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. You can use the command
5914 @code{set disassemble-next-line} to set whether to disassemble next
5915 source line when execution stops. When run under @sc{gnu} Emacs
5916 mode, the @code{info line} command causes the arrow to point to the
5917 line specified. Also, @code{info line} prints addresses in symbolic form as
5922 @item info line @var{linespec}
5923 Print the starting and ending addresses of the compiled code for
5924 source line @var{linespec}. You can specify source lines in any of
5925 the ways documented in @ref{Specify Location}.
5928 For example, we can use @code{info line} to discover the location of
5929 the object code for the first line of function
5930 @code{m4_changequote}:
5932 @c FIXME: I think this example should also show the addresses in
5933 @c symbolic form, as they usually would be displayed.
5935 (@value{GDBP}) info line m4_changequote
5936 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5940 @cindex code address and its source line
5941 We can also inquire (using @code{*@var{addr}} as the form for
5942 @var{linespec}) what source line covers a particular address:
5944 (@value{GDBP}) info line *0x63ff
5945 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5948 @cindex @code{$_} and @code{info line}
5949 @cindex @code{x} command, default address
5950 @kindex x@r{(examine), and} info line
5951 After @code{info line}, the default address for the @code{x} command
5952 is changed to the starting address of the line, so that @samp{x/i} is
5953 sufficient to begin examining the machine code (@pxref{Memory,
5954 ,Examining Memory}). Also, this address is saved as the value of the
5955 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5960 @cindex assembly instructions
5961 @cindex instructions, assembly
5962 @cindex machine instructions
5963 @cindex listing machine instructions
5965 @itemx disassemble /m
5966 This specialized command dumps a range of memory as machine
5967 instructions. It can also print mixed source+disassembly by specifying
5968 the @code{/m} modifier.
5969 The default memory range is the function surrounding the
5970 program counter of the selected frame. A single argument to this
5971 command is a program counter value; @value{GDBN} dumps the function
5972 surrounding this value. Two arguments specify a range of addresses
5973 (first inclusive, second exclusive) to dump.
5976 The following example shows the disassembly of a range of addresses of
5977 HP PA-RISC 2.0 code:
5980 (@value{GDBP}) disas 0x32c4 0x32e4
5981 Dump of assembler code from 0x32c4 to 0x32e4:
5982 0x32c4 <main+204>: addil 0,dp
5983 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5984 0x32cc <main+212>: ldil 0x3000,r31
5985 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5986 0x32d4 <main+220>: ldo 0(r31),rp
5987 0x32d8 <main+224>: addil -0x800,dp
5988 0x32dc <main+228>: ldo 0x588(r1),r26
5989 0x32e0 <main+232>: ldil 0x3000,r31
5990 End of assembler dump.
5993 Here is an example showing mixed source+assembly for Intel x86:
5996 (@value{GDBP}) disas /m main
5997 Dump of assembler code for function main:
5999 0x08048330 <main+0>: push %ebp
6000 0x08048331 <main+1>: mov %esp,%ebp
6001 0x08048333 <main+3>: sub $0x8,%esp
6002 0x08048336 <main+6>: and $0xfffffff0,%esp
6003 0x08048339 <main+9>: sub $0x10,%esp
6005 6 printf ("Hello.\n");
6006 0x0804833c <main+12>: movl $0x8048440,(%esp)
6007 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
6011 0x08048348 <main+24>: mov $0x0,%eax
6012 0x0804834d <main+29>: leave
6013 0x0804834e <main+30>: ret
6015 End of assembler dump.
6018 Some architectures have more than one commonly-used set of instruction
6019 mnemonics or other syntax.
6021 For programs that were dynamically linked and use shared libraries,
6022 instructions that call functions or branch to locations in the shared
6023 libraries might show a seemingly bogus location---it's actually a
6024 location of the relocation table. On some architectures, @value{GDBN}
6025 might be able to resolve these to actual function names.
6028 @kindex set disassembly-flavor
6029 @cindex Intel disassembly flavor
6030 @cindex AT&T disassembly flavor
6031 @item set disassembly-flavor @var{instruction-set}
6032 Select the instruction set to use when disassembling the
6033 program via the @code{disassemble} or @code{x/i} commands.
6035 Currently this command is only defined for the Intel x86 family. You
6036 can set @var{instruction-set} to either @code{intel} or @code{att}.
6037 The default is @code{att}, the AT&T flavor used by default by Unix
6038 assemblers for x86-based targets.
6040 @kindex show disassembly-flavor
6041 @item show disassembly-flavor
6042 Show the current setting of the disassembly flavor.
6046 @kindex set disassemble-next-line
6047 @kindex show disassemble-next-line
6048 @item set disassemble-next-line
6049 @itemx show disassemble-next-line
6050 Control whether or not @value{GDBN} will disassemble next source line
6051 when execution stops. If ON, GDB will display disassembly of the next
6052 source line when execution of the program being debugged stops.
6053 If AUTO (which is the default), or there's no line info to determine
6054 the source line of the next instruction, display disassembly of next
6055 instruction instead.
6060 @chapter Examining Data
6062 @cindex printing data
6063 @cindex examining data
6066 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6067 @c document because it is nonstandard... Under Epoch it displays in a
6068 @c different window or something like that.
6069 The usual way to examine data in your program is with the @code{print}
6070 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6071 evaluates and prints the value of an expression of the language your
6072 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6073 Different Languages}).
6076 @item print @var{expr}
6077 @itemx print /@var{f} @var{expr}
6078 @var{expr} is an expression (in the source language). By default the
6079 value of @var{expr} is printed in a format appropriate to its data type;
6080 you can choose a different format by specifying @samp{/@var{f}}, where
6081 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6085 @itemx print /@var{f}
6086 @cindex reprint the last value
6087 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6088 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6089 conveniently inspect the same value in an alternative format.
6092 A more low-level way of examining data is with the @code{x} command.
6093 It examines data in memory at a specified address and prints it in a
6094 specified format. @xref{Memory, ,Examining Memory}.
6096 If you are interested in information about types, or about how the
6097 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6098 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6102 * Expressions:: Expressions
6103 * Ambiguous Expressions:: Ambiguous Expressions
6104 * Variables:: Program variables
6105 * Arrays:: Artificial arrays
6106 * Output Formats:: Output formats
6107 * Memory:: Examining memory
6108 * Auto Display:: Automatic display
6109 * Print Settings:: Print settings
6110 * Value History:: Value history
6111 * Convenience Vars:: Convenience variables
6112 * Registers:: Registers
6113 * Floating Point Hardware:: Floating point hardware
6114 * Vector Unit:: Vector Unit
6115 * OS Information:: Auxiliary data provided by operating system
6116 * Memory Region Attributes:: Memory region attributes
6117 * Dump/Restore Files:: Copy between memory and a file
6118 * Core File Generation:: Cause a program dump its core
6119 * Character Sets:: Debugging programs that use a different
6120 character set than GDB does
6121 * Caching Remote Data:: Data caching for remote targets
6122 * Searching Memory:: Searching memory for a sequence of bytes
6126 @section Expressions
6129 @code{print} and many other @value{GDBN} commands accept an expression and
6130 compute its value. Any kind of constant, variable or operator defined
6131 by the programming language you are using is valid in an expression in
6132 @value{GDBN}. This includes conditional expressions, function calls,
6133 casts, and string constants. It also includes preprocessor macros, if
6134 you compiled your program to include this information; see
6137 @cindex arrays in expressions
6138 @value{GDBN} supports array constants in expressions input by
6139 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6140 you can use the command @code{print @{1, 2, 3@}} to create an array
6141 of three integers. If you pass an array to a function or assign it
6142 to a program variable, @value{GDBN} copies the array to memory that
6143 is @code{malloc}ed in the target program.
6145 Because C is so widespread, most of the expressions shown in examples in
6146 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6147 Languages}, for information on how to use expressions in other
6150 In this section, we discuss operators that you can use in @value{GDBN}
6151 expressions regardless of your programming language.
6153 @cindex casts, in expressions
6154 Casts are supported in all languages, not just in C, because it is so
6155 useful to cast a number into a pointer in order to examine a structure
6156 at that address in memory.
6157 @c FIXME: casts supported---Mod2 true?
6159 @value{GDBN} supports these operators, in addition to those common
6160 to programming languages:
6164 @samp{@@} is a binary operator for treating parts of memory as arrays.
6165 @xref{Arrays, ,Artificial Arrays}, for more information.
6168 @samp{::} allows you to specify a variable in terms of the file or
6169 function where it is defined. @xref{Variables, ,Program Variables}.
6171 @cindex @{@var{type}@}
6172 @cindex type casting memory
6173 @cindex memory, viewing as typed object
6174 @cindex casts, to view memory
6175 @item @{@var{type}@} @var{addr}
6176 Refers to an object of type @var{type} stored at address @var{addr} in
6177 memory. @var{addr} may be any expression whose value is an integer or
6178 pointer (but parentheses are required around binary operators, just as in
6179 a cast). This construct is allowed regardless of what kind of data is
6180 normally supposed to reside at @var{addr}.
6183 @node Ambiguous Expressions
6184 @section Ambiguous Expressions
6185 @cindex ambiguous expressions
6187 Expressions can sometimes contain some ambiguous elements. For instance,
6188 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6189 a single function name to be defined several times, for application in
6190 different contexts. This is called @dfn{overloading}. Another example
6191 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6192 templates and is typically instantiated several times, resulting in
6193 the same function name being defined in different contexts.
6195 In some cases and depending on the language, it is possible to adjust
6196 the expression to remove the ambiguity. For instance in C@t{++}, you
6197 can specify the signature of the function you want to break on, as in
6198 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6199 qualified name of your function often makes the expression unambiguous
6202 When an ambiguity that needs to be resolved is detected, the debugger
6203 has the capability to display a menu of numbered choices for each
6204 possibility, and then waits for the selection with the prompt @samp{>}.
6205 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6206 aborts the current command. If the command in which the expression was
6207 used allows more than one choice to be selected, the next option in the
6208 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6211 For example, the following session excerpt shows an attempt to set a
6212 breakpoint at the overloaded symbol @code{String::after}.
6213 We choose three particular definitions of that function name:
6215 @c FIXME! This is likely to change to show arg type lists, at least
6218 (@value{GDBP}) b String::after
6221 [2] file:String.cc; line number:867
6222 [3] file:String.cc; line number:860
6223 [4] file:String.cc; line number:875
6224 [5] file:String.cc; line number:853
6225 [6] file:String.cc; line number:846
6226 [7] file:String.cc; line number:735
6228 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6229 Breakpoint 2 at 0xb344: file String.cc, line 875.
6230 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6231 Multiple breakpoints were set.
6232 Use the "delete" command to delete unwanted
6239 @kindex set multiple-symbols
6240 @item set multiple-symbols @var{mode}
6241 @cindex multiple-symbols menu
6243 This option allows you to adjust the debugger behavior when an expression
6246 By default, @var{mode} is set to @code{all}. If the command with which
6247 the expression is used allows more than one choice, then @value{GDBN}
6248 automatically selects all possible choices. For instance, inserting
6249 a breakpoint on a function using an ambiguous name results in a breakpoint
6250 inserted on each possible match. However, if a unique choice must be made,
6251 then @value{GDBN} uses the menu to help you disambiguate the expression.
6252 For instance, printing the address of an overloaded function will result
6253 in the use of the menu.
6255 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6256 when an ambiguity is detected.
6258 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6259 an error due to the ambiguity and the command is aborted.
6261 @kindex show multiple-symbols
6262 @item show multiple-symbols
6263 Show the current value of the @code{multiple-symbols} setting.
6267 @section Program Variables
6269 The most common kind of expression to use is the name of a variable
6272 Variables in expressions are understood in the selected stack frame
6273 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6277 global (or file-static)
6284 visible according to the scope rules of the
6285 programming language from the point of execution in that frame
6288 @noindent This means that in the function
6303 you can examine and use the variable @code{a} whenever your program is
6304 executing within the function @code{foo}, but you can only use or
6305 examine the variable @code{b} while your program is executing inside
6306 the block where @code{b} is declared.
6308 @cindex variable name conflict
6309 There is an exception: you can refer to a variable or function whose
6310 scope is a single source file even if the current execution point is not
6311 in this file. But it is possible to have more than one such variable or
6312 function with the same name (in different source files). If that
6313 happens, referring to that name has unpredictable effects. If you wish,
6314 you can specify a static variable in a particular function or file,
6315 using the colon-colon (@code{::}) notation:
6317 @cindex colon-colon, context for variables/functions
6319 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6320 @cindex @code{::}, context for variables/functions
6323 @var{file}::@var{variable}
6324 @var{function}::@var{variable}
6328 Here @var{file} or @var{function} is the name of the context for the
6329 static @var{variable}. In the case of file names, you can use quotes to
6330 make sure @value{GDBN} parses the file name as a single word---for example,
6331 to print a global value of @code{x} defined in @file{f2.c}:
6334 (@value{GDBP}) p 'f2.c'::x
6337 @cindex C@t{++} scope resolution
6338 This use of @samp{::} is very rarely in conflict with the very similar
6339 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6340 scope resolution operator in @value{GDBN} expressions.
6341 @c FIXME: Um, so what happens in one of those rare cases where it's in
6344 @cindex wrong values
6345 @cindex variable values, wrong
6346 @cindex function entry/exit, wrong values of variables
6347 @cindex optimized code, wrong values of variables
6349 @emph{Warning:} Occasionally, a local variable may appear to have the
6350 wrong value at certain points in a function---just after entry to a new
6351 scope, and just before exit.
6353 You may see this problem when you are stepping by machine instructions.
6354 This is because, on most machines, it takes more than one instruction to
6355 set up a stack frame (including local variable definitions); if you are
6356 stepping by machine instructions, variables may appear to have the wrong
6357 values until the stack frame is completely built. On exit, it usually
6358 also takes more than one machine instruction to destroy a stack frame;
6359 after you begin stepping through that group of instructions, local
6360 variable definitions may be gone.
6362 This may also happen when the compiler does significant optimizations.
6363 To be sure of always seeing accurate values, turn off all optimization
6366 @cindex ``No symbol "foo" in current context''
6367 Another possible effect of compiler optimizations is to optimize
6368 unused variables out of existence, or assign variables to registers (as
6369 opposed to memory addresses). Depending on the support for such cases
6370 offered by the debug info format used by the compiler, @value{GDBN}
6371 might not be able to display values for such local variables. If that
6372 happens, @value{GDBN} will print a message like this:
6375 No symbol "foo" in current context.
6378 To solve such problems, either recompile without optimizations, or use a
6379 different debug info format, if the compiler supports several such
6380 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6381 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6382 produces debug info in a format that is superior to formats such as
6383 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6384 an effective form for debug info. @xref{Debugging Options,,Options
6385 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6386 Compiler Collection (GCC)}.
6387 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6388 that are best suited to C@t{++} programs.
6390 If you ask to print an object whose contents are unknown to
6391 @value{GDBN}, e.g., because its data type is not completely specified
6392 by the debug information, @value{GDBN} will say @samp{<incomplete
6393 type>}. @xref{Symbols, incomplete type}, for more about this.
6395 Strings are identified as arrays of @code{char} values without specified
6396 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6397 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6398 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6399 defines literal string type @code{"char"} as @code{char} without a sign.
6404 signed char var1[] = "A";
6407 You get during debugging
6412 $2 = @{65 'A', 0 '\0'@}
6416 @section Artificial Arrays
6418 @cindex artificial array
6420 @kindex @@@r{, referencing memory as an array}
6421 It is often useful to print out several successive objects of the
6422 same type in memory; a section of an array, or an array of
6423 dynamically determined size for which only a pointer exists in the
6426 You can do this by referring to a contiguous span of memory as an
6427 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6428 operand of @samp{@@} should be the first element of the desired array
6429 and be an individual object. The right operand should be the desired length
6430 of the array. The result is an array value whose elements are all of
6431 the type of the left argument. The first element is actually the left
6432 argument; the second element comes from bytes of memory immediately
6433 following those that hold the first element, and so on. Here is an
6434 example. If a program says
6437 int *array = (int *) malloc (len * sizeof (int));
6441 you can print the contents of @code{array} with
6447 The left operand of @samp{@@} must reside in memory. Array values made
6448 with @samp{@@} in this way behave just like other arrays in terms of
6449 subscripting, and are coerced to pointers when used in expressions.
6450 Artificial arrays most often appear in expressions via the value history
6451 (@pxref{Value History, ,Value History}), after printing one out.
6453 Another way to create an artificial array is to use a cast.
6454 This re-interprets a value as if it were an array.
6455 The value need not be in memory:
6457 (@value{GDBP}) p/x (short[2])0x12345678
6458 $1 = @{0x1234, 0x5678@}
6461 As a convenience, if you leave the array length out (as in
6462 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6463 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6465 (@value{GDBP}) p/x (short[])0x12345678
6466 $2 = @{0x1234, 0x5678@}
6469 Sometimes the artificial array mechanism is not quite enough; in
6470 moderately complex data structures, the elements of interest may not
6471 actually be adjacent---for example, if you are interested in the values
6472 of pointers in an array. One useful work-around in this situation is
6473 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6474 Variables}) as a counter in an expression that prints the first
6475 interesting value, and then repeat that expression via @key{RET}. For
6476 instance, suppose you have an array @code{dtab} of pointers to
6477 structures, and you are interested in the values of a field @code{fv}
6478 in each structure. Here is an example of what you might type:
6488 @node Output Formats
6489 @section Output Formats
6491 @cindex formatted output
6492 @cindex output formats
6493 By default, @value{GDBN} prints a value according to its data type. Sometimes
6494 this is not what you want. For example, you might want to print a number
6495 in hex, or a pointer in decimal. Or you might want to view data in memory
6496 at a certain address as a character string or as an instruction. To do
6497 these things, specify an @dfn{output format} when you print a value.
6499 The simplest use of output formats is to say how to print a value
6500 already computed. This is done by starting the arguments of the
6501 @code{print} command with a slash and a format letter. The format
6502 letters supported are:
6506 Regard the bits of the value as an integer, and print the integer in
6510 Print as integer in signed decimal.
6513 Print as integer in unsigned decimal.
6516 Print as integer in octal.
6519 Print as integer in binary. The letter @samp{t} stands for ``two''.
6520 @footnote{@samp{b} cannot be used because these format letters are also
6521 used with the @code{x} command, where @samp{b} stands for ``byte'';
6522 see @ref{Memory,,Examining Memory}.}
6525 @cindex unknown address, locating
6526 @cindex locate address
6527 Print as an address, both absolute in hexadecimal and as an offset from
6528 the nearest preceding symbol. You can use this format used to discover
6529 where (in what function) an unknown address is located:
6532 (@value{GDBP}) p/a 0x54320
6533 $3 = 0x54320 <_initialize_vx+396>
6537 The command @code{info symbol 0x54320} yields similar results.
6538 @xref{Symbols, info symbol}.
6541 Regard as an integer and print it as a character constant. This
6542 prints both the numerical value and its character representation. The
6543 character representation is replaced with the octal escape @samp{\nnn}
6544 for characters outside the 7-bit @sc{ascii} range.
6546 Without this format, @value{GDBN} displays @code{char},
6547 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6548 constants. Single-byte members of vectors are displayed as integer
6552 Regard the bits of the value as a floating point number and print
6553 using typical floating point syntax.
6556 @cindex printing strings
6557 @cindex printing byte arrays
6558 Regard as a string, if possible. With this format, pointers to single-byte
6559 data are displayed as null-terminated strings and arrays of single-byte data
6560 are displayed as fixed-length strings. Other values are displayed in their
6563 Without this format, @value{GDBN} displays pointers to and arrays of
6564 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6565 strings. Single-byte members of a vector are displayed as an integer
6569 For example, to print the program counter in hex (@pxref{Registers}), type
6576 Note that no space is required before the slash; this is because command
6577 names in @value{GDBN} cannot contain a slash.
6579 To reprint the last value in the value history with a different format,
6580 you can use the @code{print} command with just a format and no
6581 expression. For example, @samp{p/x} reprints the last value in hex.
6584 @section Examining Memory
6586 You can use the command @code{x} (for ``examine'') to examine memory in
6587 any of several formats, independently of your program's data types.
6589 @cindex examining memory
6591 @kindex x @r{(examine memory)}
6592 @item x/@var{nfu} @var{addr}
6595 Use the @code{x} command to examine memory.
6598 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6599 much memory to display and how to format it; @var{addr} is an
6600 expression giving the address where you want to start displaying memory.
6601 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6602 Several commands set convenient defaults for @var{addr}.
6605 @item @var{n}, the repeat count
6606 The repeat count is a decimal integer; the default is 1. It specifies
6607 how much memory (counting by units @var{u}) to display.
6608 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6611 @item @var{f}, the display format
6612 The display format is one of the formats used by @code{print}
6613 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6614 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6615 The default is @samp{x} (hexadecimal) initially. The default changes
6616 each time you use either @code{x} or @code{print}.
6618 @item @var{u}, the unit size
6619 The unit size is any of
6625 Halfwords (two bytes).
6627 Words (four bytes). This is the initial default.
6629 Giant words (eight bytes).
6632 Each time you specify a unit size with @code{x}, that size becomes the
6633 default unit the next time you use @code{x}. (For the @samp{s} and
6634 @samp{i} formats, the unit size is ignored and is normally not written.)
6636 @item @var{addr}, starting display address
6637 @var{addr} is the address where you want @value{GDBN} to begin displaying
6638 memory. The expression need not have a pointer value (though it may);
6639 it is always interpreted as an integer address of a byte of memory.
6640 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6641 @var{addr} is usually just after the last address examined---but several
6642 other commands also set the default address: @code{info breakpoints} (to
6643 the address of the last breakpoint listed), @code{info line} (to the
6644 starting address of a line), and @code{print} (if you use it to display
6645 a value from memory).
6648 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6649 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6650 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6651 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6652 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6654 Since the letters indicating unit sizes are all distinct from the
6655 letters specifying output formats, you do not have to remember whether
6656 unit size or format comes first; either order works. The output
6657 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6658 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6660 Even though the unit size @var{u} is ignored for the formats @samp{s}
6661 and @samp{i}, you might still want to use a count @var{n}; for example,
6662 @samp{3i} specifies that you want to see three machine instructions,
6663 including any operands. For convenience, especially when used with
6664 the @code{display} command, the @samp{i} format also prints branch delay
6665 slot instructions, if any, beyond the count specified, which immediately
6666 follow the last instruction that is within the count. The command
6667 @code{disassemble} gives an alternative way of inspecting machine
6668 instructions; see @ref{Machine Code,,Source and Machine Code}.
6670 All the defaults for the arguments to @code{x} are designed to make it
6671 easy to continue scanning memory with minimal specifications each time
6672 you use @code{x}. For example, after you have inspected three machine
6673 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6674 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6675 the repeat count @var{n} is used again; the other arguments default as
6676 for successive uses of @code{x}.
6678 @cindex @code{$_}, @code{$__}, and value history
6679 The addresses and contents printed by the @code{x} command are not saved
6680 in the value history because there is often too much of them and they
6681 would get in the way. Instead, @value{GDBN} makes these values available for
6682 subsequent use in expressions as values of the convenience variables
6683 @code{$_} and @code{$__}. After an @code{x} command, the last address
6684 examined is available for use in expressions in the convenience variable
6685 @code{$_}. The contents of that address, as examined, are available in
6686 the convenience variable @code{$__}.
6688 If the @code{x} command has a repeat count, the address and contents saved
6689 are from the last memory unit printed; this is not the same as the last
6690 address printed if several units were printed on the last line of output.
6692 @cindex remote memory comparison
6693 @cindex verify remote memory image
6694 When you are debugging a program running on a remote target machine
6695 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6696 remote machine's memory against the executable file you downloaded to
6697 the target. The @code{compare-sections} command is provided for such
6701 @kindex compare-sections
6702 @item compare-sections @r{[}@var{section-name}@r{]}
6703 Compare the data of a loadable section @var{section-name} in the
6704 executable file of the program being debugged with the same section in
6705 the remote machine's memory, and report any mismatches. With no
6706 arguments, compares all loadable sections. This command's
6707 availability depends on the target's support for the @code{"qCRC"}
6712 @section Automatic Display
6713 @cindex automatic display
6714 @cindex display of expressions
6716 If you find that you want to print the value of an expression frequently
6717 (to see how it changes), you might want to add it to the @dfn{automatic
6718 display list} so that @value{GDBN} prints its value each time your program stops.
6719 Each expression added to the list is given a number to identify it;
6720 to remove an expression from the list, you specify that number.
6721 The automatic display looks like this:
6725 3: bar[5] = (struct hack *) 0x3804
6729 This display shows item numbers, expressions and their current values. As with
6730 displays you request manually using @code{x} or @code{print}, you can
6731 specify the output format you prefer; in fact, @code{display} decides
6732 whether to use @code{print} or @code{x} depending your format
6733 specification---it uses @code{x} if you specify either the @samp{i}
6734 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6738 @item display @var{expr}
6739 Add the expression @var{expr} to the list of expressions to display
6740 each time your program stops. @xref{Expressions, ,Expressions}.
6742 @code{display} does not repeat if you press @key{RET} again after using it.
6744 @item display/@var{fmt} @var{expr}
6745 For @var{fmt} specifying only a display format and not a size or
6746 count, add the expression @var{expr} to the auto-display list but
6747 arrange to display it each time in the specified format @var{fmt}.
6748 @xref{Output Formats,,Output Formats}.
6750 @item display/@var{fmt} @var{addr}
6751 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6752 number of units, add the expression @var{addr} as a memory address to
6753 be examined each time your program stops. Examining means in effect
6754 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6757 For example, @samp{display/i $pc} can be helpful, to see the machine
6758 instruction about to be executed each time execution stops (@samp{$pc}
6759 is a common name for the program counter; @pxref{Registers, ,Registers}).
6762 @kindex delete display
6764 @item undisplay @var{dnums}@dots{}
6765 @itemx delete display @var{dnums}@dots{}
6766 Remove item numbers @var{dnums} from the list of expressions to display.
6768 @code{undisplay} does not repeat if you press @key{RET} after using it.
6769 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6771 @kindex disable display
6772 @item disable display @var{dnums}@dots{}
6773 Disable the display of item numbers @var{dnums}. A disabled display
6774 item is not printed automatically, but is not forgotten. It may be
6775 enabled again later.
6777 @kindex enable display
6778 @item enable display @var{dnums}@dots{}
6779 Enable display of item numbers @var{dnums}. It becomes effective once
6780 again in auto display of its expression, until you specify otherwise.
6783 Display the current values of the expressions on the list, just as is
6784 done when your program stops.
6786 @kindex info display
6788 Print the list of expressions previously set up to display
6789 automatically, each one with its item number, but without showing the
6790 values. This includes disabled expressions, which are marked as such.
6791 It also includes expressions which would not be displayed right now
6792 because they refer to automatic variables not currently available.
6795 @cindex display disabled out of scope
6796 If a display expression refers to local variables, then it does not make
6797 sense outside the lexical context for which it was set up. Such an
6798 expression is disabled when execution enters a context where one of its
6799 variables is not defined. For example, if you give the command
6800 @code{display last_char} while inside a function with an argument
6801 @code{last_char}, @value{GDBN} displays this argument while your program
6802 continues to stop inside that function. When it stops elsewhere---where
6803 there is no variable @code{last_char}---the display is disabled
6804 automatically. The next time your program stops where @code{last_char}
6805 is meaningful, you can enable the display expression once again.
6807 @node Print Settings
6808 @section Print Settings
6810 @cindex format options
6811 @cindex print settings
6812 @value{GDBN} provides the following ways to control how arrays, structures,
6813 and symbols are printed.
6816 These settings are useful for debugging programs in any language:
6820 @item set print address
6821 @itemx set print address on
6822 @cindex print/don't print memory addresses
6823 @value{GDBN} prints memory addresses showing the location of stack
6824 traces, structure values, pointer values, breakpoints, and so forth,
6825 even when it also displays the contents of those addresses. The default
6826 is @code{on}. For example, this is what a stack frame display looks like with
6827 @code{set print address on}:
6832 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6834 530 if (lquote != def_lquote)
6838 @item set print address off
6839 Do not print addresses when displaying their contents. For example,
6840 this is the same stack frame displayed with @code{set print address off}:
6844 (@value{GDBP}) set print addr off
6846 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6847 530 if (lquote != def_lquote)
6851 You can use @samp{set print address off} to eliminate all machine
6852 dependent displays from the @value{GDBN} interface. For example, with
6853 @code{print address off}, you should get the same text for backtraces on
6854 all machines---whether or not they involve pointer arguments.
6857 @item show print address
6858 Show whether or not addresses are to be printed.
6861 When @value{GDBN} prints a symbolic address, it normally prints the
6862 closest earlier symbol plus an offset. If that symbol does not uniquely
6863 identify the address (for example, it is a name whose scope is a single
6864 source file), you may need to clarify. One way to do this is with
6865 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6866 you can set @value{GDBN} to print the source file and line number when
6867 it prints a symbolic address:
6870 @item set print symbol-filename on
6871 @cindex source file and line of a symbol
6872 @cindex symbol, source file and line
6873 Tell @value{GDBN} to print the source file name and line number of a
6874 symbol in the symbolic form of an address.
6876 @item set print symbol-filename off
6877 Do not print source file name and line number of a symbol. This is the
6880 @item show print symbol-filename
6881 Show whether or not @value{GDBN} will print the source file name and
6882 line number of a symbol in the symbolic form of an address.
6885 Another situation where it is helpful to show symbol filenames and line
6886 numbers is when disassembling code; @value{GDBN} shows you the line
6887 number and source file that corresponds to each instruction.
6889 Also, you may wish to see the symbolic form only if the address being
6890 printed is reasonably close to the closest earlier symbol:
6893 @item set print max-symbolic-offset @var{max-offset}
6894 @cindex maximum value for offset of closest symbol
6895 Tell @value{GDBN} to only display the symbolic form of an address if the
6896 offset between the closest earlier symbol and the address is less than
6897 @var{max-offset}. The default is 0, which tells @value{GDBN}
6898 to always print the symbolic form of an address if any symbol precedes it.
6900 @item show print max-symbolic-offset
6901 Ask how large the maximum offset is that @value{GDBN} prints in a
6905 @cindex wild pointer, interpreting
6906 @cindex pointer, finding referent
6907 If you have a pointer and you are not sure where it points, try
6908 @samp{set print symbol-filename on}. Then you can determine the name
6909 and source file location of the variable where it points, using
6910 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6911 For example, here @value{GDBN} shows that a variable @code{ptt} points
6912 at another variable @code{t}, defined in @file{hi2.c}:
6915 (@value{GDBP}) set print symbol-filename on
6916 (@value{GDBP}) p/a ptt
6917 $4 = 0xe008 <t in hi2.c>
6921 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6922 does not show the symbol name and filename of the referent, even with
6923 the appropriate @code{set print} options turned on.
6926 Other settings control how different kinds of objects are printed:
6929 @item set print array
6930 @itemx set print array on
6931 @cindex pretty print arrays
6932 Pretty print arrays. This format is more convenient to read,
6933 but uses more space. The default is off.
