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
3055 When called without any arguments, @code{break} sets a breakpoint at
3056 the next instruction to be executed in the selected stack frame
3057 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3058 innermost, this makes your program stop as soon as control
3059 returns to that frame. This is similar to the effect of a
3060 @code{finish} command in the frame inside the selected frame---except
3061 that @code{finish} does not leave an active breakpoint. If you use
3062 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3063 the next time it reaches the current location; this may be useful
3066 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3067 least one instruction has been executed. If it did not do this, you
3068 would be unable to proceed past a breakpoint without first disabling the
3069 breakpoint. This rule applies whether or not the breakpoint already
3070 existed when your program stopped.
3072 @item break @dots{} if @var{cond}
3073 Set a breakpoint with condition @var{cond}; evaluate the expression
3074 @var{cond} each time the breakpoint is reached, and stop only if the
3075 value is nonzero---that is, if @var{cond} evaluates as true.
3076 @samp{@dots{}} stands for one of the possible arguments described
3077 above (or no argument) specifying where to break. @xref{Conditions,
3078 ,Break Conditions}, for more information on breakpoint conditions.
3081 @item tbreak @var{args}
3082 Set a breakpoint enabled only for one stop. @var{args} are the
3083 same as for the @code{break} command, and the breakpoint is set in the same
3084 way, but the breakpoint is automatically deleted after the first time your
3085 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3088 @cindex hardware breakpoints
3089 @item hbreak @var{args}
3090 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3091 @code{break} command and the breakpoint is set in the same way, but the
3092 breakpoint requires hardware support and some target hardware may not
3093 have this support. The main purpose of this is EPROM/ROM code
3094 debugging, so you can set a breakpoint at an instruction without
3095 changing the instruction. This can be used with the new trap-generation
3096 provided by SPARClite DSU and most x86-based targets. These targets
3097 will generate traps when a program accesses some data or instruction
3098 address that is assigned to the debug registers. However the hardware
3099 breakpoint registers can take a limited number of breakpoints. For
3100 example, on the DSU, only two data breakpoints can be set at a time, and
3101 @value{GDBN} will reject this command if more than two are used. Delete
3102 or disable unused hardware breakpoints before setting new ones
3103 (@pxref{Disabling, ,Disabling Breakpoints}).
3104 @xref{Conditions, ,Break Conditions}.
3105 For remote targets, you can restrict the number of hardware
3106 breakpoints @value{GDBN} will use, see @ref{set remote
3107 hardware-breakpoint-limit}.
3110 @item thbreak @var{args}
3111 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3112 are the same as for the @code{hbreak} command and the breakpoint is set in
3113 the same way. However, like the @code{tbreak} command,
3114 the breakpoint is automatically deleted after the
3115 first time your program stops there. Also, like the @code{hbreak}
3116 command, the breakpoint requires hardware support and some target hardware
3117 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3118 See also @ref{Conditions, ,Break Conditions}.
3121 @cindex regular expression
3122 @cindex breakpoints in functions matching a regexp
3123 @cindex set breakpoints in many functions
3124 @item rbreak @var{regex}
3125 Set breakpoints on all functions matching the regular expression
3126 @var{regex}. This command sets an unconditional breakpoint on all
3127 matches, printing a list of all breakpoints it set. Once these
3128 breakpoints are set, they are treated just like the breakpoints set with
3129 the @code{break} command. You can delete them, disable them, or make
3130 them conditional the same way as any other breakpoint.
3132 The syntax of the regular expression is the standard one used with tools
3133 like @file{grep}. Note that this is different from the syntax used by
3134 shells, so for instance @code{foo*} matches all functions that include
3135 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3136 @code{.*} leading and trailing the regular expression you supply, so to
3137 match only functions that begin with @code{foo}, use @code{^foo}.
3139 @cindex non-member C@t{++} functions, set breakpoint in
3140 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3141 breakpoints on overloaded functions that are not members of any special
3144 @cindex set breakpoints on all functions
3145 The @code{rbreak} command can be used to set breakpoints in
3146 @strong{all} the functions in a program, like this:
3149 (@value{GDBP}) rbreak .
3152 @kindex info breakpoints
3153 @cindex @code{$_} and @code{info breakpoints}
3154 @item info breakpoints @r{[}@var{n}@r{]}
3155 @itemx info break @r{[}@var{n}@r{]}
3156 @itemx info watchpoints @r{[}@var{n}@r{]}
3157 Print a table of all breakpoints, watchpoints, and catchpoints set and
3158 not deleted. Optional argument @var{n} means print information only
3159 about the specified breakpoint (or watchpoint or catchpoint). For
3160 each breakpoint, following columns are printed:
3163 @item Breakpoint Numbers
3165 Breakpoint, watchpoint, or catchpoint.
3167 Whether the breakpoint is marked to be disabled or deleted when hit.
3168 @item Enabled or Disabled
3169 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3170 that are not enabled.
3172 Where the breakpoint is in your program, as a memory address. For a
3173 pending breakpoint whose address is not yet known, this field will
3174 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3175 library that has the symbol or line referred by breakpoint is loaded.
3176 See below for details. A breakpoint with several locations will
3177 have @samp{<MULTIPLE>} in this field---see below for details.
3179 Where the breakpoint is in the source for your program, as a file and
3180 line number. For a pending breakpoint, the original string passed to
3181 the breakpoint command will be listed as it cannot be resolved until
3182 the appropriate shared library is loaded in the future.
3186 If a breakpoint is conditional, @code{info break} shows the condition on
3187 the line following the affected breakpoint; breakpoint commands, if any,
3188 are listed after that. A pending breakpoint is allowed to have a condition
3189 specified for it. The condition is not parsed for validity until a shared
3190 library is loaded that allows the pending breakpoint to resolve to a
3194 @code{info break} with a breakpoint
3195 number @var{n} as argument lists only that breakpoint. The
3196 convenience variable @code{$_} and the default examining-address for
3197 the @code{x} command are set to the address of the last breakpoint
3198 listed (@pxref{Memory, ,Examining Memory}).
3201 @code{info break} displays a count of the number of times the breakpoint
3202 has been hit. This is especially useful in conjunction with the
3203 @code{ignore} command. You can ignore a large number of breakpoint
3204 hits, look at the breakpoint info to see how many times the breakpoint
3205 was hit, and then run again, ignoring one less than that number. This
3206 will get you quickly to the last hit of that breakpoint.
3209 @value{GDBN} allows you to set any number of breakpoints at the same place in
3210 your program. There is nothing silly or meaningless about this. When
3211 the breakpoints are conditional, this is even useful
3212 (@pxref{Conditions, ,Break Conditions}).
3214 @cindex multiple locations, breakpoints
3215 @cindex breakpoints, multiple locations
3216 It is possible that a breakpoint corresponds to several locations
3217 in your program. Examples of this situation are:
3221 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3222 instances of the function body, used in different cases.
3225 For a C@t{++} template function, a given line in the function can
3226 correspond to any number of instantiations.
3229 For an inlined function, a given source line can correspond to
3230 several places where that function is inlined.
3233 In all those cases, @value{GDBN} will insert a breakpoint at all
3234 the relevant locations@footnote{
3235 As of this writing, multiple-location breakpoints work only if there's
3236 line number information for all the locations. This means that they
3237 will generally not work in system libraries, unless you have debug
3238 info with line numbers for them.}.
3240 A breakpoint with multiple locations is displayed in the breakpoint
3241 table using several rows---one header row, followed by one row for
3242 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3243 address column. The rows for individual locations contain the actual
3244 addresses for locations, and show the functions to which those
3245 locations belong. The number column for a location is of the form
3246 @var{breakpoint-number}.@var{location-number}.
3251 Num Type Disp Enb Address What
3252 1 breakpoint keep y <MULTIPLE>
3254 breakpoint already hit 1 time
3255 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3256 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3259 Each location can be individually enabled or disabled by passing
3260 @var{breakpoint-number}.@var{location-number} as argument to the
3261 @code{enable} and @code{disable} commands. Note that you cannot
3262 delete the individual locations from the list, you can only delete the
3263 entire list of locations that belong to their parent breakpoint (with
3264 the @kbd{delete @var{num}} command, where @var{num} is the number of
3265 the parent breakpoint, 1 in the above example). Disabling or enabling
3266 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3267 that belong to that breakpoint.
3269 @cindex pending breakpoints
3270 It's quite common to have a breakpoint inside a shared library.
3271 Shared libraries can be loaded and unloaded explicitly,
3272 and possibly repeatedly, as the program is executed. To support
3273 this use case, @value{GDBN} updates breakpoint locations whenever
3274 any shared library is loaded or unloaded. Typically, you would
3275 set a breakpoint in a shared library at the beginning of your
3276 debugging session, when the library is not loaded, and when the
3277 symbols from the library are not available. When you try to set
3278 breakpoint, @value{GDBN} will ask you if you want to set
3279 a so called @dfn{pending breakpoint}---breakpoint whose address
3280 is not yet resolved.
3282 After the program is run, whenever a new shared library is loaded,
3283 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3284 shared library contains the symbol or line referred to by some
3285 pending breakpoint, that breakpoint is resolved and becomes an
3286 ordinary breakpoint. When a library is unloaded, all breakpoints
3287 that refer to its symbols or source lines become pending again.
3289 This logic works for breakpoints with multiple locations, too. For
3290 example, if you have a breakpoint in a C@t{++} template function, and
3291 a newly loaded shared library has an instantiation of that template,
3292 a new location is added to the list of locations for the breakpoint.
3294 Except for having unresolved address, pending breakpoints do not
3295 differ from regular breakpoints. You can set conditions or commands,
3296 enable and disable them and perform other breakpoint operations.
3298 @value{GDBN} provides some additional commands for controlling what
3299 happens when the @samp{break} command cannot resolve breakpoint
3300 address specification to an address:
3302 @kindex set breakpoint pending
3303 @kindex show breakpoint pending
3305 @item set breakpoint pending auto
3306 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3307 location, it queries you whether a pending breakpoint should be created.
3309 @item set breakpoint pending on
3310 This indicates that an unrecognized breakpoint location should automatically
3311 result in a pending breakpoint being created.
3313 @item set breakpoint pending off
3314 This indicates that pending breakpoints are not to be created. Any
3315 unrecognized breakpoint location results in an error. This setting does
3316 not affect any pending breakpoints previously created.
3318 @item show breakpoint pending
3319 Show the current behavior setting for creating pending breakpoints.
3322 The settings above only affect the @code{break} command and its
3323 variants. Once breakpoint is set, it will be automatically updated
3324 as shared libraries are loaded and unloaded.
3326 @cindex automatic hardware breakpoints
3327 For some targets, @value{GDBN} can automatically decide if hardware or
3328 software breakpoints should be used, depending on whether the
3329 breakpoint address is read-only or read-write. This applies to
3330 breakpoints set with the @code{break} command as well as to internal
3331 breakpoints set by commands like @code{next} and @code{finish}. For
3332 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3335 You can control this automatic behaviour with the following commands::
3337 @kindex set breakpoint auto-hw
3338 @kindex show breakpoint auto-hw
3340 @item set breakpoint auto-hw on
3341 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3342 will try to use the target memory map to decide if software or hardware
3343 breakpoint must be used.
3345 @item set breakpoint auto-hw off
3346 This indicates @value{GDBN} should not automatically select breakpoint
3347 type. If the target provides a memory map, @value{GDBN} will warn when
3348 trying to set software breakpoint at a read-only address.
3351 @value{GDBN} normally implements breakpoints by replacing the program code
3352 at the breakpoint address with a special instruction, which, when
3353 executed, given control to the debugger. By default, the program
3354 code is so modified only when the program is resumed. As soon as
3355 the program stops, @value{GDBN} restores the original instructions. This
3356 behaviour guards against leaving breakpoints inserted in the
3357 target should gdb abrubptly disconnect. However, with slow remote
3358 targets, inserting and removing breakpoint can reduce the performance.
3359 This behavior can be controlled with the following commands::
3361 @kindex set breakpoint always-inserted
3362 @kindex show breakpoint always-inserted
3364 @item set breakpoint always-inserted off
3365 All breakpoints, including newly added by the user, are inserted in
3366 the target only when the target is resumed. All breakpoints are
3367 removed from the target when it stops.
3369 @item set breakpoint always-inserted on
3370 Causes all breakpoints to be inserted in the target at all times. If
3371 the user adds a new breakpoint, or changes an existing breakpoint, the
3372 breakpoints in the target are updated immediately. A breakpoint is
3373 removed from the target only when breakpoint itself is removed.
3375 @cindex non-stop mode, and @code{breakpoint always-inserted}
3376 @item set breakpoint always-inserted auto
3377 This is the default mode. If @value{GDBN} is controlling the inferior
3378 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3379 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3380 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3381 @code{breakpoint always-inserted} mode is off.
3384 @cindex negative breakpoint numbers
3385 @cindex internal @value{GDBN} breakpoints
3386 @value{GDBN} itself sometimes sets breakpoints in your program for
3387 special purposes, such as proper handling of @code{longjmp} (in C
3388 programs). These internal breakpoints are assigned negative numbers,
3389 starting with @code{-1}; @samp{info breakpoints} does not display them.
3390 You can see these breakpoints with the @value{GDBN} maintenance command
3391 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3394 @node Set Watchpoints
3395 @subsection Setting Watchpoints
3397 @cindex setting watchpoints
3398 You can use a watchpoint to stop execution whenever the value of an
3399 expression changes, without having to predict a particular place where
3400 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3401 The expression may be as simple as the value of a single variable, or
3402 as complex as many variables combined by operators. Examples include:
3406 A reference to the value of a single variable.
3409 An address cast to an appropriate data type. For example,
3410 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3411 address (assuming an @code{int} occupies 4 bytes).
3414 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3415 expression can use any operators valid in the program's native
3416 language (@pxref{Languages}).
3419 You can set a watchpoint on an expression even if the expression can
3420 not be evaluated yet. For instance, you can set a watchpoint on
3421 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3422 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3423 the expression produces a valid value. If the expression becomes
3424 valid in some other way than changing a variable (e.g.@: if the memory
3425 pointed to by @samp{*global_ptr} becomes readable as the result of a
3426 @code{malloc} call), @value{GDBN} may not stop until the next time
3427 the expression changes.
3429 @cindex software watchpoints
3430 @cindex hardware watchpoints
3431 Depending on your system, watchpoints may be implemented in software or
3432 hardware. @value{GDBN} does software watchpointing by single-stepping your
3433 program and testing the variable's value each time, which is hundreds of
3434 times slower than normal execution. (But this may still be worth it, to
3435 catch errors where you have no clue what part of your program is the
3438 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3439 x86-based targets, @value{GDBN} includes support for hardware
3440 watchpoints, which do not slow down the running of your program.
3444 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3445 Set a watchpoint for an expression. @value{GDBN} will break when the
3446 expression @var{expr} is written into by the program and its value
3447 changes. The simplest (and the most popular) use of this command is
3448 to watch the value of a single variable:
3451 (@value{GDBP}) watch foo
3454 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3455 clause, @value{GDBN} breaks only when the thread identified by
3456 @var{threadnum} changes the value of @var{expr}. If any other threads
3457 change the value of @var{expr}, @value{GDBN} will not break. Note
3458 that watchpoints restricted to a single thread in this way only work
3459 with Hardware Watchpoints.
3462 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3463 Set a watchpoint that will break when the value of @var{expr} is read
3467 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3468 Set a watchpoint that will break when @var{expr} is either read from
3469 or written into by the program.
3471 @kindex info watchpoints @r{[}@var{n}@r{]}
3472 @item info watchpoints
3473 This command prints a list of watchpoints, breakpoints, and catchpoints;
3474 it is the same as @code{info break} (@pxref{Set Breaks}).
3477 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3478 watchpoints execute very quickly, and the debugger reports a change in
3479 value at the exact instruction where the change occurs. If @value{GDBN}
3480 cannot set a hardware watchpoint, it sets a software watchpoint, which
3481 executes more slowly and reports the change in value at the next
3482 @emph{statement}, not the instruction, after the change occurs.
3484 @cindex use only software watchpoints
3485 You can force @value{GDBN} to use only software watchpoints with the
3486 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3487 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3488 the underlying system supports them. (Note that hardware-assisted
3489 watchpoints that were set @emph{before} setting
3490 @code{can-use-hw-watchpoints} to zero will still use the hardware
3491 mechanism of watching expression values.)
3494 @item set can-use-hw-watchpoints
3495 @kindex set can-use-hw-watchpoints
3496 Set whether or not to use hardware watchpoints.
3498 @item show can-use-hw-watchpoints
3499 @kindex show can-use-hw-watchpoints
3500 Show the current mode of using hardware watchpoints.
3503 For remote targets, you can restrict the number of hardware
3504 watchpoints @value{GDBN} will use, see @ref{set remote
3505 hardware-breakpoint-limit}.
3507 When you issue the @code{watch} command, @value{GDBN} reports
3510 Hardware watchpoint @var{num}: @var{expr}
3514 if it was able to set a hardware watchpoint.
3516 Currently, the @code{awatch} and @code{rwatch} commands can only set
3517 hardware watchpoints, because accesses to data that don't change the
3518 value of the watched expression cannot be detected without examining
3519 every instruction as it is being executed, and @value{GDBN} does not do
3520 that currently. If @value{GDBN} finds that it is unable to set a
3521 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3522 will print a message like this:
3525 Expression cannot be implemented with read/access watchpoint.
3528 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3529 data type of the watched expression is wider than what a hardware
3530 watchpoint on the target machine can handle. For example, some systems
3531 can only watch regions that are up to 4 bytes wide; on such systems you
3532 cannot set hardware watchpoints for an expression that yields a
3533 double-precision floating-point number (which is typically 8 bytes
3534 wide). As a work-around, it might be possible to break the large region
3535 into a series of smaller ones and watch them with separate watchpoints.
3537 If you set too many hardware watchpoints, @value{GDBN} might be unable
3538 to insert all of them when you resume the execution of your program.
3539 Since the precise number of active watchpoints is unknown until such
3540 time as the program is about to be resumed, @value{GDBN} might not be
3541 able to warn you about this when you set the watchpoints, and the
3542 warning will be printed only when the program is resumed:
3545 Hardware watchpoint @var{num}: Could not insert watchpoint
3549 If this happens, delete or disable some of the watchpoints.
3551 Watching complex expressions that reference many variables can also
3552 exhaust the resources available for hardware-assisted watchpoints.
3553 That's because @value{GDBN} needs to watch every variable in the
3554 expression with separately allocated resources.
3556 If you call a function interactively using @code{print} or @code{call},
3557 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3558 kind of breakpoint or the call completes.
3560 @value{GDBN} automatically deletes watchpoints that watch local
3561 (automatic) variables, or expressions that involve such variables, when
3562 they go out of scope, that is, when the execution leaves the block in
3563 which these variables were defined. In particular, when the program
3564 being debugged terminates, @emph{all} local variables go out of scope,
3565 and so only watchpoints that watch global variables remain set. If you
3566 rerun the program, you will need to set all such watchpoints again. One
3567 way of doing that would be to set a code breakpoint at the entry to the
3568 @code{main} function and when it breaks, set all the watchpoints.
3570 @cindex watchpoints and threads
3571 @cindex threads and watchpoints
3572 In multi-threaded programs, watchpoints will detect changes to the
3573 watched expression from every thread.
3576 @emph{Warning:} In multi-threaded programs, software watchpoints
3577 have only limited usefulness. If @value{GDBN} creates a software
3578 watchpoint, it can only watch the value of an expression @emph{in a
3579 single thread}. If you are confident that the expression can only
3580 change due to the current thread's activity (and if you are also
3581 confident that no other thread can become current), then you can use
3582 software watchpoints as usual. However, @value{GDBN} may not notice
3583 when a non-current thread's activity changes the expression. (Hardware
3584 watchpoints, in contrast, watch an expression in all threads.)
3587 @xref{set remote hardware-watchpoint-limit}.
3589 @node Set Catchpoints
3590 @subsection Setting Catchpoints
3591 @cindex catchpoints, setting
3592 @cindex exception handlers
3593 @cindex event handling
3595 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3596 kinds of program events, such as C@t{++} exceptions or the loading of a
3597 shared library. Use the @code{catch} command to set a catchpoint.
3601 @item catch @var{event}
3602 Stop when @var{event} occurs. @var{event} can be any of the following:
3605 @cindex stop on C@t{++} exceptions
3606 The throwing of a C@t{++} exception.
3609 The catching of a C@t{++} exception.
3612 @cindex Ada exception catching
3613 @cindex catch Ada exceptions
3614 An Ada exception being raised. If an exception name is specified
3615 at the end of the command (eg @code{catch exception Program_Error}),
3616 the debugger will stop only when this specific exception is raised.
3617 Otherwise, the debugger stops execution when any Ada exception is raised.
3619 When inserting an exception catchpoint on a user-defined exception whose
3620 name is identical to one of the exceptions defined by the language, the
3621 fully qualified name must be used as the exception name. Otherwise,
3622 @value{GDBN} will assume that it should stop on the pre-defined exception
3623 rather than the user-defined one. For instance, assuming an exception
3624 called @code{Constraint_Error} is defined in package @code{Pck}, then
3625 the command to use to catch such exceptions is @kbd{catch exception
3626 Pck.Constraint_Error}.
3628 @item exception unhandled
3629 An exception that was raised but is not handled by the program.
3632 A failed Ada assertion.
3635 @cindex break on fork/exec
3636 A call to @code{exec}. This is currently only available for HP-UX
3640 A call to @code{fork}. This is currently only available for HP-UX
3644 A call to @code{vfork}. This is currently only available for HP-UX
3649 @item tcatch @var{event}
3650 Set a catchpoint that is enabled only for one stop. The catchpoint is
3651 automatically deleted after the first time the event is caught.
3655 Use the @code{info break} command to list the current catchpoints.
3657 There are currently some limitations to C@t{++} exception handling
3658 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3662 If you call a function interactively, @value{GDBN} normally returns
3663 control to you when the function has finished executing. If the call
3664 raises an exception, however, the call may bypass the mechanism that
3665 returns control to you and cause your program either to abort or to
3666 simply continue running until it hits a breakpoint, catches a signal
3667 that @value{GDBN} is listening for, or exits. This is the case even if
3668 you set a catchpoint for the exception; catchpoints on exceptions are
3669 disabled within interactive calls.
3672 You cannot raise an exception interactively.
3675 You cannot install an exception handler interactively.
3678 @cindex raise exceptions
3679 Sometimes @code{catch} is not the best way to debug exception handling:
3680 if you need to know exactly where an exception is raised, it is better to
3681 stop @emph{before} the exception handler is called, since that way you
3682 can see the stack before any unwinding takes place. If you set a
3683 breakpoint in an exception handler instead, it may not be easy to find
3684 out where the exception was raised.
3686 To stop just before an exception handler is called, you need some
3687 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3688 raised by calling a library function named @code{__raise_exception}
3689 which has the following ANSI C interface:
3692 /* @var{addr} is where the exception identifier is stored.
3693 @var{id} is the exception identifier. */
3694 void __raise_exception (void **addr, void *id);
3698 To make the debugger catch all exceptions before any stack
3699 unwinding takes place, set a breakpoint on @code{__raise_exception}
3700 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3702 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3703 that depends on the value of @var{id}, you can stop your program when
3704 a specific exception is raised. You can use multiple conditional
3705 breakpoints to stop your program when any of a number of exceptions are
3710 @subsection Deleting Breakpoints
3712 @cindex clearing breakpoints, watchpoints, catchpoints
3713 @cindex deleting breakpoints, watchpoints, catchpoints
3714 It is often necessary to eliminate a breakpoint, watchpoint, or
3715 catchpoint once it has done its job and you no longer want your program
3716 to stop there. This is called @dfn{deleting} the breakpoint. A
3717 breakpoint that has been deleted no longer exists; it is forgotten.
3719 With the @code{clear} command you can delete breakpoints according to
3720 where they are in your program. With the @code{delete} command you can
3721 delete individual breakpoints, watchpoints, or catchpoints by specifying
3722 their breakpoint numbers.
3724 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3725 automatically ignores breakpoints on the first instruction to be executed
3726 when you continue execution without changing the execution address.
3731 Delete any breakpoints at the next instruction to be executed in the
3732 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3733 the innermost frame is selected, this is a good way to delete a
3734 breakpoint where your program just stopped.
3736 @item clear @var{location}
3737 Delete any breakpoints set at the specified @var{location}.
3738 @xref{Specify Location}, for the various forms of @var{location}; the
3739 most useful ones are listed below:
3742 @item clear @var{function}
3743 @itemx clear @var{filename}:@var{function}
3744 Delete any breakpoints set at entry to the named @var{function}.
3746 @item clear @var{linenum}
3747 @itemx clear @var{filename}:@var{linenum}
3748 Delete any breakpoints set at or within the code of the specified
3749 @var{linenum} of the specified @var{filename}.
3752 @cindex delete breakpoints
3754 @kindex d @r{(@code{delete})}
3755 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3756 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3757 ranges specified as arguments. If no argument is specified, delete all
3758 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3759 confirm off}). You can abbreviate this command as @code{d}.
3763 @subsection Disabling Breakpoints
3765 @cindex enable/disable a breakpoint
3766 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3767 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3768 it had been deleted, but remembers the information on the breakpoint so
3769 that you can @dfn{enable} it again later.
3771 You disable and enable breakpoints, watchpoints, and catchpoints with
3772 the @code{enable} and @code{disable} commands, optionally specifying one
3773 or more breakpoint numbers as arguments. Use @code{info break} or
3774 @code{info watch} to print a list of breakpoints, watchpoints, and
3775 catchpoints if you do not know which numbers to use.
3777 Disabling and enabling a breakpoint that has multiple locations
3778 affects all of its locations.
3780 A breakpoint, watchpoint, or catchpoint can have any of four different
3781 states of enablement:
3785 Enabled. The breakpoint stops your program. A breakpoint set
3786 with the @code{break} command starts out in this state.
3788 Disabled. The breakpoint has no effect on your program.
3790 Enabled once. The breakpoint stops your program, but then becomes
3793 Enabled for deletion. The breakpoint stops your program, but
3794 immediately after it does so it is deleted permanently. A breakpoint
3795 set with the @code{tbreak} command starts out in this state.
3798 You can use the following commands to enable or disable breakpoints,
3799 watchpoints, and catchpoints:
3803 @kindex dis @r{(@code{disable})}
3804 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3805 Disable the specified breakpoints---or all breakpoints, if none are
3806 listed. A disabled breakpoint has no effect but is not forgotten. All
3807 options such as ignore-counts, conditions and commands are remembered in
3808 case the breakpoint is enabled again later. You may abbreviate
3809 @code{disable} as @code{dis}.
3812 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3813 Enable the specified breakpoints (or all defined breakpoints). They
3814 become effective once again in stopping your program.
3816 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3817 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3818 of these breakpoints immediately after stopping your program.
3820 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3821 Enable the specified breakpoints to work once, then die. @value{GDBN}
3822 deletes any of these breakpoints as soon as your program stops there.
3823 Breakpoints set by the @code{tbreak} command start out in this state.
3826 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3827 @c confusing: tbreak is also initially enabled.
3828 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3829 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3830 subsequently, they become disabled or enabled only when you use one of
3831 the commands above. (The command @code{until} can set and delete a
3832 breakpoint of its own, but it does not change the state of your other
3833 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3837 @subsection Break Conditions
3838 @cindex conditional breakpoints
3839 @cindex breakpoint conditions
3841 @c FIXME what is scope of break condition expr? Context where wanted?
3842 @c in particular for a watchpoint?
3843 The simplest sort of breakpoint breaks every time your program reaches a
3844 specified place. You can also specify a @dfn{condition} for a
3845 breakpoint. A condition is just a Boolean expression in your
3846 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3847 a condition evaluates the expression each time your program reaches it,
3848 and your program stops only if the condition is @emph{true}.
3850 This is the converse of using assertions for program validation; in that
3851 situation, you want to stop when the assertion is violated---that is,
3852 when the condition is false. In C, if you want to test an assertion expressed
3853 by the condition @var{assert}, you should set the condition
3854 @samp{! @var{assert}} on the appropriate breakpoint.
3856 Conditions are also accepted for watchpoints; you may not need them,
3857 since a watchpoint is inspecting the value of an expression anyhow---but
3858 it might be simpler, say, to just set a watchpoint on a variable name,
3859 and specify a condition that tests whether the new value is an interesting
3862 Break conditions can have side effects, and may even call functions in
3863 your program. This can be useful, for example, to activate functions
3864 that log program progress, or to use your own print functions to
3865 format special data structures. The effects are completely predictable
3866 unless there is another enabled breakpoint at the same address. (In
3867 that case, @value{GDBN} might see the other breakpoint first and stop your
3868 program without checking the condition of this one.) Note that
3869 breakpoint commands are usually more convenient and flexible than break
3871 purpose of performing side effects when a breakpoint is reached
3872 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3874 Break conditions can be specified when a breakpoint is set, by using
3875 @samp{if} in the arguments to the @code{break} command. @xref{Set
3876 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3877 with the @code{condition} command.
3879 You can also use the @code{if} keyword with the @code{watch} command.
3880 The @code{catch} command does not recognize the @code{if} keyword;
3881 @code{condition} is the only way to impose a further condition on a
3886 @item condition @var{bnum} @var{expression}
3887 Specify @var{expression} as the break condition for breakpoint,
3888 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3889 breakpoint @var{bnum} stops your program only if the value of
3890 @var{expression} is true (nonzero, in C). When you use
3891 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3892 syntactic correctness, and to determine whether symbols in it have
3893 referents in the context of your breakpoint. If @var{expression} uses
3894 symbols not referenced in the context of the breakpoint, @value{GDBN}
3895 prints an error message:
3898 No symbol "foo" in current context.
3903 not actually evaluate @var{expression} at the time the @code{condition}
3904 command (or a command that sets a breakpoint with a condition, like
3905 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3907 @item condition @var{bnum}
3908 Remove the condition from breakpoint number @var{bnum}. It becomes
3909 an ordinary unconditional breakpoint.
3912 @cindex ignore count (of breakpoint)
3913 A special case of a breakpoint condition is to stop only when the
3914 breakpoint has been reached a certain number of times. This is so
3915 useful that there is a special way to do it, using the @dfn{ignore
3916 count} of the breakpoint. Every breakpoint has an ignore count, which
3917 is an integer. Most of the time, the ignore count is zero, and
3918 therefore has no effect. But if your program reaches a breakpoint whose
3919 ignore count is positive, then instead of stopping, it just decrements
3920 the ignore count by one and continues. As a result, if the ignore count
3921 value is @var{n}, the breakpoint does not stop the next @var{n} times
3922 your program reaches it.
3926 @item ignore @var{bnum} @var{count}
3927 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3928 The next @var{count} times the breakpoint is reached, your program's
3929 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3932 To make the breakpoint stop the next time it is reached, specify
3935 When you use @code{continue} to resume execution of your program from a
3936 breakpoint, you can specify an ignore count directly as an argument to
3937 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3938 Stepping,,Continuing and Stepping}.
3940 If a breakpoint has a positive ignore count and a condition, the
3941 condition is not checked. Once the ignore count reaches zero,
3942 @value{GDBN} resumes checking the condition.
3944 You could achieve the effect of the ignore count with a condition such
3945 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3946 is decremented each time. @xref{Convenience Vars, ,Convenience
3950 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3953 @node Break Commands
3954 @subsection Breakpoint Command Lists
3956 @cindex breakpoint commands
3957 You can give any breakpoint (or watchpoint or catchpoint) a series of
3958 commands to execute when your program stops due to that breakpoint. For
3959 example, you might want to print the values of certain expressions, or
3960 enable other breakpoints.
3964 @kindex end@r{ (breakpoint commands)}
3965 @item commands @r{[}@var{bnum}@r{]}
3966 @itemx @dots{} @var{command-list} @dots{}
3968 Specify a list of commands for breakpoint number @var{bnum}. The commands
3969 themselves appear on the following lines. Type a line containing just
3970 @code{end} to terminate the commands.
3972 To remove all commands from a breakpoint, type @code{commands} and
3973 follow it immediately with @code{end}; that is, give no commands.
3975 With no @var{bnum} argument, @code{commands} refers to the last
3976 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3977 recently encountered).
3980 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3981 disabled within a @var{command-list}.
3983 You can use breakpoint commands to start your program up again. Simply
3984 use the @code{continue} command, or @code{step}, or any other command
3985 that resumes execution.
3987 Any other commands in the command list, after a command that resumes
3988 execution, are ignored. This is because any time you resume execution
3989 (even with a simple @code{next} or @code{step}), you may encounter
3990 another breakpoint---which could have its own command list, leading to
3991 ambiguities about which list to execute.
3994 If the first command you specify in a command list is @code{silent}, the
3995 usual message about stopping at a breakpoint is not printed. This may
3996 be desirable for breakpoints that are to print a specific message and
3997 then continue. If none of the remaining commands print anything, you
3998 see no sign that the breakpoint was reached. @code{silent} is
3999 meaningful only at the beginning of a breakpoint command list.
4001 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4002 print precisely controlled output, and are often useful in silent
4003 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4005 For example, here is how you could use breakpoint commands to print the
4006 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4012 printf "x is %d\n",x
4017 One application for breakpoint commands is to compensate for one bug so
4018 you can test for another. Put a breakpoint just after the erroneous line
4019 of code, give it a condition to detect the case in which something
4020 erroneous has been done, and give it commands to assign correct values
4021 to any variables that need them. End with the @code{continue} command
4022 so that your program does not stop, and start with the @code{silent}
4023 command so that no output is produced. Here is an example:
4034 @c @ifclear BARETARGET
4035 @node Error in Breakpoints
4036 @subsection ``Cannot insert breakpoints''
4038 If you request too many active hardware-assisted breakpoints and
4039 watchpoints, you will see this error message:
4041 @c FIXME: the precise wording of this message may change; the relevant
4042 @c source change is not committed yet (Sep 3, 1999).
4044 Stopped; cannot insert breakpoints.
4045 You may have requested too many hardware breakpoints and watchpoints.
4049 This message is printed when you attempt to resume the program, since
4050 only then @value{GDBN} knows exactly how many hardware breakpoints and
4051 watchpoints it needs to insert.
4053 When this message is printed, you need to disable or remove some of the
4054 hardware-assisted breakpoints and watchpoints, and then continue.
4056 @node Breakpoint-related Warnings
4057 @subsection ``Breakpoint address adjusted...''
4058 @cindex breakpoint address adjusted
4060 Some processor architectures place constraints on the addresses at
4061 which breakpoints may be placed. For architectures thus constrained,
4062 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4063 with the constraints dictated by the architecture.
4065 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4066 a VLIW architecture in which a number of RISC-like instructions may be
4067 bundled together for parallel execution. The FR-V architecture
4068 constrains the location of a breakpoint instruction within such a
4069 bundle to the instruction with the lowest address. @value{GDBN}
4070 honors this constraint by adjusting a breakpoint's address to the
4071 first in the bundle.
4073 It is not uncommon for optimized code to have bundles which contain
4074 instructions from different source statements, thus it may happen that
4075 a breakpoint's address will be adjusted from one source statement to
4076 another. Since this adjustment may significantly alter @value{GDBN}'s
4077 breakpoint related behavior from what the user expects, a warning is
4078 printed when the breakpoint is first set and also when the breakpoint
4081 A warning like the one below is printed when setting a breakpoint
4082 that's been subject to address adjustment:
4085 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4088 Such warnings are printed both for user settable and @value{GDBN}'s
4089 internal breakpoints. If you see one of these warnings, you should
4090 verify that a breakpoint set at the adjusted address will have the
4091 desired affect. If not, the breakpoint in question may be removed and
4092 other breakpoints may be set which will have the desired behavior.
4093 E.g., it may be sufficient to place the breakpoint at a later
4094 instruction. A conditional breakpoint may also be useful in some
4095 cases to prevent the breakpoint from triggering too often.
4097 @value{GDBN} will also issue a warning when stopping at one of these
4098 adjusted breakpoints:
4101 warning: Breakpoint 1 address previously adjusted from 0x00010414
4105 When this warning is encountered, it may be too late to take remedial
4106 action except in cases where the breakpoint is hit earlier or more
4107 frequently than expected.
4109 @node Continuing and Stepping
4110 @section Continuing and Stepping
4114 @cindex resuming execution
4115 @dfn{Continuing} means resuming program execution until your program
4116 completes normally. In contrast, @dfn{stepping} means executing just
4117 one more ``step'' of your program, where ``step'' may mean either one
4118 line of source code, or one machine instruction (depending on what
4119 particular command you use). Either when continuing or when stepping,
4120 your program may stop even sooner, due to a breakpoint or a signal. (If
4121 it stops due to a signal, you may want to use @code{handle}, or use
4122 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4126 @kindex c @r{(@code{continue})}
4127 @kindex fg @r{(resume foreground execution)}
4128 @item continue @r{[}@var{ignore-count}@r{]}
4129 @itemx c @r{[}@var{ignore-count}@r{]}
4130 @itemx fg @r{[}@var{ignore-count}@r{]}
4131 Resume program execution, at the address where your program last stopped;
4132 any breakpoints set at that address are bypassed. The optional argument
4133 @var{ignore-count} allows you to specify a further number of times to
4134 ignore a breakpoint at this location; its effect is like that of
4135 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4137 The argument @var{ignore-count} is meaningful only when your program
4138 stopped due to a breakpoint. At other times, the argument to
4139 @code{continue} is ignored.
4141 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4142 debugged program is deemed to be the foreground program) are provided
4143 purely for convenience, and have exactly the same behavior as
4147 To resume execution at a different place, you can use @code{return}
4148 (@pxref{Returning, ,Returning from a Function}) to go back to the
4149 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4150 Different Address}) to go to an arbitrary location in your program.
4152 A typical technique for using stepping is to set a breakpoint
4153 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4154 beginning of the function or the section of your program where a problem
4155 is believed to lie, run your program until it stops at that breakpoint,
4156 and then step through the suspect area, examining the variables that are
4157 interesting, until you see the problem happen.
4161 @kindex s @r{(@code{step})}
4163 Continue running your program until control reaches a different source
4164 line, then stop it and return control to @value{GDBN}. This command is
4165 abbreviated @code{s}.
4168 @c "without debugging information" is imprecise; actually "without line
4169 @c numbers in the debugging information". (gcc -g1 has debugging info but
4170 @c not line numbers). But it seems complex to try to make that
4171 @c distinction here.
4172 @emph{Warning:} If you use the @code{step} command while control is
4173 within a function that was compiled without debugging information,
4174 execution proceeds until control reaches a function that does have
4175 debugging information. Likewise, it will not step into a function which
4176 is compiled without debugging information. To step through functions
4177 without debugging information, use the @code{stepi} command, described
4181 The @code{step} command only stops at the first instruction of a source
4182 line. This prevents the multiple stops that could otherwise occur in
4183 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4184 to stop if a function that has debugging information is called within
4185 the line. In other words, @code{step} @emph{steps inside} any functions
4186 called within the line.
4188 Also, the @code{step} command only enters a function if there is line
4189 number information for the function. Otherwise it acts like the
4190 @code{next} command. This avoids problems when using @code{cc -gl}
4191 on MIPS machines. Previously, @code{step} entered subroutines if there
4192 was any debugging information about the routine.
4194 @item step @var{count}
4195 Continue running as in @code{step}, but do so @var{count} times. If a
4196 breakpoint is reached, or a signal not related to stepping occurs before
4197 @var{count} steps, stepping stops right away.
4200 @kindex n @r{(@code{next})}
4201 @item next @r{[}@var{count}@r{]}
4202 Continue to the next source line in the current (innermost) stack frame.
4203 This is similar to @code{step}, but function calls that appear within
4204 the line of code are executed without stopping. Execution stops when
4205 control reaches a different line of code at the original stack level
4206 that was executing when you gave the @code{next} command. This command
4207 is abbreviated @code{n}.
4209 An argument @var{count} is a repeat count, as for @code{step}.
4212 @c FIX ME!! Do we delete this, or is there a way it fits in with
4213 @c the following paragraph? --- Vctoria
4215 @c @code{next} within a function that lacks debugging information acts like
4216 @c @code{step}, but any function calls appearing within the code of the
4217 @c function are executed without stopping.
4219 The @code{next} command only stops at the first instruction of a
4220 source line. This prevents multiple stops that could otherwise occur in
4221 @code{switch} statements, @code{for} loops, etc.
4223 @kindex set step-mode
4225 @cindex functions without line info, and stepping
4226 @cindex stepping into functions with no line info
4227 @itemx set step-mode on
4228 The @code{set step-mode on} command causes the @code{step} command to
4229 stop at the first instruction of a function which contains no debug line
4230 information rather than stepping over it.
4232 This is useful in cases where you may be interested in inspecting the
4233 machine instructions of a function which has no symbolic info and do not
4234 want @value{GDBN} to automatically skip over this function.
4236 @item set step-mode off
4237 Causes the @code{step} command to step over any functions which contains no
4238 debug information. This is the default.
4240 @item show step-mode
4241 Show whether @value{GDBN} will stop in or step over functions without
4242 source line debug information.
4245 @kindex fin @r{(@code{finish})}
4247 Continue running until just after function in the selected stack frame
4248 returns. Print the returned value (if any). This command can be
4249 abbreviated as @code{fin}.
4251 Contrast this with the @code{return} command (@pxref{Returning,
4252 ,Returning from a Function}).
4255 @kindex u @r{(@code{until})}
4256 @cindex run until specified location
4259 Continue running until a source line past the current line, in the
4260 current stack frame, is reached. This command is used to avoid single
4261 stepping through a loop more than once. It is like the @code{next}
4262 command, except that when @code{until} encounters a jump, it
4263 automatically continues execution until the program counter is greater
4264 than the address of the jump.
4266 This means that when you reach the end of a loop after single stepping
4267 though it, @code{until} makes your program continue execution until it
4268 exits the loop. In contrast, a @code{next} command at the end of a loop
4269 simply steps back to the beginning of the loop, which forces you to step
4270 through the next iteration.
4272 @code{until} always stops your program if it attempts to exit the current
4275 @code{until} may produce somewhat counterintuitive results if the order
4276 of machine code does not match the order of the source lines. For
4277 example, in the following excerpt from a debugging session, the @code{f}
4278 (@code{frame}) command shows that execution is stopped at line
4279 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4283 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4285 (@value{GDBP}) until
4286 195 for ( ; argc > 0; NEXTARG) @{
4289 This happened because, for execution efficiency, the compiler had
4290 generated code for the loop closure test at the end, rather than the
4291 start, of the loop---even though the test in a C @code{for}-loop is
4292 written before the body of the loop. The @code{until} command appeared
4293 to step back to the beginning of the loop when it advanced to this
4294 expression; however, it has not really gone to an earlier
4295 statement---not in terms of the actual machine code.
4297 @code{until} with no argument works by means of single
4298 instruction stepping, and hence is slower than @code{until} with an
4301 @item until @var{location}
4302 @itemx u @var{location}
4303 Continue running your program until either the specified location is
4304 reached, or the current stack frame returns. @var{location} is any of
4305 the forms described in @ref{Specify Location}.
4306 This form of the command uses temporary breakpoints, and
4307 hence is quicker than @code{until} without an argument. The specified
4308 location is actually reached only if it is in the current frame. This
4309 implies that @code{until} can be used to skip over recursive function
4310 invocations. For instance in the code below, if the current location is
4311 line @code{96}, issuing @code{until 99} will execute the program up to
4312 line @code{99} in the same invocation of factorial, i.e., after the inner
4313 invocations have returned.
4316 94 int factorial (int value)
4318 96 if (value > 1) @{
4319 97 value *= factorial (value - 1);
4326 @kindex advance @var{location}
4327 @itemx advance @var{location}
4328 Continue running the program up to the given @var{location}. An argument is
4329 required, which should be of one of the forms described in
4330 @ref{Specify Location}.
4331 Execution will also stop upon exit from the current stack
4332 frame. This command is similar to @code{until}, but @code{advance} will
4333 not skip over recursive function calls, and the target location doesn't
4334 have to be in the same frame as the current one.
4338 @kindex si @r{(@code{stepi})}
4340 @itemx stepi @var{arg}
4342 Execute one machine instruction, then stop and return to the debugger.
4344 It is often useful to do @samp{display/i $pc} when stepping by machine
4345 instructions. This makes @value{GDBN} automatically display the next
4346 instruction to be executed, each time your program stops. @xref{Auto
4347 Display,, Automatic Display}.
4349 An argument is a repeat count, as in @code{step}.
4353 @kindex ni @r{(@code{nexti})}
4355 @itemx nexti @var{arg}
4357 Execute one machine instruction, but if it is a function call,
4358 proceed until the function returns.
4360 An argument is a repeat count, as in @code{next}.
4367 A signal is an asynchronous event that can happen in a program. The
4368 operating system defines the possible kinds of signals, and gives each
4369 kind a name and a number. For example, in Unix @code{SIGINT} is the
4370 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4371 @code{SIGSEGV} is the signal a program gets from referencing a place in
4372 memory far away from all the areas in use; @code{SIGALRM} occurs when
4373 the alarm clock timer goes off (which happens only if your program has
4374 requested an alarm).
4376 @cindex fatal signals
4377 Some signals, including @code{SIGALRM}, are a normal part of the
4378 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4379 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4380 program has not specified in advance some other way to handle the signal.
4381 @code{SIGINT} does not indicate an error in your program, but it is normally
4382 fatal so it can carry out the purpose of the interrupt: to kill the program.
4384 @value{GDBN} has the ability to detect any occurrence of a signal in your
4385 program. You can tell @value{GDBN} in advance what to do for each kind of
4388 @cindex handling signals
4389 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4390 @code{SIGALRM} be silently passed to your program
4391 (so as not to interfere with their role in the program's functioning)
4392 but to stop your program immediately whenever an error signal happens.
4393 You can change these settings with the @code{handle} command.
4396 @kindex info signals
4400 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4401 handle each one. You can use this to see the signal numbers of all
4402 the defined types of signals.
4404 @item info signals @var{sig}
4405 Similar, but print information only about the specified signal number.
4407 @code{info handle} is an alias for @code{info signals}.
4410 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4411 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4412 can be the number of a signal or its name (with or without the
4413 @samp{SIG} at the beginning); a list of signal numbers of the form
4414 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4415 known signals. Optional arguments @var{keywords}, described below,
4416 say what change to make.
4420 The keywords allowed by the @code{handle} command can be abbreviated.
4421 Their full names are:
4425 @value{GDBN} should not stop your program when this signal happens. It may
4426 still print a message telling you that the signal has come in.
4429 @value{GDBN} should stop your program when this signal happens. This implies
4430 the @code{print} keyword as well.
4433 @value{GDBN} should print a message when this signal happens.
4436 @value{GDBN} should not mention the occurrence of the signal at all. This
4437 implies the @code{nostop} keyword as well.
4441 @value{GDBN} should allow your program to see this signal; your program
4442 can handle the signal, or else it may terminate if the signal is fatal
4443 and not handled. @code{pass} and @code{noignore} are synonyms.
4447 @value{GDBN} should not allow your program to see this signal.
4448 @code{nopass} and @code{ignore} are synonyms.
4452 When a signal stops your program, the signal is not visible to the
4454 continue. Your program sees the signal then, if @code{pass} is in
4455 effect for the signal in question @emph{at that time}. In other words,
4456 after @value{GDBN} reports a signal, you can use the @code{handle}
4457 command with @code{pass} or @code{nopass} to control whether your
4458 program sees that signal when you continue.
4460 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4461 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4462 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4465 You can also use the @code{signal} command to prevent your program from
4466 seeing a signal, or cause it to see a signal it normally would not see,
4467 or to give it any signal at any time. For example, if your program stopped
4468 due to some sort of memory reference error, you might store correct
4469 values into the erroneous variables and continue, hoping to see more
4470 execution; but your program would probably terminate immediately as
4471 a result of the fatal signal once it saw the signal. To prevent this,
4472 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4475 @cindex extra signal information
4476 @anchor{extra signal information}
4478 On some targets, @value{GDBN} can inspect extra signal information
4479 associated with the intercepted signal, before it is actually
4480 delivered to the program being debugged. This information is exported
4481 by the convenience variable @code{$_siginfo}, and consists of data
4482 that is passed by the kernel to the signal handler at the time of the
4483 receipt of a signal. The data type of the information itself is
4484 target dependent. You can see the data type using the @code{ptype
4485 $_siginfo} command. On Unix systems, it typically corresponds to the
4486 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4489 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4490 referenced address that raised a segmentation fault.
4494 (@value{GDBP}) continue
4495 Program received signal SIGSEGV, Segmentation fault.
4496 0x0000000000400766 in main ()
4498 (@value{GDBP}) ptype $_siginfo
4505 struct @{...@} _kill;
4506 struct @{...@} _timer;
4508 struct @{...@} _sigchld;
4509 struct @{...@} _sigfault;
4510 struct @{...@} _sigpoll;
4513 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4517 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4518 $1 = (void *) 0x7ffff7ff7000
4522 Depending on target support, @code{$_siginfo} may also be writable.
4525 @section Stopping and Starting Multi-thread Programs
4527 @cindex stopped threads
4528 @cindex threads, stopped
4530 @cindex continuing threads
4531 @cindex threads, continuing
4533 @value{GDBN} supports debugging programs with multiple threads
4534 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4535 are two modes of controlling execution of your program within the
4536 debugger. In the default mode, referred to as @dfn{all-stop mode},
4537 when any thread in your program stops (for example, at a breakpoint
4538 or while being stepped), all other threads in the program are also stopped by
4539 @value{GDBN}. On some targets, @value{GDBN} also supports
4540 @dfn{non-stop mode}, in which other threads can continue to run freely while
4541 you examine the stopped thread in the debugger.
4544 * All-Stop Mode:: All threads stop when GDB takes control
4545 * Non-Stop Mode:: Other threads continue to execute
4546 * Background Execution:: Running your program asynchronously
4547 * Thread-Specific Breakpoints:: Controlling breakpoints
4548 * Interrupted System Calls:: GDB may interfere with system calls
4552 @subsection All-Stop Mode
4554 @cindex all-stop mode
4556 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4557 @emph{all} threads of execution stop, not just the current thread. This
4558 allows you to examine the overall state of the program, including
4559 switching between threads, without worrying that things may change
4562 Conversely, whenever you restart the program, @emph{all} threads start
4563 executing. @emph{This is true even when single-stepping} with commands
4564 like @code{step} or @code{next}.
4566 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4567 Since thread scheduling is up to your debugging target's operating
4568 system (not controlled by @value{GDBN}), other threads may
4569 execute more than one statement while the current thread completes a
4570 single step. Moreover, in general other threads stop in the middle of a
4571 statement, rather than at a clean statement boundary, when the program
4574 You might even find your program stopped in another thread after
4575 continuing or even single-stepping. This happens whenever some other
4576 thread runs into a breakpoint, a signal, or an exception before the
4577 first thread completes whatever you requested.
4579 @cindex automatic thread selection
4580 @cindex switching threads automatically
4581 @cindex threads, automatic switching
4582 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4583 signal, it automatically selects the thread where that breakpoint or
4584 signal happened. @value{GDBN} alerts you to the context switch with a
4585 message such as @samp{[Switching to Thread @var{n}]} to identify the
4588 On some OSes, you can modify @value{GDBN}'s default behavior by
4589 locking the OS scheduler to allow only a single thread to run.
4592 @item set scheduler-locking @var{mode}
4593 @cindex scheduler locking mode
4594 @cindex lock scheduler
4595 Set the scheduler locking mode. If it is @code{off}, then there is no
4596 locking and any thread may run at any time. If @code{on}, then only the
4597 current thread may run when the inferior is resumed. The @code{step}
4598 mode optimizes for single-stepping; it prevents other threads
4599 from preempting the current thread while you are stepping, so that
4600 the focus of debugging does not change unexpectedly.
4601 Other threads only rarely (or never) get a chance to run
4602 when you step. They are more likely to run when you @samp{next} over a
4603 function call, and they are completely free to run when you use commands
4604 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4605 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4606 the current thread away from the thread that you are debugging.
4608 @item show scheduler-locking
4609 Display the current scheduler locking mode.
4613 @subsection Non-Stop Mode
4615 @cindex non-stop mode
4617 @c This section is really only a place-holder, and needs to be expanded
4618 @c with more details.
4620 For some multi-threaded targets, @value{GDBN} supports an optional
4621 mode of operation in which you can examine stopped program threads in
4622 the debugger while other threads continue to execute freely. This
4623 minimizes intrusion when debugging live systems, such as programs
4624 where some threads have real-time constraints or must continue to
4625 respond to external events. This is referred to as @dfn{non-stop} mode.
4627 In non-stop mode, when a thread stops to report a debugging event,
4628 @emph{only} that thread is stopped; @value{GDBN} does not stop other
4629 threads as well, in contrast to the all-stop mode behavior. Additionally,
4630 execution commands such as @code{continue} and @code{step} apply by default
4631 only to the current thread in non-stop mode, rather than all threads as
4632 in all-stop mode. This allows you to control threads explicitly in
4633 ways that are not possible in all-stop mode --- for example, stepping
4634 one thread while allowing others to run freely, stepping
4635 one thread while holding all others stopped, or stepping several threads
4636 independently and simultaneously.
4638 To enter non-stop mode, use this sequence of commands before you run
4639 or attach to your program:
4642 # Enable the async interface.
4645 # If using the CLI, pagination breaks non-stop.
4648 # Finally, turn it on!
4652 You can use these commands to manipulate the non-stop mode setting:
4655 @kindex set non-stop
4656 @item set non-stop on
4657 Enable selection of non-stop mode.
4658 @item set non-stop off
4659 Disable selection of non-stop mode.
4660 @kindex show non-stop
4662 Show the current non-stop enablement setting.
4665 Note these commands only reflect whether non-stop mode is enabled,
4666 not whether the currently-executing program is being run in non-stop mode.
4667 In particular, the @code{set non-stop} preference is only consulted when
4668 @value{GDBN} starts or connects to the target program, and it is generally
4669 not possible to switch modes once debugging has started. Furthermore,
4670 since not all targets support non-stop mode, even when you have enabled
4671 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
4674 In non-stop mode, all execution commands apply only to the current thread
4675 by default. That is, @code{continue} only continues one thread.
4676 To continue all threads, issue @code{continue -a} or @code{c -a}.
4678 You can use @value{GDBN}'s background execution commands
4679 (@pxref{Background Execution}) to run some threads in the background
4680 while you continue to examine or step others from @value{GDBN}.
4681 The MI execution commands (@pxref{GDB/MI Program Execution}) are
4682 always executed asynchronously in non-stop mode.
4684 Suspending execution is done with the @code{interrupt} command when
4685 running in the background, or @kbd{Ctrl-c} during foreground execution.
4686 In all-stop mode, this stops the whole process;
4687 but in non-stop mode the interrupt applies only to the current thread.
4688 To stop the whole program, use @code{interrupt -a}.
4690 Other execution commands do not currently support the @code{-a} option.
4692 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
4693 that thread current, as it does in all-stop mode. This is because the
4694 thread stop notifications are asynchronous with respect to @value{GDBN}'s
4695 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
4696 changed to a different thread just as you entered a command to operate on the
4697 previously current thread.
4699 @node Background Execution
4700 @subsection Background Execution
4702 @cindex foreground execution
4703 @cindex background execution
4704 @cindex asynchronous execution
4705 @cindex execution, foreground, background and asynchronous
4707 @value{GDBN}'s execution commands have two variants: the normal
4708 foreground (synchronous) behavior, and a background
4709 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
4710 the program to report that some thread has stopped before prompting for
4711 another command. In background execution, @value{GDBN} immediately gives
4712 a command prompt so that you can issue other commands while your program runs.
4714 You need to explicitly enable asynchronous mode before you can use
4715 background execution commands. You can use these commands to
4716 manipulate the asynchronous mode setting:
4719 @kindex set target-async
4720 @item set target-async on
4721 Enable asynchronous mode.
4722 @item set target-async off
4723 Disable asynchronous mode.
4724 @kindex show target-async
4725 @item show target-async
4726 Show the current target-async setting.
4729 If the target doesn't support async mode, @value{GDBN} issues an error
4730 message if you attempt to use the background execution commands.
4732 To specify background execution, add a @code{&} to the command. For example,
4733 the background form of the @code{continue} command is @code{continue&}, or
4734 just @code{c&}. The execution commands that accept background execution
4740 @xref{Starting, , Starting your Program}.
4744 @xref{Attach, , Debugging an Already-running Process}.
4748 @xref{Continuing and Stepping, step}.
4752 @xref{Continuing and Stepping, stepi}.
4756 @xref{Continuing and Stepping, next}.
4760 @xref{Continuing and Stepping, nexti}.
4764 @xref{Continuing and Stepping, continue}.
4768 @xref{Continuing and Stepping, finish}.
4772 @xref{Continuing and Stepping, until}.
4776 Background execution is especially useful in conjunction with non-stop
4777 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
4778 However, you can also use these commands in the normal all-stop mode with
4779 the restriction that you cannot issue another execution command until the
4780 previous one finishes. Examples of commands that are valid in all-stop
4781 mode while the program is running include @code{help} and @code{info break}.
4783 You can interrupt your program while it is running in the background by
4784 using the @code{interrupt} command.
4791 Suspend execution of the running program. In all-stop mode,
4792 @code{interrupt} stops the whole process, but in non-stop mode, it stops
4793 only the current thread. To stop the whole program in non-stop mode,
4794 use @code{interrupt -a}.
4797 @node Thread-Specific Breakpoints
4798 @subsection Thread-Specific Breakpoints
4800 When your program has multiple threads (@pxref{Threads,, Debugging
4801 Programs with Multiple Threads}), you can choose whether to set
4802 breakpoints on all threads, or on a particular thread.
4805 @cindex breakpoints and threads
4806 @cindex thread breakpoints
4807 @kindex break @dots{} thread @var{threadno}
4808 @item break @var{linespec} thread @var{threadno}
4809 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4810 @var{linespec} specifies source lines; there are several ways of
4811 writing them (@pxref{Specify Location}), but the effect is always to
4812 specify some source line.
4814 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4815 to specify that you only want @value{GDBN} to stop the program when a
4816 particular thread reaches this breakpoint. @var{threadno} is one of the
4817 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4818 column of the @samp{info threads} display.
4820 If you do not specify @samp{thread @var{threadno}} when you set a
4821 breakpoint, the breakpoint applies to @emph{all} threads of your
4824 You can use the @code{thread} qualifier on conditional breakpoints as
4825 well; in this case, place @samp{thread @var{threadno}} before the
4826 breakpoint condition, like this:
4829 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4834 @node Interrupted System Calls
4835 @subsection Interrupted System Calls
4837 @cindex thread breakpoints and system calls
4838 @cindex system calls and thread breakpoints
4839 @cindex premature return from system calls
4840 There is an unfortunate side effect when using @value{GDBN} to debug
4841 multi-threaded programs. If one thread stops for a
4842 breakpoint, or for some other reason, and another thread is blocked in a
4843 system call, then the system call may return prematurely. This is a
4844 consequence of the interaction between multiple threads and the signals
4845 that @value{GDBN} uses to implement breakpoints and other events that
4848 To handle this problem, your program should check the return value of
4849 each system call and react appropriately. This is good programming
4852 For example, do not write code like this:
4858 The call to @code{sleep} will return early if a different thread stops
4859 at a breakpoint or for some other reason.
4861 Instead, write this:
4866 unslept = sleep (unslept);
4869 A system call is allowed to return early, so the system is still
4870 conforming to its specification. But @value{GDBN} does cause your
4871 multi-threaded program to behave differently than it would without
4874 Also, @value{GDBN} uses internal breakpoints in the thread library to
4875 monitor certain events such as thread creation and thread destruction.
4876 When such an event happens, a system call in another thread may return
4877 prematurely, even though your program does not appear to stop.
4880 @node Reverse Execution
4881 @chapter Running programs backward
4882 @cindex reverse execution
4883 @cindex running programs backward
4885 When you are debugging a program, it is not unusual to realize that
4886 you have gone too far, and some event of interest has already happened.
4887 If the target environment supports it, @value{GDBN} can allow you to
4888 ``rewind'' the program by running it backward.
4890 A target environment that supports reverse execution should be able
4891 to ``undo'' the changes in machine state that have taken place as the
4892 program was executing normally. Variables, registers etc.@: should
4893 revert to their previous values. Obviously this requires a great
4894 deal of sophistication on the part of the target environment; not
4895 all target environments can support reverse execution.
4897 When a program is executed in reverse, the instructions that
4898 have most recently been executed are ``un-executed'', in reverse
4899 order. The program counter runs backward, following the previous
4900 thread of execution in reverse. As each instruction is ``un-executed'',
4901 the values of memory and/or registers that were changed by that
4902 instruction are reverted to their previous states. After executing
4903 a piece of source code in reverse, all side effects of that code
4904 should be ``undone'', and all variables should be returned to their
4905 prior values@footnote{
4906 Note that some side effects are easier to undo than others. For instance,
4907 memory and registers are relatively easy, but device I/O is hard. Some
4908 targets may be able undo things like device I/O, and some may not.
4910 The contract between @value{GDBN} and the reverse executing target
4911 requires only that the target do something reasonable when
4912 @value{GDBN} tells it to execute backwards, and then report the
4913 results back to @value{GDBN}. Whatever the target reports back to
4914 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
4915 assumes that the memory and registers that the target reports are in a
4916 consistant state, but @value{GDBN} accepts whatever it is given.
4919 If you are debugging in a target environment that supports
4920 reverse execution, @value{GDBN} provides the following commands.
4923 @kindex reverse-continue
4924 @kindex rc @r{(@code{reverse-continue})}
4925 @item reverse-continue @r{[}@var{ignore-count}@r{]}
4926 @itemx rc @r{[}@var{ignore-count}@r{]}
4927 Beginning at the point where your program last stopped, start executing
4928 in reverse. Reverse execution will stop for breakpoints and synchronous
4929 exceptions (signals), just like normal execution. Behavior of
4930 asynchronous signals depends on the target environment.
4932 @kindex reverse-step
4933 @kindex rs @r{(@code{step})}
4934 @item reverse-step @r{[}@var{count}@r{]}
4935 Run the program backward until control reaches the start of a
4936 different source line; then stop it, and return control to @value{GDBN}.
4938 Like the @code{step} command, @code{reverse-step} will only stop
4939 at the beginning of a source line. It ``un-executes'' the previously
4940 executed source line. If the previous source line included calls to
4941 debuggable functions, @code{reverse-step} will step (backward) into
4942 the called function, stopping at the beginning of the @emph{last}
4943 statement in the called function (typically a return statement).
4945 Also, as with the @code{step} command, if non-debuggable functions are
4946 called, @code{reverse-step} will run thru them backward without stopping.
4948 @kindex reverse-stepi
4949 @kindex rsi @r{(@code{reverse-stepi})}
4950 @item reverse-stepi @r{[}@var{count}@r{]}
4951 Reverse-execute one machine instruction. Note that the instruction
4952 to be reverse-executed is @emph{not} the one pointed to by the program
4953 counter, but the instruction executed prior to that one. For instance,
4954 if the last instruction was a jump, @code{reverse-stepi} will take you
4955 back from the destination of the jump to the jump instruction itself.
4957 @kindex reverse-next
4958 @kindex rn @r{(@code{reverse-next})}
4959 @item reverse-next @r{[}@var{count}@r{]}
4960 Run backward to the beginning of the previous line executed in
4961 the current (innermost) stack frame. If the line contains function
4962 calls, they will be ``un-executed'' without stopping. Starting from
4963 the first line of a function, @code{reverse-next} will take you back
4964 to the caller of that function, @emph{before} the function was called,
4965 just as the normal @code{next} command would take you from the last
4966 line of a function back to its return to its caller
4967 @footnote{Unles the code is too heavily optimized.}.
4969 @kindex reverse-nexti
4970 @kindex rni @r{(@code{reverse-nexti})}
4971 @item reverse-nexti @r{[}@var{count}@r{]}
4972 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
4973 in reverse, except that called functions are ``un-executed'' atomically.
4974 That is, if the previously executed instruction was a return from
4975 another instruction, @code{reverse-nexti} will continue to execute
4976 in reverse until the call to that function (from the current stack
4979 @kindex reverse-finish
4980 @item reverse-finish
4981 Just as the @code{finish} command takes you to the point where the
4982 current function returns, @code{reverse-finish} takes you to the point
4983 where it was called. Instead of ending up at the end of the current
4984 function invocation, you end up at the beginning.
4986 @kindex set exec-direction
4987 @item set exec-direction
4988 Set the direction of target execution.
4989 @itemx set exec-direction reverse
4990 @cindex execute forward or backward in time
4991 @value{GDBN} will perform all execution commands in reverse, until the
4992 exec-direction mode is changed to ``forward''. Affected commands include
4993 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
4994 command cannot be used in reverse mode.
4995 @item set exec-direction forward
4996 @value{GDBN} will perform all execution commands in the normal fashion.
4997 This is the default.
5002 @chapter Examining the Stack
5004 When your program has stopped, the first thing you need to know is where it
5005 stopped and how it got there.
5008 Each time your program performs a function call, information about the call
5010 That information includes the location of the call in your program,
5011 the arguments of the call,
5012 and the local variables of the function being called.
5013 The information is saved in a block of data called a @dfn{stack frame}.
5014 The stack frames are allocated in a region of memory called the @dfn{call
5017 When your program stops, the @value{GDBN} commands for examining the
5018 stack allow you to see all of this information.
5020 @cindex selected frame
5021 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5022 @value{GDBN} commands refer implicitly to the selected frame. In
5023 particular, whenever you ask @value{GDBN} for the value of a variable in
5024 your program, the value is found in the selected frame. There are
5025 special @value{GDBN} commands to select whichever frame you are
5026 interested in. @xref{Selection, ,Selecting a Frame}.
5028 When your program stops, @value{GDBN} automatically selects the
5029 currently executing frame and describes it briefly, similar to the
5030 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5033 * Frames:: Stack frames
5034 * Backtrace:: Backtraces
5035 * Selection:: Selecting a frame
5036 * Frame Info:: Information on a frame
5041 @section Stack Frames
5043 @cindex frame, definition
5045 The call stack is divided up into contiguous pieces called @dfn{stack
5046 frames}, or @dfn{frames} for short; each frame is the data associated
5047 with one call to one function. The frame contains the arguments given
5048 to the function, the function's local variables, and the address at
5049 which the function is executing.
5051 @cindex initial frame
5052 @cindex outermost frame
5053 @cindex innermost frame
5054 When your program is started, the stack has only one frame, that of the
5055 function @code{main}. This is called the @dfn{initial} frame or the
5056 @dfn{outermost} frame. Each time a function is called, a new frame is
5057 made. Each time a function returns, the frame for that function invocation
5058 is eliminated. If a function is recursive, there can be many frames for
5059 the same function. The frame for the function in which execution is
5060 actually occurring is called the @dfn{innermost} frame. This is the most
5061 recently created of all the stack frames that still exist.
5063 @cindex frame pointer
5064 Inside your program, stack frames are identified by their addresses. A
5065 stack frame consists of many bytes, each of which has its own address; each
5066 kind of computer has a convention for choosing one byte whose
5067 address serves as the address of the frame. Usually this address is kept
5068 in a register called the @dfn{frame pointer register}
5069 (@pxref{Registers, $fp}) while execution is going on in that frame.
5071 @cindex frame number
5072 @value{GDBN} assigns numbers to all existing stack frames, starting with
5073 zero for the innermost frame, one for the frame that called it,
5074 and so on upward. These numbers do not really exist in your program;
5075 they are assigned by @value{GDBN} to give you a way of designating stack
5076 frames in @value{GDBN} commands.
5078 @c The -fomit-frame-pointer below perennially causes hbox overflow
5079 @c underflow problems.
5080 @cindex frameless execution
5081 Some compilers provide a way to compile functions so that they operate
5082 without stack frames. (For example, the @value{NGCC} option
5084 @samp{-fomit-frame-pointer}
5086 generates functions without a frame.)
5087 This is occasionally done with heavily used library functions to save
5088 the frame setup time. @value{GDBN} has limited facilities for dealing
5089 with these function invocations. If the innermost function invocation
5090 has no stack frame, @value{GDBN} nevertheless regards it as though
5091 it had a separate frame, which is numbered zero as usual, allowing
5092 correct tracing of the function call chain. However, @value{GDBN} has
5093 no provision for frameless functions elsewhere in the stack.
5096 @kindex frame@r{, command}
5097 @cindex current stack frame
5098 @item frame @var{args}
5099 The @code{frame} command allows you to move from one stack frame to another,
5100 and to print the stack frame you select. @var{args} may be either the
5101 address of the frame or the stack frame number. Without an argument,
5102 @code{frame} prints the current stack frame.
5104 @kindex select-frame
5105 @cindex selecting frame silently
5107 The @code{select-frame} command allows you to move from one stack frame
5108 to another without printing the frame. This is the silent version of
5116 @cindex call stack traces
5117 A backtrace is a summary of how your program got where it is. It shows one
5118 line per frame, for many frames, starting with the currently executing
5119 frame (frame zero), followed by its caller (frame one), and on up the
5124 @kindex bt @r{(@code{backtrace})}
5127 Print a backtrace of the entire stack: one line per frame for all
5128 frames in the stack.
5130 You can stop the backtrace at any time by typing the system interrupt
5131 character, normally @kbd{Ctrl-c}.
5133 @item backtrace @var{n}
5135 Similar, but print only the innermost @var{n} frames.
5137 @item backtrace -@var{n}
5139 Similar, but print only the outermost @var{n} frames.
5141 @item backtrace full
5143 @itemx bt full @var{n}
5144 @itemx bt full -@var{n}
5145 Print the values of the local variables also. @var{n} specifies the
5146 number of frames to print, as described above.
5151 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5152 are additional aliases for @code{backtrace}.
5154 @cindex multiple threads, backtrace
5155 In a multi-threaded program, @value{GDBN} by default shows the
5156 backtrace only for the current thread. To display the backtrace for
5157 several or all of the threads, use the command @code{thread apply}
5158 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5159 apply all backtrace}, @value{GDBN} will display the backtrace for all
5160 the threads; this is handy when you debug a core dump of a
5161 multi-threaded program.
5163 Each line in the backtrace shows the frame number and the function name.
5164 The program counter value is also shown---unless you use @code{set
5165 print address off}. The backtrace also shows the source file name and
5166 line number, as well as the arguments to the function. The program
5167 counter value is omitted if it is at the beginning of the code for that
5170 Here is an example of a backtrace. It was made with the command
5171 @samp{bt 3}, so it shows the innermost three frames.
5175 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5177 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
5178 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5180 (More stack frames follow...)
5185 The display for frame zero does not begin with a program counter
5186 value, indicating that your program has stopped at the beginning of the
5187 code for line @code{993} of @code{builtin.c}.
5189 @cindex value optimized out, in backtrace
5190 @cindex function call arguments, optimized out
5191 If your program was compiled with optimizations, some compilers will
5192 optimize away arguments passed to functions if those arguments are
5193 never used after the call. Such optimizations generate code that
5194 passes arguments through registers, but doesn't store those arguments
5195 in the stack frame. @value{GDBN} has no way of displaying such
5196 arguments in stack frames other than the innermost one. Here's what
5197 such a backtrace might look like:
5201 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5203 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5204 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5206 (More stack frames follow...)
5211 The values of arguments that were not saved in their stack frames are
5212 shown as @samp{<value optimized out>}.
5214 If you need to display the values of such optimized-out arguments,
5215 either deduce that from other variables whose values depend on the one
5216 you are interested in, or recompile without optimizations.
5218 @cindex backtrace beyond @code{main} function
5219 @cindex program entry point
5220 @cindex startup code, and backtrace
5221 Most programs have a standard user entry point---a place where system
5222 libraries and startup code transition into user code. For C this is
5223 @code{main}@footnote{
5224 Note that embedded programs (the so-called ``free-standing''
5225 environment) are not required to have a @code{main} function as the
5226 entry point. They could even have multiple entry points.}.
5227 When @value{GDBN} finds the entry function in a backtrace
5228 it will terminate the backtrace, to avoid tracing into highly
5229 system-specific (and generally uninteresting) code.
5231 If you need to examine the startup code, or limit the number of levels
5232 in a backtrace, you can change this behavior:
5235 @item set backtrace past-main
5236 @itemx set backtrace past-main on
5237 @kindex set backtrace
5238 Backtraces will continue past the user entry point.
5240 @item set backtrace past-main off
5241 Backtraces will stop when they encounter the user entry point. This is the
5244 @item show backtrace past-main
5245 @kindex show backtrace
5246 Display the current user entry point backtrace policy.
5248 @item set backtrace past-entry
5249 @itemx set backtrace past-entry on
5250 Backtraces will continue past the internal entry point of an application.
5251 This entry point is encoded by the linker when the application is built,
5252 and is likely before the user entry point @code{main} (or equivalent) is called.
5254 @item set backtrace past-entry off
5255 Backtraces will stop when they encounter the internal entry point of an
5256 application. This is the default.
5258 @item show backtrace past-entry
5259 Display the current internal entry point backtrace policy.
5261 @item set backtrace limit @var{n}
5262 @itemx set backtrace limit 0
5263 @cindex backtrace limit
5264 Limit the backtrace to @var{n} levels. A value of zero means
5267 @item show backtrace limit
5268 Display the current limit on backtrace levels.
5272 @section Selecting a Frame
5274 Most commands for examining the stack and other data in your program work on
5275 whichever stack frame is selected at the moment. Here are the commands for
5276 selecting a stack frame; all of them finish by printing a brief description
5277 of the stack frame just selected.
5280 @kindex frame@r{, selecting}
5281 @kindex f @r{(@code{frame})}
5284 Select frame number @var{n}. Recall that frame zero is the innermost
5285 (currently executing) frame, frame one is the frame that called the
5286 innermost one, and so on. The highest-numbered frame is the one for
5289 @item frame @var{addr}
5291 Select the frame at address @var{addr}. This is useful mainly if the
5292 chaining of stack frames has been damaged by a bug, making it
5293 impossible for @value{GDBN} to assign numbers properly to all frames. In
5294 addition, this can be useful when your program has multiple stacks and
5295 switches between them.
5297 On the SPARC architecture, @code{frame} needs two addresses to
5298 select an arbitrary frame: a frame pointer and a stack pointer.
5300 On the MIPS and Alpha architecture, it needs two addresses: a stack
5301 pointer and a program counter.
5303 On the 29k architecture, it needs three addresses: a register stack
5304 pointer, a program counter, and a memory stack pointer.
5308 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5309 advances toward the outermost frame, to higher frame numbers, to frames
5310 that have existed longer. @var{n} defaults to one.
5313 @kindex do @r{(@code{down})}
5315 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5316 advances toward the innermost frame, to lower frame numbers, to frames
5317 that were created more recently. @var{n} defaults to one. You may
5318 abbreviate @code{down} as @code{do}.
5321 All of these commands end by printing two lines of output describing the
5322 frame. The first line shows the frame number, the function name, the
5323 arguments, and the source file and line number of execution in that
5324 frame. The second line shows the text of that source line.
5332 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5334 10 read_input_file (argv[i]);
5338 After such a printout, the @code{list} command with no arguments
5339 prints ten lines centered on the point of execution in the frame.
5340 You can also edit the program at the point of execution with your favorite
5341 editing program by typing @code{edit}.
5342 @xref{List, ,Printing Source Lines},
5346 @kindex down-silently
5348 @item up-silently @var{n}
5349 @itemx down-silently @var{n}
5350 These two commands are variants of @code{up} and @code{down},
5351 respectively; they differ in that they do their work silently, without
5352 causing display of the new frame. They are intended primarily for use
5353 in @value{GDBN} command scripts, where the output might be unnecessary and
5358 @section Information About a Frame
5360 There are several other commands to print information about the selected
5366 When used without any argument, this command does not change which
5367 frame is selected, but prints a brief description of the currently
5368 selected stack frame. It can be abbreviated @code{f}. With an
5369 argument, this command is used to select a stack frame.
5370 @xref{Selection, ,Selecting a Frame}.
5373 @kindex info f @r{(@code{info frame})}
5376 This command prints a verbose description of the selected stack frame,
5381 the address of the frame
5383 the address of the next frame down (called by this frame)
5385 the address of the next frame up (caller of this frame)
5387 the language in which the source code corresponding to this frame is written
5389 the address of the frame's arguments
5391 the address of the frame's local variables
5393 the program counter saved in it (the address of execution in the caller frame)
5395 which registers were saved in the frame
5398 @noindent The verbose description is useful when
5399 something has gone wrong that has made the stack format fail to fit
5400 the usual conventions.
5402 @item info frame @var{addr}
5403 @itemx info f @var{addr}
5404 Print a verbose description of the frame at address @var{addr}, without
5405 selecting that frame. The selected frame remains unchanged by this
5406 command. This requires the same kind of address (more than one for some
5407 architectures) that you specify in the @code{frame} command.
5408 @xref{Selection, ,Selecting a Frame}.
5412 Print the arguments of the selected frame, each on a separate line.
5416 Print the local variables of the selected frame, each on a separate
5417 line. These are all variables (declared either static or automatic)
5418 accessible at the point of execution of the selected frame.
5421 @cindex catch exceptions, list active handlers
5422 @cindex exception handlers, how to list
5424 Print a list of all the exception handlers that are active in the
5425 current stack frame at the current point of execution. To see other
5426 exception handlers, visit the associated frame (using the @code{up},
5427 @code{down}, or @code{frame} commands); then type @code{info catch}.
5428 @xref{Set Catchpoints, , Setting Catchpoints}.
5434 @chapter Examining Source Files
5436 @value{GDBN} can print parts of your program's source, since the debugging
5437 information recorded in the program tells @value{GDBN} what source files were
5438 used to build it. When your program stops, @value{GDBN} spontaneously prints
5439 the line where it stopped. Likewise, when you select a stack frame
5440 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5441 execution in that frame has stopped. You can print other portions of
5442 source files by explicit command.
5444 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5445 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5446 @value{GDBN} under @sc{gnu} Emacs}.
5449 * List:: Printing source lines
5450 * Specify Location:: How to specify code locations
5451 * Edit:: Editing source files
5452 * Search:: Searching source files
5453 * Source Path:: Specifying source directories
5454 * Machine Code:: Source and machine code
5458 @section Printing Source Lines
5461 @kindex l @r{(@code{list})}
5462 To print lines from a source file, use the @code{list} command
5463 (abbreviated @code{l}). By default, ten lines are printed.
5464 There are several ways to specify what part of the file you want to
5465 print; see @ref{Specify Location}, for the full list.
5467 Here are the forms of the @code{list} command most commonly used:
5470 @item list @var{linenum}
5471 Print lines centered around line number @var{linenum} in the
5472 current source file.
5474 @item list @var{function}
5475 Print lines centered around the beginning of function
5479 Print more lines. If the last lines printed were printed with a
5480 @code{list} command, this prints lines following the last lines
5481 printed; however, if the last line printed was a solitary line printed
5482 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5483 Stack}), this prints lines centered around that line.
5486 Print lines just before the lines last printed.
5489 @cindex @code{list}, how many lines to display
5490 By default, @value{GDBN} prints ten source lines with any of these forms of
5491 the @code{list} command. You can change this using @code{set listsize}:
5494 @kindex set listsize
5495 @item set listsize @var{count}
5496 Make the @code{list} command display @var{count} source lines (unless
5497 the @code{list} argument explicitly specifies some other number).
5499 @kindex show listsize
5501 Display the number of lines that @code{list} prints.
5504 Repeating a @code{list} command with @key{RET} discards the argument,
5505 so it is equivalent to typing just @code{list}. This is more useful
5506 than listing the same lines again. An exception is made for an
5507 argument of @samp{-}; that argument is preserved in repetition so that
5508 each repetition moves up in the source file.
5510 In general, the @code{list} command expects you to supply zero, one or two
5511 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5512 of writing them (@pxref{Specify Location}), but the effect is always
5513 to specify some source line.
5515 Here is a complete description of the possible arguments for @code{list}:
5518 @item list @var{linespec}
5519 Print lines centered around the line specified by @var{linespec}.
5521 @item list @var{first},@var{last}
5522 Print lines from @var{first} to @var{last}. Both arguments are
5523 linespecs. When a @code{list} command has two linespecs, and the
5524 source file of the second linespec is omitted, this refers to
5525 the same source file as the first linespec.
5527 @item list ,@var{last}
5528 Print lines ending with @var{last}.
5530 @item list @var{first},
5531 Print lines starting with @var{first}.
5534 Print lines just after the lines last printed.
5537 Print lines just before the lines last printed.
5540 As described in the preceding table.
5543 @node Specify Location
5544 @section Specifying a Location
5545 @cindex specifying location
5548 Several @value{GDBN} commands accept arguments that specify a location
5549 of your program's code. Since @value{GDBN} is a source-level
5550 debugger, a location usually specifies some line in the source code;
5551 for that reason, locations are also known as @dfn{linespecs}.
5553 Here are all the different ways of specifying a code location that
5554 @value{GDBN} understands:
5558 Specifies the line number @var{linenum} of the current source file.
5561 @itemx +@var{offset}
5562 Specifies the line @var{offset} lines before or after the @dfn{current
5563 line}. For the @code{list} command, the current line is the last one
5564 printed; for the breakpoint commands, this is the line at which
5565 execution stopped in the currently selected @dfn{stack frame}
5566 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5567 used as the second of the two linespecs in a @code{list} command,
5568 this specifies the line @var{offset} lines up or down from the first
5571 @item @var{filename}:@var{linenum}
5572 Specifies the line @var{linenum} in the source file @var{filename}.
5574 @item @var{function}
5575 Specifies the line that begins the body of the function @var{function}.
5576 For example, in C, this is the line with the open brace.
5578 @item @var{filename}:@var{function}
5579 Specifies the line that begins the body of the function @var{function}
5580 in the file @var{filename}. You only need the file name with a
5581 function name to avoid ambiguity when there are identically named
5582 functions in different source files.
5584 @item *@var{address}
5585 Specifies the program address @var{address}. For line-oriented
5586 commands, such as @code{list} and @code{edit}, this specifies a source
5587 line that contains @var{address}. For @code{break} and other
5588 breakpoint oriented commands, this can be used to set breakpoints in
5589 parts of your program which do not have debugging information or
5592 Here @var{address} may be any expression valid in the current working
5593 language (@pxref{Languages, working language}) that specifies a code
5594 address. In addition, as a convenience, @value{GDBN} extends the
5595 semantics of expressions used in locations to cover the situations
5596 that frequently happen during debugging. Here are the various forms
5600 @item @var{expression}
5601 Any expression valid in the current working language.
5603 @item @var{funcaddr}
5604 An address of a function or procedure derived from its name. In C,
5605 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5606 simply the function's name @var{function} (and actually a special case
5607 of a valid expression). In Pascal and Modula-2, this is
5608 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5609 (although the Pascal form also works).
5611 This form specifies the address of the function's first instruction,
5612 before the stack frame and arguments have been set up.
5614 @item '@var{filename}'::@var{funcaddr}
5615 Like @var{funcaddr} above, but also specifies the name of the source
5616 file explicitly. This is useful if the name of the function does not
5617 specify the function unambiguously, e.g., if there are several
5618 functions with identical names in different source files.
5625 @section Editing Source Files
5626 @cindex editing source files
5629 @kindex e @r{(@code{edit})}
5630 To edit the lines in a source file, use the @code{edit} command.
5631 The editing program of your choice
5632 is invoked with the current line set to
5633 the active line in the program.
5634 Alternatively, there are several ways to specify what part of the file you
5635 want to print if you want to see other parts of the program:
5638 @item edit @var{location}
5639 Edit the source file specified by @code{location}. Editing starts at
5640 that @var{location}, e.g., at the specified source line of the
5641 specified file. @xref{Specify Location}, for all the possible forms
5642 of the @var{location} argument; here are the forms of the @code{edit}
5643 command most commonly used:
5646 @item edit @var{number}
5647 Edit the current source file with @var{number} as the active line number.
5649 @item edit @var{function}
5650 Edit the file containing @var{function} at the beginning of its definition.
5655 @subsection Choosing your Editor
5656 You can customize @value{GDBN} to use any editor you want
5658 The only restriction is that your editor (say @code{ex}), recognizes the
5659 following command-line syntax:
5661 ex +@var{number} file
5663 The optional numeric value +@var{number} specifies the number of the line in
5664 the file where to start editing.}.
5665 By default, it is @file{@value{EDITOR}}, but you can change this
5666 by setting the environment variable @code{EDITOR} before using
5667 @value{GDBN}. For example, to configure @value{GDBN} to use the
5668 @code{vi} editor, you could use these commands with the @code{sh} shell:
5674 or in the @code{csh} shell,
5676 setenv EDITOR /usr/bin/vi
5681 @section Searching Source Files
5682 @cindex searching source files
5684 There are two commands for searching through the current source file for a
5689 @kindex forward-search
5690 @item forward-search @var{regexp}
5691 @itemx search @var{regexp}
5692 The command @samp{forward-search @var{regexp}} checks each line,
5693 starting with the one following the last line listed, for a match for
5694 @var{regexp}. It lists the line that is found. You can use the
5695 synonym @samp{search @var{regexp}} or abbreviate the command name as
5698 @kindex reverse-search
5699 @item reverse-search @var{regexp}
5700 The command @samp{reverse-search @var{regexp}} checks each line, starting
5701 with the one before the last line listed and going backward, for a match
5702 for @var{regexp}. It lists the line that is found. You can abbreviate
5703 this command as @code{rev}.
5707 @section Specifying Source Directories
5710 @cindex directories for source files
5711 Executable programs sometimes do not record the directories of the source
5712 files from which they were compiled, just the names. Even when they do,
5713 the directories could be moved between the compilation and your debugging
5714 session. @value{GDBN} has a list of directories to search for source files;
5715 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5716 it tries all the directories in the list, in the order they are present
5717 in the list, until it finds a file with the desired name.
5719 For example, suppose an executable references the file
5720 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5721 @file{/mnt/cross}. The file is first looked up literally; if this
5722 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5723 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5724 message is printed. @value{GDBN} does not look up the parts of the
5725 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5726 Likewise, the subdirectories of the source path are not searched: if
5727 the source path is @file{/mnt/cross}, and the binary refers to
5728 @file{foo.c}, @value{GDBN} would not find it under
5729 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5731 Plain file names, relative file names with leading directories, file
5732 names containing dots, etc.@: are all treated as described above; for
5733 instance, if the source path is @file{/mnt/cross}, and the source file
5734 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5735 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5736 that---@file{/mnt/cross/foo.c}.
5738 Note that the executable search path is @emph{not} used to locate the
5741 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5742 any information it has cached about where source files are found and where
5743 each line is in the file.
5747 When you start @value{GDBN}, its source path includes only @samp{cdir}
5748 and @samp{cwd}, in that order.
5749 To add other directories, use the @code{directory} command.
5751 The search path is used to find both program source files and @value{GDBN}
5752 script files (read using the @samp{-command} option and @samp{source} command).
5754 In addition to the source path, @value{GDBN} provides a set of commands
5755 that manage a list of source path substitution rules. A @dfn{substitution
5756 rule} specifies how to rewrite source directories stored in the program's
5757 debug information in case the sources were moved to a different
5758 directory between compilation and debugging. A rule is made of
5759 two strings, the first specifying what needs to be rewritten in
5760 the path, and the second specifying how it should be rewritten.
5761 In @ref{set substitute-path}, we name these two parts @var{from} and
5762 @var{to} respectively. @value{GDBN} does a simple string replacement
5763 of @var{from} with @var{to} at the start of the directory part of the
5764 source file name, and uses that result instead of the original file
5765 name to look up the sources.
5767 Using the previous example, suppose the @file{foo-1.0} tree has been
5768 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5769 @value{GDBN} to replace @file{/usr/src} in all source path names with
5770 @file{/mnt/cross}. The first lookup will then be
5771 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5772 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5773 substitution rule, use the @code{set substitute-path} command
5774 (@pxref{set substitute-path}).
5776 To avoid unexpected substitution results, a rule is applied only if the
5777 @var{from} part of the directory name ends at a directory separator.
5778 For instance, a rule substituting @file{/usr/source} into
5779 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5780 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5781 is applied only at the beginning of the directory name, this rule will
5782 not be applied to @file{/root/usr/source/baz.c} either.
5784 In many cases, you can achieve the same result using the @code{directory}
5785 command. However, @code{set substitute-path} can be more efficient in
5786 the case where the sources are organized in a complex tree with multiple
5787 subdirectories. With the @code{directory} command, you need to add each
5788 subdirectory of your project. If you moved the entire tree while
5789 preserving its internal organization, then @code{set substitute-path}
5790 allows you to direct the debugger to all the sources with one single
5793 @code{set substitute-path} is also more than just a shortcut command.
5794 The source path is only used if the file at the original location no
5795 longer exists. On the other hand, @code{set substitute-path} modifies
5796 the debugger behavior to look at the rewritten location instead. So, if
5797 for any reason a source file that is not relevant to your executable is
5798 located at the original location, a substitution rule is the only
5799 method available to point @value{GDBN} at the new location.
5802 @item directory @var{dirname} @dots{}
5803 @item dir @var{dirname} @dots{}
5804 Add directory @var{dirname} to the front of the source path. Several
5805 directory names may be given to this command, separated by @samp{:}
5806 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5807 part of absolute file names) or
5808 whitespace. You may specify a directory that is already in the source
5809 path; this moves it forward, so @value{GDBN} searches it sooner.
5813 @vindex $cdir@r{, convenience variable}
5814 @vindex $cwd@r{, convenience variable}
5815 @cindex compilation directory
5816 @cindex current directory
5817 @cindex working directory
5818 @cindex directory, current
5819 @cindex directory, compilation
5820 You can use the string @samp{$cdir} to refer to the compilation
5821 directory (if one is recorded), and @samp{$cwd} to refer to the current
5822 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5823 tracks the current working directory as it changes during your @value{GDBN}
5824 session, while the latter is immediately expanded to the current
5825 directory at the time you add an entry to the source path.
5828 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5830 @c RET-repeat for @code{directory} is explicitly disabled, but since
5831 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5833 @item show directories
5834 @kindex show directories
5835 Print the source path: show which directories it contains.
5837 @anchor{set substitute-path}
5838 @item set substitute-path @var{from} @var{to}
5839 @kindex set substitute-path
5840 Define a source path substitution rule, and add it at the end of the
5841 current list of existing substitution rules. If a rule with the same
5842 @var{from} was already defined, then the old rule is also deleted.
5844 For example, if the file @file{/foo/bar/baz.c} was moved to
5845 @file{/mnt/cross/baz.c}, then the command
5848 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5852 will tell @value{GDBN} to replace @samp{/usr/src} with
5853 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5854 @file{baz.c} even though it was moved.
5856 In the case when more than one substitution rule have been defined,
5857 the rules are evaluated one by one in the order where they have been
5858 defined. The first one matching, if any, is selected to perform
5861 For instance, if we had entered the following commands:
5864 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5865 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5869 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5870 @file{/mnt/include/defs.h} by using the first rule. However, it would
5871 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5872 @file{/mnt/src/lib/foo.c}.
5875 @item unset substitute-path [path]
5876 @kindex unset substitute-path
5877 If a path is specified, search the current list of substitution rules
5878 for a rule that would rewrite that path. Delete that rule if found.
5879 A warning is emitted by the debugger if no rule could be found.
5881 If no path is specified, then all substitution rules are deleted.
5883 @item show substitute-path [path]
5884 @kindex show substitute-path
5885 If a path is specified, then print the source path substitution rule
5886 which would rewrite that path, if any.
5888 If no path is specified, then print all existing source path substitution
5893 If your source path is cluttered with directories that are no longer of
5894 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5895 versions of source. You can correct the situation as follows:
5899 Use @code{directory} with no argument to reset the source path to its default value.
5902 Use @code{directory} with suitable arguments to reinstall the
5903 directories you want in the source path. You can add all the
5904 directories in one command.
5908 @section Source and Machine Code
5909 @cindex source line and its code address
5911 You can use the command @code{info line} to map source lines to program
5912 addresses (and vice versa), and the command @code{disassemble} to display
5913 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5914 mode, the @code{info line} command causes the arrow to point to the
5915 line specified. Also, @code{info line} prints addresses in symbolic form as
5920 @item info line @var{linespec}
5921 Print the starting and ending addresses of the compiled code for
5922 source line @var{linespec}. You can specify source lines in any of
5923 the ways documented in @ref{Specify Location}.
