frame display looks like with
6860 @code{set print address on}:
6865 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6867 530 if (lquote != def_lquote)
6871 @item set print address off
6872 Do not print addresses when displaying their contents. For example,
6873 this is the same stack frame displayed with @code{set print address off}:
6877 (@value{GDBP}) set print addr off
6879 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6880 530 if (lquote != def_lquote)
6884 You can use @samp{set print address off} to eliminate all machine
6885 dependent displays from the @value{GDBN} interface. For example, with
6886 @code{print address off}, you should get the same text for backtraces on
6887 all machines---whether or not they involve pointer arguments.
6890 @item show print address
6891 Show whether or not addresses are to be printed.
6894 When @value{GDBN} prints a symbolic address, it normally prints the
6895 closest earlier symbol plus an offset. If that symbol does not uniquely
6896 identify the address (for example, it is a name whose scope is a single
6897 source file), you may need to clarify. One way to do this is with
6898 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6899 you can set @value{GDBN} to print the source file and line number when
6900 it prints a symbolic address:
6903 @item set print symbol-filename on
6904 @cindex source file and line of a symbol
6905 @cindex symbol, source file and line
6906 Tell @value{GDBN} to print the source file name and line number of a
6907 symbol in the symbolic form of an address.
6909 @item set print symbol-filename off
6910 Do not print source file name and line number of a symbol. This is the
6913 @item show print symbol-filename
6914 Show whether or not @value{GDBN} will print the source file name and
6915 line number of a symbol in the symbolic form of an address.
6918 Another situation where it is helpful to show symbol filenames and line
6919 numbers is when disassembling code; @value{GDBN} shows you the line
6920 number and source file that corresponds to each instruction.
6922 Also, you may wish to see the symbolic form only if the address being
6923 printed is reasonably close to the closest earlier symbol:
6926 @item set print max-symbolic-offset @var{max-offset}
6927 @cindex maximum value for offset of closest symbol
6928 Tell @value{GDBN} to only display the symbolic form of an address if the
6929 offset between the closest earlier symbol and the address is less than
6930 @var{max-offset}. The default is 0, which tells @value{GDBN}
6931 to always print the symbolic form of an address if any symbol precedes it.
6933 @item show print max-symbolic-offset
6934 Ask how large the maximum offset is that @value{GDBN} prints in a
6938 @cindex wild pointer, interpreting
6939 @cindex pointer, finding referent
6940 If you have a pointer and you are not sure where it points, try
6941 @samp{set print symbol-filename on}. Then you can determine the name
6942 and source file location of the variable where it points, using
6943 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6944 For example, here @value{GDBN} shows that a variable @code{ptt} points
6945 at another variable @code{t}, defined in @file{hi2.c}:
6948 (@value{GDBP}) set print symbol-filename on
6949 (@value{GDBP}) p/a ptt
6950 $4 = 0xe008 <t in hi2.c>
6954 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6955 does not show the symbol name and filename of the referent, even with
6956 the appropriate @code{set print} options turned on.
6959 Other settings control how different kinds of objects are printed:
6962 @item set print array
6963 @itemx set print array on
6964 @cindex pretty print arrays
6965 Pretty print arrays. This format is more convenient to read,
6966 but uses more space. The default is off.
6968 @item set print array off
6969 Return to compressed format for arrays.
6971 @item show print array
6972 Show whether compressed or pretty format is selected for displaying
6975 @cindex print array indexes
6976 @item set print array-indexes
6977 @itemx set print array-indexes on
6978 Print the index of each element when displaying arrays. May be more
6979 convenient to locate a given element in the array or quickly find the
6980 index of a given element in that printed array. The default is off.
6982 @item set print array-indexes off
6983 Stop printing element indexes when displaying arrays.
6985 @item show print array-indexes
6986 Show whether the index of each element is printed when displaying
6989 @item set print elements @var{number-of-elements}
6990 @cindex number of array elements to print
6991 @cindex limit on number of printed array elements
6992 Set a limit on how many elements of an array @value{GDBN} will print.
6993 If @value{GDBN} is printing a large array, it stops printing after it has
6994 printed the number of elements set by the @code{set print elements} command.
6995 This limit also applies to the display of strings.
6996 When @value{GDBN} starts, this limit is set to 200.
6997 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6999 @item show print elements
7000 Display the number of elements of a large array that @value{GDBN} will print.
7001 If the number is 0, then the printing is unlimited.
7003 @item set print frame-arguments @var{value}
7004 @kindex set print frame-arguments
7005 @cindex printing frame argument values
7006 @cindex print all frame argument values
7007 @cindex print frame argument values for scalars only
7008 @cindex do not print frame argument values
7009 This command allows to control how the values of arguments are printed
7010 when the debugger prints a frame (@pxref{Frames}). The possible
7015 The values of all arguments are printed.
7018 Print the value of an argument only if it is a scalar. The value of more
7019 complex arguments such as arrays, structures, unions, etc, is replaced
7020 by @code{@dots{}}. This is the default. Here is an example where
7021 only scalar arguments are shown:
7024 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7029 None of the argument values are printed. Instead, the value of each argument
7030 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7033 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7038 By default, only scalar arguments are printed. This command can be used
7039 to configure the debugger to print the value of all arguments, regardless
7040 of their type. However, it is often advantageous to not print the value
7041 of more complex parameters. For instance, it reduces the amount of
7042 information printed in each frame, making the backtrace more readable.
7043 Also, it improves performance when displaying Ada frames, because
7044 the computation of large arguments can sometimes be CPU-intensive,
7045 especially in large applications. Setting @code{print frame-arguments}
7046 to @code{scalars} (the default) or @code{none} avoids this computation,
7047 thus speeding up the display of each Ada frame.
7049 @item show print frame-arguments
7050 Show how the value of arguments should be displayed when printing a frame.
7052 @item set print repeats
7053 @cindex repeated array elements
7054 Set the threshold for suppressing display of repeated array
7055 elements. When the number of consecutive identical elements of an
7056 array exceeds the threshold, @value{GDBN} prints the string
7057 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7058 identical repetitions, instead of displaying the identical elements
7059 themselves. Setting the threshold to zero will cause all elements to
7060 be individually printed. The default threshold is 10.
7062 @item show print repeats
7063 Display the current threshold for printing repeated identical
7066 @item set print null-stop
7067 @cindex @sc{null} elements in arrays
7068 Cause @value{GDBN} to stop printing the characters of an array when the first
7069 @sc{null} is encountered. This is useful when large arrays actually
7070 contain only short strings.
7073 @item show print null-stop
7074 Show whether @value{GDBN} stops printing an array on the first
7075 @sc{null} character.
7077 @item set print pretty on
7078 @cindex print structures in indented form
7079 @cindex indentation in structure display
7080 Cause @value{GDBN} to print structures in an indented format with one member
7081 per line, like this:
7096 @item set print pretty off
7097 Cause @value{GDBN} to print structures in a compact format, like this:
7101 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7102 meat = 0x54 "Pork"@}
7107 This is the default format.
7109 @item show print pretty
7110 Show which format @value{GDBN} is using to print structures.
7112 @item set print sevenbit-strings on
7113 @cindex eight-bit characters in strings
7114 @cindex octal escapes in strings
7115 Print using only seven-bit characters; if this option is set,
7116 @value{GDBN} displays any eight-bit characters (in strings or
7117 character values) using the notation @code{\}@var{nnn}. This setting is
7118 best if you are working in English (@sc{ascii}) and you use the
7119 high-order bit of characters as a marker or ``meta'' bit.
7121 @item set print sevenbit-strings off
7122 Print full eight-bit characters. This allows the use of more
7123 international character sets, and is the default.
7125 @item show print sevenbit-strings
7126 Show whether or not @value{GDBN} is printing only seven-bit characters.
7128 @item set print union on
7129 @cindex unions in structures, printing
7130 Tell @value{GDBN} to print unions which are contained in structures
7131 and other unions. This is the default setting.
7133 @item set print union off
7134 Tell @value{GDBN} not to print unions which are contained in
7135 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7138 @item show print union
7139 Ask @value{GDBN} whether or not it will print unions which are contained in
7140 structures and other unions.
7142 For example, given the declarations
7145 typedef enum @{Tree, Bug@} Species;
7146 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7147 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7158 struct thing foo = @{Tree, @{Acorn@}@};
7162 with @code{set print union on} in effect @samp{p foo} would print
7165 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7169 and with @code{set print union off} in effect it would print
7172 $1 = @{it = Tree, form = @{...@}@}
7176 @code{set print union} affects programs written in C-like languages
7182 These settings are of interest when debugging C@t{++} programs:
7185 @cindex demangling C@t{++} names
7186 @item set print demangle
7187 @itemx set print demangle on
7188 Print C@t{++} names in their source form rather than in the encoded
7189 (``mangled'') form passed to the assembler and linker for type-safe
7190 linkage. The default is on.
7192 @item show print demangle
7193 Show whether C@t{++} names are printed in mangled or demangled form.
7195 @item set print asm-demangle
7196 @itemx set print asm-demangle on
7197 Print C@t{++} names in their source form rather than their mangled form, even
7198 in assembler code printouts such as instruction disassemblies.
7201 @item show print asm-demangle
7202 Show whether C@t{++} names in assembly listings are printed in mangled
7205 @cindex C@t{++} symbol decoding style
7206 @cindex symbol decoding style, C@t{++}
7207 @kindex set demangle-style
7208 @item set demangle-style @var{style}
7209 Choose among several encoding schemes used by different compilers to
7210 represent C@t{++} names. The choices for @var{style} are currently:
7214 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7217 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7218 This is the default.
7221 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7224 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7227 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7228 @strong{Warning:} this setting alone is not sufficient to allow
7229 debugging @code{cfront}-generated executables. @value{GDBN} would
7230 require further enhancement to permit that.
7233 If you omit @var{style}, you will see a list of possible formats.
7235 @item show demangle-style
7236 Display the encoding style currently in use for decoding C@t{++} symbols.
7238 @item set print object
7239 @itemx set print object on
7240 @cindex derived type of an object, printing
7241 @cindex display derived types
7242 When displaying a pointer to an object, identify the @emph{actual}
7243 (derived) type of the object rather than the @emph{declared} type, using
7244 the virtual function table.
7246 @item set print object off
7247 Display only the declared type of objects, without reference to the
7248 virtual function table. This is the default setting.
7250 @item show print object
7251 Show whether actual, or declared, object types are displayed.
7253 @item set print static-members
7254 @itemx set print static-members on
7255 @cindex static members of C@t{++} objects
7256 Print static members when displaying a C@t{++} object. The default is on.
7258 @item set print static-members off
7259 Do not print static members when displaying a C@t{++} object.
7261 @item show print static-members
7262 Show whether C@t{++} static members are printed or not.
7264 @item set print pascal_static-members
7265 @itemx set print pascal_static-members on
7266 @cindex static members of Pascal objects
7267 @cindex Pascal objects, static members display
7268 Print static members when displaying a Pascal object. The default is on.
7270 @item set print pascal_static-members off
7271 Do not print static members when displaying a Pascal object.
7273 @item show print pascal_static-members
7274 Show whether Pascal static members are printed or not.
7276 @c These don't work with HP ANSI C++ yet.
7277 @item set print vtbl
7278 @itemx set print vtbl on
7279 @cindex pretty print C@t{++} virtual function tables
7280 @cindex virtual functions (C@t{++}) display
7281 @cindex VTBL display
7282 Pretty print C@t{++} virtual function tables. The default is off.
7283 (The @code{vtbl} commands do not work on programs compiled with the HP
7284 ANSI C@t{++} compiler (@code{aCC}).)
7286 @item set print vtbl off
7287 Do not pretty print C@t{++} virtual function tables.
7289 @item show print vtbl
7290 Show whether C@t{++} virtual function tables are pretty printed, or not.
7294 @section Value History
7296 @cindex value history
7297 @cindex history of values printed by @value{GDBN}
7298 Values printed by the @code{print} command are saved in the @value{GDBN}
7299 @dfn{value history}. This allows you to refer to them in other expressions.
7300 Values are kept until the symbol table is re-read or discarded
7301 (for example with the @code{file} or @code{symbol-file} commands).
7302 When the symbol table changes, the value history is discarded,
7303 since the values may contain pointers back to the types defined in the
7308 @cindex history number
7309 The values printed are given @dfn{history numbers} by which you can
7310 refer to them. These are successive integers starting with one.
7311 @code{print} shows you the history number assigned to a value by
7312 printing @samp{$@var{num} = } before the value; here @var{num} is the
7315 To refer to any previous value, use @samp{$} followed by the value's
7316 history number. The way @code{print} labels its output is designed to
7317 remind you of this. Just @code{$} refers to the most recent value in
7318 the history, and @code{$$} refers to the value before that.
7319 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7320 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7321 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7323 For example, suppose you have just printed a pointer to a structure and
7324 want to see the contents of the structure. It suffices to type
7330 If you have a chain of structures where the component @code{next} points
7331 to the next one, you can print the contents of the next one with this:
7338 You can print successive links in the chain by repeating this
7339 command---which you can do by just typing @key{RET}.
7341 Note that the history records values, not expressions. If the value of
7342 @code{x} is 4 and you type these commands:
7350 then the value recorded in the value history by the @code{print} command
7351 remains 4 even though the value of @code{x} has changed.
7356 Print the last ten values in the value history, with their item numbers.
7357 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7358 values} does not change the history.
7360 @item show values @var{n}
7361 Print ten history values centered on history item number @var{n}.
7364 Print ten history values just after the values last printed. If no more
7365 values are available, @code{show values +} produces no display.
7368 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7369 same effect as @samp{show values +}.
7371 @node Convenience Vars
7372 @section Convenience Variables
7374 @cindex convenience variables
7375 @cindex user-defined variables
7376 @value{GDBN} provides @dfn{convenience variables} that you can use within
7377 @value{GDBN} to hold on to a value and refer to it later. These variables
7378 exist entirely within @value{GDBN}; they are not part of your program, and
7379 setting a convenience variable has no direct effect on further execution
7380 of your program. That is why you can use them freely.
7382 Convenience variables are prefixed with @samp{$}. Any name preceded by
7383 @samp{$} can be used for a convenience variable, unless it is one of
7384 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7385 (Value history references, in contrast, are @emph{numbers} preceded
7386 by @samp{$}. @xref{Value History, ,Value History}.)
7388 You can save a value in a convenience variable with an assignment
7389 expression, just as you would set a variable in your program.
7393 set $foo = *object_ptr
7397 would save in @code{$foo} the value contained in the object pointed to by
7400 Using a convenience variable for the first time creates it, but its
7401 value is @code{void} until you assign a new value. You can alter the
7402 value with another assignment at any time.
7404 Convenience variables have no fixed types. You can assign a convenience
7405 variable any type of value, including structures and arrays, even if
7406 that variable already has a value of a different type. The convenience
7407 variable, when used as an expression, has the type of its current value.
7410 @kindex show convenience
7411 @cindex show all user variables
7412 @item show convenience
7413 Print a list of convenience variables used so far, and their values.
7414 Abbreviated @code{show conv}.
7416 @kindex init-if-undefined
7417 @cindex convenience variables, initializing
7418 @item init-if-undefined $@var{variable} = @var{expression}
7419 Set a convenience variable if it has not already been set. This is useful
7420 for user-defined commands that keep some state. It is similar, in concept,
7421 to using local static variables with initializers in C (except that
7422 convenience variables are global). It can also be used to allow users to
7423 override default values used in a command script.
7425 If the variable is already defined then the expression is not evaluated so
7426 any side-effects do not occur.
7429 One of the ways to use a convenience variable is as a counter to be
7430 incremented or a pointer to be advanced. For example, to print
7431 a field from successive elements of an array of structures:
7435 print bar[$i++]->contents
7439 Repeat that command by typing @key{RET}.
7441 Some convenience variables are created automatically by @value{GDBN} and given
7442 values likely to be useful.
7445 @vindex $_@r{, convenience variable}
7447 The variable @code{$_} is automatically set by the @code{x} command to
7448 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7449 commands which provide a default address for @code{x} to examine also
7450 set @code{$_} to that address; these commands include @code{info line}
7451 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7452 except when set by the @code{x} command, in which case it is a pointer
7453 to the type of @code{$__}.
7455 @vindex $__@r{, convenience variable}
7457 The variable @code{$__} is automatically set by the @code{x} command
7458 to the value found in the last address examined. Its type is chosen
7459 to match the format in which the data was printed.
7462 @vindex $_exitcode@r{, convenience variable}
7463 The variable @code{$_exitcode} is automatically set to the exit code when
7464 the program being debugged terminates.
7467 @vindex $_siginfo@r{, convenience variable}
7468 The variable @code{$_siginfo} is bound to extra signal information
7469 inspection (@pxref{extra signal information}).
7472 On HP-UX systems, if you refer to a function or variable name that
7473 begins with a dollar sign, @value{GDBN} searches for a user or system
7474 name first, before it searches for a convenience variable.
7476 @cindex convenience functions
7477 @value{GDBN} also supplies some @dfn{convenience functions}. These
7478 have a syntax similar to convenience variables. A convenience
7479 function can be used in an expression just like an ordinary function;
7480 however, a convenience function is implemented internally to
7485 @kindex help function
7486 @cindex show all convenience functions
7487 Print a list of all convenience functions.
7494 You can refer to machine register contents, in expressions, as variables
7495 with names starting with @samp{$}. The names of registers are different
7496 for each machine; use @code{info registers} to see the names used on
7500 @kindex info registers
7501 @item info registers
7502 Print the names and values of all registers except floating-point
7503 and vector registers (in the selected stack frame).
7505 @kindex info all-registers
7506 @cindex floating point registers
7507 @item info all-registers
7508 Print the names and values of all registers, including floating-point
7509 and vector registers (in the selected stack frame).
7511 @item info registers @var{regname} @dots{}
7512 Print the @dfn{relativized} value of each specified register @var{regname}.
7513 As discussed in detail below, register values are normally relative to
7514 the selected stack frame. @var{regname} may be any register name valid on
7515 the machine you are using, with or without the initial @samp{$}.
7518 @cindex stack pointer register
7519 @cindex program counter register
7520 @cindex process status register
7521 @cindex frame pointer register
7522 @cindex standard registers
7523 @value{GDBN} has four ``standard'' register names that are available (in
7524 expressions) on most machines---whenever they do not conflict with an
7525 architecture's canonical mnemonics for registers. The register names
7526 @code{$pc} and @code{$sp} are used for the program counter register and
7527 the stack pointer. @code{$fp} is used for a register that contains a
7528 pointer to the current stack frame, and @code{$ps} is used for a
7529 register that contains the processor status. For example,
7530 you could print the program counter in hex with
7537 or print the instruction to be executed next with
7544 or add four to the stack pointer@footnote{This is a way of removing
7545 one word from the stack, on machines where stacks grow downward in
7546 memory (most machines, nowadays). This assumes that the innermost
7547 stack frame is selected; setting @code{$sp} is not allowed when other
7548 stack frames are selected. To pop entire frames off the stack,
7549 regardless of machine architecture, use @code{return};
7550 see @ref{Returning, ,Returning from a Function}.} with
7556 Whenever possible, these four standard register names are available on
7557 your machine even though the machine has different canonical mnemonics,
7558 so long as there is no conflict. The @code{info registers} command
7559 shows the canonical names. For example, on the SPARC, @code{info
7560 registers} displays the processor status register as @code{$psr} but you
7561 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7562 is an alias for the @sc{eflags} register.
7564 @value{GDBN} always considers the contents of an ordinary register as an
7565 integer when the register is examined in this way. Some machines have
7566 special registers which can hold nothing but floating point; these
7567 registers are considered to have floating point values. There is no way
7568 to refer to the contents of an ordinary register as floating point value
7569 (although you can @emph{print} it as a floating point value with
7570 @samp{print/f $@var{regname}}).
7572 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7573 means that the data format in which the register contents are saved by
7574 the operating system is not the same one that your program normally
7575 sees. For example, the registers of the 68881 floating point
7576 coprocessor are always saved in ``extended'' (raw) format, but all C
7577 programs expect to work with ``double'' (virtual) format. In such
7578 cases, @value{GDBN} normally works with the virtual format only (the format
7579 that makes sense for your program), but the @code{info registers} command
7580 prints the data in both formats.
7582 @cindex SSE registers (x86)
7583 @cindex MMX registers (x86)
7584 Some machines have special registers whose contents can be interpreted
7585 in several different ways. For example, modern x86-based machines
7586 have SSE and MMX registers that can hold several values packed
7587 together in several different formats. @value{GDBN} refers to such
7588 registers in @code{struct} notation:
7591 (@value{GDBP}) print $xmm1
7593 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7594 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7595 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7596 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7597 v4_int32 = @{0, 20657912, 11, 13@},
7598 v2_int64 = @{88725056443645952, 55834574859@},
7599 uint128 = 0x0000000d0000000b013b36f800000000
7604 To set values of such registers, you need to tell @value{GDBN} which
7605 view of the register you wish to change, as if you were assigning
7606 value to a @code{struct} member:
7609 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7612 Normally, register values are relative to the selected stack frame
7613 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7614 value that the register would contain if all stack frames farther in
7615 were exited and their saved registers restored. In order to see the
7616 true contents of hardware registers, you must select the innermost
7617 frame (with @samp{frame 0}).
7619 However, @value{GDBN} must deduce where registers are saved, from the machine
7620 code generated by your compiler. If some registers are not saved, or if
7621 @value{GDBN} is unable to locate the saved registers, the selected stack
7622 frame makes no difference.
7624 @node Floating Point Hardware
7625 @section Floating Point Hardware
7626 @cindex floating point
7628 Depending on the configuration, @value{GDBN} may be able to give
7629 you more information about the status of the floating point hardware.
7634 Display hardware-dependent information about the floating
7635 point unit. The exact contents and layout vary depending on the
7636 floating point chip. Currently, @samp{info float} is supported on
7637 the ARM and x86 machines.
7641 @section Vector Unit
7644 Depending on the configuration, @value{GDBN} may be able to give you
7645 more information about the status of the vector unit.
7650 Display information about the vector unit. The exact contents and
7651 layout vary depending on the hardware.
7654 @node OS Information
7655 @section Operating System Auxiliary Information
7656 @cindex OS information
7658 @value{GDBN} provides interfaces to useful OS facilities that can help
7659 you debug your program.
7661 @cindex @code{ptrace} system call
7662 @cindex @code{struct user} contents
7663 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7664 machines), it interfaces with the inferior via the @code{ptrace}
7665 system call. The operating system creates a special sata structure,
7666 called @code{struct user}, for this interface. You can use the
7667 command @code{info udot} to display the contents of this data
7673 Display the contents of the @code{struct user} maintained by the OS
7674 kernel for the program being debugged. @value{GDBN} displays the
7675 contents of @code{struct user} as a list of hex numbers, similar to
7676 the @code{examine} command.
7679 @cindex auxiliary vector
7680 @cindex vector, auxiliary
7681 Some operating systems supply an @dfn{auxiliary vector} to programs at
7682 startup. This is akin to the arguments and environment that you
7683 specify for a program, but contains a system-dependent variety of
7684 binary values that tell system libraries important details about the
7685 hardware, operating system, and process. Each value's purpose is
7686 identified by an integer tag; the meanings are well-known but system-specific.
7687 Depending on the configuration and operating system facilities,
7688 @value{GDBN} may be able to show you this information. For remote
7689 targets, this functionality may further depend on the remote stub's
7690 support of the @samp{qXfer:auxv:read} packet, see
7691 @ref{qXfer auxiliary vector read}.
7696 Display the auxiliary vector of the inferior, which can be either a
7697 live process or a core dump file. @value{GDBN} prints each tag value
7698 numerically, and also shows names and text descriptions for recognized
7699 tags. Some values in the vector are numbers, some bit masks, and some
7700 pointers to strings or other data. @value{GDBN} displays each value in the
7701 most appropriate form for a recognized tag, and in hexadecimal for
7702 an unrecognized tag.
7705 On some targets, @value{GDBN} can access operating-system-specific information
7706 and display it to user, without interpretation. For remote targets,
7707 this functionality depends on the remote stub's support of the
7708 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
7711 @kindex info os processes
7712 @item info os processes
7713 Display the list of processes on the target. For each process,
7714 @value{GDBN} prints the process identifier, the name of the user, and
7715 the command corresponding to the process.
7718 @node Memory Region Attributes
7719 @section Memory Region Attributes
7720 @cindex memory region attributes
7722 @dfn{Memory region attributes} allow you to describe special handling
7723 required by regions of your target's memory. @value{GDBN} uses
7724 attributes to determine whether to allow certain types of memory
7725 accesses; whether to use specific width accesses; and whether to cache
7726 target memory. By default the description of memory regions is
7727 fetched from the target (if the current target supports this), but the
7728 user can override the fetched regions.
7730 Defined memory regions can be individually enabled and disabled. When a
7731 memory region is disabled, @value{GDBN} uses the default attributes when
7732 accessing memory in that region. Similarly, if no memory regions have
7733 been defined, @value{GDBN} uses the default attributes when accessing
7736 When a memory region is defined, it is given a number to identify it;
7737 to enable, disable, or remove a memory region, you specify that number.
7741 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7742 Define a memory region bounded by @var{lower} and @var{upper} with
7743 attributes @var{attributes}@dots{}, and add it to the list of regions
7744 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7745 case: it is treated as the target's maximum memory address.
7746 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7749 Discard any user changes to the memory regions and use target-supplied
7750 regions, if available, or no regions if the target does not support.
7753 @item delete mem @var{nums}@dots{}
7754 Remove memory regions @var{nums}@dots{} from the list of regions
7755 monitored by @value{GDBN}.
7758 @item disable mem @var{nums}@dots{}
7759 Disable monitoring of memory regions @var{nums}@dots{}.
7760 A disabled memory region is not forgotten.
7761 It may be enabled again later.
7764 @item enable mem @var{nums}@dots{}
7765 Enable monitoring of memory regions @var{nums}@dots{}.
7769 Print a table of all defined memory regions, with the following columns
7773 @item Memory Region Number
7774 @item Enabled or Disabled.
7775 Enabled memory regions are marked with @samp{y}.
7776 Disabled memory regions are marked with @samp{n}.
7779 The address defining the inclusive lower bound of the memory region.
7782 The address defining the exclusive upper bound of the memory region.
7785 The list of attributes set for this memory region.
7790 @subsection Attributes
7792 @subsubsection Memory Access Mode
7793 The access mode attributes set whether @value{GDBN} may make read or
7794 write accesses to a memory region.
7796 While these attributes prevent @value{GDBN} from performing invalid
7797 memory accesses, they do nothing to prevent the target system, I/O DMA,
7798 etc.@: from accessing memory.
7802 Memory is read only.
7804 Memory is write only.
7806 Memory is read/write. This is the default.
7809 @subsubsection Memory Access Size
7810 The access size attribute tells @value{GDBN} to use specific sized
7811 accesses in the memory region. Often memory mapped device registers
7812 require specific sized accesses. If no access size attribute is
7813 specified, @value{GDBN} may use accesses of any size.
7817 Use 8 bit memory accesses.
7819 Use 16 bit memory accesses.
7821 Use 32 bit memory accesses.
7823 Use 64 bit memory accesses.
7826 @c @subsubsection Hardware/Software Breakpoints
7827 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7828 @c will use hardware or software breakpoints for the internal breakpoints
7829 @c used by the step, next, finish, until, etc. commands.
7833 @c Always use hardware breakpoints
7834 @c @item swbreak (default)
7837 @subsubsection Data Cache
7838 The data cache attributes set whether @value{GDBN} will cache target
7839 memory. While this generally improves performance by reducing debug
7840 protocol overhead, it can lead to incorrect results because @value{GDBN}
7841 does not know about volatile variables or memory mapped device
7846 Enable @value{GDBN} to cache target memory.
7848 Disable @value{GDBN} from caching target memory. This is the default.
7851 @subsection Memory Access Checking
7852 @value{GDBN} can be instructed to refuse accesses to memory that is
7853 not explicitly described. This can be useful if accessing such
7854 regions has undesired effects for a specific target, or to provide
7855 better error checking. The following commands control this behaviour.
7858 @kindex set mem inaccessible-by-default
7859 @item set mem inaccessible-by-default [on|off]
7860 If @code{on} is specified, make @value{GDBN} treat memory not
7861 explicitly described by the memory ranges as non-existent and refuse accesses
7862 to such memory. The checks are only performed if there's at least one
7863 memory range defined. If @code{off} is specified, make @value{GDBN}
7864 treat the memory not explicitly described by the memory ranges as RAM.
7865 The default value is @code{on}.
7866 @kindex show mem inaccessible-by-default
7867 @item show mem inaccessible-by-default
7868 Show the current handling of accesses to unknown memory.
7872 @c @subsubsection Memory Write Verification
7873 @c The memory write verification attributes set whether @value{GDBN}
7874 @c will re-reads data after each write to verify the write was successful.
7878 @c @item noverify (default)
7881 @node Dump/Restore Files
7882 @section Copy Between Memory and a File
7883 @cindex dump/restore files
7884 @cindex append data to a file
7885 @cindex dump data to a file
7886 @cindex restore data from a file
7888 You can use the commands @code{dump}, @code{append}, and
7889 @code{restore} to copy data between target memory and a file. The
7890 @code{dump} and @code{append} commands write data to a file, and the
7891 @code{restore} command reads data from a file back into the inferior's
7892 memory. Files may be in binary, Motorola S-record, Intel hex, or
7893 Tektronix Hex format; however, @value{GDBN} can only append to binary
7899 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7900 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7901 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7902 or the value of @var{expr}, to @var{filename} in the given format.
7904 The @var{format} parameter may be any one of:
7911 Motorola S-record format.
7913 Tektronix Hex format.
7916 @value{GDBN} uses the same definitions of these formats as the
7917 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7918 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7922 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7923 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7924 Append the contents of memory from @var{start_addr} to @var{end_addr},
7925 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7926 (@value{GDBN} can only append data to files in raw binary form.)
7929 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7930 Restore the contents of file @var{filename} into memory. The
7931 @code{restore} command can automatically recognize any known @sc{bfd}
7932 file format, except for raw binary. To restore a raw binary file you
7933 must specify the optional keyword @code{binary} after the filename.
7935 If @var{bias} is non-zero, its value will be added to the addresses
7936 contained in the file. Binary files always start at address zero, so
7937 they will be restored at address @var{bias}. Other bfd files have
7938 a built-in location; they will be restored at offset @var{bias}
7941 If @var{start} and/or @var{end} are non-zero, then only data between
7942 file offset @var{start} and file offset @var{end} will be restored.
7943 These offsets are relative to the addresses in the file, before
7944 the @var{bias} argument is applied.
7948 @node Core File Generation
7949 @section How to Produce a Core File from Your Program
7950 @cindex dump core from inferior
7952 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7953 image of a running process and its process status (register values
7954 etc.). Its primary use is post-mortem debugging of a program that
7955 crashed while it ran outside a debugger. A program that crashes
7956 automatically produces a core file, unless this feature is disabled by
7957 the user. @xref{Files}, for information on invoking @value{GDBN} in
7958 the post-mortem debugging mode.
7960 Occasionally, you may wish to produce a core file of the program you
7961 are debugging in order to preserve a snapshot of its state.
7962 @value{GDBN} has a special command for that.
7966 @kindex generate-core-file
7967 @item generate-core-file [@var{file}]
7968 @itemx gcore [@var{file}]
7969 Produce a core dump of the inferior process. The optional argument
7970 @var{file} specifies the file name where to put the core dump. If not
7971 specified, the file name defaults to @file{core.@var{pid}}, where
7972 @var{pid} is the inferior process ID.
7974 Note that this command is implemented only for some systems (as of
7975 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7978 @node Character Sets
7979 @section Character Sets
7980 @cindex character sets
7982 @cindex translating between character sets
7983 @cindex host character set
7984 @cindex target character set
7986 If the program you are debugging uses a different character set to
7987 represent characters and strings than the one @value{GDBN} uses itself,
7988 @value{GDBN} can automatically translate between the character sets for
7989 you. The character set @value{GDBN} uses we call the @dfn{host
7990 character set}; the one the inferior program uses we call the
7991 @dfn{target character set}.
7993 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7994 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7995 remote protocol (@pxref{Remote Debugging}) to debug a program
7996 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7997 then the host character set is Latin-1, and the target character set is
7998 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7999 target-charset EBCDIC-US}, then @value{GDBN} translates between
8000 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8001 character and string literals in expressions.
8003 @value{GDBN} has no way to automatically recognize which character set
8004 the inferior program uses; you must tell it, using the @code{set
8005 target-charset} command, described below.
8007 Here are the commands for controlling @value{GDBN}'s character set
8011 @item set target-charset @var{charset}
8012 @kindex set target-charset
8013 Set the current target character set to @var{charset}. To display the
8014 list of supported target character sets, type
8015 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8017 @item set host-charset @var{charset}
8018 @kindex set host-charset
8019 Set the current host character set to @var{charset}.
8021 By default, @value{GDBN} uses a host character set appropriate to the
8022 system it is running on; you can override that default using the
8023 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8024 automatically determine the appropriate host character set. In this
8025 case, @value{GDBN} uses @samp{UTF-8}.
8027 @value{GDBN} can only use certain character sets as its host character
8028 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8029 @value{GDBN} will list the host character sets it supports.
8031 @item set charset @var{charset}
8033 Set the current host and target character sets to @var{charset}. As
8034 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8035 @value{GDBN} will list the names of the character sets that can be used
8036 for both host and target.
8039 @kindex show charset
8040 Show the names of the current host and target character sets.
8042 @item show host-charset
8043 @kindex show host-charset
8044 Show the name of the current host character set.
8046 @item show target-charset
8047 @kindex show target-charset
8048 Show the name of the current target character set.
8050 @item set target-wide-charset @var{charset}
8051 @kindex set target-wide-charset
8052 Set the current target's wide character set to @var{charset}. This is
8053 the character set used by the target's @code{wchar_t} type. To
8054 display the list of supported wide character sets, type
8055 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8057 @item show target-wide-charset
8058 @kindex show target-wide-charset
8059 Show the name of the current target's wide character set.
8062 Here is an example of @value{GDBN}'s character set support in action.
8063 Assume that the following source code has been placed in the file
8064 @file{charset-test.c}:
8070 = @{72, 101, 108, 108, 111, 44, 32, 119,
8071 111, 114, 108, 100, 33, 10, 0@};
8072 char ibm1047_hello[]
8073 = @{200, 133, 147, 147, 150, 107, 64, 166,
8074 150, 153, 147, 132, 90, 37, 0@};
8078 printf ("Hello, world!\n");
8082 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8083 containing the string @samp{Hello, world!} followed by a newline,
8084 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8086 We compile the program, and invoke the debugger on it:
8089 $ gcc -g charset-test.c -o charset-test
8090 $ gdb -nw charset-test
8091 GNU gdb 2001-12-19-cvs
8092 Copyright 2001 Free Software Foundation, Inc.
8097 We can use the @code{show charset} command to see what character sets
8098 @value{GDBN} is currently using to interpret and display characters and
8102 (@value{GDBP}) show charset
8103 The current host and target character set is `ISO-8859-1'.
8107 For the sake of printing this manual, let's use @sc{ascii} as our
8108 initial character set:
8110 (@value{GDBP}) set charset ASCII
8111 (@value{GDBP}) show charset
8112 The current host and target character set is `ASCII'.
8116 Let's assume that @sc{ascii} is indeed the correct character set for our
8117 host system --- in other words, let's assume that if @value{GDBN} prints
8118 characters using the @sc{ascii} character set, our terminal will display
8119 them properly. Since our current target character set is also
8120 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8123 (@value{GDBP}) print ascii_hello
8124 $1 = 0x401698 "Hello, world!\n"
8125 (@value{GDBP}) print ascii_hello[0]
8130 @value{GDBN} uses the target character set for character and string
8131 literals you use in expressions:
8134 (@value{GDBP}) print '+'
8139 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8142 @value{GDBN} relies on the user to tell it which character set the
8143 target program uses. If we print @code{ibm1047_hello} while our target
8144 character set is still @sc{ascii}, we get jibberish:
8147 (@value{GDBP}) print ibm1047_hello
8148 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8149 (@value{GDBP}) print ibm1047_hello[0]
8154 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8155 @value{GDBN} tells us the character sets it supports:
8158 (@value{GDBP}) set target-charset
8159 ASCII EBCDIC-US IBM1047 ISO-8859-1
8160 (@value{GDBP}) set target-charset
8163 We can select @sc{ibm1047} as our target character set, and examine the
8164 program's strings again. Now the @sc{ascii} string is wrong, but
8165 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8166 target character set, @sc{ibm1047}, to the host character set,
8167 @sc{ascii}, and they display correctly:
8170 (@value{GDBP}) set target-charset IBM1047
8171 (@value{GDBP}) show charset
8172 The current host character set is `ASCII'.
8173 The current target character set is `IBM1047'.
8174 (@value{GDBP}) print ascii_hello
8175 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8176 (@value{GDBP}) print ascii_hello[0]
8178 (@value{GDBP}) print ibm1047_hello
8179 $8 = 0x4016a8 "Hello, world!\n"
8180 (@value{GDBP}) print ibm1047_hello[0]
8185 As above, @value{GDBN} uses the target character set for character and
8186 string literals you use in expressions:
8189 (@value{GDBP}) print '+'
8194 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8197 @node Caching Remote Data
8198 @section Caching Data of Remote Targets
8199 @cindex caching data of remote targets
8201 @value{GDBN} can cache data exchanged between the debugger and a
8202 remote target (@pxref{Remote Debugging}). Such caching generally improves
8203 performance, because it reduces the overhead of the remote protocol by
8204 bundling memory reads and writes into large chunks. Unfortunately,
8205 @value{GDBN} does not currently know anything about volatile
8206 registers, and thus data caching will produce incorrect results when
8207 volatile registers are in use.
8210 @kindex set remotecache
8211 @item set remotecache on
8212 @itemx set remotecache off
8213 Set caching state for remote targets. When @code{ON}, use data
8214 caching. By default, this option is @code{OFF}.
8216 @kindex show remotecache
8217 @item show remotecache
8218 Show the current state of data caching for remote targets.
8222 Print the information about the data cache performance. The
8223 information displayed includes: the dcache width and depth; and for
8224 each cache line, how many times it was referenced, and its data and
8225 state (invalid, dirty, valid). This command is useful for debugging
8226 the data cache operation.
8229 @node Searching Memory
8230 @section Search Memory
8231 @cindex searching memory
8233 Memory can be searched for a particular sequence of bytes with the
8234 @code{find} command.
8238 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8239 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8240 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8241 etc. The search begins at address @var{start_addr} and continues for either
8242 @var{len} bytes or through to @var{end_addr} inclusive.
8245 @var{s} and @var{n} are optional parameters.
8246 They may be specified in either order, apart or together.
8249 @item @var{s}, search query size
8250 The size of each search query value.
8256 halfwords (two bytes)
8260 giant words (eight bytes)
8263 All values are interpreted in the current language.
8264 This means, for example, that if the current source language is C/C@t{++}
8265 then searching for the string ``hello'' includes the trailing '\0'.
8267 If the value size is not specified, it is taken from the
8268 value's type in the current language.
8269 This is useful when one wants to specify the search
8270 pattern as a mixture of types.
8271 Note that this means, for example, that in the case of C-like languages
8272 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8273 which is typically four bytes.
8275 @item @var{n}, maximum number of finds
8276 The maximum number of matches to print. The default is to print all finds.
8279 You can use strings as search values. Quote them with double-quotes
8281 The string value is copied into the search pattern byte by byte,
8282 regardless of the endianness of the target and the size specification.
8284 The address of each match found is printed as well as a count of the
8285 number of matches found.
8287 The address of the last value found is stored in convenience variable
8289 A count of the number of matches is stored in @samp{$numfound}.
8291 For example, if stopped at the @code{printf} in this function:
8297 static char hello[] = "hello-hello";
8298 static struct @{ char c; short s; int i; @}
8299 __attribute__ ((packed)) mixed
8300 = @{ 'c', 0x1234, 0x87654321 @};
8301 printf ("%s\n", hello);
8306 you get during debugging:
8309 (gdb) find &hello[0], +sizeof(hello), "hello"
8310 0x804956d <hello.1620+6>
8312 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8313 0x8049567 <hello.1620>
8314 0x804956d <hello.1620+6>
8316 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8317 0x8049567 <hello.1620>
8319 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8320 0x8049560 <mixed.1625>
8322 (gdb) print $numfound
8325 $2 = (void *) 0x8049560
8329 @chapter C Preprocessor Macros
8331 Some languages, such as C and C@t{++}, provide a way to define and invoke
8332 ``preprocessor macros'' which expand into strings of tokens.
8333 @value{GDBN} can evaluate expressions containing macro invocations, show
8334 the result of macro expansion, and show a macro's definition, including
8335 where it was defined.
8337 You may need to compile your program specially to provide @value{GDBN}
8338 with information about preprocessor macros. Most compilers do not
8339 include macros in their debugging information, even when you compile
8340 with the @option{-g} flag. @xref{Compilation}.
8342 A program may define a macro at one point, remove that definition later,
8343 and then provide a different definition after that. Thus, at different
8344 points in the program, a macro may have different definitions, or have
8345 no definition at all. If there is a current stack frame, @value{GDBN}
8346 uses the macros in scope at that frame's source code line. Otherwise,
8347 @value{GDBN} uses the macros in scope at the current listing location;
8350 Whenever @value{GDBN} evaluates an expression, it always expands any
8351 macro invocations present in the expression. @value{GDBN} also provides
8352 the following commands for working with macros explicitly.
8356 @kindex macro expand
8357 @cindex macro expansion, showing the results of preprocessor
8358 @cindex preprocessor macro expansion, showing the results of
8359 @cindex expanding preprocessor macros
8360 @item macro expand @var{expression}
8361 @itemx macro exp @var{expression}
8362 Show the results of expanding all preprocessor macro invocations in
8363 @var{expression}. Since @value{GDBN} simply expands macros, but does
8364 not parse the result, @var{expression} need not be a valid expression;
8365 it can be any string of tokens.
8368 @item macro expand-once @var{expression}
8369 @itemx macro exp1 @var{expression}
8370 @cindex expand macro once
8371 @i{(This command is not yet implemented.)} Show the results of
8372 expanding those preprocessor macro invocations that appear explicitly in
8373 @var{expression}. Macro invocations appearing in that expansion are
8374 left unchanged. This command allows you to see the effect of a
8375 particular macro more clearly, without being confused by further
8376 expansions. Since @value{GDBN} simply expands macros, but does not
8377 parse the result, @var{expression} need not be a valid expression; it
8378 can be any string of tokens.
8381 @cindex macro definition, showing
8382 @cindex definition, showing a macro's
8383 @item info macro @var{macro}
8384 Show the definition of the macro named @var{macro}, and describe the
8385 source location or compiler command-line where that definition was established.
8387 @kindex macro define
8388 @cindex user-defined macros
8389 @cindex defining macros interactively
8390 @cindex macros, user-defined
8391 @item macro define @var{macro} @var{replacement-list}
8392 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8393 Introduce a definition for a preprocessor macro named @var{macro},
8394 invocations of which are replaced by the tokens given in
8395 @var{replacement-list}. The first form of this command defines an
8396 ``object-like'' macro, which takes no arguments; the second form
8397 defines a ``function-like'' macro, which takes the arguments given in
8400 A definition introduced by this command is in scope in every
8401 expression evaluated in @value{GDBN}, until it is removed with the
8402 @code{macro undef} command, described below. The definition overrides
8403 all definitions for @var{macro} present in the program being debugged,
8404 as well as any previous user-supplied definition.
8407 @item macro undef @var{macro}
8408 Remove any user-supplied definition for the macro named @var{macro}.
8409 This command only affects definitions provided with the @code{macro
8410 define} command, described above; it cannot remove definitions present
8411 in the program being debugged.
8415 List all the macros defined using the @code{macro define} command.
8418 @cindex macros, example of debugging with
8419 Here is a transcript showing the above commands in action. First, we
8420 show our source files:
8428 #define ADD(x) (M + x)
8433 printf ("Hello, world!\n");
8435 printf ("We're so creative.\n");
8437 printf ("Goodbye, world!\n");
8444 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8445 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8446 compiler includes information about preprocessor macros in the debugging
8450 $ gcc -gdwarf-2 -g3 sample.c -o sample
8454 Now, we start @value{GDBN} on our sample program:
8458 GNU gdb 2002-05-06-cvs
8459 Copyright 2002 Free Software Foundation, Inc.
8460 GDB is free software, @dots{}
8464 We can expand macros and examine their definitions, even when the
8465 program is not running. @value{GDBN} uses the current listing position
8466 to decide which macro definitions are in scope:
8469 (@value{GDBP}) list main
8472 5 #define ADD(x) (M + x)
8477 10 printf ("Hello, world!\n");
8479 12 printf ("We're so creative.\n");
8480 (@value{GDBP}) info macro ADD
8481 Defined at /home/jimb/gdb/macros/play/sample.c:5
8482 #define ADD(x) (M + x)
8483 (@value{GDBP}) info macro Q
8484 Defined at /home/jimb/gdb/macros/play/sample.h:1
8485 included at /home/jimb/gdb/macros/play/sample.c:2
8487 (@value{GDBP}) macro expand ADD(1)
8488 expands to: (42 + 1)
8489 (@value{GDBP}) macro expand-once ADD(1)
8490 expands to: once (M + 1)
8494 In the example above, note that @code{macro expand-once} expands only
8495 the macro invocation explicit in the original text --- the invocation of
8496 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8497 which was introduced by @code{ADD}.
8499 Once the program is running, @value{GDBN} uses the macro definitions in
8500 force at the source line of the current stack frame:
8503 (@value{GDBP}) break main
8504 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8506 Starting program: /home/jimb/gdb/macros/play/sample
8508 Breakpoint 1, main () at sample.c:10
8509 10 printf ("Hello, world!\n");
8513 At line 10, the definition of the macro @code{N} at line 9 is in force:
8516 (@value{GDBP}) info macro N
8517 Defined at /home/jimb/gdb/macros/play/sample.c:9
8519 (@value{GDBP}) macro expand N Q M
8521 (@value{GDBP}) print N Q M
8526 As we step over directives that remove @code{N}'s definition, and then
8527 give it a new definition, @value{GDBN} finds the definition (or lack
8528 thereof) in force at each point:
8533 12 printf ("We're so creative.\n");
8534 (@value{GDBP}) info macro N
8535 The symbol `N' has no definition as a C/C++ preprocessor macro
8536 at /home/jimb/gdb/macros/play/sample.c:12
8539 14 printf ("Goodbye, world!\n");
8540 (@value{GDBP}) info macro N
8541 Defined at /home/jimb/gdb/macros/play/sample.c:13
8543 (@value{GDBP}) macro expand N Q M
8544 expands to: 1729 < 42
8545 (@value{GDBP}) print N Q M
8550 In addition to source files, macros can be defined on the compilation command
8551 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
8552 such a way, @value{GDBN} displays the location of their definition as line zero
8553 of the source file submitted to the compiler.
8556 (@value{GDBP}) info macro __STDC__
8557 Defined at /home/jimb/gdb/macros/play/sample.c:0
8564 @chapter Tracepoints
8565 @c This chapter is based on the documentation written by Michael
8566 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8569 In some applications, it is not feasible for the debugger to interrupt
8570 the program's execution long enough for the developer to learn
8571 anything helpful about its behavior. If the program's correctness
8572 depends on its real-time behavior, delays introduced by a debugger
8573 might cause the program to change its behavior drastically, or perhaps
8574 fail, even when the code itself is correct. It is useful to be able
8575 to observe the program's behavior without interrupting it.
8577 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8578 specify locations in the program, called @dfn{tracepoints}, and
8579 arbitrary expressions to evaluate when those tracepoints are reached.
8580 Later, using the @code{tfind} command, you can examine the values
8581 those expressions had when the program hit the tracepoints. The
8582 expressions may also denote objects in memory---structures or arrays,
8583 for example---whose values @value{GDBN} should record; while visiting
8584 a particular tracepoint, you may inspect those objects as if they were
8585 in memory at that moment. However, because @value{GDBN} records these
8586 values without interacting with you, it can do so quickly and
8587 unobtrusively, hopefully not disturbing the program's behavior.
8589 The tracepoint facility is currently available only for remote
8590 targets. @xref{Targets}. In addition, your remote target must know
8591 how to collect trace data. This functionality is implemented in the
8592 remote stub; however, none of the stubs distributed with @value{GDBN}
8593 support tracepoints as of this writing. The format of the remote
8594 packets used to implement tracepoints are described in @ref{Tracepoint
8597 This chapter describes the tracepoint commands and features.
8601 * Analyze Collected Data::
8602 * Tracepoint Variables::
8605 @node Set Tracepoints
8606 @section Commands to Set Tracepoints
8608 Before running such a @dfn{trace experiment}, an arbitrary number of
8609 tracepoints can be set. A tracepoint is actually a special type of
8610 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
8611 standard breakpoint commands. For instance, as with breakpoints,
8612 tracepoint numbers are successive integers starting from one, and many
8613 of the commands associated with tracepoints take the tracepoint number
8614 as their argument, to identify which tracepoint to work on.
8616 For each tracepoint, you can specify, in advance, some arbitrary set
8617 of data that you want the target to collect in the trace buffer when
8618 it hits that tracepoint. The collected data can include registers,
8619 local variables, or global data. Later, you can use @value{GDBN}
8620 commands to examine the values these data had at the time the
8623 Tracepoints do not support every breakpoint feature. Conditional
8624 expressions and ignore counts on tracepoints have no effect, and
8625 tracepoints cannot run @value{GDBN} commands when they are
8626 hit. Tracepoints may not be thread-specific either.
8628 This section describes commands to set tracepoints and associated
8629 conditions and actions.
8632 * Create and Delete Tracepoints::
8633 * Enable and Disable Tracepoints::
8634 * Tracepoint Passcounts::
8635 * Tracepoint Actions::
8636 * Listing Tracepoints::
8637 * Starting and Stopping Trace Experiments::
8640 @node Create and Delete Tracepoints
8641 @subsection Create and Delete Tracepoints
8644 @cindex set tracepoint
8646 @item trace @var{location}
8647 The @code{trace} command is very similar to the @code{break} command.
8648 Its argument @var{location} can be a source line, a function name, or
8649 an address in the target program. @xref{Specify Location}. The
8650 @code{trace} command defines a tracepoint, which is a point in the
8651 target program where the debugger will briefly stop, collect some
8652 data, and then allow the program to continue. Setting a tracepoint or
8653 changing its actions doesn't take effect until the next @code{tstart}
8654 command, and once a trace experiment is running, further changes will
8655 not have any effect until the next trace experiment starts.
8657 Here are some examples of using the @code{trace} command:
8660 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8662 (@value{GDBP}) @b{trace +2} // 2 lines forward
8664 (@value{GDBP}) @b{trace my_function} // first source line of function
8666 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8668 (@value{GDBP}) @b{trace *0x2117c4} // an address
8672 You can abbreviate @code{trace} as @code{tr}.
8675 @cindex last tracepoint number
8676 @cindex recent tracepoint number
8677 @cindex tracepoint number
8678 The convenience variable @code{$tpnum} records the tracepoint number
8679 of the most recently set tracepoint.
8681 @kindex delete tracepoint
8682 @cindex tracepoint deletion
8683 @item delete tracepoint @r{[}@var{num}@r{]}
8684 Permanently delete one or more tracepoints. With no argument, the
8685 default is to delete all tracepoints. Note that the regular
8686 @code{delete} command can remove tracepoints also.
8691 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8693 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8697 You can abbreviate this command as @code{del tr}.
8700 @node Enable and Disable Tracepoints
8701 @subsection Enable and Disable Tracepoints
8703 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
8706 @kindex disable tracepoint
8707 @item disable tracepoint @r{[}@var{num}@r{]}
8708 Disable tracepoint @var{num}, or all tracepoints if no argument
8709 @var{num} is given. A disabled tracepoint will have no effect during
8710 the next trace experiment, but it is not forgotten. You can re-enable
8711 a disabled tracepoint using the @code{enable tracepoint} command.
8713 @kindex enable tracepoint
8714 @item enable tracepoint @r{[}@var{num}@r{]}
8715 Enable tracepoint @var{num}, or all tracepoints. The enabled
8716 tracepoints will become effective the next time a trace experiment is
8720 @node Tracepoint Passcounts
8721 @subsection Tracepoint Passcounts
8725 @cindex tracepoint pass count
8726 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8727 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8728 automatically stop a trace experiment. If a tracepoint's passcount is
8729 @var{n}, then the trace experiment will be automatically stopped on
8730 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8731 @var{num} is not specified, the @code{passcount} command sets the
8732 passcount of the most recently defined tracepoint. If no passcount is
8733 given, the trace experiment will run until stopped explicitly by the
8739 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8740 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8742 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8743 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8744 (@value{GDBP}) @b{trace foo}
8745 (@value{GDBP}) @b{pass 3}
8746 (@value{GDBP}) @b{trace bar}
8747 (@value{GDBP}) @b{pass 2}
8748 (@value{GDBP}) @b{trace baz}
8749 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8750 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8751 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8752 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8756 @node Tracepoint Actions
8757 @subsection Tracepoint Action Lists
8761 @cindex tracepoint actions
8762 @item actions @r{[}@var{num}@r{]}
8763 This command will prompt for a list of actions to be taken when the
8764 tracepoint is hit. If the tracepoint number @var{num} is not
8765 specified, this command sets the actions for the one that was most
8766 recently defined (so that you can define a tracepoint and then say
8767 @code{actions} without bothering about its number). You specify the
8768 actions themselves on the following lines, one action at a time, and
8769 terminate the actions list with a line containing just @code{end}. So
8770 far, the only defined actions are @code{collect} and
8771 @code{while-stepping}.
8773 @cindex remove actions from a tracepoint
8774 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8775 and follow it immediately with @samp{end}.
8778 (@value{GDBP}) @b{collect @var{data}} // collect some data
8780 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8782 (@value{GDBP}) @b{end} // signals the end of actions.
8785 In the following example, the action list begins with @code{collect}
8786 commands indicating the things to be collected when the tracepoint is
8787 hit. Then, in order to single-step and collect additional data
8788 following the tracepoint, a @code{while-stepping} command is used,
8789 followed by the list of things to be collected while stepping. The
8790 @code{while-stepping} command is terminated by its own separate
8791 @code{end} command. Lastly, the action list is terminated by an
8795 (@value{GDBP}) @b{trace foo}
8796 (@value{GDBP}) @b{actions}
8797 Enter actions for tracepoint 1, one per line:
8806 @kindex collect @r{(tracepoints)}
8807 @item collect @var{expr1}, @var{expr2}, @dots{}
8808 Collect values of the given expressions when the tracepoint is hit.
8809 This command accepts a comma-separated list of any valid expressions.
8810 In addition to global, static, or local variables, the following
8811 special arguments are supported:
8815 collect all registers
8818 collect all function arguments
8821 collect all local variables.
8824 You can give several consecutive @code{collect} commands, each one
8825 with a single argument, or one @code{collect} command with several
8826 arguments separated by commas: the effect is the same.
8828 The command @code{info scope} (@pxref{Symbols, info scope}) is
8829 particularly useful for figuring out what data to collect.
8831 @kindex while-stepping @r{(tracepoints)}
8832 @item while-stepping @var{n}
8833 Perform @var{n} single-step traces after the tracepoint, collecting
8834 new data at each step. The @code{while-stepping} command is
8835 followed by the list of what to collect while stepping (followed by
8836 its own @code{end} command):
8840 > collect $regs, myglobal
8846 You may abbreviate @code{while-stepping} as @code{ws} or
8850 @node Listing Tracepoints
8851 @subsection Listing Tracepoints
8854 @kindex info tracepoints
8856 @cindex information about tracepoints
8857 @item info tracepoints @r{[}@var{num}@r{]}
8858 Display information about the tracepoint @var{num}. If you don't
8859 specify a tracepoint number, displays information about all the
8860 tracepoints defined so far. The format is similar to that used for
8861 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
8862 command, simply restricting itself to tracepoints.
8864 A tracepoint's listing may include additional information specific to
8869 its passcount as given by the @code{passcount @var{n}} command
8871 its step count as given by the @code{while-stepping @var{n}} command
8873 its action list as given by the @code{actions} command. The actions
8874 are prefixed with an @samp{A} so as to distinguish them from commands.
8878 (@value{GDBP}) @b{info trace}
8879 Num Type Disp Enb Address What
8880 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
8884 A collect globfoo, $regs
8892 This command can be abbreviated @code{info tp}.
8895 @node Starting and Stopping Trace Experiments
8896 @subsection Starting and Stopping Trace Experiments
8900 @cindex start a new trace experiment
8901 @cindex collected data discarded
8903 This command takes no arguments. It starts the trace experiment, and
8904 begins collecting data. This has the side effect of discarding all
8905 the data collected in the trace buffer during the previous trace
8909 @cindex stop a running trace experiment
8911 This command takes no arguments. It ends the trace experiment, and
8912 stops collecting data.
8914 @strong{Note}: a trace experiment and data collection may stop
8915 automatically if any tracepoint's passcount is reached
8916 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8919 @cindex status of trace data collection
8920 @cindex trace experiment, status of
8922 This command displays the status of the current trace data
8926 Here is an example of the commands we described so far:
8929 (@value{GDBP}) @b{trace gdb_c_test}
8930 (@value{GDBP}) @b{actions}
8931 Enter actions for tracepoint #1, one per line.
8932 > collect $regs,$locals,$args
8937 (@value{GDBP}) @b{tstart}
8938 [time passes @dots{}]
8939 (@value{GDBP}) @b{tstop}
8943 @node Analyze Collected Data
8944 @section Using the Collected Data
8946 After the tracepoint experiment ends, you use @value{GDBN} commands
8947 for examining the trace data. The basic idea is that each tracepoint
8948 collects a trace @dfn{snapshot} every time it is hit and another
8949 snapshot every time it single-steps. All these snapshots are
8950 consecutively numbered from zero and go into a buffer, and you can
8951 examine them later. The way you examine them is to @dfn{focus} on a
8952 specific trace snapshot. When the remote stub is focused on a trace
8953 snapshot, it will respond to all @value{GDBN} requests for memory and
8954 registers by reading from the buffer which belongs to that snapshot,
8955 rather than from @emph{real} memory or registers of the program being
8956 debugged. This means that @strong{all} @value{GDBN} commands
8957 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8958 behave as if we were currently debugging the program state as it was
8959 when the tracepoint occurred. Any requests for data that are not in
8960 the buffer will fail.
8963 * tfind:: How to select a trace snapshot
8964 * tdump:: How to display all data for a snapshot
8965 * save-tracepoints:: How to save tracepoints for a future run
8969 @subsection @code{tfind @var{n}}
8972 @cindex select trace snapshot
8973 @cindex find trace snapshot
8974 The basic command for selecting a trace snapshot from the buffer is
8975 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8976 counting from zero. If no argument @var{n} is given, the next
8977 snapshot is selected.
8979 Here are the various forms of using the @code{tfind} command.
8983 Find the first snapshot in the buffer. This is a synonym for
8984 @code{tfind 0} (since 0 is the number of the first snapshot).
8987 Stop debugging trace snapshots, resume @emph{live} debugging.
8990 Same as @samp{tfind none}.
8993 No argument means find the next trace snapshot.
8996 Find the previous trace snapshot before the current one. This permits
8997 retracing earlier steps.
8999 @item tfind tracepoint @var{num}
9000 Find the next snapshot associated with tracepoint @var{num}. Search
9001 proceeds forward from the last examined trace snapshot. If no
9002 argument @var{num} is given, it means find the next snapshot collected
9003 for the same tracepoint as the current snapshot.
9005 @item tfind pc @var{addr}
9006 Find the next snapshot associated with the value @var{addr} of the
9007 program counter. Search proceeds forward from the last examined trace
9008 snapshot. If no argument @var{addr} is given, it means find the next
9009 snapshot with the same value of PC as the current snapshot.
9011 @item tfind outside @var{addr1}, @var{addr2}
9012 Find the next snapshot whose PC is outside the given range of
9015 @item tfind range @var{addr1}, @var{addr2}
9016 Find the next snapshot whose PC is between @var{addr1} and
9017 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
9019 @item tfind line @r{[}@var{file}:@r{]}@var{n}
9020 Find the next snapshot associated with the source line @var{n}. If
9021 the optional argument @var{file} is given, refer to line @var{n} in
9022 that source file. Search proceeds forward from the last examined
9023 trace snapshot. If no argument @var{n} is given, it means find the
9024 next line other than the one currently being examined; thus saying
9025 @code{tfind line} repeatedly can appear to have the same effect as
9026 stepping from line to line in a @emph{live} debugging session.
9029 The default arguments for the @code{tfind} commands are specifically
9030 designed to make it easy to scan through the trace buffer. For
9031 instance, @code{tfind} with no argument selects the next trace
9032 snapshot, and @code{tfind -} with no argument selects the previous
9033 trace snapshot. So, by giving one @code{tfind} command, and then
9034 simply hitting @key{RET} repeatedly you can examine all the trace
9035 snapshots in order. Or, by saying @code{tfind -} and then hitting
9036 @key{RET} repeatedly you can examine the snapshots in reverse order.
9037 The @code{tfind line} command with no argument selects the snapshot
9038 for the next source line executed. The @code{tfind pc} command with
9039 no argument selects the next snapshot with the same program counter
9040 (PC) as the current frame. The @code{tfind tracepoint} command with
9041 no argument selects the next trace snapshot collected by the same
9042 tracepoint as the current one.
9044 In addition to letting you scan through the trace buffer manually,
9045 these commands make it easy to construct @value{GDBN} scripts that
9046 scan through the trace buffer and print out whatever collected data
9047 you are interested in. Thus, if we want to examine the PC, FP, and SP
9048 registers from each trace frame in the buffer, we can say this:
9051 (@value{GDBP}) @b{tfind start}
9052 (@value{GDBP}) @b{while ($trace_frame != -1)}
9053 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
9054 $trace_frame, $pc, $sp, $fp
9058 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
9059 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
9060 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
9061 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
9062 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
9063 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
9064 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
9065 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
9066 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
9067 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
9068 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
9071 Or, if we want to examine the variable @code{X} at each source line in
9075 (@value{GDBP}) @b{tfind start}
9076 (@value{GDBP}) @b{while ($trace_frame != -1)}
9077 > printf "Frame %d, X == %d\n", $trace_frame, X
9087 @subsection @code{tdump}
9089 @cindex dump all data collected at tracepoint
9090 @cindex tracepoint data, display
9092 This command takes no arguments. It prints all the data collected at
9093 the current trace snapshot.
9096 (@value{GDBP}) @b{trace 444}
9097 (@value{GDBP}) @b{actions}
9098 Enter actions for tracepoint #2, one per line:
9099 > collect $regs, $locals, $args, gdb_long_test
9102 (@value{GDBP}) @b{tstart}
9104 (@value{GDBP}) @b{tfind line 444}
9105 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
9107 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
9109 (@value{GDBP}) @b{tdump}
9110 Data collected at tracepoint 2, trace frame 1:
9111 d0 0xc4aa0085 -995491707
9115 d4 0x71aea3d 119204413
9120 a1 0x3000668 50333288
9123 a4 0x3000698 50333336
9125 fp 0x30bf3c 0x30bf3c
9126 sp 0x30bf34 0x30bf34
9128 pc 0x20b2c8 0x20b2c8
9132 p = 0x20e5b4 "gdb-test"
9139 gdb_long_test = 17 '\021'
9144 @node save-tracepoints
9145 @subsection @code{save-tracepoints @var{filename}}
9146 @kindex save-tracepoints
9147 @cindex save tracepoints for future sessions
9149 This command saves all current tracepoint definitions together with
9150 their actions and passcounts, into a file @file{@var{filename}}
9151 suitable for use in a later debugging session. To read the saved
9152 tracepoint definitions, use the @code{source} command (@pxref{Command
9155 @node Tracepoint Variables
9156 @section Convenience Variables for Tracepoints
9157 @cindex tracepoint variables
9158 @cindex convenience variables for tracepoints
9161 @vindex $trace_frame
9162 @item (int) $trace_frame
9163 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9164 snapshot is selected.
9167 @item (int) $tracepoint
9168 The tracepoint for the current trace snapshot.
9171 @item (int) $trace_line
9172 The line number for the current trace snapshot.
9175 @item (char []) $trace_file
9176 The source file for the current trace snapshot.
9179 @item (char []) $trace_func
9180 The name of the function containing @code{$tracepoint}.
9183 Note: @code{$trace_file} is not suitable for use in @code{printf},
9184 use @code{output} instead.
9186 Here's a simple example of using these convenience variables for
9187 stepping through all the trace snapshots and printing some of their
9191 (@value{GDBP}) @b{tfind start}
9193 (@value{GDBP}) @b{while $trace_frame != -1}
9194 > output $trace_file
9195 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9201 @chapter Debugging Programs That Use Overlays
9204 If your program is too large to fit completely in your target system's
9205 memory, you can sometimes use @dfn{overlays} to work around this
9206 problem. @value{GDBN} provides some support for debugging programs that
9210 * How Overlays Work:: A general explanation of overlays.
9211 * Overlay Commands:: Managing overlays in @value{GDBN}.
9212 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9213 mapped by asking the inferior.
9214 * Overlay Sample Program:: A sample program using overlays.
9217 @node How Overlays Work
9218 @section How Overlays Work
9219 @cindex mapped overlays
9220 @cindex unmapped overlays
9221 @cindex load address, overlay's
9222 @cindex mapped address
9223 @cindex overlay area
9225 Suppose you have a computer whose instruction address space is only 64
9226 kilobytes long, but which has much more memory which can be accessed by
9227 other means: special instructions, segment registers, or memory
9228 management hardware, for example. Suppose further that you want to
9229 adapt a program which is larger than 64 kilobytes to run on this system.
9231 One solution is to identify modules of your program which are relatively
9232 independent, and need not call each other directly; call these modules
9233 @dfn{overlays}. Separate the overlays from the main program, and place
9234 their machine code in the larger memory. Place your main program in
9235 instruction memory, but leave at least enough space there to hold the
9236 largest overlay as well.
9238 Now, to call a function located in an overlay, you must first copy that
9239 overlay's machine code from the large memory into the space set aside
9240 for it in the instruction memory, and then jump to its entry point
9243 @c NB: In the below the mapped area's size is greater or equal to the
9244 @c size of all overlays. This is intentional to remind the developer
9245 @c that overlays don't necessarily need to be the same size.
9249 Data Instruction Larger
9250 Address Space Address Space Address Space
9251 +-----------+ +-----------+ +-----------+
9253 +-----------+ +-----------+ +-----------+<-- overlay 1
9254 | program | | main | .----| overlay 1 | load address
9255 | variables | | program | | +-----------+
9256 | and heap | | | | | |
9257 +-----------+ | | | +-----------+<-- overlay 2
9258 | | +-----------+ | | | load address
9259 +-----------+ | | | .-| overlay 2 |
9261 mapped --->+-----------+ | | +-----------+
9263 | overlay | <-' | | |
9264 | area | <---' +-----------+<-- overlay 3
9265 | | <---. | | load address
9266 +-----------+ `--| overlay 3 |
9273 @anchor{A code overlay}A code overlay
9277 The diagram (@pxref{A code overlay}) shows a system with separate data
9278 and instruction address spaces. To map an overlay, the program copies
9279 its code from the larger address space to the instruction address space.
9280 Since the overlays shown here all use the same mapped address, only one
9281 may be mapped at a time. For a system with a single address space for
9282 data and instructions, the diagram would be similar, except that the
9283 program variables and heap would share an address space with the main
9284 program and the overlay area.
9286 An overlay loaded into instruction memory and ready for use is called a
9287 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9288 instruction memory. An overlay not present (or only partially present)
9289 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9290 is its address in the larger memory. The mapped address is also called
9291 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9292 called the @dfn{load memory address}, or @dfn{LMA}.
9294 Unfortunately, overlays are not a completely transparent way to adapt a
9295 program to limited instruction memory. They introduce a new set of
9296 global constraints you must keep in mind as you design your program:
9301 Before calling or returning to a function in an overlay, your program
9302 must make sure that overlay is actually mapped. Otherwise, the call or
9303 return will transfer control to the right address, but in the wrong
9304 overlay, and your program will probably crash.
9307 If the process of mapping an overlay is expensive on your system, you
9308 will need to choose your overlays carefully to minimize their effect on
9309 your program's performance.
9312 The executable file you load onto your system must contain each
9313 overlay's instructions, appearing at the overlay's load address, not its
9314 mapped address. However, each overlay's instructions must be relocated
9315 and its symbols defined as if the overlay were at its mapped address.
9316 You can use GNU linker scripts to specify different load and relocation
9317 addresses for pieces of your program; see @ref{Overlay Description,,,
9318 ld.info, Using ld: the GNU linker}.
9321 The procedure for loading executable files onto your system must be able
9322 to load their contents into the larger address space as well as the
9323 instruction and data spaces.
9327 The overlay system described above is rather simple, and could be
9328 improved in many ways:
9333 If your system has suitable bank switch registers or memory management
9334 hardware, you could use those facilities to make an overlay's load area
9335 contents simply appear at their mapped address in instruction space.
9336 This would probably be faster than copying the overlay to its mapped
9337 area in the usual way.
9340 If your overlays are small enough, you could set aside more than one
9341 overlay area, and have more than one overlay mapped at a time.
9344 You can use overlays to manage data, as well as instructions. In
9345 general, data overlays are even less transparent to your design than
9346 code overlays: whereas code overlays only require care when you call or
9347 return to functions, data overlays require care every time you access
9348 the data. Also, if you change the contents of a data overlay, you
9349 must copy its contents back out to its load address before you can copy a
9350 different data overlay into the same mapped area.
9355 @node Overlay Commands
9356 @section Overlay Commands
9358 To use @value{GDBN}'s overlay support, each overlay in your program must
9359 correspond to a separate section of the executable file. The section's
9360 virtual memory address and load memory address must be the overlay's
9361 mapped and load addresses. Identifying overlays with sections allows
9362 @value{GDBN} to determine the appropriate address of a function or
9363 variable, depending on whether the overlay is mapped or not.
9365 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9366 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9371 Disable @value{GDBN}'s overlay support. When overlay support is
9372 disabled, @value{GDBN} assumes that all functions and variables are
9373 always present at their mapped addresses. By default, @value{GDBN}'s
9374 overlay support is disabled.
9376 @item overlay manual
9377 @cindex manual overlay debugging
9378 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9379 relies on you to tell it which overlays are mapped, and which are not,
9380 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9381 commands described below.
9383 @item overlay map-overlay @var{overlay}
9384 @itemx overlay map @var{overlay}
9385 @cindex map an overlay
9386 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9387 be the name of the object file section containing the overlay. When an
9388 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9389 functions and variables at their mapped addresses. @value{GDBN} assumes
9390 that any other overlays whose mapped ranges overlap that of
9391 @var{overlay} are now unmapped.
9393 @item overlay unmap-overlay @var{overlay}
9394 @itemx overlay unmap @var{overlay}
9395 @cindex unmap an overlay
9396 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9397 must be the name of the object file section containing the overlay.
9398 When an overlay is unmapped, @value{GDBN} assumes it can find the
9399 overlay's functions and variables at their load addresses.
9402 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9403 consults a data structure the overlay manager maintains in the inferior
9404 to see which overlays are mapped. For details, see @ref{Automatic
9407 @item overlay load-target
9409 @cindex reloading the overlay table
9410 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9411 re-reads the table @value{GDBN} automatically each time the inferior
9412 stops, so this command should only be necessary if you have changed the
9413 overlay mapping yourself using @value{GDBN}. This command is only
9414 useful when using automatic overlay debugging.
9416 @item overlay list-overlays
9418 @cindex listing mapped overlays
9419 Display a list of the overlays currently mapped, along with their mapped
9420 addresses, load addresses, and sizes.
9424 Normally, when @value{GDBN} prints a code address, it includes the name
9425 of the function the address falls in:
9428 (@value{GDBP}) print main
9429 $3 = @{int ()@} 0x11a0 <main>
9432 When overlay debugging is enabled, @value{GDBN} recognizes code in
9433 unmapped overlays, and prints the names of unmapped functions with
9434 asterisks around them. For example, if @code{foo} is a function in an
9435 unmapped overlay, @value{GDBN} prints it this way:
9438 (@value{GDBP}) overlay list
9439 No sections are mapped.
9440 (@value{GDBP}) print foo
9441 $5 = @{int (int)@} 0x100000 <*foo*>
9444 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9448 (@value{GDBP}) overlay list
9449 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9450 mapped at 0x1016 - 0x104a
9451 (@value{GDBP}) print foo
9452 $6 = @{int (int)@} 0x1016 <foo>
9455 When overlay debugging is enabled, @value{GDBN} can find the correct
9456 address for functions and variables in an overlay, whether or not the
9457 overlay is mapped. This allows most @value{GDBN} commands, like
9458 @code{break} and @code{disassemble}, to work normally, even on unmapped
9459 code. However, @value{GDBN}'s breakpoint support has some limitations:
9463 @cindex breakpoints in overlays
9464 @cindex overlays, setting breakpoints in
9465 You can set breakpoints in functions in unmapped overlays, as long as
9466 @value{GDBN} can write to the overlay at its load address.
9468 @value{GDBN} can not set hardware or simulator-based breakpoints in
9469 unmapped overlays. However, if you set a breakpoint at the end of your
9470 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9471 you are using manual overlay management), @value{GDBN} will re-set its
9472 breakpoints properly.
9476 @node Automatic Overlay Debugging
9477 @section Automatic Overlay Debugging
9478 @cindex automatic overlay debugging
9480 @value{GDBN} can automatically track which overlays are mapped and which
9481 are not, given some simple co-operation from the overlay manager in the
9482 inferior. If you enable automatic overlay debugging with the
9483 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
9484 looks in the inferior's memory for certain variables describing the
9485 current state of the overlays.
9487 Here are the variables your overlay manager must define to support
9488 @value{GDBN}'s automatic overlay debugging:
9492 @item @code{_ovly_table}:
9493 This variable must be an array of the following structures:
9498 /* The overlay's mapped address. */
9501 /* The size of the overlay, in bytes. */
9504 /* The overlay's load address. */
9507 /* Non-zero if the overlay is currently mapped;
9509 unsigned long mapped;
9513 @item @code{_novlys}:
9514 This variable must be a four-byte signed integer, holding the total
9515 number of elements in @code{_ovly_table}.
9519 To decide whether a particular overlay is mapped or not, @value{GDBN}
9520 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9521 @code{lma} members equal the VMA and LMA of the overlay's section in the
9522 executable file. When @value{GDBN} finds a matching entry, it consults
9523 the entry's @code{mapped} member to determine whether the overlay is
9526 In addition, your overlay manager may define a function called
9527 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9528 will silently set a breakpoint there. If the overlay manager then
9529 calls this function whenever it has changed the overlay table, this
9530 will enable @value{GDBN} to accurately keep track of which overlays
9531 are in program memory, and update any breakpoints that may be set
9532 in overlays. This will allow breakpoints to work even if the
9533 overlays are kept in ROM or other non-writable memory while they
9534 are not being executed.
9536 @node Overlay Sample Program
9537 @section Overlay Sample Program
9538 @cindex overlay example program
9540 When linking a program which uses overlays, you must place the overlays
9541 at their load addresses, while relocating them to run at their mapped
9542 addresses. To do this, you must write a linker script (@pxref{Overlay
9543 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9544 since linker scripts are specific to a particular host system, target
9545 architecture, and target memory layout, this manual cannot provide
9546 portable sample code demonstrating @value{GDBN}'s overlay support.
9548 However, the @value{GDBN} source distribution does contain an overlaid
9549 program, with linker scripts for a few systems, as part of its test
9550 suite. The program consists of the following files from
9551 @file{gdb/testsuite/gdb.base}:
9555 The main program file.
9557 A simple overlay manager, used by @file{overlays.c}.
9562 Overlay modules, loaded and used by @file{overlays.c}.
9565 Linker scripts for linking the test program on the @code{d10v-elf}
9566 and @code{m32r-elf} targets.
9569 You can build the test program using the @code{d10v-elf} GCC
9570 cross-compiler like this:
9573 $ d10v-elf-gcc -g -c overlays.c
9574 $ d10v-elf-gcc -g -c ovlymgr.c
9575 $ d10v-elf-gcc -g -c foo.c
9576 $ d10v-elf-gcc -g -c bar.c
9577 $ d10v-elf-gcc -g -c baz.c
9578 $ d10v-elf-gcc -g -c grbx.c
9579 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9580 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9583 The build process is identical for any other architecture, except that
9584 you must substitute the appropriate compiler and linker script for the
9585 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9589 @chapter Using @value{GDBN} with Different Languages
9592 Although programming languages generally have common aspects, they are
9593 rarely expressed in the same manner. For instance, in ANSI C,
9594 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9595 Modula-2, it is accomplished by @code{p^}. Values can also be
9596 represented (and displayed) differently. Hex numbers in C appear as
9597 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9599 @cindex working language
9600 Language-specific information is built into @value{GDBN} for some languages,
9601 allowing you to express operations like the above in your program's
9602 native language, and allowing @value{GDBN} to output values in a manner
9603 consistent with the syntax of your program's native language. The
9604 language you use to build expressions is called the @dfn{working
9608 * Setting:: Switching between source languages
9609 * Show:: Displaying the language
9610 * Checks:: Type and range checks
9611 * Supported Languages:: Supported languages
9612 * Unsupported Languages:: Unsupported languages
9616 @section Switching Between Source Languages
9618 There are two ways to control the working language---either have @value{GDBN}
9619 set it automatically, or select it manually yourself. You can use the
9620 @code{set language} command for either purpose. On startup, @value{GDBN}
9621 defaults to setting the language automatically. The working language is
9622 used to determine how expressions you type are interpreted, how values
9625 In addition to the working language, every source file that
9626 @value{GDBN} knows about has its own working language. For some object
9627 file formats, the compiler might indicate which language a particular
9628 source file is in. However, most of the time @value{GDBN} infers the
9629 language from the name of the file. The language of a source file
9630 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9631 show each frame appropriately for its own language. There is no way to
9632 set the language of a source file from within @value{GDBN}, but you can
9633 set the language associated with a filename extension. @xref{Show, ,
9634 Displaying the Language}.
9636 This is most commonly a problem when you use a program, such
9637 as @code{cfront} or @code{f2c}, that generates C but is written in
9638 another language. In that case, make the
9639 program use @code{#line} directives in its C output; that way
9640 @value{GDBN} will know the correct language of the source code of the original
9641 program, and will display that source code, not the generated C code.
9644 * Filenames:: Filename extensions and languages.
9645 * Manually:: Setting the working language manually
9646 * Automatically:: Having @value{GDBN} infer the source language
9650 @subsection List of Filename Extensions and Languages
9652 If a source file name ends in one of the following extensions, then
9653 @value{GDBN} infers that its language is the one indicated.
9674 Objective-C source file
9681 Modula-2 source file
9685 Assembler source file. This actually behaves almost like C, but
9686 @value{GDBN} does not skip over function prologues when stepping.