6935 @item set print array off
6936 Return to compressed format for arrays.
6938 @item show print array
6939 Show whether compressed or pretty format is selected for displaying
6942 @cindex print array indexes
6943 @item set print array-indexes
6944 @itemx set print array-indexes on
6945 Print the index of each element when displaying arrays. May be more
6946 convenient to locate a given element in the array or quickly find the
6947 index of a given element in that printed array. The default is off.
6949 @item set print array-indexes off
6950 Stop printing element indexes when displaying arrays.
6952 @item show print array-indexes
6953 Show whether the index of each element is printed when displaying
6956 @item set print elements @var{number-of-elements}
6957 @cindex number of array elements to print
6958 @cindex limit on number of printed array elements
6959 Set a limit on how many elements of an array @value{GDBN} will print.
6960 If @value{GDBN} is printing a large array, it stops printing after it has
6961 printed the number of elements set by the @code{set print elements} command.
6962 This limit also applies to the display of strings.
6963 When @value{GDBN} starts, this limit is set to 200.
6964 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6966 @item show print elements
6967 Display the number of elements of a large array that @value{GDBN} will print.
6968 If the number is 0, then the printing is unlimited.
6970 @item set print frame-arguments @var{value}
6971 @cindex printing frame argument values
6972 @cindex print all frame argument values
6973 @cindex print frame argument values for scalars only
6974 @cindex do not print frame argument values
6975 This command allows to control how the values of arguments are printed
6976 when the debugger prints a frame (@pxref{Frames}). The possible
6981 The values of all arguments are printed. This is the default.
6984 Print the value of an argument only if it is a scalar. The value of more
6985 complex arguments such as arrays, structures, unions, etc, is replaced
6986 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6989 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6994 None of the argument values are printed. Instead, the value of each argument
6995 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6998 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7003 By default, all argument values are always printed. But this command
7004 can be useful in several cases. For instance, it can be used to reduce
7005 the amount of information printed in each frame, making the backtrace
7006 more readable. Also, this command can be used to improve performance
7007 when displaying Ada frames, because the computation of large arguments
7008 can sometimes be CPU-intensive, especiallly in large applications.
7009 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
7010 avoids this computation, thus speeding up the display of each Ada frame.
7012 @item show print frame-arguments
7013 Show how the value of arguments should be displayed when printing a frame.
7015 @item set print repeats
7016 @cindex repeated array elements
7017 Set the threshold for suppressing display of repeated array
7018 elements. When the number of consecutive identical elements of an
7019 array exceeds the threshold, @value{GDBN} prints the string
7020 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7021 identical repetitions, instead of displaying the identical elements
7022 themselves. Setting the threshold to zero will cause all elements to
7023 be individually printed. The default threshold is 10.
7025 @item show print repeats
7026 Display the current threshold for printing repeated identical
7029 @item set print null-stop
7030 @cindex @sc{null} elements in arrays
7031 Cause @value{GDBN} to stop printing the characters of an array when the first
7032 @sc{null} is encountered. This is useful when large arrays actually
7033 contain only short strings.
7036 @item show print null-stop
7037 Show whether @value{GDBN} stops printing an array on the first
7038 @sc{null} character.
7040 @item set print pretty on
7041 @cindex print structures in indented form
7042 @cindex indentation in structure display
7043 Cause @value{GDBN} to print structures in an indented format with one member
7044 per line, like this:
7059 @item set print pretty off
7060 Cause @value{GDBN} to print structures in a compact format, like this:
7064 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7065 meat = 0x54 "Pork"@}
7070 This is the default format.
7072 @item show print pretty
7073 Show which format @value{GDBN} is using to print structures.
7075 @item set print sevenbit-strings on
7076 @cindex eight-bit characters in strings
7077 @cindex octal escapes in strings
7078 Print using only seven-bit characters; if this option is set,
7079 @value{GDBN} displays any eight-bit characters (in strings or
7080 character values) using the notation @code{\}@var{nnn}. This setting is
7081 best if you are working in English (@sc{ascii}) and you use the
7082 high-order bit of characters as a marker or ``meta'' bit.
7084 @item set print sevenbit-strings off
7085 Print full eight-bit characters. This allows the use of more
7086 international character sets, and is the default.
7088 @item show print sevenbit-strings
7089 Show whether or not @value{GDBN} is printing only seven-bit characters.
7091 @item set print union on
7092 @cindex unions in structures, printing
7093 Tell @value{GDBN} to print unions which are contained in structures
7094 and other unions. This is the default setting.
7096 @item set print union off
7097 Tell @value{GDBN} not to print unions which are contained in
7098 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7101 @item show print union
7102 Ask @value{GDBN} whether or not it will print unions which are contained in
7103 structures and other unions.
7105 For example, given the declarations
7108 typedef enum @{Tree, Bug@} Species;
7109 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7110 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7121 struct thing foo = @{Tree, @{Acorn@}@};
7125 with @code{set print union on} in effect @samp{p foo} would print
7128 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7132 and with @code{set print union off} in effect it would print
7135 $1 = @{it = Tree, form = @{...@}@}
7139 @code{set print union} affects programs written in C-like languages
7145 These settings are of interest when debugging C@t{++} programs:
7148 @cindex demangling C@t{++} names
7149 @item set print demangle
7150 @itemx set print demangle on
7151 Print C@t{++} names in their source form rather than in the encoded
7152 (``mangled'') form passed to the assembler and linker for type-safe
7153 linkage. The default is on.
7155 @item show print demangle
7156 Show whether C@t{++} names are printed in mangled or demangled form.
7158 @item set print asm-demangle
7159 @itemx set print asm-demangle on
7160 Print C@t{++} names in their source form rather than their mangled form, even
7161 in assembler code printouts such as instruction disassemblies.
7164 @item show print asm-demangle
7165 Show whether C@t{++} names in assembly listings are printed in mangled
7168 @cindex C@t{++} symbol decoding style
7169 @cindex symbol decoding style, C@t{++}
7170 @kindex set demangle-style
7171 @item set demangle-style @var{style}
7172 Choose among several encoding schemes used by different compilers to
7173 represent C@t{++} names. The choices for @var{style} are currently:
7177 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7180 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7181 This is the default.
7184 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7187 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7190 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7191 @strong{Warning:} this setting alone is not sufficient to allow
7192 debugging @code{cfront}-generated executables. @value{GDBN} would
7193 require further enhancement to permit that.
7196 If you omit @var{style}, you will see a list of possible formats.
7198 @item show demangle-style
7199 Display the encoding style currently in use for decoding C@t{++} symbols.
7201 @item set print object
7202 @itemx set print object on
7203 @cindex derived type of an object, printing
7204 @cindex display derived types
7205 When displaying a pointer to an object, identify the @emph{actual}
7206 (derived) type of the object rather than the @emph{declared} type, using
7207 the virtual function table.
7209 @item set print object off
7210 Display only the declared type of objects, without reference to the
7211 virtual function table. This is the default setting.
7213 @item show print object
7214 Show whether actual, or declared, object types are displayed.
7216 @item set print static-members
7217 @itemx set print static-members on
7218 @cindex static members of C@t{++} objects
7219 Print static members when displaying a C@t{++} object. The default is on.
7221 @item set print static-members off
7222 Do not print static members when displaying a C@t{++} object.
7224 @item show print static-members
7225 Show whether C@t{++} static members are printed or not.
7227 @item set print pascal_static-members
7228 @itemx set print pascal_static-members on
7229 @cindex static members of Pascal objects
7230 @cindex Pascal objects, static members display
7231 Print static members when displaying a Pascal object. The default is on.
7233 @item set print pascal_static-members off
7234 Do not print static members when displaying a Pascal object.
7236 @item show print pascal_static-members
7237 Show whether Pascal static members are printed or not.
7239 @c These don't work with HP ANSI C++ yet.
7240 @item set print vtbl
7241 @itemx set print vtbl on
7242 @cindex pretty print C@t{++} virtual function tables
7243 @cindex virtual functions (C@t{++}) display
7244 @cindex VTBL display
7245 Pretty print C@t{++} virtual function tables. The default is off.
7246 (The @code{vtbl} commands do not work on programs compiled with the HP
7247 ANSI C@t{++} compiler (@code{aCC}).)
7249 @item set print vtbl off
7250 Do not pretty print C@t{++} virtual function tables.
7252 @item show print vtbl
7253 Show whether C@t{++} virtual function tables are pretty printed, or not.
7257 @section Value History
7259 @cindex value history
7260 @cindex history of values printed by @value{GDBN}
7261 Values printed by the @code{print} command are saved in the @value{GDBN}
7262 @dfn{value history}. This allows you to refer to them in other expressions.
7263 Values are kept until the symbol table is re-read or discarded
7264 (for example with the @code{file} or @code{symbol-file} commands).
7265 When the symbol table changes, the value history is discarded,
7266 since the values may contain pointers back to the types defined in the
7271 @cindex history number
7272 The values printed are given @dfn{history numbers} by which you can
7273 refer to them. These are successive integers starting with one.
7274 @code{print} shows you the history number assigned to a value by
7275 printing @samp{$@var{num} = } before the value; here @var{num} is the
7278 To refer to any previous value, use @samp{$} followed by the value's
7279 history number. The way @code{print} labels its output is designed to
7280 remind you of this. Just @code{$} refers to the most recent value in
7281 the history, and @code{$$} refers to the value before that.
7282 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7283 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7284 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7286 For example, suppose you have just printed a pointer to a structure and
7287 want to see the contents of the structure. It suffices to type
7293 If you have a chain of structures where the component @code{next} points
7294 to the next one, you can print the contents of the next one with this:
7301 You can print successive links in the chain by repeating this
7302 command---which you can do by just typing @key{RET}.
7304 Note that the history records values, not expressions. If the value of
7305 @code{x} is 4 and you type these commands:
7313 then the value recorded in the value history by the @code{print} command
7314 remains 4 even though the value of @code{x} has changed.
7319 Print the last ten values in the value history, with their item numbers.
7320 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7321 values} does not change the history.
7323 @item show values @var{n}
7324 Print ten history values centered on history item number @var{n}.
7327 Print ten history values just after the values last printed. If no more
7328 values are available, @code{show values +} produces no display.
7331 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7332 same effect as @samp{show values +}.
7334 @node Convenience Vars
7335 @section Convenience Variables
7337 @cindex convenience variables
7338 @cindex user-defined variables
7339 @value{GDBN} provides @dfn{convenience variables} that you can use within
7340 @value{GDBN} to hold on to a value and refer to it later. These variables
7341 exist entirely within @value{GDBN}; they are not part of your program, and
7342 setting a convenience variable has no direct effect on further execution
7343 of your program. That is why you can use them freely.
7345 Convenience variables are prefixed with @samp{$}. Any name preceded by
7346 @samp{$} can be used for a convenience variable, unless it is one of
7347 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7348 (Value history references, in contrast, are @emph{numbers} preceded
7349 by @samp{$}. @xref{Value History, ,Value History}.)
7351 You can save a value in a convenience variable with an assignment
7352 expression, just as you would set a variable in your program.
7356 set $foo = *object_ptr
7360 would save in @code{$foo} the value contained in the object pointed to by
7363 Using a convenience variable for the first time creates it, but its
7364 value is @code{void} until you assign a new value. You can alter the
7365 value with another assignment at any time.
7367 Convenience variables have no fixed types. You can assign a convenience
7368 variable any type of value, including structures and arrays, even if
7369 that variable already has a value of a different type. The convenience
7370 variable, when used as an expression, has the type of its current value.
7373 @kindex show convenience
7374 @cindex show all user variables
7375 @item show convenience
7376 Print a list of convenience variables used so far, and their values.
7377 Abbreviated @code{show conv}.
7379 @kindex init-if-undefined
7380 @cindex convenience variables, initializing
7381 @item init-if-undefined $@var{variable} = @var{expression}
7382 Set a convenience variable if it has not already been set. This is useful
7383 for user-defined commands that keep some state. It is similar, in concept,
7384 to using local static variables with initializers in C (except that
7385 convenience variables are global). It can also be used to allow users to
7386 override default values used in a command script.
7388 If the variable is already defined then the expression is not evaluated so
7389 any side-effects do not occur.
7392 One of the ways to use a convenience variable is as a counter to be
7393 incremented or a pointer to be advanced. For example, to print
7394 a field from successive elements of an array of structures:
7398 print bar[$i++]->contents
7402 Repeat that command by typing @key{RET}.
7404 Some convenience variables are created automatically by @value{GDBN} and given
7405 values likely to be useful.
7408 @vindex $_@r{, convenience variable}
7410 The variable @code{$_} is automatically set by the @code{x} command to
7411 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7412 commands which provide a default address for @code{x} to examine also
7413 set @code{$_} to that address; these commands include @code{info line}
7414 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7415 except when set by the @code{x} command, in which case it is a pointer
7416 to the type of @code{$__}.
7418 @vindex $__@r{, convenience variable}
7420 The variable @code{$__} is automatically set by the @code{x} command
7421 to the value found in the last address examined. Its type is chosen
7422 to match the format in which the data was printed.
7425 @vindex $_exitcode@r{, convenience variable}
7426 The variable @code{$_exitcode} is automatically set to the exit code when
7427 the program being debugged terminates.
7430 @vindex $_siginfo@r{, convenience variable}
7431 The variable @code{$_siginfo} is bound to extra signal information
7432 inspection (@pxref{extra signal information}).
7435 On HP-UX systems, if you refer to a function or variable name that
7436 begins with a dollar sign, @value{GDBN} searches for a user or system
7437 name first, before it searches for a convenience variable.
7439 @cindex convenience functions
7440 @value{GDBN} also supplies some @dfn{convenience functions}. These
7441 have a syntax similar to convenience variables. A convenience
7442 function can be used in an expression just like an ordinary function;
7443 however, a convenience function is implemented internally to
7448 @kindex help function
7449 @cindex show all convenience functions
7450 Print a list of all convenience functions.
7457 You can refer to machine register contents, in expressions, as variables
7458 with names starting with @samp{$}. The names of registers are different
7459 for each machine; use @code{info registers} to see the names used on
7463 @kindex info registers
7464 @item info registers
7465 Print the names and values of all registers except floating-point
7466 and vector registers (in the selected stack frame).
7468 @kindex info all-registers
7469 @cindex floating point registers
7470 @item info all-registers
7471 Print the names and values of all registers, including floating-point
7472 and vector registers (in the selected stack frame).
7474 @item info registers @var{regname} @dots{}
7475 Print the @dfn{relativized} value of each specified register @var{regname}.
7476 As discussed in detail below, register values are normally relative to
7477 the selected stack frame. @var{regname} may be any register name valid on
7478 the machine you are using, with or without the initial @samp{$}.
7481 @cindex stack pointer register
7482 @cindex program counter register
7483 @cindex process status register
7484 @cindex frame pointer register
7485 @cindex standard registers
7486 @value{GDBN} has four ``standard'' register names that are available (in
7487 expressions) on most machines---whenever they do not conflict with an
7488 architecture's canonical mnemonics for registers. The register names
7489 @code{$pc} and @code{$sp} are used for the program counter register and
7490 the stack pointer. @code{$fp} is used for a register that contains a
7491 pointer to the current stack frame, and @code{$ps} is used for a
7492 register that contains the processor status. For example,
7493 you could print the program counter in hex with
7500 or print the instruction to be executed next with
7507 or add four to the stack pointer@footnote{This is a way of removing
7508 one word from the stack, on machines where stacks grow downward in
7509 memory (most machines, nowadays). This assumes that the innermost
7510 stack frame is selected; setting @code{$sp} is not allowed when other
7511 stack frames are selected. To pop entire frames off the stack,
7512 regardless of machine architecture, use @code{return};
7513 see @ref{Returning, ,Returning from a Function}.} with
7519 Whenever possible, these four standard register names are available on
7520 your machine even though the machine has different canonical mnemonics,
7521 so long as there is no conflict. The @code{info registers} command
7522 shows the canonical names. For example, on the SPARC, @code{info
7523 registers} displays the processor status register as @code{$psr} but you
7524 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7525 is an alias for the @sc{eflags} register.
7527 @value{GDBN} always considers the contents of an ordinary register as an
7528 integer when the register is examined in this way. Some machines have
7529 special registers which can hold nothing but floating point; these
7530 registers are considered to have floating point values. There is no way
7531 to refer to the contents of an ordinary register as floating point value
7532 (although you can @emph{print} it as a floating point value with
7533 @samp{print/f $@var{regname}}).
7535 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7536 means that the data format in which the register contents are saved by
7537 the operating system is not the same one that your program normally
7538 sees. For example, the registers of the 68881 floating point
7539 coprocessor are always saved in ``extended'' (raw) format, but all C
7540 programs expect to work with ``double'' (virtual) format. In such
7541 cases, @value{GDBN} normally works with the virtual format only (the format
7542 that makes sense for your program), but the @code{info registers} command
7543 prints the data in both formats.
7545 @cindex SSE registers (x86)
7546 @cindex MMX registers (x86)
7547 Some machines have special registers whose contents can be interpreted
7548 in several different ways. For example, modern x86-based machines
7549 have SSE and MMX registers that can hold several values packed
7550 together in several different formats. @value{GDBN} refers to such
7551 registers in @code{struct} notation:
7554 (@value{GDBP}) print $xmm1
7556 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7557 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7558 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7559 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7560 v4_int32 = @{0, 20657912, 11, 13@},
7561 v2_int64 = @{88725056443645952, 55834574859@},
7562 uint128 = 0x0000000d0000000b013b36f800000000
7567 To set values of such registers, you need to tell @value{GDBN} which
7568 view of the register you wish to change, as if you were assigning
7569 value to a @code{struct} member:
7572 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7575 Normally, register values are relative to the selected stack frame
7576 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7577 value that the register would contain if all stack frames farther in
7578 were exited and their saved registers restored. In order to see the
7579 true contents of hardware registers, you must select the innermost
7580 frame (with @samp{frame 0}).
7582 However, @value{GDBN} must deduce where registers are saved, from the machine
7583 code generated by your compiler. If some registers are not saved, or if
7584 @value{GDBN} is unable to locate the saved registers, the selected stack
7585 frame makes no difference.
7587 @node Floating Point Hardware
7588 @section Floating Point Hardware
7589 @cindex floating point
7591 Depending on the configuration, @value{GDBN} may be able to give
7592 you more information about the status of the floating point hardware.
7597 Display hardware-dependent information about the floating
7598 point unit. The exact contents and layout vary depending on the
7599 floating point chip. Currently, @samp{info float} is supported on
7600 the ARM and x86 machines.
7604 @section Vector Unit
7607 Depending on the configuration, @value{GDBN} may be able to give you
7608 more information about the status of the vector unit.
7613 Display information about the vector unit. The exact contents and
7614 layout vary depending on the hardware.
7617 @node OS Information
7618 @section Operating System Auxiliary Information
7619 @cindex OS information
7621 @value{GDBN} provides interfaces to useful OS facilities that can help
7622 you debug your program.
7624 @cindex @code{ptrace} system call
7625 @cindex @code{struct user} contents
7626 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7627 machines), it interfaces with the inferior via the @code{ptrace}
7628 system call. The operating system creates a special sata structure,
7629 called @code{struct user}, for this interface. You can use the
7630 command @code{info udot} to display the contents of this data
7636 Display the contents of the @code{struct user} maintained by the OS
7637 kernel for the program being debugged. @value{GDBN} displays the
7638 contents of @code{struct user} as a list of hex numbers, similar to
7639 the @code{examine} command.
7642 @cindex auxiliary vector
7643 @cindex vector, auxiliary
7644 Some operating systems supply an @dfn{auxiliary vector} to programs at
7645 startup. This is akin to the arguments and environment that you
7646 specify for a program, but contains a system-dependent variety of
7647 binary values that tell system libraries important details about the
7648 hardware, operating system, and process. Each value's purpose is
7649 identified by an integer tag; the meanings are well-known but system-specific.
7650 Depending on the configuration and operating system facilities,
7651 @value{GDBN} may be able to show you this information. For remote
7652 targets, this functionality may further depend on the remote stub's
7653 support of the @samp{qXfer:auxv:read} packet, see
7654 @ref{qXfer auxiliary vector read}.
7659 Display the auxiliary vector of the inferior, which can be either a
7660 live process or a core dump file. @value{GDBN} prints each tag value
7661 numerically, and also shows names and text descriptions for recognized
7662 tags. Some values in the vector are numbers, some bit masks, and some
7663 pointers to strings or other data. @value{GDBN} displays each value in the
7664 most appropriate form for a recognized tag, and in hexadecimal for
7665 an unrecognized tag.
7668 On some targets, @value{GDBN} can access operating-system-specific information
7669 and display it to user, without interpretation. For remote targets,
7670 this functionality depends on the remote stub's support of the
7671 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
7674 @kindex info os processes
7675 @item info os processes
7676 Display the list of processes on the target. For each process,
7677 @value{GDBN} prints the process identifier, the name of the user, and
7678 the command corresponding to the process.
7681 @node Memory Region Attributes
7682 @section Memory Region Attributes
7683 @cindex memory region attributes
7685 @dfn{Memory region attributes} allow you to describe special handling
7686 required by regions of your target's memory. @value{GDBN} uses
7687 attributes to determine whether to allow certain types of memory
7688 accesses; whether to use specific width accesses; and whether to cache
7689 target memory. By default the description of memory regions is
7690 fetched from the target (if the current target supports this), but the
7691 user can override the fetched regions.
7693 Defined memory regions can be individually enabled and disabled. When a
7694 memory region is disabled, @value{GDBN} uses the default attributes when
7695 accessing memory in that region. Similarly, if no memory regions have
7696 been defined, @value{GDBN} uses the default attributes when accessing
7699 When a memory region is defined, it is given a number to identify it;
7700 to enable, disable, or remove a memory region, you specify that number.
7704 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7705 Define a memory region bounded by @var{lower} and @var{upper} with
7706 attributes @var{attributes}@dots{}, and add it to the list of regions
7707 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7708 case: it is treated as the target's maximum memory address.
7709 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7712 Discard any user changes to the memory regions and use target-supplied
7713 regions, if available, or no regions if the target does not support.
7716 @item delete mem @var{nums}@dots{}
7717 Remove memory regions @var{nums}@dots{} from the list of regions
7718 monitored by @value{GDBN}.
7721 @item disable mem @var{nums}@dots{}
7722 Disable monitoring of memory regions @var{nums}@dots{}.
7723 A disabled memory region is not forgotten.
7724 It may be enabled again later.
7727 @item enable mem @var{nums}@dots{}
7728 Enable monitoring of memory regions @var{nums}@dots{}.
7732 Print a table of all defined memory regions, with the following columns
7736 @item Memory Region Number
7737 @item Enabled or Disabled.
7738 Enabled memory regions are marked with @samp{y}.
7739 Disabled memory regions are marked with @samp{n}.
7742 The address defining the inclusive lower bound of the memory region.
7745 The address defining the exclusive upper bound of the memory region.
7748 The list of attributes set for this memory region.
7753 @subsection Attributes
7755 @subsubsection Memory Access Mode
7756 The access mode attributes set whether @value{GDBN} may make read or
7757 write accesses to a memory region.
7759 While these attributes prevent @value{GDBN} from performing invalid
7760 memory accesses, they do nothing to prevent the target system, I/O DMA,
7761 etc.@: from accessing memory.
7765 Memory is read only.
7767 Memory is write only.
7769 Memory is read/write. This is the default.
7772 @subsubsection Memory Access Size
7773 The access size attribute tells @value{GDBN} to use specific sized
7774 accesses in the memory region. Often memory mapped device registers
7775 require specific sized accesses. If no access size attribute is
7776 specified, @value{GDBN} may use accesses of any size.
7780 Use 8 bit memory accesses.
7782 Use 16 bit memory accesses.
7784 Use 32 bit memory accesses.
7786 Use 64 bit memory accesses.
7789 @c @subsubsection Hardware/Software Breakpoints
7790 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7791 @c will use hardware or software breakpoints for the internal breakpoints
7792 @c used by the step, next, finish, until, etc. commands.
7796 @c Always use hardware breakpoints
7797 @c @item swbreak (default)
7800 @subsubsection Data Cache
7801 The data cache attributes set whether @value{GDBN} will cache target
7802 memory. While this generally improves performance by reducing debug
7803 protocol overhead, it can lead to incorrect results because @value{GDBN}
7804 does not know about volatile variables or memory mapped device
7809 Enable @value{GDBN} to cache target memory.
7811 Disable @value{GDBN} from caching target memory. This is the default.
7814 @subsection Memory Access Checking
7815 @value{GDBN} can be instructed to refuse accesses to memory that is
7816 not explicitly described. This can be useful if accessing such
7817 regions has undesired effects for a specific target, or to provide
7818 better error checking. The following commands control this behaviour.
7821 @kindex set mem inaccessible-by-default
7822 @item set mem inaccessible-by-default [on|off]
7823 If @code{on} is specified, make @value{GDBN} treat memory not
7824 explicitly described by the memory ranges as non-existent and refuse accesses
7825 to such memory. The checks are only performed if there's at least one
7826 memory range defined. If @code{off} is specified, make @value{GDBN}
7827 treat the memory not explicitly described by the memory ranges as RAM.
7828 The default value is @code{on}.
7829 @kindex show mem inaccessible-by-default
7830 @item show mem inaccessible-by-default
7831 Show the current handling of accesses to unknown memory.
7835 @c @subsubsection Memory Write Verification
7836 @c The memory write verification attributes set whether @value{GDBN}
7837 @c will re-reads data after each write to verify the write was successful.
7841 @c @item noverify (default)
7844 @node Dump/Restore Files
7845 @section Copy Between Memory and a File
7846 @cindex dump/restore files
7847 @cindex append data to a file
7848 @cindex dump data to a file
7849 @cindex restore data from a file
7851 You can use the commands @code{dump}, @code{append}, and
7852 @code{restore} to copy data between target memory and a file. The
7853 @code{dump} and @code{append} commands write data to a file, and the
7854 @code{restore} command reads data from a file back into the inferior's
7855 memory. Files may be in binary, Motorola S-record, Intel hex, or
7856 Tektronix Hex format; however, @value{GDBN} can only append to binary
7862 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7863 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7864 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7865 or the value of @var{expr}, to @var{filename} in the given format.
7867 The @var{format} parameter may be any one of:
7874 Motorola S-record format.
7876 Tektronix Hex format.
7879 @value{GDBN} uses the same definitions of these formats as the
7880 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7881 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7885 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7886 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7887 Append the contents of memory from @var{start_addr} to @var{end_addr},
7888 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7889 (@value{GDBN} can only append data to files in raw binary form.)
7892 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7893 Restore the contents of file @var{filename} into memory. The
7894 @code{restore} command can automatically recognize any known @sc{bfd}
7895 file format, except for raw binary. To restore a raw binary file you
7896 must specify the optional keyword @code{binary} after the filename.
7898 If @var{bias} is non-zero, its value will be added to the addresses
7899 contained in the file. Binary files always start at address zero, so
7900 they will be restored at address @var{bias}. Other bfd files have
7901 a built-in location; they will be restored at offset @var{bias}
7904 If @var{start} and/or @var{end} are non-zero, then only data between
7905 file offset @var{start} and file offset @var{end} will be restored.
7906 These offsets are relative to the addresses in the file, before
7907 the @var{bias} argument is applied.
7911 @node Core File Generation
7912 @section How to Produce a Core File from Your Program
7913 @cindex dump core from inferior
7915 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7916 image of a running process and its process status (register values
7917 etc.). Its primary use is post-mortem debugging of a program that
7918 crashed while it ran outside a debugger. A program that crashes
7919 automatically produces a core file, unless this feature is disabled by
7920 the user. @xref{Files}, for information on invoking @value{GDBN} in
7921 the post-mortem debugging mode.
7923 Occasionally, you may wish to produce a core file of the program you
7924 are debugging in order to preserve a snapshot of its state.
7925 @value{GDBN} has a special command for that.
7929 @kindex generate-core-file
7930 @item generate-core-file [@var{file}]
7931 @itemx gcore [@var{file}]
7932 Produce a core dump of the inferior process. The optional argument
7933 @var{file} specifies the file name where to put the core dump. If not
7934 specified, the file name defaults to @file{core.@var{pid}}, where
7935 @var{pid} is the inferior process ID.
7937 Note that this command is implemented only for some systems (as of
7938 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7941 @node Character Sets
7942 @section Character Sets
7943 @cindex character sets
7945 @cindex translating between character sets
7946 @cindex host character set
7947 @cindex target character set
7949 If the program you are debugging uses a different character set to
7950 represent characters and strings than the one @value{GDBN} uses itself,
7951 @value{GDBN} can automatically translate between the character sets for
7952 you. The character set @value{GDBN} uses we call the @dfn{host
7953 character set}; the one the inferior program uses we call the
7954 @dfn{target character set}.
7956 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7957 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7958 remote protocol (@pxref{Remote Debugging}) to debug a program
7959 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7960 then the host character set is Latin-1, and the target character set is
7961 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7962 target-charset EBCDIC-US}, then @value{GDBN} translates between
7963 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7964 character and string literals in expressions.
7966 @value{GDBN} has no way to automatically recognize which character set
7967 the inferior program uses; you must tell it, using the @code{set
7968 target-charset} command, described below.
7970 Here are the commands for controlling @value{GDBN}'s character set
7974 @item set target-charset @var{charset}
7975 @kindex set target-charset
7976 Set the current target character set to @var{charset}. If you type
7977 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN}
7978 will list the target character sets it supports.
7980 @item set target-wide-charset @var{charset}
7981 @kindex set target-wide-charset
7982 Set the current target wide character set to @var{charset}. The
7983 target wide character set is the character set used by @code{wchar_t}.
7984 If you type @code{set target-charset} followed by @key{TAB}@key{TAB},
7985 @value{GDBN} will list the target character sets it supports.
7987 @item set host-charset @var{charset}
7988 @kindex set host-charset
7989 Set the current host character set to @var{charset}.
7991 By default, @value{GDBN} uses a host character set appropriate to the
7992 system it is running on; you can override that default using the
7993 @code{set host-charset} command.
7995 @value{GDBN} can only use certain character sets as its host character
7996 set. If you type @code{set target-charset} followed by
7997 @key{TAB}@key{TAB}, @value{GDBN} will list the host character sets it
8000 @item set charset @var{charset}
8002 Set the current host and target character sets to @var{charset}. As
8003 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
8004 @value{GDBN} will list the name of the character sets that can be used
8005 for both host and target.