5926 For example, we can use @code{info line} to discover the location of
5927 the object code for the first line of function
5928 @code{m4_changequote}:
5930 @c FIXME: I think this example should also show the addresses in
5931 @c symbolic form, as they usually would be displayed.
5933 (@value{GDBP}) info line m4_changequote
5934 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5938 @cindex code address and its source line
5939 We can also inquire (using @code{*@var{addr}} as the form for
5940 @var{linespec}) what source line covers a particular address:
5942 (@value{GDBP}) info line *0x63ff
5943 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5946 @cindex @code{$_} and @code{info line}
5947 @cindex @code{x} command, default address
5948 @kindex x@r{(examine), and} info line
5949 After @code{info line}, the default address for the @code{x} command
5950 is changed to the starting address of the line, so that @samp{x/i} is
5951 sufficient to begin examining the machine code (@pxref{Memory,
5952 ,Examining Memory}). Also, this address is saved as the value of the
5953 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5958 @cindex assembly instructions
5959 @cindex instructions, assembly
5960 @cindex machine instructions
5961 @cindex listing machine instructions
5963 @itemx disassemble /m
5964 This specialized command dumps a range of memory as machine
5965 instructions. It can also print mixed source+disassembly by specifying
5966 the @code{/m} modifier.
5967 The default memory range is the function surrounding the
5968 program counter of the selected frame. A single argument to this
5969 command is a program counter value; @value{GDBN} dumps the function
5970 surrounding this value. Two arguments specify a range of addresses
5971 (first inclusive, second exclusive) to dump.
5974 The following example shows the disassembly of a range of addresses of
5975 HP PA-RISC 2.0 code:
5978 (@value{GDBP}) disas 0x32c4 0x32e4
5979 Dump of assembler code from 0x32c4 to 0x32e4:
5980 0x32c4 <main+204>: addil 0,dp
5981 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5982 0x32cc <main+212>: ldil 0x3000,r31
5983 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5984 0x32d4 <main+220>: ldo 0(r31),rp
5985 0x32d8 <main+224>: addil -0x800,dp
5986 0x32dc <main+228>: ldo 0x588(r1),r26
5987 0x32e0 <main+232>: ldil 0x3000,r31
5988 End of assembler dump.
5991 Here is an example showing mixed source+assembly for Intel x86:
5994 (@value{GDBP}) disas /m main
5995 Dump of assembler code for function main:
5997 0x08048330 <main+0>: push %ebp
5998 0x08048331 <main+1>: mov %esp,%ebp
5999 0x08048333 <main+3>: sub $0x8,%esp
6000 0x08048336 <main+6>: and $0xfffffff0,%esp
6001 0x08048339 <main+9>: sub $0x10,%esp
6003 6 printf ("Hello.\n");
6004 0x0804833c <main+12>: movl $0x8048440,(%esp)
6005 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
6009 0x08048348 <main+24>: mov $0x0,%eax
6010 0x0804834d <main+29>: leave
6011 0x0804834e <main+30>: ret
6013 End of assembler dump.
6016 Some architectures have more than one commonly-used set of instruction
6017 mnemonics or other syntax.
6019 For programs that were dynamically linked and use shared libraries,
6020 instructions that call functions or branch to locations in the shared
6021 libraries might show a seemingly bogus location---it's actually a
6022 location of the relocation table. On some architectures, @value{GDBN}
6023 might be able to resolve these to actual function names.
6026 @kindex set disassembly-flavor
6027 @cindex Intel disassembly flavor
6028 @cindex AT&T disassembly flavor
6029 @item set disassembly-flavor @var{instruction-set}
6030 Select the instruction set to use when disassembling the
6031 program via the @code{disassemble} or @code{x/i} commands.
6033 Currently this command is only defined for the Intel x86 family. You
6034 can set @var{instruction-set} to either @code{intel} or @code{att}.
6035 The default is @code{att}, the AT&T flavor used by default by Unix
6036 assemblers for x86-based targets.
6038 @kindex show disassembly-flavor
6039 @item show disassembly-flavor
6040 Show the current setting of the disassembly flavor.
6045 @chapter Examining Data
6047 @cindex printing data
6048 @cindex examining data
6051 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6052 @c document because it is nonstandard... Under Epoch it displays in a
6053 @c different window or something like that.
6054 The usual way to examine data in your program is with the @code{print}
6055 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6056 evaluates and prints the value of an expression of the language your
6057 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6058 Different Languages}).
6061 @item print @var{expr}
6062 @itemx print /@var{f} @var{expr}
6063 @var{expr} is an expression (in the source language). By default the
6064 value of @var{expr} is printed in a format appropriate to its data type;
6065 you can choose a different format by specifying @samp{/@var{f}}, where
6066 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6070 @itemx print /@var{f}
6071 @cindex reprint the last value
6072 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6073 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6074 conveniently inspect the same value in an alternative format.
6077 A more low-level way of examining data is with the @code{x} command.
6078 It examines data in memory at a specified address and prints it in a
6079 specified format. @xref{Memory, ,Examining Memory}.
6081 If you are interested in information about types, or about how the
6082 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6083 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6087 * Expressions:: Expressions
6088 * Ambiguous Expressions:: Ambiguous Expressions
6089 * Variables:: Program variables
6090 * Arrays:: Artificial arrays
6091 * Output Formats:: Output formats
6092 * Memory:: Examining memory
6093 * Auto Display:: Automatic display
6094 * Print Settings:: Print settings
6095 * Value History:: Value history
6096 * Convenience Vars:: Convenience variables
6097 * Registers:: Registers
6098 * Floating Point Hardware:: Floating point hardware
6099 * Vector Unit:: Vector Unit
6100 * OS Information:: Auxiliary data provided by operating system
6101 * Memory Region Attributes:: Memory region attributes
6102 * Dump/Restore Files:: Copy between memory and a file
6103 * Core File Generation:: Cause a program dump its core
6104 * Character Sets:: Debugging programs that use a different
6105 character set than GDB does
6106 * Caching Remote Data:: Data caching for remote targets
6107 * Searching Memory:: Searching memory for a sequence of bytes
6111 @section Expressions
6114 @code{print} and many other @value{GDBN} commands accept an expression and
6115 compute its value. Any kind of constant, variable or operator defined
6116 by the programming language you are using is valid in an expression in
6117 @value{GDBN}. This includes conditional expressions, function calls,
6118 casts, and string constants. It also includes preprocessor macros, if
6119 you compiled your program to include this information; see
6122 @cindex arrays in expressions
6123 @value{GDBN} supports array constants in expressions input by
6124 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6125 you can use the command @code{print @{1, 2, 3@}} to create an array
6126 of three integers. If you pass an array to a function or assign it
6127 to a program variable, @value{GDBN} copies the array to memory that
6128 is @code{malloc}ed in the target program.
6130 Because C is so widespread, most of the expressions shown in examples in
6131 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6132 Languages}, for information on how to use expressions in other
6135 In this section, we discuss operators that you can use in @value{GDBN}
6136 expressions regardless of your programming language.
6138 @cindex casts, in expressions
6139 Casts are supported in all languages, not just in C, because it is so
6140 useful to cast a number into a pointer in order to examine a structure
6141 at that address in memory.
6142 @c FIXME: casts supported---Mod2 true?
6144 @value{GDBN} supports these operators, in addition to those common
6145 to programming languages:
6149 @samp{@@} is a binary operator for treating parts of memory as arrays.
6150 @xref{Arrays, ,Artificial Arrays}, for more information.
6153 @samp{::} allows you to specify a variable in terms of the file or
6154 function where it is defined. @xref{Variables, ,Program Variables}.
6156 @cindex @{@var{type}@}
6157 @cindex type casting memory
6158 @cindex memory, viewing as typed object
6159 @cindex casts, to view memory
6160 @item @{@var{type}@} @var{addr}
6161 Refers to an object of type @var{type} stored at address @var{addr} in
6162 memory. @var{addr} may be any expression whose value is an integer or
6163 pointer (but parentheses are required around binary operators, just as in
6164 a cast). This construct is allowed regardless of what kind of data is
6165 normally supposed to reside at @var{addr}.
6168 @node Ambiguous Expressions
6169 @section Ambiguous Expressions
6170 @cindex ambiguous expressions
6172 Expressions can sometimes contain some ambiguous elements. For instance,
6173 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6174 a single function name to be defined several times, for application in
6175 different contexts. This is called @dfn{overloading}. Another example
6176 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6177 templates and is typically instantiated several times, resulting in
6178 the same function name being defined in different contexts.
6180 In some cases and depending on the language, it is possible to adjust
6181 the expression to remove the ambiguity. For instance in C@t{++}, you
6182 can specify the signature of the function you want to break on, as in
6183 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6184 qualified name of your function often makes the expression unambiguous
6187 When an ambiguity that needs to be resolved is detected, the debugger
6188 has the capability to display a menu of numbered choices for each
6189 possibility, and then waits for the selection with the prompt @samp{>}.
6190 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6191 aborts the current command. If the command in which the expression was
6192 used allows more than one choice to be selected, the next option in the
6193 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6196 For example, the following session excerpt shows an attempt to set a
6197 breakpoint at the overloaded symbol @code{String::after}.
6198 We choose three particular definitions of that function name:
6200 @c FIXME! This is likely to change to show arg type lists, at least
6203 (@value{GDBP}) b String::after
6206 [2] file:String.cc; line number:867
6207 [3] file:String.cc; line number:860
6208 [4] file:String.cc; line number:875
6209 [5] file:String.cc; line number:853
6210 [6] file:String.cc; line number:846
6211 [7] file:String.cc; line number:735
6213 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6214 Breakpoint 2 at 0xb344: file String.cc, line 875.
6215 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6216 Multiple breakpoints were set.
6217 Use the "delete" command to delete unwanted
6224 @kindex set multiple-symbols
6225 @item set multiple-symbols @var{mode}
6226 @cindex multiple-symbols menu
6228 This option allows you to adjust the debugger behavior when an expression
6231 By default, @var{mode} is set to @code{all}. If the command with which
6232 the expression is used allows more than one choice, then @value{GDBN}
6233 automatically selects all possible choices. For instance, inserting
6234 a breakpoint on a function using an ambiguous name results in a breakpoint
6235 inserted on each possible match. However, if a unique choice must be made,
6236 then @value{GDBN} uses the menu to help you disambiguate the expression.
6237 For instance, printing the address of an overloaded function will result
6238 in the use of the menu.
6240 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6241 when an ambiguity is detected.
6243 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6244 an error due to the ambiguity and the command is aborted.
6246 @kindex show multiple-symbols
6247 @item show multiple-symbols
6248 Show the current value of the @code{multiple-symbols} setting.
6252 @section Program Variables
6254 The most common kind of expression to use is the name of a variable
6257 Variables in expressions are understood in the selected stack frame
6258 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6262 global (or file-static)
6269 visible according to the scope rules of the
6270 programming language from the point of execution in that frame
6273 @noindent This means that in the function
6288 you can examine and use the variable @code{a} whenever your program is
6289 executing within the function @code{foo}, but you can only use or
6290 examine the variable @code{b} while your program is executing inside
6291 the block where @code{b} is declared.
6293 @cindex variable name conflict
6294 There is an exception: you can refer to a variable or function whose
6295 scope is a single source file even if the current execution point is not
6296 in this file. But it is possible to have more than one such variable or
6297 function with the same name (in different source files). If that
6298 happens, referring to that name has unpredictable effects. If you wish,
6299 you can specify a static variable in a particular function or file,
6300 using the colon-colon (@code{::}) notation:
6302 @cindex colon-colon, context for variables/functions
6304 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6305 @cindex @code{::}, context for variables/functions
6308 @var{file}::@var{variable}
6309 @var{function}::@var{variable}
6313 Here @var{file} or @var{function} is the name of the context for the
6314 static @var{variable}. In the case of file names, you can use quotes to
6315 make sure @value{GDBN} parses the file name as a single word---for example,
6316 to print a global value of @code{x} defined in @file{f2.c}:
6319 (@value{GDBP}) p 'f2.c'::x
6322 @cindex C@t{++} scope resolution
6323 This use of @samp{::} is very rarely in conflict with the very similar
6324 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6325 scope resolution operator in @value{GDBN} expressions.
6326 @c FIXME: Um, so what happens in one of those rare cases where it's in
6329 @cindex wrong values
6330 @cindex variable values, wrong
6331 @cindex function entry/exit, wrong values of variables
6332 @cindex optimized code, wrong values of variables
6334 @emph{Warning:} Occasionally, a local variable may appear to have the
6335 wrong value at certain points in a function---just after entry to a new
6336 scope, and just before exit.
6338 You may see this problem when you are stepping by machine instructions.
6339 This is because, on most machines, it takes more than one instruction to
6340 set up a stack frame (including local variable definitions); if you are
6341 stepping by machine instructions, variables may appear to have the wrong
6342 values until the stack frame is completely built. On exit, it usually
6343 also takes more than one machine instruction to destroy a stack frame;
6344 after you begin stepping through that group of instructions, local
6345 variable definitions may be gone.
6347 This may also happen when the compiler does significant optimizations.
6348 To be sure of always seeing accurate values, turn off all optimization
6351 @cindex ``No symbol "foo" in current context''
6352 Another possible effect of compiler optimizations is to optimize
6353 unused variables out of existence, or assign variables to registers (as
6354 opposed to memory addresses). Depending on the support for such cases
6355 offered by the debug info format used by the compiler, @value{GDBN}
6356 might not be able to display values for such local variables. If that
6357 happens, @value{GDBN} will print a message like this:
6360 No symbol "foo" in current context.
6363 To solve such problems, either recompile without optimizations, or use a
6364 different debug info format, if the compiler supports several such
6365 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6366 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6367 produces debug info in a format that is superior to formats such as
6368 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6369 an effective form for debug info. @xref{Debugging Options,,Options
6370 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6371 Compiler Collection (GCC)}.
6372 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6373 that are best suited to C@t{++} programs.
6375 If you ask to print an object whose contents are unknown to
6376 @value{GDBN}, e.g., because its data type is not completely specified
6377 by the debug information, @value{GDBN} will say @samp{<incomplete
6378 type>}. @xref{Symbols, incomplete type}, for more about this.
6380 Strings are identified as arrays of @code{char} values without specified
6381 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6382 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6383 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6384 defines literal string type @code{"char"} as @code{char} without a sign.
6389 signed char var1[] = "A";
6392 You get during debugging
6397 $2 = @{65 'A', 0 '\0'@}
6401 @section Artificial Arrays
6403 @cindex artificial array
6405 @kindex @@@r{, referencing memory as an array}
6406 It is often useful to print out several successive objects of the
6407 same type in memory; a section of an array, or an array of
6408 dynamically determined size for which only a pointer exists in the
6411 You can do this by referring to a contiguous span of memory as an
6412 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6413 operand of @samp{@@} should be the first element of the desired array
6414 and be an individual object. The right operand should be the desired length
6415 of the array. The result is an array value whose elements are all of
6416 the type of the left argument. The first element is actually the left
6417 argument; the second element comes from bytes of memory immediately
6418 following those that hold the first element, and so on. Here is an
6419 example. If a program says
6422 int *array = (int *) malloc (len * sizeof (int));
6426 you can print the contents of @code{array} with
6432 The left operand of @samp{@@} must reside in memory. Array values made
6433 with @samp{@@} in this way behave just like other arrays in terms of
6434 subscripting, and are coerced to pointers when used in expressions.
6435 Artificial arrays most often appear in expressions via the value history
6436 (@pxref{Value History, ,Value History}), after printing one out.
6438 Another way to create an artificial array is to use a cast.
6439 This re-interprets a value as if it were an array.
6440 The value need not be in memory:
6442 (@value{GDBP}) p/x (short[2])0x12345678
6443 $1 = @{0x1234, 0x5678@}
6446 As a convenience, if you leave the array length out (as in
6447 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6448 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6450 (@value{GDBP}) p/x (short[])0x12345678
6451 $2 = @{0x1234, 0x5678@}
6454 Sometimes the artificial array mechanism is not quite enough; in
6455 moderately complex data structures, the elements of interest may not
6456 actually be adjacent---for example, if you are interested in the values
6457 of pointers in an array. One useful work-around in this situation is
6458 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6459 Variables}) as a counter in an expression that prints the first
6460 interesting value, and then repeat that expression via @key{RET}. For
6461 instance, suppose you have an array @code{dtab} of pointers to
6462 structures, and you are interested in the values of a field @code{fv}
6463 in each structure. Here is an example of what you might type:
6473 @node Output Formats
6474 @section Output Formats
6476 @cindex formatted output
6477 @cindex output formats
6478 By default, @value{GDBN} prints a value according to its data type. Sometimes
6479 this is not what you want. For example, you might want to print a number
6480 in hex, or a pointer in decimal. Or you might want to view data in memory
6481 at a certain address as a character string or as an instruction. To do
6482 these things, specify an @dfn{output format} when you print a value.
6484 The simplest use of output formats is to say how to print a value
6485 already computed. This is done by starting the arguments of the
6486 @code{print} command with a slash and a format letter. The format
6487 letters supported are:
6491 Regard the bits of the value as an integer, and print the integer in
6495 Print as integer in signed decimal.
6498 Print as integer in unsigned decimal.
6501 Print as integer in octal.
6504 Print as integer in binary. The letter @samp{t} stands for ``two''.
6505 @footnote{@samp{b} cannot be used because these format letters are also
6506 used with the @code{x} command, where @samp{b} stands for ``byte'';
6507 see @ref{Memory,,Examining Memory}.}
6510 @cindex unknown address, locating
6511 @cindex locate address
6512 Print as an address, both absolute in hexadecimal and as an offset from
6513 the nearest preceding symbol. You can use this format used to discover
6514 where (in what function) an unknown address is located:
6517 (@value{GDBP}) p/a 0x54320
6518 $3 = 0x54320 <_initialize_vx+396>
6522 The command @code{info symbol 0x54320} yields similar results.
6523 @xref{Symbols, info symbol}.
6526 Regard as an integer and print it as a character constant. This
6527 prints both the numerical value and its character representation. The
6528 character representation is replaced with the octal escape @samp{\nnn}
6529 for characters outside the 7-bit @sc{ascii} range.
6531 Without this format, @value{GDBN} displays @code{char},
6532 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6533 constants. Single-byte members of vectors are displayed as integer
6537 Regard the bits of the value as a floating point number and print
6538 using typical floating point syntax.
6541 @cindex printing strings
6542 @cindex printing byte arrays
6543 Regard as a string, if possible. With this format, pointers to single-byte
6544 data are displayed as null-terminated strings and arrays of single-byte data
6545 are displayed as fixed-length strings. Other values are displayed in their
6548 Without this format, @value{GDBN} displays pointers to and arrays of
6549 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6550 strings. Single-byte members of a vector are displayed as an integer
6554 For example, to print the program counter in hex (@pxref{Registers}), type
6561 Note that no space is required before the slash; this is because command
6562 names in @value{GDBN} cannot contain a slash.
6564 To reprint the last value in the value history with a different format,
6565 you can use the @code{print} command with just a format and no
6566 expression. For example, @samp{p/x} reprints the last value in hex.
6569 @section Examining Memory
6571 You can use the command @code{x} (for ``examine'') to examine memory in
6572 any of several formats, independently of your program's data types.
6574 @cindex examining memory
6576 @kindex x @r{(examine memory)}
6577 @item x/@var{nfu} @var{addr}
6580 Use the @code{x} command to examine memory.
6583 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6584 much memory to display and how to format it; @var{addr} is an
6585 expression giving the address where you want to start displaying memory.
6586 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6587 Several commands set convenient defaults for @var{addr}.
6590 @item @var{n}, the repeat count
6591 The repeat count is a decimal integer; the default is 1. It specifies
6592 how much memory (counting by units @var{u}) to display.
6593 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6596 @item @var{f}, the display format
6597 The display format is one of the formats used by @code{print}
6598 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6599 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6600 The default is @samp{x} (hexadecimal) initially. The default changes
6601 each time you use either @code{x} or @code{print}.
6603 @item @var{u}, the unit size
6604 The unit size is any of
6610 Halfwords (two bytes).
6612 Words (four bytes). This is the initial default.
6614 Giant words (eight bytes).
6617 Each time you specify a unit size with @code{x}, that size becomes the
6618 default unit the next time you use @code{x}. (For the @samp{s} and
6619 @samp{i} formats, the unit size is ignored and is normally not written.)
6621 @item @var{addr}, starting display address
6622 @var{addr} is the address where you want @value{GDBN} to begin displaying
6623 memory. The expression need not have a pointer value (though it may);
6624 it is always interpreted as an integer address of a byte of memory.
6625 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6626 @var{addr} is usually just after the last address examined---but several
6627 other commands also set the default address: @code{info breakpoints} (to
6628 the address of the last breakpoint listed), @code{info line} (to the
6629 starting address of a line), and @code{print} (if you use it to display
6630 a value from memory).
6633 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6634 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6635 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6636 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6637 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6639 Since the letters indicating unit sizes are all distinct from the
6640 letters specifying output formats, you do not have to remember whether
6641 unit size or format comes first; either order works. The output
6642 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6643 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6645 Even though the unit size @var{u} is ignored for the formats @samp{s}
6646 and @samp{i}, you might still want to use a count @var{n}; for example,
6647 @samp{3i} specifies that you want to see three machine instructions,
6648 including any operands. For convenience, especially when used with
6649 the @code{display} command, the @samp{i} format also prints branch delay
6650 slot instructions, if any, beyond the count specified, which immediately
6651 follow the last instruction that is within the count. The command
6652 @code{disassemble} gives an alternative way of inspecting machine
6653 instructions; see @ref{Machine Code,,Source and Machine Code}.
6655 All the defaults for the arguments to @code{x} are designed to make it
6656 easy to continue scanning memory with minimal specifications each time
6657 you use @code{x}. For example, after you have inspected three machine
6658 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6659 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6660 the repeat count @var{n} is used again; the other arguments default as
6661 for successive uses of @code{x}.
6663 @cindex @code{$_}, @code{$__}, and value history
6664 The addresses and contents printed by the @code{x} command are not saved
6665 in the value history because there is often too much of them and they
6666 would get in the way. Instead, @value{GDBN} makes these values available for
6667 subsequent use in expressions as values of the convenience variables
6668 @code{$_} and @code{$__}. After an @code{x} command, the last address
6669 examined is available for use in expressions in the convenience variable
6670 @code{$_}. The contents of that address, as examined, are available in
6671 the convenience variable @code{$__}.
6673 If the @code{x} command has a repeat count, the address and contents saved
6674 are from the last memory unit printed; this is not the same as the last
6675 address printed if several units were printed on the last line of output.
6677 @cindex remote memory comparison
6678 @cindex verify remote memory image
6679 When you are debugging a program running on a remote target machine
6680 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6681 remote machine's memory against the executable file you downloaded to
6682 the target. The @code{compare-sections} command is provided for such
6686 @kindex compare-sections
6687 @item compare-sections @r{[}@var{section-name}@r{]}
6688 Compare the data of a loadable section @var{section-name} in the
6689 executable file of the program being debugged with the same section in
6690 the remote machine's memory, and report any mismatches. With no
6691 arguments, compares all loadable sections. This command's
6692 availability depends on the target's support for the @code{"qCRC"}
6697 @section Automatic Display
6698 @cindex automatic display
6699 @cindex display of expressions
6701 If you find that you want to print the value of an expression frequently
6702 (to see how it changes), you might want to add it to the @dfn{automatic
6703 display list} so that @value{GDBN} prints its value each time your program stops.
6704 Each expression added to the list is given a number to identify it;
6705 to remove an expression from the list, you specify that number.
6706 The automatic display looks like this:
6710 3: bar[5] = (struct hack *) 0x3804
6714 This display shows item numbers, expressions and their current values. As with
6715 displays you request manually using @code{x} or @code{print}, you can
6716 specify the output format you prefer; in fact, @code{display} decides
6717 whether to use @code{print} or @code{x} depending your format
6718 specification---it uses @code{x} if you specify either the @samp{i}
6719 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6723 @item display @var{expr}
6724 Add the expression @var{expr} to the list of expressions to display
6725 each time your program stops. @xref{Expressions, ,Expressions}.
6727 @code{display} does not repeat if you press @key{RET} again after using it.
6729 @item display/@var{fmt} @var{expr}
6730 For @var{fmt} specifying only a display format and not a size or
6731 count, add the expression @var{expr} to the auto-display list but
6732 arrange to display it each time in the specified format @var{fmt}.
6733 @xref{Output Formats,,Output Formats}.
6735 @item display/@var{fmt} @var{addr}
6736 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6737 number of units, add the expression @var{addr} as a memory address to
6738 be examined each time your program stops. Examining means in effect
6739 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6742 For example, @samp{display/i $pc} can be helpful, to see the machine
6743 instruction about to be executed each time execution stops (@samp{$pc}
6744 is a common name for the program counter; @pxref{Registers, ,Registers}).
6747 @kindex delete display
6749 @item undisplay @var{dnums}@dots{}
6750 @itemx delete display @var{dnums}@dots{}
6751 Remove item numbers @var{dnums} from the list of expressions to display.
6753 @code{undisplay} does not repeat if you press @key{RET} after using it.
6754 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6756 @kindex disable display
6757 @item disable display @var{dnums}@dots{}
6758 Disable the display of item numbers @var{dnums}. A disabled display
6759 item is not printed automatically, but is not forgotten. It may be
6760 enabled again later.
6762 @kindex enable display
6763 @item enable display @var{dnums}@dots{}
6764 Enable display of item numbers @var{dnums}. It becomes effective once
6765 again in auto display of its expression, until you specify otherwise.
6768 Display the current values of the expressions on the list, just as is
6769 done when your program stops.
6771 @kindex info display
6773 Print the list of expressions previously set up to display
6774 automatically, each one with its item number, but without showing the
6775 values. This includes disabled expressions, which are marked as such.
6776 It also includes expressions which would not be displayed right now
6777 because they refer to automatic variables not currently available.
6780 @cindex display disabled out of scope
6781 If a display expression refers to local variables, then it does not make
6782 sense outside the lexical context for which it was set up. Such an
6783 expression is disabled when execution enters a context where one of its
6784 variables is not defined. For example, if you give the command
6785 @code{display last_char} while inside a function with an argument
6786 @code{last_char}, @value{GDBN} displays this argument while your program
6787 continues to stop inside that function. When it stops elsewhere---where
6788 there is no variable @code{last_char}---the display is disabled
6789 automatically. The next time your program stops where @code{last_char}
6790 is meaningful, you can enable the display expression once again.
6792 @node Print Settings
6793 @section Print Settings
6795 @cindex format options
6796 @cindex print settings
6797 @value{GDBN} provides the following ways to control how arrays, structures,
6798 and symbols are printed.
6801 These settings are useful for debugging programs in any language:
6805 @item set print address
6806 @itemx set print address on
6807 @cindex print/don't print memory addresses
6808 @value{GDBN} prints memory addresses showing the location of stack
6809 traces, structure values, pointer values, breakpoints, and so forth,
6810 even when it also displays the contents of those addresses. The default
6811 is @code{on}. For example, this is what a stack frame display looks like with
6812 @code{set print address on}:
6817 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6819 530 if (lquote != def_lquote)
6823 @item set print address off
6824 Do not print addresses when displaying their contents. For example,
6825 this is the same stack frame displayed with @code{set print address off}:
6829 (@value{GDBP}) set print addr off
6831 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6832 530 if (lquote != def_lquote)
6836 You can use @samp{set print address off} to eliminate all machine
6837 dependent displays from the @value{GDBN} interface. For example, with
6838 @code{print address off}, you should get the same text for backtraces on
6839 all machines---whether or not they involve pointer arguments.
6842 @item show print address
6843 Show whether or not addresses are to be printed.
6846 When @value{GDBN} prints a symbolic address, it normally prints the
6847 closest earlier symbol plus an offset. If that symbol does not uniquely
6848 identify the address (for example, it is a name whose scope is a single
6849 source file), you may need to clarify. One way to do this is with
6850 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6851 you can set @value{GDBN} to print the source file and line number when
6852 it prints a symbolic address:
6855 @item set print symbol-filename on
6856 @cindex source file and line of a symbol
6857 @cindex symbol, source file and line
6858 Tell @value{GDBN} to print the source file name and line number of a
6859 symbol in the symbolic form of an address.
6861 @item set print symbol-filename off
6862 Do not print source file name and line number of a symbol. This is the
6865 @item show print symbol-filename
6866 Show whether or not @value{GDBN} will print the source file name and
6867 line number of a symbol in the symbolic form of an address.
6870 Another situation where it is helpful to show symbol filenames and line
6871 numbers is when disassembling code; @value{GDBN} shows you the line
6872 number and source file that corresponds to each instruction.
6874 Also, you may wish to see the symbolic form only if the address being
6875 printed is reasonably close to the closest earlier symbol:
6878 @item set print max-symbolic-offset @var{max-offset}
6879 @cindex maximum value for offset of closest symbol
6880 Tell @value{GDBN} to only display the symbolic form of an address if the
6881 offset between the closest earlier symbol and the address is less than
6882 @var{max-offset}. The default is 0, which tells @value{GDBN}
6883 to always print the symbolic form of an address if any symbol precedes it.
6885 @item show print max-symbolic-offset
6886 Ask how large the maximum offset is that @value{GDBN} prints in a
6890 @cindex wild pointer, interpreting
6891 @cindex pointer, finding referent
6892 If you have a pointer and you are not sure where it points, try
6893 @samp{set print symbol-filename on}. Then you can determine the name
6894 and source file location of the variable where it points, using
6895 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6896 For example, here @value{GDBN} shows that a variable @code{ptt} points
6897 at another variable @code{t}, defined in @file{hi2.c}:
6900 (@value{GDBP}) set print symbol-filename on
6901 (@value{GDBP}) p/a ptt
6902 $4 = 0xe008 <t in hi2.c>
6906 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6907 does not show the symbol name and filename of the referent, even with
6908 the appropriate @code{set print} options turned on.
6911 Other settings control how different kinds of objects are printed:
6914 @item set print array
6915 @itemx set print array on
6916 @cindex pretty print arrays
6917 Pretty print arrays. This format is more convenient to read,
6918 but uses more space. The default is off.
6920 @item set print array off
6921 Return to compressed format for arrays.
6923 @item show print array
6924 Show whether compressed or pretty format is selected for displaying
6927 @cindex print array indexes
6928 @item set print array-indexes
6929 @itemx set print array-indexes on
6930 Print the index of each element when displaying arrays. May be more
6931 convenient to locate a given element in the array or quickly find the
6932 index of a given element in that printed array. The default is off.
6934 @item set print array-indexes off
6935 Stop printing element indexes when displaying arrays.
6937 @item show print array-indexes
6938 Show whether the index of each element is printed when displaying
6941 @item set print elements @var{number-of-elements}
6942 @cindex number of array elements to print
6943 @cindex limit on number of printed array elements
6944 Set a limit on how many elements of an array @value{GDBN} will print.
6945 If @value{GDBN} is printing a large array, it stops printing after it has
6946 printed the number of elements set by the @code{set print elements} command.
6947 This limit also applies to the display of strings.
6948 When @value{GDBN} starts, this limit is set to 200.
6949 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6951 @item show print elements
6952 Display the number of elements of a large array that @value{GDBN} will print.
6953 If the number is 0, then the printing is unlimited.
6955 @item set print frame-arguments @var{value}
6956 @cindex printing frame argument values
6957 @cindex print all frame argument values
6958 @cindex print frame argument values for scalars only
6959 @cindex do not print frame argument values
6960 This command allows to control how the values of arguments are printed
6961 when the debugger prints a frame (@pxref{Frames}). The possible
6966 The values of all arguments are printed. This is the default.
6969 Print the value of an argument only if it is a scalar. The value of more
6970 complex arguments such as arrays, structures, unions, etc, is replaced
6971 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6974 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6979 None of the argument values are printed. Instead, the value of each argument
6980 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6983 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6988 By default, all argument values are always printed. But this command
6989 can be useful in several cases. For instance, it can be used to reduce
6990 the amount of information printed in each frame, making the backtrace
6991 more readable. Also, this command can be used to improve performance
6992 when displaying Ada frames, because the computation of large arguments
6993 can sometimes be CPU-intensive, especiallly in large applications.
6994 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6995 avoids this computation, thus speeding up the display of each Ada frame.
6997 @item show print frame-arguments
6998 Show how the value of arguments should be displayed when printing a frame.
7000 @item set print repeats
7001 @cindex repeated array elements
7002 Set the threshold for suppressing display of repeated array
7003 elements. When the number of consecutive identical elements of an
7004 array exceeds the threshold, @value{GDBN} prints the string
7005 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7006 identical repetitions, instead of displaying the identical elements
7007 themselves. Setting the threshold to zero will cause all elements to
7008 be individually printed. The default threshold is 10.
7010 @item show print repeats
7011 Display the current threshold for printing repeated identical
7014 @item set print null-stop
7015 @cindex @sc{null} elements in arrays
7016 Cause @value{GDBN} to stop printing the characters of an array when the first
7017 @sc{null} is encountered. This is useful when large arrays actually
7018 contain only short strings.
7021 @item show print null-stop
7022 Show whether @value{GDBN} stops printing an array on the first
7023 @sc{null} character.
7025 @item set print pretty on
7026 @cindex print structures in indented form
7027 @cindex indentation in structure display
7028 Cause @value{GDBN} to print structures in an indented format with one member
7029 per line, like this:
7044 @item set print pretty off
7045 Cause @value{GDBN} to print structures in a compact format, like this:
7049 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7050 meat = 0x54 "Pork"@}
7055 This is the default format.
7057 @item show print pretty
7058 Show which format @value{GDBN} is using to print structures.
7060 @item set print sevenbit-strings on
7061 @cindex eight-bit characters in strings
7062 @cindex octal escapes in strings
7063 Print using only seven-bit characters; if this option is set,
7064 @value{GDBN} displays any eight-bit characters (in strings or
7065 character values) using the notation @code{\}@var{nnn}. This setting is
7066 best if you are working in English (@sc{ascii}) and you use the
7067 high-order bit of characters as a marker or ``meta'' bit.
7069 @item set print sevenbit-strings off
7070 Print full eight-bit characters. This allows the use of more
7071 international character sets, and is the default.
7073 @item show print sevenbit-strings
7074 Show whether or not @value{GDBN} is printing only seven-bit characters.
7076 @item set print union on
7077 @cindex unions in structures, printing
7078 Tell @value{GDBN} to print unions which are contained in structures
7079 and other unions. This is the default setting.
7081 @item set print union off
7082 Tell @value{GDBN} not to print unions which are contained in
7083 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7086 @item show print union
7087 Ask @value{GDBN} whether or not it will print unions which are contained in
7088 structures and other unions.
7090 For example, given the declarations
7093 typedef enum @{Tree, Bug@} Species;
7094 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7095 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7106 struct thing foo = @{Tree, @{Acorn@}@};
7110 with @code{set print union on} in effect @samp{p foo} would print
7113 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7117 and with @code{set print union off} in effect it would print
7120 $1 = @{it = Tree, form = @{...@}@}
7124 @code{set print union} affects programs written in C-like languages
7130 These settings are of interest when debugging C@t{++} programs:
7133 @cindex demangling C@t{++} names
7134 @item set print demangle
7135 @itemx set print demangle on
7136 Print C@t{++} names in their source form rather than in the encoded
7137 (``mangled'') form passed to the assembler and linker for type-safe
7138 linkage. The default is on.
7140 @item show print demangle
7141 Show whether C@t{++} names are printed in mangled or demangled form.
7143 @item set print asm-demangle
7144 @itemx set print asm-demangle on
7145 Print C@t{++} names in their source form rather than their mangled form, even
7146 in assembler code printouts such as instruction disassemblies.
7149 @item show print asm-demangle
7150 Show whether C@t{++} names in assembly listings are printed in mangled
7153 @cindex C@t{++} symbol decoding style
7154 @cindex symbol decoding style, C@t{++}
7155 @kindex set demangle-style
7156 @item set demangle-style @var{style}
7157 Choose among several encoding schemes used by different compilers to
7158 represent C@t{++} names. The choices for @var{style} are currently:
7162 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7165 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7166 This is the default.
7169 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7172 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7175 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7176 @strong{Warning:} this setting alone is not sufficient to allow
7177 debugging @code{cfront}-generated executables. @value{GDBN} would
7178 require further enhancement to permit that.
7181 If you omit @var{style}, you will see a list of possible formats.
7183 @item show demangle-style
7184 Display the encoding style currently in use for decoding C@t{++} symbols.
7186 @item set print object
7187 @itemx set print object on
7188 @cindex derived type of an object, printing
7189 @cindex display derived types
7190 When displaying a pointer to an object, identify the @emph{actual}
7191 (derived) type of the object rather than the @emph{declared} type, using
7192 the virtual function table.
7194 @item set print object off
7195 Display only the declared type of objects, without reference to the
7196 virtual function table. This is the default setting.
7198 @item show print object
7199 Show whether actual, or declared, object types are displayed.
7201 @item set print static-members
7202 @itemx set print static-members on
7203 @cindex static members of C@t{++} objects
7204 Print static members when displaying a C@t{++} object. The default is on.
7206 @item set print static-members off
7207 Do not print static members when displaying a C@t{++} object.
7209 @item show print static-members
7210 Show whether C@t{++} static members are printed or not.
7212 @item set print pascal_static-members
7213 @itemx set print pascal_static-members on
7214 @cindex static members of Pascal objects
7215 @cindex Pascal objects, static members display
7216 Print static members when displaying a Pascal object. The default is on.
7218 @item set print pascal_static-members off
7219 Do not print static members when displaying a Pascal object.
7221 @item show print pascal_static-members
7222 Show whether Pascal static members are printed or not.
7224 @c These don't work with HP ANSI C++ yet.
7225 @item set print vtbl
7226 @itemx set print vtbl on
7227 @cindex pretty print C@t{++} virtual function tables
7228 @cindex virtual functions (C@t{++}) display
7229 @cindex VTBL display
7230 Pretty print C@t{++} virtual function tables. The default is off.
7231 (The @code{vtbl} commands do not work on programs compiled with the HP
7232 ANSI C@t{++} compiler (@code{aCC}).)
7234 @item set print vtbl off
7235 Do not pretty print C@t{++} virtual function tables.
7237 @item show print vtbl
7238 Show whether C@t{++} virtual function tables are pretty printed, or not.
7242 @section Value History
7244 @cindex value history
7245 @cindex history of values printed by @value{GDBN}
7246 Values printed by the @code{print} command are saved in the @value{GDBN}
7247 @dfn{value history}. This allows you to refer to them in other expressions.
7248 Values are kept until the symbol table is re-read or discarded
7249 (for example with the @code{file} or @code{symbol-file} commands).
7250 When the symbol table changes, the value history is discarded,
7251 since the values may contain pointers back to the types defined in the
7256 @cindex history number
7257 The values printed are given @dfn{history numbers} by which you can
7258 refer to them. These are successive integers starting with one.
7259 @code{print} shows you the history number assigned to a value by
7260 printing @samp{$@var{num} = } before the value; here @var{num} is the
7263 To refer to any previous value, use @samp{$} followed by the value's
7264 history number. The way @code{print} labels its output is designed to
7265 remind you of this. Just @code{$} refers to the most recent value in
7266 the history, and @code{$$} refers to the value before that.
7267 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7268 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7269 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7271 For example, suppose you have just printed a pointer to a structure and
7272 want to see the contents of the structure. It suffices to type
7278 If you have a chain of structures where the component @code{next} points
7279 to the next one, you can print the contents of the next one with this:
7286 You can print successive links in the chain by repeating this
7287 command---which you can do by just typing @key{RET}.
7289 Note that the history records values, not expressions. If the value of
7290 @code{x} is 4 and you type these commands:
7298 then the value recorded in the value history by the @code{print} command
7299 remains 4 even though the value of @code{x} has changed.
7304 Print the last ten values in the value history, with their item numbers.
7305 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7306 values} does not change the history.
7308 @item show values @var{n}
7309 Print ten history values centered on history item number @var{n}.
7312 Print ten history values just after the values last printed. If no more
7313 values are available, @code{show values +} produces no display.
7316 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7317 same effect as @samp{show values +}.
7319 @node Convenience Vars
7320 @section Convenience Variables
7322 @cindex convenience variables
7323 @cindex user-defined variables
7324 @value{GDBN} provides @dfn{convenience variables} that you can use within
7325 @value{GDBN} to hold on to a value and refer to it later. These variables
7326 exist entirely within @value{GDBN}; they are not part of your program, and
7327 setting a convenience variable has no direct effect on further execution
7328 of your program. That is why you can use them freely.
7330 Convenience variables are prefixed with @samp{$}. Any name preceded by
7331 @samp{$} can be used for a convenience variable, unless it is one of
7332 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7333 (Value history references, in contrast, are @emph{numbers} preceded
7334 by @samp{$}. @xref{Value History, ,Value History}.)
7336 You can save a value in a convenience variable with an assignment
7337 expression, just as you would set a variable in your program.
7341 set $foo = *object_ptr
7345 would save in @code{$foo} the value contained in the object pointed to by
7348 Using a convenience variable for the first time creates it, but its
7349 value is @code{void} until you assign a new value. You can alter the
7350 value with another assignment at any time.
7352 Convenience variables have no fixed types. You can assign a convenience
7353 variable any type of value, including structures and arrays, even if
7354 that variable already has a value of a different type. The convenience
7355 variable, when used as an expression, has the type of its current value.
7358 @kindex show convenience
7359 @cindex show all user variables
7360 @item show convenience
7361 Print a list of convenience variables used so far, and their values.
7362 Abbreviated @code{show conv}.
7364 @kindex init-if-undefined
7365 @cindex convenience variables, initializing
7366 @item init-if-undefined $@var{variable} = @var{expression}
7367 Set a convenience variable if it has not already been set. This is useful
7368 for user-defined commands that keep some state. It is similar, in concept,
7369 to using local static variables with initializers in C (except that
7370 convenience variables are global). It can also be used to allow users to
7371 override default values used in a command script.
7373 If the variable is already defined then the expression is not evaluated so
7374 any side-effects do not occur.
7377 One of the ways to use a convenience variable is as a counter to be
7378 incremented or a pointer to be advanced. For example, to print
7379 a field from successive elements of an array of structures:
7383 print bar[$i++]->contents
7387 Repeat that command by typing @key{RET}.
7389 Some convenience variables are created automatically by @value{GDBN} and given
7390 values likely to be useful.
7393 @vindex $_@r{, convenience variable}
7395 The variable @code{$_} is automatically set by the @code{x} command to
7396 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7397 commands which provide a default address for @code{x} to examine also
7398 set @code{$_} to that address; these commands include @code{info line}
7399 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7400 except when set by the @code{x} command, in which case it is a pointer
7401 to the type of @code{$__}.
7403 @vindex $__@r{, convenience variable}
7405 The variable @code{$__} is automatically set by the @code{x} command
7406 to the value found in the last address examined. Its type is chosen
7407 to match the format in which the data was printed.
7410 @vindex $_exitcode@r{, convenience variable}
7411 The variable @code{$_exitcode} is automatically set to the exit code when
7412 the program being debugged terminates.
7415 @vindex $_siginfo@r{, convenience variable}
7416 The variable @code{$_siginfo} is bound to extra signal information
7417 inspection (@pxref{extra signal information}).
7420 On HP-UX systems, if you refer to a function or variable name that
7421 begins with a dollar sign, @value{GDBN} searches for a user or system
7422 name first, before it searches for a convenience variable.
7428 You can refer to machine register contents, in expressions, as variables
7429 with names starting with @samp{$}. The names of registers are different
7430 for each machine; use @code{info registers} to see the names used on
7434 @kindex info registers
7435 @item info registers
7436 Print the names and values of all registers except floating-point
7437 and vector registers (in the selected stack frame).
7439 @kindex info all-registers
7440 @cindex floating point registers
7441 @item info all-registers
7442 Print the names and values of all registers, including floating-point
7443 and vector registers (in the selected stack frame).
7445 @item info registers @var{regname} @dots{}
7446 Print the @dfn{relativized} value of each specified register @var{regname}.
7447 As discussed in detail below, register values are normally relative to
7448 the selected stack frame. @var{regname} may be any register name valid on
7449 the machine you are using, with or without the initial @samp{$}.
7452 @cindex stack pointer register
7453 @cindex program counter register
7454 @cindex process status register
7455 @cindex frame pointer register
7456 @cindex standard registers
7457 @value{GDBN} has four ``standard'' register names that are available (in
7458 expressions) on most machines---whenever they do not conflict with an
7459 architecture's canonical mnemonics for registers. The register names
7460 @code{$pc} and @code{$sp} are used for the program counter register and
7461 the stack pointer. @code{$fp} is used for a register that contains a
7462 pointer to the current stack frame, and @code{$ps} is used for a
7463 register that contains the processor status. For example,
7464 you could print the program counter in hex with
7471 or print the instruction to be executed next with
7478 or add four to the stack pointer@footnote{This is a way of removing
7479 one word from the stack, on machines where stacks grow downward in
7480 memory (most machines, nowadays). This assumes that the innermost
7481 stack frame is selected; setting @code{$sp} is not allowed when other
7482 stack frames are selected. To pop entire frames off the stack,
7483 regardless of machine architecture, use @code{return};
7484 see @ref{Returning, ,Returning from a Function}.} with
7490 Whenever possible, these four standard register names are available on
7491 your machine even though the machine has different canonical mnemonics,
7492 so long as there is no conflict. The @code{info registers} command
7493 shows the canonical names. For example, on the SPARC, @code{info
7494 registers} displays the processor status register as @code{$psr} but you
7495 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7496 is an alias for the @sc{eflags} register.
7498 @value{GDBN} always considers the contents of an ordinary register as an
7499 integer when the register is examined in this way. Some machines have
7500 special registers which can hold nothing but floating point; these
7501 registers are considered to have floating point values. There is no way
7502 to refer to the contents of an ordinary register as floating point value
7503 (although you can @emph{print} it as a floating point value with
7504 @samp{print/f $@var{regname}}).
7506 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7507 means that the data format in which the register contents are saved by
7508 the operating system is not the same one that your program normally
7509 sees. For example, the registers of the 68881 floating point
7510 coprocessor are always saved in ``extended'' (raw) format, but all C
7511 programs expect to work with ``double'' (virtual) format. In such
7512 cases, @value{GDBN} normally works with the virtual format only (the format
7513 that makes sense for your program), but the @code{info registers} command
7514 prints the data in both formats.
7516 @cindex SSE registers (x86)
7517 @cindex MMX registers (x86)
7518 Some machines have special registers whose contents can be interpreted
7519 in several different ways. For example, modern x86-based machines
7520 have SSE and MMX registers that can hold several values packed
7521 together in several different formats. @value{GDBN} refers to such
7522 registers in @code{struct} notation:
7525 (@value{GDBP}) print $xmm1
7527 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7528 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7529 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7530 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7531 v4_int32 = @{0, 20657912, 11, 13@},
7532 v2_int64 = @{88725056443645952, 55834574859@},
7533 uint128 = 0x0000000d0000000b013b36f800000000
7538 To set values of such registers, you need to tell @value{GDBN} which
7539 view of the register you wish to change, as if you were assigning
7540 value to a @code{struct} member:
7543 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7546 Normally, register values are relative to the selected stack frame
7547 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7548 value that the register would contain if all stack frames farther in
7549 were exited and their saved registers restored. In order to see the
7550 true contents of hardware registers, you must select the innermost
7551 frame (with @samp{frame 0}).
7553 However, @value{GDBN} must deduce where registers are saved, from the machine
7554 code generated by your compiler. If some registers are not saved, or if
7555 @value{GDBN} is unable to locate the saved registers, the selected stack
7556 frame makes no difference.
7558 @node Floating Point Hardware
7559 @section Floating Point Hardware
7560 @cindex floating point
7562 Depending on the configuration, @value{GDBN} may be able to give
7563 you more information about the status of the floating point hardware.
7568 Display hardware-dependent information about the floating
7569 point unit. The exact contents and layout vary depending on the
7570 floating point chip. Currently, @samp{info float} is supported on
7571 the ARM and x86 machines.
7575 @section Vector Unit
7578 Depending on the configuration, @value{GDBN} may be able to give you
7579 more information about the status of the vector unit.
7584 Display information about the vector unit. The exact contents and
7585 layout vary depending on the hardware.
7588 @node OS Information
7589 @section Operating System Auxiliary Information
7590 @cindex OS information
7592 @value{GDBN} provides interfaces to useful OS facilities that can help
7593 you debug your program.
7595 @cindex @code{ptrace} system call
7596 @cindex @code{struct user} contents
7597 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7598 machines), it interfaces with the inferior via the @code{ptrace}
7599 system call. The operating system creates a special sata structure,
7600 called @code{struct user}, for this interface. You can use the
7601 command @code{info udot} to display the contents of this data
7607 Display the contents of the @code{struct user} maintained by the OS
7608 kernel for the program being debugged. @value{GDBN} displays the
7609 contents of @code{struct user} as a list of hex numbers, similar to
7610 the @code{examine} command.
7613 @cindex auxiliary vector
7614 @cindex vector, auxiliary
7615 Some operating systems supply an @dfn{auxiliary vector} to programs at
7616 startup. This is akin to the arguments and environment that you
7617 specify for a program, but contains a system-dependent variety of
7618 binary values that tell system libraries important details about the
7619 hardware, operating system, and process. Each value's purpose is
7620 identified by an integer tag; the meanings are well-known but system-specific.
7621 Depending on the configuration and operating system facilities,
7622 @value{GDBN} may be able to show you this information. For remote
7623 targets, this functionality may further depend on the remote stub's
7624 support of the @samp{qXfer:auxv:read} packet, see
7625 @ref{qXfer auxiliary vector read}.
7630 Display the auxiliary vector of the inferior, which can be either a
7631 live process or a core dump file. @value{GDBN} prints each tag value
7632 numerically, and also shows names and text descriptions for recognized
7633 tags. Some values in the vector are numbers, some bit masks, and some
7634 pointers to strings or other data. @value{GDBN} displays each value in the
7635 most appropriate form for a recognized tag, and in hexadecimal for
7636 an unrecognized tag.
7639 On some targets, @value{GDBN} can access operating-system-specific information
7640 and display it to user, without interpretation. For remote targets,
7641 this functionality depends on the remote stub's support of the
7642 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
7645 @kindex info os processes
7646 @item info os processes
7647 Display the list of processes on the target. For each process,
7648 @value{GDBN} prints the process identifier, the name of the user, and
7649 the command corresponding to the process.
7652 @node Memory Region Attributes
7653 @section Memory Region Attributes
7654 @cindex memory region attributes
7656 @dfn{Memory region attributes} allow you to describe special handling
7657 required by regions of your target's memory. @value{GDBN} uses
7658 attributes to determine whether to allow certain types of memory
7659 accesses; whether to use specific width accesses; and whether to cache
7660 target memory. By default the description of memory regions is
7661 fetched from the target (if the current target supports this), but the
7662 user can override the fetched regions.
7664 Defined memory regions can be individually enabled and disabled. When a
7665 memory region is disabled, @value{GDBN} uses the default attributes when
7666 accessing memory in that region. Similarly, if no memory regions have
7667 been defined, @value{GDBN} uses the default attributes when accessing
7670 When a memory region is defined, it is given a number to identify it;
7671 to enable, disable, or remove a memory region, you specify that number.
7675 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7676 Define a memory region bounded by @var{lower} and @var{upper} with
7677 attributes @var{attributes}@dots{}, and add it to the list of regions
7678 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7679 case: it is treated as the target's maximum memory address.
7680 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7683 Discard any user changes to the memory regions and use target-supplied
7684 regions, if available, or no regions if the target does not support.
7687 @item delete mem @var{nums}@dots{}
7688 Remove memory regions @var{nums}@dots{} from the list of regions
7689 monitored by @value{GDBN}.
7692 @item disable mem @var{nums}@dots{}
7693 Disable monitoring of memory regions @var{nums}@dots{}.
7694 A disabled memory region is not forgotten.
7695 It may be enabled again later.
7698 @item enable mem @var{nums}@dots{}
7699 Enable monitoring of memory regions @var{nums}@dots{}.
7703 Print a table of all defined memory regions, with the following columns
7707 @item Memory Region Number
7708 @item Enabled or Disabled.
7709 Enabled memory regions are marked with @samp{y}.
7710 Disabled memory regions are marked with @samp{n}.
7713 The address defining the inclusive lower bound of the memory region.
7716 The address defining the exclusive upper bound of the memory region.
7719 The list of attributes set for this memory region.
7724 @subsection Attributes
7726 @subsubsection Memory Access Mode
7727 The access mode attributes set whether @value{GDBN} may make read or
7728 write accesses to a memory region.
7730 While these attributes prevent @value{GDBN} from performing invalid
7731 memory accesses, they do nothing to prevent the target system, I/O DMA,
7732 etc.@: from accessing memory.
7736 Memory is read only.
7738 Memory is write only.
7740 Memory is read/write. This is the default.
7743 @subsubsection Memory Access Size
7744 The access size attribute tells @value{GDBN} to use specific sized
7745 accesses in the memory region. Often memory mapped device registers
7746 require specific sized accesses. If no access size attribute is
7747 specified, @value{GDBN} may use accesses of any size.
7751 Use 8 bit memory accesses.
7753 Use 16 bit memory accesses.
7755 Use 32 bit memory accesses.
7757 Use 64 bit memory accesses.
7760 @c @subsubsection Hardware/Software Breakpoints
7761 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7762 @c will use hardware or software breakpoints for the internal breakpoints
7763 @c used by the step, next, finish, until, etc. commands.
7767 @c Always use hardware breakpoints
7768 @c @item swbreak (default)
7771 @subsubsection Data Cache
7772 The data cache attributes set whether @value{GDBN} will cache target
7773 memory. While this generally improves performance by reducing debug
7774 protocol overhead, it can lead to incorrect results because @value{GDBN}
7775 does not know about volatile variables or memory mapped device
7780 Enable @value{GDBN} to cache target memory.
7782 Disable @value{GDBN} from caching target memory. This is the default.
7785 @subsection Memory Access Checking
7786 @value{GDBN} can be instructed to refuse accesses to memory that is
7787 not explicitly described. This can be useful if accessing such
7788 regions has undesired effects for a specific target, or to provide
7789 better error checking. The following commands control this behaviour.
7792 @kindex set mem inaccessible-by-default
7793 @item set mem inaccessible-by-default [on|off]
7794 If @code{on} is specified, make @value{GDBN} treat memory not
7795 explicitly described by the memory ranges as non-existent and refuse accesses
7796 to such memory. The checks are only performed if there's at least one
7797 memory range defined. If @code{off} is specified, make @value{GDBN}
7798 treat the memory not explicitly described by the memory ranges as RAM.
7799 The default value is @code{on}.
7800 @kindex show mem inaccessible-by-default
7801 @item show mem inaccessible-by-default
7802 Show the current handling of accesses to unknown memory.
7806 @c @subsubsection Memory Write Verification
7807 @c The memory write verification attributes set whether @value{GDBN}
7808 @c will re-reads data after each write to verify the write was successful.
7812 @c @item noverify (default)
7815 @node Dump/Restore Files
7816 @section Copy Between Memory and a File
7817 @cindex dump/restore files
7818 @cindex append data to a file
7819 @cindex dump data to a file
7820 @cindex restore data from a file
7822 You can use the commands @code{dump}, @code{append}, and
7823 @code{restore} to copy data between target memory and a file. The
7824 @code{dump} and @code{append} commands write data to a file, and the
7825 @code{restore} command reads data from a file back into the inferior's
7826 memory. Files may be in binary, Motorola S-record, Intel hex, or
7827 Tektronix Hex format; however, @value{GDBN} can only append to binary
7833 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7834 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7835 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7836 or the value of @var{expr}, to @var{filename} in the given format.
7838 The @var{format} parameter may be any one of:
7845 Motorola S-record format.
7847 Tektronix Hex format.
7850 @value{GDBN} uses the same definitions of these formats as the
7851 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7852 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7856 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7857 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7858 Append the contents of memory from @var{start_addr} to @var{end_addr},
7859 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7860 (@value{GDBN} can only append data to files in raw binary form.)
7863 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7864 Restore the contents of file @var{filename} into memory. The
7865 @code{restore} command can automatically recognize any known @sc{bfd}
7866 file format, except for raw binary. To restore a raw binary file you
7867 must specify the optional keyword @code{binary} after the filename.
7869 If @var{bias} is non-zero, its value will be added to the addresses
7870 contained in the file. Binary files always start at address zero, so
7871 they will be restored at address @var{bias}. Other bfd files have
7872 a built-in location; they will be restored at offset @var{bias}
7875 If @var{start} and/or @var{end} are non-zero, then only data between
7876 file offset @var{start} and file offset @var{end} will be restored.
7877 These offsets are relative to the addresses in the file, before
7878 the @var{bias} argument is applied.
7882 @node Core File Generation
7883 @section How to Produce a Core File from Your Program
7884 @cindex dump core from inferior
7886 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7887 image of a running process and its process status (register values
7888 etc.). Its primary use is post-mortem debugging of a program that
7889 crashed while it ran outside a debugger. A program that crashes
7890 automatically produces a core file, unless this feature is disabled by
7891 the user. @xref{Files}, for information on invoking @value{GDBN} in
7892 the post-mortem debugging mode.
7894 Occasionally, you may wish to produce a core file of the program you
7895 are debugging in order to preserve a snapshot of its state.
7896 @value{GDBN} has a special command for that.
7900 @kindex generate-core-file
7901 @item generate-core-file [@var{file}]
7902 @itemx gcore [@var{file}]
7903 Produce a core dump of the inferior process. The optional argument
7904 @var{file} specifies the file name where to put the core dump. If not
7905 specified, the file name defaults to @file{core.@var{pid}}, where
7906 @var{pid} is the inferior process ID.
7908 Note that this command is implemented only for some systems (as of
7909 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7912 @node Character Sets
7913 @section Character Sets
7914 @cindex character sets
7916 @cindex translating between character sets
7917 @cindex host character set
7918 @cindex target character set
7920 If the program you are debugging uses a different character set to
7921 represent characters and strings than the one @value{GDBN} uses itself,
7922 @value{GDBN} can automatically translate between the character sets for
7923 you. The character set @value{GDBN} uses we call the @dfn{host
7924 character set}; the one the inferior program uses we call the
7925 @dfn{target character set}.
7927 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7928 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7929 remote protocol (@pxref{Remote Debugging}) to debug a program
7930 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7931 then the host character set is Latin-1, and the target character set is
7932 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7933 target-charset EBCDIC-US}, then @value{GDBN} translates between
7934 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7935 character and string literals in expressions.
7937 @value{GDBN} has no way to automatically recognize which character set
7938 the inferior program uses; you must tell it, using the @code{set
7939 target-charset} command, described below.
7941 Here are the commands for controlling @value{GDBN}'s character set
7945 @item set target-charset @var{charset}
7946 @kindex set target-charset
7947 Set the current target character set to @var{charset}. We list the
7948 character set names @value{GDBN} recognizes below, but if you type
7949 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7950 list the target character sets it supports.
7954 @item set host-charset @var{charset}
7955 @kindex set host-charset
7956 Set the current host character set to @var{charset}.
7958 By default, @value{GDBN} uses a host character set appropriate to the
7959 system it is running on; you can override that default using the
7960 @code{set host-charset} command.
7962 @value{GDBN} can only use certain character sets as its host character
7963 set. We list the character set names @value{GDBN} recognizes below, and
7964 indicate which can be host character sets, but if you type
7965 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7966 list the host character sets it supports.
7968 @item set charset @var{charset}
7970 Set the current host and target character sets to @var{charset}. As
7971 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7972 @value{GDBN} will list the name of the character sets that can be used
7973 for both host and target.
7977 @kindex show charset
7978 Show the names of the current host and target charsets.
7980 @itemx show host-charset
7981 @kindex show host-charset
7982 Show the name of the current host charset.
7984 @itemx show target-charset
7985 @kindex show target-charset
7986 Show the name of the current target charset.
7990 @value{GDBN} currently includes support for the following character
7996 @cindex ASCII character set
7997 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
8001 @cindex ISO 8859-1 character set
8002 @cindex ISO Latin 1 character set
8003 The ISO Latin 1 character set. This extends @sc{ascii} with accented
8004 characters needed for French, German, and Spanish. @value{GDBN} can use
8005 this as its host character set.
8009 @cindex EBCDIC character set
8010 @cindex IBM1047 character set
8011 Variants of the @sc{ebcdic} character set, used on some of IBM's
8012 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
8013 @value{GDBN} cannot use these as its host character set.
8017 Note that these are all single-byte character sets. More work inside
8018 @value{GDBN} is needed to support multi-byte or variable-width character
8019 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
8021 Here is an example of @value{GDBN}'s character set support in action.
8022 Assume that the following source code has been placed in the file
8023 @file{charset-test.c}:
8029 = @{72, 101, 108, 108, 111, 44, 32, 119,
8030 111, 114, 108, 100, 33, 10, 0@};
8031 char ibm1047_hello[]
8032 = @{200, 133, 147, 147, 150, 107, 64, 166,
8033 150, 153, 147, 132, 90, 37, 0@};
8037 printf ("Hello, world!\n");
8041 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8042 containing the string @samp{Hello, world!} followed by a newline,
8043 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8045 We compile the program, and invoke the debugger on it:
8048 $ gcc -g charset-test.c -o charset-test
8049 $ gdb -nw charset-test
8050 GNU gdb 2001-12-19-cvs
8051 Copyright 2001 Free Software Foundation, Inc.
8056 We can use the @code{show charset} command to see what character sets
8057 @value{GDBN} is currently using to interpret and display characters and
8061 (@value{GDBP}) show charset
8062 The current host and target character set is `ISO-8859-1'.
8066 For the sake of printing this manual, let's use @sc{ascii} as our
8067 initial character set:
8069 (@value{GDBP}) set charset ASCII
8070 (@value{GDBP}) show charset
8071 The current host and target character set is `ASCII'.
8075 Let's assume that @sc{ascii} is indeed the correct character set for our
8076 host system --- in other words, let's assume that if @value{GDBN} prints
8077 characters using the @sc{ascii} character set, our terminal will display
8078 them properly. Since our current target character set is also
8079 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8082 (@value{GDBP}) print ascii_hello
8083 $1 = 0x401698 "Hello, world!\n"
8084 (@value{GDBP}) print ascii_hello[0]
8089 @value{GDBN} uses the target character set for character and string
8090 literals you use in expressions:
8093 (@value{GDBP}) print '+'
8098 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8101 @value{GDBN} relies on the user to tell it which character set the
8102 target program uses. If we print @code{ibm1047_hello} while our target
8103 character set is still @sc{ascii}, we get jibberish:
8106 (@value{GDBP}) print ibm1047_hello
8107 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8108 (@value{GDBP}) print ibm1047_hello[0]
8113 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8114 @value{GDBN} tells us the character sets it supports:
8117 (@value{GDBP}) set target-charset
8118 ASCII EBCDIC-US IBM1047 ISO-8859-1
8119 (@value{GDBP}) set target-charset
8122 We can select @sc{ibm1047} as our target character set, and examine the
8123 program's strings again. Now the @sc{ascii} string is wrong, but
8124 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8125 target character set, @sc{ibm1047}, to the host character set,
8126 @sc{ascii}, and they display correctly:
8129 (@value{GDBP}) set target-charset IBM1047
8130 (@value{GDBP}) show charset
8131 The current host character set is `ASCII'.
8132 The current target character set is `IBM1047'.
8133 (@value{GDBP}) print ascii_hello
8134 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8135 (@value{GDBP}) print ascii_hello[0]
8137 (@value{GDBP}) print ibm1047_hello
8138 $8 = 0x4016a8 "Hello, world!\n"
8139 (@value{GDBP}) print ibm1047_hello[0]
8144 As above, @value{GDBN} uses the target character set for character and
8145 string literals you use in expressions:
8148 (@value{GDBP}) print '+'
8153 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8156 @node Caching Remote Data
8157 @section Caching Data of Remote Targets
8158 @cindex caching data of remote targets
8160 @value{GDBN} can cache data exchanged between the debugger and a
8161 remote target (@pxref{Remote Debugging}). Such caching generally improves
8162 performance, because it reduces the overhead of the remote protocol by
8163 bundling memory reads and writes into large chunks. Unfortunately,
8164 @value{GDBN} does not currently know anything about volatile
8165 registers, and thus data caching will produce incorrect results when
8166 volatile registers are in use.
8169 @kindex set remotecache
8170 @item set remotecache on
8171 @itemx set remotecache off
8172 Set caching state for remote targets. When @code{ON}, use data
8173 caching. By default, this option is @code{OFF}.
8175 @kindex show remotecache
8176 @item show remotecache
8177 Show the current state of data caching for remote targets.
8181 Print the information about the data cache performance. The
8182 information displayed includes: the dcache width and depth; and for
8183 each cache line, how many times it was referenced, and its data and
8184 state (invalid, dirty, valid). This command is useful for debugging
8185 the data cache operation.
8188 @node Searching Memory
8189 @section Search Memory
8190 @cindex searching memory
8192 Memory can be searched for a particular sequence of bytes with the
8193 @code{find} command.
8197 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8198 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8199 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8200 etc. The search begins at address @var{start_addr} and continues for either
8201 @var{len} bytes or through to @var{end_addr} inclusive.
8204 @var{s} and @var{n} are optional parameters.
8205 They may be specified in either order, apart or together.
8208 @item @var{s}, search query size
8209 The size of each search query value.
8215 halfwords (two bytes)
8219 giant words (eight bytes)
8222 All values are interpreted in the current language.
8223 This means, for example, that if the current source language is C/C@t{++}
8224 then searching for the string ``hello'' includes the trailing '\0'.
8226 If the value size is not specified, it is taken from the
8227 value's type in the current language.
8228 This is useful when one wants to specify the search
8229 pattern as a mixture of types.
8230 Note that this means, for example, that in the case of C-like languages
8231 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8232 which is typically four bytes.
8234 @item @var{n}, maximum number of finds
8235 The maximum number of matches to print. The default is to print all finds.
8238 You can use strings as search values. Quote them with double-quotes
8240 The string value is copied into the search pattern byte by byte,
8241 regardless of the endianness of the target and the size specification.
8243 The address of each match found is printed as well as a count of the
8244 number of matches found.
8246 The address of the last value found is stored in convenience variable
8248 A count of the number of matches is stored in @samp{$numfound}.
8250 For example, if stopped at the @code{printf} in this function:
8256 static char hello[] = "hello-hello";
8257 static struct @{ char c; short s; int i; @}
8258 __attribute__ ((packed)) mixed
8259 = @{ 'c', 0x1234, 0x87654321 @};
8260 printf ("%s\n", hello);
8265 you get during debugging:
8268 (gdb) find &hello[0], +sizeof(hello), "hello"
8269 0x804956d <hello.1620+6>
8271 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8272 0x8049567 <hello.1620>
8273 0x804956d <hello.1620+6>
8275 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8276 0x8049567 <hello.1620>
8278 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8279 0x8049560 <mixed.1625>
8281 (gdb) print $numfound
8284 $2 = (void *) 0x8049560
8288 @chapter C Preprocessor Macros
8290 Some languages, such as C and C@t{++}, provide a way to define and invoke
8291 ``preprocessor macros'' which expand into strings of tokens.
8292 @value{GDBN} can evaluate expressions containing macro invocations, show
8293 the result of macro expansion, and show a macro's definition, including
8294 where it was defined.
8296 You may need to compile your program specially to provide @value{GDBN}
8297 with information about preprocessor macros. Most compilers do not
8298 include macros in their debugging information, even when you compile
8299 with the @option{-g} flag. @xref{Compilation}.
8301 A program may define a macro at one point, remove that definition later,
8302 and then provide a different definition after that. Thus, at different
8303 points in the program, a macro may have different definitions, or have
8304 no definition at all. If there is a current stack frame, @value{GDBN}
8305 uses the macros in scope at that frame's source code line. Otherwise,
8306 @value{GDBN} uses the macros in scope at the current listing location;
8309 Whenever @value{GDBN} evaluates an expression, it always expands any
8310 macro invocations present in the expression. @value{GDBN} also provides
8311 the following commands for working with macros explicitly.
8315 @kindex macro expand
8316 @cindex macro expansion, showing the results of preprocessor
8317 @cindex preprocessor macro expansion, showing the results of
8318 @cindex expanding preprocessor macros
8319 @item macro expand @var{expression}
8320 @itemx macro exp @var{expression}
8321 Show the results of expanding all preprocessor macro invocations in
8322 @var{expression}. Since @value{GDBN} simply expands macros, but does
8323 not parse the result, @var{expression} need not be a valid expression;
8324 it can be any string of tokens.
8327 @item macro expand-once @var{expression}
8328 @itemx macro exp1 @var{expression}
8329 @cindex expand macro once
8330 @i{(This command is not yet implemented.)} Show the results of
8331 expanding those preprocessor macro invocations that appear explicitly in
8332 @var{expression}. Macro invocations appearing in that expansion are
8333 left unchanged. This command allows you to see the effect of a
8334 particular macro more clearly, without being confused by further
8335 expansions. Since @value{GDBN} simply expands macros, but does not
8336 parse the result, @var{expression} need not be a valid expression; it
8337 can be any string of tokens.
8340 @cindex macro definition, showing
8341 @cindex definition, showing a macro's
8342 @item info macro @var{macro}
8343 Show the definition of the macro named @var{macro}, and describe the
8344 source location where that definition was established.
8346 @kindex macro define
8347 @cindex user-defined macros
8348 @cindex defining macros interactively
8349 @cindex macros, user-defined
8350 @item macro define @var{macro} @var{replacement-list}
8351 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8352 Introduce a definition for a preprocessor macro named @var{macro},
8353 invocations of which are replaced by the tokens given in
8354 @var{replacement-list}. The first form of this command defines an
8355 ``object-like'' macro, which takes no arguments; the second form
8356 defines a ``function-like'' macro, which takes the arguments given in
8359 A definition introduced by this command is in scope in every
8360 expression evaluated in @value{GDBN}, until it is removed with the
8361 @code{macro undef} command, described below. The definition overrides
8362 all definitions for @var{macro} present in the program being debugged,
8363 as well as any previous user-supplied definition.
8366 @item macro undef @var{macro}
8367 Remove any user-supplied definition for the macro named @var{macro}.
8368 This command only affects definitions provided with the @code{macro
8369 define} command, described above; it cannot remove definitions present
8370 in the program being debugged.
8374 List all the macros defined using the @code{macro define} command.
8377 @cindex macros, example of debugging with
8378 Here is a transcript showing the above commands in action. First, we
8379 show our source files:
8387 #define ADD(x) (M + x)
8392 printf ("Hello, world!\n");
8394 printf ("We're so creative.\n");
8396 printf ("Goodbye, world!\n");
8403 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8404 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8405 compiler includes information about preprocessor macros in the debugging
8409 $ gcc -gdwarf-2 -g3 sample.c -o sample
8413 Now, we start @value{GDBN} on our sample program:
8417 GNU gdb 2002-05-06-cvs
8418 Copyright 2002 Free Software Foundation, Inc.
8419 GDB is free software, @dots{}
8423 We can expand macros and examine their definitions, even when the
8424 program is not running. @value{GDBN} uses the current listing position
8425 to decide which macro definitions are in scope:
8428 (@value{GDBP}) list main
8431 5 #define ADD(x) (M + x)
8436 10 printf ("Hello, world!\n");
8438 12 printf ("We're so creative.\n");
8439 (@value{GDBP}) info macro ADD
8440 Defined at /home/jimb/gdb/macros/play/sample.c:5
8441 #define ADD(x) (M + x)
8442 (@value{GDBP}) info macro Q
8443 Defined at /home/jimb/gdb/macros/play/sample.h:1
8444 included at /home/jimb/gdb/macros/play/sample.c:2
8446 (@value{GDBP}) macro expand ADD(1)
8447 expands to: (42 + 1)
8448 (@value{GDBP}) macro expand-once ADD(1)
8449 expands to: once (M + 1)
8453 In the example above, note that @code{macro expand-once} expands only
8454 the macro invocation explicit in the original text --- the invocation of
8455 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8456 which was introduced by @code{ADD}.
8458 Once the program is running, @value{GDBN} uses the macro definitions in
8459 force at the source line of the current stack frame:
8462 (@value{GDBP}) break main
8463 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8465 Starting program: /home/jimb/gdb/macros/play/sample
8467 Breakpoint 1, main () at sample.c:10
8468 10 printf ("Hello, world!\n");
8472 At line 10, the definition of the macro @code{N} at line 9 is in force:
8475 (@value{GDBP}) info macro N
8476 Defined at /home/jimb/gdb/macros/play/sample.c:9
8478 (@value{GDBP}) macro expand N Q M
8480 (@value{GDBP}) print N Q M
8485 As we step over directives that remove @code{N}'s definition, and then
8486 give it a new definition, @value{GDBN} finds the definition (or lack
8487 thereof) in force at each point:
8492 12 printf ("We're so creative.\n");
8493 (@value{GDBP}) info macro N
8494 The symbol `N' has no definition as a C/C++ preprocessor macro
8495 at /home/jimb/gdb/macros/play/sample.c:12
8498 14 printf ("Goodbye, world!\n");
8499 (@value{GDBP}) info macro N
8500 Defined at /home/jimb/gdb/macros/play/sample.c:13
8502 (@value{GDBP}) macro expand N Q M
8503 expands to: 1729 < 42
8504 (@value{GDBP}) print N Q M
8511 @chapter Tracepoints
8512 @c This chapter is based on the documentation written by Michael
8513 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8516 In some applications, it is not feasible for the debugger to interrupt
8517 the program's execution long enough for the developer to learn
8518 anything helpful about its behavior. If the program's correctness
8519 depends on its real-time behavior, delays introduced by a debugger
8520 might cause the program to change its behavior drastically, or perhaps
8521 fail, even when the code itself is correct. It is useful to be able
8522 to observe the program's behavior without interrupting it.
8524 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8525 specify locations in the program, called @dfn{tracepoints}, and
8526 arbitrary expressions to evaluate when those tracepoints are reached.
8527 Later, using the @code{tfind} command, you can examine the values
8528 those expressions had when the program hit the tracepoints. The
8529 expressions may also denote objects in memory---structures or arrays,
8530 for example---whose values @value{GDBN} should record; while visiting
8531 a particular tracepoint, you may inspect those objects as if they were
8532 in memory at that moment. However, because @value{GDBN} records these
8533 values without interacting with you, it can do so quickly and
8534 unobtrusively, hopefully not disturbing the program's behavior.
8536 The tracepoint facility is currently available only for remote
8537 targets. @xref{Targets}. In addition, your remote target must know
8538 how to collect trace data. This functionality is implemented in the
8539 remote stub; however, none of the stubs distributed with @value{GDBN}
8540 support tracepoints as of this writing. The format of the remote
8541 packets used to implement tracepoints are described in @ref{Tracepoint
8544 This chapter describes the tracepoint commands and features.
8548 * Analyze Collected Data::
8549 * Tracepoint Variables::
8552 @node Set Tracepoints
8553 @section Commands to Set Tracepoints
8555 Before running such a @dfn{trace experiment}, an arbitrary number of
8556 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
8557 tracepoint has a number assigned to it by @value{GDBN}. Like with
8558 breakpoints, tracepoint numbers are successive integers starting from
8559 one. Many of the commands associated with tracepoints take the
8560 tracepoint number as their argument, to identify which tracepoint to
8563 For each tracepoint, you can specify, in advance, some arbitrary set
8564 of data that you want the target to collect in the trace buffer when
8565 it hits that tracepoint. The collected data can include registers,
8566 local variables, or global data. Later, you can use @value{GDBN}
8567 commands to examine the values these data had at the time the
8570 This section describes commands to set tracepoints and associated
8571 conditions and actions.
8574 * Create and Delete Tracepoints::
8575 * Enable and Disable Tracepoints::
8576 * Tracepoint Passcounts::
8577 * Tracepoint Actions::
8578 * Listing Tracepoints::
8579 * Starting and Stopping Trace Experiments::
8582 @node Create and Delete Tracepoints
8583 @subsection Create and Delete Tracepoints
8586 @cindex set tracepoint
8589 The @code{trace} command is very similar to the @code{break} command.
8590 Its argument can be a source line, a function name, or an address in
8591 the target program. @xref{Set Breaks}. The @code{trace} command
8592 defines a tracepoint, which is a point in the target program where the
8593 debugger will briefly stop, collect some data, and then allow the
8594 program to continue. Setting a tracepoint or changing its commands
8595 doesn't take effect until the next @code{tstart} command; thus, you
8596 cannot change the tracepoint attributes once a trace experiment is
8599 Here are some examples of using the @code{trace} command:
8602 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8604 (@value{GDBP}) @b{trace +2} // 2 lines forward
8606 (@value{GDBP}) @b{trace my_function} // first source line of function
8608 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8610 (@value{GDBP}) @b{trace *0x2117c4} // an address
8614 You can abbreviate @code{trace} as @code{tr}.
8617 @cindex last tracepoint number
8618 @cindex recent tracepoint number
8619 @cindex tracepoint number
8620 The convenience variable @code{$tpnum} records the tracepoint number
8621 of the most recently set tracepoint.
8623 @kindex delete tracepoint
8624 @cindex tracepoint deletion
8625 @item delete tracepoint @r{[}@var{num}@r{]}
8626 Permanently delete one or more tracepoints. With no argument, the
8627 default is to delete all tracepoints.
8632 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8634 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8638 You can abbreviate this command as @code{del tr}.
8641 @node Enable and Disable Tracepoints
8642 @subsection Enable and Disable Tracepoints
8645 @kindex disable tracepoint
8646 @item disable tracepoint @r{[}@var{num}@r{]}
8647 Disable tracepoint @var{num}, or all tracepoints if no argument
8648 @var{num} is given. A disabled tracepoint will have no effect during
8649 the next trace experiment, but it is not forgotten. You can re-enable
8650 a disabled tracepoint using the @code{enable tracepoint} command.
8652 @kindex enable tracepoint
8653 @item enable tracepoint @r{[}@var{num}@r{]}
8654 Enable tracepoint @var{num}, or all tracepoints. The enabled
8655 tracepoints will become effective the next time a trace experiment is
8659 @node Tracepoint Passcounts
8660 @subsection Tracepoint Passcounts
8664 @cindex tracepoint pass count
8665 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8666 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8667 automatically stop a trace experiment. If a tracepoint's passcount is
8668 @var{n}, then the trace experiment will be automatically stopped on
8669 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8670 @var{num} is not specified, the @code{passcount} command sets the
8671 passcount of the most recently defined tracepoint. If no passcount is
8672 given, the trace experiment will run until stopped explicitly by the
8678 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8679 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8681 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8682 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8683 (@value{GDBP}) @b{trace foo}
8684 (@value{GDBP}) @b{pass 3}
8685 (@value{GDBP}) @b{trace bar}
8686 (@value{GDBP}) @b{pass 2}
8687 (@value{GDBP}) @b{trace baz}
8688 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8689 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8690 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8691 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8695 @node Tracepoint Actions
8696 @subsection Tracepoint Action Lists
8700 @cindex tracepoint actions
8701 @item actions @r{[}@var{num}@r{]}
8702 This command will prompt for a list of actions to be taken when the
8703 tracepoint is hit. If the tracepoint number @var{num} is not
8704 specified, this command sets the actions for the one that was most
8705 recently defined (so that you can define a tracepoint and then say
8706 @code{actions} without bothering about its number). You specify the
8707 actions themselves on the following lines, one action at a time, and
8708 terminate the actions list with a line containing just @code{end}. So
8709 far, the only defined actions are @code{collect} and
8710 @code{while-stepping}.
8712 @cindex remove actions from a tracepoint
8713 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8714 and follow it immediately with @samp{end}.
8717 (@value{GDBP}) @b{collect @var{data}} // collect some data
8719 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8721 (@value{GDBP}) @b{end} // signals the end of actions.
8724 In the following example, the action list begins with @code{collect}
8725 commands indicating the things to be collected when the tracepoint is
8726 hit. Then, in order to single-step and collect additional data
8727 following the tracepoint, a @code{while-stepping} command is used,
8728 followed by the list of things to be collected while stepping. The
8729 @code{while-stepping} command is terminated by its own separate
8730 @code{end} command. Lastly, the action list is terminated by an
8734 (@value{GDBP}) @b{trace foo}
8735 (@value{GDBP}) @b{actions}
8736 Enter actions for tracepoint 1, one per line:
8745 @kindex collect @r{(tracepoints)}
8746 @item collect @var{expr1}, @var{expr2}, @dots{}
8747 Collect values of the given expressions when the tracepoint is hit.
8748 This command accepts a comma-separated list of any valid expressions.
8749 In addition to global, static, or local variables, the following
8750 special arguments are supported:
8754 collect all registers
8757 collect all function arguments
8760 collect all local variables.
8763 You can give several consecutive @code{collect} commands, each one
8764 with a single argument, or one @code{collect} command with several
8765 arguments separated by commas: the effect is the same.
8767 The command @code{info scope} (@pxref{Symbols, info scope}) is
8768 particularly useful for figuring out what data to collect.
8770 @kindex while-stepping @r{(tracepoints)}
8771 @item while-stepping @var{n}
8772 Perform @var{n} single-step traces after the tracepoint, collecting
8773 new data at each step. The @code{while-stepping} command is
8774 followed by the list of what to collect while stepping (followed by
8775 its own @code{end} command):
8779 > collect $regs, myglobal
8785 You may abbreviate @code{while-stepping} as @code{ws} or
8789 @node Listing Tracepoints
8790 @subsection Listing Tracepoints
8793 @kindex info tracepoints
8795 @cindex information about tracepoints
8796 @item info tracepoints @r{[}@var{num}@r{]}
8797 Display information about the tracepoint @var{num}. If you don't specify
8798 a tracepoint number, displays information about all the tracepoints
8799 defined so far. For each tracepoint, the following information is
8806 whether it is enabled or disabled
8810 its passcount as given by the @code{passcount @var{n}} command
8812 its step count as given by the @code{while-stepping @var{n}} command
8814 where in the source files is the tracepoint set
8816 its action list as given by the @code{actions} command
8820 (@value{GDBP}) @b{info trace}
8821 Num Enb Address PassC StepC What
8822 1 y 0x002117c4 0 0 <gdb_asm>
8823 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8824 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8829 This command can be abbreviated @code{info tp}.
8832 @node Starting and Stopping Trace Experiments
8833 @subsection Starting and Stopping Trace Experiments
8837 @cindex start a new trace experiment
8838 @cindex collected data discarded
8840 This command takes no arguments. It starts the trace experiment, and
8841 begins collecting data. This has the side effect of discarding all
8842 the data collected in the trace buffer during the previous trace
8846 @cindex stop a running trace experiment
8848 This command takes no arguments. It ends the trace experiment, and
8849 stops collecting data.
8851 @strong{Note}: a trace experiment and data collection may stop
8852 automatically if any tracepoint's passcount is reached
8853 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8856 @cindex status of trace data collection
8857 @cindex trace experiment, status of
8859 This command displays the status of the current trace data
8863 Here is an example of the commands we described so far:
8866 (@value{GDBP}) @b{trace gdb_c_test}
8867 (@value{GDBP}) @b{actions}
8868 Enter actions for tracepoint #1, one per line.
8869 > collect $regs,$locals,$args
8874 (@value{GDBP}) @b{tstart}
8875 [time passes @dots{}]
8876 (@value{GDBP}) @b{tstop}
8880 @node Analyze Collected Data
8881 @section Using the Collected Data
8883 After the tracepoint experiment ends, you use @value{GDBN} commands
8884 for examining the trace data. The basic idea is that each tracepoint
8885 collects a trace @dfn{snapshot} every time it is hit and another
8886 snapshot every time it single-steps. All these snapshots are
8887 consecutively numbered from zero and go into a buffer, and you can
8888 examine them later. The way you examine them is to @dfn{focus} on a
8889 specific trace snapshot. When the remote stub is focused on a trace
8890 snapshot, it will respond to all @value{GDBN} requests for memory and
8891 registers by reading from the buffer which belongs to that snapshot,
8892 rather than from @emph{real} memory or registers of the program being
8893 debugged. This means that @strong{all} @value{GDBN} commands
8894 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8895 behave as if we were currently debugging the program state as it was
8896 when the tracepoint occurred. Any requests for data that are not in
8897 the buffer will fail.
8900 * tfind:: How to select a trace snapshot
8901 * tdump:: How to display all data for a snapshot
8902 * save-tracepoints:: How to save tracepoints for a future run
8906 @subsection @code{tfind @var{n}}
8909 @cindex select trace snapshot
8910 @cindex find trace snapshot
8911 The basic command for selecting a trace snapshot from the buffer is
8912 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8913 counting from zero. If no argument @var{n} is given, the next
8914 snapshot is selected.
8916 Here are the various forms of using the @code{tfind} command.
8920 Find the first snapshot in the buffer. This is a synonym for
8921 @code{tfind 0} (since 0 is the number of the first snapshot).
8924 Stop debugging trace snapshots, resume @emph{live} debugging.
8927 Same as @samp{tfind none}.
8930 No argument means find the next trace snapshot.
8933 Find the previous trace snapshot before the current one. This permits
8934 retracing earlier steps.
8936 @item tfind tracepoint @var{num}
8937 Find the next snapshot associated with tracepoint @var{num}. Search
8938 proceeds forward from the last examined trace snapshot. If no
8939 argument @var{num} is given, it means find the next snapshot collected
8940 for the same tracepoint as the current snapshot.
8942 @item tfind pc @var{addr}
8943 Find the next snapshot associated with the value @var{addr} of the
8944 program counter. Search proceeds forward from the last examined trace
8945 snapshot. If no argument @var{addr} is given, it means find the next
8946 snapshot with the same value of PC as the current snapshot.
8948 @item tfind outside @var{addr1}, @var{addr2}
8949 Find the next snapshot whose PC is outside the given range of
8952 @item tfind range @var{addr1}, @var{addr2}
8953 Find the next snapshot whose PC is between @var{addr1} and
8954 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8956 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8957 Find the next snapshot associated with the source line @var{n}. If
8958 the optional argument @var{file} is given, refer to line @var{n} in
8959 that source file. Search proceeds forward from the last examined
8960 trace snapshot. If no argument @var{n} is given, it means find the
8961 next line other than the one currently being examined; thus saying
8962 @code{tfind line} repeatedly can appear to have the same effect as
8963 stepping from line to line in a @emph{live} debugging session.
8966 The default arguments for the @code{tfind} commands are specifically
8967 designed to make it easy to scan through the trace buffer. For
8968 instance, @code{tfind} with no argument selects the next trace
8969 snapshot, and @code{tfind -} with no argument selects the previous
8970 trace snapshot. So, by giving one @code{tfind} command, and then
8971 simply hitting @key{RET} repeatedly you can examine all the trace
8972 snapshots in order. Or, by saying @code{tfind -} and then hitting
8973 @key{RET} repeatedly you can examine the snapshots in reverse order.
8974 The @code{tfind line} command with no argument selects the snapshot
8975 for the next source line executed. The @code{tfind pc} command with
8976 no argument selects the next snapshot with the same program counter
8977 (PC) as the current frame. The @code{tfind tracepoint} command with
8978 no argument selects the next trace snapshot collected by the same
8979 tracepoint as the current one.
8981 In addition to letting you scan through the trace buffer manually,
8982 these commands make it easy to construct @value{GDBN} scripts that
8983 scan through the trace buffer and print out whatever collected data
8984 you are interested in. Thus, if we want to examine the PC, FP, and SP
8985 registers from each trace frame in the buffer, we can say this:
8988 (@value{GDBP}) @b{tfind start}
8989 (@value{GDBP}) @b{while ($trace_frame != -1)}
8990 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8991 $trace_frame, $pc, $sp, $fp
8995 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8996 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8997 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8998 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8999 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
9000 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
9001 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
9002 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
9003 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
9004 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
9005 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
9008 Or, if we want to examine the variable @code{X} at each source line in
9012 (@value{GDBP}) @b{tfind start}
9013 (@value{GDBP}) @b{while ($trace_frame != -1)}
9014 > printf "Frame %d, X == %d\n", $trace_frame, X
9024 @subsection @code{tdump}
9026 @cindex dump all data collected at tracepoint
9027 @cindex tracepoint data, display
9029 This command takes no arguments. It prints all the data collected at
9030 the current trace snapshot.
9033 (@value{GDBP}) @b{trace 444}
9034 (@value{GDBP}) @b{actions}
9035 Enter actions for tracepoint #2, one per line:
9036 > collect $regs, $locals, $args, gdb_long_test
9039 (@value{GDBP}) @b{tstart}
9041 (@value{GDBP}) @b{tfind line 444}
9042 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
9044 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
9046 (@value{GDBP}) @b{tdump}
9047 Data collected at tracepoint 2, trace frame 1:
9048 d0 0xc4aa0085 -995491707
9052 d4 0x71aea3d 119204413
9057 a1 0x3000668 50333288
9060 a4 0x3000698 50333336
9062 fp 0x30bf3c 0x30bf3c
9063 sp 0x30bf34 0x30bf34
9065 pc 0x20b2c8 0x20b2c8
9069 p = 0x20e5b4 "gdb-test"
9076 gdb_long_test = 17 '\021'
9081 @node save-tracepoints
9082 @subsection @code{save-tracepoints @var{filename}}
9083 @kindex save-tracepoints
9084 @cindex save tracepoints for future sessions
9086 This command saves all current tracepoint definitions together with
9087 their actions and passcounts, into a file @file{@var{filename}}
9088 suitable for use in a later debugging session. To read the saved
9089 tracepoint definitions, use the @code{source} command (@pxref{Command
9092 @node Tracepoint Variables
9093 @section Convenience Variables for Tracepoints
9094 @cindex tracepoint variables
9095 @cindex convenience variables for tracepoints
9098 @vindex $trace_frame
9099 @item (int) $trace_frame
9100 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9101 snapshot is selected.
9104 @item (int) $tracepoint
9105 The tracepoint for the current trace snapshot.
9108 @item (int) $trace_line
9109 The line number for the current trace snapshot.
9112 @item (char []) $trace_file
9113 The source file for the current trace snapshot.
9116 @item (char []) $trace_func
9117 The name of the function containing @code{$tracepoint}.
9120 Note: @code{$trace_file} is not suitable for use in @code{printf},
9121 use @code{output} instead.
9123 Here's a simple example of using these convenience variables for
9124 stepping through all the trace snapshots and printing some of their
9128 (@value{GDBP}) @b{tfind start}
9130 (@value{GDBP}) @b{while $trace_frame != -1}
9131 > output $trace_file
9132 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9138 @chapter Debugging Programs That Use Overlays
9141 If your program is too large to fit completely in your target system's
9142 memory, you can sometimes use @dfn{overlays} to work around this
9143 problem. @value{GDBN} provides some support for debugging programs that
9147 * How Overlays Work:: A general explanation of overlays.
9148 * Overlay Commands:: Managing overlays in @value{GDBN}.
9149 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9150 mapped by asking the inferior.
9151 * Overlay Sample Program:: A sample program using overlays.
9154 @node How Overlays Work
9155 @section How Overlays Work
9156 @cindex mapped overlays
9157 @cindex unmapped overlays
9158 @cindex load address, overlay's
9159 @cindex mapped address
9160 @cindex overlay area
9162 Suppose you have a computer whose instruction address space is only 64
9163 kilobytes long, but which has much more memory which can be accessed by
9164 other means: special instructions, segment registers, or memory
9165 management hardware, for example. Suppose further that you want to
9166 adapt a program which is larger than 64 kilobytes to run on this system.
9168 One solution is to identify modules of your program which are relatively
9169 independent, and need not call each other directly; call these modules
9170 @dfn{overlays}. Separate the overlays from the main program, and place
9171 their machine code in the larger memory. Place your main program in
9172 instruction memory, but leave at least enough space there to hold the
9173 largest overlay as well.
9175 Now, to call a function located in an overlay, you must first copy that
9176 overlay's machine code from the large memory into the space set aside
9177 for it in the instruction memory, and then jump to its entry point
9180 @c NB: In the below the mapped area's size is greater or equal to the
9181 @c size of all overlays. This is intentional to remind the developer
9182 @c that overlays don't necessarily need to be the same size.