9689 In addition, you may set the language associated with a filename
9690 extension. @xref{Show, , Displaying the Language}.
9693 @subsection Setting the Working Language
9695 If you allow @value{GDBN} to set the language automatically,
9696 expressions are interpreted the same way in your debugging session and
9699 @kindex set language
9700 If you wish, you may set the language manually. To do this, issue the
9701 command @samp{set language @var{lang}}, where @var{lang} is the name of
9703 @code{c} or @code{modula-2}.
9704 For a list of the supported languages, type @samp{set language}.
9706 Setting the language manually prevents @value{GDBN} from updating the working
9707 language automatically. This can lead to confusion if you try
9708 to debug a program when the working language is not the same as the
9709 source language, when an expression is acceptable to both
9710 languages---but means different things. For instance, if the current
9711 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9719 might not have the effect you intended. In C, this means to add
9720 @code{b} and @code{c} and place the result in @code{a}. The result
9721 printed would be the value of @code{a}. In Modula-2, this means to compare
9722 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9725 @subsection Having @value{GDBN} Infer the Source Language
9727 To have @value{GDBN} set the working language automatically, use
9728 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9729 then infers the working language. That is, when your program stops in a
9730 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9731 working language to the language recorded for the function in that
9732 frame. If the language for a frame is unknown (that is, if the function
9733 or block corresponding to the frame was defined in a source file that
9734 does not have a recognized extension), the current working language is
9735 not changed, and @value{GDBN} issues a warning.
9737 This may not seem necessary for most programs, which are written
9738 entirely in one source language. However, program modules and libraries
9739 written in one source language can be used by a main program written in
9740 a different source language. Using @samp{set language auto} in this
9741 case frees you from having to set the working language manually.
9744 @section Displaying the Language
9746 The following commands help you find out which language is the
9747 working language, and also what language source files were written in.
9751 @kindex show language
9752 Display the current working language. This is the
9753 language you can use with commands such as @code{print} to
9754 build and compute expressions that may involve variables in your program.
9757 @kindex info frame@r{, show the source language}
9758 Display the source language for this frame. This language becomes the
9759 working language if you use an identifier from this frame.
9760 @xref{Frame Info, ,Information about a Frame}, to identify the other
9761 information listed here.
9764 @kindex info source@r{, show the source language}
9765 Display the source language of this source file.
9766 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9767 information listed here.
9770 In unusual circumstances, you may have source files with extensions
9771 not in the standard list. You can then set the extension associated
9772 with a language explicitly:
9775 @item set extension-language @var{ext} @var{language}
9776 @kindex set extension-language
9777 Tell @value{GDBN} that source files with extension @var{ext} are to be
9778 assumed as written in the source language @var{language}.
9780 @item info extensions
9781 @kindex info extensions
9782 List all the filename extensions and the associated languages.
9786 @section Type and Range Checking
9789 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9790 checking are included, but they do not yet have any effect. This
9791 section documents the intended facilities.
9793 @c FIXME remove warning when type/range code added
9795 Some languages are designed to guard you against making seemingly common
9796 errors through a series of compile- and run-time checks. These include
9797 checking the type of arguments to functions and operators, and making
9798 sure mathematical overflows are caught at run time. Checks such as
9799 these help to ensure a program's correctness once it has been compiled
9800 by eliminating type mismatches, and providing active checks for range
9801 errors when your program is running.
9803 @value{GDBN} can check for conditions like the above if you wish.
9804 Although @value{GDBN} does not check the statements in your program,
9805 it can check expressions entered directly into @value{GDBN} for
9806 evaluation via the @code{print} command, for example. As with the
9807 working language, @value{GDBN} can also decide whether or not to check
9808 automatically based on your program's source language.
9809 @xref{Supported Languages, ,Supported Languages}, for the default
9810 settings of supported languages.
9813 * Type Checking:: An overview of type checking
9814 * Range Checking:: An overview of range checking
9817 @cindex type checking
9818 @cindex checks, type
9820 @subsection An Overview of Type Checking
9822 Some languages, such as Modula-2, are strongly typed, meaning that the
9823 arguments to operators and functions have to be of the correct type,
9824 otherwise an error occurs. These checks prevent type mismatch
9825 errors from ever causing any run-time problems. For example,
9833 The second example fails because the @code{CARDINAL} 1 is not
9834 type-compatible with the @code{REAL} 2.3.
9836 For the expressions you use in @value{GDBN} commands, you can tell the
9837 @value{GDBN} type checker to skip checking;
9838 to treat any mismatches as errors and abandon the expression;
9839 or to only issue warnings when type mismatches occur,
9840 but evaluate the expression anyway. When you choose the last of
9841 these, @value{GDBN} evaluates expressions like the second example above, but
9842 also issues a warning.
9844 Even if you turn type checking off, there may be other reasons
9845 related to type that prevent @value{GDBN} from evaluating an expression.
9846 For instance, @value{GDBN} does not know how to add an @code{int} and
9847 a @code{struct foo}. These particular type errors have nothing to do
9848 with the language in use, and usually arise from expressions, such as
9849 the one described above, which make little sense to evaluate anyway.
9851 Each language defines to what degree it is strict about type. For
9852 instance, both Modula-2 and C require the arguments to arithmetical
9853 operators to be numbers. In C, enumerated types and pointers can be
9854 represented as numbers, so that they are valid arguments to mathematical
9855 operators. @xref{Supported Languages, ,Supported Languages}, for further
9856 details on specific languages.
9858 @value{GDBN} provides some additional commands for controlling the type checker:
9860 @kindex set check type
9861 @kindex show check type
9863 @item set check type auto
9864 Set type checking on or off based on the current working language.
9865 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9868 @item set check type on
9869 @itemx set check type off
9870 Set type checking on or off, overriding the default setting for the
9871 current working language. Issue a warning if the setting does not
9872 match the language default. If any type mismatches occur in
9873 evaluating an expression while type checking is on, @value{GDBN} prints a
9874 message and aborts evaluation of the expression.
9876 @item set check type warn
9877 Cause the type checker to issue warnings, but to always attempt to
9878 evaluate the expression. Evaluating the expression may still
9879 be impossible for other reasons. For example, @value{GDBN} cannot add
9880 numbers and structures.
9883 Show the current setting of the type checker, and whether or not @value{GDBN}
9884 is setting it automatically.
9887 @cindex range checking
9888 @cindex checks, range
9889 @node Range Checking
9890 @subsection An Overview of Range Checking
9892 In some languages (such as Modula-2), it is an error to exceed the
9893 bounds of a type; this is enforced with run-time checks. Such range
9894 checking is meant to ensure program correctness by making sure
9895 computations do not overflow, or indices on an array element access do
9896 not exceed the bounds of the array.
9898 For expressions you use in @value{GDBN} commands, you can tell
9899 @value{GDBN} to treat range errors in one of three ways: ignore them,
9900 always treat them as errors and abandon the expression, or issue
9901 warnings but evaluate the expression anyway.
9903 A range error can result from numerical overflow, from exceeding an
9904 array index bound, or when you type a constant that is not a member
9905 of any type. Some languages, however, do not treat overflows as an
9906 error. In many implementations of C, mathematical overflow causes the
9907 result to ``wrap around'' to lower values---for example, if @var{m} is
9908 the largest integer value, and @var{s} is the smallest, then
9911 @var{m} + 1 @result{} @var{s}
9914 This, too, is specific to individual languages, and in some cases
9915 specific to individual compilers or machines. @xref{Supported Languages, ,
9916 Supported Languages}, for further details on specific languages.
9918 @value{GDBN} provides some additional commands for controlling the range checker:
9920 @kindex set check range
9921 @kindex show check range
9923 @item set check range auto
9924 Set range checking on or off based on the current working language.
9925 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9928 @item set check range on
9929 @itemx set check range off
9930 Set range checking on or off, overriding the default setting for the
9931 current working language. A warning is issued if the setting does not
9932 match the language default. If a range error occurs and range checking is on,
9933 then a message is printed and evaluation of the expression is aborted.
9935 @item set check range warn
9936 Output messages when the @value{GDBN} range checker detects a range error,
9937 but attempt to evaluate the expression anyway. Evaluating the
9938 expression may still be impossible for other reasons, such as accessing
9939 memory that the process does not own (a typical example from many Unix
9943 Show the current setting of the range checker, and whether or not it is
9944 being set automatically by @value{GDBN}.
9947 @node Supported Languages
9948 @section Supported Languages
9950 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9951 assembly, Modula-2, and Ada.
9952 @c This is false ...
9953 Some @value{GDBN} features may be used in expressions regardless of the
9954 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9955 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9956 ,Expressions}) can be used with the constructs of any supported
9959 The following sections detail to what degree each source language is
9960 supported by @value{GDBN}. These sections are not meant to be language
9961 tutorials or references, but serve only as a reference guide to what the
9962 @value{GDBN} expression parser accepts, and what input and output
9963 formats should look like for different languages. There are many good
9964 books written on each of these languages; please look to these for a
9965 language reference or tutorial.
9969 * Objective-C:: Objective-C
9972 * Modula-2:: Modula-2
9977 @subsection C and C@t{++}
9979 @cindex C and C@t{++}
9980 @cindex expressions in C or C@t{++}
9982 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9983 to both languages. Whenever this is the case, we discuss those languages
9987 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9988 @cindex @sc{gnu} C@t{++}
9989 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9990 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9991 effectively, you must compile your C@t{++} programs with a supported
9992 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9993 compiler (@code{aCC}).
9995 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9996 format; if it doesn't work on your system, try the stabs+ debugging
9997 format. You can select those formats explicitly with the @code{g++}
9998 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9999 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
10000 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
10003 * C Operators:: C and C@t{++} operators
10004 * C Constants:: C and C@t{++} constants
10005 * C Plus Plus Expressions:: C@t{++} expressions
10006 * C Defaults:: Default settings for C and C@t{++}
10007 * C Checks:: C and C@t{++} type and range checks
10008 * Debugging C:: @value{GDBN} and C
10009 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
10010 * Decimal Floating Point:: Numbers in Decimal Floating Point format
10014 @subsubsection C and C@t{++} Operators
10016 @cindex C and C@t{++} operators
10018 Operators must be defined on values of specific types. For instance,
10019 @code{+} is defined on numbers, but not on structures. Operators are
10020 often defined on groups of types.
10022 For the purposes of C and C@t{++}, the following definitions hold:
10027 @emph{Integral types} include @code{int} with any of its storage-class
10028 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
10031 @emph{Floating-point types} include @code{float}, @code{double}, and
10032 @code{long double} (if supported by the target platform).
10035 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
10038 @emph{Scalar types} include all of the above.
10043 The following operators are supported. They are listed here
10044 in order of increasing precedence:
10048 The comma or sequencing operator. Expressions in a comma-separated list
10049 are evaluated from left to right, with the result of the entire
10050 expression being the last expression evaluated.
10053 Assignment. The value of an assignment expression is the value
10054 assigned. Defined on scalar types.
10057 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
10058 and translated to @w{@code{@var{a} = @var{a op b}}}.
10059 @w{@code{@var{op}=}} and @code{=} have the same precedence.
10060 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
10061 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
10064 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
10065 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
10069 Logical @sc{or}. Defined on integral types.
10072 Logical @sc{and}. Defined on integral types.
10075 Bitwise @sc{or}. Defined on integral types.
10078 Bitwise exclusive-@sc{or}. Defined on integral types.
10081 Bitwise @sc{and}. Defined on integral types.
10084 Equality and inequality. Defined on scalar types. The value of these
10085 expressions is 0 for false and non-zero for true.
10087 @item <@r{, }>@r{, }<=@r{, }>=
10088 Less than, greater than, less than or equal, greater than or equal.
10089 Defined on scalar types. The value of these expressions is 0 for false
10090 and non-zero for true.
10093 left shift, and right shift. Defined on integral types.
10096 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10099 Addition and subtraction. Defined on integral types, floating-point types and
10102 @item *@r{, }/@r{, }%
10103 Multiplication, division, and modulus. Multiplication and division are
10104 defined on integral and floating-point types. Modulus is defined on
10108 Increment and decrement. When appearing before a variable, the
10109 operation is performed before the variable is used in an expression;
10110 when appearing after it, the variable's value is used before the
10111 operation takes place.
10114 Pointer dereferencing. Defined on pointer types. Same precedence as
10118 Address operator. Defined on variables. Same precedence as @code{++}.
10120 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
10121 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
10122 to examine the address
10123 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
10127 Negative. Defined on integral and floating-point types. Same
10128 precedence as @code{++}.
10131 Logical negation. Defined on integral types. Same precedence as
10135 Bitwise complement operator. Defined on integral types. Same precedence as
10140 Structure member, and pointer-to-structure member. For convenience,
10141 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10142 pointer based on the stored type information.
10143 Defined on @code{struct} and @code{union} data.
10146 Dereferences of pointers to members.
10149 Array indexing. @code{@var{a}[@var{i}]} is defined as
10150 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10153 Function parameter list. Same precedence as @code{->}.
10156 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10157 and @code{class} types.
10160 Doubled colons also represent the @value{GDBN} scope operator
10161 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10165 If an operator is redefined in the user code, @value{GDBN} usually
10166 attempts to invoke the redefined version instead of using the operator's
10167 predefined meaning.
10170 @subsubsection C and C@t{++} Constants
10172 @cindex C and C@t{++} constants
10174 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10179 Integer constants are a sequence of digits. Octal constants are
10180 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10181 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10182 @samp{l}, specifying that the constant should be treated as a
10186 Floating point constants are a sequence of digits, followed by a decimal
10187 point, followed by a sequence of digits, and optionally followed by an
10188 exponent. An exponent is of the form:
10189 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10190 sequence of digits. The @samp{+} is optional for positive exponents.
10191 A floating-point constant may also end with a letter @samp{f} or
10192 @samp{F}, specifying that the constant should be treated as being of
10193 the @code{float} (as opposed to the default @code{double}) type; or with
10194 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10198 Enumerated constants consist of enumerated identifiers, or their
10199 integral equivalents.
10202 Character constants are a single character surrounded by single quotes
10203 (@code{'}), or a number---the ordinal value of the corresponding character
10204 (usually its @sc{ascii} value). Within quotes, the single character may
10205 be represented by a letter or by @dfn{escape sequences}, which are of
10206 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10207 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10208 @samp{@var{x}} is a predefined special character---for example,
10209 @samp{\n} for newline.
10212 String constants are a sequence of character constants surrounded by
10213 double quotes (@code{"}). Any valid character constant (as described
10214 above) may appear. Double quotes within the string must be preceded by
10215 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10219 Pointer constants are an integral value. You can also write pointers
10220 to constants using the C operator @samp{&}.
10223 Array constants are comma-separated lists surrounded by braces @samp{@{}
10224 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10225 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10226 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10229 @node C Plus Plus Expressions
10230 @subsubsection C@t{++} Expressions
10232 @cindex expressions in C@t{++}
10233 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10235 @cindex debugging C@t{++} programs
10236 @cindex C@t{++} compilers
10237 @cindex debug formats and C@t{++}
10238 @cindex @value{NGCC} and C@t{++}
10240 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10241 proper compiler and the proper debug format. Currently, @value{GDBN}
10242 works best when debugging C@t{++} code that is compiled with
10243 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10244 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10245 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10246 stabs+ as their default debug format, so you usually don't need to
10247 specify a debug format explicitly. Other compilers and/or debug formats
10248 are likely to work badly or not at all when using @value{GDBN} to debug
10254 @cindex member functions
10256 Member function calls are allowed; you can use expressions like
10259 count = aml->GetOriginal(x, y)
10262 @vindex this@r{, inside C@t{++} member functions}
10263 @cindex namespace in C@t{++}
10265 While a member function is active (in the selected stack frame), your
10266 expressions have the same namespace available as the member function;
10267 that is, @value{GDBN} allows implicit references to the class instance
10268 pointer @code{this} following the same rules as C@t{++}.
10270 @cindex call overloaded functions
10271 @cindex overloaded functions, calling
10272 @cindex type conversions in C@t{++}
10274 You can call overloaded functions; @value{GDBN} resolves the function
10275 call to the right definition, with some restrictions. @value{GDBN} does not
10276 perform overload resolution involving user-defined type conversions,
10277 calls to constructors, or instantiations of templates that do not exist
10278 in the program. It also cannot handle ellipsis argument lists or
10281 It does perform integral conversions and promotions, floating-point
10282 promotions, arithmetic conversions, pointer conversions, conversions of
10283 class objects to base classes, and standard conversions such as those of
10284 functions or arrays to pointers; it requires an exact match on the
10285 number of function arguments.
10287 Overload resolution is always performed, unless you have specified
10288 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10289 ,@value{GDBN} Features for C@t{++}}.
10291 You must specify @code{set overload-resolution off} in order to use an
10292 explicit function signature to call an overloaded function, as in
10294 p 'foo(char,int)'('x', 13)
10297 The @value{GDBN} command-completion facility can simplify this;
10298 see @ref{Completion, ,Command Completion}.
10300 @cindex reference declarations
10302 @value{GDBN} understands variables declared as C@t{++} references; you can use
10303 them in expressions just as you do in C@t{++} source---they are automatically
10306 In the parameter list shown when @value{GDBN} displays a frame, the values of
10307 reference variables are not displayed (unlike other variables); this
10308 avoids clutter, since references are often used for large structures.
10309 The @emph{address} of a reference variable is always shown, unless
10310 you have specified @samp{set print address off}.
10313 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10314 expressions can use it just as expressions in your program do. Since
10315 one scope may be defined in another, you can use @code{::} repeatedly if
10316 necessary, for example in an expression like
10317 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10318 resolving name scope by reference to source files, in both C and C@t{++}
10319 debugging (@pxref{Variables, ,Program Variables}).
10322 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10323 calling virtual functions correctly, printing out virtual bases of
10324 objects, calling functions in a base subobject, casting objects, and
10325 invoking user-defined operators.
10328 @subsubsection C and C@t{++} Defaults
10330 @cindex C and C@t{++} defaults
10332 If you allow @value{GDBN} to set type and range checking automatically, they
10333 both default to @code{off} whenever the working language changes to
10334 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10335 selects the working language.
10337 If you allow @value{GDBN} to set the language automatically, it
10338 recognizes source files whose names end with @file{.c}, @file{.C}, or
10339 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10340 these files, it sets the working language to C or C@t{++}.
10341 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10342 for further details.
10344 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10345 @c unimplemented. If (b) changes, it might make sense to let this node
10346 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10349 @subsubsection C and C@t{++} Type and Range Checks
10351 @cindex C and C@t{++} checks
10353 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10354 is not used. However, if you turn type checking on, @value{GDBN}
10355 considers two variables type equivalent if:
10359 The two variables are structured and have the same structure, union, or
10363 The two variables have the same type name, or types that have been
10364 declared equivalent through @code{typedef}.
10367 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10370 The two @code{struct}, @code{union}, or @code{enum} variables are
10371 declared in the same declaration. (Note: this may not be true for all C
10376 Range checking, if turned on, is done on mathematical operations. Array
10377 indices are not checked, since they are often used to index a pointer
10378 that is not itself an array.
10381 @subsubsection @value{GDBN} and C
10383 The @code{set print union} and @code{show print union} commands apply to
10384 the @code{union} type. When set to @samp{on}, any @code{union} that is
10385 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10386 appears as @samp{@{...@}}.
10388 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10389 with pointers and a memory allocation function. @xref{Expressions,
10392 @node Debugging C Plus Plus
10393 @subsubsection @value{GDBN} Features for C@t{++}
10395 @cindex commands for C@t{++}
10397 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10398 designed specifically for use with C@t{++}. Here is a summary:
10401 @cindex break in overloaded functions
10402 @item @r{breakpoint menus}
10403 When you want a breakpoint in a function whose name is overloaded,
10404 @value{GDBN} has the capability to display a menu of possible breakpoint
10405 locations to help you specify which function definition you want.
10406 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10408 @cindex overloading in C@t{++}
10409 @item rbreak @var{regex}
10410 Setting breakpoints using regular expressions is helpful for setting
10411 breakpoints on overloaded functions that are not members of any special
10413 @xref{Set Breaks, ,Setting Breakpoints}.
10415 @cindex C@t{++} exception handling
10418 Debug C@t{++} exception handling using these commands. @xref{Set
10419 Catchpoints, , Setting Catchpoints}.
10421 @cindex inheritance
10422 @item ptype @var{typename}
10423 Print inheritance relationships as well as other information for type
10425 @xref{Symbols, ,Examining the Symbol Table}.
10427 @cindex C@t{++} symbol display
10428 @item set print demangle
10429 @itemx show print demangle
10430 @itemx set print asm-demangle
10431 @itemx show print asm-demangle
10432 Control whether C@t{++} symbols display in their source form, both when
10433 displaying code as C@t{++} source and when displaying disassemblies.
10434 @xref{Print Settings, ,Print Settings}.
10436 @item set print object
10437 @itemx show print object
10438 Choose whether to print derived (actual) or declared types of objects.
10439 @xref{Print Settings, ,Print Settings}.
10441 @item set print vtbl
10442 @itemx show print vtbl
10443 Control the format for printing virtual function tables.
10444 @xref{Print Settings, ,Print Settings}.
10445 (The @code{vtbl} commands do not work on programs compiled with the HP
10446 ANSI C@t{++} compiler (@code{aCC}).)
10448 @kindex set overload-resolution
10449 @cindex overloaded functions, overload resolution
10450 @item set overload-resolution on
10451 Enable overload resolution for C@t{++} expression evaluation. The default
10452 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10453 and searches for a function whose signature matches the argument types,
10454 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10455 Expressions, ,C@t{++} Expressions}, for details).
10456 If it cannot find a match, it emits a message.
10458 @item set overload-resolution off
10459 Disable overload resolution for C@t{++} expression evaluation. For
10460 overloaded functions that are not class member functions, @value{GDBN}
10461 chooses the first function of the specified name that it finds in the
10462 symbol table, whether or not its arguments are of the correct type. For
10463 overloaded functions that are class member functions, @value{GDBN}
10464 searches for a function whose signature @emph{exactly} matches the
10467 @kindex show overload-resolution
10468 @item show overload-resolution
10469 Show the current setting of overload resolution.
10471 @item @r{Overloaded symbol names}
10472 You can specify a particular definition of an overloaded symbol, using
10473 the same notation that is used to declare such symbols in C@t{++}: type
10474 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10475 also use the @value{GDBN} command-line word completion facilities to list the
10476 available choices, or to finish the type list for you.
10477 @xref{Completion,, Command Completion}, for details on how to do this.
10480 @node Decimal Floating Point
10481 @subsubsection Decimal Floating Point format
10482 @cindex decimal floating point format
10484 @value{GDBN} can examine, set and perform computations with numbers in
10485 decimal floating point format, which in the C language correspond to the
10486 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
10487 specified by the extension to support decimal floating-point arithmetic.
10489 There are two encodings in use, depending on the architecture: BID (Binary
10490 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10491 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10494 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10495 to manipulate decimal floating point numbers, it is not possible to convert
10496 (using a cast, for example) integers wider than 32-bit to decimal float.
10498 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10499 point computations, error checking in decimal float operations ignores
10500 underflow, overflow and divide by zero exceptions.
10502 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10503 to inspect @code{_Decimal128} values stored in floating point registers. See
10504 @ref{PowerPC,,PowerPC} for more details.
10507 @subsection Objective-C
10509 @cindex Objective-C
10510 This section provides information about some commands and command
10511 options that are useful for debugging Objective-C code. See also
10512 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10513 few more commands specific to Objective-C support.
10516 * Method Names in Commands::
10517 * The Print Command with Objective-C::
10520 @node Method Names in Commands
10521 @subsubsection Method Names in Commands
10523 The following commands have been extended to accept Objective-C method
10524 names as line specifications:
10526 @kindex clear@r{, and Objective-C}
10527 @kindex break@r{, and Objective-C}
10528 @kindex info line@r{, and Objective-C}
10529 @kindex jump@r{, and Objective-C}
10530 @kindex list@r{, and Objective-C}
10534 @item @code{info line}
10539 A fully qualified Objective-C method name is specified as
10542 -[@var{Class} @var{methodName}]
10545 where the minus sign is used to indicate an instance method and a
10546 plus sign (not shown) is used to indicate a class method. The class
10547 name @var{Class} and method name @var{methodName} are enclosed in
10548 brackets, similar to the way messages are specified in Objective-C
10549 source code. For example, to set a breakpoint at the @code{create}
10550 instance method of class @code{Fruit} in the program currently being
10554 break -[Fruit create]
10557 To list ten program lines around the @code{initialize} class method,
10561 list +[NSText initialize]
10564 In the current version of @value{GDBN}, the plus or minus sign is
10565 required. In future versions of @value{GDBN}, the plus or minus
10566 sign will be optional, but you can use it to narrow the search. It
10567 is also possible to specify just a method name:
10573 You must specify the complete method name, including any colons. If
10574 your program's source files contain more than one @code{create} method,
10575 you'll be presented with a numbered list of classes that implement that
10576 method. Indicate your choice by number, or type @samp{0} to exit if
10579 As another example, to clear a breakpoint established at the
10580 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10583 clear -[NSWindow makeKeyAndOrderFront:]
10586 @node The Print Command with Objective-C
10587 @subsubsection The Print Command With Objective-C
10588 @cindex Objective-C, print objects
10589 @kindex print-object
10590 @kindex po @r{(@code{print-object})}
10592 The print command has also been extended to accept methods. For example:
10595 print -[@var{object} hash]
10598 @cindex print an Objective-C object description
10599 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10601 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10602 and print the result. Also, an additional command has been added,
10603 @code{print-object} or @code{po} for short, which is meant to print
10604 the description of an object. However, this command may only work
10605 with certain Objective-C libraries that have a particular hook
10606 function, @code{_NSPrintForDebugger}, defined.
10609 @subsection Fortran
10610 @cindex Fortran-specific support in @value{GDBN}
10612 @value{GDBN} can be used to debug programs written in Fortran, but it
10613 currently supports only the features of Fortran 77 language.
10615 @cindex trailing underscore, in Fortran symbols
10616 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10617 among them) append an underscore to the names of variables and
10618 functions. When you debug programs compiled by those compilers, you
10619 will need to refer to variables and functions with a trailing
10623 * Fortran Operators:: Fortran operators and expressions
10624 * Fortran Defaults:: Default settings for Fortran
10625 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10628 @node Fortran Operators
10629 @subsubsection Fortran Operators and Expressions
10631 @cindex Fortran operators and expressions
10633 Operators must be defined on values of specific types. For instance,
10634 @code{+} is defined on numbers, but not on characters or other non-
10635 arithmetic types. Operators are often defined on groups of types.
10639 The exponentiation operator. It raises the first operand to the power
10643 The range operator. Normally used in the form of array(low:high) to
10644 represent a section of array.
10647 The access component operator. Normally used to access elements in derived
10648 types. Also suitable for unions. As unions aren't part of regular Fortran,
10649 this can only happen when accessing a register that uses a gdbarch-defined
10653 @node Fortran Defaults
10654 @subsubsection Fortran Defaults
10656 @cindex Fortran Defaults
10658 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10659 default uses case-insensitive matches for Fortran symbols. You can
10660 change that with the @samp{set case-insensitive} command, see
10661 @ref{Symbols}, for the details.
10663 @node Special Fortran Commands
10664 @subsubsection Special Fortran Commands
10666 @cindex Special Fortran commands
10668 @value{GDBN} has some commands to support Fortran-specific features,
10669 such as displaying common blocks.
10672 @cindex @code{COMMON} blocks, Fortran
10673 @kindex info common
10674 @item info common @r{[}@var{common-name}@r{]}
10675 This command prints the values contained in the Fortran @code{COMMON}
10676 block whose name is @var{common-name}. With no argument, the names of
10677 all @code{COMMON} blocks visible at the current program location are
10684 @cindex Pascal support in @value{GDBN}, limitations
10685 Debugging Pascal programs which use sets, subranges, file variables, or
10686 nested functions does not currently work. @value{GDBN} does not support
10687 entering expressions, printing values, or similar features using Pascal
10690 The Pascal-specific command @code{set print pascal_static-members}
10691 controls whether static members of Pascal objects are displayed.
10692 @xref{Print Settings, pascal_static-members}.
10695 @subsection Modula-2
10697 @cindex Modula-2, @value{GDBN} support
10699 The extensions made to @value{GDBN} to support Modula-2 only support
10700 output from the @sc{gnu} Modula-2 compiler (which is currently being
10701 developed). Other Modula-2 compilers are not currently supported, and
10702 attempting to debug executables produced by them is most likely
10703 to give an error as @value{GDBN} reads in the executable's symbol
10706 @cindex expressions in Modula-2
10708 * M2 Operators:: Built-in operators
10709 * Built-In Func/Proc:: Built-in functions and procedures
10710 * M2 Constants:: Modula-2 constants
10711 * M2 Types:: Modula-2 types
10712 * M2 Defaults:: Default settings for Modula-2
10713 * Deviations:: Deviations from standard Modula-2
10714 * M2 Checks:: Modula-2 type and range checks
10715 * M2 Scope:: The scope operators @code{::} and @code{.}
10716 * GDB/M2:: @value{GDBN} and Modula-2
10720 @subsubsection Operators
10721 @cindex Modula-2 operators
10723 Operators must be defined on values of specific types. For instance,
10724 @code{+} is defined on numbers, but not on structures. Operators are
10725 often defined on groups of types. For the purposes of Modula-2, the
10726 following definitions hold:
10731 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10735 @emph{Character types} consist of @code{CHAR} and its subranges.
10738 @emph{Floating-point types} consist of @code{REAL}.
10741 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10745 @emph{Scalar types} consist of all of the above.
10748 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10751 @emph{Boolean types} consist of @code{BOOLEAN}.
10755 The following operators are supported, and appear in order of
10756 increasing precedence:
10760 Function argument or array index separator.
10763 Assignment. The value of @var{var} @code{:=} @var{value} is
10767 Less than, greater than on integral, floating-point, or enumerated
10771 Less than or equal to, greater than or equal to
10772 on integral, floating-point and enumerated types, or set inclusion on
10773 set types. Same precedence as @code{<}.
10775 @item =@r{, }<>@r{, }#
10776 Equality and two ways of expressing inequality, valid on scalar types.
10777 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10778 available for inequality, since @code{#} conflicts with the script
10782 Set membership. Defined on set types and the types of their members.
10783 Same precedence as @code{<}.
10786 Boolean disjunction. Defined on boolean types.
10789 Boolean conjunction. Defined on boolean types.
10792 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10795 Addition and subtraction on integral and floating-point types, or union
10796 and difference on set types.
10799 Multiplication on integral and floating-point types, or set intersection
10803 Division on floating-point types, or symmetric set difference on set
10804 types. Same precedence as @code{*}.
10807 Integer division and remainder. Defined on integral types. Same
10808 precedence as @code{*}.
10811 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10814 Pointer dereferencing. Defined on pointer types.
10817 Boolean negation. Defined on boolean types. Same precedence as
10821 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10822 precedence as @code{^}.
10825 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10828 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10832 @value{GDBN} and Modula-2 scope operators.
10836 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10837 treats the use of the operator @code{IN}, or the use of operators
10838 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10839 @code{<=}, and @code{>=} on sets as an error.
10843 @node Built-In Func/Proc
10844 @subsubsection Built-in Functions and Procedures
10845 @cindex Modula-2 built-ins
10847 Modula-2 also makes available several built-in procedures and functions.
10848 In describing these, the following metavariables are used:
10853 represents an @code{ARRAY} variable.
10856 represents a @code{CHAR} constant or variable.
10859 represents a variable or constant of integral type.
10862 represents an identifier that belongs to a set. Generally used in the
10863 same function with the metavariable @var{s}. The type of @var{s} should
10864 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10867 represents a variable or constant of integral or floating-point type.
10870 represents a variable or constant of floating-point type.
10876 represents a variable.
10879 represents a variable or constant of one of many types. See the
10880 explanation of the function for details.
10883 All Modula-2 built-in procedures also return a result, described below.
10887 Returns the absolute value of @var{n}.
10890 If @var{c} is a lower case letter, it returns its upper case
10891 equivalent, otherwise it returns its argument.
10894 Returns the character whose ordinal value is @var{i}.
10897 Decrements the value in the variable @var{v} by one. Returns the new value.
10899 @item DEC(@var{v},@var{i})
10900 Decrements the value in the variable @var{v} by @var{i}. Returns the
10903 @item EXCL(@var{m},@var{s})
10904 Removes the element @var{m} from the set @var{s}. Returns the new
10907 @item FLOAT(@var{i})
10908 Returns the floating point equivalent of the integer @var{i}.
10910 @item HIGH(@var{a})
10911 Returns the index of the last member of @var{a}.
10914 Increments the value in the variable @var{v} by one. Returns the new value.
10916 @item INC(@var{v},@var{i})
10917 Increments the value in the variable @var{v} by @var{i}. Returns the
10920 @item INCL(@var{m},@var{s})
10921 Adds the element @var{m} to the set @var{s} if it is not already
10922 there. Returns the new set.
10925 Returns the maximum value of the type @var{t}.
10928 Returns the minimum value of the type @var{t}.
10931 Returns boolean TRUE if @var{i} is an odd number.
10934 Returns the ordinal value of its argument. For example, the ordinal
10935 value of a character is its @sc{ascii} value (on machines supporting the
10936 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10937 integral, character and enumerated types.
10939 @item SIZE(@var{x})
10940 Returns the size of its argument. @var{x} can be a variable or a type.
10942 @item TRUNC(@var{r})
10943 Returns the integral part of @var{r}.
10945 @item TSIZE(@var{x})
10946 Returns the size of its argument. @var{x} can be a variable or a type.
10948 @item VAL(@var{t},@var{i})
10949 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10953 @emph{Warning:} Sets and their operations are not yet supported, so
10954 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10958 @cindex Modula-2 constants
10960 @subsubsection Constants
10962 @value{GDBN} allows you to express the constants of Modula-2 in the following
10968 Integer constants are simply a sequence of digits. When used in an
10969 expression, a constant is interpreted to be type-compatible with the
10970 rest of the expression. Hexadecimal integers are specified by a
10971 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10974 Floating point constants appear as a sequence of digits, followed by a
10975 decimal point and another sequence of digits. An optional exponent can
10976 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10977 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10978 digits of the floating point constant must be valid decimal (base 10)
10982 Character constants consist of a single character enclosed by a pair of
10983 like quotes, either single (@code{'}) or double (@code{"}). They may
10984 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10985 followed by a @samp{C}.
10988 String constants consist of a sequence of characters enclosed by a
10989 pair of like quotes, either single (@code{'}) or double (@code{"}).
10990 Escape sequences in the style of C are also allowed. @xref{C
10991 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10995 Enumerated constants consist of an enumerated identifier.
10998 Boolean constants consist of the identifiers @code{TRUE} and
11002 Pointer constants consist of integral values only.
11005 Set constants are not yet supported.
11009 @subsubsection Modula-2 Types
11010 @cindex Modula-2 types
11012 Currently @value{GDBN} can print the following data types in Modula-2
11013 syntax: array types, record types, set types, pointer types, procedure
11014 types, enumerated types, subrange types and base types. You can also
11015 print the contents of variables declared using these type.
11016 This section gives a number of simple source code examples together with
11017 sample @value{GDBN} sessions.
11019 The first example contains the following section of code:
11028 and you can request @value{GDBN} to interrogate the type and value of
11029 @code{r} and @code{s}.
11032 (@value{GDBP}) print s
11034 (@value{GDBP}) ptype s
11036 (@value{GDBP}) print r
11038 (@value{GDBP}) ptype r
11043 Likewise if your source code declares @code{s} as:
11047 s: SET ['A'..'Z'] ;
11051 then you may query the type of @code{s} by:
11054 (@value{GDBP}) ptype s
11055 type = SET ['A'..'Z']
11059 Note that at present you cannot interactively manipulate set
11060 expressions using the debugger.
11062 The following example shows how you might declare an array in Modula-2
11063 and how you can interact with @value{GDBN} to print its type and contents:
11067 s: ARRAY [-10..10] OF CHAR ;
11071 (@value{GDBP}) ptype s
11072 ARRAY [-10..10] OF CHAR
11075 Note that the array handling is not yet complete and although the type
11076 is printed correctly, expression handling still assumes that all
11077 arrays have a lower bound of zero and not @code{-10} as in the example
11080 Here are some more type related Modula-2 examples:
11084 colour = (blue, red, yellow, green) ;
11085 t = [blue..yellow] ;
11093 The @value{GDBN} interaction shows how you can query the data type
11094 and value of a variable.
11097 (@value{GDBP}) print s
11099 (@value{GDBP}) ptype t
11100 type = [blue..yellow]
11104 In this example a Modula-2 array is declared and its contents
11105 displayed. Observe that the contents are written in the same way as
11106 their @code{C} counterparts.
11110 s: ARRAY [1..5] OF CARDINAL ;
11116 (@value{GDBP}) print s
11117 $1 = @{1, 0, 0, 0, 0@}
11118 (@value{GDBP}) ptype s
11119 type = ARRAY [1..5] OF CARDINAL
11122 The Modula-2 language interface to @value{GDBN} also understands
11123 pointer types as shown in this example:
11127 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11134 and you can request that @value{GDBN} describes the type of @code{s}.
11137 (@value{GDBP}) ptype s
11138 type = POINTER TO ARRAY [1..5] OF CARDINAL
11141 @value{GDBN} handles compound types as we can see in this example.
11142 Here we combine array types, record types, pointer types and subrange
11153 myarray = ARRAY myrange OF CARDINAL ;
11154 myrange = [-2..2] ;
11156 s: POINTER TO ARRAY myrange OF foo ;
11160 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11164 (@value{GDBP}) ptype s
11165 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11168 f3 : ARRAY [-2..2] OF CARDINAL;
11173 @subsubsection Modula-2 Defaults
11174 @cindex Modula-2 defaults
11176 If type and range checking are set automatically by @value{GDBN}, they
11177 both default to @code{on} whenever the working language changes to
11178 Modula-2. This happens regardless of whether you or @value{GDBN}
11179 selected the working language.
11181 If you allow @value{GDBN} to set the language automatically, then entering
11182 code compiled from a file whose name ends with @file{.mod} sets the
11183 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11184 Infer the Source Language}, for further details.
11187 @subsubsection Deviations from Standard Modula-2
11188 @cindex Modula-2, deviations from
11190 A few changes have been made to make Modula-2 programs easier to debug.
11191 This is done primarily via loosening its type strictness:
11195 Unlike in standard Modula-2, pointer constants can be formed by
11196 integers. This allows you to modify pointer variables during
11197 debugging. (In standard Modula-2, the actual address contained in a
11198 pointer variable is hidden from you; it can only be modified
11199 through direct assignment to another pointer variable or expression that
11200 returned a pointer.)
11203 C escape sequences can be used in strings and characters to represent
11204 non-printable characters. @value{GDBN} prints out strings with these
11205 escape sequences embedded. Single non-printable characters are
11206 printed using the @samp{CHR(@var{nnn})} format.
11209 The assignment operator (@code{:=}) returns the value of its right-hand
11213 All built-in procedures both modify @emph{and} return their argument.
11217 @subsubsection Modula-2 Type and Range Checks
11218 @cindex Modula-2 checks
11221 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11224 @c FIXME remove warning when type/range checks added
11226 @value{GDBN} considers two Modula-2 variables type equivalent if:
11230 They are of types that have been declared equivalent via a @code{TYPE
11231 @var{t1} = @var{t2}} statement
11234 They have been declared on the same line. (Note: This is true of the
11235 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11238 As long as type checking is enabled, any attempt to combine variables
11239 whose types are not equivalent is an error.
11241 Range checking is done on all mathematical operations, assignment, array
11242 index bounds, and all built-in functions and procedures.
11245 @subsubsection The Scope Operators @code{::} and @code{.}
11247 @cindex @code{.}, Modula-2 scope operator
11248 @cindex colon, doubled as scope operator
11250 @vindex colon-colon@r{, in Modula-2}
11251 @c Info cannot handle :: but TeX can.
11254 @vindex ::@r{, in Modula-2}
11257 There are a few subtle differences between the Modula-2 scope operator
11258 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11263 @var{module} . @var{id}
11264 @var{scope} :: @var{id}
11268 where @var{scope} is the name of a module or a procedure,
11269 @var{module} the name of a module, and @var{id} is any declared
11270 identifier within your program, except another module.
11272 Using the @code{::} operator makes @value{GDBN} search the scope
11273 specified by @var{scope} for the identifier @var{id}. If it is not
11274 found in the specified scope, then @value{GDBN} searches all scopes
11275 enclosing the one specified by @var{scope}.
11277 Using the @code{.} operator makes @value{GDBN} search the current scope for
11278 the identifier specified by @var{id} that was imported from the
11279 definition module specified by @var{module}. With this operator, it is
11280 an error if the identifier @var{id} was not imported from definition
11281 module @var{module}, or if @var{id} is not an identifier in
11285 @subsubsection @value{GDBN} and Modula-2
11287 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11288 Five subcommands of @code{set print} and @code{show print} apply
11289 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11290 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11291 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11292 analogue in Modula-2.
11294 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11295 with any language, is not useful with Modula-2. Its
11296 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11297 created in Modula-2 as they can in C or C@t{++}. However, because an
11298 address can be specified by an integral constant, the construct
11299 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11301 @cindex @code{#} in Modula-2
11302 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11303 interpreted as the beginning of a comment. Use @code{<>} instead.
11309 The extensions made to @value{GDBN} for Ada only support
11310 output from the @sc{gnu} Ada (GNAT) compiler.
11311 Other Ada compilers are not currently supported, and
11312 attempting to debug executables produced by them is most likely
11316 @cindex expressions in Ada
11318 * Ada Mode Intro:: General remarks on the Ada syntax
11319 and semantics supported by Ada mode
11321 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11322 * Additions to Ada:: Extensions of the Ada expression syntax.
11323 * Stopping Before Main Program:: Debugging the program during elaboration.
11324 * Ada Tasks:: Listing and setting breakpoints in tasks.
11325 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
11326 * Ada Glitches:: Known peculiarities of Ada mode.
11329 @node Ada Mode Intro
11330 @subsubsection Introduction
11331 @cindex Ada mode, general
11333 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11334 syntax, with some extensions.
11335 The philosophy behind the design of this subset is
11339 That @value{GDBN} should provide basic literals and access to operations for
11340 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11341 leaving more sophisticated computations to subprograms written into the
11342 program (which therefore may be called from @value{GDBN}).
11345 That type safety and strict adherence to Ada language restrictions
11346 are not particularly important to the @value{GDBN} user.
11349 That brevity is important to the @value{GDBN} user.
11352 Thus, for brevity, the debugger acts as if all names declared in
11353 user-written packages are directly visible, even if they are not visible
11354 according to Ada rules, thus making it unnecessary to fully qualify most
11355 names with their packages, regardless of context. Where this causes
11356 ambiguity, @value{GDBN} asks the user's intent.
11358 The debugger will start in Ada mode if it detects an Ada main program.
11359 As for other languages, it will enter Ada mode when stopped in a program that
11360 was translated from an Ada source file.
11362 While in Ada mode, you may use `@t{--}' for comments. This is useful
11363 mostly for documenting command files. The standard @value{GDBN} comment
11364 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11365 middle (to allow based literals).
11367 The debugger supports limited overloading. Given a subprogram call in which
11368 the function symbol has multiple definitions, it will use the number of
11369 actual parameters and some information about their types to attempt to narrow
11370 the set of definitions. It also makes very limited use of context, preferring
11371 procedures to functions in the context of the @code{call} command, and
11372 functions to procedures elsewhere.
11374 @node Omissions from Ada
11375 @subsubsection Omissions from Ada
11376 @cindex Ada, omissions from
11378 Here are the notable omissions from the subset:
11382 Only a subset of the attributes are supported:
11386 @t{'First}, @t{'Last}, and @t{'Length}
11387 on array objects (not on types and subtypes).
11390 @t{'Min} and @t{'Max}.
11393 @t{'Pos} and @t{'Val}.
11399 @t{'Range} on array objects (not subtypes), but only as the right
11400 operand of the membership (@code{in}) operator.
11403 @t{'Access}, @t{'Unchecked_Access}, and
11404 @t{'Unrestricted_Access} (a GNAT extension).
11412 @code{Characters.Latin_1} are not available and
11413 concatenation is not implemented. Thus, escape characters in strings are
11414 not currently available.
11417 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11418 equality of representations. They will generally work correctly
11419 for strings and arrays whose elements have integer or enumeration types.
11420 They may not work correctly for arrays whose element
11421 types have user-defined equality, for arrays of real values
11422 (in particular, IEEE-conformant floating point, because of negative
11423 zeroes and NaNs), and for arrays whose elements contain unused bits with
11424 indeterminate values.
11427 The other component-by-component array operations (@code{and}, @code{or},
11428 @code{xor}, @code{not}, and relational tests other than equality)
11429 are not implemented.
11432 @cindex array aggregates (Ada)
11433 @cindex record aggregates (Ada)
11434 @cindex aggregates (Ada)
11435 There is limited support for array and record aggregates. They are
11436 permitted only on the right sides of assignments, as in these examples:
11439 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
11440 (@value{GDBP}) set An_Array := (1, others => 0)
11441 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11442 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11443 (@value{GDBP}) set A_Record := (1, "Peter", True);
11444 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
11448 discriminant's value by assigning an aggregate has an
11449 undefined effect if that discriminant is used within the record.
11450 However, you can first modify discriminants by directly assigning to
11451 them (which normally would not be allowed in Ada), and then performing an
11452 aggregate assignment. For example, given a variable @code{A_Rec}
11453 declared to have a type such as:
11456 type Rec (Len : Small_Integer := 0) is record
11458 Vals : IntArray (1 .. Len);
11462 you can assign a value with a different size of @code{Vals} with two
11466 (@value{GDBP}) set A_Rec.Len := 4
11467 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11470 As this example also illustrates, @value{GDBN} is very loose about the usual
11471 rules concerning aggregates. You may leave out some of the
11472 components of an array or record aggregate (such as the @code{Len}
11473 component in the assignment to @code{A_Rec} above); they will retain their
11474 original values upon assignment. You may freely use dynamic values as
11475 indices in component associations. You may even use overlapping or
11476 redundant component associations, although which component values are
11477 assigned in such cases is not defined.
11480 Calls to dispatching subprograms are not implemented.
11483 The overloading algorithm is much more limited (i.e., less selective)
11484 than that of real Ada. It makes only limited use of the context in
11485 which a subexpression appears to resolve its meaning, and it is much
11486 looser in its rules for allowing type matches. As a result, some
11487 function calls will be ambiguous, and the user will be asked to choose
11488 the proper resolution.
11491 The @code{new} operator is not implemented.
11494 Entry calls are not implemented.
11497 Aside from printing, arithmetic operations on the native VAX floating-point
11498 formats are not supported.
11501 It is not possible to slice a packed array.
11504 The names @code{True} and @code{False}, when not part of a qualified name,
11505 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
11507 Should your program
11508 redefine these names in a package or procedure (at best a dubious practice),
11509 you will have to use fully qualified names to access their new definitions.
11512 @node Additions to Ada
11513 @subsubsection Additions to Ada
11514 @cindex Ada, deviations from
11516 As it does for other languages, @value{GDBN} makes certain generic
11517 extensions to Ada (@pxref{Expressions}):
11521 If the expression @var{E} is a variable residing in memory (typically
11522 a local variable or array element) and @var{N} is a positive integer,
11523 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11524 @var{N}-1 adjacent variables following it in memory as an array. In
11525 Ada, this operator is generally not necessary, since its prime use is
11526 in displaying parts of an array, and slicing will usually do this in
11527 Ada. However, there are occasional uses when debugging programs in
11528 which certain debugging information has been optimized away.
11531 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11532 appears in function or file @var{B}.'' When @var{B} is a file name,
11533 you must typically surround it in single quotes.
11536 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11537 @var{type} that appears at address @var{addr}.''
11540 A name starting with @samp{$} is a convenience variable
11541 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11544 In addition, @value{GDBN} provides a few other shortcuts and outright
11545 additions specific to Ada:
11549 The assignment statement is allowed as an expression, returning
11550 its right-hand operand as its value. Thus, you may enter
11553 (@value{GDBP}) set x := y + 3
11554 (@value{GDBP}) print A(tmp := y + 1)
11558 The semicolon is allowed as an ``operator,'' returning as its value
11559 the value of its right-hand operand.
11560 This allows, for example,
11561 complex conditional breaks:
11564 (@value{GDBP}) break f
11565 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
11569 Rather than use catenation and symbolic character names to introduce special
11570 characters into strings, one may instead use a special bracket notation,
11571 which is also used to print strings. A sequence of characters of the form
11572 @samp{["@var{XX}"]} within a string or character literal denotes the
11573 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11574 sequence of characters @samp{["""]} also denotes a single quotation mark
11575 in strings. For example,
11577 "One line.["0a"]Next line.["0a"]"
11580 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11584 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11585 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11589 (@value{GDBP}) print 'max(x, y)
11593 When printing arrays, @value{GDBN} uses positional notation when the
11594 array has a lower bound of 1, and uses a modified named notation otherwise.
11595 For example, a one-dimensional array of three integers with a lower bound
11596 of 3 might print as
11603 That is, in contrast to valid Ada, only the first component has a @code{=>}
11607 You may abbreviate attributes in expressions with any unique,
11608 multi-character subsequence of
11609 their names (an exact match gets preference).
11610 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11611 in place of @t{a'length}.
11614 @cindex quoting Ada internal identifiers
11615 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11616 to lower case. The GNAT compiler uses upper-case characters for
11617 some of its internal identifiers, which are normally of no interest to users.
11618 For the rare occasions when you actually have to look at them,
11619 enclose them in angle brackets to avoid the lower-case mapping.
11622 (@value{GDBP}) print <JMPBUF_SAVE>[0]
11626 Printing an object of class-wide type or dereferencing an
11627 access-to-class-wide value will display all the components of the object's
11628 specific type (as indicated by its run-time tag). Likewise, component
11629 selection on such a value will operate on the specific type of the
11634 @node Stopping Before Main Program
11635 @subsubsection Stopping at the Very Beginning
11637 @cindex breakpointing Ada elaboration code
11638 It is sometimes necessary to debug the program during elaboration, and
11639 before reaching the main procedure.
11640 As defined in the Ada Reference
11641 Manual, the elaboration code is invoked from a procedure called
11642 @code{adainit}. To run your program up to the beginning of
11643 elaboration, simply use the following two commands:
11644 @code{tbreak adainit} and @code{run}.
11647 @subsubsection Extensions for Ada Tasks
11648 @cindex Ada, tasking
11650 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
11651 @value{GDBN} provides the following task-related commands:
11656 This command shows a list of current Ada tasks, as in the following example:
11663 (@value{GDBP}) info tasks
11664 ID TID P-ID Pri State Name
11665 1 8088000 0 15 Child Activation Wait main_task
11666 2 80a4000 1 15 Accept Statement b
11667 3 809a800 1 15 Child Activation Wait a
11668 * 4 80ae800 3 15 Runnable c
11673 In this listing, the asterisk before the last task indicates it to be the
11674 task currently being inspected.
11678 Represents @value{GDBN}'s internal task number.
11684 The parent's task ID (@value{GDBN}'s internal task number).
11687 The base priority of the task.
11690 Current state of the task.
11694 The task has been created but has not been activated. It cannot be
11698 The task is not blocked for any reason known to Ada. (It may be waiting
11699 for a mutex, though.) It is conceptually "executing" in normal mode.
11702 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
11703 that were waiting on terminate alternatives have been awakened and have
11704 terminated themselves.
11706 @item Child Activation Wait
11707 The task is waiting for created tasks to complete activation.
11709 @item Accept Statement
11710 The task is waiting on an accept or selective wait statement.
11712 @item Waiting on entry call
11713 The task is waiting on an entry call.
11715 @item Async Select Wait
11716 The task is waiting to start the abortable part of an asynchronous
11720 The task is waiting on a select statement with only a delay
11723 @item Child Termination Wait
11724 The task is sleeping having completed a master within itself, and is
11725 waiting for the tasks dependent on that master to become terminated or
11726 waiting on a terminate Phase.
11728 @item Wait Child in Term Alt
11729 The task is sleeping waiting for tasks on terminate alternatives to
11730 finish terminating.
11732 @item Accepting RV with @var{taskno}
11733 The task is accepting a rendez-vous with the task @var{taskno}.
11737 Name of the task in the program.
11741 @kindex info task @var{taskno}
11742 @item info task @var{taskno}
11743 This command shows detailled informations on the specified task, as in
11744 the following example:
11749 (@value{GDBP}) info tasks
11750 ID TID P-ID Pri State Name
11751 1 8077880 0 15 Child Activation Wait main_task
11752 * 2 807c468 1 15 Runnable task_1
11753 (@value{GDBP}) info task 2
11754 Ada Task: 0x807c468
11757 Parent: 1 (main_task)
11763 @kindex task@r{ (Ada)}
11764 @cindex current Ada task ID
11765 This command prints the ID of the current task.
11771 (@value{GDBP}) info tasks
11772 ID TID P-ID Pri State Name
11773 1 8077870 0 15 Child Activation Wait main_task
11774 * 2 807c458 1 15 Runnable t
11775 (@value{GDBP}) task
11776 [Current task is 2]
11779 @item task @var{taskno}
11780 @cindex Ada task switching
11781 This command is like the @code{thread @var{threadno}}
11782 command (@pxref{Threads}). It switches the context of debugging
11783 from the current task to the given task.
11789 (@value{GDBP}) info tasks
11790 ID TID P-ID Pri State Name
11791 1 8077870 0 15 Child Activation Wait main_task
11792 * 2 807c458 1 15 Runnable t
11793 (@value{GDBP}) task 1
11794 [Switching to task 1]
11795 #0 0x8067726 in pthread_cond_wait ()
11797 #0 0x8067726 in pthread_cond_wait ()
11798 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
11799 #2 0x805cb63 in system.task_primitives.operations.sleep ()
11800 #3 0x806153e in system.tasking.stages.activate_tasks ()
11801 #4 0x804aacc in un () at un.adb:5
11804 @item break @var{linespec} task @var{taskno}
11805 @itemx break @var{linespec} task @var{taskno} if @dots{}
11806 @cindex breakpoints and tasks, in Ada
11807 @cindex task breakpoints, in Ada
11808 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
11809 These commands are like the @code{break @dots{} thread @dots{}}
11810 command (@pxref{Thread Stops}).
11811 @var{linespec} specifies source lines, as described
11812 in @ref{Specify Location}.
11814 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
11815 to specify that you only want @value{GDBN} to stop the program when a
11816 particular Ada task reaches this breakpoint. @var{taskno} is one of the
11817 numeric task identifiers assigned by @value{GDBN}, shown in the first
11818 column of the @samp{info tasks} display.
11820 If you do not specify @samp{task @var{taskno}} when you set a
11821 breakpoint, the breakpoint applies to @emph{all} tasks of your
11824 You can use the @code{task} qualifier on conditional breakpoints as
11825 well; in this case, place @samp{task @var{taskno}} before the
11826 breakpoint condition (before the @code{if}).
11834 (@value{GDBP}) info tasks
11835 ID TID P-ID Pri State Name
11836 1 140022020 0 15 Child Activation Wait main_task
11837 2 140045060 1 15 Accept/Select Wait t2
11838 3 140044840 1 15 Runnable t1
11839 * 4 140056040 1 15 Runnable t3
11840 (@value{GDBP}) b 15 task 2
11841 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
11842 (@value{GDBP}) cont
11847 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
11849 (@value{GDBP}) info tasks
11850 ID TID P-ID Pri State Name
11851 1 140022020 0 15 Child Activation Wait main_task
11852 * 2 140045060 1 15 Runnable t2
11853 3 140044840 1 15 Runnable t1
11854 4 140056040 1 15 Delay Sleep t3
11858 @node Ada Tasks and Core Files
11859 @subsubsection Tasking Support when Debugging Core Files
11860 @cindex Ada tasking and core file debugging
11862 When inspecting a core file, as opposed to debugging a live program,
11863 tasking support may be limited or even unavailable, depending on
11864 the platform being used.
11865 For instance, on x86-linux, the list of tasks is available, but task
11866 switching is not supported. On Tru64, however, task switching will work
11869 On certain platforms, including Tru64, the debugger needs to perform some
11870 memory writes in order to provide Ada tasking support. When inspecting
11871 a core file, this means that the core file must be opened with read-write
11872 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
11873 Under these circumstances, you should make a backup copy of the core
11874 file before inspecting it with @value{GDBN}.
11877 @subsubsection Known Peculiarities of Ada Mode
11878 @cindex Ada, problems
11880 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11881 we know of several problems with and limitations of Ada mode in
11883 some of which will be fixed with planned future releases of the debugger
11884 and the GNU Ada compiler.
11888 Currently, the debugger
11889 has insufficient information to determine whether certain pointers represent
11890 pointers to objects or the objects themselves.
11891 Thus, the user may have to tack an extra @code{.all} after an expression
11892 to get it printed properly.
11895 Static constants that the compiler chooses not to materialize as objects in
11896 storage are invisible to the debugger.
11899 Named parameter associations in function argument lists are ignored (the
11900 argument lists are treated as positional).
11903 Many useful library packages are currently invisible to the debugger.
11906 Fixed-point arithmetic, conversions, input, and output is carried out using
11907 floating-point arithmetic, and may give results that only approximate those on
11911 The GNAT compiler never generates the prefix @code{Standard} for any of
11912 the standard symbols defined by the Ada language. @value{GDBN} knows about
11913 this: it will strip the prefix from names when you use it, and will never
11914 look for a name you have so qualified among local symbols, nor match against
11915 symbols in other packages or subprograms. If you have
11916 defined entities anywhere in your program other than parameters and
11917 local variables whose simple names match names in @code{Standard},
11918 GNAT's lack of qualification here can cause confusion. When this happens,
11919 you can usually resolve the confusion
11920 by qualifying the problematic names with package
11921 @code{Standard} explicitly.
11924 @node Unsupported Languages
11925 @section Unsupported Languages
11927 @cindex unsupported languages
11928 @cindex minimal language
11929 In addition to the other fully-supported programming languages,
11930 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11931 It does not represent a real programming language, but provides a set
11932 of capabilities close to what the C or assembly languages provide.
11933 This should allow most simple operations to be performed while debugging
11934 an application that uses a language currently not supported by @value{GDBN}.
11936 If the language is set to @code{auto}, @value{GDBN} will automatically
11937 select this language if the current frame corresponds to an unsupported
11941 @chapter Examining the Symbol Table
11943 The commands described in this chapter allow you to inquire about the
11944 symbols (names of variables, functions and types) defined in your
11945 program. This information is inherent in the text of your program and
11946 does not change as your program executes. @value{GDBN} finds it in your
11947 program's symbol table, in the file indicated when you started @value{GDBN}
11948 (@pxref{File Options, ,Choosing Files}), or by one of the
11949 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11951 @cindex symbol names
11952 @cindex names of symbols
11953 @cindex quoting names
11954 Occasionally, you may need to refer to symbols that contain unusual
11955 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11956 most frequent case is in referring to static variables in other
11957 source files (@pxref{Variables,,Program Variables}). File names
11958 are recorded in object files as debugging symbols, but @value{GDBN} would
11959 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11960 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11961 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11968 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11971 @cindex case-insensitive symbol names
11972 @cindex case sensitivity in symbol names
11973 @kindex set case-sensitive
11974 @item set case-sensitive on
11975 @itemx set case-sensitive off
11976 @itemx set case-sensitive auto
11977 Normally, when @value{GDBN} looks up symbols, it matches their names
11978 with case sensitivity determined by the current source language.
11979 Occasionally, you may wish to control that. The command @code{set
11980 case-sensitive} lets you do that by specifying @code{on} for
11981 case-sensitive matches or @code{off} for case-insensitive ones. If
11982 you specify @code{auto}, case sensitivity is reset to the default
11983 suitable for the source language. The default is case-sensitive
11984 matches for all languages except for Fortran, for which the default is
11985 case-insensitive matches.
11987 @kindex show case-sensitive
11988 @item show case-sensitive
11989 This command shows the current setting of case sensitivity for symbols
11992 @kindex info address
11993 @cindex address of a symbol
11994 @item info address @var{symbol}
11995 Describe where the data for @var{symbol} is stored. For a register
11996 variable, this says which register it is kept in. For a non-register
11997 local variable, this prints the stack-frame offset at which the variable
12000 Note the contrast with @samp{print &@var{symbol}}, which does not work
12001 at all for a register variable, and for a stack local variable prints
12002 the exact address of the current instantiation of the variable.
12004 @kindex info symbol
12005 @cindex symbol from address
12006 @cindex closest symbol and offset for an address
12007 @item info symbol @var{addr}
12008 Print the name of a symbol which is stored at the address @var{addr}.
12009 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
12010 nearest symbol and an offset from it:
12013 (@value{GDBP}) info symbol 0x54320
12014 _initialize_vx + 396 in section .text
12018 This is the opposite of the @code{info address} command. You can use
12019 it to find out the name of a variable or a function given its address.
12021 For dynamically linked executables, the name of executable or shared
12022 library containing the symbol is also printed:
12025 (@value{GDBP}) info symbol 0x400225
12026 _start + 5 in section .text of /tmp/a.out
12027 (@value{GDBP}) info symbol 0x2aaaac2811cf
12028 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
12032 @item whatis [@var{arg}]
12033 Print the data type of @var{arg}, which can be either an expression or
12034 a data type. With no argument, print the data type of @code{$}, the
12035 last value in the value history. If @var{arg} is an expression, it is
12036 not actually evaluated, and any side-effecting operations (such as
12037 assignments or function calls) inside it do not take place. If
12038 @var{arg} is a type name, it may be the name of a type or typedef, or
12039 for C code it may have the form @samp{class @var{class-name}},
12040 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
12041 @samp{enum @var{enum-tag}}.
12042 @xref{Expressions, ,Expressions}.
12045 @item ptype [@var{arg}]
12046 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
12047 detailed description of the type, instead of just the name of the type.
12048 @xref{Expressions, ,Expressions}.
12050 For example, for this variable declaration:
12053 struct complex @{double real; double imag;@} v;
12057 the two commands give this output:
12061 (@value{GDBP}) whatis v
12062 type = struct complex
12063 (@value{GDBP}) ptype v
12064 type = struct complex @{
12072 As with @code{whatis}, using @code{ptype} without an argument refers to
12073 the type of @code{$}, the last value in the value history.
12075 @cindex incomplete type
12076 Sometimes, programs use opaque data types or incomplete specifications
12077 of complex data structure. If the debug information included in the
12078 program does not allow @value{GDBN} to display a full declaration of
12079 the data type, it will say @samp{<incomplete type>}. For example,
12080 given these declarations:
12084 struct foo *fooptr;
12088 but no definition for @code{struct foo} itself, @value{GDBN} will say:
12091 (@value{GDBP}) ptype foo
12092 $1 = <incomplete type>
12096 ``Incomplete type'' is C terminology for data types that are not
12097 completely specified.
12100 @item info types @var{regexp}
12102 Print a brief description of all types whose names match the regular
12103 expression @var{regexp} (or all types in your program, if you supply
12104 no argument). Each complete typename is matched as though it were a
12105 complete line; thus, @samp{i type value} gives information on all
12106 types in your program whose names include the string @code{value}, but
12107 @samp{i type ^value$} gives information only on types whose complete
12108 name is @code{value}.
12110 This command differs from @code{ptype} in two ways: first, like
12111 @code{whatis}, it does not print a detailed description; second, it
12112 lists all source files where a type is defined.
12115 @cindex local variables
12116 @item info scope @var{location}
12117 List all the variables local to a particular scope. This command
12118 accepts a @var{location} argument---a function name, a source line, or
12119 an address preceded by a @samp{*}, and prints all the variables local
12120 to the scope defined by that location. (@xref{Specify Location}, for
12121 details about supported forms of @var{location}.) For example:
12124 (@value{GDBP}) @b{info scope command_line_handler}
12125 Scope for command_line_handler:
12126 Symbol rl is an argument at stack/frame offset 8, length 4.
12127 Symbol linebuffer is in static storage at address 0x150a18, length 4.
12128 Symbol linelength is in static storage at address 0x150a1c, length 4.
12129 Symbol p is a local variable in register $esi, length 4.
12130 Symbol p1 is a local variable in register $ebx, length 4.
12131 Symbol nline is a local variable in register $edx, length 4.
12132 Symbol repeat is a local variable at frame offset -8, length 4.
12136 This command is especially useful for determining what data to collect
12137 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
12140 @kindex info source
12142 Show information about the current source file---that is, the source file for
12143 the function containing the current point of execution:
12146 the name of the source file, and the directory containing it,
12148 the directory it was compiled in,
12150 its length, in lines,
12152 which programming language it is written in,
12154 whether the executable includes debugging information for that file, and
12155 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
12157 whether the debugging information includes information about
12158 preprocessor macros.
12162 @kindex info sources
12164 Print the names of all source files in your program for which there is
12165 debugging information, organized into two lists: files whose symbols
12166 have already been read, and files whose symbols will be read when needed.
12168 @kindex info functions
12169 @item info functions
12170 Print the names and data types of all defined functions.
12172 @item info functions @var{regexp}
12173 Print the names and data types of all defined functions
12174 whose names contain a match for regular expression @var{regexp}.
12175 Thus, @samp{info fun step} finds all functions whose names
12176 include @code{step}; @samp{info fun ^step} finds those whose names
12177 start with @code{step}. If a function name contains characters
12178 that conflict with the regular expression language (e.g.@:
12179 @samp{operator*()}), they may be quoted with a backslash.
12181 @kindex info variables
12182 @item info variables
12183 Print the names and data types of all variables that are declared
12184 outside of functions (i.e.@: excluding local variables).
12186 @item info variables @var{regexp}
12187 Print the names and data types of all variables (except for local
12188 variables) whose names contain a match for regular expression
12191 @kindex info classes
12192 @cindex Objective-C, classes and selectors
12194 @itemx info classes @var{regexp}
12195 Display all Objective-C classes in your program, or
12196 (with the @var{regexp} argument) all those matching a particular regular
12199 @kindex info selectors
12200 @item info selectors
12201 @itemx info selectors @var{regexp}
12202 Display all Objective-C selectors in your program, or
12203 (with the @var{regexp} argument) all those matching a particular regular
12207 This was never implemented.
12208 @kindex info methods
12210 @itemx info methods @var{regexp}
12211 The @code{info methods} command permits the user to examine all defined
12212 methods within C@t{++} program, or (with the @var{regexp} argument) a
12213 specific set of methods found in the various C@t{++} classes. Many
12214 C@t{++} classes provide a large number of methods. Thus, the output
12215 from the @code{ptype} command can be overwhelming and hard to use. The
12216 @code{info-methods} command filters the methods, printing only those
12217 which match the regular-expression @var{regexp}.
12220 @cindex reloading symbols
12221 Some systems allow individual object files that make up your program to
12222 be replaced without stopping and restarting your program. For example,
12223 in VxWorks you can simply recompile a defective object file and keep on
12224 running. If you are running on one of these systems, you can allow
12225 @value{GDBN} to reload the symbols for automatically relinked modules:
12228 @kindex set symbol-reloading
12229 @item set symbol-reloading on
12230 Replace symbol definitions for the corresponding source file when an
12231 object file with a particular name is seen again.
12233 @item set symbol-reloading off
12234 Do not replace symbol definitions when encountering object files of the
12235 same name more than once. This is the default state; if you are not
12236 running on a system that permits automatic relinking of modules, you
12237 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12238 may discard symbols when linking large programs, that may contain
12239 several modules (from different directories or libraries) with the same
12242 @kindex show symbol-reloading
12243 @item show symbol-reloading
12244 Show the current @code{on} or @code{off} setting.
12247 @cindex opaque data types
12248 @kindex set opaque-type-resolution
12249 @item set opaque-type-resolution on
12250 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12251 declared as a pointer to a @code{struct}, @code{class}, or
12252 @code{union}---for example, @code{struct MyType *}---that is used in one
12253 source file although the full declaration of @code{struct MyType} is in
12254 another source file. The default is on.
12256 A change in the setting of this subcommand will not take effect until
12257 the next time symbols for a file are loaded.
12259 @item set opaque-type-resolution off
12260 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12261 is printed as follows:
12263 @{<no data fields>@}
12266 @kindex show opaque-type-resolution
12267 @item show opaque-type-resolution
12268 Show whether opaque types are resolved or not.
12270 @kindex set print symbol-loading
12271 @cindex print messages when symbols are loaded
12272 @item set print symbol-loading
12273 @itemx set print symbol-loading on
12274 @itemx set print symbol-loading off
12275 The @code{set print symbol-loading} command allows you to enable or
12276 disable printing of messages when @value{GDBN} loads symbols.
12277 By default, these messages will be printed, and normally this is what
12278 you want. Disabling these messages is useful when debugging applications
12279 with lots of shared libraries where the quantity of output can be more
12280 annoying than useful.
12282 @kindex show print symbol-loading
12283 @item show print symbol-loading
12284 Show whether messages will be printed when @value{GDBN} loads symbols.
12286 @kindex maint print symbols
12287 @cindex symbol dump
12288 @kindex maint print psymbols
12289 @cindex partial symbol dump
12290 @item maint print symbols @var{filename}
12291 @itemx maint print psymbols @var{filename}
12292 @itemx maint print msymbols @var{filename}
12293 Write a dump of debugging symbol data into the file @var{filename}.
12294 These commands are used to debug the @value{GDBN} symbol-reading code. Only
12295 symbols with debugging data are included. If you use @samp{maint print
12296 symbols}, @value{GDBN} includes all the symbols for which it has already
12297 collected full details: that is, @var{filename} reflects symbols for
12298 only those files whose symbols @value{GDBN} has read. You can use the
12299 command @code{info sources} to find out which files these are. If you
12300 use @samp{maint print psymbols} instead, the dump shows information about
12301 symbols that @value{GDBN} only knows partially---that is, symbols defined in
12302 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
12303 @samp{maint print msymbols} dumps just the minimal symbol information
12304 required for each object file from which @value{GDBN} has read some symbols.
12305 @xref{Files, ,Commands to Specify Files}, for a discussion of how
12306 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
12308 @kindex maint info symtabs
12309 @kindex maint info psymtabs
12310 @cindex listing @value{GDBN}'s internal symbol tables
12311 @cindex symbol tables, listing @value{GDBN}'s internal
12312 @cindex full symbol tables, listing @value{GDBN}'s internal
12313 @cindex partial symbol tables, listing @value{GDBN}'s internal
12314 @item maint info symtabs @r{[} @var{regexp} @r{]}
12315 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
12317 List the @code{struct symtab} or @code{struct partial_symtab}
12318 structures whose names match @var{regexp}. If @var{regexp} is not
12319 given, list them all. The output includes expressions which you can
12320 copy into a @value{GDBN} debugging this one to examine a particular
12321 structure in more detail. For example:
12324 (@value{GDBP}) maint info psymtabs dwarf2read
12325 @{ objfile /home/gnu/build/gdb/gdb
12326 ((struct objfile *) 0x82e69d0)
12327 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
12328 ((struct partial_symtab *) 0x8474b10)
12331 text addresses 0x814d3c8 -- 0x8158074
12332 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
12333 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
12334 dependencies (none)
12337 (@value{GDBP}) maint info symtabs
12341 We see that there is one partial symbol table whose filename contains
12342 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
12343 and we see that @value{GDBN} has not read in any symtabs yet at all.
12344 If we set a breakpoint on a function, that will cause @value{GDBN} to
12345 read the symtab for the compilation unit containing that function:
12348 (@value{GDBP}) break dwarf2_psymtab_to_symtab
12349 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
12351 (@value{GDBP}) maint info symtabs
12352 @{ objfile /home/gnu/build/gdb/gdb
12353 ((struct objfile *) 0x82e69d0)
12354 @{ symtab /home/gnu/src/gdb/dwarf2read.c
12355 ((struct symtab *) 0x86c1f38)
12358 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
12359 linetable ((struct linetable *) 0x8370fa0)
12360 debugformat DWARF 2
12369 @chapter Altering Execution
12371 Once you think you have found an error in your program, you might want to
12372 find out for certain whether correcting the apparent error would lead to
12373 correct results in the rest of the run. You can find the answer by
12374 experiment, using the @value{GDBN} features for altering execution of the
12377 For example, you can store new values into variables or memory
12378 locations, give your program a signal, restart it at a different
12379 address, or even return prematurely from a function.
12382 * Assignment:: Assignment to variables
12383 * Jumping:: Continuing at a different address
12384 * Signaling:: Giving your program a signal
12385 * Returning:: Returning from a function
12386 * Calling:: Calling your program's functions
12387 * Patching:: Patching your program
12391 @section Assignment to Variables
12394 @cindex setting variables
12395 To alter the value of a variable, evaluate an assignment expression.
12396 @xref{Expressions, ,Expressions}. For example,
12403 stores the value 4 into the variable @code{x}, and then prints the
12404 value of the assignment expression (which is 4).
12405 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
12406 information on operators in supported languages.
12408 @kindex set variable
12409 @cindex variables, setting
12410 If you are not interested in seeing the value of the assignment, use the
12411 @code{set} command instead of the @code{print} command. @code{set} is
12412 really the same as @code{print} except that the expression's value is
12413 not printed and is not put in the value history (@pxref{Value History,
12414 ,Value History}). The expression is evaluated only for its effects.
12416 If the beginning of the argument string of the @code{set} command
12417 appears identical to a @code{set} subcommand, use the @code{set
12418 variable} command instead of just @code{set}. This command is identical
12419 to @code{set} except for its lack of subcommands. For example, if your
12420 program has a variable @code{width}, you get an error if you try to set
12421 a new value with just @samp{set width=13}, because @value{GDBN} has the
12422 command @code{set width}:
12425 (@value{GDBP}) whatis width
12427 (@value{GDBP}) p width
12429 (@value{GDBP}) set width=47
12430 Invalid syntax in expression.
12434 The invalid expression, of course, is @samp{=47}. In
12435 order to actually set the program's variable @code{width}, use
12438 (@value{GDBP}) set var width=47
12441 Because the @code{set} command has many subcommands that can conflict
12442 with the names of program variables, it is a good idea to use the
12443 @code{set variable} command instead of just @code{set}. For example, if
12444 your program has a variable @code{g}, you run into problems if you try
12445 to set a new value with just @samp{set g=4}, because @value{GDBN} has
12446 the command @code{set gnutarget}, abbreviated @code{set g}:
12450 (@value{GDBP}) whatis g
12454 (@value{GDBP}) set g=4
12458 The program being debugged has been started already.
12459 Start it from the beginning? (y or n) y
12460 Starting program: /home/smith/cc_progs/a.out
12461 "/home/smith/cc_progs/a.out": can't open to read symbols:
12462 Invalid bfd target.
12463 (@value{GDBP}) show g
12464 The current BFD target is "=4".
12469 The program variable @code{g} did not change, and you silently set the
12470 @code{gnutarget} to an invalid value. In order to set the variable
12474 (@value{GDBP}) set var g=4
12477 @value{GDBN} allows more implicit conversions in assignments than C; you can
12478 freely store an integer value into a pointer variable or vice versa,
12479 and you can convert any structure to any other structure that is the
12480 same length or shorter.
12481 @comment FIXME: how do structs align/pad in these conversions?
12482 @comment /doc@cygnus.com 18dec1990
12484 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12485 construct to generate a value of specified type at a specified address
12486 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12487 to memory location @code{0x83040} as an integer (which implies a certain size
12488 and representation in memory), and
12491 set @{int@}0x83040 = 4
12495 stores the value 4 into that memory location.
12498 @section Continuing at a Different Address
12500 Ordinarily, when you continue your program, you do so at the place where
12501 it stopped, with the @code{continue} command. You can instead continue at
12502 an address of your own choosing, with the following commands:
12506 @item jump @var{linespec}
12507 @itemx jump @var{location}
12508 Resume execution at line @var{linespec} or at address given by
12509 @var{location}. Execution stops again immediately if there is a
12510 breakpoint there. @xref{Specify Location}, for a description of the
12511 different forms of @var{linespec} and @var{location}. It is common
12512 practice to use the @code{tbreak} command in conjunction with
12513 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
12515 The @code{jump} command does not change the current stack frame, or
12516 the stack pointer, or the contents of any memory location or any
12517 register other than the program counter. If line @var{linespec} is in
12518 a different function from the one currently executing, the results may
12519 be bizarre if the two functions expect different patterns of arguments or
12520 of local variables. For this reason, the @code{jump} command requests
12521 confirmation if the specified line is not in the function currently
12522 executing. However, even bizarre results are predictable if you are
12523 well acquainted with the machine-language code of your program.
12526 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
12527 On many systems, you can get much the same effect as the @code{jump}
12528 command by storing a new value into the register @code{$pc}. The
12529 difference is that this does not start your program running; it only
12530 changes the address of where it @emph{will} run when you continue. For
12538 makes the next @code{continue} command or stepping command execute at
12539 address @code{0x485}, rather than at the address where your program stopped.
12540 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12542 The most common occasion to use the @code{jump} command is to back
12543 up---perhaps with more breakpoints set---over a portion of a program
12544 that has already executed, in order to examine its execution in more
12549 @section Giving your Program a Signal
12550 @cindex deliver a signal to a program
12554 @item signal @var{signal}
12555 Resume execution where your program stopped, but immediately give it the
12556 signal @var{signal}. @var{signal} can be the name or the number of a
12557 signal. For example, on many systems @code{signal 2} and @code{signal
12558 SIGINT} are both ways of sending an interrupt signal.
12560 Alternatively, if @var{signal} is zero, continue execution without
12561 giving a signal. This is useful when your program stopped on account of
12562 a signal and would ordinary see the signal when resumed with the
12563 @code{continue} command; @samp{signal 0} causes it to resume without a
12566 @code{signal} does not repeat when you press @key{RET} a second time
12567 after executing the command.
12571 Invoking the @code{signal} command is not the same as invoking the
12572 @code{kill} utility from the shell. Sending a signal with @code{kill}
12573 causes @value{GDBN} to decide what to do with the signal depending on
12574 the signal handling tables (@pxref{Signals}). The @code{signal} command
12575 passes the signal directly to your program.
12579 @section Returning from a Function
12582 @cindex returning from a function
12585 @itemx return @var{expression}
12586 You can cancel execution of a function call with the @code{return}
12587 command. If you give an
12588 @var{expression} argument, its value is used as the function's return
12592 When you use @code{return}, @value{GDBN} discards the selected stack frame
12593 (and all frames within it). You can think of this as making the
12594 discarded frame return prematurely. If you wish to specify a value to
12595 be returned, give that value as the argument to @code{return}.
12597 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12598 Frame}), and any other frames inside of it, leaving its caller as the
12599 innermost remaining frame. That frame becomes selected. The
12600 specified value is stored in the registers used for returning values
12603 The @code{return} command does not resume execution; it leaves the
12604 program stopped in the state that would exist if the function had just
12605 returned. In contrast, the @code{finish} command (@pxref{Continuing
12606 and Stepping, ,Continuing and Stepping}) resumes execution until the
12607 selected stack frame returns naturally.