8009 @kindex show charset
8010 Show the names of the current host and target charsets.
8012 @itemx show host-charset
8013 @kindex show host-charset
8014 Show the name of the current host charset.
8016 @itemx show target-charset
8017 @kindex show target-charset
8018 Show the name of the current target charset.
8022 Here is an example of @value{GDBN}'s character set support in action.
8023 Assume that the following source code has been placed in the file
8024 @file{charset-test.c}:
8030 = @{72, 101, 108, 108, 111, 44, 32, 119,
8031 111, 114, 108, 100, 33, 10, 0@};
8032 char ibm1047_hello[]
8033 = @{200, 133, 147, 147, 150, 107, 64, 166,
8034 150, 153, 147, 132, 90, 37, 0@};
8038 printf ("Hello, world!\n");
8042 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8043 containing the string @samp{Hello, world!} followed by a newline,
8044 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8046 We compile the program, and invoke the debugger on it:
8049 $ gcc -g charset-test.c -o charset-test
8050 $ gdb -nw charset-test
8051 GNU gdb 2001-12-19-cvs
8052 Copyright 2001 Free Software Foundation, Inc.
8057 We can use the @code{show charset} command to see what character sets
8058 @value{GDBN} is currently using to interpret and display characters and
8062 (@value{GDBP}) show charset
8063 The current host and target character set is `ISO-8859-1'.
8067 For the sake of printing this manual, let's use @sc{ascii} as our
8068 initial character set:
8070 (@value{GDBP}) set charset ASCII
8071 (@value{GDBP}) show charset
8072 The current host and target character set is `ASCII'.
8076 Let's assume that @sc{ascii} is indeed the correct character set for our
8077 host system --- in other words, let's assume that if @value{GDBN} prints
8078 characters using the @sc{ascii} character set, our terminal will display
8079 them properly. Since our current target character set is also
8080 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8083 (@value{GDBP}) print ascii_hello
8084 $1 = 0x401698 "Hello, world!\n"
8085 (@value{GDBP}) print ascii_hello[0]
8090 @value{GDBN} uses the target character set for character and string
8091 literals you use in expressions:
8094 (@value{GDBP}) print '+'
8099 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8102 @value{GDBN} relies on the user to tell it which character set the
8103 target program uses. If we print @code{ibm1047_hello} while our target
8104 character set is still @sc{ascii}, we get jibberish:
8107 (@value{GDBP}) print ibm1047_hello
8108 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8109 (@value{GDBP}) print ibm1047_hello[0]
8114 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8115 @value{GDBN} tells us the character sets it supports:
8118 (@value{GDBP}) set target-charset
8119 ASCII EBCDIC-US IBM1047 ISO-8859-1
8120 (@value{GDBP}) set target-charset
8123 We can select @sc{ibm1047} as our target character set, and examine the
8124 program's strings again. Now the @sc{ascii} string is wrong, but
8125 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8126 target character set, @sc{ibm1047}, to the host character set,
8127 @sc{ascii}, and they display correctly:
8130 (@value{GDBP}) set target-charset IBM1047
8131 (@value{GDBP}) show charset
8132 The current host character set is `ASCII'.
8133 The current target character set is `IBM1047'.
8134 (@value{GDBP}) print ascii_hello
8135 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8136 (@value{GDBP}) print ascii_hello[0]
8138 (@value{GDBP}) print ibm1047_hello
8139 $8 = 0x4016a8 "Hello, world!\n"
8140 (@value{GDBP}) print ibm1047_hello[0]
8145 As above, @value{GDBN} uses the target character set for character and
8146 string literals you use in expressions:
8149 (@value{GDBP}) print '+'
8154 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8157 @node Caching Remote Data
8158 @section Caching Data of Remote Targets
8159 @cindex caching data of remote targets
8161 @value{GDBN} can cache data exchanged between the debugger and a
8162 remote target (@pxref{Remote Debugging}). Such caching generally improves
8163 performance, because it reduces the overhead of the remote protocol by
8164 bundling memory reads and writes into large chunks. Unfortunately,
8165 @value{GDBN} does not currently know anything about volatile
8166 registers, and thus data caching will produce incorrect results when
8167 volatile registers are in use.
8170 @kindex set remotecache
8171 @item set remotecache on
8172 @itemx set remotecache off
8173 Set caching state for remote targets. When @code{ON}, use data
8174 caching. By default, this option is @code{OFF}.
8176 @kindex show remotecache
8177 @item show remotecache
8178 Show the current state of data caching for remote targets.
8182 Print the information about the data cache performance. The
8183 information displayed includes: the dcache width and depth; and for
8184 each cache line, how many times it was referenced, and its data and
8185 state (invalid, dirty, valid). This command is useful for debugging
8186 the data cache operation.
8189 @node Searching Memory
8190 @section Search Memory
8191 @cindex searching memory
8193 Memory can be searched for a particular sequence of bytes with the
8194 @code{find} command.
8198 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8199 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8200 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8201 etc. The search begins at address @var{start_addr} and continues for either
8202 @var{len} bytes or through to @var{end_addr} inclusive.
8205 @var{s} and @var{n} are optional parameters.
8206 They may be specified in either order, apart or together.
8209 @item @var{s}, search query size
8210 The size of each search query value.
8216 halfwords (two bytes)
8220 giant words (eight bytes)
8223 All values are interpreted in the current language.
8224 This means, for example, that if the current source language is C/C@t{++}
8225 then searching for the string ``hello'' includes the trailing '\0'.
8227 If the value size is not specified, it is taken from the
8228 value's type in the current language.
8229 This is useful when one wants to specify the search
8230 pattern as a mixture of types.
8231 Note that this means, for example, that in the case of C-like languages
8232 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8233 which is typically four bytes.
8235 @item @var{n}, maximum number of finds
8236 The maximum number of matches to print. The default is to print all finds.
8239 You can use strings as search values. Quote them with double-quotes
8241 The string value is copied into the search pattern byte by byte,
8242 regardless of the endianness of the target and the size specification.
8244 The address of each match found is printed as well as a count of the
8245 number of matches found.
8247 The address of the last value found is stored in convenience variable
8249 A count of the number of matches is stored in @samp{$numfound}.
8251 For example, if stopped at the @code{printf} in this function:
8257 static char hello[] = "hello-hello";
8258 static struct @{ char c; short s; int i; @}
8259 __attribute__ ((packed)) mixed
8260 = @{ 'c', 0x1234, 0x87654321 @};
8261 printf ("%s\n", hello);
8266 you get during debugging:
8269 (gdb) find &hello[0], +sizeof(hello), "hello"
8270 0x804956d <hello.1620+6>
8272 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8273 0x8049567 <hello.1620>
8274 0x804956d <hello.1620+6>
8276 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8277 0x8049567 <hello.1620>
8279 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8280 0x8049560 <mixed.1625>
8282 (gdb) print $numfound
8285 $2 = (void *) 0x8049560
8289 @chapter C Preprocessor Macros
8291 Some languages, such as C and C@t{++}, provide a way to define and invoke
8292 ``preprocessor macros'' which expand into strings of tokens.
8293 @value{GDBN} can evaluate expressions containing macro invocations, show
8294 the result of macro expansion, and show a macro's definition, including
8295 where it was defined.
8297 You may need to compile your program specially to provide @value{GDBN}
8298 with information about preprocessor macros. Most compilers do not
8299 include macros in their debugging information, even when you compile
8300 with the @option{-g} flag. @xref{Compilation}.
8302 A program may define a macro at one point, remove that definition later,
8303 and then provide a different definition after that. Thus, at different
8304 points in the program, a macro may have different definitions, or have
8305 no definition at all. If there is a current stack frame, @value{GDBN}
8306 uses the macros in scope at that frame's source code line. Otherwise,
8307 @value{GDBN} uses the macros in scope at the current listing location;
8310 Whenever @value{GDBN} evaluates an expression, it always expands any
8311 macro invocations present in the expression. @value{GDBN} also provides
8312 the following commands for working with macros explicitly.
8316 @kindex macro expand
8317 @cindex macro expansion, showing the results of preprocessor
8318 @cindex preprocessor macro expansion, showing the results of
8319 @cindex expanding preprocessor macros
8320 @item macro expand @var{expression}
8321 @itemx macro exp @var{expression}
8322 Show the results of expanding all preprocessor macro invocations in
8323 @var{expression}. Since @value{GDBN} simply expands macros, but does
8324 not parse the result, @var{expression} need not be a valid expression;
8325 it can be any string of tokens.
8328 @item macro expand-once @var{expression}
8329 @itemx macro exp1 @var{expression}
8330 @cindex expand macro once
8331 @i{(This command is not yet implemented.)} Show the results of
8332 expanding those preprocessor macro invocations that appear explicitly in
8333 @var{expression}. Macro invocations appearing in that expansion are
8334 left unchanged. This command allows you to see the effect of a
8335 particular macro more clearly, without being confused by further
8336 expansions. Since @value{GDBN} simply expands macros, but does not
8337 parse the result, @var{expression} need not be a valid expression; it
8338 can be any string of tokens.
8341 @cindex macro definition, showing
8342 @cindex definition, showing a macro's
8343 @item info macro @var{macro}
8344 Show the definition of the macro named @var{macro}, and describe the
8345 source location where that definition was established.
8347 @kindex macro define
8348 @cindex user-defined macros
8349 @cindex defining macros interactively
8350 @cindex macros, user-defined
8351 @item macro define @var{macro} @var{replacement-list}
8352 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8353 Introduce a definition for a preprocessor macro named @var{macro},
8354 invocations of which are replaced by the tokens given in
8355 @var{replacement-list}. The first form of this command defines an
8356 ``object-like'' macro, which takes no arguments; the second form
8357 defines a ``function-like'' macro, which takes the arguments given in
8360 A definition introduced by this command is in scope in every
8361 expression evaluated in @value{GDBN}, until it is removed with the
8362 @code{macro undef} command, described below. The definition overrides
8363 all definitions for @var{macro} present in the program being debugged,
8364 as well as any previous user-supplied definition.
8367 @item macro undef @var{macro}
8368 Remove any user-supplied definition for the macro named @var{macro}.
8369 This command only affects definitions provided with the @code{macro
8370 define} command, described above; it cannot remove definitions present
8371 in the program being debugged.
8375 List all the macros defined using the @code{macro define} command.
8378 @cindex macros, example of debugging with
8379 Here is a transcript showing the above commands in action. First, we
8380 show our source files:
8388 #define ADD(x) (M + x)
8393 printf ("Hello, world!\n");
8395 printf ("We're so creative.\n");
8397 printf ("Goodbye, world!\n");
8404 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8405 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8406 compiler includes information about preprocessor macros in the debugging
8410 $ gcc -gdwarf-2 -g3 sample.c -o sample
8414 Now, we start @value{GDBN} on our sample program:
8418 GNU gdb 2002-05-06-cvs
8419 Copyright 2002 Free Software Foundation, Inc.
8420 GDB is free software, @dots{}
8424 We can expand macros and examine their definitions, even when the
8425 program is not running. @value{GDBN} uses the current listing position
8426 to decide which macro definitions are in scope:
8429 (@value{GDBP}) list main
8432 5 #define ADD(x) (M + x)
8437 10 printf ("Hello, world!\n");
8439 12 printf ("We're so creative.\n");
8440 (@value{GDBP}) info macro ADD
8441 Defined at /home/jimb/gdb/macros/play/sample.c:5
8442 #define ADD(x) (M + x)
8443 (@value{GDBP}) info macro Q
8444 Defined at /home/jimb/gdb/macros/play/sample.h:1
8445 included at /home/jimb/gdb/macros/play/sample.c:2
8447 (@value{GDBP}) macro expand ADD(1)
8448 expands to: (42 + 1)
8449 (@value{GDBP}) macro expand-once ADD(1)
8450 expands to: once (M + 1)
8454 In the example above, note that @code{macro expand-once} expands only
8455 the macro invocation explicit in the original text --- the invocation of
8456 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8457 which was introduced by @code{ADD}.
8459 Once the program is running, @value{GDBN} uses the macro definitions in
8460 force at the source line of the current stack frame:
8463 (@value{GDBP}) break main
8464 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8466 Starting program: /home/jimb/gdb/macros/play/sample
8468 Breakpoint 1, main () at sample.c:10
8469 10 printf ("Hello, world!\n");
8473 At line 10, the definition of the macro @code{N} at line 9 is in force:
8476 (@value{GDBP}) info macro N
8477 Defined at /home/jimb/gdb/macros/play/sample.c:9
8479 (@value{GDBP}) macro expand N Q M
8481 (@value{GDBP}) print N Q M
8486 As we step over directives that remove @code{N}'s definition, and then
8487 give it a new definition, @value{GDBN} finds the definition (or lack
8488 thereof) in force at each point:
8493 12 printf ("We're so creative.\n");
8494 (@value{GDBP}) info macro N
8495 The symbol `N' has no definition as a C/C++ preprocessor macro
8496 at /home/jimb/gdb/macros/play/sample.c:12
8499 14 printf ("Goodbye, world!\n");
8500 (@value{GDBP}) info macro N
8501 Defined at /home/jimb/gdb/macros/play/sample.c:13
8503 (@value{GDBP}) macro expand N Q M
8504 expands to: 1729 < 42
8505 (@value{GDBP}) print N Q M
8512 @chapter Tracepoints
8513 @c This chapter is based on the documentation written by Michael
8514 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8517 In some applications, it is not feasible for the debugger to interrupt
8518 the program's execution long enough for the developer to learn
8519 anything helpful about its behavior. If the program's correctness
8520 depends on its real-time behavior, delays introduced by a debugger
8521 might cause the program to change its behavior drastically, or perhaps
8522 fail, even when the code itself is correct. It is useful to be able
8523 to observe the program's behavior without interrupting it.
8525 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8526 specify locations in the program, called @dfn{tracepoints}, and
8527 arbitrary expressions to evaluate when those tracepoints are reached.
8528 Later, using the @code{tfind} command, you can examine the values
8529 those expressions had when the program hit the tracepoints. The
8530 expressions may also denote objects in memory---structures or arrays,
8531 for example---whose values @value{GDBN} should record; while visiting
8532 a particular tracepoint, you may inspect those objects as if they were
8533 in memory at that moment. However, because @value{GDBN} records these
8534 values without interacting with you, it can do so quickly and
8535 unobtrusively, hopefully not disturbing the program's behavior.
8537 The tracepoint facility is currently available only for remote
8538 targets. @xref{Targets}. In addition, your remote target must know
8539 how to collect trace data. This functionality is implemented in the
8540 remote stub; however, none of the stubs distributed with @value{GDBN}
8541 support tracepoints as of this writing. The format of the remote
8542 packets used to implement tracepoints are described in @ref{Tracepoint
8545 This chapter describes the tracepoint commands and features.
8549 * Analyze Collected Data::
8550 * Tracepoint Variables::
8553 @node Set Tracepoints
8554 @section Commands to Set Tracepoints
8556 Before running such a @dfn{trace experiment}, an arbitrary number of
8557 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
8558 tracepoint has a number assigned to it by @value{GDBN}. Like with
8559 breakpoints, tracepoint numbers are successive integers starting from
8560 one. Many of the commands associated with tracepoints take the
8561 tracepoint number as their argument, to identify which tracepoint to
8564 For each tracepoint, you can specify, in advance, some arbitrary set
8565 of data that you want the target to collect in the trace buffer when
8566 it hits that tracepoint. The collected data can include registers,
8567 local variables, or global data. Later, you can use @value{GDBN}
8568 commands to examine the values these data had at the time the
8571 This section describes commands to set tracepoints and associated
8572 conditions and actions.
8575 * Create and Delete Tracepoints::
8576 * Enable and Disable Tracepoints::
8577 * Tracepoint Passcounts::
8578 * Tracepoint Actions::
8579 * Listing Tracepoints::
8580 * Starting and Stopping Trace Experiments::
8583 @node Create and Delete Tracepoints
8584 @subsection Create and Delete Tracepoints
8587 @cindex set tracepoint
8590 The @code{trace} command is very similar to the @code{break} command.
8591 Its argument can be a source line, a function name, or an address in
8592 the target program. @xref{Set Breaks}. The @code{trace} command
8593 defines a tracepoint, which is a point in the target program where the
8594 debugger will briefly stop, collect some data, and then allow the
8595 program to continue. Setting a tracepoint or changing its commands
8596 doesn't take effect until the next @code{tstart} command; thus, you
8597 cannot change the tracepoint attributes once a trace experiment is
8600 Here are some examples of using the @code{trace} command:
8603 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8605 (@value{GDBP}) @b{trace +2} // 2 lines forward
8607 (@value{GDBP}) @b{trace my_function} // first source line of function
8609 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8611 (@value{GDBP}) @b{trace *0x2117c4} // an address
8615 You can abbreviate @code{trace} as @code{tr}.
8618 @cindex last tracepoint number
8619 @cindex recent tracepoint number
8620 @cindex tracepoint number
8621 The convenience variable @code{$tpnum} records the tracepoint number
8622 of the most recently set tracepoint.
8624 @kindex delete tracepoint
8625 @cindex tracepoint deletion
8626 @item delete tracepoint @r{[}@var{num}@r{]}
8627 Permanently delete one or more tracepoints. With no argument, the
8628 default is to delete all tracepoints.
8633 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8635 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8639 You can abbreviate this command as @code{del tr}.
8642 @node Enable and Disable Tracepoints
8643 @subsection Enable and Disable Tracepoints
8646 @kindex disable tracepoint
8647 @item disable tracepoint @r{[}@var{num}@r{]}
8648 Disable tracepoint @var{num}, or all tracepoints if no argument
8649 @var{num} is given. A disabled tracepoint will have no effect during
8650 the next trace experiment, but it is not forgotten. You can re-enable
8651 a disabled tracepoint using the @code{enable tracepoint} command.
8653 @kindex enable tracepoint
8654 @item enable tracepoint @r{[}@var{num}@r{]}
8655 Enable tracepoint @var{num}, or all tracepoints. The enabled
8656 tracepoints will become effective the next time a trace experiment is
8660 @node Tracepoint Passcounts
8661 @subsection Tracepoint Passcounts
8665 @cindex tracepoint pass count
8666 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8667 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8668 automatically stop a trace experiment. If a tracepoint's passcount is
8669 @var{n}, then the trace experiment will be automatically stopped on
8670 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8671 @var{num} is not specified, the @code{passcount} command sets the
8672 passcount of the most recently defined tracepoint. If no passcount is
8673 given, the trace experiment will run until stopped explicitly by the
8679 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8680 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8682 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8683 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8684 (@value{GDBP}) @b{trace foo}
8685 (@value{GDBP}) @b{pass 3}
8686 (@value{GDBP}) @b{trace bar}
8687 (@value{GDBP}) @b{pass 2}
8688 (@value{GDBP}) @b{trace baz}
8689 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8690 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8691 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8692 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8696 @node Tracepoint Actions
8697 @subsection Tracepoint Action Lists
8701 @cindex tracepoint actions
8702 @item actions @r{[}@var{num}@r{]}
8703 This command will prompt for a list of actions to be taken when the
8704 tracepoint is hit. If the tracepoint number @var{num} is not
8705 specified, this command sets the actions for the one that was most
8706 recently defined (so that you can define a tracepoint and then say
8707 @code{actions} without bothering about its number). You specify the
8708 actions themselves on the following lines, one action at a time, and
8709 terminate the actions list with a line containing just @code{end}. So
8710 far, the only defined actions are @code{collect} and
8711 @code{while-stepping}.
8713 @cindex remove actions from a tracepoint
8714 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8715 and follow it immediately with @samp{end}.
8718 (@value{GDBP}) @b{collect @var{data}} // collect some data
8720 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8722 (@value{GDBP}) @b{end} // signals the end of actions.
8725 In the following example, the action list begins with @code{collect}
8726 commands indicating the things to be collected when the tracepoint is
8727 hit. Then, in order to single-step and collect additional data
8728 following the tracepoint, a @code{while-stepping} command is used,
8729 followed by the list of things to be collected while stepping. The
8730 @code{while-stepping} command is terminated by its own separate
8731 @code{end} command. Lastly, the action list is terminated by an
8735 (@value{GDBP}) @b{trace foo}
8736 (@value{GDBP}) @b{actions}
8737 Enter actions for tracepoint 1, one per line:
8746 @kindex collect @r{(tracepoints)}
8747 @item collect @var{expr1}, @var{expr2}, @dots{}
8748 Collect values of the given expressions when the tracepoint is hit.
8749 This command accepts a comma-separated list of any valid expressions.
8750 In addition to global, static, or local variables, the following
8751 special arguments are supported:
8755 collect all registers
8758 collect all function arguments
8761 collect all local variables.
8764 You can give several consecutive @code{collect} commands, each one
8765 with a single argument, or one @code{collect} command with several
8766 arguments separated by commas: the effect is the same.
8768 The command @code{info scope} (@pxref{Symbols, info scope}) is
8769 particularly useful for figuring out what data to collect.
8771 @kindex while-stepping @r{(tracepoints)}
8772 @item while-stepping @var{n}
8773 Perform @var{n} single-step traces after the tracepoint, collecting
8774 new data at each step. The @code{while-stepping} command is
8775 followed by the list of what to collect while stepping (followed by
8776 its own @code{end} command):
8780 > collect $regs, myglobal
8786 You may abbreviate @code{while-stepping} as @code{ws} or
8790 @node Listing Tracepoints
8791 @subsection Listing Tracepoints
8794 @kindex info tracepoints
8796 @cindex information about tracepoints
8797 @item info tracepoints @r{[}@var{num}@r{]}
8798 Display information about the tracepoint @var{num}. If you don't specify
8799 a tracepoint number, displays information about all the tracepoints
8800 defined so far. For each tracepoint, the following information is
8807 whether it is enabled or disabled
8811 its passcount as given by the @code{passcount @var{n}} command
8813 its step count as given by the @code{while-stepping @var{n}} command
8815 where in the source files is the tracepoint set
8817 its action list as given by the @code{actions} command
8821 (@value{GDBP}) @b{info trace}
8822 Num Enb Address PassC StepC What
8823 1 y 0x002117c4 0 0 <gdb_asm>
8824 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8825 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8830 This command can be abbreviated @code{info tp}.
8833 @node Starting and Stopping Trace Experiments
8834 @subsection Starting and Stopping Trace Experiments
8838 @cindex start a new trace experiment
8839 @cindex collected data discarded
8841 This command takes no arguments. It starts the trace experiment, and
8842 begins collecting data. This has the side effect of discarding all
8843 the data collected in the trace buffer during the previous trace
8847 @cindex stop a running trace experiment
8849 This command takes no arguments. It ends the trace experiment, and
8850 stops collecting data.
8852 @strong{Note}: a trace experiment and data collection may stop
8853 automatically if any tracepoint's passcount is reached
8854 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8857 @cindex status of trace data collection
8858 @cindex trace experiment, status of
8860 This command displays the status of the current trace data
8864 Here is an example of the commands we described so far:
8867 (@value{GDBP}) @b{trace gdb_c_test}
8868 (@value{GDBP}) @b{actions}
8869 Enter actions for tracepoint #1, one per line.
8870 > collect $regs,$locals,$args
8875 (@value{GDBP}) @b{tstart}
8876 [time passes @dots{}]
8877 (@value{GDBP}) @b{tstop}
8881 @node Analyze Collected Data
8882 @section Using the Collected Data
8884 After the tracepoint experiment ends, you use @value{GDBN} commands
8885 for examining the trace data. The basic idea is that each tracepoint
8886 collects a trace @dfn{snapshot} every time it is hit and another
8887 snapshot every time it single-steps. All these snapshots are
8888 consecutively numbered from zero and go into a buffer, and you can
8889 examine them later. The way you examine them is to @dfn{focus} on a
8890 specific trace snapshot. When the remote stub is focused on a trace
8891 snapshot, it will respond to all @value{GDBN} requests for memory and
8892 registers by reading from the buffer which belongs to that snapshot,
8893 rather than from @emph{real} memory or registers of the program being
8894 debugged. This means that @strong{all} @value{GDBN} commands
8895 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8896 behave as if we were currently debugging the program state as it was
8897 when the tracepoint occurred. Any requests for data that are not in
8898 the buffer will fail.
8901 * tfind:: How to select a trace snapshot
8902 * tdump:: How to display all data for a snapshot
8903 * save-tracepoints:: How to save tracepoints for a future run
8907 @subsection @code{tfind @var{n}}
8910 @cindex select trace snapshot
8911 @cindex find trace snapshot
8912 The basic command for selecting a trace snapshot from the buffer is
8913 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8914 counting from zero. If no argument @var{n} is given, the next
8915 snapshot is selected.
8917 Here are the various forms of using the @code{tfind} command.
8921 Find the first snapshot in the buffer. This is a synonym for
8922 @code{tfind 0} (since 0 is the number of the first snapshot).
8925 Stop debugging trace snapshots, resume @emph{live} debugging.
8928 Same as @samp{tfind none}.
8931 No argument means find the next trace snapshot.
8934 Find the previous trace snapshot before the current one. This permits
8935 retracing earlier steps.
8937 @item tfind tracepoint @var{num}
8938 Find the next snapshot associated with tracepoint @var{num}. Search
8939 proceeds forward from the last examined trace snapshot. If no
8940 argument @var{num} is given, it means find the next snapshot collected
8941 for the same tracepoint as the current snapshot.
8943 @item tfind pc @var{addr}
8944 Find the next snapshot associated with the value @var{addr} of the
8945 program counter. Search proceeds forward from the last examined trace
8946 snapshot. If no argument @var{addr} is given, it means find the next
8947 snapshot with the same value of PC as the current snapshot.
8949 @item tfind outside @var{addr1}, @var{addr2}
8950 Find the next snapshot whose PC is outside the given range of
8953 @item tfind range @var{addr1}, @var{addr2}
8954 Find the next snapshot whose PC is between @var{addr1} and
8955 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8957 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8958 Find the next snapshot associated with the source line @var{n}. If
8959 the optional argument @var{file} is given, refer to line @var{n} in
8960 that source file. Search proceeds forward from the last examined
8961 trace snapshot. If no argument @var{n} is given, it means find the
8962 next line other than the one currently being examined; thus saying
8963 @code{tfind line} repeatedly can appear to have the same effect as
8964 stepping from line to line in a @emph{live} debugging session.
8967 The default arguments for the @code{tfind} commands are specifically
8968 designed to make it easy to scan through the trace buffer. For
8969 instance, @code{tfind} with no argument selects the next trace
8970 snapshot, and @code{tfind -} with no argument selects the previous
8971 trace snapshot. So, by giving one @code{tfind} command, and then
8972 simply hitting @key{RET} repeatedly you can examine all the trace
8973 snapshots in order. Or, by saying @code{tfind -} and then hitting
8974 @key{RET} repeatedly you can examine the snapshots in reverse order.
8975 The @code{tfind line} command with no argument selects the snapshot
8976 for the next source line executed. The @code{tfind pc} command with
8977 no argument selects the next snapshot with the same program counter
8978 (PC) as the current frame. The @code{tfind tracepoint} command with
8979 no argument selects the next trace snapshot collected by the same
8980 tracepoint as the current one.
8982 In addition to letting you scan through the trace buffer manually,
8983 these commands make it easy to construct @value{GDBN} scripts that
8984 scan through the trace buffer and print out whatever collected data
8985 you are interested in. Thus, if we want to examine the PC, FP, and SP
8986 registers from each trace frame in the buffer, we can say this:
8989 (@value{GDBP}) @b{tfind start}
8990 (@value{GDBP}) @b{while ($trace_frame != -1)}
8991 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8992 $trace_frame, $pc, $sp, $fp
8996 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8997 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8998 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8999 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
9000 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
9001 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
9002 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
9003 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
9004 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
9005 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
9006 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
9009 Or, if we want to examine the variable @code{X} at each source line in
9013 (@value{GDBP}) @b{tfind start}
9014 (@value{GDBP}) @b{while ($trace_frame != -1)}
9015 > printf "Frame %d, X == %d\n", $trace_frame, X
9025 @subsection @code{tdump}
9027 @cindex dump all data collected at tracepoint
9028 @cindex tracepoint data, display
9030 This command takes no arguments. It prints all the data collected at
9031 the current trace snapshot.
9034 (@value{GDBP}) @b{trace 444}
9035 (@value{GDBP}) @b{actions}
9036 Enter actions for tracepoint #2, one per line:
9037 > collect $regs, $locals, $args, gdb_long_test
9040 (@value{GDBP}) @b{tstart}
9042 (@value{GDBP}) @b{tfind line 444}
9043 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
9045 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
9047 (@value{GDBP}) @b{tdump}
9048 Data collected at tracepoint 2, trace frame 1:
9049 d0 0xc4aa0085 -995491707
9053 d4 0x71aea3d 119204413
9058 a1 0x3000668 50333288
9061 a4 0x3000698 50333336
9063 fp 0x30bf3c 0x30bf3c
9064 sp 0x30bf34 0x30bf34
9066 pc 0x20b2c8 0x20b2c8
9070 p = 0x20e5b4 "gdb-test"
9077 gdb_long_test = 17 '\021'
9082 @node save-tracepoints
9083 @subsection @code{save-tracepoints @var{filename}}
9084 @kindex save-tracepoints
9085 @cindex save tracepoints for future sessions
9087 This command saves all current tracepoint definitions together with
9088 their actions and passcounts, into a file @file{@var{filename}}
9089 suitable for use in a later debugging session. To read the saved
9090 tracepoint definitions, use the @code{source} command (@pxref{Command
9093 @node Tracepoint Variables
9094 @section Convenience Variables for Tracepoints
9095 @cindex tracepoint variables
9096 @cindex convenience variables for tracepoints
9099 @vindex $trace_frame
9100 @item (int) $trace_frame
9101 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9102 snapshot is selected.
9105 @item (int) $tracepoint
9106 The tracepoint for the current trace snapshot.
9109 @item (int) $trace_line
9110 The line number for the current trace snapshot.
9113 @item (char []) $trace_file
9114 The source file for the current trace snapshot.
9117 @item (char []) $trace_func
9118 The name of the function containing @code{$tracepoint}.
9121 Note: @code{$trace_file} is not suitable for use in @code{printf},
9122 use @code{output} instead.
9124 Here's a simple example of using these convenience variables for
9125 stepping through all the trace snapshots and printing some of their
9129 (@value{GDBP}) @b{tfind start}
9131 (@value{GDBP}) @b{while $trace_frame != -1}
9132 > output $trace_file
9133 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9139 @chapter Debugging Programs That Use Overlays
9142 If your program is too large to fit completely in your target system's
9143 memory, you can sometimes use @dfn{overlays} to work around this
9144 problem. @value{GDBN} provides some support for debugging programs that
9148 * How Overlays Work:: A general explanation of overlays.
9149 * Overlay Commands:: Managing overlays in @value{GDBN}.
9150 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9151 mapped by asking the inferior.
9152 * Overlay Sample Program:: A sample program using overlays.
9155 @node How Overlays Work
9156 @section How Overlays Work
9157 @cindex mapped overlays
9158 @cindex unmapped overlays
9159 @cindex load address, overlay's
9160 @cindex mapped address
9161 @cindex overlay area
9163 Suppose you have a computer whose instruction address space is only 64
9164 kilobytes long, but which has much more memory which can be accessed by
9165 other means: special instructions, segment registers, or memory
9166 management hardware, for example. Suppose further that you want to
9167 adapt a program which is larger than 64 kilobytes to run on this system.