9186 Data Instruction Larger
9187 Address Space Address Space Address Space
9188 +-----------+ +-----------+ +-----------+
9190 +-----------+ +-----------+ +-----------+<-- overlay 1
9191 | program | | main | .----| overlay 1 | load address
9192 | variables | | program | | +-----------+
9193 | and heap | | | | | |
9194 +-----------+ | | | +-----------+<-- overlay 2
9195 | | +-----------+ | | | load address
9196 +-----------+ | | | .-| overlay 2 |
9198 mapped --->+-----------+ | | +-----------+
9200 | overlay | <-' | | |
9201 | area | <---' +-----------+<-- overlay 3
9202 | | <---. | | load address
9203 +-----------+ `--| overlay 3 |
9210 @anchor{A code overlay}A code overlay
9214 The diagram (@pxref{A code overlay}) shows a system with separate data
9215 and instruction address spaces. To map an overlay, the program copies
9216 its code from the larger address space to the instruction address space.
9217 Since the overlays shown here all use the same mapped address, only one
9218 may be mapped at a time. For a system with a single address space for
9219 data and instructions, the diagram would be similar, except that the
9220 program variables and heap would share an address space with the main
9221 program and the overlay area.
9223 An overlay loaded into instruction memory and ready for use is called a
9224 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9225 instruction memory. An overlay not present (or only partially present)
9226 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9227 is its address in the larger memory. The mapped address is also called
9228 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9229 called the @dfn{load memory address}, or @dfn{LMA}.
9231 Unfortunately, overlays are not a completely transparent way to adapt a
9232 program to limited instruction memory. They introduce a new set of
9233 global constraints you must keep in mind as you design your program:
9238 Before calling or returning to a function in an overlay, your program
9239 must make sure that overlay is actually mapped. Otherwise, the call or
9240 return will transfer control to the right address, but in the wrong
9241 overlay, and your program will probably crash.
9244 If the process of mapping an overlay is expensive on your system, you
9245 will need to choose your overlays carefully to minimize their effect on
9246 your program's performance.
9249 The executable file you load onto your system must contain each
9250 overlay's instructions, appearing at the overlay's load address, not its
9251 mapped address. However, each overlay's instructions must be relocated
9252 and its symbols defined as if the overlay were at its mapped address.
9253 You can use GNU linker scripts to specify different load and relocation
9254 addresses for pieces of your program; see @ref{Overlay Description,,,
9255 ld.info, Using ld: the GNU linker}.
9258 The procedure for loading executable files onto your system must be able
9259 to load their contents into the larger address space as well as the
9260 instruction and data spaces.
9264 The overlay system described above is rather simple, and could be
9265 improved in many ways:
9270 If your system has suitable bank switch registers or memory management
9271 hardware, you could use those facilities to make an overlay's load area
9272 contents simply appear at their mapped address in instruction space.
9273 This would probably be faster than copying the overlay to its mapped
9274 area in the usual way.
9277 If your overlays are small enough, you could set aside more than one
9278 overlay area, and have more than one overlay mapped at a time.
9281 You can use overlays to manage data, as well as instructions. In
9282 general, data overlays are even less transparent to your design than
9283 code overlays: whereas code overlays only require care when you call or
9284 return to functions, data overlays require care every time you access
9285 the data. Also, if you change the contents of a data overlay, you
9286 must copy its contents back out to its load address before you can copy a
9287 different data overlay into the same mapped area.
9292 @node Overlay Commands
9293 @section Overlay Commands
9295 To use @value{GDBN}'s overlay support, each overlay in your program must
9296 correspond to a separate section of the executable file. The section's
9297 virtual memory address and load memory address must be the overlay's
9298 mapped and load addresses. Identifying overlays with sections allows
9299 @value{GDBN} to determine the appropriate address of a function or
9300 variable, depending on whether the overlay is mapped or not.
9302 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9303 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9308 Disable @value{GDBN}'s overlay support. When overlay support is
9309 disabled, @value{GDBN} assumes that all functions and variables are
9310 always present at their mapped addresses. By default, @value{GDBN}'s
9311 overlay support is disabled.
9313 @item overlay manual
9314 @cindex manual overlay debugging
9315 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9316 relies on you to tell it which overlays are mapped, and which are not,
9317 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9318 commands described below.
9320 @item overlay map-overlay @var{overlay}
9321 @itemx overlay map @var{overlay}
9322 @cindex map an overlay
9323 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9324 be the name of the object file section containing the overlay. When an
9325 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9326 functions and variables at their mapped addresses. @value{GDBN} assumes
9327 that any other overlays whose mapped ranges overlap that of
9328 @var{overlay} are now unmapped.
9330 @item overlay unmap-overlay @var{overlay}
9331 @itemx overlay unmap @var{overlay}
9332 @cindex unmap an overlay
9333 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9334 must be the name of the object file section containing the overlay.
9335 When an overlay is unmapped, @value{GDBN} assumes it can find the
9336 overlay's functions and variables at their load addresses.
9339 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9340 consults a data structure the overlay manager maintains in the inferior
9341 to see which overlays are mapped. For details, see @ref{Automatic
9344 @item overlay load-target
9346 @cindex reloading the overlay table
9347 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9348 re-reads the table @value{GDBN} automatically each time the inferior
9349 stops, so this command should only be necessary if you have changed the
9350 overlay mapping yourself using @value{GDBN}. This command is only
9351 useful when using automatic overlay debugging.
9353 @item overlay list-overlays
9355 @cindex listing mapped overlays
9356 Display a list of the overlays currently mapped, along with their mapped
9357 addresses, load addresses, and sizes.
9361 Normally, when @value{GDBN} prints a code address, it includes the name
9362 of the function the address falls in:
9365 (@value{GDBP}) print main
9366 $3 = @{int ()@} 0x11a0 <main>
9369 When overlay debugging is enabled, @value{GDBN} recognizes code in
9370 unmapped overlays, and prints the names of unmapped functions with
9371 asterisks around them. For example, if @code{foo} is a function in an
9372 unmapped overlay, @value{GDBN} prints it this way:
9375 (@value{GDBP}) overlay list
9376 No sections are mapped.
9377 (@value{GDBP}) print foo
9378 $5 = @{int (int)@} 0x100000 <*foo*>
9381 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9385 (@value{GDBP}) overlay list
9386 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9387 mapped at 0x1016 - 0x104a
9388 (@value{GDBP}) print foo
9389 $6 = @{int (int)@} 0x1016 <foo>
9392 When overlay debugging is enabled, @value{GDBN} can find the correct
9393 address for functions and variables in an overlay, whether or not the
9394 overlay is mapped. This allows most @value{GDBN} commands, like
9395 @code{break} and @code{disassemble}, to work normally, even on unmapped
9396 code. However, @value{GDBN}'s breakpoint support has some limitations:
9400 @cindex breakpoints in overlays
9401 @cindex overlays, setting breakpoints in
9402 You can set breakpoints in functions in unmapped overlays, as long as
9403 @value{GDBN} can write to the overlay at its load address.
9405 @value{GDBN} can not set hardware or simulator-based breakpoints in
9406 unmapped overlays. However, if you set a breakpoint at the end of your
9407 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9408 you are using manual overlay management), @value{GDBN} will re-set its
9409 breakpoints properly.
9413 @node Automatic Overlay Debugging
9414 @section Automatic Overlay Debugging
9415 @cindex automatic overlay debugging
9417 @value{GDBN} can automatically track which overlays are mapped and which
9418 are not, given some simple co-operation from the overlay manager in the
9419 inferior. If you enable automatic overlay debugging with the
9420 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
9421 looks in the inferior's memory for certain variables describing the
9422 current state of the overlays.
9424 Here are the variables your overlay manager must define to support
9425 @value{GDBN}'s automatic overlay debugging:
9429 @item @code{_ovly_table}:
9430 This variable must be an array of the following structures:
9435 /* The overlay's mapped address. */
9438 /* The size of the overlay, in bytes. */
9441 /* The overlay's load address. */
9444 /* Non-zero if the overlay is currently mapped;
9446 unsigned long mapped;
9450 @item @code{_novlys}:
9451 This variable must be a four-byte signed integer, holding the total
9452 number of elements in @code{_ovly_table}.
9456 To decide whether a particular overlay is mapped or not, @value{GDBN}
9457 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9458 @code{lma} members equal the VMA and LMA of the overlay's section in the
9459 executable file. When @value{GDBN} finds a matching entry, it consults
9460 the entry's @code{mapped} member to determine whether the overlay is
9463 In addition, your overlay manager may define a function called
9464 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9465 will silently set a breakpoint there. If the overlay manager then
9466 calls this function whenever it has changed the overlay table, this
9467 will enable @value{GDBN} to accurately keep track of which overlays
9468 are in program memory, and update any breakpoints that may be set
9469 in overlays. This will allow breakpoints to work even if the
9470 overlays are kept in ROM or other non-writable memory while they
9471 are not being executed.
9473 @node Overlay Sample Program
9474 @section Overlay Sample Program
9475 @cindex overlay example program
9477 When linking a program which uses overlays, you must place the overlays
9478 at their load addresses, while relocating them to run at their mapped
9479 addresses. To do this, you must write a linker script (@pxref{Overlay
9480 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9481 since linker scripts are specific to a particular host system, target
9482 architecture, and target memory layout, this manual cannot provide
9483 portable sample code demonstrating @value{GDBN}'s overlay support.
9485 However, the @value{GDBN} source distribution does contain an overlaid
9486 program, with linker scripts for a few systems, as part of its test
9487 suite. The program consists of the following files from
9488 @file{gdb/testsuite/gdb.base}:
9492 The main program file.
9494 A simple overlay manager, used by @file{overlays.c}.
9499 Overlay modules, loaded and used by @file{overlays.c}.
9502 Linker scripts for linking the test program on the @code{d10v-elf}
9503 and @code{m32r-elf} targets.
9506 You can build the test program using the @code{d10v-elf} GCC
9507 cross-compiler like this:
9510 $ d10v-elf-gcc -g -c overlays.c
9511 $ d10v-elf-gcc -g -c ovlymgr.c
9512 $ d10v-elf-gcc -g -c foo.c
9513 $ d10v-elf-gcc -g -c bar.c
9514 $ d10v-elf-gcc -g -c baz.c
9515 $ d10v-elf-gcc -g -c grbx.c
9516 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9517 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9520 The build process is identical for any other architecture, except that
9521 you must substitute the appropriate compiler and linker script for the
9522 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9526 @chapter Using @value{GDBN} with Different Languages
9529 Although programming languages generally have common aspects, they are
9530 rarely expressed in the same manner. For instance, in ANSI C,
9531 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9532 Modula-2, it is accomplished by @code{p^}. Values can also be
9533 represented (and displayed) differently. Hex numbers in C appear as
9534 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9536 @cindex working language
9537 Language-specific information is built into @value{GDBN} for some languages,
9538 allowing you to express operations like the above in your program's
9539 native language, and allowing @value{GDBN} to output values in a manner
9540 consistent with the syntax of your program's native language. The
9541 language you use to build expressions is called the @dfn{working
9545 * Setting:: Switching between source languages
9546 * Show:: Displaying the language
9547 * Checks:: Type and range checks
9548 * Supported Languages:: Supported languages
9549 * Unsupported Languages:: Unsupported languages
9553 @section Switching Between Source Languages
9555 There are two ways to control the working language---either have @value{GDBN}
9556 set it automatically, or select it manually yourself. You can use the
9557 @code{set language} command for either purpose. On startup, @value{GDBN}
9558 defaults to setting the language automatically. The working language is
9559 used to determine how expressions you type are interpreted, how values
9562 In addition to the working language, every source file that
9563 @value{GDBN} knows about has its own working language. For some object
9564 file formats, the compiler might indicate which language a particular
9565 source file is in. However, most of the time @value{GDBN} infers the
9566 language from the name of the file. The language of a source file
9567 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9568 show each frame appropriately for its own language. There is no way to
9569 set the language of a source file from within @value{GDBN}, but you can
9570 set the language associated with a filename extension. @xref{Show, ,
9571 Displaying the Language}.
9573 This is most commonly a problem when you use a program, such
9574 as @code{cfront} or @code{f2c}, that generates C but is written in
9575 another language. In that case, make the
9576 program use @code{#line} directives in its C output; that way
9577 @value{GDBN} will know the correct language of the source code of the original
9578 program, and will display that source code, not the generated C code.
9581 * Filenames:: Filename extensions and languages.
9582 * Manually:: Setting the working language manually
9583 * Automatically:: Having @value{GDBN} infer the source language
9587 @subsection List of Filename Extensions and Languages
9589 If a source file name ends in one of the following extensions, then
9590 @value{GDBN} infers that its language is the one indicated.
9611 Objective-C source file
9618 Modula-2 source file
9622 Assembler source file. This actually behaves almost like C, but
9623 @value{GDBN} does not skip over function prologues when stepping.
9626 In addition, you may set the language associated with a filename
9627 extension. @xref{Show, , Displaying the Language}.
9630 @subsection Setting the Working Language
9632 If you allow @value{GDBN} to set the language automatically,
9633 expressions are interpreted the same way in your debugging session and
9636 @kindex set language
9637 If you wish, you may set the language manually. To do this, issue the
9638 command @samp{set language @var{lang}}, where @var{lang} is the name of
9640 @code{c} or @code{modula-2}.
9641 For a list of the supported languages, type @samp{set language}.
9643 Setting the language manually prevents @value{GDBN} from updating the working
9644 language automatically. This can lead to confusion if you try
9645 to debug a program when the working language is not the same as the
9646 source language, when an expression is acceptable to both
9647 languages---but means different things. For instance, if the current
9648 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9656 might not have the effect you intended. In C, this means to add
9657 @code{b} and @code{c} and place the result in @code{a}. The result
9658 printed would be the value of @code{a}. In Modula-2, this means to compare
9659 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9662 @subsection Having @value{GDBN} Infer the Source Language
9664 To have @value{GDBN} set the working language automatically, use
9665 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9666 then infers the working language. That is, when your program stops in a
9667 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9668 working language to the language recorded for the function in that
9669 frame. If the language for a frame is unknown (that is, if the function
9670 or block corresponding to the frame was defined in a source file that
9671 does not have a recognized extension), the current working language is
9672 not changed, and @value{GDBN} issues a warning.
9674 This may not seem necessary for most programs, which are written
9675 entirely in one source language. However, program modules and libraries
9676 written in one source language can be used by a main program written in
9677 a different source language. Using @samp{set language auto} in this
9678 case frees you from having to set the working language manually.
9681 @section Displaying the Language
9683 The following commands help you find out which language is the
9684 working language, and also what language source files were written in.
9688 @kindex show language
9689 Display the current working language. This is the
9690 language you can use with commands such as @code{print} to
9691 build and compute expressions that may involve variables in your program.
9694 @kindex info frame@r{, show the source language}
9695 Display the source language for this frame. This language becomes the
9696 working language if you use an identifier from this frame.
9697 @xref{Frame Info, ,Information about a Frame}, to identify the other
9698 information listed here.
9701 @kindex info source@r{, show the source language}
9702 Display the source language of this source file.
9703 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9704 information listed here.
9707 In unusual circumstances, you may have source files with extensions
9708 not in the standard list. You can then set the extension associated
9709 with a language explicitly:
9712 @item set extension-language @var{ext} @var{language}
9713 @kindex set extension-language
9714 Tell @value{GDBN} that source files with extension @var{ext} are to be
9715 assumed as written in the source language @var{language}.
9717 @item info extensions
9718 @kindex info extensions
9719 List all the filename extensions and the associated languages.
9723 @section Type and Range Checking
9726 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9727 checking are included, but they do not yet have any effect. This
9728 section documents the intended facilities.
9730 @c FIXME remove warning when type/range code added
9732 Some languages are designed to guard you against making seemingly common
9733 errors through a series of compile- and run-time checks. These include
9734 checking the type of arguments to functions and operators, and making
9735 sure mathematical overflows are caught at run time. Checks such as
9736 these help to ensure a program's correctness once it has been compiled
9737 by eliminating type mismatches, and providing active checks for range
9738 errors when your program is running.
9740 @value{GDBN} can check for conditions like the above if you wish.
9741 Although @value{GDBN} does not check the statements in your program,
9742 it can check expressions entered directly into @value{GDBN} for
9743 evaluation via the @code{print} command, for example. As with the
9744 working language, @value{GDBN} can also decide whether or not to check
9745 automatically based on your program's source language.
9746 @xref{Supported Languages, ,Supported Languages}, for the default
9747 settings of supported languages.
9750 * Type Checking:: An overview of type checking
9751 * Range Checking:: An overview of range checking
9754 @cindex type checking
9755 @cindex checks, type
9757 @subsection An Overview of Type Checking
9759 Some languages, such as Modula-2, are strongly typed, meaning that the
9760 arguments to operators and functions have to be of the correct type,
9761 otherwise an error occurs. These checks prevent type mismatch
9762 errors from ever causing any run-time problems. For example,
9770 The second example fails because the @code{CARDINAL} 1 is not
9771 type-compatible with the @code{REAL} 2.3.
9773 For the expressions you use in @value{GDBN} commands, you can tell the
9774 @value{GDBN} type checker to skip checking;
9775 to treat any mismatches as errors and abandon the expression;
9776 or to only issue warnings when type mismatches occur,
9777 but evaluate the expression anyway. When you choose the last of
9778 these, @value{GDBN} evaluates expressions like the second example above, but
9779 also issues a warning.
9781 Even if you turn type checking off, there may be other reasons
9782 related to type that prevent @value{GDBN} from evaluating an expression.
9783 For instance, @value{GDBN} does not know how to add an @code{int} and
9784 a @code{struct foo}. These particular type errors have nothing to do
9785 with the language in use, and usually arise from expressions, such as
9786 the one described above, which make little sense to evaluate anyway.
9788 Each language defines to what degree it is strict about type. For
9789 instance, both Modula-2 and C require the arguments to arithmetical
9790 operators to be numbers. In C, enumerated types and pointers can be
9791 represented as numbers, so that they are valid arguments to mathematical
9792 operators. @xref{Supported Languages, ,Supported Languages}, for further
9793 details on specific languages.
9795 @value{GDBN} provides some additional commands for controlling the type checker:
9797 @kindex set check type
9798 @kindex show check type
9800 @item set check type auto
9801 Set type checking on or off based on the current working language.
9802 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9805 @item set check type on
9806 @itemx set check type off
9807 Set type checking on or off, overriding the default setting for the
9808 current working language. Issue a warning if the setting does not
9809 match the language default. If any type mismatches occur in
9810 evaluating an expression while type checking is on, @value{GDBN} prints a
9811 message and aborts evaluation of the expression.
9813 @item set check type warn
9814 Cause the type checker to issue warnings, but to always attempt to
9815 evaluate the expression. Evaluating the expression may still
9816 be impossible for other reasons. For example, @value{GDBN} cannot add
9817 numbers and structures.
9820 Show the current setting of the type checker, and whether or not @value{GDBN}
9821 is setting it automatically.
9824 @cindex range checking
9825 @cindex checks, range
9826 @node Range Checking
9827 @subsection An Overview of Range Checking
9829 In some languages (such as Modula-2), it is an error to exceed the
9830 bounds of a type; this is enforced with run-time checks. Such range
9831 checking is meant to ensure program correctness by making sure
9832 computations do not overflow, or indices on an array element access do
9833 not exceed the bounds of the array.
9835 For expressions you use in @value{GDBN} commands, you can tell
9836 @value{GDBN} to treat range errors in one of three ways: ignore them,
9837 always treat them as errors and abandon the expression, or issue
9838 warnings but evaluate the expression anyway.
9840 A range error can result from numerical overflow, from exceeding an
9841 array index bound, or when you type a constant that is not a member
9842 of any type. Some languages, however, do not treat overflows as an
9843 error. In many implementations of C, mathematical overflow causes the
9844 result to ``wrap around'' to lower values---for example, if @var{m} is
9845 the largest integer value, and @var{s} is the smallest, then
9848 @var{m} + 1 @result{} @var{s}
9851 This, too, is specific to individual languages, and in some cases
9852 specific to individual compilers or machines. @xref{Supported Languages, ,
9853 Supported Languages}, for further details on specific languages.
9855 @value{GDBN} provides some additional commands for controlling the range checker:
9857 @kindex set check range
9858 @kindex show check range
9860 @item set check range auto
9861 Set range checking on or off based on the current working language.
9862 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9865 @item set check range on
9866 @itemx set check range off
9867 Set range checking on or off, overriding the default setting for the
9868 current working language. A warning is issued if the setting does not
9869 match the language default. If a range error occurs and range checking is on,
9870 then a message is printed and evaluation of the expression is aborted.
9872 @item set check range warn
9873 Output messages when the @value{GDBN} range checker detects a range error,
9874 but attempt to evaluate the expression anyway. Evaluating the
9875 expression may still be impossible for other reasons, such as accessing
9876 memory that the process does not own (a typical example from many Unix
9880 Show the current setting of the range checker, and whether or not it is
9881 being set automatically by @value{GDBN}.
9884 @node Supported Languages
9885 @section Supported Languages
9887 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9888 assembly, Modula-2, and Ada.
9889 @c This is false ...
9890 Some @value{GDBN} features may be used in expressions regardless of the
9891 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9892 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9893 ,Expressions}) can be used with the constructs of any supported
9896 The following sections detail to what degree each source language is
9897 supported by @value{GDBN}. These sections are not meant to be language
9898 tutorials or references, but serve only as a reference guide to what the
9899 @value{GDBN} expression parser accepts, and what input and output
9900 formats should look like for different languages. There are many good
9901 books written on each of these languages; please look to these for a
9902 language reference or tutorial.
9906 * Objective-C:: Objective-C
9909 * Modula-2:: Modula-2
9914 @subsection C and C@t{++}
9916 @cindex C and C@t{++}
9917 @cindex expressions in C or C@t{++}
9919 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9920 to both languages. Whenever this is the case, we discuss those languages
9924 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9925 @cindex @sc{gnu} C@t{++}
9926 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9927 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9928 effectively, you must compile your C@t{++} programs with a supported
9929 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9930 compiler (@code{aCC}).
9932 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9933 format; if it doesn't work on your system, try the stabs+ debugging
9934 format. You can select those formats explicitly with the @code{g++}
9935 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9936 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9937 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9940 * C Operators:: C and C@t{++} operators
9941 * C Constants:: C and C@t{++} constants
9942 * C Plus Plus Expressions:: C@t{++} expressions
9943 * C Defaults:: Default settings for C and C@t{++}
9944 * C Checks:: C and C@t{++} type and range checks
9945 * Debugging C:: @value{GDBN} and C
9946 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9947 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9951 @subsubsection C and C@t{++} Operators
9953 @cindex C and C@t{++} operators
9955 Operators must be defined on values of specific types. For instance,
9956 @code{+} is defined on numbers, but not on structures. Operators are
9957 often defined on groups of types.
9959 For the purposes of C and C@t{++}, the following definitions hold:
9964 @emph{Integral types} include @code{int} with any of its storage-class
9965 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9968 @emph{Floating-point types} include @code{float}, @code{double}, and
9969 @code{long double} (if supported by the target platform).
9972 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9975 @emph{Scalar types} include all of the above.
9980 The following operators are supported. They are listed here
9981 in order of increasing precedence:
9985 The comma or sequencing operator. Expressions in a comma-separated list
9986 are evaluated from left to right, with the result of the entire
9987 expression being the last expression evaluated.
9990 Assignment. The value of an assignment expression is the value
9991 assigned. Defined on scalar types.
9994 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9995 and translated to @w{@code{@var{a} = @var{a op b}}}.
9996 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9997 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9998 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
10001 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
10002 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
10006 Logical @sc{or}. Defined on integral types.
10009 Logical @sc{and}. Defined on integral types.
10012 Bitwise @sc{or}. Defined on integral types.
10015 Bitwise exclusive-@sc{or}. Defined on integral types.
10018 Bitwise @sc{and}. Defined on integral types.
10021 Equality and inequality. Defined on scalar types. The value of these
10022 expressions is 0 for false and non-zero for true.
10024 @item <@r{, }>@r{, }<=@r{, }>=
10025 Less than, greater than, less than or equal, greater than or equal.
10026 Defined on scalar types. The value of these expressions is 0 for false
10027 and non-zero for true.
10030 left shift, and right shift. Defined on integral types.
10033 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10036 Addition and subtraction. Defined on integral types, floating-point types and
10039 @item *@r{, }/@r{, }%
10040 Multiplication, division, and modulus. Multiplication and division are
10041 defined on integral and floating-point types. Modulus is defined on
10045 Increment and decrement. When appearing before a variable, the
10046 operation is performed before the variable is used in an expression;
10047 when appearing after it, the variable's value is used before the
10048 operation takes place.
10051 Pointer dereferencing. Defined on pointer types. Same precedence as
10055 Address operator. Defined on variables. Same precedence as @code{++}.
10057 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
10058 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
10059 to examine the address
10060 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
10064 Negative. Defined on integral and floating-point types. Same
10065 precedence as @code{++}.
10068 Logical negation. Defined on integral types. Same precedence as
10072 Bitwise complement operator. Defined on integral types. Same precedence as
10077 Structure member, and pointer-to-structure member. For convenience,
10078 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10079 pointer based on the stored type information.
10080 Defined on @code{struct} and @code{union} data.
10083 Dereferences of pointers to members.
10086 Array indexing. @code{@var{a}[@var{i}]} is defined as
10087 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10090 Function parameter list. Same precedence as @code{->}.
10093 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10094 and @code{class} types.
10097 Doubled colons also represent the @value{GDBN} scope operator
10098 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10102 If an operator is redefined in the user code, @value{GDBN} usually
10103 attempts to invoke the redefined version instead of using the operator's
10104 predefined meaning.
10107 @subsubsection C and C@t{++} Constants
10109 @cindex C and C@t{++} constants
10111 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10116 Integer constants are a sequence of digits. Octal constants are
10117 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10118 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10119 @samp{l}, specifying that the constant should be treated as a
10123 Floating point constants are a sequence of digits, followed by a decimal
10124 point, followed by a sequence of digits, and optionally followed by an
10125 exponent. An exponent is of the form:
10126 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10127 sequence of digits. The @samp{+} is optional for positive exponents.
10128 A floating-point constant may also end with a letter @samp{f} or
10129 @samp{F}, specifying that the constant should be treated as being of
10130 the @code{float} (as opposed to the default @code{double}) type; or with
10131 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10135 Enumerated constants consist of enumerated identifiers, or their
10136 integral equivalents.
10139 Character constants are a single character surrounded by single quotes
10140 (@code{'}), or a number---the ordinal value of the corresponding character
10141 (usually its @sc{ascii} value). Within quotes, the single character may
10142 be represented by a letter or by @dfn{escape sequences}, which are of
10143 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10144 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10145 @samp{@var{x}} is a predefined special character---for example,
10146 @samp{\n} for newline.
10149 String constants are a sequence of character constants surrounded by
10150 double quotes (@code{"}). Any valid character constant (as described
10151 above) may appear. Double quotes within the string must be preceded by
10152 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10156 Pointer constants are an integral value. You can also write pointers
10157 to constants using the C operator @samp{&}.
10160 Array constants are comma-separated lists surrounded by braces @samp{@{}
10161 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10162 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10163 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10166 @node C Plus Plus Expressions
10167 @subsubsection C@t{++} Expressions
10169 @cindex expressions in C@t{++}
10170 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10172 @cindex debugging C@t{++} programs
10173 @cindex C@t{++} compilers
10174 @cindex debug formats and C@t{++}
10175 @cindex @value{NGCC} and C@t{++}
10177 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10178 proper compiler and the proper debug format. Currently, @value{GDBN}
10179 works best when debugging C@t{++} code that is compiled with
10180 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10181 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10182 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10183 stabs+ as their default debug format, so you usually don't need to
10184 specify a debug format explicitly. Other compilers and/or debug formats
10185 are likely to work badly or not at all when using @value{GDBN} to debug
10191 @cindex member functions
10193 Member function calls are allowed; you can use expressions like
10196 count = aml->GetOriginal(x, y)
10199 @vindex this@r{, inside C@t{++} member functions}
10200 @cindex namespace in C@t{++}
10202 While a member function is active (in the selected stack frame), your
10203 expressions have the same namespace available as the member function;
10204 that is, @value{GDBN} allows implicit references to the class instance
10205 pointer @code{this} following the same rules as C@t{++}.
10207 @cindex call overloaded functions
10208 @cindex overloaded functions, calling
10209 @cindex type conversions in C@t{++}
10211 You can call overloaded functions; @value{GDBN} resolves the function
10212 call to the right definition, with some restrictions. @value{GDBN} does not
10213 perform overload resolution involving user-defined type conversions,
10214 calls to constructors, or instantiations of templates that do not exist
10215 in the program. It also cannot handle ellipsis argument lists or
10218 It does perform integral conversions and promotions, floating-point
10219 promotions, arithmetic conversions, pointer conversions, conversions of
10220 class objects to base classes, and standard conversions such as those of
10221 functions or arrays to pointers; it requires an exact match on the
10222 number of function arguments.
10224 Overload resolution is always performed, unless you have specified
10225 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10226 ,@value{GDBN} Features for C@t{++}}.
10228 You must specify @code{set overload-resolution off} in order to use an
10229 explicit function signature to call an overloaded function, as in
10231 p 'foo(char,int)'('x', 13)
10234 The @value{GDBN} command-completion facility can simplify this;
10235 see @ref{Completion, ,Command Completion}.
10237 @cindex reference declarations
10239 @value{GDBN} understands variables declared as C@t{++} references; you can use
10240 them in expressions just as you do in C@t{++} source---they are automatically
10243 In the parameter list shown when @value{GDBN} displays a frame, the values of
10244 reference variables are not displayed (unlike other variables); this
10245 avoids clutter, since references are often used for large structures.
10246 The @emph{address} of a reference variable is always shown, unless
10247 you have specified @samp{set print address off}.
10250 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10251 expressions can use it just as expressions in your program do. Since
10252 one scope may be defined in another, you can use @code{::} repeatedly if
10253 necessary, for example in an expression like
10254 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10255 resolving name scope by reference to source files, in both C and C@t{++}
10256 debugging (@pxref{Variables, ,Program Variables}).
10259 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10260 calling virtual functions correctly, printing out virtual bases of
10261 objects, calling functions in a base subobject, casting objects, and
10262 invoking user-defined operators.
10265 @subsubsection C and C@t{++} Defaults
10267 @cindex C and C@t{++} defaults
10269 If you allow @value{GDBN} to set type and range checking automatically, they
10270 both default to @code{off} whenever the working language changes to
10271 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10272 selects the working language.
10274 If you allow @value{GDBN} to set the language automatically, it
10275 recognizes source files whose names end with @file{.c}, @file{.C}, or
10276 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10277 these files, it sets the working language to C or C@t{++}.
10278 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10279 for further details.
10281 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10282 @c unimplemented. If (b) changes, it might make sense to let this node
10283 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10286 @subsubsection C and C@t{++} Type and Range Checks
10288 @cindex C and C@t{++} checks
10290 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10291 is not used. However, if you turn type checking on, @value{GDBN}
10292 considers two variables type equivalent if:
10296 The two variables are structured and have the same structure, union, or
10300 The two variables have the same type name, or types that have been
10301 declared equivalent through @code{typedef}.
10304 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10307 The two @code{struct}, @code{union}, or @code{enum} variables are
10308 declared in the same declaration. (Note: this may not be true for all C
10313 Range checking, if turned on, is done on mathematical operations. Array
10314 indices are not checked, since they are often used to index a pointer
10315 that is not itself an array.
10318 @subsubsection @value{GDBN} and C
10320 The @code{set print union} and @code{show print union} commands apply to
10321 the @code{union} type. When set to @samp{on}, any @code{union} that is
10322 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10323 appears as @samp{@{...@}}.
10325 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10326 with pointers and a memory allocation function. @xref{Expressions,
10329 @node Debugging C Plus Plus
10330 @subsubsection @value{GDBN} Features for C@t{++}
10332 @cindex commands for C@t{++}
10334 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10335 designed specifically for use with C@t{++}. Here is a summary:
10338 @cindex break in overloaded functions
10339 @item @r{breakpoint menus}
10340 When you want a breakpoint in a function whose name is overloaded,
10341 @value{GDBN} has the capability to display a menu of possible breakpoint
10342 locations to help you specify which function definition you want.
10343 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10345 @cindex overloading in C@t{++}
10346 @item rbreak @var{regex}
10347 Setting breakpoints using regular expressions is helpful for setting
10348 breakpoints on overloaded functions that are not members of any special
10350 @xref{Set Breaks, ,Setting Breakpoints}.
10352 @cindex C@t{++} exception handling
10355 Debug C@t{++} exception handling using these commands. @xref{Set
10356 Catchpoints, , Setting Catchpoints}.
10358 @cindex inheritance
10359 @item ptype @var{typename}
10360 Print inheritance relationships as well as other information for type
10362 @xref{Symbols, ,Examining the Symbol Table}.
10364 @cindex C@t{++} symbol display
10365 @item set print demangle
10366 @itemx show print demangle
10367 @itemx set print asm-demangle
10368 @itemx show print asm-demangle
10369 Control whether C@t{++} symbols display in their source form, both when
10370 displaying code as C@t{++} source and when displaying disassemblies.
10371 @xref{Print Settings, ,Print Settings}.
10373 @item set print object
10374 @itemx show print object
10375 Choose whether to print derived (actual) or declared types of objects.
10376 @xref{Print Settings, ,Print Settings}.
10378 @item set print vtbl
10379 @itemx show print vtbl
10380 Control the format for printing virtual function tables.
10381 @xref{Print Settings, ,Print Settings}.
10382 (The @code{vtbl} commands do not work on programs compiled with the HP
10383 ANSI C@t{++} compiler (@code{aCC}).)
10385 @kindex set overload-resolution
10386 @cindex overloaded functions, overload resolution
10387 @item set overload-resolution on
10388 Enable overload resolution for C@t{++} expression evaluation. The default
10389 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10390 and searches for a function whose signature matches the argument types,
10391 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10392 Expressions, ,C@t{++} Expressions}, for details).
10393 If it cannot find a match, it emits a message.
10395 @item set overload-resolution off
10396 Disable overload resolution for C@t{++} expression evaluation. For
10397 overloaded functions that are not class member functions, @value{GDBN}
10398 chooses the first function of the specified name that it finds in the
10399 symbol table, whether or not its arguments are of the correct type. For
10400 overloaded functions that are class member functions, @value{GDBN}
10401 searches for a function whose signature @emph{exactly} matches the
10404 @kindex show overload-resolution
10405 @item show overload-resolution
10406 Show the current setting of overload resolution.
10408 @item @r{Overloaded symbol names}
10409 You can specify a particular definition of an overloaded symbol, using
10410 the same notation that is used to declare such symbols in C@t{++}: type
10411 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10412 also use the @value{GDBN} command-line word completion facilities to list the
10413 available choices, or to finish the type list for you.
10414 @xref{Completion,, Command Completion}, for details on how to do this.
10417 @node Decimal Floating Point
10418 @subsubsection Decimal Floating Point format
10419 @cindex decimal floating point format
10421 @value{GDBN} can examine, set and perform computations with numbers in
10422 decimal floating point format, which in the C language correspond to the
10423 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
10424 specified by the extension to support decimal floating-point arithmetic.
10426 There are two encodings in use, depending on the architecture: BID (Binary
10427 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10428 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10431 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10432 to manipulate decimal floating point numbers, it is not possible to convert
10433 (using a cast, for example) integers wider than 32-bit to decimal float.
10435 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10436 point computations, error checking in decimal float operations ignores
10437 underflow, overflow and divide by zero exceptions.
10439 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10440 to inspect @code{_Decimal128} values stored in floating point registers. See
10441 @ref{PowerPC,,PowerPC} for more details.
10444 @subsection Objective-C
10446 @cindex Objective-C
10447 This section provides information about some commands and command
10448 options that are useful for debugging Objective-C code. See also
10449 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10450 few more commands specific to Objective-C support.
10453 * Method Names in Commands::
10454 * The Print Command with Objective-C::
10457 @node Method Names in Commands
10458 @subsubsection Method Names in Commands
10460 The following commands have been extended to accept Objective-C method
10461 names as line specifications:
10463 @kindex clear@r{, and Objective-C}
10464 @kindex break@r{, and Objective-C}
10465 @kindex info line@r{, and Objective-C}
10466 @kindex jump@r{, and Objective-C}
10467 @kindex list@r{, and Objective-C}
10471 @item @code{info line}
10476 A fully qualified Objective-C method name is specified as
10479 -[@var{Class} @var{methodName}]
10482 where the minus sign is used to indicate an instance method and a
10483 plus sign (not shown) is used to indicate a class method. The class
10484 name @var{Class} and method name @var{methodName} are enclosed in
10485 brackets, similar to the way messages are specified in Objective-C
10486 source code. For example, to set a breakpoint at the @code{create}
10487 instance method of class @code{Fruit} in the program currently being
10491 break -[Fruit create]
10494 To list ten program lines around the @code{initialize} class method,
10498 list +[NSText initialize]
10501 In the current version of @value{GDBN}, the plus or minus sign is
10502 required. In future versions of @value{GDBN}, the plus or minus
10503 sign will be optional, but you can use it to narrow the search. It
10504 is also possible to specify just a method name:
10510 You must specify the complete method name, including any colons. If
10511 your program's source files contain more than one @code{create} method,
10512 you'll be presented with a numbered list of classes that implement that
10513 method. Indicate your choice by number, or type @samp{0} to exit if
10516 As another example, to clear a breakpoint established at the
10517 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10520 clear -[NSWindow makeKeyAndOrderFront:]
10523 @node The Print Command with Objective-C
10524 @subsubsection The Print Command With Objective-C
10525 @cindex Objective-C, print objects
10526 @kindex print-object
10527 @kindex po @r{(@code{print-object})}
10529 The print command has also been extended to accept methods. For example:
10532 print -[@var{object} hash]
10535 @cindex print an Objective-C object description
10536 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10538 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10539 and print the result. Also, an additional command has been added,
10540 @code{print-object} or @code{po} for short, which is meant to print
10541 the description of an object. However, this command may only work
10542 with certain Objective-C libraries that have a particular hook
10543 function, @code{_NSPrintForDebugger}, defined.
10546 @subsection Fortran
10547 @cindex Fortran-specific support in @value{GDBN}
10549 @value{GDBN} can be used to debug programs written in Fortran, but it
10550 currently supports only the features of Fortran 77 language.
10552 @cindex trailing underscore, in Fortran symbols
10553 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10554 among them) append an underscore to the names of variables and
10555 functions. When you debug programs compiled by those compilers, you
10556 will need to refer to variables and functions with a trailing
10560 * Fortran Operators:: Fortran operators and expressions
10561 * Fortran Defaults:: Default settings for Fortran
10562 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10565 @node Fortran Operators
10566 @subsubsection Fortran Operators and Expressions
10568 @cindex Fortran operators and expressions
10570 Operators must be defined on values of specific types. For instance,
10571 @code{+} is defined on numbers, but not on characters or other non-
10572 arithmetic types. Operators are often defined on groups of types.
10576 The exponentiation operator. It raises the first operand to the power
10580 The range operator. Normally used in the form of array(low:high) to
10581 represent a section of array.
10584 The access component operator. Normally used to access elements in derived
10585 types. Also suitable for unions. As unions aren't part of regular Fortran,
10586 this can only happen when accessing a register that uses a gdbarch-defined
10590 @node Fortran Defaults
10591 @subsubsection Fortran Defaults
10593 @cindex Fortran Defaults
10595 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10596 default uses case-insensitive matches for Fortran symbols. You can
10597 change that with the @samp{set case-insensitive} command, see
10598 @ref{Symbols}, for the details.
10600 @node Special Fortran Commands
10601 @subsubsection Special Fortran Commands
10603 @cindex Special Fortran commands
10605 @value{GDBN} has some commands to support Fortran-specific features,
10606 such as displaying common blocks.
10609 @cindex @code{COMMON} blocks, Fortran
10610 @kindex info common
10611 @item info common @r{[}@var{common-name}@r{]}
10612 This command prints the values contained in the Fortran @code{COMMON}
10613 block whose name is @var{common-name}. With no argument, the names of
10614 all @code{COMMON} blocks visible at the current program location are
10621 @cindex Pascal support in @value{GDBN}, limitations
10622 Debugging Pascal programs which use sets, subranges, file variables, or
10623 nested functions does not currently work. @value{GDBN} does not support
10624 entering expressions, printing values, or similar features using Pascal
10627 The Pascal-specific command @code{set print pascal_static-members}
10628 controls whether static members of Pascal objects are displayed.
10629 @xref{Print Settings, pascal_static-members}.
10632 @subsection Modula-2
10634 @cindex Modula-2, @value{GDBN} support
10636 The extensions made to @value{GDBN} to support Modula-2 only support
10637 output from the @sc{gnu} Modula-2 compiler (which is currently being
10638 developed). Other Modula-2 compilers are not currently supported, and
10639 attempting to debug executables produced by them is most likely
10640 to give an error as @value{GDBN} reads in the executable's symbol
10643 @cindex expressions in Modula-2
10645 * M2 Operators:: Built-in operators
10646 * Built-In Func/Proc:: Built-in functions and procedures
10647 * M2 Constants:: Modula-2 constants
10648 * M2 Types:: Modula-2 types
10649 * M2 Defaults:: Default settings for Modula-2
10650 * Deviations:: Deviations from standard Modula-2
10651 * M2 Checks:: Modula-2 type and range checks
10652 * M2 Scope:: The scope operators @code{::} and @code{.}
10653 * GDB/M2:: @value{GDBN} and Modula-2
10657 @subsubsection Operators
10658 @cindex Modula-2 operators
10660 Operators must be defined on values of specific types. For instance,
10661 @code{+} is defined on numbers, but not on structures. Operators are
10662 often defined on groups of types. For the purposes of Modula-2, the
10663 following definitions hold:
10668 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10672 @emph{Character types} consist of @code{CHAR} and its subranges.
10675 @emph{Floating-point types} consist of @code{REAL}.
10678 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10682 @emph{Scalar types} consist of all of the above.
10685 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10688 @emph{Boolean types} consist of @code{BOOLEAN}.
10692 The following operators are supported, and appear in order of
10693 increasing precedence:
10697 Function argument or array index separator.
10700 Assignment. The value of @var{var} @code{:=} @var{value} is
10704 Less than, greater than on integral, floating-point, or enumerated
10708 Less than or equal to, greater than or equal to
10709 on integral, floating-point and enumerated types, or set inclusion on
10710 set types. Same precedence as @code{<}.
10712 @item =@r{, }<>@r{, }#
10713 Equality and two ways of expressing inequality, valid on scalar types.
10714 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10715 available for inequality, since @code{#} conflicts with the script
10719 Set membership. Defined on set types and the types of their members.
10720 Same precedence as @code{<}.
10723 Boolean disjunction. Defined on boolean types.
10726 Boolean conjunction. Defined on boolean types.
10729 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10732 Addition and subtraction on integral and floating-point types, or union
10733 and difference on set types.
10736 Multiplication on integral and floating-point types, or set intersection
10740 Division on floating-point types, or symmetric set difference on set
10741 types. Same precedence as @code{*}.
10744 Integer division and remainder. Defined on integral types. Same
10745 precedence as @code{*}.
10748 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10751 Pointer dereferencing. Defined on pointer types.
10754 Boolean negation. Defined on boolean types. Same precedence as
10758 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10759 precedence as @code{^}.
10762 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10765 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10769 @value{GDBN} and Modula-2 scope operators.
10773 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10774 treats the use of the operator @code{IN}, or the use of operators
10775 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10776 @code{<=}, and @code{>=} on sets as an error.
10780 @node Built-In Func/Proc
10781 @subsubsection Built-in Functions and Procedures
10782 @cindex Modula-2 built-ins
10784 Modula-2 also makes available several built-in procedures and functions.
10785 In describing these, the following metavariables are used:
10790 represents an @code{ARRAY} variable.
10793 represents a @code{CHAR} constant or variable.
10796 represents a variable or constant of integral type.
10799 represents an identifier that belongs to a set. Generally used in the
10800 same function with the metavariable @var{s}. The type of @var{s} should
10801 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10804 represents a variable or constant of integral or floating-point type.
10807 represents a variable or constant of floating-point type.
10813 represents a variable.
10816 represents a variable or constant of one of many types. See the
10817 explanation of the function for details.
10820 All Modula-2 built-in procedures also return a result, described below.
10824 Returns the absolute value of @var{n}.
10827 If @var{c} is a lower case letter, it returns its upper case
10828 equivalent, otherwise it returns its argument.
10831 Returns the character whose ordinal value is @var{i}.
10834 Decrements the value in the variable @var{v} by one. Returns the new value.
10836 @item DEC(@var{v},@var{i})
10837 Decrements the value in the variable @var{v} by @var{i}. Returns the
10840 @item EXCL(@var{m},@var{s})
10841 Removes the element @var{m} from the set @var{s}. Returns the new
10844 @item FLOAT(@var{i})
10845 Returns the floating point equivalent of the integer @var{i}.
10847 @item HIGH(@var{a})
10848 Returns the index of the last member of @var{a}.
10851 Increments the value in the variable @var{v} by one. Returns the new value.
10853 @item INC(@var{v},@var{i})
10854 Increments the value in the variable @var{v} by @var{i}. Returns the
10857 @item INCL(@var{m},@var{s})
10858 Adds the element @var{m} to the set @var{s} if it is not already
10859 there. Returns the new set.
10862 Returns the maximum value of the type @var{t}.
10865 Returns the minimum value of the type @var{t}.
10868 Returns boolean TRUE if @var{i} is an odd number.
10871 Returns the ordinal value of its argument. For example, the ordinal
10872 value of a character is its @sc{ascii} value (on machines supporting the
10873 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10874 integral, character and enumerated types.
10876 @item SIZE(@var{x})
10877 Returns the size of its argument. @var{x} can be a variable or a type.
10879 @item TRUNC(@var{r})
10880 Returns the integral part of @var{r}.
10882 @item TSIZE(@var{x})
10883 Returns the size of its argument. @var{x} can be a variable or a type.
10885 @item VAL(@var{t},@var{i})
10886 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10890 @emph{Warning:} Sets and their operations are not yet supported, so
10891 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10895 @cindex Modula-2 constants
10897 @subsubsection Constants
10899 @value{GDBN} allows you to express the constants of Modula-2 in the following
10905 Integer constants are simply a sequence of digits. When used in an
10906 expression, a constant is interpreted to be type-compatible with the
10907 rest of the expression. Hexadecimal integers are specified by a
10908 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10911 Floating point constants appear as a sequence of digits, followed by a
10912 decimal point and another sequence of digits. An optional exponent can
10913 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10914 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10915 digits of the floating point constant must be valid decimal (base 10)
10919 Character constants consist of a single character enclosed by a pair of
10920 like quotes, either single (@code{'}) or double (@code{"}). They may
10921 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10922 followed by a @samp{C}.
10925 String constants consist of a sequence of characters enclosed by a
10926 pair of like quotes, either single (@code{'}) or double (@code{"}).
10927 Escape sequences in the style of C are also allowed. @xref{C
10928 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10932 Enumerated constants consist of an enumerated identifier.
10935 Boolean constants consist of the identifiers @code{TRUE} and
10939 Pointer constants consist of integral values only.
10942 Set constants are not yet supported.
10946 @subsubsection Modula-2 Types
10947 @cindex Modula-2 types
10949 Currently @value{GDBN} can print the following data types in Modula-2
10950 syntax: array types, record types, set types, pointer types, procedure
10951 types, enumerated types, subrange types and base types. You can also
10952 print the contents of variables declared using these type.
10953 This section gives a number of simple source code examples together with
10954 sample @value{GDBN} sessions.
10956 The first example contains the following section of code:
10965 and you can request @value{GDBN} to interrogate the type and value of
10966 @code{r} and @code{s}.
10969 (@value{GDBP}) print s
10971 (@value{GDBP}) ptype s
10973 (@value{GDBP}) print r
10975 (@value{GDBP}) ptype r
10980 Likewise if your source code declares @code{s} as:
10984 s: SET ['A'..'Z'] ;
10988 then you may query the type of @code{s} by:
10991 (@value{GDBP}) ptype s
10992 type = SET ['A'..'Z']
10996 Note that at present you cannot interactively manipulate set
10997 expressions using the debugger.
10999 The following example shows how you might declare an array in Modula-2
11000 and how you can interact with @value{GDBN} to print its type and contents:
11004 s: ARRAY [-10..10] OF CHAR ;
11008 (@value{GDBP}) ptype s
11009 ARRAY [-10..10] OF CHAR
11012 Note that the array handling is not yet complete and although the type
11013 is printed correctly, expression handling still assumes that all
11014 arrays have a lower bound of zero and not @code{-10} as in the example
11017 Here are some more type related Modula-2 examples:
11021 colour = (blue, red, yellow, green) ;
11022 t = [blue..yellow] ;
11030 The @value{GDBN} interaction shows how you can query the data type
11031 and value of a variable.
11034 (@value{GDBP}) print s
11036 (@value{GDBP}) ptype t
11037 type = [blue..yellow]
11041 In this example a Modula-2 array is declared and its contents
11042 displayed. Observe that the contents are written in the same way as
11043 their @code{C} counterparts.
11047 s: ARRAY [1..5] OF CARDINAL ;
11053 (@value{GDBP}) print s
11054 $1 = @{1, 0, 0, 0, 0@}
11055 (@value{GDBP}) ptype s
11056 type = ARRAY [1..5] OF CARDINAL
11059 The Modula-2 language interface to @value{GDBN} also understands
11060 pointer types as shown in this example:
11064 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11071 and you can request that @value{GDBN} describes the type of @code{s}.
11074 (@value{GDBP}) ptype s
11075 type = POINTER TO ARRAY [1..5] OF CARDINAL
11078 @value{GDBN} handles compound types as we can see in this example.
11079 Here we combine array types, record types, pointer types and subrange
11090 myarray = ARRAY myrange OF CARDINAL ;
11091 myrange = [-2..2] ;
11093 s: POINTER TO ARRAY myrange OF foo ;
11097 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11101 (@value{GDBP}) ptype s
11102 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11105 f3 : ARRAY [-2..2] OF CARDINAL;
11110 @subsubsection Modula-2 Defaults
11111 @cindex Modula-2 defaults
11113 If type and range checking are set automatically by @value{GDBN}, they
11114 both default to @code{on} whenever the working language changes to
11115 Modula-2. This happens regardless of whether you or @value{GDBN}
11116 selected the working language.
11118 If you allow @value{GDBN} to set the language automatically, then entering
11119 code compiled from a file whose name ends with @file{.mod} sets the
11120 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11121 Infer the Source Language}, for further details.
11124 @subsubsection Deviations from Standard Modula-2
11125 @cindex Modula-2, deviations from
11127 A few changes have been made to make Modula-2 programs easier to debug.
11128 This is done primarily via loosening its type strictness:
11132 Unlike in standard Modula-2, pointer constants can be formed by
11133 integers. This allows you to modify pointer variables during
11134 debugging. (In standard Modula-2, the actual address contained in a
11135 pointer variable is hidden from you; it can only be modified
11136 through direct assignment to another pointer variable or expression that
11137 returned a pointer.)
11140 C escape sequences can be used in strings and characters to represent
11141 non-printable characters. @value{GDBN} prints out strings with these
11142 escape sequences embedded. Single non-printable characters are
11143 printed using the @samp{CHR(@var{nnn})} format.
11146 The assignment operator (@code{:=}) returns the value of its right-hand
11150 All built-in procedures both modify @emph{and} return their argument.
11154 @subsubsection Modula-2 Type and Range Checks
11155 @cindex Modula-2 checks
11158 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11161 @c FIXME remove warning when type/range checks added
11163 @value{GDBN} considers two Modula-2 variables type equivalent if:
11167 They are of types that have been declared equivalent via a @code{TYPE
11168 @var{t1} = @var{t2}} statement
11171 They have been declared on the same line. (Note: This is true of the
11172 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11175 As long as type checking is enabled, any attempt to combine variables
11176 whose types are not equivalent is an error.
11178 Range checking is done on all mathematical operations, assignment, array
11179 index bounds, and all built-in functions and procedures.
11182 @subsubsection The Scope Operators @code{::} and @code{.}
11184 @cindex @code{.}, Modula-2 scope operator
11185 @cindex colon, doubled as scope operator
11187 @vindex colon-colon@r{, in Modula-2}
11188 @c Info cannot handle :: but TeX can.
11191 @vindex ::@r{, in Modula-2}
11194 There are a few subtle differences between the Modula-2 scope operator
11195 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11200 @var{module} . @var{id}
11201 @var{scope} :: @var{id}
11205 where @var{scope} is the name of a module or a procedure,
11206 @var{module} the name of a module, and @var{id} is any declared
11207 identifier within your program, except another module.
11209 Using the @code{::} operator makes @value{GDBN} search the scope
11210 specified by @var{scope} for the identifier @var{id}. If it is not
11211 found in the specified scope, then @value{GDBN} searches all scopes
11212 enclosing the one specified by @var{scope}.
11214 Using the @code{.} operator makes @value{GDBN} search the current scope for
11215 the identifier specified by @var{id} that was imported from the
11216 definition module specified by @var{module}. With this operator, it is
11217 an error if the identifier @var{id} was not imported from definition
11218 module @var{module}, or if @var{id} is not an identifier in
11222 @subsubsection @value{GDBN} and Modula-2
11224 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11225 Five subcommands of @code{set print} and @code{show print} apply
11226 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11227 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11228 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11229 analogue in Modula-2.
11231 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11232 with any language, is not useful with Modula-2. Its
11233 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11234 created in Modula-2 as they can in C or C@t{++}. However, because an
11235 address can be specified by an integral constant, the construct
11236 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11238 @cindex @code{#} in Modula-2
11239 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11240 interpreted as the beginning of a comment. Use @code{<>} instead.
11246 The extensions made to @value{GDBN} for Ada only support
11247 output from the @sc{gnu} Ada (GNAT) compiler.
11248 Other Ada compilers are not currently supported, and
11249 attempting to debug executables produced by them is most likely
11253 @cindex expressions in Ada
11255 * Ada Mode Intro:: General remarks on the Ada syntax
11256 and semantics supported by Ada mode
11258 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11259 * Additions to Ada:: Extensions of the Ada expression syntax.
11260 * Stopping Before Main Program:: Debugging the program during elaboration.
11261 * Ada Tasks:: Listing and setting breakpoints in tasks.
11262 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
11263 * Ada Glitches:: Known peculiarities of Ada mode.
11266 @node Ada Mode Intro
11267 @subsubsection Introduction
11268 @cindex Ada mode, general
11270 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11271 syntax, with some extensions.
11272 The philosophy behind the design of this subset is
11276 That @value{GDBN} should provide basic literals and access to operations for
11277 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11278 leaving more sophisticated computations to subprograms written into the
11279 program (which therefore may be called from @value{GDBN}).
11282 That type safety and strict adherence to Ada language restrictions
11283 are not particularly important to the @value{GDBN} user.
11286 That brevity is important to the @value{GDBN} user.
11289 Thus, for brevity, the debugger acts as if all names declared in
11290 user-written packages are directly visible, even if they are not visible
11291 according to Ada rules, thus making it unnecessary to fully qualify most
11292 names with their packages, regardless of context. Where this causes
11293 ambiguity, @value{GDBN} asks the user's intent.
11295 The debugger will start in Ada mode if it detects an Ada main program.
11296 As for other languages, it will enter Ada mode when stopped in a program that
11297 was translated from an Ada source file.
11299 While in Ada mode, you may use `@t{--}' for comments. This is useful
11300 mostly for documenting command files. The standard @value{GDBN} comment
11301 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11302 middle (to allow based literals).
11304 The debugger supports limited overloading. Given a subprogram call in which
11305 the function symbol has multiple definitions, it will use the number of
11306 actual parameters and some information about their types to attempt to narrow
11307 the set of definitions. It also makes very limited use of context, preferring
11308 procedures to functions in the context of the @code{call} command, and
11309 functions to procedures elsewhere.
11311 @node Omissions from Ada
11312 @subsubsection Omissions from Ada
11313 @cindex Ada, omissions from
11315 Here are the notable omissions from the subset:
11319 Only a subset of the attributes are supported:
11323 @t{'First}, @t{'Last}, and @t{'Length}
11324 on array objects (not on types and subtypes).
11327 @t{'Min} and @t{'Max}.
11330 @t{'Pos} and @t{'Val}.
11336 @t{'Range} on array objects (not subtypes), but only as the right
11337 operand of the membership (@code{in}) operator.
11340 @t{'Access}, @t{'Unchecked_Access}, and
11341 @t{'Unrestricted_Access} (a GNAT extension).
11349 @code{Characters.Latin_1} are not available and
11350 concatenation is not implemented. Thus, escape characters in strings are
11351 not currently available.
11354 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11355 equality of representations. They will generally work correctly
11356 for strings and arrays whose elements have integer or enumeration types.
11357 They may not work correctly for arrays whose element
11358 types have user-defined equality, for arrays of real values
11359 (in particular, IEEE-conformant floating point, because of negative
11360 zeroes and NaNs), and for arrays whose elements contain unused bits with
11361 indeterminate values.
11364 The other component-by-component array operations (@code{and}, @code{or},
11365 @code{xor}, @code{not}, and relational tests other than equality)
11366 are not implemented.
11369 @cindex array aggregates (Ada)
11370 @cindex record aggregates (Ada)
11371 @cindex aggregates (Ada)
11372 There is limited support for array and record aggregates. They are
11373 permitted only on the right sides of assignments, as in these examples:
11376 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
11377 (@value{GDBP}) set An_Array := (1, others => 0)
11378 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11379 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11380 (@value{GDBP}) set A_Record := (1, "Peter", True);
11381 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
11385 discriminant's value by assigning an aggregate has an
11386 undefined effect if that discriminant is used within the record.
11387 However, you can first modify discriminants by directly assigning to
11388 them (which normally would not be allowed in Ada), and then performing an
11389 aggregate assignment. For example, given a variable @code{A_Rec}
11390 declared to have a type such as:
11393 type Rec (Len : Small_Integer := 0) is record
11395 Vals : IntArray (1 .. Len);
11399 you can assign a value with a different size of @code{Vals} with two
11403 (@value{GDBP}) set A_Rec.Len := 4
11404 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11407 As this example also illustrates, @value{GDBN} is very loose about the usual
11408 rules concerning aggregates. You may leave out some of the
11409 components of an array or record aggregate (such as the @code{Len}
11410 component in the assignment to @code{A_Rec} above); they will retain their
11411 original values upon assignment. You may freely use dynamic values as
11412 indices in component associations. You may even use overlapping or
11413 redundant component associations, although which component values are
11414 assigned in such cases is not defined.
11417 Calls to dispatching subprograms are not implemented.
11420 The overloading algorithm is much more limited (i.e., less selective)
11421 than that of real Ada. It makes only limited use of the context in
11422 which a subexpression appears to resolve its meaning, and it is much
11423 looser in its rules for allowing type matches. As a result, some
11424 function calls will be ambiguous, and the user will be asked to choose
11425 the proper resolution.
11428 The @code{new} operator is not implemented.
11431 Entry calls are not implemented.
11434 Aside from printing, arithmetic operations on the native VAX floating-point
11435 formats are not supported.
11438 It is not possible to slice a packed array.
11441 The names @code{True} and @code{False}, when not part of a qualified name,
11442 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
11444 Should your program
11445 redefine these names in a package or procedure (at best a dubious practice),
11446 you will have to use fully qualified names to access their new definitions.
11449 @node Additions to Ada
11450 @subsubsection Additions to Ada
11451 @cindex Ada, deviations from
11453 As it does for other languages, @value{GDBN} makes certain generic
11454 extensions to Ada (@pxref{Expressions}):
11458 If the expression @var{E} is a variable residing in memory (typically
11459 a local variable or array element) and @var{N} is a positive integer,
11460 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11461 @var{N}-1 adjacent variables following it in memory as an array. In
11462 Ada, this operator is generally not necessary, since its prime use is
11463 in displaying parts of an array, and slicing will usually do this in
11464 Ada. However, there are occasional uses when debugging programs in
11465 which certain debugging information has been optimized away.
11468 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11469 appears in function or file @var{B}.'' When @var{B} is a file name,
11470 you must typically surround it in single quotes.
11473 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11474 @var{type} that appears at address @var{addr}.''
11477 A name starting with @samp{$} is a convenience variable
11478 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11481 In addition, @value{GDBN} provides a few other shortcuts and outright
11482 additions specific to Ada:
11486 The assignment statement is allowed as an expression, returning
11487 its right-hand operand as its value. Thus, you may enter
11490 (@value{GDBP}) set x := y + 3
11491 (@value{GDBP}) print A(tmp := y + 1)
11495 The semicolon is allowed as an ``operator,'' returning as its value
11496 the value of its right-hand operand.
11497 This allows, for example,
11498 complex conditional breaks:
11501 (@value{GDBP}) break f
11502 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
11506 Rather than use catenation and symbolic character names to introduce special
11507 characters into strings, one may instead use a special bracket notation,
11508 which is also used to print strings. A sequence of characters of the form
11509 @samp{["@var{XX}"]} within a string or character literal denotes the
11510 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11511 sequence of characters @samp{["""]} also denotes a single quotation mark
11512 in strings. For example,
11514 "One line.["0a"]Next line.["0a"]"
11517 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11521 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11522 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11526 (@value{GDBP}) print 'max(x, y)
11530 When printing arrays, @value{GDBN} uses positional notation when the
11531 array has a lower bound of 1, and uses a modified named notation otherwise.
11532 For example, a one-dimensional array of three integers with a lower bound
11533 of 3 might print as
11540 That is, in contrast to valid Ada, only the first component has a @code{=>}
11544 You may abbreviate attributes in expressions with any unique,
11545 multi-character subsequence of
11546 their names (an exact match gets preference).
11547 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11548 in place of @t{a'length}.
11551 @cindex quoting Ada internal identifiers
11552 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11553 to lower case. The GNAT compiler uses upper-case characters for
11554 some of its internal identifiers, which are normally of no interest to users.
11555 For the rare occasions when you actually have to look at them,
11556 enclose them in angle brackets to avoid the lower-case mapping.
11559 (@value{GDBP}) print <JMPBUF_SAVE>[0]
11563 Printing an object of class-wide type or dereferencing an
11564 access-to-class-wide value will display all the components of the object's
11565 specific type (as indicated by its run-time tag). Likewise, component
11566 selection on such a value will operate on the specific type of the
11571 @node Stopping Before Main Program
11572 @subsubsection Stopping at the Very Beginning
11574 @cindex breakpointing Ada elaboration code
11575 It is sometimes necessary to debug the program during elaboration, and
11576 before reaching the main procedure.
11577 As defined in the Ada Reference
11578 Manual, the elaboration code is invoked from a procedure called
11579 @code{adainit}. To run your program up to the beginning of
11580 elaboration, simply use the following two commands:
11581 @code{tbreak adainit} and @code{run}.
11584 @subsubsection Extensions for Ada Tasks
11585 @cindex Ada, tasking
11587 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
11588 @value{GDBN} provides the following task-related commands:
11593 This command shows a list of current Ada tasks, as in the following example:
11600 (@value{GDBP}) info tasks
11601 ID TID P-ID Pri State Name
11602 1 8088000 0 15 Child Activation Wait main_task
11603 2 80a4000 1 15 Accept Statement b
11604 3 809a800 1 15 Child Activation Wait a
11605 * 4 80ae800 3 15 Running c
11610 In this listing, the asterisk before the last task indicates it to be the
11611 task currently being inspected.
11615 Represents @value{GDBN}'s internal task number.
11621 The parent's task ID (@value{GDBN}'s internal task number).
11624 The base priority of the task.
11627 Current state of the task.
11631 The task has been created but has not been activated. It cannot be
11635 The task currently running.
11638 The task is not blocked for any reason known to Ada. (It may be waiting
11639 for a mutex, though.) It is conceptually "executing" in normal mode.
11642 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
11643 that were waiting on terminate alternatives have been awakened and have
11644 terminated themselves.
11646 @item Child Activation Wait
11647 The task is waiting for created tasks to complete activation.
11649 @item Accept Statement
11650 The task is waiting on an accept or selective wait statement.
11652 @item Waiting on entry call
11653 The task is waiting on an entry call.
11655 @item Async Select Wait
11656 The task is waiting to start the abortable part of an asynchronous
11660 The task is waiting on a select statement with only a delay
11663 @item Child Termination Wait
11664 The task is sleeping having completed a master within itself, and is
11665 waiting for the tasks dependent on that master to become terminated or
11666 waiting on a terminate Phase.
11668 @item Wait Child in Term Alt
11669 The task is sleeping waiting for tasks on terminate alternatives to
11670 finish terminating.
11672 @item Accepting RV with @var{taskno}
11673 The task is accepting a rendez-vous with the task @var{taskno}.
11677 Name of the task in the program.
11681 @kindex info task @var{taskno}
11682 @item info task @var{taskno}
11683 This command shows detailled informations on the specified task, as in
11684 the following example:
11689 (@value{GDBP}) info tasks
11690 ID TID P-ID Pri State Name
11691 1 8077880 0 15 Child Activation Wait main_task
11692 * 2 807c468 1 15 Running task_1
11693 (@value{GDBP}) info task 2
11694 Ada Task: 0x807c468
11697 Parent: 1 (main_task)
11703 @kindex task@r{ (Ada)}
11704 @cindex current Ada task ID
11705 This command prints the ID of the current task.
11711 (@value{GDBP}) info tasks
11712 ID TID P-ID Pri State Name
11713 1 8077870 0 15 Child Activation Wait main_task
11714 * 2 807c458 1 15 Running t
11715 (@value{GDBP}) task
11716 [Current task is 2]
11719 @item task @var{taskno}
11720 @cindex Ada task switching
11721 This command is like the @code{thread @var{threadno}}
11722 command (@pxref{Threads}). It switches the context of debugging
11723 from the current task to the given task.
11729 (@value{GDBP}) info tasks
11730 ID TID P-ID Pri State Name
11731 1 8077870 0 15 Child Activation Wait main_task
11732 * 2 807c458 1 15 Running t
11733 (@value{GDBP}) task 1
11734 [Switching to task 1]
11735 #0 0x8067726 in pthread_cond_wait ()
11737 #0 0x8067726 in pthread_cond_wait ()
11738 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
11739 #2 0x805cb63 in system.task_primitives.operations.sleep ()
11740 #3 0x806153e in system.tasking.stages.activate_tasks ()
11741 #4 0x804aacc in un () at un.adb:5
11746 @node Ada Tasks and Core Files
11747 @subsubsection Tasking Support when Debugging Core Files
11748 @cindex Ada tasking and core file debugging
11750 When inspecting a core file, as opposed to debugging a live program,
11751 tasking support may be limited or even unavailable, depending on
11752 the platform being used.
11753 For instance, on x86-linux, the list of tasks is available, but task
11754 switching is not supported. On Tru64, however, task switching will work
11757 On certain platforms, including Tru64, the debugger needs to perform some
11758 memory writes in order to provide Ada tasking support. When inspecting
11759 a core file, this means that the core file must be opened with read-write
11760 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
11761 Under these circumstances, you should make a backup copy of the core
11762 file before inspecting it with @value{GDBN}.
11765 @subsubsection Known Peculiarities of Ada Mode
11766 @cindex Ada, problems
11768 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11769 we know of several problems with and limitations of Ada mode in
11771 some of which will be fixed with planned future releases of the debugger
11772 and the GNU Ada compiler.
11776 Currently, the debugger
11777 has insufficient information to determine whether certain pointers represent
11778 pointers to objects or the objects themselves.
11779 Thus, the user may have to tack an extra @code{.all} after an expression
11780 to get it printed properly.
11783 Static constants that the compiler chooses not to materialize as objects in
11784 storage are invisible to the debugger.
11787 Named parameter associations in function argument lists are ignored (the
11788 argument lists are treated as positional).
11791 Many useful library packages are currently invisible to the debugger.
11794 Fixed-point arithmetic, conversions, input, and output is carried out using
11795 floating-point arithmetic, and may give results that only approximate those on
11799 The GNAT compiler never generates the prefix @code{Standard} for any of
11800 the standard symbols defined by the Ada language. @value{GDBN} knows about
11801 this: it will strip the prefix from names when you use it, and will never
11802 look for a name you have so qualified among local symbols, nor match against
11803 symbols in other packages or subprograms. If you have
11804 defined entities anywhere in your program other than parameters and
11805 local variables whose simple names match names in @code{Standard},
11806 GNAT's lack of qualification here can cause confusion. When this happens,
11807 you can usually resolve the confusion
11808 by qualifying the problematic names with package
11809 @code{Standard} explicitly.
11812 @node Unsupported Languages
11813 @section Unsupported Languages
11815 @cindex unsupported languages
11816 @cindex minimal language
11817 In addition to the other fully-supported programming languages,
11818 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11819 It does not represent a real programming language, but provides a set
11820 of capabilities close to what the C or assembly languages provide.
11821 This should allow most simple operations to be performed while debugging
11822 an application that uses a language currently not supported by @value{GDBN}.
11824 If the language is set to @code{auto}, @value{GDBN} will automatically
11825 select this language if the current frame corresponds to an unsupported
11829 @chapter Examining the Symbol Table
11831 The commands described in this chapter allow you to inquire about the
11832 symbols (names of variables, functions and types) defined in your
11833 program. This information is inherent in the text of your program and
11834 does not change as your program executes. @value{GDBN} finds it in your
11835 program's symbol table, in the file indicated when you started @value{GDBN}
11836 (@pxref{File Options, ,Choosing Files}), or by one of the
11837 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11839 @cindex symbol names
11840 @cindex names of symbols
11841 @cindex quoting names
11842 Occasionally, you may need to refer to symbols that contain unusual
11843 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11844 most frequent case is in referring to static variables in other
11845 source files (@pxref{Variables,,Program Variables}). File names
11846 are recorded in object files as debugging symbols, but @value{GDBN} would
11847 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11848 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11849 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11856 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11859 @cindex case-insensitive symbol names
11860 @cindex case sensitivity in symbol names
11861 @kindex set case-sensitive
11862 @item set case-sensitive on
11863 @itemx set case-sensitive off
11864 @itemx set case-sensitive auto
11865 Normally, when @value{GDBN} looks up symbols, it matches their names
11866 with case sensitivity determined by the current source language.
11867 Occasionally, you may wish to control that. The command @code{set
11868 case-sensitive} lets you do that by specifying @code{on} for
11869 case-sensitive matches or @code{off} for case-insensitive ones. If
11870 you specify @code{auto}, case sensitivity is reset to the default
11871 suitable for the source language. The default is case-sensitive
11872 matches for all languages except for Fortran, for which the default is
11873 case-insensitive matches.
11875 @kindex show case-sensitive
11876 @item show case-sensitive
11877 This command shows the current setting of case sensitivity for symbols
11880 @kindex info address
11881 @cindex address of a symbol
11882 @item info address @var{symbol}
11883 Describe where the data for @var{symbol} is stored. For a register
11884 variable, this says which register it is kept in. For a non-register
11885 local variable, this prints the stack-frame offset at which the variable
11888 Note the contrast with @samp{print &@var{symbol}}, which does not work
11889 at all for a register variable, and for a stack local variable prints
11890 the exact address of the current instantiation of the variable.
11892 @kindex info symbol
11893 @cindex symbol from address
11894 @cindex closest symbol and offset for an address
11895 @item info symbol @var{addr}
11896 Print the name of a symbol which is stored at the address @var{addr}.
11897 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11898 nearest symbol and an offset from it:
11901 (@value{GDBP}) info symbol 0x54320
11902 _initialize_vx + 396 in section .text
11906 This is the opposite of the @code{info address} command. You can use
11907 it to find out the name of a variable or a function given its address.
11909 For dynamically linked executables, the name of executable or shared
11910 library containing the symbol is also printed:
11913 (@value{GDBP}) info symbol 0x400225
11914 _start + 5 in section .text of /tmp/a.out
11915 (@value{GDBP}) info symbol 0x2aaaac2811cf
11916 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
11920 @item whatis [@var{arg}]
11921 Print the data type of @var{arg}, which can be either an expression or
11922 a data type. With no argument, print the data type of @code{$}, the
11923 last value in the value history. If @var{arg} is an expression, it is
11924 not actually evaluated, and any side-effecting operations (such as
11925 assignments or function calls) inside it do not take place. If
11926 @var{arg} is a type name, it may be the name of a type or typedef, or
11927 for C code it may have the form @samp{class @var{class-name}},
11928 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11929 @samp{enum @var{enum-tag}}.
11930 @xref{Expressions, ,Expressions}.
11933 @item ptype [@var{arg}]
11934 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11935 detailed description of the type, instead of just the name of the type.
11936 @xref{Expressions, ,Expressions}.
11938 For example, for this variable declaration:
11941 struct complex @{double real; double imag;@} v;
11945 the two commands give this output:
11949 (@value{GDBP}) whatis v
11950 type = struct complex
11951 (@value{GDBP}) ptype v
11952 type = struct complex @{
11960 As with @code{whatis}, using @code{ptype} without an argument refers to
11961 the type of @code{$}, the last value in the value history.
11963 @cindex incomplete type
11964 Sometimes, programs use opaque data types or incomplete specifications
11965 of complex data structure. If the debug information included in the
11966 program does not allow @value{GDBN} to display a full declaration of
11967 the data type, it will say @samp{<incomplete type>}. For example,
11968 given these declarations:
11972 struct foo *fooptr;
11976 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11979 (@value{GDBP}) ptype foo
11980 $1 = <incomplete type>
11984 ``Incomplete type'' is C terminology for data types that are not
11985 completely specified.
11988 @item info types @var{regexp}
11990 Print a brief description of all types whose names match the regular
11991 expression @var{regexp} (or all types in your program, if you supply
11992 no argument). Each complete typename is matched as though it were a
11993 complete line; thus, @samp{i type value} gives information on all
11994 types in your program whose names include the string @code{value}, but
11995 @samp{i type ^value$} gives information only on types whose complete
11996 name is @code{value}.
11998 This command differs from @code{ptype} in two ways: first, like
11999 @code{whatis}, it does not print a detailed description; second, it
12000 lists all source files where a type is defined.
12003 @cindex local variables
12004 @item info scope @var{location}
12005 List all the variables local to a particular scope. This command
12006 accepts a @var{location} argument---a function name, a source line, or
12007 an address preceded by a @samp{*}, and prints all the variables local
12008 to the scope defined by that location. (@xref{Specify Location}, for
12009 details about supported forms of @var{location}.) For example:
12012 (@value{GDBP}) @b{info scope command_line_handler}
12013 Scope for command_line_handler:
12014 Symbol rl is an argument at stack/frame offset 8, length 4.
12015 Symbol linebuffer is in static storage at address 0x150a18, length 4.
12016 Symbol linelength is in static storage at address 0x150a1c, length 4.
12017 Symbol p is a local variable in register $esi, length 4.
12018 Symbol p1 is a local variable in register $ebx, length 4.
12019 Symbol nline is a local variable in register $edx, length 4.
12020 Symbol repeat is a local variable at frame offset -8, length 4.
12024 This command is especially useful for determining what data to collect
12025 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
12028 @kindex info source
12030 Show information about the current source file---that is, the source file for
12031 the function containing the current point of execution:
12034 the name of the source file, and the directory containing it,
12036 the directory it was compiled in,
12038 its length, in lines,
12040 which programming language it is written in,
12042 whether the executable includes debugging information for that file, and
12043 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
12045 whether the debugging information includes information about
12046 preprocessor macros.
12050 @kindex info sources
12052 Print the names of all source files in your program for which there is
12053 debugging information, organized into two lists: files whose symbols
12054 have already been read, and files whose symbols will be read when needed.
12056 @kindex info functions
12057 @item info functions
12058 Print the names and data types of all defined functions.
12060 @item info functions @var{regexp}
12061 Print the names and data types of all defined functions
12062 whose names contain a match for regular expression @var{regexp}.
12063 Thus, @samp{info fun step} finds all functions whose names
12064 include @code{step}; @samp{info fun ^step} finds those whose names
12065 start with @code{step}. If a function name contains characters
12066 that conflict with the regular expression language (e.g.@:
12067 @samp{operator*()}), they may be quoted with a backslash.
12069 @kindex info variables
12070 @item info variables
12071 Print the names and data types of all variables that are declared
12072 outside of functions (i.e.@: excluding local variables).
12074 @item info variables @var{regexp}
12075 Print the names and data types of all variables (except for local
12076 variables) whose names contain a match for regular expression
12079 @kindex info classes
12080 @cindex Objective-C, classes and selectors
12082 @itemx info classes @var{regexp}
12083 Display all Objective-C classes in your program, or
12084 (with the @var{regexp} argument) all those matching a particular regular
12087 @kindex info selectors
12088 @item info selectors
12089 @itemx info selectors @var{regexp}
12090 Display all Objective-C selectors in your program, or
12091 (with the @var{regexp} argument) all those matching a particular regular
12095 This was never implemented.
12096 @kindex info methods
12098 @itemx info methods @var{regexp}
12099 The @code{info methods} command permits the user to examine all defined
12100 methods within C@t{++} program, or (with the @var{regexp} argument) a
12101 specific set of methods found in the various C@t{++} classes. Many
12102 C@t{++} classes provide a large number of methods. Thus, the output
12103 from the @code{ptype} command can be overwhelming and hard to use. The
12104 @code{info-methods} command filters the methods, printing only those
12105 which match the regular-expression @var{regexp}.
12108 @cindex reloading symbols
12109 Some systems allow individual object files that make up your program to
12110 be replaced without stopping and restarting your program. For example,
12111 in VxWorks you can simply recompile a defective object file and keep on
12112 running. If you are running on one of these systems, you can allow
12113 @value{GDBN} to reload the symbols for automatically relinked modules:
12116 @kindex set symbol-reloading
12117 @item set symbol-reloading on
12118 Replace symbol definitions for the corresponding source file when an
12119 object file with a particular name is seen again.
12121 @item set symbol-reloading off
12122 Do not replace symbol definitions when encountering object files of the
12123 same name more than once. This is the default state; if you are not
12124 running on a system that permits automatic relinking of modules, you
12125 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12126 may discard symbols when linking large programs, that may contain
12127 several modules (from different directories or libraries) with the same
12130 @kindex show symbol-reloading
12131 @item show symbol-reloading
12132 Show the current @code{on} or @code{off} setting.
12135 @cindex opaque data types
12136 @kindex set opaque-type-resolution
12137 @item set opaque-type-resolution on
12138 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12139 declared as a pointer to a @code{struct}, @code{class}, or
12140 @code{union}---for example, @code{struct MyType *}---that is used in one
12141 source file although the full declaration of @code{struct MyType} is in
12142 another source file. The default is on.
12144 A change in the setting of this subcommand will not take effect until
12145 the next time symbols for a file are loaded.
12147 @item set opaque-type-resolution off
12148 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12149 is printed as follows:
12151 @{<no data fields>@}
12154 @kindex show opaque-type-resolution
12155 @item show opaque-type-resolution
12156 Show whether opaque types are resolved or not.
12158 @kindex set print symbol-loading
12159 @cindex print messages when symbols are loaded
12160 @item set print symbol-loading
12161 @itemx set print symbol-loading on
12162 @itemx set print symbol-loading off
12163 The @code{set print symbol-loading} command allows you to enable or
12164 disable printing of messages when @value{GDBN} loads symbols.
12165 By default, these messages will be printed, and normally this is what
12166 you want. Disabling these messages is useful when debugging applications
12167 with lots of shared libraries where the quantity of output can be more
12168 annoying than useful.
12170 @kindex show print symbol-loading
12171 @item show print symbol-loading
12172 Show whether messages will be printed when @value{GDBN} loads symbols.
12174 @kindex maint print symbols
12175 @cindex symbol dump
12176 @kindex maint print psymbols
12177 @cindex partial symbol dump
12178 @item maint print symbols @var{filename}
12179 @itemx maint print psymbols @var{filename}
12180 @itemx maint print msymbols @var{filename}
12181 Write a dump of debugging symbol data into the file @var{filename}.
12182 These commands are used to debug the @value{GDBN} symbol-reading code. Only
12183 symbols with debugging data are included. If you use @samp{maint print
12184 symbols}, @value{GDBN} includes all the symbols for which it has already
12185 collected full details: that is, @var{filename} reflects symbols for
12186 only those files whose symbols @value{GDBN} has read. You can use the
12187 command @code{info sources} to find out which files these are. If you
12188 use @samp{maint print psymbols} instead, the dump shows information about
12189 symbols that @value{GDBN} only knows partially---that is, symbols defined in
12190 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
12191 @samp{maint print msymbols} dumps just the minimal symbol information
12192 required for each object file from which @value{GDBN} has read some symbols.
12193 @xref{Files, ,Commands to Specify Files}, for a discussion of how
12194 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
12196 @kindex maint info symtabs
12197 @kindex maint info psymtabs
12198 @cindex listing @value{GDBN}'s internal symbol tables
12199 @cindex symbol tables, listing @value{GDBN}'s internal
12200 @cindex full symbol tables, listing @value{GDBN}'s internal
12201 @cindex partial symbol tables, listing @value{GDBN}'s internal
12202 @item maint info symtabs @r{[} @var{regexp} @r{]}
12203 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
12205 List the @code{struct symtab} or @code{struct partial_symtab}
12206 structures whose names match @var{regexp}. If @var{regexp} is not
12207 given, list them all. The output includes expressions which you can
12208 copy into a @value{GDBN} debugging this one to examine a particular
12209 structure in more detail. For example:
12212 (@value{GDBP}) maint info psymtabs dwarf2read
12213 @{ objfile /home/gnu/build/gdb/gdb
12214 ((struct objfile *) 0x82e69d0)
12215 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
12216 ((struct partial_symtab *) 0x8474b10)
12219 text addresses 0x814d3c8 -- 0x8158074
12220 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
12221 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
12222 dependencies (none)
12225 (@value{GDBP}) maint info symtabs
12229 We see that there is one partial symbol table whose filename contains
12230 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
12231 and we see that @value{GDBN} has not read in any symtabs yet at all.
12232 If we set a breakpoint on a function, that will cause @value{GDBN} to
12233 read the symtab for the compilation unit containing that function:
12236 (@value{GDBP}) break dwarf2_psymtab_to_symtab
12237 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
12239 (@value{GDBP}) maint info symtabs
12240 @{ objfile /home/gnu/build/gdb/gdb
12241 ((struct objfile *) 0x82e69d0)
12242 @{ symtab /home/gnu/src/gdb/dwarf2read.c
12243 ((struct symtab *) 0x86c1f38)
12246 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
12247 linetable ((struct linetable *) 0x8370fa0)
12248 debugformat DWARF 2
12257 @chapter Altering Execution
12259 Once you think you have found an error in your program, you might want to
12260 find out for certain whether correcting the apparent error would lead to
12261 correct results in the rest of the run. You can find the answer by
12262 experiment, using the @value{GDBN} features for altering execution of the
12265 For example, you can store new values into variables or memory
12266 locations, give your program a signal, restart it at a different
12267 address, or even return prematurely from a function.
12270 * Assignment:: Assignment to variables
12271 * Jumping:: Continuing at a different address
12272 * Signaling:: Giving your program a signal
12273 * Returning:: Returning from a function
12274 * Calling:: Calling your program's functions
12275 * Patching:: Patching your program
12279 @section Assignment to Variables
12282 @cindex setting variables
12283 To alter the value of a variable, evaluate an assignment expression.
12284 @xref{Expressions, ,Expressions}. For example,
12291 stores the value 4 into the variable @code{x}, and then prints the
12292 value of the assignment expression (which is 4).
12293 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
12294 information on operators in supported languages.
12296 @kindex set variable
12297 @cindex variables, setting
12298 If you are not interested in seeing the value of the assignment, use the
12299 @code{set} command instead of the @code{print} command. @code{set} is
12300 really the same as @code{print} except that the expression's value is
12301 not printed and is not put in the value history (@pxref{Value History,
12302 ,Value History}). The expression is evaluated only for its effects.
12304 If the beginning of the argument string of the @code{set} command
12305 appears identical to a @code{set} subcommand, use the @code{set
12306 variable} command instead of just @code{set}. This command is identical
12307 to @code{set} except for its lack of subcommands. For example, if your
12308 program has a variable @code{width}, you get an error if you try to set
12309 a new value with just @samp{set width=13}, because @value{GDBN} has the
12310 command @code{set width}:
12313 (@value{GDBP}) whatis width
12315 (@value{GDBP}) p width
12317 (@value{GDBP}) set width=47
12318 Invalid syntax in expression.
12322 The invalid expression, of course, is @samp{=47}. In
12323 order to actually set the program's variable @code{width}, use
12326 (@value{GDBP}) set var width=47
12329 Because the @code{set} command has many subcommands that can conflict
12330 with the names of program variables, it is a good idea to use the
12331 @code{set variable} command instead of just @code{set}. For example, if
12332 your program has a variable @code{g}, you run into problems if you try
12333 to set a new value with just @samp{set g=4}, because @value{GDBN} has
12334 the command @code{set gnutarget}, abbreviated @code{set g}:
12338 (@value{GDBP}) whatis g
12342 (@value{GDBP}) set g=4
12346 The program being debugged has been started already.
12347 Start it from the beginning? (y or n) y
12348 Starting program: /home/smith/cc_progs/a.out
12349 "/home/smith/cc_progs/a.out": can't open to read symbols:
12350 Invalid bfd target.
12351 (@value{GDBP}) show g
12352 The current BFD target is "=4".
12357 The program variable @code{g} did not change, and you silently set the
12358 @code{gnutarget} to an invalid value. In order to set the variable
12362 (@value{GDBP}) set var g=4
12365 @value{GDBN} allows more implicit conversions in assignments than C; you can
12366 freely store an integer value into a pointer variable or vice versa,
12367 and you can convert any structure to any other structure that is the
12368 same length or shorter.
12369 @comment FIXME: how do structs align/pad in these conversions?
12370 @comment /doc@cygnus.com 18dec1990
12372 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12373 construct to generate a value of specified type at a specified address
12374 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12375 to memory location @code{0x83040} as an integer (which implies a certain size
12376 and representation in memory), and
12379 set @{int@}0x83040 = 4
12383 stores the value 4 into that memory location.
12386 @section Continuing at a Different Address
12388 Ordinarily, when you continue your program, you do so at the place where
12389 it stopped, with the @code{continue} command. You can instead continue at
12390 an address of your own choosing, with the following commands:
12394 @item jump @var{linespec}
12395 @itemx jump @var{location}
12396 Resume execution at line @var{linespec} or at address given by
12397 @var{location}. Execution stops again immediately if there is a
12398 breakpoint there. @xref{Specify Location}, for a description of the
12399 different forms of @var{linespec} and @var{location}. It is common
12400 practice to use the @code{tbreak} command in conjunction with
12401 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
12403 The @code{jump} command does not change the current stack frame, or
12404 the stack pointer, or the contents of any memory location or any
12405 register other than the program counter. If line @var{linespec} is in
12406 a different function from the one currently executing, the results may
12407 be bizarre if the two functions expect different patterns of arguments or
12408 of local variables. For this reason, the @code{jump} command requests
12409 confirmation if the specified line is not in the function currently
12410 executing. However, even bizarre results are predictable if you are
12411 well acquainted with the machine-language code of your program.
12414 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
12415 On many systems, you can get much the same effect as the @code{jump}
12416 command by storing a new value into the register @code{$pc}. The
12417 difference is that this does not start your program running; it only
12418 changes the address of where it @emph{will} run when you continue. For
12426 makes the next @code{continue} command or stepping command execute at
12427 address @code{0x485}, rather than at the address where your program stopped.
12428 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12430 The most common occasion to use the @code{jump} command is to back
12431 up---perhaps with more breakpoints set---over a portion of a program
12432 that has already executed, in order to examine its execution in more
12437 @section Giving your Program a Signal
12438 @cindex deliver a signal to a program
12442 @item signal @var{signal}
12443 Resume execution where your program stopped, but immediately give it the
12444 signal @var{signal}. @var{signal} can be the name or the number of a
12445 signal. For example, on many systems @code{signal 2} and @code{signal
12446 SIGINT} are both ways of sending an interrupt signal.
12448 Alternatively, if @var{signal} is zero, continue execution without
12449 giving a signal. This is useful when your program stopped on account of
12450 a signal and would ordinary see the signal when resumed with the
12451 @code{continue} command; @samp{signal 0} causes it to resume without a
12454 @code{signal} does not repeat when you press @key{RET} a second time
12455 after executing the command.
12459 Invoking the @code{signal} command is not the same as invoking the
12460 @code{kill} utility from the shell. Sending a signal with @code{kill}
12461 causes @value{GDBN} to decide what to do with the signal depending on
12462 the signal handling tables (@pxref{Signals}). The @code{signal} command
12463 passes the signal directly to your program.
12467 @section Returning from a Function
12470 @cindex returning from a function
12473 @itemx return @var{expression}
12474 You can cancel execution of a function call with the @code{return}
12475 command. If you give an
12476 @var{expression} argument, its value is used as the function's return
12480 When you use @code{return}, @value{GDBN} discards the selected stack frame
12481 (and all frames within it). You can think of this as making the
12482 discarded frame return prematurely. If you wish to specify a value to
12483 be returned, give that value as the argument to @code{return}.
12485 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12486 Frame}), and any other frames inside of it, leaving its caller as the
12487 innermost remaining frame. That frame becomes selected. The
12488 specified value is stored in the registers used for returning values
12491 The @code{return} command does not resume execution; it leaves the
12492 program stopped in the state that would exist if the function had just
12493 returned. In contrast, the @code{finish} command (@pxref{Continuing
12494 and Stepping, ,Continuing and Stepping}) resumes execution until the
12495 selected stack frame returns naturally.
12498 @section Calling Program Functions
12501 @cindex calling functions
12502 @cindex inferior functions, calling
12503 @item print @var{expr}
12504 Evaluate the expression @var{expr} and display the resulting value.
12505 @var{expr} may include calls to functions in the program being
12509 @item call @var{expr}
12510 Evaluate the expression @var{expr} without displaying @code{void}
12513 You can use this variant of the @code{print} command if you want to
12514 execute a function from your program that does not return anything
12515 (a.k.a.@: @dfn{a void function}), but without cluttering the output
12516 with @code{void} returned values that @value{GDBN} will otherwise
12517 print. If the result is not void, it is printed and saved in the
12521 It is possible for the function you call via the @code{print} or
12522 @code{call} command to generate a signal (e.g., if there's a bug in
12523 the function, or if you passed it incorrect arguments). What happens
12524 in that case is controlled by the @code{set unwindonsignal} command.
12527 @item set unwindonsignal
12528 @kindex set unwindonsignal
12529 @cindex unwind stack in called functions
12530 @cindex call dummy stack unwinding
12531 Set unwinding of the stack if a signal is received while in a function
12532 that @value{GDBN} called in the program being debugged. If set to on,
12533 @value{GDBN} unwinds the stack it created for the call and restores
12534 the context to what it was before the call. If set to off (the
12535 default), @value{GDBN} stops in the frame where the signal was
12538 @item show unwindonsignal
12539 @kindex show unwindonsignal
12540 Show the current setting of stack unwinding in the functions called by
12544 @cindex weak alias functions
12545 Sometimes, a function you wish to call is actually a @dfn{weak alias}
12546 for another function. In such case, @value{GDBN} might not pick up
12547 the type information, including the types of the function arguments,
12548 which causes @value{GDBN} to call the inferior function incorrectly.
12549 As a result, the called function will function erroneously and may
12550 even crash. A solution to that is to use the name of the aliased
12554 @section Patching Programs
12556 @cindex patching binaries
12557 @cindex writing into executables
12558 @cindex writing into corefiles
12560 By default, @value{GDBN} opens the file containing your program's
12561 executable code (or the corefile) read-only. This prevents accidental
12562 alterations to machine code; but it also prevents you from intentionally
12563 patching your program's binary.
12565 If you'd like to be able to patch the binary, you can specify that
12566 explicitly with the @code{set write} command. For example, you might
12567 want to turn on internal debugging flags, or even to make emergency
12573 @itemx set write off
12574 If you specify @samp{set write on}, @value{GDBN} opens executable and
12575 core files for both reading and writing; if you specify @kbd{set write
12576 off} (the default), @value{GDBN} opens them read-only.
12578 If you have already loaded a file, you must load it again (using the
12579 @code{exec-file} or @code{core-file} command) after changing @code{set
12580 write}, for your new setting to take effect.
12584 Display whether executable files and core files are opened for writing
12585 as well as reading.
12589 @chapter @value{GDBN} Files
12591 @value{GDBN} needs to know the file name of the program to be debugged,
12592 both in order to read its symbol table and in order to start your
12593 program. To debug a core dump of a previous run, you must also tell
12594 @value{GDBN} the name of the core dump file.