12609 @value{GDBN} needs to know how the @var{expression} argument should be set for
12610 the inferior. The concrete registers assignment depends on the OS ABI and the
12611 type being returned by the selected stack frame. For example it is common for
12612 OS ABI to return floating point values in FPU registers while integer values in
12613 CPU registers. Still some ABIs return even floating point values in CPU
12614 registers. Larger integer widths (such as @code{long long int}) also have
12615 specific placement rules. @value{GDBN} already knows the OS ABI from its
12616 current target so it needs to find out also the type being returned to make the
12617 assignment into the right register(s).
12619 Normally, the selected stack frame has debug info. @value{GDBN} will always
12620 use the debug info instead of the implicit type of @var{expression} when the
12621 debug info is available. For example, if you type @kbd{return -1}, and the
12622 function in the current stack frame is declared to return a @code{long long
12623 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
12624 into a @code{long long int}:
12627 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
12629 (@value{GDBP}) return -1
12630 Make func return now? (y or n) y
12631 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
12632 43 printf ("result=%lld\n", func ());
12636 However, if the selected stack frame does not have a debug info, e.g., if the
12637 function was compiled without debug info, @value{GDBN} has to find out the type
12638 to return from user. Specifying a different type by mistake may set the value
12639 in different inferior registers than the caller code expects. For example,
12640 typing @kbd{return -1} with its implicit type @code{int} would set only a part
12641 of a @code{long long int} result for a debug info less function (on 32-bit
12642 architectures). Therefore the user is required to specify the return type by
12643 an appropriate cast explicitly:
12646 Breakpoint 2, 0x0040050b in func ()
12647 (@value{GDBP}) return -1
12648 Return value type not available for selected stack frame.
12649 Please use an explicit cast of the value to return.
12650 (@value{GDBP}) return (long long int) -1
12651 Make selected stack frame return now? (y or n) y
12652 #0 0x00400526 in main ()
12657 @section Calling Program Functions
12660 @cindex calling functions
12661 @cindex inferior functions, calling
12662 @item print @var{expr}
12663 Evaluate the expression @var{expr} and display the resulting value.
12664 @var{expr} may include calls to functions in the program being
12668 @item call @var{expr}
12669 Evaluate the expression @var{expr} without displaying @code{void}
12672 You can use this variant of the @code{print} command if you want to
12673 execute a function from your program that does not return anything
12674 (a.k.a.@: @dfn{a void function}), but without cluttering the output
12675 with @code{void} returned values that @value{GDBN} will otherwise
12676 print. If the result is not void, it is printed and saved in the
12680 It is possible for the function you call via the @code{print} or
12681 @code{call} command to generate a signal (e.g., if there's a bug in
12682 the function, or if you passed it incorrect arguments). What happens
12683 in that case is controlled by the @code{set unwindonsignal} command.
12686 @item set unwindonsignal
12687 @kindex set unwindonsignal
12688 @cindex unwind stack in called functions
12689 @cindex call dummy stack unwinding
12690 Set unwinding of the stack if a signal is received while in a function
12691 that @value{GDBN} called in the program being debugged. If set to on,
12692 @value{GDBN} unwinds the stack it created for the call and restores
12693 the context to what it was before the call. If set to off (the
12694 default), @value{GDBN} stops in the frame where the signal was
12697 @item show unwindonsignal
12698 @kindex show unwindonsignal
12699 Show the current setting of stack unwinding in the functions called by
12703 @cindex weak alias functions
12704 Sometimes, a function you wish to call is actually a @dfn{weak alias}
12705 for another function. In such case, @value{GDBN} might not pick up
12706 the type information, including the types of the function arguments,
12707 which causes @value{GDBN} to call the inferior function incorrectly.
12708 As a result, the called function will function erroneously and may
12709 even crash. A solution to that is to use the name of the aliased
12713 @section Patching Programs
12715 @cindex patching binaries
12716 @cindex writing into executables
12717 @cindex writing into corefiles
12719 By default, @value{GDBN} opens the file containing your program's
12720 executable code (or the corefile) read-only. This prevents accidental
12721 alterations to machine code; but it also prevents you from intentionally
12722 patching your program's binary.
12724 If you'd like to be able to patch the binary, you can specify that
12725 explicitly with the @code{set write} command. For example, you might
12726 want to turn on internal debugging flags, or even to make emergency
12732 @itemx set write off
12733 If you specify @samp{set write on}, @value{GDBN} opens executable and
12734 core files for both reading and writing; if you specify @kbd{set write
12735 off} (the default), @value{GDBN} opens them read-only.
12737 If you have already loaded a file, you must load it again (using the
12738 @code{exec-file} or @code{core-file} command) after changing @code{set
12739 write}, for your new setting to take effect.
12743 Display whether executable files and core files are opened for writing
12744 as well as reading.
12748 @chapter @value{GDBN} Files
12750 @value{GDBN} needs to know the file name of the program to be debugged,
12751 both in order to read its symbol table and in order to start your
12752 program. To debug a core dump of a previous run, you must also tell
12753 @value{GDBN} the name of the core dump file.
12756 * Files:: Commands to specify files
12757 * Separate Debug Files:: Debugging information in separate files
12758 * Symbol Errors:: Errors reading symbol files
12759 * Data Files:: GDB data files
12763 @section Commands to Specify Files
12765 @cindex symbol table
12766 @cindex core dump file
12768 You may want to specify executable and core dump file names. The usual
12769 way to do this is at start-up time, using the arguments to
12770 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
12771 Out of @value{GDBN}}).
12773 Occasionally it is necessary to change to a different file during a
12774 @value{GDBN} session. Or you may run @value{GDBN} and forget to
12775 specify a file you want to use. Or you are debugging a remote target
12776 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
12777 Program}). In these situations the @value{GDBN} commands to specify
12778 new files are useful.
12781 @cindex executable file
12783 @item file @var{filename}
12784 Use @var{filename} as the program to be debugged. It is read for its
12785 symbols and for the contents of pure memory. It is also the program
12786 executed when you use the @code{run} command. If you do not specify a
12787 directory and the file is not found in the @value{GDBN} working directory,
12788 @value{GDBN} uses the environment variable @code{PATH} as a list of
12789 directories to search, just as the shell does when looking for a program
12790 to run. You can change the value of this variable, for both @value{GDBN}
12791 and your program, using the @code{path} command.
12793 @cindex unlinked object files
12794 @cindex patching object files
12795 You can load unlinked object @file{.o} files into @value{GDBN} using
12796 the @code{file} command. You will not be able to ``run'' an object
12797 file, but you can disassemble functions and inspect variables. Also,
12798 if the underlying BFD functionality supports it, you could use
12799 @kbd{gdb -write} to patch object files using this technique. Note
12800 that @value{GDBN} can neither interpret nor modify relocations in this
12801 case, so branches and some initialized variables will appear to go to
12802 the wrong place. But this feature is still handy from time to time.
12805 @code{file} with no argument makes @value{GDBN} discard any information it
12806 has on both executable file and the symbol table.
12809 @item exec-file @r{[} @var{filename} @r{]}
12810 Specify that the program to be run (but not the symbol table) is found
12811 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12812 if necessary to locate your program. Omitting @var{filename} means to
12813 discard information on the executable file.
12815 @kindex symbol-file
12816 @item symbol-file @r{[} @var{filename} @r{]}
12817 Read symbol table information from file @var{filename}. @code{PATH} is
12818 searched when necessary. Use the @code{file} command to get both symbol
12819 table and program to run from the same file.
12821 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12822 program's symbol table.
12824 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12825 some breakpoints and auto-display expressions. This is because they may
12826 contain pointers to the internal data recording symbols and data types,
12827 which are part of the old symbol table data being discarded inside
12830 @code{symbol-file} does not repeat if you press @key{RET} again after
12833 When @value{GDBN} is configured for a particular environment, it
12834 understands debugging information in whatever format is the standard
12835 generated for that environment; you may use either a @sc{gnu} compiler, or
12836 other compilers that adhere to the local conventions.
12837 Best results are usually obtained from @sc{gnu} compilers; for example,
12838 using @code{@value{NGCC}} you can generate debugging information for
12841 For most kinds of object files, with the exception of old SVR3 systems
12842 using COFF, the @code{symbol-file} command does not normally read the
12843 symbol table in full right away. Instead, it scans the symbol table
12844 quickly to find which source files and which symbols are present. The
12845 details are read later, one source file at a time, as they are needed.
12847 The purpose of this two-stage reading strategy is to make @value{GDBN}
12848 start up faster. For the most part, it is invisible except for
12849 occasional pauses while the symbol table details for a particular source
12850 file are being read. (The @code{set verbose} command can turn these
12851 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12852 Warnings and Messages}.)
12854 We have not implemented the two-stage strategy for COFF yet. When the
12855 symbol table is stored in COFF format, @code{symbol-file} reads the
12856 symbol table data in full right away. Note that ``stabs-in-COFF''
12857 still does the two-stage strategy, since the debug info is actually
12861 @cindex reading symbols immediately
12862 @cindex symbols, reading immediately
12863 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12864 @itemx file @var{filename} @r{[} -readnow @r{]}
12865 You can override the @value{GDBN} two-stage strategy for reading symbol
12866 tables by using the @samp{-readnow} option with any of the commands that
12867 load symbol table information, if you want to be sure @value{GDBN} has the
12868 entire symbol table available.
12870 @c FIXME: for now no mention of directories, since this seems to be in
12871 @c flux. 13mar1992 status is that in theory GDB would look either in
12872 @c current dir or in same dir as myprog; but issues like competing
12873 @c GDB's, or clutter in system dirs, mean that in practice right now
12874 @c only current dir is used. FFish says maybe a special GDB hierarchy
12875 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
12879 @item core-file @r{[}@var{filename}@r{]}
12881 Specify the whereabouts of a core dump file to be used as the ``contents
12882 of memory''. Traditionally, core files contain only some parts of the
12883 address space of the process that generated them; @value{GDBN} can access the
12884 executable file itself for other parts.
12886 @code{core-file} with no argument specifies that no core file is
12889 Note that the core file is ignored when your program is actually running
12890 under @value{GDBN}. So, if you have been running your program and you
12891 wish to debug a core file instead, you must kill the subprocess in which
12892 the program is running. To do this, use the @code{kill} command
12893 (@pxref{Kill Process, ,Killing the Child Process}).
12895 @kindex add-symbol-file
12896 @cindex dynamic linking
12897 @item add-symbol-file @var{filename} @var{address}
12898 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12899 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12900 The @code{add-symbol-file} command reads additional symbol table
12901 information from the file @var{filename}. You would use this command
12902 when @var{filename} has been dynamically loaded (by some other means)
12903 into the program that is running. @var{address} should be the memory
12904 address at which the file has been loaded; @value{GDBN} cannot figure
12905 this out for itself. You can additionally specify an arbitrary number
12906 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12907 section name and base address for that section. You can specify any
12908 @var{address} as an expression.
12910 The symbol table of the file @var{filename} is added to the symbol table
12911 originally read with the @code{symbol-file} command. You can use the
12912 @code{add-symbol-file} command any number of times; the new symbol data
12913 thus read keeps adding to the old. To discard all old symbol data
12914 instead, use the @code{symbol-file} command without any arguments.
12916 @cindex relocatable object files, reading symbols from
12917 @cindex object files, relocatable, reading symbols from
12918 @cindex reading symbols from relocatable object files
12919 @cindex symbols, reading from relocatable object files
12920 @cindex @file{.o} files, reading symbols from
12921 Although @var{filename} is typically a shared library file, an
12922 executable file, or some other object file which has been fully
12923 relocated for loading into a process, you can also load symbolic
12924 information from relocatable @file{.o} files, as long as:
12928 the file's symbolic information refers only to linker symbols defined in
12929 that file, not to symbols defined by other object files,
12931 every section the file's symbolic information refers to has actually
12932 been loaded into the inferior, as it appears in the file, and
12934 you can determine the address at which every section was loaded, and
12935 provide these to the @code{add-symbol-file} command.
12939 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12940 relocatable files into an already running program; such systems
12941 typically make the requirements above easy to meet. However, it's
12942 important to recognize that many native systems use complex link
12943 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12944 assembly, for example) that make the requirements difficult to meet. In
12945 general, one cannot assume that using @code{add-symbol-file} to read a
12946 relocatable object file's symbolic information will have the same effect
12947 as linking the relocatable object file into the program in the normal
12950 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12952 @kindex add-symbol-file-from-memory
12953 @cindex @code{syscall DSO}
12954 @cindex load symbols from memory
12955 @item add-symbol-file-from-memory @var{address}
12956 Load symbols from the given @var{address} in a dynamically loaded
12957 object file whose image is mapped directly into the inferior's memory.
12958 For example, the Linux kernel maps a @code{syscall DSO} into each
12959 process's address space; this DSO provides kernel-specific code for
12960 some system calls. The argument can be any expression whose
12961 evaluation yields the address of the file's shared object file header.
12962 For this command to work, you must have used @code{symbol-file} or
12963 @code{exec-file} commands in advance.
12965 @kindex add-shared-symbol-files
12967 @item add-shared-symbol-files @var{library-file}
12968 @itemx assf @var{library-file}
12969 The @code{add-shared-symbol-files} command can currently be used only
12970 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12971 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12972 @value{GDBN} automatically looks for shared libraries, however if
12973 @value{GDBN} does not find yours, you can invoke
12974 @code{add-shared-symbol-files}. It takes one argument: the shared
12975 library's file name. @code{assf} is a shorthand alias for
12976 @code{add-shared-symbol-files}.
12979 @item section @var{section} @var{addr}
12980 The @code{section} command changes the base address of the named
12981 @var{section} of the exec file to @var{addr}. This can be used if the
12982 exec file does not contain section addresses, (such as in the
12983 @code{a.out} format), or when the addresses specified in the file
12984 itself are wrong. Each section must be changed separately. The
12985 @code{info files} command, described below, lists all the sections and
12989 @kindex info target
12992 @code{info files} and @code{info target} are synonymous; both print the
12993 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12994 including the names of the executable and core dump files currently in
12995 use by @value{GDBN}, and the files from which symbols were loaded. The
12996 command @code{help target} lists all possible targets rather than
12999 @kindex maint info sections
13000 @item maint info sections
13001 Another command that can give you extra information about program sections
13002 is @code{maint info sections}. In addition to the section information
13003 displayed by @code{info files}, this command displays the flags and file
13004 offset of each section in the executable and core dump files. In addition,
13005 @code{maint info sections} provides the following command options (which
13006 may be arbitrarily combined):
13010 Display sections for all loaded object files, including shared libraries.
13011 @item @var{sections}
13012 Display info only for named @var{sections}.
13013 @item @var{section-flags}
13014 Display info only for sections for which @var{section-flags} are true.
13015 The section flags that @value{GDBN} currently knows about are:
13018 Section will have space allocated in the process when loaded.
13019 Set for all sections except those containing debug information.
13021 Section will be loaded from the file into the child process memory.
13022 Set for pre-initialized code and data, clear for @code{.bss} sections.
13024 Section needs to be relocated before loading.
13026 Section cannot be modified by the child process.
13028 Section contains executable code only.
13030 Section contains data only (no executable code).
13032 Section will reside in ROM.
13034 Section contains data for constructor/destructor lists.
13036 Section is not empty.
13038 An instruction to the linker to not output the section.
13039 @item COFF_SHARED_LIBRARY
13040 A notification to the linker that the section contains
13041 COFF shared library information.
13043 Section contains common symbols.
13046 @kindex set trust-readonly-sections
13047 @cindex read-only sections
13048 @item set trust-readonly-sections on
13049 Tell @value{GDBN} that readonly sections in your object file
13050 really are read-only (i.e.@: that their contents will not change).
13051 In that case, @value{GDBN} can fetch values from these sections
13052 out of the object file, rather than from the target program.
13053 For some targets (notably embedded ones), this can be a significant
13054 enhancement to debugging performance.
13056 The default is off.
13058 @item set trust-readonly-sections off
13059 Tell @value{GDBN} not to trust readonly sections. This means that
13060 the contents of the section might change while the program is running,
13061 and must therefore be fetched from the target when needed.
13063 @item show trust-readonly-sections
13064 Show the current setting of trusting readonly sections.
13067 All file-specifying commands allow both absolute and relative file names
13068 as arguments. @value{GDBN} always converts the file name to an absolute file
13069 name and remembers it that way.
13071 @cindex shared libraries
13072 @anchor{Shared Libraries}
13073 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
13074 and IBM RS/6000 AIX shared libraries.
13076 On MS-Windows @value{GDBN} must be linked with the Expat library to support
13077 shared libraries. @xref{Expat}.
13079 @value{GDBN} automatically loads symbol definitions from shared libraries
13080 when you use the @code{run} command, or when you examine a core file.
13081 (Before you issue the @code{run} command, @value{GDBN} does not understand
13082 references to a function in a shared library, however---unless you are
13083 debugging a core file).
13085 On HP-UX, if the program loads a library explicitly, @value{GDBN}
13086 automatically loads the symbols at the time of the @code{shl_load} call.
13088 @c FIXME: some @value{GDBN} release may permit some refs to undef
13089 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
13090 @c FIXME...lib; check this from time to time when updating manual
13092 There are times, however, when you may wish to not automatically load
13093 symbol definitions from shared libraries, such as when they are
13094 particularly large or there are many of them.
13096 To control the automatic loading of shared library symbols, use the
13100 @kindex set auto-solib-add
13101 @item set auto-solib-add @var{mode}
13102 If @var{mode} is @code{on}, symbols from all shared object libraries
13103 will be loaded automatically when the inferior begins execution, you
13104 attach to an independently started inferior, or when the dynamic linker
13105 informs @value{GDBN} that a new library has been loaded. If @var{mode}
13106 is @code{off}, symbols must be loaded manually, using the
13107 @code{sharedlibrary} command. The default value is @code{on}.
13109 @cindex memory used for symbol tables
13110 If your program uses lots of shared libraries with debug info that
13111 takes large amounts of memory, you can decrease the @value{GDBN}
13112 memory footprint by preventing it from automatically loading the
13113 symbols from shared libraries. To that end, type @kbd{set
13114 auto-solib-add off} before running the inferior, then load each
13115 library whose debug symbols you do need with @kbd{sharedlibrary
13116 @var{regexp}}, where @var{regexp} is a regular expression that matches
13117 the libraries whose symbols you want to be loaded.
13119 @kindex show auto-solib-add
13120 @item show auto-solib-add
13121 Display the current autoloading mode.
13124 @cindex load shared library
13125 To explicitly load shared library symbols, use the @code{sharedlibrary}
13129 @kindex info sharedlibrary
13132 @itemx info sharedlibrary
13133 Print the names of the shared libraries which are currently loaded.
13135 @kindex sharedlibrary
13137 @item sharedlibrary @var{regex}
13138 @itemx share @var{regex}
13139 Load shared object library symbols for files matching a
13140 Unix regular expression.
13141 As with files loaded automatically, it only loads shared libraries
13142 required by your program for a core file or after typing @code{run}. If
13143 @var{regex} is omitted all shared libraries required by your program are
13146 @item nosharedlibrary
13147 @kindex nosharedlibrary
13148 @cindex unload symbols from shared libraries
13149 Unload all shared object library symbols. This discards all symbols
13150 that have been loaded from all shared libraries. Symbols from shared
13151 libraries that were loaded by explicit user requests are not
13155 Sometimes you may wish that @value{GDBN} stops and gives you control
13156 when any of shared library events happen. Use the @code{set
13157 stop-on-solib-events} command for this:
13160 @item set stop-on-solib-events
13161 @kindex set stop-on-solib-events
13162 This command controls whether @value{GDBN} should give you control
13163 when the dynamic linker notifies it about some shared library event.
13164 The most common event of interest is loading or unloading of a new
13167 @item show stop-on-solib-events
13168 @kindex show stop-on-solib-events
13169 Show whether @value{GDBN} stops and gives you control when shared
13170 library events happen.
13173 Shared libraries are also supported in many cross or remote debugging
13174 configurations. @value{GDBN} needs to have access to the target's libraries;
13175 this can be accomplished either by providing copies of the libraries
13176 on the host system, or by asking @value{GDBN} to automatically retrieve the
13177 libraries from the target. If copies of the target libraries are
13178 provided, they need to be the same as the target libraries, although the
13179 copies on the target can be stripped as long as the copies on the host are
13182 @cindex where to look for shared libraries
13183 For remote debugging, you need to tell @value{GDBN} where the target
13184 libraries are, so that it can load the correct copies---otherwise, it
13185 may try to load the host's libraries. @value{GDBN} has two variables
13186 to specify the search directories for target libraries.
13189 @cindex prefix for shared library file names
13190 @cindex system root, alternate
13191 @kindex set solib-absolute-prefix
13192 @kindex set sysroot
13193 @item set sysroot @var{path}
13194 Use @var{path} as the system root for the program being debugged. Any
13195 absolute shared library paths will be prefixed with @var{path}; many
13196 runtime loaders store the absolute paths to the shared library in the
13197 target program's memory. If you use @code{set sysroot} to find shared
13198 libraries, they need to be laid out in the same way that they are on
13199 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
13202 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
13203 retrieve the target libraries from the remote system. This is only
13204 supported when using a remote target that supports the @code{remote get}
13205 command (@pxref{File Transfer,,Sending files to a remote system}).
13206 The part of @var{path} following the initial @file{remote:}
13207 (if present) is used as system root prefix on the remote file system.
13208 @footnote{If you want to specify a local system root using a directory
13209 that happens to be named @file{remote:}, you need to use some equivalent
13210 variant of the name like @file{./remote:}.}
13212 The @code{set solib-absolute-prefix} command is an alias for @code{set
13215 @cindex default system root
13216 @cindex @samp{--with-sysroot}
13217 You can set the default system root by using the configure-time
13218 @samp{--with-sysroot} option. If the system root is inside
13219 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13220 @samp{--exec-prefix}), then the default system root will be updated
13221 automatically if the installed @value{GDBN} is moved to a new
13224 @kindex show sysroot
13226 Display the current shared library prefix.
13228 @kindex set solib-search-path
13229 @item set solib-search-path @var{path}
13230 If this variable is set, @var{path} is a colon-separated list of
13231 directories to search for shared libraries. @samp{solib-search-path}
13232 is used after @samp{sysroot} fails to locate the library, or if the
13233 path to the library is relative instead of absolute. If you want to
13234 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13235 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13236 finding your host's libraries. @samp{sysroot} is preferred; setting
13237 it to a nonexistent directory may interfere with automatic loading
13238 of shared library symbols.
13240 @kindex show solib-search-path
13241 @item show solib-search-path
13242 Display the current shared library search path.
13246 @node Separate Debug Files
13247 @section Debugging Information in Separate Files
13248 @cindex separate debugging information files
13249 @cindex debugging information in separate files
13250 @cindex @file{.debug} subdirectories
13251 @cindex debugging information directory, global
13252 @cindex global debugging information directory
13253 @cindex build ID, and separate debugging files
13254 @cindex @file{.build-id} directory
13256 @value{GDBN} allows you to put a program's debugging information in a
13257 file separate from the executable itself, in a way that allows
13258 @value{GDBN} to find and load the debugging information automatically.
13259 Since debugging information can be very large---sometimes larger
13260 than the executable code itself---some systems distribute debugging
13261 information for their executables in separate files, which users can
13262 install only when they need to debug a problem.
13264 @value{GDBN} supports two ways of specifying the separate debug info
13269 The executable contains a @dfn{debug link} that specifies the name of
13270 the separate debug info file. The separate debug file's name is
13271 usually @file{@var{executable}.debug}, where @var{executable} is the
13272 name of the corresponding executable file without leading directories
13273 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
13274 debug link specifies a CRC32 checksum for the debug file, which
13275 @value{GDBN} uses to validate that the executable and the debug file
13276 came from the same build.
13279 The executable contains a @dfn{build ID}, a unique bit string that is
13280 also present in the corresponding debug info file. (This is supported
13281 only on some operating systems, notably those which use the ELF format
13282 for binary files and the @sc{gnu} Binutils.) For more details about
13283 this feature, see the description of the @option{--build-id}
13284 command-line option in @ref{Options, , Command Line Options, ld.info,
13285 The GNU Linker}. The debug info file's name is not specified
13286 explicitly by the build ID, but can be computed from the build ID, see
13290 Depending on the way the debug info file is specified, @value{GDBN}
13291 uses two different methods of looking for the debug file:
13295 For the ``debug link'' method, @value{GDBN} looks up the named file in
13296 the directory of the executable file, then in a subdirectory of that
13297 directory named @file{.debug}, and finally under the global debug
13298 directory, in a subdirectory whose name is identical to the leading
13299 directories of the executable's absolute file name.
13302 For the ``build ID'' method, @value{GDBN} looks in the
13303 @file{.build-id} subdirectory of the global debug directory for a file
13304 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
13305 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
13306 are the rest of the bit string. (Real build ID strings are 32 or more
13307 hex characters, not 10.)
13310 So, for example, suppose you ask @value{GDBN} to debug
13311 @file{/usr/bin/ls}, which has a debug link that specifies the
13312 file @file{ls.debug}, and a build ID whose value in hex is
13313 @code{abcdef1234}. If the global debug directory is
13314 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
13315 debug information files, in the indicated order:
13319 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
13321 @file{/usr/bin/ls.debug}
13323 @file{/usr/bin/.debug/ls.debug}
13325 @file{/usr/lib/debug/usr/bin/ls.debug}.
13328 You can set the global debugging info directory's name, and view the
13329 name @value{GDBN} is currently using.
13333 @kindex set debug-file-directory
13334 @item set debug-file-directory @var{directory}
13335 Set the directory which @value{GDBN} searches for separate debugging
13336 information files to @var{directory}.
13338 @kindex show debug-file-directory
13339 @item show debug-file-directory
13340 Show the directory @value{GDBN} searches for separate debugging
13345 @cindex @code{.gnu_debuglink} sections
13346 @cindex debug link sections
13347 A debug link is a special section of the executable file named
13348 @code{.gnu_debuglink}. The section must contain:
13352 A filename, with any leading directory components removed, followed by
13355 zero to three bytes of padding, as needed to reach the next four-byte
13356 boundary within the section, and
13358 a four-byte CRC checksum, stored in the same endianness used for the
13359 executable file itself. The checksum is computed on the debugging
13360 information file's full contents by the function given below, passing
13361 zero as the @var{crc} argument.
13364 Any executable file format can carry a debug link, as long as it can
13365 contain a section named @code{.gnu_debuglink} with the contents
13368 @cindex @code{.note.gnu.build-id} sections
13369 @cindex build ID sections
13370 The build ID is a special section in the executable file (and in other
13371 ELF binary files that @value{GDBN} may consider). This section is
13372 often named @code{.note.gnu.build-id}, but that name is not mandatory.
13373 It contains unique identification for the built files---the ID remains
13374 the same across multiple builds of the same build tree. The default
13375 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
13376 content for the build ID string. The same section with an identical
13377 value is present in the original built binary with symbols, in its
13378 stripped variant, and in the separate debugging information file.
13380 The debugging information file itself should be an ordinary
13381 executable, containing a full set of linker symbols, sections, and
13382 debugging information. The sections of the debugging information file
13383 should have the same names, addresses, and sizes as the original file,
13384 but they need not contain any data---much like a @code{.bss} section
13385 in an ordinary executable.
13387 The @sc{gnu} binary utilities (Binutils) package includes the
13388 @samp{objcopy} utility that can produce
13389 the separated executable / debugging information file pairs using the
13390 following commands:
13393 @kbd{objcopy --only-keep-debug foo foo.debug}
13398 These commands remove the debugging
13399 information from the executable file @file{foo} and place it in the file
13400 @file{foo.debug}. You can use the first, second or both methods to link the
13405 The debug link method needs the following additional command to also leave
13406 behind a debug link in @file{foo}:
13409 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
13412 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
13413 a version of the @code{strip} command such that the command @kbd{strip foo -f
13414 foo.debug} has the same functionality as the two @code{objcopy} commands and
13415 the @code{ln -s} command above, together.
13418 Build ID gets embedded into the main executable using @code{ld --build-id} or
13419 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
13420 compatibility fixes for debug files separation are present in @sc{gnu} binary
13421 utilities (Binutils) package since version 2.18.
13426 Since there are many different ways to compute CRC's for the debug
13427 link (different polynomials, reversals, byte ordering, etc.), the
13428 simplest way to describe the CRC used in @code{.gnu_debuglink}
13429 sections is to give the complete code for a function that computes it:
13431 @kindex gnu_debuglink_crc32
13434 gnu_debuglink_crc32 (unsigned long crc,
13435 unsigned char *buf, size_t len)
13437 static const unsigned long crc32_table[256] =
13439 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
13440 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
13441 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
13442 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
13443 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
13444 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
13445 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
13446 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
13447 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
13448 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
13449 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
13450 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
13451 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
13452 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
13453 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
13454 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
13455 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
13456 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
13457 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
13458 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
13459 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
13460 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
13461 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
13462 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
13463 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
13464 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
13465 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
13466 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
13467 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
13468 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
13469 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
13470 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
13471 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
13472 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
13473 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
13474 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
13475 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
13476 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
13477 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
13478 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
13479 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
13480 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
13481 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
13482 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
13483 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
13484 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
13485 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
13486 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
13487 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
13488 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
13489 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
13492 unsigned char *end;
13494 crc = ~crc & 0xffffffff;
13495 for (end = buf + len; buf < end; ++buf)
13496 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
13497 return ~crc & 0xffffffff;
13502 This computation does not apply to the ``build ID'' method.
13505 @node Symbol Errors
13506 @section Errors Reading Symbol Files
13508 While reading a symbol file, @value{GDBN} occasionally encounters problems,
13509 such as symbol types it does not recognize, or known bugs in compiler
13510 output. By default, @value{GDBN} does not notify you of such problems, since
13511 they are relatively common and primarily of interest to people
13512 debugging compilers. If you are interested in seeing information
13513 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
13514 only one message about each such type of problem, no matter how many
13515 times the problem occurs; or you can ask @value{GDBN} to print more messages,
13516 to see how many times the problems occur, with the @code{set
13517 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
13520 The messages currently printed, and their meanings, include:
13523 @item inner block not inside outer block in @var{symbol}
13525 The symbol information shows where symbol scopes begin and end
13526 (such as at the start of a function or a block of statements). This
13527 error indicates that an inner scope block is not fully contained
13528 in its outer scope blocks.
13530 @value{GDBN} circumvents the problem by treating the inner block as if it had
13531 the same scope as the outer block. In the error message, @var{symbol}
13532 may be shown as ``@code{(don't know)}'' if the outer block is not a
13535 @item block at @var{address} out of order
13537 The symbol information for symbol scope blocks should occur in
13538 order of increasing addresses. This error indicates that it does not
13541 @value{GDBN} does not circumvent this problem, and has trouble
13542 locating symbols in the source file whose symbols it is reading. (You
13543 can often determine what source file is affected by specifying
13544 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
13547 @item bad block start address patched
13549 The symbol information for a symbol scope block has a start address
13550 smaller than the address of the preceding source line. This is known
13551 to occur in the SunOS 4.1.1 (and earlier) C compiler.
13553 @value{GDBN} circumvents the problem by treating the symbol scope block as
13554 starting on the previous source line.
13556 @item bad string table offset in symbol @var{n}
13559 Symbol number @var{n} contains a pointer into the string table which is
13560 larger than the size of the string table.
13562 @value{GDBN} circumvents the problem by considering the symbol to have the
13563 name @code{foo}, which may cause other problems if many symbols end up
13566 @item unknown symbol type @code{0x@var{nn}}
13568 The symbol information contains new data types that @value{GDBN} does
13569 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
13570 uncomprehended information, in hexadecimal.
13572 @value{GDBN} circumvents the error by ignoring this symbol information.
13573 This usually allows you to debug your program, though certain symbols
13574 are not accessible. If you encounter such a problem and feel like
13575 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
13576 on @code{complain}, then go up to the function @code{read_dbx_symtab}
13577 and examine @code{*bufp} to see the symbol.
13579 @item stub type has NULL name
13581 @value{GDBN} could not find the full definition for a struct or class.
13583 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
13584 The symbol information for a C@t{++} member function is missing some
13585 information that recent versions of the compiler should have output for
13588 @item info mismatch between compiler and debugger
13590 @value{GDBN} could not parse a type specification output by the compiler.
13595 @section GDB Data Files
13597 @cindex prefix for data files
13598 @value{GDBN} will sometimes read an auxiliary data file. These files
13599 are kept in a directory known as the @dfn{data directory}.
13601 You can set the data directory's name, and view the name @value{GDBN}
13602 is currently using.
13605 @kindex set data-directory
13606 @item set data-directory @var{directory}
13607 Set the directory which @value{GDBN} searches for auxiliary data files
13608 to @var{directory}.
13610 @kindex show data-directory
13611 @item show data-directory
13612 Show the directory @value{GDBN} searches for auxiliary data files.
13615 @cindex default data directory
13616 @cindex @samp{--with-gdb-datadir}
13617 You can set the default data directory by using the configure-time
13618 @samp{--with-gdb-datadir} option. If the data directory is inside
13619 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13620 @samp{--exec-prefix}), then the default data directory will be updated
13621 automatically if the installed @value{GDBN} is moved to a new
13625 @chapter Specifying a Debugging Target
13627 @cindex debugging target
13628 A @dfn{target} is the execution environment occupied by your program.
13630 Often, @value{GDBN} runs in the same host environment as your program;
13631 in that case, the debugging target is specified as a side effect when
13632 you use the @code{file} or @code{core} commands. When you need more
13633 flexibility---for example, running @value{GDBN} on a physically separate
13634 host, or controlling a standalone system over a serial port or a
13635 realtime system over a TCP/IP connection---you can use the @code{target}
13636 command to specify one of the target types configured for @value{GDBN}
13637 (@pxref{Target Commands, ,Commands for Managing Targets}).
13639 @cindex target architecture
13640 It is possible to build @value{GDBN} for several different @dfn{target
13641 architectures}. When @value{GDBN} is built like that, you can choose
13642 one of the available architectures with the @kbd{set architecture}
13646 @kindex set architecture
13647 @kindex show architecture
13648 @item set architecture @var{arch}
13649 This command sets the current target architecture to @var{arch}. The
13650 value of @var{arch} can be @code{"auto"}, in addition to one of the
13651 supported architectures.
13653 @item show architecture
13654 Show the current target architecture.
13656 @item set processor
13658 @kindex set processor
13659 @kindex show processor
13660 These are alias commands for, respectively, @code{set architecture}
13661 and @code{show architecture}.
13665 * Active Targets:: Active targets
13666 * Target Commands:: Commands for managing targets
13667 * Byte Order:: Choosing target byte order
13670 @node Active Targets
13671 @section Active Targets
13673 @cindex stacking targets
13674 @cindex active targets
13675 @cindex multiple targets
13677 There are three classes of targets: processes, core files, and
13678 executable files. @value{GDBN} can work concurrently on up to three
13679 active targets, one in each class. This allows you to (for example)
13680 start a process and inspect its activity without abandoning your work on
13683 For example, if you execute @samp{gdb a.out}, then the executable file
13684 @code{a.out} is the only active target. If you designate a core file as
13685 well---presumably from a prior run that crashed and coredumped---then
13686 @value{GDBN} has two active targets and uses them in tandem, looking
13687 first in the corefile target, then in the executable file, to satisfy
13688 requests for memory addresses. (Typically, these two classes of target
13689 are complementary, since core files contain only a program's
13690 read-write memory---variables and so on---plus machine status, while
13691 executable files contain only the program text and initialized data.)
13693 When you type @code{run}, your executable file becomes an active process
13694 target as well. When a process target is active, all @value{GDBN}
13695 commands requesting memory addresses refer to that target; addresses in
13696 an active core file or executable file target are obscured while the
13697 process target is active.
13699 Use the @code{core-file} and @code{exec-file} commands to select a new
13700 core file or executable target (@pxref{Files, ,Commands to Specify
13701 Files}). To specify as a target a process that is already running, use
13702 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
13705 @node Target Commands
13706 @section Commands for Managing Targets
13709 @item target @var{type} @var{parameters}
13710 Connects the @value{GDBN} host environment to a target machine or
13711 process. A target is typically a protocol for talking to debugging
13712 facilities. You use the argument @var{type} to specify the type or
13713 protocol of the target machine.
13715 Further @var{parameters} are interpreted by the target protocol, but
13716 typically include things like device names or host names to connect
13717 with, process numbers, and baud rates.
13719 The @code{target} command does not repeat if you press @key{RET} again
13720 after executing the command.
13722 @kindex help target
13724 Displays the names of all targets available. To display targets
13725 currently selected, use either @code{info target} or @code{info files}
13726 (@pxref{Files, ,Commands to Specify Files}).
13728 @item help target @var{name}
13729 Describe a particular target, including any parameters necessary to
13732 @kindex set gnutarget
13733 @item set gnutarget @var{args}
13734 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
13735 knows whether it is reading an @dfn{executable},
13736 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
13737 with the @code{set gnutarget} command. Unlike most @code{target} commands,
13738 with @code{gnutarget} the @code{target} refers to a program, not a machine.
13741 @emph{Warning:} To specify a file format with @code{set gnutarget},
13742 you must know the actual BFD name.
13746 @xref{Files, , Commands to Specify Files}.
13748 @kindex show gnutarget
13749 @item show gnutarget
13750 Use the @code{show gnutarget} command to display what file format
13751 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
13752 @value{GDBN} will determine the file format for each file automatically,
13753 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
13756 @cindex common targets
13757 Here are some common targets (available, or not, depending on the GDB
13762 @item target exec @var{program}
13763 @cindex executable file target
13764 An executable file. @samp{target exec @var{program}} is the same as
13765 @samp{exec-file @var{program}}.
13767 @item target core @var{filename}
13768 @cindex core dump file target
13769 A core dump file. @samp{target core @var{filename}} is the same as
13770 @samp{core-file @var{filename}}.
13772 @item target remote @var{medium}
13773 @cindex remote target
13774 A remote system connected to @value{GDBN} via a serial line or network
13775 connection. This command tells @value{GDBN} to use its own remote
13776 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
13778 For example, if you have a board connected to @file{/dev/ttya} on the
13779 machine running @value{GDBN}, you could say:
13782 target remote /dev/ttya
13785 @code{target remote} supports the @code{load} command. This is only
13786 useful if you have some other way of getting the stub to the target
13787 system, and you can put it somewhere in memory where it won't get
13788 clobbered by the download.
13791 @cindex built-in simulator target
13792 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
13800 works; however, you cannot assume that a specific memory map, device
13801 drivers, or even basic I/O is available, although some simulators do
13802 provide these. For info about any processor-specific simulator details,
13803 see the appropriate section in @ref{Embedded Processors, ,Embedded
13808 Some configurations may include these targets as well:
13812 @item target nrom @var{dev}
13813 @cindex NetROM ROM emulator target
13814 NetROM ROM emulator. This target only supports downloading.
13818 Different targets are available on different configurations of @value{GDBN};
13819 your configuration may have more or fewer targets.
13821 Many remote targets require you to download the executable's code once
13822 you've successfully established a connection. You may wish to control
13823 various aspects of this process.
13828 @kindex set hash@r{, for remote monitors}
13829 @cindex hash mark while downloading
13830 This command controls whether a hash mark @samp{#} is displayed while
13831 downloading a file to the remote monitor. If on, a hash mark is
13832 displayed after each S-record is successfully downloaded to the
13836 @kindex show hash@r{, for remote monitors}
13837 Show the current status of displaying the hash mark.
13839 @item set debug monitor
13840 @kindex set debug monitor
13841 @cindex display remote monitor communications
13842 Enable or disable display of communications messages between
13843 @value{GDBN} and the remote monitor.
13845 @item show debug monitor
13846 @kindex show debug monitor
13847 Show the current status of displaying communications between
13848 @value{GDBN} and the remote monitor.
13853 @kindex load @var{filename}
13854 @item load @var{filename}
13856 Depending on what remote debugging facilities are configured into
13857 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13858 is meant to make @var{filename} (an executable) available for debugging
13859 on the remote system---by downloading, or dynamic linking, for example.
13860 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
13861 the @code{add-symbol-file} command.
13863 If your @value{GDBN} does not have a @code{load} command, attempting to
13864 execute it gets the error message ``@code{You can't do that when your
13865 target is @dots{}}''
13867 The file is loaded at whatever address is specified in the executable.
13868 For some object file formats, you can specify the load address when you
13869 link the program; for other formats, like a.out, the object file format
13870 specifies a fixed address.
13871 @c FIXME! This would be a good place for an xref to the GNU linker doc.
13873 Depending on the remote side capabilities, @value{GDBN} may be able to
13874 load programs into flash memory.
13876 @code{load} does not repeat if you press @key{RET} again after using it.
13880 @section Choosing Target Byte Order
13882 @cindex choosing target byte order
13883 @cindex target byte order
13885 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
13886 offer the ability to run either big-endian or little-endian byte
13887 orders. Usually the executable or symbol will include a bit to
13888 designate the endian-ness, and you will not need to worry about
13889 which to use. However, you may still find it useful to adjust
13890 @value{GDBN}'s idea of processor endian-ness manually.
13894 @item set endian big
13895 Instruct @value{GDBN} to assume the target is big-endian.
13897 @item set endian little
13898 Instruct @value{GDBN} to assume the target is little-endian.
13900 @item set endian auto
13901 Instruct @value{GDBN} to use the byte order associated with the
13905 Display @value{GDBN}'s current idea of the target byte order.
13909 Note that these commands merely adjust interpretation of symbolic
13910 data on the host, and that they have absolutely no effect on the
13914 @node Remote Debugging
13915 @chapter Debugging Remote Programs
13916 @cindex remote debugging
13918 If you are trying to debug a program running on a machine that cannot run
13919 @value{GDBN} in the usual way, it is often useful to use remote debugging.
13920 For example, you might use remote debugging on an operating system kernel,
13921 or on a small system which does not have a general purpose operating system
13922 powerful enough to run a full-featured debugger.
13924 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
13925 to make this work with particular debugging targets. In addition,
13926 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
13927 but not specific to any particular target system) which you can use if you
13928 write the remote stubs---the code that runs on the remote system to
13929 communicate with @value{GDBN}.
13931 Other remote targets may be available in your
13932 configuration of @value{GDBN}; use @code{help target} to list them.
13935 * Connecting:: Connecting to a remote target
13936 * File Transfer:: Sending files to a remote system
13937 * Server:: Using the gdbserver program
13938 * Remote Configuration:: Remote configuration
13939 * Remote Stub:: Implementing a remote stub
13943 @section Connecting to a Remote Target
13945 On the @value{GDBN} host machine, you will need an unstripped copy of
13946 your program, since @value{GDBN} needs symbol and debugging information.
13947 Start up @value{GDBN} as usual, using the name of the local copy of your
13948 program as the first argument.
13950 @cindex @code{target remote}
13951 @value{GDBN} can communicate with the target over a serial line, or
13952 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13953 each case, @value{GDBN} uses the same protocol for debugging your
13954 program; only the medium carrying the debugging packets varies. The
13955 @code{target remote} command establishes a connection to the target.
13956 Its arguments indicate which medium to use:
13960 @item target remote @var{serial-device}
13961 @cindex serial line, @code{target remote}
13962 Use @var{serial-device} to communicate with the target. For example,
13963 to use a serial line connected to the device named @file{/dev/ttyb}:
13966 target remote /dev/ttyb
13969 If you're using a serial line, you may want to give @value{GDBN} the
13970 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13971 (@pxref{Remote Configuration, set remotebaud}) before the
13972 @code{target} command.
13974 @item target remote @code{@var{host}:@var{port}}
13975 @itemx target remote @code{tcp:@var{host}:@var{port}}
13976 @cindex @acronym{TCP} port, @code{target remote}
13977 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13978 The @var{host} may be either a host name or a numeric @acronym{IP}
13979 address; @var{port} must be a decimal number. The @var{host} could be
13980 the target machine itself, if it is directly connected to the net, or
13981 it might be a terminal server which in turn has a serial line to the
13984 For example, to connect to port 2828 on a terminal server named
13988 target remote manyfarms:2828
13991 If your remote target is actually running on the same machine as your
13992 debugger session (e.g.@: a simulator for your target running on the
13993 same host), you can omit the hostname. For example, to connect to
13994 port 1234 on your local machine:
13997 target remote :1234
14001 Note that the colon is still required here.
14003 @item target remote @code{udp:@var{host}:@var{port}}
14004 @cindex @acronym{UDP} port, @code{target remote}
14005 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
14006 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
14009 target remote udp:manyfarms:2828
14012 When using a @acronym{UDP} connection for remote debugging, you should
14013 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
14014 can silently drop packets on busy or unreliable networks, which will
14015 cause havoc with your debugging session.
14017 @item target remote | @var{command}
14018 @cindex pipe, @code{target remote} to
14019 Run @var{command} in the background and communicate with it using a
14020 pipe. The @var{command} is a shell command, to be parsed and expanded
14021 by the system's command shell, @code{/bin/sh}; it should expect remote
14022 protocol packets on its standard input, and send replies on its
14023 standard output. You could use this to run a stand-alone simulator
14024 that speaks the remote debugging protocol, to make net connections
14025 using programs like @code{ssh}, or for other similar tricks.
14027 If @var{command} closes its standard output (perhaps by exiting),
14028 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
14029 program has already exited, this will have no effect.)
14033 Once the connection has been established, you can use all the usual
14034 commands to examine and change data. The remote program is already
14035 running; you can use @kbd{step} and @kbd{continue}, and you do not
14036 need to use @kbd{run}.
14038 @cindex interrupting remote programs
14039 @cindex remote programs, interrupting
14040 Whenever @value{GDBN} is waiting for the remote program, if you type the
14041 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
14042 program. This may or may not succeed, depending in part on the hardware
14043 and the serial drivers the remote system uses. If you type the
14044 interrupt character once again, @value{GDBN} displays this prompt:
14047 Interrupted while waiting for the program.
14048 Give up (and stop debugging it)? (y or n)
14051 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
14052 (If you decide you want to try again later, you can use @samp{target
14053 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
14054 goes back to waiting.
14057 @kindex detach (remote)
14059 When you have finished debugging the remote program, you can use the
14060 @code{detach} command to release it from @value{GDBN} control.
14061 Detaching from the target normally resumes its execution, but the results
14062 will depend on your particular remote stub. After the @code{detach}
14063 command, @value{GDBN} is free to connect to another target.
14067 The @code{disconnect} command behaves like @code{detach}, except that
14068 the target is generally not resumed. It will wait for @value{GDBN}
14069 (this instance or another one) to connect and continue debugging. After
14070 the @code{disconnect} command, @value{GDBN} is again free to connect to
14073 @cindex send command to remote monitor
14074 @cindex extend @value{GDBN} for remote targets
14075 @cindex add new commands for external monitor
14077 @item monitor @var{cmd}
14078 This command allows you to send arbitrary commands directly to the
14079 remote monitor. Since @value{GDBN} doesn't care about the commands it
14080 sends like this, this command is the way to extend @value{GDBN}---you
14081 can add new commands that only the external monitor will understand
14085 @node File Transfer
14086 @section Sending files to a remote system
14087 @cindex remote target, file transfer
14088 @cindex file transfer
14089 @cindex sending files to remote systems
14091 Some remote targets offer the ability to transfer files over the same
14092 connection used to communicate with @value{GDBN}. This is convenient
14093 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
14094 running @code{gdbserver} over a network interface. For other targets,
14095 e.g.@: embedded devices with only a single serial port, this may be
14096 the only way to upload or download files.
14098 Not all remote targets support these commands.
14102 @item remote put @var{hostfile} @var{targetfile}
14103 Copy file @var{hostfile} from the host system (the machine running
14104 @value{GDBN}) to @var{targetfile} on the target system.
14107 @item remote get @var{targetfile} @var{hostfile}
14108 Copy file @var{targetfile} from the target system to @var{hostfile}
14109 on the host system.
14111 @kindex remote delete
14112 @item remote delete @var{targetfile}
14113 Delete @var{targetfile} from the target system.
14118 @section Using the @code{gdbserver} Program
14121 @cindex remote connection without stubs
14122 @code{gdbserver} is a control program for Unix-like systems, which
14123 allows you to connect your program with a remote @value{GDBN} via
14124 @code{target remote}---but without linking in the usual debugging stub.
14126 @code{gdbserver} is not a complete replacement for the debugging stubs,
14127 because it requires essentially the same operating-system facilities
14128 that @value{GDBN} itself does. In fact, a system that can run
14129 @code{gdbserver} to connect to a remote @value{GDBN} could also run
14130 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
14131 because it is a much smaller program than @value{GDBN} itself. It is
14132 also easier to port than all of @value{GDBN}, so you may be able to get
14133 started more quickly on a new system by using @code{gdbserver}.
14134 Finally, if you develop code for real-time systems, you may find that
14135 the tradeoffs involved in real-time operation make it more convenient to
14136 do as much development work as possible on another system, for example
14137 by cross-compiling. You can use @code{gdbserver} to make a similar
14138 choice for debugging.
14140 @value{GDBN} and @code{gdbserver} communicate via either a serial line
14141 or a TCP connection, using the standard @value{GDBN} remote serial
14145 @emph{Warning:} @code{gdbserver} does not have any built-in security.
14146 Do not run @code{gdbserver} connected to any public network; a
14147 @value{GDBN} connection to @code{gdbserver} provides access to the
14148 target system with the same privileges as the user running
14152 @subsection Running @code{gdbserver}
14153 @cindex arguments, to @code{gdbserver}
14155 Run @code{gdbserver} on the target system. You need a copy of the
14156 program you want to debug, including any libraries it requires.
14157 @code{gdbserver} does not need your program's symbol table, so you can
14158 strip the program if necessary to save space. @value{GDBN} on the host
14159 system does all the symbol handling.
14161 To use the server, you must tell it how to communicate with @value{GDBN};
14162 the name of your program; and the arguments for your program. The usual
14166 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
14169 @var{comm} is either a device name (to use a serial line) or a TCP
14170 hostname and portnumber. For example, to debug Emacs with the argument
14171 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
14175 target> gdbserver /dev/com1 emacs foo.txt
14178 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
14181 To use a TCP connection instead of a serial line:
14184 target> gdbserver host:2345 emacs foo.txt
14187 The only difference from the previous example is the first argument,
14188 specifying that you are communicating with the host @value{GDBN} via
14189 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
14190 expect a TCP connection from machine @samp{host} to local TCP port 2345.
14191 (Currently, the @samp{host} part is ignored.) You can choose any number
14192 you want for the port number as long as it does not conflict with any
14193 TCP ports already in use on the target system (for example, @code{23} is
14194 reserved for @code{telnet}).@footnote{If you choose a port number that
14195 conflicts with another service, @code{gdbserver} prints an error message
14196 and exits.} You must use the same port number with the host @value{GDBN}
14197 @code{target remote} command.
14199 @subsubsection Attaching to a Running Program
14201 On some targets, @code{gdbserver} can also attach to running programs.
14202 This is accomplished via the @code{--attach} argument. The syntax is:
14205 target> gdbserver --attach @var{comm} @var{pid}
14208 @var{pid} is the process ID of a currently running process. It isn't necessary
14209 to point @code{gdbserver} at a binary for the running process.
14212 @cindex attach to a program by name
14213 You can debug processes by name instead of process ID if your target has the
14214 @code{pidof} utility:
14217 target> gdbserver --attach @var{comm} `pidof @var{program}`
14220 In case more than one copy of @var{program} is running, or @var{program}
14221 has multiple threads, most versions of @code{pidof} support the
14222 @code{-s} option to only return the first process ID.
14224 @subsubsection Multi-Process Mode for @code{gdbserver}
14225 @cindex gdbserver, multiple processes
14226 @cindex multiple processes with gdbserver
14228 When you connect to @code{gdbserver} using @code{target remote},
14229 @code{gdbserver} debugs the specified program only once. When the
14230 program exits, or you detach from it, @value{GDBN} closes the connection
14231 and @code{gdbserver} exits.
14233 If you connect using @kbd{target extended-remote}, @code{gdbserver}
14234 enters multi-process mode. When the debugged program exits, or you
14235 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
14236 though no program is running. The @code{run} and @code{attach}
14237 commands instruct @code{gdbserver} to run or attach to a new program.
14238 The @code{run} command uses @code{set remote exec-file} (@pxref{set
14239 remote exec-file}) to select the program to run. Command line
14240 arguments are supported, except for wildcard expansion and I/O
14241 redirection (@pxref{Arguments}).
14243 To start @code{gdbserver} without supplying an initial command to run
14244 or process ID to attach, use the @option{--multi} command line option.
14245 Then you can connect using @kbd{target extended-remote} and start
14246 the program you want to debug.
14248 @code{gdbserver} does not automatically exit in multi-process mode.
14249 You can terminate it by using @code{monitor exit}
14250 (@pxref{Monitor Commands for gdbserver}).
14252 @subsubsection Other Command-Line Arguments for @code{gdbserver}
14254 The @option{--debug} option tells @code{gdbserver} to display extra
14255 status information about the debugging process. The
14256 @option{--remote-debug} option tells @code{gdbserver} to display
14257 remote protocol debug output. These options are intended for
14258 @code{gdbserver} development and for bug reports to the developers.
14260 The @option{--wrapper} option specifies a wrapper to launch programs
14261 for debugging. The option should be followed by the name of the
14262 wrapper, then any command-line arguments to pass to the wrapper, then
14263 @kbd{--} indicating the end of the wrapper arguments.
14265 @code{gdbserver} runs the specified wrapper program with a combined
14266 command line including the wrapper arguments, then the name of the
14267 program to debug, then any arguments to the program. The wrapper
14268 runs until it executes your program, and then @value{GDBN} gains control.
14270 You can use any program that eventually calls @code{execve} with
14271 its arguments as a wrapper. Several standard Unix utilities do
14272 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
14273 with @code{exec "$@@"} will also work.
14275 For example, you can use @code{env} to pass an environment variable to
14276 the debugged program, without setting the variable in @code{gdbserver}'s
14280 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
14283 @subsection Connecting to @code{gdbserver}
14285 Run @value{GDBN} on the host system.
14287 First make sure you have the necessary symbol files. Load symbols for
14288 your application using the @code{file} command before you connect. Use
14289 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
14290 was compiled with the correct sysroot using @code{--with-sysroot}).
14292 The symbol file and target libraries must exactly match the executable
14293 and libraries on the target, with one exception: the files on the host
14294 system should not be stripped, even if the files on the target system
14295 are. Mismatched or missing files will lead to confusing results
14296 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
14297 files may also prevent @code{gdbserver} from debugging multi-threaded
14300 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
14301 For TCP connections, you must start up @code{gdbserver} prior to using
14302 the @code{target remote} command. Otherwise you may get an error whose
14303 text depends on the host system, but which usually looks something like
14304 @samp{Connection refused}. Don't use the @code{load}
14305 command in @value{GDBN} when using @code{gdbserver}, since the program is
14306 already on the target.
14308 @subsection Monitor Commands for @code{gdbserver}
14309 @cindex monitor commands, for @code{gdbserver}
14310 @anchor{Monitor Commands for gdbserver}
14312 During a @value{GDBN} session using @code{gdbserver}, you can use the
14313 @code{monitor} command to send special requests to @code{gdbserver}.
14314 Here are the available commands.
14318 List the available monitor commands.
14320 @item monitor set debug 0
14321 @itemx monitor set debug 1
14322 Disable or enable general debugging messages.
14324 @item monitor set remote-debug 0
14325 @itemx monitor set remote-debug 1
14326 Disable or enable specific debugging messages associated with the remote
14327 protocol (@pxref{Remote Protocol}).
14330 Tell gdbserver to exit immediately. This command should be followed by
14331 @code{disconnect} to close the debugging session. @code{gdbserver} will
14332 detach from any attached processes and kill any processes it created.
14333 Use @code{monitor exit} to terminate @code{gdbserver} at the end
14334 of a multi-process mode debug session.
14338 @node Remote Configuration
14339 @section Remote Configuration
14342 @kindex show remote
14343 This section documents the configuration options available when
14344 debugging remote programs. For the options related to the File I/O
14345 extensions of the remote protocol, see @ref{system,
14346 system-call-allowed}.
14349 @item set remoteaddresssize @var{bits}
14350 @cindex address size for remote targets
14351 @cindex bits in remote address
14352 Set the maximum size of address in a memory packet to the specified
14353 number of bits. @value{GDBN} will mask off the address bits above
14354 that number, when it passes addresses to the remote target. The
14355 default value is the number of bits in the target's address.
14357 @item show remoteaddresssize
14358 Show the current value of remote address size in bits.
14360 @item set remotebaud @var{n}
14361 @cindex baud rate for remote targets
14362 Set the baud rate for the remote serial I/O to @var{n} baud. The
14363 value is used to set the speed of the serial port used for debugging
14366 @item show remotebaud
14367 Show the current speed of the remote connection.
14369 @item set remotebreak
14370 @cindex interrupt remote programs
14371 @cindex BREAK signal instead of Ctrl-C
14372 @anchor{set remotebreak}
14373 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
14374 when you type @kbd{Ctrl-c} to interrupt the program running
14375 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
14376 character instead. The default is off, since most remote systems
14377 expect to see @samp{Ctrl-C} as the interrupt signal.
14379 @item show remotebreak
14380 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
14381 interrupt the remote program.
14383 @item set remoteflow on
14384 @itemx set remoteflow off
14385 @kindex set remoteflow
14386 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
14387 on the serial port used to communicate to the remote target.
14389 @item show remoteflow
14390 @kindex show remoteflow
14391 Show the current setting of hardware flow control.
14393 @item set remotelogbase @var{base}
14394 Set the base (a.k.a.@: radix) of logging serial protocol
14395 communications to @var{base}. Supported values of @var{base} are:
14396 @code{ascii}, @code{octal}, and @code{hex}. The default is
14399 @item show remotelogbase
14400 Show the current setting of the radix for logging remote serial
14403 @item set remotelogfile @var{file}
14404 @cindex record serial communications on file
14405 Record remote serial communications on the named @var{file}. The
14406 default is not to record at all.
14408 @item show remotelogfile.
14409 Show the current setting of the file name on which to record the
14410 serial communications.
14412 @item set remotetimeout @var{num}
14413 @cindex timeout for serial communications
14414 @cindex remote timeout
14415 Set the timeout limit to wait for the remote target to respond to
14416 @var{num} seconds. The default is 2 seconds.
14418 @item show remotetimeout
14419 Show the current number of seconds to wait for the remote target
14422 @cindex limit hardware breakpoints and watchpoints
14423 @cindex remote target, limit break- and watchpoints
14424 @anchor{set remote hardware-watchpoint-limit}
14425 @anchor{set remote hardware-breakpoint-limit}
14426 @item set remote hardware-watchpoint-limit @var{limit}
14427 @itemx set remote hardware-breakpoint-limit @var{limit}
14428 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
14429 watchpoints. A limit of -1, the default, is treated as unlimited.
14431 @item set remote exec-file @var{filename}
14432 @itemx show remote exec-file
14433 @anchor{set remote exec-file}
14434 @cindex executable file, for remote target
14435 Select the file used for @code{run} with @code{target
14436 extended-remote}. This should be set to a filename valid on the
14437 target system. If it is not set, the target will use a default
14438 filename (e.g.@: the last program run).
14442 @item set tcp auto-retry on
14443 @cindex auto-retry, for remote TCP target
14444 Enable auto-retry for remote TCP connections. This is useful if the remote
14445 debugging agent is launched in parallel with @value{GDBN}; there is a race
14446 condition because the agent may not become ready to accept the connection
14447 before @value{GDBN} attempts to connect. When auto-retry is
14448 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
14449 to establish the connection using the timeout specified by
14450 @code{set tcp connect-timeout}.
14452 @item set tcp auto-retry off
14453 Do not auto-retry failed TCP connections.
14455 @item show tcp auto-retry
14456 Show the current auto-retry setting.
14458 @item set tcp connect-timeout @var{seconds}
14459 @cindex connection timeout, for remote TCP target
14460 @cindex timeout, for remote target connection
14461 Set the timeout for establishing a TCP connection to the remote target to
14462 @var{seconds}. The timeout affects both polling to retry failed connections
14463 (enabled by @code{set tcp auto-retry on}) and waiting for connections
14464 that are merely slow to complete, and represents an approximate cumulative
14467 @item show tcp connect-timeout
14468 Show the current connection timeout setting.
14471 @cindex remote packets, enabling and disabling
14472 The @value{GDBN} remote protocol autodetects the packets supported by
14473 your debugging stub. If you need to override the autodetection, you
14474 can use these commands to enable or disable individual packets. Each
14475 packet can be set to @samp{on} (the remote target supports this
14476 packet), @samp{off} (the remote target does not support this packet),
14477 or @samp{auto} (detect remote target support for this packet). They
14478 all default to @samp{auto}. For more information about each packet,
14479 see @ref{Remote Protocol}.
14481 During normal use, you should not have to use any of these commands.
14482 If you do, that may be a bug in your remote debugging stub, or a bug
14483 in @value{GDBN}. You may want to report the problem to the
14484 @value{GDBN} developers.
14486 For each packet @var{name}, the command to enable or disable the
14487 packet is @code{set remote @var{name}-packet}. The available settings
14490 @multitable @columnfractions 0.28 0.32 0.25
14493 @tab Related Features
14495 @item @code{fetch-register}
14497 @tab @code{info registers}
14499 @item @code{set-register}
14503 @item @code{binary-download}
14505 @tab @code{load}, @code{set}
14507 @item @code{read-aux-vector}
14508 @tab @code{qXfer:auxv:read}
14509 @tab @code{info auxv}
14511 @item @code{symbol-lookup}
14512 @tab @code{qSymbol}
14513 @tab Detecting multiple threads
14515 @item @code{attach}
14516 @tab @code{vAttach}
14519 @item @code{verbose-resume}
14521 @tab Stepping or resuming multiple threads
14527 @item @code{software-breakpoint}
14531 @item @code{hardware-breakpoint}
14535 @item @code{write-watchpoint}
14539 @item @code{read-watchpoint}
14543 @item @code{access-watchpoint}
14547 @item @code{target-features}
14548 @tab @code{qXfer:features:read}
14549 @tab @code{set architecture}
14551 @item @code{library-info}
14552 @tab @code{qXfer:libraries:read}
14553 @tab @code{info sharedlibrary}
14555 @item @code{memory-map}
14556 @tab @code{qXfer:memory-map:read}
14557 @tab @code{info mem}
14559 @item @code{read-spu-object}
14560 @tab @code{qXfer:spu:read}
14561 @tab @code{info spu}
14563 @item @code{write-spu-object}
14564 @tab @code{qXfer:spu:write}
14565 @tab @code{info spu}
14567 @item @code{read-siginfo-object}
14568 @tab @code{qXfer:siginfo:read}
14569 @tab @code{print $_siginfo}
14571 @item @code{write-siginfo-object}
14572 @tab @code{qXfer:siginfo:write}
14573 @tab @code{set $_siginfo}
14575 @item @code{get-thread-local-@*storage-address}
14576 @tab @code{qGetTLSAddr}
14577 @tab Displaying @code{__thread} variables
14579 @item @code{search-memory}
14580 @tab @code{qSearch:memory}
14583 @item @code{supported-packets}
14584 @tab @code{qSupported}
14585 @tab Remote communications parameters
14587 @item @code{pass-signals}
14588 @tab @code{QPassSignals}
14589 @tab @code{handle @var{signal}}
14591 @item @code{hostio-close-packet}
14592 @tab @code{vFile:close}
14593 @tab @code{remote get}, @code{remote put}
14595 @item @code{hostio-open-packet}
14596 @tab @code{vFile:open}
14597 @tab @code{remote get}, @code{remote put}
14599 @item @code{hostio-pread-packet}
14600 @tab @code{vFile:pread}
14601 @tab @code{remote get}, @code{remote put}
14603 @item @code{hostio-pwrite-packet}
14604 @tab @code{vFile:pwrite}
14605 @tab @code{remote get}, @code{remote put}
14607 @item @code{hostio-unlink-packet}
14608 @tab @code{vFile:unlink}
14609 @tab @code{remote delete}
14611 @item @code{noack-packet}
14612 @tab @code{QStartNoAckMode}
14613 @tab Packet acknowledgment
14615 @item @code{osdata}
14616 @tab @code{qXfer:osdata:read}
14617 @tab @code{info os}
14619 @item @code{query-attached}
14620 @tab @code{qAttached}
14621 @tab Querying remote process attach state.
14625 @section Implementing a Remote Stub
14627 @cindex debugging stub, example
14628 @cindex remote stub, example
14629 @cindex stub example, remote debugging
14630 The stub files provided with @value{GDBN} implement the target side of the
14631 communication protocol, and the @value{GDBN} side is implemented in the
14632 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
14633 these subroutines to communicate, and ignore the details. (If you're
14634 implementing your own stub file, you can still ignore the details: start
14635 with one of the existing stub files. @file{sparc-stub.c} is the best
14636 organized, and therefore the easiest to read.)
14638 @cindex remote serial debugging, overview
14639 To debug a program running on another machine (the debugging
14640 @dfn{target} machine), you must first arrange for all the usual
14641 prerequisites for the program to run by itself. For example, for a C
14646 A startup routine to set up the C runtime environment; these usually
14647 have a name like @file{crt0}. The startup routine may be supplied by
14648 your hardware supplier, or you may have to write your own.
14651 A C subroutine library to support your program's
14652 subroutine calls, notably managing input and output.
14655 A way of getting your program to the other machine---for example, a
14656 download program. These are often supplied by the hardware
14657 manufacturer, but you may have to write your own from hardware
14661 The next step is to arrange for your program to use a serial port to
14662 communicate with the machine where @value{GDBN} is running (the @dfn{host}
14663 machine). In general terms, the scheme looks like this:
14667 @value{GDBN} already understands how to use this protocol; when everything
14668 else is set up, you can simply use the @samp{target remote} command
14669 (@pxref{Targets,,Specifying a Debugging Target}).
14671 @item On the target,
14672 you must link with your program a few special-purpose subroutines that
14673 implement the @value{GDBN} remote serial protocol. The file containing these
14674 subroutines is called a @dfn{debugging stub}.
14676 On certain remote targets, you can use an auxiliary program
14677 @code{gdbserver} instead of linking a stub into your program.
14678 @xref{Server,,Using the @code{gdbserver} Program}, for details.
14681 The debugging stub is specific to the architecture of the remote
14682 machine; for example, use @file{sparc-stub.c} to debug programs on
14685 @cindex remote serial stub list
14686 These working remote stubs are distributed with @value{GDBN}:
14691 @cindex @file{i386-stub.c}
14694 For Intel 386 and compatible architectures.
14697 @cindex @file{m68k-stub.c}
14698 @cindex Motorola 680x0
14700 For Motorola 680x0 architectures.
14703 @cindex @file{sh-stub.c}
14706 For Renesas SH architectures.
14709 @cindex @file{sparc-stub.c}
14711 For @sc{sparc} architectures.
14713 @item sparcl-stub.c
14714 @cindex @file{sparcl-stub.c}
14717 For Fujitsu @sc{sparclite} architectures.
14721 The @file{README} file in the @value{GDBN} distribution may list other
14722 recently added stubs.
14725 * Stub Contents:: What the stub can do for you
14726 * Bootstrapping:: What you must do for the stub
14727 * Debug Session:: Putting it all together
14730 @node Stub Contents
14731 @subsection What the Stub Can Do for You
14733 @cindex remote serial stub
14734 The debugging stub for your architecture supplies these three
14738 @item set_debug_traps
14739 @findex set_debug_traps
14740 @cindex remote serial stub, initialization
14741 This routine arranges for @code{handle_exception} to run when your
14742 program stops. You must call this subroutine explicitly near the
14743 beginning of your program.
14745 @item handle_exception
14746 @findex handle_exception
14747 @cindex remote serial stub, main routine
14748 This is the central workhorse, but your program never calls it
14749 explicitly---the setup code arranges for @code{handle_exception} to
14750 run when a trap is triggered.
14752 @code{handle_exception} takes control when your program stops during
14753 execution (for example, on a breakpoint), and mediates communications
14754 with @value{GDBN} on the host machine. This is where the communications
14755 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
14756 representative on the target machine. It begins by sending summary
14757 information on the state of your program, then continues to execute,
14758 retrieving and transmitting any information @value{GDBN} needs, until you
14759 execute a @value{GDBN} command that makes your program resume; at that point,
14760 @code{handle_exception} returns control to your own code on the target
14764 @cindex @code{breakpoint} subroutine, remote
14765 Use this auxiliary subroutine to make your program contain a
14766 breakpoint. Depending on the particular situation, this may be the only
14767 way for @value{GDBN} to get control. For instance, if your target
14768 machine has some sort of interrupt button, you won't need to call this;
14769 pressing the interrupt button transfers control to
14770 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
14771 simply receiving characters on the serial port may also trigger a trap;
14772 again, in that situation, you don't need to call @code{breakpoint} from
14773 your own program---simply running @samp{target remote} from the host
14774 @value{GDBN} session gets control.
14776 Call @code{breakpoint} if none of these is true, or if you simply want
14777 to make certain your program stops at a predetermined point for the
14778 start of your debugging session.
14781 @node Bootstrapping
14782 @subsection What You Must Do for the Stub
14784 @cindex remote stub, support routines
14785 The debugging stubs that come with @value{GDBN} are set up for a particular
14786 chip architecture, but they have no information about the rest of your
14787 debugging target machine.
14789 First of all you need to tell the stub how to communicate with the
14793 @item int getDebugChar()
14794 @findex getDebugChar
14795 Write this subroutine to read a single character from the serial port.
14796 It may be identical to @code{getchar} for your target system; a
14797 different name is used to allow you to distinguish the two if you wish.
14799 @item void putDebugChar(int)
14800 @findex putDebugChar
14801 Write this subroutine to write a single character to the serial port.
14802 It may be identical to @code{putchar} for your target system; a
14803 different name is used to allow you to distinguish the two if you wish.
14806 @cindex control C, and remote debugging
14807 @cindex interrupting remote targets
14808 If you want @value{GDBN} to be able to stop your program while it is
14809 running, you need to use an interrupt-driven serial driver, and arrange
14810 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
14811 character). That is the character which @value{GDBN} uses to tell the
14812 remote system to stop.
14814 Getting the debugging target to return the proper status to @value{GDBN}
14815 probably requires changes to the standard stub; one quick and dirty way
14816 is to just execute a breakpoint instruction (the ``dirty'' part is that
14817 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
14819 Other routines you need to supply are:
14822 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
14823 @findex exceptionHandler
14824 Write this function to install @var{exception_address} in the exception
14825 handling tables. You need to do this because the stub does not have any
14826 way of knowing what the exception handling tables on your target system
14827 are like (for example, the processor's table might be in @sc{rom},
14828 containing entries which point to a table in @sc{ram}).
14829 @var{exception_number} is the exception number which should be changed;
14830 its meaning is architecture-dependent (for example, different numbers
14831 might represent divide by zero, misaligned access, etc). When this
14832 exception occurs, control should be transferred directly to
14833 @var{exception_address}, and the processor state (stack, registers,
14834 and so on) should be just as it is when a processor exception occurs. So if
14835 you want to use a jump instruction to reach @var{exception_address}, it
14836 should be a simple jump, not a jump to subroutine.
14838 For the 386, @var{exception_address} should be installed as an interrupt
14839 gate so that interrupts are masked while the handler runs. The gate
14840 should be at privilege level 0 (the most privileged level). The
14841 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
14842 help from @code{exceptionHandler}.
14844 @item void flush_i_cache()
14845 @findex flush_i_cache
14846 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
14847 instruction cache, if any, on your target machine. If there is no
14848 instruction cache, this subroutine may be a no-op.
14850 On target machines that have instruction caches, @value{GDBN} requires this
14851 function to make certain that the state of your program is stable.
14855 You must also make sure this library routine is available:
14858 @item void *memset(void *, int, int)
14860 This is the standard library function @code{memset} that sets an area of
14861 memory to a known value. If you have one of the free versions of
14862 @code{libc.a}, @code{memset} can be found there; otherwise, you must
14863 either obtain it from your hardware manufacturer, or write your own.
14866 If you do not use the GNU C compiler, you may need other standard
14867 library subroutines as well; this varies from one stub to another,
14868 but in general the stubs are likely to use any of the common library
14869 subroutines which @code{@value{NGCC}} generates as inline code.
14872 @node Debug Session
14873 @subsection Putting it All Together
14875 @cindex remote serial debugging summary
14876 In summary, when your program is ready to debug, you must follow these
14881 Make sure you have defined the supporting low-level routines
14882 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
14884 @code{getDebugChar}, @code{putDebugChar},
14885 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
14889 Insert these lines near the top of your program:
14897 For the 680x0 stub only, you need to provide a variable called
14898 @code{exceptionHook}. Normally you just use:
14901 void (*exceptionHook)() = 0;
14905 but if before calling @code{set_debug_traps}, you set it to point to a
14906 function in your program, that function is called when
14907 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
14908 error). The function indicated by @code{exceptionHook} is called with
14909 one parameter: an @code{int} which is the exception number.
14912 Compile and link together: your program, the @value{GDBN} debugging stub for
14913 your target architecture, and the supporting subroutines.
14916 Make sure you have a serial connection between your target machine and
14917 the @value{GDBN} host, and identify the serial port on the host.
14920 @c The "remote" target now provides a `load' command, so we should
14921 @c document that. FIXME.
14922 Download your program to your target machine (or get it there by
14923 whatever means the manufacturer provides), and start it.
14926 Start @value{GDBN} on the host, and connect to the target
14927 (@pxref{Connecting,,Connecting to a Remote Target}).
14931 @node Configurations
14932 @chapter Configuration-Specific Information
14934 While nearly all @value{GDBN} commands are available for all native and
14935 cross versions of the debugger, there are some exceptions. This chapter
14936 describes things that are only available in certain configurations.
14938 There are three major categories of configurations: native
14939 configurations, where the host and target are the same, embedded
14940 operating system configurations, which are usually the same for several
14941 different processor architectures, and bare embedded processors, which
14942 are quite different from each other.
14947 * Embedded Processors::
14954 This section describes details specific to particular native
14959 * BSD libkvm Interface:: Debugging BSD kernel memory images
14960 * SVR4 Process Information:: SVR4 process information
14961 * DJGPP Native:: Features specific to the DJGPP port
14962 * Cygwin Native:: Features specific to the Cygwin port
14963 * Hurd Native:: Features specific to @sc{gnu} Hurd
14964 * Neutrino:: Features specific to QNX Neutrino
14965 * Darwin:: Features specific to Darwin
14971 On HP-UX systems, if you refer to a function or variable name that
14972 begins with a dollar sign, @value{GDBN} searches for a user or system
14973 name first, before it searches for a convenience variable.
14976 @node BSD libkvm Interface
14977 @subsection BSD libkvm Interface
14980 @cindex kernel memory image
14981 @cindex kernel crash dump
14983 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14984 interface that provides a uniform interface for accessing kernel virtual
14985 memory images, including live systems and crash dumps. @value{GDBN}
14986 uses this interface to allow you to debug live kernels and kernel crash
14987 dumps on many native BSD configurations. This is implemented as a
14988 special @code{kvm} debugging target. For debugging a live system, load
14989 the currently running kernel into @value{GDBN} and connect to the
14993 (@value{GDBP}) @b{target kvm}
14996 For debugging crash dumps, provide the file name of the crash dump as an
15000 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
15003 Once connected to the @code{kvm} target, the following commands are
15009 Set current context from the @dfn{Process Control Block} (PCB) address.
15012 Set current context from proc address. This command isn't available on
15013 modern FreeBSD systems.
15016 @node SVR4 Process Information
15017 @subsection SVR4 Process Information
15019 @cindex examine process image
15020 @cindex process info via @file{/proc}
15022 Many versions of SVR4 and compatible systems provide a facility called
15023 @samp{/proc} that can be used to examine the image of a running
15024 process using file-system subroutines. If @value{GDBN} is configured
15025 for an operating system with this facility, the command @code{info
15026 proc} is available to report information about the process running
15027 your program, or about any process running on your system. @code{info
15028 proc} works only on SVR4 systems that include the @code{procfs} code.
15029 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
15030 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
15036 @itemx info proc @var{process-id}
15037 Summarize available information about any running process. If a
15038 process ID is specified by @var{process-id}, display information about
15039 that process; otherwise display information about the program being
15040 debugged. The summary includes the debugged process ID, the command
15041 line used to invoke it, its current working directory, and its
15042 executable file's absolute file name.
15044 On some systems, @var{process-id} can be of the form
15045 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
15046 within a process. If the optional @var{pid} part is missing, it means
15047 a thread from the process being debugged (the leading @samp{/} still
15048 needs to be present, or else @value{GDBN} will interpret the number as
15049 a process ID rather than a thread ID).
15051 @item info proc mappings
15052 @cindex memory address space mappings
15053 Report the memory address space ranges accessible in the program, with
15054 information on whether the process has read, write, or execute access
15055 rights to each range. On @sc{gnu}/Linux systems, each memory range
15056 includes the object file which is mapped to that range, instead of the
15057 memory access rights to that range.
15059 @item info proc stat
15060 @itemx info proc status
15061 @cindex process detailed status information
15062 These subcommands are specific to @sc{gnu}/Linux systems. They show
15063 the process-related information, including the user ID and group ID;
15064 how many threads are there in the process; its virtual memory usage;
15065 the signals that are pending, blocked, and ignored; its TTY; its
15066 consumption of system and user time; its stack size; its @samp{nice}
15067 value; etc. For more information, see the @samp{proc} man page
15068 (type @kbd{man 5 proc} from your shell prompt).
15070 @item info proc all
15071 Show all the information about the process described under all of the
15072 above @code{info proc} subcommands.
15075 @comment These sub-options of 'info proc' were not included when
15076 @comment procfs.c was re-written. Keep their descriptions around
15077 @comment against the day when someone finds the time to put them back in.
15078 @kindex info proc times
15079 @item info proc times
15080 Starting time, user CPU time, and system CPU time for your program and
15083 @kindex info proc id
15085 Report on the process IDs related to your program: its own process ID,
15086 the ID of its parent, the process group ID, and the session ID.
15089 @item set procfs-trace
15090 @kindex set procfs-trace
15091 @cindex @code{procfs} API calls
15092 This command enables and disables tracing of @code{procfs} API calls.
15094 @item show procfs-trace
15095 @kindex show procfs-trace
15096 Show the current state of @code{procfs} API call tracing.
15098 @item set procfs-file @var{file}
15099 @kindex set procfs-file
15100 Tell @value{GDBN} to write @code{procfs} API trace to the named
15101 @var{file}. @value{GDBN} appends the trace info to the previous
15102 contents of the file. The default is to display the trace on the
15105 @item show procfs-file
15106 @kindex show procfs-file
15107 Show the file to which @code{procfs} API trace is written.
15109 @item proc-trace-entry
15110 @itemx proc-trace-exit
15111 @itemx proc-untrace-entry
15112 @itemx proc-untrace-exit
15113 @kindex proc-trace-entry
15114 @kindex proc-trace-exit
15115 @kindex proc-untrace-entry
15116 @kindex proc-untrace-exit
15117 These commands enable and disable tracing of entries into and exits
15118 from the @code{syscall} interface.