9169 One solution is to identify modules of your program which are relatively
9170 independent, and need not call each other directly; call these modules
9171 @dfn{overlays}. Separate the overlays from the main program, and place
9172 their machine code in the larger memory. Place your main program in
9173 instruction memory, but leave at least enough space there to hold the
9174 largest overlay as well.
9176 Now, to call a function located in an overlay, you must first copy that
9177 overlay's machine code from the large memory into the space set aside
9178 for it in the instruction memory, and then jump to its entry point
9181 @c NB: In the below the mapped area's size is greater or equal to the
9182 @c size of all overlays. This is intentional to remind the developer
9183 @c that overlays don't necessarily need to be the same size.
9187 Data Instruction Larger
9188 Address Space Address Space Address Space
9189 +-----------+ +-----------+ +-----------+
9191 +-----------+ +-----------+ +-----------+<-- overlay 1
9192 | program | | main | .----| overlay 1 | load address
9193 | variables | | program | | +-----------+
9194 | and heap | | | | | |
9195 +-----------+ | | | +-----------+<-- overlay 2
9196 | | +-----------+ | | | load address
9197 +-----------+ | | | .-| overlay 2 |
9199 mapped --->+-----------+ | | +-----------+
9201 | overlay | <-' | | |
9202 | area | <---' +-----------+<-- overlay 3
9203 | | <---. | | load address
9204 +-----------+ `--| overlay 3 |
9211 @anchor{A code overlay}A code overlay
9215 The diagram (@pxref{A code overlay}) shows a system with separate data
9216 and instruction address spaces. To map an overlay, the program copies
9217 its code from the larger address space to the instruction address space.
9218 Since the overlays shown here all use the same mapped address, only one
9219 may be mapped at a time. For a system with a single address space for
9220 data and instructions, the diagram would be similar, except that the
9221 program variables and heap would share an address space with the main
9222 program and the overlay area.
9224 An overlay loaded into instruction memory and ready for use is called a
9225 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9226 instruction memory. An overlay not present (or only partially present)
9227 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9228 is its address in the larger memory. The mapped address is also called
9229 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9230 called the @dfn{load memory address}, or @dfn{LMA}.
9232 Unfortunately, overlays are not a completely transparent way to adapt a
9233 program to limited instruction memory. They introduce a new set of
9234 global constraints you must keep in mind as you design your program:
9239 Before calling or returning to a function in an overlay, your program
9240 must make sure that overlay is actually mapped. Otherwise, the call or
9241 return will transfer control to the right address, but in the wrong
9242 overlay, and your program will probably crash.
9245 If the process of mapping an overlay is expensive on your system, you
9246 will need to choose your overlays carefully to minimize their effect on
9247 your program's performance.
9250 The executable file you load onto your system must contain each
9251 overlay's instructions, appearing at the overlay's load address, not its
9252 mapped address. However, each overlay's instructions must be relocated
9253 and its symbols defined as if the overlay were at its mapped address.
9254 You can use GNU linker scripts to specify different load and relocation
9255 addresses for pieces of your program; see @ref{Overlay Description,,,
9256 ld.info, Using ld: the GNU linker}.
9259 The procedure for loading executable files onto your system must be able
9260 to load their contents into the larger address space as well as the
9261 instruction and data spaces.
9265 The overlay system described above is rather simple, and could be
9266 improved in many ways:
9271 If your system has suitable bank switch registers or memory management
9272 hardware, you could use those facilities to make an overlay's load area
9273 contents simply appear at their mapped address in instruction space.
9274 This would probably be faster than copying the overlay to its mapped
9275 area in the usual way.
9278 If your overlays are small enough, you could set aside more than one
9279 overlay area, and have more than one overlay mapped at a time.
9282 You can use overlays to manage data, as well as instructions. In
9283 general, data overlays are even less transparent to your design than
9284 code overlays: whereas code overlays only require care when you call or
9285 return to functions, data overlays require care every time you access
9286 the data. Also, if you change the contents of a data overlay, you
9287 must copy its contents back out to its load address before you can copy a
9288 different data overlay into the same mapped area.
9293 @node Overlay Commands
9294 @section Overlay Commands
9296 To use @value{GDBN}'s overlay support, each overlay in your program must
9297 correspond to a separate section of the executable file. The section's
9298 virtual memory address and load memory address must be the overlay's
9299 mapped and load addresses. Identifying overlays with sections allows
9300 @value{GDBN} to determine the appropriate address of a function or
9301 variable, depending on whether the overlay is mapped or not.
9303 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9304 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9309 Disable @value{GDBN}'s overlay support. When overlay support is
9310 disabled, @value{GDBN} assumes that all functions and variables are
9311 always present at their mapped addresses. By default, @value{GDBN}'s
9312 overlay support is disabled.
9314 @item overlay manual
9315 @cindex manual overlay debugging
9316 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9317 relies on you to tell it which overlays are mapped, and which are not,
9318 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9319 commands described below.
9321 @item overlay map-overlay @var{overlay}
9322 @itemx overlay map @var{overlay}
9323 @cindex map an overlay
9324 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9325 be the name of the object file section containing the overlay. When an
9326 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9327 functions and variables at their mapped addresses. @value{GDBN} assumes
9328 that any other overlays whose mapped ranges overlap that of
9329 @var{overlay} are now unmapped.
9331 @item overlay unmap-overlay @var{overlay}
9332 @itemx overlay unmap @var{overlay}
9333 @cindex unmap an overlay
9334 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9335 must be the name of the object file section containing the overlay.
9336 When an overlay is unmapped, @value{GDBN} assumes it can find the
9337 overlay's functions and variables at their load addresses.
9340 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9341 consults a data structure the overlay manager maintains in the inferior
9342 to see which overlays are mapped. For details, see @ref{Automatic
9345 @item overlay load-target
9347 @cindex reloading the overlay table
9348 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9349 re-reads the table @value{GDBN} automatically each time the inferior
9350 stops, so this command should only be necessary if you have changed the
9351 overlay mapping yourself using @value{GDBN}. This command is only
9352 useful when using automatic overlay debugging.
9354 @item overlay list-overlays
9356 @cindex listing mapped overlays
9357 Display a list of the overlays currently mapped, along with their mapped
9358 addresses, load addresses, and sizes.
9362 Normally, when @value{GDBN} prints a code address, it includes the name
9363 of the function the address falls in:
9366 (@value{GDBP}) print main
9367 $3 = @{int ()@} 0x11a0 <main>
9370 When overlay debugging is enabled, @value{GDBN} recognizes code in
9371 unmapped overlays, and prints the names of unmapped functions with
9372 asterisks around them. For example, if @code{foo} is a function in an
9373 unmapped overlay, @value{GDBN} prints it this way:
9376 (@value{GDBP}) overlay list
9377 No sections are mapped.
9378 (@value{GDBP}) print foo
9379 $5 = @{int (int)@} 0x100000 <*foo*>
9382 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9386 (@value{GDBP}) overlay list
9387 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9388 mapped at 0x1016 - 0x104a
9389 (@value{GDBP}) print foo
9390 $6 = @{int (int)@} 0x1016 <foo>
9393 When overlay debugging is enabled, @value{GDBN} can find the correct
9394 address for functions and variables in an overlay, whether or not the
9395 overlay is mapped. This allows most @value{GDBN} commands, like
9396 @code{break} and @code{disassemble}, to work normally, even on unmapped
9397 code. However, @value{GDBN}'s breakpoint support has some limitations:
9401 @cindex breakpoints in overlays
9402 @cindex overlays, setting breakpoints in
9403 You can set breakpoints in functions in unmapped overlays, as long as
9404 @value{GDBN} can write to the overlay at its load address.
9406 @value{GDBN} can not set hardware or simulator-based breakpoints in
9407 unmapped overlays. However, if you set a breakpoint at the end of your
9408 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9409 you are using manual overlay management), @value{GDBN} will re-set its
9410 breakpoints properly.
9414 @node Automatic Overlay Debugging
9415 @section Automatic Overlay Debugging
9416 @cindex automatic overlay debugging
9418 @value{GDBN} can automatically track which overlays are mapped and which
9419 are not, given some simple co-operation from the overlay manager in the
9420 inferior. If you enable automatic overlay debugging with the
9421 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
9422 looks in the inferior's memory for certain variables describing the
9423 current state of the overlays.
9425 Here are the variables your overlay manager must define to support
9426 @value{GDBN}'s automatic overlay debugging:
9430 @item @code{_ovly_table}:
9431 This variable must be an array of the following structures:
9436 /* The overlay's mapped address. */
9439 /* The size of the overlay, in bytes. */
9442 /* The overlay's load address. */
9445 /* Non-zero if the overlay is currently mapped;
9447 unsigned long mapped;
9451 @item @code{_novlys}:
9452 This variable must be a four-byte signed integer, holding the total
9453 number of elements in @code{_ovly_table}.
9457 To decide whether a particular overlay is mapped or not, @value{GDBN}
9458 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9459 @code{lma} members equal the VMA and LMA of the overlay's section in the
9460 executable file. When @value{GDBN} finds a matching entry, it consults
9461 the entry's @code{mapped} member to determine whether the overlay is
9464 In addition, your overlay manager may define a function called
9465 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9466 will silently set a breakpoint there. If the overlay manager then
9467 calls this function whenever it has changed the overlay table, this
9468 will enable @value{GDBN} to accurately keep track of which overlays
9469 are in program memory, and update any breakpoints that may be set
9470 in overlays. This will allow breakpoints to work even if the
9471 overlays are kept in ROM or other non-writable memory while they
9472 are not being executed.
9474 @node Overlay Sample Program
9475 @section Overlay Sample Program
9476 @cindex overlay example program
9478 When linking a program which uses overlays, you must place the overlays
9479 at their load addresses, while relocating them to run at their mapped
9480 addresses. To do this, you must write a linker script (@pxref{Overlay
9481 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9482 since linker scripts are specific to a particular host system, target
9483 architecture, and target memory layout, this manual cannot provide
9484 portable sample code demonstrating @value{GDBN}'s overlay support.
9486 However, the @value{GDBN} source distribution does contain an overlaid
9487 program, with linker scripts for a few systems, as part of its test
9488 suite. The program consists of the following files from
9489 @file{gdb/testsuite/gdb.base}:
9493 The main program file.
9495 A simple overlay manager, used by @file{overlays.c}.
9500 Overlay modules, loaded and used by @file{overlays.c}.
9503 Linker scripts for linking the test program on the @code{d10v-elf}
9504 and @code{m32r-elf} targets.
9507 You can build the test program using the @code{d10v-elf} GCC
9508 cross-compiler like this:
9511 $ d10v-elf-gcc -g -c overlays.c
9512 $ d10v-elf-gcc -g -c ovlymgr.c
9513 $ d10v-elf-gcc -g -c foo.c
9514 $ d10v-elf-gcc -g -c bar.c
9515 $ d10v-elf-gcc -g -c baz.c
9516 $ d10v-elf-gcc -g -c grbx.c
9517 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9518 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9521 The build process is identical for any other architecture, except that
9522 you must substitute the appropriate compiler and linker script for the
9523 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9527 @chapter Using @value{GDBN} with Different Languages
9530 Although programming languages generally have common aspects, they are
9531 rarely expressed in the same manner. For instance, in ANSI C,
9532 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9533 Modula-2, it is accomplished by @code{p^}. Values can also be
9534 represented (and displayed) differently. Hex numbers in C appear as
9535 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9537 @cindex working language
9538 Language-specific information is built into @value{GDBN} for some languages,
9539 allowing you to express operations like the above in your program's
9540 native language, and allowing @value{GDBN} to output values in a manner
9541 consistent with the syntax of your program's native language. The
9542 language you use to build expressions is called the @dfn{working
9546 * Setting:: Switching between source languages
9547 * Show:: Displaying the language
9548 * Checks:: Type and range checks
9549 * Supported Languages:: Supported languages
9550 * Unsupported Languages:: Unsupported languages
9554 @section Switching Between Source Languages
9556 There are two ways to control the working language---either have @value{GDBN}
9557 set it automatically, or select it manually yourself. You can use the
9558 @code{set language} command for either purpose. On startup, @value{GDBN}
9559 defaults to setting the language automatically. The working language is
9560 used to determine how expressions you type are interpreted, how values
9563 In addition to the working language, every source file that
9564 @value{GDBN} knows about has its own working language. For some object
9565 file formats, the compiler might indicate which language a particular
9566 source file is in. However, most of the time @value{GDBN} infers the
9567 language from the name of the file. The language of a source file
9568 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9569 show each frame appropriately for its own language. There is no way to
9570 set the language of a source file from within @value{GDBN}, but you can
9571 set the language associated with a filename extension. @xref{Show, ,
9572 Displaying the Language}.
9574 This is most commonly a problem when you use a program, such
9575 as @code{cfront} or @code{f2c}, that generates C but is written in
9576 another language. In that case, make the
9577 program use @code{#line} directives in its C output; that way
9578 @value{GDBN} will know the correct language of the source code of the original
9579 program, and will display that source code, not the generated C code.
9582 * Filenames:: Filename extensions and languages.
9583 * Manually:: Setting the working language manually
9584 * Automatically:: Having @value{GDBN} infer the source language
9588 @subsection List of Filename Extensions and Languages
9590 If a source file name ends in one of the following extensions, then
9591 @value{GDBN} infers that its language is the one indicated.
9612 Objective-C source file
9619 Modula-2 source file
9623 Assembler source file. This actually behaves almost like C, but
9624 @value{GDBN} does not skip over function prologues when stepping.
9627 In addition, you may set the language associated with a filename
9628 extension. @xref{Show, , Displaying the Language}.
9631 @subsection Setting the Working Language
9633 If you allow @value{GDBN} to set the language automatically,
9634 expressions are interpreted the same way in your debugging session and
9637 @kindex set language
9638 If you wish, you may set the language manually. To do this, issue the
9639 command @samp{set language @var{lang}}, where @var{lang} is the name of
9641 @code{c} or @code{modula-2}.
9642 For a list of the supported languages, type @samp{set language}.
9644 Setting the language manually prevents @value{GDBN} from updating the working
9645 language automatically. This can lead to confusion if you try
9646 to debug a program when the working language is not the same as the
9647 source language, when an expression is acceptable to both
9648 languages---but means different things. For instance, if the current
9649 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9657 might not have the effect you intended. In C, this means to add
9658 @code{b} and @code{c} and place the result in @code{a}. The result
9659 printed would be the value of @code{a}. In Modula-2, this means to compare
9660 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9663 @subsection Having @value{GDBN} Infer the Source Language
9665 To have @value{GDBN} set the working language automatically, use
9666 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9667 then infers the working language. That is, when your program stops in a
9668 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9669 working language to the language recorded for the function in that
9670 frame. If the language for a frame is unknown (that is, if the function
9671 or block corresponding to the frame was defined in a source file that
9672 does not have a recognized extension), the current working language is
9673 not changed, and @value{GDBN} issues a warning.
9675 This may not seem necessary for most programs, which are written
9676 entirely in one source language. However, program modules and libraries
9677 written in one source language can be used by a main program written in
9678 a different source language. Using @samp{set language auto} in this
9679 case frees you from having to set the working language manually.
9682 @section Displaying the Language
9684 The following commands help you find out which language is the
9685 working language, and also what language source files were written in.
9689 @kindex show language
9690 Display the current working language. This is the
9691 language you can use with commands such as @code{print} to
9692 build and compute expressions that may involve variables in your program.
9695 @kindex info frame@r{, show the source language}
9696 Display the source language for this frame. This language becomes the
9697 working language if you use an identifier from this frame.
9698 @xref{Frame Info, ,Information about a Frame}, to identify the other
9699 information listed here.
9702 @kindex info source@r{, show the source language}
9703 Display the source language of this source file.
9704 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9705 information listed here.
9708 In unusual circumstances, you may have source files with extensions
9709 not in the standard list. You can then set the extension associated
9710 with a language explicitly:
9713 @item set extension-language @var{ext} @var{language}
9714 @kindex set extension-language
9715 Tell @value{GDBN} that source files with extension @var{ext} are to be
9716 assumed as written in the source language @var{language}.
9718 @item info extensions
9719 @kindex info extensions
9720 List all the filename extensions and the associated languages.
9724 @section Type and Range Checking
9727 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9728 checking are included, but they do not yet have any effect. This
9729 section documents the intended facilities.
9731 @c FIXME remove warning when type/range code added
9733 Some languages are designed to guard you against making seemingly common
9734 errors through a series of compile- and run-time checks. These include
9735 checking the type of arguments to functions and operators, and making
9736 sure mathematical overflows are caught at run time. Checks such as
9737 these help to ensure a program's correctness once it has been compiled
9738 by eliminating type mismatches, and providing active checks for range
9739 errors when your program is running.
9741 @value{GDBN} can check for conditions like the above if you wish.
9742 Although @value{GDBN} does not check the statements in your program,
9743 it can check expressions entered directly into @value{GDBN} for
9744 evaluation via the @code{print} command, for example. As with the
9745 working language, @value{GDBN} can also decide whether or not to check
9746 automatically based on your program's source language.
9747 @xref{Supported Languages, ,Supported Languages}, for the default
9748 settings of supported languages.
9751 * Type Checking:: An overview of type checking
9752 * Range Checking:: An overview of range checking
9755 @cindex type checking
9756 @cindex checks, type
9758 @subsection An Overview of Type Checking
9760 Some languages, such as Modula-2, are strongly typed, meaning that the
9761 arguments to operators and functions have to be of the correct type,
9762 otherwise an error occurs. These checks prevent type mismatch
9763 errors from ever causing any run-time problems. For example,
9771 The second example fails because the @code{CARDINAL} 1 is not
9772 type-compatible with the @code{REAL} 2.3.
9774 For the expressions you use in @value{GDBN} commands, you can tell the
9775 @value{GDBN} type checker to skip checking;
9776 to treat any mismatches as errors and abandon the expression;
9777 or to only issue warnings when type mismatches occur,
9778 but evaluate the expression anyway. When you choose the last of
9779 these, @value{GDBN} evaluates expressions like the second example above, but
9780 also issues a warning.
9782 Even if you turn type checking off, there may be other reasons
9783 related to type that prevent @value{GDBN} from evaluating an expression.
9784 For instance, @value{GDBN} does not know how to add an @code{int} and
9785 a @code{struct foo}. These particular type errors have nothing to do
9786 with the language in use, and usually arise from expressions, such as
9787 the one described above, which make little sense to evaluate anyway.
9789 Each language defines to what degree it is strict about type. For
9790 instance, both Modula-2 and C require the arguments to arithmetical
9791 operators to be numbers. In C, enumerated types and pointers can be
9792 represented as numbers, so that they are valid arguments to mathematical
9793 operators. @xref{Supported Languages, ,Supported Languages}, for further
9794 details on specific languages.
9796 @value{GDBN} provides some additional commands for controlling the type checker:
9798 @kindex set check type
9799 @kindex show check type
9801 @item set check type auto
9802 Set type checking on or off based on the current working language.
9803 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9806 @item set check type on
9807 @itemx set check type off
9808 Set type checking on or off, overriding the default setting for the
9809 current working language. Issue a warning if the setting does not
9810 match the language default. If any type mismatches occur in
9811 evaluating an expression while type checking is on, @value{GDBN} prints a
9812 message and aborts evaluation of the expression.
9814 @item set check type warn
9815 Cause the type checker to issue warnings, but to always attempt to
9816 evaluate the expression. Evaluating the expression may still
9817 be impossible for other reasons. For example, @value{GDBN} cannot add
9818 numbers and structures.
9821 Show the current setting of the type checker, and whether or not @value{GDBN}
9822 is setting it automatically.
9825 @cindex range checking
9826 @cindex checks, range
9827 @node Range Checking
9828 @subsection An Overview of Range Checking
9830 In some languages (such as Modula-2), it is an error to exceed the
9831 bounds of a type; this is enforced with run-time checks. Such range
9832 checking is meant to ensure program correctness by making sure
9833 computations do not overflow, or indices on an array element access do
9834 not exceed the bounds of the array.
9836 For expressions you use in @value{GDBN} commands, you can tell
9837 @value{GDBN} to treat range errors in one of three ways: ignore them,
9838 always treat them as errors and abandon the expression, or issue
9839 warnings but evaluate the expression anyway.
9841 A range error can result from numerical overflow, from exceeding an
9842 array index bound, or when you type a constant that is not a member
9843 of any type. Some languages, however, do not treat overflows as an
9844 error. In many implementations of C, mathematical overflow causes the
9845 result to ``wrap around'' to lower values---for example, if @var{m} is
9846 the largest integer value, and @var{s} is the smallest, then
9849 @var{m} + 1 @result{} @var{s}
9852 This, too, is specific to individual languages, and in some cases
9853 specific to individual compilers or machines. @xref{Supported Languages, ,
9854 Supported Languages}, for further details on specific languages.
9856 @value{GDBN} provides some additional commands for controlling the range checker:
9858 @kindex set check range
9859 @kindex show check range
9861 @item set check range auto
9862 Set range checking on or off based on the current working language.
9863 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9866 @item set check range on
9867 @itemx set check range off
9868 Set range checking on or off, overriding the default setting for the
9869 current working language. A warning is issued if the setting does not
9870 match the language default. If a range error occurs and range checking is on,
9871 then a message is printed and evaluation of the expression is aborted.
9873 @item set check range warn
9874 Output messages when the @value{GDBN} range checker detects a range error,
9875 but attempt to evaluate the expression anyway. Evaluating the
9876 expression may still be impossible for other reasons, such as accessing
9877 memory that the process does not own (a typical example from many Unix
9881 Show the current setting of the range checker, and whether or not it is
9882 being set automatically by @value{GDBN}.
9885 @node Supported Languages
9886 @section Supported Languages
9888 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9889 assembly, Modula-2, and Ada.
9890 @c This is false ...
9891 Some @value{GDBN} features may be used in expressions regardless of the
9892 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9893 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9894 ,Expressions}) can be used with the constructs of any supported
9897 The following sections detail to what degree each source language is
9898 supported by @value{GDBN}. These sections are not meant to be language
9899 tutorials or references, but serve only as a reference guide to what the
9900 @value{GDBN} expression parser accepts, and what input and output
9901 formats should look like for different languages. There are many good
9902 books written on each of these languages; please look to these for a
9903 language reference or tutorial.
9907 * Objective-C:: Objective-C
9910 * Modula-2:: Modula-2
9915 @subsection C and C@t{++}
9917 @cindex C and C@t{++}
9918 @cindex expressions in C or C@t{++}
9920 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9921 to both languages. Whenever this is the case, we discuss those languages
9925 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9926 @cindex @sc{gnu} C@t{++}
9927 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9928 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9929 effectively, you must compile your C@t{++} programs with a supported
9930 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9931 compiler (@code{aCC}).
9933 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9934 format; if it doesn't work on your system, try the stabs+ debugging
9935 format. You can select those formats explicitly with the @code{g++}
9936 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9937 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9938 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9941 * C Operators:: C and C@t{++} operators
9942 * C Constants:: C and C@t{++} constants
9943 * C Plus Plus Expressions:: C@t{++} expressions
9944 * C Defaults:: Default settings for C and C@t{++}
9945 * C Checks:: C and C@t{++} type and range checks
9946 * Debugging C:: @value{GDBN} and C
9947 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9948 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9952 @subsubsection C and C@t{++} Operators
9954 @cindex C and C@t{++} operators
9956 Operators must be defined on values of specific types. For instance,
9957 @code{+} is defined on numbers, but not on structures. Operators are
9958 often defined on groups of types.
9960 For the purposes of C and C@t{++}, the following definitions hold:
9965 @emph{Integral types} include @code{int} with any of its storage-class
9966 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9969 @emph{Floating-point types} include @code{float}, @code{double}, and
9970 @code{long double} (if supported by the target platform).
9973 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9976 @emph{Scalar types} include all of the above.
9981 The following operators are supported. They are listed here
9982 in order of increasing precedence:
9986 The comma or sequencing operator. Expressions in a comma-separated list
9987 are evaluated from left to right, with the result of the entire
9988 expression being the last expression evaluated.
9991 Assignment. The value of an assignment expression is the value
9992 assigned. Defined on scalar types.
9995 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9996 and translated to @w{@code{@var{a} = @var{a op b}}}.
9997 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9998 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9999 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
10002 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
10003 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
10007 Logical @sc{or}. Defined on integral types.
10010 Logical @sc{and}. Defined on integral types.
10013 Bitwise @sc{or}. Defined on integral types.
10016 Bitwise exclusive-@sc{or}. Defined on integral types.
10019 Bitwise @sc{and}. Defined on integral types.
10022 Equality and inequality. Defined on scalar types. The value of these
10023 expressions is 0 for false and non-zero for true.
10025 @item <@r{, }>@r{, }<=@r{, }>=
10026 Less than, greater than, less than or equal, greater than or equal.
10027 Defined on scalar types. The value of these expressions is 0 for false
10028 and non-zero for true.
10031 left shift, and right shift. Defined on integral types.
10034 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10037 Addition and subtraction. Defined on integral types, floating-point types and
10040 @item *@r{, }/@r{, }%
10041 Multiplication, division, and modulus. Multiplication and division are
10042 defined on integral and floating-point types. Modulus is defined on
10046 Increment and decrement. When appearing before a variable, the
10047 operation is performed before the variable is used in an expression;
10048 when appearing after it, the variable's value is used before the
10049 operation takes place.
10052 Pointer dereferencing. Defined on pointer types. Same precedence as
10056 Address operator. Defined on variables. Same precedence as @code{++}.
10058 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
10059 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
10060 to examine the address
10061 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
10065 Negative. Defined on integral and floating-point types. Same
10066 precedence as @code{++}.
10069 Logical negation. Defined on integral types. Same precedence as
10073 Bitwise complement operator. Defined on integral types. Same precedence as
10078 Structure member, and pointer-to-structure member. For convenience,
10079 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10080 pointer based on the stored type information.
10081 Defined on @code{struct} and @code{union} data.
10084 Dereferences of pointers to members.
10087 Array indexing. @code{@var{a}[@var{i}]} is defined as
10088 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10091 Function parameter list. Same precedence as @code{->}.
10094 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10095 and @code{class} types.
10098 Doubled colons also represent the @value{GDBN} scope operator
10099 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10103 If an operator is redefined in the user code, @value{GDBN} usually
10104 attempts to invoke the redefined version instead of using the operator's
10105 predefined meaning.
10108 @subsubsection C and C@t{++} Constants
10110 @cindex C and C@t{++} constants
10112 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10117 Integer constants are a sequence of digits. Octal constants are
10118 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10119 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10120 @samp{l}, specifying that the constant should be treated as a
10124 Floating point constants are a sequence of digits, followed by a decimal
10125 point, followed by a sequence of digits, and optionally followed by an
10126 exponent. An exponent is of the form:
10127 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10128 sequence of digits. The @samp{+} is optional for positive exponents.
10129 A floating-point constant may also end with a letter @samp{f} or
10130 @samp{F}, specifying that the constant should be treated as being of
10131 the @code{float} (as opposed to the default @code{double}) type; or with
10132 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10136 Enumerated constants consist of enumerated identifiers, or their
10137 integral equivalents.
10140 Character constants are a single character surrounded by single quotes
10141 (@code{'}), or a number---the ordinal value of the corresponding character
10142 (usually its @sc{ascii} value). Within quotes, the single character may
10143 be represented by a letter or by @dfn{escape sequences}, which are of
10144 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10145 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10146 @samp{@var{x}} is a predefined special character---for example,
10147 @samp{\n} for newline.
10150 String constants are a sequence of character constants surrounded by
10151 double quotes (@code{"}). Any valid character constant (as described
10152 above) may appear. Double quotes within the string must be preceded by
10153 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10157 Pointer constants are an integral value. You can also write pointers
10158 to constants using the C operator @samp{&}.
10161 Array constants are comma-separated lists surrounded by braces @samp{@{}
10162 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10163 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10164 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10167 @node C Plus Plus Expressions
10168 @subsubsection C@t{++} Expressions
10170 @cindex expressions in C@t{++}
10171 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10173 @cindex debugging C@t{++} programs
10174 @cindex C@t{++} compilers
10175 @cindex debug formats and C@t{++}
10176 @cindex @value{NGCC} and C@t{++}
10178 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10179 proper compiler and the proper debug format. Currently, @value{GDBN}
10180 works best when debugging C@t{++} code that is compiled with
10181 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10182 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10183 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10184 stabs+ as their default debug format, so you usually don't need to
10185 specify a debug format explicitly. Other compilers and/or debug formats
10186 are likely to work badly or not at all when using @value{GDBN} to debug
10192 @cindex member functions
10194 Member function calls are allowed; you can use expressions like
10197 count = aml->GetOriginal(x, y)
10200 @vindex this@r{, inside C@t{++} member functions}
10201 @cindex namespace in C@t{++}
10203 While a member function is active (in the selected stack frame), your
10204 expressions have the same namespace available as the member function;
10205 that is, @value{GDBN} allows implicit references to the class instance
10206 pointer @code{this} following the same rules as C@t{++}.
10208 @cindex call overloaded functions
10209 @cindex overloaded functions, calling
10210 @cindex type conversions in C@t{++}
10212 You can call overloaded functions; @value{GDBN} resolves the function
10213 call to the right definition, with some restrictions. @value{GDBN} does not
10214 perform overload resolution involving user-defined type conversions,
10215 calls to constructors, or instantiations of templates that do not exist
10216 in the program. It also cannot handle ellipsis argument lists or
10219 It does perform integral conversions and promotions, floating-point
10220 promotions, arithmetic conversions, pointer conversions, conversions of
10221 class objects to base classes, and standard conversions such as those of
10222 functions or arrays to pointers; it requires an exact match on the
10223 number of function arguments.
10225 Overload resolution is always performed, unless you have specified
10226 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10227 ,@value{GDBN} Features for C@t{++}}.
10229 You must specify @code{set overload-resolution off} in order to use an
10230 explicit function signature to call an overloaded function, as in
10232 p 'foo(char,int)'('x', 13)
10235 The @value{GDBN} command-completion facility can simplify this;
10236 see @ref{Completion, ,Command Completion}.
10238 @cindex reference declarations
10240 @value{GDBN} understands variables declared as C@t{++} references; you can use
10241 them in expressions just as you do in C@t{++} source---they are automatically
10244 In the parameter list shown when @value{GDBN} displays a frame, the values of
10245 reference variables are not displayed (unlike other variables); this
10246 avoids clutter, since references are often used for large structures.
10247 The @emph{address} of a reference variable is always shown, unless
10248 you have specified @samp{set print address off}.
10251 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10252 expressions can use it just as expressions in your program do. Since
10253 one scope may be defined in another, you can use @code{::} repeatedly if
10254 necessary, for example in an expression like
10255 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10256 resolving name scope by reference to source files, in both C and C@t{++}
10257 debugging (@pxref{Variables, ,Program Variables}).
10260 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10261 calling virtual functions correctly, printing out virtual bases of
10262 objects, calling functions in a base subobject, casting objects, and
10263 invoking user-defined operators.
10266 @subsubsection C and C@t{++} Defaults
10268 @cindex C and C@t{++} defaults
10270 If you allow @value{GDBN} to set type and range checking automatically, they
10271 both default to @code{off} whenever the working language changes to
10272 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10273 selects the working language.