12597 * Files:: Commands to specify files
12598 * Separate Debug Files:: Debugging information in separate files
12599 * Symbol Errors:: Errors reading symbol files
12603 @section Commands to Specify Files
12605 @cindex symbol table
12606 @cindex core dump file
12608 You may want to specify executable and core dump file names. The usual
12609 way to do this is at start-up time, using the arguments to
12610 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
12611 Out of @value{GDBN}}).
12613 Occasionally it is necessary to change to a different file during a
12614 @value{GDBN} session. Or you may run @value{GDBN} and forget to
12615 specify a file you want to use. Or you are debugging a remote target
12616 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
12617 Program}). In these situations the @value{GDBN} commands to specify
12618 new files are useful.
12621 @cindex executable file
12623 @item file @var{filename}
12624 Use @var{filename} as the program to be debugged. It is read for its
12625 symbols and for the contents of pure memory. It is also the program
12626 executed when you use the @code{run} command. If you do not specify a
12627 directory and the file is not found in the @value{GDBN} working directory,
12628 @value{GDBN} uses the environment variable @code{PATH} as a list of
12629 directories to search, just as the shell does when looking for a program
12630 to run. You can change the value of this variable, for both @value{GDBN}
12631 and your program, using the @code{path} command.
12633 @cindex unlinked object files
12634 @cindex patching object files
12635 You can load unlinked object @file{.o} files into @value{GDBN} using
12636 the @code{file} command. You will not be able to ``run'' an object
12637 file, but you can disassemble functions and inspect variables. Also,
12638 if the underlying BFD functionality supports it, you could use
12639 @kbd{gdb -write} to patch object files using this technique. Note
12640 that @value{GDBN} can neither interpret nor modify relocations in this
12641 case, so branches and some initialized variables will appear to go to
12642 the wrong place. But this feature is still handy from time to time.
12645 @code{file} with no argument makes @value{GDBN} discard any information it
12646 has on both executable file and the symbol table.
12649 @item exec-file @r{[} @var{filename} @r{]}
12650 Specify that the program to be run (but not the symbol table) is found
12651 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12652 if necessary to locate your program. Omitting @var{filename} means to
12653 discard information on the executable file.
12655 @kindex symbol-file
12656 @item symbol-file @r{[} @var{filename} @r{]}
12657 Read symbol table information from file @var{filename}. @code{PATH} is
12658 searched when necessary. Use the @code{file} command to get both symbol
12659 table and program to run from the same file.
12661 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12662 program's symbol table.
12664 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12665 some breakpoints and auto-display expressions. This is because they may
12666 contain pointers to the internal data recording symbols and data types,
12667 which are part of the old symbol table data being discarded inside
12670 @code{symbol-file} does not repeat if you press @key{RET} again after
12673 When @value{GDBN} is configured for a particular environment, it
12674 understands debugging information in whatever format is the standard
12675 generated for that environment; you may use either a @sc{gnu} compiler, or
12676 other compilers that adhere to the local conventions.
12677 Best results are usually obtained from @sc{gnu} compilers; for example,
12678 using @code{@value{NGCC}} you can generate debugging information for
12681 For most kinds of object files, with the exception of old SVR3 systems
12682 using COFF, the @code{symbol-file} command does not normally read the
12683 symbol table in full right away. Instead, it scans the symbol table
12684 quickly to find which source files and which symbols are present. The
12685 details are read later, one source file at a time, as they are needed.
12687 The purpose of this two-stage reading strategy is to make @value{GDBN}
12688 start up faster. For the most part, it is invisible except for
12689 occasional pauses while the symbol table details for a particular source
12690 file are being read. (The @code{set verbose} command can turn these
12691 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12692 Warnings and Messages}.)
12694 We have not implemented the two-stage strategy for COFF yet. When the
12695 symbol table is stored in COFF format, @code{symbol-file} reads the
12696 symbol table data in full right away. Note that ``stabs-in-COFF''
12697 still does the two-stage strategy, since the debug info is actually
12701 @cindex reading symbols immediately
12702 @cindex symbols, reading immediately
12703 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12704 @itemx file @var{filename} @r{[} -readnow @r{]}
12705 You can override the @value{GDBN} two-stage strategy for reading symbol
12706 tables by using the @samp{-readnow} option with any of the commands that
12707 load symbol table information, if you want to be sure @value{GDBN} has the
12708 entire symbol table available.
12710 @c FIXME: for now no mention of directories, since this seems to be in
12711 @c flux. 13mar1992 status is that in theory GDB would look either in
12712 @c current dir or in same dir as myprog; but issues like competing
12713 @c GDB's, or clutter in system dirs, mean that in practice right now
12714 @c only current dir is used. FFish says maybe a special GDB hierarchy
12715 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
12719 @item core-file @r{[}@var{filename}@r{]}
12721 Specify the whereabouts of a core dump file to be used as the ``contents
12722 of memory''. Traditionally, core files contain only some parts of the
12723 address space of the process that generated them; @value{GDBN} can access the
12724 executable file itself for other parts.
12726 @code{core-file} with no argument specifies that no core file is
12729 Note that the core file is ignored when your program is actually running
12730 under @value{GDBN}. So, if you have been running your program and you
12731 wish to debug a core file instead, you must kill the subprocess in which
12732 the program is running. To do this, use the @code{kill} command
12733 (@pxref{Kill Process, ,Killing the Child Process}).
12735 @kindex add-symbol-file
12736 @cindex dynamic linking
12737 @item add-symbol-file @var{filename} @var{address}
12738 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12739 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12740 The @code{add-symbol-file} command reads additional symbol table
12741 information from the file @var{filename}. You would use this command
12742 when @var{filename} has been dynamically loaded (by some other means)
12743 into the program that is running. @var{address} should be the memory
12744 address at which the file has been loaded; @value{GDBN} cannot figure
12745 this out for itself. You can additionally specify an arbitrary number
12746 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12747 section name and base address for that section. You can specify any
12748 @var{address} as an expression.
12750 The symbol table of the file @var{filename} is added to the symbol table
12751 originally read with the @code{symbol-file} command. You can use the
12752 @code{add-symbol-file} command any number of times; the new symbol data
12753 thus read keeps adding to the old. To discard all old symbol data
12754 instead, use the @code{symbol-file} command without any arguments.
12756 @cindex relocatable object files, reading symbols from
12757 @cindex object files, relocatable, reading symbols from
12758 @cindex reading symbols from relocatable object files
12759 @cindex symbols, reading from relocatable object files
12760 @cindex @file{.o} files, reading symbols from
12761 Although @var{filename} is typically a shared library file, an
12762 executable file, or some other object file which has been fully
12763 relocated for loading into a process, you can also load symbolic
12764 information from relocatable @file{.o} files, as long as:
12768 the file's symbolic information refers only to linker symbols defined in
12769 that file, not to symbols defined by other object files,
12771 every section the file's symbolic information refers to has actually
12772 been loaded into the inferior, as it appears in the file, and
12774 you can determine the address at which every section was loaded, and
12775 provide these to the @code{add-symbol-file} command.
12779 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12780 relocatable files into an already running program; such systems
12781 typically make the requirements above easy to meet. However, it's
12782 important to recognize that many native systems use complex link
12783 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12784 assembly, for example) that make the requirements difficult to meet. In
12785 general, one cannot assume that using @code{add-symbol-file} to read a
12786 relocatable object file's symbolic information will have the same effect
12787 as linking the relocatable object file into the program in the normal
12790 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12792 @kindex add-symbol-file-from-memory
12793 @cindex @code{syscall DSO}
12794 @cindex load symbols from memory
12795 @item add-symbol-file-from-memory @var{address}
12796 Load symbols from the given @var{address} in a dynamically loaded
12797 object file whose image is mapped directly into the inferior's memory.
12798 For example, the Linux kernel maps a @code{syscall DSO} into each
12799 process's address space; this DSO provides kernel-specific code for
12800 some system calls. The argument can be any expression whose
12801 evaluation yields the address of the file's shared object file header.
12802 For this command to work, you must have used @code{symbol-file} or
12803 @code{exec-file} commands in advance.
12805 @kindex add-shared-symbol-files
12807 @item add-shared-symbol-files @var{library-file}
12808 @itemx assf @var{library-file}
12809 The @code{add-shared-symbol-files} command can currently be used only
12810 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12811 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12812 @value{GDBN} automatically looks for shared libraries, however if
12813 @value{GDBN} does not find yours, you can invoke
12814 @code{add-shared-symbol-files}. It takes one argument: the shared
12815 library's file name. @code{assf} is a shorthand alias for
12816 @code{add-shared-symbol-files}.
12819 @item section @var{section} @var{addr}
12820 The @code{section} command changes the base address of the named
12821 @var{section} of the exec file to @var{addr}. This can be used if the
12822 exec file does not contain section addresses, (such as in the
12823 @code{a.out} format), or when the addresses specified in the file
12824 itself are wrong. Each section must be changed separately. The
12825 @code{info files} command, described below, lists all the sections and
12829 @kindex info target
12832 @code{info files} and @code{info target} are synonymous; both print the
12833 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12834 including the names of the executable and core dump files currently in
12835 use by @value{GDBN}, and the files from which symbols were loaded. The
12836 command @code{help target} lists all possible targets rather than
12839 @kindex maint info sections
12840 @item maint info sections
12841 Another command that can give you extra information about program sections
12842 is @code{maint info sections}. In addition to the section information
12843 displayed by @code{info files}, this command displays the flags and file
12844 offset of each section in the executable and core dump files. In addition,
12845 @code{maint info sections} provides the following command options (which
12846 may be arbitrarily combined):
12850 Display sections for all loaded object files, including shared libraries.
12851 @item @var{sections}
12852 Display info only for named @var{sections}.
12853 @item @var{section-flags}
12854 Display info only for sections for which @var{section-flags} are true.
12855 The section flags that @value{GDBN} currently knows about are:
12858 Section will have space allocated in the process when loaded.
12859 Set for all sections except those containing debug information.
12861 Section will be loaded from the file into the child process memory.
12862 Set for pre-initialized code and data, clear for @code{.bss} sections.
12864 Section needs to be relocated before loading.
12866 Section cannot be modified by the child process.
12868 Section contains executable code only.
12870 Section contains data only (no executable code).
12872 Section will reside in ROM.
12874 Section contains data for constructor/destructor lists.
12876 Section is not empty.
12878 An instruction to the linker to not output the section.
12879 @item COFF_SHARED_LIBRARY
12880 A notification to the linker that the section contains
12881 COFF shared library information.
12883 Section contains common symbols.
12886 @kindex set trust-readonly-sections
12887 @cindex read-only sections
12888 @item set trust-readonly-sections on
12889 Tell @value{GDBN} that readonly sections in your object file
12890 really are read-only (i.e.@: that their contents will not change).
12891 In that case, @value{GDBN} can fetch values from these sections
12892 out of the object file, rather than from the target program.
12893 For some targets (notably embedded ones), this can be a significant
12894 enhancement to debugging performance.
12896 The default is off.
12898 @item set trust-readonly-sections off
12899 Tell @value{GDBN} not to trust readonly sections. This means that
12900 the contents of the section might change while the program is running,
12901 and must therefore be fetched from the target when needed.
12903 @item show trust-readonly-sections
12904 Show the current setting of trusting readonly sections.
12907 All file-specifying commands allow both absolute and relative file names
12908 as arguments. @value{GDBN} always converts the file name to an absolute file
12909 name and remembers it that way.
12911 @cindex shared libraries
12912 @anchor{Shared Libraries}
12913 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
12914 and IBM RS/6000 AIX shared libraries.
12916 On MS-Windows @value{GDBN} must be linked with the Expat library to support
12917 shared libraries. @xref{Expat}.
12919 @value{GDBN} automatically loads symbol definitions from shared libraries
12920 when you use the @code{run} command, or when you examine a core file.
12921 (Before you issue the @code{run} command, @value{GDBN} does not understand
12922 references to a function in a shared library, however---unless you are
12923 debugging a core file).
12925 On HP-UX, if the program loads a library explicitly, @value{GDBN}
12926 automatically loads the symbols at the time of the @code{shl_load} call.
12928 @c FIXME: some @value{GDBN} release may permit some refs to undef
12929 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
12930 @c FIXME...lib; check this from time to time when updating manual
12932 There are times, however, when you may wish to not automatically load
12933 symbol definitions from shared libraries, such as when they are
12934 particularly large or there are many of them.
12936 To control the automatic loading of shared library symbols, use the
12940 @kindex set auto-solib-add
12941 @item set auto-solib-add @var{mode}
12942 If @var{mode} is @code{on}, symbols from all shared object libraries
12943 will be loaded automatically when the inferior begins execution, you
12944 attach to an independently started inferior, or when the dynamic linker
12945 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12946 is @code{off}, symbols must be loaded manually, using the
12947 @code{sharedlibrary} command. The default value is @code{on}.
12949 @cindex memory used for symbol tables
12950 If your program uses lots of shared libraries with debug info that
12951 takes large amounts of memory, you can decrease the @value{GDBN}
12952 memory footprint by preventing it from automatically loading the
12953 symbols from shared libraries. To that end, type @kbd{set
12954 auto-solib-add off} before running the inferior, then load each
12955 library whose debug symbols you do need with @kbd{sharedlibrary
12956 @var{regexp}}, where @var{regexp} is a regular expression that matches
12957 the libraries whose symbols you want to be loaded.
12959 @kindex show auto-solib-add
12960 @item show auto-solib-add
12961 Display the current autoloading mode.
12964 @cindex load shared library
12965 To explicitly load shared library symbols, use the @code{sharedlibrary}
12969 @kindex info sharedlibrary
12972 @itemx info sharedlibrary
12973 Print the names of the shared libraries which are currently loaded.
12975 @kindex sharedlibrary
12977 @item sharedlibrary @var{regex}
12978 @itemx share @var{regex}
12979 Load shared object library symbols for files matching a
12980 Unix regular expression.
12981 As with files loaded automatically, it only loads shared libraries
12982 required by your program for a core file or after typing @code{run}. If
12983 @var{regex} is omitted all shared libraries required by your program are
12986 @item nosharedlibrary
12987 @kindex nosharedlibrary
12988 @cindex unload symbols from shared libraries
12989 Unload all shared object library symbols. This discards all symbols
12990 that have been loaded from all shared libraries. Symbols from shared
12991 libraries that were loaded by explicit user requests are not
12995 Sometimes you may wish that @value{GDBN} stops and gives you control
12996 when any of shared library events happen. Use the @code{set
12997 stop-on-solib-events} command for this:
13000 @item set stop-on-solib-events
13001 @kindex set stop-on-solib-events
13002 This command controls whether @value{GDBN} should give you control
13003 when the dynamic linker notifies it about some shared library event.
13004 The most common event of interest is loading or unloading of a new
13007 @item show stop-on-solib-events
13008 @kindex show stop-on-solib-events
13009 Show whether @value{GDBN} stops and gives you control when shared
13010 library events happen.
13013 Shared libraries are also supported in many cross or remote debugging
13014 configurations. @value{GDBN} needs to have access to the target's libraries;
13015 this can be accomplished either by providing copies of the libraries
13016 on the host system, or by asking @value{GDBN} to automatically retrieve the
13017 libraries from the target. If copies of the target libraries are
13018 provided, they need to be the same as the target libraries, although the
13019 copies on the target can be stripped as long as the copies on the host are
13022 @cindex where to look for shared libraries
13023 For remote debugging, you need to tell @value{GDBN} where the target
13024 libraries are, so that it can load the correct copies---otherwise, it
13025 may try to load the host's libraries. @value{GDBN} has two variables
13026 to specify the search directories for target libraries.
13029 @cindex prefix for shared library file names
13030 @cindex system root, alternate
13031 @kindex set solib-absolute-prefix
13032 @kindex set sysroot
13033 @item set sysroot @var{path}
13034 Use @var{path} as the system root for the program being debugged. Any
13035 absolute shared library paths will be prefixed with @var{path}; many
13036 runtime loaders store the absolute paths to the shared library in the
13037 target program's memory. If you use @code{set sysroot} to find shared
13038 libraries, they need to be laid out in the same way that they are on
13039 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
13042 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
13043 retrieve the target libraries from the remote system. This is only
13044 supported when using a remote target that supports the @code{remote get}
13045 command (@pxref{File Transfer,,Sending files to a remote system}).
13046 The part of @var{path} following the initial @file{remote:}
13047 (if present) is used as system root prefix on the remote file system.
13048 @footnote{If you want to specify a local system root using a directory
13049 that happens to be named @file{remote:}, you need to use some equivalent
13050 variant of the name like @file{./remote:}.}
13052 The @code{set solib-absolute-prefix} command is an alias for @code{set
13055 @cindex default system root
13056 @cindex @samp{--with-sysroot}
13057 You can set the default system root by using the configure-time
13058 @samp{--with-sysroot} option. If the system root is inside
13059 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13060 @samp{--exec-prefix}), then the default system root will be updated
13061 automatically if the installed @value{GDBN} is moved to a new
13064 @kindex show sysroot
13066 Display the current shared library prefix.
13068 @kindex set solib-search-path
13069 @item set solib-search-path @var{path}
13070 If this variable is set, @var{path} is a colon-separated list of
13071 directories to search for shared libraries. @samp{solib-search-path}
13072 is used after @samp{sysroot} fails to locate the library, or if the
13073 path to the library is relative instead of absolute. If you want to
13074 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13075 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13076 finding your host's libraries. @samp{sysroot} is preferred; setting
13077 it to a nonexistent directory may interfere with automatic loading
13078 of shared library symbols.
13080 @kindex show solib-search-path
13081 @item show solib-search-path
13082 Display the current shared library search path.
13086 @node Separate Debug Files
13087 @section Debugging Information in Separate Files
13088 @cindex separate debugging information files
13089 @cindex debugging information in separate files
13090 @cindex @file{.debug} subdirectories
13091 @cindex debugging information directory, global
13092 @cindex global debugging information directory
13093 @cindex build ID, and separate debugging files
13094 @cindex @file{.build-id} directory
13096 @value{GDBN} allows you to put a program's debugging information in a
13097 file separate from the executable itself, in a way that allows
13098 @value{GDBN} to find and load the debugging information automatically.
13099 Since debugging information can be very large---sometimes larger
13100 than the executable code itself---some systems distribute debugging
13101 information for their executables in separate files, which users can
13102 install only when they need to debug a problem.
13104 @value{GDBN} supports two ways of specifying the separate debug info
13109 The executable contains a @dfn{debug link} that specifies the name of
13110 the separate debug info file. The separate debug file's name is
13111 usually @file{@var{executable}.debug}, where @var{executable} is the
13112 name of the corresponding executable file without leading directories
13113 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
13114 debug link specifies a CRC32 checksum for the debug file, which
13115 @value{GDBN} uses to validate that the executable and the debug file
13116 came from the same build.
13119 The executable contains a @dfn{build ID}, a unique bit string that is
13120 also present in the corresponding debug info file. (This is supported
13121 only on some operating systems, notably those which use the ELF format
13122 for binary files and the @sc{gnu} Binutils.) For more details about
13123 this feature, see the description of the @option{--build-id}
13124 command-line option in @ref{Options, , Command Line Options, ld.info,
13125 The GNU Linker}. The debug info file's name is not specified
13126 explicitly by the build ID, but can be computed from the build ID, see
13130 Depending on the way the debug info file is specified, @value{GDBN}
13131 uses two different methods of looking for the debug file:
13135 For the ``debug link'' method, @value{GDBN} looks up the named file in
13136 the directory of the executable file, then in a subdirectory of that
13137 directory named @file{.debug}, and finally under the global debug
13138 directory, in a subdirectory whose name is identical to the leading
13139 directories of the executable's absolute file name.
13142 For the ``build ID'' method, @value{GDBN} looks in the
13143 @file{.build-id} subdirectory of the global debug directory for a file
13144 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
13145 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
13146 are the rest of the bit string. (Real build ID strings are 32 or more
13147 hex characters, not 10.)
13150 So, for example, suppose you ask @value{GDBN} to debug
13151 @file{/usr/bin/ls}, which has a debug link that specifies the
13152 file @file{ls.debug}, and a build ID whose value in hex is
13153 @code{abcdef1234}. If the global debug directory is
13154 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
13155 debug information files, in the indicated order:
13159 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
13161 @file{/usr/bin/ls.debug}
13163 @file{/usr/bin/.debug/ls.debug}
13165 @file{/usr/lib/debug/usr/bin/ls.debug}.
13168 You can set the global debugging info directory's name, and view the
13169 name @value{GDBN} is currently using.
13173 @kindex set debug-file-directory
13174 @item set debug-file-directory @var{directory}
13175 Set the directory which @value{GDBN} searches for separate debugging
13176 information files to @var{directory}.
13178 @kindex show debug-file-directory
13179 @item show debug-file-directory
13180 Show the directory @value{GDBN} searches for separate debugging
13185 @cindex @code{.gnu_debuglink} sections
13186 @cindex debug link sections
13187 A debug link is a special section of the executable file named
13188 @code{.gnu_debuglink}. The section must contain:
13192 A filename, with any leading directory components removed, followed by
13195 zero to three bytes of padding, as needed to reach the next four-byte
13196 boundary within the section, and
13198 a four-byte CRC checksum, stored in the same endianness used for the
13199 executable file itself. The checksum is computed on the debugging
13200 information file's full contents by the function given below, passing
13201 zero as the @var{crc} argument.
13204 Any executable file format can carry a debug link, as long as it can
13205 contain a section named @code{.gnu_debuglink} with the contents
13208 @cindex @code{.note.gnu.build-id} sections
13209 @cindex build ID sections
13210 The build ID is a special section in the executable file (and in other
13211 ELF binary files that @value{GDBN} may consider). This section is
13212 often named @code{.note.gnu.build-id}, but that name is not mandatory.
13213 It contains unique identification for the built files---the ID remains
13214 the same across multiple builds of the same build tree. The default
13215 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
13216 content for the build ID string. The same section with an identical
13217 value is present in the original built binary with symbols, in its
13218 stripped variant, and in the separate debugging information file.
13220 The debugging information file itself should be an ordinary
13221 executable, containing a full set of linker symbols, sections, and
13222 debugging information. The sections of the debugging information file
13223 should have the same names, addresses, and sizes as the original file,
13224 but they need not contain any data---much like a @code{.bss} section
13225 in an ordinary executable.
13227 The @sc{gnu} binary utilities (Binutils) package includes the
13228 @samp{objcopy} utility that can produce
13229 the separated executable / debugging information file pairs using the
13230 following commands:
13233 @kbd{objcopy --only-keep-debug foo foo.debug}
13238 These commands remove the debugging
13239 information from the executable file @file{foo} and place it in the file
13240 @file{foo.debug}. You can use the first, second or both methods to link the
13245 The debug link method needs the following additional command to also leave
13246 behind a debug link in @file{foo}:
13249 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
13252 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
13253 a version of the @code{strip} command such that the command @kbd{strip foo -f
13254 foo.debug} has the same functionality as the two @code{objcopy} commands and
13255 the @code{ln -s} command above, together.
13258 Build ID gets embedded into the main executable using @code{ld --build-id} or
13259 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
13260 compatibility fixes for debug files separation are present in @sc{gnu} binary
13261 utilities (Binutils) package since version 2.18.
13266 Since there are many different ways to compute CRC's for the debug
13267 link (different polynomials, reversals, byte ordering, etc.), the
13268 simplest way to describe the CRC used in @code{.gnu_debuglink}
13269 sections is to give the complete code for a function that computes it:
13271 @kindex gnu_debuglink_crc32
13274 gnu_debuglink_crc32 (unsigned long crc,
13275 unsigned char *buf, size_t len)
13277 static const unsigned long crc32_table[256] =
13279 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
13280 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
13281 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
13282 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
13283 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
13284 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
13285 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
13286 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
13287 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
13288 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
13289 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
13290 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
13291 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
13292 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
13293 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
13294 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
13295 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
13296 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
13297 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
13298 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
13299 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
13300 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
13301 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
13302 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
13303 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
13304 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
13305 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
13306 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
13307 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
13308 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
13309 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
13310 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
13311 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
13312 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
13313 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
13314 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
13315 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
13316 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
13317 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
13318 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
13319 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
13320 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
13321 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
13322 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
13323 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
13324 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
13325 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
13326 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
13327 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
13328 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
13329 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
13332 unsigned char *end;
13334 crc = ~crc & 0xffffffff;
13335 for (end = buf + len; buf < end; ++buf)
13336 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
13337 return ~crc & 0xffffffff;
13342 This computation does not apply to the ``build ID'' method.
13345 @node Symbol Errors
13346 @section Errors Reading Symbol Files
13348 While reading a symbol file, @value{GDBN} occasionally encounters problems,
13349 such as symbol types it does not recognize, or known bugs in compiler
13350 output. By default, @value{GDBN} does not notify you of such problems, since
13351 they are relatively common and primarily of interest to people
13352 debugging compilers. If you are interested in seeing information
13353 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
13354 only one message about each such type of problem, no matter how many
13355 times the problem occurs; or you can ask @value{GDBN} to print more messages,
13356 to see how many times the problems occur, with the @code{set
13357 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
13360 The messages currently printed, and their meanings, include:
13363 @item inner block not inside outer block in @var{symbol}
13365 The symbol information shows where symbol scopes begin and end
13366 (such as at the start of a function or a block of statements). This
13367 error indicates that an inner scope block is not fully contained
13368 in its outer scope blocks.
13370 @value{GDBN} circumvents the problem by treating the inner block as if it had
13371 the same scope as the outer block. In the error message, @var{symbol}
13372 may be shown as ``@code{(don't know)}'' if the outer block is not a
13375 @item block at @var{address} out of order
13377 The symbol information for symbol scope blocks should occur in
13378 order of increasing addresses. This error indicates that it does not
13381 @value{GDBN} does not circumvent this problem, and has trouble
13382 locating symbols in the source file whose symbols it is reading. (You
13383 can often determine what source file is affected by specifying
13384 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
13387 @item bad block start address patched
13389 The symbol information for a symbol scope block has a start address
13390 smaller than the address of the preceding source line. This is known
13391 to occur in the SunOS 4.1.1 (and earlier) C compiler.
13393 @value{GDBN} circumvents the problem by treating the symbol scope block as
13394 starting on the previous source line.
13396 @item bad string table offset in symbol @var{n}
13399 Symbol number @var{n} contains a pointer into the string table which is
13400 larger than the size of the string table.
13402 @value{GDBN} circumvents the problem by considering the symbol to have the
13403 name @code{foo}, which may cause other problems if many symbols end up
13406 @item unknown symbol type @code{0x@var{nn}}
13408 The symbol information contains new data types that @value{GDBN} does
13409 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
13410 uncomprehended information, in hexadecimal.
13412 @value{GDBN} circumvents the error by ignoring this symbol information.
13413 This usually allows you to debug your program, though certain symbols
13414 are not accessible. If you encounter such a problem and feel like
13415 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
13416 on @code{complain}, then go up to the function @code{read_dbx_symtab}
13417 and examine @code{*bufp} to see the symbol.
13419 @item stub type has NULL name
13421 @value{GDBN} could not find the full definition for a struct or class.
13423 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
13424 The symbol information for a C@t{++} member function is missing some
13425 information that recent versions of the compiler should have output for
13428 @item info mismatch between compiler and debugger
13430 @value{GDBN} could not parse a type specification output by the compiler.
13435 @chapter Specifying a Debugging Target
13437 @cindex debugging target
13438 A @dfn{target} is the execution environment occupied by your program.
13440 Often, @value{GDBN} runs in the same host environment as your program;
13441 in that case, the debugging target is specified as a side effect when
13442 you use the @code{file} or @code{core} commands. When you need more
13443 flexibility---for example, running @value{GDBN} on a physically separate
13444 host, or controlling a standalone system over a serial port or a
13445 realtime system over a TCP/IP connection---you can use the @code{target}
13446 command to specify one of the target types configured for @value{GDBN}
13447 (@pxref{Target Commands, ,Commands for Managing Targets}).
13449 @cindex target architecture
13450 It is possible to build @value{GDBN} for several different @dfn{target
13451 architectures}. When @value{GDBN} is built like that, you can choose
13452 one of the available architectures with the @kbd{set architecture}
13456 @kindex set architecture
13457 @kindex show architecture
13458 @item set architecture @var{arch}
13459 This command sets the current target architecture to @var{arch}. The
13460 value of @var{arch} can be @code{"auto"}, in addition to one of the
13461 supported architectures.
13463 @item show architecture
13464 Show the current target architecture.
13466 @item set processor
13468 @kindex set processor
13469 @kindex show processor
13470 These are alias commands for, respectively, @code{set architecture}
13471 and @code{show architecture}.
13475 * Active Targets:: Active targets
13476 * Target Commands:: Commands for managing targets
13477 * Byte Order:: Choosing target byte order
13480 @node Active Targets
13481 @section Active Targets
13483 @cindex stacking targets
13484 @cindex active targets
13485 @cindex multiple targets
13487 There are three classes of targets: processes, core files, and
13488 executable files. @value{GDBN} can work concurrently on up to three
13489 active targets, one in each class. This allows you to (for example)
13490 start a process and inspect its activity without abandoning your work on
13493 For example, if you execute @samp{gdb a.out}, then the executable file
13494 @code{a.out} is the only active target. If you designate a core file as
13495 well---presumably from a prior run that crashed and coredumped---then
13496 @value{GDBN} has two active targets and uses them in tandem, looking
13497 first in the corefile target, then in the executable file, to satisfy
13498 requests for memory addresses. (Typically, these two classes of target
13499 are complementary, since core files contain only a program's
13500 read-write memory---variables and so on---plus machine status, while
13501 executable files contain only the program text and initialized data.)
13503 When you type @code{run}, your executable file becomes an active process
13504 target as well. When a process target is active, all @value{GDBN}
13505 commands requesting memory addresses refer to that target; addresses in
13506 an active core file or executable file target are obscured while the
13507 process target is active.
13509 Use the @code{core-file} and @code{exec-file} commands to select a new
13510 core file or executable target (@pxref{Files, ,Commands to Specify
13511 Files}). To specify as a target a process that is already running, use
13512 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
13515 @node Target Commands
13516 @section Commands for Managing Targets
13519 @item target @var{type} @var{parameters}
13520 Connects the @value{GDBN} host environment to a target machine or
13521 process. A target is typically a protocol for talking to debugging
13522 facilities. You use the argument @var{type} to specify the type or
13523 protocol of the target machine.
13525 Further @var{parameters} are interpreted by the target protocol, but
13526 typically include things like device names or host names to connect
13527 with, process numbers, and baud rates.
13529 The @code{target} command does not repeat if you press @key{RET} again
13530 after executing the command.
13532 @kindex help target
13534 Displays the names of all targets available. To display targets
13535 currently selected, use either @code{info target} or @code{info files}
13536 (@pxref{Files, ,Commands to Specify Files}).
13538 @item help target @var{name}
13539 Describe a particular target, including any parameters necessary to
13542 @kindex set gnutarget
13543 @item set gnutarget @var{args}
13544 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
13545 knows whether it is reading an @dfn{executable},
13546 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
13547 with the @code{set gnutarget} command. Unlike most @code{target} commands,
13548 with @code{gnutarget} the @code{target} refers to a program, not a machine.
13551 @emph{Warning:} To specify a file format with @code{set gnutarget},
13552 you must know the actual BFD name.
13556 @xref{Files, , Commands to Specify Files}.
13558 @kindex show gnutarget
13559 @item show gnutarget
13560 Use the @code{show gnutarget} command to display what file format
13561 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
13562 @value{GDBN} will determine the file format for each file automatically,
13563 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
13566 @cindex common targets
13567 Here are some common targets (available, or not, depending on the GDB
13572 @item target exec @var{program}
13573 @cindex executable file target
13574 An executable file. @samp{target exec @var{program}} is the same as
13575 @samp{exec-file @var{program}}.
13577 @item target core @var{filename}
13578 @cindex core dump file target
13579 A core dump file. @samp{target core @var{filename}} is the same as
13580 @samp{core-file @var{filename}}.
13582 @item target remote @var{medium}
13583 @cindex remote target
13584 A remote system connected to @value{GDBN} via a serial line or network
13585 connection. This command tells @value{GDBN} to use its own remote
13586 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
13588 For example, if you have a board connected to @file{/dev/ttya} on the
13589 machine running @value{GDBN}, you could say:
13592 target remote /dev/ttya
13595 @code{target remote} supports the @code{load} command. This is only
13596 useful if you have some other way of getting the stub to the target
13597 system, and you can put it somewhere in memory where it won't get
13598 clobbered by the download.
13601 @cindex built-in simulator target
13602 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
13610 works; however, you cannot assume that a specific memory map, device
13611 drivers, or even basic I/O is available, although some simulators do
13612 provide these. For info about any processor-specific simulator details,
13613 see the appropriate section in @ref{Embedded Processors, ,Embedded
13618 Some configurations may include these targets as well:
13622 @item target nrom @var{dev}
13623 @cindex NetROM ROM emulator target
13624 NetROM ROM emulator. This target only supports downloading.
13628 Different targets are available on different configurations of @value{GDBN};
13629 your configuration may have more or fewer targets.
13631 Many remote targets require you to download the executable's code once
13632 you've successfully established a connection. You may wish to control
13633 various aspects of this process.
13638 @kindex set hash@r{, for remote monitors}
13639 @cindex hash mark while downloading
13640 This command controls whether a hash mark @samp{#} is displayed while
13641 downloading a file to the remote monitor. If on, a hash mark is
13642 displayed after each S-record is successfully downloaded to the
13646 @kindex show hash@r{, for remote monitors}
13647 Show the current status of displaying the hash mark.
13649 @item set debug monitor
13650 @kindex set debug monitor
13651 @cindex display remote monitor communications
13652 Enable or disable display of communications messages between
13653 @value{GDBN} and the remote monitor.
13655 @item show debug monitor
13656 @kindex show debug monitor
13657 Show the current status of displaying communications between
13658 @value{GDBN} and the remote monitor.
13663 @kindex load @var{filename}
13664 @item load @var{filename}
13666 Depending on what remote debugging facilities are configured into
13667 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13668 is meant to make @var{filename} (an executable) available for debugging
13669 on the remote system---by downloading, or dynamic linking, for example.
13670 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
13671 the @code{add-symbol-file} command.
13673 If your @value{GDBN} does not have a @code{load} command, attempting to
13674 execute it gets the error message ``@code{You can't do that when your
13675 target is @dots{}}''
13677 The file is loaded at whatever address is specified in the executable.
13678 For some object file formats, you can specify the load address when you
13679 link the program; for other formats, like a.out, the object file format
13680 specifies a fixed address.
13681 @c FIXME! This would be a good place for an xref to the GNU linker doc.
13683 Depending on the remote side capabilities, @value{GDBN} may be able to
13684 load programs into flash memory.
13686 @code{load} does not repeat if you press @key{RET} again after using it.
13690 @section Choosing Target Byte Order
13692 @cindex choosing target byte order
13693 @cindex target byte order
13695 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
13696 offer the ability to run either big-endian or little-endian byte
13697 orders. Usually the executable or symbol will include a bit to
13698 designate the endian-ness, and you will not need to worry about
13699 which to use. However, you may still find it useful to adjust
13700 @value{GDBN}'s idea of processor endian-ness manually.
13704 @item set endian big
13705 Instruct @value{GDBN} to assume the target is big-endian.
13707 @item set endian little
13708 Instruct @value{GDBN} to assume the target is little-endian.
13710 @item set endian auto
13711 Instruct @value{GDBN} to use the byte order associated with the
13715 Display @value{GDBN}'s current idea of the target byte order.
13719 Note that these commands merely adjust interpretation of symbolic
13720 data on the host, and that they have absolutely no effect on the
13724 @node Remote Debugging
13725 @chapter Debugging Remote Programs
13726 @cindex remote debugging
13728 If you are trying to debug a program running on a machine that cannot run
13729 @value{GDBN} in the usual way, it is often useful to use remote debugging.
13730 For example, you might use remote debugging on an operating system kernel,
13731 or on a small system which does not have a general purpose operating system
13732 powerful enough to run a full-featured debugger.
13734 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
13735 to make this work with particular debugging targets. In addition,
13736 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
13737 but not specific to any particular target system) which you can use if you
13738 write the remote stubs---the code that runs on the remote system to
13739 communicate with @value{GDBN}.
13741 Other remote targets may be available in your
13742 configuration of @value{GDBN}; use @code{help target} to list them.
13745 * Connecting:: Connecting to a remote target
13746 * File Transfer:: Sending files to a remote system
13747 * Server:: Using the gdbserver program
13748 * Remote Configuration:: Remote configuration
13749 * Remote Stub:: Implementing a remote stub
13753 @section Connecting to a Remote Target
13755 On the @value{GDBN} host machine, you will need an unstripped copy of
13756 your program, since @value{GDBN} needs symbol and debugging information.
13757 Start up @value{GDBN} as usual, using the name of the local copy of your
13758 program as the first argument.
13760 @cindex @code{target remote}
13761 @value{GDBN} can communicate with the target over a serial line, or
13762 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13763 each case, @value{GDBN} uses the same protocol for debugging your
13764 program; only the medium carrying the debugging packets varies. The
13765 @code{target remote} command establishes a connection to the target.
13766 Its arguments indicate which medium to use:
13770 @item target remote @var{serial-device}
13771 @cindex serial line, @code{target remote}
13772 Use @var{serial-device} to communicate with the target. For example,
13773 to use a serial line connected to the device named @file{/dev/ttyb}:
13776 target remote /dev/ttyb
13779 If you're using a serial line, you may want to give @value{GDBN} the
13780 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13781 (@pxref{Remote Configuration, set remotebaud}) before the
13782 @code{target} command.
13784 @item target remote @code{@var{host}:@var{port}}
13785 @itemx target remote @code{tcp:@var{host}:@var{port}}
13786 @cindex @acronym{TCP} port, @code{target remote}
13787 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13788 The @var{host} may be either a host name or a numeric @acronym{IP}
13789 address; @var{port} must be a decimal number. The @var{host} could be
13790 the target machine itself, if it is directly connected to the net, or
13791 it might be a terminal server which in turn has a serial line to the
13794 For example, to connect to port 2828 on a terminal server named
13798 target remote manyfarms:2828
13801 If your remote target is actually running on the same machine as your
13802 debugger session (e.g.@: a simulator for your target running on the
13803 same host), you can omit the hostname. For example, to connect to
13804 port 1234 on your local machine:
13807 target remote :1234
13811 Note that the colon is still required here.
13813 @item target remote @code{udp:@var{host}:@var{port}}
13814 @cindex @acronym{UDP} port, @code{target remote}
13815 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13816 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13819 target remote udp:manyfarms:2828
13822 When using a @acronym{UDP} connection for remote debugging, you should
13823 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13824 can silently drop packets on busy or unreliable networks, which will
13825 cause havoc with your debugging session.
13827 @item target remote | @var{command}
13828 @cindex pipe, @code{target remote} to
13829 Run @var{command} in the background and communicate with it using a
13830 pipe. The @var{command} is a shell command, to be parsed and expanded
13831 by the system's command shell, @code{/bin/sh}; it should expect remote
13832 protocol packets on its standard input, and send replies on its
13833 standard output. You could use this to run a stand-alone simulator
13834 that speaks the remote debugging protocol, to make net connections
13835 using programs like @code{ssh}, or for other similar tricks.
13837 If @var{command} closes its standard output (perhaps by exiting),
13838 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13839 program has already exited, this will have no effect.)
13843 Once the connection has been established, you can use all the usual
13844 commands to examine and change data. The remote program is already
13845 running; you can use @kbd{step} and @kbd{continue}, and you do not
13846 need to use @kbd{run}.
13848 @cindex interrupting remote programs
13849 @cindex remote programs, interrupting
13850 Whenever @value{GDBN} is waiting for the remote program, if you type the
13851 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13852 program. This may or may not succeed, depending in part on the hardware
13853 and the serial drivers the remote system uses. If you type the
13854 interrupt character once again, @value{GDBN} displays this prompt:
13857 Interrupted while waiting for the program.
13858 Give up (and stop debugging it)? (y or n)
13861 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13862 (If you decide you want to try again later, you can use @samp{target
13863 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13864 goes back to waiting.
13867 @kindex detach (remote)
13869 When you have finished debugging the remote program, you can use the
13870 @code{detach} command to release it from @value{GDBN} control.
13871 Detaching from the target normally resumes its execution, but the results
13872 will depend on your particular remote stub. After the @code{detach}
13873 command, @value{GDBN} is free to connect to another target.
13877 The @code{disconnect} command behaves like @code{detach}, except that
13878 the target is generally not resumed. It will wait for @value{GDBN}
13879 (this instance or another one) to connect and continue debugging. After
13880 the @code{disconnect} command, @value{GDBN} is again free to connect to
13883 @cindex send command to remote monitor
13884 @cindex extend @value{GDBN} for remote targets
13885 @cindex add new commands for external monitor
13887 @item monitor @var{cmd}
13888 This command allows you to send arbitrary commands directly to the
13889 remote monitor. Since @value{GDBN} doesn't care about the commands it
13890 sends like this, this command is the way to extend @value{GDBN}---you
13891 can add new commands that only the external monitor will understand
13895 @node File Transfer
13896 @section Sending files to a remote system
13897 @cindex remote target, file transfer
13898 @cindex file transfer
13899 @cindex sending files to remote systems
13901 Some remote targets offer the ability to transfer files over the same
13902 connection used to communicate with @value{GDBN}. This is convenient
13903 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
13904 running @code{gdbserver} over a network interface. For other targets,
13905 e.g.@: embedded devices with only a single serial port, this may be
13906 the only way to upload or download files.
13908 Not all remote targets support these commands.
13912 @item remote put @var{hostfile} @var{targetfile}
13913 Copy file @var{hostfile} from the host system (the machine running
13914 @value{GDBN}) to @var{targetfile} on the target system.
13917 @item remote get @var{targetfile} @var{hostfile}
13918 Copy file @var{targetfile} from the target system to @var{hostfile}
13919 on the host system.
13921 @kindex remote delete
13922 @item remote delete @var{targetfile}
13923 Delete @var{targetfile} from the target system.
13928 @section Using the @code{gdbserver} Program
13931 @cindex remote connection without stubs
13932 @code{gdbserver} is a control program for Unix-like systems, which
13933 allows you to connect your program with a remote @value{GDBN} via
13934 @code{target remote}---but without linking in the usual debugging stub.
13936 @code{gdbserver} is not a complete replacement for the debugging stubs,
13937 because it requires essentially the same operating-system facilities
13938 that @value{GDBN} itself does. In fact, a system that can run
13939 @code{gdbserver} to connect to a remote @value{GDBN} could also run
13940 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
13941 because it is a much smaller program than @value{GDBN} itself. It is
13942 also easier to port than all of @value{GDBN}, so you may be able to get
13943 started more quickly on a new system by using @code{gdbserver}.
13944 Finally, if you develop code for real-time systems, you may find that
13945 the tradeoffs involved in real-time operation make it more convenient to
13946 do as much development work as possible on another system, for example
13947 by cross-compiling. You can use @code{gdbserver} to make a similar
13948 choice for debugging.
13950 @value{GDBN} and @code{gdbserver} communicate via either a serial line
13951 or a TCP connection, using the standard @value{GDBN} remote serial
13955 @emph{Warning:} @code{gdbserver} does not have any built-in security.
13956 Do not run @code{gdbserver} connected to any public network; a
13957 @value{GDBN} connection to @code{gdbserver} provides access to the
13958 target system with the same privileges as the user running
13962 @subsection Running @code{gdbserver}
13963 @cindex arguments, to @code{gdbserver}
13965 Run @code{gdbserver} on the target system. You need a copy of the
13966 program you want to debug, including any libraries it requires.
13967 @code{gdbserver} does not need your program's symbol table, so you can
13968 strip the program if necessary to save space. @value{GDBN} on the host
13969 system does all the symbol handling.
13971 To use the server, you must tell it how to communicate with @value{GDBN};
13972 the name of your program; and the arguments for your program. The usual
13976 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
13979 @var{comm} is either a device name (to use a serial line) or a TCP
13980 hostname and portnumber. For example, to debug Emacs with the argument
13981 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
13985 target> gdbserver /dev/com1 emacs foo.txt
13988 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
13991 To use a TCP connection instead of a serial line:
13994 target> gdbserver host:2345 emacs foo.txt
13997 The only difference from the previous example is the first argument,
13998 specifying that you are communicating with the host @value{GDBN} via
13999 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
14000 expect a TCP connection from machine @samp{host} to local TCP port 2345.
14001 (Currently, the @samp{host} part is ignored.) You can choose any number
14002 you want for the port number as long as it does not conflict with any
14003 TCP ports already in use on the target system (for example, @code{23} is
14004 reserved for @code{telnet}).@footnote{If you choose a port number that
14005 conflicts with another service, @code{gdbserver} prints an error message
14006 and exits.} You must use the same port number with the host @value{GDBN}
14007 @code{target remote} command.
14009 @subsubsection Attaching to a Running Program
14011 On some targets, @code{gdbserver} can also attach to running programs.
14012 This is accomplished via the @code{--attach} argument. The syntax is:
14015 target> gdbserver --attach @var{comm} @var{pid}
14018 @var{pid} is the process ID of a currently running process. It isn't necessary
14019 to point @code{gdbserver} at a binary for the running process.
14022 @cindex attach to a program by name
14023 You can debug processes by name instead of process ID if your target has the
14024 @code{pidof} utility:
14027 target> gdbserver --attach @var{comm} `pidof @var{program}`
14030 In case more than one copy of @var{program} is running, or @var{program}
14031 has multiple threads, most versions of @code{pidof} support the
14032 @code{-s} option to only return the first process ID.
14034 @subsubsection Multi-Process Mode for @code{gdbserver}
14035 @cindex gdbserver, multiple processes
14036 @cindex multiple processes with gdbserver
14038 When you connect to @code{gdbserver} using @code{target remote},
14039 @code{gdbserver} debugs the specified program only once. When the
14040 program exits, or you detach from it, @value{GDBN} closes the connection
14041 and @code{gdbserver} exits.
14043 If you connect using @kbd{target extended-remote}, @code{gdbserver}
14044 enters multi-process mode. When the debugged program exits, or you
14045 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
14046 though no program is running. The @code{run} and @code{attach}
14047 commands instruct @code{gdbserver} to run or attach to a new program.
14048 The @code{run} command uses @code{set remote exec-file} (@pxref{set
14049 remote exec-file}) to select the program to run. Command line
14050 arguments are supported, except for wildcard expansion and I/O
14051 redirection (@pxref{Arguments}).
14053 To start @code{gdbserver} without supplying an initial command to run
14054 or process ID to attach, use the @option{--multi} command line option.
14055 Then you can connect using @kbd{target extended-remote} and start
14056 the program you want to debug.
14058 @code{gdbserver} does not automatically exit in multi-process mode.
14059 You can terminate it by using @code{monitor exit}
14060 (@pxref{Monitor Commands for gdbserver}).
14062 @subsubsection Other Command-Line Arguments for @code{gdbserver}
14064 The @option{--debug} option tells @code{gdbserver} to display extra
14065 status information about the debugging process. The
14066 @option{--remote-debug} option tells @code{gdbserver} to display
14067 remote protocol debug output. These options are intended for
14068 @code{gdbserver} development and for bug reports to the developers.
14070 The @option{--wrapper} option specifies a wrapper to launch programs
14071 for debugging. The option should be followed by the name of the
14072 wrapper, then any command-line arguments to pass to the wrapper, then
14073 @kbd{--} indicating the end of the wrapper arguments.
14075 @code{gdbserver} runs the specified wrapper program with a combined
14076 command line including the wrapper arguments, then the name of the
14077 program to debug, then any arguments to the program. The wrapper
14078 runs until it executes your program, and then @value{GDBN} gains control.
14080 You can use any program that eventually calls @code{execve} with
14081 its arguments as a wrapper. Several standard Unix utilities do
14082 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
14083 with @code{exec "$@@"} will also work.
14085 For example, you can use @code{env} to pass an environment variable to
14086 the debugged program, without setting the variable in @code{gdbserver}'s
14090 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
14093 @subsection Connecting to @code{gdbserver}
14095 Run @value{GDBN} on the host system.
14097 First make sure you have the necessary symbol files. Load symbols for
14098 your application using the @code{file} command before you connect. Use
14099 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
14100 was compiled with the correct sysroot using @code{--with-sysroot}).
14102 The symbol file and target libraries must exactly match the executable
14103 and libraries on the target, with one exception: the files on the host
14104 system should not be stripped, even if the files on the target system
14105 are. Mismatched or missing files will lead to confusing results
14106 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
14107 files may also prevent @code{gdbserver} from debugging multi-threaded
14110 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
14111 For TCP connections, you must start up @code{gdbserver} prior to using
14112 the @code{target remote} command. Otherwise you may get an error whose
14113 text depends on the host system, but which usually looks something like
14114 @samp{Connection refused}. Don't use the @code{load}
14115 command in @value{GDBN} when using @code{gdbserver}, since the program is
14116 already on the target.
14118 @subsection Monitor Commands for @code{gdbserver}
14119 @cindex monitor commands, for @code{gdbserver}
14120 @anchor{Monitor Commands for gdbserver}
14122 During a @value{GDBN} session using @code{gdbserver}, you can use the
14123 @code{monitor} command to send special requests to @code{gdbserver}.
14124 Here are the available commands.
14128 List the available monitor commands.
14130 @item monitor set debug 0
14131 @itemx monitor set debug 1
14132 Disable or enable general debugging messages.
14134 @item monitor set remote-debug 0
14135 @itemx monitor set remote-debug 1
14136 Disable or enable specific debugging messages associated with the remote
14137 protocol (@pxref{Remote Protocol}).
14140 Tell gdbserver to exit immediately. This command should be followed by
14141 @code{disconnect} to close the debugging session. @code{gdbserver} will
14142 detach from any attached processes and kill any processes it created.
14143 Use @code{monitor exit} to terminate @code{gdbserver} at the end
14144 of a multi-process mode debug session.
14148 @node Remote Configuration
14149 @section Remote Configuration
14152 @kindex show remote
14153 This section documents the configuration options available when
14154 debugging remote programs. For the options related to the File I/O
14155 extensions of the remote protocol, see @ref{system,
14156 system-call-allowed}.
14159 @item set remoteaddresssize @var{bits}
14160 @cindex address size for remote targets
14161 @cindex bits in remote address
14162 Set the maximum size of address in a memory packet to the specified
14163 number of bits. @value{GDBN} will mask off the address bits above
14164 that number, when it passes addresses to the remote target. The
14165 default value is the number of bits in the target's address.
14167 @item show remoteaddresssize
14168 Show the current value of remote address size in bits.
14170 @item set remotebaud @var{n}
14171 @cindex baud rate for remote targets
14172 Set the baud rate for the remote serial I/O to @var{n} baud. The
14173 value is used to set the speed of the serial port used for debugging
14176 @item show remotebaud
14177 Show the current speed of the remote connection.
14179 @item set remotebreak
14180 @cindex interrupt remote programs
14181 @cindex BREAK signal instead of Ctrl-C
14182 @anchor{set remotebreak}
14183 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
14184 when you type @kbd{Ctrl-c} to interrupt the program running
14185 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
14186 character instead. The default is off, since most remote systems
14187 expect to see @samp{Ctrl-C} as the interrupt signal.
14189 @item show remotebreak
14190 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
14191 interrupt the remote program.
14193 @item set remoteflow on
14194 @itemx set remoteflow off
14195 @kindex set remoteflow
14196 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
14197 on the serial port used to communicate to the remote target.
14199 @item show remoteflow
14200 @kindex show remoteflow
14201 Show the current setting of hardware flow control.
14203 @item set remotelogbase @var{base}
14204 Set the base (a.k.a.@: radix) of logging serial protocol
14205 communications to @var{base}. Supported values of @var{base} are:
14206 @code{ascii}, @code{octal}, and @code{hex}. The default is
14209 @item show remotelogbase
14210 Show the current setting of the radix for logging remote serial
14213 @item set remotelogfile @var{file}
14214 @cindex record serial communications on file
14215 Record remote serial communications on the named @var{file}. The
14216 default is not to record at all.
14218 @item show remotelogfile.
14219 Show the current setting of the file name on which to record the
14220 serial communications.
14222 @item set remotetimeout @var{num}
14223 @cindex timeout for serial communications
14224 @cindex remote timeout
14225 Set the timeout limit to wait for the remote target to respond to
14226 @var{num} seconds. The default is 2 seconds.
14228 @item show remotetimeout
14229 Show the current number of seconds to wait for the remote target
14232 @cindex limit hardware breakpoints and watchpoints
14233 @cindex remote target, limit break- and watchpoints
14234 @anchor{set remote hardware-watchpoint-limit}
14235 @anchor{set remote hardware-breakpoint-limit}
14236 @item set remote hardware-watchpoint-limit @var{limit}
14237 @itemx set remote hardware-breakpoint-limit @var{limit}
14238 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
14239 watchpoints. A limit of -1, the default, is treated as unlimited.
14241 @item set remote exec-file @var{filename}
14242 @itemx show remote exec-file
14243 @anchor{set remote exec-file}
14244 @cindex executable file, for remote target
14245 Select the file used for @code{run} with @code{target
14246 extended-remote}. This should be set to a filename valid on the
14247 target system. If it is not set, the target will use a default
14248 filename (e.g.@: the last program run).
14252 @item set tcp auto-retry on
14253 @cindex auto-retry, for remote TCP target
14254 Enable auto-retry for remote TCP connections. This is useful if the remote
14255 debugging agent is launched in parallel with @value{GDBN}; there is a race
14256 condition because the agent may not become ready to accept the connection
14257 before @value{GDBN} attempts to connect. When auto-retry is
14258 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
14259 to establish the connection using the timeout specified by
14260 @code{set tcp connect-timeout}.
14262 @item set tcp auto-retry off
14263 Do not auto-retry failed TCP connections.
14265 @item show tcp auto-retry
14266 Show the current auto-retry setting.
14268 @item set tcp connect-timeout @var{seconds}
14269 @cindex connection timeout, for remote TCP target
14270 @cindex timeout, for remote target connection
14271 Set the timeout for establishing a TCP connection to the remote target to
14272 @var{seconds}. The timeout affects both polling to retry failed connections
14273 (enabled by @code{set tcp auto-retry on}) and waiting for connections
14274 that are merely slow to complete, and represents an approximate cumulative
14277 @item show tcp connect-timeout
14278 Show the current connection timeout setting.
14281 @cindex remote packets, enabling and disabling
14282 The @value{GDBN} remote protocol autodetects the packets supported by
14283 your debugging stub. If you need to override the autodetection, you
14284 can use these commands to enable or disable individual packets. Each
14285 packet can be set to @samp{on} (the remote target supports this
14286 packet), @samp{off} (the remote target does not support this packet),
14287 or @samp{auto} (detect remote target support for this packet). They
14288 all default to @samp{auto}. For more information about each packet,
14289 see @ref{Remote Protocol}.
14291 During normal use, you should not have to use any of these commands.
14292 If you do, that may be a bug in your remote debugging stub, or a bug
14293 in @value{GDBN}. You may want to report the problem to the
14294 @value{GDBN} developers.
14296 For each packet @var{name}, the command to enable or disable the
14297 packet is @code{set remote @var{name}-packet}. The available settings
14300 @multitable @columnfractions 0.28 0.32 0.25
14303 @tab Related Features
14305 @item @code{fetch-register}
14307 @tab @code{info registers}
14309 @item @code{set-register}
14313 @item @code{binary-download}
14315 @tab @code{load}, @code{set}
14317 @item @code{read-aux-vector}
14318 @tab @code{qXfer:auxv:read}
14319 @tab @code{info auxv}
14321 @item @code{symbol-lookup}
14322 @tab @code{qSymbol}
14323 @tab Detecting multiple threads
14325 @item @code{attach}
14326 @tab @code{vAttach}
14329 @item @code{verbose-resume}
14331 @tab Stepping or resuming multiple threads
14337 @item @code{software-breakpoint}
14341 @item @code{hardware-breakpoint}
14345 @item @code{write-watchpoint}
14349 @item @code{read-watchpoint}
14353 @item @code{access-watchpoint}
14357 @item @code{target-features}
14358 @tab @code{qXfer:features:read}
14359 @tab @code{set architecture}
14361 @item @code{library-info}
14362 @tab @code{qXfer:libraries:read}
14363 @tab @code{info sharedlibrary}
14365 @item @code{memory-map}
14366 @tab @code{qXfer:memory-map:read}
14367 @tab @code{info mem}
14369 @item @code{read-spu-object}
14370 @tab @code{qXfer:spu:read}
14371 @tab @code{info spu}
14373 @item @code{write-spu-object}
14374 @tab @code{qXfer:spu:write}
14375 @tab @code{info spu}
14377 @item @code{read-siginfo-object}
14378 @tab @code{qXfer:siginfo:read}
14379 @tab @code{print $_siginfo}
14381 @item @code{write-siginfo-object}
14382 @tab @code{qXfer:siginfo:write}
14383 @tab @code{set $_siginfo}
14385 @item @code{get-thread-local-@*storage-address}
14386 @tab @code{qGetTLSAddr}
14387 @tab Displaying @code{__thread} variables
14389 @item @code{search-memory}
14390 @tab @code{qSearch:memory}
14393 @item @code{supported-packets}
14394 @tab @code{qSupported}
14395 @tab Remote communications parameters
14397 @item @code{pass-signals}
14398 @tab @code{QPassSignals}
14399 @tab @code{handle @var{signal}}
14401 @item @code{hostio-close-packet}
14402 @tab @code{vFile:close}
14403 @tab @code{remote get}, @code{remote put}
14405 @item @code{hostio-open-packet}
14406 @tab @code{vFile:open}
14407 @tab @code{remote get}, @code{remote put}
14409 @item @code{hostio-pread-packet}
14410 @tab @code{vFile:pread}
14411 @tab @code{remote get}, @code{remote put}
14413 @item @code{hostio-pwrite-packet}
14414 @tab @code{vFile:pwrite}
14415 @tab @code{remote get}, @code{remote put}
14417 @item @code{hostio-unlink-packet}
14418 @tab @code{vFile:unlink}
14419 @tab @code{remote delete}
14421 @item @code{noack-packet}
14422 @tab @code{QStartNoAckMode}
14423 @tab Packet acknowledgment
14425 @item @code{osdata}
14426 @tab @code{qXfer:osdata:read}
14427 @tab @code{info os}
14431 @section Implementing a Remote Stub
14433 @cindex debugging stub, example
14434 @cindex remote stub, example
14435 @cindex stub example, remote debugging
14436 The stub files provided with @value{GDBN} implement the target side of the
14437 communication protocol, and the @value{GDBN} side is implemented in the
14438 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
14439 these subroutines to communicate, and ignore the details. (If you're
14440 implementing your own stub file, you can still ignore the details: start
14441 with one of the existing stub files. @file{sparc-stub.c} is the best
14442 organized, and therefore the easiest to read.)
14444 @cindex remote serial debugging, overview
14445 To debug a program running on another machine (the debugging
14446 @dfn{target} machine), you must first arrange for all the usual
14447 prerequisites for the program to run by itself. For example, for a C
14452 A startup routine to set up the C runtime environment; these usually
14453 have a name like @file{crt0}. The startup routine may be supplied by
14454 your hardware supplier, or you may have to write your own.
14457 A C subroutine library to support your program's
14458 subroutine calls, notably managing input and output.
14461 A way of getting your program to the other machine---for example, a
14462 download program. These are often supplied by the hardware
14463 manufacturer, but you may have to write your own from hardware
14467 The next step is to arrange for your program to use a serial port to
14468 communicate with the machine where @value{GDBN} is running (the @dfn{host}
14469 machine). In general terms, the scheme looks like this:
14473 @value{GDBN} already understands how to use this protocol; when everything
14474 else is set up, you can simply use the @samp{target remote} command
14475 (@pxref{Targets,,Specifying a Debugging Target}).
14477 @item On the target,
14478 you must link with your program a few special-purpose subroutines that
14479 implement the @value{GDBN} remote serial protocol. The file containing these
14480 subroutines is called a @dfn{debugging stub}.
14482 On certain remote targets, you can use an auxiliary program
14483 @code{gdbserver} instead of linking a stub into your program.
14484 @xref{Server,,Using the @code{gdbserver} Program}, for details.
14487 The debugging stub is specific to the architecture of the remote
14488 machine; for example, use @file{sparc-stub.c} to debug programs on
14491 @cindex remote serial stub list
14492 These working remote stubs are distributed with @value{GDBN}:
14497 @cindex @file{i386-stub.c}
14500 For Intel 386 and compatible architectures.
14503 @cindex @file{m68k-stub.c}
14504 @cindex Motorola 680x0
14506 For Motorola 680x0 architectures.
14509 @cindex @file{sh-stub.c}
14512 For Renesas SH architectures.
14515 @cindex @file{sparc-stub.c}
14517 For @sc{sparc} architectures.
14519 @item sparcl-stub.c
14520 @cindex @file{sparcl-stub.c}
14523 For Fujitsu @sc{sparclite} architectures.
14527 The @file{README} file in the @value{GDBN} distribution may list other
14528 recently added stubs.
14531 * Stub Contents:: What the stub can do for you
14532 * Bootstrapping:: What you must do for the stub
14533 * Debug Session:: Putting it all together
14536 @node Stub Contents
14537 @subsection What the Stub Can Do for You
14539 @cindex remote serial stub
14540 The debugging stub for your architecture supplies these three
14544 @item set_debug_traps
14545 @findex set_debug_traps
14546 @cindex remote serial stub, initialization
14547 This routine arranges for @code{handle_exception} to run when your
14548 program stops. You must call this subroutine explicitly near the
14549 beginning of your program.
14551 @item handle_exception
14552 @findex handle_exception
14553 @cindex remote serial stub, main routine
14554 This is the central workhorse, but your program never calls it
14555 explicitly---the setup code arranges for @code{handle_exception} to
14556 run when a trap is triggered.
14558 @code{handle_exception} takes control when your program stops during
14559 execution (for example, on a breakpoint), and mediates communications
14560 with @value{GDBN} on the host machine. This is where the communications
14561 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
14562 representative on the target machine. It begins by sending summary
14563 information on the state of your program, then continues to execute,
14564 retrieving and transmitting any information @value{GDBN} needs, until you
14565 execute a @value{GDBN} command that makes your program resume; at that point,
14566 @code{handle_exception} returns control to your own code on the target
14570 @cindex @code{breakpoint} subroutine, remote
14571 Use this auxiliary subroutine to make your program contain a
14572 breakpoint. Depending on the particular situation, this may be the only
14573 way for @value{GDBN} to get control. For instance, if your target
14574 machine has some sort of interrupt button, you won't need to call this;
14575 pressing the interrupt button transfers control to
14576 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
14577 simply receiving characters on the serial port may also trigger a trap;
14578 again, in that situation, you don't need to call @code{breakpoint} from
14579 your own program---simply running @samp{target remote} from the host
14580 @value{GDBN} session gets control.
14582 Call @code{breakpoint} if none of these is true, or if you simply want
14583 to make certain your program stops at a predetermined point for the
14584 start of your debugging session.
14587 @node Bootstrapping
14588 @subsection What You Must Do for the Stub
14590 @cindex remote stub, support routines
14591 The debugging stubs that come with @value{GDBN} are set up for a particular
14592 chip architecture, but they have no information about the rest of your
14593 debugging target machine.
14595 First of all you need to tell the stub how to communicate with the
14599 @item int getDebugChar()
14600 @findex getDebugChar
14601 Write this subroutine to read a single character from the serial port.
14602 It may be identical to @code{getchar} for your target system; a
14603 different name is used to allow you to distinguish the two if you wish.
14605 @item void putDebugChar(int)
14606 @findex putDebugChar
14607 Write this subroutine to write a single character to the serial port.
14608 It may be identical to @code{putchar} for your target system; a
14609 different name is used to allow you to distinguish the two if you wish.
14612 @cindex control C, and remote debugging
14613 @cindex interrupting remote targets
14614 If you want @value{GDBN} to be able to stop your program while it is
14615 running, you need to use an interrupt-driven serial driver, and arrange
14616 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
14617 character). That is the character which @value{GDBN} uses to tell the
14618 remote system to stop.
14620 Getting the debugging target to return the proper status to @value{GDBN}
14621 probably requires changes to the standard stub; one quick and dirty way
14622 is to just execute a breakpoint instruction (the ``dirty'' part is that
14623 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
14625 Other routines you need to supply are:
14628 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
14629 @findex exceptionHandler
14630 Write this function to install @var{exception_address} in the exception
14631 handling tables. You need to do this because the stub does not have any
14632 way of knowing what the exception handling tables on your target system
14633 are like (for example, the processor's table might be in @sc{rom},
14634 containing entries which point to a table in @sc{ram}).
14635 @var{exception_number} is the exception number which should be changed;
14636 its meaning is architecture-dependent (for example, different numbers
14637 might represent divide by zero, misaligned access, etc). When this
14638 exception occurs, control should be transferred directly to
14639 @var{exception_address}, and the processor state (stack, registers,
14640 and so on) should be just as it is when a processor exception occurs. So if
14641 you want to use a jump instruction to reach @var{exception_address}, it
14642 should be a simple jump, not a jump to subroutine.
14644 For the 386, @var{exception_address} should be installed as an interrupt
14645 gate so that interrupts are masked while the handler runs. The gate
14646 should be at privilege level 0 (the most privileged level). The
14647 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
14648 help from @code{exceptionHandler}.
14650 @item void flush_i_cache()
14651 @findex flush_i_cache
14652 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
14653 instruction cache, if any, on your target machine. If there is no
14654 instruction cache, this subroutine may be a no-op.
14656 On target machines that have instruction caches, @value{GDBN} requires this
14657 function to make certain that the state of your program is stable.
14661 You must also make sure this library routine is available:
14664 @item void *memset(void *, int, int)
14666 This is the standard library function @code{memset} that sets an area of
14667 memory to a known value. If you have one of the free versions of
14668 @code{libc.a}, @code{memset} can be found there; otherwise, you must
14669 either obtain it from your hardware manufacturer, or write your own.
14672 If you do not use the GNU C compiler, you may need other standard
14673 library subroutines as well; this varies from one stub to another,
14674 but in general the stubs are likely to use any of the common library
14675 subroutines which @code{@value{NGCC}} generates as inline code.
14678 @node Debug Session
14679 @subsection Putting it All Together
14681 @cindex remote serial debugging summary
14682 In summary, when your program is ready to debug, you must follow these
14687 Make sure you have defined the supporting low-level routines
14688 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
14690 @code{getDebugChar}, @code{putDebugChar},
14691 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
14695 Insert these lines near the top of your program:
14703 For the 680x0 stub only, you need to provide a variable called
14704 @code{exceptionHook}. Normally you just use:
14707 void (*exceptionHook)() = 0;
14711 but if before calling @code{set_debug_traps}, you set it to point to a
14712 function in your program, that function is called when
14713 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
14714 error). The function indicated by @code{exceptionHook} is called with
14715 one parameter: an @code{int} which is the exception number.
14718 Compile and link together: your program, the @value{GDBN} debugging stub for
14719 your target architecture, and the supporting subroutines.
14722 Make sure you have a serial connection between your target machine and
14723 the @value{GDBN} host, and identify the serial port on the host.
14726 @c The "remote" target now provides a `load' command, so we should
14727 @c document that. FIXME.
14728 Download your program to your target machine (or get it there by
14729 whatever means the manufacturer provides), and start it.
14732 Start @value{GDBN} on the host, and connect to the target
14733 (@pxref{Connecting,,Connecting to a Remote Target}).
14737 @node Configurations
14738 @chapter Configuration-Specific Information
14740 While nearly all @value{GDBN} commands are available for all native and
14741 cross versions of the debugger, there are some exceptions. This chapter
14742 describes things that are only available in certain configurations.
14744 There are three major categories of configurations: native
14745 configurations, where the host and target are the same, embedded
14746 operating system configurations, which are usually the same for several
14747 different processor architectures, and bare embedded processors, which
14748 are quite different from each other.
14753 * Embedded Processors::
14760 This section describes details specific to particular native
14765 * BSD libkvm Interface:: Debugging BSD kernel memory images
14766 * SVR4 Process Information:: SVR4 process information
14767 * DJGPP Native:: Features specific to the DJGPP port
14768 * Cygwin Native:: Features specific to the Cygwin port
14769 * Hurd Native:: Features specific to @sc{gnu} Hurd
14770 * Neutrino:: Features specific to QNX Neutrino
14771 * Darwin:: Features specific to Darwin
14777 On HP-UX systems, if you refer to a function or variable name that
14778 begins with a dollar sign, @value{GDBN} searches for a user or system
14779 name first, before it searches for a convenience variable.
14782 @node BSD libkvm Interface
14783 @subsection BSD libkvm Interface
14786 @cindex kernel memory image
14787 @cindex kernel crash dump
14789 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14790 interface that provides a uniform interface for accessing kernel virtual
14791 memory images, including live systems and crash dumps. @value{GDBN}
14792 uses this interface to allow you to debug live kernels and kernel crash
14793 dumps on many native BSD configurations. This is implemented as a
14794 special @code{kvm} debugging target. For debugging a live system, load
14795 the currently running kernel into @value{GDBN} and connect to the
14799 (@value{GDBP}) @b{target kvm}
14802 For debugging crash dumps, provide the file name of the crash dump as an
14806 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14809 Once connected to the @code{kvm} target, the following commands are
14815 Set current context from the @dfn{Process Control Block} (PCB) address.
14818 Set current context from proc address. This command isn't available on
14819 modern FreeBSD systems.
14822 @node SVR4 Process Information
14823 @subsection SVR4 Process Information
14825 @cindex examine process image
14826 @cindex process info via @file{/proc}
14828 Many versions of SVR4 and compatible systems provide a facility called
14829 @samp{/proc} that can be used to examine the image of a running
14830 process using file-system subroutines. If @value{GDBN} is configured
14831 for an operating system with this facility, the command @code{info
14832 proc} is available to report information about the process running
14833 your program, or about any process running on your system. @code{info
14834 proc} works only on SVR4 systems that include the @code{procfs} code.
14835 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14836 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14842 @itemx info proc @var{process-id}
14843 Summarize available information about any running process. If a
14844 process ID is specified by @var{process-id}, display information about
14845 that process; otherwise display information about the program being
14846 debugged. The summary includes the debugged process ID, the command
14847 line used to invoke it, its current working directory, and its
14848 executable file's absolute file name.
14850 On some systems, @var{process-id} can be of the form
14851 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14852 within a process. If the optional @var{pid} part is missing, it means
14853 a thread from the process being debugged (the leading @samp{/} still
14854 needs to be present, or else @value{GDBN} will interpret the number as
14855 a process ID rather than a thread ID).
14857 @item info proc mappings
14858 @cindex memory address space mappings
14859 Report the memory address space ranges accessible in the program, with
14860 information on whether the process has read, write, or execute access
14861 rights to each range. On @sc{gnu}/Linux systems, each memory range
14862 includes the object file which is mapped to that range, instead of the
14863 memory access rights to that range.
14865 @item info proc stat
14866 @itemx info proc status
14867 @cindex process detailed status information
14868 These subcommands are specific to @sc{gnu}/Linux systems. They show
14869 the process-related information, including the user ID and group ID;
14870 how many threads are there in the process; its virtual memory usage;
14871 the signals that are pending, blocked, and ignored; its TTY; its
14872 consumption of system and user time; its stack size; its @samp{nice}
14873 value; etc. For more information, see the @samp{proc} man page
14874 (type @kbd{man 5 proc} from your shell prompt).
14876 @item info proc all
14877 Show all the information about the process described under all of the
14878 above @code{info proc} subcommands.
14881 @comment These sub-options of 'info proc' were not included when
14882 @comment procfs.c was re-written. Keep their descriptions around
14883 @comment against the day when someone finds the time to put them back in.
14884 @kindex info proc times
14885 @item info proc times
14886 Starting time, user CPU time, and system CPU time for your program and
14889 @kindex info proc id
14891 Report on the process IDs related to your program: its own process ID,
14892 the ID of its parent, the process group ID, and the session ID.
14895 @item set procfs-trace
14896 @kindex set procfs-trace
14897 @cindex @code{procfs} API calls
14898 This command enables and disables tracing of @code{procfs} API calls.
14900 @item show procfs-trace
14901 @kindex show procfs-trace
14902 Show the current state of @code{procfs} API call tracing.
14904 @item set procfs-file @var{file}
14905 @kindex set procfs-file
14906 Tell @value{GDBN} to write @code{procfs} API trace to the named
14907 @var{file}. @value{GDBN} appends the trace info to the previous
14908 contents of the file. The default is to display the trace on the
14911 @item show procfs-file
14912 @kindex show procfs-file
14913 Show the file to which @code{procfs} API trace is written.
14915 @item proc-trace-entry
14916 @itemx proc-trace-exit
14917 @itemx proc-untrace-entry
14918 @itemx proc-untrace-exit
14919 @kindex proc-trace-entry
14920 @kindex proc-trace-exit
14921 @kindex proc-untrace-entry
14922 @kindex proc-untrace-exit
14923 These commands enable and disable tracing of entries into and exits
14924 from the @code{syscall} interface.
14927 @kindex info pidlist
14928 @cindex process list, QNX Neutrino
14929 For QNX Neutrino only, this command displays the list of all the
14930 processes and all the threads within each process.
14933 @kindex info meminfo
14934 @cindex mapinfo list, QNX Neutrino
14935 For QNX Neutrino only, this command displays the list of all mapinfos.
14939 @subsection Features for Debugging @sc{djgpp} Programs
14940 @cindex @sc{djgpp} debugging
14941 @cindex native @sc{djgpp} debugging
14942 @cindex MS-DOS-specific commands
14945 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
14946 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
14947 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
14948 top of real-mode DOS systems and their emulations.
14950 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
14951 defines a few commands specific to the @sc{djgpp} port. This
14952 subsection describes those commands.
14957 This is a prefix of @sc{djgpp}-specific commands which print
14958 information about the target system and important OS structures.
14961 @cindex MS-DOS system info
14962 @cindex free memory information (MS-DOS)
14963 @item info dos sysinfo
14964 This command displays assorted information about the underlying
14965 platform: the CPU type and features, the OS version and flavor, the
14966 DPMI version, and the available conventional and DPMI memory.
14971 @cindex segment descriptor tables
14972 @cindex descriptor tables display
14974 @itemx info dos ldt
14975 @itemx info dos idt
14976 These 3 commands display entries from, respectively, Global, Local,
14977 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
14978 tables are data structures which store a descriptor for each segment
14979 that is currently in use. The segment's selector is an index into a
14980 descriptor table; the table entry for that index holds the
14981 descriptor's base address and limit, and its attributes and access
14984 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
14985 segment (used for both data and the stack), and a DOS segment (which
14986 allows access to DOS/BIOS data structures and absolute addresses in
14987 conventional memory). However, the DPMI host will usually define
14988 additional segments in order to support the DPMI environment.
14990 @cindex garbled pointers
14991 These commands allow to display entries from the descriptor tables.
14992 Without an argument, all entries from the specified table are
14993 displayed. An argument, which should be an integer expression, means
14994 display a single entry whose index is given by the argument. For
14995 example, here's a convenient way to display information about the
14996 debugged program's data segment:
14999 @exdent @code{(@value{GDBP}) info dos ldt $ds}
15000 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
15004 This comes in handy when you want to see whether a pointer is outside
15005 the data segment's limit (i.e.@: @dfn{garbled}).
15007 @cindex page tables display (MS-DOS)
15009 @itemx info dos pte
15010 These two commands display entries from, respectively, the Page
15011 Directory and the Page Tables. Page Directories and Page Tables are
15012 data structures which control how virtual memory addresses are mapped
15013 into physical addresses. A Page Table includes an entry for every
15014 page of memory that is mapped into the program's address space; there
15015 may be several Page Tables, each one holding up to 4096 entries. A
15016 Page Directory has up to 4096 entries, one each for every Page Table
15017 that is currently in use.
15019 Without an argument, @kbd{info dos pde} displays the entire Page
15020 Directory, and @kbd{info dos pte} displays all the entries in all of
15021 the Page Tables. An argument, an integer expression, given to the
15022 @kbd{info dos pde} command means display only that entry from the Page
15023 Directory table. An argument given to the @kbd{info dos pte} command
15024 means display entries from a single Page Table, the one pointed to by
15025 the specified entry in the Page Directory.
15027 @cindex direct memory access (DMA) on MS-DOS
15028 These commands are useful when your program uses @dfn{DMA} (Direct
15029 Memory Access), which needs physical addresses to program the DMA
15032 These commands are supported only with some DPMI servers.
15034 @cindex physical address from linear address
15035 @item info dos address-pte @var{addr}
15036 This command displays the Page Table entry for a specified linear
15037 address. The argument @var{addr} is a linear address which should
15038 already have the appropriate segment's base address added to it,
15039 because this command accepts addresses which may belong to @emph{any}
15040 segment. For example, here's how to display the Page Table entry for
15041 the page where a variable @code{i} is stored:
15044 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
15045 @exdent @code{Page Table entry for address 0x11a00d30:}
15046 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
15050 This says that @code{i} is stored at offset @code{0xd30} from the page
15051 whose physical base address is @code{0x02698000}, and shows all the
15052 attributes of that page.
15054 Note that you must cast the addresses of variables to a @code{char *},
15055 since otherwise the value of @code{__djgpp_base_address}, the base
15056 address of all variables and functions in a @sc{djgpp} program, will
15057 be added using the rules of C pointer arithmetics: if @code{i} is
15058 declared an @code{int}, @value{GDBN} will add 4 times the value of
15059 @code{__djgpp_base_address} to the address of @code{i}.
15061 Here's another example, it displays the Page Table entry for the
15065 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
15066 @exdent @code{Page Table entry for address 0x29110:}
15067 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
15071 (The @code{+ 3} offset is because the transfer buffer's address is the
15072 3rd member of the @code{_go32_info_block} structure.) The output
15073 clearly shows that this DPMI server maps the addresses in conventional
15074 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
15075 linear (@code{0x29110}) addresses are identical.
15077 This command is supported only with some DPMI servers.
15080 @cindex DOS serial data link, remote debugging
15081 In addition to native debugging, the DJGPP port supports remote
15082 debugging via a serial data link. The following commands are specific
15083 to remote serial debugging in the DJGPP port of @value{GDBN}.
15086 @kindex set com1base
15087 @kindex set com1irq
15088 @kindex set com2base
15089 @kindex set com2irq
15090 @kindex set com3base
15091 @kindex set com3irq
15092 @kindex set com4base
15093 @kindex set com4irq
15094 @item set com1base @var{addr}
15095 This command sets the base I/O port address of the @file{COM1} serial
15098 @item set com1irq @var{irq}
15099 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
15100 for the @file{COM1} serial port.
15102 There are similar commands @samp{set com2base}, @samp{set com3irq},
15103 etc.@: for setting the port address and the @code{IRQ} lines for the
15106 @kindex show com1base
15107 @kindex show com1irq
15108 @kindex show com2base
15109 @kindex show com2irq
15110 @kindex show com3base
15111 @kindex show com3irq
15112 @kindex show com4base
15113 @kindex show com4irq
15114 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
15115 display the current settings of the base address and the @code{IRQ}
15116 lines used by the COM ports.
15119 @kindex info serial
15120 @cindex DOS serial port status
15121 This command prints the status of the 4 DOS serial ports. For each
15122 port, it prints whether it's active or not, its I/O base address and
15123 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
15124 counts of various errors encountered so far.
15128 @node Cygwin Native
15129 @subsection Features for Debugging MS Windows PE Executables
15130 @cindex MS Windows debugging
15131 @cindex native Cygwin debugging
15132 @cindex Cygwin-specific commands
15134 @value{GDBN} supports native debugging of MS Windows programs, including
15135 DLLs with and without symbolic debugging information. There are various
15136 additional Cygwin-specific commands, described in this section.
15137 Working with DLLs that have no debugging symbols is described in
15138 @ref{Non-debug DLL Symbols}.
15143 This is a prefix of MS Windows-specific commands which print
15144 information about the target system and important OS structures.
15146 @item info w32 selector
15147 This command displays information returned by
15148 the Win32 API @code{GetThreadSelectorEntry} function.
15149 It takes an optional argument that is evaluated to
15150 a long value to give the information about this given selector.
15151 Without argument, this command displays information
15152 about the six segment registers.
15156 This is a Cygwin-specific alias of @code{info shared}.
15158 @kindex dll-symbols
15160 This command loads symbols from a dll similarly to
15161 add-sym command but without the need to specify a base address.
15163 @kindex set cygwin-exceptions
15164 @cindex debugging the Cygwin DLL
15165 @cindex Cygwin DLL, debugging
15166 @item set cygwin-exceptions @var{mode}
15167 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
15168 happen inside the Cygwin DLL. If @var{mode} is @code{off},
15169 @value{GDBN} will delay recognition of exceptions, and may ignore some
15170 exceptions which seem to be caused by internal Cygwin DLL
15171 ``bookkeeping''. This option is meant primarily for debugging the
15172 Cygwin DLL itself; the default value is @code{off} to avoid annoying
15173 @value{GDBN} users with false @code{SIGSEGV} signals.
15175 @kindex show cygwin-exceptions
15176 @item show cygwin-exceptions
15177 Displays whether @value{GDBN} will break on exceptions that happen
15178 inside the Cygwin DLL itself.
15180 @kindex set new-console
15181 @item set new-console @var{mode}
15182 If @var{mode} is @code{on} the debuggee will
15183 be started in a new console on next start.
15184 If @var{mode} is @code{off}i, the debuggee will
15185 be started in the same console as the debugger.
15187 @kindex show new-console
15188 @item show new-console
15189 Displays whether a new console is used
15190 when the debuggee is started.
15192 @kindex set new-group
15193 @item set new-group @var{mode}
15194 This boolean value controls whether the debuggee should
15195 start a new group or stay in the same group as the debugger.
15196 This affects the way the Windows OS handles
15199 @kindex show new-group
15200 @item show new-group
15201 Displays current value of new-group boolean.
15203 @kindex set debugevents
15204 @item set debugevents
15205 This boolean value adds debug output concerning kernel events related
15206 to the debuggee seen by the debugger. This includes events that
15207 signal thread and process creation and exit, DLL loading and
15208 unloading, console interrupts, and debugging messages produced by the
15209 Windows @code{OutputDebugString} API call.
15211 @kindex set debugexec
15212 @item set debugexec
15213 This boolean value adds debug output concerning execute events
15214 (such as resume thread) seen by the debugger.
15216 @kindex set debugexceptions
15217 @item set debugexceptions
15218 This boolean value adds debug output concerning exceptions in the
15219 debuggee seen by the debugger.
15221 @kindex set debugmemory
15222 @item set debugmemory
15223 This boolean value adds debug output concerning debuggee memory reads
15224 and writes by the debugger.
15228 This boolean values specifies whether the debuggee is called
15229 via a shell or directly (default value is on).
15233 Displays if the debuggee will be started with a shell.
15238 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
15241 @node Non-debug DLL Symbols
15242 @subsubsection Support for DLLs without Debugging Symbols
15243 @cindex DLLs with no debugging symbols
15244 @cindex Minimal symbols and DLLs
15246 Very often on windows, some of the DLLs that your program relies on do
15247 not include symbolic debugging information (for example,
15248 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
15249 symbols in a DLL, it relies on the minimal amount of symbolic
15250 information contained in the DLL's export table. This section
15251 describes working with such symbols, known internally to @value{GDBN} as
15252 ``minimal symbols''.
15254 Note that before the debugged program has started execution, no DLLs
15255 will have been loaded. The easiest way around this problem is simply to
15256 start the program --- either by setting a breakpoint or letting the
15257 program run once to completion. It is also possible to force
15258 @value{GDBN} to load a particular DLL before starting the executable ---
15259 see the shared library information in @ref{Files}, or the
15260 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
15261 explicitly loading symbols from a DLL with no debugging information will
15262 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
15263 which may adversely affect symbol lookup performance.
15265 @subsubsection DLL Name Prefixes
15267 In keeping with the naming conventions used by the Microsoft debugging
15268 tools, DLL export symbols are made available with a prefix based on the
15269 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
15270 also entered into the symbol table, so @code{CreateFileA} is often
15271 sufficient. In some cases there will be name clashes within a program
15272 (particularly if the executable itself includes full debugging symbols)
15273 necessitating the use of the fully qualified name when referring to the
15274 contents of the DLL. Use single-quotes around the name to avoid the
15275 exclamation mark (``!'') being interpreted as a language operator.
15277 Note that the internal name of the DLL may be all upper-case, even
15278 though the file name of the DLL is lower-case, or vice-versa. Since
15279 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
15280 some confusion. If in doubt, try the @code{info functions} and
15281 @code{info variables} commands or even @code{maint print msymbols}
15282 (@pxref{Symbols}). Here's an example:
15285 (@value{GDBP}) info function CreateFileA
15286 All functions matching regular expression "CreateFileA":
15288 Non-debugging symbols:
15289 0x77e885f4 CreateFileA
15290 0x77e885f4 KERNEL32!CreateFileA
15294 (@value{GDBP}) info function !
15295 All functions matching regular expression "!":
15297 Non-debugging symbols:
15298 0x6100114c cygwin1!__assert
15299 0x61004034 cygwin1!_dll_crt0@@0
15300 0x61004240 cygwin1!dll_crt0(per_process *)
15304 @subsubsection Working with Minimal Symbols
15306 Symbols extracted from a DLL's export table do not contain very much
15307 type information. All that @value{GDBN} can do is guess whether a symbol
15308 refers to a function or variable depending on the linker section that
15309 contains the symbol. Also note that the actual contents of the memory
15310 contained in a DLL are not available unless the program is running. This
15311 means that you cannot examine the contents of a variable or disassemble
15312 a function within a DLL without a running program.
15314 Variables are generally treated as pointers and dereferenced
15315 automatically. For this reason, it is often necessary to prefix a
15316 variable name with the address-of operator (``&'') and provide explicit
15317 type information in the command. Here's an example of the type of
15321 (@value{GDBP}) print 'cygwin1!__argv'
15326 (@value{GDBP}) x 'cygwin1!__argv'
15327 0x10021610: "\230y\""
15330 And two possible solutions:
15333 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
15334 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
15338 (@value{GDBP}) x/2x &'cygwin1!__argv'
15339 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
15340 (@value{GDBP}) x/x 0x10021608
15341 0x10021608: 0x0022fd98
15342 (@value{GDBP}) x/s 0x0022fd98
15343 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
15346 Setting a break point within a DLL is possible even before the program
15347 starts execution. However, under these circumstances, @value{GDBN} can't
15348 examine the initial instructions of the function in order to skip the
15349 function's frame set-up code. You can work around this by using ``*&''
15350 to set the breakpoint at a raw memory address:
15353 (@value{GDBP}) break *&'python22!PyOS_Readline'
15354 Breakpoint 1 at 0x1e04eff0
15357 The author of these extensions is not entirely convinced that setting a
15358 break point within a shared DLL like @file{kernel32.dll} is completely
15362 @subsection Commands Specific to @sc{gnu} Hurd Systems
15363 @cindex @sc{gnu} Hurd debugging
15365 This subsection describes @value{GDBN} commands specific to the
15366 @sc{gnu} Hurd native debugging.
15371 @kindex set signals@r{, Hurd command}
15372 @kindex set sigs@r{, Hurd command}
15373 This command toggles the state of inferior signal interception by
15374 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
15375 affected by this command. @code{sigs} is a shorthand alias for
15380 @kindex show signals@r{, Hurd command}
15381 @kindex show sigs@r{, Hurd command}
15382 Show the current state of intercepting inferior's signals.
15384 @item set signal-thread
15385 @itemx set sigthread
15386 @kindex set signal-thread
15387 @kindex set sigthread
15388 This command tells @value{GDBN} which thread is the @code{libc} signal
15389 thread. That thread is run when a signal is delivered to a running
15390 process. @code{set sigthread} is the shorthand alias of @code{set
15393 @item show signal-thread
15394 @itemx show sigthread
15395 @kindex show signal-thread
15396 @kindex show sigthread
15397 These two commands show which thread will run when the inferior is
15398 delivered a signal.
15401 @kindex set stopped@r{, Hurd command}
15402 This commands tells @value{GDBN} that the inferior process is stopped,
15403 as with the @code{SIGSTOP} signal. The stopped process can be
15404 continued by delivering a signal to it.
15407 @kindex show stopped@r{, Hurd command}
15408 This command shows whether @value{GDBN} thinks the debuggee is
15411 @item set exceptions
15412 @kindex set exceptions@r{, Hurd command}
15413 Use this command to turn off trapping of exceptions in the inferior.
15414 When exception trapping is off, neither breakpoints nor
15415 single-stepping will work. To restore the default, set exception
15418 @item show exceptions
15419 @kindex show exceptions@r{, Hurd command}
15420 Show the current state of trapping exceptions in the inferior.
15422 @item set task pause
15423 @kindex set task@r{, Hurd commands}
15424 @cindex task attributes (@sc{gnu} Hurd)
15425 @cindex pause current task (@sc{gnu} Hurd)
15426 This command toggles task suspension when @value{GDBN} has control.
15427 Setting it to on takes effect immediately, and the task is suspended
15428 whenever @value{GDBN} gets control. Setting it to off will take
15429 effect the next time the inferior is continued. If this option is set
15430 to off, you can use @code{set thread default pause on} or @code{set
15431 thread pause on} (see below) to pause individual threads.
15433 @item show task pause
15434 @kindex show task@r{, Hurd commands}
15435 Show the current state of task suspension.
15437 @item set task detach-suspend-count
15438 @cindex task suspend count
15439 @cindex detach from task, @sc{gnu} Hurd
15440 This command sets the suspend count the task will be left with when
15441 @value{GDBN} detaches from it.
15443 @item show task detach-suspend-count
15444 Show the suspend count the task will be left with when detaching.
15446 @item set task exception-port
15447 @itemx set task excp
15448 @cindex task exception port, @sc{gnu} Hurd
15449 This command sets the task exception port to which @value{GDBN} will
15450 forward exceptions. The argument should be the value of the @dfn{send
15451 rights} of the task. @code{set task excp} is a shorthand alias.
15453 @item set noninvasive
15454 @cindex noninvasive task options
15455 This command switches @value{GDBN} to a mode that is the least
15456 invasive as far as interfering with the inferior is concerned. This
15457 is the same as using @code{set task pause}, @code{set exceptions}, and
15458 @code{set signals} to values opposite to the defaults.
15460 @item info send-rights
15461 @itemx info receive-rights
15462 @itemx info port-rights
15463 @itemx info port-sets
15464 @itemx info dead-names
15467 @cindex send rights, @sc{gnu} Hurd
15468 @cindex receive rights, @sc{gnu} Hurd
15469 @cindex port rights, @sc{gnu} Hurd
15470 @cindex port sets, @sc{gnu} Hurd
15471 @cindex dead names, @sc{gnu} Hurd
15472 These commands display information about, respectively, send rights,
15473 receive rights, port rights, port sets, and dead names of a task.
15474 There are also shorthand aliases: @code{info ports} for @code{info
15475 port-rights} and @code{info psets} for @code{info port-sets}.
15477 @item set thread pause
15478 @kindex set thread@r{, Hurd command}
15479 @cindex thread properties, @sc{gnu} Hurd
15480 @cindex pause current thread (@sc{gnu} Hurd)
15481 This command toggles current thread suspension when @value{GDBN} has
15482 control. Setting it to on takes effect immediately, and the current
15483 thread is suspended whenever @value{GDBN} gets control. Setting it to
15484 off will take effect the next time the inferior is continued.
15485 Normally, this command has no effect, since when @value{GDBN} has
15486 control, the whole task is suspended. However, if you used @code{set
15487 task pause off} (see above), this command comes in handy to suspend
15488 only the current thread.
15490 @item show thread pause
15491 @kindex show thread@r{, Hurd command}
15492 This command shows the state of current thread suspension.
15494 @item set thread run
15495 This command sets whether the current thread is allowed to run.
15497 @item show thread run
15498 Show whether the current thread is allowed to run.
15500 @item set thread detach-suspend-count
15501 @cindex thread suspend count, @sc{gnu} Hurd
15502 @cindex detach from thread, @sc{gnu} Hurd
15503 This command sets the suspend count @value{GDBN} will leave on a
15504 thread when detaching. This number is relative to the suspend count
15505 found by @value{GDBN} when it notices the thread; use @code{set thread
15506 takeover-suspend-count} to force it to an absolute value.