15121 @kindex info pidlist
15122 @cindex process list, QNX Neutrino
15123 For QNX Neutrino only, this command displays the list of all the
15124 processes and all the threads within each process.
15127 @kindex info meminfo
15128 @cindex mapinfo list, QNX Neutrino
15129 For QNX Neutrino only, this command displays the list of all mapinfos.
15133 @subsection Features for Debugging @sc{djgpp} Programs
15134 @cindex @sc{djgpp} debugging
15135 @cindex native @sc{djgpp} debugging
15136 @cindex MS-DOS-specific commands
15139 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
15140 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
15141 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
15142 top of real-mode DOS systems and their emulations.
15144 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
15145 defines a few commands specific to the @sc{djgpp} port. This
15146 subsection describes those commands.
15151 This is a prefix of @sc{djgpp}-specific commands which print
15152 information about the target system and important OS structures.
15155 @cindex MS-DOS system info
15156 @cindex free memory information (MS-DOS)
15157 @item info dos sysinfo
15158 This command displays assorted information about the underlying
15159 platform: the CPU type and features, the OS version and flavor, the
15160 DPMI version, and the available conventional and DPMI memory.
15165 @cindex segment descriptor tables
15166 @cindex descriptor tables display
15168 @itemx info dos ldt
15169 @itemx info dos idt
15170 These 3 commands display entries from, respectively, Global, Local,
15171 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
15172 tables are data structures which store a descriptor for each segment
15173 that is currently in use. The segment's selector is an index into a
15174 descriptor table; the table entry for that index holds the
15175 descriptor's base address and limit, and its attributes and access
15178 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
15179 segment (used for both data and the stack), and a DOS segment (which
15180 allows access to DOS/BIOS data structures and absolute addresses in
15181 conventional memory). However, the DPMI host will usually define
15182 additional segments in order to support the DPMI environment.
15184 @cindex garbled pointers
15185 These commands allow to display entries from the descriptor tables.
15186 Without an argument, all entries from the specified table are
15187 displayed. An argument, which should be an integer expression, means
15188 display a single entry whose index is given by the argument. For
15189 example, here's a convenient way to display information about the
15190 debugged program's data segment:
15193 @exdent @code{(@value{GDBP}) info dos ldt $ds}
15194 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
15198 This comes in handy when you want to see whether a pointer is outside
15199 the data segment's limit (i.e.@: @dfn{garbled}).
15201 @cindex page tables display (MS-DOS)
15203 @itemx info dos pte
15204 These two commands display entries from, respectively, the Page
15205 Directory and the Page Tables. Page Directories and Page Tables are
15206 data structures which control how virtual memory addresses are mapped
15207 into physical addresses. A Page Table includes an entry for every
15208 page of memory that is mapped into the program's address space; there
15209 may be several Page Tables, each one holding up to 4096 entries. A
15210 Page Directory has up to 4096 entries, one each for every Page Table
15211 that is currently in use.
15213 Without an argument, @kbd{info dos pde} displays the entire Page
15214 Directory, and @kbd{info dos pte} displays all the entries in all of
15215 the Page Tables. An argument, an integer expression, given to the
15216 @kbd{info dos pde} command means display only that entry from the Page
15217 Directory table. An argument given to the @kbd{info dos pte} command
15218 means display entries from a single Page Table, the one pointed to by
15219 the specified entry in the Page Directory.
15221 @cindex direct memory access (DMA) on MS-DOS
15222 These commands are useful when your program uses @dfn{DMA} (Direct
15223 Memory Access), which needs physical addresses to program the DMA
15226 These commands are supported only with some DPMI servers.
15228 @cindex physical address from linear address
15229 @item info dos address-pte @var{addr}
15230 This command displays the Page Table entry for a specified linear
15231 address. The argument @var{addr} is a linear address which should
15232 already have the appropriate segment's base address added to it,
15233 because this command accepts addresses which may belong to @emph{any}
15234 segment. For example, here's how to display the Page Table entry for
15235 the page where a variable @code{i} is stored:
15238 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
15239 @exdent @code{Page Table entry for address 0x11a00d30:}
15240 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
15244 This says that @code{i} is stored at offset @code{0xd30} from the page
15245 whose physical base address is @code{0x02698000}, and shows all the
15246 attributes of that page.
15248 Note that you must cast the addresses of variables to a @code{char *},
15249 since otherwise the value of @code{__djgpp_base_address}, the base
15250 address of all variables and functions in a @sc{djgpp} program, will
15251 be added using the rules of C pointer arithmetics: if @code{i} is
15252 declared an @code{int}, @value{GDBN} will add 4 times the value of
15253 @code{__djgpp_base_address} to the address of @code{i}.
15255 Here's another example, it displays the Page Table entry for the
15259 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
15260 @exdent @code{Page Table entry for address 0x29110:}
15261 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
15265 (The @code{+ 3} offset is because the transfer buffer's address is the
15266 3rd member of the @code{_go32_info_block} structure.) The output
15267 clearly shows that this DPMI server maps the addresses in conventional
15268 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
15269 linear (@code{0x29110}) addresses are identical.
15271 This command is supported only with some DPMI servers.
15274 @cindex DOS serial data link, remote debugging
15275 In addition to native debugging, the DJGPP port supports remote
15276 debugging via a serial data link. The following commands are specific
15277 to remote serial debugging in the DJGPP port of @value{GDBN}.
15280 @kindex set com1base
15281 @kindex set com1irq
15282 @kindex set com2base
15283 @kindex set com2irq
15284 @kindex set com3base
15285 @kindex set com3irq
15286 @kindex set com4base
15287 @kindex set com4irq
15288 @item set com1base @var{addr}
15289 This command sets the base I/O port address of the @file{COM1} serial
15292 @item set com1irq @var{irq}
15293 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
15294 for the @file{COM1} serial port.
15296 There are similar commands @samp{set com2base}, @samp{set com3irq},
15297 etc.@: for setting the port address and the @code{IRQ} lines for the
15300 @kindex show com1base
15301 @kindex show com1irq
15302 @kindex show com2base
15303 @kindex show com2irq
15304 @kindex show com3base
15305 @kindex show com3irq
15306 @kindex show com4base
15307 @kindex show com4irq
15308 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
15309 display the current settings of the base address and the @code{IRQ}
15310 lines used by the COM ports.
15313 @kindex info serial
15314 @cindex DOS serial port status
15315 This command prints the status of the 4 DOS serial ports. For each
15316 port, it prints whether it's active or not, its I/O base address and
15317 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
15318 counts of various errors encountered so far.
15322 @node Cygwin Native
15323 @subsection Features for Debugging MS Windows PE Executables
15324 @cindex MS Windows debugging
15325 @cindex native Cygwin debugging
15326 @cindex Cygwin-specific commands
15328 @value{GDBN} supports native debugging of MS Windows programs, including
15329 DLLs with and without symbolic debugging information. There are various
15330 additional Cygwin-specific commands, described in this section.
15331 Working with DLLs that have no debugging symbols is described in
15332 @ref{Non-debug DLL Symbols}.
15337 This is a prefix of MS Windows-specific commands which print
15338 information about the target system and important OS structures.
15340 @item info w32 selector
15341 This command displays information returned by
15342 the Win32 API @code{GetThreadSelectorEntry} function.
15343 It takes an optional argument that is evaluated to
15344 a long value to give the information about this given selector.
15345 Without argument, this command displays information
15346 about the six segment registers.
15350 This is a Cygwin-specific alias of @code{info shared}.
15352 @kindex dll-symbols
15354 This command loads symbols from a dll similarly to
15355 add-sym command but without the need to specify a base address.
15357 @kindex set cygwin-exceptions
15358 @cindex debugging the Cygwin DLL
15359 @cindex Cygwin DLL, debugging
15360 @item set cygwin-exceptions @var{mode}
15361 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
15362 happen inside the Cygwin DLL. If @var{mode} is @code{off},
15363 @value{GDBN} will delay recognition of exceptions, and may ignore some
15364 exceptions which seem to be caused by internal Cygwin DLL
15365 ``bookkeeping''. This option is meant primarily for debugging the
15366 Cygwin DLL itself; the default value is @code{off} to avoid annoying
15367 @value{GDBN} users with false @code{SIGSEGV} signals.
15369 @kindex show cygwin-exceptions
15370 @item show cygwin-exceptions
15371 Displays whether @value{GDBN} will break on exceptions that happen
15372 inside the Cygwin DLL itself.
15374 @kindex set new-console
15375 @item set new-console @var{mode}
15376 If @var{mode} is @code{on} the debuggee will
15377 be started in a new console on next start.
15378 If @var{mode} is @code{off}i, the debuggee will
15379 be started in the same console as the debugger.
15381 @kindex show new-console
15382 @item show new-console
15383 Displays whether a new console is used
15384 when the debuggee is started.
15386 @kindex set new-group
15387 @item set new-group @var{mode}
15388 This boolean value controls whether the debuggee should
15389 start a new group or stay in the same group as the debugger.
15390 This affects the way the Windows OS handles
15393 @kindex show new-group
15394 @item show new-group
15395 Displays current value of new-group boolean.
15397 @kindex set debugevents
15398 @item set debugevents
15399 This boolean value adds debug output concerning kernel events related
15400 to the debuggee seen by the debugger. This includes events that
15401 signal thread and process creation and exit, DLL loading and
15402 unloading, console interrupts, and debugging messages produced by the
15403 Windows @code{OutputDebugString} API call.
15405 @kindex set debugexec
15406 @item set debugexec
15407 This boolean value adds debug output concerning execute events
15408 (such as resume thread) seen by the debugger.
15410 @kindex set debugexceptions
15411 @item set debugexceptions
15412 This boolean value adds debug output concerning exceptions in the
15413 debuggee seen by the debugger.
15415 @kindex set debugmemory
15416 @item set debugmemory
15417 This boolean value adds debug output concerning debuggee memory reads
15418 and writes by the debugger.
15422 This boolean values specifies whether the debuggee is called
15423 via a shell or directly (default value is on).
15427 Displays if the debuggee will be started with a shell.
15432 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
15435 @node Non-debug DLL Symbols
15436 @subsubsection Support for DLLs without Debugging Symbols
15437 @cindex DLLs with no debugging symbols
15438 @cindex Minimal symbols and DLLs
15440 Very often on windows, some of the DLLs that your program relies on do
15441 not include symbolic debugging information (for example,
15442 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
15443 symbols in a DLL, it relies on the minimal amount of symbolic
15444 information contained in the DLL's export table. This section
15445 describes working with such symbols, known internally to @value{GDBN} as
15446 ``minimal symbols''.
15448 Note that before the debugged program has started execution, no DLLs
15449 will have been loaded. The easiest way around this problem is simply to
15450 start the program --- either by setting a breakpoint or letting the
15451 program run once to completion. It is also possible to force
15452 @value{GDBN} to load a particular DLL before starting the executable ---
15453 see the shared library information in @ref{Files}, or the
15454 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
15455 explicitly loading symbols from a DLL with no debugging information will
15456 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
15457 which may adversely affect symbol lookup performance.
15459 @subsubsection DLL Name Prefixes
15461 In keeping with the naming conventions used by the Microsoft debugging
15462 tools, DLL export symbols are made available with a prefix based on the
15463 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
15464 also entered into the symbol table, so @code{CreateFileA} is often
15465 sufficient. In some cases there will be name clashes within a program
15466 (particularly if the executable itself includes full debugging symbols)
15467 necessitating the use of the fully qualified name when referring to the
15468 contents of the DLL. Use single-quotes around the name to avoid the
15469 exclamation mark (``!'') being interpreted as a language operator.
15471 Note that the internal name of the DLL may be all upper-case, even
15472 though the file name of the DLL is lower-case, or vice-versa. Since
15473 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
15474 some confusion. If in doubt, try the @code{info functions} and
15475 @code{info variables} commands or even @code{maint print msymbols}
15476 (@pxref{Symbols}). Here's an example:
15479 (@value{GDBP}) info function CreateFileA
15480 All functions matching regular expression "CreateFileA":
15482 Non-debugging symbols:
15483 0x77e885f4 CreateFileA
15484 0x77e885f4 KERNEL32!CreateFileA
15488 (@value{GDBP}) info function !
15489 All functions matching regular expression "!":
15491 Non-debugging symbols:
15492 0x6100114c cygwin1!__assert
15493 0x61004034 cygwin1!_dll_crt0@@0
15494 0x61004240 cygwin1!dll_crt0(per_process *)
15498 @subsubsection Working with Minimal Symbols
15500 Symbols extracted from a DLL's export table do not contain very much
15501 type information. All that @value{GDBN} can do is guess whether a symbol
15502 refers to a function or variable depending on the linker section that
15503 contains the symbol. Also note that the actual contents of the memory
15504 contained in a DLL are not available unless the program is running. This
15505 means that you cannot examine the contents of a variable or disassemble
15506 a function within a DLL without a running program.
15508 Variables are generally treated as pointers and dereferenced
15509 automatically. For this reason, it is often necessary to prefix a
15510 variable name with the address-of operator (``&'') and provide explicit
15511 type information in the command. Here's an example of the type of
15515 (@value{GDBP}) print 'cygwin1!__argv'
15520 (@value{GDBP}) x 'cygwin1!__argv'
15521 0x10021610: "\230y\""
15524 And two possible solutions:
15527 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
15528 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
15532 (@value{GDBP}) x/2x &'cygwin1!__argv'
15533 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
15534 (@value{GDBP}) x/x 0x10021608
15535 0x10021608: 0x0022fd98
15536 (@value{GDBP}) x/s 0x0022fd98
15537 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
15540 Setting a break point within a DLL is possible even before the program
15541 starts execution. However, under these circumstances, @value{GDBN} can't
15542 examine the initial instructions of the function in order to skip the
15543 function's frame set-up code. You can work around this by using ``*&''
15544 to set the breakpoint at a raw memory address:
15547 (@value{GDBP}) break *&'python22!PyOS_Readline'
15548 Breakpoint 1 at 0x1e04eff0
15551 The author of these extensions is not entirely convinced that setting a
15552 break point within a shared DLL like @file{kernel32.dll} is completely
15556 @subsection Commands Specific to @sc{gnu} Hurd Systems
15557 @cindex @sc{gnu} Hurd debugging
15559 This subsection describes @value{GDBN} commands specific to the
15560 @sc{gnu} Hurd native debugging.
15565 @kindex set signals@r{, Hurd command}
15566 @kindex set sigs@r{, Hurd command}
15567 This command toggles the state of inferior signal interception by
15568 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
15569 affected by this command. @code{sigs} is a shorthand alias for
15574 @kindex show signals@r{, Hurd command}
15575 @kindex show sigs@r{, Hurd command}
15576 Show the current state of intercepting inferior's signals.
15578 @item set signal-thread
15579 @itemx set sigthread
15580 @kindex set signal-thread
15581 @kindex set sigthread
15582 This command tells @value{GDBN} which thread is the @code{libc} signal
15583 thread. That thread is run when a signal is delivered to a running
15584 process. @code{set sigthread} is the shorthand alias of @code{set
15587 @item show signal-thread
15588 @itemx show sigthread
15589 @kindex show signal-thread
15590 @kindex show sigthread
15591 These two commands show which thread will run when the inferior is
15592 delivered a signal.
15595 @kindex set stopped@r{, Hurd command}
15596 This commands tells @value{GDBN} that the inferior process is stopped,
15597 as with the @code{SIGSTOP} signal. The stopped process can be
15598 continued by delivering a signal to it.
15601 @kindex show stopped@r{, Hurd command}
15602 This command shows whether @value{GDBN} thinks the debuggee is
15605 @item set exceptions
15606 @kindex set exceptions@r{, Hurd command}
15607 Use this command to turn off trapping of exceptions in the inferior.
15608 When exception trapping is off, neither breakpoints nor
15609 single-stepping will work. To restore the default, set exception
15612 @item show exceptions
15613 @kindex show exceptions@r{, Hurd command}
15614 Show the current state of trapping exceptions in the inferior.
15616 @item set task pause
15617 @kindex set task@r{, Hurd commands}
15618 @cindex task attributes (@sc{gnu} Hurd)
15619 @cindex pause current task (@sc{gnu} Hurd)
15620 This command toggles task suspension when @value{GDBN} has control.
15621 Setting it to on takes effect immediately, and the task is suspended
15622 whenever @value{GDBN} gets control. Setting it to off will take
15623 effect the next time the inferior is continued. If this option is set
15624 to off, you can use @code{set thread default pause on} or @code{set
15625 thread pause on} (see below) to pause individual threads.
15627 @item show task pause
15628 @kindex show task@r{, Hurd commands}
15629 Show the current state of task suspension.
15631 @item set task detach-suspend-count
15632 @cindex task suspend count
15633 @cindex detach from task, @sc{gnu} Hurd
15634 This command sets the suspend count the task will be left with when
15635 @value{GDBN} detaches from it.
15637 @item show task detach-suspend-count
15638 Show the suspend count the task will be left with when detaching.
15640 @item set task exception-port
15641 @itemx set task excp
15642 @cindex task exception port, @sc{gnu} Hurd
15643 This command sets the task exception port to which @value{GDBN} will
15644 forward exceptions. The argument should be the value of the @dfn{send
15645 rights} of the task. @code{set task excp} is a shorthand alias.
15647 @item set noninvasive
15648 @cindex noninvasive task options
15649 This command switches @value{GDBN} to a mode that is the least
15650 invasive as far as interfering with the inferior is concerned. This
15651 is the same as using @code{set task pause}, @code{set exceptions}, and
15652 @code{set signals} to values opposite to the defaults.
15654 @item info send-rights
15655 @itemx info receive-rights
15656 @itemx info port-rights
15657 @itemx info port-sets
15658 @itemx info dead-names
15661 @cindex send rights, @sc{gnu} Hurd
15662 @cindex receive rights, @sc{gnu} Hurd
15663 @cindex port rights, @sc{gnu} Hurd
15664 @cindex port sets, @sc{gnu} Hurd
15665 @cindex dead names, @sc{gnu} Hurd
15666 These commands display information about, respectively, send rights,
15667 receive rights, port rights, port sets, and dead names of a task.
15668 There are also shorthand aliases: @code{info ports} for @code{info
15669 port-rights} and @code{info psets} for @code{info port-sets}.
15671 @item set thread pause
15672 @kindex set thread@r{, Hurd command}
15673 @cindex thread properties, @sc{gnu} Hurd
15674 @cindex pause current thread (@sc{gnu} Hurd)
15675 This command toggles current thread suspension when @value{GDBN} has
15676 control. Setting it to on takes effect immediately, and the current
15677 thread is suspended whenever @value{GDBN} gets control. Setting it to
15678 off will take effect the next time the inferior is continued.
15679 Normally, this command has no effect, since when @value{GDBN} has
15680 control, the whole task is suspended. However, if you used @code{set
15681 task pause off} (see above), this command comes in handy to suspend
15682 only the current thread.
15684 @item show thread pause
15685 @kindex show thread@r{, Hurd command}
15686 This command shows the state of current thread suspension.
15688 @item set thread run
15689 This command sets whether the current thread is allowed to run.
15691 @item show thread run
15692 Show whether the current thread is allowed to run.
15694 @item set thread detach-suspend-count
15695 @cindex thread suspend count, @sc{gnu} Hurd
15696 @cindex detach from thread, @sc{gnu} Hurd
15697 This command sets the suspend count @value{GDBN} will leave on a
15698 thread when detaching. This number is relative to the suspend count
15699 found by @value{GDBN} when it notices the thread; use @code{set thread
15700 takeover-suspend-count} to force it to an absolute value.
15702 @item show thread detach-suspend-count
15703 Show the suspend count @value{GDBN} will leave on the thread when
15706 @item set thread exception-port
15707 @itemx set thread excp
15708 Set the thread exception port to which to forward exceptions. This
15709 overrides the port set by @code{set task exception-port} (see above).
15710 @code{set thread excp} is the shorthand alias.
15712 @item set thread takeover-suspend-count
15713 Normally, @value{GDBN}'s thread suspend counts are relative to the
15714 value @value{GDBN} finds when it notices each thread. This command
15715 changes the suspend counts to be absolute instead.
15717 @item set thread default
15718 @itemx show thread default
15719 @cindex thread default settings, @sc{gnu} Hurd
15720 Each of the above @code{set thread} commands has a @code{set thread
15721 default} counterpart (e.g., @code{set thread default pause}, @code{set
15722 thread default exception-port}, etc.). The @code{thread default}
15723 variety of commands sets the default thread properties for all
15724 threads; you can then change the properties of individual threads with
15725 the non-default commands.
15730 @subsection QNX Neutrino
15731 @cindex QNX Neutrino
15733 @value{GDBN} provides the following commands specific to the QNX
15737 @item set debug nto-debug
15738 @kindex set debug nto-debug
15739 When set to on, enables debugging messages specific to the QNX
15742 @item show debug nto-debug
15743 @kindex show debug nto-debug
15744 Show the current state of QNX Neutrino messages.
15751 @value{GDBN} provides the following commands specific to the Darwin target:
15754 @item set debug darwin @var{num}
15755 @kindex set debug darwin
15756 When set to a non zero value, enables debugging messages specific to
15757 the Darwin support. Higher values produce more verbose output.
15759 @item show debug darwin
15760 @kindex show debug darwin
15761 Show the current state of Darwin messages.
15763 @item set debug mach-o @var{num}
15764 @kindex set debug mach-o
15765 When set to a non zero value, enables debugging messages while
15766 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
15767 file format used on Darwin for object and executable files.) Higher
15768 values produce more verbose output. This is a command to diagnose
15769 problems internal to @value{GDBN} and should not be needed in normal
15772 @item show debug mach-o
15773 @kindex show debug mach-o
15774 Show the current state of Mach-O file messages.
15776 @item set mach-exceptions on
15777 @itemx set mach-exceptions off
15778 @kindex set mach-exceptions
15779 On Darwin, faults are first reported as a Mach exception and are then
15780 mapped to a Posix signal. Use this command to turn on trapping of
15781 Mach exceptions in the inferior. This might be sometimes useful to
15782 better understand the cause of a fault. The default is off.
15784 @item show mach-exceptions
15785 @kindex show mach-exceptions
15786 Show the current state of exceptions trapping.
15791 @section Embedded Operating Systems
15793 This section describes configurations involving the debugging of
15794 embedded operating systems that are available for several different
15798 * VxWorks:: Using @value{GDBN} with VxWorks
15801 @value{GDBN} includes the ability to debug programs running on
15802 various real-time operating systems.
15805 @subsection Using @value{GDBN} with VxWorks
15811 @kindex target vxworks
15812 @item target vxworks @var{machinename}
15813 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
15814 is the target system's machine name or IP address.
15818 On VxWorks, @code{load} links @var{filename} dynamically on the
15819 current target system as well as adding its symbols in @value{GDBN}.
15821 @value{GDBN} enables developers to spawn and debug tasks running on networked
15822 VxWorks targets from a Unix host. Already-running tasks spawned from
15823 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
15824 both the Unix host and on the VxWorks target. The program
15825 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
15826 installed with the name @code{vxgdb}, to distinguish it from a
15827 @value{GDBN} for debugging programs on the host itself.)
15830 @item VxWorks-timeout @var{args}
15831 @kindex vxworks-timeout
15832 All VxWorks-based targets now support the option @code{vxworks-timeout}.
15833 This option is set by the user, and @var{args} represents the number of
15834 seconds @value{GDBN} waits for responses to rpc's. You might use this if
15835 your VxWorks target is a slow software simulator or is on the far side
15836 of a thin network line.
15839 The following information on connecting to VxWorks was current when
15840 this manual was produced; newer releases of VxWorks may use revised
15843 @findex INCLUDE_RDB
15844 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
15845 to include the remote debugging interface routines in the VxWorks
15846 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
15847 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
15848 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
15849 source debugging task @code{tRdbTask} when VxWorks is booted. For more
15850 information on configuring and remaking VxWorks, see the manufacturer's
15852 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
15854 Once you have included @file{rdb.a} in your VxWorks system image and set
15855 your Unix execution search path to find @value{GDBN}, you are ready to
15856 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
15857 @code{vxgdb}, depending on your installation).
15859 @value{GDBN} comes up showing the prompt:
15866 * VxWorks Connection:: Connecting to VxWorks
15867 * VxWorks Download:: VxWorks download
15868 * VxWorks Attach:: Running tasks
15871 @node VxWorks Connection
15872 @subsubsection Connecting to VxWorks
15874 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
15875 network. To connect to a target whose host name is ``@code{tt}'', type:
15878 (vxgdb) target vxworks tt
15882 @value{GDBN} displays messages like these:
15885 Attaching remote machine across net...
15890 @value{GDBN} then attempts to read the symbol tables of any object modules
15891 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
15892 these files by searching the directories listed in the command search
15893 path (@pxref{Environment, ,Your Program's Environment}); if it fails
15894 to find an object file, it displays a message such as:
15897 prog.o: No such file or directory.
15900 When this happens, add the appropriate directory to the search path with
15901 the @value{GDBN} command @code{path}, and execute the @code{target}
15904 @node VxWorks Download
15905 @subsubsection VxWorks Download
15907 @cindex download to VxWorks
15908 If you have connected to the VxWorks target and you want to debug an
15909 object that has not yet been loaded, you can use the @value{GDBN}
15910 @code{load} command to download a file from Unix to VxWorks
15911 incrementally. The object file given as an argument to the @code{load}
15912 command is actually opened twice: first by the VxWorks target in order
15913 to download the code, then by @value{GDBN} in order to read the symbol
15914 table. This can lead to problems if the current working directories on
15915 the two systems differ. If both systems have NFS mounted the same
15916 filesystems, you can avoid these problems by using absolute paths.
15917 Otherwise, it is simplest to set the working directory on both systems
15918 to the directory in which the object file resides, and then to reference
15919 the file by its name, without any path. For instance, a program
15920 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
15921 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
15922 program, type this on VxWorks:
15925 -> cd "@var{vxpath}/vw/demo/rdb"
15929 Then, in @value{GDBN}, type:
15932 (vxgdb) cd @var{hostpath}/vw/demo/rdb
15933 (vxgdb) load prog.o
15936 @value{GDBN} displays a response similar to this:
15939 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
15942 You can also use the @code{load} command to reload an object module
15943 after editing and recompiling the corresponding source file. Note that
15944 this makes @value{GDBN} delete all currently-defined breakpoints,
15945 auto-displays, and convenience variables, and to clear the value
15946 history. (This is necessary in order to preserve the integrity of
15947 debugger's data structures that reference the target system's symbol
15950 @node VxWorks Attach
15951 @subsubsection Running Tasks
15953 @cindex running VxWorks tasks
15954 You can also attach to an existing task using the @code{attach} command as
15958 (vxgdb) attach @var{task}
15962 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
15963 or suspended when you attach to it. Running tasks are suspended at
15964 the time of attachment.
15966 @node Embedded Processors
15967 @section Embedded Processors
15969 This section goes into details specific to particular embedded
15972 @cindex send command to simulator
15973 Whenever a specific embedded processor has a simulator, @value{GDBN}
15974 allows to send an arbitrary command to the simulator.
15977 @item sim @var{command}
15978 @kindex sim@r{, a command}
15979 Send an arbitrary @var{command} string to the simulator. Consult the
15980 documentation for the specific simulator in use for information about
15981 acceptable commands.
15987 * M32R/D:: Renesas M32R/D
15988 * M68K:: Motorola M68K
15989 * MIPS Embedded:: MIPS Embedded
15990 * OpenRISC 1000:: OpenRisc 1000
15991 * PA:: HP PA Embedded
15992 * PowerPC Embedded:: PowerPC Embedded
15993 * Sparclet:: Tsqware Sparclet
15994 * Sparclite:: Fujitsu Sparclite
15995 * Z8000:: Zilog Z8000
15998 * Super-H:: Renesas Super-H
16007 @item target rdi @var{dev}
16008 ARM Angel monitor, via RDI library interface to ADP protocol. You may
16009 use this target to communicate with both boards running the Angel
16010 monitor, or with the EmbeddedICE JTAG debug device.
16013 @item target rdp @var{dev}
16018 @value{GDBN} provides the following ARM-specific commands:
16021 @item set arm disassembler
16023 This commands selects from a list of disassembly styles. The
16024 @code{"std"} style is the standard style.
16026 @item show arm disassembler
16028 Show the current disassembly style.
16030 @item set arm apcs32
16031 @cindex ARM 32-bit mode
16032 This command toggles ARM operation mode between 32-bit and 26-bit.
16034 @item show arm apcs32
16035 Display the current usage of the ARM 32-bit mode.
16037 @item set arm fpu @var{fputype}
16038 This command sets the ARM floating-point unit (FPU) type. The
16039 argument @var{fputype} can be one of these:
16043 Determine the FPU type by querying the OS ABI.
16045 Software FPU, with mixed-endian doubles on little-endian ARM
16048 GCC-compiled FPA co-processor.
16050 Software FPU with pure-endian doubles.
16056 Show the current type of the FPU.
16059 This command forces @value{GDBN} to use the specified ABI.
16062 Show the currently used ABI.
16064 @item set arm fallback-mode (arm|thumb|auto)
16065 @value{GDBN} uses the symbol table, when available, to determine
16066 whether instructions are ARM or Thumb. This command controls
16067 @value{GDBN}'s default behavior when the symbol table is not
16068 available. The default is @samp{auto}, which causes @value{GDBN} to
16069 use the current execution mode (from the @code{T} bit in the @code{CPSR}
16072 @item show arm fallback-mode
16073 Show the current fallback instruction mode.
16075 @item set arm force-mode (arm|thumb|auto)
16076 This command overrides use of the symbol table to determine whether
16077 instructions are ARM or Thumb. The default is @samp{auto}, which
16078 causes @value{GDBN} to use the symbol table and then the setting
16079 of @samp{set arm fallback-mode}.
16081 @item show arm force-mode
16082 Show the current forced instruction mode.
16084 @item set debug arm
16085 Toggle whether to display ARM-specific debugging messages from the ARM
16086 target support subsystem.
16088 @item show debug arm
16089 Show whether ARM-specific debugging messages are enabled.
16092 The following commands are available when an ARM target is debugged
16093 using the RDI interface:
16096 @item rdilogfile @r{[}@var{file}@r{]}
16098 @cindex ADP (Angel Debugger Protocol) logging
16099 Set the filename for the ADP (Angel Debugger Protocol) packet log.
16100 With an argument, sets the log file to the specified @var{file}. With
16101 no argument, show the current log file name. The default log file is
16104 @item rdilogenable @r{[}@var{arg}@r{]}
16105 @kindex rdilogenable
16106 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
16107 enables logging, with an argument 0 or @code{"no"} disables it. With
16108 no arguments displays the current setting. When logging is enabled,
16109 ADP packets exchanged between @value{GDBN} and the RDI target device
16110 are logged to a file.
16112 @item set rdiromatzero
16113 @kindex set rdiromatzero
16114 @cindex ROM at zero address, RDI
16115 Tell @value{GDBN} whether the target has ROM at address 0. If on,
16116 vector catching is disabled, so that zero address can be used. If off
16117 (the default), vector catching is enabled. For this command to take
16118 effect, it needs to be invoked prior to the @code{target rdi} command.
16120 @item show rdiromatzero
16121 @kindex show rdiromatzero
16122 Show the current setting of ROM at zero address.
16124 @item set rdiheartbeat
16125 @kindex set rdiheartbeat
16126 @cindex RDI heartbeat
16127 Enable or disable RDI heartbeat packets. It is not recommended to
16128 turn on this option, since it confuses ARM and EPI JTAG interface, as
16129 well as the Angel monitor.
16131 @item show rdiheartbeat
16132 @kindex show rdiheartbeat
16133 Show the setting of RDI heartbeat packets.
16138 @subsection Renesas M32R/D and M32R/SDI
16141 @kindex target m32r
16142 @item target m32r @var{dev}
16143 Renesas M32R/D ROM monitor.
16145 @kindex target m32rsdi
16146 @item target m32rsdi @var{dev}
16147 Renesas M32R SDI server, connected via parallel port to the board.
16150 The following @value{GDBN} commands are specific to the M32R monitor:
16153 @item set download-path @var{path}
16154 @kindex set download-path
16155 @cindex find downloadable @sc{srec} files (M32R)
16156 Set the default path for finding downloadable @sc{srec} files.
16158 @item show download-path
16159 @kindex show download-path
16160 Show the default path for downloadable @sc{srec} files.
16162 @item set board-address @var{addr}
16163 @kindex set board-address
16164 @cindex M32-EVA target board address
16165 Set the IP address for the M32R-EVA target board.
16167 @item show board-address
16168 @kindex show board-address
16169 Show the current IP address of the target board.
16171 @item set server-address @var{addr}
16172 @kindex set server-address
16173 @cindex download server address (M32R)
16174 Set the IP address for the download server, which is the @value{GDBN}'s
16177 @item show server-address
16178 @kindex show server-address
16179 Display the IP address of the download server.
16181 @item upload @r{[}@var{file}@r{]}
16182 @kindex upload@r{, M32R}
16183 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
16184 upload capability. If no @var{file} argument is given, the current
16185 executable file is uploaded.
16187 @item tload @r{[}@var{file}@r{]}
16188 @kindex tload@r{, M32R}
16189 Test the @code{upload} command.
16192 The following commands are available for M32R/SDI:
16197 @cindex reset SDI connection, M32R
16198 This command resets the SDI connection.
16202 This command shows the SDI connection status.
16205 @kindex debug_chaos
16206 @cindex M32R/Chaos debugging
16207 Instructs the remote that M32R/Chaos debugging is to be used.
16209 @item use_debug_dma
16210 @kindex use_debug_dma
16211 Instructs the remote to use the DEBUG_DMA method of accessing memory.
16214 @kindex use_mon_code
16215 Instructs the remote to use the MON_CODE method of accessing memory.
16218 @kindex use_ib_break
16219 Instructs the remote to set breakpoints by IB break.
16221 @item use_dbt_break
16222 @kindex use_dbt_break
16223 Instructs the remote to set breakpoints by DBT.
16229 The Motorola m68k configuration includes ColdFire support, and a
16230 target command for the following ROM monitor.
16234 @kindex target dbug
16235 @item target dbug @var{dev}
16236 dBUG ROM monitor for Motorola ColdFire.
16240 @node MIPS Embedded
16241 @subsection MIPS Embedded
16243 @cindex MIPS boards
16244 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
16245 MIPS board attached to a serial line. This is available when
16246 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
16249 Use these @value{GDBN} commands to specify the connection to your target board:
16252 @item target mips @var{port}
16253 @kindex target mips @var{port}
16254 To run a program on the board, start up @code{@value{GDBP}} with the
16255 name of your program as the argument. To connect to the board, use the
16256 command @samp{target mips @var{port}}, where @var{port} is the name of
16257 the serial port connected to the board. If the program has not already
16258 been downloaded to the board, you may use the @code{load} command to
16259 download it. You can then use all the usual @value{GDBN} commands.
16261 For example, this sequence connects to the target board through a serial
16262 port, and loads and runs a program called @var{prog} through the
16266 host$ @value{GDBP} @var{prog}
16267 @value{GDBN} is free software and @dots{}
16268 (@value{GDBP}) target mips /dev/ttyb
16269 (@value{GDBP}) load @var{prog}
16273 @item target mips @var{hostname}:@var{portnumber}
16274 On some @value{GDBN} host configurations, you can specify a TCP
16275 connection (for instance, to a serial line managed by a terminal
16276 concentrator) instead of a serial port, using the syntax
16277 @samp{@var{hostname}:@var{portnumber}}.
16279 @item target pmon @var{port}
16280 @kindex target pmon @var{port}
16283 @item target ddb @var{port}
16284 @kindex target ddb @var{port}
16285 NEC's DDB variant of PMON for Vr4300.
16287 @item target lsi @var{port}
16288 @kindex target lsi @var{port}
16289 LSI variant of PMON.
16291 @kindex target r3900
16292 @item target r3900 @var{dev}
16293 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
16295 @kindex target array
16296 @item target array @var{dev}
16297 Array Tech LSI33K RAID controller board.
16303 @value{GDBN} also supports these special commands for MIPS targets:
16306 @item set mipsfpu double
16307 @itemx set mipsfpu single
16308 @itemx set mipsfpu none
16309 @itemx set mipsfpu auto
16310 @itemx show mipsfpu
16311 @kindex set mipsfpu
16312 @kindex show mipsfpu
16313 @cindex MIPS remote floating point
16314 @cindex floating point, MIPS remote
16315 If your target board does not support the MIPS floating point
16316 coprocessor, you should use the command @samp{set mipsfpu none} (if you
16317 need this, you may wish to put the command in your @value{GDBN} init
16318 file). This tells @value{GDBN} how to find the return value of
16319 functions which return floating point values. It also allows
16320 @value{GDBN} to avoid saving the floating point registers when calling
16321 functions on the board. If you are using a floating point coprocessor
16322 with only single precision floating point support, as on the @sc{r4650}
16323 processor, use the command @samp{set mipsfpu single}. The default
16324 double precision floating point coprocessor may be selected using
16325 @samp{set mipsfpu double}.
16327 In previous versions the only choices were double precision or no
16328 floating point, so @samp{set mipsfpu on} will select double precision
16329 and @samp{set mipsfpu off} will select no floating point.
16331 As usual, you can inquire about the @code{mipsfpu} variable with
16332 @samp{show mipsfpu}.
16334 @item set timeout @var{seconds}
16335 @itemx set retransmit-timeout @var{seconds}
16336 @itemx show timeout
16337 @itemx show retransmit-timeout
16338 @cindex @code{timeout}, MIPS protocol
16339 @cindex @code{retransmit-timeout}, MIPS protocol
16340 @kindex set timeout
16341 @kindex show timeout
16342 @kindex set retransmit-timeout
16343 @kindex show retransmit-timeout
16344 You can control the timeout used while waiting for a packet, in the MIPS
16345 remote protocol, with the @code{set timeout @var{seconds}} command. The
16346 default is 5 seconds. Similarly, you can control the timeout used while
16347 waiting for an acknowledgment of a packet with the @code{set
16348 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
16349 You can inspect both values with @code{show timeout} and @code{show
16350 retransmit-timeout}. (These commands are @emph{only} available when
16351 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
16353 The timeout set by @code{set timeout} does not apply when @value{GDBN}
16354 is waiting for your program to stop. In that case, @value{GDBN} waits
16355 forever because it has no way of knowing how long the program is going
16356 to run before stopping.
16358 @item set syn-garbage-limit @var{num}
16359 @kindex set syn-garbage-limit@r{, MIPS remote}
16360 @cindex synchronize with remote MIPS target
16361 Limit the maximum number of characters @value{GDBN} should ignore when
16362 it tries to synchronize with the remote target. The default is 10
16363 characters. Setting the limit to -1 means there's no limit.
16365 @item show syn-garbage-limit
16366 @kindex show syn-garbage-limit@r{, MIPS remote}
16367 Show the current limit on the number of characters to ignore when
16368 trying to synchronize with the remote system.
16370 @item set monitor-prompt @var{prompt}
16371 @kindex set monitor-prompt@r{, MIPS remote}
16372 @cindex remote monitor prompt
16373 Tell @value{GDBN} to expect the specified @var{prompt} string from the
16374 remote monitor. The default depends on the target:
16384 @item show monitor-prompt
16385 @kindex show monitor-prompt@r{, MIPS remote}
16386 Show the current strings @value{GDBN} expects as the prompt from the
16389 @item set monitor-warnings
16390 @kindex set monitor-warnings@r{, MIPS remote}
16391 Enable or disable monitor warnings about hardware breakpoints. This
16392 has effect only for the @code{lsi} target. When on, @value{GDBN} will
16393 display warning messages whose codes are returned by the @code{lsi}
16394 PMON monitor for breakpoint commands.
16396 @item show monitor-warnings
16397 @kindex show monitor-warnings@r{, MIPS remote}
16398 Show the current setting of printing monitor warnings.
16400 @item pmon @var{command}
16401 @kindex pmon@r{, MIPS remote}
16402 @cindex send PMON command
16403 This command allows sending an arbitrary @var{command} string to the
16404 monitor. The monitor must be in debug mode for this to work.
16407 @node OpenRISC 1000
16408 @subsection OpenRISC 1000
16409 @cindex OpenRISC 1000
16411 @cindex or1k boards
16412 See OR1k Architecture document (@uref{www.opencores.org}) for more information
16413 about platform and commands.
16417 @kindex target jtag
16418 @item target jtag jtag://@var{host}:@var{port}
16420 Connects to remote JTAG server.
16421 JTAG remote server can be either an or1ksim or JTAG server,
16422 connected via parallel port to the board.
16424 Example: @code{target jtag jtag://localhost:9999}
16427 @item or1ksim @var{command}
16428 If connected to @code{or1ksim} OpenRISC 1000 Architectural
16429 Simulator, proprietary commands can be executed.
16431 @kindex info or1k spr
16432 @item info or1k spr
16433 Displays spr groups.
16435 @item info or1k spr @var{group}
16436 @itemx info or1k spr @var{groupno}
16437 Displays register names in selected group.
16439 @item info or1k spr @var{group} @var{register}
16440 @itemx info or1k spr @var{register}
16441 @itemx info or1k spr @var{groupno} @var{registerno}
16442 @itemx info or1k spr @var{registerno}
16443 Shows information about specified spr register.
16446 @item spr @var{group} @var{register} @var{value}
16447 @itemx spr @var{register @var{value}}
16448 @itemx spr @var{groupno} @var{registerno @var{value}}
16449 @itemx spr @var{registerno @var{value}}
16450 Writes @var{value} to specified spr register.
16453 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
16454 It is very similar to @value{GDBN} trace, except it does not interfere with normal
16455 program execution and is thus much faster. Hardware breakpoints/watchpoint
16456 triggers can be set using:
16459 Load effective address/data
16461 Store effective address/data
16463 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
16468 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
16469 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
16471 @code{htrace} commands:
16472 @cindex OpenRISC 1000 htrace
16475 @item hwatch @var{conditional}
16476 Set hardware watchpoint on combination of Load/Store Effective Address(es)
16477 or Data. For example:
16479 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16481 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16485 Display information about current HW trace configuration.
16487 @item htrace trigger @var{conditional}
16488 Set starting criteria for HW trace.
16490 @item htrace qualifier @var{conditional}
16491 Set acquisition qualifier for HW trace.
16493 @item htrace stop @var{conditional}
16494 Set HW trace stopping criteria.
16496 @item htrace record [@var{data}]*
16497 Selects the data to be recorded, when qualifier is met and HW trace was
16500 @item htrace enable
16501 @itemx htrace disable
16502 Enables/disables the HW trace.
16504 @item htrace rewind [@var{filename}]
16505 Clears currently recorded trace data.
16507 If filename is specified, new trace file is made and any newly collected data
16508 will be written there.
16510 @item htrace print [@var{start} [@var{len}]]
16511 Prints trace buffer, using current record configuration.
16513 @item htrace mode continuous
16514 Set continuous trace mode.
16516 @item htrace mode suspend
16517 Set suspend trace mode.
16521 @node PowerPC Embedded
16522 @subsection PowerPC Embedded
16524 @value{GDBN} provides the following PowerPC-specific commands:
16527 @kindex set powerpc
16528 @item set powerpc soft-float
16529 @itemx show powerpc soft-float
16530 Force @value{GDBN} to use (or not use) a software floating point calling
16531 convention. By default, @value{GDBN} selects the calling convention based
16532 on the selected architecture and the provided executable file.
16534 @item set powerpc vector-abi
16535 @itemx show powerpc vector-abi
16536 Force @value{GDBN} to use the specified calling convention for vector
16537 arguments and return values. The valid options are @samp{auto};
16538 @samp{generic}, to avoid vector registers even if they are present;
16539 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
16540 registers. By default, @value{GDBN} selects the calling convention
16541 based on the selected architecture and the provided executable file.
16543 @kindex target dink32
16544 @item target dink32 @var{dev}
16545 DINK32 ROM monitor.
16547 @kindex target ppcbug
16548 @item target ppcbug @var{dev}
16549 @kindex target ppcbug1
16550 @item target ppcbug1 @var{dev}
16551 PPCBUG ROM monitor for PowerPC.
16554 @item target sds @var{dev}
16555 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
16558 @cindex SDS protocol
16559 The following commands specific to the SDS protocol are supported
16563 @item set sdstimeout @var{nsec}
16564 @kindex set sdstimeout
16565 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
16566 default is 2 seconds.
16568 @item show sdstimeout
16569 @kindex show sdstimeout
16570 Show the current value of the SDS timeout.
16572 @item sds @var{command}
16573 @kindex sds@r{, a command}
16574 Send the specified @var{command} string to the SDS monitor.
16579 @subsection HP PA Embedded
16583 @kindex target op50n
16584 @item target op50n @var{dev}
16585 OP50N monitor, running on an OKI HPPA board.
16587 @kindex target w89k
16588 @item target w89k @var{dev}
16589 W89K monitor, running on a Winbond HPPA board.
16594 @subsection Tsqware Sparclet
16598 @value{GDBN} enables developers to debug tasks running on
16599 Sparclet targets from a Unix host.
16600 @value{GDBN} uses code that runs on
16601 both the Unix host and on the Sparclet target. The program
16602 @code{@value{GDBP}} is installed and executed on the Unix host.
16605 @item remotetimeout @var{args}
16606 @kindex remotetimeout
16607 @value{GDBN} supports the option @code{remotetimeout}.
16608 This option is set by the user, and @var{args} represents the number of
16609 seconds @value{GDBN} waits for responses.
16612 @cindex compiling, on Sparclet
16613 When compiling for debugging, include the options @samp{-g} to get debug
16614 information and @samp{-Ttext} to relocate the program to where you wish to
16615 load it on the target. You may also want to add the options @samp{-n} or
16616 @samp{-N} in order to reduce the size of the sections. Example:
16619 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
16622 You can use @code{objdump} to verify that the addresses are what you intended:
16625 sparclet-aout-objdump --headers --syms prog
16628 @cindex running, on Sparclet
16630 your Unix execution search path to find @value{GDBN}, you are ready to
16631 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
16632 (or @code{sparclet-aout-gdb}, depending on your installation).
16634 @value{GDBN} comes up showing the prompt:
16641 * Sparclet File:: Setting the file to debug
16642 * Sparclet Connection:: Connecting to Sparclet
16643 * Sparclet Download:: Sparclet download
16644 * Sparclet Execution:: Running and debugging
16647 @node Sparclet File
16648 @subsubsection Setting File to Debug
16650 The @value{GDBN} command @code{file} lets you choose with program to debug.
16653 (gdbslet) file prog
16657 @value{GDBN} then attempts to read the symbol table of @file{prog}.
16658 @value{GDBN} locates
16659 the file by searching the directories listed in the command search
16661 If the file was compiled with debug information (option @samp{-g}), source
16662 files will be searched as well.
16663 @value{GDBN} locates
16664 the source files by searching the directories listed in the directory search
16665 path (@pxref{Environment, ,Your Program's Environment}).
16667 to find a file, it displays a message such as:
16670 prog: No such file or directory.
16673 When this happens, add the appropriate directories to the search paths with
16674 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
16675 @code{target} command again.
16677 @node Sparclet Connection
16678 @subsubsection Connecting to Sparclet
16680 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
16681 To connect to a target on serial port ``@code{ttya}'', type:
16684 (gdbslet) target sparclet /dev/ttya
16685 Remote target sparclet connected to /dev/ttya
16686 main () at ../prog.c:3
16690 @value{GDBN} displays messages like these:
16696 @node Sparclet Download
16697 @subsubsection Sparclet Download
16699 @cindex download to Sparclet
16700 Once connected to the Sparclet target,
16701 you can use the @value{GDBN}
16702 @code{load} command to download the file from the host to the target.
16703 The file name and load offset should be given as arguments to the @code{load}
16705 Since the file format is aout, the program must be loaded to the starting
16706 address. You can use @code{objdump} to find out what this value is. The load
16707 offset is an offset which is added to the VMA (virtual memory address)
16708 of each of the file's sections.
16709 For instance, if the program
16710 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
16711 and bss at 0x12010170, in @value{GDBN}, type:
16714 (gdbslet) load prog 0x12010000
16715 Loading section .text, size 0xdb0 vma 0x12010000
16718 If the code is loaded at a different address then what the program was linked
16719 to, you may need to use the @code{section} and @code{add-symbol-file} commands
16720 to tell @value{GDBN} where to map the symbol table.
16722 @node Sparclet Execution
16723 @subsubsection Running and Debugging
16725 @cindex running and debugging Sparclet programs
16726 You can now begin debugging the task using @value{GDBN}'s execution control
16727 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
16728 manual for the list of commands.
16732 Breakpoint 1 at 0x12010000: file prog.c, line 3.
16734 Starting program: prog
16735 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
16736 3 char *symarg = 0;
16738 4 char *execarg = "hello!";
16743 @subsection Fujitsu Sparclite
16747 @kindex target sparclite
16748 @item target sparclite @var{dev}
16749 Fujitsu sparclite boards, used only for the purpose of loading.
16750 You must use an additional command to debug the program.
16751 For example: target remote @var{dev} using @value{GDBN} standard
16757 @subsection Zilog Z8000
16760 @cindex simulator, Z8000
16761 @cindex Zilog Z8000 simulator
16763 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
16766 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
16767 unsegmented variant of the Z8000 architecture) or the Z8001 (the
16768 segmented variant). The simulator recognizes which architecture is
16769 appropriate by inspecting the object code.
16772 @item target sim @var{args}
16774 @kindex target sim@r{, with Z8000}
16775 Debug programs on a simulated CPU. If the simulator supports setup
16776 options, specify them via @var{args}.
16780 After specifying this target, you can debug programs for the simulated
16781 CPU in the same style as programs for your host computer; use the
16782 @code{file} command to load a new program image, the @code{run} command
16783 to run your program, and so on.
16785 As well as making available all the usual machine registers
16786 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
16787 additional items of information as specially named registers:
16792 Counts clock-ticks in the simulator.
16795 Counts instructions run in the simulator.
16798 Execution time in 60ths of a second.
16802 You can refer to these values in @value{GDBN} expressions with the usual
16803 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
16804 conditional breakpoint that suspends only after at least 5000
16805 simulated clock ticks.
16808 @subsection Atmel AVR
16811 When configured for debugging the Atmel AVR, @value{GDBN} supports the
16812 following AVR-specific commands:
16815 @item info io_registers
16816 @kindex info io_registers@r{, AVR}
16817 @cindex I/O registers (Atmel AVR)
16818 This command displays information about the AVR I/O registers. For
16819 each register, @value{GDBN} prints its number and value.
16826 When configured for debugging CRIS, @value{GDBN} provides the
16827 following CRIS-specific commands:
16830 @item set cris-version @var{ver}
16831 @cindex CRIS version
16832 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
16833 The CRIS version affects register names and sizes. This command is useful in
16834 case autodetection of the CRIS version fails.
16836 @item show cris-version
16837 Show the current CRIS version.
16839 @item set cris-dwarf2-cfi
16840 @cindex DWARF-2 CFI and CRIS
16841 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
16842 Change to @samp{off} when using @code{gcc-cris} whose version is below
16845 @item show cris-dwarf2-cfi
16846 Show the current state of using DWARF-2 CFI.
16848 @item set cris-mode @var{mode}
16850 Set the current CRIS mode to @var{mode}. It should only be changed when
16851 debugging in guru mode, in which case it should be set to
16852 @samp{guru} (the default is @samp{normal}).
16854 @item show cris-mode
16855 Show the current CRIS mode.
16859 @subsection Renesas Super-H
16862 For the Renesas Super-H processor, @value{GDBN} provides these
16867 @kindex regs@r{, Super-H}
16868 Show the values of all Super-H registers.
16870 @item set sh calling-convention @var{convention}
16871 @kindex set sh calling-convention
16872 Set the calling-convention used when calling functions from @value{GDBN}.
16873 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
16874 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
16875 convention. If the DWARF-2 information of the called function specifies
16876 that the function follows the Renesas calling convention, the function
16877 is called using the Renesas calling convention. If the calling convention
16878 is set to @samp{renesas}, the Renesas calling convention is always used,
16879 regardless of the DWARF-2 information. This can be used to override the
16880 default of @samp{gcc} if debug information is missing, or the compiler
16881 does not emit the DWARF-2 calling convention entry for a function.
16883 @item show sh calling-convention
16884 @kindex show sh calling-convention
16885 Show the current calling convention setting.
16890 @node Architectures
16891 @section Architectures
16893 This section describes characteristics of architectures that affect
16894 all uses of @value{GDBN} with the architecture, both native and cross.
16901 * HPPA:: HP PA architecture
16902 * SPU:: Cell Broadband Engine SPU architecture
16907 @subsection x86 Architecture-specific Issues
16910 @item set struct-convention @var{mode}
16911 @kindex set struct-convention
16912 @cindex struct return convention
16913 @cindex struct/union returned in registers
16914 Set the convention used by the inferior to return @code{struct}s and
16915 @code{union}s from functions to @var{mode}. Possible values of
16916 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
16917 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
16918 are returned on the stack, while @code{"reg"} means that a
16919 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
16920 be returned in a register.
16922 @item show struct-convention
16923 @kindex show struct-convention
16924 Show the current setting of the convention to return @code{struct}s
16933 @kindex set rstack_high_address
16934 @cindex AMD 29K register stack
16935 @cindex register stack, AMD29K
16936 @item set rstack_high_address @var{address}
16937 On AMD 29000 family processors, registers are saved in a separate
16938 @dfn{register stack}. There is no way for @value{GDBN} to determine the
16939 extent of this stack. Normally, @value{GDBN} just assumes that the
16940 stack is ``large enough''. This may result in @value{GDBN} referencing
16941 memory locations that do not exist. If necessary, you can get around
16942 this problem by specifying the ending address of the register stack with
16943 the @code{set rstack_high_address} command. The argument should be an
16944 address, which you probably want to precede with @samp{0x} to specify in
16947 @kindex show rstack_high_address
16948 @item show rstack_high_address
16949 Display the current limit of the register stack, on AMD 29000 family
16957 See the following section.
16962 @cindex stack on Alpha
16963 @cindex stack on MIPS
16964 @cindex Alpha stack
16966 Alpha- and MIPS-based computers use an unusual stack frame, which
16967 sometimes requires @value{GDBN} to search backward in the object code to
16968 find the beginning of a function.
16970 @cindex response time, MIPS debugging
16971 To improve response time (especially for embedded applications, where
16972 @value{GDBN} may be restricted to a slow serial line for this search)
16973 you may want to limit the size of this search, using one of these
16977 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
16978 @item set heuristic-fence-post @var{limit}
16979 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
16980 search for the beginning of a function. A value of @var{0} (the
16981 default) means there is no limit. However, except for @var{0}, the
16982 larger the limit the more bytes @code{heuristic-fence-post} must search
16983 and therefore the longer it takes to run. You should only need to use
16984 this command when debugging a stripped executable.
16986 @item show heuristic-fence-post
16987 Display the current limit.
16991 These commands are available @emph{only} when @value{GDBN} is configured
16992 for debugging programs on Alpha or MIPS processors.
16994 Several MIPS-specific commands are available when debugging MIPS
16998 @item set mips abi @var{arg}
16999 @kindex set mips abi
17000 @cindex set ABI for MIPS
17001 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
17002 values of @var{arg} are:
17006 The default ABI associated with the current binary (this is the
17017 @item show mips abi
17018 @kindex show mips abi
17019 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
17022 @itemx show mipsfpu
17023 @xref{MIPS Embedded, set mipsfpu}.
17025 @item set mips mask-address @var{arg}
17026 @kindex set mips mask-address
17027 @cindex MIPS addresses, masking
17028 This command determines whether the most-significant 32 bits of 64-bit
17029 MIPS addresses are masked off. The argument @var{arg} can be
17030 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
17031 setting, which lets @value{GDBN} determine the correct value.
17033 @item show mips mask-address
17034 @kindex show mips mask-address
17035 Show whether the upper 32 bits of MIPS addresses are masked off or
17038 @item set remote-mips64-transfers-32bit-regs
17039 @kindex set remote-mips64-transfers-32bit-regs
17040 This command controls compatibility with 64-bit MIPS targets that
17041 transfer data in 32-bit quantities. If you have an old MIPS 64 target
17042 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
17043 and 64 bits for other registers, set this option to @samp{on}.
17045 @item show remote-mips64-transfers-32bit-regs
17046 @kindex show remote-mips64-transfers-32bit-regs
17047 Show the current setting of compatibility with older MIPS 64 targets.
17049 @item set debug mips
17050 @kindex set debug mips
17051 This command turns on and off debugging messages for the MIPS-specific
17052 target code in @value{GDBN}.
17054 @item show debug mips
17055 @kindex show debug mips
17056 Show the current setting of MIPS debugging messages.
17062 @cindex HPPA support
17064 When @value{GDBN} is debugging the HP PA architecture, it provides the
17065 following special commands:
17068 @item set debug hppa
17069 @kindex set debug hppa
17070 This command determines whether HPPA architecture-specific debugging
17071 messages are to be displayed.
17073 @item show debug hppa
17074 Show whether HPPA debugging messages are displayed.
17076 @item maint print unwind @var{address}
17077 @kindex maint print unwind@r{, HPPA}
17078 This command displays the contents of the unwind table entry at the
17079 given @var{address}.
17085 @subsection Cell Broadband Engine SPU architecture
17086 @cindex Cell Broadband Engine
17089 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
17090 it provides the following special commands:
17093 @item info spu event
17095 Display SPU event facility status. Shows current event mask
17096 and pending event status.
17098 @item info spu signal
17099 Display SPU signal notification facility status. Shows pending
17100 signal-control word and signal notification mode of both signal
17101 notification channels.
17103 @item info spu mailbox
17104 Display SPU mailbox facility status. Shows all pending entries,
17105 in order of processing, in each of the SPU Write Outbound,
17106 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
17109 Display MFC DMA status. Shows all pending commands in the MFC
17110 DMA queue. For each entry, opcode, tag, class IDs, effective
17111 and local store addresses and transfer size are shown.
17113 @item info spu proxydma
17114 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
17115 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
17116 and local store addresses and transfer size are shown.
17121 @subsection PowerPC
17122 @cindex PowerPC architecture
17124 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
17125 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
17126 numbers stored in the floating point registers. These values must be stored
17127 in two consecutive registers, always starting at an even register like
17128 @code{f0} or @code{f2}.
17130 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
17131 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
17132 @code{f2} and @code{f3} for @code{$dl1} and so on.
17134 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
17135 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
17138 @node Controlling GDB
17139 @chapter Controlling @value{GDBN}
17141 You can alter the way @value{GDBN} interacts with you by using the
17142 @code{set} command. For commands controlling how @value{GDBN} displays
17143 data, see @ref{Print Settings, ,Print Settings}. Other settings are
17148 * Editing:: Command editing
17149 * Command History:: Command history
17150 * Screen Size:: Screen size
17151 * Numbers:: Numbers
17152 * ABI:: Configuring the current ABI
17153 * Messages/Warnings:: Optional warnings and messages
17154 * Debugging Output:: Optional messages about internal happenings
17162 @value{GDBN} indicates its readiness to read a command by printing a string
17163 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
17164 can change the prompt string with the @code{set prompt} command. For
17165 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
17166 the prompt in one of the @value{GDBN} sessions so that you can always tell
17167 which one you are talking to.
17169 @emph{Note:} @code{set prompt} does not add a space for you after the
17170 prompt you set. This allows you to set a prompt which ends in a space
17171 or a prompt that does not.
17175 @item set prompt @var{newprompt}
17176 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
17178 @kindex show prompt
17180 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
17184 @section Command Editing
17186 @cindex command line editing
17188 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
17189 @sc{gnu} library provides consistent behavior for programs which provide a
17190 command line interface to the user. Advantages are @sc{gnu} Emacs-style
17191 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
17192 substitution, and a storage and recall of command history across
17193 debugging sessions.
17195 You may control the behavior of command line editing in @value{GDBN} with the
17196 command @code{set}.
17199 @kindex set editing
17202 @itemx set editing on
17203 Enable command line editing (enabled by default).
17205 @item set editing off
17206 Disable command line editing.
17208 @kindex show editing
17210 Show whether command line editing is enabled.
17213 @xref{Command Line Editing}, for more details about the Readline
17214 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
17215 encouraged to read that chapter.
17217 @node Command History
17218 @section Command History
17219 @cindex command history
17221 @value{GDBN} can keep track of the commands you type during your
17222 debugging sessions, so that you can be certain of precisely what
17223 happened. Use these commands to manage the @value{GDBN} command
17226 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
17227 package, to provide the history facility. @xref{Using History
17228 Interactively}, for the detailed description of the History library.
17230 To issue a command to @value{GDBN} without affecting certain aspects of
17231 the state which is seen by users, prefix it with @samp{server }
17232 (@pxref{Server Prefix}). This
17233 means that this command will not affect the command history, nor will it
17234 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
17235 pressed on a line by itself.
17237 @cindex @code{server}, command prefix
17238 The server prefix does not affect the recording of values into the value
17239 history; to print a value without recording it into the value history,
17240 use the @code{output} command instead of the @code{print} command.
17242 Here is the description of @value{GDBN} commands related to command
17246 @cindex history substitution
17247 @cindex history file
17248 @kindex set history filename
17249 @cindex @env{GDBHISTFILE}, environment variable
17250 @item set history filename @var{fname}
17251 Set the name of the @value{GDBN} command history file to @var{fname}.
17252 This is the file where @value{GDBN} reads an initial command history
17253 list, and where it writes the command history from this session when it
17254 exits. You can access this list through history expansion or through
17255 the history command editing characters listed below. This file defaults
17256 to the value of the environment variable @code{GDBHISTFILE}, or to
17257 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
17260 @cindex save command history
17261 @kindex set history save
17262 @item set history save
17263 @itemx set history save on
17264 Record command history in a file, whose name may be specified with the
17265 @code{set history filename} command. By default, this option is disabled.
17267 @item set history save off
17268 Stop recording command history in a file.
17270 @cindex history size
17271 @kindex set history size
17272 @cindex @env{HISTSIZE}, environment variable
17273 @item set history size @var{size}
17274 Set the number of commands which @value{GDBN} keeps in its history list.
17275 This defaults to the value of the environment variable
17276 @code{HISTSIZE}, or to 256 if this variable is not set.
17279 History expansion assigns special meaning to the character @kbd{!}.
17280 @xref{Event Designators}, for more details.
17282 @cindex history expansion, turn on/off
17283 Since @kbd{!} is also the logical not operator in C, history expansion
17284 is off by default. If you decide to enable history expansion with the
17285 @code{set history expansion on} command, you may sometimes need to
17286 follow @kbd{!} (when it is used as logical not, in an expression) with
17287 a space or a tab to prevent it from being expanded. The readline
17288 history facilities do not attempt substitution on the strings
17289 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
17291 The commands to control history expansion are:
17294 @item set history expansion on
17295 @itemx set history expansion
17296 @kindex set history expansion
17297 Enable history expansion. History expansion is off by default.
17299 @item set history expansion off
17300 Disable history expansion.
17303 @kindex show history
17305 @itemx show history filename
17306 @itemx show history save
17307 @itemx show history size
17308 @itemx show history expansion
17309 These commands display the state of the @value{GDBN} history parameters.
17310 @code{show history} by itself displays all four states.
17315 @kindex show commands
17316 @cindex show last commands
17317 @cindex display command history
17318 @item show commands
17319 Display the last ten commands in the command history.
17321 @item show commands @var{n}
17322 Print ten commands centered on command number @var{n}.
17324 @item show commands +
17325 Print ten commands just after the commands last printed.
17329 @section Screen Size
17330 @cindex size of screen
17331 @cindex pauses in output
17333 Certain commands to @value{GDBN} may produce large amounts of
17334 information output to the screen. To help you read all of it,
17335 @value{GDBN} pauses and asks you for input at the end of each page of
17336 output. Type @key{RET} when you want to continue the output, or @kbd{q}
17337 to discard the remaining output. Also, the screen width setting
17338 determines when to wrap lines of output. Depending on what is being
17339 printed, @value{GDBN} tries to break the line at a readable place,
17340 rather than simply letting it overflow onto the following line.
17342 Normally @value{GDBN} knows the size of the screen from the terminal
17343 driver software. For example, on Unix @value{GDBN} uses the termcap data base
17344 together with the value of the @code{TERM} environment variable and the
17345 @code{stty rows} and @code{stty cols} settings. If this is not correct,
17346 you can override it with the @code{set height} and @code{set
17353 @kindex show height
17354 @item set height @var{lpp}
17356 @itemx set width @var{cpl}
17358 These @code{set} commands specify a screen height of @var{lpp} lines and
17359 a screen width of @var{cpl} characters. The associated @code{show}
17360 commands display the current settings.
17362 If you specify a height of zero lines, @value{GDBN} does not pause during
17363 output no matter how long the output is. This is useful if output is to a
17364 file or to an editor buffer.
17366 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
17367 from wrapping its output.
17369 @item set pagination on
17370 @itemx set pagination off
17371 @kindex set pagination
17372 Turn the output pagination on or off; the default is on. Turning
17373 pagination off is the alternative to @code{set height 0}.
17375 @item show pagination
17376 @kindex show pagination
17377 Show the current pagination mode.
17382 @cindex number representation
17383 @cindex entering numbers
17385 You can always enter numbers in octal, decimal, or hexadecimal in
17386 @value{GDBN} by the usual conventions: octal numbers begin with
17387 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
17388 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
17389 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
17390 10; likewise, the default display for numbers---when no particular
17391 format is specified---is base 10. You can change the default base for
17392 both input and output with the commands described below.
17395 @kindex set input-radix
17396 @item set input-radix @var{base}
17397 Set the default base for numeric input. Supported choices
17398 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17399 specified either unambiguously or using the current input radix; for
17403 set input-radix 012
17404 set input-radix 10.
17405 set input-radix 0xa
17409 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
17410 leaves the input radix unchanged, no matter what it was, since
17411 @samp{10}, being without any leading or trailing signs of its base, is
17412 interpreted in the current radix. Thus, if the current radix is 16,
17413 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
17416 @kindex set output-radix
17417 @item set output-radix @var{base}
17418 Set the default base for numeric display. Supported choices
17419 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17420 specified either unambiguously or using the current input radix.
17422 @kindex show input-radix
17423 @item show input-radix
17424 Display the current default base for numeric input.
17426 @kindex show output-radix
17427 @item show output-radix
17428 Display the current default base for numeric display.
17430 @item set radix @r{[}@var{base}@r{]}
17434 These commands set and show the default base for both input and output
17435 of numbers. @code{set radix} sets the radix of input and output to
17436 the same base; without an argument, it resets the radix back to its
17437 default value of 10.
17442 @section Configuring the Current ABI
17444 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
17445 application automatically. However, sometimes you need to override its
17446 conclusions. Use these commands to manage @value{GDBN}'s view of the
17453 One @value{GDBN} configuration can debug binaries for multiple operating
17454 system targets, either via remote debugging or native emulation.
17455 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
17456 but you can override its conclusion using the @code{set osabi} command.
17457 One example where this is useful is in debugging of binaries which use
17458 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
17459 not have the same identifying marks that the standard C library for your
17464 Show the OS ABI currently in use.
17467 With no argument, show the list of registered available OS ABI's.
17469 @item set osabi @var{abi}
17470 Set the current OS ABI to @var{abi}.
17473 @cindex float promotion
17475 Generally, the way that an argument of type @code{float} is passed to a
17476 function depends on whether the function is prototyped. For a prototyped
17477 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
17478 according to the architecture's convention for @code{float}. For unprototyped
17479 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
17480 @code{double} and then passed.
17482 Unfortunately, some forms of debug information do not reliably indicate whether
17483 a function is prototyped. If @value{GDBN} calls a function that is not marked
17484 as prototyped, it consults @kbd{set coerce-float-to-double}.
17487 @kindex set coerce-float-to-double
17488 @item set coerce-float-to-double
17489 @itemx set coerce-float-to-double on
17490 Arguments of type @code{float} will be promoted to @code{double} when passed
17491 to an unprototyped function. This is the default setting.
17493 @item set coerce-float-to-double off
17494 Arguments of type @code{float} will be passed directly to unprototyped
17497 @kindex show coerce-float-to-double
17498 @item show coerce-float-to-double
17499 Show the current setting of promoting @code{float} to @code{double}.
17503 @kindex show cp-abi
17504 @value{GDBN} needs to know the ABI used for your program's C@t{++}
17505 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
17506 used to build your application. @value{GDBN} only fully supports
17507 programs with a single C@t{++} ABI; if your program contains code using
17508 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
17509 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
17510 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
17511 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
17512 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
17513 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
17518 Show the C@t{++} ABI currently in use.
17521 With no argument, show the list of supported C@t{++} ABI's.
17523 @item set cp-abi @var{abi}
17524 @itemx set cp-abi auto
17525 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
17528 @node Messages/Warnings
17529 @section Optional Warnings and Messages
17531 @cindex verbose operation
17532 @cindex optional warnings
17533 By default, @value{GDBN} is silent about its inner workings. If you are
17534 running on a slow machine, you may want to use the @code{set verbose}
17535 command. This makes @value{GDBN} tell you when it does a lengthy
17536 internal operation, so you will not think it has crashed.
17538 Currently, the messages controlled by @code{set verbose} are those
17539 which announce that the symbol table for a source file is being read;
17540 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
17543 @kindex set verbose
17544 @item set verbose on
17545 Enables @value{GDBN} output of certain informational messages.
17547 @item set verbose off
17548 Disables @value{GDBN} output of certain informational messages.
17550 @kindex show verbose
17552 Displays whether @code{set verbose} is on or off.
17555 By default, if @value{GDBN} encounters bugs in the symbol table of an
17556 object file, it is silent; but if you are debugging a compiler, you may
17557 find this information useful (@pxref{Symbol Errors, ,Errors Reading
17562 @kindex set complaints
17563 @item set complaints @var{limit}
17564 Permits @value{GDBN} to output @var{limit} complaints about each type of
17565 unusual symbols before becoming silent about the problem. Set
17566 @var{limit} to zero to suppress all complaints; set it to a large number
17567 to prevent complaints from being suppressed.
17569 @kindex show complaints
17570 @item show complaints
17571 Displays how many symbol complaints @value{GDBN} is permitted to produce.
17575 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
17576 lot of stupid questions to confirm certain commands. For example, if
17577 you try to run a program which is already running:
17581 The program being debugged has been started already.
17582 Start it from the beginning? (y or n)
17585 If you are willing to unflinchingly face the consequences of your own
17586 commands, you can disable this ``feature'':
17590 @kindex set confirm
17592 @cindex confirmation
17593 @cindex stupid questions
17594 @item set confirm off
17595 Disables confirmation requests.
17597 @item set confirm on
17598 Enables confirmation requests (the default).
17600 @kindex show confirm
17602 Displays state of confirmation requests.
17606 @cindex command tracing
17607 If you need to debug user-defined commands or sourced files you may find it
17608 useful to enable @dfn{command tracing}. In this mode each command will be
17609 printed as it is executed, prefixed with one or more @samp{+} symbols, the
17610 quantity denoting the call depth of each command.
17613 @kindex set trace-commands
17614 @cindex command scripts, debugging
17615 @item set trace-commands on
17616 Enable command tracing.
17617 @item set trace-commands off
17618 Disable command tracing.
17619 @item show trace-commands
17620 Display the current state of command tracing.
17623 @node Debugging Output
17624 @section Optional Messages about Internal Happenings
17625 @cindex optional debugging messages
17627 @value{GDBN} has commands that enable optional debugging messages from
17628 various @value{GDBN} subsystems; normally these commands are of
17629 interest to @value{GDBN} maintainers, or when reporting a bug. This
17630 section documents those commands.
17633 @kindex set exec-done-display
17634 @item set exec-done-display
17635 Turns on or off the notification of asynchronous commands'
17636 completion. When on, @value{GDBN} will print a message when an
17637 asynchronous command finishes its execution. The default is off.
17638 @kindex show exec-done-display
17639 @item show exec-done-display
17640 Displays the current setting of asynchronous command completion
17643 @cindex gdbarch debugging info
17644 @cindex architecture debugging info
17645 @item set debug arch
17646 Turns on or off display of gdbarch debugging info. The default is off
17648 @item show debug arch
17649 Displays the current state of displaying gdbarch debugging info.
17650 @item set debug aix-thread
17651 @cindex AIX threads
17652 Display debugging messages about inner workings of the AIX thread
17654 @item show debug aix-thread
17655 Show the current state of AIX thread debugging info display.
17656 @item set debug dwarf2-die
17657 @cindex DWARF2 DIEs
17658 Dump DWARF2 DIEs after they are read in.
17659 The value is the number of nesting levels to print.
17660 A value of zero turns off the display.
17661 @item show debug dwarf2-die
17662 Show the current state of DWARF2 DIE debugging.
17663 @item set debug displaced
17664 @cindex displaced stepping debugging info
17665 Turns on or off display of @value{GDBN} debugging info for the
17666 displaced stepping support. The default is off.
17667 @item show debug displaced
17668 Displays the current state of displaying @value{GDBN} debugging info
17669 related to displaced stepping.
17670 @item set debug event
17671 @cindex event debugging info
17672 Turns on or off display of @value{GDBN} event debugging info. The
17674 @item show debug event
17675 Displays the current state of displaying @value{GDBN} event debugging
17677 @item set debug expression
17678 @cindex expression debugging info
17679 Turns on or off display of debugging info about @value{GDBN}
17680 expression parsing. The default is off.
17681 @item show debug expression
17682 Displays the current state of displaying debugging info about
17683 @value{GDBN} expression parsing.
17684 @item set debug frame
17685 @cindex frame debugging info
17686 Turns on or off display of @value{GDBN} frame debugging info. The
17688 @item show debug frame
17689 Displays the current state of displaying @value{GDBN} frame debugging
17691 @item set debug infrun
17692 @cindex inferior debugging info
17693 Turns on or off display of @value{GDBN} debugging info for running the inferior.
17694 The default is off. @file{infrun.c} contains GDB's runtime state machine used
17695 for implementing operations such as single-stepping the inferior.
17696 @item show debug infrun
17697 Displays the current state of @value{GDBN} inferior debugging.
17698 @item set debug lin-lwp
17699 @cindex @sc{gnu}/Linux LWP debug messages
17700 @cindex Linux lightweight processes
17701 Turns on or off debugging messages from the Linux LWP debug support.
17702 @item show debug lin-lwp
17703 Show the current state of Linux LWP debugging messages.
17704 @item set debug lin-lwp-async
17705 @cindex @sc{gnu}/Linux LWP async debug messages
17706 @cindex Linux lightweight processes
17707 Turns on or off debugging messages from the Linux LWP async debug support.
17708 @item show debug lin-lwp-async
17709 Show the current state of Linux LWP async debugging messages.
17710 @item set debug observer
17711 @cindex observer debugging info
17712 Turns on or off display of @value{GDBN} observer debugging. This
17713 includes info such as the notification of observable events.
17714 @item show debug observer
17715 Displays the current state of observer debugging.
17716 @item set debug overload
17717 @cindex C@t{++} overload debugging info
17718 Turns on or off display of @value{GDBN} C@t{++} overload debugging
17719 info. This includes info such as ranking of functions, etc. The default
17721 @item show debug overload
17722 Displays the current state of displaying @value{GDBN} C@t{++} overload
17724 @cindex packets, reporting on stdout
17725 @cindex serial connections, debugging
17726 @cindex debug remote protocol
17727 @cindex remote protocol debugging
17728 @cindex display remote packets
17729 @item set debug remote
17730 Turns on or off display of reports on all packets sent back and forth across
17731 the serial line to the remote machine. The info is printed on the
17732 @value{GDBN} standard output stream. The default is off.
17733 @item show debug remote
17734 Displays the state of display of remote packets.
17735 @item set debug serial
17736 Turns on or off display of @value{GDBN} serial debugging info. The
17738 @item show debug serial
17739 Displays the current state of displaying @value{GDBN} serial debugging
17741 @item set debug solib-frv
17742 @cindex FR-V shared-library debugging
17743 Turns on or off debugging messages for FR-V shared-library code.
17744 @item show debug solib-frv
17745 Display the current state of FR-V shared-library code debugging
17747 @item set debug target
17748 @cindex target debugging info
17749 Turns on or off display of @value{GDBN} target debugging info. This info
17750 includes what is going on at the target level of GDB, as it happens. The
17751 default is 0. Set it to 1 to track events, and to 2 to also track the
17752 value of large memory transfers. Changes to this flag do not take effect
17753 until the next time you connect to a target or use the @code{run} command.
17754 @item show debug target
17755 Displays the current state of displaying @value{GDBN} target debugging
17757 @item set debug timestamp
17758 @cindex timestampping debugging info
17759 Turns on or off display of timestamps with @value{GDBN} debugging info.
17760 When enabled, seconds and microseconds are displayed before each debugging
17762 @item show debug timestamp
17763 Displays the current state of displaying timestamps with @value{GDBN}
17765 @item set debugvarobj
17766 @cindex variable object debugging info
17767 Turns on or off display of @value{GDBN} variable object debugging
17768 info. The default is off.
17769 @item show debugvarobj
17770 Displays the current state of displaying @value{GDBN} variable object
17772 @item set debug xml
17773 @cindex XML parser debugging
17774 Turns on or off debugging messages for built-in XML parsers.
17775 @item show debug xml
17776 Displays the current state of XML debugging messages.
17779 @node Extending GDB
17780 @chapter Extending @value{GDBN}
17781 @cindex extending GDB
17783 @value{GDBN} provides two mechanisms for extension. The first is based
17784 on composition of @value{GDBN} commands, and the second is based on the
17785 Python scripting language.
17788 * Sequences:: Canned Sequences of Commands
17789 * Python:: Scripting @value{GDBN} using Python
17793 @section Canned Sequences of Commands
17795 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
17796 Command Lists}), @value{GDBN} provides two ways to store sequences of
17797 commands for execution as a unit: user-defined commands and command
17801 * Define:: How to define your own commands
17802 * Hooks:: Hooks for user-defined commands
17803 * Command Files:: How to write scripts of commands to be stored in a file
17804 * Output:: Commands for controlled output
17808 @subsection User-defined Commands
17810 @cindex user-defined command
17811 @cindex arguments, to user-defined commands
17812 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
17813 which you assign a new name as a command. This is done with the
17814 @code{define} command. User commands may accept up to 10 arguments
17815 separated by whitespace. Arguments are accessed within the user command
17816 via @code{$arg0@dots{}$arg9}. A trivial example:
17820 print $arg0 + $arg1 + $arg2
17825 To execute the command use:
17832 This defines the command @code{adder}, which prints the sum of
17833 its three arguments. Note the arguments are text substitutions, so they may
17834 reference variables, use complex expressions, or even perform inferior
17837 @cindex argument count in user-defined commands
17838 @cindex how many arguments (user-defined commands)
17839 In addition, @code{$argc} may be used to find out how many arguments have
17840 been passed. This expands to a number in the range 0@dots{}10.
17845 print $arg0 + $arg1
17848 print $arg0 + $arg1 + $arg2
17856 @item define @var{commandname}
17857 Define a command named @var{commandname}. If there is already a command
17858 by that name, you are asked to confirm that you want to redefine it.