10275 If you allow @value{GDBN} to set the language automatically, it
10276 recognizes source files whose names end with @file{.c}, @file{.C}, or
10277 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10278 these files, it sets the working language to C or C@t{++}.
10279 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10280 for further details.
10282 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10283 @c unimplemented. If (b) changes, it might make sense to let this node
10284 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10287 @subsubsection C and C@t{++} Type and Range Checks
10289 @cindex C and C@t{++} checks
10291 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10292 is not used. However, if you turn type checking on, @value{GDBN}
10293 considers two variables type equivalent if:
10297 The two variables are structured and have the same structure, union, or
10301 The two variables have the same type name, or types that have been
10302 declared equivalent through @code{typedef}.
10305 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10308 The two @code{struct}, @code{union}, or @code{enum} variables are
10309 declared in the same declaration. (Note: this may not be true for all C
10314 Range checking, if turned on, is done on mathematical operations. Array
10315 indices are not checked, since they are often used to index a pointer
10316 that is not itself an array.
10319 @subsubsection @value{GDBN} and C
10321 The @code{set print union} and @code{show print union} commands apply to
10322 the @code{union} type. When set to @samp{on}, any @code{union} that is
10323 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10324 appears as @samp{@{...@}}.
10326 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10327 with pointers and a memory allocation function. @xref{Expressions,
10330 @node Debugging C Plus Plus
10331 @subsubsection @value{GDBN} Features for C@t{++}
10333 @cindex commands for C@t{++}
10335 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10336 designed specifically for use with C@t{++}. Here is a summary:
10339 @cindex break in overloaded functions
10340 @item @r{breakpoint menus}
10341 When you want a breakpoint in a function whose name is overloaded,
10342 @value{GDBN} has the capability to display a menu of possible breakpoint
10343 locations to help you specify which function definition you want.
10344 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10346 @cindex overloading in C@t{++}
10347 @item rbreak @var{regex}
10348 Setting breakpoints using regular expressions is helpful for setting
10349 breakpoints on overloaded functions that are not members of any special
10351 @xref{Set Breaks, ,Setting Breakpoints}.
10353 @cindex C@t{++} exception handling
10356 Debug C@t{++} exception handling using these commands. @xref{Set
10357 Catchpoints, , Setting Catchpoints}.
10359 @cindex inheritance
10360 @item ptype @var{typename}
10361 Print inheritance relationships as well as other information for type
10363 @xref{Symbols, ,Examining the Symbol Table}.
10365 @cindex C@t{++} symbol display
10366 @item set print demangle
10367 @itemx show print demangle
10368 @itemx set print asm-demangle
10369 @itemx show print asm-demangle
10370 Control whether C@t{++} symbols display in their source form, both when
10371 displaying code as C@t{++} source and when displaying disassemblies.
10372 @xref{Print Settings, ,Print Settings}.
10374 @item set print object
10375 @itemx show print object
10376 Choose whether to print derived (actual) or declared types of objects.
10377 @xref{Print Settings, ,Print Settings}.
10379 @item set print vtbl
10380 @itemx show print vtbl
10381 Control the format for printing virtual function tables.
10382 @xref{Print Settings, ,Print Settings}.
10383 (The @code{vtbl} commands do not work on programs compiled with the HP
10384 ANSI C@t{++} compiler (@code{aCC}).)
10386 @kindex set overload-resolution
10387 @cindex overloaded functions, overload resolution
10388 @item set overload-resolution on
10389 Enable overload resolution for C@t{++} expression evaluation. The default
10390 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10391 and searches for a function whose signature matches the argument types,
10392 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10393 Expressions, ,C@t{++} Expressions}, for details).
10394 If it cannot find a match, it emits a message.
10396 @item set overload-resolution off
10397 Disable overload resolution for C@t{++} expression evaluation. For
10398 overloaded functions that are not class member functions, @value{GDBN}
10399 chooses the first function of the specified name that it finds in the
10400 symbol table, whether or not its arguments are of the correct type. For
10401 overloaded functions that are class member functions, @value{GDBN}
10402 searches for a function whose signature @emph{exactly} matches the
10405 @kindex show overload-resolution
10406 @item show overload-resolution
10407 Show the current setting of overload resolution.
10409 @item @r{Overloaded symbol names}
10410 You can specify a particular definition of an overloaded symbol, using
10411 the same notation that is used to declare such symbols in C@t{++}: type
10412 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10413 also use the @value{GDBN} command-line word completion facilities to list the
10414 available choices, or to finish the type list for you.
10415 @xref{Completion,, Command Completion}, for details on how to do this.
10418 @node Decimal Floating Point
10419 @subsubsection Decimal Floating Point format
10420 @cindex decimal floating point format
10422 @value{GDBN} can examine, set and perform computations with numbers in
10423 decimal floating point format, which in the C language correspond to the
10424 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
10425 specified by the extension to support decimal floating-point arithmetic.
10427 There are two encodings in use, depending on the architecture: BID (Binary
10428 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10429 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10432 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10433 to manipulate decimal floating point numbers, it is not possible to convert
10434 (using a cast, for example) integers wider than 32-bit to decimal float.
10436 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10437 point computations, error checking in decimal float operations ignores
10438 underflow, overflow and divide by zero exceptions.
10440 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10441 to inspect @code{_Decimal128} values stored in floating point registers. See
10442 @ref{PowerPC,,PowerPC} for more details.
10445 @subsection Objective-C
10447 @cindex Objective-C
10448 This section provides information about some commands and command
10449 options that are useful for debugging Objective-C code. See also
10450 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10451 few more commands specific to Objective-C support.
10454 * Method Names in Commands::
10455 * The Print Command with Objective-C::
10458 @node Method Names in Commands
10459 @subsubsection Method Names in Commands
10461 The following commands have been extended to accept Objective-C method
10462 names as line specifications:
10464 @kindex clear@r{, and Objective-C}
10465 @kindex break@r{, and Objective-C}
10466 @kindex info line@r{, and Objective-C}
10467 @kindex jump@r{, and Objective-C}
10468 @kindex list@r{, and Objective-C}
10472 @item @code{info line}
10477 A fully qualified Objective-C method name is specified as
10480 -[@var{Class} @var{methodName}]
10483 where the minus sign is used to indicate an instance method and a
10484 plus sign (not shown) is used to indicate a class method. The class
10485 name @var{Class} and method name @var{methodName} are enclosed in
10486 brackets, similar to the way messages are specified in Objective-C
10487 source code. For example, to set a breakpoint at the @code{create}
10488 instance method of class @code{Fruit} in the program currently being
10492 break -[Fruit create]
10495 To list ten program lines around the @code{initialize} class method,
10499 list +[NSText initialize]
10502 In the current version of @value{GDBN}, the plus or minus sign is
10503 required. In future versions of @value{GDBN}, the plus or minus
10504 sign will be optional, but you can use it to narrow the search. It
10505 is also possible to specify just a method name:
10511 You must specify the complete method name, including any colons. If
10512 your program's source files contain more than one @code{create} method,
10513 you'll be presented with a numbered list of classes that implement that
10514 method. Indicate your choice by number, or type @samp{0} to exit if
10517 As another example, to clear a breakpoint established at the
10518 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10521 clear -[NSWindow makeKeyAndOrderFront:]
10524 @node The Print Command with Objective-C
10525 @subsubsection The Print Command With Objective-C
10526 @cindex Objective-C, print objects
10527 @kindex print-object
10528 @kindex po @r{(@code{print-object})}
10530 The print command has also been extended to accept methods. For example:
10533 print -[@var{object} hash]
10536 @cindex print an Objective-C object description
10537 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10539 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10540 and print the result. Also, an additional command has been added,
10541 @code{print-object} or @code{po} for short, which is meant to print
10542 the description of an object. However, this command may only work
10543 with certain Objective-C libraries that have a particular hook
10544 function, @code{_NSPrintForDebugger}, defined.
10547 @subsection Fortran
10548 @cindex Fortran-specific support in @value{GDBN}
10550 @value{GDBN} can be used to debug programs written in Fortran, but it
10551 currently supports only the features of Fortran 77 language.
10553 @cindex trailing underscore, in Fortran symbols
10554 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10555 among them) append an underscore to the names of variables and
10556 functions. When you debug programs compiled by those compilers, you
10557 will need to refer to variables and functions with a trailing
10561 * Fortran Operators:: Fortran operators and expressions
10562 * Fortran Defaults:: Default settings for Fortran
10563 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10566 @node Fortran Operators
10567 @subsubsection Fortran Operators and Expressions
10569 @cindex Fortran operators and expressions
10571 Operators must be defined on values of specific types. For instance,
10572 @code{+} is defined on numbers, but not on characters or other non-
10573 arithmetic types. Operators are often defined on groups of types.
10577 The exponentiation operator. It raises the first operand to the power
10581 The range operator. Normally used in the form of array(low:high) to
10582 represent a section of array.
10585 The access component operator. Normally used to access elements in derived
10586 types. Also suitable for unions. As unions aren't part of regular Fortran,
10587 this can only happen when accessing a register that uses a gdbarch-defined
10591 @node Fortran Defaults
10592 @subsubsection Fortran Defaults
10594 @cindex Fortran Defaults
10596 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10597 default uses case-insensitive matches for Fortran symbols. You can
10598 change that with the @samp{set case-insensitive} command, see
10599 @ref{Symbols}, for the details.
10601 @node Special Fortran Commands
10602 @subsubsection Special Fortran Commands
10604 @cindex Special Fortran commands
10606 @value{GDBN} has some commands to support Fortran-specific features,
10607 such as displaying common blocks.
10610 @cindex @code{COMMON} blocks, Fortran
10611 @kindex info common
10612 @item info common @r{[}@var{common-name}@r{]}
10613 This command prints the values contained in the Fortran @code{COMMON}
10614 block whose name is @var{common-name}. With no argument, the names of
10615 all @code{COMMON} blocks visible at the current program location are
10622 @cindex Pascal support in @value{GDBN}, limitations
10623 Debugging Pascal programs which use sets, subranges, file variables, or
10624 nested functions does not currently work. @value{GDBN} does not support
10625 entering expressions, printing values, or similar features using Pascal
10628 The Pascal-specific command @code{set print pascal_static-members}
10629 controls whether static members of Pascal objects are displayed.
10630 @xref{Print Settings, pascal_static-members}.
10633 @subsection Modula-2
10635 @cindex Modula-2, @value{GDBN} support
10637 The extensions made to @value{GDBN} to support Modula-2 only support
10638 output from the @sc{gnu} Modula-2 compiler (which is currently being
10639 developed). Other Modula-2 compilers are not currently supported, and
10640 attempting to debug executables produced by them is most likely
10641 to give an error as @value{GDBN} reads in the executable's symbol
10644 @cindex expressions in Modula-2
10646 * M2 Operators:: Built-in operators
10647 * Built-In Func/Proc:: Built-in functions and procedures
10648 * M2 Constants:: Modula-2 constants
10649 * M2 Types:: Modula-2 types
10650 * M2 Defaults:: Default settings for Modula-2
10651 * Deviations:: Deviations from standard Modula-2
10652 * M2 Checks:: Modula-2 type and range checks
10653 * M2 Scope:: The scope operators @code{::} and @code{.}
10654 * GDB/M2:: @value{GDBN} and Modula-2
10658 @subsubsection Operators
10659 @cindex Modula-2 operators
10661 Operators must be defined on values of specific types. For instance,
10662 @code{+} is defined on numbers, but not on structures. Operators are
10663 often defined on groups of types. For the purposes of Modula-2, the
10664 following definitions hold:
10669 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10673 @emph{Character types} consist of @code{CHAR} and its subranges.
10676 @emph{Floating-point types} consist of @code{REAL}.
10679 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10683 @emph{Scalar types} consist of all of the above.
10686 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10689 @emph{Boolean types} consist of @code{BOOLEAN}.
10693 The following operators are supported, and appear in order of
10694 increasing precedence:
10698 Function argument or array index separator.
10701 Assignment. The value of @var{var} @code{:=} @var{value} is
10705 Less than, greater than on integral, floating-point, or enumerated
10709 Less than or equal to, greater than or equal to
10710 on integral, floating-point and enumerated types, or set inclusion on
10711 set types. Same precedence as @code{<}.
10713 @item =@r{, }<>@r{, }#
10714 Equality and two ways of expressing inequality, valid on scalar types.
10715 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10716 available for inequality, since @code{#} conflicts with the script
10720 Set membership. Defined on set types and the types of their members.
10721 Same precedence as @code{<}.
10724 Boolean disjunction. Defined on boolean types.
10727 Boolean conjunction. Defined on boolean types.
10730 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10733 Addition and subtraction on integral and floating-point types, or union
10734 and difference on set types.
10737 Multiplication on integral and floating-point types, or set intersection
10741 Division on floating-point types, or symmetric set difference on set
10742 types. Same precedence as @code{*}.
10745 Integer division and remainder. Defined on integral types. Same
10746 precedence as @code{*}.
10749 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10752 Pointer dereferencing. Defined on pointer types.
10755 Boolean negation. Defined on boolean types. Same precedence as
10759 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10760 precedence as @code{^}.
10763 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10766 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10770 @value{GDBN} and Modula-2 scope operators.
10774 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10775 treats the use of the operator @code{IN}, or the use of operators
10776 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10777 @code{<=}, and @code{>=} on sets as an error.
10781 @node Built-In Func/Proc
10782 @subsubsection Built-in Functions and Procedures
10783 @cindex Modula-2 built-ins
10785 Modula-2 also makes available several built-in procedures and functions.
10786 In describing these, the following metavariables are used:
10791 represents an @code{ARRAY} variable.
10794 represents a @code{CHAR} constant or variable.
10797 represents a variable or constant of integral type.
10800 represents an identifier that belongs to a set. Generally used in the
10801 same function with the metavariable @var{s}. The type of @var{s} should
10802 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10805 represents a variable or constant of integral or floating-point type.
10808 represents a variable or constant of floating-point type.
10814 represents a variable.
10817 represents a variable or constant of one of many types. See the
10818 explanation of the function for details.
10821 All Modula-2 built-in procedures also return a result, described below.
10825 Returns the absolute value of @var{n}.
10828 If @var{c} is a lower case letter, it returns its upper case
10829 equivalent, otherwise it returns its argument.
10832 Returns the character whose ordinal value is @var{i}.
10835 Decrements the value in the variable @var{v} by one. Returns the new value.
10837 @item DEC(@var{v},@var{i})
10838 Decrements the value in the variable @var{v} by @var{i}. Returns the
10841 @item EXCL(@var{m},@var{s})
10842 Removes the element @var{m} from the set @var{s}. Returns the new
10845 @item FLOAT(@var{i})
10846 Returns the floating point equivalent of the integer @var{i}.
10848 @item HIGH(@var{a})
10849 Returns the index of the last member of @var{a}.
10852 Increments the value in the variable @var{v} by one. Returns the new value.
10854 @item INC(@var{v},@var{i})
10855 Increments the value in the variable @var{v} by @var{i}. Returns the
10858 @item INCL(@var{m},@var{s})
10859 Adds the element @var{m} to the set @var{s} if it is not already
10860 there. Returns the new set.
10863 Returns the maximum value of the type @var{t}.
10866 Returns the minimum value of the type @var{t}.
10869 Returns boolean TRUE if @var{i} is an odd number.
10872 Returns the ordinal value of its argument. For example, the ordinal
10873 value of a character is its @sc{ascii} value (on machines supporting the
10874 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10875 integral, character and enumerated types.
10877 @item SIZE(@var{x})
10878 Returns the size of its argument. @var{x} can be a variable or a type.
10880 @item TRUNC(@var{r})
10881 Returns the integral part of @var{r}.
10883 @item TSIZE(@var{x})
10884 Returns the size of its argument. @var{x} can be a variable or a type.
10886 @item VAL(@var{t},@var{i})
10887 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10891 @emph{Warning:} Sets and their operations are not yet supported, so
10892 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10896 @cindex Modula-2 constants
10898 @subsubsection Constants
10900 @value{GDBN} allows you to express the constants of Modula-2 in the following
10906 Integer constants are simply a sequence of digits. When used in an
10907 expression, a constant is interpreted to be type-compatible with the
10908 rest of the expression. Hexadecimal integers are specified by a
10909 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10912 Floating point constants appear as a sequence of digits, followed by a
10913 decimal point and another sequence of digits. An optional exponent can
10914 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10915 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10916 digits of the floating point constant must be valid decimal (base 10)
10920 Character constants consist of a single character enclosed by a pair of
10921 like quotes, either single (@code{'}) or double (@code{"}). They may
10922 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10923 followed by a @samp{C}.
10926 String constants consist of a sequence of characters enclosed by a
10927 pair of like quotes, either single (@code{'}) or double (@code{"}).
10928 Escape sequences in the style of C are also allowed. @xref{C
10929 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10933 Enumerated constants consist of an enumerated identifier.
10936 Boolean constants consist of the identifiers @code{TRUE} and
10940 Pointer constants consist of integral values only.
10943 Set constants are not yet supported.
10947 @subsubsection Modula-2 Types
10948 @cindex Modula-2 types
10950 Currently @value{GDBN} can print the following data types in Modula-2
10951 syntax: array types, record types, set types, pointer types, procedure
10952 types, enumerated types, subrange types and base types. You can also
10953 print the contents of variables declared using these type.
10954 This section gives a number of simple source code examples together with
10955 sample @value{GDBN} sessions.
10957 The first example contains the following section of code:
10966 and you can request @value{GDBN} to interrogate the type and value of
10967 @code{r} and @code{s}.
10970 (@value{GDBP}) print s
10972 (@value{GDBP}) ptype s
10974 (@value{GDBP}) print r
10976 (@value{GDBP}) ptype r
10981 Likewise if your source code declares @code{s} as:
10985 s: SET ['A'..'Z'] ;
10989 then you may query the type of @code{s} by:
10992 (@value{GDBP}) ptype s
10993 type = SET ['A'..'Z']
10997 Note that at present you cannot interactively manipulate set
10998 expressions using the debugger.
11000 The following example shows how you might declare an array in Modula-2
11001 and how you can interact with @value{GDBN} to print its type and contents:
11005 s: ARRAY [-10..10] OF CHAR ;
11009 (@value{GDBP}) ptype s
11010 ARRAY [-10..10] OF CHAR
11013 Note that the array handling is not yet complete and although the type
11014 is printed correctly, expression handling still assumes that all
11015 arrays have a lower bound of zero and not @code{-10} as in the example
11018 Here are some more type related Modula-2 examples:
11022 colour = (blue, red, yellow, green) ;
11023 t = [blue..yellow] ;
11031 The @value{GDBN} interaction shows how you can query the data type
11032 and value of a variable.
11035 (@value{GDBP}) print s
11037 (@value{GDBP}) ptype t
11038 type = [blue..yellow]
11042 In this example a Modula-2 array is declared and its contents
11043 displayed. Observe that the contents are written in the same way as
11044 their @code{C} counterparts.
11048 s: ARRAY [1..5] OF CARDINAL ;
11054 (@value{GDBP}) print s
11055 $1 = @{1, 0, 0, 0, 0@}
11056 (@value{GDBP}) ptype s
11057 type = ARRAY [1..5] OF CARDINAL
11060 The Modula-2 language interface to @value{GDBN} also understands
11061 pointer types as shown in this example:
11065 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11072 and you can request that @value{GDBN} describes the type of @code{s}.
11075 (@value{GDBP}) ptype s
11076 type = POINTER TO ARRAY [1..5] OF CARDINAL
11079 @value{GDBN} handles compound types as we can see in this example.
11080 Here we combine array types, record types, pointer types and subrange
11091 myarray = ARRAY myrange OF CARDINAL ;
11092 myrange = [-2..2] ;
11094 s: POINTER TO ARRAY myrange OF foo ;
11098 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11102 (@value{GDBP}) ptype s
11103 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11106 f3 : ARRAY [-2..2] OF CARDINAL;
11111 @subsubsection Modula-2 Defaults
11112 @cindex Modula-2 defaults
11114 If type and range checking are set automatically by @value{GDBN}, they
11115 both default to @code{on} whenever the working language changes to
11116 Modula-2. This happens regardless of whether you or @value{GDBN}
11117 selected the working language.
11119 If you allow @value{GDBN} to set the language automatically, then entering
11120 code compiled from a file whose name ends with @file{.mod} sets the
11121 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11122 Infer the Source Language}, for further details.
11125 @subsubsection Deviations from Standard Modula-2
11126 @cindex Modula-2, deviations from
11128 A few changes have been made to make Modula-2 programs easier to debug.
11129 This is done primarily via loosening its type strictness:
11133 Unlike in standard Modula-2, pointer constants can be formed by
11134 integers. This allows you to modify pointer variables during
11135 debugging. (In standard Modula-2, the actual address contained in a
11136 pointer variable is hidden from you; it can only be modified
11137 through direct assignment to another pointer variable or expression that
11138 returned a pointer.)
11141 C escape sequences can be used in strings and characters to represent
11142 non-printable characters. @value{GDBN} prints out strings with these
11143 escape sequences embedded. Single non-printable characters are
11144 printed using the @samp{CHR(@var{nnn})} format.
11147 The assignment operator (@code{:=}) returns the value of its right-hand
11151 All built-in procedures both modify @emph{and} return their argument.
11155 @subsubsection Modula-2 Type and Range Checks
11156 @cindex Modula-2 checks
11159 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11162 @c FIXME remove warning when type/range checks added
11164 @value{GDBN} considers two Modula-2 variables type equivalent if:
11168 They are of types that have been declared equivalent via a @code{TYPE
11169 @var{t1} = @var{t2}} statement
11172 They have been declared on the same line. (Note: This is true of the
11173 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11176 As long as type checking is enabled, any attempt to combine variables
11177 whose types are not equivalent is an error.
11179 Range checking is done on all mathematical operations, assignment, array
11180 index bounds, and all built-in functions and procedures.
11183 @subsubsection The Scope Operators @code{::} and @code{.}
11185 @cindex @code{.}, Modula-2 scope operator
11186 @cindex colon, doubled as scope operator
11188 @vindex colon-colon@r{, in Modula-2}
11189 @c Info cannot handle :: but TeX can.
11192 @vindex ::@r{, in Modula-2}
11195 There are a few subtle differences between the Modula-2 scope operator
11196 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11201 @var{module} . @var{id}
11202 @var{scope} :: @var{id}
11206 where @var{scope} is the name of a module or a procedure,
11207 @var{module} the name of a module, and @var{id} is any declared
11208 identifier within your program, except another module.
11210 Using the @code{::} operator makes @value{GDBN} search the scope
11211 specified by @var{scope} for the identifier @var{id}. If it is not
11212 found in the specified scope, then @value{GDBN} searches all scopes
11213 enclosing the one specified by @var{scope}.
11215 Using the @code{.} operator makes @value{GDBN} search the current scope for
11216 the identifier specified by @var{id} that was imported from the
11217 definition module specified by @var{module}. With this operator, it is
11218 an error if the identifier @var{id} was not imported from definition
11219 module @var{module}, or if @var{id} is not an identifier in
11223 @subsubsection @value{GDBN} and Modula-2
11225 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11226 Five subcommands of @code{set print} and @code{show print} apply
11227 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11228 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11229 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11230 analogue in Modula-2.
11232 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11233 with any language, is not useful with Modula-2. Its
11234 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11235 created in Modula-2 as they can in C or C@t{++}. However, because an
11236 address can be specified by an integral constant, the construct
11237 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11239 @cindex @code{#} in Modula-2
11240 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11241 interpreted as the beginning of a comment. Use @code{<>} instead.
11247 The extensions made to @value{GDBN} for Ada only support
11248 output from the @sc{gnu} Ada (GNAT) compiler.
11249 Other Ada compilers are not currently supported, and
11250 attempting to debug executables produced by them is most likely
11254 @cindex expressions in Ada
11256 * Ada Mode Intro:: General remarks on the Ada syntax
11257 and semantics supported by Ada mode
11259 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11260 * Additions to Ada:: Extensions of the Ada expression syntax.
11261 * Stopping Before Main Program:: Debugging the program during elaboration.
11262 * Ada Tasks:: Listing and setting breakpoints in tasks.
11263 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
11264 * Ada Glitches:: Known peculiarities of Ada mode.
11267 @node Ada Mode Intro
11268 @subsubsection Introduction
11269 @cindex Ada mode, general
11271 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11272 syntax, with some extensions.
11273 The philosophy behind the design of this subset is
11277 That @value{GDBN} should provide basic literals and access to operations for
11278 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11279 leaving more sophisticated computations to subprograms written into the
11280 program (which therefore may be called from @value{GDBN}).
11283 That type safety and strict adherence to Ada language restrictions
11284 are not particularly important to the @value{GDBN} user.
11287 That brevity is important to the @value{GDBN} user.
11290 Thus, for brevity, the debugger acts as if all names declared in
11291 user-written packages are directly visible, even if they are not visible
11292 according to Ada rules, thus making it unnecessary to fully qualify most
11293 names with their packages, regardless of context. Where this causes
11294 ambiguity, @value{GDBN} asks the user's intent.
11296 The debugger will start in Ada mode if it detects an Ada main program.
11297 As for other languages, it will enter Ada mode when stopped in a program that
11298 was translated from an Ada source file.
11300 While in Ada mode, you may use `@t{--}' for comments. This is useful
11301 mostly for documenting command files. The standard @value{GDBN} comment
11302 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11303 middle (to allow based literals).
11305 The debugger supports limited overloading. Given a subprogram call in which
11306 the function symbol has multiple definitions, it will use the number of
11307 actual parameters and some information about their types to attempt to narrow
11308 the set of definitions. It also makes very limited use of context, preferring
11309 procedures to functions in the context of the @code{call} command, and
11310 functions to procedures elsewhere.
11312 @node Omissions from Ada
11313 @subsubsection Omissions from Ada
11314 @cindex Ada, omissions from
11316 Here are the notable omissions from the subset:
11320 Only a subset of the attributes are supported:
11324 @t{'First}, @t{'Last}, and @t{'Length}
11325 on array objects (not on types and subtypes).
11328 @t{'Min} and @t{'Max}.
11331 @t{'Pos} and @t{'Val}.
11337 @t{'Range} on array objects (not subtypes), but only as the right
11338 operand of the membership (@code{in}) operator.
11341 @t{'Access}, @t{'Unchecked_Access}, and
11342 @t{'Unrestricted_Access} (a GNAT extension).
11350 @code{Characters.Latin_1} are not available and
11351 concatenation is not implemented. Thus, escape characters in strings are
11352 not currently available.
11355 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11356 equality of representations. They will generally work correctly
11357 for strings and arrays whose elements have integer or enumeration types.
11358 They may not work correctly for arrays whose element
11359 types have user-defined equality, for arrays of real values
11360 (in particular, IEEE-conformant floating point, because of negative
11361 zeroes and NaNs), and for arrays whose elements contain unused bits with
11362 indeterminate values.
11365 The other component-by-component array operations (@code{and}, @code{or},
11366 @code{xor}, @code{not}, and relational tests other than equality)
11367 are not implemented.
11370 @cindex array aggregates (Ada)
11371 @cindex record aggregates (Ada)
11372 @cindex aggregates (Ada)
11373 There is limited support for array and record aggregates. They are
11374 permitted only on the right sides of assignments, as in these examples:
11377 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
11378 (@value{GDBP}) set An_Array := (1, others => 0)
11379 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11380 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11381 (@value{GDBP}) set A_Record := (1, "Peter", True);
11382 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
11386 discriminant's value by assigning an aggregate has an
11387 undefined effect if that discriminant is used within the record.
11388 However, you can first modify discriminants by directly assigning to
11389 them (which normally would not be allowed in Ada), and then performing an
11390 aggregate assignment. For example, given a variable @code{A_Rec}
11391 declared to have a type such as:
11394 type Rec (Len : Small_Integer := 0) is record
11396 Vals : IntArray (1 .. Len);
11400 you can assign a value with a different size of @code{Vals} with two
11404 (@value{GDBP}) set A_Rec.Len := 4
11405 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11408 As this example also illustrates, @value{GDBN} is very loose about the usual
11409 rules concerning aggregates. You may leave out some of the
11410 components of an array or record aggregate (such as the @code{Len}
11411 component in the assignment to @code{A_Rec} above); they will retain their
11412 original values upon assignment. You may freely use dynamic values as
11413 indices in component associations. You may even use overlapping or
11414 redundant component associations, although which component values are
11415 assigned in such cases is not defined.
11418 Calls to dispatching subprograms are not implemented.
11421 The overloading algorithm is much more limited (i.e., less selective)
11422 than that of real Ada. It makes only limited use of the context in
11423 which a subexpression appears to resolve its meaning, and it is much
11424 looser in its rules for allowing type matches. As a result, some
11425 function calls will be ambiguous, and the user will be asked to choose
11426 the proper resolution.
11429 The @code{new} operator is not implemented.
11432 Entry calls are not implemented.
11435 Aside from printing, arithmetic operations on the native VAX floating-point
11436 formats are not supported.
11439 It is not possible to slice a packed array.
11442 The names @code{True} and @code{False}, when not part of a qualified name,
11443 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
11445 Should your program
11446 redefine these names in a package or procedure (at best a dubious practice),
11447 you will have to use fully qualified names to access their new definitions.
11450 @node Additions to Ada
11451 @subsubsection Additions to Ada
11452 @cindex Ada, deviations from
11454 As it does for other languages, @value{GDBN} makes certain generic
11455 extensions to Ada (@pxref{Expressions}):
11459 If the expression @var{E} is a variable residing in memory (typically
11460 a local variable or array element) and @var{N} is a positive integer,
11461 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11462 @var{N}-1 adjacent variables following it in memory as an array. In
11463 Ada, this operator is generally not necessary, since its prime use is
11464 in displaying parts of an array, and slicing will usually do this in
11465 Ada. However, there are occasional uses when debugging programs in
11466 which certain debugging information has been optimized away.
11469 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11470 appears in function or file @var{B}.'' When @var{B} is a file name,
11471 you must typically surround it in single quotes.
11474 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11475 @var{type} that appears at address @var{addr}.''
11478 A name starting with @samp{$} is a convenience variable
11479 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11482 In addition, @value{GDBN} provides a few other shortcuts and outright
11483 additions specific to Ada:
11487 The assignment statement is allowed as an expression, returning
11488 its right-hand operand as its value. Thus, you may enter
11491 (@value{GDBP}) set x := y + 3
11492 (@value{GDBP}) print A(tmp := y + 1)
11496 The semicolon is allowed as an ``operator,'' returning as its value
11497 the value of its right-hand operand.
11498 This allows, for example,
11499 complex conditional breaks:
11502 (@value{GDBP}) break f
11503 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
11507 Rather than use catenation and symbolic character names to introduce special
11508 characters into strings, one may instead use a special bracket notation,
11509 which is also used to print strings. A sequence of characters of the form
11510 @samp{["@var{XX}"]} within a string or character literal denotes the
11511 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11512 sequence of characters @samp{["""]} also denotes a single quotation mark
11513 in strings. For example,
11515 "One line.["0a"]Next line.["0a"]"
11518 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11522 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11523 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11527 (@value{GDBP}) print 'max(x, y)
11531 When printing arrays, @value{GDBN} uses positional notation when the
11532 array has a lower bound of 1, and uses a modified named notation otherwise.