15508 @item show thread detach-suspend-count
15509 Show the suspend count @value{GDBN} will leave on the thread when
15512 @item set thread exception-port
15513 @itemx set thread excp
15514 Set the thread exception port to which to forward exceptions. This
15515 overrides the port set by @code{set task exception-port} (see above).
15516 @code{set thread excp} is the shorthand alias.
15518 @item set thread takeover-suspend-count
15519 Normally, @value{GDBN}'s thread suspend counts are relative to the
15520 value @value{GDBN} finds when it notices each thread. This command
15521 changes the suspend counts to be absolute instead.
15523 @item set thread default
15524 @itemx show thread default
15525 @cindex thread default settings, @sc{gnu} Hurd
15526 Each of the above @code{set thread} commands has a @code{set thread
15527 default} counterpart (e.g., @code{set thread default pause}, @code{set
15528 thread default exception-port}, etc.). The @code{thread default}
15529 variety of commands sets the default thread properties for all
15530 threads; you can then change the properties of individual threads with
15531 the non-default commands.
15536 @subsection QNX Neutrino
15537 @cindex QNX Neutrino
15539 @value{GDBN} provides the following commands specific to the QNX
15543 @item set debug nto-debug
15544 @kindex set debug nto-debug
15545 When set to on, enables debugging messages specific to the QNX
15548 @item show debug nto-debug
15549 @kindex show debug nto-debug
15550 Show the current state of QNX Neutrino messages.
15557 @value{GDBN} provides the following commands specific to the Darwin target:
15560 @item set debug darwin @var{num}
15561 @kindex set debug darwin
15562 When set to a non zero value, enables debugging messages specific to
15563 the Darwin support. Higher values produce more verbose output.
15565 @item show debug darwin
15566 @kindex show debug darwin
15567 Show the current state of Darwin messages.
15569 @item set debug mach-o @var{num}
15570 @kindex set debug mach-o
15571 When set to a non zero value, enables debugging messages while
15572 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
15573 file format used on Darwin for object and executable files.) Higher
15574 values produce more verbose output. This is a command to diagnose
15575 problems internal to @value{GDBN} and should not be needed in normal
15578 @item show debug mach-o
15579 @kindex show debug mach-o
15580 Show the current state of Mach-O file messages.
15582 @item set mach-exceptions on
15583 @itemx set mach-exceptions off
15584 @kindex set mach-exceptions
15585 On Darwin, faults are first reported as a Mach exception and are then
15586 mapped to a Posix signal. Use this command to turn on trapping of
15587 Mach exceptions in the inferior. This might be sometimes useful to
15588 better understand the cause of a fault. The default is off.
15590 @item show mach-exceptions
15591 @kindex show mach-exceptions
15592 Show the current state of exceptions trapping.
15597 @section Embedded Operating Systems
15599 This section describes configurations involving the debugging of
15600 embedded operating systems that are available for several different
15604 * VxWorks:: Using @value{GDBN} with VxWorks
15607 @value{GDBN} includes the ability to debug programs running on
15608 various real-time operating systems.
15611 @subsection Using @value{GDBN} with VxWorks
15617 @kindex target vxworks
15618 @item target vxworks @var{machinename}
15619 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
15620 is the target system's machine name or IP address.
15624 On VxWorks, @code{load} links @var{filename} dynamically on the
15625 current target system as well as adding its symbols in @value{GDBN}.
15627 @value{GDBN} enables developers to spawn and debug tasks running on networked
15628 VxWorks targets from a Unix host. Already-running tasks spawned from
15629 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
15630 both the Unix host and on the VxWorks target. The program
15631 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
15632 installed with the name @code{vxgdb}, to distinguish it from a
15633 @value{GDBN} for debugging programs on the host itself.)
15636 @item VxWorks-timeout @var{args}
15637 @kindex vxworks-timeout
15638 All VxWorks-based targets now support the option @code{vxworks-timeout}.
15639 This option is set by the user, and @var{args} represents the number of
15640 seconds @value{GDBN} waits for responses to rpc's. You might use this if
15641 your VxWorks target is a slow software simulator or is on the far side
15642 of a thin network line.
15645 The following information on connecting to VxWorks was current when
15646 this manual was produced; newer releases of VxWorks may use revised
15649 @findex INCLUDE_RDB
15650 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
15651 to include the remote debugging interface routines in the VxWorks
15652 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
15653 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
15654 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
15655 source debugging task @code{tRdbTask} when VxWorks is booted. For more
15656 information on configuring and remaking VxWorks, see the manufacturer's
15658 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
15660 Once you have included @file{rdb.a} in your VxWorks system image and set
15661 your Unix execution search path to find @value{GDBN}, you are ready to
15662 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
15663 @code{vxgdb}, depending on your installation).
15665 @value{GDBN} comes up showing the prompt:
15672 * VxWorks Connection:: Connecting to VxWorks
15673 * VxWorks Download:: VxWorks download
15674 * VxWorks Attach:: Running tasks
15677 @node VxWorks Connection
15678 @subsubsection Connecting to VxWorks
15680 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
15681 network. To connect to a target whose host name is ``@code{tt}'', type:
15684 (vxgdb) target vxworks tt
15688 @value{GDBN} displays messages like these:
15691 Attaching remote machine across net...
15696 @value{GDBN} then attempts to read the symbol tables of any object modules
15697 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
15698 these files by searching the directories listed in the command search
15699 path (@pxref{Environment, ,Your Program's Environment}); if it fails
15700 to find an object file, it displays a message such as:
15703 prog.o: No such file or directory.
15706 When this happens, add the appropriate directory to the search path with
15707 the @value{GDBN} command @code{path}, and execute the @code{target}
15710 @node VxWorks Download
15711 @subsubsection VxWorks Download
15713 @cindex download to VxWorks
15714 If you have connected to the VxWorks target and you want to debug an
15715 object that has not yet been loaded, you can use the @value{GDBN}
15716 @code{load} command to download a file from Unix to VxWorks
15717 incrementally. The object file given as an argument to the @code{load}
15718 command is actually opened twice: first by the VxWorks target in order
15719 to download the code, then by @value{GDBN} in order to read the symbol
15720 table. This can lead to problems if the current working directories on
15721 the two systems differ. If both systems have NFS mounted the same
15722 filesystems, you can avoid these problems by using absolute paths.
15723 Otherwise, it is simplest to set the working directory on both systems
15724 to the directory in which the object file resides, and then to reference
15725 the file by its name, without any path. For instance, a program
15726 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
15727 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
15728 program, type this on VxWorks:
15731 -> cd "@var{vxpath}/vw/demo/rdb"
15735 Then, in @value{GDBN}, type:
15738 (vxgdb) cd @var{hostpath}/vw/demo/rdb
15739 (vxgdb) load prog.o
15742 @value{GDBN} displays a response similar to this:
15745 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
15748 You can also use the @code{load} command to reload an object module
15749 after editing and recompiling the corresponding source file. Note that
15750 this makes @value{GDBN} delete all currently-defined breakpoints,
15751 auto-displays, and convenience variables, and to clear the value
15752 history. (This is necessary in order to preserve the integrity of
15753 debugger's data structures that reference the target system's symbol
15756 @node VxWorks Attach
15757 @subsubsection Running Tasks
15759 @cindex running VxWorks tasks
15760 You can also attach to an existing task using the @code{attach} command as
15764 (vxgdb) attach @var{task}
15768 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
15769 or suspended when you attach to it. Running tasks are suspended at
15770 the time of attachment.
15772 @node Embedded Processors
15773 @section Embedded Processors
15775 This section goes into details specific to particular embedded
15778 @cindex send command to simulator
15779 Whenever a specific embedded processor has a simulator, @value{GDBN}
15780 allows to send an arbitrary command to the simulator.
15783 @item sim @var{command}
15784 @kindex sim@r{, a command}
15785 Send an arbitrary @var{command} string to the simulator. Consult the
15786 documentation for the specific simulator in use for information about
15787 acceptable commands.
15793 * M32R/D:: Renesas M32R/D
15794 * M68K:: Motorola M68K
15795 * MIPS Embedded:: MIPS Embedded
15796 * OpenRISC 1000:: OpenRisc 1000
15797 * PA:: HP PA Embedded
15798 * PowerPC Embedded:: PowerPC Embedded
15799 * Sparclet:: Tsqware Sparclet
15800 * Sparclite:: Fujitsu Sparclite
15801 * Z8000:: Zilog Z8000
15804 * Super-H:: Renesas Super-H
15813 @item target rdi @var{dev}
15814 ARM Angel monitor, via RDI library interface to ADP protocol. You may
15815 use this target to communicate with both boards running the Angel
15816 monitor, or with the EmbeddedICE JTAG debug device.
15819 @item target rdp @var{dev}
15824 @value{GDBN} provides the following ARM-specific commands:
15827 @item set arm disassembler
15829 This commands selects from a list of disassembly styles. The
15830 @code{"std"} style is the standard style.
15832 @item show arm disassembler
15834 Show the current disassembly style.
15836 @item set arm apcs32
15837 @cindex ARM 32-bit mode
15838 This command toggles ARM operation mode between 32-bit and 26-bit.
15840 @item show arm apcs32
15841 Display the current usage of the ARM 32-bit mode.
15843 @item set arm fpu @var{fputype}
15844 This command sets the ARM floating-point unit (FPU) type. The
15845 argument @var{fputype} can be one of these:
15849 Determine the FPU type by querying the OS ABI.
15851 Software FPU, with mixed-endian doubles on little-endian ARM
15854 GCC-compiled FPA co-processor.
15856 Software FPU with pure-endian doubles.
15862 Show the current type of the FPU.
15865 This command forces @value{GDBN} to use the specified ABI.
15868 Show the currently used ABI.
15870 @item set arm fallback-mode (arm|thumb|auto)
15871 @value{GDBN} uses the symbol table, when available, to determine
15872 whether instructions are ARM or Thumb. This command controls
15873 @value{GDBN}'s default behavior when the symbol table is not
15874 available. The default is @samp{auto}, which causes @value{GDBN} to
15875 use the current execution mode (from the @code{T} bit in the @code{CPSR}
15878 @item show arm fallback-mode
15879 Show the current fallback instruction mode.
15881 @item set arm force-mode (arm|thumb|auto)
15882 This command overrides use of the symbol table to determine whether
15883 instructions are ARM or Thumb. The default is @samp{auto}, which
15884 causes @value{GDBN} to use the symbol table and then the setting
15885 of @samp{set arm fallback-mode}.
15887 @item show arm force-mode
15888 Show the current forced instruction mode.
15890 @item set debug arm
15891 Toggle whether to display ARM-specific debugging messages from the ARM
15892 target support subsystem.
15894 @item show debug arm
15895 Show whether ARM-specific debugging messages are enabled.
15898 The following commands are available when an ARM target is debugged
15899 using the RDI interface:
15902 @item rdilogfile @r{[}@var{file}@r{]}
15904 @cindex ADP (Angel Debugger Protocol) logging
15905 Set the filename for the ADP (Angel Debugger Protocol) packet log.
15906 With an argument, sets the log file to the specified @var{file}. With
15907 no argument, show the current log file name. The default log file is
15910 @item rdilogenable @r{[}@var{arg}@r{]}
15911 @kindex rdilogenable
15912 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
15913 enables logging, with an argument 0 or @code{"no"} disables it. With
15914 no arguments displays the current setting. When logging is enabled,
15915 ADP packets exchanged between @value{GDBN} and the RDI target device
15916 are logged to a file.
15918 @item set rdiromatzero
15919 @kindex set rdiromatzero
15920 @cindex ROM at zero address, RDI
15921 Tell @value{GDBN} whether the target has ROM at address 0. If on,
15922 vector catching is disabled, so that zero address can be used. If off
15923 (the default), vector catching is enabled. For this command to take
15924 effect, it needs to be invoked prior to the @code{target rdi} command.
15926 @item show rdiromatzero
15927 @kindex show rdiromatzero
15928 Show the current setting of ROM at zero address.
15930 @item set rdiheartbeat
15931 @kindex set rdiheartbeat
15932 @cindex RDI heartbeat
15933 Enable or disable RDI heartbeat packets. It is not recommended to
15934 turn on this option, since it confuses ARM and EPI JTAG interface, as
15935 well as the Angel monitor.
15937 @item show rdiheartbeat
15938 @kindex show rdiheartbeat
15939 Show the setting of RDI heartbeat packets.
15944 @subsection Renesas M32R/D and M32R/SDI
15947 @kindex target m32r
15948 @item target m32r @var{dev}
15949 Renesas M32R/D ROM monitor.
15951 @kindex target m32rsdi
15952 @item target m32rsdi @var{dev}
15953 Renesas M32R SDI server, connected via parallel port to the board.
15956 The following @value{GDBN} commands are specific to the M32R monitor:
15959 @item set download-path @var{path}
15960 @kindex set download-path
15961 @cindex find downloadable @sc{srec} files (M32R)
15962 Set the default path for finding downloadable @sc{srec} files.
15964 @item show download-path
15965 @kindex show download-path
15966 Show the default path for downloadable @sc{srec} files.
15968 @item set board-address @var{addr}
15969 @kindex set board-address
15970 @cindex M32-EVA target board address
15971 Set the IP address for the M32R-EVA target board.
15973 @item show board-address
15974 @kindex show board-address
15975 Show the current IP address of the target board.
15977 @item set server-address @var{addr}
15978 @kindex set server-address
15979 @cindex download server address (M32R)
15980 Set the IP address for the download server, which is the @value{GDBN}'s
15983 @item show server-address
15984 @kindex show server-address
15985 Display the IP address of the download server.
15987 @item upload @r{[}@var{file}@r{]}
15988 @kindex upload@r{, M32R}
15989 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
15990 upload capability. If no @var{file} argument is given, the current
15991 executable file is uploaded.
15993 @item tload @r{[}@var{file}@r{]}
15994 @kindex tload@r{, M32R}
15995 Test the @code{upload} command.
15998 The following commands are available for M32R/SDI:
16003 @cindex reset SDI connection, M32R
16004 This command resets the SDI connection.
16008 This command shows the SDI connection status.
16011 @kindex debug_chaos
16012 @cindex M32R/Chaos debugging
16013 Instructs the remote that M32R/Chaos debugging is to be used.
16015 @item use_debug_dma
16016 @kindex use_debug_dma
16017 Instructs the remote to use the DEBUG_DMA method of accessing memory.
16020 @kindex use_mon_code
16021 Instructs the remote to use the MON_CODE method of accessing memory.
16024 @kindex use_ib_break
16025 Instructs the remote to set breakpoints by IB break.
16027 @item use_dbt_break
16028 @kindex use_dbt_break
16029 Instructs the remote to set breakpoints by DBT.
16035 The Motorola m68k configuration includes ColdFire support, and a
16036 target command for the following ROM monitor.
16040 @kindex target dbug
16041 @item target dbug @var{dev}
16042 dBUG ROM monitor for Motorola ColdFire.
16046 @node MIPS Embedded
16047 @subsection MIPS Embedded
16049 @cindex MIPS boards
16050 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
16051 MIPS board attached to a serial line. This is available when
16052 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
16055 Use these @value{GDBN} commands to specify the connection to your target board:
16058 @item target mips @var{port}
16059 @kindex target mips @var{port}
16060 To run a program on the board, start up @code{@value{GDBP}} with the
16061 name of your program as the argument. To connect to the board, use the
16062 command @samp{target mips @var{port}}, where @var{port} is the name of
16063 the serial port connected to the board. If the program has not already
16064 been downloaded to the board, you may use the @code{load} command to
16065 download it. You can then use all the usual @value{GDBN} commands.
16067 For example, this sequence connects to the target board through a serial
16068 port, and loads and runs a program called @var{prog} through the
16072 host$ @value{GDBP} @var{prog}
16073 @value{GDBN} is free software and @dots{}
16074 (@value{GDBP}) target mips /dev/ttyb
16075 (@value{GDBP}) load @var{prog}
16079 @item target mips @var{hostname}:@var{portnumber}
16080 On some @value{GDBN} host configurations, you can specify a TCP
16081 connection (for instance, to a serial line managed by a terminal
16082 concentrator) instead of a serial port, using the syntax
16083 @samp{@var{hostname}:@var{portnumber}}.
16085 @item target pmon @var{port}
16086 @kindex target pmon @var{port}
16089 @item target ddb @var{port}
16090 @kindex target ddb @var{port}
16091 NEC's DDB variant of PMON for Vr4300.
16093 @item target lsi @var{port}
16094 @kindex target lsi @var{port}
16095 LSI variant of PMON.
16097 @kindex target r3900
16098 @item target r3900 @var{dev}
16099 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
16101 @kindex target array
16102 @item target array @var{dev}
16103 Array Tech LSI33K RAID controller board.
16109 @value{GDBN} also supports these special commands for MIPS targets:
16112 @item set mipsfpu double
16113 @itemx set mipsfpu single
16114 @itemx set mipsfpu none
16115 @itemx set mipsfpu auto
16116 @itemx show mipsfpu
16117 @kindex set mipsfpu
16118 @kindex show mipsfpu
16119 @cindex MIPS remote floating point
16120 @cindex floating point, MIPS remote
16121 If your target board does not support the MIPS floating point
16122 coprocessor, you should use the command @samp{set mipsfpu none} (if you
16123 need this, you may wish to put the command in your @value{GDBN} init
16124 file). This tells @value{GDBN} how to find the return value of
16125 functions which return floating point values. It also allows
16126 @value{GDBN} to avoid saving the floating point registers when calling
16127 functions on the board. If you are using a floating point coprocessor
16128 with only single precision floating point support, as on the @sc{r4650}
16129 processor, use the command @samp{set mipsfpu single}. The default
16130 double precision floating point coprocessor may be selected using
16131 @samp{set mipsfpu double}.
16133 In previous versions the only choices were double precision or no
16134 floating point, so @samp{set mipsfpu on} will select double precision
16135 and @samp{set mipsfpu off} will select no floating point.
16137 As usual, you can inquire about the @code{mipsfpu} variable with
16138 @samp{show mipsfpu}.
16140 @item set timeout @var{seconds}
16141 @itemx set retransmit-timeout @var{seconds}
16142 @itemx show timeout
16143 @itemx show retransmit-timeout
16144 @cindex @code{timeout}, MIPS protocol
16145 @cindex @code{retransmit-timeout}, MIPS protocol
16146 @kindex set timeout
16147 @kindex show timeout
16148 @kindex set retransmit-timeout
16149 @kindex show retransmit-timeout
16150 You can control the timeout used while waiting for a packet, in the MIPS
16151 remote protocol, with the @code{set timeout @var{seconds}} command. The
16152 default is 5 seconds. Similarly, you can control the timeout used while
16153 waiting for an acknowledgment of a packet with the @code{set
16154 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
16155 You can inspect both values with @code{show timeout} and @code{show
16156 retransmit-timeout}. (These commands are @emph{only} available when
16157 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
16159 The timeout set by @code{set timeout} does not apply when @value{GDBN}
16160 is waiting for your program to stop. In that case, @value{GDBN} waits
16161 forever because it has no way of knowing how long the program is going
16162 to run before stopping.
16164 @item set syn-garbage-limit @var{num}
16165 @kindex set syn-garbage-limit@r{, MIPS remote}
16166 @cindex synchronize with remote MIPS target
16167 Limit the maximum number of characters @value{GDBN} should ignore when
16168 it tries to synchronize with the remote target. The default is 10
16169 characters. Setting the limit to -1 means there's no limit.
16171 @item show syn-garbage-limit
16172 @kindex show syn-garbage-limit@r{, MIPS remote}
16173 Show the current limit on the number of characters to ignore when
16174 trying to synchronize with the remote system.
16176 @item set monitor-prompt @var{prompt}
16177 @kindex set monitor-prompt@r{, MIPS remote}
16178 @cindex remote monitor prompt
16179 Tell @value{GDBN} to expect the specified @var{prompt} string from the
16180 remote monitor. The default depends on the target:
16190 @item show monitor-prompt
16191 @kindex show monitor-prompt@r{, MIPS remote}
16192 Show the current strings @value{GDBN} expects as the prompt from the
16195 @item set monitor-warnings
16196 @kindex set monitor-warnings@r{, MIPS remote}
16197 Enable or disable monitor warnings about hardware breakpoints. This
16198 has effect only for the @code{lsi} target. When on, @value{GDBN} will
16199 display warning messages whose codes are returned by the @code{lsi}
16200 PMON monitor for breakpoint commands.
16202 @item show monitor-warnings
16203 @kindex show monitor-warnings@r{, MIPS remote}
16204 Show the current setting of printing monitor warnings.
16206 @item pmon @var{command}
16207 @kindex pmon@r{, MIPS remote}
16208 @cindex send PMON command
16209 This command allows sending an arbitrary @var{command} string to the
16210 monitor. The monitor must be in debug mode for this to work.
16213 @node OpenRISC 1000
16214 @subsection OpenRISC 1000
16215 @cindex OpenRISC 1000
16217 @cindex or1k boards
16218 See OR1k Architecture document (@uref{www.opencores.org}) for more information
16219 about platform and commands.
16223 @kindex target jtag
16224 @item target jtag jtag://@var{host}:@var{port}
16226 Connects to remote JTAG server.
16227 JTAG remote server can be either an or1ksim or JTAG server,
16228 connected via parallel port to the board.
16230 Example: @code{target jtag jtag://localhost:9999}
16233 @item or1ksim @var{command}
16234 If connected to @code{or1ksim} OpenRISC 1000 Architectural
16235 Simulator, proprietary commands can be executed.
16237 @kindex info or1k spr
16238 @item info or1k spr
16239 Displays spr groups.
16241 @item info or1k spr @var{group}
16242 @itemx info or1k spr @var{groupno}
16243 Displays register names in selected group.
16245 @item info or1k spr @var{group} @var{register}
16246 @itemx info or1k spr @var{register}
16247 @itemx info or1k spr @var{groupno} @var{registerno}
16248 @itemx info or1k spr @var{registerno}
16249 Shows information about specified spr register.
16252 @item spr @var{group} @var{register} @var{value}
16253 @itemx spr @var{register @var{value}}
16254 @itemx spr @var{groupno} @var{registerno @var{value}}
16255 @itemx spr @var{registerno @var{value}}
16256 Writes @var{value} to specified spr register.
16259 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
16260 It is very similar to @value{GDBN} trace, except it does not interfere with normal
16261 program execution and is thus much faster. Hardware breakpoints/watchpoint
16262 triggers can be set using:
16265 Load effective address/data
16267 Store effective address/data
16269 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
16274 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
16275 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
16277 @code{htrace} commands:
16278 @cindex OpenRISC 1000 htrace
16281 @item hwatch @var{conditional}
16282 Set hardware watchpoint on combination of Load/Store Effective Address(es)
16283 or Data. For example:
16285 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16287 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16291 Display information about current HW trace configuration.
16293 @item htrace trigger @var{conditional}
16294 Set starting criteria for HW trace.
16296 @item htrace qualifier @var{conditional}
16297 Set acquisition qualifier for HW trace.
16299 @item htrace stop @var{conditional}
16300 Set HW trace stopping criteria.
16302 @item htrace record [@var{data}]*
16303 Selects the data to be recorded, when qualifier is met and HW trace was
16306 @item htrace enable
16307 @itemx htrace disable
16308 Enables/disables the HW trace.
16310 @item htrace rewind [@var{filename}]
16311 Clears currently recorded trace data.
16313 If filename is specified, new trace file is made and any newly collected data
16314 will be written there.
16316 @item htrace print [@var{start} [@var{len}]]
16317 Prints trace buffer, using current record configuration.
16319 @item htrace mode continuous
16320 Set continuous trace mode.
16322 @item htrace mode suspend
16323 Set suspend trace mode.
16327 @node PowerPC Embedded
16328 @subsection PowerPC Embedded
16330 @value{GDBN} provides the following PowerPC-specific commands:
16333 @kindex set powerpc
16334 @item set powerpc soft-float
16335 @itemx show powerpc soft-float
16336 Force @value{GDBN} to use (or not use) a software floating point calling
16337 convention. By default, @value{GDBN} selects the calling convention based
16338 on the selected architecture and the provided executable file.
16340 @item set powerpc vector-abi
16341 @itemx show powerpc vector-abi
16342 Force @value{GDBN} to use the specified calling convention for vector
16343 arguments and return values. The valid options are @samp{auto};
16344 @samp{generic}, to avoid vector registers even if they are present;
16345 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
16346 registers. By default, @value{GDBN} selects the calling convention
16347 based on the selected architecture and the provided executable file.
16349 @kindex target dink32
16350 @item target dink32 @var{dev}
16351 DINK32 ROM monitor.
16353 @kindex target ppcbug
16354 @item target ppcbug @var{dev}
16355 @kindex target ppcbug1
16356 @item target ppcbug1 @var{dev}
16357 PPCBUG ROM monitor for PowerPC.
16360 @item target sds @var{dev}
16361 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
16364 @cindex SDS protocol
16365 The following commands specific to the SDS protocol are supported
16369 @item set sdstimeout @var{nsec}
16370 @kindex set sdstimeout
16371 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
16372 default is 2 seconds.
16374 @item show sdstimeout
16375 @kindex show sdstimeout
16376 Show the current value of the SDS timeout.
16378 @item sds @var{command}
16379 @kindex sds@r{, a command}
16380 Send the specified @var{command} string to the SDS monitor.
16385 @subsection HP PA Embedded
16389 @kindex target op50n
16390 @item target op50n @var{dev}
16391 OP50N monitor, running on an OKI HPPA board.
16393 @kindex target w89k
16394 @item target w89k @var{dev}
16395 W89K monitor, running on a Winbond HPPA board.
16400 @subsection Tsqware Sparclet
16404 @value{GDBN} enables developers to debug tasks running on
16405 Sparclet targets from a Unix host.
16406 @value{GDBN} uses code that runs on
16407 both the Unix host and on the Sparclet target. The program
16408 @code{@value{GDBP}} is installed and executed on the Unix host.
16411 @item remotetimeout @var{args}
16412 @kindex remotetimeout
16413 @value{GDBN} supports the option @code{remotetimeout}.
16414 This option is set by the user, and @var{args} represents the number of
16415 seconds @value{GDBN} waits for responses.
16418 @cindex compiling, on Sparclet
16419 When compiling for debugging, include the options @samp{-g} to get debug
16420 information and @samp{-Ttext} to relocate the program to where you wish to
16421 load it on the target. You may also want to add the options @samp{-n} or
16422 @samp{-N} in order to reduce the size of the sections. Example:
16425 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
16428 You can use @code{objdump} to verify that the addresses are what you intended:
16431 sparclet-aout-objdump --headers --syms prog
16434 @cindex running, on Sparclet
16436 your Unix execution search path to find @value{GDBN}, you are ready to
16437 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
16438 (or @code{sparclet-aout-gdb}, depending on your installation).
16440 @value{GDBN} comes up showing the prompt:
16447 * Sparclet File:: Setting the file to debug
16448 * Sparclet Connection:: Connecting to Sparclet
16449 * Sparclet Download:: Sparclet download
16450 * Sparclet Execution:: Running and debugging
16453 @node Sparclet File
16454 @subsubsection Setting File to Debug
16456 The @value{GDBN} command @code{file} lets you choose with program to debug.
16459 (gdbslet) file prog
16463 @value{GDBN} then attempts to read the symbol table of @file{prog}.
16464 @value{GDBN} locates
16465 the file by searching the directories listed in the command search
16467 If the file was compiled with debug information (option @samp{-g}), source
16468 files will be searched as well.
16469 @value{GDBN} locates
16470 the source files by searching the directories listed in the directory search
16471 path (@pxref{Environment, ,Your Program's Environment}).
16473 to find a file, it displays a message such as:
16476 prog: No such file or directory.
16479 When this happens, add the appropriate directories to the search paths with
16480 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
16481 @code{target} command again.
16483 @node Sparclet Connection
16484 @subsubsection Connecting to Sparclet
16486 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
16487 To connect to a target on serial port ``@code{ttya}'', type:
16490 (gdbslet) target sparclet /dev/ttya
16491 Remote target sparclet connected to /dev/ttya
16492 main () at ../prog.c:3
16496 @value{GDBN} displays messages like these:
16502 @node Sparclet Download
16503 @subsubsection Sparclet Download
16505 @cindex download to Sparclet
16506 Once connected to the Sparclet target,
16507 you can use the @value{GDBN}
16508 @code{load} command to download the file from the host to the target.
16509 The file name and load offset should be given as arguments to the @code{load}
16511 Since the file format is aout, the program must be loaded to the starting
16512 address. You can use @code{objdump} to find out what this value is. The load
16513 offset is an offset which is added to the VMA (virtual memory address)
16514 of each of the file's sections.
16515 For instance, if the program
16516 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
16517 and bss at 0x12010170, in @value{GDBN}, type:
16520 (gdbslet) load prog 0x12010000
16521 Loading section .text, size 0xdb0 vma 0x12010000
16524 If the code is loaded at a different address then what the program was linked
16525 to, you may need to use the @code{section} and @code{add-symbol-file} commands
16526 to tell @value{GDBN} where to map the symbol table.
16528 @node Sparclet Execution
16529 @subsubsection Running and Debugging
16531 @cindex running and debugging Sparclet programs
16532 You can now begin debugging the task using @value{GDBN}'s execution control
16533 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
16534 manual for the list of commands.
16538 Breakpoint 1 at 0x12010000: file prog.c, line 3.
16540 Starting program: prog
16541 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
16542 3 char *symarg = 0;
16544 4 char *execarg = "hello!";
16549 @subsection Fujitsu Sparclite
16553 @kindex target sparclite
16554 @item target sparclite @var{dev}
16555 Fujitsu sparclite boards, used only for the purpose of loading.
16556 You must use an additional command to debug the program.
16557 For example: target remote @var{dev} using @value{GDBN} standard
16563 @subsection Zilog Z8000
16566 @cindex simulator, Z8000
16567 @cindex Zilog Z8000 simulator
16569 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
16572 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
16573 unsegmented variant of the Z8000 architecture) or the Z8001 (the
16574 segmented variant). The simulator recognizes which architecture is
16575 appropriate by inspecting the object code.
16578 @item target sim @var{args}
16580 @kindex target sim@r{, with Z8000}
16581 Debug programs on a simulated CPU. If the simulator supports setup
16582 options, specify them via @var{args}.
16586 After specifying this target, you can debug programs for the simulated
16587 CPU in the same style as programs for your host computer; use the
16588 @code{file} command to load a new program image, the @code{run} command
16589 to run your program, and so on.
16591 As well as making available all the usual machine registers
16592 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
16593 additional items of information as specially named registers:
16598 Counts clock-ticks in the simulator.
16601 Counts instructions run in the simulator.
16604 Execution time in 60ths of a second.
16608 You can refer to these values in @value{GDBN} expressions with the usual
16609 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
16610 conditional breakpoint that suspends only after at least 5000
16611 simulated clock ticks.
16614 @subsection Atmel AVR
16617 When configured for debugging the Atmel AVR, @value{GDBN} supports the
16618 following AVR-specific commands:
16621 @item info io_registers
16622 @kindex info io_registers@r{, AVR}
16623 @cindex I/O registers (Atmel AVR)
16624 This command displays information about the AVR I/O registers. For
16625 each register, @value{GDBN} prints its number and value.
16632 When configured for debugging CRIS, @value{GDBN} provides the
16633 following CRIS-specific commands:
16636 @item set cris-version @var{ver}
16637 @cindex CRIS version
16638 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
16639 The CRIS version affects register names and sizes. This command is useful in
16640 case autodetection of the CRIS version fails.
16642 @item show cris-version
16643 Show the current CRIS version.
16645 @item set cris-dwarf2-cfi
16646 @cindex DWARF-2 CFI and CRIS
16647 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
16648 Change to @samp{off} when using @code{gcc-cris} whose version is below
16651 @item show cris-dwarf2-cfi
16652 Show the current state of using DWARF-2 CFI.
16654 @item set cris-mode @var{mode}
16656 Set the current CRIS mode to @var{mode}. It should only be changed when
16657 debugging in guru mode, in which case it should be set to
16658 @samp{guru} (the default is @samp{normal}).
16660 @item show cris-mode
16661 Show the current CRIS mode.
16665 @subsection Renesas Super-H
16668 For the Renesas Super-H processor, @value{GDBN} provides these
16673 @kindex regs@r{, Super-H}
16674 Show the values of all Super-H registers.
16676 @item set sh calling-convention @var{convention}
16677 @kindex set sh calling-convention
16678 Set the calling-convention used when calling functions from @value{GDBN}.
16679 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
16680 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
16681 convention. If the DWARF-2 information of the called function specifies
16682 that the function follows the Renesas calling convention, the function
16683 is called using the Renesas calling convention. If the calling convention
16684 is set to @samp{renesas}, the Renesas calling convention is always used,
16685 regardless of the DWARF-2 information. This can be used to override the
16686 default of @samp{gcc} if debug information is missing, or the compiler
16687 does not emit the DWARF-2 calling convention entry for a function.
16689 @item show sh calling-convention
16690 @kindex show sh calling-convention
16691 Show the current calling convention setting.
16696 @node Architectures
16697 @section Architectures
16699 This section describes characteristics of architectures that affect
16700 all uses of @value{GDBN} with the architecture, both native and cross.
16707 * HPPA:: HP PA architecture
16708 * SPU:: Cell Broadband Engine SPU architecture
16713 @subsection x86 Architecture-specific Issues
16716 @item set struct-convention @var{mode}
16717 @kindex set struct-convention
16718 @cindex struct return convention
16719 @cindex struct/union returned in registers
16720 Set the convention used by the inferior to return @code{struct}s and
16721 @code{union}s from functions to @var{mode}. Possible values of
16722 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
16723 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
16724 are returned on the stack, while @code{"reg"} means that a
16725 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
16726 be returned in a register.
16728 @item show struct-convention
16729 @kindex show struct-convention
16730 Show the current setting of the convention to return @code{struct}s
16739 @kindex set rstack_high_address
16740 @cindex AMD 29K register stack
16741 @cindex register stack, AMD29K
16742 @item set rstack_high_address @var{address}
16743 On AMD 29000 family processors, registers are saved in a separate
16744 @dfn{register stack}. There is no way for @value{GDBN} to determine the
16745 extent of this stack. Normally, @value{GDBN} just assumes that the
16746 stack is ``large enough''. This may result in @value{GDBN} referencing
16747 memory locations that do not exist. If necessary, you can get around
16748 this problem by specifying the ending address of the register stack with
16749 the @code{set rstack_high_address} command. The argument should be an
16750 address, which you probably want to precede with @samp{0x} to specify in
16753 @kindex show rstack_high_address
16754 @item show rstack_high_address
16755 Display the current limit of the register stack, on AMD 29000 family
16763 See the following section.
16768 @cindex stack on Alpha
16769 @cindex stack on MIPS
16770 @cindex Alpha stack
16772 Alpha- and MIPS-based computers use an unusual stack frame, which
16773 sometimes requires @value{GDBN} to search backward in the object code to
16774 find the beginning of a function.
16776 @cindex response time, MIPS debugging
16777 To improve response time (especially for embedded applications, where
16778 @value{GDBN} may be restricted to a slow serial line for this search)
16779 you may want to limit the size of this search, using one of these
16783 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
16784 @item set heuristic-fence-post @var{limit}
16785 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
16786 search for the beginning of a function. A value of @var{0} (the
16787 default) means there is no limit. However, except for @var{0}, the
16788 larger the limit the more bytes @code{heuristic-fence-post} must search
16789 and therefore the longer it takes to run. You should only need to use
16790 this command when debugging a stripped executable.
16792 @item show heuristic-fence-post
16793 Display the current limit.
16797 These commands are available @emph{only} when @value{GDBN} is configured
16798 for debugging programs on Alpha or MIPS processors.
16800 Several MIPS-specific commands are available when debugging MIPS
16804 @item set mips abi @var{arg}
16805 @kindex set mips abi
16806 @cindex set ABI for MIPS
16807 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
16808 values of @var{arg} are:
16812 The default ABI associated with the current binary (this is the
16823 @item show mips abi
16824 @kindex show mips abi
16825 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
16828 @itemx show mipsfpu
16829 @xref{MIPS Embedded, set mipsfpu}.
16831 @item set mips mask-address @var{arg}
16832 @kindex set mips mask-address
16833 @cindex MIPS addresses, masking
16834 This command determines whether the most-significant 32 bits of 64-bit
16835 MIPS addresses are masked off. The argument @var{arg} can be
16836 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
16837 setting, which lets @value{GDBN} determine the correct value.
16839 @item show mips mask-address
16840 @kindex show mips mask-address
16841 Show whether the upper 32 bits of MIPS addresses are masked off or
16844 @item set remote-mips64-transfers-32bit-regs
16845 @kindex set remote-mips64-transfers-32bit-regs
16846 This command controls compatibility with 64-bit MIPS targets that
16847 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16848 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16849 and 64 bits for other registers, set this option to @samp{on}.
16851 @item show remote-mips64-transfers-32bit-regs
16852 @kindex show remote-mips64-transfers-32bit-regs
16853 Show the current setting of compatibility with older MIPS 64 targets.
16855 @item set debug mips
16856 @kindex set debug mips
16857 This command turns on and off debugging messages for the MIPS-specific
16858 target code in @value{GDBN}.
16860 @item show debug mips
16861 @kindex show debug mips
16862 Show the current setting of MIPS debugging messages.
16868 @cindex HPPA support
16870 When @value{GDBN} is debugging the HP PA architecture, it provides the
16871 following special commands:
16874 @item set debug hppa
16875 @kindex set debug hppa
16876 This command determines whether HPPA architecture-specific debugging
16877 messages are to be displayed.
16879 @item show debug hppa
16880 Show whether HPPA debugging messages are displayed.
16882 @item maint print unwind @var{address}
16883 @kindex maint print unwind@r{, HPPA}
16884 This command displays the contents of the unwind table entry at the
16885 given @var{address}.
16891 @subsection Cell Broadband Engine SPU architecture
16892 @cindex Cell Broadband Engine
16895 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
16896 it provides the following special commands:
16899 @item info spu event
16901 Display SPU event facility status. Shows current event mask
16902 and pending event status.
16904 @item info spu signal
16905 Display SPU signal notification facility status. Shows pending
16906 signal-control word and signal notification mode of both signal
16907 notification channels.
16909 @item info spu mailbox
16910 Display SPU mailbox facility status. Shows all pending entries,
16911 in order of processing, in each of the SPU Write Outbound,
16912 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
16915 Display MFC DMA status. Shows all pending commands in the MFC
16916 DMA queue. For each entry, opcode, tag, class IDs, effective
16917 and local store addresses and transfer size are shown.
16919 @item info spu proxydma
16920 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
16921 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
16922 and local store addresses and transfer size are shown.
16927 @subsection PowerPC
16928 @cindex PowerPC architecture
16930 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
16931 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
16932 numbers stored in the floating point registers. These values must be stored
16933 in two consecutive registers, always starting at an even register like
16934 @code{f0} or @code{f2}.
16936 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
16937 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
16938 @code{f2} and @code{f3} for @code{$dl1} and so on.
16940 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
16941 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
16944 @node Controlling GDB
16945 @chapter Controlling @value{GDBN}
16947 You can alter the way @value{GDBN} interacts with you by using the
16948 @code{set} command. For commands controlling how @value{GDBN} displays
16949 data, see @ref{Print Settings, ,Print Settings}. Other settings are
16954 * Editing:: Command editing
16955 * Command History:: Command history
16956 * Screen Size:: Screen size
16957 * Numbers:: Numbers
16958 * ABI:: Configuring the current ABI
16959 * Messages/Warnings:: Optional warnings and messages
16960 * Debugging Output:: Optional messages about internal happenings
16968 @value{GDBN} indicates its readiness to read a command by printing a string
16969 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
16970 can change the prompt string with the @code{set prompt} command. For
16971 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
16972 the prompt in one of the @value{GDBN} sessions so that you can always tell
16973 which one you are talking to.
16975 @emph{Note:} @code{set prompt} does not add a space for you after the
16976 prompt you set. This allows you to set a prompt which ends in a space
16977 or a prompt that does not.
16981 @item set prompt @var{newprompt}
16982 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
16984 @kindex show prompt
16986 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
16990 @section Command Editing
16992 @cindex command line editing
16994 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
16995 @sc{gnu} library provides consistent behavior for programs which provide a
16996 command line interface to the user. Advantages are @sc{gnu} Emacs-style
16997 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
16998 substitution, and a storage and recall of command history across
16999 debugging sessions.
17001 You may control the behavior of command line editing in @value{GDBN} with the
17002 command @code{set}.
17005 @kindex set editing
17008 @itemx set editing on
17009 Enable command line editing (enabled by default).
17011 @item set editing off
17012 Disable command line editing.
17014 @kindex show editing
17016 Show whether command line editing is enabled.
17019 @xref{Command Line Editing}, for more details about the Readline
17020 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
17021 encouraged to read that chapter.
17023 @node Command History
17024 @section Command History
17025 @cindex command history
17027 @value{GDBN} can keep track of the commands you type during your
17028 debugging sessions, so that you can be certain of precisely what
17029 happened. Use these commands to manage the @value{GDBN} command
17032 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
17033 package, to provide the history facility. @xref{Using History
17034 Interactively}, for the detailed description of the History library.
17036 To issue a command to @value{GDBN} without affecting certain aspects of
17037 the state which is seen by users, prefix it with @samp{server }
17038 (@pxref{Server Prefix}). This
17039 means that this command will not affect the command history, nor will it
17040 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
17041 pressed on a line by itself.
17043 @cindex @code{server}, command prefix
17044 The server prefix does not affect the recording of values into the value
17045 history; to print a value without recording it into the value history,
17046 use the @code{output} command instead of the @code{print} command.
17048 Here is the description of @value{GDBN} commands related to command
17052 @cindex history substitution
17053 @cindex history file
17054 @kindex set history filename
17055 @cindex @env{GDBHISTFILE}, environment variable
17056 @item set history filename @var{fname}
17057 Set the name of the @value{GDBN} command history file to @var{fname}.
17058 This is the file where @value{GDBN} reads an initial command history
17059 list, and where it writes the command history from this session when it
17060 exits. You can access this list through history expansion or through
17061 the history command editing characters listed below. This file defaults
17062 to the value of the environment variable @code{GDBHISTFILE}, or to
17063 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
17066 @cindex save command history
17067 @kindex set history save
17068 @item set history save
17069 @itemx set history save on
17070 Record command history in a file, whose name may be specified with the
17071 @code{set history filename} command. By default, this option is disabled.
17073 @item set history save off
17074 Stop recording command history in a file.
17076 @cindex history size
17077 @kindex set history size
17078 @cindex @env{HISTSIZE}, environment variable
17079 @item set history size @var{size}
17080 Set the number of commands which @value{GDBN} keeps in its history list.
17081 This defaults to the value of the environment variable
17082 @code{HISTSIZE}, or to 256 if this variable is not set.
17085 History expansion assigns special meaning to the character @kbd{!}.
17086 @xref{Event Designators}, for more details.
17088 @cindex history expansion, turn on/off
17089 Since @kbd{!} is also the logical not operator in C, history expansion
17090 is off by default. If you decide to enable history expansion with the
17091 @code{set history expansion on} command, you may sometimes need to
17092 follow @kbd{!} (when it is used as logical not, in an expression) with
17093 a space or a tab to prevent it from being expanded. The readline
17094 history facilities do not attempt substitution on the strings
17095 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
17097 The commands to control history expansion are:
17100 @item set history expansion on
17101 @itemx set history expansion
17102 @kindex set history expansion
17103 Enable history expansion. History expansion is off by default.
17105 @item set history expansion off
17106 Disable history expansion.
17109 @kindex show history
17111 @itemx show history filename
17112 @itemx show history save
17113 @itemx show history size
17114 @itemx show history expansion
17115 These commands display the state of the @value{GDBN} history parameters.
17116 @code{show history} by itself displays all four states.
17121 @kindex show commands
17122 @cindex show last commands
17123 @cindex display command history
17124 @item show commands
17125 Display the last ten commands in the command history.
17127 @item show commands @var{n}
17128 Print ten commands centered on command number @var{n}.
17130 @item show commands +
17131 Print ten commands just after the commands last printed.
17135 @section Screen Size
17136 @cindex size of screen
17137 @cindex pauses in output
17139 Certain commands to @value{GDBN} may produce large amounts of
17140 information output to the screen. To help you read all of it,
17141 @value{GDBN} pauses and asks you for input at the end of each page of
17142 output. Type @key{RET} when you want to continue the output, or @kbd{q}
17143 to discard the remaining output. Also, the screen width setting
17144 determines when to wrap lines of output. Depending on what is being
17145 printed, @value{GDBN} tries to break the line at a readable place,
17146 rather than simply letting it overflow onto the following line.
17148 Normally @value{GDBN} knows the size of the screen from the terminal
17149 driver software. For example, on Unix @value{GDBN} uses the termcap data base
17150 together with the value of the @code{TERM} environment variable and the
17151 @code{stty rows} and @code{stty cols} settings. If this is not correct,
17152 you can override it with the @code{set height} and @code{set
17159 @kindex show height
17160 @item set height @var{lpp}
17162 @itemx set width @var{cpl}
17164 These @code{set} commands specify a screen height of @var{lpp} lines and
17165 a screen width of @var{cpl} characters. The associated @code{show}
17166 commands display the current settings.
17168 If you specify a height of zero lines, @value{GDBN} does not pause during
17169 output no matter how long the output is. This is useful if output is to a
17170 file or to an editor buffer.
17172 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
17173 from wrapping its output.
17175 @item set pagination on
17176 @itemx set pagination off
17177 @kindex set pagination
17178 Turn the output pagination on or off; the default is on. Turning
17179 pagination off is the alternative to @code{set height 0}.
17181 @item show pagination
17182 @kindex show pagination
17183 Show the current pagination mode.
17188 @cindex number representation
17189 @cindex entering numbers
17191 You can always enter numbers in octal, decimal, or hexadecimal in
17192 @value{GDBN} by the usual conventions: octal numbers begin with
17193 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
17194 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
17195 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
17196 10; likewise, the default display for numbers---when no particular
17197 format is specified---is base 10. You can change the default base for
17198 both input and output with the commands described below.
17201 @kindex set input-radix
17202 @item set input-radix @var{base}
17203 Set the default base for numeric input. Supported choices
17204 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17205 specified either unambiguously or using the current input radix; for
17209 set input-radix 012
17210 set input-radix 10.
17211 set input-radix 0xa
17215 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
17216 leaves the input radix unchanged, no matter what it was, since
17217 @samp{10}, being without any leading or trailing signs of its base, is
17218 interpreted in the current radix. Thus, if the current radix is 16,
17219 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
17222 @kindex set output-radix
17223 @item set output-radix @var{base}
17224 Set the default base for numeric display. Supported choices
17225 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17226 specified either unambiguously or using the current input radix.
17228 @kindex show input-radix
17229 @item show input-radix
17230 Display the current default base for numeric input.
17232 @kindex show output-radix
17233 @item show output-radix
17234 Display the current default base for numeric display.
17236 @item set radix @r{[}@var{base}@r{]}
17240 These commands set and show the default base for both input and output
17241 of numbers. @code{set radix} sets the radix of input and output to
17242 the same base; without an argument, it resets the radix back to its
17243 default value of 10.
17248 @section Configuring the Current ABI
17250 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
17251 application automatically. However, sometimes you need to override its
17252 conclusions. Use these commands to manage @value{GDBN}'s view of the
17259 One @value{GDBN} configuration can debug binaries for multiple operating
17260 system targets, either via remote debugging or native emulation.
17261 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
17262 but you can override its conclusion using the @code{set osabi} command.
17263 One example where this is useful is in debugging of binaries which use
17264 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
17265 not have the same identifying marks that the standard C library for your
17270 Show the OS ABI currently in use.
17273 With no argument, show the list of registered available OS ABI's.
17275 @item set osabi @var{abi}
17276 Set the current OS ABI to @var{abi}.
17279 @cindex float promotion
17281 Generally, the way that an argument of type @code{float} is passed to a
17282 function depends on whether the function is prototyped. For a prototyped
17283 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
17284 according to the architecture's convention for @code{float}. For unprototyped
17285 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
17286 @code{double} and then passed.
17288 Unfortunately, some forms of debug information do not reliably indicate whether
17289 a function is prototyped. If @value{GDBN} calls a function that is not marked
17290 as prototyped, it consults @kbd{set coerce-float-to-double}.
17293 @kindex set coerce-float-to-double
17294 @item set coerce-float-to-double
17295 @itemx set coerce-float-to-double on
17296 Arguments of type @code{float} will be promoted to @code{double} when passed
17297 to an unprototyped function. This is the default setting.
17299 @item set coerce-float-to-double off
17300 Arguments of type @code{float} will be passed directly to unprototyped
17303 @kindex show coerce-float-to-double
17304 @item show coerce-float-to-double
17305 Show the current setting of promoting @code{float} to @code{double}.
17309 @kindex show cp-abi
17310 @value{GDBN} needs to know the ABI used for your program's C@t{++}
17311 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
17312 used to build your application. @value{GDBN} only fully supports
17313 programs with a single C@t{++} ABI; if your program contains code using
17314 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
17315 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
17316 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
17317 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
17318 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
17319 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
17324 Show the C@t{++} ABI currently in use.
17327 With no argument, show the list of supported C@t{++} ABI's.
17329 @item set cp-abi @var{abi}
17330 @itemx set cp-abi auto
17331 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
17334 @node Messages/Warnings
17335 @section Optional Warnings and Messages
17337 @cindex verbose operation
17338 @cindex optional warnings
17339 By default, @value{GDBN} is silent about its inner workings. If you are
17340 running on a slow machine, you may want to use the @code{set verbose}
17341 command. This makes @value{GDBN} tell you when it does a lengthy
17342 internal operation, so you will not think it has crashed.
17344 Currently, the messages controlled by @code{set verbose} are those
17345 which announce that the symbol table for a source file is being read;
17346 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
17349 @kindex set verbose
17350 @item set verbose on
17351 Enables @value{GDBN} output of certain informational messages.
17353 @item set verbose off
17354 Disables @value{GDBN} output of certain informational messages.
17356 @kindex show verbose
17358 Displays whether @code{set verbose} is on or off.
17361 By default, if @value{GDBN} encounters bugs in the symbol table of an
17362 object file, it is silent; but if you are debugging a compiler, you may
17363 find this information useful (@pxref{Symbol Errors, ,Errors Reading
17368 @kindex set complaints
17369 @item set complaints @var{limit}
17370 Permits @value{GDBN} to output @var{limit} complaints about each type of
17371 unusual symbols before becoming silent about the problem. Set
17372 @var{limit} to zero to suppress all complaints; set it to a large number
17373 to prevent complaints from being suppressed.
17375 @kindex show complaints
17376 @item show complaints
17377 Displays how many symbol complaints @value{GDBN} is permitted to produce.
17381 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
17382 lot of stupid questions to confirm certain commands. For example, if
17383 you try to run a program which is already running:
17387 The program being debugged has been started already.
17388 Start it from the beginning? (y or n)
17391 If you are willing to unflinchingly face the consequences of your own
17392 commands, you can disable this ``feature'':
17396 @kindex set confirm
17398 @cindex confirmation
17399 @cindex stupid questions
17400 @item set confirm off
17401 Disables confirmation requests.
17403 @item set confirm on
17404 Enables confirmation requests (the default).
17406 @kindex show confirm
17408 Displays state of confirmation requests.
17412 @cindex command tracing
17413 If you need to debug user-defined commands or sourced files you may find it
17414 useful to enable @dfn{command tracing}. In this mode each command will be
17415 printed as it is executed, prefixed with one or more @samp{+} symbols, the
17416 quantity denoting the call depth of each command.
17419 @kindex set trace-commands
17420 @cindex command scripts, debugging
17421 @item set trace-commands on
17422 Enable command tracing.
17423 @item set trace-commands off
17424 Disable command tracing.
17425 @item show trace-commands
17426 Display the current state of command tracing.
17429 @node Debugging Output
17430 @section Optional Messages about Internal Happenings
17431 @cindex optional debugging messages
17433 @value{GDBN} has commands that enable optional debugging messages from
17434 various @value{GDBN} subsystems; normally these commands are of
17435 interest to @value{GDBN} maintainers, or when reporting a bug. This
17436 section documents those commands.
17439 @kindex set exec-done-display
17440 @item set exec-done-display
17441 Turns on or off the notification of asynchronous commands'
17442 completion. When on, @value{GDBN} will print a message when an
17443 asynchronous command finishes its execution. The default is off.
17444 @kindex show exec-done-display
17445 @item show exec-done-display
17446 Displays the current setting of asynchronous command completion
17449 @cindex gdbarch debugging info
17450 @cindex architecture debugging info
17451 @item set debug arch
17452 Turns on or off display of gdbarch debugging info. The default is off
17454 @item show debug arch
17455 Displays the current state of displaying gdbarch debugging info.
17456 @item set debug aix-thread
17457 @cindex AIX threads
17458 Display debugging messages about inner workings of the AIX thread
17460 @item show debug aix-thread
17461 Show the current state of AIX thread debugging info display.
17462 @item set debug dwarf2-die
17463 @cindex DWARF2 DIEs
17464 Dump DWARF2 DIEs after they are read in.
17465 The value is the number of nesting levels to print.
17466 A value of zero turns off the display.
17467 @item show debug dwarf2-die
17468 Show the current state of DWARF2 DIE debugging.
17469 @item set debug displaced
17470 @cindex displaced stepping debugging info
17471 Turns on or off display of @value{GDBN} debugging info for the
17472 displaced stepping support. The default is off.
17473 @item show debug displaced
17474 Displays the current state of displaying @value{GDBN} debugging info
17475 related to displaced stepping.
17476 @item set debug event
17477 @cindex event debugging info
17478 Turns on or off display of @value{GDBN} event debugging info. The
17480 @item show debug event
17481 Displays the current state of displaying @value{GDBN} event debugging
17483 @item set debug expression
17484 @cindex expression debugging info
17485 Turns on or off display of debugging info about @value{GDBN}
17486 expression parsing. The default is off.
17487 @item show debug expression
17488 Displays the current state of displaying debugging info about
17489 @value{GDBN} expression parsing.
17490 @item set debug frame
17491 @cindex frame debugging info
17492 Turns on or off display of @value{GDBN} frame debugging info. The
17494 @item show debug frame
17495 Displays the current state of displaying @value{GDBN} frame debugging
17497 @item set debug infrun
17498 @cindex inferior debugging info
17499 Turns on or off display of @value{GDBN} debugging info for running the inferior.
17500 The default is off. @file{infrun.c} contains GDB's runtime state machine used
17501 for implementing operations such as single-stepping the inferior.
17502 @item show debug infrun
17503 Displays the current state of @value{GDBN} inferior debugging.
17504 @item set debug lin-lwp
17505 @cindex @sc{gnu}/Linux LWP debug messages
17506 @cindex Linux lightweight processes
17507 Turns on or off debugging messages from the Linux LWP debug support.
17508 @item show debug lin-lwp
17509 Show the current state of Linux LWP debugging messages.
17510 @item set debug lin-lwp-async
17511 @cindex @sc{gnu}/Linux LWP async debug messages
17512 @cindex Linux lightweight processes
17513 Turns on or off debugging messages from the Linux LWP async debug support.
17514 @item show debug lin-lwp-async
17515 Show the current state of Linux LWP async debugging messages.
17516 @item set debug observer
17517 @cindex observer debugging info
17518 Turns on or off display of @value{GDBN} observer debugging. This
17519 includes info such as the notification of observable events.
17520 @item show debug observer
17521 Displays the current state of observer debugging.
17522 @item set debug overload
17523 @cindex C@t{++} overload debugging info
17524 Turns on or off display of @value{GDBN} C@t{++} overload debugging
17525 info. This includes info such as ranking of functions, etc. The default
17527 @item show debug overload
17528 Displays the current state of displaying @value{GDBN} C@t{++} overload
17530 @cindex packets, reporting on stdout
17531 @cindex serial connections, debugging
17532 @cindex debug remote protocol
17533 @cindex remote protocol debugging
17534 @cindex display remote packets
17535 @item set debug remote
17536 Turns on or off display of reports on all packets sent back and forth across
17537 the serial line to the remote machine. The info is printed on the
17538 @value{GDBN} standard output stream. The default is off.
17539 @item show debug remote
17540 Displays the state of display of remote packets.
17541 @item set debug serial
17542 Turns on or off display of @value{GDBN} serial debugging info. The
17544 @item show debug serial
17545 Displays the current state of displaying @value{GDBN} serial debugging
17547 @item set debug solib-frv
17548 @cindex FR-V shared-library debugging
17549 Turns on or off debugging messages for FR-V shared-library code.
17550 @item show debug solib-frv
17551 Display the current state of FR-V shared-library code debugging
17553 @item set debug target
17554 @cindex target debugging info
17555 Turns on or off display of @value{GDBN} target debugging info. This info
17556 includes what is going on at the target level of GDB, as it happens. The
17557 default is 0. Set it to 1 to track events, and to 2 to also track the
17558 value of large memory transfers. Changes to this flag do not take effect
17559 until the next time you connect to a target or use the @code{run} command.
17560 @item show debug target
17561 Displays the current state of displaying @value{GDBN} target debugging
17563 @item set debug timestamp
17564 @cindex timestampping debugging info
17565 Turns on or off display of timestamps with @value{GDBN} debugging info.
17566 When enabled, seconds and microseconds are displayed before each debugging
17568 @item show debug timestamp
17569 Displays the current state of displaying timestamps with @value{GDBN}
17571 @item set debugvarobj
17572 @cindex variable object debugging info
17573 Turns on or off display of @value{GDBN} variable object debugging
17574 info. The default is off.
17575 @item show debugvarobj
17576 Displays the current state of displaying @value{GDBN} variable object
17578 @item set debug xml
17579 @cindex XML parser debugging
17580 Turns on or off debugging messages for built-in XML parsers.
17581 @item show debug xml
17582 Displays the current state of XML debugging messages.
17585 @node Extending GDB
17586 @chapter Extending @value{GDBN}
17587 @cindex extending GDB
17589 @value{GDBN} provides two mechanisms for extension. The first is based
17590 on composition of @value{GDBN} commands, and the second is based on the
17591 Python scripting language.
17594 * Sequences:: Canned Sequences of Commands
17595 * Python:: Scripting @value{GDBN} using Python
17599 @section Canned Sequences of Commands
17601 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
17602 Command Lists}), @value{GDBN} provides two ways to store sequences of
17603 commands for execution as a unit: user-defined commands and command
17607 * Define:: How to define your own commands
17608 * Hooks:: Hooks for user-defined commands
17609 * Command Files:: How to write scripts of commands to be stored in a file
17610 * Output:: Commands for controlled output
17614 @subsection User-defined Commands
17616 @cindex user-defined command
17617 @cindex arguments, to user-defined commands
17618 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
17619 which you assign a new name as a command. This is done with the
17620 @code{define} command. User commands may accept up to 10 arguments
17621 separated by whitespace. Arguments are accessed within the user command
17622 via @code{$arg0@dots{}$arg9}. A trivial example:
17626 print $arg0 + $arg1 + $arg2
17631 To execute the command use:
17638 This defines the command @code{adder}, which prints the sum of
17639 its three arguments. Note the arguments are text substitutions, so they may
17640 reference variables, use complex expressions, or even perform inferior
17643 @cindex argument count in user-defined commands
17644 @cindex how many arguments (user-defined commands)
17645 In addition, @code{$argc} may be used to find out how many arguments have
17646 been passed. This expands to a number in the range 0@dots{}10.
17651 print $arg0 + $arg1
17654 print $arg0 + $arg1 + $arg2
17662 @item define @var{commandname}
17663 Define a command named @var{commandname}. If there is already a command
17664 by that name, you are asked to confirm that you want to redefine it.
17665 @var{commandname} may be a bare command name consisting of letters,
17666 numbers, dashes, and underscores. It may also start with any predefined
17667 prefix command. For example, @samp{define target my-target} creates
17668 a user-defined @samp{target my-target} command.
17670 The definition of the command is made up of other @value{GDBN} command lines,
17671 which are given following the @code{define} command. The end of these
17672 commands is marked by a line containing @code{end}.
17675 @kindex end@r{ (user-defined commands)}
17676 @item document @var{commandname}
17677 Document the user-defined command @var{commandname}, so that it can be
17678 accessed by @code{help}. The command @var{commandname} must already be
17679 defined. This command reads lines of documentation just as @code{define}
17680 reads the lines of the command definition, ending with @code{end}.
17681 After the @code{document} command is finished, @code{help} on command
17682 @var{commandname} displays the documentation you have written.
17684 You may use the @code{document} command again to change the
17685 documentation of a command. Redefining the command with @code{define}
17686 does not change the documentation.
17688 @kindex dont-repeat
17689 @cindex don't repeat command
17691 Used inside a user-defined command, this tells @value{GDBN} that this
17692 command should not be repeated when the user hits @key{RET}
17693 (@pxref{Command Syntax, repeat last command}).
17695 @kindex help user-defined
17696 @item help user-defined
17697 List all user-defined commands, with the first line of the documentation
17702 @itemx show user @var{commandname}
17703 Display the @value{GDBN} commands used to define @var{commandname} (but
17704 not its documentation). If no @var{commandname} is given, display the
17705 definitions for all user-defined commands.
17707 @cindex infinite recursion in user-defined commands
17708 @kindex show max-user-call-depth
17709 @kindex set max-user-call-depth
17710 @item show max-user-call-depth
17711 @itemx set max-user-call-depth
17712 The value of @code{max-user-call-depth} controls how many recursion
17713 levels are allowed in user-defined commands before @value{GDBN} suspects an
17714 infinite recursion and aborts the command.
17717 In addition to the above commands, user-defined commands frequently
17718 use control flow commands, described in @ref{Command Files}.
17720 When user-defined commands are executed, the
17721 commands of the definition are not printed. An error in any command
17722 stops execution of the user-defined command.
17724 If used interactively, commands that would ask for confirmation proceed
17725 without asking when used inside a user-defined command. Many @value{GDBN}
17726 commands that normally print messages to say what they are doing omit the
17727 messages when used in a user-defined command.
17730 @subsection User-defined Command Hooks
17731 @cindex command hooks
17732 @cindex hooks, for commands
17733 @cindex hooks, pre-command
17736 You may define @dfn{hooks}, which are a special kind of user-defined
17737 command. Whenever you run the command @samp{foo}, if the user-defined
17738 command @samp{hook-foo} exists, it is executed (with no arguments)
17739 before that command.
17741 @cindex hooks, post-command
17743 A hook may also be defined which is run after the command you executed.
17744 Whenever you run the command @samp{foo}, if the user-defined command
17745 @samp{hookpost-foo} exists, it is executed (with no arguments) after
17746 that command. Post-execution hooks may exist simultaneously with
17747 pre-execution hooks, for the same command.
17749 It is valid for a hook to call the command which it hooks. If this
17750 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
17752 @c It would be nice if hookpost could be passed a parameter indicating
17753 @c if the command it hooks executed properly or not. FIXME!
17755 @kindex stop@r{, a pseudo-command}
17756 In addition, a pseudo-command, @samp{stop} exists. Defining
17757 (@samp{hook-stop}) makes the associated commands execute every time
17758 execution stops in your program: before breakpoint commands are run,
17759 displays are printed, or the stack frame is printed.
17761 For example, to ignore @code{SIGALRM} signals while
17762 single-stepping, but treat them normally during normal execution,
17767 handle SIGALRM nopass
17771 handle SIGALRM pass
17774 define hook-continue
17775 handle SIGALRM pass
17779 As a further example, to hook at the beginning and end of the @code{echo}
17780 command, and to add extra text to the beginning and end of the message,
17788 define hookpost-echo
17792 (@value{GDBP}) echo Hello World
17793 <<<---Hello World--->>>
17798 You can define a hook for any single-word command in @value{GDBN}, but
17799 not for command aliases; you should define a hook for the basic command
17800 name, e.g.@: @code{backtrace} rather than @code{bt}.
17801 @c FIXME! So how does Joe User discover whether a command is an alias
17803 You can hook a multi-word command by adding @code{hook-} or
17804 @code{hookpost-} to the last word of the command, e.g.@:
17805 @samp{define target hook-remote} to add a hook to @samp{target remote}.
17807 If an error occurs during the execution of your hook, execution of
17808 @value{GDBN} commands stops and @value{GDBN} issues a prompt
17809 (before the command that you actually typed had a chance to run).
17811 If you try to define a hook which does not match any known command, you
17812 get a warning from the @code{define} command.
17814 @node Command Files
17815 @subsection Command Files
17817 @cindex command files
17818 @cindex scripting commands
17819 A command file for @value{GDBN} is a text file made of lines that are
17820 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
17821 also be included. An empty line in a command file does nothing; it
17822 does not mean to repeat the last command, as it would from the
17825 You can request the execution of a command file with the @code{source}
17830 @cindex execute commands from a file
17831 @item source [@code{-v}] @var{filename}
17832 Execute the command file @var{filename}.
17835 The lines in a command file are generally executed sequentially,
17836 unless the order of execution is changed by one of the
17837 @emph{flow-control commands} described below. The commands are not
17838 printed as they are executed. An error in any command terminates
17839 execution of the command file and control is returned to the console.
17841 @value{GDBN} searches for @var{filename} in the current directory and then
17842 on the search path (specified with the @samp{directory} command).
17844 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
17845 each command as it is executed. The option must be given before
17846 @var{filename}, and is interpreted as part of the filename anywhere else.
17848 Commands that would ask for confirmation if used interactively proceed
17849 without asking when used in a command file. Many @value{GDBN} commands that
17850 normally print messages to say what they are doing omit the messages
17851 when called from command files.
17853 @value{GDBN} also accepts command input from standard input. In this
17854 mode, normal output goes to standard output and error output goes to
17855 standard error. Errors in a command file supplied on standard input do
17856 not terminate execution of the command file---execution continues with
17860 gdb < cmds > log 2>&1
17863 (The syntax above will vary depending on the shell used.) This example
17864 will execute commands from the file @file{cmds}. All output and errors
17865 would be directed to @file{log}.
17867 Since commands stored on command files tend to be more general than
17868 commands typed interactively, they frequently need to deal with
17869 complicated situations, such as different or unexpected values of
17870 variables and symbols, changes in how the program being debugged is
17871 built, etc. @value{GDBN} provides a set of flow-control commands to
17872 deal with these complexities. Using these commands, you can write
17873 complex scripts that loop over data structures, execute commands
17874 conditionally, etc.
17881 This command allows to include in your script conditionally executed
17882 commands. The @code{if} command takes a single argument, which is an
17883 expression to evaluate. It is followed by a series of commands that
17884 are executed only if the expression is true (its value is nonzero).
17885 There can then optionally be an @code{else} line, followed by a series
17886 of commands that are only executed if the expression was false. The
17887 end of the list is marked by a line containing @code{end}.
17891 This command allows to write loops. Its syntax is similar to
17892 @code{if}: the command takes a single argument, which is an expression
17893 to evaluate, and must be followed by the commands to execute, one per
17894 line, terminated by an @code{end}. These commands are called the
17895 @dfn{body} of the loop. The commands in the body of @code{while} are
17896 executed repeatedly as long as the expression evaluates to true.
17900 This command exits the @code{while} loop in whose body it is included.
17901 Execution of the script continues after that @code{while}s @code{end}
17904 @kindex loop_continue
17905 @item loop_continue
17906 This command skips the execution of the rest of the body of commands
17907 in the @code{while} loop in whose body it is included. Execution
17908 branches to the beginning of the @code{while} loop, where it evaluates
17909 the controlling expression.
17911 @kindex end@r{ (if/else/while commands)}
17913 Terminate the block of commands that are the body of @code{if},
17914 @code{else}, or @code{while} flow-control commands.
17919 @subsection Commands for Controlled Output
17921 During the execution of a command file or a user-defined command, normal
17922 @value{GDBN} output is suppressed; the only output that appears is what is
17923 explicitly printed by the commands in the definition. This section
17924 describes three commands useful for generating exactly the output you
17929 @item echo @var{text}
17930 @c I do not consider backslash-space a standard C escape sequence
17931 @c because it is not in ANSI.
17932 Print @var{text}. Nonprinting characters can be included in
17933 @var{text} using C escape sequences, such as @samp{\n} to print a
17934 newline. @strong{No newline is printed unless you specify one.}
17935 In addition to the standard C escape sequences, a backslash followed
17936 by a space stands for a space. This is useful for displaying a
17937 string with spaces at the beginning or the end, since leading and
17938 trailing spaces are otherwise trimmed from all arguments.
17939 To print @samp{@w{ }and foo =@w{ }}, use the command
17940 @samp{echo \@w{ }and foo = \@w{ }}.
17942 A backslash at the end of @var{text} can be used, as in C, to continue
17943 the command onto subsequent lines. For example,
17946 echo This is some text\n\
17947 which is continued\n\
17948 onto several lines.\n
17951 produces the same output as
17954 echo This is some text\n
17955 echo which is continued\n
17956 echo onto several lines.\n
17960 @item output @var{expression}
17961 Print the value of @var{expression} and nothing but that value: no
17962 newlines, no @samp{$@var{nn} = }. The value is not entered in the
17963 value history either. @xref{Expressions, ,Expressions}, for more information
17966 @item output/@var{fmt} @var{expression}
17967 Print the value of @var{expression} in format @var{fmt}. You can use
17968 the same formats as for @code{print}. @xref{Output Formats,,Output
17969 Formats}, for more information.
17972 @item printf @var{template}, @var{expressions}@dots{}
17973 Print the values of one or more @var{expressions} under the control of
17974 the string @var{template}. To print several values, make
17975 @var{expressions} be a comma-separated list of individual expressions,
17976 which may be either numbers or pointers. Their values are printed as
17977 specified by @var{template}, exactly as a C program would do by
17978 executing the code below:
17981 printf (@var{template}, @var{expressions}@dots{});
17984 As in @code{C} @code{printf}, ordinary characters in @var{template}
17985 are printed verbatim, while @dfn{conversion specification} introduced
17986 by the @samp{%} character cause subsequent @var{expressions} to be
17987 evaluated, their values converted and formatted according to type and
17988 style information encoded in the conversion specifications, and then
17991 For example, you can print two values in hex like this:
17994 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
17997 @code{printf} supports all the standard @code{C} conversion
17998 specifications, including the flags and modifiers between the @samp{%}
17999 character and the conversion letter, with the following exceptions:
18003 The argument-ordering modifiers, such as @samp{2$}, are not supported.
18006 The modifier @samp{*} is not supported for specifying precision or
18010 The @samp{'} flag (for separation of digits into groups according to
18011 @code{LC_NUMERIC'}) is not supported.
18014 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
18018 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
18021 The conversion letters @samp{a} and @samp{A} are not supported.
18025 Note that the @samp{ll} type modifier is supported only if the
18026 underlying @code{C} implementation used to build @value{GDBN} supports
18027 the @code{long long int} type, and the @samp{L} type modifier is
18028 supported only if @code{long double} type is available.
18030 As in @code{C}, @code{printf} supports simple backslash-escape
18031 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
18032 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
18033 single character. Octal and hexadecimal escape sequences are not
18036 Additionally, @code{printf} supports conversion specifications for DFP
18037 (@dfn{Decimal Floating Point}) types using the following length modifiers
18038 together with a floating point specifier.
18043 @samp{H} for printing @code{Decimal32} types.
18046 @samp{D} for printing @code{Decimal64} types.
18049 @samp{DD} for printing @code{Decimal128} types.
18052 If the underlying @code{C} implementation used to build @value{GDBN} has
18053 support for the three length modifiers for DFP types, other modifiers
18054 such as width and precision will also be available for @value{GDBN} to use.
18056 In case there is no such @code{C} support, no additional modifiers will be
18057 available and the value will be printed in the standard way.
18059 Here's an example of printing DFP types using the above conversion letters:
18061 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
18067 @section Scripting @value{GDBN} using Python
18068 @cindex python scripting
18069 @cindex scripting with python
18071 You can script @value{GDBN} using the @uref{http://www.python.org/,
18072 Python programming language}. This feature is available only if
18073 @value{GDBN} was configured using @option{--with-python}.
18076 * Python Commands:: Accessing Python from @value{GDBN}.
18077 * Python API:: Accessing @value{GDBN} from Python.
18080 @node Python Commands
18081 @subsection Python Commands
18082 @cindex python commands
18083 @cindex commands to access python
18085 @value{GDBN} provides one command for accessing the Python interpreter,
18086 and one related setting:
18090 @item python @r{[}@var{code}@r{]}
18091 The @code{python} command can be used to evaluate Python code.
18093 If given an argument, the @code{python} command will evaluate the
18094 argument as a Python command. For example:
18097 (@value{GDBP}) python print 23
18101 If you do not provide an argument to @code{python}, it will act as a
18102 multi-line command, like @code{define}. In this case, the Python
18103 script is made up of subsequent command lines, given after the
18104 @code{python} command. This command list is terminated using a line
18105 containing @code{end}. For example:
18108 (@value{GDBP}) python
18110 End with a line saying just "end".
18116 @kindex maint set python print-stack
18117 @item maint set python print-stack
18118 By default, @value{GDBN} will print a stack trace when an error occurs
18119 in a Python script. This can be controlled using @code{maint set
18120 python print-stack}: if @code{on}, the default, then Python stack
18121 printing is enabled; if @code{off}, then Python stack printing is
18126 @subsection Python API
18128 @cindex programming in python
18130 @cindex python stdout
18131 @cindex python pagination
18132 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
18133 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
18134 A Python program which outputs to one of these streams may have its
18135 output interrupted by the user (@pxref{Screen Size}). In this
18136 situation, a Python @code{KeyboardInterrupt} exception is thrown.
18139 * Basic Python:: Basic Python Functions.
18140 * Exception Handling::
18141 * Values From Inferior::
18142 * Commands In Python:: Implementing new commands in Python.
18146 @subsubsection Basic Python
18148 @cindex python functions
18149 @cindex python module
18151 @value{GDBN} introduces a new Python module, named @code{gdb}. All
18152 methods and classes added by @value{GDBN} are placed in this module.
18153 @value{GDBN} automatically @code{import}s the @code{gdb} module for
18154 use in all scripts evaluated by the @code{python} command.
18156 @findex gdb.execute
18157 @defun execute command [from_tty]
18158 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
18159 If a GDB exception happens while @var{command} runs, it is
18160 translated as described in @ref{Exception Handling,,Exception Handling}.
18161 If no exceptions occur, this function returns @code{None}.
18163 @var{from_tty} specifies whether @value{GDBN} ought to consider this
18164 command as having originated from the user invoking it interactively.
18165 It must be a boolean value. If omitted, it defaults to @code{False}.
18168 @findex gdb.get_parameter
18169 @defun get_parameter parameter
18170 Return the value of a @value{GDBN} parameter. @var{parameter} is a
18171 string naming the parameter to look up; @var{parameter} may contain
18172 spaces if the parameter has a multi-part name. For example,
18173 @samp{print object} is a valid parameter name.
18175 If the named parameter does not exist, this function throws a
18176 @code{RuntimeError}. Otherwise, the parameter's value is converted to
18177 a Python value of the appropriate type, and returned.
18180 @findex gdb.history
18181 @defun history number
18182 Return a value from @value{GDBN}'s value history (@pxref{Value
18183 History}). @var{number} indicates which history element to return.
18184 If @var{number} is negative, then @value{GDBN} will take its absolute value
18185 and count backward from the last element (i.e., the most recent element) to
18186 find the value to return. If @var{number} is zero, then @value{GDBN} will
18187 return the most recent element. If the element specified by @var{number}
18188 doesn't exist in the value history, a @code{RuntimeError} exception will be
18191 If no exception is raised, the return value is always an instance of
18192 @code{gdb.Value} (@pxref{Values From Inferior}).
18196 @defun write string
18197 Print a string to @value{GDBN}'s paginated standard output stream.
18198 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
18199 call this function.
18204 Flush @value{GDBN}'s paginated standard output stream. Flushing
18205 @code{sys.stdout} or @code{sys.stderr} will automatically call this
18209 @node Exception Handling
18210 @subsubsection Exception Handling
18211 @cindex python exceptions
18212 @cindex exceptions, python
18214 When executing the @code{python} command, Python exceptions
18215 uncaught within the Python code are translated to calls to
18216 @value{GDBN} error-reporting mechanism. If the command that called
18217 @code{python} does not handle the error, @value{GDBN} will
18218 terminate it and print an error message containing the Python
18219 exception name, the associated value, and the Python call stack
18220 backtrace at the point where the exception was raised. Example:
18223 (@value{GDBP}) python print foo
18224 Traceback (most recent call last):
18225 File "<string>", line 1, in <module>
18226 NameError: name 'foo' is not defined
18229 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
18230 code are converted to Python @code{RuntimeError} exceptions. User
18231 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
18232 prompt) is translated to a Python @code{KeyboardInterrupt}
18233 exception. If you catch these exceptions in your Python code, your
18234 exception handler will see @code{RuntimeError} or
18235 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
18236 message as its value, and the Python call stack backtrace at the
18237 Python statement closest to where the @value{GDBN} error occured as the
18240 @node Values From Inferior
18241 @subsubsection Values From Inferior
18242 @cindex values from inferior, with Python
18243 @cindex python, working with values from inferior
18245 @cindex @code{gdb.Value}
18246 @value{GDBN} provides values it obtains from the inferior program in
18247 an object of type @code{gdb.Value}. @value{GDBN} uses this object
18248 for its internal bookkeeping of the inferior's values, and for
18249 fetching values when necessary.
18251 Inferior values that are simple scalars can be used directly in
18252 Python expressions that are valid for the value's data type. Here's
18253 an example for an integer or floating-point value @code{some_val}:
18260 As result of this, @code{bar} will also be a @code{gdb.Value} object
18261 whose values are of the same type as those of @code{some_val}.
18263 Inferior values that are structures or instances of some class can
18264 be accessed using the Python @dfn{dictionary syntax}. For example, if
18265 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
18266 can access its @code{foo} element with:
18269 bar = some_val['foo']
18272 Again, @code{bar} will also be a @code{gdb.Value} object.
18274 For pointer data types, @code{gdb.Value} provides a method for
18275 dereferencing the pointer to obtain the object it points to.
18277 @defmethod Value dereference
18278 This method returns a new @code{gdb.Value} object whose contents is
18279 the object pointed to by the pointer. For example, if @code{foo} is
18280 a C pointer to an @code{int}, declared in your C program as
18287 then you can use the corresponding @code{gdb.Value} to access what
18288 @code{foo} points to like this:
18291 bar = foo.dereference ()
18294 The result @code{bar} will be a @code{gdb.Value} object holding the
18295 value pointed to by @code{foo}.
18298 @defmethod Value string @r{[}encoding @r{[}errors@r{]}@r{]}
18299 If this @code{gdb.Value} represents a string, then this method
18300 converts the contents to a Python string. Otherwise, this method will
18301 throw an exception.
18303 Strings are recognized in a language-specific way; whether a given
18304 @code{gdb.Value} represents a string is determined by the current
18307 For C-like languages, a value is a string if it is a pointer to or an
18308 array of characters or ints. The string is assumed to be terminated
18309 by a zero of the appropriate width.
18311 If the optional @var{encoding} argument is given, it must be a string
18312 naming the encoding of the string in the @code{gdb.Value}, such as
18313 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
18314 the same encodings as the corresponding argument to Python's
18315 @code{string.decode} method, and the Python codec machinery will be used
18316 to convert the string. If @var{encoding} is not given, or if
18317 @var{encoding} is the empty string, then either the @code{target-charset}
18318 (@pxref{Character Sets}) will be used, or a language-specific encoding
18319 will be used, if the current language is able to supply one.
18321 The optional @var{errors} argument is the same as the corresponding
18322 argument to Python's @code{string.decode} method.
18325 @node Commands In Python
18326 @subsubsection Commands In Python
18328 @cindex commands in python
18329 @cindex python commands
18331 @tindex gdb.Command
18332 You can implement new @value{GDBN} CLI commands in Python. A CLI
18333 command is implemented using an instance of the @code{gdb.Command}
18334 class, most commonly using a subclass.
18336 @defmethod Command __init__ name @var{command-class} @r{[}@var{completer-class} @var{prefix}@r{]}
18337 The object initializer for @code{Command} registers the new command
18338 with @value{GDBN}. This initializer is normally invoked from the
18339 subclass' own @code{__init__} method.
18341 @var{name} is the name of the command. If @var{name} consists of
18342 multiple words, then the initial words are looked for as prefix
18343 commands. In this case, if one of the prefix commands does not exist,
18344 an exception is raised.
18346 There is no support for multi-line commands.
18348 @var{command-class} should be one of the @samp{COMMAND_} constants
18349 defined below. This argument tells @value{GDBN} how to categorize the
18350 new command in the help system.
18352 @var{completer-class} is an optional argument. If given, it should be
18353 one of the @samp{COMPLETE_} constants defined below. This argument
18354 tells @value{GDBN} how to perform completion for this command. If not
18355 given, @value{GDBN} will attempt to complete using the object's
18356 @code{complete} method (see below); if no such method is found, an
18357 error will occur when completion is attempted.
18359 @var{prefix} is an optional argument. If @code{True}, then the new
18360 command is a prefix command; sub-commands of this command may be
18363 The help text for the new command is taken from the Python
18364 documentation string for the command's class, if there is one. If no
18365 documentation string is provided, the default value ``This command is
18366 not documented.'' is used.
18369 @cindex don't repeat Python command
18370 @defmethod Command dont_repeat
18371 By default, a @value{GDBN} command is repeated when the user enters a
18372 blank line at the command prompt. A command can suppress this
18373 behavior by invoking the @code{dont_repeat} method. This is similar
18374 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
18377 @defmethod Command invoke argument from_tty
18378 This method is called by @value{GDBN} when this command is invoked.
18380 @var{argument} is a string. It is the argument to the command, after
18381 leading and trailing whitespace has been stripped.
18383 @var{from_tty} is a boolean argument. When true, this means that the
18384 command was entered by the user at the terminal; when false it means
18385 that the command came from elsewhere.
18387 If this method throws an exception, it is turned into a @value{GDBN}
18388 @code{error} call. Otherwise, the return value is ignored.
18391 @cindex completion of Python commands
18392 @defmethod Command complete text word
18393 This method is called by @value{GDBN} when the user attempts
18394 completion on this command. All forms of completion are handled by
18395 this method, that is, the @key{TAB} and @key{M-?} key bindings
18396 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
18399 The arguments @var{text} and @var{word} are both strings. @var{text}
18400 holds the complete command line up to the cursor's location.
18401 @var{word} holds the last word of the command line; this is computed
18402 using a word-breaking heuristic.
18404 The @code{complete} method can return several values:
18407 If the return value is a sequence, the contents of the sequence are
18408 used as the completions. It is up to @code{complete} to ensure that the
18409 contents actually do complete the word. A zero-length sequence is
18410 allowed, it means that there were no completions available. Only
18411 string elements of the sequence are used; other elements in the
18412 sequence are ignored.
18415 If the return value is one of the @samp{COMPLETE_} constants defined
18416 below, then the corresponding @value{GDBN}-internal completion
18417 function is invoked, and its result is used.
18420 All other results are treated as though there were no available
18425 When a new command is registered, it must be declared as a member of
18426 some general class of commands. This is used to classify top-level
18427 commands in the on-line help system; note that prefix commands are not
18428 listed under their own category but rather that of their top-level
18429 command. The available classifications are represented by constants
18430 defined in the @code{gdb} module:
18433 @findex COMMAND_NONE
18434 @findex gdb.COMMAND_NONE
18436 The command does not belong to any particular class. A command in
18437 this category will not be displayed in any of the help categories.
18439 @findex COMMAND_RUNNING
18440 @findex gdb.COMMAND_RUNNING
18441 @item COMMAND_RUNNING
18442 The command is related to running the inferior. For example,
18443 @code{start}, @code{step}, and @code{continue} are in this category.
18444 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
18445 commands in this category.
18447 @findex COMMAND_DATA
18448 @findex gdb.COMMAND_DATA
18450 The command is related to data or variables. For example,
18451 @code{call}, @code{find}, and @code{print} are in this category. Type
18452 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
18455 @findex COMMAND_STACK
18456 @findex gdb.COMMAND_STACK
18457 @item COMMAND_STACK
18458 The command has to do with manipulation of the stack. For example,
18459 @code{backtrace}, @code{frame}, and @code{return} are in this
18460 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
18461 list of commands in this category.
18463 @findex COMMAND_FILES
18464 @findex gdb.COMMAND_FILES
18465 @item COMMAND_FILES
18466 This class is used for file-related commands. For example,
18467 @code{file}, @code{list} and @code{section} are in this category.
18468 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
18469 commands in this category.
18471 @findex COMMAND_SUPPORT
18472 @findex gdb.COMMAND_SUPPORT
18473 @item COMMAND_SUPPORT
18474 This should be used for ``support facilities'', generally meaning
18475 things that are useful to the user when interacting with @value{GDBN},
18476 but not related to the state of the inferior. For example,
18477 @code{help}, @code{make}, and @code{shell} are in this category. Type
18478 @kbd{help support} at the @value{GDBN} prompt to see a list of
18479 commands in this category.
18481 @findex COMMAND_STATUS
18482 @findex gdb.COMMAND_STATUS
18483 @item COMMAND_STATUS
18484 The command is an @samp{info}-related command, that is, related to the
18485 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
18486 and @code{show} are in this category. Type @kbd{help status} at the
18487 @value{GDBN} prompt to see a list of commands in this category.
18489 @findex COMMAND_BREAKPOINTS
18490 @findex gdb.COMMAND_BREAKPOINTS
18491 @item COMMAND_BREAKPOINTS
18492 The command has to do with breakpoints. For example, @code{break},
18493 @code{clear}, and @code{delete} are in this category. Type @kbd{help
18494 breakpoints} at the @value{GDBN} prompt to see a list of commands in
18497 @findex COMMAND_TRACEPOINTS
18498 @findex gdb.COMMAND_TRACEPOINTS
18499 @item COMMAND_TRACEPOINTS
18500 The command has to do with tracepoints. For example, @code{trace},
18501 @code{actions}, and @code{tfind} are in this category. Type
18502 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
18503 commands in this category.
18505 @findex COMMAND_OBSCURE
18506 @findex gdb.COMMAND_OBSCURE
18507 @item COMMAND_OBSCURE
18508 The command is only used in unusual circumstances, or is not of
18509 general interest to users. For example, @code{checkpoint},
18510 @code{fork}, and @code{stop} are in this category. Type @kbd{help
18511 obscure} at the @value{GDBN} prompt to see a list of commands in this
18514 @findex COMMAND_MAINTENANCE
18515 @findex gdb.COMMAND_MAINTENANCE
18516 @item COMMAND_MAINTENANCE
18517 The command is only useful to @value{GDBN} maintainers. The
18518 @code{maintenance} and @code{flushregs} commands are in this category.
18519 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
18520 commands in this category.
18523 A new command can use a predefined completion function, either by
18524 specifying it via an argument at initialization, or by returning it
18525 from the @code{complete} method. These predefined completion
18526 constants are all defined in the @code{gdb} module:
18529 @findex COMPLETE_NONE
18530 @findex gdb.COMPLETE_NONE
18531 @item COMPLETE_NONE
18532 This constant means that no completion should be done.
18534 @findex COMPLETE_FILENAME
18535 @findex gdb.COMPLETE_FILENAME
18536 @item COMPLETE_FILENAME
18537 This constant means that filename completion should be performed.
18539 @findex COMPLETE_LOCATION
18540 @findex gdb.COMPLETE_LOCATION
18541 @item COMPLETE_LOCATION
18542 This constant means that location completion should be done.
18543 @xref{Specify Location}.
18545 @findex COMPLETE_COMMAND
18546 @findex gdb.COMPLETE_COMMAND
18547 @item COMPLETE_COMMAND
18548 This constant means that completion should examine @value{GDBN}
18551 @findex COMPLETE_SYMBOL
18552 @findex gdb.COMPLETE_SYMBOL
18553 @item COMPLETE_SYMBOL
18554 This constant means that completion should be done using symbol names
18558 The following code snippet shows how a trivial CLI command can be
18559 implemented in Python:
18562 class HelloWorld (gdb.Command):
18563 """Greet the whole world."""
18565 def __init__ (self):
18566 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
18568 def invoke (self, arg, from_tty):
18569 print "Hello, World!"
18574 The last line instantiates the class, and is necessary to trigger the
18575 registration of the command with @value{GDBN}. Depending on how the
18576 Python code is read into @value{GDBN}, you may need to import the
18577 @code{gdb} module explicitly.
18580 @chapter Command Interpreters
18581 @cindex command interpreters
18583 @value{GDBN} supports multiple command interpreters, and some command
18584 infrastructure to allow users or user interface writers to switch
18585 between interpreters or run commands in other interpreters.
18587 @value{GDBN} currently supports two command interpreters, the console
18588 interpreter (sometimes called the command-line interpreter or @sc{cli})
18589 and the machine interface interpreter (or @sc{gdb/mi}). This manual
18590 describes both of these interfaces in great detail.
18592 By default, @value{GDBN} will start with the console interpreter.
18593 However, the user may choose to start @value{GDBN} with another
18594 interpreter by specifying the @option{-i} or @option{--interpreter}
18595 startup options. Defined interpreters include:
18599 @cindex console interpreter
18600 The traditional console or command-line interpreter. This is the most often
18601 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
18602 @value{GDBN} will use this interpreter.
18605 @cindex mi interpreter
18606 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
18607 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
18608 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
18612 @cindex mi2 interpreter
18613 The current @sc{gdb/mi} interface.
18616 @cindex mi1 interpreter
18617 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
18621 @cindex invoke another interpreter
18622 The interpreter being used by @value{GDBN} may not be dynamically
18623 switched at runtime. Although possible, this could lead to a very
18624 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
18625 enters the command "interpreter-set console" in a console view,
18626 @value{GDBN} would switch to using the console interpreter, rendering
18627 the IDE inoperable!
18629 @kindex interpreter-exec
18630 Although you may only choose a single interpreter at startup, you may execute
18631 commands in any interpreter from the current interpreter using the appropriate
18632 command. If you are running the console interpreter, simply use the
18633 @code{interpreter-exec} command:
18636 interpreter-exec mi "-data-list-register-names"
18639 @sc{gdb/mi} has a similar command, although it is only available in versions of
18640 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
18643 @chapter @value{GDBN} Text User Interface
18645 @cindex Text User Interface
18648 * TUI Overview:: TUI overview
18649 * TUI Keys:: TUI key bindings
18650 * TUI Single Key Mode:: TUI single key mode
18651 * TUI Commands:: TUI-specific commands
18652 * TUI Configuration:: TUI configuration variables
18655 The @value{GDBN} Text User Interface (TUI) is a terminal
18656 interface which uses the @code{curses} library to show the source
18657 file, the assembly output, the program registers and @value{GDBN}
18658 commands in separate text windows. The TUI mode is supported only
18659 on platforms where a suitable version of the @code{curses} library
18662 @pindex @value{GDBTUI}
18663 The TUI mode is enabled by default when you invoke @value{GDBN} as
18664 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
18665 You can also switch in and out of TUI mode while @value{GDBN} runs by
18666 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
18667 @xref{TUI Keys, ,TUI Key Bindings}.
18670 @section TUI Overview
18672 In TUI mode, @value{GDBN} can display several text windows:
18676 This window is the @value{GDBN} command window with the @value{GDBN}
18677 prompt and the @value{GDBN} output. The @value{GDBN} input is still
18678 managed using readline.
18681 The source window shows the source file of the program. The current
18682 line and active breakpoints are displayed in this window.
18685 The assembly window shows the disassembly output of the program.
18688 This window shows the processor registers. Registers are highlighted
18689 when their values change.
18692 The source and assembly windows show the current program position
18693 by highlighting the current line and marking it with a @samp{>} marker.
18694 Breakpoints are indicated with two markers. The first marker
18695 indicates the breakpoint type:
18699 Breakpoint which was hit at least once.
18702 Breakpoint which was never hit.
18705 Hardware breakpoint which was hit at least once.
18708 Hardware breakpoint which was never hit.
18711 The second marker indicates whether the breakpoint is enabled or not:
18715 Breakpoint is enabled.
18718 Breakpoint is disabled.
18721 The source, assembly and register windows are updated when the current
18722 thread changes, when the frame changes, or when the program counter
18725 These windows are not all visible at the same time. The command
18726 window is always visible. The others can be arranged in several
18737 source and assembly,
18740 source and registers, or
18743 assembly and registers.