17859 @var{commandname} may be a bare command name consisting of letters,
17860 numbers, dashes, and underscores. It may also start with any predefined
17861 prefix command. For example, @samp{define target my-target} creates
17862 a user-defined @samp{target my-target} command.
17864 The definition of the command is made up of other @value{GDBN} command lines,
17865 which are given following the @code{define} command. The end of these
17866 commands is marked by a line containing @code{end}.
17869 @kindex end@r{ (user-defined commands)}
17870 @item document @var{commandname}
17871 Document the user-defined command @var{commandname}, so that it can be
17872 accessed by @code{help}. The command @var{commandname} must already be
17873 defined. This command reads lines of documentation just as @code{define}
17874 reads the lines of the command definition, ending with @code{end}.
17875 After the @code{document} command is finished, @code{help} on command
17876 @var{commandname} displays the documentation you have written.
17878 You may use the @code{document} command again to change the
17879 documentation of a command. Redefining the command with @code{define}
17880 does not change the documentation.
17882 @kindex dont-repeat
17883 @cindex don't repeat command
17885 Used inside a user-defined command, this tells @value{GDBN} that this
17886 command should not be repeated when the user hits @key{RET}
17887 (@pxref{Command Syntax, repeat last command}).
17889 @kindex help user-defined
17890 @item help user-defined
17891 List all user-defined commands, with the first line of the documentation
17896 @itemx show user @var{commandname}
17897 Display the @value{GDBN} commands used to define @var{commandname} (but
17898 not its documentation). If no @var{commandname} is given, display the
17899 definitions for all user-defined commands.
17901 @cindex infinite recursion in user-defined commands
17902 @kindex show max-user-call-depth
17903 @kindex set max-user-call-depth
17904 @item show max-user-call-depth
17905 @itemx set max-user-call-depth
17906 The value of @code{max-user-call-depth} controls how many recursion
17907 levels are allowed in user-defined commands before @value{GDBN} suspects an
17908 infinite recursion and aborts the command.
17911 In addition to the above commands, user-defined commands frequently
17912 use control flow commands, described in @ref{Command Files}.
17914 When user-defined commands are executed, the
17915 commands of the definition are not printed. An error in any command
17916 stops execution of the user-defined command.
17918 If used interactively, commands that would ask for confirmation proceed
17919 without asking when used inside a user-defined command. Many @value{GDBN}
17920 commands that normally print messages to say what they are doing omit the
17921 messages when used in a user-defined command.
17924 @subsection User-defined Command Hooks
17925 @cindex command hooks
17926 @cindex hooks, for commands
17927 @cindex hooks, pre-command
17930 You may define @dfn{hooks}, which are a special kind of user-defined
17931 command. Whenever you run the command @samp{foo}, if the user-defined
17932 command @samp{hook-foo} exists, it is executed (with no arguments)
17933 before that command.
17935 @cindex hooks, post-command
17937 A hook may also be defined which is run after the command you executed.
17938 Whenever you run the command @samp{foo}, if the user-defined command
17939 @samp{hookpost-foo} exists, it is executed (with no arguments) after
17940 that command. Post-execution hooks may exist simultaneously with
17941 pre-execution hooks, for the same command.
17943 It is valid for a hook to call the command which it hooks. If this
17944 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
17946 @c It would be nice if hookpost could be passed a parameter indicating
17947 @c if the command it hooks executed properly or not. FIXME!
17949 @kindex stop@r{, a pseudo-command}
17950 In addition, a pseudo-command, @samp{stop} exists. Defining
17951 (@samp{hook-stop}) makes the associated commands execute every time
17952 execution stops in your program: before breakpoint commands are run,
17953 displays are printed, or the stack frame is printed.
17955 For example, to ignore @code{SIGALRM} signals while
17956 single-stepping, but treat them normally during normal execution,
17961 handle SIGALRM nopass
17965 handle SIGALRM pass
17968 define hook-continue
17969 handle SIGALRM pass
17973 As a further example, to hook at the beginning and end of the @code{echo}
17974 command, and to add extra text to the beginning and end of the message,
17982 define hookpost-echo
17986 (@value{GDBP}) echo Hello World
17987 <<<---Hello World--->>>
17992 You can define a hook for any single-word command in @value{GDBN}, but
17993 not for command aliases; you should define a hook for the basic command
17994 name, e.g.@: @code{backtrace} rather than @code{bt}.
17995 @c FIXME! So how does Joe User discover whether a command is an alias
17997 You can hook a multi-word command by adding @code{hook-} or
17998 @code{hookpost-} to the last word of the command, e.g.@:
17999 @samp{define target hook-remote} to add a hook to @samp{target remote}.
18001 If an error occurs during the execution of your hook, execution of
18002 @value{GDBN} commands stops and @value{GDBN} issues a prompt
18003 (before the command that you actually typed had a chance to run).
18005 If you try to define a hook which does not match any known command, you
18006 get a warning from the @code{define} command.
18008 @node Command Files
18009 @subsection Command Files
18011 @cindex command files
18012 @cindex scripting commands
18013 A command file for @value{GDBN} is a text file made of lines that are
18014 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
18015 also be included. An empty line in a command file does nothing; it
18016 does not mean to repeat the last command, as it would from the
18019 You can request the execution of a command file with the @code{source}
18024 @cindex execute commands from a file
18025 @item source [@code{-v}] @var{filename}
18026 Execute the command file @var{filename}.
18029 The lines in a command file are generally executed sequentially,
18030 unless the order of execution is changed by one of the
18031 @emph{flow-control commands} described below. The commands are not
18032 printed as they are executed. An error in any command terminates
18033 execution of the command file and control is returned to the console.
18035 @value{GDBN} searches for @var{filename} in the current directory and then
18036 on the search path (specified with the @samp{directory} command).
18038 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
18039 each command as it is executed. The option must be given before
18040 @var{filename}, and is interpreted as part of the filename anywhere else.
18042 Commands that would ask for confirmation if used interactively proceed
18043 without asking when used in a command file. Many @value{GDBN} commands that
18044 normally print messages to say what they are doing omit the messages
18045 when called from command files.
18047 @value{GDBN} also accepts command input from standard input. In this
18048 mode, normal output goes to standard output and error output goes to
18049 standard error. Errors in a command file supplied on standard input do
18050 not terminate execution of the command file---execution continues with
18054 gdb < cmds > log 2>&1
18057 (The syntax above will vary depending on the shell used.) This example
18058 will execute commands from the file @file{cmds}. All output and errors
18059 would be directed to @file{log}.
18061 Since commands stored on command files tend to be more general than
18062 commands typed interactively, they frequently need to deal with
18063 complicated situations, such as different or unexpected values of
18064 variables and symbols, changes in how the program being debugged is
18065 built, etc. @value{GDBN} provides a set of flow-control commands to
18066 deal with these complexities. Using these commands, you can write
18067 complex scripts that loop over data structures, execute commands
18068 conditionally, etc.
18075 This command allows to include in your script conditionally executed
18076 commands. The @code{if} command takes a single argument, which is an
18077 expression to evaluate. It is followed by a series of commands that
18078 are executed only if the expression is true (its value is nonzero).
18079 There can then optionally be an @code{else} line, followed by a series
18080 of commands that are only executed if the expression was false. The
18081 end of the list is marked by a line containing @code{end}.
18085 This command allows to write loops. Its syntax is similar to
18086 @code{if}: the command takes a single argument, which is an expression
18087 to evaluate, and must be followed by the commands to execute, one per
18088 line, terminated by an @code{end}. These commands are called the
18089 @dfn{body} of the loop. The commands in the body of @code{while} are
18090 executed repeatedly as long as the expression evaluates to true.
18094 This command exits the @code{while} loop in whose body it is included.
18095 Execution of the script continues after that @code{while}s @code{end}
18098 @kindex loop_continue
18099 @item loop_continue
18100 This command skips the execution of the rest of the body of commands
18101 in the @code{while} loop in whose body it is included. Execution
18102 branches to the beginning of the @code{while} loop, where it evaluates
18103 the controlling expression.
18105 @kindex end@r{ (if/else/while commands)}
18107 Terminate the block of commands that are the body of @code{if},
18108 @code{else}, or @code{while} flow-control commands.
18113 @subsection Commands for Controlled Output
18115 During the execution of a command file or a user-defined command, normal
18116 @value{GDBN} output is suppressed; the only output that appears is what is
18117 explicitly printed by the commands in the definition. This section
18118 describes three commands useful for generating exactly the output you
18123 @item echo @var{text}
18124 @c I do not consider backslash-space a standard C escape sequence
18125 @c because it is not in ANSI.
18126 Print @var{text}. Nonprinting characters can be included in
18127 @var{text} using C escape sequences, such as @samp{\n} to print a
18128 newline. @strong{No newline is printed unless you specify one.}
18129 In addition to the standard C escape sequences, a backslash followed
18130 by a space stands for a space. This is useful for displaying a
18131 string with spaces at the beginning or the end, since leading and
18132 trailing spaces are otherwise trimmed from all arguments.
18133 To print @samp{@w{ }and foo =@w{ }}, use the command
18134 @samp{echo \@w{ }and foo = \@w{ }}.
18136 A backslash at the end of @var{text} can be used, as in C, to continue
18137 the command onto subsequent lines. For example,
18140 echo This is some text\n\
18141 which is continued\n\
18142 onto several lines.\n
18145 produces the same output as
18148 echo This is some text\n
18149 echo which is continued\n
18150 echo onto several lines.\n
18154 @item output @var{expression}
18155 Print the value of @var{expression} and nothing but that value: no
18156 newlines, no @samp{$@var{nn} = }. The value is not entered in the
18157 value history either. @xref{Expressions, ,Expressions}, for more information
18160 @item output/@var{fmt} @var{expression}
18161 Print the value of @var{expression} in format @var{fmt}. You can use
18162 the same formats as for @code{print}. @xref{Output Formats,,Output
18163 Formats}, for more information.
18166 @item printf @var{template}, @var{expressions}@dots{}
18167 Print the values of one or more @var{expressions} under the control of
18168 the string @var{template}. To print several values, make
18169 @var{expressions} be a comma-separated list of individual expressions,
18170 which may be either numbers or pointers. Their values are printed as
18171 specified by @var{template}, exactly as a C program would do by
18172 executing the code below:
18175 printf (@var{template}, @var{expressions}@dots{});
18178 As in @code{C} @code{printf}, ordinary characters in @var{template}
18179 are printed verbatim, while @dfn{conversion specification} introduced
18180 by the @samp{%} character cause subsequent @var{expressions} to be
18181 evaluated, their values converted and formatted according to type and
18182 style information encoded in the conversion specifications, and then
18185 For example, you can print two values in hex like this:
18188 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
18191 @code{printf} supports all the standard @code{C} conversion
18192 specifications, including the flags and modifiers between the @samp{%}
18193 character and the conversion letter, with the following exceptions:
18197 The argument-ordering modifiers, such as @samp{2$}, are not supported.
18200 The modifier @samp{*} is not supported for specifying precision or
18204 The @samp{'} flag (for separation of digits into groups according to
18205 @code{LC_NUMERIC'}) is not supported.
18208 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
18212 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
18215 The conversion letters @samp{a} and @samp{A} are not supported.
18219 Note that the @samp{ll} type modifier is supported only if the
18220 underlying @code{C} implementation used to build @value{GDBN} supports
18221 the @code{long long int} type, and the @samp{L} type modifier is
18222 supported only if @code{long double} type is available.
18224 As in @code{C}, @code{printf} supports simple backslash-escape
18225 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
18226 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
18227 single character. Octal and hexadecimal escape sequences are not
18230 Additionally, @code{printf} supports conversion specifications for DFP
18231 (@dfn{Decimal Floating Point}) types using the following length modifiers
18232 together with a floating point specifier.
18237 @samp{H} for printing @code{Decimal32} types.
18240 @samp{D} for printing @code{Decimal64} types.
18243 @samp{DD} for printing @code{Decimal128} types.
18246 If the underlying @code{C} implementation used to build @value{GDBN} has
18247 support for the three length modifiers for DFP types, other modifiers
18248 such as width and precision will also be available for @value{GDBN} to use.
18250 In case there is no such @code{C} support, no additional modifiers will be
18251 available and the value will be printed in the standard way.
18253 Here's an example of printing DFP types using the above conversion letters:
18255 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
18261 @section Scripting @value{GDBN} using Python
18262 @cindex python scripting
18263 @cindex scripting with python
18265 You can script @value{GDBN} using the @uref{http://www.python.org/,
18266 Python programming language}. This feature is available only if
18267 @value{GDBN} was configured using @option{--with-python}.
18270 * Python Commands:: Accessing Python from @value{GDBN}.
18271 * Python API:: Accessing @value{GDBN} from Python.
18274 @node Python Commands
18275 @subsection Python Commands
18276 @cindex python commands
18277 @cindex commands to access python
18279 @value{GDBN} provides one command for accessing the Python interpreter,
18280 and one related setting:
18284 @item python @r{[}@var{code}@r{]}
18285 The @code{python} command can be used to evaluate Python code.
18287 If given an argument, the @code{python} command will evaluate the
18288 argument as a Python command. For example:
18291 (@value{GDBP}) python print 23
18295 If you do not provide an argument to @code{python}, it will act as a
18296 multi-line command, like @code{define}. In this case, the Python
18297 script is made up of subsequent command lines, given after the
18298 @code{python} command. This command list is terminated using a line
18299 containing @code{end}. For example:
18302 (@value{GDBP}) python
18304 End with a line saying just "end".
18310 @kindex maint set python print-stack
18311 @item maint set python print-stack
18312 By default, @value{GDBN} will print a stack trace when an error occurs
18313 in a Python script. This can be controlled using @code{maint set
18314 python print-stack}: if @code{on}, the default, then Python stack
18315 printing is enabled; if @code{off}, then Python stack printing is
18320 @subsection Python API
18322 @cindex programming in python
18324 @cindex python stdout
18325 @cindex python pagination
18326 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
18327 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
18328 A Python program which outputs to one of these streams may have its
18329 output interrupted by the user (@pxref{Screen Size}). In this
18330 situation, a Python @code{KeyboardInterrupt} exception is thrown.
18333 * Basic Python:: Basic Python Functions.
18334 * Exception Handling::
18335 * Values From Inferior::
18336 * Commands In Python:: Implementing new commands in Python.
18337 * Functions In Python:: Writing new convenience functions.
18338 * Frames In Python:: Acessing inferior stack frames from Python.
18342 @subsubsection Basic Python
18344 @cindex python functions
18345 @cindex python module
18347 @value{GDBN} introduces a new Python module, named @code{gdb}. All
18348 methods and classes added by @value{GDBN} are placed in this module.
18349 @value{GDBN} automatically @code{import}s the @code{gdb} module for
18350 use in all scripts evaluated by the @code{python} command.
18352 @findex gdb.execute
18353 @defun execute command [from_tty]
18354 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
18355 If a GDB exception happens while @var{command} runs, it is
18356 translated as described in @ref{Exception Handling,,Exception Handling}.
18357 If no exceptions occur, this function returns @code{None}.
18359 @var{from_tty} specifies whether @value{GDBN} ought to consider this
18360 command as having originated from the user invoking it interactively.
18361 It must be a boolean value. If omitted, it defaults to @code{False}.
18364 @findex gdb.get_parameter
18365 @defun get_parameter parameter
18366 Return the value of a @value{GDBN} parameter. @var{parameter} is a
18367 string naming the parameter to look up; @var{parameter} may contain
18368 spaces if the parameter has a multi-part name. For example,
18369 @samp{print object} is a valid parameter name.
18371 If the named parameter does not exist, this function throws a
18372 @code{RuntimeError}. Otherwise, the parameter's value is converted to
18373 a Python value of the appropriate type, and returned.
18376 @findex gdb.history
18377 @defun history number
18378 Return a value from @value{GDBN}'s value history (@pxref{Value
18379 History}). @var{number} indicates which history element to return.
18380 If @var{number} is negative, then @value{GDBN} will take its absolute value
18381 and count backward from the last element (i.e., the most recent element) to
18382 find the value to return. If @var{number} is zero, then @value{GDBN} will
18383 return the most recent element. If the element specified by @var{number}
18384 doesn't exist in the value history, a @code{RuntimeError} exception will be
18387 If no exception is raised, the return value is always an instance of
18388 @code{gdb.Value} (@pxref{Values From Inferior}).
18392 @defun write string
18393 Print a string to @value{GDBN}'s paginated standard output stream.
18394 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
18395 call this function.
18400 Flush @value{GDBN}'s paginated standard output stream. Flushing
18401 @code{sys.stdout} or @code{sys.stderr} will automatically call this
18405 @node Exception Handling
18406 @subsubsection Exception Handling
18407 @cindex python exceptions
18408 @cindex exceptions, python
18410 When executing the @code{python} command, Python exceptions
18411 uncaught within the Python code are translated to calls to
18412 @value{GDBN} error-reporting mechanism. If the command that called
18413 @code{python} does not handle the error, @value{GDBN} will
18414 terminate it and print an error message containing the Python
18415 exception name, the associated value, and the Python call stack
18416 backtrace at the point where the exception was raised. Example:
18419 (@value{GDBP}) python print foo
18420 Traceback (most recent call last):
18421 File "<string>", line 1, in <module>
18422 NameError: name 'foo' is not defined
18425 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
18426 code are converted to Python @code{RuntimeError} exceptions. User
18427 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
18428 prompt) is translated to a Python @code{KeyboardInterrupt}
18429 exception. If you catch these exceptions in your Python code, your
18430 exception handler will see @code{RuntimeError} or
18431 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
18432 message as its value, and the Python call stack backtrace at the
18433 Python statement closest to where the @value{GDBN} error occured as the
18436 @node Values From Inferior
18437 @subsubsection Values From Inferior
18438 @cindex values from inferior, with Python
18439 @cindex python, working with values from inferior
18441 @cindex @code{gdb.Value}
18442 @value{GDBN} provides values it obtains from the inferior program in
18443 an object of type @code{gdb.Value}. @value{GDBN} uses this object
18444 for its internal bookkeeping of the inferior's values, and for
18445 fetching values when necessary.
18447 Inferior values that are simple scalars can be used directly in
18448 Python expressions that are valid for the value's data type. Here's
18449 an example for an integer or floating-point value @code{some_val}:
18456 As result of this, @code{bar} will also be a @code{gdb.Value} object
18457 whose values are of the same type as those of @code{some_val}.
18459 Inferior values that are structures or instances of some class can
18460 be accessed using the Python @dfn{dictionary syntax}. For example, if
18461 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
18462 can access its @code{foo} element with:
18465 bar = some_val['foo']
18468 Again, @code{bar} will also be a @code{gdb.Value} object.
18470 The following attributes are provided:
18473 @defmethod Value address
18474 If this object is addressable, this read-only attribute holds a
18475 @code{gdb.Value} object representing the address. Otherwise,
18476 this attribute holds @code{None}.
18479 @cindex optimized out value in Python
18480 @defmethod Value is_optimized_out
18481 This read-only boolean attribute is true if the compiler optimized out
18482 this value, thus it is not available for fetching from the inferior.
18486 The following methods are provided:
18489 @defmethod Value dereference
18490 For pointer data types, this method returns a new @code{gdb.Value} object
18491 whose contents is the object pointed to by the pointer. For example, if
18492 @code{foo} is a C pointer to an @code{int}, declared in your C program as
18499 then you can use the corresponding @code{gdb.Value} to access what
18500 @code{foo} points to like this:
18503 bar = foo.dereference ()
18506 The result @code{bar} will be a @code{gdb.Value} object holding the
18507 value pointed to by @code{foo}.
18510 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]}
18511 If this @code{gdb.Value} represents a string, then this method
18512 converts the contents to a Python string. Otherwise, this method will
18513 throw an exception.
18515 Strings are recognized in a language-specific way; whether a given
18516 @code{gdb.Value} represents a string is determined by the current
18519 For C-like languages, a value is a string if it is a pointer to or an
18520 array of characters or ints. The string is assumed to be terminated
18521 by a zero of the appropriate width.
18523 If the optional @var{encoding} argument is given, it must be a string
18524 naming the encoding of the string in the @code{gdb.Value}, such as
18525 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
18526 the same encodings as the corresponding argument to Python's
18527 @code{string.decode} method, and the Python codec machinery will be used
18528 to convert the string. If @var{encoding} is not given, or if
18529 @var{encoding} is the empty string, then either the @code{target-charset}
18530 (@pxref{Character Sets}) will be used, or a language-specific encoding
18531 will be used, if the current language is able to supply one.
18533 The optional @var{errors} argument is the same as the corresponding
18534 argument to Python's @code{string.decode} method.
18538 @node Commands In Python
18539 @subsubsection Commands In Python
18541 @cindex commands in python
18542 @cindex python commands
18543 You can implement new @value{GDBN} CLI commands in Python. A CLI
18544 command is implemented using an instance of the @code{gdb.Command}
18545 class, most commonly using a subclass.
18547 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
18548 The object initializer for @code{Command} registers the new command
18549 with @value{GDBN}. This initializer is normally invoked from the
18550 subclass' own @code{__init__} method.
18552 @var{name} is the name of the command. If @var{name} consists of
18553 multiple words, then the initial words are looked for as prefix
18554 commands. In this case, if one of the prefix commands does not exist,
18555 an exception is raised.
18557 There is no support for multi-line commands.
18559 @var{command_class} should be one of the @samp{COMMAND_} constants
18560 defined below. This argument tells @value{GDBN} how to categorize the
18561 new command in the help system.
18563 @var{completer_class} is an optional argument. If given, it should be
18564 one of the @samp{COMPLETE_} constants defined below. This argument
18565 tells @value{GDBN} how to perform completion for this command. If not
18566 given, @value{GDBN} will attempt to complete using the object's
18567 @code{complete} method (see below); if no such method is found, an
18568 error will occur when completion is attempted.
18570 @var{prefix} is an optional argument. If @code{True}, then the new
18571 command is a prefix command; sub-commands of this command may be
18574 The help text for the new command is taken from the Python
18575 documentation string for the command's class, if there is one. If no
18576 documentation string is provided, the default value ``This command is
18577 not documented.'' is used.
18580 @cindex don't repeat Python command
18581 @defmethod Command dont_repeat
18582 By default, a @value{GDBN} command is repeated when the user enters a
18583 blank line at the command prompt. A command can suppress this
18584 behavior by invoking the @code{dont_repeat} method. This is similar
18585 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
18588 @defmethod Command invoke argument from_tty
18589 This method is called by @value{GDBN} when this command is invoked.
18591 @var{argument} is a string. It is the argument to the command, after
18592 leading and trailing whitespace has been stripped.
18594 @var{from_tty} is a boolean argument. When true, this means that the
18595 command was entered by the user at the terminal; when false it means
18596 that the command came from elsewhere.
18598 If this method throws an exception, it is turned into a @value{GDBN}
18599 @code{error} call. Otherwise, the return value is ignored.
18602 @cindex completion of Python commands
18603 @defmethod Command complete text word
18604 This method is called by @value{GDBN} when the user attempts
18605 completion on this command. All forms of completion are handled by
18606 this method, that is, the @key{TAB} and @key{M-?} key bindings
18607 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
18610 The arguments @var{text} and @var{word} are both strings. @var{text}
18611 holds the complete command line up to the cursor's location.
18612 @var{word} holds the last word of the command line; this is computed
18613 using a word-breaking heuristic.
18615 The @code{complete} method can return several values:
18618 If the return value is a sequence, the contents of the sequence are
18619 used as the completions. It is up to @code{complete} to ensure that the
18620 contents actually do complete the word. A zero-length sequence is
18621 allowed, it means that there were no completions available. Only
18622 string elements of the sequence are used; other elements in the
18623 sequence are ignored.
18626 If the return value is one of the @samp{COMPLETE_} constants defined
18627 below, then the corresponding @value{GDBN}-internal completion
18628 function is invoked, and its result is used.
18631 All other results are treated as though there were no available
18636 When a new command is registered, it must be declared as a member of
18637 some general class of commands. This is used to classify top-level
18638 commands in the on-line help system; note that prefix commands are not
18639 listed under their own category but rather that of their top-level
18640 command. The available classifications are represented by constants
18641 defined in the @code{gdb} module:
18644 @findex COMMAND_NONE
18645 @findex gdb.COMMAND_NONE
18647 The command does not belong to any particular class. A command in
18648 this category will not be displayed in any of the help categories.
18650 @findex COMMAND_RUNNING
18651 @findex gdb.COMMAND_RUNNING
18652 @item COMMAND_RUNNING
18653 The command is related to running the inferior. For example,
18654 @code{start}, @code{step}, and @code{continue} are in this category.
18655 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
18656 commands in this category.
18658 @findex COMMAND_DATA
18659 @findex gdb.COMMAND_DATA
18661 The command is related to data or variables. For example,
18662 @code{call}, @code{find}, and @code{print} are in this category. Type
18663 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
18666 @findex COMMAND_STACK
18667 @findex gdb.COMMAND_STACK
18668 @item COMMAND_STACK
18669 The command has to do with manipulation of the stack. For example,
18670 @code{backtrace}, @code{frame}, and @code{return} are in this
18671 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
18672 list of commands in this category.
18674 @findex COMMAND_FILES
18675 @findex gdb.COMMAND_FILES
18676 @item COMMAND_FILES
18677 This class is used for file-related commands. For example,
18678 @code{file}, @code{list} and @code{section} are in this category.
18679 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
18680 commands in this category.
18682 @findex COMMAND_SUPPORT
18683 @findex gdb.COMMAND_SUPPORT
18684 @item COMMAND_SUPPORT
18685 This should be used for ``support facilities'', generally meaning
18686 things that are useful to the user when interacting with @value{GDBN},
18687 but not related to the state of the inferior. For example,
18688 @code{help}, @code{make}, and @code{shell} are in this category. Type
18689 @kbd{help support} at the @value{GDBN} prompt to see a list of
18690 commands in this category.
18692 @findex COMMAND_STATUS
18693 @findex gdb.COMMAND_STATUS
18694 @item COMMAND_STATUS
18695 The command is an @samp{info}-related command, that is, related to the
18696 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
18697 and @code{show} are in this category. Type @kbd{help status} at the
18698 @value{GDBN} prompt to see a list of commands in this category.
18700 @findex COMMAND_BREAKPOINTS
18701 @findex gdb.COMMAND_BREAKPOINTS
18702 @item COMMAND_BREAKPOINTS
18703 The command has to do with breakpoints. For example, @code{break},
18704 @code{clear}, and @code{delete} are in this category. Type @kbd{help
18705 breakpoints} at the @value{GDBN} prompt to see a list of commands in
18708 @findex COMMAND_TRACEPOINTS
18709 @findex gdb.COMMAND_TRACEPOINTS
18710 @item COMMAND_TRACEPOINTS
18711 The command has to do with tracepoints. For example, @code{trace},
18712 @code{actions}, and @code{tfind} are in this category. Type
18713 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
18714 commands in this category.
18716 @findex COMMAND_OBSCURE
18717 @findex gdb.COMMAND_OBSCURE
18718 @item COMMAND_OBSCURE
18719 The command is only used in unusual circumstances, or is not of
18720 general interest to users. For example, @code{checkpoint},
18721 @code{fork}, and @code{stop} are in this category. Type @kbd{help
18722 obscure} at the @value{GDBN} prompt to see a list of commands in this
18725 @findex COMMAND_MAINTENANCE
18726 @findex gdb.COMMAND_MAINTENANCE
18727 @item COMMAND_MAINTENANCE
18728 The command is only useful to @value{GDBN} maintainers. The
18729 @code{maintenance} and @code{flushregs} commands are in this category.
18730 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
18731 commands in this category.
18734 A new command can use a predefined completion function, either by
18735 specifying it via an argument at initialization, or by returning it
18736 from the @code{complete} method. These predefined completion
18737 constants are all defined in the @code{gdb} module:
18740 @findex COMPLETE_NONE
18741 @findex gdb.COMPLETE_NONE
18742 @item COMPLETE_NONE
18743 This constant means that no completion should be done.
18745 @findex COMPLETE_FILENAME
18746 @findex gdb.COMPLETE_FILENAME
18747 @item COMPLETE_FILENAME
18748 This constant means that filename completion should be performed.
18750 @findex COMPLETE_LOCATION
18751 @findex gdb.COMPLETE_LOCATION
18752 @item COMPLETE_LOCATION
18753 This constant means that location completion should be done.
18754 @xref{Specify Location}.
18756 @findex COMPLETE_COMMAND
18757 @findex gdb.COMPLETE_COMMAND
18758 @item COMPLETE_COMMAND
18759 This constant means that completion should examine @value{GDBN}
18762 @findex COMPLETE_SYMBOL
18763 @findex gdb.COMPLETE_SYMBOL
18764 @item COMPLETE_SYMBOL
18765 This constant means that completion should be done using symbol names
18769 The following code snippet shows how a trivial CLI command can be
18770 implemented in Python:
18773 class HelloWorld (gdb.Command):
18774 """Greet the whole world."""
18776 def __init__ (self):
18777 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
18779 def invoke (self, arg, from_tty):
18780 print "Hello, World!"
18785 The last line instantiates the class, and is necessary to trigger the
18786 registration of the command with @value{GDBN}. Depending on how the
18787 Python code is read into @value{GDBN}, you may need to import the
18788 @code{gdb} module explicitly.
18790 @node Functions In Python
18791 @subsubsection Writing new convenience functions
18793 @cindex writing convenience functions
18794 @cindex convenience functions in python
18795 @cindex python convenience functions
18796 @tindex gdb.Function
18798 You can implement new convenience functions (@pxref{Convenience Vars})
18799 in Python. A convenience function is an instance of a subclass of the
18800 class @code{gdb.Function}.
18802 @defmethod Function __init__ name
18803 The initializer for @code{Function} registers the new function with
18804 @value{GDBN}. The argument @var{name} is the name of the function,
18805 a string. The function will be visible to the user as a convenience
18806 variable of type @code{internal function}, whose name is the same as
18807 the given @var{name}.
18809 The documentation for the new function is taken from the documentation
18810 string for the new class.
18813 @defmethod Function invoke @var{*args}
18814 When a convenience function is evaluated, its arguments are converted
18815 to instances of @code{gdb.Value}, and then the function's
18816 @code{invoke} method is called. Note that @value{GDBN} does not
18817 predetermine the arity of convenience functions. Instead, all
18818 available arguments are passed to @code{invoke}, following the
18819 standard Python calling convention. In particular, a convenience
18820 function can have default values for parameters without ill effect.
18822 The return value of this method is used as its value in the enclosing
18823 expression. If an ordinary Python value is returned, it is converted
18824 to a @code{gdb.Value} following the usual rules.
18827 The following code snippet shows how a trivial convenience function can
18828 be implemented in Python:
18831 class Greet (gdb.Function):
18832 """Return string to greet someone.
18833 Takes a name as argument."""
18835 def __init__ (self):
18836 super (Greet, self).__init__ ("greet")
18838 def invoke (self, name):
18839 return "Hello, %s!" % name.string ()
18844 The last line instantiates the class, and is necessary to trigger the
18845 registration of the function with @value{GDBN}. Depending on how the
18846 Python code is read into @value{GDBN}, you may need to import the
18847 @code{gdb} module explicitly.
18849 @node Frames In Python
18850 @subsubsection Acessing inferior stack frames from Python.
18852 @cindex frames in python
18853 When the debugged program stops, @value{GDBN} is able to analyze its call
18854 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
18855 represents a frame in the stack. A @code{gdb.Frame} object is only valid
18856 while its corresponding frame exists in the inferior's stack. If you try
18857 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
18860 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
18864 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
18868 The following frame-related functions are available in the @code{gdb} module:
18870 @findex gdb.selected_frame
18871 @defun selected_frame
18872 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
18875 @defun frame_stop_reason_string reason
18876 Return a string explaining the reason why @value{GDBN} stopped unwinding
18877 frames, as expressed by the given @var{reason} code (an integer, see the
18878 @code{unwind_stop_reason} method further down in this section).
18881 A @code{gdb.Frame} object has the following methods:
18884 @defmethod Frame is_valid
18885 Returns true if the @code{gdb.Frame} object is valid, false if not.
18886 A frame object can become invalid if the frame it refers to doesn't
18887 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
18888 an exception if it is invalid at the time the method is called.
18891 @defmethod Frame name
18892 Returns the function name of the frame, or @code{None} if it can't be
18896 @defmethod Frame type
18897 Returns the type of the frame. The value can be one of
18898 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
18899 or @code{gdb.SENTINEL_FRAME}.
18902 @defmethod Frame unwind_stop_reason
18903 Return an integer representing the reason why it's not possible to find
18904 more frames toward the outermost frame. Use
18905 @code{gdb.frame_stop_reason_string} to convert the value returned by this
18906 function to a string.
18909 @defmethod Frame pc
18910 Returns the frame's resume address.
18913 @defmethod Frame older
18914 Return the frame that called this frame.
18917 @defmethod Frame newer
18918 Return the frame called by this frame.
18921 @defmethod Frame read_var variable
18922 Return the value of the given variable in this frame. @var{variable} must
18928 @chapter Command Interpreters
18929 @cindex command interpreters
18931 @value{GDBN} supports multiple command interpreters, and some command
18932 infrastructure to allow users or user interface writers to switch
18933 between interpreters or run commands in other interpreters.
18935 @value{GDBN} currently supports two command interpreters, the console
18936 interpreter (sometimes called the command-line interpreter or @sc{cli})
18937 and the machine interface interpreter (or @sc{gdb/mi}). This manual
18938 describes both of these interfaces in great detail.
18940 By default, @value{GDBN} will start with the console interpreter.
18941 However, the user may choose to start @value{GDBN} with another
18942 interpreter by specifying the @option{-i} or @option{--interpreter}
18943 startup options. Defined interpreters include:
18947 @cindex console interpreter
18948 The traditional console or command-line interpreter. This is the most often
18949 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
18950 @value{GDBN} will use this interpreter.
18953 @cindex mi interpreter
18954 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
18955 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
18956 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
18960 @cindex mi2 interpreter
18961 The current @sc{gdb/mi} interface.
18964 @cindex mi1 interpreter
18965 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
18969 @cindex invoke another interpreter
18970 The interpreter being used by @value{GDBN} may not be dynamically
18971 switched at runtime. Although possible, this could lead to a very
18972 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
18973 enters the command "interpreter-set console" in a console view,
18974 @value{GDBN} would switch to using the console interpreter, rendering
18975 the IDE inoperable!
18977 @kindex interpreter-exec
18978 Although you may only choose a single interpreter at startup, you may execute
18979 commands in any interpreter from the current interpreter using the appropriate
18980 command. If you are running the console interpreter, simply use the
18981 @code{interpreter-exec} command:
18984 interpreter-exec mi "-data-list-register-names"
18987 @sc{gdb/mi} has a similar command, although it is only available in versions of
18988 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
18991 @chapter @value{GDBN} Text User Interface
18993 @cindex Text User Interface
18996 * TUI Overview:: TUI overview
18997 * TUI Keys:: TUI key bindings
18998 * TUI Single Key Mode:: TUI single key mode
18999 * TUI Commands:: TUI-specific commands
19000 * TUI Configuration:: TUI configuration variables
19003 The @value{GDBN} Text User Interface (TUI) is a terminal
19004 interface which uses the @code{curses} library to show the source
19005 file, the assembly output, the program registers and @value{GDBN}
19006 commands in separate text windows. The TUI mode is supported only
19007 on platforms where a suitable version of the @code{curses} library
19010 @pindex @value{GDBTUI}
19011 The TUI mode is enabled by default when you invoke @value{GDBN} as
19012 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
19013 You can also switch in and out of TUI mode while @value{GDBN} runs by
19014 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
19015 @xref{TUI Keys, ,TUI Key Bindings}.
19018 @section TUI Overview
19020 In TUI mode, @value{GDBN} can display several text windows:
19024 This window is the @value{GDBN} command window with the @value{GDBN}
19025 prompt and the @value{GDBN} output. The @value{GDBN} input is still
19026 managed using readline.
19029 The source window shows the source file of the program. The current
19030 line and active breakpoints are displayed in this window.
19033 The assembly window shows the disassembly output of the program.
19036 This window shows the processor registers. Registers are highlighted
19037 when their values change.
19040 The source and assembly windows show the current program position
19041 by highlighting the current line and marking it with a @samp{>} marker.
19042 Breakpoints are indicated with two markers. The first marker
19043 indicates the breakpoint type:
19047 Breakpoint which was hit at least once.
19050 Breakpoint which was never hit.
19053 Hardware breakpoint which was hit at least once.
19056 Hardware breakpoint which was never hit.
19059 The second marker indicates whether the breakpoint is enabled or not:
19063 Breakpoint is enabled.
19066 Breakpoint is disabled.
19069 The source, assembly and register windows are updated when the current
19070 thread changes, when the frame changes, or when the program counter
19073 These windows are not all visible at the same time. The command
19074 window is always visible. The others can be arranged in several
19085 source and assembly,
19088 source and registers, or
19091 assembly and registers.
19094 A status line above the command window shows the following information:
19098 Indicates the current @value{GDBN} target.
19099 (@pxref{Targets, ,Specifying a Debugging Target}).
19102 Gives the current process or thread number.
19103 When no process is being debugged, this field is set to @code{No process}.
19106 Gives the current function name for the selected frame.
19107 The name is demangled if demangling is turned on (@pxref{Print Settings}).
19108 When there is no symbol corresponding to the current program counter,
19109 the string @code{??} is displayed.
19112 Indicates the current line number for the selected frame.
19113 When the current line number is not known, the string @code{??} is displayed.
19116 Indicates the current program counter address.
19120 @section TUI Key Bindings
19121 @cindex TUI key bindings
19123 The TUI installs several key bindings in the readline keymaps
19124 (@pxref{Command Line Editing}). The following key bindings
19125 are installed for both TUI mode and the @value{GDBN} standard mode.
19134 Enter or leave the TUI mode. When leaving the TUI mode,
19135 the curses window management stops and @value{GDBN} operates using
19136 its standard mode, writing on the terminal directly. When reentering
19137 the TUI mode, control is given back to the curses windows.
19138 The screen is then refreshed.
19142 Use a TUI layout with only one window. The layout will
19143 either be @samp{source} or @samp{assembly}. When the TUI mode
19144 is not active, it will switch to the TUI mode.
19146 Think of this key binding as the Emacs @kbd{C-x 1} binding.
19150 Use a TUI layout with at least two windows. When the current
19151 layout already has two windows, the next layout with two windows is used.
19152 When a new layout is chosen, one window will always be common to the
19153 previous layout and the new one.
19155 Think of it as the Emacs @kbd{C-x 2} binding.
19159 Change the active window. The TUI associates several key bindings
19160 (like scrolling and arrow keys) with the active window. This command
19161 gives the focus to the next TUI window.
19163 Think of it as the Emacs @kbd{C-x o} binding.
19167 Switch in and out of the TUI SingleKey mode that binds single
19168 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
19171 The following key bindings only work in the TUI mode:
19176 Scroll the active window one page up.
19180 Scroll the active window one page down.
19184 Scroll the active window one line up.
19188 Scroll the active window one line down.
19192 Scroll the active window one column left.
19196 Scroll the active window one column right.
19200 Refresh the screen.
19203 Because the arrow keys scroll the active window in the TUI mode, they
19204 are not available for their normal use by readline unless the command
19205 window has the focus. When another window is active, you must use
19206 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
19207 and @kbd{C-f} to control the command window.
19209 @node TUI Single Key Mode
19210 @section TUI Single Key Mode
19211 @cindex TUI single key mode
19213 The TUI also provides a @dfn{SingleKey} mode, which binds several
19214 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
19215 switch into this mode, where the following key bindings are used:
19218 @kindex c @r{(SingleKey TUI key)}
19222 @kindex d @r{(SingleKey TUI key)}
19226 @kindex f @r{(SingleKey TUI key)}
19230 @kindex n @r{(SingleKey TUI key)}
19234 @kindex q @r{(SingleKey TUI key)}
19236 exit the SingleKey mode.
19238 @kindex r @r{(SingleKey TUI key)}
19242 @kindex s @r{(SingleKey TUI key)}
19246 @kindex u @r{(SingleKey TUI key)}
19250 @kindex v @r{(SingleKey TUI key)}
19254 @kindex w @r{(SingleKey TUI key)}
19259 Other keys temporarily switch to the @value{GDBN} command prompt.
19260 The key that was pressed is inserted in the editing buffer so that
19261 it is possible to type most @value{GDBN} commands without interaction
19262 with the TUI SingleKey mode. Once the command is entered the TUI
19263 SingleKey mode is restored. The only way to permanently leave
19264 this mode is by typing @kbd{q} or @kbd{C-x s}.
19268 @section TUI-specific Commands
19269 @cindex TUI commands
19271 The TUI has specific commands to control the text windows.
19272 These commands are always available, even when @value{GDBN} is not in
19273 the TUI mode. When @value{GDBN} is in the standard mode, most
19274 of these commands will automatically switch to the TUI mode.
19279 List and give the size of all displayed windows.
19283 Display the next layout.
19286 Display the previous layout.
19289 Display the source window only.
19292 Display the assembly window only.
19295 Display the source and assembly window.
19298 Display the register window together with the source or assembly window.
19302 Make the next window active for scrolling.
19305 Make the previous window active for scrolling.
19308 Make the source window active for scrolling.
19311 Make the assembly window active for scrolling.
19314 Make the register window active for scrolling.
19317 Make the command window active for scrolling.
19321 Refresh the screen. This is similar to typing @kbd{C-L}.
19323 @item tui reg float
19325 Show the floating point registers in the register window.
19327 @item tui reg general
19328 Show the general registers in the register window.
19331 Show the next register group. The list of register groups as well as
19332 their order is target specific. The predefined register groups are the
19333 following: @code{general}, @code{float}, @code{system}, @code{vector},
19334 @code{all}, @code{save}, @code{restore}.
19336 @item tui reg system
19337 Show the system registers in the register window.
19341 Update the source window and the current execution point.
19343 @item winheight @var{name} +@var{count}
19344 @itemx winheight @var{name} -@var{count}
19346 Change the height of the window @var{name} by @var{count}
19347 lines. Positive counts increase the height, while negative counts
19350 @item tabset @var{nchars}
19352 Set the width of tab stops to be @var{nchars} characters.
19355 @node TUI Configuration
19356 @section TUI Configuration Variables
19357 @cindex TUI configuration variables
19359 Several configuration variables control the appearance of TUI windows.
19362 @item set tui border-kind @var{kind}
19363 @kindex set tui border-kind
19364 Select the border appearance for the source, assembly and register windows.
19365 The possible values are the following:
19368 Use a space character to draw the border.
19371 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
19374 Use the Alternate Character Set to draw the border. The border is
19375 drawn using character line graphics if the terminal supports them.
19378 @item set tui border-mode @var{mode}
19379 @kindex set tui border-mode
19380 @itemx set tui active-border-mode @var{mode}
19381 @kindex set tui active-border-mode
19382 Select the display attributes for the borders of the inactive windows
19383 or the active window. The @var{mode} can be one of the following:
19386 Use normal attributes to display the border.
19392 Use reverse video mode.
19395 Use half bright mode.
19397 @item half-standout
19398 Use half bright and standout mode.
19401 Use extra bright or bold mode.
19403 @item bold-standout
19404 Use extra bright or bold and standout mode.
19409 @chapter Using @value{GDBN} under @sc{gnu} Emacs
19412 @cindex @sc{gnu} Emacs
19413 A special interface allows you to use @sc{gnu} Emacs to view (and
19414 edit) the source files for the program you are debugging with
19417 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
19418 executable file you want to debug as an argument. This command starts
19419 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
19420 created Emacs buffer.
19421 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
19423 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
19428 All ``terminal'' input and output goes through an Emacs buffer, called
19431 This applies both to @value{GDBN} commands and their output, and to the input
19432 and output done by the program you are debugging.
19434 This is useful because it means that you can copy the text of previous
19435 commands and input them again; you can even use parts of the output
19438 All the facilities of Emacs' Shell mode are available for interacting
19439 with your program. In particular, you can send signals the usual
19440 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
19444 @value{GDBN} displays source code through Emacs.
19446 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
19447 source file for that frame and puts an arrow (@samp{=>}) at the
19448 left margin of the current line. Emacs uses a separate buffer for
19449 source display, and splits the screen to show both your @value{GDBN} session
19452 Explicit @value{GDBN} @code{list} or search commands still produce output as
19453 usual, but you probably have no reason to use them from Emacs.
19456 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
19457 a graphical mode, enabled by default, which provides further buffers
19458 that can control the execution and describe the state of your program.
19459 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
19461 If you specify an absolute file name when prompted for the @kbd{M-x
19462 gdb} argument, then Emacs sets your current working directory to where
19463 your program resides. If you only specify the file name, then Emacs
19464 sets your current working directory to to the directory associated
19465 with the previous buffer. In this case, @value{GDBN} may find your
19466 program by searching your environment's @code{PATH} variable, but on
19467 some operating systems it might not find the source. So, although the
19468 @value{GDBN} input and output session proceeds normally, the auxiliary
19469 buffer does not display the current source and line of execution.
19471 The initial working directory of @value{GDBN} is printed on the top
19472 line of the GUD buffer and this serves as a default for the commands
19473 that specify files for @value{GDBN} to operate on. @xref{Files,
19474 ,Commands to Specify Files}.
19476 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
19477 need to call @value{GDBN} by a different name (for example, if you
19478 keep several configurations around, with different names) you can
19479 customize the Emacs variable @code{gud-gdb-command-name} to run the
19482 In the GUD buffer, you can use these special Emacs commands in
19483 addition to the standard Shell mode commands:
19487 Describe the features of Emacs' GUD Mode.
19490 Execute to another source line, like the @value{GDBN} @code{step} command; also
19491 update the display window to show the current file and location.
19494 Execute to next source line in this function, skipping all function
19495 calls, like the @value{GDBN} @code{next} command. Then update the display window
19496 to show the current file and location.
19499 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
19500 display window accordingly.
19503 Execute until exit from the selected stack frame, like the @value{GDBN}
19504 @code{finish} command.
19507 Continue execution of your program, like the @value{GDBN} @code{continue}
19511 Go up the number of frames indicated by the numeric argument
19512 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
19513 like the @value{GDBN} @code{up} command.
19516 Go down the number of frames indicated by the numeric argument, like the
19517 @value{GDBN} @code{down} command.
19520 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
19521 tells @value{GDBN} to set a breakpoint on the source line point is on.
19523 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
19524 separate frame which shows a backtrace when the GUD buffer is current.
19525 Move point to any frame in the stack and type @key{RET} to make it
19526 become the current frame and display the associated source in the
19527 source buffer. Alternatively, click @kbd{Mouse-2} to make the
19528 selected frame become the current one. In graphical mode, the
19529 speedbar displays watch expressions.
19531 If you accidentally delete the source-display buffer, an easy way to get
19532 it back is to type the command @code{f} in the @value{GDBN} buffer, to
19533 request a frame display; when you run under Emacs, this recreates
19534 the source buffer if necessary to show you the context of the current
19537 The source files displayed in Emacs are in ordinary Emacs buffers
19538 which are visiting the source files in the usual way. You can edit
19539 the files with these buffers if you wish; but keep in mind that @value{GDBN}
19540 communicates with Emacs in terms of line numbers. If you add or
19541 delete lines from the text, the line numbers that @value{GDBN} knows cease
19542 to correspond properly with the code.
19544 A more detailed description of Emacs' interaction with @value{GDBN} is
19545 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
19548 @c The following dropped because Epoch is nonstandard. Reactivate
19549 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
19551 @kindex Emacs Epoch environment
19555 Version 18 of @sc{gnu} Emacs has a built-in window system
19556 called the @code{epoch}
19557 environment. Users of this environment can use a new command,
19558 @code{inspect} which performs identically to @code{print} except that
19559 each value is printed in its own window.
19564 @chapter The @sc{gdb/mi} Interface
19566 @unnumberedsec Function and Purpose
19568 @cindex @sc{gdb/mi}, its purpose
19569 @sc{gdb/mi} is a line based machine oriented text interface to
19570 @value{GDBN} and is activated by specifying using the
19571 @option{--interpreter} command line option (@pxref{Mode Options}). It
19572 is specifically intended to support the development of systems which
19573 use the debugger as just one small component of a larger system.
19575 This chapter is a specification of the @sc{gdb/mi} interface. It is written
19576 in the form of a reference manual.
19578 Note that @sc{gdb/mi} is still under construction, so some of the
19579 features described below are incomplete and subject to change
19580 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
19582 @unnumberedsec Notation and Terminology
19584 @cindex notational conventions, for @sc{gdb/mi}
19585 This chapter uses the following notation:
19589 @code{|} separates two alternatives.
19592 @code{[ @var{something} ]} indicates that @var{something} is optional:
19593 it may or may not be given.
19596 @code{( @var{group} )*} means that @var{group} inside the parentheses
19597 may repeat zero or more times.
19600 @code{( @var{group} )+} means that @var{group} inside the parentheses
19601 may repeat one or more times.
19604 @code{"@var{string}"} means a literal @var{string}.
19608 @heading Dependencies
19612 * GDB/MI General Design::
19613 * GDB/MI Command Syntax::
19614 * GDB/MI Compatibility with CLI::
19615 * GDB/MI Development and Front Ends::
19616 * GDB/MI Output Records::
19617 * GDB/MI Simple Examples::
19618 * GDB/MI Command Description Format::
19619 * GDB/MI Breakpoint Commands::
19620 * GDB/MI Program Context::
19621 * GDB/MI Thread Commands::
19622 * GDB/MI Program Execution::
19623 * GDB/MI Stack Manipulation::
19624 * GDB/MI Variable Objects::
19625 * GDB/MI Data Manipulation::
19626 * GDB/MI Tracepoint Commands::
19627 * GDB/MI Symbol Query::
19628 * GDB/MI File Commands::
19630 * GDB/MI Kod Commands::
19631 * GDB/MI Memory Overlay Commands::
19632 * GDB/MI Signal Handling Commands::
19634 * GDB/MI Target Manipulation::
19635 * GDB/MI File Transfer Commands::
19636 * GDB/MI Miscellaneous Commands::
19639 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19640 @node GDB/MI General Design
19641 @section @sc{gdb/mi} General Design
19642 @cindex GDB/MI General Design
19644 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
19645 parts---commands sent to @value{GDBN}, responses to those commands
19646 and notifications. Each command results in exactly one response,
19647 indicating either successful completion of the command, or an error.
19648 For the commands that do not resume the target, the response contains the
19649 requested information. For the commands that resume the target, the
19650 response only indicates whether the target was successfully resumed.
19651 Notifications is the mechanism for reporting changes in the state of the
19652 target, or in @value{GDBN} state, that cannot conveniently be associated with
19653 a command and reported as part of that command response.
19655 The important examples of notifications are:
19659 Exec notifications. These are used to report changes in
19660 target state---when a target is resumed, or stopped. It would not
19661 be feasible to include this information in response of resuming
19662 commands, because one resume commands can result in multiple events in
19663 different threads. Also, quite some time may pass before any event
19664 happens in the target, while a frontend needs to know whether the resuming
19665 command itself was successfully executed.
19668 Console output, and status notifications. Console output
19669 notifications are used to report output of CLI commands, as well as
19670 diagnostics for other commands. Status notifications are used to
19671 report the progress of a long-running operation. Naturally, including
19672 this information in command response would mean no output is produced
19673 until the command is finished, which is undesirable.
19676 General notifications. Commands may have various side effects on
19677 the @value{GDBN} or target state beyond their official purpose. For example,
19678 a command may change the selected thread. Although such changes can
19679 be included in command response, using notification allows for more
19680 orthogonal frontend design.
19684 There's no guarantee that whenever an MI command reports an error,
19685 @value{GDBN} or the target are in any specific state, and especially,
19686 the state is not reverted to the state before the MI command was
19687 processed. Therefore, whenever an MI command results in an error,
19688 we recommend that the frontend refreshes all the information shown in
19689 the user interface.
19691 @subsection Context management
19693 In most cases when @value{GDBN} accesses the target, this access is
19694 done in context of a specific thread and frame (@pxref{Frames}).
19695 Often, even when accessing global data, the target requires that a thread
19696 be specified. The CLI interface maintains the selected thread and frame,
19697 and supplies them to target on each command. This is convenient,
19698 because a command line user would not want to specify that information
19699 explicitly on each command, and because user interacts with
19700 @value{GDBN} via a single terminal, so no confusion is possible as
19701 to what thread and frame are the current ones.
19703 In the case of MI, the concept of selected thread and frame is less
19704 useful. First, a frontend can easily remember this information
19705 itself. Second, a graphical frontend can have more than one window,
19706 each one used for debugging a different thread, and the frontend might
19707 want to access additional threads for internal purposes. This
19708 increases the risk that by relying on implicitly selected thread, the
19709 frontend may be operating on a wrong one. Therefore, each MI command
19710 should explicitly specify which thread and frame to operate on. To
19711 make it possible, each MI command accepts the @samp{--thread} and
19712 @samp{--frame} options, the value to each is @value{GDBN} identifier
19713 for thread and frame to operate on.
19715 Usually, each top-level window in a frontend allows the user to select
19716 a thread and a frame, and remembers the user selection for further
19717 operations. However, in some cases @value{GDBN} may suggest that the
19718 current thread be changed. For example, when stopping on a breakpoint
19719 it is reasonable to switch to the thread where breakpoint is hit. For
19720 another example, if the user issues the CLI @samp{thread} command via
19721 the frontend, it is desirable to change the frontend's selected thread to the
19722 one specified by user. @value{GDBN} communicates the suggestion to
19723 change current thread using the @samp{=thread-selected} notification.
19724 No such notification is available for the selected frame at the moment.
19726 Note that historically, MI shares the selected thread with CLI, so
19727 frontends used the @code{-thread-select} to execute commands in the
19728 right context. However, getting this to work right is cumbersome. The
19729 simplest way is for frontend to emit @code{-thread-select} command
19730 before every command. This doubles the number of commands that need
19731 to be sent. The alternative approach is to suppress @code{-thread-select}
19732 if the selected thread in @value{GDBN} is supposed to be identical to the
19733 thread the frontend wants to operate on. However, getting this
19734 optimization right can be tricky. In particular, if the frontend
19735 sends several commands to @value{GDBN}, and one of the commands changes the
19736 selected thread, then the behaviour of subsequent commands will
19737 change. So, a frontend should either wait for response from such
19738 problematic commands, or explicitly add @code{-thread-select} for
19739 all subsequent commands. No frontend is known to do this exactly
19740 right, so it is suggested to just always pass the @samp{--thread} and
19741 @samp{--frame} options.
19743 @subsection Asynchronous command execution and non-stop mode
19745 On some targets, @value{GDBN} is capable of processing MI commands
19746 even while the target is running. This is called @dfn{asynchronous
19747 command execution} (@pxref{Background Execution}). The frontend may
19748 specify a preferrence for asynchronous execution using the
19749 @code{-gdb-set target-async 1} command, which should be emitted before
19750 either running the executable or attaching to the target. After the
19751 frontend has started the executable or attached to the target, it can
19752 find if asynchronous execution is enabled using the
19753 @code{-list-target-features} command.
19755 Even if @value{GDBN} can accept a command while target is running,
19756 many commands that access the target do not work when the target is
19757 running. Therefore, asynchronous command execution is most useful
19758 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
19759 it is possible to examine the state of one thread, while other threads
19762 When a given thread is running, MI commands that try to access the
19763 target in the context of that thread may not work, or may work only on
19764 some targets. In particular, commands that try to operate on thread's
19765 stack will not work, on any target. Commands that read memory, or
19766 modify breakpoints, may work or not work, depending on the target. Note
19767 that even commands that operate on global state, such as @code{print},
19768 @code{set}, and breakpoint commands, still access the target in the
19769 context of a specific thread, so frontend should try to find a
19770 stopped thread and perform the operation on that thread (using the
19771 @samp{--thread} option).
19773 Which commands will work in the context of a running thread is
19774 highly target dependent. However, the two commands
19775 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
19776 to find the state of a thread, will always work.
19778 @subsection Thread groups
19779 @value{GDBN} may be used to debug several processes at the same time.
19780 On some platfroms, @value{GDBN} may support debugging of several
19781 hardware systems, each one having several cores with several different
19782 processes running on each core. This section describes the MI
19783 mechanism to support such debugging scenarios.
19785 The key observation is that regardless of the structure of the
19786 target, MI can have a global list of threads, because most commands that
19787 accept the @samp{--thread} option do not need to know what process that
19788 thread belongs to. Therefore, it is not necessary to introduce
19789 neither additional @samp{--process} option, nor an notion of the
19790 current process in the MI interface. The only strictly new feature
19791 that is required is the ability to find how the threads are grouped
19794 To allow the user to discover such grouping, and to support arbitrary
19795 hierarchy of machines/cores/processes, MI introduces the concept of a
19796 @dfn{thread group}. Thread group is a collection of threads and other
19797 thread groups. A thread group always has a string identifier, a type,
19798 and may have additional attributes specific to the type. A new
19799 command, @code{-list-thread-groups}, returns the list of top-level
19800 thread groups, which correspond to processes that @value{GDBN} is
19801 debugging at the moment. By passing an identifier of a thread group
19802 to the @code{-list-thread-groups} command, it is possible to obtain
19803 the members of specific thread group.
19805 To allow the user to easily discover processes, and other objects, he
19806 wishes to debug, a concept of @dfn{available thread group} is
19807 introduced. Available thread group is an thread group that
19808 @value{GDBN} is not debugging, but that can be attached to, using the
19809 @code{-target-attach} command. The list of available top-level thread
19810 groups can be obtained using @samp{-list-thread-groups --available}.
19811 In general, the content of a thread group may be only retrieved only
19812 after attaching to that thread group.
19814 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19815 @node GDB/MI Command Syntax
19816 @section @sc{gdb/mi} Command Syntax
19819 * GDB/MI Input Syntax::
19820 * GDB/MI Output Syntax::
19823 @node GDB/MI Input Syntax
19824 @subsection @sc{gdb/mi} Input Syntax
19826 @cindex input syntax for @sc{gdb/mi}
19827 @cindex @sc{gdb/mi}, input syntax
19829 @item @var{command} @expansion{}
19830 @code{@var{cli-command} | @var{mi-command}}
19832 @item @var{cli-command} @expansion{}
19833 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
19834 @var{cli-command} is any existing @value{GDBN} CLI command.
19836 @item @var{mi-command} @expansion{}
19837 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
19838 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
19840 @item @var{token} @expansion{}
19841 "any sequence of digits"
19843 @item @var{option} @expansion{}
19844 @code{"-" @var{parameter} [ " " @var{parameter} ]}
19846 @item @var{parameter} @expansion{}
19847 @code{@var{non-blank-sequence} | @var{c-string}}
19849 @item @var{operation} @expansion{}
19850 @emph{any of the operations described in this chapter}
19852 @item @var{non-blank-sequence} @expansion{}
19853 @emph{anything, provided it doesn't contain special characters such as
19854 "-", @var{nl}, """ and of course " "}
19856 @item @var{c-string} @expansion{}
19857 @code{""" @var{seven-bit-iso-c-string-content} """}
19859 @item @var{nl} @expansion{}
19868 The CLI commands are still handled by the @sc{mi} interpreter; their
19869 output is described below.
19872 The @code{@var{token}}, when present, is passed back when the command
19876 Some @sc{mi} commands accept optional arguments as part of the parameter
19877 list. Each option is identified by a leading @samp{-} (dash) and may be
19878 followed by an optional argument parameter. Options occur first in the
19879 parameter list and can be delimited from normal parameters using
19880 @samp{--} (this is useful when some parameters begin with a dash).
19887 We want easy access to the existing CLI syntax (for debugging).
19890 We want it to be easy to spot a @sc{mi} operation.
19893 @node GDB/MI Output Syntax
19894 @subsection @sc{gdb/mi} Output Syntax
19896 @cindex output syntax of @sc{gdb/mi}
19897 @cindex @sc{gdb/mi}, output syntax
19898 The output from @sc{gdb/mi} consists of zero or more out-of-band records
19899 followed, optionally, by a single result record. This result record
19900 is for the most recent command. The sequence of output records is
19901 terminated by @samp{(gdb)}.
19903 If an input command was prefixed with a @code{@var{token}} then the
19904 corresponding output for that command will also be prefixed by that same
19908 @item @var{output} @expansion{}
19909 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
19911 @item @var{result-record} @expansion{}
19912 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
19914 @item @var{out-of-band-record} @expansion{}
19915 @code{@var{async-record} | @var{stream-record}}
19917 @item @var{async-record} @expansion{}
19918 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
19920 @item @var{exec-async-output} @expansion{}
19921 @code{[ @var{token} ] "*" @var{async-output}}
19923 @item @var{status-async-output} @expansion{}
19924 @code{[ @var{token} ] "+" @var{async-output}}
19926 @item @var{notify-async-output} @expansion{}
19927 @code{[ @var{token} ] "=" @var{async-output}}
19929 @item @var{async-output} @expansion{}
19930 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
19932 @item @var{result-class} @expansion{}
19933 @code{"done" | "running" | "connected" | "error" | "exit"}
19935 @item @var{async-class} @expansion{}
19936 @code{"stopped" | @var{others}} (where @var{others} will be added
19937 depending on the needs---this is still in development).
19939 @item @var{result} @expansion{}
19940 @code{ @var{variable} "=" @var{value}}
19942 @item @var{variable} @expansion{}
19943 @code{ @var{string} }
19945 @item @var{value} @expansion{}
19946 @code{ @var{const} | @var{tuple} | @var{list} }
19948 @item @var{const} @expansion{}
19949 @code{@var{c-string}}
19951 @item @var{tuple} @expansion{}
19952 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
19954 @item @var{list} @expansion{}
19955 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
19956 @var{result} ( "," @var{result} )* "]" }
19958 @item @var{stream-record} @expansion{}
19959 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
19961 @item @var{console-stream-output} @expansion{}
19962 @code{"~" @var{c-string}}
19964 @item @var{target-stream-output} @expansion{}
19965 @code{"@@" @var{c-string}}
19967 @item @var{log-stream-output} @expansion{}
19968 @code{"&" @var{c-string}}
19970 @item @var{nl} @expansion{}
19973 @item @var{token} @expansion{}
19974 @emph{any sequence of digits}.
19982 All output sequences end in a single line containing a period.
19985 The @code{@var{token}} is from the corresponding request. Note that
19986 for all async output, while the token is allowed by the grammar and
19987 may be output by future versions of @value{GDBN} for select async
19988 output messages, it is generally omitted. Frontends should treat
19989 all async output as reporting general changes in the state of the
19990 target and there should be no need to associate async output to any
19994 @cindex status output in @sc{gdb/mi}
19995 @var{status-async-output} contains on-going status information about the
19996 progress of a slow operation. It can be discarded. All status output is
19997 prefixed by @samp{+}.
20000 @cindex async output in @sc{gdb/mi}
20001 @var{exec-async-output} contains asynchronous state change on the target
20002 (stopped, started, disappeared). All async output is prefixed by
20006 @cindex notify output in @sc{gdb/mi}
20007 @var{notify-async-output} contains supplementary information that the
20008 client should handle (e.g., a new breakpoint information). All notify
20009 output is prefixed by @samp{=}.
20012 @cindex console output in @sc{gdb/mi}
20013 @var{console-stream-output} is output that should be displayed as is in the
20014 console. It is the textual response to a CLI command. All the console
20015 output is prefixed by @samp{~}.
20018 @cindex target output in @sc{gdb/mi}
20019 @var{target-stream-output} is the output produced by the target program.
20020 All the target output is prefixed by @samp{@@}.
20023 @cindex log output in @sc{gdb/mi}
20024 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
20025 instance messages that should be displayed as part of an error log. All
20026 the log output is prefixed by @samp{&}.
20029 @cindex list output in @sc{gdb/mi}
20030 New @sc{gdb/mi} commands should only output @var{lists} containing
20036 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
20037 details about the various output records.
20039 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20040 @node GDB/MI Compatibility with CLI
20041 @section @sc{gdb/mi} Compatibility with CLI
20043 @cindex compatibility, @sc{gdb/mi} and CLI
20044 @cindex @sc{gdb/mi}, compatibility with CLI
20046 For the developers convenience CLI commands can be entered directly,
20047 but there may be some unexpected behaviour. For example, commands
20048 that query the user will behave as if the user replied yes, breakpoint
20049 command lists are not executed and some CLI commands, such as
20050 @code{if}, @code{when} and @code{define}, prompt for further input with
20051 @samp{>}, which is not valid MI output.
20053 This feature may be removed at some stage in the future and it is
20054 recommended that front ends use the @code{-interpreter-exec} command
20055 (@pxref{-interpreter-exec}).
20057 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20058 @node GDB/MI Development and Front Ends
20059 @section @sc{gdb/mi} Development and Front Ends
20060 @cindex @sc{gdb/mi} development
20062 The application which takes the MI output and presents the state of the
20063 program being debugged to the user is called a @dfn{front end}.
20065 Although @sc{gdb/mi} is still incomplete, it is currently being used
20066 by a variety of front ends to @value{GDBN}. This makes it difficult
20067 to introduce new functionality without breaking existing usage. This
20068 section tries to minimize the problems by describing how the protocol
20071 Some changes in MI need not break a carefully designed front end, and
20072 for these the MI version will remain unchanged. The following is a
20073 list of changes that may occur within one level, so front ends should
20074 parse MI output in a way that can handle them:
20078 New MI commands may be added.
20081 New fields may be added to the output of any MI command.
20084 The range of values for fields with specified values, e.g.,
20085 @code{in_scope} (@pxref{-var-update}) may be extended.
20087 @c The format of field's content e.g type prefix, may change so parse it
20088 @c at your own risk. Yes, in general?
20090 @c The order of fields may change? Shouldn't really matter but it might
20091 @c resolve inconsistencies.
20094 If the changes are likely to break front ends, the MI version level
20095 will be increased by one. This will allow the front end to parse the
20096 output according to the MI version. Apart from mi0, new versions of
20097 @value{GDBN} will not support old versions of MI and it will be the
20098 responsibility of the front end to work with the new one.
20100 @c Starting with mi3, add a new command -mi-version that prints the MI
20103 The best way to avoid unexpected changes in MI that might break your front
20104 end is to make your project known to @value{GDBN} developers and
20105 follow development on @email{gdb@@sourceware.org} and
20106 @email{gdb-patches@@sourceware.org}.
20107 @cindex mailing lists
20109 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20110 @node GDB/MI Output Records
20111 @section @sc{gdb/mi} Output Records
20114 * GDB/MI Result Records::
20115 * GDB/MI Stream Records::
20116 * GDB/MI Async Records::
20117 * GDB/MI Frame Information::
20120 @node GDB/MI Result Records
20121 @subsection @sc{gdb/mi} Result Records
20123 @cindex result records in @sc{gdb/mi}
20124 @cindex @sc{gdb/mi}, result records
20125 In addition to a number of out-of-band notifications, the response to a
20126 @sc{gdb/mi} command includes one of the following result indications:
20130 @item "^done" [ "," @var{results} ]
20131 The synchronous operation was successful, @code{@var{results}} are the return
20136 @c Is this one correct? Should it be an out-of-band notification?
20137 The asynchronous operation was successfully started. The target is
20142 @value{GDBN} has connected to a remote target.
20144 @item "^error" "," @var{c-string}
20146 The operation failed. The @code{@var{c-string}} contains the corresponding
20151 @value{GDBN} has terminated.
20155 @node GDB/MI Stream Records
20156 @subsection @sc{gdb/mi} Stream Records
20158 @cindex @sc{gdb/mi}, stream records
20159 @cindex stream records in @sc{gdb/mi}
20160 @value{GDBN} internally maintains a number of output streams: the console, the
20161 target, and the log. The output intended for each of these streams is
20162 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
20164 Each stream record begins with a unique @dfn{prefix character} which
20165 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
20166 Syntax}). In addition to the prefix, each stream record contains a
20167 @code{@var{string-output}}. This is either raw text (with an implicit new
20168 line) or a quoted C string (which does not contain an implicit newline).
20171 @item "~" @var{string-output}
20172 The console output stream contains text that should be displayed in the
20173 CLI console window. It contains the textual responses to CLI commands.
20175 @item "@@" @var{string-output}
20176 The target output stream contains any textual output from the running
20177 target. This is only present when GDB's event loop is truly
20178 asynchronous, which is currently only the case for remote targets.
20180 @item "&" @var{string-output}
20181 The log stream contains debugging messages being produced by @value{GDBN}'s
20185 @node GDB/MI Async Records
20186 @subsection @sc{gdb/mi} Async Records
20188 @cindex async records in @sc{gdb/mi}
20189 @cindex @sc{gdb/mi}, async records
20190 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
20191 additional changes that have occurred. Those changes can either be a
20192 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
20193 target activity (e.g., target stopped).
20195 The following is the list of possible async records:
20199 @item *running,thread-id="@var{thread}"
20200 The target is now running. The @var{thread} field tells which
20201 specific thread is now running, and can be @samp{all} if all threads
20202 are running. The frontend should assume that no interaction with a
20203 running thread is possible after this notification is produced.
20204 The frontend should not assume that this notification is output
20205 only once for any command. @value{GDBN} may emit this notification
20206 several times, either for different threads, because it cannot resume
20207 all threads together, or even for a single thread, if the thread must
20208 be stepped though some code before letting it run freely.
20210 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}"
20211 The target has stopped. The @var{reason} field can have one of the
20215 @item breakpoint-hit
20216 A breakpoint was reached.
20217 @item watchpoint-trigger
20218 A watchpoint was triggered.
20219 @item read-watchpoint-trigger
20220 A read watchpoint was triggered.
20221 @item access-watchpoint-trigger
20222 An access watchpoint was triggered.
20223 @item function-finished
20224 An -exec-finish or similar CLI command was accomplished.
20225 @item location-reached
20226 An -exec-until or similar CLI command was accomplished.
20227 @item watchpoint-scope
20228 A watchpoint has gone out of scope.
20229 @item end-stepping-range
20230 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
20231 similar CLI command was accomplished.
20232 @item exited-signalled
20233 The inferior exited because of a signal.
20235 The inferior exited.
20236 @item exited-normally
20237 The inferior exited normally.
20238 @item signal-received
20239 A signal was received by the inferior.
20242 The @var{id} field identifies the thread that directly caused the stop
20243 -- for example by hitting a breakpoint. Depending on whether all-stop
20244 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
20245 stop all threads, or only the thread that directly triggered the stop.
20246 If all threads are stopped, the @var{stopped} field will have the
20247 value of @code{"all"}. Otherwise, the value of the @var{stopped}
20248 field will be a list of thread identifiers. Presently, this list will
20249 always include a single thread, but frontend should be prepared to see
20250 several threads in the list.
20252 @item =thread-group-created,id="@var{id}"
20253 @itemx =thread-group-exited,id="@var{id}"
20254 A thread thread group either was attached to, or has exited/detached
20255 from. The @var{id} field contains the @value{GDBN} identifier of the
20258 @item =thread-created,id="@var{id}",group-id="@var{gid}"
20259 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
20260 A thread either was created, or has exited. The @var{id} field
20261 contains the @value{GDBN} identifier of the thread. The @var{gid}
20262 field identifies the thread group this thread belongs to.
20264 @item =thread-selected,id="@var{id}"
20265 Informs that the selected thread was changed as result of the last
20266 command. This notification is not emitted as result of @code{-thread-select}
20267 command but is emitted whenever an MI command that is not documented
20268 to change the selected thread actually changes it. In particular,
20269 invoking, directly or indirectly (via user-defined command), the CLI
20270 @code{thread} command, will generate this notification.
20272 We suggest that in response to this notification, front ends
20273 highlight the selected thread and cause subsequent commands to apply to
20276 @item =library-loaded,...
20277 Reports that a new library file was loaded by the program. This
20278 notification has 4 fields---@var{id}, @var{target-name},
20279 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
20280 opaque identifier of the library. For remote debugging case,
20281 @var{target-name} and @var{host-name} fields give the name of the
20282 library file on the target, and on the host respectively. For native
20283 debugging, both those fields have the same value. The
20284 @var{symbols-loaded} field reports if the debug symbols for this
20285 library are loaded.
20287 @item =library-unloaded,...
20288 Reports that a library was unloaded by the program. This notification
20289 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
20290 the same meaning as for the @code{=library-loaded} notification
20294 @node GDB/MI Frame Information
20295 @subsection @sc{gdb/mi} Frame Information
20297 Response from many MI commands includes an information about stack
20298 frame. This information is a tuple that may have the following
20303 The level of the stack frame. The innermost frame has the level of
20304 zero. This field is always present.
20307 The name of the function corresponding to the frame. This field may
20308 be absent if @value{GDBN} is unable to determine the function name.
20311 The code address for the frame. This field is always present.
20314 The name of the source files that correspond to the frame's code
20315 address. This field may be absent.
20318 The source line corresponding to the frames' code address. This field
20322 The name of the binary file (either executable or shared library) the
20323 corresponds to the frame's code address. This field may be absent.
20328 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20329 @node GDB/MI Simple Examples
20330 @section Simple Examples of @sc{gdb/mi} Interaction
20331 @cindex @sc{gdb/mi}, simple examples
20333 This subsection presents several simple examples of interaction using
20334 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
20335 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
20336 the output received from @sc{gdb/mi}.
20338 Note the line breaks shown in the examples are here only for
20339 readability, they don't appear in the real output.
20341 @subheading Setting a Breakpoint
20343 Setting a breakpoint generates synchronous output which contains detailed
20344 information of the breakpoint.
20347 -> -break-insert main
20348 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20349 enabled="y",addr="0x08048564",func="main",file="myprog.c",
20350 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
20354 @subheading Program Execution
20356 Program execution generates asynchronous records and MI gives the
20357 reason that execution stopped.
20363 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
20364 frame=@{addr="0x08048564",func="main",
20365 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
20366 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
20371 <- *stopped,reason="exited-normally"
20375 @subheading Quitting @value{GDBN}
20377 Quitting @value{GDBN} just prints the result class @samp{^exit}.
20385 @subheading A Bad Command
20387 Here's what happens if you pass a non-existent command:
20391 <- ^error,msg="Undefined MI command: rubbish"
20396 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20397 @node GDB/MI Command Description Format
20398 @section @sc{gdb/mi} Command Description Format
20400 The remaining sections describe blocks of commands. Each block of
20401 commands is laid out in a fashion similar to this section.
20403 @subheading Motivation
20405 The motivation for this collection of commands.
20407 @subheading Introduction
20409 A brief introduction to this collection of commands as a whole.
20411 @subheading Commands
20413 For each command in the block, the following is described:
20415 @subsubheading Synopsis
20418 -command @var{args}@dots{}
20421 @subsubheading Result
20423 @subsubheading @value{GDBN} Command
20425 The corresponding @value{GDBN} CLI command(s), if any.
20427 @subsubheading Example
20429 Example(s) formatted for readability. Some of the described commands have
20430 not been implemented yet and these are labeled N.A.@: (not available).
20433 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20434 @node GDB/MI Breakpoint Commands
20435 @section @sc{gdb/mi} Breakpoint Commands
20437 @cindex breakpoint commands for @sc{gdb/mi}
20438 @cindex @sc{gdb/mi}, breakpoint commands
20439 This section documents @sc{gdb/mi} commands for manipulating
20442 @subheading The @code{-break-after} Command
20443 @findex -break-after
20445 @subsubheading Synopsis
20448 -break-after @var{number} @var{count}
20451 The breakpoint number @var{number} is not in effect until it has been
20452 hit @var{count} times. To see how this is reflected in the output of
20453 the @samp{-break-list} command, see the description of the
20454 @samp{-break-list} command below.
20456 @subsubheading @value{GDBN} Command
20458 The corresponding @value{GDBN} command is @samp{ignore}.
20460 @subsubheading Example
20465 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20466 enabled="y",addr="0x000100d0",func="main",file="hello.c",
20467 fullname="/home/foo/hello.c",line="5",times="0"@}
20474 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20475 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20476 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20477 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20478 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20479 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20480 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20481 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20482 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20483 line="5",times="0",ignore="3"@}]@}
20488 @subheading The @code{-break-catch} Command
20489 @findex -break-catch
20491 @subheading The @code{-break-commands} Command
20492 @findex -break-commands
20496 @subheading The @code{-break-condition} Command
20497 @findex -break-condition
20499 @subsubheading Synopsis
20502 -break-condition @var{number} @var{expr}
20505 Breakpoint @var{number} will stop the program only if the condition in
20506 @var{expr} is true. The condition becomes part of the
20507 @samp{-break-list} output (see the description of the @samp{-break-list}
20510 @subsubheading @value{GDBN} Command
20512 The corresponding @value{GDBN} command is @samp{condition}.
20514 @subsubheading Example
20518 -break-condition 1 1
20522 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20523 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20524 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20525 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20526 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20527 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20528 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20529 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20530 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20531 line="5",cond="1",times="0",ignore="3"@}]@}
20535 @subheading The @code{-break-delete} Command
20536 @findex -break-delete
20538 @subsubheading Synopsis
20541 -break-delete ( @var{breakpoint} )+
20544 Delete the breakpoint(s) whose number(s) are specified in the argument
20545 list. This is obviously reflected in the breakpoint list.
20547 @subsubheading @value{GDBN} Command
20549 The corresponding @value{GDBN} command is @samp{delete}.
20551 @subsubheading Example
20559 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20560 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20561 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20562 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20563 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20564 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20565 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20570 @subheading The @code{-break-disable} Command
20571 @findex -break-disable
20573 @subsubheading Synopsis
20576 -break-disable ( @var{breakpoint} )+
20579 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
20580 break list is now set to @samp{n} for the named @var{breakpoint}(s).
20582 @subsubheading @value{GDBN} Command
20584 The corresponding @value{GDBN} command is @samp{disable}.
20586 @subsubheading Example
20594 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20595 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20596 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20597 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20598 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20599 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20600 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20601 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
20602 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20603 line="5",times="0"@}]@}
20607 @subheading The @code{-break-enable} Command
20608 @findex -break-enable
20610 @subsubheading Synopsis
20613 -break-enable ( @var{breakpoint} )+
20616 Enable (previously disabled) @var{breakpoint}(s).
20618 @subsubheading @value{GDBN} Command
20620 The corresponding @value{GDBN} command is @samp{enable}.
20622 @subsubheading Example
20630 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20631 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20632 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20633 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20634 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20635 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20636 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20637 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20638 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20639 line="5",times="0"@}]@}
20643 @subheading The @code{-break-info} Command
20644 @findex -break-info
20646 @subsubheading Synopsis
20649 -break-info @var{breakpoint}
20653 Get information about a single breakpoint.
20655 @subsubheading @value{GDBN} Command
20657 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
20659 @subsubheading Example
20662 @subheading The @code{-break-insert} Command
20663 @findex -break-insert
20665 @subsubheading Synopsis
20668 -break-insert [ -t ] [ -h ] [ -f ] [ -d ]
20669 [ -c @var{condition} ] [ -i @var{ignore-count} ]
20670 [ -p @var{thread} ] [ @var{location} ]
20674 If specified, @var{location}, can be one of:
20681 @item filename:linenum
20682 @item filename:function
20686 The possible optional parameters of this command are:
20690 Insert a temporary breakpoint.
20692 Insert a hardware breakpoint.
20693 @item -c @var{condition}
20694 Make the breakpoint conditional on @var{condition}.
20695 @item -i @var{ignore-count}
20696 Initialize the @var{ignore-count}.
20698 If @var{location} cannot be parsed (for example if it
20699 refers to unknown files or functions), create a pending
20700 breakpoint. Without this flag, @value{GDBN} will report
20701 an error, and won't create a breakpoint, if @var{location}
20704 Create a disabled breakpoint.
20707 @subsubheading Result
20709 The result is in the form:
20712 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
20713 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
20714 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
20715 times="@var{times}"@}
20719 where @var{number} is the @value{GDBN} number for this breakpoint,
20720 @var{funcname} is the name of the function where the breakpoint was
20721 inserted, @var{filename} is the name of the source file which contains
20722 this function, @var{lineno} is the source line number within that file
20723 and @var{times} the number of times that the breakpoint has been hit
20724 (always 0 for -break-insert but may be greater for -break-info or -break-list
20725 which use the same output).