11533 For example, a one-dimensional array of three integers with a lower bound
11534 of 3 might print as
11541 That is, in contrast to valid Ada, only the first component has a @code{=>}
11545 You may abbreviate attributes in expressions with any unique,
11546 multi-character subsequence of
11547 their names (an exact match gets preference).
11548 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11549 in place of @t{a'length}.
11552 @cindex quoting Ada internal identifiers
11553 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11554 to lower case. The GNAT compiler uses upper-case characters for
11555 some of its internal identifiers, which are normally of no interest to users.
11556 For the rare occasions when you actually have to look at them,
11557 enclose them in angle brackets to avoid the lower-case mapping.
11560 (@value{GDBP}) print <JMPBUF_SAVE>[0]
11564 Printing an object of class-wide type or dereferencing an
11565 access-to-class-wide value will display all the components of the object's
11566 specific type (as indicated by its run-time tag). Likewise, component
11567 selection on such a value will operate on the specific type of the
11572 @node Stopping Before Main Program
11573 @subsubsection Stopping at the Very Beginning
11575 @cindex breakpointing Ada elaboration code
11576 It is sometimes necessary to debug the program during elaboration, and
11577 before reaching the main procedure.
11578 As defined in the Ada Reference
11579 Manual, the elaboration code is invoked from a procedure called
11580 @code{adainit}. To run your program up to the beginning of
11581 elaboration, simply use the following two commands:
11582 @code{tbreak adainit} and @code{run}.
11585 @subsubsection Extensions for Ada Tasks
11586 @cindex Ada, tasking
11588 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
11589 @value{GDBN} provides the following task-related commands:
11594 This command shows a list of current Ada tasks, as in the following example:
11601 (@value{GDBP}) info tasks
11602 ID TID P-ID Pri State Name
11603 1 8088000 0 15 Child Activation Wait main_task
11604 2 80a4000 1 15 Accept Statement b
11605 3 809a800 1 15 Child Activation Wait a
11606 * 4 80ae800 3 15 Running c
11611 In this listing, the asterisk before the last task indicates it to be the
11612 task currently being inspected.
11616 Represents @value{GDBN}'s internal task number.
11622 The parent's task ID (@value{GDBN}'s internal task number).
11625 The base priority of the task.
11628 Current state of the task.
11632 The task has been created but has not been activated. It cannot be
11636 The task currently running.
11639 The task is not blocked for any reason known to Ada. (It may be waiting
11640 for a mutex, though.) It is conceptually "executing" in normal mode.
11643 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
11644 that were waiting on terminate alternatives have been awakened and have
11645 terminated themselves.
11647 @item Child Activation Wait
11648 The task is waiting for created tasks to complete activation.
11650 @item Accept Statement
11651 The task is waiting on an accept or selective wait statement.
11653 @item Waiting on entry call
11654 The task is waiting on an entry call.
11656 @item Async Select Wait
11657 The task is waiting to start the abortable part of an asynchronous
11661 The task is waiting on a select statement with only a delay
11664 @item Child Termination Wait
11665 The task is sleeping having completed a master within itself, and is
11666 waiting for the tasks dependent on that master to become terminated or
11667 waiting on a terminate Phase.
11669 @item Wait Child in Term Alt
11670 The task is sleeping waiting for tasks on terminate alternatives to
11671 finish terminating.
11673 @item Accepting RV with @var{taskno}
11674 The task is accepting a rendez-vous with the task @var{taskno}.
11678 Name of the task in the program.
11682 @kindex info task @var{taskno}
11683 @item info task @var{taskno}
11684 This command shows detailled informations on the specified task, as in
11685 the following example:
11690 (@value{GDBP}) info tasks
11691 ID TID P-ID Pri State Name
11692 1 8077880 0 15 Child Activation Wait main_task
11693 * 2 807c468 1 15 Running task_1
11694 (@value{GDBP}) info task 2
11695 Ada Task: 0x807c468
11698 Parent: 1 (main_task)
11704 @kindex task@r{ (Ada)}
11705 @cindex current Ada task ID
11706 This command prints the ID of the current task.
11712 (@value{GDBP}) info tasks
11713 ID TID P-ID Pri State Name
11714 1 8077870 0 15 Child Activation Wait main_task
11715 * 2 807c458 1 15 Running t
11716 (@value{GDBP}) task
11717 [Current task is 2]
11720 @item task @var{taskno}
11721 @cindex Ada task switching
11722 This command is like the @code{thread @var{threadno}}
11723 command (@pxref{Threads}). It switches the context of debugging
11724 from the current task to the given task.
11730 (@value{GDBP}) info tasks
11731 ID TID P-ID Pri State Name
11732 1 8077870 0 15 Child Activation Wait main_task
11733 * 2 807c458 1 15 Running t
11734 (@value{GDBP}) task 1
11735 [Switching to task 1]
11736 #0 0x8067726 in pthread_cond_wait ()
11738 #0 0x8067726 in pthread_cond_wait ()
11739 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
11740 #2 0x805cb63 in system.task_primitives.operations.sleep ()
11741 #3 0x806153e in system.tasking.stages.activate_tasks ()
11742 #4 0x804aacc in un () at un.adb:5
11747 @node Ada Tasks and Core Files
11748 @subsubsection Tasking Support when Debugging Core Files
11749 @cindex Ada tasking and core file debugging
11751 When inspecting a core file, as opposed to debugging a live program,
11752 tasking support may be limited or even unavailable, depending on
11753 the platform being used.
11754 For instance, on x86-linux, the list of tasks is available, but task
11755 switching is not supported. On Tru64, however, task switching will work
11758 On certain platforms, including Tru64, the debugger needs to perform some
11759 memory writes in order to provide Ada tasking support. When inspecting
11760 a core file, this means that the core file must be opened with read-write
11761 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
11762 Under these circumstances, you should make a backup copy of the core
11763 file before inspecting it with @value{GDBN}.
11766 @subsubsection Known Peculiarities of Ada Mode
11767 @cindex Ada, problems
11769 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11770 we know of several problems with and limitations of Ada mode in
11772 some of which will be fixed with planned future releases of the debugger
11773 and the GNU Ada compiler.
11777 Currently, the debugger
11778 has insufficient information to determine whether certain pointers represent
11779 pointers to objects or the objects themselves.
11780 Thus, the user may have to tack an extra @code{.all} after an expression
11781 to get it printed properly.
11784 Static constants that the compiler chooses not to materialize as objects in
11785 storage are invisible to the debugger.
11788 Named parameter associations in function argument lists are ignored (the
11789 argument lists are treated as positional).
11792 Many useful library packages are currently invisible to the debugger.
11795 Fixed-point arithmetic, conversions, input, and output is carried out using
11796 floating-point arithmetic, and may give results that only approximate those on
11800 The GNAT compiler never generates the prefix @code{Standard} for any of
11801 the standard symbols defined by the Ada language. @value{GDBN} knows about
11802 this: it will strip the prefix from names when you use it, and will never
11803 look for a name you have so qualified among local symbols, nor match against
11804 symbols in other packages or subprograms. If you have
11805 defined entities anywhere in your program other than parameters and
11806 local variables whose simple names match names in @code{Standard},
11807 GNAT's lack of qualification here can cause confusion. When this happens,
11808 you can usually resolve the confusion
11809 by qualifying the problematic names with package
11810 @code{Standard} explicitly.
11813 @node Unsupported Languages
11814 @section Unsupported Languages
11816 @cindex unsupported languages
11817 @cindex minimal language
11818 In addition to the other fully-supported programming languages,
11819 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11820 It does not represent a real programming language, but provides a set
11821 of capabilities close to what the C or assembly languages provide.
11822 This should allow most simple operations to be performed while debugging
11823 an application that uses a language currently not supported by @value{GDBN}.
11825 If the language is set to @code{auto}, @value{GDBN} will automatically
11826 select this language if the current frame corresponds to an unsupported
11830 @chapter Examining the Symbol Table
11832 The commands described in this chapter allow you to inquire about the
11833 symbols (names of variables, functions and types) defined in your
11834 program. This information is inherent in the text of your program and
11835 does not change as your program executes. @value{GDBN} finds it in your
11836 program's symbol table, in the file indicated when you started @value{GDBN}
11837 (@pxref{File Options, ,Choosing Files}), or by one of the
11838 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11840 @cindex symbol names
11841 @cindex names of symbols
11842 @cindex quoting names
11843 Occasionally, you may need to refer to symbols that contain unusual
11844 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11845 most frequent case is in referring to static variables in other
11846 source files (@pxref{Variables,,Program Variables}). File names
11847 are recorded in object files as debugging symbols, but @value{GDBN} would
11848 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11849 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11850 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11857 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11860 @cindex case-insensitive symbol names
11861 @cindex case sensitivity in symbol names
11862 @kindex set case-sensitive
11863 @item set case-sensitive on
11864 @itemx set case-sensitive off
11865 @itemx set case-sensitive auto
11866 Normally, when @value{GDBN} looks up symbols, it matches their names
11867 with case sensitivity determined by the current source language.
11868 Occasionally, you may wish to control that. The command @code{set
11869 case-sensitive} lets you do that by specifying @code{on} for
11870 case-sensitive matches or @code{off} for case-insensitive ones. If
11871 you specify @code{auto}, case sensitivity is reset to the default
11872 suitable for the source language. The default is case-sensitive
11873 matches for all languages except for Fortran, for which the default is
11874 case-insensitive matches.
11876 @kindex show case-sensitive
11877 @item show case-sensitive
11878 This command shows the current setting of case sensitivity for symbols
11881 @kindex info address
11882 @cindex address of a symbol
11883 @item info address @var{symbol}
11884 Describe where the data for @var{symbol} is stored. For a register
11885 variable, this says which register it is kept in. For a non-register
11886 local variable, this prints the stack-frame offset at which the variable
11889 Note the contrast with @samp{print &@var{symbol}}, which does not work
11890 at all for a register variable, and for a stack local variable prints
11891 the exact address of the current instantiation of the variable.
11893 @kindex info symbol
11894 @cindex symbol from address
11895 @cindex closest symbol and offset for an address
11896 @item info symbol @var{addr}
11897 Print the name of a symbol which is stored at the address @var{addr}.
11898 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11899 nearest symbol and an offset from it:
11902 (@value{GDBP}) info symbol 0x54320
11903 _initialize_vx + 396 in section .text
11907 This is the opposite of the @code{info address} command. You can use
11908 it to find out the name of a variable or a function given its address.
11910 For dynamically linked executables, the name of executable or shared
11911 library containing the symbol is also printed:
11914 (@value{GDBP}) info symbol 0x400225
11915 _start + 5 in section .text of /tmp/a.out
11916 (@value{GDBP}) info symbol 0x2aaaac2811cf
11917 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
11921 @item whatis [@var{arg}]
11922 Print the data type of @var{arg}, which can be either an expression or
11923 a data type. With no argument, print the data type of @code{$}, the
11924 last value in the value history. If @var{arg} is an expression, it is
11925 not actually evaluated, and any side-effecting operations (such as
11926 assignments or function calls) inside it do not take place. If
11927 @var{arg} is a type name, it may be the name of a type or typedef, or
11928 for C code it may have the form @samp{class @var{class-name}},
11929 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11930 @samp{enum @var{enum-tag}}.
11931 @xref{Expressions, ,Expressions}.
11934 @item ptype [@var{arg}]
11935 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11936 detailed description of the type, instead of just the name of the type.
11937 @xref{Expressions, ,Expressions}.
11939 For example, for this variable declaration:
11942 struct complex @{double real; double imag;@} v;
11946 the two commands give this output:
11950 (@value{GDBP}) whatis v
11951 type = struct complex
11952 (@value{GDBP}) ptype v
11953 type = struct complex @{
11961 As with @code{whatis}, using @code{ptype} without an argument refers to
11962 the type of @code{$}, the last value in the value history.
11964 @cindex incomplete type
11965 Sometimes, programs use opaque data types or incomplete specifications
11966 of complex data structure. If the debug information included in the
11967 program does not allow @value{GDBN} to display a full declaration of
11968 the data type, it will say @samp{<incomplete type>}. For example,
11969 given these declarations:
11973 struct foo *fooptr;
11977 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11980 (@value{GDBP}) ptype foo
11981 $1 = <incomplete type>
11985 ``Incomplete type'' is C terminology for data types that are not
11986 completely specified.
11989 @item info types @var{regexp}
11991 Print a brief description of all types whose names match the regular
11992 expression @var{regexp} (or all types in your program, if you supply
11993 no argument). Each complete typename is matched as though it were a
11994 complete line; thus, @samp{i type value} gives information on all
11995 types in your program whose names include the string @code{value}, but
11996 @samp{i type ^value$} gives information only on types whose complete
11997 name is @code{value}.
11999 This command differs from @code{ptype} in two ways: first, like
12000 @code{whatis}, it does not print a detailed description; second, it
12001 lists all source files where a type is defined.
12004 @cindex local variables
12005 @item info scope @var{location}
12006 List all the variables local to a particular scope. This command
12007 accepts a @var{location} argument---a function name, a source line, or
12008 an address preceded by a @samp{*}, and prints all the variables local
12009 to the scope defined by that location. (@xref{Specify Location}, for
12010 details about supported forms of @var{location}.) For example:
12013 (@value{GDBP}) @b{info scope command_line_handler}
12014 Scope for command_line_handler:
12015 Symbol rl is an argument at stack/frame offset 8, length 4.
12016 Symbol linebuffer is in static storage at address 0x150a18, length 4.
12017 Symbol linelength is in static storage at address 0x150a1c, length 4.
12018 Symbol p is a local variable in register $esi, length 4.
12019 Symbol p1 is a local variable in register $ebx, length 4.
12020 Symbol nline is a local variable in register $edx, length 4.
12021 Symbol repeat is a local variable at frame offset -8, length 4.
12025 This command is especially useful for determining what data to collect
12026 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
12029 @kindex info source
12031 Show information about the current source file---that is, the source file for
12032 the function containing the current point of execution:
12035 the name of the source file, and the directory containing it,
12037 the directory it was compiled in,
12039 its length, in lines,
12041 which programming language it is written in,
12043 whether the executable includes debugging information for that file, and
12044 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
12046 whether the debugging information includes information about
12047 preprocessor macros.
12051 @kindex info sources
12053 Print the names of all source files in your program for which there is
12054 debugging information, organized into two lists: files whose symbols
12055 have already been read, and files whose symbols will be read when needed.
12057 @kindex info functions
12058 @item info functions
12059 Print the names and data types of all defined functions.
12061 @item info functions @var{regexp}
12062 Print the names and data types of all defined functions
12063 whose names contain a match for regular expression @var{regexp}.
12064 Thus, @samp{info fun step} finds all functions whose names
12065 include @code{step}; @samp{info fun ^step} finds those whose names
12066 start with @code{step}. If a function name contains characters
12067 that conflict with the regular expression language (e.g.@:
12068 @samp{operator*()}), they may be quoted with a backslash.
12070 @kindex info variables
12071 @item info variables
12072 Print the names and data types of all variables that are declared
12073 outside of functions (i.e.@: excluding local variables).
12075 @item info variables @var{regexp}
12076 Print the names and data types of all variables (except for local
12077 variables) whose names contain a match for regular expression
12080 @kindex info classes
12081 @cindex Objective-C, classes and selectors
12083 @itemx info classes @var{regexp}
12084 Display all Objective-C classes in your program, or
12085 (with the @var{regexp} argument) all those matching a particular regular
12088 @kindex info selectors
12089 @item info selectors
12090 @itemx info selectors @var{regexp}
12091 Display all Objective-C selectors in your program, or
12092 (with the @var{regexp} argument) all those matching a particular regular
12096 This was never implemented.
12097 @kindex info methods
12099 @itemx info methods @var{regexp}
12100 The @code{info methods} command permits the user to examine all defined
12101 methods within C@t{++} program, or (with the @var{regexp} argument) a
12102 specific set of methods found in the various C@t{++} classes. Many
12103 C@t{++} classes provide a large number of methods. Thus, the output
12104 from the @code{ptype} command can be overwhelming and hard to use. The
12105 @code{info-methods} command filters the methods, printing only those
12106 which match the regular-expression @var{regexp}.
12109 @cindex reloading symbols
12110 Some systems allow individual object files that make up your program to
12111 be replaced without stopping and restarting your program. For example,
12112 in VxWorks you can simply recompile a defective object file and keep on
12113 running. If you are running on one of these systems, you can allow
12114 @value{GDBN} to reload the symbols for automatically relinked modules:
12117 @kindex set symbol-reloading
12118 @item set symbol-reloading on
12119 Replace symbol definitions for the corresponding source file when an
12120 object file with a particular name is seen again.
12122 @item set symbol-reloading off
12123 Do not replace symbol definitions when encountering object files of the
12124 same name more than once. This is the default state; if you are not
12125 running on a system that permits automatic relinking of modules, you
12126 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12127 may discard symbols when linking large programs, that may contain
12128 several modules (from different directories or libraries) with the same
12131 @kindex show symbol-reloading
12132 @item show symbol-reloading
12133 Show the current @code{on} or @code{off} setting.
12136 @cindex opaque data types
12137 @kindex set opaque-type-resolution
12138 @item set opaque-type-resolution on
12139 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12140 declared as a pointer to a @code{struct}, @code{class}, or
12141 @code{union}---for example, @code{struct MyType *}---that is used in one
12142 source file although the full declaration of @code{struct MyType} is in
12143 another source file. The default is on.
12145 A change in the setting of this subcommand will not take effect until
12146 the next time symbols for a file are loaded.
12148 @item set opaque-type-resolution off
12149 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12150 is printed as follows:
12152 @{<no data fields>@}
12155 @kindex show opaque-type-resolution
12156 @item show opaque-type-resolution
12157 Show whether opaque types are resolved or not.
12159 @kindex set print symbol-loading
12160 @cindex print messages when symbols are loaded
12161 @item set print symbol-loading
12162 @itemx set print symbol-loading on
12163 @itemx set print symbol-loading off
12164 The @code{set print symbol-loading} command allows you to enable or
12165 disable printing of messages when @value{GDBN} loads symbols.
12166 By default, these messages will be printed, and normally this is what
12167 you want. Disabling these messages is useful when debugging applications
12168 with lots of shared libraries where the quantity of output can be more
12169 annoying than useful.
12171 @kindex show print symbol-loading
12172 @item show print symbol-loading
12173 Show whether messages will be printed when @value{GDBN} loads symbols.
12175 @kindex maint print symbols
12176 @cindex symbol dump
12177 @kindex maint print psymbols
12178 @cindex partial symbol dump
12179 @item maint print symbols @var{filename}
12180 @itemx maint print psymbols @var{filename}
12181 @itemx maint print msymbols @var{filename}
12182 Write a dump of debugging symbol data into the file @var{filename}.
12183 These commands are used to debug the @value{GDBN} symbol-reading code. Only
12184 symbols with debugging data are included. If you use @samp{maint print
12185 symbols}, @value{GDBN} includes all the symbols for which it has already
12186 collected full details: that is, @var{filename} reflects symbols for
12187 only those files whose symbols @value{GDBN} has read. You can use the
12188 command @code{info sources} to find out which files these are. If you
12189 use @samp{maint print psymbols} instead, the dump shows information about
12190 symbols that @value{GDBN} only knows partially---that is, symbols defined in
12191 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
12192 @samp{maint print msymbols} dumps just the minimal symbol information
12193 required for each object file from which @value{GDBN} has read some symbols.
12194 @xref{Files, ,Commands to Specify Files}, for a discussion of how
12195 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
12197 @kindex maint info symtabs
12198 @kindex maint info psymtabs
12199 @cindex listing @value{GDBN}'s internal symbol tables
12200 @cindex symbol tables, listing @value{GDBN}'s internal
12201 @cindex full symbol tables, listing @value{GDBN}'s internal
12202 @cindex partial symbol tables, listing @value{GDBN}'s internal
12203 @item maint info symtabs @r{[} @var{regexp} @r{]}
12204 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
12206 List the @code{struct symtab} or @code{struct partial_symtab}
12207 structures whose names match @var{regexp}. If @var{regexp} is not
12208 given, list them all. The output includes expressions which you can
12209 copy into a @value{GDBN} debugging this one to examine a particular
12210 structure in more detail. For example:
12213 (@value{GDBP}) maint info psymtabs dwarf2read
12214 @{ objfile /home/gnu/build/gdb/gdb
12215 ((struct objfile *) 0x82e69d0)
12216 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
12217 ((struct partial_symtab *) 0x8474b10)
12220 text addresses 0x814d3c8 -- 0x8158074
12221 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
12222 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
12223 dependencies (none)
12226 (@value{GDBP}) maint info symtabs
12230 We see that there is one partial symbol table whose filename contains
12231 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
12232 and we see that @value{GDBN} has not read in any symtabs yet at all.
12233 If we set a breakpoint on a function, that will cause @value{GDBN} to
12234 read the symtab for the compilation unit containing that function:
12237 (@value{GDBP}) break dwarf2_psymtab_to_symtab
12238 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
12240 (@value{GDBP}) maint info symtabs
12241 @{ objfile /home/gnu/build/gdb/gdb
12242 ((struct objfile *) 0x82e69d0)
12243 @{ symtab /home/gnu/src/gdb/dwarf2read.c
12244 ((struct symtab *) 0x86c1f38)
12247 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
12248 linetable ((struct linetable *) 0x8370fa0)
12249 debugformat DWARF 2
12258 @chapter Altering Execution
12260 Once you think you have found an error in your program, you might want to
12261 find out for certain whether correcting the apparent error would lead to
12262 correct results in the rest of the run. You can find the answer by
12263 experiment, using the @value{GDBN} features for altering execution of the
12266 For example, you can store new values into variables or memory
12267 locations, give your program a signal, restart it at a different
12268 address, or even return prematurely from a function.
12271 * Assignment:: Assignment to variables
12272 * Jumping:: Continuing at a different address
12273 * Signaling:: Giving your program a signal
12274 * Returning:: Returning from a function
12275 * Calling:: Calling your program's functions
12276 * Patching:: Patching your program
12280 @section Assignment to Variables
12283 @cindex setting variables
12284 To alter the value of a variable, evaluate an assignment expression.
12285 @xref{Expressions, ,Expressions}. For example,
12292 stores the value 4 into the variable @code{x}, and then prints the
12293 value of the assignment expression (which is 4).
12294 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
12295 information on operators in supported languages.
12297 @kindex set variable
12298 @cindex variables, setting
12299 If you are not interested in seeing the value of the assignment, use the
12300 @code{set} command instead of the @code{print} command. @code{set} is
12301 really the same as @code{print} except that the expression's value is
12302 not printed and is not put in the value history (@pxref{Value History,
12303 ,Value History}). The expression is evaluated only for its effects.
12305 If the beginning of the argument string of the @code{set} command
12306 appears identical to a @code{set} subcommand, use the @code{set
12307 variable} command instead of just @code{set}. This command is identical
12308 to @code{set} except for its lack of subcommands. For example, if your
12309 program has a variable @code{width}, you get an error if you try to set
12310 a new value with just @samp{set width=13}, because @value{GDBN} has the
12311 command @code{set width}:
12314 (@value{GDBP}) whatis width
12316 (@value{GDBP}) p width
12318 (@value{GDBP}) set width=47
12319 Invalid syntax in expression.
12323 The invalid expression, of course, is @samp{=47}. In
12324 order to actually set the program's variable @code{width}, use
12327 (@value{GDBP}) set var width=47
12330 Because the @code{set} command has many subcommands that can conflict
12331 with the names of program variables, it is a good idea to use the
12332 @code{set variable} command instead of just @code{set}. For example, if
12333 your program has a variable @code{g}, you run into problems if you try
12334 to set a new value with just @samp{set g=4}, because @value{GDBN} has
12335 the command @code{set gnutarget}, abbreviated @code{set g}:
12339 (@value{GDBP}) whatis g
12343 (@value{GDBP}) set g=4
12347 The program being debugged has been started already.
12348 Start it from the beginning? (y or n) y
12349 Starting program: /home/smith/cc_progs/a.out
12350 "/home/smith/cc_progs/a.out": can't open to read symbols:
12351 Invalid bfd target.
12352 (@value{GDBP}) show g
12353 The current BFD target is "=4".
12358 The program variable @code{g} did not change, and you silently set the
12359 @code{gnutarget} to an invalid value. In order to set the variable
12363 (@value{GDBP}) set var g=4
12366 @value{GDBN} allows more implicit conversions in assignments than C; you can
12367 freely store an integer value into a pointer variable or vice versa,
12368 and you can convert any structure to any other structure that is the
12369 same length or shorter.
12370 @comment FIXME: how do structs align/pad in these conversions?
12371 @comment /doc@cygnus.com 18dec1990
12373 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12374 construct to generate a value of specified type at a specified address
12375 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12376 to memory location @code{0x83040} as an integer (which implies a certain size
12377 and representation in memory), and
12380 set @{int@}0x83040 = 4
12384 stores the value 4 into that memory location.
12387 @section Continuing at a Different Address
12389 Ordinarily, when you continue your program, you do so at the place where
12390 it stopped, with the @code{continue} command. You can instead continue at
12391 an address of your own choosing, with the following commands:
12395 @item jump @var{linespec}
12396 @itemx jump @var{location}
12397 Resume execution at line @var{linespec} or at address given by
12398 @var{location}. Execution stops again immediately if there is a
12399 breakpoint there. @xref{Specify Location}, for a description of the
12400 different forms of @var{linespec} and @var{location}. It is common
12401 practice to use the @code{tbreak} command in conjunction with
12402 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
12404 The @code{jump} command does not change the current stack frame, or
12405 the stack pointer, or the contents of any memory location or any
12406 register other than the program counter. If line @var{linespec} is in
12407 a different function from the one currently executing, the results may
12408 be bizarre if the two functions expect different patterns of arguments or
12409 of local variables. For this reason, the @code{jump} command requests
12410 confirmation if the specified line is not in the function currently
12411 executing. However, even bizarre results are predictable if you are
12412 well acquainted with the machine-language code of your program.
12415 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
12416 On many systems, you can get much the same effect as the @code{jump}
12417 command by storing a new value into the register @code{$pc}. The
12418 difference is that this does not start your program running; it only
12419 changes the address of where it @emph{will} run when you continue. For
12427 makes the next @code{continue} command or stepping command execute at
12428 address @code{0x485}, rather than at the address where your program stopped.
12429 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12431 The most common occasion to use the @code{jump} command is to back
12432 up---perhaps with more breakpoints set---over a portion of a program
12433 that has already executed, in order to examine its execution in more
12438 @section Giving your Program a Signal
12439 @cindex deliver a signal to a program
12443 @item signal @var{signal}
12444 Resume execution where your program stopped, but immediately give it the
12445 signal @var{signal}. @var{signal} can be the name or the number of a
12446 signal. For example, on many systems @code{signal 2} and @code{signal
12447 SIGINT} are both ways of sending an interrupt signal.
12449 Alternatively, if @var{signal} is zero, continue execution without
12450 giving a signal. This is useful when your program stopped on account of
12451 a signal and would ordinary see the signal when resumed with the
12452 @code{continue} command; @samp{signal 0} causes it to resume without a
12455 @code{signal} does not repeat when you press @key{RET} a second time
12456 after executing the command.
12460 Invoking the @code{signal} command is not the same as invoking the
12461 @code{kill} utility from the shell. Sending a signal with @code{kill}
12462 causes @value{GDBN} to decide what to do with the signal depending on
12463 the signal handling tables (@pxref{Signals}). The @code{signal} command
12464 passes the signal directly to your program.
12468 @section Returning from a Function
12471 @cindex returning from a function
12474 @itemx return @var{expression}
12475 You can cancel execution of a function call with the @code{return}
12476 command. If you give an
12477 @var{expression} argument, its value is used as the function's return
12481 When you use @code{return}, @value{GDBN} discards the selected stack frame
12482 (and all frames within it). You can think of this as making the
12483 discarded frame return prematurely. If you wish to specify a value to
12484 be returned, give that value as the argument to @code{return}.
12486 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12487 Frame}), and any other frames inside of it, leaving its caller as the
12488 innermost remaining frame. That frame becomes selected. The
12489 specified value is stored in the registers used for returning values
12492 The @code{return} command does not resume execution; it leaves the
12493 program stopped in the state that would exist if the function had just
12494 returned. In contrast, the @code{finish} command (@pxref{Continuing
12495 and Stepping, ,Continuing and Stepping}) resumes execution until the
12496 selected stack frame returns naturally.
12498 @value{GDBN} needs to know how the @var{expression} argument should be set for
12499 the inferior. The concrete registers assignment depends on the OS ABI and the
12500 type being returned by the selected stack frame. For example it is common for
12501 OS ABI to return floating point values in FPU registers while integer values in
12502 CPU registers. Still some ABIs return even floating point values in CPU
12503 registers. Larger integer widths (such as @code{long long int}) also have
12504 specific placement rules. @value{GDBN} already knows the OS ABI from its
12505 current target so it needs to find out also the type being returned to make the
12506 assignment into the right register(s).
12508 Normally, the selected stack frame has debug info. @value{GDBN} will always
12509 use the debug info instead of the implicit type of @var{expression} when the
12510 debug info is available. For example, if you type @kbd{return -1}, and the
12511 function in the current stack frame is declared to return a @code{long long
12512 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
12513 into a @code{long long int}:
12516 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
12518 (@value{GDBP}) return -1
12519 Make func return now? (y or n) y
12520 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
12521 43 printf ("result=%lld\n", func ());
12525 However, if the selected stack frame does not have a debug info, e.g., if the
12526 function was compiled without debug info, @value{GDBN} has to find out the type
12527 to return from user. Specifying a different type by mistake may set the value
12528 in different inferior registers than the caller code expects. For example,
12529 typing @kbd{return -1} with its implicit type @code{int} would set only a part
12530 of a @code{long long int} result for a debug info less function (on 32-bit
12531 architectures). Therefore the user is required to specify the return type by
12532 an appropriate cast explicitly:
12535 Breakpoint 2, 0x0040050b in func ()
12536 (@value{GDBP}) return -1
12537 Return value type not available for selected stack frame.
12538 Please use an explicit cast of the value to return.
12539 (@value{GDBP}) return (long long int) -1
12540 Make selected stack frame return now? (y or n) y
12541 #0 0x00400526 in main ()
12546 @section Calling Program Functions
12549 @cindex calling functions
12550 @cindex inferior functions, calling
12551 @item print @var{expr}
12552 Evaluate the expression @var{expr} and display the resulting value.
12553 @var{expr} may include calls to functions in the program being
12557 @item call @var{expr}
12558 Evaluate the expression @var{expr} without displaying @code{void}
12561 You can use this variant of the @code{print} command if you want to
12562 execute a function from your program that does not return anything
12563 (a.k.a.@: @dfn{a void function}), but without cluttering the output
12564 with @code{void} returned values that @value{GDBN} will otherwise
12565 print. If the result is not void, it is printed and saved in the
12569 It is possible for the function you call via the @code{print} or
12570 @code{call} command to generate a signal (e.g., if there's a bug in
12571 the function, or if you passed it incorrect arguments). What happens
12572 in that case is controlled by the @code{set unwindonsignal} command.