18746 A status line above the command window shows the following information:
18750 Indicates the current @value{GDBN} target.
18751 (@pxref{Targets, ,Specifying a Debugging Target}).
18754 Gives the current process or thread number.
18755 When no process is being debugged, this field is set to @code{No process}.
18758 Gives the current function name for the selected frame.
18759 The name is demangled if demangling is turned on (@pxref{Print Settings}).
18760 When there is no symbol corresponding to the current program counter,
18761 the string @code{??} is displayed.
18764 Indicates the current line number for the selected frame.
18765 When the current line number is not known, the string @code{??} is displayed.
18768 Indicates the current program counter address.
18772 @section TUI Key Bindings
18773 @cindex TUI key bindings
18775 The TUI installs several key bindings in the readline keymaps
18776 (@pxref{Command Line Editing}). The following key bindings
18777 are installed for both TUI mode and the @value{GDBN} standard mode.
18786 Enter or leave the TUI mode. When leaving the TUI mode,
18787 the curses window management stops and @value{GDBN} operates using
18788 its standard mode, writing on the terminal directly. When reentering
18789 the TUI mode, control is given back to the curses windows.
18790 The screen is then refreshed.
18794 Use a TUI layout with only one window. The layout will
18795 either be @samp{source} or @samp{assembly}. When the TUI mode
18796 is not active, it will switch to the TUI mode.
18798 Think of this key binding as the Emacs @kbd{C-x 1} binding.
18802 Use a TUI layout with at least two windows. When the current
18803 layout already has two windows, the next layout with two windows is used.
18804 When a new layout is chosen, one window will always be common to the
18805 previous layout and the new one.
18807 Think of it as the Emacs @kbd{C-x 2} binding.
18811 Change the active window. The TUI associates several key bindings
18812 (like scrolling and arrow keys) with the active window. This command
18813 gives the focus to the next TUI window.
18815 Think of it as the Emacs @kbd{C-x o} binding.
18819 Switch in and out of the TUI SingleKey mode that binds single
18820 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
18823 The following key bindings only work in the TUI mode:
18828 Scroll the active window one page up.
18832 Scroll the active window one page down.
18836 Scroll the active window one line up.
18840 Scroll the active window one line down.
18844 Scroll the active window one column left.
18848 Scroll the active window one column right.
18852 Refresh the screen.
18855 Because the arrow keys scroll the active window in the TUI mode, they
18856 are not available for their normal use by readline unless the command
18857 window has the focus. When another window is active, you must use
18858 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
18859 and @kbd{C-f} to control the command window.
18861 @node TUI Single Key Mode
18862 @section TUI Single Key Mode
18863 @cindex TUI single key mode
18865 The TUI also provides a @dfn{SingleKey} mode, which binds several
18866 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
18867 switch into this mode, where the following key bindings are used:
18870 @kindex c @r{(SingleKey TUI key)}
18874 @kindex d @r{(SingleKey TUI key)}
18878 @kindex f @r{(SingleKey TUI key)}
18882 @kindex n @r{(SingleKey TUI key)}
18886 @kindex q @r{(SingleKey TUI key)}
18888 exit the SingleKey mode.
18890 @kindex r @r{(SingleKey TUI key)}
18894 @kindex s @r{(SingleKey TUI key)}
18898 @kindex u @r{(SingleKey TUI key)}
18902 @kindex v @r{(SingleKey TUI key)}
18906 @kindex w @r{(SingleKey TUI key)}
18911 Other keys temporarily switch to the @value{GDBN} command prompt.
18912 The key that was pressed is inserted in the editing buffer so that
18913 it is possible to type most @value{GDBN} commands without interaction
18914 with the TUI SingleKey mode. Once the command is entered the TUI
18915 SingleKey mode is restored. The only way to permanently leave
18916 this mode is by typing @kbd{q} or @kbd{C-x s}.
18920 @section TUI-specific Commands
18921 @cindex TUI commands
18923 The TUI has specific commands to control the text windows.
18924 These commands are always available, even when @value{GDBN} is not in
18925 the TUI mode. When @value{GDBN} is in the standard mode, most
18926 of these commands will automatically switch to the TUI mode.
18931 List and give the size of all displayed windows.
18935 Display the next layout.
18938 Display the previous layout.
18941 Display the source window only.
18944 Display the assembly window only.
18947 Display the source and assembly window.
18950 Display the register window together with the source or assembly window.
18954 Make the next window active for scrolling.
18957 Make the previous window active for scrolling.
18960 Make the source window active for scrolling.
18963 Make the assembly window active for scrolling.
18966 Make the register window active for scrolling.
18969 Make the command window active for scrolling.
18973 Refresh the screen. This is similar to typing @kbd{C-L}.
18975 @item tui reg float
18977 Show the floating point registers in the register window.
18979 @item tui reg general
18980 Show the general registers in the register window.
18983 Show the next register group. The list of register groups as well as
18984 their order is target specific. The predefined register groups are the
18985 following: @code{general}, @code{float}, @code{system}, @code{vector},
18986 @code{all}, @code{save}, @code{restore}.
18988 @item tui reg system
18989 Show the system registers in the register window.
18993 Update the source window and the current execution point.
18995 @item winheight @var{name} +@var{count}
18996 @itemx winheight @var{name} -@var{count}
18998 Change the height of the window @var{name} by @var{count}
18999 lines. Positive counts increase the height, while negative counts
19002 @item tabset @var{nchars}
19004 Set the width of tab stops to be @var{nchars} characters.
19007 @node TUI Configuration
19008 @section TUI Configuration Variables
19009 @cindex TUI configuration variables
19011 Several configuration variables control the appearance of TUI windows.
19014 @item set tui border-kind @var{kind}
19015 @kindex set tui border-kind
19016 Select the border appearance for the source, assembly and register windows.
19017 The possible values are the following:
19020 Use a space character to draw the border.
19023 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
19026 Use the Alternate Character Set to draw the border. The border is
19027 drawn using character line graphics if the terminal supports them.
19030 @item set tui border-mode @var{mode}
19031 @kindex set tui border-mode
19032 @itemx set tui active-border-mode @var{mode}
19033 @kindex set tui active-border-mode
19034 Select the display attributes for the borders of the inactive windows
19035 or the active window. The @var{mode} can be one of the following:
19038 Use normal attributes to display the border.
19044 Use reverse video mode.
19047 Use half bright mode.
19049 @item half-standout
19050 Use half bright and standout mode.
19053 Use extra bright or bold mode.
19055 @item bold-standout
19056 Use extra bright or bold and standout mode.
19061 @chapter Using @value{GDBN} under @sc{gnu} Emacs
19064 @cindex @sc{gnu} Emacs
19065 A special interface allows you to use @sc{gnu} Emacs to view (and
19066 edit) the source files for the program you are debugging with
19069 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
19070 executable file you want to debug as an argument. This command starts
19071 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
19072 created Emacs buffer.
19073 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
19075 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
19080 All ``terminal'' input and output goes through an Emacs buffer, called
19083 This applies both to @value{GDBN} commands and their output, and to the input
19084 and output done by the program you are debugging.
19086 This is useful because it means that you can copy the text of previous
19087 commands and input them again; you can even use parts of the output
19090 All the facilities of Emacs' Shell mode are available for interacting
19091 with your program. In particular, you can send signals the usual
19092 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
19096 @value{GDBN} displays source code through Emacs.
19098 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
19099 source file for that frame and puts an arrow (@samp{=>}) at the
19100 left margin of the current line. Emacs uses a separate buffer for
19101 source display, and splits the screen to show both your @value{GDBN} session
19104 Explicit @value{GDBN} @code{list} or search commands still produce output as
19105 usual, but you probably have no reason to use them from Emacs.
19108 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
19109 a graphical mode, enabled by default, which provides further buffers
19110 that can control the execution and describe the state of your program.
19111 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
19113 If you specify an absolute file name when prompted for the @kbd{M-x
19114 gdb} argument, then Emacs sets your current working directory to where
19115 your program resides. If you only specify the file name, then Emacs
19116 sets your current working directory to to the directory associated
19117 with the previous buffer. In this case, @value{GDBN} may find your
19118 program by searching your environment's @code{PATH} variable, but on
19119 some operating systems it might not find the source. So, although the
19120 @value{GDBN} input and output session proceeds normally, the auxiliary
19121 buffer does not display the current source and line of execution.
19123 The initial working directory of @value{GDBN} is printed on the top
19124 line of the GUD buffer and this serves as a default for the commands
19125 that specify files for @value{GDBN} to operate on. @xref{Files,
19126 ,Commands to Specify Files}.
19128 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
19129 need to call @value{GDBN} by a different name (for example, if you
19130 keep several configurations around, with different names) you can
19131 customize the Emacs variable @code{gud-gdb-command-name} to run the
19134 In the GUD buffer, you can use these special Emacs commands in
19135 addition to the standard Shell mode commands:
19139 Describe the features of Emacs' GUD Mode.
19142 Execute to another source line, like the @value{GDBN} @code{step} command; also
19143 update the display window to show the current file and location.
19146 Execute to next source line in this function, skipping all function
19147 calls, like the @value{GDBN} @code{next} command. Then update the display window
19148 to show the current file and location.
19151 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
19152 display window accordingly.
19155 Execute until exit from the selected stack frame, like the @value{GDBN}
19156 @code{finish} command.
19159 Continue execution of your program, like the @value{GDBN} @code{continue}
19163 Go up the number of frames indicated by the numeric argument
19164 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
19165 like the @value{GDBN} @code{up} command.
19168 Go down the number of frames indicated by the numeric argument, like the
19169 @value{GDBN} @code{down} command.
19172 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
19173 tells @value{GDBN} to set a breakpoint on the source line point is on.
19175 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
19176 separate frame which shows a backtrace when the GUD buffer is current.
19177 Move point to any frame in the stack and type @key{RET} to make it
19178 become the current frame and display the associated source in the
19179 source buffer. Alternatively, click @kbd{Mouse-2} to make the
19180 selected frame become the current one. In graphical mode, the
19181 speedbar displays watch expressions.
19183 If you accidentally delete the source-display buffer, an easy way to get
19184 it back is to type the command @code{f} in the @value{GDBN} buffer, to
19185 request a frame display; when you run under Emacs, this recreates
19186 the source buffer if necessary to show you the context of the current
19189 The source files displayed in Emacs are in ordinary Emacs buffers
19190 which are visiting the source files in the usual way. You can edit
19191 the files with these buffers if you wish; but keep in mind that @value{GDBN}
19192 communicates with Emacs in terms of line numbers. If you add or
19193 delete lines from the text, the line numbers that @value{GDBN} knows cease
19194 to correspond properly with the code.
19196 A more detailed description of Emacs' interaction with @value{GDBN} is
19197 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
19200 @c The following dropped because Epoch is nonstandard. Reactivate
19201 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
19203 @kindex Emacs Epoch environment
19207 Version 18 of @sc{gnu} Emacs has a built-in window system
19208 called the @code{epoch}
19209 environment. Users of this environment can use a new command,
19210 @code{inspect} which performs identically to @code{print} except that
19211 each value is printed in its own window.
19216 @chapter The @sc{gdb/mi} Interface
19218 @unnumberedsec Function and Purpose
19220 @cindex @sc{gdb/mi}, its purpose
19221 @sc{gdb/mi} is a line based machine oriented text interface to
19222 @value{GDBN} and is activated by specifying using the
19223 @option{--interpreter} command line option (@pxref{Mode Options}). It
19224 is specifically intended to support the development of systems which
19225 use the debugger as just one small component of a larger system.
19227 This chapter is a specification of the @sc{gdb/mi} interface. It is written
19228 in the form of a reference manual.
19230 Note that @sc{gdb/mi} is still under construction, so some of the
19231 features described below are incomplete and subject to change
19232 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
19234 @unnumberedsec Notation and Terminology
19236 @cindex notational conventions, for @sc{gdb/mi}
19237 This chapter uses the following notation:
19241 @code{|} separates two alternatives.
19244 @code{[ @var{something} ]} indicates that @var{something} is optional:
19245 it may or may not be given.
19248 @code{( @var{group} )*} means that @var{group} inside the parentheses
19249 may repeat zero or more times.
19252 @code{( @var{group} )+} means that @var{group} inside the parentheses
19253 may repeat one or more times.
19256 @code{"@var{string}"} means a literal @var{string}.
19260 @heading Dependencies
19264 * GDB/MI General Design::
19265 * GDB/MI Command Syntax::
19266 * GDB/MI Compatibility with CLI::
19267 * GDB/MI Development and Front Ends::
19268 * GDB/MI Output Records::
19269 * GDB/MI Simple Examples::
19270 * GDB/MI Command Description Format::
19271 * GDB/MI Breakpoint Commands::
19272 * GDB/MI Program Context::
19273 * GDB/MI Thread Commands::
19274 * GDB/MI Program Execution::
19275 * GDB/MI Stack Manipulation::
19276 * GDB/MI Variable Objects::
19277 * GDB/MI Data Manipulation::
19278 * GDB/MI Tracepoint Commands::
19279 * GDB/MI Symbol Query::
19280 * GDB/MI File Commands::
19282 * GDB/MI Kod Commands::
19283 * GDB/MI Memory Overlay Commands::
19284 * GDB/MI Signal Handling Commands::
19286 * GDB/MI Target Manipulation::
19287 * GDB/MI File Transfer Commands::
19288 * GDB/MI Miscellaneous Commands::
19291 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19292 @node GDB/MI General Design
19293 @section @sc{gdb/mi} General Design
19294 @cindex GDB/MI General Design
19296 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
19297 parts---commands sent to @value{GDBN}, responses to those commands
19298 and notifications. Each command results in exactly one response,
19299 indicating either successful completion of the command, or an error.
19300 For the commands that do not resume the target, the response contains the
19301 requested information. For the commands that resume the target, the
19302 response only indicates whether the target was successfully resumed.
19303 Notifications is the mechanism for reporting changes in the state of the
19304 target, or in @value{GDBN} state, that cannot conveniently be associated with
19305 a command and reported as part of that command response.
19307 The important examples of notifications are:
19311 Exec notifications. These are used to report changes in
19312 target state---when a target is resumed, or stopped. It would not
19313 be feasible to include this information in response of resuming
19314 commands, because one resume commands can result in multiple events in
19315 different threads. Also, quite some time may pass before any event
19316 happens in the target, while a frontend needs to know whether the resuming
19317 command itself was successfully executed.
19320 Console output, and status notifications. Console output
19321 notifications are used to report output of CLI commands, as well as
19322 diagnostics for other commands. Status notifications are used to
19323 report the progress of a long-running operation. Naturally, including
19324 this information in command response would mean no output is produced
19325 until the command is finished, which is undesirable.
19328 General notifications. Commands may have various side effects on
19329 the @value{GDBN} or target state beyond their official purpose. For example,
19330 a command may change the selected thread. Although such changes can
19331 be included in command response, using notification allows for more
19332 orthogonal frontend design.
19336 There's no guarantee that whenever an MI command reports an error,
19337 @value{GDBN} or the target are in any specific state, and especially,
19338 the state is not reverted to the state before the MI command was
19339 processed. Therefore, whenever an MI command results in an error,
19340 we recommend that the frontend refreshes all the information shown in
19341 the user interface.
19343 @subsection Context management
19345 In most cases when @value{GDBN} accesses the target, this access is
19346 done in context of a specific thread and frame (@pxref{Frames}).
19347 Often, even when accessing global data, the target requires that a thread
19348 be specified. The CLI interface maintains the selected thread and frame,
19349 and supplies them to target on each command. This is convenient,
19350 because a command line user would not want to specify that information
19351 explicitly on each command, and because user interacts with
19352 @value{GDBN} via a single terminal, so no confusion is possible as
19353 to what thread and frame are the current ones.
19355 In the case of MI, the concept of selected thread and frame is less
19356 useful. First, a frontend can easily remember this information
19357 itself. Second, a graphical frontend can have more than one window,
19358 each one used for debugging a different thread, and the frontend might
19359 want to access additional threads for internal purposes. This
19360 increases the risk that by relying on implicitly selected thread, the
19361 frontend may be operating on a wrong one. Therefore, each MI command
19362 should explicitly specify which thread and frame to operate on. To
19363 make it possible, each MI command accepts the @samp{--thread} and
19364 @samp{--frame} options, the value to each is @value{GDBN} identifier
19365 for thread and frame to operate on.
19367 Usually, each top-level window in a frontend allows the user to select
19368 a thread and a frame, and remembers the user selection for further
19369 operations. However, in some cases @value{GDBN} may suggest that the
19370 current thread be changed. For example, when stopping on a breakpoint
19371 it is reasonable to switch to the thread where breakpoint is hit. For
19372 another example, if the user issues the CLI @samp{thread} command via
19373 the frontend, it is desirable to change the frontend's selected thread to the
19374 one specified by user. @value{GDBN} communicates the suggestion to
19375 change current thread using the @samp{=thread-selected} notification.
19376 No such notification is available for the selected frame at the moment.
19378 Note that historically, MI shares the selected thread with CLI, so
19379 frontends used the @code{-thread-select} to execute commands in the
19380 right context. However, getting this to work right is cumbersome. The
19381 simplest way is for frontend to emit @code{-thread-select} command
19382 before every command. This doubles the number of commands that need
19383 to be sent. The alternative approach is to suppress @code{-thread-select}
19384 if the selected thread in @value{GDBN} is supposed to be identical to the
19385 thread the frontend wants to operate on. However, getting this
19386 optimization right can be tricky. In particular, if the frontend
19387 sends several commands to @value{GDBN}, and one of the commands changes the
19388 selected thread, then the behaviour of subsequent commands will
19389 change. So, a frontend should either wait for response from such
19390 problematic commands, or explicitly add @code{-thread-select} for
19391 all subsequent commands. No frontend is known to do this exactly
19392 right, so it is suggested to just always pass the @samp{--thread} and
19393 @samp{--frame} options.
19395 @subsection Asynchronous command execution and non-stop mode
19397 On some targets, @value{GDBN} is capable of processing MI commands
19398 even while the target is running. This is called @dfn{asynchronous
19399 command execution} (@pxref{Background Execution}). The frontend may
19400 specify a preferrence for asynchronous execution using the
19401 @code{-gdb-set target-async 1} command, which should be emitted before
19402 either running the executable or attaching to the target. After the
19403 frontend has started the executable or attached to the target, it can
19404 find if asynchronous execution is enabled using the
19405 @code{-list-target-features} command.
19407 Even if @value{GDBN} can accept a command while target is running,
19408 many commands that access the target do not work when the target is
19409 running. Therefore, asynchronous command execution is most useful
19410 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
19411 it is possible to examine the state of one thread, while other threads
19414 When a given thread is running, MI commands that try to access the
19415 target in the context of that thread may not work, or may work only on
19416 some targets. In particular, commands that try to operate on thread's
19417 stack will not work, on any target. Commands that read memory, or
19418 modify breakpoints, may work or not work, depending on the target. Note
19419 that even commands that operate on global state, such as @code{print},
19420 @code{set}, and breakpoint commands, still access the target in the
19421 context of a specific thread, so frontend should try to find a
19422 stopped thread and perform the operation on that thread (using the
19423 @samp{--thread} option).
19425 Which commands will work in the context of a running thread is
19426 highly target dependent. However, the two commands
19427 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
19428 to find the state of a thread, will always work.
19430 @subsection Thread groups
19431 @value{GDBN} may be used to debug several processes at the same time.
19432 On some platfroms, @value{GDBN} may support debugging of several
19433 hardware systems, each one having several cores with several different
19434 processes running on each core. This section describes the MI
19435 mechanism to support such debugging scenarios.
19437 The key observation is that regardless of the structure of the
19438 target, MI can have a global list of threads, because most commands that
19439 accept the @samp{--thread} option do not need to know what process that
19440 thread belongs to. Therefore, it is not necessary to introduce
19441 neither additional @samp{--process} option, nor an notion of the
19442 current process in the MI interface. The only strictly new feature
19443 that is required is the ability to find how the threads are grouped
19446 To allow the user to discover such grouping, and to support arbitrary
19447 hierarchy of machines/cores/processes, MI introduces the concept of a
19448 @dfn{thread group}. Thread group is a collection of threads and other
19449 thread groups. A thread group always has a string identifier, a type,
19450 and may have additional attributes specific to the type. A new
19451 command, @code{-list-thread-groups}, returns the list of top-level
19452 thread groups, which correspond to processes that @value{GDBN} is
19453 debugging at the moment. By passing an identifier of a thread group
19454 to the @code{-list-thread-groups} command, it is possible to obtain
19455 the members of specific thread group.
19457 To allow the user to easily discover processes, and other objects, he
19458 wishes to debug, a concept of @dfn{available thread group} is
19459 introduced. Available thread group is an thread group that
19460 @value{GDBN} is not debugging, but that can be attached to, using the
19461 @code{-target-attach} command. The list of available top-level thread
19462 groups can be obtained using @samp{-list-thread-groups --available}.
19463 In general, the content of a thread group may be only retrieved only
19464 after attaching to that thread group.
19466 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19467 @node GDB/MI Command Syntax
19468 @section @sc{gdb/mi} Command Syntax
19471 * GDB/MI Input Syntax::
19472 * GDB/MI Output Syntax::
19475 @node GDB/MI Input Syntax
19476 @subsection @sc{gdb/mi} Input Syntax
19478 @cindex input syntax for @sc{gdb/mi}
19479 @cindex @sc{gdb/mi}, input syntax
19481 @item @var{command} @expansion{}
19482 @code{@var{cli-command} | @var{mi-command}}
19484 @item @var{cli-command} @expansion{}
19485 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
19486 @var{cli-command} is any existing @value{GDBN} CLI command.
19488 @item @var{mi-command} @expansion{}
19489 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
19490 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
19492 @item @var{token} @expansion{}
19493 "any sequence of digits"
19495 @item @var{option} @expansion{}
19496 @code{"-" @var{parameter} [ " " @var{parameter} ]}
19498 @item @var{parameter} @expansion{}
19499 @code{@var{non-blank-sequence} | @var{c-string}}
19501 @item @var{operation} @expansion{}
19502 @emph{any of the operations described in this chapter}
19504 @item @var{non-blank-sequence} @expansion{}
19505 @emph{anything, provided it doesn't contain special characters such as
19506 "-", @var{nl}, """ and of course " "}
19508 @item @var{c-string} @expansion{}
19509 @code{""" @var{seven-bit-iso-c-string-content} """}
19511 @item @var{nl} @expansion{}
19520 The CLI commands are still handled by the @sc{mi} interpreter; their
19521 output is described below.
19524 The @code{@var{token}}, when present, is passed back when the command
19528 Some @sc{mi} commands accept optional arguments as part of the parameter
19529 list. Each option is identified by a leading @samp{-} (dash) and may be
19530 followed by an optional argument parameter. Options occur first in the
19531 parameter list and can be delimited from normal parameters using
19532 @samp{--} (this is useful when some parameters begin with a dash).
19539 We want easy access to the existing CLI syntax (for debugging).
19542 We want it to be easy to spot a @sc{mi} operation.
19545 @node GDB/MI Output Syntax
19546 @subsection @sc{gdb/mi} Output Syntax
19548 @cindex output syntax of @sc{gdb/mi}
19549 @cindex @sc{gdb/mi}, output syntax
19550 The output from @sc{gdb/mi} consists of zero or more out-of-band records
19551 followed, optionally, by a single result record. This result record
19552 is for the most recent command. The sequence of output records is
19553 terminated by @samp{(gdb)}.
19555 If an input command was prefixed with a @code{@var{token}} then the
19556 corresponding output for that command will also be prefixed by that same
19560 @item @var{output} @expansion{}
19561 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
19563 @item @var{result-record} @expansion{}
19564 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
19566 @item @var{out-of-band-record} @expansion{}
19567 @code{@var{async-record} | @var{stream-record}}
19569 @item @var{async-record} @expansion{}
19570 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
19572 @item @var{exec-async-output} @expansion{}
19573 @code{[ @var{token} ] "*" @var{async-output}}
19575 @item @var{status-async-output} @expansion{}
19576 @code{[ @var{token} ] "+" @var{async-output}}
19578 @item @var{notify-async-output} @expansion{}
19579 @code{[ @var{token} ] "=" @var{async-output}}
19581 @item @var{async-output} @expansion{}
19582 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
19584 @item @var{result-class} @expansion{}
19585 @code{"done" | "running" | "connected" | "error" | "exit"}
19587 @item @var{async-class} @expansion{}
19588 @code{"stopped" | @var{others}} (where @var{others} will be added
19589 depending on the needs---this is still in development).
19591 @item @var{result} @expansion{}
19592 @code{ @var{variable} "=" @var{value}}
19594 @item @var{variable} @expansion{}
19595 @code{ @var{string} }
19597 @item @var{value} @expansion{}
19598 @code{ @var{const} | @var{tuple} | @var{list} }
19600 @item @var{const} @expansion{}
19601 @code{@var{c-string}}
19603 @item @var{tuple} @expansion{}
19604 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
19606 @item @var{list} @expansion{}
19607 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
19608 @var{result} ( "," @var{result} )* "]" }
19610 @item @var{stream-record} @expansion{}
19611 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
19613 @item @var{console-stream-output} @expansion{}
19614 @code{"~" @var{c-string}}
19616 @item @var{target-stream-output} @expansion{}
19617 @code{"@@" @var{c-string}}
19619 @item @var{log-stream-output} @expansion{}
19620 @code{"&" @var{c-string}}
19622 @item @var{nl} @expansion{}
19625 @item @var{token} @expansion{}
19626 @emph{any sequence of digits}.
19634 All output sequences end in a single line containing a period.
19637 The @code{@var{token}} is from the corresponding request. Note that
19638 for all async output, while the token is allowed by the grammar and
19639 may be output by future versions of @value{GDBN} for select async
19640 output messages, it is generally omitted. Frontends should treat
19641 all async output as reporting general changes in the state of the
19642 target and there should be no need to associate async output to any
19646 @cindex status output in @sc{gdb/mi}
19647 @var{status-async-output} contains on-going status information about the
19648 progress of a slow operation. It can be discarded. All status output is
19649 prefixed by @samp{+}.
19652 @cindex async output in @sc{gdb/mi}
19653 @var{exec-async-output} contains asynchronous state change on the target
19654 (stopped, started, disappeared). All async output is prefixed by
19658 @cindex notify output in @sc{gdb/mi}
19659 @var{notify-async-output} contains supplementary information that the
19660 client should handle (e.g., a new breakpoint information). All notify
19661 output is prefixed by @samp{=}.
19664 @cindex console output in @sc{gdb/mi}
19665 @var{console-stream-output} is output that should be displayed as is in the
19666 console. It is the textual response to a CLI command. All the console
19667 output is prefixed by @samp{~}.
19670 @cindex target output in @sc{gdb/mi}
19671 @var{target-stream-output} is the output produced by the target program.
19672 All the target output is prefixed by @samp{@@}.
19675 @cindex log output in @sc{gdb/mi}
19676 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
19677 instance messages that should be displayed as part of an error log. All
19678 the log output is prefixed by @samp{&}.
19681 @cindex list output in @sc{gdb/mi}
19682 New @sc{gdb/mi} commands should only output @var{lists} containing
19688 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
19689 details about the various output records.
19691 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19692 @node GDB/MI Compatibility with CLI
19693 @section @sc{gdb/mi} Compatibility with CLI
19695 @cindex compatibility, @sc{gdb/mi} and CLI
19696 @cindex @sc{gdb/mi}, compatibility with CLI
19698 For the developers convenience CLI commands can be entered directly,
19699 but there may be some unexpected behaviour. For example, commands
19700 that query the user will behave as if the user replied yes, breakpoint
19701 command lists are not executed and some CLI commands, such as
19702 @code{if}, @code{when} and @code{define}, prompt for further input with
19703 @samp{>}, which is not valid MI output.
19705 This feature may be removed at some stage in the future and it is
19706 recommended that front ends use the @code{-interpreter-exec} command
19707 (@pxref{-interpreter-exec}).
19709 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19710 @node GDB/MI Development and Front Ends
19711 @section @sc{gdb/mi} Development and Front Ends
19712 @cindex @sc{gdb/mi} development
19714 The application which takes the MI output and presents the state of the
19715 program being debugged to the user is called a @dfn{front end}.
19717 Although @sc{gdb/mi} is still incomplete, it is currently being used
19718 by a variety of front ends to @value{GDBN}. This makes it difficult
19719 to introduce new functionality without breaking existing usage. This
19720 section tries to minimize the problems by describing how the protocol
19723 Some changes in MI need not break a carefully designed front end, and
19724 for these the MI version will remain unchanged. The following is a
19725 list of changes that may occur within one level, so front ends should
19726 parse MI output in a way that can handle them:
19730 New MI commands may be added.
19733 New fields may be added to the output of any MI command.
19736 The range of values for fields with specified values, e.g.,
19737 @code{in_scope} (@pxref{-var-update}) may be extended.
19739 @c The format of field's content e.g type prefix, may change so parse it
19740 @c at your own risk. Yes, in general?
19742 @c The order of fields may change? Shouldn't really matter but it might
19743 @c resolve inconsistencies.
19746 If the changes are likely to break front ends, the MI version level
19747 will be increased by one. This will allow the front end to parse the
19748 output according to the MI version. Apart from mi0, new versions of
19749 @value{GDBN} will not support old versions of MI and it will be the
19750 responsibility of the front end to work with the new one.
19752 @c Starting with mi3, add a new command -mi-version that prints the MI
19755 The best way to avoid unexpected changes in MI that might break your front
19756 end is to make your project known to @value{GDBN} developers and
19757 follow development on @email{gdb@@sourceware.org} and
19758 @email{gdb-patches@@sourceware.org}.
19759 @cindex mailing lists
19761 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19762 @node GDB/MI Output Records
19763 @section @sc{gdb/mi} Output Records
19766 * GDB/MI Result Records::
19767 * GDB/MI Stream Records::
19768 * GDB/MI Async Records::
19769 * GDB/MI Frame Information::
19772 @node GDB/MI Result Records
19773 @subsection @sc{gdb/mi} Result Records
19775 @cindex result records in @sc{gdb/mi}
19776 @cindex @sc{gdb/mi}, result records
19777 In addition to a number of out-of-band notifications, the response to a
19778 @sc{gdb/mi} command includes one of the following result indications:
19782 @item "^done" [ "," @var{results} ]
19783 The synchronous operation was successful, @code{@var{results}} are the return
19788 @c Is this one correct? Should it be an out-of-band notification?
19789 The asynchronous operation was successfully started. The target is
19794 @value{GDBN} has connected to a remote target.
19796 @item "^error" "," @var{c-string}
19798 The operation failed. The @code{@var{c-string}} contains the corresponding
19803 @value{GDBN} has terminated.
19807 @node GDB/MI Stream Records
19808 @subsection @sc{gdb/mi} Stream Records
19810 @cindex @sc{gdb/mi}, stream records
19811 @cindex stream records in @sc{gdb/mi}
19812 @value{GDBN} internally maintains a number of output streams: the console, the
19813 target, and the log. The output intended for each of these streams is
19814 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
19816 Each stream record begins with a unique @dfn{prefix character} which
19817 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
19818 Syntax}). In addition to the prefix, each stream record contains a
19819 @code{@var{string-output}}. This is either raw text (with an implicit new
19820 line) or a quoted C string (which does not contain an implicit newline).
19823 @item "~" @var{string-output}
19824 The console output stream contains text that should be displayed in the
19825 CLI console window. It contains the textual responses to CLI commands.
19827 @item "@@" @var{string-output}
19828 The target output stream contains any textual output from the running
19829 target. This is only present when GDB's event loop is truly
19830 asynchronous, which is currently only the case for remote targets.
19832 @item "&" @var{string-output}
19833 The log stream contains debugging messages being produced by @value{GDBN}'s
19837 @node GDB/MI Async Records
19838 @subsection @sc{gdb/mi} Async Records
19840 @cindex async records in @sc{gdb/mi}
19841 @cindex @sc{gdb/mi}, async records
19842 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
19843 additional changes that have occurred. Those changes can either be a
19844 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
19845 target activity (e.g., target stopped).
19847 The following is the list of possible async records:
19851 @item *running,thread-id="@var{thread}"
19852 The target is now running. The @var{thread} field tells which
19853 specific thread is now running, and can be @samp{all} if all threads
19854 are running. The frontend should assume that no interaction with a
19855 running thread is possible after this notification is produced.
19856 The frontend should not assume that this notification is output
19857 only once for any command. @value{GDBN} may emit this notification
19858 several times, either for different threads, because it cannot resume
19859 all threads together, or even for a single thread, if the thread must
19860 be stepped though some code before letting it run freely.
19862 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}"
19863 The target has stopped. The @var{reason} field can have one of the
19867 @item breakpoint-hit
19868 A breakpoint was reached.
19869 @item watchpoint-trigger
19870 A watchpoint was triggered.
19871 @item read-watchpoint-trigger
19872 A read watchpoint was triggered.
19873 @item access-watchpoint-trigger
19874 An access watchpoint was triggered.
19875 @item function-finished
19876 An -exec-finish or similar CLI command was accomplished.
19877 @item location-reached
19878 An -exec-until or similar CLI command was accomplished.
19879 @item watchpoint-scope
19880 A watchpoint has gone out of scope.
19881 @item end-stepping-range
19882 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
19883 similar CLI command was accomplished.
19884 @item exited-signalled
19885 The inferior exited because of a signal.
19887 The inferior exited.
19888 @item exited-normally
19889 The inferior exited normally.
19890 @item signal-received
19891 A signal was received by the inferior.
19894 The @var{id} field identifies the thread that directly caused the stop
19895 -- for example by hitting a breakpoint. Depending on whether all-stop
19896 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
19897 stop all threads, or only the thread that directly triggered the stop.
19898 If all threads are stopped, the @var{stopped} field will have the
19899 value of @code{"all"}. Otherwise, the value of the @var{stopped}
19900 field will be a list of thread identifiers. Presently, this list will
19901 always include a single thread, but frontend should be prepared to see
19902 several threads in the list.
19904 @item =thread-group-created,id="@var{id}"
19905 @itemx =thread-group-exited,id="@var{id}"
19906 A thread thread group either was attached to, or has exited/detached
19907 from. The @var{id} field contains the @value{GDBN} identifier of the
19910 @item =thread-created,id="@var{id}",group-id="@var{gid}"
19911 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
19912 A thread either was created, or has exited. The @var{id} field
19913 contains the @value{GDBN} identifier of the thread. The @var{gid}
19914 field identifies the thread group this thread belongs to.
19916 @item =thread-selected,id="@var{id}"
19917 Informs that the selected thread was changed as result of the last
19918 command. This notification is not emitted as result of @code{-thread-select}
19919 command but is emitted whenever an MI command that is not documented
19920 to change the selected thread actually changes it. In particular,
19921 invoking, directly or indirectly (via user-defined command), the CLI
19922 @code{thread} command, will generate this notification.
19924 We suggest that in response to this notification, front ends
19925 highlight the selected thread and cause subsequent commands to apply to
19928 @item =library-loaded,...
19929 Reports that a new library file was loaded by the program. This
19930 notification has 4 fields---@var{id}, @var{target-name},
19931 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
19932 opaque identifier of the library. For remote debugging case,
19933 @var{target-name} and @var{host-name} fields give the name of the
19934 library file on the target, and on the host respectively. For native
19935 debugging, both those fields have the same value. The
19936 @var{symbols-loaded} field reports if the debug symbols for this
19937 library are loaded.
19939 @item =library-unloaded,...
19940 Reports that a library was unloaded by the program. This notification
19941 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
19942 the same meaning as for the @code{=library-loaded} notification
19946 @node GDB/MI Frame Information
19947 @subsection @sc{gdb/mi} Frame Information
19949 Response from many MI commands includes an information about stack
19950 frame. This information is a tuple that may have the following
19955 The level of the stack frame. The innermost frame has the level of
19956 zero. This field is always present.
19959 The name of the function corresponding to the frame. This field may
19960 be absent if @value{GDBN} is unable to determine the function name.
19963 The code address for the frame. This field is always present.
19966 The name of the source files that correspond to the frame's code
19967 address. This field may be absent.
19970 The source line corresponding to the frames' code address. This field
19974 The name of the binary file (either executable or shared library) the
19975 corresponds to the frame's code address. This field may be absent.
19980 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19981 @node GDB/MI Simple Examples
19982 @section Simple Examples of @sc{gdb/mi} Interaction
19983 @cindex @sc{gdb/mi}, simple examples
19985 This subsection presents several simple examples of interaction using
19986 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
19987 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
19988 the output received from @sc{gdb/mi}.
19990 Note the line breaks shown in the examples are here only for
19991 readability, they don't appear in the real output.
19993 @subheading Setting a Breakpoint
19995 Setting a breakpoint generates synchronous output which contains detailed
19996 information of the breakpoint.
19999 -> -break-insert main
20000 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20001 enabled="y",addr="0x08048564",func="main",file="myprog.c",
20002 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
20006 @subheading Program Execution
20008 Program execution generates asynchronous records and MI gives the
20009 reason that execution stopped.
20015 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
20016 frame=@{addr="0x08048564",func="main",
20017 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
20018 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
20023 <- *stopped,reason="exited-normally"
20027 @subheading Quitting @value{GDBN}
20029 Quitting @value{GDBN} just prints the result class @samp{^exit}.
20037 @subheading A Bad Command
20039 Here's what happens if you pass a non-existent command:
20043 <- ^error,msg="Undefined MI command: rubbish"
20048 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20049 @node GDB/MI Command Description Format
20050 @section @sc{gdb/mi} Command Description Format
20052 The remaining sections describe blocks of commands. Each block of
20053 commands is laid out in a fashion similar to this section.
20055 @subheading Motivation
20057 The motivation for this collection of commands.
20059 @subheading Introduction
20061 A brief introduction to this collection of commands as a whole.
20063 @subheading Commands
20065 For each command in the block, the following is described:
20067 @subsubheading Synopsis
20070 -command @var{args}@dots{}
20073 @subsubheading Result
20075 @subsubheading @value{GDBN} Command
20077 The corresponding @value{GDBN} CLI command(s), if any.
20079 @subsubheading Example
20081 Example(s) formatted for readability. Some of the described commands have
20082 not been implemented yet and these are labeled N.A.@: (not available).
20085 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20086 @node GDB/MI Breakpoint Commands
20087 @section @sc{gdb/mi} Breakpoint Commands
20089 @cindex breakpoint commands for @sc{gdb/mi}
20090 @cindex @sc{gdb/mi}, breakpoint commands
20091 This section documents @sc{gdb/mi} commands for manipulating
20094 @subheading The @code{-break-after} Command
20095 @findex -break-after
20097 @subsubheading Synopsis
20100 -break-after @var{number} @var{count}
20103 The breakpoint number @var{number} is not in effect until it has been
20104 hit @var{count} times. To see how this is reflected in the output of
20105 the @samp{-break-list} command, see the description of the
20106 @samp{-break-list} command below.
20108 @subsubheading @value{GDBN} Command
20110 The corresponding @value{GDBN} command is @samp{ignore}.
20112 @subsubheading Example
20117 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20118 enabled="y",addr="0x000100d0",func="main",file="hello.c",
20119 fullname="/home/foo/hello.c",line="5",times="0"@}
20126 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20127 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20128 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20129 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20130 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20131 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20132 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20133 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20134 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20135 line="5",times="0",ignore="3"@}]@}
20140 @subheading The @code{-break-catch} Command
20141 @findex -break-catch
20143 @subheading The @code{-break-commands} Command
20144 @findex -break-commands
20148 @subheading The @code{-break-condition} Command
20149 @findex -break-condition
20151 @subsubheading Synopsis
20154 -break-condition @var{number} @var{expr}
20157 Breakpoint @var{number} will stop the program only if the condition in
20158 @var{expr} is true. The condition becomes part of the
20159 @samp{-break-list} output (see the description of the @samp{-break-list}
20162 @subsubheading @value{GDBN} Command
20164 The corresponding @value{GDBN} command is @samp{condition}.
20166 @subsubheading Example
20170 -break-condition 1 1
20174 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20175 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20176 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20177 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20178 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20179 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20180 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20181 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20182 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20183 line="5",cond="1",times="0",ignore="3"@}]@}
20187 @subheading The @code{-break-delete} Command
20188 @findex -break-delete
20190 @subsubheading Synopsis
20193 -break-delete ( @var{breakpoint} )+
20196 Delete the breakpoint(s) whose number(s) are specified in the argument
20197 list. This is obviously reflected in the breakpoint list.
20199 @subsubheading @value{GDBN} Command
20201 The corresponding @value{GDBN} command is @samp{delete}.
20203 @subsubheading Example
20211 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20212 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20213 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20214 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20215 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20216 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20217 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20222 @subheading The @code{-break-disable} Command
20223 @findex -break-disable
20225 @subsubheading Synopsis
20228 -break-disable ( @var{breakpoint} )+
20231 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
20232 break list is now set to @samp{n} for the named @var{breakpoint}(s).
20234 @subsubheading @value{GDBN} Command
20236 The corresponding @value{GDBN} command is @samp{disable}.
20238 @subsubheading Example
20246 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20247 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20248 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20249 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20250 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20251 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20252 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20253 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
20254 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20255 line="5",times="0"@}]@}
20259 @subheading The @code{-break-enable} Command
20260 @findex -break-enable
20262 @subsubheading Synopsis
20265 -break-enable ( @var{breakpoint} )+
20268 Enable (previously disabled) @var{breakpoint}(s).
20270 @subsubheading @value{GDBN} Command
20272 The corresponding @value{GDBN} command is @samp{enable}.
20274 @subsubheading Example
20282 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20283 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20284 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20285 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20286 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20287 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20288 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20289 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20290 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20291 line="5",times="0"@}]@}
20295 @subheading The @code{-break-info} Command
20296 @findex -break-info
20298 @subsubheading Synopsis
20301 -break-info @var{breakpoint}
20305 Get information about a single breakpoint.
20307 @subsubheading @value{GDBN} Command
20309 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
20311 @subsubheading Example
20314 @subheading The @code{-break-insert} Command
20315 @findex -break-insert
20317 @subsubheading Synopsis
20320 -break-insert [ -t ] [ -h ] [ -f ] [ -d ]
20321 [ -c @var{condition} ] [ -i @var{ignore-count} ]
20322 [ -p @var{thread} ] [ @var{location} ]
20326 If specified, @var{location}, can be one of:
20333 @item filename:linenum
20334 @item filename:function
20338 The possible optional parameters of this command are:
20342 Insert a temporary breakpoint.
20344 Insert a hardware breakpoint.
20345 @item -c @var{condition}
20346 Make the breakpoint conditional on @var{condition}.
20347 @item -i @var{ignore-count}
20348 Initialize the @var{ignore-count}.
20350 If @var{location} cannot be parsed (for example if it
20351 refers to unknown files or functions), create a pending
20352 breakpoint. Without this flag, @value{GDBN} will report
20353 an error, and won't create a breakpoint, if @var{location}
20356 Create a disabled breakpoint.
20359 @subsubheading Result
20361 The result is in the form:
20364 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
20365 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
20366 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
20367 times="@var{times}"@}
20371 where @var{number} is the @value{GDBN} number for this breakpoint,
20372 @var{funcname} is the name of the function where the breakpoint was
20373 inserted, @var{filename} is the name of the source file which contains
20374 this function, @var{lineno} is the source line number within that file
20375 and @var{times} the number of times that the breakpoint has been hit
20376 (always 0 for -break-insert but may be greater for -break-info or -break-list
20377 which use the same output).
20379 Note: this format is open to change.
20380 @c An out-of-band breakpoint instead of part of the result?
20382 @subsubheading @value{GDBN} Command
20384 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
20385 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
20387 @subsubheading Example
20392 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
20393 fullname="/home/foo/recursive2.c,line="4",times="0"@}
20395 -break-insert -t foo
20396 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
20397 fullname="/home/foo/recursive2.c,line="11",times="0"@}
20400 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20401 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20402 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20403 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20404 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20405 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20406 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20407 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20408 addr="0x0001072c", func="main",file="recursive2.c",
20409 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
20410 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
20411 addr="0x00010774",func="foo",file="recursive2.c",
20412 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
20414 -break-insert -r foo.*
20415 ~int foo(int, int);
20416 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
20417 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
20421 @subheading The @code{-break-list} Command
20422 @findex -break-list
20424 @subsubheading Synopsis
20430 Displays the list of inserted breakpoints, showing the following fields:
20434 number of the breakpoint
20436 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
20438 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
20441 is the breakpoint enabled or no: @samp{y} or @samp{n}
20443 memory location at which the breakpoint is set
20445 logical location of the breakpoint, expressed by function name, file
20448 number of times the breakpoint has been hit
20451 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
20452 @code{body} field is an empty list.
20454 @subsubheading @value{GDBN} Command
20456 The corresponding @value{GDBN} command is @samp{info break}.
20458 @subsubheading Example
20463 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20464 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20465 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20466 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20467 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20468 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20469 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20470 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20471 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
20472 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20473 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
20474 line="13",times="0"@}]@}
20478 Here's an example of the result when there are no breakpoints:
20483 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20484 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20485 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20486 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20487 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20488 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20489 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20494 @subheading The @code{-break-watch} Command
20495 @findex -break-watch
20497 @subsubheading Synopsis
20500 -break-watch [ -a | -r ]
20503 Create a watchpoint. With the @samp{-a} option it will create an
20504 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
20505 read from or on a write to the memory location. With the @samp{-r}
20506 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
20507 trigger only when the memory location is accessed for reading. Without
20508 either of the options, the watchpoint created is a regular watchpoint,
20509 i.e., it will trigger when the memory location is accessed for writing.
20510 @xref{Set Watchpoints, , Setting Watchpoints}.
20512 Note that @samp{-break-list} will report a single list of watchpoints and
20513 breakpoints inserted.
20515 @subsubheading @value{GDBN} Command
20517 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
20520 @subsubheading Example
20522 Setting a watchpoint on a variable in the @code{main} function:
20527 ^done,wpt=@{number="2",exp="x"@}
20532 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
20533 value=@{old="-268439212",new="55"@},
20534 frame=@{func="main",args=[],file="recursive2.c",
20535 fullname="/home/foo/bar/recursive2.c",line="5"@}
20539 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
20540 the program execution twice: first for the variable changing value, then
20541 for the watchpoint going out of scope.
20546 ^done,wpt=@{number="5",exp="C"@}
20551 *stopped,reason="watchpoint-trigger",
20552 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
20553 frame=@{func="callee4",args=[],
20554 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20555 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20560 *stopped,reason="watchpoint-scope",wpnum="5",
20561 frame=@{func="callee3",args=[@{name="strarg",
20562 value="0x11940 \"A string argument.\""@}],
20563 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20564 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20568 Listing breakpoints and watchpoints, at different points in the program
20569 execution. Note that once the watchpoint goes out of scope, it is
20575 ^done,wpt=@{number="2",exp="C"@}
20578 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20579 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20580 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20581 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20582 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20583 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20584 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20585 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20586 addr="0x00010734",func="callee4",
20587 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20588 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
20589 bkpt=@{number="2",type="watchpoint",disp="keep",
20590 enabled="y",addr="",what="C",times="0"@}]@}
20595 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
20596 value=@{old="-276895068",new="3"@},
20597 frame=@{func="callee4",args=[],
20598 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20599 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20602 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20603 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20604 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20605 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20606 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20607 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20608 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20609 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20610 addr="0x00010734",func="callee4",
20611 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20612 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
20613 bkpt=@{number="2",type="watchpoint",disp="keep",
20614 enabled="y",addr="",what="C",times="-5"@}]@}
20618 ^done,reason="watchpoint-scope",wpnum="2",
20619 frame=@{func="callee3",args=[@{name="strarg",
20620 value="0x11940 \"A string argument.\""@}],
20621 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20622 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20625 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20626 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20627 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20628 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20629 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20630 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20631 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20632 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20633 addr="0x00010734",func="callee4",
20634 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20635 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
20640 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20641 @node GDB/MI Program Context
20642 @section @sc{gdb/mi} Program Context
20644 @subheading The @code{-exec-arguments} Command
20645 @findex -exec-arguments
20648 @subsubheading Synopsis
20651 -exec-arguments @var{args}
20654 Set the inferior program arguments, to be used in the next
20657 @subsubheading @value{GDBN} Command
20659 The corresponding @value{GDBN} command is @samp{set args}.
20661 @subsubheading Example
20665 -exec-arguments -v word
20671 @subheading The @code{-exec-show-arguments} Command
20672 @findex -exec-show-arguments
20674 @subsubheading Synopsis
20677 -exec-show-arguments
20680 Print the arguments of the program.
20682 @subsubheading @value{GDBN} Command
20684 The corresponding @value{GDBN} command is @samp{show args}.
20686 @subsubheading Example
20690 @subheading The @code{-environment-cd} Command
20691 @findex -environment-cd
20693 @subsubheading Synopsis
20696 -environment-cd @var{pathdir}
20699 Set @value{GDBN}'s working directory.
20701 @subsubheading @value{GDBN} Command
20703 The corresponding @value{GDBN} command is @samp{cd}.
20705 @subsubheading Example
20709 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20715 @subheading The @code{-environment-directory} Command
20716 @findex -environment-directory
20718 @subsubheading Synopsis
20721 -environment-directory [ -r ] [ @var{pathdir} ]+
20724 Add directories @var{pathdir} to beginning of search path for source files.
20725 If the @samp{-r} option is used, the search path is reset to the default
20726 search path. If directories @var{pathdir} are supplied in addition to the
20727 @samp{-r} option, the search path is first reset and then addition
20729 Multiple directories may be specified, separated by blanks. Specifying
20730 multiple directories in a single command
20731 results in the directories added to the beginning of the
20732 search path in the same order they were presented in the command.
20733 If blanks are needed as
20734 part of a directory name, double-quotes should be used around
20735 the name. In the command output, the path will show up separated
20736 by the system directory-separator character. The directory-separator
20737 character must not be used
20738 in any directory name.
20739 If no directories are specified, the current search path is displayed.
20741 @subsubheading @value{GDBN} Command
20743 The corresponding @value{GDBN} command is @samp{dir}.
20745 @subsubheading Example
20749 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20750 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
20752 -environment-directory ""
20753 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
20755 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
20756 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
20758 -environment-directory -r
20759 ^done,source-path="$cdir:$cwd"
20764 @subheading The @code{-environment-path} Command
20765 @findex -environment-path
20767 @subsubheading Synopsis
20770 -environment-path [ -r ] [ @var{pathdir} ]+
20773 Add directories @var{pathdir} to beginning of search path for object files.
20774 If the @samp{-r} option is used, the search path is reset to the original
20775 search path that existed at gdb start-up. If directories @var{pathdir} are
20776 supplied in addition to the
20777 @samp{-r} option, the search path is first reset and then addition
20779 Multiple directories may be specified, separated by blanks. Specifying
20780 multiple directories in a single command
20781 results in the directories added to the beginning of the
20782 search path in the same order they were presented in the command.
20783 If blanks are needed as
20784 part of a directory name, double-quotes should be used around
20785 the name. In the command output, the path will show up separated
20786 by the system directory-separator character. The directory-separator
20787 character must not be used
20788 in any directory name.
20789 If no directories are specified, the current path is displayed.
20792 @subsubheading @value{GDBN} Command
20794 The corresponding @value{GDBN} command is @samp{path}.
20796 @subsubheading Example
20801 ^done,path="/usr/bin"
20803 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
20804 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
20806 -environment-path -r /usr/local/bin
20807 ^done,path="/usr/local/bin:/usr/bin"
20812 @subheading The @code{-environment-pwd} Command
20813 @findex -environment-pwd
20815 @subsubheading Synopsis
20821 Show the current working directory.
20823 @subsubheading @value{GDBN} Command
20825 The corresponding @value{GDBN} command is @samp{pwd}.
20827 @subsubheading Example
20832 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
20836 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20837 @node GDB/MI Thread Commands
20838 @section @sc{gdb/mi} Thread Commands
20841 @subheading The @code{-thread-info} Command
20842 @findex -thread-info
20844 @subsubheading Synopsis
20847 -thread-info [ @var{thread-id} ]
20850 Reports information about either a specific thread, if
20851 the @var{thread-id} parameter is present, or about all
20852 threads. When printing information about all threads,
20853 also reports the current thread.
20855 @subsubheading @value{GDBN} Command
20857 The @samp{info thread} command prints the same information
20860 @subsubheading Example
20865 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
20866 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
20867 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
20868 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
20869 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
20870 current-thread-id="1"
20874 The @samp{state} field may have the following values:
20878 The thread is stopped. Frame information is available for stopped
20882 The thread is running. There's no frame information for running
20887 @subheading The @code{-thread-list-ids} Command
20888 @findex -thread-list-ids
20890 @subsubheading Synopsis
20896 Produces a list of the currently known @value{GDBN} thread ids. At the
20897 end of the list it also prints the total number of such threads.
20899 This command is retained for historical reasons, the
20900 @code{-thread-info} command should be used instead.
20902 @subsubheading @value{GDBN} Command
20904 Part of @samp{info threads} supplies the same information.
20906 @subsubheading Example
20911 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20912 current-thread-id="1",number-of-threads="3"
20917 @subheading The @code{-thread-select} Command
20918 @findex -thread-select
20920 @subsubheading Synopsis
20923 -thread-select @var{threadnum}
20926 Make @var{threadnum} the current thread. It prints the number of the new
20927 current thread, and the topmost frame for that thread.
20929 This command is deprecated in favor of explicitly using the
20930 @samp{--thread} option to each command.
20932 @subsubheading @value{GDBN} Command
20934 The corresponding @value{GDBN} command is @samp{thread}.
20936 @subsubheading Example
20943 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20944 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20948 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20949 number-of-threads="3"
20952 ^done,new-thread-id="3",
20953 frame=@{level="0",func="vprintf",
20954 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20955 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20959 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20960 @node GDB/MI Program Execution
20961 @section @sc{gdb/mi} Program Execution
20963 These are the asynchronous commands which generate the out-of-band
20964 record @samp{*stopped}. Currently @value{GDBN} only really executes
20965 asynchronously with remote targets and this interaction is mimicked in
20968 @subheading The @code{-exec-continue} Command
20969 @findex -exec-continue
20971 @subsubheading Synopsis
20974 -exec-continue [--all|--thread-group N]
20977 Resumes the execution of the inferior program until a breakpoint is
20978 encountered, or until the inferior exits. In all-stop mode
20979 (@pxref{All-Stop Mode}), may resume only one thread, or all threads,
20980 depending on the value of the @samp{scheduler-locking} variable. In
20981 non-stop mode (@pxref{Non-Stop Mode}), if the @samp{--all} is not
20982 specified, only the thread specified with the @samp{--thread} option
20983 (or current thread, if no @samp{--thread} is provided) is resumed. If
20984 @samp{--all} is specified, all threads will be resumed. The
20985 @samp{--all} option is ignored in all-stop mode. If the
20986 @samp{--thread-group} options is specified, then all threads in that
20987 thread group are resumed.
20989 @subsubheading @value{GDBN} Command
20991 The corresponding @value{GDBN} corresponding is @samp{continue}.
20993 @subsubheading Example
21000 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
21001 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
21007 @subheading The @code{-exec-finish} Command
21008 @findex -exec-finish
21010 @subsubheading Synopsis
21016 Resumes the execution of the inferior program until the current
21017 function is exited. Displays the results returned by the function.
21019 @subsubheading @value{GDBN} Command
21021 The corresponding @value{GDBN} command is @samp{finish}.
21023 @subsubheading Example
21025 Function returning @code{void}.
21032 *stopped,reason="function-finished",frame=@{func="main",args=[],
21033 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
21037 Function returning other than @code{void}. The name of the internal
21038 @value{GDBN} variable storing the result is printed, together with the
21045 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
21046 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
21047 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21048 gdb-result-var="$1",return-value="0"
21053 @subheading The @code{-exec-interrupt} Command
21054 @findex -exec-interrupt
21056 @subsubheading Synopsis
21059 -exec-interrupt [--all|--thread-group N]
21062 Interrupts the background execution of the target. Note how the token
21063 associated with the stop message is the one for the execution command
21064 that has been interrupted. The token for the interrupt itself only
21065 appears in the @samp{^done} output. If the user is trying to
21066 interrupt a non-running program, an error message will be printed.
21068 Note that when asynchronous execution is enabled, this command is
21069 asynchronous just like other execution commands. That is, first the
21070 @samp{^done} response will be printed, and the target stop will be
21071 reported after that using the @samp{*stopped} notification.
21073 In non-stop mode, only the context thread is interrupted by default.
21074 All threads will be interrupted if the @samp{--all} option is
21075 specified. If the @samp{--thread-group} option is specified, all
21076 threads in that group will be interrupted.
21078 @subsubheading @value{GDBN} Command
21080 The corresponding @value{GDBN} command is @samp{interrupt}.
21082 @subsubheading Example
21093 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
21094 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
21095 fullname="/home/foo/bar/try.c",line="13"@}
21100 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
21105 @subheading The @code{-exec-next} Command
21108 @subsubheading Synopsis
21114 Resumes execution of the inferior program, stopping when the beginning
21115 of the next source line is reached.
21117 @subsubheading @value{GDBN} Command
21119 The corresponding @value{GDBN} command is @samp{next}.
21121 @subsubheading Example
21127 *stopped,reason="end-stepping-range",line="8",file="hello.c"
21132 @subheading The @code{-exec-next-instruction} Command
21133 @findex -exec-next-instruction
21135 @subsubheading Synopsis
21138 -exec-next-instruction
21141 Executes one machine instruction. If the instruction is a function
21142 call, continues until the function returns. If the program stops at an
21143 instruction in the middle of a source line, the address will be
21146 @subsubheading @value{GDBN} Command
21148 The corresponding @value{GDBN} command is @samp{nexti}.
21150 @subsubheading Example
21154 -exec-next-instruction
21158 *stopped,reason="end-stepping-range",
21159 addr="0x000100d4",line="5",file="hello.c"
21164 @subheading The @code{-exec-return} Command
21165 @findex -exec-return
21167 @subsubheading Synopsis
21173 Makes current function return immediately. Doesn't execute the inferior.
21174 Displays the new current frame.
21176 @subsubheading @value{GDBN} Command
21178 The corresponding @value{GDBN} command is @samp{return}.
21180 @subsubheading Example
21184 200-break-insert callee4
21185 200^done,bkpt=@{number="1",addr="0x00010734",
21186 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21191 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21192 frame=@{func="callee4",args=[],
21193 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21194 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21200 111^done,frame=@{level="0",func="callee3",
21201 args=[@{name="strarg",
21202 value="0x11940 \"A string argument.\""@}],
21203 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21204 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
21209 @subheading The @code{-exec-run} Command
21212 @subsubheading Synopsis
21218 Starts execution of the inferior from the beginning. The inferior
21219 executes until either a breakpoint is encountered or the program
21220 exits. In the latter case the output will include an exit code, if
21221 the program has exited exceptionally.
21223 @subsubheading @value{GDBN} Command
21225 The corresponding @value{GDBN} command is @samp{run}.
21227 @subsubheading Examples
21232 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
21237 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21238 frame=@{func="main",args=[],file="recursive2.c",
21239 fullname="/home/foo/bar/recursive2.c",line="4"@}
21244 Program exited normally:
21252 *stopped,reason="exited-normally"
21257 Program exited exceptionally:
21265 *stopped,reason="exited",exit-code="01"
21269 Another way the program can terminate is if it receives a signal such as
21270 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
21274 *stopped,reason="exited-signalled",signal-name="SIGINT",
21275 signal-meaning="Interrupt"
21279 @c @subheading -exec-signal
21282 @subheading The @code{-exec-step} Command
21285 @subsubheading Synopsis
21291 Resumes execution of the inferior program, stopping when the beginning
21292 of the next source line is reached, if the next source line is not a
21293 function call. If it is, stop at the first instruction of the called
21296 @subsubheading @value{GDBN} Command
21298 The corresponding @value{GDBN} command is @samp{step}.
21300 @subsubheading Example
21302 Stepping into a function:
21308 *stopped,reason="end-stepping-range",
21309 frame=@{func="foo",args=[@{name="a",value="10"@},
21310 @{name="b",value="0"@}],file="recursive2.c",
21311 fullname="/home/foo/bar/recursive2.c",line="11"@}
21321 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
21326 @subheading The @code{-exec-step-instruction} Command
21327 @findex -exec-step-instruction
21329 @subsubheading Synopsis
21332 -exec-step-instruction
21335 Resumes the inferior which executes one machine instruction. The
21336 output, once @value{GDBN} has stopped, will vary depending on whether
21337 we have stopped in the middle of a source line or not. In the former
21338 case, the address at which the program stopped will be printed as
21341 @subsubheading @value{GDBN} Command
21343 The corresponding @value{GDBN} command is @samp{stepi}.
21345 @subsubheading Example
21349 -exec-step-instruction
21353 *stopped,reason="end-stepping-range",
21354 frame=@{func="foo",args=[],file="try.c",
21355 fullname="/home/foo/bar/try.c",line="10"@}
21357 -exec-step-instruction
21361 *stopped,reason="end-stepping-range",
21362 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
21363 fullname="/home/foo/bar/try.c",line="10"@}
21368 @subheading The @code{-exec-until} Command
21369 @findex -exec-until
21371 @subsubheading Synopsis
21374 -exec-until [ @var{location} ]
21377 Executes the inferior until the @var{location} specified in the
21378 argument is reached. If there is no argument, the inferior executes
21379 until a source line greater than the current one is reached. The
21380 reason for stopping in this case will be @samp{location-reached}.
21382 @subsubheading @value{GDBN} Command
21384 The corresponding @value{GDBN} command is @samp{until}.
21386 @subsubheading Example
21390 -exec-until recursive2.c:6
21394 *stopped,reason="location-reached",frame=@{func="main",args=[],
21395 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
21400 @subheading -file-clear
21401 Is this going away????
21404 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21405 @node GDB/MI Stack Manipulation
21406 @section @sc{gdb/mi} Stack Manipulation Commands
21409 @subheading The @code{-stack-info-frame} Command
21410 @findex -stack-info-frame
21412 @subsubheading Synopsis
21418 Get info on the selected frame.
21420 @subsubheading @value{GDBN} Command
21422 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
21423 (without arguments).
21425 @subsubheading Example
21430 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
21431 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21432 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
21436 @subheading The @code{-stack-info-depth} Command
21437 @findex -stack-info-depth
21439 @subsubheading Synopsis
21442 -stack-info-depth [ @var{max-depth} ]
21445 Return the depth of the stack. If the integer argument @var{max-depth}
21446 is specified, do not count beyond @var{max-depth} frames.
21448 @subsubheading @value{GDBN} Command
21450 There's no equivalent @value{GDBN} command.
21452 @subsubheading Example
21454 For a stack with frame levels 0 through 11:
21461 -stack-info-depth 4
21464 -stack-info-depth 12
21467 -stack-info-depth 11
21470 -stack-info-depth 13
21475 @subheading The @code{-stack-list-arguments} Command
21476 @findex -stack-list-arguments
21478 @subsubheading Synopsis
21481 -stack-list-arguments @var{show-values}
21482 [ @var{low-frame} @var{high-frame} ]
21485 Display a list of the arguments for the frames between @var{low-frame}
21486 and @var{high-frame} (inclusive). If @var{low-frame} and
21487 @var{high-frame} are not provided, list the arguments for the whole
21488 call stack. If the two arguments are equal, show the single frame
21489 at the corresponding level. It is an error if @var{low-frame} is
21490 larger than the actual number of frames. On the other hand,
21491 @var{high-frame} may be larger than the actual number of frames, in
21492 which case only existing frames will be returned.
21494 The @var{show-values} argument must have a value of 0 or 1. A value of
21495 0 means that only the names of the arguments are listed, a value of 1
21496 means that both names and values of the arguments are printed.
21498 @subsubheading @value{GDBN} Command
21500 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
21501 @samp{gdb_get_args} command which partially overlaps with the
21502 functionality of @samp{-stack-list-arguments}.
21504 @subsubheading Example
21511 frame=@{level="0",addr="0x00010734",func="callee4",
21512 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21513 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
21514 frame=@{level="1",addr="0x0001076c",func="callee3",
21515 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21516 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
21517 frame=@{level="2",addr="0x0001078c",func="callee2",
21518 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21519 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
21520 frame=@{level="3",addr="0x000107b4",func="callee1",
21521 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21522 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
21523 frame=@{level="4",addr="0x000107e0",func="main",
21524 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21525 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
21527 -stack-list-arguments 0
21530 frame=@{level="0",args=[]@},
21531 frame=@{level="1",args=[name="strarg"]@},
21532 frame=@{level="2",args=[name="intarg",name="strarg"]@},
21533 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
21534 frame=@{level="4",args=[]@}]
21536 -stack-list-arguments 1
21539 frame=@{level="0",args=[]@},
21541 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21542 frame=@{level="2",args=[
21543 @{name="intarg",value="2"@},
21544 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21545 @{frame=@{level="3",args=[
21546 @{name="intarg",value="2"@},
21547 @{name="strarg",value="0x11940 \"A string argument.\""@},
21548 @{name="fltarg",value="3.5"@}]@},
21549 frame=@{level="4",args=[]@}]
21551 -stack-list-arguments 0 2 2
21552 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
21554 -stack-list-arguments 1 2 2
21555 ^done,stack-args=[frame=@{level="2",
21556 args=[@{name="intarg",value="2"@},
21557 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
21561 @c @subheading -stack-list-exception-handlers
21564 @subheading The @code{-stack-list-frames} Command
21565 @findex -stack-list-frames
21567 @subsubheading Synopsis
21570 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
21573 List the frames currently on the stack. For each frame it displays the
21578 The frame number, 0 being the topmost frame, i.e., the innermost function.
21580 The @code{$pc} value for that frame.
21584 File name of the source file where the function lives.
21586 Line number corresponding to the @code{$pc}.
21589 If invoked without arguments, this command prints a backtrace for the
21590 whole stack. If given two integer arguments, it shows the frames whose
21591 levels are between the two arguments (inclusive). If the two arguments
21592 are equal, it shows the single frame at the corresponding level. It is
21593 an error if @var{low-frame} is larger than the actual number of
21594 frames. On the other hand, @var{high-frame} may be larger than the
21595 actual number of frames, in which case only existing frames will be returned.
21597 @subsubheading @value{GDBN} Command
21599 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
21601 @subsubheading Example
21603 Full stack backtrace:
21609 [frame=@{level="0",addr="0x0001076c",func="foo",
21610 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
21611 frame=@{level="1",addr="0x000107a4",func="foo",
21612 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21613 frame=@{level="2",addr="0x000107a4",func="foo",
21614 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21615 frame=@{level="3",addr="0x000107a4",func="foo",
21616 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21617 frame=@{level="4",addr="0x000107a4",func="foo",
21618 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21619 frame=@{level="5",addr="0x000107a4",func="foo",
21620 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21621 frame=@{level="6",addr="0x000107a4",func="foo",
21622 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21623 frame=@{level="7",addr="0x000107a4",func="foo",
21624 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21625 frame=@{level="8",addr="0x000107a4",func="foo",
21626 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21627 frame=@{level="9",addr="0x000107a4",func="foo",
21628 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21629 frame=@{level="10",addr="0x000107a4",func="foo",
21630 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21631 frame=@{level="11",addr="0x00010738",func="main",
21632 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
21636 Show frames between @var{low_frame} and @var{high_frame}:
21640 -stack-list-frames 3 5
21642 [frame=@{level="3",addr="0x000107a4",func="foo",
21643 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21644 frame=@{level="4",addr="0x000107a4",func="foo",
21645 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21646 frame=@{level="5",addr="0x000107a4",func="foo",
21647 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21651 Show a single frame:
21655 -stack-list-frames 3 3
21657 [frame=@{level="3",addr="0x000107a4",func="foo",
21658 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21663 @subheading The @code{-stack-list-locals} Command
21664 @findex -stack-list-locals
21666 @subsubheading Synopsis
21669 -stack-list-locals @var{print-values}
21672 Display the local variable names for the selected frame. If
21673 @var{print-values} is 0 or @code{--no-values}, print only the names of
21674 the variables; if it is 1 or @code{--all-values}, print also their
21675 values; and if it is 2 or @code{--simple-values}, print the name,
21676 type and value for simple data types and the name and type for arrays,
21677 structures and unions. In this last case, a frontend can immediately
21678 display the value of simple data types and create variable objects for
21679 other data types when the user wishes to explore their values in
21682 @subsubheading @value{GDBN} Command
21684 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
21686 @subsubheading Example
21690 -stack-list-locals 0
21691 ^done,locals=[name="A",name="B",name="C"]
21693 -stack-list-locals --all-values
21694 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
21695 @{name="C",value="@{1, 2, 3@}"@}]
21696 -stack-list-locals --simple-values
21697 ^done,locals=[@{name="A",type="int",value="1"@},
21698 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
21703 @subheading The @code{-stack-select-frame} Command
21704 @findex -stack-select-frame
21706 @subsubheading Synopsis
21709 -stack-select-frame @var{framenum}
21712 Change the selected frame. Select a different frame @var{framenum} on
21715 This command in deprecated in favor of passing the @samp{--frame}
21716 option to every command.
21718 @subsubheading @value{GDBN} Command
21720 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
21721 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
21723 @subsubheading Example
21727 -stack-select-frame 2
21732 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21733 @node GDB/MI Variable Objects
21734 @section @sc{gdb/mi} Variable Objects
21738 @subheading Motivation for Variable Objects in @sc{gdb/mi}
21740 For the implementation of a variable debugger window (locals, watched
21741 expressions, etc.), we are proposing the adaptation of the existing code
21742 used by @code{Insight}.
21744 The two main reasons for that are:
21748 It has been proven in practice (it is already on its second generation).
21751 It will shorten development time (needless to say how important it is
21755 The original interface was designed to be used by Tcl code, so it was
21756 slightly changed so it could be used through @sc{gdb/mi}. This section
21757 describes the @sc{gdb/mi} operations that will be available and gives some
21758 hints about their use.
21760 @emph{Note}: In addition to the set of operations described here, we
21761 expect the @sc{gui} implementation of a variable window to require, at
21762 least, the following operations:
21765 @item @code{-gdb-show} @code{output-radix}
21766 @item @code{-stack-list-arguments}
21767 @item @code{-stack-list-locals}
21768 @item @code{-stack-select-frame}
21773 @subheading Introduction to Variable Objects
21775 @cindex variable objects in @sc{gdb/mi}
21777 Variable objects are "object-oriented" MI interface for examining and
21778 changing values of expressions. Unlike some other MI interfaces that
21779 work with expressions, variable objects are specifically designed for
21780 simple and efficient presentation in the frontend. A variable object
21781 is identified by string name. When a variable object is created, the
21782 frontend specifies the expression for that variable object. The
21783 expression can be a simple variable, or it can be an arbitrary complex
21784 expression, and can even involve CPU registers. After creating a
21785 variable object, the frontend can invoke other variable object
21786 operations---for example to obtain or change the value of a variable
21787 object, or to change display format.
21789 Variable objects have hierarchical tree structure. Any variable object
21790 that corresponds to a composite type, such as structure in C, has
21791 a number of child variable objects, for example corresponding to each
21792 element of a structure. A child variable object can itself have
21793 children, recursively. Recursion ends when we reach
21794 leaf variable objects, which always have built-in types. Child variable
21795 objects are created only by explicit request, so if a frontend
21796 is not interested in the children of a particular variable object, no
21797 child will be created.
21799 For a leaf variable object it is possible to obtain its value as a
21800 string, or set the value from a string. String value can be also
21801 obtained for a non-leaf variable object, but it's generally a string
21802 that only indicates the type of the object, and does not list its
21803 contents. Assignment to a non-leaf variable object is not allowed.
21805 A frontend does not need to read the values of all variable objects each time
21806 the program stops. Instead, MI provides an update command that lists all
21807 variable objects whose values has changed since the last update
21808 operation. This considerably reduces the amount of data that must
21809 be transferred to the frontend. As noted above, children variable
21810 objects are created on demand, and only leaf variable objects have a
21811 real value. As result, gdb will read target memory only for leaf
21812 variables that frontend has created.
21814 The automatic update is not always desirable. For example, a frontend
21815 might want to keep a value of some expression for future reference,
21816 and never update it. For another example, fetching memory is
21817 relatively slow for embedded targets, so a frontend might want
21818 to disable automatic update for the variables that are either not
21819 visible on the screen, or ``closed''. This is possible using so
21820 called ``frozen variable objects''. Such variable objects are never
21821 implicitly updated.
21823 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
21824 fixed variable object, the expression is parsed when the variable
21825 object is created, including associating identifiers to specific
21826 variables. The meaning of expression never changes. For a floating
21827 variable object the values of variables whose names appear in the
21828 expressions are re-evaluated every time in the context of the current
21829 frame. Consider this example:
21834 struct work_state state;
21841 If a fixed variable object for the @code{state} variable is created in
21842 this function, and we enter the recursive call, the the variable
21843 object will report the value of @code{state} in the top-level
21844 @code{do_work} invocation. On the other hand, a floating variable
21845 object will report the value of @code{state} in the current frame.
21847 If an expression specified when creating a fixed variable object
21848 refers to a local variable, the variable object becomes bound to the
21849 thread and frame in which the variable object is created. When such
21850 variable object is updated, @value{GDBN} makes sure that the
21851 thread/frame combination the variable object is bound to still exists,
21852 and re-evaluates the variable object in context of that thread/frame.
21854 The following is the complete set of @sc{gdb/mi} operations defined to
21855 access this functionality:
21857 @multitable @columnfractions .4 .6
21858 @item @strong{Operation}
21859 @tab @strong{Description}
21861 @item @code{-var-create}
21862 @tab create a variable object
21863 @item @code{-var-delete}
21864 @tab delete the variable object and/or its children
21865 @item @code{-var-set-format}
21866 @tab set the display format of this variable
21867 @item @code{-var-show-format}
21868 @tab show the display format of this variable
21869 @item @code{-var-info-num-children}
21870 @tab tells how many children this object has
21871 @item @code{-var-list-children}
21872 @tab return a list of the object's children
21873 @item @code{-var-info-type}
21874 @tab show the type of this variable object
21875 @item @code{-var-info-expression}
21876 @tab print parent-relative expression that this variable object represents
21877 @item @code{-var-info-path-expression}
21878 @tab print full expression that this variable object represents
21879 @item @code{-var-show-attributes}
21880 @tab is this variable editable? does it exist here?
21881 @item @code{-var-evaluate-expression}
21882 @tab get the value of this variable
21883 @item @code{-var-assign}
21884 @tab set the value of this variable
21885 @item @code{-var-update}
21886 @tab update the variable and its children
21887 @item @code{-var-set-frozen}
21888 @tab set frozeness attribute
21891 In the next subsection we describe each operation in detail and suggest
21892 how it can be used.
21894 @subheading Description And Use of Operations on Variable Objects
21896 @subheading The @code{-var-create} Command
21897 @findex -var-create
21899 @subsubheading Synopsis
21902 -var-create @{@var{name} | "-"@}
21903 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
21906 This operation creates a variable object, which allows the monitoring of
21907 a variable, the result of an expression, a memory cell or a CPU
21910 The @var{name} parameter is the string by which the object can be
21911 referenced. It must be unique. If @samp{-} is specified, the varobj
21912 system will generate a string ``varNNNNNN'' automatically. It will be
21913 unique provided that one does not specify @var{name} of that format.
21914 The command fails if a duplicate name is found.
21916 The frame under which the expression should be evaluated can be
21917 specified by @var{frame-addr}. A @samp{*} indicates that the current
21918 frame should be used. A @samp{@@} indicates that a floating variable
21919 object must be created.
21921 @var{expression} is any expression valid on the current language set (must not
21922 begin with a @samp{*}), or one of the following:
21926 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
21929 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
21932 @samp{$@var{regname}} --- a CPU register name
21935 @subsubheading Result
21937 This operation returns the name, number of children and the type of the
21938 object created. Type is returned as a string as the ones generated by
21939 the @value{GDBN} CLI. If a fixed variable object is bound to a
21940 specific thread, the thread is is also printed:
21943 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}"
21947 @subheading The @code{-var-delete} Command
21948 @findex -var-delete
21950 @subsubheading Synopsis
21953 -var-delete [ -c ] @var{name}
21956 Deletes a previously created variable object and all of its children.
21957 With the @samp{-c} option, just deletes the children.
21959 Returns an error if the object @var{name} is not found.
21962 @subheading The @code{-var-set-format} Command
21963 @findex -var-set-format
21965 @subsubheading Synopsis
21968 -var-set-format @var{name} @var{format-spec}
21971 Sets the output format for the value of the object @var{name} to be
21974 @anchor{-var-set-format}
21975 The syntax for the @var{format-spec} is as follows:
21978 @var{format-spec} @expansion{}
21979 @{binary | decimal | hexadecimal | octal | natural@}
21982 The natural format is the default format choosen automatically
21983 based on the variable type (like decimal for an @code{int}, hex
21984 for pointers, etc.).
21986 For a variable with children, the format is set only on the
21987 variable itself, and the children are not affected.
21989 @subheading The @code{-var-show-format} Command
21990 @findex -var-show-format
21992 @subsubheading Synopsis
21995 -var-show-format @var{name}
21998 Returns the format used to display the value of the object @var{name}.
22001 @var{format} @expansion{}
22006 @subheading The @code{-var-info-num-children} Command
22007 @findex -var-info-num-children
22009 @subsubheading Synopsis
22012 -var-info-num-children @var{name}
22015 Returns the number of children of a variable object @var{name}:
22022 @subheading The @code{-var-list-children} Command
22023 @findex -var-list-children
22025 @subsubheading Synopsis
22028 -var-list-children [@var{print-values}] @var{name}
22030 @anchor{-var-list-children}
22032 Return a list of the children of the specified variable object and
22033 create variable objects for them, if they do not already exist. With
22034 a single argument or if @var{print-values} has a value for of 0 or
22035 @code{--no-values}, print only the names of the variables; if
22036 @var{print-values} is 1 or @code{--all-values}, also print their
22037 values; and if it is 2 or @code{--simple-values} print the name and
22038 value for simple data types and just the name for arrays, structures
22041 @subsubheading Example
22045 -var-list-children n
22046 ^done,numchild=@var{n},children=[@{name=@var{name},
22047 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
22049 -var-list-children --all-values n
22050 ^done,numchild=@var{n},children=[@{name=@var{name},
22051 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
22055 @subheading The @code{-var-info-type} Command
22056 @findex -var-info-type
22058 @subsubheading Synopsis
22061 -var-info-type @var{name}
22064 Returns the type of the specified variable @var{name}. The type is
22065 returned as a string in the same format as it is output by the
22069 type=@var{typename}
22073 @subheading The @code{-var-info-expression} Command
22074 @findex -var-info-expression
22076 @subsubheading Synopsis
22079 -var-info-expression @var{name}
22082 Returns a string that is suitable for presenting this
22083 variable object in user interface. The string is generally
22084 not valid expression in the current language, and cannot be evaluated.
22086 For example, if @code{a} is an array, and variable object
22087 @code{A} was created for @code{a}, then we'll get this output:
22090 (gdb) -var-info-expression A.1
22091 ^done,lang="C",exp="1"
22095 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
22097 Note that the output of the @code{-var-list-children} command also
22098 includes those expressions, so the @code{-var-info-expression} command
22101 @subheading The @code{-var-info-path-expression} Command
22102 @findex -var-info-path-expression
22104 @subsubheading Synopsis
22107 -var-info-path-expression @var{name}
22110 Returns an expression that can be evaluated in the current
22111 context and will yield the same value that a variable object has.
22112 Compare this with the @code{-var-info-expression} command, which
22113 result can be used only for UI presentation. Typical use of
22114 the @code{-var-info-path-expression} command is creating a
22115 watchpoint from a variable object.
22117 For example, suppose @code{C} is a C@t{++} class, derived from class
22118 @code{Base}, and that the @code{Base} class has a member called
22119 @code{m_size}. Assume a variable @code{c} is has the type of
22120 @code{C} and a variable object @code{C} was created for variable
22121 @code{c}. Then, we'll get this output:
22123 (gdb) -var-info-path-expression C.Base.public.m_size
22124 ^done,path_expr=((Base)c).m_size)
22127 @subheading The @code{-var-show-attributes} Command
22128 @findex -var-show-attributes
22130 @subsubheading Synopsis
22133 -var-show-attributes @var{name}
22136 List attributes of the specified variable object @var{name}:
22139 status=@var{attr} [ ( ,@var{attr} )* ]
22143 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
22145 @subheading The @code{-var-evaluate-expression} Command
22146 @findex -var-evaluate-expression
22148 @subsubheading Synopsis
22151 -var-evaluate-expression [-f @var{format-spec}] @var{name}
22154 Evaluates the expression that is represented by the specified variable
22155 object and returns its value as a string. The format of the string
22156 can be specified with the @samp{-f} option. The possible values of
22157 this option are the same as for @code{-var-set-format}
22158 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
22159 the current display format will be used. The current display format
22160 can be changed using the @code{-var-set-format} command.
22166 Note that one must invoke @code{-var-list-children} for a variable
22167 before the value of a child variable can be evaluated.
22169 @subheading The @code{-var-assign} Command
22170 @findex -var-assign
22172 @subsubheading Synopsis
22175 -var-assign @var{name} @var{expression}
22178 Assigns the value of @var{expression} to the variable object specified
22179 by @var{name}. The object must be @samp{editable}. If the variable's
22180 value is altered by the assign, the variable will show up in any
22181 subsequent @code{-var-update} list.
22183 @subsubheading Example
22191 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
22195 @subheading The @code{-var-update} Command
22196 @findex -var-update
22198 @subsubheading Synopsis
22201 -var-update [@var{print-values}] @{@var{name} | "*"@}
22204 Reevaluate the expressions corresponding to the variable object
22205 @var{name} and all its direct and indirect children, and return the
22206 list of variable objects whose values have changed; @var{name} must
22207 be a root variable object. Here, ``changed'' means that the result of
22208 @code{-var-evaluate-expression} before and after the
22209 @code{-var-update} is different. If @samp{*} is used as the variable
22210 object names, all existing variable objects are updated, except
22211 for frozen ones (@pxref{-var-set-frozen}). The option
22212 @var{print-values} determines whether both names and values, or just
22213 names are printed. The possible values of this option are the same
22214 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
22215 recommended to use the @samp{--all-values} option, to reduce the
22216 number of MI commands needed on each program stop.
22218 With the @samp{*} parameter, if a variable object is bound to a
22219 currently running thread, it will not be updated, without any
22222 @subsubheading Example
22229 -var-update --all-values var1
22230 ^done,changelist=[@{name="var1",value="3",in_scope="true",
22231 type_changed="false"@}]
22235 @anchor{-var-update}
22236 The field in_scope may take three values:
22240 The variable object's current value is valid.
22243 The variable object does not currently hold a valid value but it may
22244 hold one in the future if its associated expression comes back into
22248 The variable object no longer holds a valid value.
22249 This can occur when the executable file being debugged has changed,
22250 either through recompilation or by using the @value{GDBN} @code{file}
22251 command. The front end should normally choose to delete these variable
22255 In the future new values may be added to this list so the front should
22256 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
22258 @subheading The @code{-var-set-frozen} Command
22259 @findex -var-set-frozen
22260 @anchor{-var-set-frozen}
22262 @subsubheading Synopsis
22265 -var-set-frozen @var{name} @var{flag}
22268 Set the frozenness flag on the variable object @var{name}. The
22269 @var{flag} parameter should be either @samp{1} to make the variable
22270 frozen or @samp{0} to make it unfrozen. If a variable object is
22271 frozen, then neither itself, nor any of its children, are
22272 implicitly updated by @code{-var-update} of
22273 a parent variable or by @code{-var-update *}. Only
22274 @code{-var-update} of the variable itself will update its value and
22275 values of its children. After a variable object is unfrozen, it is
22276 implicitly updated by all subsequent @code{-var-update} operations.
22277 Unfreezing a variable does not update it, only subsequent
22278 @code{-var-update} does.
22280 @subsubheading Example
22284 -var-set-frozen V 1
22290 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22291 @node GDB/MI Data Manipulation
22292 @section @sc{gdb/mi} Data Manipulation
22294 @cindex data manipulation, in @sc{gdb/mi}
22295 @cindex @sc{gdb/mi}, data manipulation
22296 This section describes the @sc{gdb/mi} commands that manipulate data:
22297 examine memory and registers, evaluate expressions, etc.
22299 @c REMOVED FROM THE INTERFACE.
22300 @c @subheading -data-assign
22301 @c Change the value of a program variable. Plenty of side effects.
22302 @c @subsubheading GDB Command
22304 @c @subsubheading Example
22307 @subheading The @code{-data-disassemble} Command
22308 @findex -data-disassemble
22310 @subsubheading Synopsis
22314 [ -s @var{start-addr} -e @var{end-addr} ]
22315 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
22323 @item @var{start-addr}
22324 is the beginning address (or @code{$pc})
22325 @item @var{end-addr}
22327 @item @var{filename}
22328 is the name of the file to disassemble
22329 @item @var{linenum}
22330 is the line number to disassemble around
22332 is the number of disassembly lines to be produced. If it is -1,
22333 the whole function will be disassembled, in case no @var{end-addr} is
22334 specified. If @var{end-addr} is specified as a non-zero value, and
22335 @var{lines} is lower than the number of disassembly lines between
22336 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
22337 displayed; if @var{lines} is higher than the number of lines between
22338 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
22341 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
22345 @subsubheading Result
22347 The output for each instruction is composed of four fields:
22356 Note that whatever included in the instruction field, is not manipulated
22357 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
22359 @subsubheading @value{GDBN} Command
22361 There's no direct mapping from this command to the CLI.
22363 @subsubheading Example
22365 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
22369 -data-disassemble -s $pc -e "$pc + 20" -- 0
22372 @{address="0x000107c0",func-name="main",offset="4",
22373 inst="mov 2, %o0"@},
22374 @{address="0x000107c4",func-name="main",offset="8",
22375 inst="sethi %hi(0x11800), %o2"@},
22376 @{address="0x000107c8",func-name="main",offset="12",
22377 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
22378 @{address="0x000107cc",func-name="main",offset="16",
22379 inst="sethi %hi(0x11800), %o2"@},
22380 @{address="0x000107d0",func-name="main",offset="20",
22381 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
22385 Disassemble the whole @code{main} function. Line 32 is part of
22389 -data-disassemble -f basics.c -l 32 -- 0
22391 @{address="0x000107bc",func-name="main",offset="0",
22392 inst="save %sp, -112, %sp"@},
22393 @{address="0x000107c0",func-name="main",offset="4",
22394 inst="mov 2, %o0"@},
22395 @{address="0x000107c4",func-name="main",offset="8",
22396 inst="sethi %hi(0x11800), %o2"@},
22398 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
22399 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
22403 Disassemble 3 instructions from the start of @code{main}:
22407 -data-disassemble -f basics.c -l 32 -n 3 -- 0
22409 @{address="0x000107bc",func-name="main",offset="0",
22410 inst="save %sp, -112, %sp"@},
22411 @{address="0x000107c0",func-name="main",offset="4",
22412 inst="mov 2, %o0"@},
22413 @{address="0x000107c4",func-name="main",offset="8",
22414 inst="sethi %hi(0x11800), %o2"@}]
22418 Disassemble 3 instructions from the start of @code{main} in mixed mode:
22422 -data-disassemble -f basics.c -l 32 -n 3 -- 1
22424 src_and_asm_line=@{line="31",
22425 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22426 testsuite/gdb.mi/basics.c",line_asm_insn=[
22427 @{address="0x000107bc",func-name="main",offset="0",
22428 inst="save %sp, -112, %sp"@}]@},
22429 src_and_asm_line=@{line="32",
22430 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22431 testsuite/gdb.mi/basics.c",line_asm_insn=[
22432 @{address="0x000107c0",func-name="main",offset="4",
22433 inst="mov 2, %o0"@},
22434 @{address="0x000107c4",func-name="main",offset="8",
22435 inst="sethi %hi(0x11800), %o2"@}]@}]
22440 @subheading The @code{-data-evaluate-expression} Command
22441 @findex -data-evaluate-expression
22443 @subsubheading Synopsis
22446 -data-evaluate-expression @var{expr}
22449 Evaluate @var{expr} as an expression. The expression could contain an
22450 inferior function call. The function call will execute synchronously.
22451 If the expression contains spaces, it must be enclosed in double quotes.
22453 @subsubheading @value{GDBN} Command
22455 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
22456 @samp{call}. In @code{gdbtk} only, there's a corresponding
22457 @samp{gdb_eval} command.
22459 @subsubheading Example
22461 In the following example, the numbers that precede the commands are the
22462 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
22463 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
22467 211-data-evaluate-expression A
22470 311-data-evaluate-expression &A
22471 311^done,value="0xefffeb7c"
22473 411-data-evaluate-expression A+3
22476 511-data-evaluate-expression "A + 3"
22482 @subheading The @code{-data-list-changed-registers} Command
22483 @findex -data-list-changed-registers
22485 @subsubheading Synopsis
22488 -data-list-changed-registers
22491 Display a list of the registers that have changed.
22493 @subsubheading @value{GDBN} Command
22495 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
22496 has the corresponding command @samp{gdb_changed_register_list}.
22498 @subsubheading Example
22500 On a PPC MBX board:
22508 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
22509 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
22512 -data-list-changed-registers
22513 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
22514 "10","11","13","14","15","16","17","18","19","20","21","22","23",
22515 "24","25","26","27","28","30","31","64","65","66","67","69"]
22520 @subheading The @code{-data-list-register-names} Command
22521 @findex -data-list-register-names
22523 @subsubheading Synopsis
22526 -data-list-register-names [ ( @var{regno} )+ ]
22529 Show a list of register names for the current target. If no arguments
22530 are given, it shows a list of the names of all the registers. If
22531 integer numbers are given as arguments, it will print a list of the
22532 names of the registers corresponding to the arguments. To ensure
22533 consistency between a register name and its number, the output list may
22534 include empty register names.
22536 @subsubheading @value{GDBN} Command
22538 @value{GDBN} does not have a command which corresponds to
22539 @samp{-data-list-register-names}. In @code{gdbtk} there is a
22540 corresponding command @samp{gdb_regnames}.
22542 @subsubheading Example
22544 For the PPC MBX board:
22547 -data-list-register-names
22548 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
22549 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
22550 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
22551 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
22552 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
22553 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
22554 "", "pc","ps","cr","lr","ctr","xer"]
22556 -data-list-register-names 1 2 3
22557 ^done,register-names=["r1","r2","r3"]
22561 @subheading The @code{-data-list-register-values} Command
22562 @findex -data-list-register-values
22564 @subsubheading Synopsis
22567 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
22570 Display the registers' contents. @var{fmt} is the format according to
22571 which the registers' contents are to be returned, followed by an optional
22572 list of numbers specifying the registers to display. A missing list of
22573 numbers indicates that the contents of all the registers must be returned.
22575 Allowed formats for @var{fmt} are:
22592 @subsubheading @value{GDBN} Command
22594 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
22595 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
22597 @subsubheading Example
22599 For a PPC MBX board (note: line breaks are for readability only, they
22600 don't appear in the actual output):
22604 -data-list-register-values r 64 65
22605 ^done,register-values=[@{number="64",value="0xfe00a300"@},
22606 @{number="65",value="0x00029002"@}]
22608 -data-list-register-values x
22609 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
22610 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
22611 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
22612 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
22613 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
22614 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
22615 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
22616 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
22617 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
22618 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
22619 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
22620 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
22621 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
22622 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
22623 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
22624 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
22625 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
22626 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
22627 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
22628 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
22629 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
22630 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
22631 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
22632 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
22633 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
22634 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
22635 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
22636 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
22637 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
22638 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
22639 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
22640 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
22641 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
22642 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
22643 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
22644 @{number="69",value="0x20002b03"@}]
22649 @subheading The @code{-data-read-memory} Command
22650 @findex -data-read-memory
22652 @subsubheading Synopsis
22655 -data-read-memory [ -o @var{byte-offset} ]
22656 @var{address} @var{word-format} @var{word-size}
22657 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
22664 @item @var{address}
22665 An expression specifying the address of the first memory word to be
22666 read. Complex expressions containing embedded white space should be
22667 quoted using the C convention.