20727 Note: this format is open to change.
20728 @c An out-of-band breakpoint instead of part of the result?
20730 @subsubheading @value{GDBN} Command
20732 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
20733 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
20735 @subsubheading Example
20740 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
20741 fullname="/home/foo/recursive2.c,line="4",times="0"@}
20743 -break-insert -t foo
20744 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
20745 fullname="/home/foo/recursive2.c,line="11",times="0"@}
20748 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20749 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20750 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20751 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20752 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20753 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20754 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20755 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20756 addr="0x0001072c", func="main",file="recursive2.c",
20757 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
20758 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
20759 addr="0x00010774",func="foo",file="recursive2.c",
20760 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
20762 -break-insert -r foo.*
20763 ~int foo(int, int);
20764 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
20765 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
20769 @subheading The @code{-break-list} Command
20770 @findex -break-list
20772 @subsubheading Synopsis
20778 Displays the list of inserted breakpoints, showing the following fields:
20782 number of the breakpoint
20784 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
20786 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
20789 is the breakpoint enabled or no: @samp{y} or @samp{n}
20791 memory location at which the breakpoint is set
20793 logical location of the breakpoint, expressed by function name, file
20796 number of times the breakpoint has been hit
20799 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
20800 @code{body} field is an empty list.
20802 @subsubheading @value{GDBN} Command
20804 The corresponding @value{GDBN} command is @samp{info break}.
20806 @subsubheading Example
20811 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20812 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20813 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20814 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20815 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20816 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20817 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20818 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20819 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
20820 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20821 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
20822 line="13",times="0"@}]@}
20826 Here's an example of the result when there are no breakpoints:
20831 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20832 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20833 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20834 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20835 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20836 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20837 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20842 @subheading The @code{-break-watch} Command
20843 @findex -break-watch
20845 @subsubheading Synopsis
20848 -break-watch [ -a | -r ]
20851 Create a watchpoint. With the @samp{-a} option it will create an
20852 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
20853 read from or on a write to the memory location. With the @samp{-r}
20854 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
20855 trigger only when the memory location is accessed for reading. Without
20856 either of the options, the watchpoint created is a regular watchpoint,
20857 i.e., it will trigger when the memory location is accessed for writing.
20858 @xref{Set Watchpoints, , Setting Watchpoints}.
20860 Note that @samp{-break-list} will report a single list of watchpoints and
20861 breakpoints inserted.
20863 @subsubheading @value{GDBN} Command
20865 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
20868 @subsubheading Example
20870 Setting a watchpoint on a variable in the @code{main} function:
20875 ^done,wpt=@{number="2",exp="x"@}
20880 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
20881 value=@{old="-268439212",new="55"@},
20882 frame=@{func="main",args=[],file="recursive2.c",
20883 fullname="/home/foo/bar/recursive2.c",line="5"@}
20887 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
20888 the program execution twice: first for the variable changing value, then
20889 for the watchpoint going out of scope.
20894 ^done,wpt=@{number="5",exp="C"@}
20899 *stopped,reason="watchpoint-trigger",
20900 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
20901 frame=@{func="callee4",args=[],
20902 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20903 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20908 *stopped,reason="watchpoint-scope",wpnum="5",
20909 frame=@{func="callee3",args=[@{name="strarg",
20910 value="0x11940 \"A string argument.\""@}],
20911 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20912 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20916 Listing breakpoints and watchpoints, at different points in the program
20917 execution. Note that once the watchpoint goes out of scope, it is
20923 ^done,wpt=@{number="2",exp="C"@}
20926 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20927 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20928 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20929 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20930 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20931 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20932 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20933 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20934 addr="0x00010734",func="callee4",
20935 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20936 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
20937 bkpt=@{number="2",type="watchpoint",disp="keep",
20938 enabled="y",addr="",what="C",times="0"@}]@}
20943 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
20944 value=@{old="-276895068",new="3"@},
20945 frame=@{func="callee4",args=[],
20946 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20947 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20950 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20951 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20952 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20953 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20954 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20955 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20956 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20957 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20958 addr="0x00010734",func="callee4",
20959 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20960 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
20961 bkpt=@{number="2",type="watchpoint",disp="keep",
20962 enabled="y",addr="",what="C",times="-5"@}]@}
20966 ^done,reason="watchpoint-scope",wpnum="2",
20967 frame=@{func="callee3",args=[@{name="strarg",
20968 value="0x11940 \"A string argument.\""@}],
20969 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20970 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20973 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20974 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20975 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20976 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20977 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20978 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20979 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20980 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20981 addr="0x00010734",func="callee4",
20982 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20983 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
20988 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20989 @node GDB/MI Program Context
20990 @section @sc{gdb/mi} Program Context
20992 @subheading The @code{-exec-arguments} Command
20993 @findex -exec-arguments
20996 @subsubheading Synopsis
20999 -exec-arguments @var{args}
21002 Set the inferior program arguments, to be used in the next
21005 @subsubheading @value{GDBN} Command
21007 The corresponding @value{GDBN} command is @samp{set args}.
21009 @subsubheading Example
21013 -exec-arguments -v word
21019 @subheading The @code{-exec-show-arguments} Command
21020 @findex -exec-show-arguments
21022 @subsubheading Synopsis
21025 -exec-show-arguments
21028 Print the arguments of the program.
21030 @subsubheading @value{GDBN} Command
21032 The corresponding @value{GDBN} command is @samp{show args}.
21034 @subsubheading Example
21038 @subheading The @code{-environment-cd} Command
21039 @findex -environment-cd
21041 @subsubheading Synopsis
21044 -environment-cd @var{pathdir}
21047 Set @value{GDBN}'s working directory.
21049 @subsubheading @value{GDBN} Command
21051 The corresponding @value{GDBN} command is @samp{cd}.
21053 @subsubheading Example
21057 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
21063 @subheading The @code{-environment-directory} Command
21064 @findex -environment-directory
21066 @subsubheading Synopsis
21069 -environment-directory [ -r ] [ @var{pathdir} ]+
21072 Add directories @var{pathdir} to beginning of search path for source files.
21073 If the @samp{-r} option is used, the search path is reset to the default
21074 search path. If directories @var{pathdir} are supplied in addition to the
21075 @samp{-r} option, the search path is first reset and then addition
21077 Multiple directories may be specified, separated by blanks. Specifying
21078 multiple directories in a single command
21079 results in the directories added to the beginning of the
21080 search path in the same order they were presented in the command.
21081 If blanks are needed as
21082 part of a directory name, double-quotes should be used around
21083 the name. In the command output, the path will show up separated
21084 by the system directory-separator character. The directory-separator
21085 character must not be used
21086 in any directory name.
21087 If no directories are specified, the current search path is displayed.
21089 @subsubheading @value{GDBN} Command
21091 The corresponding @value{GDBN} command is @samp{dir}.
21093 @subsubheading Example
21097 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
21098 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
21100 -environment-directory ""
21101 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
21103 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
21104 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
21106 -environment-directory -r
21107 ^done,source-path="$cdir:$cwd"
21112 @subheading The @code{-environment-path} Command
21113 @findex -environment-path
21115 @subsubheading Synopsis
21118 -environment-path [ -r ] [ @var{pathdir} ]+
21121 Add directories @var{pathdir} to beginning of search path for object files.
21122 If the @samp{-r} option is used, the search path is reset to the original
21123 search path that existed at gdb start-up. If directories @var{pathdir} are
21124 supplied in addition to the
21125 @samp{-r} option, the search path is first reset and then addition
21127 Multiple directories may be specified, separated by blanks. Specifying
21128 multiple directories in a single command
21129 results in the directories added to the beginning of the
21130 search path in the same order they were presented in the command.
21131 If blanks are needed as
21132 part of a directory name, double-quotes should be used around
21133 the name. In the command output, the path will show up separated
21134 by the system directory-separator character. The directory-separator
21135 character must not be used
21136 in any directory name.
21137 If no directories are specified, the current path is displayed.
21140 @subsubheading @value{GDBN} Command
21142 The corresponding @value{GDBN} command is @samp{path}.
21144 @subsubheading Example
21149 ^done,path="/usr/bin"
21151 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
21152 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
21154 -environment-path -r /usr/local/bin
21155 ^done,path="/usr/local/bin:/usr/bin"
21160 @subheading The @code{-environment-pwd} Command
21161 @findex -environment-pwd
21163 @subsubheading Synopsis
21169 Show the current working directory.
21171 @subsubheading @value{GDBN} Command
21173 The corresponding @value{GDBN} command is @samp{pwd}.
21175 @subsubheading Example
21180 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
21184 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21185 @node GDB/MI Thread Commands
21186 @section @sc{gdb/mi} Thread Commands
21189 @subheading The @code{-thread-info} Command
21190 @findex -thread-info
21192 @subsubheading Synopsis
21195 -thread-info [ @var{thread-id} ]
21198 Reports information about either a specific thread, if
21199 the @var{thread-id} parameter is present, or about all
21200 threads. When printing information about all threads,
21201 also reports the current thread.
21203 @subsubheading @value{GDBN} Command
21205 The @samp{info thread} command prints the same information
21208 @subsubheading Example
21213 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
21214 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
21215 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
21216 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
21217 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
21218 current-thread-id="1"
21222 The @samp{state} field may have the following values:
21226 The thread is stopped. Frame information is available for stopped
21230 The thread is running. There's no frame information for running
21235 @subheading The @code{-thread-list-ids} Command
21236 @findex -thread-list-ids
21238 @subsubheading Synopsis
21244 Produces a list of the currently known @value{GDBN} thread ids. At the
21245 end of the list it also prints the total number of such threads.
21247 This command is retained for historical reasons, the
21248 @code{-thread-info} command should be used instead.
21250 @subsubheading @value{GDBN} Command
21252 Part of @samp{info threads} supplies the same information.
21254 @subsubheading Example
21259 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
21260 current-thread-id="1",number-of-threads="3"
21265 @subheading The @code{-thread-select} Command
21266 @findex -thread-select
21268 @subsubheading Synopsis
21271 -thread-select @var{threadnum}
21274 Make @var{threadnum} the current thread. It prints the number of the new
21275 current thread, and the topmost frame for that thread.
21277 This command is deprecated in favor of explicitly using the
21278 @samp{--thread} option to each command.
21280 @subsubheading @value{GDBN} Command
21282 The corresponding @value{GDBN} command is @samp{thread}.
21284 @subsubheading Example
21291 *stopped,reason="end-stepping-range",thread-id="2",line="187",
21292 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
21296 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
21297 number-of-threads="3"
21300 ^done,new-thread-id="3",
21301 frame=@{level="0",func="vprintf",
21302 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
21303 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
21307 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21308 @node GDB/MI Program Execution
21309 @section @sc{gdb/mi} Program Execution
21311 These are the asynchronous commands which generate the out-of-band
21312 record @samp{*stopped}. Currently @value{GDBN} only really executes
21313 asynchronously with remote targets and this interaction is mimicked in
21316 @subheading The @code{-exec-continue} Command
21317 @findex -exec-continue
21319 @subsubheading Synopsis
21322 -exec-continue [--all|--thread-group N]
21325 Resumes the execution of the inferior program until a breakpoint is
21326 encountered, or until the inferior exits. In all-stop mode
21327 (@pxref{All-Stop Mode}), may resume only one thread, or all threads,
21328 depending on the value of the @samp{scheduler-locking} variable. In
21329 non-stop mode (@pxref{Non-Stop Mode}), if the @samp{--all} is not
21330 specified, only the thread specified with the @samp{--thread} option
21331 (or current thread, if no @samp{--thread} is provided) is resumed. If
21332 @samp{--all} is specified, all threads will be resumed. The
21333 @samp{--all} option is ignored in all-stop mode. If the
21334 @samp{--thread-group} options is specified, then all threads in that
21335 thread group are resumed.
21337 @subsubheading @value{GDBN} Command
21339 The corresponding @value{GDBN} corresponding is @samp{continue}.
21341 @subsubheading Example
21348 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
21349 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
21355 @subheading The @code{-exec-finish} Command
21356 @findex -exec-finish
21358 @subsubheading Synopsis
21364 Resumes the execution of the inferior program until the current
21365 function is exited. Displays the results returned by the function.
21367 @subsubheading @value{GDBN} Command
21369 The corresponding @value{GDBN} command is @samp{finish}.
21371 @subsubheading Example
21373 Function returning @code{void}.
21380 *stopped,reason="function-finished",frame=@{func="main",args=[],
21381 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
21385 Function returning other than @code{void}. The name of the internal
21386 @value{GDBN} variable storing the result is printed, together with the
21393 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
21394 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
21395 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21396 gdb-result-var="$1",return-value="0"
21401 @subheading The @code{-exec-interrupt} Command
21402 @findex -exec-interrupt
21404 @subsubheading Synopsis
21407 -exec-interrupt [--all|--thread-group N]
21410 Interrupts the background execution of the target. Note how the token
21411 associated with the stop message is the one for the execution command
21412 that has been interrupted. The token for the interrupt itself only
21413 appears in the @samp{^done} output. If the user is trying to
21414 interrupt a non-running program, an error message will be printed.
21416 Note that when asynchronous execution is enabled, this command is
21417 asynchronous just like other execution commands. That is, first the
21418 @samp{^done} response will be printed, and the target stop will be
21419 reported after that using the @samp{*stopped} notification.
21421 In non-stop mode, only the context thread is interrupted by default.
21422 All threads will be interrupted if the @samp{--all} option is
21423 specified. If the @samp{--thread-group} option is specified, all
21424 threads in that group will be interrupted.
21426 @subsubheading @value{GDBN} Command
21428 The corresponding @value{GDBN} command is @samp{interrupt}.
21430 @subsubheading Example
21441 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
21442 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
21443 fullname="/home/foo/bar/try.c",line="13"@}
21448 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
21452 @subheading The @code{-exec-jump} Command
21455 @subsubheading Synopsis
21458 -exec-jump @var{location}
21461 Resumes execution of the inferior program at the location specified by
21462 parameter. @xref{Specify Location}, for a description of the
21463 different forms of @var{location}.
21465 @subsubheading @value{GDBN} Command
21467 The corresponding @value{GDBN} command is @samp{jump}.
21469 @subsubheading Example
21472 -exec-jump foo.c:10
21473 *running,thread-id="all"
21478 @subheading The @code{-exec-next} Command
21481 @subsubheading Synopsis
21487 Resumes execution of the inferior program, stopping when the beginning
21488 of the next source line is reached.
21490 @subsubheading @value{GDBN} Command
21492 The corresponding @value{GDBN} command is @samp{next}.
21494 @subsubheading Example
21500 *stopped,reason="end-stepping-range",line="8",file="hello.c"
21505 @subheading The @code{-exec-next-instruction} Command
21506 @findex -exec-next-instruction
21508 @subsubheading Synopsis
21511 -exec-next-instruction
21514 Executes one machine instruction. If the instruction is a function
21515 call, continues until the function returns. If the program stops at an
21516 instruction in the middle of a source line, the address will be
21519 @subsubheading @value{GDBN} Command
21521 The corresponding @value{GDBN} command is @samp{nexti}.
21523 @subsubheading Example
21527 -exec-next-instruction
21531 *stopped,reason="end-stepping-range",
21532 addr="0x000100d4",line="5",file="hello.c"
21537 @subheading The @code{-exec-return} Command
21538 @findex -exec-return
21540 @subsubheading Synopsis
21546 Makes current function return immediately. Doesn't execute the inferior.
21547 Displays the new current frame.
21549 @subsubheading @value{GDBN} Command
21551 The corresponding @value{GDBN} command is @samp{return}.
21553 @subsubheading Example
21557 200-break-insert callee4
21558 200^done,bkpt=@{number="1",addr="0x00010734",
21559 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21564 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21565 frame=@{func="callee4",args=[],
21566 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21567 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21573 111^done,frame=@{level="0",func="callee3",
21574 args=[@{name="strarg",
21575 value="0x11940 \"A string argument.\""@}],
21576 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21577 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
21582 @subheading The @code{-exec-run} Command
21585 @subsubheading Synopsis
21591 Starts execution of the inferior from the beginning. The inferior
21592 executes until either a breakpoint is encountered or the program
21593 exits. In the latter case the output will include an exit code, if
21594 the program has exited exceptionally.
21596 @subsubheading @value{GDBN} Command
21598 The corresponding @value{GDBN} command is @samp{run}.
21600 @subsubheading Examples
21605 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
21610 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21611 frame=@{func="main",args=[],file="recursive2.c",
21612 fullname="/home/foo/bar/recursive2.c",line="4"@}
21617 Program exited normally:
21625 *stopped,reason="exited-normally"
21630 Program exited exceptionally:
21638 *stopped,reason="exited",exit-code="01"
21642 Another way the program can terminate is if it receives a signal such as
21643 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
21647 *stopped,reason="exited-signalled",signal-name="SIGINT",
21648 signal-meaning="Interrupt"
21652 @c @subheading -exec-signal
21655 @subheading The @code{-exec-step} Command
21658 @subsubheading Synopsis
21664 Resumes execution of the inferior program, stopping when the beginning
21665 of the next source line is reached, if the next source line is not a
21666 function call. If it is, stop at the first instruction of the called
21669 @subsubheading @value{GDBN} Command
21671 The corresponding @value{GDBN} command is @samp{step}.
21673 @subsubheading Example
21675 Stepping into a function:
21681 *stopped,reason="end-stepping-range",
21682 frame=@{func="foo",args=[@{name="a",value="10"@},
21683 @{name="b",value="0"@}],file="recursive2.c",
21684 fullname="/home/foo/bar/recursive2.c",line="11"@}
21694 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
21699 @subheading The @code{-exec-step-instruction} Command
21700 @findex -exec-step-instruction
21702 @subsubheading Synopsis
21705 -exec-step-instruction
21708 Resumes the inferior which executes one machine instruction. The
21709 output, once @value{GDBN} has stopped, will vary depending on whether
21710 we have stopped in the middle of a source line or not. In the former
21711 case, the address at which the program stopped will be printed as
21714 @subsubheading @value{GDBN} Command
21716 The corresponding @value{GDBN} command is @samp{stepi}.
21718 @subsubheading Example
21722 -exec-step-instruction
21726 *stopped,reason="end-stepping-range",
21727 frame=@{func="foo",args=[],file="try.c",
21728 fullname="/home/foo/bar/try.c",line="10"@}
21730 -exec-step-instruction
21734 *stopped,reason="end-stepping-range",
21735 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
21736 fullname="/home/foo/bar/try.c",line="10"@}
21741 @subheading The @code{-exec-until} Command
21742 @findex -exec-until
21744 @subsubheading Synopsis
21747 -exec-until [ @var{location} ]
21750 Executes the inferior until the @var{location} specified in the
21751 argument is reached. If there is no argument, the inferior executes
21752 until a source line greater than the current one is reached. The
21753 reason for stopping in this case will be @samp{location-reached}.
21755 @subsubheading @value{GDBN} Command
21757 The corresponding @value{GDBN} command is @samp{until}.
21759 @subsubheading Example
21763 -exec-until recursive2.c:6
21767 *stopped,reason="location-reached",frame=@{func="main",args=[],
21768 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
21773 @subheading -file-clear
21774 Is this going away????
21777 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21778 @node GDB/MI Stack Manipulation
21779 @section @sc{gdb/mi} Stack Manipulation Commands
21782 @subheading The @code{-stack-info-frame} Command
21783 @findex -stack-info-frame
21785 @subsubheading Synopsis
21791 Get info on the selected frame.
21793 @subsubheading @value{GDBN} Command
21795 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
21796 (without arguments).
21798 @subsubheading Example
21803 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
21804 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21805 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
21809 @subheading The @code{-stack-info-depth} Command
21810 @findex -stack-info-depth
21812 @subsubheading Synopsis
21815 -stack-info-depth [ @var{max-depth} ]
21818 Return the depth of the stack. If the integer argument @var{max-depth}
21819 is specified, do not count beyond @var{max-depth} frames.
21821 @subsubheading @value{GDBN} Command
21823 There's no equivalent @value{GDBN} command.
21825 @subsubheading Example
21827 For a stack with frame levels 0 through 11:
21834 -stack-info-depth 4
21837 -stack-info-depth 12
21840 -stack-info-depth 11
21843 -stack-info-depth 13
21848 @subheading The @code{-stack-list-arguments} Command
21849 @findex -stack-list-arguments
21851 @subsubheading Synopsis
21854 -stack-list-arguments @var{show-values}
21855 [ @var{low-frame} @var{high-frame} ]
21858 Display a list of the arguments for the frames between @var{low-frame}
21859 and @var{high-frame} (inclusive). If @var{low-frame} and
21860 @var{high-frame} are not provided, list the arguments for the whole
21861 call stack. If the two arguments are equal, show the single frame
21862 at the corresponding level. It is an error if @var{low-frame} is
21863 larger than the actual number of frames. On the other hand,
21864 @var{high-frame} may be larger than the actual number of frames, in
21865 which case only existing frames will be returned.
21867 The @var{show-values} argument must have a value of 0 or 1. A value of
21868 0 means that only the names of the arguments are listed, a value of 1
21869 means that both names and values of the arguments are printed.
21871 @subsubheading @value{GDBN} Command
21873 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
21874 @samp{gdb_get_args} command which partially overlaps with the
21875 functionality of @samp{-stack-list-arguments}.
21877 @subsubheading Example
21884 frame=@{level="0",addr="0x00010734",func="callee4",
21885 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21886 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
21887 frame=@{level="1",addr="0x0001076c",func="callee3",
21888 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21889 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
21890 frame=@{level="2",addr="0x0001078c",func="callee2",
21891 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21892 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
21893 frame=@{level="3",addr="0x000107b4",func="callee1",
21894 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21895 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
21896 frame=@{level="4",addr="0x000107e0",func="main",
21897 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21898 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
21900 -stack-list-arguments 0
21903 frame=@{level="0",args=[]@},
21904 frame=@{level="1",args=[name="strarg"]@},
21905 frame=@{level="2",args=[name="intarg",name="strarg"]@},
21906 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
21907 frame=@{level="4",args=[]@}]
21909 -stack-list-arguments 1
21912 frame=@{level="0",args=[]@},
21914 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21915 frame=@{level="2",args=[
21916 @{name="intarg",value="2"@},
21917 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21918 @{frame=@{level="3",args=[
21919 @{name="intarg",value="2"@},
21920 @{name="strarg",value="0x11940 \"A string argument.\""@},
21921 @{name="fltarg",value="3.5"@}]@},
21922 frame=@{level="4",args=[]@}]
21924 -stack-list-arguments 0 2 2
21925 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
21927 -stack-list-arguments 1 2 2
21928 ^done,stack-args=[frame=@{level="2",
21929 args=[@{name="intarg",value="2"@},
21930 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
21934 @c @subheading -stack-list-exception-handlers
21937 @subheading The @code{-stack-list-frames} Command
21938 @findex -stack-list-frames
21940 @subsubheading Synopsis
21943 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
21946 List the frames currently on the stack. For each frame it displays the
21951 The frame number, 0 being the topmost frame, i.e., the innermost function.
21953 The @code{$pc} value for that frame.
21957 File name of the source file where the function lives.
21959 Line number corresponding to the @code{$pc}.
21962 If invoked without arguments, this command prints a backtrace for the
21963 whole stack. If given two integer arguments, it shows the frames whose
21964 levels are between the two arguments (inclusive). If the two arguments
21965 are equal, it shows the single frame at the corresponding level. It is
21966 an error if @var{low-frame} is larger than the actual number of
21967 frames. On the other hand, @var{high-frame} may be larger than the
21968 actual number of frames, in which case only existing frames will be returned.
21970 @subsubheading @value{GDBN} Command
21972 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
21974 @subsubheading Example
21976 Full stack backtrace:
21982 [frame=@{level="0",addr="0x0001076c",func="foo",
21983 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
21984 frame=@{level="1",addr="0x000107a4",func="foo",
21985 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21986 frame=@{level="2",addr="0x000107a4",func="foo",
21987 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21988 frame=@{level="3",addr="0x000107a4",func="foo",
21989 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21990 frame=@{level="4",addr="0x000107a4",func="foo",
21991 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21992 frame=@{level="5",addr="0x000107a4",func="foo",
21993 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21994 frame=@{level="6",addr="0x000107a4",func="foo",
21995 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21996 frame=@{level="7",addr="0x000107a4",func="foo",
21997 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21998 frame=@{level="8",addr="0x000107a4",func="foo",
21999 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22000 frame=@{level="9",addr="0x000107a4",func="foo",
22001 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22002 frame=@{level="10",addr="0x000107a4",func="foo",
22003 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22004 frame=@{level="11",addr="0x00010738",func="main",
22005 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
22009 Show frames between @var{low_frame} and @var{high_frame}:
22013 -stack-list-frames 3 5
22015 [frame=@{level="3",addr="0x000107a4",func="foo",
22016 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22017 frame=@{level="4",addr="0x000107a4",func="foo",
22018 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22019 frame=@{level="5",addr="0x000107a4",func="foo",
22020 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
22024 Show a single frame:
22028 -stack-list-frames 3 3
22030 [frame=@{level="3",addr="0x000107a4",func="foo",
22031 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
22036 @subheading The @code{-stack-list-locals} Command
22037 @findex -stack-list-locals
22039 @subsubheading Synopsis
22042 -stack-list-locals @var{print-values}
22045 Display the local variable names for the selected frame. If
22046 @var{print-values} is 0 or @code{--no-values}, print only the names of
22047 the variables; if it is 1 or @code{--all-values}, print also their
22048 values; and if it is 2 or @code{--simple-values}, print the name,
22049 type and value for simple data types and the name and type for arrays,
22050 structures and unions. In this last case, a frontend can immediately
22051 display the value of simple data types and create variable objects for
22052 other data types when the user wishes to explore their values in
22055 @subsubheading @value{GDBN} Command
22057 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
22059 @subsubheading Example
22063 -stack-list-locals 0
22064 ^done,locals=[name="A",name="B",name="C"]
22066 -stack-list-locals --all-values
22067 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
22068 @{name="C",value="@{1, 2, 3@}"@}]
22069 -stack-list-locals --simple-values
22070 ^done,locals=[@{name="A",type="int",value="1"@},
22071 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
22076 @subheading The @code{-stack-select-frame} Command
22077 @findex -stack-select-frame
22079 @subsubheading Synopsis
22082 -stack-select-frame @var{framenum}
22085 Change the selected frame. Select a different frame @var{framenum} on
22088 This command in deprecated in favor of passing the @samp{--frame}
22089 option to every command.
22091 @subsubheading @value{GDBN} Command
22093 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
22094 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
22096 @subsubheading Example
22100 -stack-select-frame 2
22105 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22106 @node GDB/MI Variable Objects
22107 @section @sc{gdb/mi} Variable Objects
22111 @subheading Motivation for Variable Objects in @sc{gdb/mi}
22113 For the implementation of a variable debugger window (locals, watched
22114 expressions, etc.), we are proposing the adaptation of the existing code
22115 used by @code{Insight}.
22117 The two main reasons for that are:
22121 It has been proven in practice (it is already on its second generation).
22124 It will shorten development time (needless to say how important it is
22128 The original interface was designed to be used by Tcl code, so it was
22129 slightly changed so it could be used through @sc{gdb/mi}. This section
22130 describes the @sc{gdb/mi} operations that will be available and gives some
22131 hints about their use.
22133 @emph{Note}: In addition to the set of operations described here, we
22134 expect the @sc{gui} implementation of a variable window to require, at
22135 least, the following operations:
22138 @item @code{-gdb-show} @code{output-radix}
22139 @item @code{-stack-list-arguments}
22140 @item @code{-stack-list-locals}
22141 @item @code{-stack-select-frame}
22146 @subheading Introduction to Variable Objects
22148 @cindex variable objects in @sc{gdb/mi}
22150 Variable objects are "object-oriented" MI interface for examining and
22151 changing values of expressions. Unlike some other MI interfaces that
22152 work with expressions, variable objects are specifically designed for
22153 simple and efficient presentation in the frontend. A variable object
22154 is identified by string name. When a variable object is created, the
22155 frontend specifies the expression for that variable object. The
22156 expression can be a simple variable, or it can be an arbitrary complex
22157 expression, and can even involve CPU registers. After creating a
22158 variable object, the frontend can invoke other variable object
22159 operations---for example to obtain or change the value of a variable
22160 object, or to change display format.
22162 Variable objects have hierarchical tree structure. Any variable object
22163 that corresponds to a composite type, such as structure in C, has
22164 a number of child variable objects, for example corresponding to each
22165 element of a structure. A child variable object can itself have
22166 children, recursively. Recursion ends when we reach
22167 leaf variable objects, which always have built-in types. Child variable
22168 objects are created only by explicit request, so if a frontend
22169 is not interested in the children of a particular variable object, no
22170 child will be created.
22172 For a leaf variable object it is possible to obtain its value as a
22173 string, or set the value from a string. String value can be also
22174 obtained for a non-leaf variable object, but it's generally a string
22175 that only indicates the type of the object, and does not list its
22176 contents. Assignment to a non-leaf variable object is not allowed.
22178 A frontend does not need to read the values of all variable objects each time
22179 the program stops. Instead, MI provides an update command that lists all
22180 variable objects whose values has changed since the last update
22181 operation. This considerably reduces the amount of data that must
22182 be transferred to the frontend. As noted above, children variable
22183 objects are created on demand, and only leaf variable objects have a
22184 real value. As result, gdb will read target memory only for leaf
22185 variables that frontend has created.
22187 The automatic update is not always desirable. For example, a frontend
22188 might want to keep a value of some expression for future reference,
22189 and never update it. For another example, fetching memory is
22190 relatively slow for embedded targets, so a frontend might want
22191 to disable automatic update for the variables that are either not
22192 visible on the screen, or ``closed''. This is possible using so
22193 called ``frozen variable objects''. Such variable objects are never
22194 implicitly updated.
22196 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
22197 fixed variable object, the expression is parsed when the variable
22198 object is created, including associating identifiers to specific
22199 variables. The meaning of expression never changes. For a floating
22200 variable object the values of variables whose names appear in the
22201 expressions are re-evaluated every time in the context of the current
22202 frame. Consider this example:
22207 struct work_state state;
22214 If a fixed variable object for the @code{state} variable is created in
22215 this function, and we enter the recursive call, the the variable
22216 object will report the value of @code{state} in the top-level
22217 @code{do_work} invocation. On the other hand, a floating variable
22218 object will report the value of @code{state} in the current frame.
22220 If an expression specified when creating a fixed variable object
22221 refers to a local variable, the variable object becomes bound to the
22222 thread and frame in which the variable object is created. When such
22223 variable object is updated, @value{GDBN} makes sure that the
22224 thread/frame combination the variable object is bound to still exists,
22225 and re-evaluates the variable object in context of that thread/frame.
22227 The following is the complete set of @sc{gdb/mi} operations defined to
22228 access this functionality:
22230 @multitable @columnfractions .4 .6
22231 @item @strong{Operation}
22232 @tab @strong{Description}
22234 @item @code{-var-create}
22235 @tab create a variable object
22236 @item @code{-var-delete}
22237 @tab delete the variable object and/or its children
22238 @item @code{-var-set-format}
22239 @tab set the display format of this variable
22240 @item @code{-var-show-format}
22241 @tab show the display format of this variable
22242 @item @code{-var-info-num-children}
22243 @tab tells how many children this object has
22244 @item @code{-var-list-children}
22245 @tab return a list of the object's children
22246 @item @code{-var-info-type}
22247 @tab show the type of this variable object
22248 @item @code{-var-info-expression}
22249 @tab print parent-relative expression that this variable object represents
22250 @item @code{-var-info-path-expression}
22251 @tab print full expression that this variable object represents
22252 @item @code{-var-show-attributes}
22253 @tab is this variable editable? does it exist here?
22254 @item @code{-var-evaluate-expression}
22255 @tab get the value of this variable
22256 @item @code{-var-assign}
22257 @tab set the value of this variable
22258 @item @code{-var-update}
22259 @tab update the variable and its children
22260 @item @code{-var-set-frozen}
22261 @tab set frozeness attribute
22264 In the next subsection we describe each operation in detail and suggest
22265 how it can be used.
22267 @subheading Description And Use of Operations on Variable Objects
22269 @subheading The @code{-var-create} Command
22270 @findex -var-create
22272 @subsubheading Synopsis
22275 -var-create @{@var{name} | "-"@}
22276 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
22279 This operation creates a variable object, which allows the monitoring of
22280 a variable, the result of an expression, a memory cell or a CPU
22283 The @var{name} parameter is the string by which the object can be
22284 referenced. It must be unique. If @samp{-} is specified, the varobj
22285 system will generate a string ``varNNNNNN'' automatically. It will be
22286 unique provided that one does not specify @var{name} of that format.
22287 The command fails if a duplicate name is found.
22289 The frame under which the expression should be evaluated can be
22290 specified by @var{frame-addr}. A @samp{*} indicates that the current
22291 frame should be used. A @samp{@@} indicates that a floating variable
22292 object must be created.
22294 @var{expression} is any expression valid on the current language set (must not
22295 begin with a @samp{*}), or one of the following:
22299 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
22302 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
22305 @samp{$@var{regname}} --- a CPU register name
22308 @subsubheading Result
22310 This operation returns the name, number of children and the type of the
22311 object created. Type is returned as a string as the ones generated by
22312 the @value{GDBN} CLI. If a fixed variable object is bound to a
22313 specific thread, the thread is is also printed:
22316 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}"
22320 @subheading The @code{-var-delete} Command
22321 @findex -var-delete
22323 @subsubheading Synopsis
22326 -var-delete [ -c ] @var{name}
22329 Deletes a previously created variable object and all of its children.
22330 With the @samp{-c} option, just deletes the children.
22332 Returns an error if the object @var{name} is not found.
22335 @subheading The @code{-var-set-format} Command
22336 @findex -var-set-format
22338 @subsubheading Synopsis
22341 -var-set-format @var{name} @var{format-spec}
22344 Sets the output format for the value of the object @var{name} to be
22347 @anchor{-var-set-format}
22348 The syntax for the @var{format-spec} is as follows:
22351 @var{format-spec} @expansion{}
22352 @{binary | decimal | hexadecimal | octal | natural@}
22355 The natural format is the default format choosen automatically
22356 based on the variable type (like decimal for an @code{int}, hex
22357 for pointers, etc.).
22359 For a variable with children, the format is set only on the
22360 variable itself, and the children are not affected.
22362 @subheading The @code{-var-show-format} Command
22363 @findex -var-show-format
22365 @subsubheading Synopsis
22368 -var-show-format @var{name}
22371 Returns the format used to display the value of the object @var{name}.
22374 @var{format} @expansion{}
22379 @subheading The @code{-var-info-num-children} Command
22380 @findex -var-info-num-children
22382 @subsubheading Synopsis
22385 -var-info-num-children @var{name}
22388 Returns the number of children of a variable object @var{name}:
22395 @subheading The @code{-var-list-children} Command
22396 @findex -var-list-children
22398 @subsubheading Synopsis
22401 -var-list-children [@var{print-values}] @var{name}
22403 @anchor{-var-list-children}
22405 Return a list of the children of the specified variable object and
22406 create variable objects for them, if they do not already exist. With
22407 a single argument or if @var{print-values} has a value for of 0 or
22408 @code{--no-values}, print only the names of the variables; if
22409 @var{print-values} is 1 or @code{--all-values}, also print their
22410 values; and if it is 2 or @code{--simple-values} print the name and
22411 value for simple data types and just the name for arrays, structures
22414 @subsubheading Example
22418 -var-list-children n
22419 ^done,numchild=@var{n},children=[@{name=@var{name},
22420 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
22422 -var-list-children --all-values n
22423 ^done,numchild=@var{n},children=[@{name=@var{name},
22424 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
22428 @subheading The @code{-var-info-type} Command
22429 @findex -var-info-type
22431 @subsubheading Synopsis
22434 -var-info-type @var{name}
22437 Returns the type of the specified variable @var{name}. The type is
22438 returned as a string in the same format as it is output by the
22442 type=@var{typename}
22446 @subheading The @code{-var-info-expression} Command
22447 @findex -var-info-expression
22449 @subsubheading Synopsis
22452 -var-info-expression @var{name}
22455 Returns a string that is suitable for presenting this
22456 variable object in user interface. The string is generally
22457 not valid expression in the current language, and cannot be evaluated.
22459 For example, if @code{a} is an array, and variable object
22460 @code{A} was created for @code{a}, then we'll get this output:
22463 (gdb) -var-info-expression A.1
22464 ^done,lang="C",exp="1"
22468 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
22470 Note that the output of the @code{-var-list-children} command also
22471 includes those expressions, so the @code{-var-info-expression} command
22474 @subheading The @code{-var-info-path-expression} Command
22475 @findex -var-info-path-expression
22477 @subsubheading Synopsis
22480 -var-info-path-expression @var{name}
22483 Returns an expression that can be evaluated in the current
22484 context and will yield the same value that a variable object has.
22485 Compare this with the @code{-var-info-expression} command, which
22486 result can be used only for UI presentation. Typical use of
22487 the @code{-var-info-path-expression} command is creating a
22488 watchpoint from a variable object.
22490 For example, suppose @code{C} is a C@t{++} class, derived from class
22491 @code{Base}, and that the @code{Base} class has a member called
22492 @code{m_size}. Assume a variable @code{c} is has the type of
22493 @code{C} and a variable object @code{C} was created for variable
22494 @code{c}. Then, we'll get this output:
22496 (gdb) -var-info-path-expression C.Base.public.m_size
22497 ^done,path_expr=((Base)c).m_size)
22500 @subheading The @code{-var-show-attributes} Command
22501 @findex -var-show-attributes
22503 @subsubheading Synopsis
22506 -var-show-attributes @var{name}
22509 List attributes of the specified variable object @var{name}:
22512 status=@var{attr} [ ( ,@var{attr} )* ]
22516 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
22518 @subheading The @code{-var-evaluate-expression} Command
22519 @findex -var-evaluate-expression
22521 @subsubheading Synopsis
22524 -var-evaluate-expression [-f @var{format-spec}] @var{name}
22527 Evaluates the expression that is represented by the specified variable
22528 object and returns its value as a string. The format of the string
22529 can be specified with the @samp{-f} option. The possible values of
22530 this option are the same as for @code{-var-set-format}
22531 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
22532 the current display format will be used. The current display format
22533 can be changed using the @code{-var-set-format} command.
22539 Note that one must invoke @code{-var-list-children} for a variable
22540 before the value of a child variable can be evaluated.
22542 @subheading The @code{-var-assign} Command
22543 @findex -var-assign
22545 @subsubheading Synopsis
22548 -var-assign @var{name} @var{expression}
22551 Assigns the value of @var{expression} to the variable object specified
22552 by @var{name}. The object must be @samp{editable}. If the variable's
22553 value is altered by the assign, the variable will show up in any
22554 subsequent @code{-var-update} list.
22556 @subsubheading Example
22564 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
22568 @subheading The @code{-var-update} Command
22569 @findex -var-update
22571 @subsubheading Synopsis
22574 -var-update [@var{print-values}] @{@var{name} | "*"@}
22577 Reevaluate the expressions corresponding to the variable object
22578 @var{name} and all its direct and indirect children, and return the
22579 list of variable objects whose values have changed; @var{name} must
22580 be a root variable object. Here, ``changed'' means that the result of
22581 @code{-var-evaluate-expression} before and after the
22582 @code{-var-update} is different. If @samp{*} is used as the variable
22583 object names, all existing variable objects are updated, except
22584 for frozen ones (@pxref{-var-set-frozen}). The option
22585 @var{print-values} determines whether both names and values, or just
22586 names are printed. The possible values of this option are the same
22587 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
22588 recommended to use the @samp{--all-values} option, to reduce the
22589 number of MI commands needed on each program stop.
22591 With the @samp{*} parameter, if a variable object is bound to a
22592 currently running thread, it will not be updated, without any
22595 @subsubheading Example
22602 -var-update --all-values var1
22603 ^done,changelist=[@{name="var1",value="3",in_scope="true",
22604 type_changed="false"@}]
22608 @anchor{-var-update}
22609 The field in_scope may take three values:
22613 The variable object's current value is valid.
22616 The variable object does not currently hold a valid value but it may
22617 hold one in the future if its associated expression comes back into
22621 The variable object no longer holds a valid value.
22622 This can occur when the executable file being debugged has changed,
22623 either through recompilation or by using the @value{GDBN} @code{file}
22624 command. The front end should normally choose to delete these variable
22628 In the future new values may be added to this list so the front should
22629 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
22631 @subheading The @code{-var-set-frozen} Command
22632 @findex -var-set-frozen
22633 @anchor{-var-set-frozen}
22635 @subsubheading Synopsis
22638 -var-set-frozen @var{name} @var{flag}
22641 Set the frozenness flag on the variable object @var{name}. The
22642 @var{flag} parameter should be either @samp{1} to make the variable
22643 frozen or @samp{0} to make it unfrozen. If a variable object is
22644 frozen, then neither itself, nor any of its children, are
22645 implicitly updated by @code{-var-update} of
22646 a parent variable or by @code{-var-update *}. Only
22647 @code{-var-update} of the variable itself will update its value and
22648 values of its children. After a variable object is unfrozen, it is
22649 implicitly updated by all subsequent @code{-var-update} operations.
22650 Unfreezing a variable does not update it, only subsequent
22651 @code{-var-update} does.
22653 @subsubheading Example
22657 -var-set-frozen V 1
22663 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22664 @node GDB/MI Data Manipulation
22665 @section @sc{gdb/mi} Data Manipulation
22667 @cindex data manipulation, in @sc{gdb/mi}
22668 @cindex @sc{gdb/mi}, data manipulation
22669 This section describes the @sc{gdb/mi} commands that manipulate data:
22670 examine memory and registers, evaluate expressions, etc.
22672 @c REMOVED FROM THE INTERFACE.
22673 @c @subheading -data-assign
22674 @c Change the value of a program variable. Plenty of side effects.
22675 @c @subsubheading GDB Command
22677 @c @subsubheading Example
22680 @subheading The @code{-data-disassemble} Command
22681 @findex -data-disassemble
22683 @subsubheading Synopsis
22687 [ -s @var{start-addr} -e @var{end-addr} ]
22688 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
22696 @item @var{start-addr}
22697 is the beginning address (or @code{$pc})
22698 @item @var{end-addr}
22700 @item @var{filename}
22701 is the name of the file to disassemble
22702 @item @var{linenum}
22703 is the line number to disassemble around
22705 is the number of disassembly lines to be produced. If it is -1,
22706 the whole function will be disassembled, in case no @var{end-addr} is
22707 specified. If @var{end-addr} is specified as a non-zero value, and
22708 @var{lines} is lower than the number of disassembly lines between
22709 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
22710 displayed; if @var{lines} is higher than the number of lines between
22711 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
22714 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
22718 @subsubheading Result
22720 The output for each instruction is composed of four fields:
22729 Note that whatever included in the instruction field, is not manipulated
22730 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
22732 @subsubheading @value{GDBN} Command
22734 There's no direct mapping from this command to the CLI.
22736 @subsubheading Example
22738 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
22742 -data-disassemble -s $pc -e "$pc + 20" -- 0
22745 @{address="0x000107c0",func-name="main",offset="4",
22746 inst="mov 2, %o0"@},
22747 @{address="0x000107c4",func-name="main",offset="8",
22748 inst="sethi %hi(0x11800), %o2"@},
22749 @{address="0x000107c8",func-name="main",offset="12",
22750 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
22751 @{address="0x000107cc",func-name="main",offset="16",
22752 inst="sethi %hi(0x11800), %o2"@},
22753 @{address="0x000107d0",func-name="main",offset="20",
22754 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
22758 Disassemble the whole @code{main} function. Line 32 is part of
22762 -data-disassemble -f basics.c -l 32 -- 0
22764 @{address="0x000107bc",func-name="main",offset="0",
22765 inst="save %sp, -112, %sp"@},
22766 @{address="0x000107c0",func-name="main",offset="4",
22767 inst="mov 2, %o0"@},
22768 @{address="0x000107c4",func-name="main",offset="8",
22769 inst="sethi %hi(0x11800), %o2"@},
22771 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
22772 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
22776 Disassemble 3 instructions from the start of @code{main}:
22780 -data-disassemble -f basics.c -l 32 -n 3 -- 0
22782 @{address="0x000107bc",func-name="main",offset="0",
22783 inst="save %sp, -112, %sp"@},
22784 @{address="0x000107c0",func-name="main",offset="4",
22785 inst="mov 2, %o0"@},
22786 @{address="0x000107c4",func-name="main",offset="8",
22787 inst="sethi %hi(0x11800), %o2"@}]
22791 Disassemble 3 instructions from the start of @code{main} in mixed mode:
22795 -data-disassemble -f basics.c -l 32 -n 3 -- 1
22797 src_and_asm_line=@{line="31",
22798 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22799 testsuite/gdb.mi/basics.c",line_asm_insn=[
22800 @{address="0x000107bc",func-name="main",offset="0",
22801 inst="save %sp, -112, %sp"@}]@},
22802 src_and_asm_line=@{line="32",
22803 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22804 testsuite/gdb.mi/basics.c",line_asm_insn=[
22805 @{address="0x000107c0",func-name="main",offset="4",
22806 inst="mov 2, %o0"@},
22807 @{address="0x000107c4",func-name="main",offset="8",
22808 inst="sethi %hi(0x11800), %o2"@}]@}]
22813 @subheading The @code{-data-evaluate-expression} Command
22814 @findex -data-evaluate-expression
22816 @subsubheading Synopsis
22819 -data-evaluate-expression @var{expr}
22822 Evaluate @var{expr} as an expression. The expression could contain an
22823 inferior function call. The function call will execute synchronously.
22824 If the expression contains spaces, it must be enclosed in double quotes.
22826 @subsubheading @value{GDBN} Command
22828 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
22829 @samp{call}. In @code{gdbtk} only, there's a corresponding
22830 @samp{gdb_eval} command.
22832 @subsubheading Example
22834 In the following example, the numbers that precede the commands are the
22835 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
22836 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
22840 211-data-evaluate-expression A
22843 311-data-evaluate-expression &A
22844 311^done,value="0xefffeb7c"
22846 411-data-evaluate-expression A+3
22849 511-data-evaluate-expression "A + 3"
22855 @subheading The @code{-data-list-changed-registers} Command
22856 @findex -data-list-changed-registers
22858 @subsubheading Synopsis
22861 -data-list-changed-registers
22864 Display a list of the registers that have changed.
22866 @subsubheading @value{GDBN} Command
22868 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
22869 has the corresponding command @samp{gdb_changed_register_list}.
22871 @subsubheading Example
22873 On a PPC MBX board:
22881 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
22882 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
22885 -data-list-changed-registers
22886 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
22887 "10","11","13","14","15","16","17","18","19","20","21","22","23",
22888 "24","25","26","27","28","30","31","64","65","66","67","69"]
22893 @subheading The @code{-data-list-register-names} Command
22894 @findex -data-list-register-names
22896 @subsubheading Synopsis
22899 -data-list-register-names [ ( @var{regno} )+ ]
22902 Show a list of register names for the current target. If no arguments
22903 are given, it shows a list of the names of all the registers. If
22904 integer numbers are given as arguments, it will print a list of the
22905 names of the registers corresponding to the arguments. To ensure
22906 consistency between a register name and its number, the output list may
22907 include empty register names.
22909 @subsubheading @value{GDBN} Command
22911 @value{GDBN} does not have a command which corresponds to
22912 @samp{-data-list-register-names}. In @code{gdbtk} there is a
22913 corresponding command @samp{gdb_regnames}.
22915 @subsubheading Example
22917 For the PPC MBX board:
22920 -data-list-register-names
22921 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
22922 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
22923 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
22924 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
22925 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
22926 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
22927 "", "pc","ps","cr","lr","ctr","xer"]
22929 -data-list-register-names 1 2 3
22930 ^done,register-names=["r1","r2","r3"]
22934 @subheading The @code{-data-list-register-values} Command
22935 @findex -data-list-register-values
22937 @subsubheading Synopsis
22940 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
22943 Display the registers' contents. @var{fmt} is the format according to
22944 which the registers' contents are to be returned, followed by an optional
22945 list of numbers specifying the registers to display. A missing list of
22946 numbers indicates that the contents of all the registers must be returned.
22948 Allowed formats for @var{fmt} are:
22965 @subsubheading @value{GDBN} Command
22967 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
22968 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
22970 @subsubheading Example
22972 For a PPC MBX board (note: line breaks are for readability only, they
22973 don't appear in the actual output):
22977 -data-list-register-values r 64 65
22978 ^done,register-values=[@{number="64",value="0xfe00a300"@},
22979 @{number="65",value="0x00029002"@}]
22981 -data-list-register-values x
22982 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
22983 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
22984 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
22985 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
22986 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
22987 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
22988 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
22989 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
22990 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
22991 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
22992 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
22993 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
22994 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
22995 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
22996 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
22997 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
22998 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
22999 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
23000 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
23001 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
23002 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
23003 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
23004 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
23005 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
23006 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
23007 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
23008 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
23009 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
23010 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
23011 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
23012 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
23013 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
23014 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
23015 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
23016 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
23017 @{number="69",value="0x20002b03"@}]
23022 @subheading The @code{-data-read-memory} Command
23023 @findex -data-read-memory
23025 @subsubheading Synopsis
23028 -data-read-memory [ -o @var{byte-offset} ]
23029 @var{address} @var{word-format} @var{word-size}
23030 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
23037 @item @var{address}
23038 An expression specifying the address of the first memory word to be
23039 read. Complex expressions containing embedded white space should be
23040 quoted using the C convention.
23042 @item @var{word-format}
23043 The format to be used to print the memory words. The notation is the
23044 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
23047 @item @var{word-size}
23048 The size of each memory word in bytes.
23050 @item @var{nr-rows}
23051 The number of rows in the output table.
23053 @item @var{nr-cols}
23054 The number of columns in the output table.
23057 If present, indicates that each row should include an @sc{ascii} dump. The
23058 value of @var{aschar} is used as a padding character when a byte is not a
23059 member of the printable @sc{ascii} character set (printable @sc{ascii}
23060 characters are those whose code is between 32 and 126, inclusively).
23062 @item @var{byte-offset}
23063 An offset to add to the @var{address} before fetching memory.
23066 This command displays memory contents as a table of @var{nr-rows} by
23067 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
23068 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
23069 (returned as @samp{total-bytes}). Should less than the requested number
23070 of bytes be returned by the target, the missing words are identified
23071 using @samp{N/A}. The number of bytes read from the target is returned
23072 in @samp{nr-bytes} and the starting address used to read memory in
23075 The address of the next/previous row or page is available in
23076 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
23079 @subsubheading @value{GDBN} Command
23081 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
23082 @samp{gdb_get_mem} memory read command.
23084 @subsubheading Example
23086 Read six bytes of memory starting at @code{bytes+6} but then offset by
23087 @code{-6} bytes. Format as three rows of two columns. One byte per
23088 word. Display each word in hex.
23092 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
23093 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
23094 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
23095 prev-page="0x0000138a",memory=[
23096 @{addr="0x00001390",data=["0x00","0x01"]@},
23097 @{addr="0x00001392",data=["0x02","0x03"]@},
23098 @{addr="0x00001394",data=["0x04","0x05"]@}]
23102 Read two bytes of memory starting at address @code{shorts + 64} and
23103 display as a single word formatted in decimal.
23107 5-data-read-memory shorts+64 d 2 1 1
23108 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
23109 next-row="0x00001512",prev-row="0x0000150e",
23110 next-page="0x00001512",prev-page="0x0000150e",memory=[
23111 @{addr="0x00001510",data=["128"]@}]
23115 Read thirty two bytes of memory starting at @code{bytes+16} and format
23116 as eight rows of four columns. Include a string encoding with @samp{x}
23117 used as the non-printable character.
23121 4-data-read-memory bytes+16 x 1 8 4 x
23122 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
23123 next-row="0x000013c0",prev-row="0x0000139c",
23124 next-page="0x000013c0",prev-page="0x00001380",memory=[
23125 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
23126 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
23127 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
23128 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
23129 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
23130 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
23131 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
23132 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
23136 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23137 @node GDB/MI Tracepoint Commands
23138 @section @sc{gdb/mi} Tracepoint Commands
23140 The tracepoint commands are not yet implemented.
23142 @c @subheading -trace-actions
23144 @c @subheading -trace-delete
23146 @c @subheading -trace-disable
23148 @c @subheading -trace-dump
23150 @c @subheading -trace-enable
23152 @c @subheading -trace-exists
23154 @c @subheading -trace-find
23156 @c @subheading -trace-frame-number
23158 @c @subheading -trace-info
23160 @c @subheading -trace-insert
23162 @c @subheading -trace-list
23164 @c @subheading -trace-pass-count
23166 @c @subheading -trace-save
23168 @c @subheading -trace-start
23170 @c @subheading -trace-stop
23173 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23174 @node GDB/MI Symbol Query
23175 @section @sc{gdb/mi} Symbol Query Commands
23178 @subheading The @code{-symbol-info-address} Command
23179 @findex -symbol-info-address
23181 @subsubheading Synopsis
23184 -symbol-info-address @var{symbol}
23187 Describe where @var{symbol} is stored.
23189 @subsubheading @value{GDBN} Command
23191 The corresponding @value{GDBN} command is @samp{info address}.
23193 @subsubheading Example
23197 @subheading The @code{-symbol-info-file} Command
23198 @findex -symbol-info-file
23200 @subsubheading Synopsis
23206 Show the file for the symbol.
23208 @subsubheading @value{GDBN} Command
23210 There's no equivalent @value{GDBN} command. @code{gdbtk} has
23211 @samp{gdb_find_file}.
23213 @subsubheading Example
23217 @subheading The @code{-symbol-info-function} Command
23218 @findex -symbol-info-function
23220 @subsubheading Synopsis
23223 -symbol-info-function
23226 Show which function the symbol lives in.
23228 @subsubheading @value{GDBN} Command
23230 @samp{gdb_get_function} in @code{gdbtk}.
23232 @subsubheading Example
23236 @subheading The @code{-symbol-info-line} Command
23237 @findex -symbol-info-line
23239 @subsubheading Synopsis
23245 Show the core addresses of the code for a source line.
23247 @subsubheading @value{GDBN} Command
23249 The corresponding @value{GDBN} command is @samp{info line}.
23250 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
23252 @subsubheading Example
23256 @subheading The @code{-symbol-info-symbol} Command
23257 @findex -symbol-info-symbol
23259 @subsubheading Synopsis
23262 -symbol-info-symbol @var{addr}
23265 Describe what symbol is at location @var{addr}.
23267 @subsubheading @value{GDBN} Command
23269 The corresponding @value{GDBN} command is @samp{info symbol}.
23271 @subsubheading Example
23275 @subheading The @code{-symbol-list-functions} Command
23276 @findex -symbol-list-functions
23278 @subsubheading Synopsis
23281 -symbol-list-functions
23284 List the functions in the executable.
23286 @subsubheading @value{GDBN} Command
23288 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
23289 @samp{gdb_search} in @code{gdbtk}.
23291 @subsubheading Example
23295 @subheading The @code{-symbol-list-lines} Command
23296 @findex -symbol-list-lines
23298 @subsubheading Synopsis
23301 -symbol-list-lines @var{filename}
23304 Print the list of lines that contain code and their associated program
23305 addresses for the given source filename. The entries are sorted in
23306 ascending PC order.
23308 @subsubheading @value{GDBN} Command
23310 There is no corresponding @value{GDBN} command.
23312 @subsubheading Example
23315 -symbol-list-lines basics.c
23316 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
23321 @subheading The @code{-symbol-list-types} Command
23322 @findex -symbol-list-types
23324 @subsubheading Synopsis
23330 List all the type names.
23332 @subsubheading @value{GDBN} Command
23334 The corresponding commands are @samp{info types} in @value{GDBN},
23335 @samp{gdb_search} in @code{gdbtk}.
23337 @subsubheading Example
23341 @subheading The @code{-symbol-list-variables} Command
23342 @findex -symbol-list-variables
23344 @subsubheading Synopsis
23347 -symbol-list-variables
23350 List all the global and static variable names.
23352 @subsubheading @value{GDBN} Command
23354 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
23356 @subsubheading Example
23360 @subheading The @code{-symbol-locate} Command
23361 @findex -symbol-locate
23363 @subsubheading Synopsis
23369 @subsubheading @value{GDBN} Command
23371 @samp{gdb_loc} in @code{gdbtk}.
23373 @subsubheading Example
23377 @subheading The @code{-symbol-type} Command
23378 @findex -symbol-type
23380 @subsubheading Synopsis
23383 -symbol-type @var{variable}
23386 Show type of @var{variable}.
23388 @subsubheading @value{GDBN} Command
23390 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
23391 @samp{gdb_obj_variable}.
23393 @subsubheading Example
23397 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23398 @node GDB/MI File Commands
23399 @section @sc{gdb/mi} File Commands
23401 This section describes the GDB/MI commands to specify executable file names
23402 and to read in and obtain symbol table information.
23404 @subheading The @code{-file-exec-and-symbols} Command
23405 @findex -file-exec-and-symbols
23407 @subsubheading Synopsis
23410 -file-exec-and-symbols @var{file}
23413 Specify the executable file to be debugged. This file is the one from
23414 which the symbol table is also read. If no file is specified, the
23415 command clears the executable and symbol information. If breakpoints
23416 are set when using this command with no arguments, @value{GDBN} will produce
23417 error messages. Otherwise, no output is produced, except a completion
23420 @subsubheading @value{GDBN} Command
23422 The corresponding @value{GDBN} command is @samp{file}.
23424 @subsubheading Example
23428 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23434 @subheading The @code{-file-exec-file} Command
23435 @findex -file-exec-file
23437 @subsubheading Synopsis
23440 -file-exec-file @var{file}
23443 Specify the executable file to be debugged. Unlike
23444 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
23445 from this file. If used without argument, @value{GDBN} clears the information
23446 about the executable file. No output is produced, except a completion
23449 @subsubheading @value{GDBN} Command
23451 The corresponding @value{GDBN} command is @samp{exec-file}.
23453 @subsubheading Example
23457 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23463 @subheading The @code{-file-list-exec-sections} Command
23464 @findex -file-list-exec-sections
23466 @subsubheading Synopsis
23469 -file-list-exec-sections
23472 List the sections of the current executable file.
23474 @subsubheading @value{GDBN} Command
23476 The @value{GDBN} command @samp{info file} shows, among the rest, the same
23477 information as this command. @code{gdbtk} has a corresponding command
23478 @samp{gdb_load_info}.
23480 @subsubheading Example
23484 @subheading The @code{-file-list-exec-source-file} Command
23485 @findex -file-list-exec-source-file
23487 @subsubheading Synopsis
23490 -file-list-exec-source-file
23493 List the line number, the current source file, and the absolute path
23494 to the current source file for the current executable. The macro
23495 information field has a value of @samp{1} or @samp{0} depending on
23496 whether or not the file includes preprocessor macro information.
23498 @subsubheading @value{GDBN} Command
23500 The @value{GDBN} equivalent is @samp{info source}
23502 @subsubheading Example
23506 123-file-list-exec-source-file
23507 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
23512 @subheading The @code{-file-list-exec-source-files} Command
23513 @findex -file-list-exec-source-files
23515 @subsubheading Synopsis
23518 -file-list-exec-source-files
23521 List the source files for the current executable.
23523 It will always output the filename, but only when @value{GDBN} can find
23524 the absolute file name of a source file, will it output the fullname.
23526 @subsubheading @value{GDBN} Command
23528 The @value{GDBN} equivalent is @samp{info sources}.
23529 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
23531 @subsubheading Example
23534 -file-list-exec-source-files
23536 @{file=foo.c,fullname=/home/foo.c@},
23537 @{file=/home/bar.c,fullname=/home/bar.c@},
23538 @{file=gdb_could_not_find_fullpath.c@}]
23542 @subheading The @code{-file-list-shared-libraries} Command
23543 @findex -file-list-shared-libraries
23545 @subsubheading Synopsis
23548 -file-list-shared-libraries
23551 List the shared libraries in the program.
23553 @subsubheading @value{GDBN} Command
23555 The corresponding @value{GDBN} command is @samp{info shared}.
23557 @subsubheading Example
23561 @subheading The @code{-file-list-symbol-files} Command
23562 @findex -file-list-symbol-files
23564 @subsubheading Synopsis
23567 -file-list-symbol-files
23572 @subsubheading @value{GDBN} Command
23574 The corresponding @value{GDBN} command is @samp{info file} (part of it).
23576 @subsubheading Example
23580 @subheading The @code{-file-symbol-file} Command
23581 @findex -file-symbol-file
23583 @subsubheading Synopsis
23586 -file-symbol-file @var{file}
23589 Read symbol table info from the specified @var{file} argument. When
23590 used without arguments, clears @value{GDBN}'s symbol table info. No output is
23591 produced, except for a completion notification.
23593 @subsubheading @value{GDBN} Command
23595 The corresponding @value{GDBN} command is @samp{symbol-file}.
23597 @subsubheading Example
23601 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23607 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23608 @node GDB/MI Memory Overlay Commands
23609 @section @sc{gdb/mi} Memory Overlay Commands
23611 The memory overlay commands are not implemented.
23613 @c @subheading -overlay-auto
23615 @c @subheading -overlay-list-mapping-state
23617 @c @subheading -overlay-list-overlays
23619 @c @subheading -overlay-map
23621 @c @subheading -overlay-off
23623 @c @subheading -overlay-on
23625 @c @subheading -overlay-unmap
23627 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23628 @node GDB/MI Signal Handling Commands
23629 @section @sc{gdb/mi} Signal Handling Commands
23631 Signal handling commands are not implemented.
23633 @c @subheading -signal-handle
23635 @c @subheading -signal-list-handle-actions
23637 @c @subheading -signal-list-signal-types
23641 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23642 @node GDB/MI Target Manipulation
23643 @section @sc{gdb/mi} Target Manipulation Commands
23646 @subheading The @code{-target-attach} Command
23647 @findex -target-attach
23649 @subsubheading Synopsis
23652 -target-attach @var{pid} | @var{gid} | @var{file}
23655 Attach to a process @var{pid} or a file @var{file} outside of
23656 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
23657 group, the id previously returned by
23658 @samp{-list-thread-groups --available} must be used.
23660 @subsubheading @value{GDBN} Command
23662 The corresponding @value{GDBN} command is @samp{attach}.
23664 @subsubheading Example
23668 =thread-created,id="1"
23669 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
23674 @subheading The @code{-target-compare-sections} Command
23675 @findex -target-compare-sections
23677 @subsubheading Synopsis
23680 -target-compare-sections [ @var{section} ]
23683 Compare data of section @var{section} on target to the exec file.
23684 Without the argument, all sections are compared.
23686 @subsubheading @value{GDBN} Command
23688 The @value{GDBN} equivalent is @samp{compare-sections}.
23690 @subsubheading Example
23694 @subheading The @code{-target-detach} Command
23695 @findex -target-detach
23697 @subsubheading Synopsis
23700 -target-detach [ @var{pid} | @var{gid} ]
23703 Detach from the remote target which normally resumes its execution.
23704 If either @var{pid} or @var{gid} is specified, detaches from either
23705 the specified process, or specified thread group. There's no output.
23707 @subsubheading @value{GDBN} Command
23709 The corresponding @value{GDBN} command is @samp{detach}.
23711 @subsubheading Example
23721 @subheading The @code{-target-disconnect} Command
23722 @findex -target-disconnect
23724 @subsubheading Synopsis
23730 Disconnect from the remote target. There's no output and the target is
23731 generally not resumed.
23733 @subsubheading @value{GDBN} Command
23735 The corresponding @value{GDBN} command is @samp{disconnect}.
23737 @subsubheading Example
23747 @subheading The @code{-target-download} Command
23748 @findex -target-download
23750 @subsubheading Synopsis
23756 Loads the executable onto the remote target.
23757 It prints out an update message every half second, which includes the fields:
23761 The name of the section.
23763 The size of what has been sent so far for that section.
23765 The size of the section.
23767 The total size of what was sent so far (the current and the previous sections).
23769 The size of the overall executable to download.
23773 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
23774 @sc{gdb/mi} Output Syntax}).
23776 In addition, it prints the name and size of the sections, as they are
23777 downloaded. These messages include the following fields:
23781 The name of the section.
23783 The size of the section.
23785 The size of the overall executable to download.
23789 At the end, a summary is printed.
23791 @subsubheading @value{GDBN} Command
23793 The corresponding @value{GDBN} command is @samp{load}.
23795 @subsubheading Example
23797 Note: each status message appears on a single line. Here the messages
23798 have been broken down so that they can fit onto a page.
23803 +download,@{section=".text",section-size="6668",total-size="9880"@}
23804 +download,@{section=".text",section-sent="512",section-size="6668",
23805 total-sent="512",total-size="9880"@}
23806 +download,@{section=".text",section-sent="1024",section-size="6668",
23807 total-sent="1024",total-size="9880"@}
23808 +download,@{section=".text",section-sent="1536",section-size="6668",
23809 total-sent="1536",total-size="9880"@}
23810 +download,@{section=".text",section-sent="2048",section-size="6668",
23811 total-sent="2048",total-size="9880"@}
23812 +download,@{section=".text",section-sent="2560",section-size="6668",
23813 total-sent="2560",total-size="9880"@}
23814 +download,@{section=".text",section-sent="3072",section-size="6668",
23815 total-sent="3072",total-size="9880"@}
23816 +download,@{section=".text",section-sent="3584",section-size="6668",
23817 total-sent="3584",total-size="9880"@}
23818 +download,@{section=".text",section-sent="4096",section-size="6668",
23819 total-sent="4096",total-size="9880"@}
23820 +download,@{section=".text",section-sent="4608",section-size="6668",
23821 total-sent="4608",total-size="9880"@}
23822 +download,@{section=".text",section-sent="5120",section-size="6668",
23823 total-sent="5120",total-size="9880"@}
23824 +download,@{section=".text",section-sent="5632",section-size="6668",
23825 total-sent="5632",total-size="9880"@}
23826 +download,@{section=".text",section-sent="6144",section-size="6668",
23827 total-sent="6144",total-size="9880"@}
23828 +download,@{section=".text",section-sent="6656",section-size="6668",
23829 total-sent="6656",total-size="9880"@}
23830 +download,@{section=".init",section-size="28",total-size="9880"@}
23831 +download,@{section=".fini",section-size="28",total-size="9880"@}
23832 +download,@{section=".data",section-size="3156",total-size="9880"@}
23833 +download,@{section=".data",section-sent="512",section-size="3156",
23834 total-sent="7236",total-size="9880"@}
23835 +download,@{section=".data",section-sent="1024",section-size="3156",
23836 total-sent="7748",total-size="9880"@}
23837 +download,@{section=".data",section-sent="1536",section-size="3156",
23838 total-sent="8260",total-size="9880"@}
23839 +download,@{section=".data",section-sent="2048",section-size="3156",
23840 total-sent="8772",total-size="9880"@}
23841 +download,@{section=".data",section-sent="2560",section-size="3156",
23842 total-sent="9284",total-size="9880"@}
23843 +download,@{section=".data",section-sent="3072",section-size="3156",
23844 total-sent="9796",total-size="9880"@}
23845 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
23851 @subheading The @code{-target-exec-status} Command
23852 @findex -target-exec-status
23854 @subsubheading Synopsis
23857 -target-exec-status
23860 Provide information on the state of the target (whether it is running or
23861 not, for instance).
23863 @subsubheading @value{GDBN} Command
23865 There's no equivalent @value{GDBN} command.
23867 @subsubheading Example
23871 @subheading The @code{-target-list-available-targets} Command
23872 @findex -target-list-available-targets
23874 @subsubheading Synopsis
23877 -target-list-available-targets
23880 List the possible targets to connect to.
23882 @subsubheading @value{GDBN} Command
23884 The corresponding @value{GDBN} command is @samp{help target}.
23886 @subsubheading Example
23890 @subheading The @code{-target-list-current-targets} Command
23891 @findex -target-list-current-targets
23893 @subsubheading Synopsis
23896 -target-list-current-targets
23899 Describe the current target.
23901 @subsubheading @value{GDBN} Command
23903 The corresponding information is printed by @samp{info file} (among
23906 @subsubheading Example
23910 @subheading The @code{-target-list-parameters} Command
23911 @findex -target-list-parameters
23913 @subsubheading Synopsis
23916 -target-list-parameters
23921 @subsubheading @value{GDBN} Command
23925 @subsubheading Example
23929 @subheading The @code{-target-select} Command
23930 @findex -target-select
23932 @subsubheading Synopsis
23935 -target-select @var{type} @var{parameters @dots{}}
23938 Connect @value{GDBN} to the remote target. This command takes two args:
23942 The type of target, for instance @samp{remote}, etc.
23943 @item @var{parameters}
23944 Device names, host names and the like. @xref{Target Commands, ,
23945 Commands for Managing Targets}, for more details.
23948 The output is a connection notification, followed by the address at
23949 which the target program is, in the following form:
23952 ^connected,addr="@var{address}",func="@var{function name}",
23953 args=[@var{arg list}]
23956 @subsubheading @value{GDBN} Command
23958 The corresponding @value{GDBN} command is @samp{target}.
23960 @subsubheading Example
23964 -target-select remote /dev/ttya
23965 ^connected,addr="0xfe00a300",func="??",args=[]
23969 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23970 @node GDB/MI File Transfer Commands
23971 @section @sc{gdb/mi} File Transfer Commands
23974 @subheading The @code{-target-file-put} Command
23975 @findex -target-file-put
23977 @subsubheading Synopsis
23980 -target-file-put @var{hostfile} @var{targetfile}
23983 Copy file @var{hostfile} from the host system (the machine running
23984 @value{GDBN}) to @var{targetfile} on the target system.
23986 @subsubheading @value{GDBN} Command
23988 The corresponding @value{GDBN} command is @samp{remote put}.
23990 @subsubheading Example
23994 -target-file-put localfile remotefile
24000 @subheading The @code{-target-file-get} Command
24001 @findex -target-file-get
24003 @subsubheading Synopsis
24006 -target-file-get @var{targetfile} @var{hostfile}
24009 Copy file @var{targetfile} from the target system to @var{hostfile}
24010 on the host system.
24012 @subsubheading @value{GDBN} Command
24014 The corresponding @value{GDBN} command is @samp{remote get}.
24016 @subsubheading Example
24020 -target-file-get remotefile localfile
24026 @subheading The @code{-target-file-delete} Command
24027 @findex -target-file-delete
24029 @subsubheading Synopsis
24032 -target-file-delete @var{targetfile}
24035 Delete @var{targetfile} from the target system.
24037 @subsubheading @value{GDBN} Command
24039 The corresponding @value{GDBN} command is @samp{remote delete}.
24041 @subsubheading Example
24045 -target-file-delete remotefile
24051 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24052 @node GDB/MI Miscellaneous Commands
24053 @section Miscellaneous @sc{gdb/mi} Commands
24055 @c @subheading -gdb-complete
24057 @subheading The @code{-gdb-exit} Command
24060 @subsubheading Synopsis
24066 Exit @value{GDBN} immediately.
24068 @subsubheading @value{GDBN} Command
24070 Approximately corresponds to @samp{quit}.
24072 @subsubheading Example
24081 @subheading The @code{-exec-abort} Command
24082 @findex -exec-abort
24084 @subsubheading Synopsis
24090 Kill the inferior running program.
24092 @subsubheading @value{GDBN} Command
24094 The corresponding @value{GDBN} command is @samp{kill}.
24096 @subsubheading Example
24100 @subheading The @code{-gdb-set} Command
24103 @subsubheading Synopsis
24109 Set an internal @value{GDBN} variable.
24110 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
24112 @subsubheading @value{GDBN} Command
24114 The corresponding @value{GDBN} command is @samp{set}.
24116 @subsubheading Example
24126 @subheading The @code{-gdb-show} Command
24129 @subsubheading Synopsis
24135 Show the current value of a @value{GDBN} variable.
24137 @subsubheading @value{GDBN} Command
24139 The corresponding @value{GDBN} command is @samp{show}.
24141 @subsubheading Example
24150 @c @subheading -gdb-source
24153 @subheading The @code{-gdb-version} Command
24154 @findex -gdb-version
24156 @subsubheading Synopsis
24162 Show version information for @value{GDBN}. Used mostly in testing.
24164 @subsubheading @value{GDBN} Command
24166 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
24167 default shows this information when you start an interactive session.
24169 @subsubheading Example
24171 @c This example modifies the actual output from GDB to avoid overfull
24177 ~Copyright 2000 Free Software Foundation, Inc.
24178 ~GDB is free software, covered by the GNU General Public License, and
24179 ~you are welcome to change it and/or distribute copies of it under
24180 ~ certain conditions.
24181 ~Type "show copying" to see the conditions.
24182 ~There is absolutely no warranty for GDB. Type "show warranty" for
24184 ~This GDB was configured as
24185 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
24190 @subheading The @code{-list-features} Command
24191 @findex -list-features
24193 Returns a list of particular features of the MI protocol that
24194 this version of gdb implements. A feature can be a command,
24195 or a new field in an output of some command, or even an
24196 important bugfix. While a frontend can sometimes detect presence
24197 of a feature at runtime, it is easier to perform detection at debugger
24200 The command returns a list of strings, with each string naming an
24201 available feature. Each returned string is just a name, it does not
24202 have any internal structure. The list of possible feature names
24208 (gdb) -list-features
24209 ^done,result=["feature1","feature2"]
24212 The current list of features is:
24215 @item frozen-varobjs
24216 Indicates presence of the @code{-var-set-frozen} command, as well
24217 as possible presense of the @code{frozen} field in the output
24218 of @code{-varobj-create}.
24219 @item pending-breakpoints
24220 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
24222 Indicates presence of the @code{-thread-info} command.
24226 @subheading The @code{-list-target-features} Command
24227 @findex -list-target-features
24229 Returns a list of particular features that are supported by the
24230 target. Those features affect the permitted MI commands, but
24231 unlike the features reported by the @code{-list-features} command, the
24232 features depend on which target GDB is using at the moment. Whenever
24233 a target can change, due to commands such as @code{-target-select},
24234 @code{-target-attach} or @code{-exec-run}, the list of target features
24235 may change, and the frontend should obtain it again.
24239 (gdb) -list-features
24240 ^done,result=["async"]
24243 The current list of features is:
24247 Indicates that the target is capable of asynchronous command
24248 execution, which means that @value{GDBN} will accept further commands
24249 while the target is running.
24253 @subheading The @code{-list-thread-groups} Command
24254 @findex -list-thread-groups
24256 @subheading Synopsis
24259 -list-thread-groups [ --available ] [ @var{group} ]
24262 When used without the @var{group} parameter, lists top-level thread
24263 groups that are being debugged. When used with the @var{group}
24264 parameter, the children of the specified group are listed. The
24265 children can be either threads, or other groups. At present,
24266 @value{GDBN} will not report both threads and groups as children at
24267 the same time, but it may change in future.
24269 With the @samp{--available} option, instead of reporting groups that
24270 are been debugged, GDB will report all thread groups available on the
24271 target. Using the @samp{--available} option together with @var{group}
24274 @subheading Example
24278 -list-thread-groups
24279 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
24280 -list-thread-groups 17
24281 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
24282 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
24283 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
24284 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
24285 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
24288 @subheading The @code{-interpreter-exec} Command
24289 @findex -interpreter-exec
24291 @subheading Synopsis
24294 -interpreter-exec @var{interpreter} @var{command}
24296 @anchor{-interpreter-exec}
24298 Execute the specified @var{command} in the given @var{interpreter}.
24300 @subheading @value{GDBN} Command
24302 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
24304 @subheading Example
24308 -interpreter-exec console "break main"
24309 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
24310 &"During symbol reading, bad structure-type format.\n"
24311 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
24316 @subheading The @code{-inferior-tty-set} Command
24317 @findex -inferior-tty-set
24319 @subheading Synopsis
24322 -inferior-tty-set /dev/pts/1
24325 Set terminal for future runs of the program being debugged.
24327 @subheading @value{GDBN} Command
24329 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
24331 @subheading Example
24335 -inferior-tty-set /dev/pts/1
24340 @subheading The @code{-inferior-tty-show} Command
24341 @findex -inferior-tty-show
24343 @subheading Synopsis
24349 Show terminal for future runs of program being debugged.
24351 @subheading @value{GDBN} Command
24353 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
24355 @subheading Example
24359 -inferior-tty-set /dev/pts/1
24363 ^done,inferior_tty_terminal="/dev/pts/1"
24367 @subheading The @code{-enable-timings} Command
24368 @findex -enable-timings
24370 @subheading Synopsis
24373 -enable-timings [yes | no]
24376 Toggle the printing of the wallclock, user and system times for an MI
24377 command as a field in its output. This command is to help frontend
24378 developers optimize the performance of their code. No argument is
24379 equivalent to @samp{yes}.
24381 @subheading @value{GDBN} Command
24385 @subheading Example
24393 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24394 addr="0x080484ed",func="main",file="myprog.c",
24395 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
24396 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
24404 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24405 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
24406 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
24407 fullname="/home/nickrob/myprog.c",line="73"@}
24412 @chapter @value{GDBN} Annotations
24414 This chapter describes annotations in @value{GDBN}. Annotations were
24415 designed to interface @value{GDBN} to graphical user interfaces or other
24416 similar programs which want to interact with @value{GDBN} at a
24417 relatively high level.
24419 The annotation mechanism has largely been superseded by @sc{gdb/mi}
24423 This is Edition @value{EDITION}, @value{DATE}.
24427 * Annotations Overview:: What annotations are; the general syntax.
24428 * Server Prefix:: Issuing a command without affecting user state.
24429 * Prompting:: Annotations marking @value{GDBN}'s need for input.
24430 * Errors:: Annotations for error messages.
24431 * Invalidation:: Some annotations describe things now invalid.
24432 * Annotations for Running::
24433 Whether the program is running, how it stopped, etc.
24434 * Source Annotations:: Annotations describing source code.
24437 @node Annotations Overview
24438 @section What is an Annotation?