12575 @item set unwindonsignal
12576 @kindex set unwindonsignal
12577 @cindex unwind stack in called functions
12578 @cindex call dummy stack unwinding
12579 Set unwinding of the stack if a signal is received while in a function
12580 that @value{GDBN} called in the program being debugged. If set to on,
12581 @value{GDBN} unwinds the stack it created for the call and restores
12582 the context to what it was before the call. If set to off (the
12583 default), @value{GDBN} stops in the frame where the signal was
12586 @item show unwindonsignal
12587 @kindex show unwindonsignal
12588 Show the current setting of stack unwinding in the functions called by
12592 @cindex weak alias functions
12593 Sometimes, a function you wish to call is actually a @dfn{weak alias}
12594 for another function. In such case, @value{GDBN} might not pick up
12595 the type information, including the types of the function arguments,
12596 which causes @value{GDBN} to call the inferior function incorrectly.
12597 As a result, the called function will function erroneously and may
12598 even crash. A solution to that is to use the name of the aliased
12602 @section Patching Programs
12604 @cindex patching binaries
12605 @cindex writing into executables
12606 @cindex writing into corefiles
12608 By default, @value{GDBN} opens the file containing your program's
12609 executable code (or the corefile) read-only. This prevents accidental
12610 alterations to machine code; but it also prevents you from intentionally
12611 patching your program's binary.
12613 If you'd like to be able to patch the binary, you can specify that
12614 explicitly with the @code{set write} command. For example, you might
12615 want to turn on internal debugging flags, or even to make emergency
12621 @itemx set write off
12622 If you specify @samp{set write on}, @value{GDBN} opens executable and
12623 core files for both reading and writing; if you specify @kbd{set write
12624 off} (the default), @value{GDBN} opens them read-only.
12626 If you have already loaded a file, you must load it again (using the
12627 @code{exec-file} or @code{core-file} command) after changing @code{set
12628 write}, for your new setting to take effect.
12632 Display whether executable files and core files are opened for writing
12633 as well as reading.
12637 @chapter @value{GDBN} Files
12639 @value{GDBN} needs to know the file name of the program to be debugged,
12640 both in order to read its symbol table and in order to start your
12641 program. To debug a core dump of a previous run, you must also tell
12642 @value{GDBN} the name of the core dump file.
12645 * Files:: Commands to specify files
12646 * Separate Debug Files:: Debugging information in separate files
12647 * Symbol Errors:: Errors reading symbol files
12651 @section Commands to Specify Files
12653 @cindex symbol table
12654 @cindex core dump file
12656 You may want to specify executable and core dump file names. The usual
12657 way to do this is at start-up time, using the arguments to
12658 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
12659 Out of @value{GDBN}}).
12661 Occasionally it is necessary to change to a different file during a
12662 @value{GDBN} session. Or you may run @value{GDBN} and forget to
12663 specify a file you want to use. Or you are debugging a remote target
12664 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
12665 Program}). In these situations the @value{GDBN} commands to specify
12666 new files are useful.
12669 @cindex executable file
12671 @item file @var{filename}
12672 Use @var{filename} as the program to be debugged. It is read for its
12673 symbols and for the contents of pure memory. It is also the program
12674 executed when you use the @code{run} command. If you do not specify a
12675 directory and the file is not found in the @value{GDBN} working directory,
12676 @value{GDBN} uses the environment variable @code{PATH} as a list of
12677 directories to search, just as the shell does when looking for a program
12678 to run. You can change the value of this variable, for both @value{GDBN}
12679 and your program, using the @code{path} command.
12681 @cindex unlinked object files
12682 @cindex patching object files
12683 You can load unlinked object @file{.o} files into @value{GDBN} using
12684 the @code{file} command. You will not be able to ``run'' an object
12685 file, but you can disassemble functions and inspect variables. Also,
12686 if the underlying BFD functionality supports it, you could use
12687 @kbd{gdb -write} to patch object files using this technique. Note
12688 that @value{GDBN} can neither interpret nor modify relocations in this
12689 case, so branches and some initialized variables will appear to go to
12690 the wrong place. But this feature is still handy from time to time.
12693 @code{file} with no argument makes @value{GDBN} discard any information it
12694 has on both executable file and the symbol table.
12697 @item exec-file @r{[} @var{filename} @r{]}
12698 Specify that the program to be run (but not the symbol table) is found
12699 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12700 if necessary to locate your program. Omitting @var{filename} means to
12701 discard information on the executable file.
12703 @kindex symbol-file
12704 @item symbol-file @r{[} @var{filename} @r{]}
12705 Read symbol table information from file @var{filename}. @code{PATH} is
12706 searched when necessary. Use the @code{file} command to get both symbol
12707 table and program to run from the same file.
12709 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12710 program's symbol table.
12712 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12713 some breakpoints and auto-display expressions. This is because they may
12714 contain pointers to the internal data recording symbols and data types,
12715 which are part of the old symbol table data being discarded inside
12718 @code{symbol-file} does not repeat if you press @key{RET} again after
12721 When @value{GDBN} is configured for a particular environment, it
12722 understands debugging information in whatever format is the standard
12723 generated for that environment; you may use either a @sc{gnu} compiler, or
12724 other compilers that adhere to the local conventions.
12725 Best results are usually obtained from @sc{gnu} compilers; for example,
12726 using @code{@value{NGCC}} you can generate debugging information for
12729 For most kinds of object files, with the exception of old SVR3 systems
12730 using COFF, the @code{symbol-file} command does not normally read the
12731 symbol table in full right away. Instead, it scans the symbol table
12732 quickly to find which source files and which symbols are present. The
12733 details are read later, one source file at a time, as they are needed.
12735 The purpose of this two-stage reading strategy is to make @value{GDBN}
12736 start up faster. For the most part, it is invisible except for
12737 occasional pauses while the symbol table details for a particular source
12738 file are being read. (The @code{set verbose} command can turn these
12739 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12740 Warnings and Messages}.)
12742 We have not implemented the two-stage strategy for COFF yet. When the
12743 symbol table is stored in COFF format, @code{symbol-file} reads the
12744 symbol table data in full right away. Note that ``stabs-in-COFF''
12745 still does the two-stage strategy, since the debug info is actually
12749 @cindex reading symbols immediately
12750 @cindex symbols, reading immediately
12751 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12752 @itemx file @var{filename} @r{[} -readnow @r{]}
12753 You can override the @value{GDBN} two-stage strategy for reading symbol
12754 tables by using the @samp{-readnow} option with any of the commands that
12755 load symbol table information, if you want to be sure @value{GDBN} has the
12756 entire symbol table available.
12758 @c FIXME: for now no mention of directories, since this seems to be in
12759 @c flux. 13mar1992 status is that in theory GDB would look either in
12760 @c current dir or in same dir as myprog; but issues like competing
12761 @c GDB's, or clutter in system dirs, mean that in practice right now
12762 @c only current dir is used. FFish says maybe a special GDB hierarchy
12763 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
12767 @item core-file @r{[}@var{filename}@r{]}
12769 Specify the whereabouts of a core dump file to be used as the ``contents
12770 of memory''. Traditionally, core files contain only some parts of the
12771 address space of the process that generated them; @value{GDBN} can access the
12772 executable file itself for other parts.
12774 @code{core-file} with no argument specifies that no core file is
12777 Note that the core file is ignored when your program is actually running
12778 under @value{GDBN}. So, if you have been running your program and you
12779 wish to debug a core file instead, you must kill the subprocess in which
12780 the program is running. To do this, use the @code{kill} command
12781 (@pxref{Kill Process, ,Killing the Child Process}).
12783 @kindex add-symbol-file
12784 @cindex dynamic linking
12785 @item add-symbol-file @var{filename} @var{address}
12786 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12787 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12788 The @code{add-symbol-file} command reads additional symbol table
12789 information from the file @var{filename}. You would use this command
12790 when @var{filename} has been dynamically loaded (by some other means)
12791 into the program that is running. @var{address} should be the memory
12792 address at which the file has been loaded; @value{GDBN} cannot figure
12793 this out for itself. You can additionally specify an arbitrary number
12794 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12795 section name and base address for that section. You can specify any
12796 @var{address} as an expression.
12798 The symbol table of the file @var{filename} is added to the symbol table
12799 originally read with the @code{symbol-file} command. You can use the
12800 @code{add-symbol-file} command any number of times; the new symbol data
12801 thus read keeps adding to the old. To discard all old symbol data
12802 instead, use the @code{symbol-file} command without any arguments.
12804 @cindex relocatable object files, reading symbols from
12805 @cindex object files, relocatable, reading symbols from
12806 @cindex reading symbols from relocatable object files
12807 @cindex symbols, reading from relocatable object files
12808 @cindex @file{.o} files, reading symbols from
12809 Although @var{filename} is typically a shared library file, an
12810 executable file, or some other object file which has been fully
12811 relocated for loading into a process, you can also load symbolic
12812 information from relocatable @file{.o} files, as long as:
12816 the file's symbolic information refers only to linker symbols defined in
12817 that file, not to symbols defined by other object files,
12819 every section the file's symbolic information refers to has actually
12820 been loaded into the inferior, as it appears in the file, and
12822 you can determine the address at which every section was loaded, and
12823 provide these to the @code{add-symbol-file} command.
12827 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12828 relocatable files into an already running program; such systems
12829 typically make the requirements above easy to meet. However, it's
12830 important to recognize that many native systems use complex link
12831 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12832 assembly, for example) that make the requirements difficult to meet. In
12833 general, one cannot assume that using @code{add-symbol-file} to read a
12834 relocatable object file's symbolic information will have the same effect
12835 as linking the relocatable object file into the program in the normal
12838 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12840 @kindex add-symbol-file-from-memory
12841 @cindex @code{syscall DSO}
12842 @cindex load symbols from memory
12843 @item add-symbol-file-from-memory @var{address}
12844 Load symbols from the given @var{address} in a dynamically loaded
12845 object file whose image is mapped directly into the inferior's memory.
12846 For example, the Linux kernel maps a @code{syscall DSO} into each
12847 process's address space; this DSO provides kernel-specific code for
12848 some system calls. The argument can be any expression whose
12849 evaluation yields the address of the file's shared object file header.
12850 For this command to work, you must have used @code{symbol-file} or
12851 @code{exec-file} commands in advance.
12853 @kindex add-shared-symbol-files
12855 @item add-shared-symbol-files @var{library-file}
12856 @itemx assf @var{library-file}
12857 The @code{add-shared-symbol-files} command can currently be used only
12858 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12859 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12860 @value{GDBN} automatically looks for shared libraries, however if
12861 @value{GDBN} does not find yours, you can invoke
12862 @code{add-shared-symbol-files}. It takes one argument: the shared
12863 library's file name. @code{assf} is a shorthand alias for
12864 @code{add-shared-symbol-files}.
12867 @item section @var{section} @var{addr}
12868 The @code{section} command changes the base address of the named
12869 @var{section} of the exec file to @var{addr}. This can be used if the
12870 exec file does not contain section addresses, (such as in the
12871 @code{a.out} format), or when the addresses specified in the file
12872 itself are wrong. Each section must be changed separately. The
12873 @code{info files} command, described below, lists all the sections and
12877 @kindex info target
12880 @code{info files} and @code{info target} are synonymous; both print the
12881 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12882 including the names of the executable and core dump files currently in
12883 use by @value{GDBN}, and the files from which symbols were loaded. The
12884 command @code{help target} lists all possible targets rather than
12887 @kindex maint info sections
12888 @item maint info sections
12889 Another command that can give you extra information about program sections
12890 is @code{maint info sections}. In addition to the section information
12891 displayed by @code{info files}, this command displays the flags and file
12892 offset of each section in the executable and core dump files. In addition,
12893 @code{maint info sections} provides the following command options (which
12894 may be arbitrarily combined):
12898 Display sections for all loaded object files, including shared libraries.
12899 @item @var{sections}
12900 Display info only for named @var{sections}.
12901 @item @var{section-flags}
12902 Display info only for sections for which @var{section-flags} are true.
12903 The section flags that @value{GDBN} currently knows about are:
12906 Section will have space allocated in the process when loaded.
12907 Set for all sections except those containing debug information.
12909 Section will be loaded from the file into the child process memory.
12910 Set for pre-initialized code and data, clear for @code{.bss} sections.
12912 Section needs to be relocated before loading.
12914 Section cannot be modified by the child process.
12916 Section contains executable code only.
12918 Section contains data only (no executable code).
12920 Section will reside in ROM.
12922 Section contains data for constructor/destructor lists.
12924 Section is not empty.
12926 An instruction to the linker to not output the section.
12927 @item COFF_SHARED_LIBRARY
12928 A notification to the linker that the section contains
12929 COFF shared library information.
12931 Section contains common symbols.
12934 @kindex set trust-readonly-sections
12935 @cindex read-only sections
12936 @item set trust-readonly-sections on
12937 Tell @value{GDBN} that readonly sections in your object file
12938 really are read-only (i.e.@: that their contents will not change).
12939 In that case, @value{GDBN} can fetch values from these sections
12940 out of the object file, rather than from the target program.
12941 For some targets (notably embedded ones), this can be a significant
12942 enhancement to debugging performance.
12944 The default is off.
12946 @item set trust-readonly-sections off
12947 Tell @value{GDBN} not to trust readonly sections. This means that
12948 the contents of the section might change while the program is running,
12949 and must therefore be fetched from the target when needed.
12951 @item show trust-readonly-sections
12952 Show the current setting of trusting readonly sections.
12955 All file-specifying commands allow both absolute and relative file names
12956 as arguments. @value{GDBN} always converts the file name to an absolute file
12957 name and remembers it that way.
12959 @cindex shared libraries
12960 @anchor{Shared Libraries}
12961 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
12962 and IBM RS/6000 AIX shared libraries.
12964 On MS-Windows @value{GDBN} must be linked with the Expat library to support
12965 shared libraries. @xref{Expat}.
12967 @value{GDBN} automatically loads symbol definitions from shared libraries
12968 when you use the @code{run} command, or when you examine a core file.
12969 (Before you issue the @code{run} command, @value{GDBN} does not understand
12970 references to a function in a shared library, however---unless you are
12971 debugging a core file).
12973 On HP-UX, if the program loads a library explicitly, @value{GDBN}
12974 automatically loads the symbols at the time of the @code{shl_load} call.
12976 @c FIXME: some @value{GDBN} release may permit some refs to undef
12977 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
12978 @c FIXME...lib; check this from time to time when updating manual
12980 There are times, however, when you may wish to not automatically load
12981 symbol definitions from shared libraries, such as when they are
12982 particularly large or there are many of them.
12984 To control the automatic loading of shared library symbols, use the
12988 @kindex set auto-solib-add
12989 @item set auto-solib-add @var{mode}
12990 If @var{mode} is @code{on}, symbols from all shared object libraries
12991 will be loaded automatically when the inferior begins execution, you
12992 attach to an independently started inferior, or when the dynamic linker
12993 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12994 is @code{off}, symbols must be loaded manually, using the
12995 @code{sharedlibrary} command. The default value is @code{on}.
12997 @cindex memory used for symbol tables
12998 If your program uses lots of shared libraries with debug info that
12999 takes large amounts of memory, you can decrease the @value{GDBN}
13000 memory footprint by preventing it from automatically loading the
13001 symbols from shared libraries. To that end, type @kbd{set
13002 auto-solib-add off} before running the inferior, then load each
13003 library whose debug symbols you do need with @kbd{sharedlibrary
13004 @var{regexp}}, where @var{regexp} is a regular expression that matches
13005 the libraries whose symbols you want to be loaded.
13007 @kindex show auto-solib-add
13008 @item show auto-solib-add
13009 Display the current autoloading mode.
13012 @cindex load shared library
13013 To explicitly load shared library symbols, use the @code{sharedlibrary}
13017 @kindex info sharedlibrary
13020 @itemx info sharedlibrary
13021 Print the names of the shared libraries which are currently loaded.
13023 @kindex sharedlibrary
13025 @item sharedlibrary @var{regex}
13026 @itemx share @var{regex}
13027 Load shared object library symbols for files matching a
13028 Unix regular expression.
13029 As with files loaded automatically, it only loads shared libraries
13030 required by your program for a core file or after typing @code{run}. If
13031 @var{regex} is omitted all shared libraries required by your program are
13034 @item nosharedlibrary
13035 @kindex nosharedlibrary
13036 @cindex unload symbols from shared libraries
13037 Unload all shared object library symbols. This discards all symbols
13038 that have been loaded from all shared libraries. Symbols from shared
13039 libraries that were loaded by explicit user requests are not
13043 Sometimes you may wish that @value{GDBN} stops and gives you control
13044 when any of shared library events happen. Use the @code{set
13045 stop-on-solib-events} command for this:
13048 @item set stop-on-solib-events
13049 @kindex set stop-on-solib-events
13050 This command controls whether @value{GDBN} should give you control
13051 when the dynamic linker notifies it about some shared library event.
13052 The most common event of interest is loading or unloading of a new
13055 @item show stop-on-solib-events
13056 @kindex show stop-on-solib-events
13057 Show whether @value{GDBN} stops and gives you control when shared
13058 library events happen.
13061 Shared libraries are also supported in many cross or remote debugging
13062 configurations. @value{GDBN} needs to have access to the target's libraries;
13063 this can be accomplished either by providing copies of the libraries
13064 on the host system, or by asking @value{GDBN} to automatically retrieve the
13065 libraries from the target. If copies of the target libraries are
13066 provided, they need to be the same as the target libraries, although the
13067 copies on the target can be stripped as long as the copies on the host are
13070 @cindex where to look for shared libraries
13071 For remote debugging, you need to tell @value{GDBN} where the target
13072 libraries are, so that it can load the correct copies---otherwise, it
13073 may try to load the host's libraries. @value{GDBN} has two variables
13074 to specify the search directories for target libraries.
13077 @cindex prefix for shared library file names
13078 @cindex system root, alternate
13079 @kindex set solib-absolute-prefix
13080 @kindex set sysroot
13081 @item set sysroot @var{path}
13082 Use @var{path} as the system root for the program being debugged. Any
13083 absolute shared library paths will be prefixed with @var{path}; many
13084 runtime loaders store the absolute paths to the shared library in the
13085 target program's memory. If you use @code{set sysroot} to find shared
13086 libraries, they need to be laid out in the same way that they are on
13087 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
13090 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
13091 retrieve the target libraries from the remote system. This is only
13092 supported when using a remote target that supports the @code{remote get}
13093 command (@pxref{File Transfer,,Sending files to a remote system}).
13094 The part of @var{path} following the initial @file{remote:}
13095 (if present) is used as system root prefix on the remote file system.
13096 @footnote{If you want to specify a local system root using a directory
13097 that happens to be named @file{remote:}, you need to use some equivalent
13098 variant of the name like @file{./remote:}.}
13100 The @code{set solib-absolute-prefix} command is an alias for @code{set
13103 @cindex default system root
13104 @cindex @samp{--with-sysroot}
13105 You can set the default system root by using the configure-time
13106 @samp{--with-sysroot} option. If the system root is inside
13107 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13108 @samp{--exec-prefix}), then the default system root will be updated
13109 automatically if the installed @value{GDBN} is moved to a new
13112 @kindex show sysroot
13114 Display the current shared library prefix.
13116 @kindex set solib-search-path
13117 @item set solib-search-path @var{path}
13118 If this variable is set, @var{path} is a colon-separated list of
13119 directories to search for shared libraries. @samp{solib-search-path}
13120 is used after @samp{sysroot} fails to locate the library, or if the
13121 path to the library is relative instead of absolute. If you want to
13122 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13123 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13124 finding your host's libraries. @samp{sysroot} is preferred; setting
13125 it to a nonexistent directory may interfere with automatic loading
13126 of shared library symbols.
13128 @kindex show solib-search-path
13129 @item show solib-search-path
13130 Display the current shared library search path.
13134 @node Separate Debug Files
13135 @section Debugging Information in Separate Files
13136 @cindex separate debugging information files
13137 @cindex debugging information in separate files
13138 @cindex @file{.debug} subdirectories
13139 @cindex debugging information directory, global
13140 @cindex global debugging information directory
13141 @cindex build ID, and separate debugging files
13142 @cindex @file{.build-id} directory
13144 @value{GDBN} allows you to put a program's debugging information in a
13145 file separate from the executable itself, in a way that allows
13146 @value{GDBN} to find and load the debugging information automatically.
13147 Since debugging information can be very large---sometimes larger
13148 than the executable code itself---some systems distribute debugging
13149 information for their executables in separate files, which users can
13150 install only when they need to debug a problem.
13152 @value{GDBN} supports two ways of specifying the separate debug info
13157 The executable contains a @dfn{debug link} that specifies the name of
13158 the separate debug info file. The separate debug file's name is
13159 usually @file{@var{executable}.debug}, where @var{executable} is the
13160 name of the corresponding executable file without leading directories
13161 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
13162 debug link specifies a CRC32 checksum for the debug file, which
13163 @value{GDBN} uses to validate that the executable and the debug file
13164 came from the same build.
13167 The executable contains a @dfn{build ID}, a unique bit string that is
13168 also present in the corresponding debug info file. (This is supported
13169 only on some operating systems, notably those which use the ELF format
13170 for binary files and the @sc{gnu} Binutils.) For more details about
13171 this feature, see the description of the @option{--build-id}
13172 command-line option in @ref{Options, , Command Line Options, ld.info,
13173 The GNU Linker}. The debug info file's name is not specified
13174 explicitly by the build ID, but can be computed from the build ID, see
13178 Depending on the way the debug info file is specified, @value{GDBN}
13179 uses two different methods of looking for the debug file:
13183 For the ``debug link'' method, @value{GDBN} looks up the named file in
13184 the directory of the executable file, then in a subdirectory of that
13185 directory named @file{.debug}, and finally under the global debug
13186 directory, in a subdirectory whose name is identical to the leading
13187 directories of the executable's absolute file name.
13190 For the ``build ID'' method, @value{GDBN} looks in the
13191 @file{.build-id} subdirectory of the global debug directory for a file
13192 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
13193 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
13194 are the rest of the bit string. (Real build ID strings are 32 or more
13195 hex characters, not 10.)
13198 So, for example, suppose you ask @value{GDBN} to debug
13199 @file{/usr/bin/ls}, which has a debug link that specifies the
13200 file @file{ls.debug}, and a build ID whose value in hex is
13201 @code{abcdef1234}. If the global debug directory is
13202 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
13203 debug information files, in the indicated order:
13207 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
13209 @file{/usr/bin/ls.debug}
13211 @file{/usr/bin/.debug/ls.debug}
13213 @file{/usr/lib/debug/usr/bin/ls.debug}.
13216 You can set the global debugging info directory's name, and view the
13217 name @value{GDBN} is currently using.
13221 @kindex set debug-file-directory
13222 @item set debug-file-directory @var{directory}
13223 Set the directory which @value{GDBN} searches for separate debugging
13224 information files to @var{directory}.
13226 @kindex show debug-file-directory
13227 @item show debug-file-directory
13228 Show the directory @value{GDBN} searches for separate debugging
13233 @cindex @code{.gnu_debuglink} sections
13234 @cindex debug link sections
13235 A debug link is a special section of the executable file named
13236 @code{.gnu_debuglink}. The section must contain:
13240 A filename, with any leading directory components removed, followed by
13243 zero to three bytes of padding, as needed to reach the next four-byte
13244 boundary within the section, and
13246 a four-byte CRC checksum, stored in the same endianness used for the
13247 executable file itself. The checksum is computed on the debugging
13248 information file's full contents by the function given below, passing
13249 zero as the @var{crc} argument.
13252 Any executable file format can carry a debug link, as long as it can
13253 contain a section named @code{.gnu_debuglink} with the contents
13256 @cindex @code{.note.gnu.build-id} sections
13257 @cindex build ID sections
13258 The build ID is a special section in the executable file (and in other
13259 ELF binary files that @value{GDBN} may consider). This section is
13260 often named @code{.note.gnu.build-id}, but that name is not mandatory.
13261 It contains unique identification for the built files---the ID remains
13262 the same across multiple builds of the same build tree. The default
13263 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
13264 content for the build ID string. The same section with an identical
13265 value is present in the original built binary with symbols, in its
13266 stripped variant, and in the separate debugging information file.
13268 The debugging information file itself should be an ordinary
13269 executable, containing a full set of linker symbols, sections, and
13270 debugging information. The sections of the debugging information file
13271 should have the same names, addresses, and sizes as the original file,
13272 but they need not contain any data---much like a @code{.bss} section
13273 in an ordinary executable.
13275 The @sc{gnu} binary utilities (Binutils) package includes the
13276 @samp{objcopy} utility that can produce
13277 the separated executable / debugging information file pairs using the
13278 following commands:
13281 @kbd{objcopy --only-keep-debug foo foo.debug}
13286 These commands remove the debugging
13287 information from the executable file @file{foo} and place it in the file
13288 @file{foo.debug}. You can use the first, second or both methods to link the
13293 The debug link method needs the following additional command to also leave
13294 behind a debug link in @file{foo}:
13297 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
13300 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
13301 a version of the @code{strip} command such that the command @kbd{strip foo -f
13302 foo.debug} has the same functionality as the two @code{objcopy} commands and
13303 the @code{ln -s} command above, together.
13306 Build ID gets embedded into the main executable using @code{ld --build-id} or
13307 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
13308 compatibility fixes for debug files separation are present in @sc{gnu} binary
13309 utilities (Binutils) package since version 2.18.
13314 Since there are many different ways to compute CRC's for the debug
13315 link (different polynomials, reversals, byte ordering, etc.), the
13316 simplest way to describe the CRC used in @code{.gnu_debuglink}
13317 sections is to give the complete code for a function that computes it:
13319 @kindex gnu_debuglink_crc32
13322 gnu_debuglink_crc32 (unsigned long crc,
13323 unsigned char *buf, size_t len)
13325 static const unsigned long crc32_table[256] =
13327 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
13328 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
13329 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
13330 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
13331 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
13332 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
13333 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
13334 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
13335 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
13336 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
13337 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
13338 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
13339 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
13340 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
13341 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
13342 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
13343 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
13344 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
13345 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
13346 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
13347 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
13348 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
13349 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
13350 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
13351 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
13352 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
13353 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
13354 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
13355 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
13356 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
13357 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
13358 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
13359 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
13360 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
13361 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
13362 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
13363 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
13364 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
13365 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
13366 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
13367 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
13368 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
13369 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
13370 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
13371 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
13372 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
13373 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
13374 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
13375 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
13376 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
13377 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
13380 unsigned char *end;
13382 crc = ~crc & 0xffffffff;
13383 for (end = buf + len; buf < end; ++buf)
13384 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
13385 return ~crc & 0xffffffff;
13390 This computation does not apply to the ``build ID'' method.
13393 @node Symbol Errors
13394 @section Errors Reading Symbol Files
13396 While reading a symbol file, @value{GDBN} occasionally encounters problems,
13397 such as symbol types it does not recognize, or known bugs in compiler
13398 output. By default, @value{GDBN} does not notify you of such problems, since
13399 they are relatively common and primarily of interest to people
13400 debugging compilers. If you are interested in seeing information
13401 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
13402 only one message about each such type of problem, no matter how many
13403 times the problem occurs; or you can ask @value{GDBN} to print more messages,
13404 to see how many times the problems occur, with the @code{set
13405 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
13408 The messages currently printed, and their meanings, include:
13411 @item inner block not inside outer block in @var{symbol}
13413 The symbol information shows where symbol scopes begin and end
13414 (such as at the start of a function or a block of statements). This
13415 error indicates that an inner scope block is not fully contained
13416 in its outer scope blocks.
13418 @value{GDBN} circumvents the problem by treating the inner block as if it had
13419 the same scope as the outer block. In the error message, @var{symbol}
13420 may be shown as ``@code{(don't know)}'' if the outer block is not a
13423 @item block at @var{address} out of order
13425 The symbol information for symbol scope blocks should occur in
13426 order of increasing addresses. This error indicates that it does not
13429 @value{GDBN} does not circumvent this problem, and has trouble
13430 locating symbols in the source file whose symbols it is reading. (You
13431 can often determine what source file is affected by specifying
13432 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
13435 @item bad block start address patched
13437 The symbol information for a symbol scope block has a start address
13438 smaller than the address of the preceding source line. This is known
13439 to occur in the SunOS 4.1.1 (and earlier) C compiler.
13441 @value{GDBN} circumvents the problem by treating the symbol scope block as
13442 starting on the previous source line.
13444 @item bad string table offset in symbol @var{n}
13447 Symbol number @var{n} contains a pointer into the string table which is
13448 larger than the size of the string table.
13450 @value{GDBN} circumvents the problem by considering the symbol to have the
13451 name @code{foo}, which may cause other problems if many symbols end up
13454 @item unknown symbol type @code{0x@var{nn}}
13456 The symbol information contains new data types that @value{GDBN} does
13457 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
13458 uncomprehended information, in hexadecimal.
13460 @value{GDBN} circumvents the error by ignoring this symbol information.
13461 This usually allows you to debug your program, though certain symbols
13462 are not accessible. If you encounter such a problem and feel like
13463 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
13464 on @code{complain}, then go up to the function @code{read_dbx_symtab}
13465 and examine @code{*bufp} to see the symbol.
13467 @item stub type has NULL name
13469 @value{GDBN} could not find the full definition for a struct or class.
13471 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
13472 The symbol information for a C@t{++} member function is missing some
13473 information that recent versions of the compiler should have output for
13476 @item info mismatch between compiler and debugger
13478 @value{GDBN} could not parse a type specification output by the compiler.
13483 @chapter Specifying a Debugging Target
13485 @cindex debugging target
13486 A @dfn{target} is the execution environment occupied by your program.
13488 Often, @value{GDBN} runs in the same host environment as your program;
13489 in that case, the debugging target is specified as a side effect when
13490 you use the @code{file} or @code{core} commands. When you need more
13491 flexibility---for example, running @value{GDBN} on a physically separate
13492 host, or controlling a standalone system over a serial port or a
13493 realtime system over a TCP/IP connection---you can use the @code{target}
13494 command to specify one of the target types configured for @value{GDBN}
13495 (@pxref{Target Commands, ,Commands for Managing Targets}).
13497 @cindex target architecture
13498 It is possible to build @value{GDBN} for several different @dfn{target
13499 architectures}. When @value{GDBN} is built like that, you can choose
13500 one of the available architectures with the @kbd{set architecture}
13504 @kindex set architecture
13505 @kindex show architecture
13506 @item set architecture @var{arch}
13507 This command sets the current target architecture to @var{arch}. The
13508 value of @var{arch} can be @code{"auto"}, in addition to one of the
13509 supported architectures.