22669 @item @var{word-format}
22670 The format to be used to print the memory words. The notation is the
22671 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
22674 @item @var{word-size}
22675 The size of each memory word in bytes.
22677 @item @var{nr-rows}
22678 The number of rows in the output table.
22680 @item @var{nr-cols}
22681 The number of columns in the output table.
22684 If present, indicates that each row should include an @sc{ascii} dump. The
22685 value of @var{aschar} is used as a padding character when a byte is not a
22686 member of the printable @sc{ascii} character set (printable @sc{ascii}
22687 characters are those whose code is between 32 and 126, inclusively).
22689 @item @var{byte-offset}
22690 An offset to add to the @var{address} before fetching memory.
22693 This command displays memory contents as a table of @var{nr-rows} by
22694 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
22695 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
22696 (returned as @samp{total-bytes}). Should less than the requested number
22697 of bytes be returned by the target, the missing words are identified
22698 using @samp{N/A}. The number of bytes read from the target is returned
22699 in @samp{nr-bytes} and the starting address used to read memory in
22702 The address of the next/previous row or page is available in
22703 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
22706 @subsubheading @value{GDBN} Command
22708 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
22709 @samp{gdb_get_mem} memory read command.
22711 @subsubheading Example
22713 Read six bytes of memory starting at @code{bytes+6} but then offset by
22714 @code{-6} bytes. Format as three rows of two columns. One byte per
22715 word. Display each word in hex.
22719 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
22720 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
22721 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
22722 prev-page="0x0000138a",memory=[
22723 @{addr="0x00001390",data=["0x00","0x01"]@},
22724 @{addr="0x00001392",data=["0x02","0x03"]@},
22725 @{addr="0x00001394",data=["0x04","0x05"]@}]
22729 Read two bytes of memory starting at address @code{shorts + 64} and
22730 display as a single word formatted in decimal.
22734 5-data-read-memory shorts+64 d 2 1 1
22735 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
22736 next-row="0x00001512",prev-row="0x0000150e",
22737 next-page="0x00001512",prev-page="0x0000150e",memory=[
22738 @{addr="0x00001510",data=["128"]@}]
22742 Read thirty two bytes of memory starting at @code{bytes+16} and format
22743 as eight rows of four columns. Include a string encoding with @samp{x}
22744 used as the non-printable character.
22748 4-data-read-memory bytes+16 x 1 8 4 x
22749 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
22750 next-row="0x000013c0",prev-row="0x0000139c",
22751 next-page="0x000013c0",prev-page="0x00001380",memory=[
22752 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
22753 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
22754 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
22755 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
22756 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
22757 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
22758 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
22759 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
22763 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22764 @node GDB/MI Tracepoint Commands
22765 @section @sc{gdb/mi} Tracepoint Commands
22767 The tracepoint commands are not yet implemented.
22769 @c @subheading -trace-actions
22771 @c @subheading -trace-delete
22773 @c @subheading -trace-disable
22775 @c @subheading -trace-dump
22777 @c @subheading -trace-enable
22779 @c @subheading -trace-exists
22781 @c @subheading -trace-find
22783 @c @subheading -trace-frame-number
22785 @c @subheading -trace-info
22787 @c @subheading -trace-insert
22789 @c @subheading -trace-list
22791 @c @subheading -trace-pass-count
22793 @c @subheading -trace-save
22795 @c @subheading -trace-start
22797 @c @subheading -trace-stop
22800 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22801 @node GDB/MI Symbol Query
22802 @section @sc{gdb/mi} Symbol Query Commands
22805 @subheading The @code{-symbol-info-address} Command
22806 @findex -symbol-info-address
22808 @subsubheading Synopsis
22811 -symbol-info-address @var{symbol}
22814 Describe where @var{symbol} is stored.
22816 @subsubheading @value{GDBN} Command
22818 The corresponding @value{GDBN} command is @samp{info address}.
22820 @subsubheading Example
22824 @subheading The @code{-symbol-info-file} Command
22825 @findex -symbol-info-file
22827 @subsubheading Synopsis
22833 Show the file for the symbol.
22835 @subsubheading @value{GDBN} Command
22837 There's no equivalent @value{GDBN} command. @code{gdbtk} has
22838 @samp{gdb_find_file}.
22840 @subsubheading Example
22844 @subheading The @code{-symbol-info-function} Command
22845 @findex -symbol-info-function
22847 @subsubheading Synopsis
22850 -symbol-info-function
22853 Show which function the symbol lives in.
22855 @subsubheading @value{GDBN} Command
22857 @samp{gdb_get_function} in @code{gdbtk}.
22859 @subsubheading Example
22863 @subheading The @code{-symbol-info-line} Command
22864 @findex -symbol-info-line
22866 @subsubheading Synopsis
22872 Show the core addresses of the code for a source line.
22874 @subsubheading @value{GDBN} Command
22876 The corresponding @value{GDBN} command is @samp{info line}.
22877 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
22879 @subsubheading Example
22883 @subheading The @code{-symbol-info-symbol} Command
22884 @findex -symbol-info-symbol
22886 @subsubheading Synopsis
22889 -symbol-info-symbol @var{addr}
22892 Describe what symbol is at location @var{addr}.
22894 @subsubheading @value{GDBN} Command
22896 The corresponding @value{GDBN} command is @samp{info symbol}.
22898 @subsubheading Example
22902 @subheading The @code{-symbol-list-functions} Command
22903 @findex -symbol-list-functions
22905 @subsubheading Synopsis
22908 -symbol-list-functions
22911 List the functions in the executable.
22913 @subsubheading @value{GDBN} Command
22915 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
22916 @samp{gdb_search} in @code{gdbtk}.
22918 @subsubheading Example
22922 @subheading The @code{-symbol-list-lines} Command
22923 @findex -symbol-list-lines
22925 @subsubheading Synopsis
22928 -symbol-list-lines @var{filename}
22931 Print the list of lines that contain code and their associated program
22932 addresses for the given source filename. The entries are sorted in
22933 ascending PC order.
22935 @subsubheading @value{GDBN} Command
22937 There is no corresponding @value{GDBN} command.
22939 @subsubheading Example
22942 -symbol-list-lines basics.c
22943 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
22948 @subheading The @code{-symbol-list-types} Command
22949 @findex -symbol-list-types
22951 @subsubheading Synopsis
22957 List all the type names.
22959 @subsubheading @value{GDBN} Command
22961 The corresponding commands are @samp{info types} in @value{GDBN},
22962 @samp{gdb_search} in @code{gdbtk}.
22964 @subsubheading Example
22968 @subheading The @code{-symbol-list-variables} Command
22969 @findex -symbol-list-variables
22971 @subsubheading Synopsis
22974 -symbol-list-variables
22977 List all the global and static variable names.
22979 @subsubheading @value{GDBN} Command
22981 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
22983 @subsubheading Example
22987 @subheading The @code{-symbol-locate} Command
22988 @findex -symbol-locate
22990 @subsubheading Synopsis
22996 @subsubheading @value{GDBN} Command
22998 @samp{gdb_loc} in @code{gdbtk}.
23000 @subsubheading Example
23004 @subheading The @code{-symbol-type} Command
23005 @findex -symbol-type
23007 @subsubheading Synopsis
23010 -symbol-type @var{variable}
23013 Show type of @var{variable}.
23015 @subsubheading @value{GDBN} Command
23017 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
23018 @samp{gdb_obj_variable}.
23020 @subsubheading Example
23024 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23025 @node GDB/MI File Commands
23026 @section @sc{gdb/mi} File Commands
23028 This section describes the GDB/MI commands to specify executable file names
23029 and to read in and obtain symbol table information.
23031 @subheading The @code{-file-exec-and-symbols} Command
23032 @findex -file-exec-and-symbols
23034 @subsubheading Synopsis
23037 -file-exec-and-symbols @var{file}
23040 Specify the executable file to be debugged. This file is the one from
23041 which the symbol table is also read. If no file is specified, the
23042 command clears the executable and symbol information. If breakpoints
23043 are set when using this command with no arguments, @value{GDBN} will produce
23044 error messages. Otherwise, no output is produced, except a completion
23047 @subsubheading @value{GDBN} Command
23049 The corresponding @value{GDBN} command is @samp{file}.
23051 @subsubheading Example
23055 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23061 @subheading The @code{-file-exec-file} Command
23062 @findex -file-exec-file
23064 @subsubheading Synopsis
23067 -file-exec-file @var{file}
23070 Specify the executable file to be debugged. Unlike
23071 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
23072 from this file. If used without argument, @value{GDBN} clears the information
23073 about the executable file. No output is produced, except a completion
23076 @subsubheading @value{GDBN} Command
23078 The corresponding @value{GDBN} command is @samp{exec-file}.
23080 @subsubheading Example
23084 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23090 @subheading The @code{-file-list-exec-sections} Command
23091 @findex -file-list-exec-sections
23093 @subsubheading Synopsis
23096 -file-list-exec-sections
23099 List the sections of the current executable file.
23101 @subsubheading @value{GDBN} Command
23103 The @value{GDBN} command @samp{info file} shows, among the rest, the same
23104 information as this command. @code{gdbtk} has a corresponding command
23105 @samp{gdb_load_info}.
23107 @subsubheading Example
23111 @subheading The @code{-file-list-exec-source-file} Command
23112 @findex -file-list-exec-source-file
23114 @subsubheading Synopsis
23117 -file-list-exec-source-file
23120 List the line number, the current source file, and the absolute path
23121 to the current source file for the current executable. The macro
23122 information field has a value of @samp{1} or @samp{0} depending on
23123 whether or not the file includes preprocessor macro information.
23125 @subsubheading @value{GDBN} Command
23127 The @value{GDBN} equivalent is @samp{info source}
23129 @subsubheading Example
23133 123-file-list-exec-source-file
23134 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
23139 @subheading The @code{-file-list-exec-source-files} Command
23140 @findex -file-list-exec-source-files
23142 @subsubheading Synopsis
23145 -file-list-exec-source-files
23148 List the source files for the current executable.
23150 It will always output the filename, but only when @value{GDBN} can find
23151 the absolute file name of a source file, will it output the fullname.
23153 @subsubheading @value{GDBN} Command
23155 The @value{GDBN} equivalent is @samp{info sources}.
23156 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
23158 @subsubheading Example
23161 -file-list-exec-source-files
23163 @{file=foo.c,fullname=/home/foo.c@},
23164 @{file=/home/bar.c,fullname=/home/bar.c@},
23165 @{file=gdb_could_not_find_fullpath.c@}]
23169 @subheading The @code{-file-list-shared-libraries} Command
23170 @findex -file-list-shared-libraries
23172 @subsubheading Synopsis
23175 -file-list-shared-libraries
23178 List the shared libraries in the program.
23180 @subsubheading @value{GDBN} Command
23182 The corresponding @value{GDBN} command is @samp{info shared}.
23184 @subsubheading Example
23188 @subheading The @code{-file-list-symbol-files} Command
23189 @findex -file-list-symbol-files
23191 @subsubheading Synopsis
23194 -file-list-symbol-files
23199 @subsubheading @value{GDBN} Command
23201 The corresponding @value{GDBN} command is @samp{info file} (part of it).
23203 @subsubheading Example
23207 @subheading The @code{-file-symbol-file} Command
23208 @findex -file-symbol-file
23210 @subsubheading Synopsis
23213 -file-symbol-file @var{file}
23216 Read symbol table info from the specified @var{file} argument. When
23217 used without arguments, clears @value{GDBN}'s symbol table info. No output is
23218 produced, except for a completion notification.
23220 @subsubheading @value{GDBN} Command
23222 The corresponding @value{GDBN} command is @samp{symbol-file}.
23224 @subsubheading Example
23228 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23234 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23235 @node GDB/MI Memory Overlay Commands
23236 @section @sc{gdb/mi} Memory Overlay Commands
23238 The memory overlay commands are not implemented.
23240 @c @subheading -overlay-auto
23242 @c @subheading -overlay-list-mapping-state
23244 @c @subheading -overlay-list-overlays
23246 @c @subheading -overlay-map
23248 @c @subheading -overlay-off
23250 @c @subheading -overlay-on
23252 @c @subheading -overlay-unmap
23254 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23255 @node GDB/MI Signal Handling Commands
23256 @section @sc{gdb/mi} Signal Handling Commands
23258 Signal handling commands are not implemented.
23260 @c @subheading -signal-handle
23262 @c @subheading -signal-list-handle-actions
23264 @c @subheading -signal-list-signal-types
23268 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23269 @node GDB/MI Target Manipulation
23270 @section @sc{gdb/mi} Target Manipulation Commands
23273 @subheading The @code{-target-attach} Command
23274 @findex -target-attach
23276 @subsubheading Synopsis
23279 -target-attach @var{pid} | @var{gid} | @var{file}
23282 Attach to a process @var{pid} or a file @var{file} outside of
23283 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
23284 group, the id previously returned by
23285 @samp{-list-thread-groups --available} must be used.
23287 @subsubheading @value{GDBN} Command
23289 The corresponding @value{GDBN} command is @samp{attach}.
23291 @subsubheading Example
23295 =thread-created,id="1"
23296 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
23301 @subheading The @code{-target-compare-sections} Command
23302 @findex -target-compare-sections
23304 @subsubheading Synopsis
23307 -target-compare-sections [ @var{section} ]
23310 Compare data of section @var{section} on target to the exec file.
23311 Without the argument, all sections are compared.
23313 @subsubheading @value{GDBN} Command
23315 The @value{GDBN} equivalent is @samp{compare-sections}.
23317 @subsubheading Example
23321 @subheading The @code{-target-detach} Command
23322 @findex -target-detach
23324 @subsubheading Synopsis
23327 -target-detach [ @var{pid} | @var{gid} ]
23330 Detach from the remote target which normally resumes its execution.
23331 If either @var{pid} or @var{gid} is specified, detaches from either
23332 the specified process, or specified thread group. There's no output.
23334 @subsubheading @value{GDBN} Command
23336 The corresponding @value{GDBN} command is @samp{detach}.
23338 @subsubheading Example
23348 @subheading The @code{-target-disconnect} Command
23349 @findex -target-disconnect
23351 @subsubheading Synopsis
23357 Disconnect from the remote target. There's no output and the target is
23358 generally not resumed.
23360 @subsubheading @value{GDBN} Command
23362 The corresponding @value{GDBN} command is @samp{disconnect}.
23364 @subsubheading Example
23374 @subheading The @code{-target-download} Command
23375 @findex -target-download
23377 @subsubheading Synopsis
23383 Loads the executable onto the remote target.
23384 It prints out an update message every half second, which includes the fields:
23388 The name of the section.
23390 The size of what has been sent so far for that section.
23392 The size of the section.
23394 The total size of what was sent so far (the current and the previous sections).
23396 The size of the overall executable to download.
23400 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
23401 @sc{gdb/mi} Output Syntax}).
23403 In addition, it prints the name and size of the sections, as they are
23404 downloaded. These messages include the following fields:
23408 The name of the section.
23410 The size of the section.
23412 The size of the overall executable to download.
23416 At the end, a summary is printed.
23418 @subsubheading @value{GDBN} Command
23420 The corresponding @value{GDBN} command is @samp{load}.
23422 @subsubheading Example
23424 Note: each status message appears on a single line. Here the messages
23425 have been broken down so that they can fit onto a page.
23430 +download,@{section=".text",section-size="6668",total-size="9880"@}
23431 +download,@{section=".text",section-sent="512",section-size="6668",
23432 total-sent="512",total-size="9880"@}
23433 +download,@{section=".text",section-sent="1024",section-size="6668",
23434 total-sent="1024",total-size="9880"@}
23435 +download,@{section=".text",section-sent="1536",section-size="6668",
23436 total-sent="1536",total-size="9880"@}
23437 +download,@{section=".text",section-sent="2048",section-size="6668",
23438 total-sent="2048",total-size="9880"@}
23439 +download,@{section=".text",section-sent="2560",section-size="6668",
23440 total-sent="2560",total-size="9880"@}
23441 +download,@{section=".text",section-sent="3072",section-size="6668",
23442 total-sent="3072",total-size="9880"@}
23443 +download,@{section=".text",section-sent="3584",section-size="6668",
23444 total-sent="3584",total-size="9880"@}
23445 +download,@{section=".text",section-sent="4096",section-size="6668",
23446 total-sent="4096",total-size="9880"@}
23447 +download,@{section=".text",section-sent="4608",section-size="6668",
23448 total-sent="4608",total-size="9880"@}
23449 +download,@{section=".text",section-sent="5120",section-size="6668",
23450 total-sent="5120",total-size="9880"@}
23451 +download,@{section=".text",section-sent="5632",section-size="6668",
23452 total-sent="5632",total-size="9880"@}
23453 +download,@{section=".text",section-sent="6144",section-size="6668",
23454 total-sent="6144",total-size="9880"@}
23455 +download,@{section=".text",section-sent="6656",section-size="6668",
23456 total-sent="6656",total-size="9880"@}
23457 +download,@{section=".init",section-size="28",total-size="9880"@}
23458 +download,@{section=".fini",section-size="28",total-size="9880"@}
23459 +download,@{section=".data",section-size="3156",total-size="9880"@}
23460 +download,@{section=".data",section-sent="512",section-size="3156",
23461 total-sent="7236",total-size="9880"@}
23462 +download,@{section=".data",section-sent="1024",section-size="3156",
23463 total-sent="7748",total-size="9880"@}
23464 +download,@{section=".data",section-sent="1536",section-size="3156",
23465 total-sent="8260",total-size="9880"@}
23466 +download,@{section=".data",section-sent="2048",section-size="3156",
23467 total-sent="8772",total-size="9880"@}
23468 +download,@{section=".data",section-sent="2560",section-size="3156",
23469 total-sent="9284",total-size="9880"@}
23470 +download,@{section=".data",section-sent="3072",section-size="3156",
23471 total-sent="9796",total-size="9880"@}
23472 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
23478 @subheading The @code{-target-exec-status} Command
23479 @findex -target-exec-status
23481 @subsubheading Synopsis
23484 -target-exec-status
23487 Provide information on the state of the target (whether it is running or
23488 not, for instance).
23490 @subsubheading @value{GDBN} Command
23492 There's no equivalent @value{GDBN} command.
23494 @subsubheading Example
23498 @subheading The @code{-target-list-available-targets} Command
23499 @findex -target-list-available-targets
23501 @subsubheading Synopsis
23504 -target-list-available-targets
23507 List the possible targets to connect to.
23509 @subsubheading @value{GDBN} Command
23511 The corresponding @value{GDBN} command is @samp{help target}.
23513 @subsubheading Example
23517 @subheading The @code{-target-list-current-targets} Command
23518 @findex -target-list-current-targets
23520 @subsubheading Synopsis
23523 -target-list-current-targets
23526 Describe the current target.
23528 @subsubheading @value{GDBN} Command
23530 The corresponding information is printed by @samp{info file} (among
23533 @subsubheading Example
23537 @subheading The @code{-target-list-parameters} Command
23538 @findex -target-list-parameters
23540 @subsubheading Synopsis
23543 -target-list-parameters
23548 @subsubheading @value{GDBN} Command
23552 @subsubheading Example
23556 @subheading The @code{-target-select} Command
23557 @findex -target-select
23559 @subsubheading Synopsis
23562 -target-select @var{type} @var{parameters @dots{}}
23565 Connect @value{GDBN} to the remote target. This command takes two args:
23569 The type of target, for instance @samp{remote}, etc.
23570 @item @var{parameters}
23571 Device names, host names and the like. @xref{Target Commands, ,
23572 Commands for Managing Targets}, for more details.
23575 The output is a connection notification, followed by the address at
23576 which the target program is, in the following form:
23579 ^connected,addr="@var{address}",func="@var{function name}",
23580 args=[@var{arg list}]
23583 @subsubheading @value{GDBN} Command
23585 The corresponding @value{GDBN} command is @samp{target}.
23587 @subsubheading Example
23591 -target-select remote /dev/ttya
23592 ^connected,addr="0xfe00a300",func="??",args=[]
23596 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23597 @node GDB/MI File Transfer Commands
23598 @section @sc{gdb/mi} File Transfer Commands
23601 @subheading The @code{-target-file-put} Command
23602 @findex -target-file-put
23604 @subsubheading Synopsis
23607 -target-file-put @var{hostfile} @var{targetfile}
23610 Copy file @var{hostfile} from the host system (the machine running
23611 @value{GDBN}) to @var{targetfile} on the target system.
23613 @subsubheading @value{GDBN} Command
23615 The corresponding @value{GDBN} command is @samp{remote put}.
23617 @subsubheading Example
23621 -target-file-put localfile remotefile
23627 @subheading The @code{-target-file-get} Command
23628 @findex -target-file-get
23630 @subsubheading Synopsis
23633 -target-file-get @var{targetfile} @var{hostfile}
23636 Copy file @var{targetfile} from the target system to @var{hostfile}
23637 on the host system.
23639 @subsubheading @value{GDBN} Command
23641 The corresponding @value{GDBN} command is @samp{remote get}.
23643 @subsubheading Example
23647 -target-file-get remotefile localfile
23653 @subheading The @code{-target-file-delete} Command
23654 @findex -target-file-delete
23656 @subsubheading Synopsis
23659 -target-file-delete @var{targetfile}
23662 Delete @var{targetfile} from the target system.
23664 @subsubheading @value{GDBN} Command
23666 The corresponding @value{GDBN} command is @samp{remote delete}.
23668 @subsubheading Example
23672 -target-file-delete remotefile
23678 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23679 @node GDB/MI Miscellaneous Commands
23680 @section Miscellaneous @sc{gdb/mi} Commands
23682 @c @subheading -gdb-complete
23684 @subheading The @code{-gdb-exit} Command
23687 @subsubheading Synopsis
23693 Exit @value{GDBN} immediately.
23695 @subsubheading @value{GDBN} Command
23697 Approximately corresponds to @samp{quit}.
23699 @subsubheading Example
23708 @subheading The @code{-exec-abort} Command
23709 @findex -exec-abort
23711 @subsubheading Synopsis
23717 Kill the inferior running program.
23719 @subsubheading @value{GDBN} Command
23721 The corresponding @value{GDBN} command is @samp{kill}.
23723 @subsubheading Example
23727 @subheading The @code{-gdb-set} Command
23730 @subsubheading Synopsis
23736 Set an internal @value{GDBN} variable.
23737 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
23739 @subsubheading @value{GDBN} Command
23741 The corresponding @value{GDBN} command is @samp{set}.
23743 @subsubheading Example
23753 @subheading The @code{-gdb-show} Command
23756 @subsubheading Synopsis
23762 Show the current value of a @value{GDBN} variable.
23764 @subsubheading @value{GDBN} Command
23766 The corresponding @value{GDBN} command is @samp{show}.
23768 @subsubheading Example
23777 @c @subheading -gdb-source
23780 @subheading The @code{-gdb-version} Command
23781 @findex -gdb-version
23783 @subsubheading Synopsis
23789 Show version information for @value{GDBN}. Used mostly in testing.
23791 @subsubheading @value{GDBN} Command
23793 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
23794 default shows this information when you start an interactive session.
23796 @subsubheading Example
23798 @c This example modifies the actual output from GDB to avoid overfull
23804 ~Copyright 2000 Free Software Foundation, Inc.
23805 ~GDB is free software, covered by the GNU General Public License, and
23806 ~you are welcome to change it and/or distribute copies of it under
23807 ~ certain conditions.
23808 ~Type "show copying" to see the conditions.
23809 ~There is absolutely no warranty for GDB. Type "show warranty" for
23811 ~This GDB was configured as
23812 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
23817 @subheading The @code{-list-features} Command
23818 @findex -list-features
23820 Returns a list of particular features of the MI protocol that
23821 this version of gdb implements. A feature can be a command,
23822 or a new field in an output of some command, or even an
23823 important bugfix. While a frontend can sometimes detect presence
23824 of a feature at runtime, it is easier to perform detection at debugger
23827 The command returns a list of strings, with each string naming an
23828 available feature. Each returned string is just a name, it does not
23829 have any internal structure. The list of possible feature names
23835 (gdb) -list-features
23836 ^done,result=["feature1","feature2"]
23839 The current list of features is:
23842 @item frozen-varobjs
23843 Indicates presence of the @code{-var-set-frozen} command, as well
23844 as possible presense of the @code{frozen} field in the output
23845 of @code{-varobj-create}.
23846 @item pending-breakpoints
23847 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
23849 Indicates presence of the @code{-thread-info} command.
23853 @subheading The @code{-list-target-features} Command
23854 @findex -list-target-features
23856 Returns a list of particular features that are supported by the
23857 target. Those features affect the permitted MI commands, but
23858 unlike the features reported by the @code{-list-features} command, the
23859 features depend on which target GDB is using at the moment. Whenever
23860 a target can change, due to commands such as @code{-target-select},
23861 @code{-target-attach} or @code{-exec-run}, the list of target features
23862 may change, and the frontend should obtain it again.
23866 (gdb) -list-features
23867 ^done,result=["async"]
23870 The current list of features is:
23874 Indicates that the target is capable of asynchronous command
23875 execution, which means that @value{GDBN} will accept further commands
23876 while the target is running.
23880 @subheading The @code{-list-thread-groups} Command
23881 @findex -list-thread-groups
23883 @subheading Synopsis
23886 -list-thread-groups [ --available ] [ @var{group} ]
23889 When used without the @var{group} parameter, lists top-level thread
23890 groups that are being debugged. When used with the @var{group}
23891 parameter, the children of the specified group are listed. The
23892 children can be either threads, or other groups. At present,
23893 @value{GDBN} will not report both threads and groups as children at
23894 the same time, but it may change in future.
23896 With the @samp{--available} option, instead of reporting groups that
23897 are been debugged, GDB will report all thread groups available on the
23898 target. Using the @samp{--available} option together with @var{group}
23901 @subheading Example
23905 -list-thread-groups
23906 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
23907 -list-thread-groups 17
23908 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
23909 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
23910 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
23911 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
23912 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
23915 @subheading The @code{-interpreter-exec} Command
23916 @findex -interpreter-exec
23918 @subheading Synopsis
23921 -interpreter-exec @var{interpreter} @var{command}
23923 @anchor{-interpreter-exec}
23925 Execute the specified @var{command} in the given @var{interpreter}.
23927 @subheading @value{GDBN} Command
23929 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
23931 @subheading Example
23935 -interpreter-exec console "break main"
23936 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
23937 &"During symbol reading, bad structure-type format.\n"
23938 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
23943 @subheading The @code{-inferior-tty-set} Command
23944 @findex -inferior-tty-set
23946 @subheading Synopsis
23949 -inferior-tty-set /dev/pts/1
23952 Set terminal for future runs of the program being debugged.
23954 @subheading @value{GDBN} Command
23956 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
23958 @subheading Example
23962 -inferior-tty-set /dev/pts/1
23967 @subheading The @code{-inferior-tty-show} Command
23968 @findex -inferior-tty-show
23970 @subheading Synopsis
23976 Show terminal for future runs of program being debugged.
23978 @subheading @value{GDBN} Command
23980 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
23982 @subheading Example
23986 -inferior-tty-set /dev/pts/1
23990 ^done,inferior_tty_terminal="/dev/pts/1"
23994 @subheading The @code{-enable-timings} Command
23995 @findex -enable-timings
23997 @subheading Synopsis
24000 -enable-timings [yes | no]
24003 Toggle the printing of the wallclock, user and system times for an MI
24004 command as a field in its output. This command is to help frontend
24005 developers optimize the performance of their code. No argument is
24006 equivalent to @samp{yes}.
24008 @subheading @value{GDBN} Command
24012 @subheading Example
24020 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24021 addr="0x080484ed",func="main",file="myprog.c",
24022 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
24023 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
24031 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24032 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
24033 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
24034 fullname="/home/nickrob/myprog.c",line="73"@}
24039 @chapter @value{GDBN} Annotations
24041 This chapter describes annotations in @value{GDBN}. Annotations were
24042 designed to interface @value{GDBN} to graphical user interfaces or other
24043 similar programs which want to interact with @value{GDBN} at a
24044 relatively high level.
24046 The annotation mechanism has largely been superseded by @sc{gdb/mi}
24050 This is Edition @value{EDITION}, @value{DATE}.
24054 * Annotations Overview:: What annotations are; the general syntax.
24055 * Server Prefix:: Issuing a command without affecting user state.
24056 * Prompting:: Annotations marking @value{GDBN}'s need for input.
24057 * Errors:: Annotations for error messages.
24058 * Invalidation:: Some annotations describe things now invalid.
24059 * Annotations for Running::
24060 Whether the program is running, how it stopped, etc.
24061 * Source Annotations:: Annotations describing source code.
24064 @node Annotations Overview
24065 @section What is an Annotation?
24066 @cindex annotations
24068 Annotations start with a newline character, two @samp{control-z}
24069 characters, and the name of the annotation. If there is no additional
24070 information associated with this annotation, the name of the annotation
24071 is followed immediately by a newline. If there is additional
24072 information, the name of the annotation is followed by a space, the
24073 additional information, and a newline. The additional information
24074 cannot contain newline characters.
24076 Any output not beginning with a newline and two @samp{control-z}
24077 characters denotes literal output from @value{GDBN}. Currently there is
24078 no need for @value{GDBN} to output a newline followed by two
24079 @samp{control-z} characters, but if there was such a need, the
24080 annotations could be extended with an @samp{escape} annotation which
24081 means those three characters as output.
24083 The annotation @var{level}, which is specified using the
24084 @option{--annotate} command line option (@pxref{Mode Options}), controls
24085 how much information @value{GDBN} prints together with its prompt,
24086 values of expressions, source lines, and other types of output. Level 0
24087 is for no annotations, level 1 is for use when @value{GDBN} is run as a
24088 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
24089 for programs that control @value{GDBN}, and level 2 annotations have
24090 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
24091 Interface, annotate, GDB's Obsolete Annotations}).
24094 @kindex set annotate
24095 @item set annotate @var{level}
24096 The @value{GDBN} command @code{set annotate} sets the level of
24097 annotations to the specified @var{level}.
24099 @item show annotate
24100 @kindex show annotate
24101 Show the current annotation level.
24104 This chapter describes level 3 annotations.
24106 A simple example of starting up @value{GDBN} with annotations is:
24109 $ @kbd{gdb --annotate=3}
24111 Copyright 2003 Free Software Foundation, Inc.
24112 GDB is free software, covered by the GNU General Public License,
24113 and you are welcome to change it and/or distribute copies of it
24114 under certain conditions.
24115 Type "show copying" to see the conditions.
24116 There is absolutely no warranty for GDB. Type "show warranty"
24118 This GDB was configured as "i386-pc-linux-gnu"
24129 Here @samp{quit} is input to @value{GDBN}; the rest is output from
24130 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
24131 denotes a @samp{control-z} character) are annotations; the rest is
24132 output from @value{GDBN}.
24134 @node Server Prefix
24135 @section The Server Prefix
24136 @cindex server prefix
24138 If you prefix a command with @samp{server } then it will not affect
24139 the command history, nor will it affect @value{GDBN}'s notion of which
24140 command to repeat if @key{RET} is pressed on a line by itself. This
24141 means that commands can be run behind a user's back by a front-end in
24142 a transparent manner.
24144 The server prefix does not affect the recording of values into the value
24145 history; to print a value without recording it into the value history,
24146 use the @code{output} command instead of the @code{print} command.
24149 @section Annotation for @value{GDBN} Input
24151 @cindex annotations for prompts
24152 When @value{GDBN} prompts for input, it annotates this fact so it is possible
24153 to know when to send output, when the output from a given command is
24156 Different kinds of input each have a different @dfn{input type}. Each
24157 input type has three annotations: a @code{pre-} annotation, which
24158 denotes the beginning of any prompt which is being output, a plain
24159 annotation, which denotes the end of the prompt, and then a @code{post-}
24160 annotation which denotes the end of any echo which may (or may not) be
24161 associated with the input. For example, the @code{prompt} input type
24162 features the following annotations:
24170 The input types are
24173 @findex pre-prompt annotation
24174 @findex prompt annotation
24175 @findex post-prompt annotation
24177 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
24179 @findex pre-commands annotation
24180 @findex commands annotation
24181 @findex post-commands annotation
24183 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
24184 command. The annotations are repeated for each command which is input.
24186 @findex pre-overload-choice annotation
24187 @findex overload-choice annotation
24188 @findex post-overload-choice annotation
24189 @item overload-choice
24190 When @value{GDBN} wants the user to select between various overloaded functions.
24192 @findex pre-query annotation
24193 @findex query annotation
24194 @findex post-query annotation
24196 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
24198 @findex pre-prompt-for-continue annotation
24199 @findex prompt-for-continue annotation
24200 @findex post-prompt-for-continue annotation
24201 @item prompt-for-continue
24202 When @value{GDBN} is asking the user to press return to continue. Note: Don't
24203 expect this to work well; instead use @code{set height 0} to disable
24204 prompting. This is because the counting of lines is buggy in the
24205 presence of annotations.
24210 @cindex annotations for errors, warnings and interrupts
24212 @findex quit annotation
24217 This annotation occurs right before @value{GDBN} responds to an interrupt.
24219 @findex error annotation
24224 This annotation occurs right before @value{GDBN} responds to an error.
24226 Quit and error annotations indicate that any annotations which @value{GDBN} was
24227 in the middle of may end abruptly. For example, if a
24228 @code{value-history-begin} annotation is followed by a @code{error}, one
24229 cannot expect to receive the matching @code{value-history-end}. One
24230 cannot expect not to receive it either, however; an error annotation
24231 does not necessarily mean that @value{GDBN} is immediately returning all the way
24234 @findex error-begin annotation
24235 A quit or error annotation may be preceded by
24241 Any output between that and the quit or error annotation is the error
24244 Warning messages are not yet annotated.
24245 @c If we want to change that, need to fix warning(), type_error(),
24246 @c range_error(), and possibly other places.
24249 @section Invalidation Notices
24251 @cindex annotations for invalidation messages
24252 The following annotations say that certain pieces of state may have
24256 @findex frames-invalid annotation
24257 @item ^Z^Zframes-invalid
24259 The frames (for example, output from the @code{backtrace} command) may
24262 @findex breakpoints-invalid annotation
24263 @item ^Z^Zbreakpoints-invalid
24265 The breakpoints may have changed. For example, the user just added or
24266 deleted a breakpoint.
24269 @node Annotations for Running
24270 @section Running the Program
24271 @cindex annotations for running programs
24273 @findex starting annotation
24274 @findex stopping annotation
24275 When the program starts executing due to a @value{GDBN} command such as
24276 @code{step} or @code{continue},
24282 is output. When the program stops,
24288 is output. Before the @code{stopped} annotation, a variety of
24289 annotations describe how the program stopped.
24292 @findex exited annotation
24293 @item ^Z^Zexited @var{exit-status}
24294 The program exited, and @var{exit-status} is the exit status (zero for
24295 successful exit, otherwise nonzero).
24297 @findex signalled annotation
24298 @findex signal-name annotation
24299 @findex signal-name-end annotation
24300 @findex signal-string annotation
24301 @findex signal-string-end annotation
24302 @item ^Z^Zsignalled
24303 The program exited with a signal. After the @code{^Z^Zsignalled}, the
24304 annotation continues:
24310 ^Z^Zsignal-name-end
24314 ^Z^Zsignal-string-end
24319 where @var{name} is the name of the signal, such as @code{SIGILL} or
24320 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
24321 as @code{Illegal Instruction} or @code{Segmentation fault}.
24322 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
24323 user's benefit and have no particular format.
24325 @findex signal annotation
24327 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
24328 just saying that the program received the signal, not that it was
24329 terminated with it.
24331 @findex breakpoint annotation
24332 @item ^Z^Zbreakpoint @var{number}
24333 The program hit breakpoint number @var{number}.
24335 @findex watchpoint annotation
24336 @item ^Z^Zwatchpoint @var{number}
24337 The program hit watchpoint number @var{number}.
24340 @node Source Annotations
24341 @section Displaying Source
24342 @cindex annotations for source display
24344 @findex source annotation
24345 The following annotation is used instead of displaying source code:
24348 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
24351 where @var{filename} is an absolute file name indicating which source
24352 file, @var{line} is the line number within that file (where 1 is the
24353 first line in the file), @var{character} is the character position
24354 within the file (where 0 is the first character in the file) (for most
24355 debug formats this will necessarily point to the beginning of a line),
24356 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
24357 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
24358 @var{addr} is the address in the target program associated with the
24359 source which is being displayed. @var{addr} is in the form @samp{0x}
24360 followed by one or more lowercase hex digits (note that this does not
24361 depend on the language).
24364 @chapter Reporting Bugs in @value{GDBN}
24365 @cindex bugs in @value{GDBN}
24366 @cindex reporting bugs in @value{GDBN}
24368 Your bug reports play an essential role in making @value{GDBN} reliable.
24370 Reporting a bug may help you by bringing a solution to your problem, or it
24371 may not. But in any case the principal function of a bug report is to help
24372 the entire community by making the next version of @value{GDBN} work better. Bug
24373 reports are your contribution to the maintenance of @value{GDBN}.
24375 In order for a bug report to serve its purpose, you must include the
24376 information that enables us to fix the bug.
24379 * Bug Criteria:: Have you found a bug?
24380 * Bug Reporting:: How to report bugs
24384 @section Have You Found a Bug?
24385 @cindex bug criteria
24387 If you are not sure whether you have found a bug, here are some guidelines:
24390 @cindex fatal signal
24391 @cindex debugger crash
24392 @cindex crash of debugger
24394 If the debugger gets a fatal signal, for any input whatever, that is a
24395 @value{GDBN} bug. Reliable debuggers never crash.
24397 @cindex error on valid input
24399 If @value{GDBN} produces an error message for valid input, that is a
24400 bug. (Note that if you're cross debugging, the problem may also be
24401 somewhere in the connection to the target.)
24403 @cindex invalid input
24405 If @value{GDBN} does not produce an error message for invalid input,
24406 that is a bug. However, you should note that your idea of
24407 ``invalid input'' might be our idea of ``an extension'' or ``support
24408 for traditional practice''.
24411 If you are an experienced user of debugging tools, your suggestions
24412 for improvement of @value{GDBN} are welcome in any case.
24415 @node Bug Reporting
24416 @section How to Report Bugs
24417 @cindex bug reports
24418 @cindex @value{GDBN} bugs, reporting
24420 A number of companies and individuals offer support for @sc{gnu} products.
24421 If you obtained @value{GDBN} from a support organization, we recommend you
24422 contact that organization first.
24424 You can find contact information for many support companies and
24425 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
24427 @c should add a web page ref...
24430 @ifset BUGURL_DEFAULT
24431 In any event, we also recommend that you submit bug reports for
24432 @value{GDBN}. The preferred method is to submit them directly using
24433 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
24434 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
24437 @strong{Do not send bug reports to @samp{info-gdb}, or to
24438 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
24439 not want to receive bug reports. Those that do have arranged to receive
24442 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
24443 serves as a repeater. The mailing list and the newsgroup carry exactly
24444 the same messages. Often people think of posting bug reports to the
24445 newsgroup instead of mailing them. This appears to work, but it has one
24446 problem which can be crucial: a newsgroup posting often lacks a mail
24447 path back to the sender. Thus, if we need to ask for more information,
24448 we may be unable to reach you. For this reason, it is better to send
24449 bug reports to the mailing list.
24451 @ifclear BUGURL_DEFAULT
24452 In any event, we also recommend that you submit bug reports for
24453 @value{GDBN} to @value{BUGURL}.
24457 The fundamental principle of reporting bugs usefully is this:
24458 @strong{report all the facts}. If you are not sure whether to state a
24459 fact or leave it out, state it!
24461 Often people omit facts because they think they know what causes the
24462 problem and assume that some details do not matter. Thus, you might
24463 assume that the name of the variable you use in an example does not matter.
24464 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
24465 stray memory reference which happens to fetch from the location where that
24466 name is stored in memory; perhaps, if the name were different, the contents
24467 of that location would fool the debugger into doing the right thing despite
24468 the bug. Play it safe and give a specific, complete example. That is the
24469 easiest thing for you to do, and the most helpful.
24471 Keep in mind that the purpose of a bug report is to enable us to fix the
24472 bug. It may be that the bug has been reported previously, but neither
24473 you nor we can know that unless your bug report is complete and
24476 Sometimes people give a few sketchy facts and ask, ``Does this ring a
24477 bell?'' Those bug reports are useless, and we urge everyone to
24478 @emph{refuse to respond to them} except to chide the sender to report
24481 To enable us to fix the bug, you should include all these things:
24485 The version of @value{GDBN}. @value{GDBN} announces it if you start
24486 with no arguments; you can also print it at any time using @code{show
24489 Without this, we will not know whether there is any point in looking for
24490 the bug in the current version of @value{GDBN}.
24493 The type of machine you are using, and the operating system name and
24497 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
24498 ``@value{GCC}--2.8.1''.
24501 What compiler (and its version) was used to compile the program you are
24502 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
24503 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
24504 to get this information; for other compilers, see the documentation for
24508 The command arguments you gave the compiler to compile your example and
24509 observe the bug. For example, did you use @samp{-O}? To guarantee
24510 you will not omit something important, list them all. A copy of the
24511 Makefile (or the output from make) is sufficient.
24513 If we were to try to guess the arguments, we would probably guess wrong
24514 and then we might not encounter the bug.
24517 A complete input script, and all necessary source files, that will
24521 A description of what behavior you observe that you believe is
24522 incorrect. For example, ``It gets a fatal signal.''
24524 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
24525 will certainly notice it. But if the bug is incorrect output, we might
24526 not notice unless it is glaringly wrong. You might as well not give us
24527 a chance to make a mistake.
24529 Even if the problem you experience is a fatal signal, you should still
24530 say so explicitly. Suppose something strange is going on, such as, your
24531 copy of @value{GDBN} is out of synch, or you have encountered a bug in
24532 the C library on your system. (This has happened!) Your copy might
24533 crash and ours would not. If you told us to expect a crash, then when
24534 ours fails to crash, we would know that the bug was not happening for
24535 us. If you had not told us to expect a crash, then we would not be able
24536 to draw any conclusion from our observations.
24539 @cindex recording a session script
24540 To collect all this information, you can use a session recording program
24541 such as @command{script}, which is available on many Unix systems.
24542 Just run your @value{GDBN} session inside @command{script} and then
24543 include the @file{typescript} file with your bug report.
24545 Another way to record a @value{GDBN} session is to run @value{GDBN}
24546 inside Emacs and then save the entire buffer to a file.
24549 If you wish to suggest changes to the @value{GDBN} source, send us context
24550 diffs. If you even discuss something in the @value{GDBN} source, refer to
24551 it by context, not by line number.
24553 The line numbers in our development sources will not match those in your
24554 sources. Your line numbers would convey no useful information to us.
24558 Here are some things that are not necessary:
24562 A description of the envelope of the bug.
24564 Often people who encounter a bug spend a lot of time investigating
24565 which changes to the input file will make the bug go away and which
24566 changes will not affect it.
24568 This is often time consuming and not very useful, because the way we
24569 will find the bug is by running a single example under the debugger
24570 with breakpoints, not by pure deduction from a series of examples.
24571 We recommend that you save your time for something else.
24573 Of course, if you can find a simpler example to report @emph{instead}
24574 of the original one, that is a convenience for us. Errors in the
24575 output will be easier to spot, running under the debugger will take
24576 less time, and so on.
24578 However, simplification is not vital; if you do not want to do this,
24579 report the bug anyway and send us the entire test case you used.
24582 A patch for the bug.
24584 A patch for the bug does help us if it is a good one. But do not omit
24585 the necessary information, such as the test case, on the assumption that
24586 a patch is all we need. We might see problems with your patch and decide
24587 to fix the problem another way, or we might not understand it at all.
24589 Sometimes with a program as complicated as @value{GDBN} it is very hard to
24590 construct an example that will make the program follow a certain path
24591 through the code. If you do not send us the example, we will not be able
24592 to construct one, so we will not be able to verify that the bug is fixed.
24594 And if we cannot understand what bug you are trying to fix, or why your
24595 patch should be an improvement, we will not install it. A test case will
24596 help us to understand.
24599 A guess about what the bug is or what it depends on.
24601 Such guesses are usually wrong. Even we cannot guess right about such
24602 things without first using the debugger to find the facts.
24605 @c The readline documentation is distributed with the readline code
24606 @c and consists of the two following files:
24608 @c inc-hist.texinfo
24609 @c Use -I with makeinfo to point to the appropriate directory,
24610 @c environment var TEXINPUTS with TeX.
24611 @include rluser.texi
24612 @include inc-hist.texinfo
24615 @node Formatting Documentation
24616 @appendix Formatting Documentation
24618 @cindex @value{GDBN} reference card
24619 @cindex reference card
24620 The @value{GDBN} 4 release includes an already-formatted reference card, ready
24621 for printing with PostScript or Ghostscript, in the @file{gdb}
24622 subdirectory of the main source directory@footnote{In
24623 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
24624 release.}. If you can use PostScript or Ghostscript with your printer,
24625 you can print the reference card immediately with @file{refcard.ps}.
24627 The release also includes the source for the reference card. You
24628 can format it, using @TeX{}, by typing:
24634 The @value{GDBN} reference card is designed to print in @dfn{landscape}
24635 mode on US ``letter'' size paper;
24636 that is, on a sheet 11 inches wide by 8.5 inches
24637 high. You will need to specify this form of printing as an option to
24638 your @sc{dvi} output program.
24640 @cindex documentation
24642 All the documentation for @value{GDBN} comes as part of the machine-readable
24643 distribution. The documentation is written in Texinfo format, which is
24644 a documentation system that uses a single source file to produce both
24645 on-line information and a printed manual. You can use one of the Info
24646 formatting commands to create the on-line version of the documentation
24647 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
24649 @value{GDBN} includes an already formatted copy of the on-line Info
24650 version of this manual in the @file{gdb} subdirectory. The main Info
24651 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
24652 subordinate files matching @samp{gdb.info*} in the same directory. If
24653 necessary, you can print out these files, or read them with any editor;
24654 but they are easier to read using the @code{info} subsystem in @sc{gnu}
24655 Emacs or the standalone @code{info} program, available as part of the
24656 @sc{gnu} Texinfo distribution.
24658 If you want to format these Info files yourself, you need one of the
24659 Info formatting programs, such as @code{texinfo-format-buffer} or
24662 If you have @code{makeinfo} installed, and are in the top level
24663 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
24664 version @value{GDBVN}), you can make the Info file by typing:
24671 If you want to typeset and print copies of this manual, you need @TeX{},
24672 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
24673 Texinfo definitions file.
24675 @TeX{} is a typesetting program; it does not print files directly, but
24676 produces output files called @sc{dvi} files. To print a typeset
24677 document, you need a program to print @sc{dvi} files. If your system
24678 has @TeX{} installed, chances are it has such a program. The precise
24679 command to use depends on your system; @kbd{lpr -d} is common; another
24680 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
24681 require a file name without any extension or a @samp{.dvi} extension.
24683 @TeX{} also requires a macro definitions file called
24684 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
24685 written in Texinfo format. On its own, @TeX{} cannot either read or
24686 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
24687 and is located in the @file{gdb-@var{version-number}/texinfo}
24690 If you have @TeX{} and a @sc{dvi} printer program installed, you can
24691 typeset and print this manual. First switch to the @file{gdb}
24692 subdirectory of the main source directory (for example, to
24693 @file{gdb-@value{GDBVN}/gdb}) and type:
24699 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
24701 @node Installing GDB
24702 @appendix Installing @value{GDBN}
24703 @cindex installation
24706 * Requirements:: Requirements for building @value{GDBN}
24707 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
24708 * Separate Objdir:: Compiling @value{GDBN} in another directory
24709 * Config Names:: Specifying names for hosts and targets
24710 * Configure Options:: Summary of options for configure
24711 * System-wide configuration:: Having a system-wide init file
24715 @section Requirements for Building @value{GDBN}
24716 @cindex building @value{GDBN}, requirements for
24718 Building @value{GDBN} requires various tools and packages to be available.
24719 Other packages will be used only if they are found.
24721 @heading Tools/Packages Necessary for Building @value{GDBN}
24723 @item ISO C90 compiler
24724 @value{GDBN} is written in ISO C90. It should be buildable with any
24725 working C90 compiler, e.g.@: GCC.
24729 @heading Tools/Packages Optional for Building @value{GDBN}
24733 @value{GDBN} can use the Expat XML parsing library. This library may be
24734 included with your operating system distribution; if it is not, you
24735 can get the latest version from @url{http://expat.sourceforge.net}.
24736 The @file{configure} script will search for this library in several
24737 standard locations; if it is installed in an unusual path, you can
24738 use the @option{--with-libexpat-prefix} option to specify its location.
24744 Remote protocol memory maps (@pxref{Memory Map Format})
24746 Target descriptions (@pxref{Target Descriptions})
24748 Remote shared library lists (@pxref{Library List Format})
24750 MS-Windows shared libraries (@pxref{Shared Libraries})
24754 @cindex compressed debug sections
24755 @value{GDBN} will use the @samp{zlib} library, if available, to read
24756 compressed debug sections. Some linkers, such as GNU gold, are capable
24757 of producing binaries with compressed debug sections. If @value{GDBN}
24758 is compiled with @samp{zlib}, it will be able to read the debug
24759 information in such binaries.
24761 The @samp{zlib} library is likely included with your operating system
24762 distribution; if it is not, you can get the latest version from
24763 @url{http://zlib.net}.
24767 @node Running Configure
24768 @section Invoking the @value{GDBN} @file{configure} Script
24769 @cindex configuring @value{GDBN}
24770 @value{GDBN} comes with a @file{configure} script that automates the process
24771 of preparing @value{GDBN} for installation; you can then use @code{make} to
24772 build the @code{gdb} program.
24774 @c irrelevant in info file; it's as current as the code it lives with.
24775 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
24776 look at the @file{README} file in the sources; we may have improved the
24777 installation procedures since publishing this manual.}
24780 The @value{GDBN} distribution includes all the source code you need for
24781 @value{GDBN} in a single directory, whose name is usually composed by
24782 appending the version number to @samp{gdb}.
24784 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
24785 @file{gdb-@value{GDBVN}} directory. That directory contains:
24788 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
24789 script for configuring @value{GDBN} and all its supporting libraries
24791 @item gdb-@value{GDBVN}/gdb
24792 the source specific to @value{GDBN} itself
24794 @item gdb-@value{GDBVN}/bfd
24795 source for the Binary File Descriptor library
24797 @item gdb-@value{GDBVN}/include
24798 @sc{gnu} include files
24800 @item gdb-@value{GDBVN}/libiberty
24801 source for the @samp{-liberty} free software library
24803 @item gdb-@value{GDBVN}/opcodes
24804 source for the library of opcode tables and disassemblers
24806 @item gdb-@value{GDBVN}/readline
24807 source for the @sc{gnu} command-line interface
24809 @item gdb-@value{GDBVN}/glob
24810 source for the @sc{gnu} filename pattern-matching subroutine
24812 @item gdb-@value{GDBVN}/mmalloc
24813 source for the @sc{gnu} memory-mapped malloc package
24816 The simplest way to configure and build @value{GDBN} is to run @file{configure}
24817 from the @file{gdb-@var{version-number}} source directory, which in
24818 this example is the @file{gdb-@value{GDBVN}} directory.
24820 First switch to the @file{gdb-@var{version-number}} source directory
24821 if you are not already in it; then run @file{configure}. Pass the
24822 identifier for the platform on which @value{GDBN} will run as an
24828 cd gdb-@value{GDBVN}
24829 ./configure @var{host}
24834 where @var{host} is an identifier such as @samp{sun4} or
24835 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
24836 (You can often leave off @var{host}; @file{configure} tries to guess the
24837 correct value by examining your system.)
24839 Running @samp{configure @var{host}} and then running @code{make} builds the
24840 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
24841 libraries, then @code{gdb} itself. The configured source files, and the
24842 binaries, are left in the corresponding source directories.
24845 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
24846 system does not recognize this automatically when you run a different
24847 shell, you may need to run @code{sh} on it explicitly:
24850 sh configure @var{host}
24853 If you run @file{configure} from a directory that contains source
24854 directories for multiple libraries or programs, such as the
24855 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
24857 creates configuration files for every directory level underneath (unless
24858 you tell it not to, with the @samp{--norecursion} option).
24860 You should run the @file{configure} script from the top directory in the
24861 source tree, the @file{gdb-@var{version-number}} directory. If you run
24862 @file{configure} from one of the subdirectories, you will configure only
24863 that subdirectory. That is usually not what you want. In particular,
24864 if you run the first @file{configure} from the @file{gdb} subdirectory
24865 of the @file{gdb-@var{version-number}} directory, you will omit the
24866 configuration of @file{bfd}, @file{readline}, and other sibling
24867 directories of the @file{gdb} subdirectory. This leads to build errors
24868 about missing include files such as @file{bfd/bfd.h}.
24870 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
24871 However, you should make sure that the shell on your path (named by
24872 the @samp{SHELL} environment variable) is publicly readable. Remember
24873 that @value{GDBN} uses the shell to start your program---some systems refuse to
24874 let @value{GDBN} debug child processes whose programs are not readable.
24876 @node Separate Objdir
24877 @section Compiling @value{GDBN} in Another Directory
24879 If you want to run @value{GDBN} versions for several host or target machines,
24880 you need a different @code{gdb} compiled for each combination of
24881 host and target. @file{configure} is designed to make this easy by
24882 allowing you to generate each configuration in a separate subdirectory,
24883 rather than in the source directory. If your @code{make} program
24884 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
24885 @code{make} in each of these directories builds the @code{gdb}
24886 program specified there.
24888 To build @code{gdb} in a separate directory, run @file{configure}
24889 with the @samp{--srcdir} option to specify where to find the source.
24890 (You also need to specify a path to find @file{configure}
24891 itself from your working directory. If the path to @file{configure}
24892 would be the same as the argument to @samp{--srcdir}, you can leave out
24893 the @samp{--srcdir} option; it is assumed.)
24895 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
24896 separate directory for a Sun 4 like this:
24900 cd gdb-@value{GDBVN}
24903 ../gdb-@value{GDBVN}/configure sun4
24908 When @file{configure} builds a configuration using a remote source
24909 directory, it creates a tree for the binaries with the same structure
24910 (and using the same names) as the tree under the source directory. In
24911 the example, you'd find the Sun 4 library @file{libiberty.a} in the
24912 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
24913 @file{gdb-sun4/gdb}.
24915 Make sure that your path to the @file{configure} script has just one
24916 instance of @file{gdb} in it. If your path to @file{configure} looks
24917 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
24918 one subdirectory of @value{GDBN}, not the whole package. This leads to
24919 build errors about missing include files such as @file{bfd/bfd.h}.
24921 One popular reason to build several @value{GDBN} configurations in separate
24922 directories is to configure @value{GDBN} for cross-compiling (where
24923 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
24924 programs that run on another machine---the @dfn{target}).
24925 You specify a cross-debugging target by
24926 giving the @samp{--target=@var{target}} option to @file{configure}.
24928 When you run @code{make} to build a program or library, you must run
24929 it in a configured directory---whatever directory you were in when you
24930 called @file{configure} (or one of its subdirectories).
24932 The @code{Makefile} that @file{configure} generates in each source
24933 directory also runs recursively. If you type @code{make} in a source
24934 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
24935 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
24936 will build all the required libraries, and then build GDB.
24938 When you have multiple hosts or targets configured in separate
24939 directories, you can run @code{make} on them in parallel (for example,
24940 if they are NFS-mounted on each of the hosts); they will not interfere
24944 @section Specifying Names for Hosts and Targets
24946 The specifications used for hosts and targets in the @file{configure}
24947 script are based on a three-part naming scheme, but some short predefined
24948 aliases are also supported. The full naming scheme encodes three pieces
24949 of information in the following pattern:
24952 @var{architecture}-@var{vendor}-@var{os}
24955 For example, you can use the alias @code{sun4} as a @var{host} argument,
24956 or as the value for @var{target} in a @code{--target=@var{target}}
24957 option. The equivalent full name is @samp{sparc-sun-sunos4}.
24959 The @file{configure} script accompanying @value{GDBN} does not provide
24960 any query facility to list all supported host and target names or
24961 aliases. @file{configure} calls the Bourne shell script
24962 @code{config.sub} to map abbreviations to full names; you can read the
24963 script, if you wish, or you can use it to test your guesses on
24964 abbreviations---for example:
24967 % sh config.sub i386-linux
24969 % sh config.sub alpha-linux
24970 alpha-unknown-linux-gnu
24971 % sh config.sub hp9k700
24973 % sh config.sub sun4
24974 sparc-sun-sunos4.1.1
24975 % sh config.sub sun3
24976 m68k-sun-sunos4.1.1
24977 % sh config.sub i986v
24978 Invalid configuration `i986v': machine `i986v' not recognized
24982 @code{config.sub} is also distributed in the @value{GDBN} source
24983 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
24985 @node Configure Options
24986 @section @file{configure} Options
24988 Here is a summary of the @file{configure} options and arguments that
24989 are most often useful for building @value{GDBN}. @file{configure} also has
24990 several other options not listed here. @inforef{What Configure
24991 Does,,configure.info}, for a full explanation of @file{configure}.
24994 configure @r{[}--help@r{]}
24995 @r{[}--prefix=@var{dir}@r{]}
24996 @r{[}--exec-prefix=@var{dir}@r{]}
24997 @r{[}--srcdir=@var{dirname}@r{]}
24998 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
24999 @r{[}--target=@var{target}@r{]}
25004 You may introduce options with a single @samp{-} rather than
25005 @samp{--} if you prefer; but you may abbreviate option names if you use
25010 Display a quick summary of how to invoke @file{configure}.
25012 @item --prefix=@var{dir}
25013 Configure the source to install programs and files under directory
25016 @item --exec-prefix=@var{dir}
25017 Configure the source to install programs under directory
25020 @c avoid splitting the warning from the explanation:
25022 @item --srcdir=@var{dirname}
25023 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
25024 @code{make} that implements the @code{VPATH} feature.}@*
25025 Use this option to make configurations in directories separate from the
25026 @value{GDBN} source directories. Among other things, you can use this to
25027 build (or maintain) several configurations simultaneously, in separate
25028 directories. @file{configure} writes configuration-specific files in
25029 the current directory, but arranges for them to use the source in the
25030 directory @var{dirname}. @file{configure} creates directories under
25031 the working directory in parallel to the source directories below
25034 @item --norecursion
25035 Configure only the directory level where @file{configure} is executed; do not
25036 propagate configuration to subdirectories.
25038 @item --target=@var{target}
25039 Configure @value{GDBN} for cross-debugging programs running on the specified
25040 @var{target}. Without this option, @value{GDBN} is configured to debug
25041 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
25043 There is no convenient way to generate a list of all available targets.
25045 @item @var{host} @dots{}
25046 Configure @value{GDBN} to run on the specified @var{host}.
25048 There is no convenient way to generate a list of all available hosts.
25051 There are many other options available as well, but they are generally
25052 needed for special purposes only.
25054 @node System-wide configuration
25055 @section System-wide configuration and settings
25056 @cindex system-wide init file
25058 @value{GDBN} can be configured to have a system-wide init file;
25059 this file will be read and executed at startup (@pxref{Startup, , What
25060 @value{GDBN} does during startup}).
25062 Here is the corresponding configure option:
25065 @item --with-system-gdbinit=@var{file}
25066 Specify that the default location of the system-wide init file is
25070 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
25071 it may be subject to relocation. Two possible cases:
25075 If the default location of this init file contains @file{$prefix},
25076 it will be subject to relocation. Suppose that the configure options
25077 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
25078 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
25079 init file is looked for as @file{$install/etc/gdbinit} instead of
25080 @file{$prefix/etc/gdbinit}.
25083 By contrast, if the default location does not contain the prefix,
25084 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
25085 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
25086 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
25087 wherever @value{GDBN} is installed.
25090 @node Maintenance Commands
25091 @appendix Maintenance Commands
25092 @cindex maintenance commands
25093 @cindex internal commands
25095 In addition to commands intended for @value{GDBN} users, @value{GDBN}
25096 includes a number of commands intended for @value{GDBN} developers,
25097 that are not documented elsewhere in this manual. These commands are
25098 provided here for reference. (For commands that turn on debugging
25099 messages, see @ref{Debugging Output}.)
25102 @kindex maint agent
25103 @item maint agent @var{expression}
25104 Translate the given @var{expression} into remote agent bytecodes.
25105 This command is useful for debugging the Agent Expression mechanism
25106 (@pxref{Agent Expressions}).
25108 @kindex maint info breakpoints
25109 @item @anchor{maint info breakpoints}maint info breakpoints
25110 Using the same format as @samp{info breakpoints}, display both the
25111 breakpoints you've set explicitly, and those @value{GDBN} is using for
25112 internal purposes. Internal breakpoints are shown with negative
25113 breakpoint numbers. The type column identifies what kind of breakpoint
25118 Normal, explicitly set breakpoint.
25121 Normal, explicitly set watchpoint.
25124 Internal breakpoint, used to handle correctly stepping through
25125 @code{longjmp} calls.
25127 @item longjmp resume
25128 Internal breakpoint at the target of a @code{longjmp}.
25131 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
25134 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
25137 Shared library events.
25141 @kindex set displaced-stepping
25142 @kindex show displaced-stepping
25143 @cindex displaced stepping support
25144 @cindex out-of-line single-stepping
25145 @item set displaced-stepping
25146 @itemx show displaced-stepping
25147 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
25148 if the target supports it. Displaced stepping is a way to single-step
25149 over breakpoints without removing them from the inferior, by executing
25150 an out-of-line copy of the instruction that was originally at the
25151 breakpoint location. It is also known as out-of-line single-stepping.
25154 @item set displaced-stepping on
25155 If the target architecture supports it, @value{GDBN} will use
25156 displaced stepping to step over breakpoints.
25158 @item set displaced-stepping off
25159 @value{GDBN} will not use displaced stepping to step over breakpoints,
25160 even if such is supported by the target architecture.
25162 @cindex non-stop mode, and @samp{set displaced-stepping}
25163 @item set displaced-stepping auto
25164 This is the default mode. @value{GDBN} will use displaced stepping
25165 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
25166 architecture supports displaced stepping.
25169 @kindex maint check-symtabs
25170 @item maint check-symtabs
25171 Check the consistency of psymtabs and symtabs.
25173 @kindex maint cplus first_component
25174 @item maint cplus first_component @var{name}
25175 Print the first C@t{++} class/namespace component of @var{name}.
25177 @kindex maint cplus namespace
25178 @item maint cplus namespace
25179 Print the list of possible C@t{++} namespaces.
25181 @kindex maint demangle
25182 @item maint demangle @var{name}
25183 Demangle a C@t{++} or Objective-C mangled @var{name}.
25185 @kindex maint deprecate
25186 @kindex maint undeprecate
25187 @cindex deprecated commands
25188 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
25189 @itemx maint undeprecate @var{command}
25190 Deprecate or undeprecate the named @var{command}. Deprecated commands
25191 cause @value{GDBN} to issue a warning when you use them. The optional
25192 argument @var{replacement} says which newer command should be used in
25193 favor of the deprecated one; if it is given, @value{GDBN} will mention
25194 the replacement as part of the warning.
25196 @kindex maint dump-me
25197 @item maint dump-me
25198 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
25199 Cause a fatal signal in the debugger and force it to dump its core.
25200 This is supported only on systems which support aborting a program
25201 with the @code{SIGQUIT} signal.
25203 @kindex maint internal-error
25204 @kindex maint internal-warning
25205 @item maint internal-error @r{[}@var{message-text}@r{]}
25206 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
25207 Cause @value{GDBN} to call the internal function @code{internal_error}
25208 or @code{internal_warning} and hence behave as though an internal error
25209 or internal warning has been detected. In addition to reporting the
25210 internal problem, these functions give the user the opportunity to
25211 either quit @value{GDBN} or create a core file of the current
25212 @value{GDBN} session.
25214 These commands take an optional parameter @var{message-text} that is
25215 used as the text of the error or warning message.
25217 Here's an example of using @code{internal-error}:
25220 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
25221 @dots{}/maint.c:121: internal-error: testing, 1, 2
25222 A problem internal to GDB has been detected. Further
25223 debugging may prove unreliable.
25224 Quit this debugging session? (y or n) @kbd{n}
25225 Create a core file? (y or n) @kbd{n}
25229 @cindex @value{GDBN} internal error
25230 @cindex internal errors, control of @value{GDBN} behavior
25232 @kindex maint set internal-error
25233 @kindex maint show internal-error
25234 @kindex maint set internal-warning
25235 @kindex maint show internal-warning
25236 @item maint set internal-error @var{action} [ask|yes|no]
25237 @itemx maint show internal-error @var{action}
25238 @itemx maint set internal-warning @var{action} [ask|yes|no]
25239 @itemx maint show internal-warning @var{action}
25240 When @value{GDBN} reports an internal problem (error or warning) it
25241 gives the user the opportunity to both quit @value{GDBN} and create a
25242 core file of the current @value{GDBN} session. These commands let you
25243 override the default behaviour for each particular @var{action},
25244 described in the table below.
25248 You can specify that @value{GDBN} should always (yes) or never (no)
25249 quit. The default is to ask the user what to do.
25252 You can specify that @value{GDBN} should always (yes) or never (no)
25253 create a core file. The default is to ask the user what to do.
25256 @kindex maint packet
25257 @item maint packet @var{text}
25258 If @value{GDBN} is talking to an inferior via the serial protocol,
25259 then this command sends the string @var{text} to the inferior, and
25260 displays the response packet. @value{GDBN} supplies the initial
25261 @samp{$} character, the terminating @samp{#} character, and the
25264 @kindex maint print architecture
25265 @item maint print architecture @r{[}@var{file}@r{]}
25266 Print the entire architecture configuration. The optional argument
25267 @var{file} names the file where the output goes.
25269 @kindex maint print c-tdesc
25270 @item maint print c-tdesc
25271 Print the current target description (@pxref{Target Descriptions}) as
25272 a C source file. The created source file can be used in @value{GDBN}
25273 when an XML parser is not available to parse the description.
25275 @kindex maint print dummy-frames
25276 @item maint print dummy-frames
25277 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
25280 (@value{GDBP}) @kbd{b add}
25282 (@value{GDBP}) @kbd{print add(2,3)}
25283 Breakpoint 2, add (a=2, b=3) at @dots{}
25285 The program being debugged stopped while in a function called from GDB.
25287 (@value{GDBP}) @kbd{maint print dummy-frames}
25288 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
25289 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
25290 call_lo=0x01014000 call_hi=0x01014001
25294 Takes an optional file parameter.
25296 @kindex maint print registers
25297 @kindex maint print raw-registers
25298 @kindex maint print cooked-registers
25299 @kindex maint print register-groups
25300 @item maint print registers @r{[}@var{file}@r{]}
25301 @itemx maint print raw-registers @r{[}@var{file}@r{]}
25302 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
25303 @itemx maint print register-groups @r{[}@var{file}@r{]}
25304 Print @value{GDBN}'s internal register data structures.
25306 The command @code{maint print raw-registers} includes the contents of
25307 the raw register cache; the command @code{maint print cooked-registers}
25308 includes the (cooked) value of all registers; and the command
25309 @code{maint print register-groups} includes the groups that each
25310 register is a member of. @xref{Registers,, Registers, gdbint,
25311 @value{GDBN} Internals}.
25313 These commands take an optional parameter, a file name to which to
25314 write the information.
25316 @kindex maint print reggroups
25317 @item maint print reggroups @r{[}@var{file}@r{]}
25318 Print @value{GDBN}'s internal register group data structures. The
25319 optional argument @var{file} tells to what file to write the
25322 The register groups info looks like this:
25325 (@value{GDBP}) @kbd{maint print reggroups}
25338 This command forces @value{GDBN} to flush its internal register cache.
25340 @kindex maint print objfiles
25341 @cindex info for known object files
25342 @item maint print objfiles
25343 Print a dump of all known object files. For each object file, this
25344 command prints its name, address in memory, and all of its psymtabs
25347 @kindex maint print statistics
25348 @cindex bcache statistics
25349 @item maint print statistics
25350 This command prints, for each object file in the program, various data
25351 about that object file followed by the byte cache (@dfn{bcache})
25352 statistics for the object file. The objfile data includes the number
25353 of minimal, partial, full, and stabs symbols, the number of types
25354 defined by the objfile, the number of as yet unexpanded psym tables,
25355 the number of line tables and string tables, and the amount of memory
25356 used by the various tables. The bcache statistics include the counts,
25357 sizes, and counts of duplicates of all and unique objects, max,
25358 average, and median entry size, total memory used and its overhead and
25359 savings, and various measures of the hash table size and chain
25362 @kindex maint print target-stack
25363 @cindex target stack description
25364 @item maint print target-stack
25365 A @dfn{target} is an interface between the debugger and a particular
25366 kind of file or process. Targets can be stacked in @dfn{strata},
25367 so that more than one target can potentially respond to a request.
25368 In particular, memory accesses will walk down the stack of targets
25369 until they find a target that is interested in handling that particular
25372 This command prints a short description of each layer that was pushed on
25373 the @dfn{target stack}, starting from the top layer down to the bottom one.
25375 @kindex maint print type
25376 @cindex type chain of a data type
25377 @item maint print type @var{expr}
25378 Print the type chain for a type specified by @var{expr}. The argument
25379 can be either a type name or a symbol. If it is a symbol, the type of
25380 that symbol is described. The type chain produced by this command is
25381 a recursive definition of the data type as stored in @value{GDBN}'s
25382 data structures, including its flags and contained types.
25384 @kindex maint set dwarf2 max-cache-age
25385 @kindex maint show dwarf2 max-cache-age
25386 @item maint set dwarf2 max-cache-age
25387 @itemx maint show dwarf2 max-cache-age
25388 Control the DWARF 2 compilation unit cache.
25390 @cindex DWARF 2 compilation units cache
25391 In object files with inter-compilation-unit references, such as those
25392 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
25393 reader needs to frequently refer to previously read compilation units.
25394 This setting controls how long a compilation unit will remain in the
25395 cache if it is not referenced. A higher limit means that cached
25396 compilation units will be stored in memory longer, and more total
25397 memory will be used. Setting it to zero disables caching, which will
25398 slow down @value{GDBN} startup, but reduce memory consumption.
25400 @kindex maint set profile
25401 @kindex maint show profile
25402 @cindex profiling GDB
25403 @item maint set profile
25404 @itemx maint show profile
25405 Control profiling of @value{GDBN}.
25407 Profiling will be disabled until you use the @samp{maint set profile}
25408 command to enable it. When you enable profiling, the system will begin
25409 collecting timing and execution count data; when you disable profiling or
25410 exit @value{GDBN}, the results will be written to a log file. Remember that
25411 if you use profiling, @value{GDBN} will overwrite the profiling log file
25412 (often called @file{gmon.out}). If you have a record of important profiling
25413 data in a @file{gmon.out} file, be sure to move it to a safe location.
25415 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
25416 compiled with the @samp{-pg} compiler option.
25418 @kindex maint show-debug-regs
25419 @cindex x86 hardware debug registers
25420 @item maint show-debug-regs
25421 Control whether to show variables that mirror the x86 hardware debug
25422 registers. Use @code{ON} to enable, @code{OFF} to disable. If
25423 enabled, the debug registers values are shown when @value{GDBN} inserts or
25424 removes a hardware breakpoint or watchpoint, and when the inferior
25425 triggers a hardware-assisted breakpoint or watchpoint.
25427 @kindex maint space
25428 @cindex memory used by commands
25430 Control whether to display memory usage for each command. If set to a
25431 nonzero value, @value{GDBN} will display how much memory each command
25432 took, following the command's own output. This can also be requested
25433 by invoking @value{GDBN} with the @option{--statistics} command-line
25434 switch (@pxref{Mode Options}).
25437 @cindex time of command execution
25439 Control whether to display the execution time for each command. If
25440 set to a nonzero value, @value{GDBN} will display how much time it
25441 took to execute each command, following the command's own output.
25442 The time is not printed for the commands that run the target, since
25443 there's no mechanism currently to compute how much time was spend
25444 by @value{GDBN} and how much time was spend by the program been debugged.
25445 it's not possibly currently
25446 This can also be requested by invoking @value{GDBN} with the
25447 @option{--statistics} command-line switch (@pxref{Mode Options}).
25449 @kindex maint translate-address
25450 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
25451 Find the symbol stored at the location specified by the address
25452 @var{addr} and an optional section name @var{section}. If found,
25453 @value{GDBN} prints the name of the closest symbol and an offset from
25454 the symbol's location to the specified address. This is similar to
25455 the @code{info address} command (@pxref{Symbols}), except that this
25456 command also allows to find symbols in other sections.
25458 If section was not specified, the section in which the symbol was found
25459 is also printed. For dynamically linked executables, the name of
25460 executable or shared library containing the symbol is printed as well.
25464 The following command is useful for non-interactive invocations of
25465 @value{GDBN}, such as in the test suite.
25468 @item set watchdog @var{nsec}
25469 @kindex set watchdog
25470 @cindex watchdog timer
25471 @cindex timeout for commands
25472 Set the maximum number of seconds @value{GDBN} will wait for the
25473 target operation to finish. If this time expires, @value{GDBN}
25474 reports and error and the command is aborted.
25476 @item show watchdog
25477 Show the current setting of the target wait timeout.
25480 @node Remote Protocol
25481 @appendix @value{GDBN} Remote Serial Protocol
25486 * Stop Reply Packets::
25487 * General Query Packets::
25488 * Register Packet Format::
25489 * Tracepoint Packets::
25490 * Host I/O Packets::
25492 * Notification Packets::
25493 * Remote Non-Stop::
25494 * Packet Acknowledgment::
25496 * File-I/O Remote Protocol Extension::
25497 * Library List Format::
25498 * Memory Map Format::
25504 There may be occasions when you need to know something about the
25505 protocol---for example, if there is only one serial port to your target
25506 machine, you might want your program to do something special if it
25507 recognizes a packet meant for @value{GDBN}.
25509 In the examples below, @samp{->} and @samp{<-} are used to indicate
25510 transmitted and received data, respectively.
25512 @cindex protocol, @value{GDBN} remote serial
25513 @cindex serial protocol, @value{GDBN} remote
25514 @cindex remote serial protocol
25515 All @value{GDBN} commands and responses (other than acknowledgments
25516 and notifications, see @ref{Notification Packets}) are sent as a
25517 @var{packet}. A @var{packet} is introduced with the character
25518 @samp{$}, the actual @var{packet-data}, and the terminating character
25519 @samp{#} followed by a two-digit @var{checksum}:
25522 @code{$}@var{packet-data}@code{#}@var{checksum}
25526 @cindex checksum, for @value{GDBN} remote
25528 The two-digit @var{checksum} is computed as the modulo 256 sum of all
25529 characters between the leading @samp{$} and the trailing @samp{#} (an
25530 eight bit unsigned checksum).
25532 Implementors should note that prior to @value{GDBN} 5.0 the protocol
25533 specification also included an optional two-digit @var{sequence-id}:
25536 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
25539 @cindex sequence-id, for @value{GDBN} remote
25541 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
25542 has never output @var{sequence-id}s. Stubs that handle packets added
25543 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
25545 When either the host or the target machine receives a packet, the first
25546 response expected is an acknowledgment: either @samp{+} (to indicate
25547 the package was received correctly) or @samp{-} (to request
25551 -> @code{$}@var{packet-data}@code{#}@var{checksum}
25556 The @samp{+}/@samp{-} acknowledgments can be disabled
25557 once a connection is established.
25558 @xref{Packet Acknowledgment}, for details.
25560 The host (@value{GDBN}) sends @var{command}s, and the target (the
25561 debugging stub incorporated in your program) sends a @var{response}. In
25562 the case of step and continue @var{command}s, the response is only sent
25563 when the operation has completed, and the target has again stopped all
25564 threads in all attached processes. This is the default all-stop mode
25565 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
25566 execution mode; see @ref{Remote Non-Stop}, for details.
25568 @var{packet-data} consists of a sequence of characters with the
25569 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
25572 @cindex remote protocol, field separator
25573 Fields within the packet should be separated using @samp{,} @samp{;} or
25574 @samp{:}. Except where otherwise noted all numbers are represented in
25575 @sc{hex} with leading zeros suppressed.
25577 Implementors should note that prior to @value{GDBN} 5.0, the character
25578 @samp{:} could not appear as the third character in a packet (as it
25579 would potentially conflict with the @var{sequence-id}).
25581 @cindex remote protocol, binary data
25582 @anchor{Binary Data}
25583 Binary data in most packets is encoded either as two hexadecimal
25584 digits per byte of binary data. This allowed the traditional remote
25585 protocol to work over connections which were only seven-bit clean.
25586 Some packets designed more recently assume an eight-bit clean
25587 connection, and use a more efficient encoding to send and receive
25590 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
25591 as an escape character. Any escaped byte is transmitted as the escape
25592 character followed by the original character XORed with @code{0x20}.
25593 For example, the byte @code{0x7d} would be transmitted as the two
25594 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
25595 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
25596 @samp{@}}) must always be escaped. Responses sent by the stub
25597 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
25598 is not interpreted as the start of a run-length encoded sequence
25601 Response @var{data} can be run-length encoded to save space.
25602 Run-length encoding replaces runs of identical characters with one
25603 instance of the repeated character, followed by a @samp{*} and a
25604 repeat count. The repeat count is itself sent encoded, to avoid
25605 binary characters in @var{data}: a value of @var{n} is sent as
25606 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
25607 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
25608 code 32) for a repeat count of 3. (This is because run-length
25609 encoding starts to win for counts 3 or more.) Thus, for example,
25610 @samp{0* } is a run-length encoding of ``0000'': the space character
25611 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
25614 The printable characters @samp{#} and @samp{$} or with a numeric value
25615 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
25616 seven repeats (@samp{$}) can be expanded using a repeat count of only
25617 five (@samp{"}). For example, @samp{00000000} can be encoded as
25620 The error response returned for some packets includes a two character
25621 error number. That number is not well defined.
25623 @cindex empty response, for unsupported packets
25624 For any @var{command} not supported by the stub, an empty response
25625 (@samp{$#00}) should be returned. That way it is possible to extend the
25626 protocol. A newer @value{GDBN} can tell if a packet is supported based
25629 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
25630 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
25636 The following table provides a complete list of all currently defined
25637 @var{command}s and their corresponding response @var{data}.
25638 @xref{File-I/O Remote Protocol Extension}, for details about the File
25639 I/O extension of the remote protocol.
25641 Each packet's description has a template showing the packet's overall
25642 syntax, followed by an explanation of the packet's meaning. We
25643 include spaces in some of the templates for clarity; these are not
25644 part of the packet's syntax. No @value{GDBN} packet uses spaces to
25645 separate its components. For example, a template like @samp{foo
25646 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
25647 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
25648 @var{baz}. @value{GDBN} does not transmit a space character between the
25649 @samp{foo} and the @var{bar}, or between the @var{bar} and the
25652 @cindex @var{thread-id}, in remote protocol
25653 @anchor{thread-id syntax}
25654 Several packets and replies include a @var{thread-id} field to identify
25655 a thread. Normally these are positive numbers with a target-specific
25656 interpretation, formatted as big-endian hex strings. A @var{thread-id}
25657 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
25660 In addition, the remote protocol supports a multiprocess feature in
25661 which the @var{thread-id} syntax is extended to optionally include both
25662 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
25663 The @var{pid} (process) and @var{tid} (thread) components each have the
25664 format described above: a positive number with target-specific
25665 interpretation formatted as a big-endian hex string, literal @samp{-1}
25666 to indicate all processes or threads (respectively), or @samp{0} to
25667 indicate an arbitrary process or thread. Specifying just a process, as
25668 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
25669 error to specify all processes but a specific thread, such as
25670 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
25671 for those packets and replies explicitly documented to include a process
25672 ID, rather than a @var{thread-id}.
25674 The multiprocess @var{thread-id} syntax extensions are only used if both
25675 @value{GDBN} and the stub report support for the @samp{multiprocess}
25676 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
25679 Note that all packet forms beginning with an upper- or lower-case
25680 letter, other than those described here, are reserved for future use.
25682 Here are the packet descriptions.
25687 @cindex @samp{!} packet
25688 @anchor{extended mode}
25689 Enable extended mode. In extended mode, the remote server is made
25690 persistent. The @samp{R} packet is used to restart the program being
25696 The remote target both supports and has enabled extended mode.
25700 @cindex @samp{?} packet
25701 Indicate the reason the target halted. The reply is the same as for
25702 step and continue. This packet has a special interpretation when the
25703 target is in non-stop mode; see @ref{Remote Non-Stop}.
25706 @xref{Stop Reply Packets}, for the reply specifications.
25708 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
25709 @cindex @samp{A} packet
25710 Initialized @code{argv[]} array passed into program. @var{arglen}
25711 specifies the number of bytes in the hex encoded byte stream
25712 @var{arg}. See @code{gdbserver} for more details.
25717 The arguments were set.
25723 @cindex @samp{b} packet
25724 (Don't use this packet; its behavior is not well-defined.)
25725 Change the serial line speed to @var{baud}.
25727 JTC: @emph{When does the transport layer state change? When it's
25728 received, or after the ACK is transmitted. In either case, there are
25729 problems if the command or the acknowledgment packet is dropped.}
25731 Stan: @emph{If people really wanted to add something like this, and get
25732 it working for the first time, they ought to modify ser-unix.c to send
25733 some kind of out-of-band message to a specially-setup stub and have the
25734 switch happen "in between" packets, so that from remote protocol's point
25735 of view, nothing actually happened.}
25737 @item B @var{addr},@var{mode}
25738 @cindex @samp{B} packet
25739 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
25740 breakpoint at @var{addr}.
25742 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
25743 (@pxref{insert breakpoint or watchpoint packet}).
25746 @cindex @samp{bc} packet
25747 Backward continue. Execute the target system in reverse. No parameter.
25748 @xref{Reverse Execution}, for more information.
25751 @xref{Stop Reply Packets}, for the reply specifications.
25754 @cindex @samp{bs} packet
25755 Backward single step. Execute one instruction in reverse. No parameter.
25756 @xref{Reverse Execution}, for more information.
25759 @xref{Stop Reply Packets}, for the reply specifications.
25761 @item c @r{[}@var{addr}@r{]}
25762 @cindex @samp{c} packet
25763 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
25764 resume at current address.
25767 @xref{Stop Reply Packets}, for the reply specifications.
25769 @item C @var{sig}@r{[};@var{addr}@r{]}
25770 @cindex @samp{C} packet
25771 Continue with signal @var{sig} (hex signal number). If
25772 @samp{;@var{addr}} is omitted, resume at same address.
25775 @xref{Stop Reply Packets}, for the reply specifications.
25778 @cindex @samp{d} packet
25781 Don't use this packet; instead, define a general set packet
25782 (@pxref{General Query Packets}).
25786 @cindex @samp{D} packet
25787 The first form of the packet is used to detach @value{GDBN} from the
25788 remote system. It is sent to the remote target
25789 before @value{GDBN} disconnects via the @code{detach} command.
25791 The second form, including a process ID, is used when multiprocess
25792 protocol extensions are enabled (@pxref{multiprocess extensions}), to
25793 detach only a specific process. The @var{pid} is specified as a
25794 big-endian hex string.
25804 @item F @var{RC},@var{EE},@var{CF};@var{XX}
25805 @cindex @samp{F} packet
25806 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
25807 This is part of the File-I/O protocol extension. @xref{File-I/O
25808 Remote Protocol Extension}, for the specification.
25811 @anchor{read registers packet}
25812 @cindex @samp{g} packet
25813 Read general registers.
25817 @item @var{XX@dots{}}
25818 Each byte of register data is described by two hex digits. The bytes
25819 with the register are transmitted in target byte order. The size of
25820 each register and their position within the @samp{g} packet are
25821 determined by the @value{GDBN} internal gdbarch functions
25822 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
25823 specification of several standard @samp{g} packets is specified below.
25828 @item G @var{XX@dots{}}
25829 @cindex @samp{G} packet
25830 Write general registers. @xref{read registers packet}, for a
25831 description of the @var{XX@dots{}} data.
25841 @item H @var{c} @var{thread-id}
25842 @cindex @samp{H} packet
25843 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
25844 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
25845 should be @samp{c} for step and continue operations, @samp{g} for other
25846 operations. The thread designator @var{thread-id} has the format and
25847 interpretation described in @ref{thread-id syntax}.
25858 @c 'H': How restrictive (or permissive) is the thread model. If a
25859 @c thread is selected and stopped, are other threads allowed
25860 @c to continue to execute? As I mentioned above, I think the
25861 @c semantics of each command when a thread is selected must be
25862 @c described. For example:
25864 @c 'g': If the stub supports threads and a specific thread is
25865 @c selected, returns the register block from that thread;
25866 @c otherwise returns current registers.
25868 @c 'G' If the stub supports threads and a specific thread is
25869 @c selected, sets the registers of the register block of
25870 @c that thread; otherwise sets current registers.
25872 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
25873 @anchor{cycle step packet}
25874 @cindex @samp{i} packet
25875 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
25876 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
25877 step starting at that address.
25880 @cindex @samp{I} packet
25881 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
25885 @cindex @samp{k} packet
25888 FIXME: @emph{There is no description of how to operate when a specific
25889 thread context has been selected (i.e.@: does 'k' kill only that
25892 @item m @var{addr},@var{length}
25893 @cindex @samp{m} packet
25894 Read @var{length} bytes of memory starting at address @var{addr}.
25895 Note that @var{addr} may not be aligned to any particular boundary.
25897 The stub need not use any particular size or alignment when gathering
25898 data from memory for the response; even if @var{addr} is word-aligned
25899 and @var{length} is a multiple of the word size, the stub is free to
25900 use byte accesses, or not. For this reason, this packet may not be
25901 suitable for accessing memory-mapped I/O devices.
25902 @cindex alignment of remote memory accesses
25903 @cindex size of remote memory accesses
25904 @cindex memory, alignment and size of remote accesses
25908 @item @var{XX@dots{}}
25909 Memory contents; each byte is transmitted as a two-digit hexadecimal
25910 number. The reply may contain fewer bytes than requested if the
25911 server was able to read only part of the region of memory.
25916 @item M @var{addr},@var{length}:@var{XX@dots{}}
25917 @cindex @samp{M} packet
25918 Write @var{length} bytes of memory starting at address @var{addr}.
25919 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
25920 hexadecimal number.
25927 for an error (this includes the case where only part of the data was
25932 @cindex @samp{p} packet
25933 Read the value of register @var{n}; @var{n} is in hex.
25934 @xref{read registers packet}, for a description of how the returned
25935 register value is encoded.
25939 @item @var{XX@dots{}}
25940 the register's value
25944 Indicating an unrecognized @var{query}.
25947 @item P @var{n@dots{}}=@var{r@dots{}}
25948 @anchor{write register packet}
25949 @cindex @samp{P} packet
25950 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
25951 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
25952 digits for each byte in the register (target byte order).
25962 @item q @var{name} @var{params}@dots{}
25963 @itemx Q @var{name} @var{params}@dots{}
25964 @cindex @samp{q} packet
25965 @cindex @samp{Q} packet
25966 General query (@samp{q}) and set (@samp{Q}). These packets are
25967 described fully in @ref{General Query Packets}.
25970 @cindex @samp{r} packet
25971 Reset the entire system.
25973 Don't use this packet; use the @samp{R} packet instead.
25976 @cindex @samp{R} packet
25977 Restart the program being debugged. @var{XX}, while needed, is ignored.
25978 This packet is only available in extended mode (@pxref{extended mode}).
25980 The @samp{R} packet has no reply.
25982 @item s @r{[}@var{addr}@r{]}
25983 @cindex @samp{s} packet
25984 Single step. @var{addr} is the address at which to resume. If
25985 @var{addr} is omitted, resume at same address.
25988 @xref{Stop Reply Packets}, for the reply specifications.
25990 @item S @var{sig}@r{[};@var{addr}@r{]}
25991 @anchor{step with signal packet}
25992 @cindex @samp{S} packet
25993 Step with signal. This is analogous to the @samp{C} packet, but
25994 requests a single-step, rather than a normal resumption of execution.
25997 @xref{Stop Reply Packets}, for the reply specifications.
25999 @item t @var{addr}:@var{PP},@var{MM}
26000 @cindex @samp{t} packet
26001 Search backwards starting at address @var{addr} for a match with pattern
26002 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
26003 @var{addr} must be at least 3 digits.
26005 @item T @var{thread-id}
26006 @cindex @samp{T} packet
26007 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
26012 thread is still alive
26018 Packets starting with @samp{v} are identified by a multi-letter name,
26019 up to the first @samp{;} or @samp{?} (or the end of the packet).
26021 @item vAttach;@var{pid}
26022 @cindex @samp{vAttach} packet
26023 Attach to a new process with the specified process ID @var{pid}.
26024 The process ID is a
26025 hexadecimal integer identifying the process. In all-stop mode, all
26026 threads in the attached process are stopped; in non-stop mode, it may be
26027 attached without being stopped if that is supported by the target.
26029 @c In non-stop mode, on a successful vAttach, the stub should set the
26030 @c current thread to a thread of the newly-attached process. After
26031 @c attaching, GDB queries for the attached process's thread ID with qC.
26032 @c Also note that, from a user perspective, whether or not the
26033 @c target is stopped on attach in non-stop mode depends on whether you
26034 @c use the foreground or background version of the attach command, not
26035 @c on what vAttach does; GDB does the right thing with respect to either
26036 @c stopping or restarting threads.
26038 This packet is only available in extended mode (@pxref{extended mode}).
26044 @item @r{Any stop packet}
26045 for success in all-stop mode (@pxref{Stop Reply Packets})
26047 for success in non-stop mode (@pxref{Remote Non-Stop})
26050 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
26051 @cindex @samp{vCont} packet
26052 Resume the inferior, specifying different actions for each thread.
26053 If an action is specified with no @var{thread-id}, then it is applied to any
26054 threads that don't have a specific action specified; if no default action is
26055 specified then other threads should remain stopped in all-stop mode and
26056 in their current state in non-stop mode.
26057 Specifying multiple
26058 default actions is an error; specifying no actions is also an error.
26059 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
26061 Currently supported actions are:
26067 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
26071 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
26075 Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
26078 The optional argument @var{addr} normally associated with the
26079 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
26080 not supported in @samp{vCont}.
26082 The @samp{t} and @samp{T} actions are only relevant in non-stop mode
26083 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
26084 A stop reply should be generated for any affected thread not already stopped.
26085 When a thread is stopped by means of a @samp{t} action,
26086 the corresponding stop reply should indicate that the thread has stopped with
26087 signal @samp{0}, regardless of whether the target uses some other signal
26088 as an implementation detail.
26091 @xref{Stop Reply Packets}, for the reply specifications.
26094 @cindex @samp{vCont?} packet
26095 Request a list of actions supported by the @samp{vCont} packet.
26099 @item vCont@r{[};@var{action}@dots{}@r{]}
26100 The @samp{vCont} packet is supported. Each @var{action} is a supported
26101 command in the @samp{vCont} packet.
26103 The @samp{vCont} packet is not supported.
26106 @item vFile:@var{operation}:@var{parameter}@dots{}
26107 @cindex @samp{vFile} packet
26108 Perform a file operation on the target system. For details,
26109 see @ref{Host I/O Packets}.
26111 @item vFlashErase:@var{addr},@var{length}
26112 @cindex @samp{vFlashErase} packet
26113 Direct the stub to erase @var{length} bytes of flash starting at
26114 @var{addr}. The region may enclose any number of flash blocks, but
26115 its start and end must fall on block boundaries, as indicated by the
26116 flash block size appearing in the memory map (@pxref{Memory Map
26117 Format}). @value{GDBN} groups flash memory programming operations
26118 together, and sends a @samp{vFlashDone} request after each group; the
26119 stub is allowed to delay erase operation until the @samp{vFlashDone}
26120 packet is received.
26122 The stub must support @samp{vCont} if it reports support for
26123 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
26124 this case @samp{vCont} actions can be specified to apply to all threads
26125 in a process by using the @samp{p@var{pid}.-1} form of the
26136 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
26137 @cindex @samp{vFlashWrite} packet
26138 Direct the stub to write data to flash address @var{addr}. The data
26139 is passed in binary form using the same encoding as for the @samp{X}
26140 packet (@pxref{Binary Data}). The memory ranges specified by
26141 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
26142 not overlap, and must appear in order of increasing addresses
26143 (although @samp{vFlashErase} packets for higher addresses may already
26144 have been received; the ordering is guaranteed only between
26145 @samp{vFlashWrite} packets). If a packet writes to an address that was
26146 neither erased by a preceding @samp{vFlashErase} packet nor by some other
26147 target-specific method, the results are unpredictable.