24439 @cindex annotations
24441 Annotations start with a newline character, two @samp{control-z}
24442 characters, and the name of the annotation. If there is no additional
24443 information associated with this annotation, the name of the annotation
24444 is followed immediately by a newline. If there is additional
24445 information, the name of the annotation is followed by a space, the
24446 additional information, and a newline. The additional information
24447 cannot contain newline characters.
24449 Any output not beginning with a newline and two @samp{control-z}
24450 characters denotes literal output from @value{GDBN}. Currently there is
24451 no need for @value{GDBN} to output a newline followed by two
24452 @samp{control-z} characters, but if there was such a need, the
24453 annotations could be extended with an @samp{escape} annotation which
24454 means those three characters as output.
24456 The annotation @var{level}, which is specified using the
24457 @option{--annotate} command line option (@pxref{Mode Options}), controls
24458 how much information @value{GDBN} prints together with its prompt,
24459 values of expressions, source lines, and other types of output. Level 0
24460 is for no annotations, level 1 is for use when @value{GDBN} is run as a
24461 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
24462 for programs that control @value{GDBN}, and level 2 annotations have
24463 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
24464 Interface, annotate, GDB's Obsolete Annotations}).
24467 @kindex set annotate
24468 @item set annotate @var{level}
24469 The @value{GDBN} command @code{set annotate} sets the level of
24470 annotations to the specified @var{level}.
24472 @item show annotate
24473 @kindex show annotate
24474 Show the current annotation level.
24477 This chapter describes level 3 annotations.
24479 A simple example of starting up @value{GDBN} with annotations is:
24482 $ @kbd{gdb --annotate=3}
24484 Copyright 2003 Free Software Foundation, Inc.
24485 GDB is free software, covered by the GNU General Public License,
24486 and you are welcome to change it and/or distribute copies of it
24487 under certain conditions.
24488 Type "show copying" to see the conditions.
24489 There is absolutely no warranty for GDB. Type "show warranty"
24491 This GDB was configured as "i386-pc-linux-gnu"
24502 Here @samp{quit} is input to @value{GDBN}; the rest is output from
24503 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
24504 denotes a @samp{control-z} character) are annotations; the rest is
24505 output from @value{GDBN}.
24507 @node Server Prefix
24508 @section The Server Prefix
24509 @cindex server prefix
24511 If you prefix a command with @samp{server } then it will not affect
24512 the command history, nor will it affect @value{GDBN}'s notion of which
24513 command to repeat if @key{RET} is pressed on a line by itself. This
24514 means that commands can be run behind a user's back by a front-end in
24515 a transparent manner.
24517 The server prefix does not affect the recording of values into the value
24518 history; to print a value without recording it into the value history,
24519 use the @code{output} command instead of the @code{print} command.
24522 @section Annotation for @value{GDBN} Input
24524 @cindex annotations for prompts
24525 When @value{GDBN} prompts for input, it annotates this fact so it is possible
24526 to know when to send output, when the output from a given command is
24529 Different kinds of input each have a different @dfn{input type}. Each
24530 input type has three annotations: a @code{pre-} annotation, which
24531 denotes the beginning of any prompt which is being output, a plain
24532 annotation, which denotes the end of the prompt, and then a @code{post-}
24533 annotation which denotes the end of any echo which may (or may not) be
24534 associated with the input. For example, the @code{prompt} input type
24535 features the following annotations:
24543 The input types are
24546 @findex pre-prompt annotation
24547 @findex prompt annotation
24548 @findex post-prompt annotation
24550 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
24552 @findex pre-commands annotation
24553 @findex commands annotation
24554 @findex post-commands annotation
24556 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
24557 command. The annotations are repeated for each command which is input.
24559 @findex pre-overload-choice annotation
24560 @findex overload-choice annotation
24561 @findex post-overload-choice annotation
24562 @item overload-choice
24563 When @value{GDBN} wants the user to select between various overloaded functions.
24565 @findex pre-query annotation
24566 @findex query annotation
24567 @findex post-query annotation
24569 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
24571 @findex pre-prompt-for-continue annotation
24572 @findex prompt-for-continue annotation
24573 @findex post-prompt-for-continue annotation
24574 @item prompt-for-continue
24575 When @value{GDBN} is asking the user to press return to continue. Note: Don't
24576 expect this to work well; instead use @code{set height 0} to disable
24577 prompting. This is because the counting of lines is buggy in the
24578 presence of annotations.
24583 @cindex annotations for errors, warnings and interrupts
24585 @findex quit annotation
24590 This annotation occurs right before @value{GDBN} responds to an interrupt.
24592 @findex error annotation
24597 This annotation occurs right before @value{GDBN} responds to an error.
24599 Quit and error annotations indicate that any annotations which @value{GDBN} was
24600 in the middle of may end abruptly. For example, if a
24601 @code{value-history-begin} annotation is followed by a @code{error}, one
24602 cannot expect to receive the matching @code{value-history-end}. One
24603 cannot expect not to receive it either, however; an error annotation
24604 does not necessarily mean that @value{GDBN} is immediately returning all the way
24607 @findex error-begin annotation
24608 A quit or error annotation may be preceded by
24614 Any output between that and the quit or error annotation is the error
24617 Warning messages are not yet annotated.
24618 @c If we want to change that, need to fix warning(), type_error(),
24619 @c range_error(), and possibly other places.
24622 @section Invalidation Notices
24624 @cindex annotations for invalidation messages
24625 The following annotations say that certain pieces of state may have
24629 @findex frames-invalid annotation
24630 @item ^Z^Zframes-invalid
24632 The frames (for example, output from the @code{backtrace} command) may
24635 @findex breakpoints-invalid annotation
24636 @item ^Z^Zbreakpoints-invalid
24638 The breakpoints may have changed. For example, the user just added or
24639 deleted a breakpoint.
24642 @node Annotations for Running
24643 @section Running the Program
24644 @cindex annotations for running programs
24646 @findex starting annotation
24647 @findex stopping annotation
24648 When the program starts executing due to a @value{GDBN} command such as
24649 @code{step} or @code{continue},
24655 is output. When the program stops,
24661 is output. Before the @code{stopped} annotation, a variety of
24662 annotations describe how the program stopped.
24665 @findex exited annotation
24666 @item ^Z^Zexited @var{exit-status}
24667 The program exited, and @var{exit-status} is the exit status (zero for
24668 successful exit, otherwise nonzero).
24670 @findex signalled annotation
24671 @findex signal-name annotation
24672 @findex signal-name-end annotation
24673 @findex signal-string annotation
24674 @findex signal-string-end annotation
24675 @item ^Z^Zsignalled
24676 The program exited with a signal. After the @code{^Z^Zsignalled}, the
24677 annotation continues:
24683 ^Z^Zsignal-name-end
24687 ^Z^Zsignal-string-end
24692 where @var{name} is the name of the signal, such as @code{SIGILL} or
24693 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
24694 as @code{Illegal Instruction} or @code{Segmentation fault}.
24695 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
24696 user's benefit and have no particular format.
24698 @findex signal annotation
24700 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
24701 just saying that the program received the signal, not that it was
24702 terminated with it.
24704 @findex breakpoint annotation
24705 @item ^Z^Zbreakpoint @var{number}
24706 The program hit breakpoint number @var{number}.
24708 @findex watchpoint annotation
24709 @item ^Z^Zwatchpoint @var{number}
24710 The program hit watchpoint number @var{number}.
24713 @node Source Annotations
24714 @section Displaying Source
24715 @cindex annotations for source display
24717 @findex source annotation
24718 The following annotation is used instead of displaying source code:
24721 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
24724 where @var{filename} is an absolute file name indicating which source
24725 file, @var{line} is the line number within that file (where 1 is the
24726 first line in the file), @var{character} is the character position
24727 within the file (where 0 is the first character in the file) (for most
24728 debug formats this will necessarily point to the beginning of a line),
24729 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
24730 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
24731 @var{addr} is the address in the target program associated with the
24732 source which is being displayed. @var{addr} is in the form @samp{0x}
24733 followed by one or more lowercase hex digits (note that this does not
24734 depend on the language).
24737 @chapter Reporting Bugs in @value{GDBN}
24738 @cindex bugs in @value{GDBN}
24739 @cindex reporting bugs in @value{GDBN}
24741 Your bug reports play an essential role in making @value{GDBN} reliable.
24743 Reporting a bug may help you by bringing a solution to your problem, or it
24744 may not. But in any case the principal function of a bug report is to help
24745 the entire community by making the next version of @value{GDBN} work better. Bug
24746 reports are your contribution to the maintenance of @value{GDBN}.
24748 In order for a bug report to serve its purpose, you must include the
24749 information that enables us to fix the bug.
24752 * Bug Criteria:: Have you found a bug?
24753 * Bug Reporting:: How to report bugs
24757 @section Have You Found a Bug?
24758 @cindex bug criteria
24760 If you are not sure whether you have found a bug, here are some guidelines:
24763 @cindex fatal signal
24764 @cindex debugger crash
24765 @cindex crash of debugger
24767 If the debugger gets a fatal signal, for any input whatever, that is a
24768 @value{GDBN} bug. Reliable debuggers never crash.
24770 @cindex error on valid input
24772 If @value{GDBN} produces an error message for valid input, that is a
24773 bug. (Note that if you're cross debugging, the problem may also be
24774 somewhere in the connection to the target.)
24776 @cindex invalid input
24778 If @value{GDBN} does not produce an error message for invalid input,
24779 that is a bug. However, you should note that your idea of
24780 ``invalid input'' might be our idea of ``an extension'' or ``support
24781 for traditional practice''.
24784 If you are an experienced user of debugging tools, your suggestions
24785 for improvement of @value{GDBN} are welcome in any case.
24788 @node Bug Reporting
24789 @section How to Report Bugs
24790 @cindex bug reports
24791 @cindex @value{GDBN} bugs, reporting
24793 A number of companies and individuals offer support for @sc{gnu} products.
24794 If you obtained @value{GDBN} from a support organization, we recommend you
24795 contact that organization first.
24797 You can find contact information for many support companies and
24798 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
24800 @c should add a web page ref...
24803 @ifset BUGURL_DEFAULT
24804 In any event, we also recommend that you submit bug reports for
24805 @value{GDBN}. The preferred method is to submit them directly using
24806 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
24807 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
24810 @strong{Do not send bug reports to @samp{info-gdb}, or to
24811 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
24812 not want to receive bug reports. Those that do have arranged to receive
24815 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
24816 serves as a repeater. The mailing list and the newsgroup carry exactly
24817 the same messages. Often people think of posting bug reports to the
24818 newsgroup instead of mailing them. This appears to work, but it has one
24819 problem which can be crucial: a newsgroup posting often lacks a mail
24820 path back to the sender. Thus, if we need to ask for more information,
24821 we may be unable to reach you. For this reason, it is better to send
24822 bug reports to the mailing list.
24824 @ifclear BUGURL_DEFAULT
24825 In any event, we also recommend that you submit bug reports for
24826 @value{GDBN} to @value{BUGURL}.
24830 The fundamental principle of reporting bugs usefully is this:
24831 @strong{report all the facts}. If you are not sure whether to state a
24832 fact or leave it out, state it!
24834 Often people omit facts because they think they know what causes the
24835 problem and assume that some details do not matter. Thus, you might
24836 assume that the name of the variable you use in an example does not matter.
24837 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
24838 stray memory reference which happens to fetch from the location where that
24839 name is stored in memory; perhaps, if the name were different, the contents
24840 of that location would fool the debugger into doing the right thing despite
24841 the bug. Play it safe and give a specific, complete example. That is the
24842 easiest thing for you to do, and the most helpful.
24844 Keep in mind that the purpose of a bug report is to enable us to fix the
24845 bug. It may be that the bug has been reported previously, but neither
24846 you nor we can know that unless your bug report is complete and
24849 Sometimes people give a few sketchy facts and ask, ``Does this ring a
24850 bell?'' Those bug reports are useless, and we urge everyone to
24851 @emph{refuse to respond to them} except to chide the sender to report
24854 To enable us to fix the bug, you should include all these things:
24858 The version of @value{GDBN}. @value{GDBN} announces it if you start
24859 with no arguments; you can also print it at any time using @code{show
24862 Without this, we will not know whether there is any point in looking for
24863 the bug in the current version of @value{GDBN}.
24866 The type of machine you are using, and the operating system name and
24870 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
24871 ``@value{GCC}--2.8.1''.
24874 What compiler (and its version) was used to compile the program you are
24875 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
24876 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
24877 to get this information; for other compilers, see the documentation for
24881 The command arguments you gave the compiler to compile your example and
24882 observe the bug. For example, did you use @samp{-O}? To guarantee
24883 you will not omit something important, list them all. A copy of the
24884 Makefile (or the output from make) is sufficient.
24886 If we were to try to guess the arguments, we would probably guess wrong
24887 and then we might not encounter the bug.
24890 A complete input script, and all necessary source files, that will
24894 A description of what behavior you observe that you believe is
24895 incorrect. For example, ``It gets a fatal signal.''
24897 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
24898 will certainly notice it. But if the bug is incorrect output, we might
24899 not notice unless it is glaringly wrong. You might as well not give us
24900 a chance to make a mistake.
24902 Even if the problem you experience is a fatal signal, you should still
24903 say so explicitly. Suppose something strange is going on, such as, your
24904 copy of @value{GDBN} is out of synch, or you have encountered a bug in
24905 the C library on your system. (This has happened!) Your copy might
24906 crash and ours would not. If you told us to expect a crash, then when
24907 ours fails to crash, we would know that the bug was not happening for
24908 us. If you had not told us to expect a crash, then we would not be able
24909 to draw any conclusion from our observations.
24912 @cindex recording a session script
24913 To collect all this information, you can use a session recording program
24914 such as @command{script}, which is available on many Unix systems.
24915 Just run your @value{GDBN} session inside @command{script} and then
24916 include the @file{typescript} file with your bug report.
24918 Another way to record a @value{GDBN} session is to run @value{GDBN}
24919 inside Emacs and then save the entire buffer to a file.
24922 If you wish to suggest changes to the @value{GDBN} source, send us context
24923 diffs. If you even discuss something in the @value{GDBN} source, refer to
24924 it by context, not by line number.
24926 The line numbers in our development sources will not match those in your
24927 sources. Your line numbers would convey no useful information to us.
24931 Here are some things that are not necessary:
24935 A description of the envelope of the bug.
24937 Often people who encounter a bug spend a lot of time investigating
24938 which changes to the input file will make the bug go away and which
24939 changes will not affect it.
24941 This is often time consuming and not very useful, because the way we
24942 will find the bug is by running a single example under the debugger
24943 with breakpoints, not by pure deduction from a series of examples.
24944 We recommend that you save your time for something else.
24946 Of course, if you can find a simpler example to report @emph{instead}
24947 of the original one, that is a convenience for us. Errors in the
24948 output will be easier to spot, running under the debugger will take
24949 less time, and so on.
24951 However, simplification is not vital; if you do not want to do this,
24952 report the bug anyway and send us the entire test case you used.
24955 A patch for the bug.
24957 A patch for the bug does help us if it is a good one. But do not omit
24958 the necessary information, such as the test case, on the assumption that
24959 a patch is all we need. We might see problems with your patch and decide
24960 to fix the problem another way, or we might not understand it at all.
24962 Sometimes with a program as complicated as @value{GDBN} it is very hard to
24963 construct an example that will make the program follow a certain path
24964 through the code. If you do not send us the example, we will not be able
24965 to construct one, so we will not be able to verify that the bug is fixed.
24967 And if we cannot understand what bug you are trying to fix, or why your
24968 patch should be an improvement, we will not install it. A test case will
24969 help us to understand.
24972 A guess about what the bug is or what it depends on.
24974 Such guesses are usually wrong. Even we cannot guess right about such
24975 things without first using the debugger to find the facts.
24978 @c The readline documentation is distributed with the readline code
24979 @c and consists of the two following files:
24981 @c inc-hist.texinfo
24982 @c Use -I with makeinfo to point to the appropriate directory,
24983 @c environment var TEXINPUTS with TeX.
24984 @include rluser.texi
24985 @include inc-hist.texinfo
24988 @node Formatting Documentation
24989 @appendix Formatting Documentation
24991 @cindex @value{GDBN} reference card
24992 @cindex reference card
24993 The @value{GDBN} 4 release includes an already-formatted reference card, ready
24994 for printing with PostScript or Ghostscript, in the @file{gdb}
24995 subdirectory of the main source directory@footnote{In
24996 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
24997 release.}. If you can use PostScript or Ghostscript with your printer,
24998 you can print the reference card immediately with @file{refcard.ps}.
25000 The release also includes the source for the reference card. You
25001 can format it, using @TeX{}, by typing:
25007 The @value{GDBN} reference card is designed to print in @dfn{landscape}
25008 mode on US ``letter'' size paper;
25009 that is, on a sheet 11 inches wide by 8.5 inches
25010 high. You will need to specify this form of printing as an option to
25011 your @sc{dvi} output program.
25013 @cindex documentation
25015 All the documentation for @value{GDBN} comes as part of the machine-readable
25016 distribution. The documentation is written in Texinfo format, which is
25017 a documentation system that uses a single source file to produce both
25018 on-line information and a printed manual. You can use one of the Info
25019 formatting commands to create the on-line version of the documentation
25020 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
25022 @value{GDBN} includes an already formatted copy of the on-line Info
25023 version of this manual in the @file{gdb} subdirectory. The main Info
25024 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
25025 subordinate files matching @samp{gdb.info*} in the same directory. If
25026 necessary, you can print out these files, or read them with any editor;
25027 but they are easier to read using the @code{info} subsystem in @sc{gnu}
25028 Emacs or the standalone @code{info} program, available as part of the
25029 @sc{gnu} Texinfo distribution.
25031 If you want to format these Info files yourself, you need one of the
25032 Info formatting programs, such as @code{texinfo-format-buffer} or
25035 If you have @code{makeinfo} installed, and are in the top level
25036 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
25037 version @value{GDBVN}), you can make the Info file by typing:
25044 If you want to typeset and print copies of this manual, you need @TeX{},
25045 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
25046 Texinfo definitions file.
25048 @TeX{} is a typesetting program; it does not print files directly, but
25049 produces output files called @sc{dvi} files. To print a typeset
25050 document, you need a program to print @sc{dvi} files. If your system
25051 has @TeX{} installed, chances are it has such a program. The precise
25052 command to use depends on your system; @kbd{lpr -d} is common; another
25053 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
25054 require a file name without any extension or a @samp{.dvi} extension.
25056 @TeX{} also requires a macro definitions file called
25057 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
25058 written in Texinfo format. On its own, @TeX{} cannot either read or
25059 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
25060 and is located in the @file{gdb-@var{version-number}/texinfo}
25063 If you have @TeX{} and a @sc{dvi} printer program installed, you can
25064 typeset and print this manual. First switch to the @file{gdb}
25065 subdirectory of the main source directory (for example, to
25066 @file{gdb-@value{GDBVN}/gdb}) and type:
25072 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
25074 @node Installing GDB
25075 @appendix Installing @value{GDBN}
25076 @cindex installation
25079 * Requirements:: Requirements for building @value{GDBN}
25080 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
25081 * Separate Objdir:: Compiling @value{GDBN} in another directory
25082 * Config Names:: Specifying names for hosts and targets
25083 * Configure Options:: Summary of options for configure
25084 * System-wide configuration:: Having a system-wide init file
25088 @section Requirements for Building @value{GDBN}
25089 @cindex building @value{GDBN}, requirements for
25091 Building @value{GDBN} requires various tools and packages to be available.
25092 Other packages will be used only if they are found.
25094 @heading Tools/Packages Necessary for Building @value{GDBN}
25096 @item ISO C90 compiler
25097 @value{GDBN} is written in ISO C90. It should be buildable with any
25098 working C90 compiler, e.g.@: GCC.
25102 @heading Tools/Packages Optional for Building @value{GDBN}
25106 @value{GDBN} can use the Expat XML parsing library. This library may be
25107 included with your operating system distribution; if it is not, you
25108 can get the latest version from @url{http://expat.sourceforge.net}.
25109 The @file{configure} script will search for this library in several
25110 standard locations; if it is installed in an unusual path, you can
25111 use the @option{--with-libexpat-prefix} option to specify its location.
25117 Remote protocol memory maps (@pxref{Memory Map Format})
25119 Target descriptions (@pxref{Target Descriptions})
25121 Remote shared library lists (@pxref{Library List Format})
25123 MS-Windows shared libraries (@pxref{Shared Libraries})
25127 @cindex compressed debug sections
25128 @value{GDBN} will use the @samp{zlib} library, if available, to read
25129 compressed debug sections. Some linkers, such as GNU gold, are capable
25130 of producing binaries with compressed debug sections. If @value{GDBN}
25131 is compiled with @samp{zlib}, it will be able to read the debug
25132 information in such binaries.
25134 The @samp{zlib} library is likely included with your operating system
25135 distribution; if it is not, you can get the latest version from
25136 @url{http://zlib.net}.
25139 @value{GDBN}'s features related to character sets (@pxref{Character
25140 Sets}) require a functioning @code{iconv} implementation. If you are
25141 on a GNU system, then this is provided by the GNU C Library. Some
25142 other systems also provide a working @code{iconv}.
25144 On systems with @code{iconv}, you can install GNU Libiconv. If you
25145 have previously installed Libiconv, you can use the
25146 @option{--with-libiconv-prefix} option to configure.
25148 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
25149 arrange to build Libiconv if a directory named @file{libiconv} appears
25150 in the top-most source directory. If Libiconv is built this way, and
25151 if the operating system does not provide a suitable @code{iconv}
25152 implementation, then the just-built library will automatically be used
25153 by @value{GDBN}. One easy way to set this up is to download GNU
25154 Libiconv, unpack it, and then rename the directory holding the
25155 Libiconv source code to @samp{libiconv}.
25158 @node Running Configure
25159 @section Invoking the @value{GDBN} @file{configure} Script
25160 @cindex configuring @value{GDBN}
25161 @value{GDBN} comes with a @file{configure} script that automates the process
25162 of preparing @value{GDBN} for installation; you can then use @code{make} to
25163 build the @code{gdb} program.
25165 @c irrelevant in info file; it's as current as the code it lives with.
25166 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
25167 look at the @file{README} file in the sources; we may have improved the
25168 installation procedures since publishing this manual.}
25171 The @value{GDBN} distribution includes all the source code you need for
25172 @value{GDBN} in a single directory, whose name is usually composed by
25173 appending the version number to @samp{gdb}.
25175 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
25176 @file{gdb-@value{GDBVN}} directory. That directory contains:
25179 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
25180 script for configuring @value{GDBN} and all its supporting libraries
25182 @item gdb-@value{GDBVN}/gdb
25183 the source specific to @value{GDBN} itself
25185 @item gdb-@value{GDBVN}/bfd
25186 source for the Binary File Descriptor library
25188 @item gdb-@value{GDBVN}/include
25189 @sc{gnu} include files
25191 @item gdb-@value{GDBVN}/libiberty
25192 source for the @samp{-liberty} free software library
25194 @item gdb-@value{GDBVN}/opcodes
25195 source for the library of opcode tables and disassemblers
25197 @item gdb-@value{GDBVN}/readline
25198 source for the @sc{gnu} command-line interface
25200 @item gdb-@value{GDBVN}/glob
25201 source for the @sc{gnu} filename pattern-matching subroutine
25203 @item gdb-@value{GDBVN}/mmalloc
25204 source for the @sc{gnu} memory-mapped malloc package
25207 The simplest way to configure and build @value{GDBN} is to run @file{configure}
25208 from the @file{gdb-@var{version-number}} source directory, which in
25209 this example is the @file{gdb-@value{GDBVN}} directory.
25211 First switch to the @file{gdb-@var{version-number}} source directory
25212 if you are not already in it; then run @file{configure}. Pass the
25213 identifier for the platform on which @value{GDBN} will run as an
25219 cd gdb-@value{GDBVN}
25220 ./configure @var{host}
25225 where @var{host} is an identifier such as @samp{sun4} or
25226 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
25227 (You can often leave off @var{host}; @file{configure} tries to guess the
25228 correct value by examining your system.)
25230 Running @samp{configure @var{host}} and then running @code{make} builds the
25231 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
25232 libraries, then @code{gdb} itself. The configured source files, and the
25233 binaries, are left in the corresponding source directories.
25236 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
25237 system does not recognize this automatically when you run a different
25238 shell, you may need to run @code{sh} on it explicitly:
25241 sh configure @var{host}
25244 If you run @file{configure} from a directory that contains source
25245 directories for multiple libraries or programs, such as the
25246 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
25248 creates configuration files for every directory level underneath (unless
25249 you tell it not to, with the @samp{--norecursion} option).
25251 You should run the @file{configure} script from the top directory in the
25252 source tree, the @file{gdb-@var{version-number}} directory. If you run
25253 @file{configure} from one of the subdirectories, you will configure only
25254 that subdirectory. That is usually not what you want. In particular,
25255 if you run the first @file{configure} from the @file{gdb} subdirectory
25256 of the @file{gdb-@var{version-number}} directory, you will omit the
25257 configuration of @file{bfd}, @file{readline}, and other sibling
25258 directories of the @file{gdb} subdirectory. This leads to build errors
25259 about missing include files such as @file{bfd/bfd.h}.
25261 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
25262 However, you should make sure that the shell on your path (named by
25263 the @samp{SHELL} environment variable) is publicly readable. Remember
25264 that @value{GDBN} uses the shell to start your program---some systems refuse to
25265 let @value{GDBN} debug child processes whose programs are not readable.
25267 @node Separate Objdir
25268 @section Compiling @value{GDBN} in Another Directory
25270 If you want to run @value{GDBN} versions for several host or target machines,
25271 you need a different @code{gdb} compiled for each combination of
25272 host and target. @file{configure} is designed to make this easy by
25273 allowing you to generate each configuration in a separate subdirectory,
25274 rather than in the source directory. If your @code{make} program
25275 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
25276 @code{make} in each of these directories builds the @code{gdb}
25277 program specified there.
25279 To build @code{gdb} in a separate directory, run @file{configure}
25280 with the @samp{--srcdir} option to specify where to find the source.
25281 (You also need to specify a path to find @file{configure}
25282 itself from your working directory. If the path to @file{configure}
25283 would be the same as the argument to @samp{--srcdir}, you can leave out
25284 the @samp{--srcdir} option; it is assumed.)
25286 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
25287 separate directory for a Sun 4 like this:
25291 cd gdb-@value{GDBVN}
25294 ../gdb-@value{GDBVN}/configure sun4
25299 When @file{configure} builds a configuration using a remote source
25300 directory, it creates a tree for the binaries with the same structure
25301 (and using the same names) as the tree under the source directory. In
25302 the example, you'd find the Sun 4 library @file{libiberty.a} in the
25303 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
25304 @file{gdb-sun4/gdb}.
25306 Make sure that your path to the @file{configure} script has just one
25307 instance of @file{gdb} in it. If your path to @file{configure} looks
25308 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
25309 one subdirectory of @value{GDBN}, not the whole package. This leads to
25310 build errors about missing include files such as @file{bfd/bfd.h}.
25312 One popular reason to build several @value{GDBN} configurations in separate
25313 directories is to configure @value{GDBN} for cross-compiling (where
25314 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
25315 programs that run on another machine---the @dfn{target}).
25316 You specify a cross-debugging target by
25317 giving the @samp{--target=@var{target}} option to @file{configure}.
25319 When you run @code{make} to build a program or library, you must run
25320 it in a configured directory---whatever directory you were in when you
25321 called @file{configure} (or one of its subdirectories).
25323 The @code{Makefile} that @file{configure} generates in each source
25324 directory also runs recursively. If you type @code{make} in a source
25325 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
25326 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
25327 will build all the required libraries, and then build GDB.
25329 When you have multiple hosts or targets configured in separate
25330 directories, you can run @code{make} on them in parallel (for example,
25331 if they are NFS-mounted on each of the hosts); they will not interfere
25335 @section Specifying Names for Hosts and Targets
25337 The specifications used for hosts and targets in the @file{configure}
25338 script are based on a three-part naming scheme, but some short predefined
25339 aliases are also supported. The full naming scheme encodes three pieces
25340 of information in the following pattern:
25343 @var{architecture}-@var{vendor}-@var{os}
25346 For example, you can use the alias @code{sun4} as a @var{host} argument,
25347 or as the value for @var{target} in a @code{--target=@var{target}}
25348 option. The equivalent full name is @samp{sparc-sun-sunos4}.
25350 The @file{configure} script accompanying @value{GDBN} does not provide
25351 any query facility to list all supported host and target names or
25352 aliases. @file{configure} calls the Bourne shell script
25353 @code{config.sub} to map abbreviations to full names; you can read the
25354 script, if you wish, or you can use it to test your guesses on
25355 abbreviations---for example:
25358 % sh config.sub i386-linux
25360 % sh config.sub alpha-linux
25361 alpha-unknown-linux-gnu
25362 % sh config.sub hp9k700
25364 % sh config.sub sun4
25365 sparc-sun-sunos4.1.1
25366 % sh config.sub sun3
25367 m68k-sun-sunos4.1.1
25368 % sh config.sub i986v
25369 Invalid configuration `i986v': machine `i986v' not recognized
25373 @code{config.sub} is also distributed in the @value{GDBN} source
25374 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
25376 @node Configure Options
25377 @section @file{configure} Options
25379 Here is a summary of the @file{configure} options and arguments that
25380 are most often useful for building @value{GDBN}. @file{configure} also has
25381 several other options not listed here. @inforef{What Configure
25382 Does,,configure.info}, for a full explanation of @file{configure}.
25385 configure @r{[}--help@r{]}
25386 @r{[}--prefix=@var{dir}@r{]}
25387 @r{[}--exec-prefix=@var{dir}@r{]}
25388 @r{[}--srcdir=@var{dirname}@r{]}
25389 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
25390 @r{[}--target=@var{target}@r{]}
25395 You may introduce options with a single @samp{-} rather than
25396 @samp{--} if you prefer; but you may abbreviate option names if you use
25401 Display a quick summary of how to invoke @file{configure}.
25403 @item --prefix=@var{dir}
25404 Configure the source to install programs and files under directory
25407 @item --exec-prefix=@var{dir}
25408 Configure the source to install programs under directory
25411 @c avoid splitting the warning from the explanation:
25413 @item --srcdir=@var{dirname}
25414 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
25415 @code{make} that implements the @code{VPATH} feature.}@*
25416 Use this option to make configurations in directories separate from the
25417 @value{GDBN} source directories. Among other things, you can use this to
25418 build (or maintain) several configurations simultaneously, in separate
25419 directories. @file{configure} writes configuration-specific files in
25420 the current directory, but arranges for them to use the source in the
25421 directory @var{dirname}. @file{configure} creates directories under
25422 the working directory in parallel to the source directories below
25425 @item --norecursion
25426 Configure only the directory level where @file{configure} is executed; do not
25427 propagate configuration to subdirectories.
25429 @item --target=@var{target}
25430 Configure @value{GDBN} for cross-debugging programs running on the specified
25431 @var{target}. Without this option, @value{GDBN} is configured to debug
25432 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
25434 There is no convenient way to generate a list of all available targets.
25436 @item @var{host} @dots{}
25437 Configure @value{GDBN} to run on the specified @var{host}.
25439 There is no convenient way to generate a list of all available hosts.
25442 There are many other options available as well, but they are generally
25443 needed for special purposes only.
25445 @node System-wide configuration
25446 @section System-wide configuration and settings
25447 @cindex system-wide init file
25449 @value{GDBN} can be configured to have a system-wide init file;
25450 this file will be read and executed at startup (@pxref{Startup, , What
25451 @value{GDBN} does during startup}).
25453 Here is the corresponding configure option:
25456 @item --with-system-gdbinit=@var{file}
25457 Specify that the default location of the system-wide init file is
25461 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
25462 it may be subject to relocation. Two possible cases:
25466 If the default location of this init file contains @file{$prefix},
25467 it will be subject to relocation. Suppose that the configure options
25468 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
25469 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
25470 init file is looked for as @file{$install/etc/gdbinit} instead of
25471 @file{$prefix/etc/gdbinit}.
25474 By contrast, if the default location does not contain the prefix,
25475 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
25476 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
25477 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
25478 wherever @value{GDBN} is installed.
25481 @node Maintenance Commands
25482 @appendix Maintenance Commands
25483 @cindex maintenance commands
25484 @cindex internal commands
25486 In addition to commands intended for @value{GDBN} users, @value{GDBN}
25487 includes a number of commands intended for @value{GDBN} developers,
25488 that are not documented elsewhere in this manual. These commands are
25489 provided here for reference. (For commands that turn on debugging
25490 messages, see @ref{Debugging Output}.)
25493 @kindex maint agent
25494 @item maint agent @var{expression}
25495 Translate the given @var{expression} into remote agent bytecodes.
25496 This command is useful for debugging the Agent Expression mechanism
25497 (@pxref{Agent Expressions}).
25499 @kindex maint info breakpoints
25500 @item @anchor{maint info breakpoints}maint info breakpoints
25501 Using the same format as @samp{info breakpoints}, display both the
25502 breakpoints you've set explicitly, and those @value{GDBN} is using for
25503 internal purposes. Internal breakpoints are shown with negative
25504 breakpoint numbers. The type column identifies what kind of breakpoint
25509 Normal, explicitly set breakpoint.
25512 Normal, explicitly set watchpoint.
25515 Internal breakpoint, used to handle correctly stepping through
25516 @code{longjmp} calls.
25518 @item longjmp resume
25519 Internal breakpoint at the target of a @code{longjmp}.
25522 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
25525 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
25528 Shared library events.
25532 @kindex set displaced-stepping
25533 @kindex show displaced-stepping
25534 @cindex displaced stepping support
25535 @cindex out-of-line single-stepping
25536 @item set displaced-stepping
25537 @itemx show displaced-stepping
25538 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
25539 if the target supports it. Displaced stepping is a way to single-step
25540 over breakpoints without removing them from the inferior, by executing
25541 an out-of-line copy of the instruction that was originally at the
25542 breakpoint location. It is also known as out-of-line single-stepping.
25545 @item set displaced-stepping on
25546 If the target architecture supports it, @value{GDBN} will use
25547 displaced stepping to step over breakpoints.
25549 @item set displaced-stepping off
25550 @value{GDBN} will not use displaced stepping to step over breakpoints,
25551 even if such is supported by the target architecture.
25553 @cindex non-stop mode, and @samp{set displaced-stepping}
25554 @item set displaced-stepping auto
25555 This is the default mode. @value{GDBN} will use displaced stepping
25556 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
25557 architecture supports displaced stepping.
25560 @kindex maint check-symtabs
25561 @item maint check-symtabs
25562 Check the consistency of psymtabs and symtabs.
25564 @kindex maint cplus first_component
25565 @item maint cplus first_component @var{name}
25566 Print the first C@t{++} class/namespace component of @var{name}.
25568 @kindex maint cplus namespace
25569 @item maint cplus namespace
25570 Print the list of possible C@t{++} namespaces.
25572 @kindex maint demangle
25573 @item maint demangle @var{name}
25574 Demangle a C@t{++} or Objective-C mangled @var{name}.
25576 @kindex maint deprecate
25577 @kindex maint undeprecate
25578 @cindex deprecated commands
25579 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
25580 @itemx maint undeprecate @var{command}
25581 Deprecate or undeprecate the named @var{command}. Deprecated commands
25582 cause @value{GDBN} to issue a warning when you use them. The optional
25583 argument @var{replacement} says which newer command should be used in
25584 favor of the deprecated one; if it is given, @value{GDBN} will mention
25585 the replacement as part of the warning.
25587 @kindex maint dump-me
25588 @item maint dump-me
25589 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
25590 Cause a fatal signal in the debugger and force it to dump its core.
25591 This is supported only on systems which support aborting a program
25592 with the @code{SIGQUIT} signal.
25594 @kindex maint internal-error
25595 @kindex maint internal-warning
25596 @item maint internal-error @r{[}@var{message-text}@r{]}
25597 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
25598 Cause @value{GDBN} to call the internal function @code{internal_error}
25599 or @code{internal_warning} and hence behave as though an internal error
25600 or internal warning has been detected. In addition to reporting the
25601 internal problem, these functions give the user the opportunity to
25602 either quit @value{GDBN} or create a core file of the current
25603 @value{GDBN} session.
25605 These commands take an optional parameter @var{message-text} that is
25606 used as the text of the error or warning message.
25608 Here's an example of using @code{internal-error}:
25611 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
25612 @dots{}/maint.c:121: internal-error: testing, 1, 2
25613 A problem internal to GDB has been detected. Further
25614 debugging may prove unreliable.
25615 Quit this debugging session? (y or n) @kbd{n}
25616 Create a core file? (y or n) @kbd{n}
25620 @cindex @value{GDBN} internal error
25621 @cindex internal errors, control of @value{GDBN} behavior
25623 @kindex maint set internal-error
25624 @kindex maint show internal-error
25625 @kindex maint set internal-warning
25626 @kindex maint show internal-warning
25627 @item maint set internal-error @var{action} [ask|yes|no]
25628 @itemx maint show internal-error @var{action}
25629 @itemx maint set internal-warning @var{action} [ask|yes|no]
25630 @itemx maint show internal-warning @var{action}
25631 When @value{GDBN} reports an internal problem (error or warning) it
25632 gives the user the opportunity to both quit @value{GDBN} and create a
25633 core file of the current @value{GDBN} session. These commands let you
25634 override the default behaviour for each particular @var{action},
25635 described in the table below.
25639 You can specify that @value{GDBN} should always (yes) or never (no)
25640 quit. The default is to ask the user what to do.
25643 You can specify that @value{GDBN} should always (yes) or never (no)
25644 create a core file. The default is to ask the user what to do.
25647 @kindex maint packet
25648 @item maint packet @var{text}
25649 If @value{GDBN} is talking to an inferior via the serial protocol,
25650 then this command sends the string @var{text} to the inferior, and
25651 displays the response packet. @value{GDBN} supplies the initial
25652 @samp{$} character, the terminating @samp{#} character, and the
25655 @kindex maint print architecture
25656 @item maint print architecture @r{[}@var{file}@r{]}
25657 Print the entire architecture configuration. The optional argument
25658 @var{file} names the file where the output goes.
25660 @kindex maint print c-tdesc
25661 @item maint print c-tdesc
25662 Print the current target description (@pxref{Target Descriptions}) as
25663 a C source file. The created source file can be used in @value{GDBN}
25664 when an XML parser is not available to parse the description.
25666 @kindex maint print dummy-frames
25667 @item maint print dummy-frames
25668 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
25671 (@value{GDBP}) @kbd{b add}
25673 (@value{GDBP}) @kbd{print add(2,3)}
25674 Breakpoint 2, add (a=2, b=3) at @dots{}
25676 The program being debugged stopped while in a function called from GDB.
25678 (@value{GDBP}) @kbd{maint print dummy-frames}
25679 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
25680 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
25681 call_lo=0x01014000 call_hi=0x01014001
25685 Takes an optional file parameter.
25687 @kindex maint print registers
25688 @kindex maint print raw-registers
25689 @kindex maint print cooked-registers
25690 @kindex maint print register-groups
25691 @item maint print registers @r{[}@var{file}@r{]}
25692 @itemx maint print raw-registers @r{[}@var{file}@r{]}
25693 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
25694 @itemx maint print register-groups @r{[}@var{file}@r{]}
25695 Print @value{GDBN}'s internal register data structures.
25697 The command @code{maint print raw-registers} includes the contents of
25698 the raw register cache; the command @code{maint print cooked-registers}
25699 includes the (cooked) value of all registers; and the command
25700 @code{maint print register-groups} includes the groups that each
25701 register is a member of. @xref{Registers,, Registers, gdbint,
25702 @value{GDBN} Internals}.
25704 These commands take an optional parameter, a file name to which to
25705 write the information.
25707 @kindex maint print reggroups
25708 @item maint print reggroups @r{[}@var{file}@r{]}
25709 Print @value{GDBN}'s internal register group data structures. The
25710 optional argument @var{file} tells to what file to write the
25713 The register groups info looks like this:
25716 (@value{GDBP}) @kbd{maint print reggroups}
25729 This command forces @value{GDBN} to flush its internal register cache.
25731 @kindex maint print objfiles
25732 @cindex info for known object files
25733 @item maint print objfiles
25734 Print a dump of all known object files. For each object file, this
25735 command prints its name, address in memory, and all of its psymtabs
25738 @kindex maint print statistics
25739 @cindex bcache statistics
25740 @item maint print statistics
25741 This command prints, for each object file in the program, various data
25742 about that object file followed by the byte cache (@dfn{bcache})
25743 statistics for the object file. The objfile data includes the number
25744 of minimal, partial, full, and stabs symbols, the number of types
25745 defined by the objfile, the number of as yet unexpanded psym tables,
25746 the number of line tables and string tables, and the amount of memory
25747 used by the various tables. The bcache statistics include the counts,
25748 sizes, and counts of duplicates of all and unique objects, max,
25749 average, and median entry size, total memory used and its overhead and
25750 savings, and various measures of the hash table size and chain
25753 @kindex maint print target-stack
25754 @cindex target stack description
25755 @item maint print target-stack
25756 A @dfn{target} is an interface between the debugger and a particular
25757 kind of file or process. Targets can be stacked in @dfn{strata},
25758 so that more than one target can potentially respond to a request.
25759 In particular, memory accesses will walk down the stack of targets
25760 until they find a target that is interested in handling that particular
25763 This command prints a short description of each layer that was pushed on
25764 the @dfn{target stack}, starting from the top layer down to the bottom one.
25766 @kindex maint print type
25767 @cindex type chain of a data type
25768 @item maint print type @var{expr}
25769 Print the type chain for a type specified by @var{expr}. The argument
25770 can be either a type name or a symbol. If it is a symbol, the type of
25771 that symbol is described. The type chain produced by this command is
25772 a recursive definition of the data type as stored in @value{GDBN}'s
25773 data structures, including its flags and contained types.
25775 @kindex maint set dwarf2 max-cache-age
25776 @kindex maint show dwarf2 max-cache-age
25777 @item maint set dwarf2 max-cache-age
25778 @itemx maint show dwarf2 max-cache-age
25779 Control the DWARF 2 compilation unit cache.
25781 @cindex DWARF 2 compilation units cache
25782 In object files with inter-compilation-unit references, such as those
25783 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
25784 reader needs to frequently refer to previously read compilation units.
25785 This setting controls how long a compilation unit will remain in the
25786 cache if it is not referenced. A higher limit means that cached
25787 compilation units will be stored in memory longer, and more total
25788 memory will be used. Setting it to zero disables caching, which will
25789 slow down @value{GDBN} startup, but reduce memory consumption.
25791 @kindex maint set profile
25792 @kindex maint show profile
25793 @cindex profiling GDB
25794 @item maint set profile
25795 @itemx maint show profile
25796 Control profiling of @value{GDBN}.
25798 Profiling will be disabled until you use the @samp{maint set profile}
25799 command to enable it. When you enable profiling, the system will begin
25800 collecting timing and execution count data; when you disable profiling or
25801 exit @value{GDBN}, the results will be written to a log file. Remember that
25802 if you use profiling, @value{GDBN} will overwrite the profiling log file
25803 (often called @file{gmon.out}). If you have a record of important profiling
25804 data in a @file{gmon.out} file, be sure to move it to a safe location.
25806 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
25807 compiled with the @samp{-pg} compiler option.
25809 @kindex maint show-debug-regs
25810 @cindex hardware debug registers
25811 @item maint show-debug-regs
25812 Control whether to show variables that mirror the hardware debug
25813 registers. Use @code{ON} to enable, @code{OFF} to disable. If
25814 enabled, the debug registers values are shown when @value{GDBN} inserts or
25815 removes a hardware breakpoint or watchpoint, and when the inferior
25816 triggers a hardware-assisted breakpoint or watchpoint.
25818 @kindex maint space
25819 @cindex memory used by commands
25821 Control whether to display memory usage for each command. If set to a
25822 nonzero value, @value{GDBN} will display how much memory each command
25823 took, following the command's own output. This can also be requested
25824 by invoking @value{GDBN} with the @option{--statistics} command-line
25825 switch (@pxref{Mode Options}).
25828 @cindex time of command execution
25830 Control whether to display the execution time for each command. If
25831 set to a nonzero value, @value{GDBN} will display how much time it
25832 took to execute each command, following the command's own output.
25833 The time is not printed for the commands that run the target, since
25834 there's no mechanism currently to compute how much time was spend
25835 by @value{GDBN} and how much time was spend by the program been debugged.
25836 it's not possibly currently
25837 This can also be requested by invoking @value{GDBN} with the
25838 @option{--statistics} command-line switch (@pxref{Mode Options}).
25840 @kindex maint translate-address
25841 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
25842 Find the symbol stored at the location specified by the address
25843 @var{addr} and an optional section name @var{section}. If found,
25844 @value{GDBN} prints the name of the closest symbol and an offset from
25845 the symbol's location to the specified address. This is similar to
25846 the @code{info address} command (@pxref{Symbols}), except that this
25847 command also allows to find symbols in other sections.
25849 If section was not specified, the section in which the symbol was found
25850 is also printed. For dynamically linked executables, the name of
25851 executable or shared library containing the symbol is printed as well.
25855 The following command is useful for non-interactive invocations of
25856 @value{GDBN}, such as in the test suite.
25859 @item set watchdog @var{nsec}
25860 @kindex set watchdog
25861 @cindex watchdog timer
25862 @cindex timeout for commands
25863 Set the maximum number of seconds @value{GDBN} will wait for the
25864 target operation to finish. If this time expires, @value{GDBN}
25865 reports and error and the command is aborted.
25867 @item show watchdog
25868 Show the current setting of the target wait timeout.
25871 @node Remote Protocol
25872 @appendix @value{GDBN} Remote Serial Protocol
25877 * Stop Reply Packets::
25878 * General Query Packets::
25879 * Register Packet Format::
25880 * Tracepoint Packets::
25881 * Host I/O Packets::
25883 * Notification Packets::
25884 * Remote Non-Stop::
25885 * Packet Acknowledgment::
25887 * File-I/O Remote Protocol Extension::
25888 * Library List Format::
25889 * Memory Map Format::
25895 There may be occasions when you need to know something about the
25896 protocol---for example, if there is only one serial port to your target
25897 machine, you might want your program to do something special if it
25898 recognizes a packet meant for @value{GDBN}.
25900 In the examples below, @samp{->} and @samp{<-} are used to indicate
25901 transmitted and received data, respectively.
25903 @cindex protocol, @value{GDBN} remote serial
25904 @cindex serial protocol, @value{GDBN} remote
25905 @cindex remote serial protocol
25906 All @value{GDBN} commands and responses (other than acknowledgments
25907 and notifications, see @ref{Notification Packets}) are sent as a
25908 @var{packet}. A @var{packet} is introduced with the character
25909 @samp{$}, the actual @var{packet-data}, and the terminating character
25910 @samp{#} followed by a two-digit @var{checksum}:
25913 @code{$}@var{packet-data}@code{#}@var{checksum}
25917 @cindex checksum, for @value{GDBN} remote
25919 The two-digit @var{checksum} is computed as the modulo 256 sum of all
25920 characters between the leading @samp{$} and the trailing @samp{#} (an
25921 eight bit unsigned checksum).
25923 Implementors should note that prior to @value{GDBN} 5.0 the protocol
25924 specification also included an optional two-digit @var{sequence-id}:
25927 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
25930 @cindex sequence-id, for @value{GDBN} remote
25932 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
25933 has never output @var{sequence-id}s. Stubs that handle packets added
25934 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
25936 When either the host or the target machine receives a packet, the first
25937 response expected is an acknowledgment: either @samp{+} (to indicate
25938 the package was received correctly) or @samp{-} (to request
25942 -> @code{$}@var{packet-data}@code{#}@var{checksum}
25947 The @samp{+}/@samp{-} acknowledgments can be disabled
25948 once a connection is established.
25949 @xref{Packet Acknowledgment}, for details.
25951 The host (@value{GDBN}) sends @var{command}s, and the target (the
25952 debugging stub incorporated in your program) sends a @var{response}. In
25953 the case of step and continue @var{command}s, the response is only sent
25954 when the operation has completed, and the target has again stopped all
25955 threads in all attached processes. This is the default all-stop mode
25956 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
25957 execution mode; see @ref{Remote Non-Stop}, for details.
25959 @var{packet-data} consists of a sequence of characters with the
25960 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
25963 @cindex remote protocol, field separator
25964 Fields within the packet should be separated using @samp{,} @samp{;} or
25965 @samp{:}. Except where otherwise noted all numbers are represented in
25966 @sc{hex} with leading zeros suppressed.
25968 Implementors should note that prior to @value{GDBN} 5.0, the character
25969 @samp{:} could not appear as the third character in a packet (as it
25970 would potentially conflict with the @var{sequence-id}).
25972 @cindex remote protocol, binary data
25973 @anchor{Binary Data}
25974 Binary data in most packets is encoded either as two hexadecimal
25975 digits per byte of binary data. This allowed the traditional remote
25976 protocol to work over connections which were only seven-bit clean.
25977 Some packets designed more recently assume an eight-bit clean
25978 connection, and use a more efficient encoding to send and receive
25981 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
25982 as an escape character. Any escaped byte is transmitted as the escape
25983 character followed by the original character XORed with @code{0x20}.
25984 For example, the byte @code{0x7d} would be transmitted as the two
25985 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
25986 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
25987 @samp{@}}) must always be escaped. Responses sent by the stub
25988 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
25989 is not interpreted as the start of a run-length encoded sequence
25992 Response @var{data} can be run-length encoded to save space.
25993 Run-length encoding replaces runs of identical characters with one
25994 instance of the repeated character, followed by a @samp{*} and a
25995 repeat count. The repeat count is itself sent encoded, to avoid
25996 binary characters in @var{data}: a value of @var{n} is sent as
25997 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
25998 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
25999 code 32) for a repeat count of 3. (This is because run-length
26000 encoding starts to win for counts 3 or more.) Thus, for example,
26001 @samp{0* } is a run-length encoding of ``0000'': the space character
26002 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
26005 The printable characters @samp{#} and @samp{$} or with a numeric value
26006 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
26007 seven repeats (@samp{$}) can be expanded using a repeat count of only
26008 five (@samp{"}). For example, @samp{00000000} can be encoded as
26011 The error response returned for some packets includes a two character
26012 error number. That number is not well defined.
26014 @cindex empty response, for unsupported packets
26015 For any @var{command} not supported by the stub, an empty response
26016 (@samp{$#00}) should be returned. That way it is possible to extend the
26017 protocol. A newer @value{GDBN} can tell if a packet is supported based
26020 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
26021 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
26027 The following table provides a complete list of all currently defined
26028 @var{command}s and their corresponding response @var{data}.
26029 @xref{File-I/O Remote Protocol Extension}, for details about the File
26030 I/O extension of the remote protocol.
26032 Each packet's description has a template showing the packet's overall
26033 syntax, followed by an explanation of the packet's meaning. We
26034 include spaces in some of the templates for clarity; these are not
26035 part of the packet's syntax. No @value{GDBN} packet uses spaces to
26036 separate its components. For example, a template like @samp{foo
26037 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
26038 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
26039 @var{baz}. @value{GDBN} does not transmit a space character between the
26040 @samp{foo} and the @var{bar}, or between the @var{bar} and the
26043 @cindex @var{thread-id}, in remote protocol
26044 @anchor{thread-id syntax}
26045 Several packets and replies include a @var{thread-id} field to identify
26046 a thread. Normally these are positive numbers with a target-specific
26047 interpretation, formatted as big-endian hex strings. A @var{thread-id}
26048 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
26051 In addition, the remote protocol supports a multiprocess feature in
26052 which the @var{thread-id} syntax is extended to optionally include both
26053 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
26054 The @var{pid} (process) and @var{tid} (thread) components each have the
26055 format described above: a positive number with target-specific
26056 interpretation formatted as a big-endian hex string, literal @samp{-1}
26057 to indicate all processes or threads (respectively), or @samp{0} to
26058 indicate an arbitrary process or thread. Specifying just a process, as
26059 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
26060 error to specify all processes but a specific thread, such as
26061 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
26062 for those packets and replies explicitly documented to include a process
26063 ID, rather than a @var{thread-id}.
26065 The multiprocess @var{thread-id} syntax extensions are only used if both
26066 @value{GDBN} and the stub report support for the @samp{multiprocess}
26067 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
26070 Note that all packet forms beginning with an upper- or lower-case
26071 letter, other than those described here, are reserved for future use.
26073 Here are the packet descriptions.
26078 @cindex @samp{!} packet
26079 @anchor{extended mode}
26080 Enable extended mode. In extended mode, the remote server is made
26081 persistent. The @samp{R} packet is used to restart the program being
26087 The remote target both supports and has enabled extended mode.
26091 @cindex @samp{?} packet
26092 Indicate the reason the target halted. The reply is the same as for
26093 step and continue. This packet has a special interpretation when the
26094 target is in non-stop mode; see @ref{Remote Non-Stop}.
26097 @xref{Stop Reply Packets}, for the reply specifications.
26099 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
26100 @cindex @samp{A} packet
26101 Initialized @code{argv[]} array passed into program. @var{arglen}
26102 specifies the number of bytes in the hex encoded byte stream
26103 @var{arg}. See @code{gdbserver} for more details.
26108 The arguments were set.
26114 @cindex @samp{b} packet
26115 (Don't use this packet; its behavior is not well-defined.)
26116 Change the serial line speed to @var{baud}.
26118 JTC: @emph{When does the transport layer state change? When it's
26119 received, or after the ACK is transmitted. In either case, there are
26120 problems if the command or the acknowledgment packet is dropped.}
26122 Stan: @emph{If people really wanted to add something like this, and get
26123 it working for the first time, they ought to modify ser-unix.c to send
26124 some kind of out-of-band message to a specially-setup stub and have the
26125 switch happen "in between" packets, so that from remote protocol's point
26126 of view, nothing actually happened.}
26128 @item B @var{addr},@var{mode}
26129 @cindex @samp{B} packet
26130 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
26131 breakpoint at @var{addr}.
26133 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
26134 (@pxref{insert breakpoint or watchpoint packet}).
26137 @cindex @samp{bc} packet
26138 Backward continue. Execute the target system in reverse. No parameter.
26139 @xref{Reverse Execution}, for more information.
26142 @xref{Stop Reply Packets}, for the reply specifications.
26145 @cindex @samp{bs} packet
26146 Backward single step. Execute one instruction in reverse. No parameter.
26147 @xref{Reverse Execution}, for more information.
26150 @xref{Stop Reply Packets}, for the reply specifications.
26152 @item c @r{[}@var{addr}@r{]}
26153 @cindex @samp{c} packet
26154 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
26155 resume at current address.
26158 @xref{Stop Reply Packets}, for the reply specifications.
26160 @item C @var{sig}@r{[};@var{addr}@r{]}
26161 @cindex @samp{C} packet
26162 Continue with signal @var{sig} (hex signal number). If
26163 @samp{;@var{addr}} is omitted, resume at same address.
26166 @xref{Stop Reply Packets}, for the reply specifications.
26169 @cindex @samp{d} packet
26172 Don't use this packet; instead, define a general set packet
26173 (@pxref{General Query Packets}).
26177 @cindex @samp{D} packet
26178 The first form of the packet is used to detach @value{GDBN} from the
26179 remote system. It is sent to the remote target
26180 before @value{GDBN} disconnects via the @code{detach} command.
26182 The second form, including a process ID, is used when multiprocess
26183 protocol extensions are enabled (@pxref{multiprocess extensions}), to
26184 detach only a specific process. The @var{pid} is specified as a
26185 big-endian hex string.
26195 @item F @var{RC},@var{EE},@var{CF};@var{XX}
26196 @cindex @samp{F} packet
26197 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
26198 This is part of the File-I/O protocol extension. @xref{File-I/O
26199 Remote Protocol Extension}, for the specification.
26202 @anchor{read registers packet}
26203 @cindex @samp{g} packet
26204 Read general registers.
26208 @item @var{XX@dots{}}
26209 Each byte of register data is described by two hex digits. The bytes
26210 with the register are transmitted in target byte order. The size of
26211 each register and their position within the @samp{g} packet are
26212 determined by the @value{GDBN} internal gdbarch functions
26213 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
26214 specification of several standard @samp{g} packets is specified below.
26219 @item G @var{XX@dots{}}
26220 @cindex @samp{G} packet
26221 Write general registers. @xref{read registers packet}, for a
26222 description of the @var{XX@dots{}} data.
26232 @item H @var{c} @var{thread-id}
26233 @cindex @samp{H} packet
26234 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
26235 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
26236 should be @samp{c} for step and continue operations, @samp{g} for other
26237 operations. The thread designator @var{thread-id} has the format and
26238 interpretation described in @ref{thread-id syntax}.
26249 @c 'H': How restrictive (or permissive) is the thread model. If a
26250 @c thread is selected and stopped, are other threads allowed
26251 @c to continue to execute? As I mentioned above, I think the
26252 @c semantics of each command when a thread is selected must be
26253 @c described. For example:
26255 @c 'g': If the stub supports threads and a specific thread is
26256 @c selected, returns the register block from that thread;
26257 @c otherwise returns current registers.
26259 @c 'G' If the stub supports threads and a specific thread is
26260 @c selected, sets the registers of the register block of
26261 @c that thread; otherwise sets current registers.
26263 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
26264 @anchor{cycle step packet}
26265 @cindex @samp{i} packet
26266 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
26267 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
26268 step starting at that address.
26271 @cindex @samp{I} packet
26272 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
26276 @cindex @samp{k} packet
26279 FIXME: @emph{There is no description of how to operate when a specific
26280 thread context has been selected (i.e.@: does 'k' kill only that
26283 @item m @var{addr},@var{length}
26284 @cindex @samp{m} packet
26285 Read @var{length} bytes of memory starting at address @var{addr}.
26286 Note that @var{addr} may not be aligned to any particular boundary.
26288 The stub need not use any particular size or alignment when gathering
26289 data from memory for the response; even if @var{addr} is word-aligned
26290 and @var{length} is a multiple of the word size, the stub is free to
26291 use byte accesses, or not. For this reason, this packet may not be
26292 suitable for accessing memory-mapped I/O devices.
26293 @cindex alignment of remote memory accesses
26294 @cindex size of remote memory accesses
26295 @cindex memory, alignment and size of remote accesses
26299 @item @var{XX@dots{}}
26300 Memory contents; each byte is transmitted as a two-digit hexadecimal
26301 number. The reply may contain fewer bytes than requested if the
26302 server was able to read only part of the region of memory.
26307 @item M @var{addr},@var{length}:@var{XX@dots{}}
26308 @cindex @samp{M} packet
26309 Write @var{length} bytes of memory starting at address @var{addr}.
26310 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
26311 hexadecimal number.
26318 for an error (this includes the case where only part of the data was
26323 @cindex @samp{p} packet
26324 Read the value of register @var{n}; @var{n} is in hex.
26325 @xref{read registers packet}, for a description of how the returned
26326 register value is encoded.
26330 @item @var{XX@dots{}}
26331 the register's value
26335 Indicating an unrecognized @var{query}.
26338 @item P @var{n@dots{}}=@var{r@dots{}}
26339 @anchor{write register packet}
26340 @cindex @samp{P} packet
26341 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
26342 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
26343 digits for each byte in the register (target byte order).
26353 @item q @var{name} @var{params}@dots{}
26354 @itemx Q @var{name} @var{params}@dots{}
26355 @cindex @samp{q} packet
26356 @cindex @samp{Q} packet
26357 General query (@samp{q}) and set (@samp{Q}). These packets are
26358 described fully in @ref{General Query Packets}.
26361 @cindex @samp{r} packet
26362 Reset the entire system.
26364 Don't use this packet; use the @samp{R} packet instead.
26367 @cindex @samp{R} packet
26368 Restart the program being debugged. @var{XX}, while needed, is ignored.
26369 This packet is only available in extended mode (@pxref{extended mode}).
26371 The @samp{R} packet has no reply.
26373 @item s @r{[}@var{addr}@r{]}
26374 @cindex @samp{s} packet
26375 Single step. @var{addr} is the address at which to resume. If
26376 @var{addr} is omitted, resume at same address.
26379 @xref{Stop Reply Packets}, for the reply specifications.
26381 @item S @var{sig}@r{[};@var{addr}@r{]}
26382 @anchor{step with signal packet}
26383 @cindex @samp{S} packet
26384 Step with signal. This is analogous to the @samp{C} packet, but
26385 requests a single-step, rather than a normal resumption of execution.
26388 @xref{Stop Reply Packets}, for the reply specifications.
26390 @item t @var{addr}:@var{PP},@var{MM}
26391 @cindex @samp{t} packet
26392 Search backwards starting at address @var{addr} for a match with pattern
26393 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
26394 @var{addr} must be at least 3 digits.
26396 @item T @var{thread-id}
26397 @cindex @samp{T} packet
26398 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
26403 thread is still alive
26409 Packets starting with @samp{v} are identified by a multi-letter name,
26410 up to the first @samp{;} or @samp{?} (or the end of the packet).
26412 @item vAttach;@var{pid}
26413 @cindex @samp{vAttach} packet
26414 Attach to a new process with the specified process ID @var{pid}.
26415 The process ID is a
26416 hexadecimal integer identifying the process. In all-stop mode, all
26417 threads in the attached process are stopped; in non-stop mode, it may be
26418 attached without being stopped if that is supported by the target.
26420 @c In non-stop mode, on a successful vAttach, the stub should set the
26421 @c current thread to a thread of the newly-attached process. After
26422 @c attaching, GDB queries for the attached process's thread ID with qC.
26423 @c Also note that, from a user perspective, whether or not the
26424 @c target is stopped on attach in non-stop mode depends on whether you
26425 @c use the foreground or background version of the attach command, not
26426 @c on what vAttach does; GDB does the right thing with respect to either
26427 @c stopping or restarting threads.
26429 This packet is only available in extended mode (@pxref{extended mode}).
26435 @item @r{Any stop packet}
26436 for success in all-stop mode (@pxref{Stop Reply Packets})
26438 for success in non-stop mode (@pxref{Remote Non-Stop})
26441 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
26442 @cindex @samp{vCont} packet
26443 Resume the inferior, specifying different actions for each thread.
26444 If an action is specified with no @var{thread-id}, then it is applied to any
26445 threads that don't have a specific action specified; if no default action is
26446 specified then other threads should remain stopped in all-stop mode and
26447 in their current state in non-stop mode.
26448 Specifying multiple
26449 default actions is an error; specifying no actions is also an error.
26450 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
26452 Currently supported actions are:
26458 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
26462 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
26466 Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
26469 The optional argument @var{addr} normally associated with the
26470 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
26471 not supported in @samp{vCont}.
26473 The @samp{t} and @samp{T} actions are only relevant in non-stop mode
26474 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
26475 A stop reply should be generated for any affected thread not already stopped.
26476 When a thread is stopped by means of a @samp{t} action,
26477 the corresponding stop reply should indicate that the thread has stopped with
26478 signal @samp{0}, regardless of whether the target uses some other signal
26479 as an implementation detail.
26482 @xref{Stop Reply Packets}, for the reply specifications.
26485 @cindex @samp{vCont?} packet
26486 Request a list of actions supported by the @samp{vCont} packet.
26490 @item vCont@r{[};@var{action}@dots{}@r{]}
26491 The @samp{vCont} packet is supported. Each @var{action} is a supported
26492 command in the @samp{vCont} packet.
26494 The @samp{vCont} packet is not supported.
26497 @item vFile:@var{operation}:@var{parameter}@dots{}
26498 @cindex @samp{vFile} packet
26499 Perform a file operation on the target system. For details,
26500 see @ref{Host I/O Packets}.
26502 @item vFlashErase:@var{addr},@var{length}
26503 @cindex @samp{vFlashErase} packet
26504 Direct the stub to erase @var{length} bytes of flash starting at
26505 @var{addr}. The region may enclose any number of flash blocks, but
26506 its start and end must fall on block boundaries, as indicated by the
26507 flash block size appearing in the memory map (@pxref{Memory Map
26508 Format}). @value{GDBN} groups flash memory programming operations
26509 together, and sends a @samp{vFlashDone} request after each group; the
26510 stub is allowed to delay erase operation until the @samp{vFlashDone}
26511 packet is received.
26513 The stub must support @samp{vCont} if it reports support for
26514 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
26515 this case @samp{vCont} actions can be specified to apply to all threads
26516 in a process by using the @samp{p@var{pid}.-1} form of the
26527 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
26528 @cindex @samp{vFlashWrite} packet
26529 Direct the stub to write data to flash address @var{addr}. The data
26530 is passed in binary form using the same encoding as for the @samp{X}
26531 packet (@pxref{Binary Data}). The memory ranges specified by
26532 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
26533 not overlap, and must appear in order of increasing addresses
26534 (although @samp{vFlashErase} packets for higher addresses may already
26535 have been received; the ordering is guaranteed only between
26536 @samp{vFlashWrite} packets). If a packet writes to an address that was
26537 neither erased by a preceding @samp{vFlashErase} packet nor by some other
26538 target-specific method, the results are unpredictable.
26546 for vFlashWrite addressing non-flash memory
26552 @cindex @samp{vFlashDone} packet
26553 Indicate to the stub that flash programming operation is finished.
26554 The stub is permitted to delay or batch the effects of a group of
26555 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
26556 @samp{vFlashDone} packet is received. The contents of the affected
26557 regions of flash memory are unpredictable until the @samp{vFlashDone}
26558 request is completed.
26560 @item vKill;@var{pid}
26561 @cindex @samp{vKill} packet
26562 Kill the process with the specified process ID. @var{pid} is a
26563 hexadecimal integer identifying the process. This packet is used in
26564 preference to @samp{k} when multiprocess protocol extensions are
26565 supported; see @ref{multiprocess extensions}.
26575 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
26576 @cindex @samp{vRun} packet
26577 Run the program @var{filename}, passing it each @var{argument} on its
26578 command line. The file and arguments are hex-encoded strings. If
26579 @var{filename} is an empty string, the stub may use a default program
26580 (e.g.@: the last program run). The program is created in the stopped
26583 @c FIXME: What about non-stop mode?
26585 This packet is only available in extended mode (@pxref{extended mode}).
26591 @item @r{Any stop packet}
26592 for success (@pxref{Stop Reply Packets})
26596 @anchor{vStopped packet}
26597 @cindex @samp{vStopped} packet
26599 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
26600 reply and prompt for the stub to report another one.
26604 @item @r{Any stop packet}
26605 if there is another unreported stop event (@pxref{Stop Reply Packets})
26607 if there are no unreported stop events
26610 @item X @var{addr},@var{length}:@var{XX@dots{}}
26612 @cindex @samp{X} packet
26613 Write data to memory, where the data is transmitted in binary.
26614 @var{addr} is address, @var{length} is number of bytes,
26615 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
26625 @item z @var{type},@var{addr},@var{length}
26626 @itemx Z @var{type},@var{addr},@var{length}
26627 @anchor{insert breakpoint or watchpoint packet}
26628 @cindex @samp{z} packet
26629 @cindex @samp{Z} packets
26630 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
26631 watchpoint starting at address @var{address} and covering the next
26632 @var{length} bytes.
26634 Each breakpoint and watchpoint packet @var{type} is documented
26637 @emph{Implementation notes: A remote target shall return an empty string
26638 for an unrecognized breakpoint or watchpoint packet @var{type}. A
26639 remote target shall support either both or neither of a given
26640 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
26641 avoid potential problems with duplicate packets, the operations should
26642 be implemented in an idempotent way.}
26644 @item z0,@var{addr},@var{length}
26645 @itemx Z0,@var{addr},@var{length}
26646 @cindex @samp{z0} packet
26647 @cindex @samp{Z0} packet
26648 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
26649 @var{addr} of size @var{length}.
26651 A memory breakpoint is implemented by replacing the instruction at
26652 @var{addr} with a software breakpoint or trap instruction. The
26653 @var{length} is used by targets that indicates the size of the
26654 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
26655 @sc{mips} can insert either a 2 or 4 byte breakpoint).
26657 @emph{Implementation note: It is possible for a target to copy or move
26658 code that contains memory breakpoints (e.g., when implementing
26659 overlays). The behavior of this packet, in the presence of such a
26660 target, is not defined.}
26672 @item z1,@var{addr},@var{length}
26673 @itemx Z1,@var{addr},@var{length}
26674 @cindex @samp{z1} packet
26675 @cindex @samp{Z1} packet
26676 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
26677 address @var{addr} of size @var{length}.
26679 A hardware breakpoint is implemented using a mechanism that is not
26680 dependant on being able to modify the target's memory.
26682 @emph{Implementation note: A hardware breakpoint is not affected by code
26695 @item z2,@var{addr},@var{length}
26696 @itemx Z2,@var{addr},@var{length}
26697 @cindex @samp{z2} packet
26698 @cindex @samp{Z2} packet
26699 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
26711 @item z3,@var{addr},@var{length}
26712 @itemx Z3,@var{addr},@var{length}
26713 @cindex @samp{z3} packet
26714 @cindex @samp{Z3} packet
26715 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
26727 @item z4,@var{addr},@var{length}
26728 @itemx Z4,@var{addr},@var{length}
26729 @cindex @samp{z4} packet
26730 @cindex @samp{Z4} packet
26731 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
26745 @node Stop Reply Packets
26746 @section Stop Reply Packets
26747 @cindex stop reply packets
26749 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
26750 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
26751 receive any of the below as a reply. Except for @samp{?}
26752 and @samp{vStopped}, that reply is only returned
26753 when the target halts. In the below the exact meaning of @dfn{signal
26754 number} is defined by the header @file{include/gdb/signals.h} in the
26755 @value{GDBN} source code.
26757 As in the description of request packets, we include spaces in the
26758 reply templates for clarity; these are not part of the reply packet's
26759 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
26765 The program received signal number @var{AA} (a two-digit hexadecimal
26766 number). This is equivalent to a @samp{T} response with no
26767 @var{n}:@var{r} pairs.
26769 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
26770 @cindex @samp{T} packet reply
26771 The program received signal number @var{AA} (a two-digit hexadecimal
26772 number). This is equivalent to an @samp{S} response, except that the
26773 @samp{@var{n}:@var{r}} pairs can carry values of important registers
26774 and other information directly in the stop reply packet, reducing
26775 round-trip latency. Single-step and breakpoint traps are reported
26776 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
26780 If @var{n} is a hexadecimal number, it is a register number, and the
26781 corresponding @var{r} gives that register's value. @var{r} is a
26782 series of bytes in target byte order, with each byte given by a
26783 two-digit hex number.
26786 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
26787 the stopped thread, as specified in @ref{thread-id syntax}.
26790 If @var{n} is a recognized @dfn{stop reason}, it describes a more
26791 specific event that stopped the target. The currently defined stop
26792 reasons are listed below. @var{aa} should be @samp{05}, the trap
26793 signal. At most one stop reason should be present.
26796 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
26797 and go on to the next; this allows us to extend the protocol in the
26801 The currently defined stop reasons are:
26807 The packet indicates a watchpoint hit, and @var{r} is the data address, in
26810 @cindex shared library events, remote reply
26812 The packet indicates that the loaded libraries have changed.
26813 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
26814 list of loaded libraries. @var{r} is ignored.
26816 @cindex replay log events, remote reply
26818 The packet indicates that the target cannot continue replaying
26819 logged execution events, because it has reached the end (or the
26820 beginning when executing backward) of the log. The value of @var{r}
26821 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
26822 for more information.
26828 @itemx W @var{AA} ; process:@var{pid}
26829 The process exited, and @var{AA} is the exit status. This is only
26830 applicable to certain targets.
26832 The second form of the response, including the process ID of the exited
26833 process, can be used only when @value{GDBN} has reported support for
26834 multiprocess protocol extensions; see @ref{multiprocess extensions}.
26835 The @var{pid} is formatted as a big-endian hex string.
26838 @itemx X @var{AA} ; process:@var{pid}
26839 The process terminated with signal @var{AA}.
26841 The second form of the response, including the process ID of the
26842 terminated process, can be used only when @value{GDBN} has reported
26843 support for multiprocess protocol extensions; see @ref{multiprocess
26844 extensions}. The @var{pid} is formatted as a big-endian hex string.
26846 @item O @var{XX}@dots{}
26847 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
26848 written as the program's console output. This can happen at any time
26849 while the program is running and the debugger should continue to wait
26850 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
26852 @item F @var{call-id},@var{parameter}@dots{}
26853 @var{call-id} is the identifier which says which host system call should
26854 be called. This is just the name of the function. Translation into the
26855 correct system call is only applicable as it's defined in @value{GDBN}.
26856 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
26859 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
26860 this very system call.
26862 The target replies with this packet when it expects @value{GDBN} to
26863 call a host system call on behalf of the target. @value{GDBN} replies
26864 with an appropriate @samp{F} packet and keeps up waiting for the next
26865 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
26866 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
26867 Protocol Extension}, for more details.
26871 @node General Query Packets
26872 @section General Query Packets
26873 @cindex remote query requests
26875 Packets starting with @samp{q} are @dfn{general query packets};
26876 packets starting with @samp{Q} are @dfn{general set packets}. General
26877 query and set packets are a semi-unified form for retrieving and
26878 sending information to and from the stub.
26880 The initial letter of a query or set packet is followed by a name
26881 indicating what sort of thing the packet applies to. For example,
26882 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
26883 definitions with the stub. These packet names follow some
26888 The name must not contain commas, colons or semicolons.
26890 Most @value{GDBN} query and set packets have a leading upper case
26893 The names of custom vendor packets should use a company prefix, in
26894 lower case, followed by a period. For example, packets designed at
26895 the Acme Corporation might begin with @samp{qacme.foo} (for querying
26896 foos) or @samp{Qacme.bar} (for setting bars).
26899 The name of a query or set packet should be separated from any
26900 parameters by a @samp{:}; the parameters themselves should be
26901 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
26902 full packet name, and check for a separator or the end of the packet,
26903 in case two packet names share a common prefix. New packets should not begin
26904 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
26905 packets predate these conventions, and have arguments without any terminator
26906 for the packet name; we suspect they are in widespread use in places that
26907 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
26908 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
26911 Like the descriptions of the other packets, each description here
26912 has a template showing the packet's overall syntax, followed by an
26913 explanation of the packet's meaning. We include spaces in some of the
26914 templates for clarity; these are not part of the packet's syntax. No
26915 @value{GDBN} packet uses spaces to separate its components.
26917 Here are the currently defined query and set packets:
26922 @cindex current thread, remote request
26923 @cindex @samp{qC} packet
26924 Return the current thread ID.
26928 @item QC @var{thread-id}
26929 Where @var{thread-id} is a thread ID as documented in
26930 @ref{thread-id syntax}.
26931 @item @r{(anything else)}
26932 Any other reply implies the old thread ID.
26935 @item qCRC:@var{addr},@var{length}
26936 @cindex CRC of memory block, remote request
26937 @cindex @samp{qCRC} packet
26938 Compute the CRC checksum of a block of memory.
26942 An error (such as memory fault)
26943 @item C @var{crc32}
26944 The specified memory region's checksum is @var{crc32}.
26948 @itemx qsThreadInfo
26949 @cindex list active threads, remote request
26950 @cindex @samp{qfThreadInfo} packet
26951 @cindex @samp{qsThreadInfo} packet
26952 Obtain a list of all active thread IDs from the target (OS). Since there
26953 may be too many active threads to fit into one reply packet, this query
26954 works iteratively: it may require more than one query/reply sequence to
26955 obtain the entire list of threads. The first query of the sequence will
26956 be the @samp{qfThreadInfo} query; subsequent queries in the
26957 sequence will be the @samp{qsThreadInfo} query.
26959 NOTE: This packet replaces the @samp{qL} query (see below).
26963 @item m @var{thread-id}
26965 @item m @var{thread-id},@var{thread-id}@dots{}
26966 a comma-separated list of thread IDs
26968 (lower case letter @samp{L}) denotes end of list.
26971 In response to each query, the target will reply with a list of one or
26972 more thread IDs, separated by commas.
26973 @value{GDBN} will respond to each reply with a request for more thread
26974 ids (using the @samp{qs} form of the query), until the target responds
26975 with @samp{l} (lower-case el, for @dfn{last}).
26976 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
26979 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
26980 @cindex get thread-local storage address, remote request
26981 @cindex @samp{qGetTLSAddr} packet
26982 Fetch the address associated with thread local storage specified
26983 by @var{thread-id}, @var{offset}, and @var{lm}.
26985 @var{thread-id} is the thread ID associated with the
26986 thread for which to fetch the TLS address. @xref{thread-id syntax}.
26988 @var{offset} is the (big endian, hex encoded) offset associated with the
26989 thread local variable. (This offset is obtained from the debug
26990 information associated with the variable.)
26992 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
26993 the load module associated with the thread local storage. For example,
26994 a @sc{gnu}/Linux system will pass the link map address of the shared
26995 object associated with the thread local storage under consideration.
26996 Other operating environments may choose to represent the load module
26997 differently, so the precise meaning of this parameter will vary.
27001 @item @var{XX}@dots{}
27002 Hex encoded (big endian) bytes representing the address of the thread
27003 local storage requested.
27006 An error occurred. @var{nn} are hex digits.
27009 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
27012 @item qL @var{startflag} @var{threadcount} @var{nextthread}
27013 Obtain thread information from RTOS. Where: @var{startflag} (one hex
27014 digit) is one to indicate the first query and zero to indicate a
27015 subsequent query; @var{threadcount} (two hex digits) is the maximum
27016 number of threads the response packet can contain; and @var{nextthread}
27017 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
27018 returned in the response as @var{argthread}.
27020 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
27024 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
27025 Where: @var{count} (two hex digits) is the number of threads being
27026 returned; @var{done} (one hex digit) is zero to indicate more threads
27027 and one indicates no further threads; @var{argthreadid} (eight hex
27028 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
27029 is a sequence of thread IDs from the target. @var{threadid} (eight hex
27030 digits). See @code{remote.c:parse_threadlist_response()}.
27034 @cindex section offsets, remote request
27035 @cindex @samp{qOffsets} packet
27036 Get section offsets that the target used when relocating the downloaded
27041 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
27042 Relocate the @code{Text} section by @var{xxx} from its original address.
27043 Relocate the @code{Data} section by @var{yyy} from its original address.
27044 If the object file format provides segment information (e.g.@: @sc{elf}
27045 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
27046 segments by the supplied offsets.
27048 @emph{Note: while a @code{Bss} offset may be included in the response,
27049 @value{GDBN} ignores this and instead applies the @code{Data} offset
27050 to the @code{Bss} section.}
27052 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
27053 Relocate the first segment of the object file, which conventionally
27054 contains program code, to a starting address of @var{xxx}. If
27055 @samp{DataSeg} is specified, relocate the second segment, which
27056 conventionally contains modifiable data, to a starting address of
27057 @var{yyy}. @value{GDBN} will report an error if the object file
27058 does not contain segment information, or does not contain at least
27059 as many segments as mentioned in the reply. Extra segments are
27060 kept at fixed offsets relative to the last relocated segment.