26155 for vFlashWrite addressing non-flash memory
26161 @cindex @samp{vFlashDone} packet
26162 Indicate to the stub that flash programming operation is finished.
26163 The stub is permitted to delay or batch the effects of a group of
26164 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
26165 @samp{vFlashDone} packet is received. The contents of the affected
26166 regions of flash memory are unpredictable until the @samp{vFlashDone}
26167 request is completed.
26169 @item vKill;@var{pid}
26170 @cindex @samp{vKill} packet
26171 Kill the process with the specified process ID. @var{pid} is a
26172 hexadecimal integer identifying the process. This packet is used in
26173 preference to @samp{k} when multiprocess protocol extensions are
26174 supported; see @ref{multiprocess extensions}.
26184 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
26185 @cindex @samp{vRun} packet
26186 Run the program @var{filename}, passing it each @var{argument} on its
26187 command line. The file and arguments are hex-encoded strings. If
26188 @var{filename} is an empty string, the stub may use a default program
26189 (e.g.@: the last program run). The program is created in the stopped
26192 @c FIXME: What about non-stop mode?
26194 This packet is only available in extended mode (@pxref{extended mode}).
26200 @item @r{Any stop packet}
26201 for success (@pxref{Stop Reply Packets})
26205 @anchor{vStopped packet}
26206 @cindex @samp{vStopped} packet
26208 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
26209 reply and prompt for the stub to report another one.
26213 @item @r{Any stop packet}
26214 if there is another unreported stop event (@pxref{Stop Reply Packets})
26216 if there are no unreported stop events
26219 @item X @var{addr},@var{length}:@var{XX@dots{}}
26221 @cindex @samp{X} packet
26222 Write data to memory, where the data is transmitted in binary.
26223 @var{addr} is address, @var{length} is number of bytes,
26224 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
26234 @item z @var{type},@var{addr},@var{length}
26235 @itemx Z @var{type},@var{addr},@var{length}
26236 @anchor{insert breakpoint or watchpoint packet}
26237 @cindex @samp{z} packet
26238 @cindex @samp{Z} packets
26239 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
26240 watchpoint starting at address @var{address} and covering the next
26241 @var{length} bytes.
26243 Each breakpoint and watchpoint packet @var{type} is documented
26246 @emph{Implementation notes: A remote target shall return an empty string
26247 for an unrecognized breakpoint or watchpoint packet @var{type}. A
26248 remote target shall support either both or neither of a given
26249 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
26250 avoid potential problems with duplicate packets, the operations should
26251 be implemented in an idempotent way.}
26253 @item z0,@var{addr},@var{length}
26254 @itemx Z0,@var{addr},@var{length}
26255 @cindex @samp{z0} packet
26256 @cindex @samp{Z0} packet
26257 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
26258 @var{addr} of size @var{length}.
26260 A memory breakpoint is implemented by replacing the instruction at
26261 @var{addr} with a software breakpoint or trap instruction. The
26262 @var{length} is used by targets that indicates the size of the
26263 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
26264 @sc{mips} can insert either a 2 or 4 byte breakpoint).
26266 @emph{Implementation note: It is possible for a target to copy or move
26267 code that contains memory breakpoints (e.g., when implementing
26268 overlays). The behavior of this packet, in the presence of such a
26269 target, is not defined.}
26281 @item z1,@var{addr},@var{length}
26282 @itemx Z1,@var{addr},@var{length}
26283 @cindex @samp{z1} packet
26284 @cindex @samp{Z1} packet
26285 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
26286 address @var{addr} of size @var{length}.
26288 A hardware breakpoint is implemented using a mechanism that is not
26289 dependant on being able to modify the target's memory.
26291 @emph{Implementation note: A hardware breakpoint is not affected by code
26304 @item z2,@var{addr},@var{length}
26305 @itemx Z2,@var{addr},@var{length}
26306 @cindex @samp{z2} packet
26307 @cindex @samp{Z2} packet
26308 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
26320 @item z3,@var{addr},@var{length}
26321 @itemx Z3,@var{addr},@var{length}
26322 @cindex @samp{z3} packet
26323 @cindex @samp{Z3} packet
26324 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
26336 @item z4,@var{addr},@var{length}
26337 @itemx Z4,@var{addr},@var{length}
26338 @cindex @samp{z4} packet
26339 @cindex @samp{Z4} packet
26340 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
26354 @node Stop Reply Packets
26355 @section Stop Reply Packets
26356 @cindex stop reply packets
26358 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
26359 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
26360 receive any of the below as a reply. Except for @samp{?}
26361 and @samp{vStopped}, that reply is only returned
26362 when the target halts. In the below the exact meaning of @dfn{signal
26363 number} is defined by the header @file{include/gdb/signals.h} in the
26364 @value{GDBN} source code.
26366 As in the description of request packets, we include spaces in the
26367 reply templates for clarity; these are not part of the reply packet's
26368 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
26374 The program received signal number @var{AA} (a two-digit hexadecimal
26375 number). This is equivalent to a @samp{T} response with no
26376 @var{n}:@var{r} pairs.
26378 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
26379 @cindex @samp{T} packet reply
26380 The program received signal number @var{AA} (a two-digit hexadecimal
26381 number). This is equivalent to an @samp{S} response, except that the
26382 @samp{@var{n}:@var{r}} pairs can carry values of important registers
26383 and other information directly in the stop reply packet, reducing
26384 round-trip latency. Single-step and breakpoint traps are reported
26385 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
26389 If @var{n} is a hexadecimal number, it is a register number, and the
26390 corresponding @var{r} gives that register's value. @var{r} is a
26391 series of bytes in target byte order, with each byte given by a
26392 two-digit hex number.
26395 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
26396 the stopped thread, as specified in @ref{thread-id syntax}.
26399 If @var{n} is a recognized @dfn{stop reason}, it describes a more
26400 specific event that stopped the target. The currently defined stop
26401 reasons are listed below. @var{aa} should be @samp{05}, the trap
26402 signal. At most one stop reason should be present.
26405 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
26406 and go on to the next; this allows us to extend the protocol in the
26410 The currently defined stop reasons are:
26416 The packet indicates a watchpoint hit, and @var{r} is the data address, in
26419 @cindex shared library events, remote reply
26421 The packet indicates that the loaded libraries have changed.
26422 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
26423 list of loaded libraries. @var{r} is ignored.
26425 @cindex replay log events, remote reply
26427 The packet indicates that the target cannot continue replaying
26428 logged execution events, because it has reached the end (or the
26429 beginning when executing backward) of the log. The value of @var{r}
26430 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
26431 for more information.
26437 @itemx W @var{AA} ; process:@var{pid}
26438 The process exited, and @var{AA} is the exit status. This is only
26439 applicable to certain targets.
26441 The second form of the response, including the process ID of the exited
26442 process, can be used only when @value{GDBN} has reported support for
26443 multiprocess protocol extensions; see @ref{multiprocess extensions}.
26444 The @var{pid} is formatted as a big-endian hex string.
26447 @itemx X @var{AA} ; process:@var{pid}
26448 The process terminated with signal @var{AA}.
26450 The second form of the response, including the process ID of the
26451 terminated process, can be used only when @value{GDBN} has reported
26452 support for multiprocess protocol extensions; see @ref{multiprocess
26453 extensions}. The @var{pid} is formatted as a big-endian hex string.
26455 @item O @var{XX}@dots{}
26456 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
26457 written as the program's console output. This can happen at any time
26458 while the program is running and the debugger should continue to wait
26459 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
26461 @item F @var{call-id},@var{parameter}@dots{}
26462 @var{call-id} is the identifier which says which host system call should
26463 be called. This is just the name of the function. Translation into the
26464 correct system call is only applicable as it's defined in @value{GDBN}.
26465 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
26468 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
26469 this very system call.
26471 The target replies with this packet when it expects @value{GDBN} to
26472 call a host system call on behalf of the target. @value{GDBN} replies
26473 with an appropriate @samp{F} packet and keeps up waiting for the next
26474 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
26475 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
26476 Protocol Extension}, for more details.
26480 @node General Query Packets
26481 @section General Query Packets
26482 @cindex remote query requests
26484 Packets starting with @samp{q} are @dfn{general query packets};
26485 packets starting with @samp{Q} are @dfn{general set packets}. General
26486 query and set packets are a semi-unified form for retrieving and
26487 sending information to and from the stub.
26489 The initial letter of a query or set packet is followed by a name
26490 indicating what sort of thing the packet applies to. For example,
26491 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
26492 definitions with the stub. These packet names follow some
26497 The name must not contain commas, colons or semicolons.
26499 Most @value{GDBN} query and set packets have a leading upper case
26502 The names of custom vendor packets should use a company prefix, in
26503 lower case, followed by a period. For example, packets designed at
26504 the Acme Corporation might begin with @samp{qacme.foo} (for querying
26505 foos) or @samp{Qacme.bar} (for setting bars).
26508 The name of a query or set packet should be separated from any
26509 parameters by a @samp{:}; the parameters themselves should be
26510 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
26511 full packet name, and check for a separator or the end of the packet,
26512 in case two packet names share a common prefix. New packets should not begin
26513 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
26514 packets predate these conventions, and have arguments without any terminator
26515 for the packet name; we suspect they are in widespread use in places that
26516 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
26517 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
26520 Like the descriptions of the other packets, each description here
26521 has a template showing the packet's overall syntax, followed by an
26522 explanation of the packet's meaning. We include spaces in some of the
26523 templates for clarity; these are not part of the packet's syntax. No
26524 @value{GDBN} packet uses spaces to separate its components.
26526 Here are the currently defined query and set packets:
26531 @cindex current thread, remote request
26532 @cindex @samp{qC} packet
26533 Return the current thread ID.
26537 @item QC @var{thread-id}
26538 Where @var{thread-id} is a thread ID as documented in
26539 @ref{thread-id syntax}.
26540 @item @r{(anything else)}
26541 Any other reply implies the old thread ID.
26544 @item qCRC:@var{addr},@var{length}
26545 @cindex CRC of memory block, remote request
26546 @cindex @samp{qCRC} packet
26547 Compute the CRC checksum of a block of memory.
26551 An error (such as memory fault)
26552 @item C @var{crc32}
26553 The specified memory region's checksum is @var{crc32}.
26557 @itemx qsThreadInfo
26558 @cindex list active threads, remote request
26559 @cindex @samp{qfThreadInfo} packet
26560 @cindex @samp{qsThreadInfo} packet
26561 Obtain a list of all active thread IDs from the target (OS). Since there
26562 may be too many active threads to fit into one reply packet, this query
26563 works iteratively: it may require more than one query/reply sequence to
26564 obtain the entire list of threads. The first query of the sequence will
26565 be the @samp{qfThreadInfo} query; subsequent queries in the
26566 sequence will be the @samp{qsThreadInfo} query.
26568 NOTE: This packet replaces the @samp{qL} query (see below).
26572 @item m @var{thread-id}
26574 @item m @var{thread-id},@var{thread-id}@dots{}
26575 a comma-separated list of thread IDs
26577 (lower case letter @samp{L}) denotes end of list.
26580 In response to each query, the target will reply with a list of one or
26581 more thread IDs, separated by commas.
26582 @value{GDBN} will respond to each reply with a request for more thread
26583 ids (using the @samp{qs} form of the query), until the target responds
26584 with @samp{l} (lower-case el, for @dfn{last}).
26585 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
26588 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
26589 @cindex get thread-local storage address, remote request
26590 @cindex @samp{qGetTLSAddr} packet
26591 Fetch the address associated with thread local storage specified
26592 by @var{thread-id}, @var{offset}, and @var{lm}.
26594 @var{thread-id} is the thread ID associated with the
26595 thread for which to fetch the TLS address. @xref{thread-id syntax}.
26597 @var{offset} is the (big endian, hex encoded) offset associated with the
26598 thread local variable. (This offset is obtained from the debug
26599 information associated with the variable.)
26601 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
26602 the load module associated with the thread local storage. For example,
26603 a @sc{gnu}/Linux system will pass the link map address of the shared
26604 object associated with the thread local storage under consideration.
26605 Other operating environments may choose to represent the load module
26606 differently, so the precise meaning of this parameter will vary.
26610 @item @var{XX}@dots{}
26611 Hex encoded (big endian) bytes representing the address of the thread
26612 local storage requested.
26615 An error occurred. @var{nn} are hex digits.
26618 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
26621 @item qL @var{startflag} @var{threadcount} @var{nextthread}
26622 Obtain thread information from RTOS. Where: @var{startflag} (one hex
26623 digit) is one to indicate the first query and zero to indicate a
26624 subsequent query; @var{threadcount} (two hex digits) is the maximum
26625 number of threads the response packet can contain; and @var{nextthread}
26626 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
26627 returned in the response as @var{argthread}.
26629 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
26633 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
26634 Where: @var{count} (two hex digits) is the number of threads being
26635 returned; @var{done} (one hex digit) is zero to indicate more threads
26636 and one indicates no further threads; @var{argthreadid} (eight hex
26637 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
26638 is a sequence of thread IDs from the target. @var{threadid} (eight hex
26639 digits). See @code{remote.c:parse_threadlist_response()}.
26643 @cindex section offsets, remote request
26644 @cindex @samp{qOffsets} packet
26645 Get section offsets that the target used when relocating the downloaded
26650 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
26651 Relocate the @code{Text} section by @var{xxx} from its original address.
26652 Relocate the @code{Data} section by @var{yyy} from its original address.
26653 If the object file format provides segment information (e.g.@: @sc{elf}
26654 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
26655 segments by the supplied offsets.
26657 @emph{Note: while a @code{Bss} offset may be included in the response,
26658 @value{GDBN} ignores this and instead applies the @code{Data} offset
26659 to the @code{Bss} section.}
26661 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
26662 Relocate the first segment of the object file, which conventionally
26663 contains program code, to a starting address of @var{xxx}. If
26664 @samp{DataSeg} is specified, relocate the second segment, which
26665 conventionally contains modifiable data, to a starting address of
26666 @var{yyy}. @value{GDBN} will report an error if the object file
26667 does not contain segment information, or does not contain at least
26668 as many segments as mentioned in the reply. Extra segments are
26669 kept at fixed offsets relative to the last relocated segment.
26672 @item qP @var{mode} @var{thread-id}
26673 @cindex thread information, remote request
26674 @cindex @samp{qP} packet
26675 Returns information on @var{thread-id}. Where: @var{mode} is a hex
26676 encoded 32 bit mode; @var{thread-id} is a thread ID
26677 (@pxref{thread-id syntax}).
26679 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
26682 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
26686 @cindex non-stop mode, remote request
26687 @cindex @samp{QNonStop} packet
26689 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
26690 @xref{Remote Non-Stop}, for more information.
26695 The request succeeded.
26698 An error occurred. @var{nn} are hex digits.
26701 An empty reply indicates that @samp{QNonStop} is not supported by
26705 This packet is not probed by default; the remote stub must request it,
26706 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26707 Use of this packet is controlled by the @code{set non-stop} command;
26708 @pxref{Non-Stop Mode}.
26710 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
26711 @cindex pass signals to inferior, remote request
26712 @cindex @samp{QPassSignals} packet
26713 @anchor{QPassSignals}
26714 Each listed @var{signal} should be passed directly to the inferior process.
26715 Signals are numbered identically to continue packets and stop replies
26716 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
26717 strictly greater than the previous item. These signals do not need to stop
26718 the inferior, or be reported to @value{GDBN}. All other signals should be
26719 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
26720 combine; any earlier @samp{QPassSignals} list is completely replaced by the
26721 new list. This packet improves performance when using @samp{handle
26722 @var{signal} nostop noprint pass}.
26727 The request succeeded.
26730 An error occurred. @var{nn} are hex digits.
26733 An empty reply indicates that @samp{QPassSignals} is not supported by
26737 Use of this packet is controlled by the @code{set remote pass-signals}
26738 command (@pxref{Remote Configuration, set remote pass-signals}).
26739 This packet is not probed by default; the remote stub must request it,
26740 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26742 @item qRcmd,@var{command}
26743 @cindex execute remote command, remote request
26744 @cindex @samp{qRcmd} packet
26745 @var{command} (hex encoded) is passed to the local interpreter for
26746 execution. Invalid commands should be reported using the output
26747 string. Before the final result packet, the target may also respond
26748 with a number of intermediate @samp{O@var{output}} console output
26749 packets. @emph{Implementors should note that providing access to a
26750 stubs's interpreter may have security implications}.
26755 A command response with no output.
26757 A command response with the hex encoded output string @var{OUTPUT}.
26759 Indicate a badly formed request.
26761 An empty reply indicates that @samp{qRcmd} is not recognized.
26764 (Note that the @code{qRcmd} packet's name is separated from the
26765 command by a @samp{,}, not a @samp{:}, contrary to the naming
26766 conventions above. Please don't use this packet as a model for new
26769 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
26770 @cindex searching memory, in remote debugging
26771 @cindex @samp{qSearch:memory} packet
26772 @anchor{qSearch memory}
26773 Search @var{length} bytes at @var{address} for @var{search-pattern}.
26774 @var{address} and @var{length} are encoded in hex.
26775 @var{search-pattern} is a sequence of bytes, hex encoded.
26780 The pattern was not found.
26782 The pattern was found at @var{address}.
26784 A badly formed request or an error was encountered while searching memory.
26786 An empty reply indicates that @samp{qSearch:memory} is not recognized.
26789 @item QStartNoAckMode
26790 @cindex @samp{QStartNoAckMode} packet
26791 @anchor{QStartNoAckMode}
26792 Request that the remote stub disable the normal @samp{+}/@samp{-}
26793 protocol acknowledgments (@pxref{Packet Acknowledgment}).
26798 The stub has switched to no-acknowledgment mode.
26799 @value{GDBN} acknowledges this reponse,
26800 but neither the stub nor @value{GDBN} shall send or expect further
26801 @samp{+}/@samp{-} acknowledgments in the current connection.
26803 An empty reply indicates that the stub does not support no-acknowledgment mode.
26806 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
26807 @cindex supported packets, remote query
26808 @cindex features of the remote protocol
26809 @cindex @samp{qSupported} packet
26810 @anchor{qSupported}
26811 Tell the remote stub about features supported by @value{GDBN}, and
26812 query the stub for features it supports. This packet allows
26813 @value{GDBN} and the remote stub to take advantage of each others'
26814 features. @samp{qSupported} also consolidates multiple feature probes
26815 at startup, to improve @value{GDBN} performance---a single larger
26816 packet performs better than multiple smaller probe packets on
26817 high-latency links. Some features may enable behavior which must not
26818 be on by default, e.g.@: because it would confuse older clients or
26819 stubs. Other features may describe packets which could be
26820 automatically probed for, but are not. These features must be
26821 reported before @value{GDBN} will use them. This ``default
26822 unsupported'' behavior is not appropriate for all packets, but it
26823 helps to keep the initial connection time under control with new
26824 versions of @value{GDBN} which support increasing numbers of packets.
26828 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
26829 The stub supports or does not support each returned @var{stubfeature},
26830 depending on the form of each @var{stubfeature} (see below for the
26833 An empty reply indicates that @samp{qSupported} is not recognized,
26834 or that no features needed to be reported to @value{GDBN}.
26837 The allowed forms for each feature (either a @var{gdbfeature} in the
26838 @samp{qSupported} packet, or a @var{stubfeature} in the response)
26842 @item @var{name}=@var{value}
26843 The remote protocol feature @var{name} is supported, and associated
26844 with the specified @var{value}. The format of @var{value} depends
26845 on the feature, but it must not include a semicolon.
26847 The remote protocol feature @var{name} is supported, and does not
26848 need an associated value.
26850 The remote protocol feature @var{name} is not supported.
26852 The remote protocol feature @var{name} may be supported, and
26853 @value{GDBN} should auto-detect support in some other way when it is
26854 needed. This form will not be used for @var{gdbfeature} notifications,
26855 but may be used for @var{stubfeature} responses.
26858 Whenever the stub receives a @samp{qSupported} request, the
26859 supplied set of @value{GDBN} features should override any previous
26860 request. This allows @value{GDBN} to put the stub in a known
26861 state, even if the stub had previously been communicating with
26862 a different version of @value{GDBN}.
26864 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
26869 This feature indicates whether @value{GDBN} supports multiprocess
26870 extensions to the remote protocol. @value{GDBN} does not use such
26871 extensions unless the stub also reports that it supports them by
26872 including @samp{multiprocess+} in its @samp{qSupported} reply.
26873 @xref{multiprocess extensions}, for details.
26876 Stubs should ignore any unknown values for
26877 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
26878 packet supports receiving packets of unlimited length (earlier
26879 versions of @value{GDBN} may reject overly long responses). Additional values
26880 for @var{gdbfeature} may be defined in the future to let the stub take
26881 advantage of new features in @value{GDBN}, e.g.@: incompatible
26882 improvements in the remote protocol---the @samp{multiprocess} feature is
26883 an example of such a feature. The stub's reply should be independent
26884 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
26885 describes all the features it supports, and then the stub replies with
26886 all the features it supports.
26888 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
26889 responses, as long as each response uses one of the standard forms.
26891 Some features are flags. A stub which supports a flag feature
26892 should respond with a @samp{+} form response. Other features
26893 require values, and the stub should respond with an @samp{=}
26896 Each feature has a default value, which @value{GDBN} will use if
26897 @samp{qSupported} is not available or if the feature is not mentioned
26898 in the @samp{qSupported} response. The default values are fixed; a
26899 stub is free to omit any feature responses that match the defaults.
26901 Not all features can be probed, but for those which can, the probing
26902 mechanism is useful: in some cases, a stub's internal
26903 architecture may not allow the protocol layer to know some information
26904 about the underlying target in advance. This is especially common in
26905 stubs which may be configured for multiple targets.
26907 These are the currently defined stub features and their properties:
26909 @multitable @columnfractions 0.35 0.2 0.12 0.2
26910 @c NOTE: The first row should be @headitem, but we do not yet require
26911 @c a new enough version of Texinfo (4.7) to use @headitem.
26913 @tab Value Required
26917 @item @samp{PacketSize}
26922 @item @samp{qXfer:auxv:read}
26927 @item @samp{qXfer:features:read}
26932 @item @samp{qXfer:libraries:read}
26937 @item @samp{qXfer:memory-map:read}
26942 @item @samp{qXfer:spu:read}
26947 @item @samp{qXfer:spu:write}
26952 @item @samp{qXfer:siginfo:read}
26957 @item @samp{qXfer:siginfo:write}
26962 @item @samp{QNonStop}
26967 @item @samp{QPassSignals}
26972 @item @samp{QStartNoAckMode}
26977 @item @samp{multiprocess}
26984 These are the currently defined stub features, in more detail:
26987 @cindex packet size, remote protocol
26988 @item PacketSize=@var{bytes}
26989 The remote stub can accept packets up to at least @var{bytes} in
26990 length. @value{GDBN} will send packets up to this size for bulk
26991 transfers, and will never send larger packets. This is a limit on the
26992 data characters in the packet, including the frame and checksum.
26993 There is no trailing NUL byte in a remote protocol packet; if the stub
26994 stores packets in a NUL-terminated format, it should allow an extra
26995 byte in its buffer for the NUL. If this stub feature is not supported,
26996 @value{GDBN} guesses based on the size of the @samp{g} packet response.
26998 @item qXfer:auxv:read
26999 The remote stub understands the @samp{qXfer:auxv:read} packet
27000 (@pxref{qXfer auxiliary vector read}).
27002 @item qXfer:features:read
27003 The remote stub understands the @samp{qXfer:features:read} packet
27004 (@pxref{qXfer target description read}).
27006 @item qXfer:libraries:read
27007 The remote stub understands the @samp{qXfer:libraries:read} packet
27008 (@pxref{qXfer library list read}).
27010 @item qXfer:memory-map:read
27011 The remote stub understands the @samp{qXfer:memory-map:read} packet
27012 (@pxref{qXfer memory map read}).
27014 @item qXfer:spu:read
27015 The remote stub understands the @samp{qXfer:spu:read} packet
27016 (@pxref{qXfer spu read}).
27018 @item qXfer:spu:write
27019 The remote stub understands the @samp{qXfer:spu:write} packet
27020 (@pxref{qXfer spu write}).
27022 @item qXfer:siginfo:read
27023 The remote stub understands the @samp{qXfer:siginfo:read} packet
27024 (@pxref{qXfer siginfo read}).
27026 @item qXfer:siginfo:write
27027 The remote stub understands the @samp{qXfer:siginfo:write} packet
27028 (@pxref{qXfer siginfo write}).
27031 The remote stub understands the @samp{QNonStop} packet
27032 (@pxref{QNonStop}).
27035 The remote stub understands the @samp{QPassSignals} packet
27036 (@pxref{QPassSignals}).
27038 @item QStartNoAckMode
27039 The remote stub understands the @samp{QStartNoAckMode} packet and
27040 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
27043 @anchor{multiprocess extensions}
27044 @cindex multiprocess extensions, in remote protocol
27045 The remote stub understands the multiprocess extensions to the remote
27046 protocol syntax. The multiprocess extensions affect the syntax of
27047 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
27048 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
27049 replies. Note that reporting this feature indicates support for the
27050 syntactic extensions only, not that the stub necessarily supports
27051 debugging of more than one process at a time. The stub must not use
27052 multiprocess extensions in packet replies unless @value{GDBN} has also
27053 indicated it supports them in its @samp{qSupported} request.
27055 @item qXfer:osdata:read
27056 The remote stub understands the @samp{qXfer:osdata:read} packet
27057 ((@pxref{qXfer osdata read}).
27062 @cindex symbol lookup, remote request
27063 @cindex @samp{qSymbol} packet
27064 Notify the target that @value{GDBN} is prepared to serve symbol lookup
27065 requests. Accept requests from the target for the values of symbols.
27070 The target does not need to look up any (more) symbols.
27071 @item qSymbol:@var{sym_name}
27072 The target requests the value of symbol @var{sym_name} (hex encoded).
27073 @value{GDBN} may provide the value by using the
27074 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
27078 @item qSymbol:@var{sym_value}:@var{sym_name}
27079 Set the value of @var{sym_name} to @var{sym_value}.
27081 @var{sym_name} (hex encoded) is the name of a symbol whose value the
27082 target has previously requested.
27084 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
27085 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
27091 The target does not need to look up any (more) symbols.
27092 @item qSymbol:@var{sym_name}
27093 The target requests the value of a new symbol @var{sym_name} (hex
27094 encoded). @value{GDBN} will continue to supply the values of symbols
27095 (if available), until the target ceases to request them.
27100 @xref{Tracepoint Packets}.
27102 @item qThreadExtraInfo,@var{thread-id}
27103 @cindex thread attributes info, remote request
27104 @cindex @samp{qThreadExtraInfo} packet
27105 Obtain a printable string description of a thread's attributes from
27106 the target OS. @var{thread-id} is a thread ID;
27107 see @ref{thread-id syntax}. This
27108 string may contain anything that the target OS thinks is interesting
27109 for @value{GDBN} to tell the user about the thread. The string is
27110 displayed in @value{GDBN}'s @code{info threads} display. Some
27111 examples of possible thread extra info strings are @samp{Runnable}, or
27112 @samp{Blocked on Mutex}.
27116 @item @var{XX}@dots{}
27117 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
27118 comprising the printable string containing the extra information about
27119 the thread's attributes.
27122 (Note that the @code{qThreadExtraInfo} packet's name is separated from
27123 the command by a @samp{,}, not a @samp{:}, contrary to the naming
27124 conventions above. Please don't use this packet as a model for new
27132 @xref{Tracepoint Packets}.
27134 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
27135 @cindex read special object, remote request
27136 @cindex @samp{qXfer} packet
27137 @anchor{qXfer read}
27138 Read uninterpreted bytes from the target's special data area
27139 identified by the keyword @var{object}. Request @var{length} bytes
27140 starting at @var{offset} bytes into the data. The content and
27141 encoding of @var{annex} is specific to @var{object}; it can supply
27142 additional details about what data to access.
27144 Here are the specific requests of this form defined so far. All
27145 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
27146 formats, listed below.
27149 @item qXfer:auxv:read::@var{offset},@var{length}
27150 @anchor{qXfer auxiliary vector read}
27151 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
27152 auxiliary vector}. Note @var{annex} must be empty.
27154 This packet is not probed by default; the remote stub must request it,
27155 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27157 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
27158 @anchor{qXfer target description read}
27159 Access the @dfn{target description}. @xref{Target Descriptions}. The
27160 annex specifies which XML document to access. The main description is
27161 always loaded from the @samp{target.xml} annex.
27163 This packet is not probed by default; the remote stub must request it,
27164 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27166 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
27167 @anchor{qXfer library list read}
27168 Access the target's list of loaded libraries. @xref{Library List Format}.
27169 The annex part of the generic @samp{qXfer} packet must be empty
27170 (@pxref{qXfer read}).
27172 Targets which maintain a list of libraries in the program's memory do
27173 not need to implement this packet; it is designed for platforms where
27174 the operating system manages the list of loaded libraries.
27176 This packet is not probed by default; the remote stub must request it,
27177 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27179 @item qXfer:memory-map:read::@var{offset},@var{length}
27180 @anchor{qXfer memory map read}
27181 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
27182 annex part of the generic @samp{qXfer} packet must be empty
27183 (@pxref{qXfer read}).
27185 This packet is not probed by default; the remote stub must request it,
27186 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27188 @item qXfer:siginfo:read::@var{offset},@var{length}
27189 @anchor{qXfer siginfo read}
27190 Read contents of the extra signal information on the target
27191 system. The annex part of the generic @samp{qXfer} packet must be
27192 empty (@pxref{qXfer read}).
27194 This packet is not probed by default; the remote stub must request it,
27195 by supplying an appropriate @samp{qSupported} response
27196 (@pxref{qSupported}).
27198 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
27199 @anchor{qXfer spu read}
27200 Read contents of an @code{spufs} file on the target system. The
27201 annex specifies which file to read; it must be of the form
27202 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27203 in the target process, and @var{name} identifes the @code{spufs} file
27204 in that context to be accessed.
27206 This packet is not probed by default; the remote stub must request it,
27207 by supplying an appropriate @samp{qSupported} response
27208 (@pxref{qSupported}).
27210 @item qXfer:osdata:read::@var{offset},@var{length}
27211 @anchor{qXfer osdata read}
27212 Access the target's @dfn{operating system information}.
27213 @xref{Operating System Information}.
27220 Data @var{data} (@pxref{Binary Data}) has been read from the
27221 target. There may be more data at a higher address (although
27222 it is permitted to return @samp{m} even for the last valid
27223 block of data, as long as at least one byte of data was read).
27224 @var{data} may have fewer bytes than the @var{length} in the
27228 Data @var{data} (@pxref{Binary Data}) has been read from the target.
27229 There is no more data to be read. @var{data} may have fewer bytes
27230 than the @var{length} in the request.
27233 The @var{offset} in the request is at the end of the data.
27234 There is no more data to be read.
27237 The request was malformed, or @var{annex} was invalid.
27240 The offset was invalid, or there was an error encountered reading the data.
27241 @var{nn} is a hex-encoded @code{errno} value.
27244 An empty reply indicates the @var{object} string was not recognized by
27245 the stub, or that the object does not support reading.
27248 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
27249 @cindex write data into object, remote request
27250 @anchor{qXfer write}
27251 Write uninterpreted bytes into the target's special data area
27252 identified by the keyword @var{object}, starting at @var{offset} bytes
27253 into the data. @var{data}@dots{} is the binary-encoded data
27254 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
27255 is specific to @var{object}; it can supply additional details about what data
27258 Here are the specific requests of this form defined so far. All
27259 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
27260 formats, listed below.
27263 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
27264 @anchor{qXfer siginfo write}
27265 Write @var{data} to the extra signal information on the target system.
27266 The annex part of the generic @samp{qXfer} packet must be
27267 empty (@pxref{qXfer write}).
27269 This packet is not probed by default; the remote stub must request it,
27270 by supplying an appropriate @samp{qSupported} response
27271 (@pxref{qSupported}).
27273 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
27274 @anchor{qXfer spu write}
27275 Write @var{data} to an @code{spufs} file on the target system. The
27276 annex specifies which file to write; it must be of the form
27277 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27278 in the target process, and @var{name} identifes the @code{spufs} file
27279 in that context to be accessed.
27281 This packet is not probed by default; the remote stub must request it,
27282 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27288 @var{nn} (hex encoded) is the number of bytes written.
27289 This may be fewer bytes than supplied in the request.
27292 The request was malformed, or @var{annex} was invalid.
27295 The offset was invalid, or there was an error encountered writing the data.
27296 @var{nn} is a hex-encoded @code{errno} value.
27299 An empty reply indicates the @var{object} string was not
27300 recognized by the stub, or that the object does not support writing.
27303 @item qXfer:@var{object}:@var{operation}:@dots{}
27304 Requests of this form may be added in the future. When a stub does
27305 not recognize the @var{object} keyword, or its support for
27306 @var{object} does not recognize the @var{operation} keyword, the stub
27307 must respond with an empty packet.
27311 @node Register Packet Format
27312 @section Register Packet Format
27314 The following @code{g}/@code{G} packets have previously been defined.
27315 In the below, some thirty-two bit registers are transferred as
27316 sixty-four bits. Those registers should be zero/sign extended (which?)
27317 to fill the space allocated. Register bytes are transferred in target
27318 byte order. The two nibbles within a register byte are transferred
27319 most-significant - least-significant.
27325 All registers are transferred as thirty-two bit quantities in the order:
27326 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
27327 registers; fsr; fir; fp.
27331 All registers are transferred as sixty-four bit quantities (including
27332 thirty-two bit registers such as @code{sr}). The ordering is the same
27337 @node Tracepoint Packets
27338 @section Tracepoint Packets
27339 @cindex tracepoint packets
27340 @cindex packets, tracepoint
27342 Here we describe the packets @value{GDBN} uses to implement
27343 tracepoints (@pxref{Tracepoints}).
27347 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
27348 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
27349 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
27350 the tracepoint is disabled. @var{step} is the tracepoint's step
27351 count, and @var{pass} is its pass count. If the trailing @samp{-} is
27352 present, further @samp{QTDP} packets will follow to specify this
27353 tracepoint's actions.
27358 The packet was understood and carried out.
27360 The packet was not recognized.
27363 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
27364 Define actions to be taken when a tracepoint is hit. @var{n} and
27365 @var{addr} must be the same as in the initial @samp{QTDP} packet for
27366 this tracepoint. This packet may only be sent immediately after
27367 another @samp{QTDP} packet that ended with a @samp{-}. If the
27368 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
27369 specifying more actions for this tracepoint.
27371 In the series of action packets for a given tracepoint, at most one
27372 can have an @samp{S} before its first @var{action}. If such a packet
27373 is sent, it and the following packets define ``while-stepping''
27374 actions. Any prior packets define ordinary actions --- that is, those
27375 taken when the tracepoint is first hit. If no action packet has an
27376 @samp{S}, then all the packets in the series specify ordinary
27377 tracepoint actions.
27379 The @samp{@var{action}@dots{}} portion of the packet is a series of
27380 actions, concatenated without separators. Each action has one of the
27386 Collect the registers whose bits are set in @var{mask}. @var{mask} is
27387 a hexadecimal number whose @var{i}'th bit is set if register number
27388 @var{i} should be collected. (The least significant bit is numbered
27389 zero.) Note that @var{mask} may be any number of digits long; it may
27390 not fit in a 32-bit word.
27392 @item M @var{basereg},@var{offset},@var{len}
27393 Collect @var{len} bytes of memory starting at the address in register
27394 number @var{basereg}, plus @var{offset}. If @var{basereg} is
27395 @samp{-1}, then the range has a fixed address: @var{offset} is the
27396 address of the lowest byte to collect. The @var{basereg},
27397 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
27398 values (the @samp{-1} value for @var{basereg} is a special case).
27400 @item X @var{len},@var{expr}
27401 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
27402 it directs. @var{expr} is an agent expression, as described in
27403 @ref{Agent Expressions}. Each byte of the expression is encoded as a
27404 two-digit hex number in the packet; @var{len} is the number of bytes
27405 in the expression (and thus one-half the number of hex digits in the
27410 Any number of actions may be packed together in a single @samp{QTDP}
27411 packet, as long as the packet does not exceed the maximum packet
27412 length (400 bytes, for many stubs). There may be only one @samp{R}
27413 action per tracepoint, and it must precede any @samp{M} or @samp{X}
27414 actions. Any registers referred to by @samp{M} and @samp{X} actions
27415 must be collected by a preceding @samp{R} action. (The
27416 ``while-stepping'' actions are treated as if they were attached to a
27417 separate tracepoint, as far as these restrictions are concerned.)
27422 The packet was understood and carried out.
27424 The packet was not recognized.
27427 @item QTFrame:@var{n}
27428 Select the @var{n}'th tracepoint frame from the buffer, and use the
27429 register and memory contents recorded there to answer subsequent
27430 request packets from @value{GDBN}.
27432 A successful reply from the stub indicates that the stub has found the
27433 requested frame. The response is a series of parts, concatenated
27434 without separators, describing the frame we selected. Each part has
27435 one of the following forms:
27439 The selected frame is number @var{n} in the trace frame buffer;
27440 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
27441 was no frame matching the criteria in the request packet.
27444 The selected trace frame records a hit of tracepoint number @var{t};
27445 @var{t} is a hexadecimal number.
27449 @item QTFrame:pc:@var{addr}
27450 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27451 currently selected frame whose PC is @var{addr};
27452 @var{addr} is a hexadecimal number.
27454 @item QTFrame:tdp:@var{t}
27455 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27456 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
27457 is a hexadecimal number.
27459 @item QTFrame:range:@var{start}:@var{end}
27460 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27461 currently selected frame whose PC is between @var{start} (inclusive)
27462 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
27465 @item QTFrame:outside:@var{start}:@var{end}
27466 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
27467 frame @emph{outside} the given range of addresses.
27470 Begin the tracepoint experiment. Begin collecting data from tracepoint
27471 hits in the trace frame buffer.
27474 End the tracepoint experiment. Stop collecting trace frames.
27477 Clear the table of tracepoints, and empty the trace frame buffer.
27479 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
27480 Establish the given ranges of memory as ``transparent''. The stub
27481 will answer requests for these ranges from memory's current contents,
27482 if they were not collected as part of the tracepoint hit.
27484 @value{GDBN} uses this to mark read-only regions of memory, like those
27485 containing program code. Since these areas never change, they should
27486 still have the same contents they did when the tracepoint was hit, so
27487 there's no reason for the stub to refuse to provide their contents.
27490 Ask the stub if there is a trace experiment running right now.
27495 There is no trace experiment running.
27497 There is a trace experiment running.
27503 @node Host I/O Packets
27504 @section Host I/O Packets
27505 @cindex Host I/O, remote protocol
27506 @cindex file transfer, remote protocol
27508 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
27509 operations on the far side of a remote link. For example, Host I/O is
27510 used to upload and download files to a remote target with its own
27511 filesystem. Host I/O uses the same constant values and data structure
27512 layout as the target-initiated File-I/O protocol. However, the
27513 Host I/O packets are structured differently. The target-initiated
27514 protocol relies on target memory to store parameters and buffers.
27515 Host I/O requests are initiated by @value{GDBN}, and the
27516 target's memory is not involved. @xref{File-I/O Remote Protocol
27517 Extension}, for more details on the target-initiated protocol.
27519 The Host I/O request packets all encode a single operation along with
27520 its arguments. They have this format:
27524 @item vFile:@var{operation}: @var{parameter}@dots{}
27525 @var{operation} is the name of the particular request; the target
27526 should compare the entire packet name up to the second colon when checking
27527 for a supported operation. The format of @var{parameter} depends on
27528 the operation. Numbers are always passed in hexadecimal. Negative
27529 numbers have an explicit minus sign (i.e.@: two's complement is not
27530 used). Strings (e.g.@: filenames) are encoded as a series of
27531 hexadecimal bytes. The last argument to a system call may be a
27532 buffer of escaped binary data (@pxref{Binary Data}).
27536 The valid responses to Host I/O packets are:
27540 @item F @var{result} [, @var{errno}] [; @var{attachment}]
27541 @var{result} is the integer value returned by this operation, usually
27542 non-negative for success and -1 for errors. If an error has occured,
27543 @var{errno} will be included in the result. @var{errno} will have a
27544 value defined by the File-I/O protocol (@pxref{Errno Values}). For
27545 operations which return data, @var{attachment} supplies the data as a
27546 binary buffer. Binary buffers in response packets are escaped in the
27547 normal way (@pxref{Binary Data}). See the individual packet
27548 documentation for the interpretation of @var{result} and
27552 An empty response indicates that this operation is not recognized.
27556 These are the supported Host I/O operations:
27559 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
27560 Open a file at @var{pathname} and return a file descriptor for it, or
27561 return -1 if an error occurs. @var{pathname} is a string,
27562 @var{flags} is an integer indicating a mask of open flags
27563 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
27564 of mode bits to use if the file is created (@pxref{mode_t Values}).
27565 @xref{open}, for details of the open flags and mode values.
27567 @item vFile:close: @var{fd}
27568 Close the open file corresponding to @var{fd} and return 0, or
27569 -1 if an error occurs.
27571 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
27572 Read data from the open file corresponding to @var{fd}. Up to
27573 @var{count} bytes will be read from the file, starting at @var{offset}
27574 relative to the start of the file. The target may read fewer bytes;
27575 common reasons include packet size limits and an end-of-file
27576 condition. The number of bytes read is returned. Zero should only be
27577 returned for a successful read at the end of the file, or if
27578 @var{count} was zero.
27580 The data read should be returned as a binary attachment on success.
27581 If zero bytes were read, the response should include an empty binary
27582 attachment (i.e.@: a trailing semicolon). The return value is the
27583 number of target bytes read; the binary attachment may be longer if
27584 some characters were escaped.
27586 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
27587 Write @var{data} (a binary buffer) to the open file corresponding
27588 to @var{fd}. Start the write at @var{offset} from the start of the
27589 file. Unlike many @code{write} system calls, there is no
27590 separate @var{count} argument; the length of @var{data} in the
27591 packet is used. @samp{vFile:write} returns the number of bytes written,
27592 which may be shorter than the length of @var{data}, or -1 if an
27595 @item vFile:unlink: @var{pathname}
27596 Delete the file at @var{pathname} on the target. Return 0,
27597 or -1 if an error occurs. @var{pathname} is a string.
27602 @section Interrupts
27603 @cindex interrupts (remote protocol)
27605 When a program on the remote target is running, @value{GDBN} may
27606 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
27607 control of which is specified via @value{GDBN}'s @samp{remotebreak}
27608 setting (@pxref{set remotebreak}).
27610 The precise meaning of @code{BREAK} is defined by the transport
27611 mechanism and may, in fact, be undefined. @value{GDBN} does not
27612 currently define a @code{BREAK} mechanism for any of the network
27613 interfaces except for TCP, in which case @value{GDBN} sends the
27614 @code{telnet} BREAK sequence.
27616 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
27617 transport mechanisms. It is represented by sending the single byte
27618 @code{0x03} without any of the usual packet overhead described in
27619 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
27620 transmitted as part of a packet, it is considered to be packet data
27621 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
27622 (@pxref{X packet}), used for binary downloads, may include an unescaped
27623 @code{0x03} as part of its packet.
27625 Stubs are not required to recognize these interrupt mechanisms and the
27626 precise meaning associated with receipt of the interrupt is
27627 implementation defined. If the target supports debugging of multiple
27628 threads and/or processes, it should attempt to interrupt all
27629 currently-executing threads and processes.
27630 If the stub is successful at interrupting the
27631 running program, it should send one of the stop
27632 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
27633 of successfully stopping the program in all-stop mode, and a stop reply
27634 for each stopped thread in non-stop mode.
27635 Interrupts received while the
27636 program is stopped are discarded.
27638 @node Notification Packets
27639 @section Notification Packets
27640 @cindex notification packets
27641 @cindex packets, notification
27643 The @value{GDBN} remote serial protocol includes @dfn{notifications},
27644 packets that require no acknowledgment. Both the GDB and the stub
27645 may send notifications (although the only notifications defined at
27646 present are sent by the stub). Notifications carry information
27647 without incurring the round-trip latency of an acknowledgment, and so
27648 are useful for low-impact communications where occasional packet loss
27651 A notification packet has the form @samp{% @var{data} #
27652 @var{checksum}}, where @var{data} is the content of the notification,
27653 and @var{checksum} is a checksum of @var{data}, computed and formatted
27654 as for ordinary @value{GDBN} packets. A notification's @var{data}
27655 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
27656 receiving a notification, the recipient sends no @samp{+} or @samp{-}
27657 to acknowledge the notification's receipt or to report its corruption.
27659 Every notification's @var{data} begins with a name, which contains no
27660 colon characters, followed by a colon character.
27662 Recipients should silently ignore corrupted notifications and
27663 notifications they do not understand. Recipients should restart
27664 timeout periods on receipt of a well-formed notification, whether or
27665 not they understand it.
27667 Senders should only send the notifications described here when this
27668 protocol description specifies that they are permitted. In the
27669 future, we may extend the protocol to permit existing notifications in
27670 new contexts; this rule helps older senders avoid confusing newer
27673 (Older versions of @value{GDBN} ignore bytes received until they see
27674 the @samp{$} byte that begins an ordinary packet, so new stubs may
27675 transmit notifications without fear of confusing older clients. There
27676 are no notifications defined for @value{GDBN} to send at the moment, but we
27677 assume that most older stubs would ignore them, as well.)
27679 The following notification packets from the stub to @value{GDBN} are
27683 @item Stop: @var{reply}
27684 Report an asynchronous stop event in non-stop mode.
27685 The @var{reply} has the form of a stop reply, as
27686 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
27687 for information on how these notifications are acknowledged by
27691 @node Remote Non-Stop
27692 @section Remote Protocol Support for Non-Stop Mode
27694 @value{GDBN}'s remote protocol supports non-stop debugging of
27695 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
27696 supports non-stop mode, it should report that to @value{GDBN} by including
27697 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
27699 @value{GDBN} typically sends a @samp{QNonStop} packet only when
27700 establishing a new connection with the stub. Entering non-stop mode
27701 does not alter the state of any currently-running threads, but targets
27702 must stop all threads in any already-attached processes when entering
27703 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
27704 probe the target state after a mode change.
27706 In non-stop mode, when an attached process encounters an event that
27707 would otherwise be reported with a stop reply, it uses the
27708 asynchronous notification mechanism (@pxref{Notification Packets}) to
27709 inform @value{GDBN}. In contrast to all-stop mode, where all threads
27710 in all processes are stopped when a stop reply is sent, in non-stop
27711 mode only the thread reporting the stop event is stopped. That is,
27712 when reporting a @samp{S} or @samp{T} response to indicate completion
27713 of a step operation, hitting a breakpoint, or a fault, only the
27714 affected thread is stopped; any other still-running threads continue
27715 to run. When reporting a @samp{W} or @samp{X} response, all running
27716 threads belonging to other attached processes continue to run.
27718 Only one stop reply notification at a time may be pending; if
27719 additional stop events occur before @value{GDBN} has acknowledged the
27720 previous notification, they must be queued by the stub for later
27721 synchronous transmission in response to @samp{vStopped} packets from
27722 @value{GDBN}. Because the notification mechanism is unreliable,
27723 the stub is permitted to resend a stop reply notification
27724 if it believes @value{GDBN} may not have received it. @value{GDBN}
27725 ignores additional stop reply notifications received before it has
27726 finished processing a previous notification and the stub has completed
27727 sending any queued stop events.
27729 Otherwise, @value{GDBN} must be prepared to receive a stop reply
27730 notification at any time. Specifically, they may appear when
27731 @value{GDBN} is not otherwise reading input from the stub, or when
27732 @value{GDBN} is expecting to read a normal synchronous response or a
27733 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
27734 Notification packets are distinct from any other communication from
27735 the stub so there is no ambiguity.
27737 After receiving a stop reply notification, @value{GDBN} shall
27738 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
27739 as a regular, synchronous request to the stub. Such acknowledgment
27740 is not required to happen immediately, as @value{GDBN} is permitted to
27741 send other, unrelated packets to the stub first, which the stub should
27744 Upon receiving a @samp{vStopped} packet, if the stub has other queued
27745 stop events to report to @value{GDBN}, it shall respond by sending a
27746 normal stop reply response. @value{GDBN} shall then send another
27747 @samp{vStopped} packet to solicit further responses; again, it is
27748 permitted to send other, unrelated packets as well which the stub
27749 should process normally.
27751 If the stub receives a @samp{vStopped} packet and there are no
27752 additional stop events to report, the stub shall return an @samp{OK}
27753 response. At this point, if further stop events occur, the stub shall
27754 send a new stop reply notification, @value{GDBN} shall accept the
27755 notification, and the process shall be repeated.
27757 In non-stop mode, the target shall respond to the @samp{?} packet as
27758 follows. First, any incomplete stop reply notification/@samp{vStopped}
27759 sequence in progress is abandoned. The target must begin a new
27760 sequence reporting stop events for all stopped threads, whether or not
27761 it has previously reported those events to @value{GDBN}. The first
27762 stop reply is sent as a synchronous reply to the @samp{?} packet, and
27763 subsequent stop replies are sent as responses to @samp{vStopped} packets
27764 using the mechanism described above. The target must not send
27765 asynchronous stop reply notifications until the sequence is complete.
27766 If all threads are running when the target receives the @samp{?} packet,
27767 or if the target is not attached to any process, it shall respond
27770 @node Packet Acknowledgment
27771 @section Packet Acknowledgment
27773 @cindex acknowledgment, for @value{GDBN} remote
27774 @cindex packet acknowledgment, for @value{GDBN} remote
27775 By default, when either the host or the target machine receives a packet,
27776 the first response expected is an acknowledgment: either @samp{+} (to indicate
27777 the package was received correctly) or @samp{-} (to request retransmission).
27778 This mechanism allows the @value{GDBN} remote protocol to operate over
27779 unreliable transport mechanisms, such as a serial line.
27781 In cases where the transport mechanism is itself reliable (such as a pipe or
27782 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
27783 It may be desirable to disable them in that case to reduce communication
27784 overhead, or for other reasons. This can be accomplished by means of the
27785 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
27787 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
27788 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
27789 and response format still includes the normal checksum, as described in
27790 @ref{Overview}, but the checksum may be ignored by the receiver.
27792 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
27793 no-acknowledgment mode, it should report that to @value{GDBN}
27794 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
27795 @pxref{qSupported}.
27796 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
27797 disabled via the @code{set remote noack-packet off} command
27798 (@pxref{Remote Configuration}),
27799 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
27800 Only then may the stub actually turn off packet acknowledgments.
27801 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
27802 response, which can be safely ignored by the stub.
27804 Note that @code{set remote noack-packet} command only affects negotiation
27805 between @value{GDBN} and the stub when subsequent connections are made;
27806 it does not affect the protocol acknowledgment state for any current
27808 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
27809 new connection is established,
27810 there is also no protocol request to re-enable the acknowledgments
27811 for the current connection, once disabled.
27816 Example sequence of a target being re-started. Notice how the restart
27817 does not get any direct output:
27822 @emph{target restarts}
27825 <- @code{T001:1234123412341234}
27829 Example sequence of a target being stepped by a single instruction:
27832 -> @code{G1445@dots{}}
27837 <- @code{T001:1234123412341234}
27841 <- @code{1455@dots{}}
27845 @node File-I/O Remote Protocol Extension
27846 @section File-I/O Remote Protocol Extension
27847 @cindex File-I/O remote protocol extension
27850 * File-I/O Overview::
27851 * Protocol Basics::
27852 * The F Request Packet::
27853 * The F Reply Packet::
27854 * The Ctrl-C Message::
27856 * List of Supported Calls::
27857 * Protocol-specific Representation of Datatypes::
27859 * File-I/O Examples::
27862 @node File-I/O Overview
27863 @subsection File-I/O Overview
27864 @cindex file-i/o overview
27866 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
27867 target to use the host's file system and console I/O to perform various
27868 system calls. System calls on the target system are translated into a
27869 remote protocol packet to the host system, which then performs the needed
27870 actions and returns a response packet to the target system.
27871 This simulates file system operations even on targets that lack file systems.
27873 The protocol is defined to be independent of both the host and target systems.
27874 It uses its own internal representation of datatypes and values. Both
27875 @value{GDBN} and the target's @value{GDBN} stub are responsible for
27876 translating the system-dependent value representations into the internal
27877 protocol representations when data is transmitted.
27879 The communication is synchronous. A system call is possible only when
27880 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
27881 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
27882 the target is stopped to allow deterministic access to the target's
27883 memory. Therefore File-I/O is not interruptible by target signals. On
27884 the other hand, it is possible to interrupt File-I/O by a user interrupt
27885 (@samp{Ctrl-C}) within @value{GDBN}.
27887 The target's request to perform a host system call does not finish
27888 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
27889 after finishing the system call, the target returns to continuing the
27890 previous activity (continue, step). No additional continue or step
27891 request from @value{GDBN} is required.
27894 (@value{GDBP}) continue
27895 <- target requests 'system call X'
27896 target is stopped, @value{GDBN} executes system call
27897 -> @value{GDBN} returns result
27898 ... target continues, @value{GDBN} returns to wait for the target
27899 <- target hits breakpoint and sends a Txx packet
27902 The protocol only supports I/O on the console and to regular files on
27903 the host file system. Character or block special devices, pipes,
27904 named pipes, sockets or any other communication method on the host
27905 system are not supported by this protocol.
27907 File I/O is not supported in non-stop mode.
27909 @node Protocol Basics
27910 @subsection Protocol Basics
27911 @cindex protocol basics, file-i/o
27913 The File-I/O protocol uses the @code{F} packet as the request as well
27914 as reply packet. Since a File-I/O system call can only occur when
27915 @value{GDBN} is waiting for a response from the continuing or stepping target,
27916 the File-I/O request is a reply that @value{GDBN} has to expect as a result
27917 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
27918 This @code{F} packet contains all information needed to allow @value{GDBN}
27919 to call the appropriate host system call:
27923 A unique identifier for the requested system call.
27926 All parameters to the system call. Pointers are given as addresses
27927 in the target memory address space. Pointers to strings are given as
27928 pointer/length pair. Numerical values are given as they are.
27929 Numerical control flags are given in a protocol-specific representation.
27933 At this point, @value{GDBN} has to perform the following actions.
27937 If the parameters include pointer values to data needed as input to a
27938 system call, @value{GDBN} requests this data from the target with a
27939 standard @code{m} packet request. This additional communication has to be
27940 expected by the target implementation and is handled as any other @code{m}
27944 @value{GDBN} translates all value from protocol representation to host
27945 representation as needed. Datatypes are coerced into the host types.
27948 @value{GDBN} calls the system call.
27951 It then coerces datatypes back to protocol representation.
27954 If the system call is expected to return data in buffer space specified
27955 by pointer parameters to the call, the data is transmitted to the
27956 target using a @code{M} or @code{X} packet. This packet has to be expected
27957 by the target implementation and is handled as any other @code{M} or @code{X}
27962 Eventually @value{GDBN} replies with another @code{F} packet which contains all
27963 necessary information for the target to continue. This at least contains
27970 @code{errno}, if has been changed by the system call.
27977 After having done the needed type and value coercion, the target continues
27978 the latest continue or step action.
27980 @node The F Request Packet
27981 @subsection The @code{F} Request Packet
27982 @cindex file-i/o request packet
27983 @cindex @code{F} request packet
27985 The @code{F} request packet has the following format:
27988 @item F@var{call-id},@var{parameter@dots{}}
27990 @var{call-id} is the identifier to indicate the host system call to be called.
27991 This is just the name of the function.
27993 @var{parameter@dots{}} are the parameters to the system call.
27994 Parameters are hexadecimal integer values, either the actual values in case
27995 of scalar datatypes, pointers to target buffer space in case of compound
27996 datatypes and unspecified memory areas, or pointer/length pairs in case
27997 of string parameters. These are appended to the @var{call-id} as a
27998 comma-delimited list. All values are transmitted in ASCII
27999 string representation, pointer/length pairs separated by a slash.
28005 @node The F Reply Packet
28006 @subsection The @code{F} Reply Packet
28007 @cindex file-i/o reply packet
28008 @cindex @code{F} reply packet
28010 The @code{F} reply packet has the following format:
28014 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
28016 @var{retcode} is the return code of the system call as hexadecimal value.
28018 @var{errno} is the @code{errno} set by the call, in protocol-specific
28020 This parameter can be omitted if the call was successful.
28022 @var{Ctrl-C flag} is only sent if the user requested a break. In this
28023 case, @var{errno} must be sent as well, even if the call was successful.
28024 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
28031 or, if the call was interrupted before the host call has been performed:
28038 assuming 4 is the protocol-specific representation of @code{EINTR}.
28043 @node The Ctrl-C Message
28044 @subsection The @samp{Ctrl-C} Message
28045 @cindex ctrl-c message, in file-i/o protocol
28047 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
28048 reply packet (@pxref{The F Reply Packet}),
28049 the target should behave as if it had
28050 gotten a break message. The meaning for the target is ``system call
28051 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
28052 (as with a break message) and return to @value{GDBN} with a @code{T02}
28055 It's important for the target to know in which
28056 state the system call was interrupted. There are two possible cases:
28060 The system call hasn't been performed on the host yet.
28063 The system call on the host has been finished.
28067 These two states can be distinguished by the target by the value of the
28068 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
28069 call hasn't been performed. This is equivalent to the @code{EINTR} handling
28070 on POSIX systems. In any other case, the target may presume that the
28071 system call has been finished --- successfully or not --- and should behave
28072 as if the break message arrived right after the system call.
28074 @value{GDBN} must behave reliably. If the system call has not been called
28075 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
28076 @code{errno} in the packet. If the system call on the host has been finished
28077 before the user requests a break, the full action must be finished by
28078 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
28079 The @code{F} packet may only be sent when either nothing has happened
28080 or the full action has been completed.
28083 @subsection Console I/O
28084 @cindex console i/o as part of file-i/o
28086 By default and if not explicitly closed by the target system, the file
28087 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
28088 on the @value{GDBN} console is handled as any other file output operation
28089 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
28090 by @value{GDBN} so that after the target read request from file descriptor
28091 0 all following typing is buffered until either one of the following
28096 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
28098 system call is treated as finished.
28101 The user presses @key{RET}. This is treated as end of input with a trailing
28105 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
28106 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
28110 If the user has typed more characters than fit in the buffer given to
28111 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
28112 either another @code{read(0, @dots{})} is requested by the target, or debugging
28113 is stopped at the user's request.
28116 @node List of Supported Calls
28117 @subsection List of Supported Calls
28118 @cindex list of supported file-i/o calls
28135 @unnumberedsubsubsec open
28136 @cindex open, file-i/o system call
28141 int open(const char *pathname, int flags);
28142 int open(const char *pathname, int flags, mode_t mode);
28146 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
28149 @var{flags} is the bitwise @code{OR} of the following values:
28153 If the file does not exist it will be created. The host
28154 rules apply as far as file ownership and time stamps
28158 When used with @code{O_CREAT}, if the file already exists it is
28159 an error and open() fails.
28162 If the file already exists and the open mode allows
28163 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
28164 truncated to zero length.
28167 The file is opened in append mode.
28170 The file is opened for reading only.
28173 The file is opened for writing only.
28176 The file is opened for reading and writing.
28180 Other bits are silently ignored.
28184 @var{mode} is the bitwise @code{OR} of the following values:
28188 User has read permission.
28191 User has write permission.
28194 Group has read permission.
28197 Group has write permission.
28200 Others have read permission.
28203 Others have write permission.
28207 Other bits are silently ignored.
28210 @item Return value:
28211 @code{open} returns the new file descriptor or -1 if an error
28218 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
28221 @var{pathname} refers to a directory.
28224 The requested access is not allowed.
28227 @var{pathname} was too long.
28230 A directory component in @var{pathname} does not exist.
28233 @var{pathname} refers to a device, pipe, named pipe or socket.
28236 @var{pathname} refers to a file on a read-only filesystem and
28237 write access was requested.
28240 @var{pathname} is an invalid pointer value.
28243 No space on device to create the file.
28246 The process already has the maximum number of files open.
28249 The limit on the total number of files open on the system
28253 The call was interrupted by the user.
28259 @unnumberedsubsubsec close
28260 @cindex close, file-i/o system call
28269 @samp{Fclose,@var{fd}}
28271 @item Return value:
28272 @code{close} returns zero on success, or -1 if an error occurred.
28278 @var{fd} isn't a valid open file descriptor.
28281 The call was interrupted by the user.
28287 @unnumberedsubsubsec read
28288 @cindex read, file-i/o system call
28293 int read(int fd, void *buf, unsigned int count);
28297 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
28299 @item Return value:
28300 On success, the number of bytes read is returned.
28301 Zero indicates end of file. If count is zero, read
28302 returns zero as well. On error, -1 is returned.
28308 @var{fd} is not a valid file descriptor or is not open for
28312 @var{bufptr} is an invalid pointer value.
28315 The call was interrupted by the user.
28321 @unnumberedsubsubsec write
28322 @cindex write, file-i/o system call
28327 int write(int fd, const void *buf, unsigned int count);
28331 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
28333 @item Return value:
28334 On success, the number of bytes written are returned.
28335 Zero indicates nothing was written. On error, -1
28342 @var{fd} is not a valid file descriptor or is not open for
28346 @var{bufptr} is an invalid pointer value.
28349 An attempt was made to write a file that exceeds the
28350 host-specific maximum file size allowed.
28353 No space on device to write the data.
28356 The call was interrupted by the user.
28362 @unnumberedsubsubsec lseek
28363 @cindex lseek, file-i/o system call
28368 long lseek (int fd, long offset, int flag);
28372 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
28374 @var{flag} is one of:
28378 The offset is set to @var{offset} bytes.
28381 The offset is set to its current location plus @var{offset}
28385 The offset is set to the size of the file plus @var{offset}
28389 @item Return value:
28390 On success, the resulting unsigned offset in bytes from
28391 the beginning of the file is returned. Otherwise, a
28392 value of -1 is returned.
28398 @var{fd} is not a valid open file descriptor.
28401 @var{fd} is associated with the @value{GDBN} console.
28404 @var{flag} is not a proper value.
28407 The call was interrupted by the user.
28413 @unnumberedsubsubsec rename
28414 @cindex rename, file-i/o system call
28419 int rename(const char *oldpath, const char *newpath);
28423 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
28425 @item Return value:
28426 On success, zero is returned. On error, -1 is returned.
28432 @var{newpath} is an existing directory, but @var{oldpath} is not a
28436 @var{newpath} is a non-empty directory.
28439 @var{oldpath} or @var{newpath} is a directory that is in use by some
28443 An attempt was made to make a directory a subdirectory
28447 A component used as a directory in @var{oldpath} or new
28448 path is not a directory. Or @var{oldpath} is a directory
28449 and @var{newpath} exists but is not a directory.
28452 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
28455 No access to the file or the path of the file.
28459 @var{oldpath} or @var{newpath} was too long.
28462 A directory component in @var{oldpath} or @var{newpath} does not exist.
28465 The file is on a read-only filesystem.
28468 The device containing the file has no room for the new
28472 The call was interrupted by the user.
28478 @unnumberedsubsubsec unlink
28479 @cindex unlink, file-i/o system call
28484 int unlink(const char *pathname);
28488 @samp{Funlink,@var{pathnameptr}/@var{len}}
28490 @item Return value:
28491 On success, zero is returned. On error, -1 is returned.
28497 No access to the file or the path of the file.
28500 The system does not allow unlinking of directories.
28503 The file @var{pathname} cannot be unlinked because it's
28504 being used by another process.
28507 @var{pathnameptr} is an invalid pointer value.
28510 @var{pathname} was too long.
28513 A directory component in @var{pathname} does not exist.
28516 A component of the path is not a directory.
28519 The file is on a read-only filesystem.
28522 The call was interrupted by the user.
28528 @unnumberedsubsubsec stat/fstat
28529 @cindex fstat, file-i/o system call
28530 @cindex stat, file-i/o system call
28535 int stat(const char *pathname, struct stat *buf);
28536 int fstat(int fd, struct stat *buf);
28540 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
28541 @samp{Ffstat,@var{fd},@var{bufptr}}
28543 @item Return value:
28544 On success, zero is returned. On error, -1 is returned.
28550 @var{fd} is not a valid open file.
28553 A directory component in @var{pathname} does not exist or the
28554 path is an empty string.
28557 A component of the path is not a directory.
28560 @var{pathnameptr} is an invalid pointer value.
28563 No access to the file or the path of the file.
28566 @var{pathname} was too long.
28569 The call was interrupted by the user.
28575 @unnumberedsubsubsec gettimeofday
28576 @cindex gettimeofday, file-i/o system call
28581 int gettimeofday(struct timeval *tv, void *tz);
28585 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
28587 @item Return value:
28588 On success, 0 is returned, -1 otherwise.
28594 @var{tz} is a non-NULL pointer.
28597 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
28603 @unnumberedsubsubsec isatty
28604 @cindex isatty, file-i/o system call
28609 int isatty(int fd);
28613 @samp{Fisatty,@var{fd}}
28615 @item Return value:
28616 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
28622 The call was interrupted by the user.
28627 Note that the @code{isatty} call is treated as a special case: it returns
28628 1 to the target if the file descriptor is attached
28629 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
28630 would require implementing @code{ioctl} and would be more complex than
28635 @unnumberedsubsubsec system
28636 @cindex system, file-i/o system call
28641 int system(const char *command);
28645 @samp{Fsystem,@var{commandptr}/@var{len}}
28647 @item Return value:
28648 If @var{len} is zero, the return value indicates whether a shell is
28649 available. A zero return value indicates a shell is not available.
28650 For non-zero @var{len}, the value returned is -1 on error and the
28651 return status of the command otherwise. Only the exit status of the
28652 command is returned, which is extracted from the host's @code{system}
28653 return value by calling @code{WEXITSTATUS(retval)}. In case
28654 @file{/bin/sh} could not be executed, 127 is returned.
28660 The call was interrupted by the user.
28665 @value{GDBN} takes over the full task of calling the necessary host calls
28666 to perform the @code{system} call. The return value of @code{system} on
28667 the host is simplified before it's returned
28668 to the target. Any termination signal information from the child process
28669 is discarded, and the return value consists
28670 entirely of the exit status of the called command.
28672 Due to security concerns, the @code{system} call is by default refused
28673 by @value{GDBN}. The user has to allow this call explicitly with the
28674 @code{set remote system-call-allowed 1} command.
28677 @item set remote system-call-allowed
28678 @kindex set remote system-call-allowed
28679 Control whether to allow the @code{system} calls in the File I/O
28680 protocol for the remote target. The default is zero (disabled).
28682 @item show remote system-call-allowed
28683 @kindex show remote system-call-allowed
28684 Show whether the @code{system} calls are allowed in the File I/O
28688 @node Protocol-specific Representation of Datatypes
28689 @subsection Protocol-specific Representation of Datatypes
28690 @cindex protocol-specific representation of datatypes, in file-i/o protocol
28693 * Integral Datatypes::
28695 * Memory Transfer::
28700 @node Integral Datatypes
28701 @unnumberedsubsubsec Integral Datatypes
28702 @cindex integral datatypes, in file-i/o protocol
28704 The integral datatypes used in the system calls are @code{int},
28705 @code{unsigned int}, @code{long}, @code{unsigned long},
28706 @code{mode_t}, and @code{time_t}.
28708 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
28709 implemented as 32 bit values in this protocol.
28711 @code{long} and @code{unsigned long} are implemented as 64 bit types.
28713 @xref{Limits}, for corresponding MIN and MAX values (similar to those
28714 in @file{limits.h}) to allow range checking on host and target.
28716 @code{time_t} datatypes are defined as seconds since the Epoch.
28718 All integral datatypes transferred as part of a memory read or write of a
28719 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
28722 @node Pointer Values
28723 @unnumberedsubsubsec Pointer Values
28724 @cindex pointer values, in file-i/o protocol
28726 Pointers to target data are transmitted as they are. An exception
28727 is made for pointers to buffers for which the length isn't
28728 transmitted as part of the function call, namely strings. Strings
28729 are transmitted as a pointer/length pair, both as hex values, e.g.@:
28736 which is a pointer to data of length 18 bytes at position 0x1aaf.
28737 The length is defined as the full string length in bytes, including
28738 the trailing null byte. For example, the string @code{"hello world"}
28739 at address 0x123456 is transmitted as
28745 @node Memory Transfer
28746 @unnumberedsubsubsec Memory Transfer
28747 @cindex memory transfer, in file-i/o protocol
28749 Structured data which is transferred using a memory read or write (for
28750 example, a @code{struct stat}) is expected to be in a protocol-specific format
28751 with all scalar multibyte datatypes being big endian. Translation to
28752 this representation needs to be done both by the target before the @code{F}
28753 packet is sent, and by @value{GDBN} before
28754 it transfers memory to the target. Transferred pointers to structured
28755 data should point to the already-coerced data at any time.
28759 @unnumberedsubsubsec struct stat
28760 @cindex struct stat, in file-i/o protocol
28762 The buffer of type @code{struct stat} used by the target and @value{GDBN}
28763 is defined as follows:
28767 unsigned int st_dev; /* device */
28768 unsigned int st_ino; /* inode */
28769 mode_t st_mode; /* protection */
28770 unsigned int st_nlink; /* number of hard links */
28771 unsigned int st_uid; /* user ID of owner */
28772 unsigned int st_gid; /* group ID of owner */
28773 unsigned int st_rdev; /* device type (if inode device) */
28774 unsigned long st_size; /* total size, in bytes */
28775 unsigned long st_blksize; /* blocksize for filesystem I/O */
28776 unsigned long st_blocks; /* number of blocks allocated */
28777 time_t st_atime; /* time of last access */
28778 time_t st_mtime; /* time of last modification */
28779 time_t st_ctime; /* time of last change */
28783 The integral datatypes conform to the definitions given in the
28784 appropriate section (see @ref{Integral Datatypes}, for details) so this
28785 structure is of size 64 bytes.
28787 The values of several fields have a restricted meaning and/or
28793 A value of 0 represents a file, 1 the console.
28796 No valid meaning for the target. Transmitted unchanged.
28799 Valid mode bits are described in @ref{Constants}. Any other
28800 bits have currently no meaning for the target.
28805 No valid meaning for the target. Transmitted unchanged.
28810 These values have a host and file system dependent
28811 accuracy. Especially on Windows hosts, the file system may not
28812 support exact timing values.
28815 The target gets a @code{struct stat} of the above representation and is
28816 responsible for coercing it to the target representation before
28819 Note that due to size differences between the host, target, and protocol
28820 representations of @code{struct stat} members, these members could eventually
28821 get truncated on the target.
28823 @node struct timeval
28824 @unnumberedsubsubsec struct timeval
28825 @cindex struct timeval, in file-i/o protocol
28827 The buffer of type @code{struct timeval} used by the File-I/O protocol
28828 is defined as follows:
28832 time_t tv_sec; /* second */
28833 long tv_usec; /* microsecond */
28837 The integral datatypes conform to the definitions given in the
28838 appropriate section (see @ref{Integral Datatypes}, for details) so this
28839 structure is of size 8 bytes.
28842 @subsection Constants
28843 @cindex constants, in file-i/o protocol
28845 The following values are used for the constants inside of the
28846 protocol. @value{GDBN} and target are responsible for translating these
28847 values before and after the call as needed.
28858 @unnumberedsubsubsec Open Flags
28859 @cindex open flags, in file-i/o protocol
28861 All values are given in hexadecimal representation.
28873 @node mode_t Values
28874 @unnumberedsubsubsec mode_t Values
28875 @cindex mode_t values, in file-i/o protocol
28877 All values are given in octal representation.
28894 @unnumberedsubsubsec Errno Values
28895 @cindex errno values, in file-i/o protocol
28897 All values are given in decimal representation.
28922 @code{EUNKNOWN} is used as a fallback error value if a host system returns
28923 any error value not in the list of supported error numbers.
28926 @unnumberedsubsubsec Lseek Flags
28927 @cindex lseek flags, in file-i/o protocol
28936 @unnumberedsubsubsec Limits
28937 @cindex limits, in file-i/o protocol
28939 All values are given in decimal representation.
28942 INT_MIN -2147483648
28944 UINT_MAX 4294967295
28945 LONG_MIN -9223372036854775808
28946 LONG_MAX 9223372036854775807
28947 ULONG_MAX 18446744073709551615
28950 @node File-I/O Examples
28951 @subsection File-I/O Examples
28952 @cindex file-i/o examples
28954 Example sequence of a write call, file descriptor 3, buffer is at target
28955 address 0x1234, 6 bytes should be written:
28958 <- @code{Fwrite,3,1234,6}
28959 @emph{request memory read from target}
28962 @emph{return "6 bytes written"}
28966 Example sequence of a read call, file descriptor 3, buffer is at target
28967 address 0x1234, 6 bytes should be read:
28970 <- @code{Fread,3,1234,6}
28971 @emph{request memory write to target}
28972 -> @code{X1234,6:XXXXXX}
28973 @emph{return "6 bytes read"}
28977 Example sequence of a read call, call fails on the host due to invalid
28978 file descriptor (@code{EBADF}):
28981 <- @code{Fread,3,1234,6}
28985 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
28989 <- @code{Fread,3,1234,6}
28994 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
28998 <- @code{Fread,3,1234,6}
28999 -> @code{X1234,6:XXXXXX}
29003 @node Library List Format
29004 @section Library List Format
29005 @cindex library list format, remote protocol
29007 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
29008 same process as your application to manage libraries. In this case,
29009 @value{GDBN} can use the loader's symbol table and normal memory
29010 operations to maintain a list of shared libraries. On other
29011 platforms, the operating system manages loaded libraries.
29012 @value{GDBN} can not retrieve the list of currently loaded libraries
29013 through memory operations, so it uses the @samp{qXfer:libraries:read}
29014 packet (@pxref{qXfer library list read}) instead. The remote stub
29015 queries the target's operating system and reports which libraries
29018 The @samp{qXfer:libraries:read} packet returns an XML document which
29019 lists loaded libraries and their offsets. Each library has an
29020 associated name and one or more segment or section base addresses,
29021 which report where the library was loaded in memory.
29023 For the common case of libraries that are fully linked binaries, the
29024 library should have a list of segments. If the target supports
29025 dynamic linking of a relocatable object file, its library XML element
29026 should instead include a list of allocated sections. The segment or
29027 section bases are start addresses, not relocation offsets; they do not
29028 depend on the library's link-time base addresses.
29030 @value{GDBN} must be linked with the Expat library to support XML
29031 library lists. @xref{Expat}.
29033 A simple memory map, with one loaded library relocated by a single
29034 offset, looks like this:
29038 <library name="/lib/libc.so.6">
29039 <segment address="0x10000000"/>
29044 Another simple memory map, with one loaded library with three
29045 allocated sections (.text, .data, .bss), looks like this:
29049 <library name="sharedlib.o">
29050 <section address="0x10000000"/>
29051 <section address="0x20000000"/>
29052 <section address="0x30000000"/>
29057 The format of a library list is described by this DTD:
29060 <!-- library-list: Root element with versioning -->
29061 <!ELEMENT library-list (library)*>
29062 <!ATTLIST library-list version CDATA #FIXED "1.0">
29063 <!ELEMENT library (segment*, section*)>
29064 <!ATTLIST library name CDATA #REQUIRED>
29065 <!ELEMENT segment EMPTY>
29066 <!ATTLIST segment address CDATA #REQUIRED>
29067 <!ELEMENT section EMPTY>
29068 <!ATTLIST section address CDATA #REQUIRED>
29071 In addition, segments and section descriptors cannot be mixed within a
29072 single library element, and you must supply at least one segment or
29073 section for each library.
29075 @node Memory Map Format
29076 @section Memory Map Format
29077 @cindex memory map format
29079 To be able to write into flash memory, @value{GDBN} needs to obtain a
29080 memory map from the target. This section describes the format of the
29083 The memory map is obtained using the @samp{qXfer:memory-map:read}
29084 (@pxref{qXfer memory map read}) packet and is an XML document that
29085 lists memory regions.
29087 @value{GDBN} must be linked with the Expat library to support XML
29088 memory maps. @xref{Expat}.
29090 The top-level structure of the document is shown below:
29093 <?xml version="1.0"?>
29094 <!DOCTYPE memory-map
29095 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
29096 "http://sourceware.org/gdb/gdb-memory-map.dtd">
29102 Each region can be either:
29107 A region of RAM starting at @var{addr} and extending for @var{length}
29111 <memory type="ram" start="@var{addr}" length="@var{length}"/>
29116 A region of read-only memory:
29119 <memory type="rom" start="@var{addr}" length="@var{length}"/>
29124 A region of flash memory, with erasure blocks @var{blocksize}
29128 <memory type="flash" start="@var{addr}" length="@var{length}">
29129 <property name="blocksize">@var{blocksize}</property>
29135 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
29136 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
29137 packets to write to addresses in such ranges.
29139 The formal DTD for memory map format is given below:
29142 <!-- ................................................... -->
29143 <!-- Memory Map XML DTD ................................ -->
29144 <!-- File: memory-map.dtd .............................. -->
29145 <!-- .................................... .............. -->
29146 <!-- memory-map.dtd -->
29147 <!-- memory-map: Root element with versioning -->
29148 <!ELEMENT memory-map (memory | property)>
29149 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
29150 <!ELEMENT memory (property)>
29151 <!-- memory: Specifies a memory region,
29152 and its type, or device. -->
29153 <!ATTLIST memory type CDATA #REQUIRED
29154 start CDATA #REQUIRED
29155 length CDATA #REQUIRED
29156 device CDATA #IMPLIED>
29157 <!-- property: Generic attribute tag -->
29158 <!ELEMENT property (#PCDATA | property)*>
29159 <!ATTLIST property name CDATA #REQUIRED>
29162 @include agentexpr.texi
29164 @node Target Descriptions
29165 @appendix Target Descriptions
29166 @cindex target descriptions
29168 @strong{Warning:} target descriptions are still under active development,
29169 and the contents and format may change between @value{GDBN} releases.
29170 The format is expected to stabilize in the future.
29172 One of the challenges of using @value{GDBN} to debug embedded systems
29173 is that there are so many minor variants of each processor
29174 architecture in use. It is common practice for vendors to start with
29175 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
29176 and then make changes to adapt it to a particular market niche. Some
29177 architectures have hundreds of variants, available from dozens of
29178 vendors. This leads to a number of problems:
29182 With so many different customized processors, it is difficult for
29183 the @value{GDBN} maintainers to keep up with the changes.
29185 Since individual variants may have short lifetimes or limited
29186 audiences, it may not be worthwhile to carry information about every
29187 variant in the @value{GDBN} source tree.
29189 When @value{GDBN} does support the architecture of the embedded system
29190 at hand, the task of finding the correct architecture name to give the
29191 @command{set architecture} command can be error-prone.
29194 To address these problems, the @value{GDBN} remote protocol allows a
29195 target system to not only identify itself to @value{GDBN}, but to
29196 actually describe its own features. This lets @value{GDBN} support
29197 processor variants it has never seen before --- to the extent that the
29198 descriptions are accurate, and that @value{GDBN} understands them.
29200 @value{GDBN} must be linked with the Expat library to support XML
29201 target descriptions. @xref{Expat}.
29204 * Retrieving Descriptions:: How descriptions are fetched from a target.
29205 * Target Description Format:: The contents of a target description.
29206 * Predefined Target Types:: Standard types available for target
29208 * Standard Target Features:: Features @value{GDBN} knows about.
29211 @node Retrieving Descriptions
29212 @section Retrieving Descriptions
29214 Target descriptions can be read from the target automatically, or
29215 specified by the user manually. The default behavior is to read the
29216 description from the target. @value{GDBN} retrieves it via the remote
29217 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
29218 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
29219 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
29220 XML document, of the form described in @ref{Target Description
29223 Alternatively, you can specify a file to read for the target description.
29224 If a file is set, the target will not be queried. The commands to
29225 specify a file are:
29228 @cindex set tdesc filename
29229 @item set tdesc filename @var{path}
29230 Read the target description from @var{path}.
29232 @cindex unset tdesc filename
29233 @item unset tdesc filename
29234 Do not read the XML target description from a file. @value{GDBN}
29235 will use the description supplied by the current target.
29237 @cindex show tdesc filename
29238 @item show tdesc filename
29239 Show the filename to read for a target description, if any.
29243 @node Target Description Format
29244 @section Target Description Format
29245 @cindex target descriptions, XML format
29247 A target description annex is an @uref{http://www.w3.org/XML/, XML}
29248 document which complies with the Document Type Definition provided in
29249 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
29250 means you can use generally available tools like @command{xmllint} to
29251 check that your feature descriptions are well-formed and valid.
29252 However, to help people unfamiliar with XML write descriptions for
29253 their targets, we also describe the grammar here.
29255 Target descriptions can identify the architecture of the remote target
29256 and (for some architectures) provide information about custom register
29257 sets. @value{GDBN} can use this information to autoconfigure for your
29258 target, or to warn you if you connect to an unsupported target.
29260 Here is a simple target description:
29263 <target version="1.0">
29264 <architecture>i386:x86-64</architecture>
29269 This minimal description only says that the target uses
29270 the x86-64 architecture.
29272 A target description has the following overall form, with [ ] marking
29273 optional elements and @dots{} marking repeatable elements. The elements
29274 are explained further below.
29277 <?xml version="1.0"?>
29278 <!DOCTYPE target SYSTEM "gdb-target.dtd">
29279 <target version="1.0">
29280 @r{[}@var{architecture}@r{]}
29281 @r{[}@var{feature}@dots{}@r{]}
29286 The description is generally insensitive to whitespace and line
29287 breaks, under the usual common-sense rules. The XML version
29288 declaration and document type declaration can generally be omitted
29289 (@value{GDBN} does not require them), but specifying them may be
29290 useful for XML validation tools. The @samp{version} attribute for
29291 @samp{<target>} may also be omitted, but we recommend
29292 including it; if future versions of @value{GDBN} use an incompatible
29293 revision of @file{gdb-target.dtd}, they will detect and report
29294 the version mismatch.
29296 @subsection Inclusion
29297 @cindex target descriptions, inclusion
29300 @cindex <xi:include>
29303 It can sometimes be valuable to split a target description up into
29304 several different annexes, either for organizational purposes, or to
29305 share files between different possible target descriptions. You can
29306 divide a description into multiple files by replacing any element of
29307 the target description with an inclusion directive of the form:
29310 <xi:include href="@var{document}"/>
29314 When @value{GDBN} encounters an element of this form, it will retrieve
29315 the named XML @var{document}, and replace the inclusion directive with
29316 the contents of that document. If the current description was read
29317 using @samp{qXfer}, then so will be the included document;
29318 @var{document} will be interpreted as the name of an annex. If the
29319 current description was read from a file, @value{GDBN} will look for
29320 @var{document} as a file in the same directory where it found the
29321 original description.
29323 @subsection Architecture
29324 @cindex <architecture>
29326 An @samp{<architecture>} element has this form:
29329 <architecture>@var{arch}</architecture>
29332 @var{arch} is an architecture name from the same selection
29333 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
29334 Debugging Target}).
29336 @subsection Features
29339 Each @samp{<feature>} describes some logical portion of the target
29340 system. Features are currently used to describe available CPU
29341 registers and the types of their contents. A @samp{<feature>} element
29345 <feature name="@var{name}">
29346 @r{[}@var{type}@dots{}@r{]}
29352 Each feature's name should be unique within the description. The name
29353 of a feature does not matter unless @value{GDBN} has some special
29354 knowledge of the contents of that feature; if it does, the feature
29355 should have its standard name. @xref{Standard Target Features}.
29359 Any register's value is a collection of bits which @value{GDBN} must
29360 interpret. The default interpretation is a two's complement integer,
29361 but other types can be requested by name in the register description.
29362 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
29363 Target Types}), and the description can define additional composite types.
29365 Each type element must have an @samp{id} attribute, which gives
29366 a unique (within the containing @samp{<feature>}) name to the type.
29367 Types must be defined before they are used.
29370 Some targets offer vector registers, which can be treated as arrays
29371 of scalar elements. These types are written as @samp{<vector>} elements,
29372 specifying the array element type, @var{type}, and the number of elements,
29376 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
29380 If a register's value is usefully viewed in multiple ways, define it
29381 with a union type containing the useful representations. The
29382 @samp{<union>} element contains one or more @samp{<field>} elements,
29383 each of which has a @var{name} and a @var{type}:
29386 <union id="@var{id}">
29387 <field name="@var{name}" type="@var{type}"/>
29392 @subsection Registers
29395 Each register is represented as an element with this form:
29398 <reg name="@var{name}"
29399 bitsize="@var{size}"
29400 @r{[}regnum="@var{num}"@r{]}
29401 @r{[}save-restore="@var{save-restore}"@r{]}
29402 @r{[}type="@var{type}"@r{]}
29403 @r{[}group="@var{group}"@r{]}/>
29407 The components are as follows:
29412 The register's name; it must be unique within the target description.
29415 The register's size, in bits.
29418 The register's number. If omitted, a register's number is one greater
29419 than that of the previous register (either in the current feature or in
29420 a preceeding feature); the first register in the target description
29421 defaults to zero. This register number is used to read or write
29422 the register; e.g.@: it is used in the remote @code{p} and @code{P}
29423 packets, and registers appear in the @code{g} and @code{G} packets
29424 in order of increasing register number.
29427 Whether the register should be preserved across inferior function
29428 calls; this must be either @code{yes} or @code{no}. The default is
29429 @code{yes}, which is appropriate for most registers except for
29430 some system control registers; this is not related to the target's
29434 The type of the register. @var{type} may be a predefined type, a type
29435 defined in the current feature, or one of the special types @code{int}
29436 and @code{float}. @code{int} is an integer type of the correct size
29437 for @var{bitsize}, and @code{float} is a floating point type (in the
29438 architecture's normal floating point format) of the correct size for
29439 @var{bitsize}. The default is @code{int}.
29442 The register group to which this register belongs. @var{group} must
29443 be either @code{general}, @code{float}, or @code{vector}. If no
29444 @var{group} is specified, @value{GDBN} will not display the register
29445 in @code{info registers}.
29449 @node Predefined Target Types
29450 @section Predefined Target Types
29451 @cindex target descriptions, predefined types
29453 Type definitions in the self-description can build up composite types
29454 from basic building blocks, but can not define fundamental types. Instead,
29455 standard identifiers are provided by @value{GDBN} for the fundamental
29456 types. The currently supported types are:
29465 Signed integer types holding the specified number of bits.
29472 Unsigned integer types holding the specified number of bits.
29476 Pointers to unspecified code and data. The program counter and
29477 any dedicated return address register may be marked as code
29478 pointers; printing a code pointer converts it into a symbolic
29479 address. The stack pointer and any dedicated address registers
29480 may be marked as data pointers.
29483 Single precision IEEE floating point.
29486 Double precision IEEE floating point.
29489 The 12-byte extended precision format used by ARM FPA registers.
29493 @node Standard Target Features
29494 @section Standard Target Features
29495 @cindex target descriptions, standard features
29497 A target description must contain either no registers or all the
29498 target's registers. If the description contains no registers, then
29499 @value{GDBN} will assume a default register layout, selected based on
29500 the architecture. If the description contains any registers, the
29501 default layout will not be used; the standard registers must be
29502 described in the target description, in such a way that @value{GDBN}
29503 can recognize them.
29505 This is accomplished by giving specific names to feature elements
29506 which contain standard registers. @value{GDBN} will look for features
29507 with those names and verify that they contain the expected registers;
29508 if any known feature is missing required registers, or if any required
29509 feature is missing, @value{GDBN} will reject the target
29510 description. You can add additional registers to any of the
29511 standard features --- @value{GDBN} will display them just as if
29512 they were added to an unrecognized feature.
29514 This section lists the known features and their expected contents.
29515 Sample XML documents for these features are included in the
29516 @value{GDBN} source tree, in the directory @file{gdb/features}.
29518 Names recognized by @value{GDBN} should include the name of the
29519 company or organization which selected the name, and the overall
29520 architecture to which the feature applies; so e.g.@: the feature
29521 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
29523 The names of registers are not case sensitive for the purpose
29524 of recognizing standard features, but @value{GDBN} will only display
29525 registers using the capitalization used in the description.
29531 * PowerPC Features::
29536 @subsection ARM Features
29537 @cindex target descriptions, ARM features
29539 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
29540 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
29541 @samp{lr}, @samp{pc}, and @samp{cpsr}.
29543 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
29544 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
29546 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
29547 it should contain at least registers @samp{wR0} through @samp{wR15} and
29548 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
29549 @samp{wCSSF}, and @samp{wCASF} registers are optional.
29551 @node MIPS Features
29552 @subsection MIPS Features
29553 @cindex target descriptions, MIPS features
29555 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
29556 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
29557 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
29560 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
29561 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
29562 registers. They may be 32-bit or 64-bit depending on the target.
29564 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
29565 it may be optional in a future version of @value{GDBN}. It should
29566 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
29567 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
29569 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
29570 contain a single register, @samp{restart}, which is used by the
29571 Linux kernel to control restartable syscalls.
29573 @node M68K Features
29574 @subsection M68K Features
29575 @cindex target descriptions, M68K features
29578 @item @samp{org.gnu.gdb.m68k.core}
29579 @itemx @samp{org.gnu.gdb.coldfire.core}
29580 @itemx @samp{org.gnu.gdb.fido.core}
29581 One of those features must be always present.
29582 The feature that is present determines which flavor of m68k is
29583 used. The feature that is present should contain registers
29584 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
29585 @samp{sp}, @samp{ps} and @samp{pc}.
29587 @item @samp{org.gnu.gdb.coldfire.fp}
29588 This feature is optional. If present, it should contain registers
29589 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
29593 @node PowerPC Features
29594 @subsection PowerPC Features
29595 @cindex target descriptions, PowerPC features
29597 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
29598 targets. It should contain registers @samp{r0} through @samp{r31},
29599 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
29600 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
29602 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
29603 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
29605 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
29606 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
29609 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
29610 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
29611 will combine these registers with the floating point registers
29612 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
29613 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
29614 through @samp{vs63}, the set of vector registers for POWER7.
29616 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
29617 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
29618 @samp{spefscr}. SPE targets should provide 32-bit registers in
29619 @samp{org.gnu.gdb.power.core} and provide the upper halves in
29620 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
29621 these to present registers @samp{ev0} through @samp{ev31} to the
29624 @node Operating System Information
29625 @appendix Operating System Information
29626 @cindex operating system information
29632 Users of @value{GDBN} often wish to obtain information about the state of
29633 the operating system running on the target---for example the list of
29634 processes, or the list of open files. This section describes the
29635 mechanism that makes it possible. This mechanism is similar to the
29636 target features mechanism (@pxref{Target Descriptions}), but focuses
29637 on a different aspect of target.
29639 Operating system information is retrived from the target via the
29640 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
29641 read}). The object name in the request should be @samp{osdata}, and
29642 the @var{annex} identifies the data to be fetched.
29645 @appendixsection Process list
29646 @cindex operating system information, process list
29648 When requesting the process list, the @var{annex} field in the
29649 @samp{qXfer} request should be @samp{processes}. The returned data is
29650 an XML document. The formal syntax of this document is defined in
29651 @file{gdb/features/osdata.dtd}.
29653 An example document is:
29656 <?xml version="1.0"?>
29657 <!DOCTYPE target SYSTEM "osdata.dtd">
29658 <osdata type="processes">
29660 <column name="pid">1</column>
29661 <column name="user">root</column>
29662 <column name="command">/sbin/init</column>
29667 Each item should include a column whose name is @samp{pid}. The value
29668 of that column should identify the process on the target. The
29669 @samp{user} and @samp{command} columns are optional, and will be
29670 displayed by @value{GDBN}. Target may provide additional columns,
29671 which @value{GDBN} currently ignores.
29685 % I think something like @colophon should be in texinfo. In the
29687 \long\def\colophon{\hbox to0pt{}\vfill
29688 \centerline{The body of this manual is set in}
29689 \centerline{\fontname\tenrm,}
29690 \centerline{with headings in {\bf\fontname\tenbf}}
29691 \centerline{and examples in {\tt\fontname\tentt}.}
29692 \centerline{{\it\fontname\tenit\/},}
29693 \centerline{{\bf\fontname\tenbf}, and}
29694 \centerline{{\sl\fontname\tensl\/}}
29695 \centerline{are used for emphasis.}\vfill}
29697 % Blame: doc@cygnus.com, 1991.