27063 @item qP @var{mode} @var{thread-id}
27064 @cindex thread information, remote request
27065 @cindex @samp{qP} packet
27066 Returns information on @var{thread-id}. Where: @var{mode} is a hex
27067 encoded 32 bit mode; @var{thread-id} is a thread ID
27068 (@pxref{thread-id syntax}).
27070 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
27073 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
27077 @cindex non-stop mode, remote request
27078 @cindex @samp{QNonStop} packet
27080 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
27081 @xref{Remote Non-Stop}, for more information.
27086 The request succeeded.
27089 An error occurred. @var{nn} are hex digits.
27092 An empty reply indicates that @samp{QNonStop} is not supported by
27096 This packet is not probed by default; the remote stub must request it,
27097 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27098 Use of this packet is controlled by the @code{set non-stop} command;
27099 @pxref{Non-Stop Mode}.
27101 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
27102 @cindex pass signals to inferior, remote request
27103 @cindex @samp{QPassSignals} packet
27104 @anchor{QPassSignals}
27105 Each listed @var{signal} should be passed directly to the inferior process.
27106 Signals are numbered identically to continue packets and stop replies
27107 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
27108 strictly greater than the previous item. These signals do not need to stop
27109 the inferior, or be reported to @value{GDBN}. All other signals should be
27110 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
27111 combine; any earlier @samp{QPassSignals} list is completely replaced by the
27112 new list. This packet improves performance when using @samp{handle
27113 @var{signal} nostop noprint pass}.
27118 The request succeeded.
27121 An error occurred. @var{nn} are hex digits.
27124 An empty reply indicates that @samp{QPassSignals} is not supported by
27128 Use of this packet is controlled by the @code{set remote pass-signals}
27129 command (@pxref{Remote Configuration, set remote pass-signals}).
27130 This packet is not probed by default; the remote stub must request it,
27131 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27133 @item qRcmd,@var{command}
27134 @cindex execute remote command, remote request
27135 @cindex @samp{qRcmd} packet
27136 @var{command} (hex encoded) is passed to the local interpreter for
27137 execution. Invalid commands should be reported using the output
27138 string. Before the final result packet, the target may also respond
27139 with a number of intermediate @samp{O@var{output}} console output
27140 packets. @emph{Implementors should note that providing access to a
27141 stubs's interpreter may have security implications}.
27146 A command response with no output.
27148 A command response with the hex encoded output string @var{OUTPUT}.
27150 Indicate a badly formed request.
27152 An empty reply indicates that @samp{qRcmd} is not recognized.
27155 (Note that the @code{qRcmd} packet's name is separated from the
27156 command by a @samp{,}, not a @samp{:}, contrary to the naming
27157 conventions above. Please don't use this packet as a model for new
27160 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
27161 @cindex searching memory, in remote debugging
27162 @cindex @samp{qSearch:memory} packet
27163 @anchor{qSearch memory}
27164 Search @var{length} bytes at @var{address} for @var{search-pattern}.
27165 @var{address} and @var{length} are encoded in hex.
27166 @var{search-pattern} is a sequence of bytes, hex encoded.
27171 The pattern was not found.
27173 The pattern was found at @var{address}.
27175 A badly formed request or an error was encountered while searching memory.
27177 An empty reply indicates that @samp{qSearch:memory} is not recognized.
27180 @item QStartNoAckMode
27181 @cindex @samp{QStartNoAckMode} packet
27182 @anchor{QStartNoAckMode}
27183 Request that the remote stub disable the normal @samp{+}/@samp{-}
27184 protocol acknowledgments (@pxref{Packet Acknowledgment}).
27189 The stub has switched to no-acknowledgment mode.
27190 @value{GDBN} acknowledges this reponse,
27191 but neither the stub nor @value{GDBN} shall send or expect further
27192 @samp{+}/@samp{-} acknowledgments in the current connection.
27194 An empty reply indicates that the stub does not support no-acknowledgment mode.
27197 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
27198 @cindex supported packets, remote query
27199 @cindex features of the remote protocol
27200 @cindex @samp{qSupported} packet
27201 @anchor{qSupported}
27202 Tell the remote stub about features supported by @value{GDBN}, and
27203 query the stub for features it supports. This packet allows
27204 @value{GDBN} and the remote stub to take advantage of each others'
27205 features. @samp{qSupported} also consolidates multiple feature probes
27206 at startup, to improve @value{GDBN} performance---a single larger
27207 packet performs better than multiple smaller probe packets on
27208 high-latency links. Some features may enable behavior which must not
27209 be on by default, e.g.@: because it would confuse older clients or
27210 stubs. Other features may describe packets which could be
27211 automatically probed for, but are not. These features must be
27212 reported before @value{GDBN} will use them. This ``default
27213 unsupported'' behavior is not appropriate for all packets, but it
27214 helps to keep the initial connection time under control with new
27215 versions of @value{GDBN} which support increasing numbers of packets.
27219 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
27220 The stub supports or does not support each returned @var{stubfeature},
27221 depending on the form of each @var{stubfeature} (see below for the
27224 An empty reply indicates that @samp{qSupported} is not recognized,
27225 or that no features needed to be reported to @value{GDBN}.
27228 The allowed forms for each feature (either a @var{gdbfeature} in the
27229 @samp{qSupported} packet, or a @var{stubfeature} in the response)
27233 @item @var{name}=@var{value}
27234 The remote protocol feature @var{name} is supported, and associated
27235 with the specified @var{value}. The format of @var{value} depends
27236 on the feature, but it must not include a semicolon.
27238 The remote protocol feature @var{name} is supported, and does not
27239 need an associated value.
27241 The remote protocol feature @var{name} is not supported.
27243 The remote protocol feature @var{name} may be supported, and
27244 @value{GDBN} should auto-detect support in some other way when it is
27245 needed. This form will not be used for @var{gdbfeature} notifications,
27246 but may be used for @var{stubfeature} responses.
27249 Whenever the stub receives a @samp{qSupported} request, the
27250 supplied set of @value{GDBN} features should override any previous
27251 request. This allows @value{GDBN} to put the stub in a known
27252 state, even if the stub had previously been communicating with
27253 a different version of @value{GDBN}.
27255 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
27260 This feature indicates whether @value{GDBN} supports multiprocess
27261 extensions to the remote protocol. @value{GDBN} does not use such
27262 extensions unless the stub also reports that it supports them by
27263 including @samp{multiprocess+} in its @samp{qSupported} reply.
27264 @xref{multiprocess extensions}, for details.
27267 Stubs should ignore any unknown values for
27268 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
27269 packet supports receiving packets of unlimited length (earlier
27270 versions of @value{GDBN} may reject overly long responses). Additional values
27271 for @var{gdbfeature} may be defined in the future to let the stub take
27272 advantage of new features in @value{GDBN}, e.g.@: incompatible
27273 improvements in the remote protocol---the @samp{multiprocess} feature is
27274 an example of such a feature. The stub's reply should be independent
27275 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
27276 describes all the features it supports, and then the stub replies with
27277 all the features it supports.
27279 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
27280 responses, as long as each response uses one of the standard forms.
27282 Some features are flags. A stub which supports a flag feature
27283 should respond with a @samp{+} form response. Other features
27284 require values, and the stub should respond with an @samp{=}
27287 Each feature has a default value, which @value{GDBN} will use if
27288 @samp{qSupported} is not available or if the feature is not mentioned
27289 in the @samp{qSupported} response. The default values are fixed; a
27290 stub is free to omit any feature responses that match the defaults.
27292 Not all features can be probed, but for those which can, the probing
27293 mechanism is useful: in some cases, a stub's internal
27294 architecture may not allow the protocol layer to know some information
27295 about the underlying target in advance. This is especially common in
27296 stubs which may be configured for multiple targets.
27298 These are the currently defined stub features and their properties:
27300 @multitable @columnfractions 0.35 0.2 0.12 0.2
27301 @c NOTE: The first row should be @headitem, but we do not yet require
27302 @c a new enough version of Texinfo (4.7) to use @headitem.
27304 @tab Value Required
27308 @item @samp{PacketSize}
27313 @item @samp{qXfer:auxv:read}
27318 @item @samp{qXfer:features:read}
27323 @item @samp{qXfer:libraries:read}
27328 @item @samp{qXfer:memory-map:read}
27333 @item @samp{qXfer:spu:read}
27338 @item @samp{qXfer:spu:write}
27343 @item @samp{qXfer:siginfo:read}
27348 @item @samp{qXfer:siginfo:write}
27353 @item @samp{QNonStop}
27358 @item @samp{QPassSignals}
27363 @item @samp{QStartNoAckMode}
27368 @item @samp{multiprocess}
27375 These are the currently defined stub features, in more detail:
27378 @cindex packet size, remote protocol
27379 @item PacketSize=@var{bytes}
27380 The remote stub can accept packets up to at least @var{bytes} in
27381 length. @value{GDBN} will send packets up to this size for bulk
27382 transfers, and will never send larger packets. This is a limit on the
27383 data characters in the packet, including the frame and checksum.
27384 There is no trailing NUL byte in a remote protocol packet; if the stub
27385 stores packets in a NUL-terminated format, it should allow an extra
27386 byte in its buffer for the NUL. If this stub feature is not supported,
27387 @value{GDBN} guesses based on the size of the @samp{g} packet response.
27389 @item qXfer:auxv:read
27390 The remote stub understands the @samp{qXfer:auxv:read} packet
27391 (@pxref{qXfer auxiliary vector read}).
27393 @item qXfer:features:read
27394 The remote stub understands the @samp{qXfer:features:read} packet
27395 (@pxref{qXfer target description read}).
27397 @item qXfer:libraries:read
27398 The remote stub understands the @samp{qXfer:libraries:read} packet
27399 (@pxref{qXfer library list read}).
27401 @item qXfer:memory-map:read
27402 The remote stub understands the @samp{qXfer:memory-map:read} packet
27403 (@pxref{qXfer memory map read}).
27405 @item qXfer:spu:read
27406 The remote stub understands the @samp{qXfer:spu:read} packet
27407 (@pxref{qXfer spu read}).
27409 @item qXfer:spu:write
27410 The remote stub understands the @samp{qXfer:spu:write} packet
27411 (@pxref{qXfer spu write}).
27413 @item qXfer:siginfo:read
27414 The remote stub understands the @samp{qXfer:siginfo:read} packet
27415 (@pxref{qXfer siginfo read}).
27417 @item qXfer:siginfo:write
27418 The remote stub understands the @samp{qXfer:siginfo:write} packet
27419 (@pxref{qXfer siginfo write}).
27422 The remote stub understands the @samp{QNonStop} packet
27423 (@pxref{QNonStop}).
27426 The remote stub understands the @samp{QPassSignals} packet
27427 (@pxref{QPassSignals}).
27429 @item QStartNoAckMode
27430 The remote stub understands the @samp{QStartNoAckMode} packet and
27431 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
27434 @anchor{multiprocess extensions}
27435 @cindex multiprocess extensions, in remote protocol
27436 The remote stub understands the multiprocess extensions to the remote
27437 protocol syntax. The multiprocess extensions affect the syntax of
27438 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
27439 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
27440 replies. Note that reporting this feature indicates support for the
27441 syntactic extensions only, not that the stub necessarily supports
27442 debugging of more than one process at a time. The stub must not use
27443 multiprocess extensions in packet replies unless @value{GDBN} has also
27444 indicated it supports them in its @samp{qSupported} request.
27446 @item qXfer:osdata:read
27447 The remote stub understands the @samp{qXfer:osdata:read} packet
27448 ((@pxref{qXfer osdata read}).
27453 @cindex symbol lookup, remote request
27454 @cindex @samp{qSymbol} packet
27455 Notify the target that @value{GDBN} is prepared to serve symbol lookup
27456 requests. Accept requests from the target for the values of symbols.
27461 The target does not need to look up any (more) symbols.
27462 @item qSymbol:@var{sym_name}
27463 The target requests the value of symbol @var{sym_name} (hex encoded).
27464 @value{GDBN} may provide the value by using the
27465 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
27469 @item qSymbol:@var{sym_value}:@var{sym_name}
27470 Set the value of @var{sym_name} to @var{sym_value}.
27472 @var{sym_name} (hex encoded) is the name of a symbol whose value the
27473 target has previously requested.
27475 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
27476 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
27482 The target does not need to look up any (more) symbols.
27483 @item qSymbol:@var{sym_name}
27484 The target requests the value of a new symbol @var{sym_name} (hex
27485 encoded). @value{GDBN} will continue to supply the values of symbols
27486 (if available), until the target ceases to request them.
27491 @xref{Tracepoint Packets}.
27493 @item qThreadExtraInfo,@var{thread-id}
27494 @cindex thread attributes info, remote request
27495 @cindex @samp{qThreadExtraInfo} packet
27496 Obtain a printable string description of a thread's attributes from
27497 the target OS. @var{thread-id} is a thread ID;
27498 see @ref{thread-id syntax}. This
27499 string may contain anything that the target OS thinks is interesting
27500 for @value{GDBN} to tell the user about the thread. The string is
27501 displayed in @value{GDBN}'s @code{info threads} display. Some
27502 examples of possible thread extra info strings are @samp{Runnable}, or
27503 @samp{Blocked on Mutex}.
27507 @item @var{XX}@dots{}
27508 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
27509 comprising the printable string containing the extra information about
27510 the thread's attributes.
27513 (Note that the @code{qThreadExtraInfo} packet's name is separated from
27514 the command by a @samp{,}, not a @samp{:}, contrary to the naming
27515 conventions above. Please don't use this packet as a model for new
27523 @xref{Tracepoint Packets}.
27525 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
27526 @cindex read special object, remote request
27527 @cindex @samp{qXfer} packet
27528 @anchor{qXfer read}
27529 Read uninterpreted bytes from the target's special data area
27530 identified by the keyword @var{object}. Request @var{length} bytes
27531 starting at @var{offset} bytes into the data. The content and
27532 encoding of @var{annex} is specific to @var{object}; it can supply
27533 additional details about what data to access.
27535 Here are the specific requests of this form defined so far. All
27536 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
27537 formats, listed below.
27540 @item qXfer:auxv:read::@var{offset},@var{length}
27541 @anchor{qXfer auxiliary vector read}
27542 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
27543 auxiliary vector}. Note @var{annex} must be empty.
27545 This packet is not probed by default; the remote stub must request it,
27546 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27548 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
27549 @anchor{qXfer target description read}
27550 Access the @dfn{target description}. @xref{Target Descriptions}. The
27551 annex specifies which XML document to access. The main description is
27552 always loaded from the @samp{target.xml} annex.
27554 This packet is not probed by default; the remote stub must request it,
27555 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27557 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
27558 @anchor{qXfer library list read}
27559 Access the target's list of loaded libraries. @xref{Library List Format}.
27560 The annex part of the generic @samp{qXfer} packet must be empty
27561 (@pxref{qXfer read}).
27563 Targets which maintain a list of libraries in the program's memory do
27564 not need to implement this packet; it is designed for platforms where
27565 the operating system manages the list of loaded libraries.
27567 This packet is not probed by default; the remote stub must request it,
27568 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27570 @item qXfer:memory-map:read::@var{offset},@var{length}
27571 @anchor{qXfer memory map read}
27572 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
27573 annex part of the generic @samp{qXfer} packet must be empty
27574 (@pxref{qXfer read}).
27576 This packet is not probed by default; the remote stub must request it,
27577 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27579 @item qXfer:siginfo:read::@var{offset},@var{length}
27580 @anchor{qXfer siginfo read}
27581 Read contents of the extra signal information on the target
27582 system. The annex part of the generic @samp{qXfer} packet must be
27583 empty (@pxref{qXfer read}).
27585 This packet is not probed by default; the remote stub must request it,
27586 by supplying an appropriate @samp{qSupported} response
27587 (@pxref{qSupported}).
27589 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
27590 @anchor{qXfer spu read}
27591 Read contents of an @code{spufs} file on the target system. The
27592 annex specifies which file to read; it must be of the form
27593 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27594 in the target process, and @var{name} identifes the @code{spufs} file
27595 in that context to be accessed.
27597 This packet is not probed by default; the remote stub must request it,
27598 by supplying an appropriate @samp{qSupported} response
27599 (@pxref{qSupported}).
27601 @item qXfer:osdata:read::@var{offset},@var{length}
27602 @anchor{qXfer osdata read}
27603 Access the target's @dfn{operating system information}.
27604 @xref{Operating System Information}.
27611 Data @var{data} (@pxref{Binary Data}) has been read from the
27612 target. There may be more data at a higher address (although
27613 it is permitted to return @samp{m} even for the last valid
27614 block of data, as long as at least one byte of data was read).
27615 @var{data} may have fewer bytes than the @var{length} in the
27619 Data @var{data} (@pxref{Binary Data}) has been read from the target.
27620 There is no more data to be read. @var{data} may have fewer bytes
27621 than the @var{length} in the request.
27624 The @var{offset} in the request is at the end of the data.
27625 There is no more data to be read.
27628 The request was malformed, or @var{annex} was invalid.
27631 The offset was invalid, or there was an error encountered reading the data.
27632 @var{nn} is a hex-encoded @code{errno} value.
27635 An empty reply indicates the @var{object} string was not recognized by
27636 the stub, or that the object does not support reading.
27639 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
27640 @cindex write data into object, remote request
27641 @anchor{qXfer write}
27642 Write uninterpreted bytes into the target's special data area
27643 identified by the keyword @var{object}, starting at @var{offset} bytes
27644 into the data. @var{data}@dots{} is the binary-encoded data
27645 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
27646 is specific to @var{object}; it can supply additional details about what data
27649 Here are the specific requests of this form defined so far. All
27650 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
27651 formats, listed below.
27654 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
27655 @anchor{qXfer siginfo write}
27656 Write @var{data} to the extra signal information on the target system.
27657 The annex part of the generic @samp{qXfer} packet must be
27658 empty (@pxref{qXfer write}).
27660 This packet is not probed by default; the remote stub must request it,
27661 by supplying an appropriate @samp{qSupported} response
27662 (@pxref{qSupported}).
27664 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
27665 @anchor{qXfer spu write}
27666 Write @var{data} to an @code{spufs} file on the target system. The
27667 annex specifies which file to write; it must be of the form
27668 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27669 in the target process, and @var{name} identifes the @code{spufs} file
27670 in that context to be accessed.
27672 This packet is not probed by default; the remote stub must request it,
27673 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27679 @var{nn} (hex encoded) is the number of bytes written.
27680 This may be fewer bytes than supplied in the request.
27683 The request was malformed, or @var{annex} was invalid.
27686 The offset was invalid, or there was an error encountered writing the data.
27687 @var{nn} is a hex-encoded @code{errno} value.
27690 An empty reply indicates the @var{object} string was not
27691 recognized by the stub, or that the object does not support writing.
27694 @item qXfer:@var{object}:@var{operation}:@dots{}
27695 Requests of this form may be added in the future. When a stub does
27696 not recognize the @var{object} keyword, or its support for
27697 @var{object} does not recognize the @var{operation} keyword, the stub
27698 must respond with an empty packet.
27700 @item qAttached:@var{pid}
27701 @cindex query attached, remote request
27702 @cindex @samp{qAttached} packet
27703 Return an indication of whether the remote server attached to an
27704 existing process or created a new process. When the multiprocess
27705 protocol extensions are supported (@pxref{multiprocess extensions}),
27706 @var{pid} is an integer in hexadecimal format identifying the target
27707 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
27708 the query packet will be simplified as @samp{qAttached}.
27710 This query is used, for example, to know whether the remote process
27711 should be detached or killed when a @value{GDBN} session is ended with
27712 the @code{quit} command.
27717 The remote server attached to an existing process.
27719 The remote server created a new process.
27721 A badly formed request or an error was encountered.
27726 @node Register Packet Format
27727 @section Register Packet Format
27729 The following @code{g}/@code{G} packets have previously been defined.
27730 In the below, some thirty-two bit registers are transferred as
27731 sixty-four bits. Those registers should be zero/sign extended (which?)
27732 to fill the space allocated. Register bytes are transferred in target
27733 byte order. The two nibbles within a register byte are transferred
27734 most-significant - least-significant.
27740 All registers are transferred as thirty-two bit quantities in the order:
27741 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
27742 registers; fsr; fir; fp.
27746 All registers are transferred as sixty-four bit quantities (including
27747 thirty-two bit registers such as @code{sr}). The ordering is the same
27752 @node Tracepoint Packets
27753 @section Tracepoint Packets
27754 @cindex tracepoint packets
27755 @cindex packets, tracepoint
27757 Here we describe the packets @value{GDBN} uses to implement
27758 tracepoints (@pxref{Tracepoints}).
27762 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
27763 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
27764 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
27765 the tracepoint is disabled. @var{step} is the tracepoint's step
27766 count, and @var{pass} is its pass count. If the trailing @samp{-} is
27767 present, further @samp{QTDP} packets will follow to specify this
27768 tracepoint's actions.
27773 The packet was understood and carried out.
27775 The packet was not recognized.
27778 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
27779 Define actions to be taken when a tracepoint is hit. @var{n} and
27780 @var{addr} must be the same as in the initial @samp{QTDP} packet for
27781 this tracepoint. This packet may only be sent immediately after
27782 another @samp{QTDP} packet that ended with a @samp{-}. If the
27783 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
27784 specifying more actions for this tracepoint.
27786 In the series of action packets for a given tracepoint, at most one
27787 can have an @samp{S} before its first @var{action}. If such a packet
27788 is sent, it and the following packets define ``while-stepping''
27789 actions. Any prior packets define ordinary actions --- that is, those
27790 taken when the tracepoint is first hit. If no action packet has an
27791 @samp{S}, then all the packets in the series specify ordinary
27792 tracepoint actions.
27794 The @samp{@var{action}@dots{}} portion of the packet is a series of
27795 actions, concatenated without separators. Each action has one of the
27801 Collect the registers whose bits are set in @var{mask}. @var{mask} is
27802 a hexadecimal number whose @var{i}'th bit is set if register number
27803 @var{i} should be collected. (The least significant bit is numbered
27804 zero.) Note that @var{mask} may be any number of digits long; it may
27805 not fit in a 32-bit word.
27807 @item M @var{basereg},@var{offset},@var{len}
27808 Collect @var{len} bytes of memory starting at the address in register
27809 number @var{basereg}, plus @var{offset}. If @var{basereg} is
27810 @samp{-1}, then the range has a fixed address: @var{offset} is the
27811 address of the lowest byte to collect. The @var{basereg},
27812 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
27813 values (the @samp{-1} value for @var{basereg} is a special case).
27815 @item X @var{len},@var{expr}
27816 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
27817 it directs. @var{expr} is an agent expression, as described in
27818 @ref{Agent Expressions}. Each byte of the expression is encoded as a
27819 two-digit hex number in the packet; @var{len} is the number of bytes
27820 in the expression (and thus one-half the number of hex digits in the
27825 Any number of actions may be packed together in a single @samp{QTDP}
27826 packet, as long as the packet does not exceed the maximum packet
27827 length (400 bytes, for many stubs). There may be only one @samp{R}
27828 action per tracepoint, and it must precede any @samp{M} or @samp{X}
27829 actions. Any registers referred to by @samp{M} and @samp{X} actions
27830 must be collected by a preceding @samp{R} action. (The
27831 ``while-stepping'' actions are treated as if they were attached to a
27832 separate tracepoint, as far as these restrictions are concerned.)
27837 The packet was understood and carried out.
27839 The packet was not recognized.
27842 @item QTFrame:@var{n}
27843 Select the @var{n}'th tracepoint frame from the buffer, and use the
27844 register and memory contents recorded there to answer subsequent
27845 request packets from @value{GDBN}.
27847 A successful reply from the stub indicates that the stub has found the
27848 requested frame. The response is a series of parts, concatenated
27849 without separators, describing the frame we selected. Each part has
27850 one of the following forms:
27854 The selected frame is number @var{n} in the trace frame buffer;
27855 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
27856 was no frame matching the criteria in the request packet.
27859 The selected trace frame records a hit of tracepoint number @var{t};
27860 @var{t} is a hexadecimal number.
27864 @item QTFrame:pc:@var{addr}
27865 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27866 currently selected frame whose PC is @var{addr};
27867 @var{addr} is a hexadecimal number.
27869 @item QTFrame:tdp:@var{t}
27870 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27871 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
27872 is a hexadecimal number.
27874 @item QTFrame:range:@var{start}:@var{end}
27875 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27876 currently selected frame whose PC is between @var{start} (inclusive)
27877 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
27880 @item QTFrame:outside:@var{start}:@var{end}
27881 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
27882 frame @emph{outside} the given range of addresses.
27885 Begin the tracepoint experiment. Begin collecting data from tracepoint
27886 hits in the trace frame buffer.
27889 End the tracepoint experiment. Stop collecting trace frames.
27892 Clear the table of tracepoints, and empty the trace frame buffer.
27894 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
27895 Establish the given ranges of memory as ``transparent''. The stub
27896 will answer requests for these ranges from memory's current contents,
27897 if they were not collected as part of the tracepoint hit.
27899 @value{GDBN} uses this to mark read-only regions of memory, like those
27900 containing program code. Since these areas never change, they should
27901 still have the same contents they did when the tracepoint was hit, so
27902 there's no reason for the stub to refuse to provide their contents.
27905 Ask the stub if there is a trace experiment running right now.
27910 There is no trace experiment running.
27912 There is a trace experiment running.
27918 @node Host I/O Packets
27919 @section Host I/O Packets
27920 @cindex Host I/O, remote protocol
27921 @cindex file transfer, remote protocol
27923 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
27924 operations on the far side of a remote link. For example, Host I/O is
27925 used to upload and download files to a remote target with its own
27926 filesystem. Host I/O uses the same constant values and data structure
27927 layout as the target-initiated File-I/O protocol. However, the
27928 Host I/O packets are structured differently. The target-initiated
27929 protocol relies on target memory to store parameters and buffers.
27930 Host I/O requests are initiated by @value{GDBN}, and the
27931 target's memory is not involved. @xref{File-I/O Remote Protocol
27932 Extension}, for more details on the target-initiated protocol.
27934 The Host I/O request packets all encode a single operation along with
27935 its arguments. They have this format:
27939 @item vFile:@var{operation}: @var{parameter}@dots{}
27940 @var{operation} is the name of the particular request; the target
27941 should compare the entire packet name up to the second colon when checking
27942 for a supported operation. The format of @var{parameter} depends on
27943 the operation. Numbers are always passed in hexadecimal. Negative
27944 numbers have an explicit minus sign (i.e.@: two's complement is not
27945 used). Strings (e.g.@: filenames) are encoded as a series of
27946 hexadecimal bytes. The last argument to a system call may be a
27947 buffer of escaped binary data (@pxref{Binary Data}).
27951 The valid responses to Host I/O packets are:
27955 @item F @var{result} [, @var{errno}] [; @var{attachment}]
27956 @var{result} is the integer value returned by this operation, usually
27957 non-negative for success and -1 for errors. If an error has occured,
27958 @var{errno} will be included in the result. @var{errno} will have a
27959 value defined by the File-I/O protocol (@pxref{Errno Values}). For
27960 operations which return data, @var{attachment} supplies the data as a
27961 binary buffer. Binary buffers in response packets are escaped in the
27962 normal way (@pxref{Binary Data}). See the individual packet
27963 documentation for the interpretation of @var{result} and
27967 An empty response indicates that this operation is not recognized.
27971 These are the supported Host I/O operations:
27974 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
27975 Open a file at @var{pathname} and return a file descriptor for it, or
27976 return -1 if an error occurs. @var{pathname} is a string,
27977 @var{flags} is an integer indicating a mask of open flags
27978 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
27979 of mode bits to use if the file is created (@pxref{mode_t Values}).
27980 @xref{open}, for details of the open flags and mode values.
27982 @item vFile:close: @var{fd}
27983 Close the open file corresponding to @var{fd} and return 0, or
27984 -1 if an error occurs.
27986 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
27987 Read data from the open file corresponding to @var{fd}. Up to
27988 @var{count} bytes will be read from the file, starting at @var{offset}
27989 relative to the start of the file. The target may read fewer bytes;
27990 common reasons include packet size limits and an end-of-file
27991 condition. The number of bytes read is returned. Zero should only be
27992 returned for a successful read at the end of the file, or if
27993 @var{count} was zero.
27995 The data read should be returned as a binary attachment on success.
27996 If zero bytes were read, the response should include an empty binary
27997 attachment (i.e.@: a trailing semicolon). The return value is the
27998 number of target bytes read; the binary attachment may be longer if
27999 some characters were escaped.
28001 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
28002 Write @var{data} (a binary buffer) to the open file corresponding
28003 to @var{fd}. Start the write at @var{offset} from the start of the
28004 file. Unlike many @code{write} system calls, there is no
28005 separate @var{count} argument; the length of @var{data} in the
28006 packet is used. @samp{vFile:write} returns the number of bytes written,
28007 which may be shorter than the length of @var{data}, or -1 if an
28010 @item vFile:unlink: @var{pathname}
28011 Delete the file at @var{pathname} on the target. Return 0,
28012 or -1 if an error occurs. @var{pathname} is a string.
28017 @section Interrupts
28018 @cindex interrupts (remote protocol)
28020 When a program on the remote target is running, @value{GDBN} may
28021 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
28022 control of which is specified via @value{GDBN}'s @samp{remotebreak}
28023 setting (@pxref{set remotebreak}).
28025 The precise meaning of @code{BREAK} is defined by the transport
28026 mechanism and may, in fact, be undefined. @value{GDBN} does not
28027 currently define a @code{BREAK} mechanism for any of the network
28028 interfaces except for TCP, in which case @value{GDBN} sends the
28029 @code{telnet} BREAK sequence.
28031 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
28032 transport mechanisms. It is represented by sending the single byte
28033 @code{0x03} without any of the usual packet overhead described in
28034 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
28035 transmitted as part of a packet, it is considered to be packet data
28036 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
28037 (@pxref{X packet}), used for binary downloads, may include an unescaped
28038 @code{0x03} as part of its packet.
28040 Stubs are not required to recognize these interrupt mechanisms and the
28041 precise meaning associated with receipt of the interrupt is
28042 implementation defined. If the target supports debugging of multiple
28043 threads and/or processes, it should attempt to interrupt all
28044 currently-executing threads and processes.
28045 If the stub is successful at interrupting the
28046 running program, it should send one of the stop
28047 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
28048 of successfully stopping the program in all-stop mode, and a stop reply
28049 for each stopped thread in non-stop mode.
28050 Interrupts received while the
28051 program is stopped are discarded.
28053 @node Notification Packets
28054 @section Notification Packets
28055 @cindex notification packets
28056 @cindex packets, notification
28058 The @value{GDBN} remote serial protocol includes @dfn{notifications},
28059 packets that require no acknowledgment. Both the GDB and the stub
28060 may send notifications (although the only notifications defined at
28061 present are sent by the stub). Notifications carry information
28062 without incurring the round-trip latency of an acknowledgment, and so
28063 are useful for low-impact communications where occasional packet loss
28066 A notification packet has the form @samp{% @var{data} #
28067 @var{checksum}}, where @var{data} is the content of the notification,
28068 and @var{checksum} is a checksum of @var{data}, computed and formatted
28069 as for ordinary @value{GDBN} packets. A notification's @var{data}
28070 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
28071 receiving a notification, the recipient sends no @samp{+} or @samp{-}
28072 to acknowledge the notification's receipt or to report its corruption.
28074 Every notification's @var{data} begins with a name, which contains no
28075 colon characters, followed by a colon character.
28077 Recipients should silently ignore corrupted notifications and
28078 notifications they do not understand. Recipients should restart
28079 timeout periods on receipt of a well-formed notification, whether or
28080 not they understand it.
28082 Senders should only send the notifications described here when this
28083 protocol description specifies that they are permitted. In the
28084 future, we may extend the protocol to permit existing notifications in
28085 new contexts; this rule helps older senders avoid confusing newer
28088 (Older versions of @value{GDBN} ignore bytes received until they see
28089 the @samp{$} byte that begins an ordinary packet, so new stubs may
28090 transmit notifications without fear of confusing older clients. There
28091 are no notifications defined for @value{GDBN} to send at the moment, but we
28092 assume that most older stubs would ignore them, as well.)
28094 The following notification packets from the stub to @value{GDBN} are
28098 @item Stop: @var{reply}
28099 Report an asynchronous stop event in non-stop mode.
28100 The @var{reply} has the form of a stop reply, as
28101 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
28102 for information on how these notifications are acknowledged by
28106 @node Remote Non-Stop
28107 @section Remote Protocol Support for Non-Stop Mode
28109 @value{GDBN}'s remote protocol supports non-stop debugging of
28110 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
28111 supports non-stop mode, it should report that to @value{GDBN} by including
28112 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
28114 @value{GDBN} typically sends a @samp{QNonStop} packet only when
28115 establishing a new connection with the stub. Entering non-stop mode
28116 does not alter the state of any currently-running threads, but targets
28117 must stop all threads in any already-attached processes when entering
28118 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
28119 probe the target state after a mode change.
28121 In non-stop mode, when an attached process encounters an event that
28122 would otherwise be reported with a stop reply, it uses the
28123 asynchronous notification mechanism (@pxref{Notification Packets}) to
28124 inform @value{GDBN}. In contrast to all-stop mode, where all threads
28125 in all processes are stopped when a stop reply is sent, in non-stop
28126 mode only the thread reporting the stop event is stopped. That is,
28127 when reporting a @samp{S} or @samp{T} response to indicate completion
28128 of a step operation, hitting a breakpoint, or a fault, only the
28129 affected thread is stopped; any other still-running threads continue
28130 to run. When reporting a @samp{W} or @samp{X} response, all running
28131 threads belonging to other attached processes continue to run.
28133 Only one stop reply notification at a time may be pending; if
28134 additional stop events occur before @value{GDBN} has acknowledged the
28135 previous notification, they must be queued by the stub for later
28136 synchronous transmission in response to @samp{vStopped} packets from
28137 @value{GDBN}. Because the notification mechanism is unreliable,
28138 the stub is permitted to resend a stop reply notification
28139 if it believes @value{GDBN} may not have received it. @value{GDBN}
28140 ignores additional stop reply notifications received before it has
28141 finished processing a previous notification and the stub has completed
28142 sending any queued stop events.
28144 Otherwise, @value{GDBN} must be prepared to receive a stop reply
28145 notification at any time. Specifically, they may appear when
28146 @value{GDBN} is not otherwise reading input from the stub, or when
28147 @value{GDBN} is expecting to read a normal synchronous response or a
28148 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
28149 Notification packets are distinct from any other communication from
28150 the stub so there is no ambiguity.
28152 After receiving a stop reply notification, @value{GDBN} shall
28153 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
28154 as a regular, synchronous request to the stub. Such acknowledgment
28155 is not required to happen immediately, as @value{GDBN} is permitted to
28156 send other, unrelated packets to the stub first, which the stub should
28159 Upon receiving a @samp{vStopped} packet, if the stub has other queued
28160 stop events to report to @value{GDBN}, it shall respond by sending a
28161 normal stop reply response. @value{GDBN} shall then send another
28162 @samp{vStopped} packet to solicit further responses; again, it is
28163 permitted to send other, unrelated packets as well which the stub
28164 should process normally.
28166 If the stub receives a @samp{vStopped} packet and there are no
28167 additional stop events to report, the stub shall return an @samp{OK}
28168 response. At this point, if further stop events occur, the stub shall
28169 send a new stop reply notification, @value{GDBN} shall accept the
28170 notification, and the process shall be repeated.
28172 In non-stop mode, the target shall respond to the @samp{?} packet as
28173 follows. First, any incomplete stop reply notification/@samp{vStopped}
28174 sequence in progress is abandoned. The target must begin a new
28175 sequence reporting stop events for all stopped threads, whether or not
28176 it has previously reported those events to @value{GDBN}. The first
28177 stop reply is sent as a synchronous reply to the @samp{?} packet, and
28178 subsequent stop replies are sent as responses to @samp{vStopped} packets
28179 using the mechanism described above. The target must not send
28180 asynchronous stop reply notifications until the sequence is complete.
28181 If all threads are running when the target receives the @samp{?} packet,
28182 or if the target is not attached to any process, it shall respond
28185 @node Packet Acknowledgment
28186 @section Packet Acknowledgment
28188 @cindex acknowledgment, for @value{GDBN} remote
28189 @cindex packet acknowledgment, for @value{GDBN} remote
28190 By default, when either the host or the target machine receives a packet,
28191 the first response expected is an acknowledgment: either @samp{+} (to indicate
28192 the package was received correctly) or @samp{-} (to request retransmission).
28193 This mechanism allows the @value{GDBN} remote protocol to operate over
28194 unreliable transport mechanisms, such as a serial line.
28196 In cases where the transport mechanism is itself reliable (such as a pipe or
28197 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
28198 It may be desirable to disable them in that case to reduce communication
28199 overhead, or for other reasons. This can be accomplished by means of the
28200 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
28202 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
28203 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
28204 and response format still includes the normal checksum, as described in
28205 @ref{Overview}, but the checksum may be ignored by the receiver.
28207 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
28208 no-acknowledgment mode, it should report that to @value{GDBN}
28209 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
28210 @pxref{qSupported}.
28211 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
28212 disabled via the @code{set remote noack-packet off} command
28213 (@pxref{Remote Configuration}),
28214 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
28215 Only then may the stub actually turn off packet acknowledgments.
28216 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
28217 response, which can be safely ignored by the stub.
28219 Note that @code{set remote noack-packet} command only affects negotiation
28220 between @value{GDBN} and the stub when subsequent connections are made;
28221 it does not affect the protocol acknowledgment state for any current
28223 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
28224 new connection is established,
28225 there is also no protocol request to re-enable the acknowledgments
28226 for the current connection, once disabled.
28231 Example sequence of a target being re-started. Notice how the restart
28232 does not get any direct output:
28237 @emph{target restarts}
28240 <- @code{T001:1234123412341234}
28244 Example sequence of a target being stepped by a single instruction:
28247 -> @code{G1445@dots{}}
28252 <- @code{T001:1234123412341234}
28256 <- @code{1455@dots{}}
28260 @node File-I/O Remote Protocol Extension
28261 @section File-I/O Remote Protocol Extension
28262 @cindex File-I/O remote protocol extension
28265 * File-I/O Overview::
28266 * Protocol Basics::
28267 * The F Request Packet::
28268 * The F Reply Packet::
28269 * The Ctrl-C Message::
28271 * List of Supported Calls::
28272 * Protocol-specific Representation of Datatypes::
28274 * File-I/O Examples::
28277 @node File-I/O Overview
28278 @subsection File-I/O Overview
28279 @cindex file-i/o overview
28281 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
28282 target to use the host's file system and console I/O to perform various
28283 system calls. System calls on the target system are translated into a
28284 remote protocol packet to the host system, which then performs the needed
28285 actions and returns a response packet to the target system.
28286 This simulates file system operations even on targets that lack file systems.
28288 The protocol is defined to be independent of both the host and target systems.
28289 It uses its own internal representation of datatypes and values. Both
28290 @value{GDBN} and the target's @value{GDBN} stub are responsible for
28291 translating the system-dependent value representations into the internal
28292 protocol representations when data is transmitted.
28294 The communication is synchronous. A system call is possible only when
28295 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
28296 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
28297 the target is stopped to allow deterministic access to the target's
28298 memory. Therefore File-I/O is not interruptible by target signals. On
28299 the other hand, it is possible to interrupt File-I/O by a user interrupt
28300 (@samp{Ctrl-C}) within @value{GDBN}.
28302 The target's request to perform a host system call does not finish
28303 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
28304 after finishing the system call, the target returns to continuing the
28305 previous activity (continue, step). No additional continue or step
28306 request from @value{GDBN} is required.
28309 (@value{GDBP}) continue
28310 <- target requests 'system call X'
28311 target is stopped, @value{GDBN} executes system call
28312 -> @value{GDBN} returns result
28313 ... target continues, @value{GDBN} returns to wait for the target
28314 <- target hits breakpoint and sends a Txx packet
28317 The protocol only supports I/O on the console and to regular files on
28318 the host file system. Character or block special devices, pipes,
28319 named pipes, sockets or any other communication method on the host
28320 system are not supported by this protocol.
28322 File I/O is not supported in non-stop mode.
28324 @node Protocol Basics
28325 @subsection Protocol Basics
28326 @cindex protocol basics, file-i/o
28328 The File-I/O protocol uses the @code{F} packet as the request as well
28329 as reply packet. Since a File-I/O system call can only occur when
28330 @value{GDBN} is waiting for a response from the continuing or stepping target,
28331 the File-I/O request is a reply that @value{GDBN} has to expect as a result
28332 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
28333 This @code{F} packet contains all information needed to allow @value{GDBN}
28334 to call the appropriate host system call:
28338 A unique identifier for the requested system call.
28341 All parameters to the system call. Pointers are given as addresses
28342 in the target memory address space. Pointers to strings are given as
28343 pointer/length pair. Numerical values are given as they are.
28344 Numerical control flags are given in a protocol-specific representation.
28348 At this point, @value{GDBN} has to perform the following actions.
28352 If the parameters include pointer values to data needed as input to a
28353 system call, @value{GDBN} requests this data from the target with a
28354 standard @code{m} packet request. This additional communication has to be
28355 expected by the target implementation and is handled as any other @code{m}
28359 @value{GDBN} translates all value from protocol representation to host
28360 representation as needed. Datatypes are coerced into the host types.
28363 @value{GDBN} calls the system call.
28366 It then coerces datatypes back to protocol representation.
28369 If the system call is expected to return data in buffer space specified
28370 by pointer parameters to the call, the data is transmitted to the
28371 target using a @code{M} or @code{X} packet. This packet has to be expected
28372 by the target implementation and is handled as any other @code{M} or @code{X}
28377 Eventually @value{GDBN} replies with another @code{F} packet which contains all
28378 necessary information for the target to continue. This at least contains
28385 @code{errno}, if has been changed by the system call.
28392 After having done the needed type and value coercion, the target continues
28393 the latest continue or step action.
28395 @node The F Request Packet
28396 @subsection The @code{F} Request Packet
28397 @cindex file-i/o request packet
28398 @cindex @code{F} request packet
28400 The @code{F} request packet has the following format:
28403 @item F@var{call-id},@var{parameter@dots{}}
28405 @var{call-id} is the identifier to indicate the host system call to be called.
28406 This is just the name of the function.
28408 @var{parameter@dots{}} are the parameters to the system call.
28409 Parameters are hexadecimal integer values, either the actual values in case
28410 of scalar datatypes, pointers to target buffer space in case of compound
28411 datatypes and unspecified memory areas, or pointer/length pairs in case
28412 of string parameters. These are appended to the @var{call-id} as a
28413 comma-delimited list. All values are transmitted in ASCII
28414 string representation, pointer/length pairs separated by a slash.
28420 @node The F Reply Packet
28421 @subsection The @code{F} Reply Packet
28422 @cindex file-i/o reply packet
28423 @cindex @code{F} reply packet
28425 The @code{F} reply packet has the following format:
28429 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
28431 @var{retcode} is the return code of the system call as hexadecimal value.
28433 @var{errno} is the @code{errno} set by the call, in protocol-specific
28435 This parameter can be omitted if the call was successful.
28437 @var{Ctrl-C flag} is only sent if the user requested a break. In this
28438 case, @var{errno} must be sent as well, even if the call was successful.
28439 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
28446 or, if the call was interrupted before the host call has been performed:
28453 assuming 4 is the protocol-specific representation of @code{EINTR}.
28458 @node The Ctrl-C Message
28459 @subsection The @samp{Ctrl-C} Message
28460 @cindex ctrl-c message, in file-i/o protocol
28462 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
28463 reply packet (@pxref{The F Reply Packet}),
28464 the target should behave as if it had
28465 gotten a break message. The meaning for the target is ``system call
28466 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
28467 (as with a break message) and return to @value{GDBN} with a @code{T02}
28470 It's important for the target to know in which
28471 state the system call was interrupted. There are two possible cases:
28475 The system call hasn't been performed on the host yet.
28478 The system call on the host has been finished.
28482 These two states can be distinguished by the target by the value of the
28483 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
28484 call hasn't been performed. This is equivalent to the @code{EINTR} handling
28485 on POSIX systems. In any other case, the target may presume that the
28486 system call has been finished --- successfully or not --- and should behave
28487 as if the break message arrived right after the system call.
28489 @value{GDBN} must behave reliably. If the system call has not been called
28490 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
28491 @code{errno} in the packet. If the system call on the host has been finished
28492 before the user requests a break, the full action must be finished by
28493 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
28494 The @code{F} packet may only be sent when either nothing has happened
28495 or the full action has been completed.
28498 @subsection Console I/O
28499 @cindex console i/o as part of file-i/o
28501 By default and if not explicitly closed by the target system, the file
28502 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
28503 on the @value{GDBN} console is handled as any other file output operation
28504 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
28505 by @value{GDBN} so that after the target read request from file descriptor
28506 0 all following typing is buffered until either one of the following
28511 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
28513 system call is treated as finished.
28516 The user presses @key{RET}. This is treated as end of input with a trailing
28520 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
28521 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
28525 If the user has typed more characters than fit in the buffer given to
28526 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
28527 either another @code{read(0, @dots{})} is requested by the target, or debugging
28528 is stopped at the user's request.
28531 @node List of Supported Calls
28532 @subsection List of Supported Calls
28533 @cindex list of supported file-i/o calls
28550 @unnumberedsubsubsec open
28551 @cindex open, file-i/o system call
28556 int open(const char *pathname, int flags);
28557 int open(const char *pathname, int flags, mode_t mode);
28561 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
28564 @var{flags} is the bitwise @code{OR} of the following values:
28568 If the file does not exist it will be created. The host
28569 rules apply as far as file ownership and time stamps
28573 When used with @code{O_CREAT}, if the file already exists it is
28574 an error and open() fails.
28577 If the file already exists and the open mode allows
28578 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
28579 truncated to zero length.
28582 The file is opened in append mode.
28585 The file is opened for reading only.
28588 The file is opened for writing only.
28591 The file is opened for reading and writing.
28595 Other bits are silently ignored.
28599 @var{mode} is the bitwise @code{OR} of the following values:
28603 User has read permission.
28606 User has write permission.
28609 Group has read permission.
28612 Group has write permission.
28615 Others have read permission.
28618 Others have write permission.
28622 Other bits are silently ignored.
28625 @item Return value:
28626 @code{open} returns the new file descriptor or -1 if an error
28633 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
28636 @var{pathname} refers to a directory.
28639 The requested access is not allowed.
28642 @var{pathname} was too long.
28645 A directory component in @var{pathname} does not exist.
28648 @var{pathname} refers to a device, pipe, named pipe or socket.
28651 @var{pathname} refers to a file on a read-only filesystem and
28652 write access was requested.
28655 @var{pathname} is an invalid pointer value.
28658 No space on device to create the file.
28661 The process already has the maximum number of files open.
28664 The limit on the total number of files open on the system
28668 The call was interrupted by the user.
28674 @unnumberedsubsubsec close
28675 @cindex close, file-i/o system call
28684 @samp{Fclose,@var{fd}}
28686 @item Return value:
28687 @code{close} returns zero on success, or -1 if an error occurred.
28693 @var{fd} isn't a valid open file descriptor.
28696 The call was interrupted by the user.
28702 @unnumberedsubsubsec read
28703 @cindex read, file-i/o system call
28708 int read(int fd, void *buf, unsigned int count);
28712 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
28714 @item Return value:
28715 On success, the number of bytes read is returned.
28716 Zero indicates end of file. If count is zero, read
28717 returns zero as well. On error, -1 is returned.
28723 @var{fd} is not a valid file descriptor or is not open for
28727 @var{bufptr} is an invalid pointer value.
28730 The call was interrupted by the user.
28736 @unnumberedsubsubsec write
28737 @cindex write, file-i/o system call
28742 int write(int fd, const void *buf, unsigned int count);
28746 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
28748 @item Return value:
28749 On success, the number of bytes written are returned.
28750 Zero indicates nothing was written. On error, -1
28757 @var{fd} is not a valid file descriptor or is not open for
28761 @var{bufptr} is an invalid pointer value.
28764 An attempt was made to write a file that exceeds the
28765 host-specific maximum file size allowed.
28768 No space on device to write the data.
28771 The call was interrupted by the user.
28777 @unnumberedsubsubsec lseek
28778 @cindex lseek, file-i/o system call
28783 long lseek (int fd, long offset, int flag);
28787 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
28789 @var{flag} is one of:
28793 The offset is set to @var{offset} bytes.
28796 The offset is set to its current location plus @var{offset}
28800 The offset is set to the size of the file plus @var{offset}
28804 @item Return value:
28805 On success, the resulting unsigned offset in bytes from
28806 the beginning of the file is returned. Otherwise, a
28807 value of -1 is returned.
28813 @var{fd} is not a valid open file descriptor.
28816 @var{fd} is associated with the @value{GDBN} console.
28819 @var{flag} is not a proper value.
28822 The call was interrupted by the user.
28828 @unnumberedsubsubsec rename
28829 @cindex rename, file-i/o system call
28834 int rename(const char *oldpath, const char *newpath);
28838 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
28840 @item Return value:
28841 On success, zero is returned. On error, -1 is returned.
28847 @var{newpath} is an existing directory, but @var{oldpath} is not a
28851 @var{newpath} is a non-empty directory.
28854 @var{oldpath} or @var{newpath} is a directory that is in use by some
28858 An attempt was made to make a directory a subdirectory
28862 A component used as a directory in @var{oldpath} or new
28863 path is not a directory. Or @var{oldpath} is a directory
28864 and @var{newpath} exists but is not a directory.
28867 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
28870 No access to the file or the path of the file.
28874 @var{oldpath} or @var{newpath} was too long.
28877 A directory component in @var{oldpath} or @var{newpath} does not exist.
28880 The file is on a read-only filesystem.
28883 The device containing the file has no room for the new
28887 The call was interrupted by the user.
28893 @unnumberedsubsubsec unlink
28894 @cindex unlink, file-i/o system call
28899 int unlink(const char *pathname);
28903 @samp{Funlink,@var{pathnameptr}/@var{len}}
28905 @item Return value:
28906 On success, zero is returned. On error, -1 is returned.
28912 No access to the file or the path of the file.
28915 The system does not allow unlinking of directories.
28918 The file @var{pathname} cannot be unlinked because it's
28919 being used by another process.
28922 @var{pathnameptr} is an invalid pointer value.
28925 @var{pathname} was too long.
28928 A directory component in @var{pathname} does not exist.
28931 A component of the path is not a directory.
28934 The file is on a read-only filesystem.
28937 The call was interrupted by the user.
28943 @unnumberedsubsubsec stat/fstat
28944 @cindex fstat, file-i/o system call
28945 @cindex stat, file-i/o system call
28950 int stat(const char *pathname, struct stat *buf);
28951 int fstat(int fd, struct stat *buf);
28955 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
28956 @samp{Ffstat,@var{fd},@var{bufptr}}
28958 @item Return value:
28959 On success, zero is returned. On error, -1 is returned.
28965 @var{fd} is not a valid open file.
28968 A directory component in @var{pathname} does not exist or the
28969 path is an empty string.
28972 A component of the path is not a directory.
28975 @var{pathnameptr} is an invalid pointer value.
28978 No access to the file or the path of the file.
28981 @var{pathname} was too long.
28984 The call was interrupted by the user.
28990 @unnumberedsubsubsec gettimeofday
28991 @cindex gettimeofday, file-i/o system call
28996 int gettimeofday(struct timeval *tv, void *tz);
29000 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
29002 @item Return value:
29003 On success, 0 is returned, -1 otherwise.
29009 @var{tz} is a non-NULL pointer.
29012 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
29018 @unnumberedsubsubsec isatty
29019 @cindex isatty, file-i/o system call
29024 int isatty(int fd);
29028 @samp{Fisatty,@var{fd}}
29030 @item Return value:
29031 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
29037 The call was interrupted by the user.
29042 Note that the @code{isatty} call is treated as a special case: it returns
29043 1 to the target if the file descriptor is attached
29044 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
29045 would require implementing @code{ioctl} and would be more complex than
29050 @unnumberedsubsubsec system
29051 @cindex system, file-i/o system call
29056 int system(const char *command);
29060 @samp{Fsystem,@var{commandptr}/@var{len}}
29062 @item Return value:
29063 If @var{len} is zero, the return value indicates whether a shell is
29064 available. A zero return value indicates a shell is not available.
29065 For non-zero @var{len}, the value returned is -1 on error and the
29066 return status of the command otherwise. Only the exit status of the
29067 command is returned, which is extracted from the host's @code{system}
29068 return value by calling @code{WEXITSTATUS(retval)}. In case
29069 @file{/bin/sh} could not be executed, 127 is returned.
29075 The call was interrupted by the user.
29080 @value{GDBN} takes over the full task of calling the necessary host calls
29081 to perform the @code{system} call. The return value of @code{system} on
29082 the host is simplified before it's returned
29083 to the target. Any termination signal information from the child process
29084 is discarded, and the return value consists
29085 entirely of the exit status of the called command.
29087 Due to security concerns, the @code{system} call is by default refused
29088 by @value{GDBN}. The user has to allow this call explicitly with the
29089 @code{set remote system-call-allowed 1} command.
29092 @item set remote system-call-allowed
29093 @kindex set remote system-call-allowed
29094 Control whether to allow the @code{system} calls in the File I/O
29095 protocol for the remote target. The default is zero (disabled).
29097 @item show remote system-call-allowed
29098 @kindex show remote system-call-allowed
29099 Show whether the @code{system} calls are allowed in the File I/O
29103 @node Protocol-specific Representation of Datatypes
29104 @subsection Protocol-specific Representation of Datatypes
29105 @cindex protocol-specific representation of datatypes, in file-i/o protocol
29108 * Integral Datatypes::
29110 * Memory Transfer::
29115 @node Integral Datatypes
29116 @unnumberedsubsubsec Integral Datatypes
29117 @cindex integral datatypes, in file-i/o protocol
29119 The integral datatypes used in the system calls are @code{int},
29120 @code{unsigned int}, @code{long}, @code{unsigned long},
29121 @code{mode_t}, and @code{time_t}.
29123 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
29124 implemented as 32 bit values in this protocol.
29126 @code{long} and @code{unsigned long} are implemented as 64 bit types.
29128 @xref{Limits}, for corresponding MIN and MAX values (similar to those
29129 in @file{limits.h}) to allow range checking on host and target.
29131 @code{time_t} datatypes are defined as seconds since the Epoch.
29133 All integral datatypes transferred as part of a memory read or write of a
29134 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
29137 @node Pointer Values
29138 @unnumberedsubsubsec Pointer Values
29139 @cindex pointer values, in file-i/o protocol
29141 Pointers to target data are transmitted as they are. An exception
29142 is made for pointers to buffers for which the length isn't
29143 transmitted as part of the function call, namely strings. Strings
29144 are transmitted as a pointer/length pair, both as hex values, e.g.@:
29151 which is a pointer to data of length 18 bytes at position 0x1aaf.
29152 The length is defined as the full string length in bytes, including
29153 the trailing null byte. For example, the string @code{"hello world"}
29154 at address 0x123456 is transmitted as
29160 @node Memory Transfer
29161 @unnumberedsubsubsec Memory Transfer
29162 @cindex memory transfer, in file-i/o protocol
29164 Structured data which is transferred using a memory read or write (for
29165 example, a @code{struct stat}) is expected to be in a protocol-specific format
29166 with all scalar multibyte datatypes being big endian. Translation to
29167 this representation needs to be done both by the target before the @code{F}
29168 packet is sent, and by @value{GDBN} before
29169 it transfers memory to the target. Transferred pointers to structured
29170 data should point to the already-coerced data at any time.
29174 @unnumberedsubsubsec struct stat
29175 @cindex struct stat, in file-i/o protocol
29177 The buffer of type @code{struct stat} used by the target and @value{GDBN}
29178 is defined as follows:
29182 unsigned int st_dev; /* device */
29183 unsigned int st_ino; /* inode */
29184 mode_t st_mode; /* protection */
29185 unsigned int st_nlink; /* number of hard links */
29186 unsigned int st_uid; /* user ID of owner */
29187 unsigned int st_gid; /* group ID of owner */
29188 unsigned int st_rdev; /* device type (if inode device) */
29189 unsigned long st_size; /* total size, in bytes */
29190 unsigned long st_blksize; /* blocksize for filesystem I/O */
29191 unsigned long st_blocks; /* number of blocks allocated */
29192 time_t st_atime; /* time of last access */
29193 time_t st_mtime; /* time of last modification */
29194 time_t st_ctime; /* time of last change */
29198 The integral datatypes conform to the definitions given in the
29199 appropriate section (see @ref{Integral Datatypes}, for details) so this
29200 structure is of size 64 bytes.
29202 The values of several fields have a restricted meaning and/or
29208 A value of 0 represents a file, 1 the console.
29211 No valid meaning for the target. Transmitted unchanged.
29214 Valid mode bits are described in @ref{Constants}. Any other
29215 bits have currently no meaning for the target.
29220 No valid meaning for the target. Transmitted unchanged.
29225 These values have a host and file system dependent
29226 accuracy. Especially on Windows hosts, the file system may not
29227 support exact timing values.
29230 The target gets a @code{struct stat} of the above representation and is
29231 responsible for coercing it to the target representation before
29234 Note that due to size differences between the host, target, and protocol
29235 representations of @code{struct stat} members, these members could eventually
29236 get truncated on the target.
29238 @node struct timeval
29239 @unnumberedsubsubsec struct timeval
29240 @cindex struct timeval, in file-i/o protocol
29242 The buffer of type @code{struct timeval} used by the File-I/O protocol
29243 is defined as follows:
29247 time_t tv_sec; /* second */
29248 long tv_usec; /* microsecond */
29252 The integral datatypes conform to the definitions given in the
29253 appropriate section (see @ref{Integral Datatypes}, for details) so this
29254 structure is of size 8 bytes.
29257 @subsection Constants
29258 @cindex constants, in file-i/o protocol
29260 The following values are used for the constants inside of the
29261 protocol. @value{GDBN} and target are responsible for translating these
29262 values before and after the call as needed.
29273 @unnumberedsubsubsec Open Flags
29274 @cindex open flags, in file-i/o protocol
29276 All values are given in hexadecimal representation.
29288 @node mode_t Values
29289 @unnumberedsubsubsec mode_t Values
29290 @cindex mode_t values, in file-i/o protocol
29292 All values are given in octal representation.
29309 @unnumberedsubsubsec Errno Values
29310 @cindex errno values, in file-i/o protocol
29312 All values are given in decimal representation.
29337 @code{EUNKNOWN} is used as a fallback error value if a host system returns
29338 any error value not in the list of supported error numbers.
29341 @unnumberedsubsubsec Lseek Flags
29342 @cindex lseek flags, in file-i/o protocol
29351 @unnumberedsubsubsec Limits
29352 @cindex limits, in file-i/o protocol
29354 All values are given in decimal representation.
29357 INT_MIN -2147483648
29359 UINT_MAX 4294967295
29360 LONG_MIN -9223372036854775808
29361 LONG_MAX 9223372036854775807
29362 ULONG_MAX 18446744073709551615
29365 @node File-I/O Examples
29366 @subsection File-I/O Examples
29367 @cindex file-i/o examples
29369 Example sequence of a write call, file descriptor 3, buffer is at target
29370 address 0x1234, 6 bytes should be written:
29373 <- @code{Fwrite,3,1234,6}
29374 @emph{request memory read from target}
29377 @emph{return "6 bytes written"}
29381 Example sequence of a read call, file descriptor 3, buffer is at target
29382 address 0x1234, 6 bytes should be read:
29385 <- @code{Fread,3,1234,6}
29386 @emph{request memory write to target}
29387 -> @code{X1234,6:XXXXXX}
29388 @emph{return "6 bytes read"}
29392 Example sequence of a read call, call fails on the host due to invalid
29393 file descriptor (@code{EBADF}):
29396 <- @code{Fread,3,1234,6}
29400 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
29404 <- @code{Fread,3,1234,6}
29409 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
29413 <- @code{Fread,3,1234,6}
29414 -> @code{X1234,6:XXXXXX}
29418 @node Library List Format
29419 @section Library List Format
29420 @cindex library list format, remote protocol
29422 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
29423 same process as your application to manage libraries. In this case,
29424 @value{GDBN} can use the loader's symbol table and normal memory
29425 operations to maintain a list of shared libraries. On other
29426 platforms, the operating system manages loaded libraries.
29427 @value{GDBN} can not retrieve the list of currently loaded libraries
29428 through memory operations, so it uses the @samp{qXfer:libraries:read}
29429 packet (@pxref{qXfer library list read}) instead. The remote stub
29430 queries the target's operating system and reports which libraries
29433 The @samp{qXfer:libraries:read} packet returns an XML document which
29434 lists loaded libraries and their offsets. Each library has an
29435 associated name and one or more segment or section base addresses,
29436 which report where the library was loaded in memory.
29438 For the common case of libraries that are fully linked binaries, the
29439 library should have a list of segments. If the target supports
29440 dynamic linking of a relocatable object file, its library XML element
29441 should instead include a list of allocated sections. The segment or
29442 section bases are start addresses, not relocation offsets; they do not
29443 depend on the library's link-time base addresses.
29445 @value{GDBN} must be linked with the Expat library to support XML
29446 library lists. @xref{Expat}.
29448 A simple memory map, with one loaded library relocated by a single
29449 offset, looks like this:
29453 <library name="/lib/libc.so.6">
29454 <segment address="0x10000000"/>
29459 Another simple memory map, with one loaded library with three
29460 allocated sections (.text, .data, .bss), looks like this:
29464 <library name="sharedlib.o">
29465 <section address="0x10000000"/>
29466 <section address="0x20000000"/>
29467 <section address="0x30000000"/>
29472 The format of a library list is described by this DTD:
29475 <!-- library-list: Root element with versioning -->
29476 <!ELEMENT library-list (library)*>
29477 <!ATTLIST library-list version CDATA #FIXED "1.0">
29478 <!ELEMENT library (segment*, section*)>
29479 <!ATTLIST library name CDATA #REQUIRED>
29480 <!ELEMENT segment EMPTY>
29481 <!ATTLIST segment address CDATA #REQUIRED>
29482 <!ELEMENT section EMPTY>
29483 <!ATTLIST section address CDATA #REQUIRED>
29486 In addition, segments and section descriptors cannot be mixed within a
29487 single library element, and you must supply at least one segment or
29488 section for each library.
29490 @node Memory Map Format
29491 @section Memory Map Format
29492 @cindex memory map format
29494 To be able to write into flash memory, @value{GDBN} needs to obtain a
29495 memory map from the target. This section describes the format of the
29498 The memory map is obtained using the @samp{qXfer:memory-map:read}
29499 (@pxref{qXfer memory map read}) packet and is an XML document that
29500 lists memory regions.
29502 @value{GDBN} must be linked with the Expat library to support XML
29503 memory maps. @xref{Expat}.
29505 The top-level structure of the document is shown below:
29508 <?xml version="1.0"?>
29509 <!DOCTYPE memory-map
29510 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
29511 "http://sourceware.org/gdb/gdb-memory-map.dtd">
29517 Each region can be either:
29522 A region of RAM starting at @var{addr} and extending for @var{length}
29526 <memory type="ram" start="@var{addr}" length="@var{length}"/>
29531 A region of read-only memory:
29534 <memory type="rom" start="@var{addr}" length="@var{length}"/>
29539 A region of flash memory, with erasure blocks @var{blocksize}
29543 <memory type="flash" start="@var{addr}" length="@var{length}">
29544 <property name="blocksize">@var{blocksize}</property>
29550 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
29551 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
29552 packets to write to addresses in such ranges.
29554 The formal DTD for memory map format is given below:
29557 <!-- ................................................... -->
29558 <!-- Memory Map XML DTD ................................ -->
29559 <!-- File: memory-map.dtd .............................. -->
29560 <!-- .................................... .............. -->
29561 <!-- memory-map.dtd -->
29562 <!-- memory-map: Root element with versioning -->
29563 <!ELEMENT memory-map (memory | property)>
29564 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
29565 <!ELEMENT memory (property)>
29566 <!-- memory: Specifies a memory region,
29567 and its type, or device. -->
29568 <!ATTLIST memory type CDATA #REQUIRED
29569 start CDATA #REQUIRED
29570 length CDATA #REQUIRED
29571 device CDATA #IMPLIED>
29572 <!-- property: Generic attribute tag -->
29573 <!ELEMENT property (#PCDATA | property)*>
29574 <!ATTLIST property name CDATA #REQUIRED>
29577 @include agentexpr.texi
29579 @node Target Descriptions
29580 @appendix Target Descriptions
29581 @cindex target descriptions
29583 @strong{Warning:} target descriptions are still under active development,
29584 and the contents and format may change between @value{GDBN} releases.
29585 The format is expected to stabilize in the future.
29587 One of the challenges of using @value{GDBN} to debug embedded systems
29588 is that there are so many minor variants of each processor
29589 architecture in use. It is common practice for vendors to start with
29590 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
29591 and then make changes to adapt it to a particular market niche. Some
29592 architectures have hundreds of variants, available from dozens of
29593 vendors. This leads to a number of problems:
29597 With so many different customized processors, it is difficult for
29598 the @value{GDBN} maintainers to keep up with the changes.
29600 Since individual variants may have short lifetimes or limited
29601 audiences, it may not be worthwhile to carry information about every
29602 variant in the @value{GDBN} source tree.
29604 When @value{GDBN} does support the architecture of the embedded system
29605 at hand, the task of finding the correct architecture name to give the
29606 @command{set architecture} command can be error-prone.
29609 To address these problems, the @value{GDBN} remote protocol allows a
29610 target system to not only identify itself to @value{GDBN}, but to
29611 actually describe its own features. This lets @value{GDBN} support
29612 processor variants it has never seen before --- to the extent that the
29613 descriptions are accurate, and that @value{GDBN} understands them.
29615 @value{GDBN} must be linked with the Expat library to support XML
29616 target descriptions. @xref{Expat}.
29619 * Retrieving Descriptions:: How descriptions are fetched from a target.
29620 * Target Description Format:: The contents of a target description.
29621 * Predefined Target Types:: Standard types available for target
29623 * Standard Target Features:: Features @value{GDBN} knows about.
29626 @node Retrieving Descriptions
29627 @section Retrieving Descriptions
29629 Target descriptions can be read from the target automatically, or
29630 specified by the user manually. The default behavior is to read the
29631 description from the target. @value{GDBN} retrieves it via the remote
29632 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
29633 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
29634 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
29635 XML document, of the form described in @ref{Target Description
29638 Alternatively, you can specify a file to read for the target description.
29639 If a file is set, the target will not be queried. The commands to
29640 specify a file are:
29643 @cindex set tdesc filename
29644 @item set tdesc filename @var{path}
29645 Read the target description from @var{path}.
29647 @cindex unset tdesc filename
29648 @item unset tdesc filename
29649 Do not read the XML target description from a file. @value{GDBN}
29650 will use the description supplied by the current target.
29652 @cindex show tdesc filename
29653 @item show tdesc filename
29654 Show the filename to read for a target description, if any.
29658 @node Target Description Format
29659 @section Target Description Format
29660 @cindex target descriptions, XML format
29662 A target description annex is an @uref{http://www.w3.org/XML/, XML}
29663 document which complies with the Document Type Definition provided in
29664 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
29665 means you can use generally available tools like @command{xmllint} to
29666 check that your feature descriptions are well-formed and valid.
29667 However, to help people unfamiliar with XML write descriptions for
29668 their targets, we also describe the grammar here.
29670 Target descriptions can identify the architecture of the remote target
29671 and (for some architectures) provide information about custom register
29672 sets. @value{GDBN} can use this information to autoconfigure for your
29673 target, or to warn you if you connect to an unsupported target.
29675 Here is a simple target description:
29678 <target version="1.0">
29679 <architecture>i386:x86-64</architecture>
29684 This minimal description only says that the target uses
29685 the x86-64 architecture.
29687 A target description has the following overall form, with [ ] marking
29688 optional elements and @dots{} marking repeatable elements. The elements
29689 are explained further below.
29692 <?xml version="1.0"?>
29693 <!DOCTYPE target SYSTEM "gdb-target.dtd">
29694 <target version="1.0">
29695 @r{[}@var{architecture}@r{]}
29696 @r{[}@var{feature}@dots{}@r{]}
29701 The description is generally insensitive to whitespace and line
29702 breaks, under the usual common-sense rules. The XML version
29703 declaration and document type declaration can generally be omitted
29704 (@value{GDBN} does not require them), but specifying them may be
29705 useful for XML validation tools. The @samp{version} attribute for
29706 @samp{<target>} may also be omitted, but we recommend
29707 including it; if future versions of @value{GDBN} use an incompatible
29708 revision of @file{gdb-target.dtd}, they will detect and report
29709 the version mismatch.
29711 @subsection Inclusion
29712 @cindex target descriptions, inclusion
29715 @cindex <xi:include>
29718 It can sometimes be valuable to split a target description up into
29719 several different annexes, either for organizational purposes, or to
29720 share files between different possible target descriptions. You can
29721 divide a description into multiple files by replacing any element of
29722 the target description with an inclusion directive of the form:
29725 <xi:include href="@var{document}"/>
29729 When @value{GDBN} encounters an element of this form, it will retrieve
29730 the named XML @var{document}, and replace the inclusion directive with
29731 the contents of that document. If the current description was read
29732 using @samp{qXfer}, then so will be the included document;
29733 @var{document} will be interpreted as the name of an annex. If the
29734 current description was read from a file, @value{GDBN} will look for
29735 @var{document} as a file in the same directory where it found the
29736 original description.
29738 @subsection Architecture
29739 @cindex <architecture>
29741 An @samp{<architecture>} element has this form:
29744 <architecture>@var{arch}</architecture>
29747 @var{arch} is an architecture name from the same selection
29748 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
29749 Debugging Target}).
29751 @subsection Features
29754 Each @samp{<feature>} describes some logical portion of the target
29755 system. Features are currently used to describe available CPU
29756 registers and the types of their contents. A @samp{<feature>} element
29760 <feature name="@var{name}">
29761 @r{[}@var{type}@dots{}@r{]}
29767 Each feature's name should be unique within the description. The name
29768 of a feature does not matter unless @value{GDBN} has some special
29769 knowledge of the contents of that feature; if it does, the feature
29770 should have its standard name. @xref{Standard Target Features}.
29774 Any register's value is a collection of bits which @value{GDBN} must
29775 interpret. The default interpretation is a two's complement integer,
29776 but other types can be requested by name in the register description.
29777 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
29778 Target Types}), and the description can define additional composite types.
29780 Each type element must have an @samp{id} attribute, which gives
29781 a unique (within the containing @samp{<feature>}) name to the type.
29782 Types must be defined before they are used.
29785 Some targets offer vector registers, which can be treated as arrays
29786 of scalar elements. These types are written as @samp{<vector>} elements,
29787 specifying the array element type, @var{type}, and the number of elements,
29791 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
29795 If a register's value is usefully viewed in multiple ways, define it
29796 with a union type containing the useful representations. The
29797 @samp{<union>} element contains one or more @samp{<field>} elements,
29798 each of which has a @var{name} and a @var{type}:
29801 <union id="@var{id}">
29802 <field name="@var{name}" type="@var{type}"/>
29807 @subsection Registers
29810 Each register is represented as an element with this form:
29813 <reg name="@var{name}"
29814 bitsize="@var{size}"
29815 @r{[}regnum="@var{num}"@r{]}
29816 @r{[}save-restore="@var{save-restore}"@r{]}
29817 @r{[}type="@var{type}"@r{]}
29818 @r{[}group="@var{group}"@r{]}/>
29822 The components are as follows:
29827 The register's name; it must be unique within the target description.
29830 The register's size, in bits.
29833 The register's number. If omitted, a register's number is one greater
29834 than that of the previous register (either in the current feature or in
29835 a preceeding feature); the first register in the target description
29836 defaults to zero. This register number is used to read or write
29837 the register; e.g.@: it is used in the remote @code{p} and @code{P}
29838 packets, and registers appear in the @code{g} and @code{G} packets
29839 in order of increasing register number.
29842 Whether the register should be preserved across inferior function
29843 calls; this must be either @code{yes} or @code{no}. The default is
29844 @code{yes}, which is appropriate for most registers except for
29845 some system control registers; this is not related to the target's
29849 The type of the register. @var{type} may be a predefined type, a type
29850 defined in the current feature, or one of the special types @code{int}
29851 and @code{float}. @code{int} is an integer type of the correct size
29852 for @var{bitsize}, and @code{float} is a floating point type (in the
29853 architecture's normal floating point format) of the correct size for
29854 @var{bitsize}. The default is @code{int}.
29857 The register group to which this register belongs. @var{group} must
29858 be either @code{general}, @code{float}, or @code{vector}. If no
29859 @var{group} is specified, @value{GDBN} will not display the register
29860 in @code{info registers}.
29864 @node Predefined Target Types
29865 @section Predefined Target Types
29866 @cindex target descriptions, predefined types
29868 Type definitions in the self-description can build up composite types
29869 from basic building blocks, but can not define fundamental types. Instead,
29870 standard identifiers are provided by @value{GDBN} for the fundamental
29871 types. The currently supported types are:
29880 Signed integer types holding the specified number of bits.
29887 Unsigned integer types holding the specified number of bits.
29891 Pointers to unspecified code and data. The program counter and
29892 any dedicated return address register may be marked as code
29893 pointers; printing a code pointer converts it into a symbolic
29894 address. The stack pointer and any dedicated address registers
29895 may be marked as data pointers.
29898 Single precision IEEE floating point.
29901 Double precision IEEE floating point.
29904 The 12-byte extended precision format used by ARM FPA registers.
29908 @node Standard Target Features
29909 @section Standard Target Features
29910 @cindex target descriptions, standard features
29912 A target description must contain either no registers or all the
29913 target's registers. If the description contains no registers, then
29914 @value{GDBN} will assume a default register layout, selected based on
29915 the architecture. If the description contains any registers, the
29916 default layout will not be used; the standard registers must be
29917 described in the target description, in such a way that @value{GDBN}
29918 can recognize them.
29920 This is accomplished by giving specific names to feature elements
29921 which contain standard registers. @value{GDBN} will look for features
29922 with those names and verify that they contain the expected registers;
29923 if any known feature is missing required registers, or if any required
29924 feature is missing, @value{GDBN} will reject the target
29925 description. You can add additional registers to any of the
29926 standard features --- @value{GDBN} will display them just as if
29927 they were added to an unrecognized feature.
29929 This section lists the known features and their expected contents.
29930 Sample XML documents for these features are included in the
29931 @value{GDBN} source tree, in the directory @file{gdb/features}.
29933 Names recognized by @value{GDBN} should include the name of the
29934 company or organization which selected the name, and the overall
29935 architecture to which the feature applies; so e.g.@: the feature
29936 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
29938 The names of registers are not case sensitive for the purpose
29939 of recognizing standard features, but @value{GDBN} will only display
29940 registers using the capitalization used in the description.
29946 * PowerPC Features::
29951 @subsection ARM Features
29952 @cindex target descriptions, ARM features
29954 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
29955 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
29956 @samp{lr}, @samp{pc}, and @samp{cpsr}.
29958 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
29959 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
29961 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
29962 it should contain at least registers @samp{wR0} through @samp{wR15} and
29963 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
29964 @samp{wCSSF}, and @samp{wCASF} registers are optional.
29966 @node MIPS Features
29967 @subsection MIPS Features
29968 @cindex target descriptions, MIPS features
29970 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
29971 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
29972 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
29975 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
29976 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
29977 registers. They may be 32-bit or 64-bit depending on the target.
29979 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
29980 it may be optional in a future version of @value{GDBN}. It should
29981 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
29982 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
29984 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
29985 contain a single register, @samp{restart}, which is used by the
29986 Linux kernel to control restartable syscalls.
29988 @node M68K Features
29989 @subsection M68K Features
29990 @cindex target descriptions, M68K features
29993 @item @samp{org.gnu.gdb.m68k.core}
29994 @itemx @samp{org.gnu.gdb.coldfire.core}
29995 @itemx @samp{org.gnu.gdb.fido.core}
29996 One of those features must be always present.
29997 The feature that is present determines which flavor of m68k is
29998 used. The feature that is present should contain registers
29999 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
30000 @samp{sp}, @samp{ps} and @samp{pc}.
30002 @item @samp{org.gnu.gdb.coldfire.fp}
30003 This feature is optional. If present, it should contain registers
30004 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
30008 @node PowerPC Features
30009 @subsection PowerPC Features
30010 @cindex target descriptions, PowerPC features
30012 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
30013 targets. It should contain registers @samp{r0} through @samp{r31},
30014 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
30015 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
30017 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
30018 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
30020 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
30021 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
30024 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
30025 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
30026 will combine these registers with the floating point registers
30027 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
30028 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
30029 through @samp{vs63}, the set of vector registers for POWER7.
30031 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
30032 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
30033 @samp{spefscr}. SPE targets should provide 32-bit registers in
30034 @samp{org.gnu.gdb.power.core} and provide the upper halves in
30035 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
30036 these to present registers @samp{ev0} through @samp{ev31} to the
30039 @node Operating System Information
30040 @appendix Operating System Information
30041 @cindex operating system information
30047 Users of @value{GDBN} often wish to obtain information about the state of
30048 the operating system running on the target---for example the list of
30049 processes, or the list of open files. This section describes the
30050 mechanism that makes it possible. This mechanism is similar to the
30051 target features mechanism (@pxref{Target Descriptions}), but focuses
30052 on a different aspect of target.
30054 Operating system information is retrived from the target via the
30055 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
30056 read}). The object name in the request should be @samp{osdata}, and
30057 the @var{annex} identifies the data to be fetched.
30060 @appendixsection Process list
30061 @cindex operating system information, process list
30063 When requesting the process list, the @var{annex} field in the
30064 @samp{qXfer} request should be @samp{processes}. The returned data is
30065 an XML document. The formal syntax of this document is defined in
30066 @file{gdb/features/osdata.dtd}.
30068 An example document is:
30071 <?xml version="1.0"?>
30072 <!DOCTYPE target SYSTEM "osdata.dtd">
30073 <osdata type="processes">
30075 <column name="pid">1</column>
30076 <column name="user">root</column>
30077 <column name="command">/sbin/init</column>
30082 Each item should include a column whose name is @samp{pid}. The value
30083 of that column should identify the process on the target. The
30084 @samp{user} and @samp{command} columns are optional, and will be
30085 displayed by @value{GDBN}. Target may provide additional columns,
30086 which @value{GDBN} currently ignores.
30100 % I think something like @colophon should be in texinfo. In the
30102 \long\def\colophon{\hbox to0pt{}\vfill
30103 \centerline{The body of this manual is set in}
30104 \centerline{\fontname\tenrm,}
30105 \centerline{with headings in {\bf\fontname\tenbf}}
30106 \centerline{and examples in {\tt\fontname\tentt}.}
30107 \centerline{{\it\fontname\tenit\/},}
30108 \centerline{{\bf\fontname\tenbf}, and}
30109 \centerline{{\sl\fontname\tensl\/}}
30110 \centerline{are used for emphasis.}\vfill}
30112 % Blame: doc@cygnus.com, 1991.