13511 @item show architecture
13512 Show the current target architecture.
13514 @item set processor
13516 @kindex set processor
13517 @kindex show processor
13518 These are alias commands for, respectively, @code{set architecture}
13519 and @code{show architecture}.
13523 * Active Targets:: Active targets
13524 * Target Commands:: Commands for managing targets
13525 * Byte Order:: Choosing target byte order
13528 @node Active Targets
13529 @section Active Targets
13531 @cindex stacking targets
13532 @cindex active targets
13533 @cindex multiple targets
13535 There are three classes of targets: processes, core files, and
13536 executable files. @value{GDBN} can work concurrently on up to three
13537 active targets, one in each class. This allows you to (for example)
13538 start a process and inspect its activity without abandoning your work on
13541 For example, if you execute @samp{gdb a.out}, then the executable file
13542 @code{a.out} is the only active target. If you designate a core file as
13543 well---presumably from a prior run that crashed and coredumped---then
13544 @value{GDBN} has two active targets and uses them in tandem, looking
13545 first in the corefile target, then in the executable file, to satisfy
13546 requests for memory addresses. (Typically, these two classes of target
13547 are complementary, since core files contain only a program's
13548 read-write memory---variables and so on---plus machine status, while
13549 executable files contain only the program text and initialized data.)
13551 When you type @code{run}, your executable file becomes an active process
13552 target as well. When a process target is active, all @value{GDBN}
13553 commands requesting memory addresses refer to that target; addresses in
13554 an active core file or executable file target are obscured while the
13555 process target is active.
13557 Use the @code{core-file} and @code{exec-file} commands to select a new
13558 core file or executable target (@pxref{Files, ,Commands to Specify
13559 Files}). To specify as a target a process that is already running, use
13560 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
13563 @node Target Commands
13564 @section Commands for Managing Targets
13567 @item target @var{type} @var{parameters}
13568 Connects the @value{GDBN} host environment to a target machine or
13569 process. A target is typically a protocol for talking to debugging
13570 facilities. You use the argument @var{type} to specify the type or
13571 protocol of the target machine.
13573 Further @var{parameters} are interpreted by the target protocol, but
13574 typically include things like device names or host names to connect
13575 with, process numbers, and baud rates.
13577 The @code{target} command does not repeat if you press @key{RET} again
13578 after executing the command.
13580 @kindex help target
13582 Displays the names of all targets available. To display targets
13583 currently selected, use either @code{info target} or @code{info files}
13584 (@pxref{Files, ,Commands to Specify Files}).
13586 @item help target @var{name}
13587 Describe a particular target, including any parameters necessary to
13590 @kindex set gnutarget
13591 @item set gnutarget @var{args}
13592 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
13593 knows whether it is reading an @dfn{executable},
13594 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
13595 with the @code{set gnutarget} command. Unlike most @code{target} commands,
13596 with @code{gnutarget} the @code{target} refers to a program, not a machine.
13599 @emph{Warning:} To specify a file format with @code{set gnutarget},
13600 you must know the actual BFD name.
13604 @xref{Files, , Commands to Specify Files}.
13606 @kindex show gnutarget
13607 @item show gnutarget
13608 Use the @code{show gnutarget} command to display what file format
13609 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
13610 @value{GDBN} will determine the file format for each file automatically,
13611 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
13614 @cindex common targets
13615 Here are some common targets (available, or not, depending on the GDB
13620 @item target exec @var{program}
13621 @cindex executable file target
13622 An executable file. @samp{target exec @var{program}} is the same as
13623 @samp{exec-file @var{program}}.
13625 @item target core @var{filename}
13626 @cindex core dump file target
13627 A core dump file. @samp{target core @var{filename}} is the same as
13628 @samp{core-file @var{filename}}.
13630 @item target remote @var{medium}
13631 @cindex remote target
13632 A remote system connected to @value{GDBN} via a serial line or network
13633 connection. This command tells @value{GDBN} to use its own remote
13634 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
13636 For example, if you have a board connected to @file{/dev/ttya} on the
13637 machine running @value{GDBN}, you could say:
13640 target remote /dev/ttya
13643 @code{target remote} supports the @code{load} command. This is only
13644 useful if you have some other way of getting the stub to the target
13645 system, and you can put it somewhere in memory where it won't get
13646 clobbered by the download.
13649 @cindex built-in simulator target
13650 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
13658 works; however, you cannot assume that a specific memory map, device
13659 drivers, or even basic I/O is available, although some simulators do
13660 provide these. For info about any processor-specific simulator details,
13661 see the appropriate section in @ref{Embedded Processors, ,Embedded
13666 Some configurations may include these targets as well:
13670 @item target nrom @var{dev}
13671 @cindex NetROM ROM emulator target
13672 NetROM ROM emulator. This target only supports downloading.
13676 Different targets are available on different configurations of @value{GDBN};
13677 your configuration may have more or fewer targets.
13679 Many remote targets require you to download the executable's code once
13680 you've successfully established a connection. You may wish to control
13681 various aspects of this process.
13686 @kindex set hash@r{, for remote monitors}
13687 @cindex hash mark while downloading
13688 This command controls whether a hash mark @samp{#} is displayed while
13689 downloading a file to the remote monitor. If on, a hash mark is
13690 displayed after each S-record is successfully downloaded to the
13694 @kindex show hash@r{, for remote monitors}
13695 Show the current status of displaying the hash mark.
13697 @item set debug monitor
13698 @kindex set debug monitor
13699 @cindex display remote monitor communications
13700 Enable or disable display of communications messages between
13701 @value{GDBN} and the remote monitor.
13703 @item show debug monitor
13704 @kindex show debug monitor
13705 Show the current status of displaying communications between
13706 @value{GDBN} and the remote monitor.
13711 @kindex load @var{filename}
13712 @item load @var{filename}
13714 Depending on what remote debugging facilities are configured into
13715 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13716 is meant to make @var{filename} (an executable) available for debugging
13717 on the remote system---by downloading, or dynamic linking, for example.
13718 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
13719 the @code{add-symbol-file} command.
13721 If your @value{GDBN} does not have a @code{load} command, attempting to
13722 execute it gets the error message ``@code{You can't do that when your
13723 target is @dots{}}''
13725 The file is loaded at whatever address is specified in the executable.
13726 For some object file formats, you can specify the load address when you
13727 link the program; for other formats, like a.out, the object file format
13728 specifies a fixed address.
13729 @c FIXME! This would be a good place for an xref to the GNU linker doc.
13731 Depending on the remote side capabilities, @value{GDBN} may be able to
13732 load programs into flash memory.
13734 @code{load} does not repeat if you press @key{RET} again after using it.
13738 @section Choosing Target Byte Order
13740 @cindex choosing target byte order
13741 @cindex target byte order
13743 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
13744 offer the ability to run either big-endian or little-endian byte
13745 orders. Usually the executable or symbol will include a bit to
13746 designate the endian-ness, and you will not need to worry about
13747 which to use. However, you may still find it useful to adjust
13748 @value{GDBN}'s idea of processor endian-ness manually.
13752 @item set endian big
13753 Instruct @value{GDBN} to assume the target is big-endian.
13755 @item set endian little
13756 Instruct @value{GDBN} to assume the target is little-endian.
13758 @item set endian auto
13759 Instruct @value{GDBN} to use the byte order associated with the
13763 Display @value{GDBN}'s current idea of the target byte order.
13767 Note that these commands merely adjust interpretation of symbolic
13768 data on the host, and that they have absolutely no effect on the
13772 @node Remote Debugging
13773 @chapter Debugging Remote Programs
13774 @cindex remote debugging
13776 If you are trying to debug a program running on a machine that cannot run
13777 @value{GDBN} in the usual way, it is often useful to use remote debugging.
13778 For example, you might use remote debugging on an operating system kernel,
13779 or on a small system which does not have a general purpose operating system
13780 powerful enough to run a full-featured debugger.
13782 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
13783 to make this work with particular debugging targets. In addition,
13784 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
13785 but not specific to any particular target system) which you can use if you
13786 write the remote stubs---the code that runs on the remote system to
13787 communicate with @value{GDBN}.
13789 Other remote targets may be available in your
13790 configuration of @value{GDBN}; use @code{help target} to list them.
13793 * Connecting:: Connecting to a remote target
13794 * File Transfer:: Sending files to a remote system
13795 * Server:: Using the gdbserver program
13796 * Remote Configuration:: Remote configuration
13797 * Remote Stub:: Implementing a remote stub
13801 @section Connecting to a Remote Target
13803 On the @value{GDBN} host machine, you will need an unstripped copy of
13804 your program, since @value{GDBN} needs symbol and debugging information.
13805 Start up @value{GDBN} as usual, using the name of the local copy of your
13806 program as the first argument.
13808 @cindex @code{target remote}
13809 @value{GDBN} can communicate with the target over a serial line, or
13810 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13811 each case, @value{GDBN} uses the same protocol for debugging your
13812 program; only the medium carrying the debugging packets varies. The
13813 @code{target remote} command establishes a connection to the target.
13814 Its arguments indicate which medium to use:
13818 @item target remote @var{serial-device}
13819 @cindex serial line, @code{target remote}
13820 Use @var{serial-device} to communicate with the target. For example,
13821 to use a serial line connected to the device named @file{/dev/ttyb}:
13824 target remote /dev/ttyb
13827 If you're using a serial line, you may want to give @value{GDBN} the
13828 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13829 (@pxref{Remote Configuration, set remotebaud}) before the
13830 @code{target} command.
13832 @item target remote @code{@var{host}:@var{port}}
13833 @itemx target remote @code{tcp:@var{host}:@var{port}}
13834 @cindex @acronym{TCP} port, @code{target remote}
13835 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13836 The @var{host} may be either a host name or a numeric @acronym{IP}
13837 address; @var{port} must be a decimal number. The @var{host} could be
13838 the target machine itself, if it is directly connected to the net, or
13839 it might be a terminal server which in turn has a serial line to the
13842 For example, to connect to port 2828 on a terminal server named
13846 target remote manyfarms:2828
13849 If your remote target is actually running on the same machine as your
13850 debugger session (e.g.@: a simulator for your target running on the
13851 same host), you can omit the hostname. For example, to connect to
13852 port 1234 on your local machine:
13855 target remote :1234
13859 Note that the colon is still required here.
13861 @item target remote @code{udp:@var{host}:@var{port}}
13862 @cindex @acronym{UDP} port, @code{target remote}
13863 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13864 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13867 target remote udp:manyfarms:2828
13870 When using a @acronym{UDP} connection for remote debugging, you should
13871 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13872 can silently drop packets on busy or unreliable networks, which will
13873 cause havoc with your debugging session.
13875 @item target remote | @var{command}
13876 @cindex pipe, @code{target remote} to
13877 Run @var{command} in the background and communicate with it using a
13878 pipe. The @var{command} is a shell command, to be parsed and expanded
13879 by the system's command shell, @code{/bin/sh}; it should expect remote
13880 protocol packets on its standard input, and send replies on its
13881 standard output. You could use this to run a stand-alone simulator
13882 that speaks the remote debugging protocol, to make net connections
13883 using programs like @code{ssh}, or for other similar tricks.
13885 If @var{command} closes its standard output (perhaps by exiting),
13886 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13887 program has already exited, this will have no effect.)
13891 Once the connection has been established, you can use all the usual
13892 commands to examine and change data. The remote program is already
13893 running; you can use @kbd{step} and @kbd{continue}, and you do not
13894 need to use @kbd{run}.
13896 @cindex interrupting remote programs
13897 @cindex remote programs, interrupting
13898 Whenever @value{GDBN} is waiting for the remote program, if you type the
13899 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13900 program. This may or may not succeed, depending in part on the hardware
13901 and the serial drivers the remote system uses. If you type the
13902 interrupt character once again, @value{GDBN} displays this prompt:
13905 Interrupted while waiting for the program.
13906 Give up (and stop debugging it)? (y or n)
13909 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13910 (If you decide you want to try again later, you can use @samp{target
13911 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13912 goes back to waiting.
13915 @kindex detach (remote)
13917 When you have finished debugging the remote program, you can use the
13918 @code{detach} command to release it from @value{GDBN} control.
13919 Detaching from the target normally resumes its execution, but the results
13920 will depend on your particular remote stub. After the @code{detach}
13921 command, @value{GDBN} is free to connect to another target.
13925 The @code{disconnect} command behaves like @code{detach}, except that
13926 the target is generally not resumed. It will wait for @value{GDBN}
13927 (this instance or another one) to connect and continue debugging. After
13928 the @code{disconnect} command, @value{GDBN} is again free to connect to
13931 @cindex send command to remote monitor
13932 @cindex extend @value{GDBN} for remote targets
13933 @cindex add new commands for external monitor
13935 @item monitor @var{cmd}
13936 This command allows you to send arbitrary commands directly to the
13937 remote monitor. Since @value{GDBN} doesn't care about the commands it
13938 sends like this, this command is the way to extend @value{GDBN}---you
13939 can add new commands that only the external monitor will understand
13943 @node File Transfer
13944 @section Sending files to a remote system
13945 @cindex remote target, file transfer
13946 @cindex file transfer
13947 @cindex sending files to remote systems
13949 Some remote targets offer the ability to transfer files over the same
13950 connection used to communicate with @value{GDBN}. This is convenient
13951 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
13952 running @code{gdbserver} over a network interface. For other targets,
13953 e.g.@: embedded devices with only a single serial port, this may be
13954 the only way to upload or download files.
13956 Not all remote targets support these commands.
13960 @item remote put @var{hostfile} @var{targetfile}
13961 Copy file @var{hostfile} from the host system (the machine running
13962 @value{GDBN}) to @var{targetfile} on the target system.
13965 @item remote get @var{targetfile} @var{hostfile}
13966 Copy file @var{targetfile} from the target system to @var{hostfile}
13967 on the host system.
13969 @kindex remote delete
13970 @item remote delete @var{targetfile}
13971 Delete @var{targetfile} from the target system.
13976 @section Using the @code{gdbserver} Program
13979 @cindex remote connection without stubs
13980 @code{gdbserver} is a control program for Unix-like systems, which
13981 allows you to connect your program with a remote @value{GDBN} via
13982 @code{target remote}---but without linking in the usual debugging stub.
13984 @code{gdbserver} is not a complete replacement for the debugging stubs,
13985 because it requires essentially the same operating-system facilities
13986 that @value{GDBN} itself does. In fact, a system that can run
13987 @code{gdbserver} to connect to a remote @value{GDBN} could also run
13988 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
13989 because it is a much smaller program than @value{GDBN} itself. It is
13990 also easier to port than all of @value{GDBN}, so you may be able to get
13991 started more quickly on a new system by using @code{gdbserver}.
13992 Finally, if you develop code for real-time systems, you may find that
13993 the tradeoffs involved in real-time operation make it more convenient to
13994 do as much development work as possible on another system, for example
13995 by cross-compiling. You can use @code{gdbserver} to make a similar
13996 choice for debugging.
13998 @value{GDBN} and @code{gdbserver} communicate via either a serial line
13999 or a TCP connection, using the standard @value{GDBN} remote serial
14003 @emph{Warning:} @code{gdbserver} does not have any built-in security.
14004 Do not run @code{gdbserver} connected to any public network; a
14005 @value{GDBN} connection to @code{gdbserver} provides access to the
14006 target system with the same privileges as the user running
14010 @subsection Running @code{gdbserver}
14011 @cindex arguments, to @code{gdbserver}
14013 Run @code{gdbserver} on the target system. You need a copy of the
14014 program you want to debug, including any libraries it requires.
14015 @code{gdbserver} does not need your program's symbol table, so you can
14016 strip the program if necessary to save space. @value{GDBN} on the host
14017 system does all the symbol handling.
14019 To use the server, you must tell it how to communicate with @value{GDBN};
14020 the name of your program; and the arguments for your program. The usual
14024 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
14027 @var{comm} is either a device name (to use a serial line) or a TCP
14028 hostname and portnumber. For example, to debug Emacs with the argument
14029 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
14033 target> gdbserver /dev/com1 emacs foo.txt
14036 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
14039 To use a TCP connection instead of a serial line:
14042 target> gdbserver host:2345 emacs foo.txt
14045 The only difference from the previous example is the first argument,
14046 specifying that you are communicating with the host @value{GDBN} via
14047 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
14048 expect a TCP connection from machine @samp{host} to local TCP port 2345.
14049 (Currently, the @samp{host} part is ignored.) You can choose any number
14050 you want for the port number as long as it does not conflict with any
14051 TCP ports already in use on the target system (for example, @code{23} is
14052 reserved for @code{telnet}).@footnote{If you choose a port number that
14053 conflicts with another service, @code{gdbserver} prints an error message
14054 and exits.} You must use the same port number with the host @value{GDBN}
14055 @code{target remote} command.
14057 @subsubsection Attaching to a Running Program
14059 On some targets, @code{gdbserver} can also attach to running programs.
14060 This is accomplished via the @code{--attach} argument. The syntax is:
14063 target> gdbserver --attach @var{comm} @var{pid}
14066 @var{pid} is the process ID of a currently running process. It isn't necessary
14067 to point @code{gdbserver} at a binary for the running process.
14070 @cindex attach to a program by name
14071 You can debug processes by name instead of process ID if your target has the
14072 @code{pidof} utility:
14075 target> gdbserver --attach @var{comm} `pidof @var{program}`
14078 In case more than one copy of @var{program} is running, or @var{program}
14079 has multiple threads, most versions of @code{pidof} support the
14080 @code{-s} option to only return the first process ID.
14082 @subsubsection Multi-Process Mode for @code{gdbserver}
14083 @cindex gdbserver, multiple processes
14084 @cindex multiple processes with gdbserver
14086 When you connect to @code{gdbserver} using @code{target remote},
14087 @code{gdbserver} debugs the specified program only once. When the
14088 program exits, or you detach from it, @value{GDBN} closes the connection
14089 and @code{gdbserver} exits.
14091 If you connect using @kbd{target extended-remote}, @code{gdbserver}
14092 enters multi-process mode. When the debugged program exits, or you
14093 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
14094 though no program is running. The @code{run} and @code{attach}
14095 commands instruct @code{gdbserver} to run or attach to a new program.
14096 The @code{run} command uses @code{set remote exec-file} (@pxref{set
14097 remote exec-file}) to select the program to run. Command line
14098 arguments are supported, except for wildcard expansion and I/O
14099 redirection (@pxref{Arguments}).
14101 To start @code{gdbserver} without supplying an initial command to run
14102 or process ID to attach, use the @option{--multi} command line option.
14103 Then you can connect using @kbd{target extended-remote} and start
14104 the program you want to debug.
14106 @code{gdbserver} does not automatically exit in multi-process mode.
14107 You can terminate it by using @code{monitor exit}
14108 (@pxref{Monitor Commands for gdbserver}).
14110 @subsubsection Other Command-Line Arguments for @code{gdbserver}
14112 The @option{--debug} option tells @code{gdbserver} to display extra
14113 status information about the debugging process. The
14114 @option{--remote-debug} option tells @code{gdbserver} to display
14115 remote protocol debug output. These options are intended for
14116 @code{gdbserver} development and for bug reports to the developers.
14118 The @option{--wrapper} option specifies a wrapper to launch programs
14119 for debugging. The option should be followed by the name of the
14120 wrapper, then any command-line arguments to pass to the wrapper, then
14121 @kbd{--} indicating the end of the wrapper arguments.
14123 @code{gdbserver} runs the specified wrapper program with a combined
14124 command line including the wrapper arguments, then the name of the
14125 program to debug, then any arguments to the program. The wrapper
14126 runs until it executes your program, and then @value{GDBN} gains control.
14128 You can use any program that eventually calls @code{execve} with
14129 its arguments as a wrapper. Several standard Unix utilities do
14130 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
14131 with @code{exec "$@@"} will also work.
14133 For example, you can use @code{env} to pass an environment variable to
14134 the debugged program, without setting the variable in @code{gdbserver}'s
14138 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
14141 @subsection Connecting to @code{gdbserver}
14143 Run @value{GDBN} on the host system.
14145 First make sure you have the necessary symbol files. Load symbols for
14146 your application using the @code{file} command before you connect. Use
14147 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
14148 was compiled with the correct sysroot using @code{--with-sysroot}).
14150 The symbol file and target libraries must exactly match the executable
14151 and libraries on the target, with one exception: the files on the host
14152 system should not be stripped, even if the files on the target system
14153 are. Mismatched or missing files will lead to confusing results
14154 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
14155 files may also prevent @code{gdbserver} from debugging multi-threaded
14158 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
14159 For TCP connections, you must start up @code{gdbserver} prior to using
14160 the @code{target remote} command. Otherwise you may get an error whose
14161 text depends on the host system, but which usually looks something like
14162 @samp{Connection refused}. Don't use the @code{load}
14163 command in @value{GDBN} when using @code{gdbserver}, since the program is
14164 already on the target.
14166 @subsection Monitor Commands for @code{gdbserver}
14167 @cindex monitor commands, for @code{gdbserver}
14168 @anchor{Monitor Commands for gdbserver}
14170 During a @value{GDBN} session using @code{gdbserver}, you can use the
14171 @code{monitor} command to send special requests to @code{gdbserver}.
14172 Here are the available commands.
14176 List the available monitor commands.
14178 @item monitor set debug 0
14179 @itemx monitor set debug 1
14180 Disable or enable general debugging messages.
14182 @item monitor set remote-debug 0
14183 @itemx monitor set remote-debug 1
14184 Disable or enable specific debugging messages associated with the remote
14185 protocol (@pxref{Remote Protocol}).
14188 Tell gdbserver to exit immediately. This command should be followed by
14189 @code{disconnect} to close the debugging session. @code{gdbserver} will
14190 detach from any attached processes and kill any processes it created.
14191 Use @code{monitor exit} to terminate @code{gdbserver} at the end
14192 of a multi-process mode debug session.
14196 @node Remote Configuration
14197 @section Remote Configuration
14200 @kindex show remote
14201 This section documents the configuration options available when
14202 debugging remote programs. For the options related to the File I/O
14203 extensions of the remote protocol, see @ref{system,
14204 system-call-allowed}.
14207 @item set remoteaddresssize @var{bits}
14208 @cindex address size for remote targets
14209 @cindex bits in remote address
14210 Set the maximum size of address in a memory packet to the specified
14211 number of bits. @value{GDBN} will mask off the address bits above
14212 that number, when it passes addresses to the remote target. The
14213 default value is the number of bits in the target's address.
14215 @item show remoteaddresssize
14216 Show the current value of remote address size in bits.
14218 @item set remotebaud @var{n}
14219 @cindex baud rate for remote targets
14220 Set the baud rate for the remote serial I/O to @var{n} baud. The
14221 value is used to set the speed of the serial port used for debugging
14224 @item show remotebaud
14225 Show the current speed of the remote connection.
14227 @item set remotebreak
14228 @cindex interrupt remote programs
14229 @cindex BREAK signal instead of Ctrl-C
14230 @anchor{set remotebreak}
14231 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
14232 when you type @kbd{Ctrl-c} to interrupt the program running
14233 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
14234 character instead. The default is off, since most remote systems
14235 expect to see @samp{Ctrl-C} as the interrupt signal.
14237 @item show remotebreak
14238 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
14239 interrupt the remote program.
14241 @item set remoteflow on
14242 @itemx set remoteflow off
14243 @kindex set remoteflow
14244 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
14245 on the serial port used to communicate to the remote target.
14247 @item show remoteflow
14248 @kindex show remoteflow
14249 Show the current setting of hardware flow control.
14251 @item set remotelogbase @var{base}
14252 Set the base (a.k.a.@: radix) of logging serial protocol
14253 communications to @var{base}. Supported values of @var{base} are:
14254 @code{ascii}, @code{octal}, and @code{hex}. The default is
14257 @item show remotelogbase
14258 Show the current setting of the radix for logging remote serial
14261 @item set remotelogfile @var{file}
14262 @cindex record serial communications on file
14263 Record remote serial communications on the named @var{file}. The
14264 default is not to record at all.
14266 @item show remotelogfile.
14267 Show the current setting of the file name on which to record the
14268 serial communications.
14270 @item set remotetimeout @var{num}
14271 @cindex timeout for serial communications
14272 @cindex remote timeout
14273 Set the timeout limit to wait for the remote target to respond to
14274 @var{num} seconds. The default is 2 seconds.
14276 @item show remotetimeout
14277 Show the current number of seconds to wait for the remote target
14280 @cindex limit hardware breakpoints and watchpoints
14281 @cindex remote target, limit break- and watchpoints
14282 @anchor{set remote hardware-watchpoint-limit}
14283 @anchor{set remote hardware-breakpoint-limit}
14284 @item set remote hardware-watchpoint-limit @var{limit}
14285 @itemx set remote hardware-breakpoint-limit @var{limit}
14286 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
14287 watchpoints. A limit of -1, the default, is treated as unlimited.
14289 @item set remote exec-file @var{filename}
14290 @itemx show remote exec-file
14291 @anchor{set remote exec-file}
14292 @cindex executable file, for remote target
14293 Select the file used for @code{run} with @code{target
14294 extended-remote}. This should be set to a filename valid on the
14295 target system. If it is not set, the target will use a default
14296 filename (e.g.@: the last program run).
14300 @item set tcp auto-retry on
14301 @cindex auto-retry, for remote TCP target
14302 Enable auto-retry for remote TCP connections. This is useful if the remote
14303 debugging agent is launched in parallel with @value{GDBN}; there is a race
14304 condition because the agent may not become ready to accept the connection
14305 before @value{GDBN} attempts to connect. When auto-retry is
14306 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
14307 to establish the connection using the timeout specified by
14308 @code{set tcp connect-timeout}.
14310 @item set tcp auto-retry off
14311 Do not auto-retry failed TCP connections.
14313 @item show tcp auto-retry
14314 Show the current auto-retry setting.
14316 @item set tcp connect-timeout @var{seconds}
14317 @cindex connection timeout, for remote TCP target
14318 @cindex timeout, for remote target connection
14319 Set the timeout for establishing a TCP connection to the remote target to
14320 @var{seconds}. The timeout affects both polling to retry failed connections
14321 (enabled by @code{set tcp auto-retry on}) and waiting for connections
14322 that are merely slow to complete, and represents an approximate cumulative
14325 @item show tcp connect-timeout
14326 Show the current connection timeout setting.
14329 @cindex remote packets, enabling and disabling
14330 The @value{GDBN} remote protocol autodetects the packets supported by
14331 your debugging stub. If you need to override the autodetection, you
14332 can use these commands to enable or disable individual packets. Each
14333 packet can be set to @samp{on} (the remote target supports this
14334 packet), @samp{off} (the remote target does not support this packet),
14335 or @samp{auto} (detect remote target support for this packet). They
14336 all default to @samp{auto}. For more information about each packet,
14337 see @ref{Remote Protocol}.
14339 During normal use, you should not have to use any of these commands.
14340 If you do, that may be a bug in your remote debugging stub, or a bug
14341 in @value{GDBN}. You may want to report the problem to the
14342 @value{GDBN} developers.
14344 For each packet @var{name}, the command to enable or disable the
14345 packet is @code{set remote @var{name}-packet}. The available settings
14348 @multitable @columnfractions 0.28 0.32 0.25
14351 @tab Related Features
14353 @item @code{fetch-register}
14355 @tab @code{info registers}
14357 @item @code{set-register}
14361 @item @code{binary-download}
14363 @tab @code{load}, @code{set}
14365 @item @code{read-aux-vector}
14366 @tab @code{qXfer:auxv:read}
14367 @tab @code{info auxv}
14369 @item @code{symbol-lookup}
14370 @tab @code{qSymbol}
14371 @tab Detecting multiple threads
14373 @item @code{attach}
14374 @tab @code{vAttach}
14377 @item @code{verbose-resume}
14379 @tab Stepping or resuming multiple threads
14385 @item @code{software-breakpoint}
14389 @item @code{hardware-breakpoint}
14393 @item @code{write-watchpoint}
14397 @item @code{read-watchpoint}
14401 @item @code{access-watchpoint}
14405 @item @code{target-features}
14406 @tab @code{qXfer:features:read}
14407 @tab @code{set architecture}
14409 @item @code{library-info}
14410 @tab @code{qXfer:libraries:read}
14411 @tab @code{info sharedlibrary}
14413 @item @code{memory-map}
14414 @tab @code{qXfer:memory-map:read}
14415 @tab @code{info mem}
14417 @item @code{read-spu-object}
14418 @tab @code{qXfer:spu:read}
14419 @tab @code{info spu}
14421 @item @code{write-spu-object}
14422 @tab @code{qXfer:spu:write}
14423 @tab @code{info spu}
14425 @item @code{read-siginfo-object}
14426 @tab @code{qXfer:siginfo:read}
14427 @tab @code{print $_siginfo}
14429 @item @code{write-siginfo-object}
14430 @tab @code{qXfer:siginfo:write}
14431 @tab @code{set $_siginfo}
14433 @item @code{get-thread-local-@*storage-address}
14434 @tab @code{qGetTLSAddr}
14435 @tab Displaying @code{__thread} variables
14437 @item @code{search-memory}
14438 @tab @code{qSearch:memory}
14441 @item @code{supported-packets}
14442 @tab @code{qSupported}
14443 @tab Remote communications parameters
14445 @item @code{pass-signals}
14446 @tab @code{QPassSignals}
14447 @tab @code{handle @var{signal}}
14449 @item @code{hostio-close-packet}
14450 @tab @code{vFile:close}
14451 @tab @code{remote get}, @code{remote put}
14453 @item @code{hostio-open-packet}
14454 @tab @code{vFile:open}
14455 @tab @code{remote get}, @code{remote put}
14457 @item @code{hostio-pread-packet}
14458 @tab @code{vFile:pread}
14459 @tab @code{remote get}, @code{remote put}
14461 @item @code{hostio-pwrite-packet}
14462 @tab @code{vFile:pwrite}
14463 @tab @code{remote get}, @code{remote put}
14465 @item @code{hostio-unlink-packet}
14466 @tab @code{vFile:unlink}
14467 @tab @code{remote delete}
14469 @item @code{noack-packet}
14470 @tab @code{QStartNoAckMode}
14471 @tab Packet acknowledgment
14473 @item @code{osdata}
14474 @tab @code{qXfer:osdata:read}
14475 @tab @code{info os}
14477 @item @code{query-attached}
14478 @tab @code{qAttached}
14479 @tab Querying remote process attach state.
14483 @section Implementing a Remote Stub
14485 @cindex debugging stub, example
14486 @cindex remote stub, example
14487 @cindex stub example, remote debugging
14488 The stub files provided with @value{GDBN} implement the target side of the
14489 communication protocol, and the @value{GDBN} side is implemented in the
14490 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
14491 these subroutines to communicate, and ignore the details. (If you're
14492 implementing your own stub file, you can still ignore the details: start
14493 with one of the existing stub files. @file{sparc-stub.c} is the best
14494 organized, and therefore the easiest to read.)
14496 @cindex remote serial debugging, overview
14497 To debug a program running on another machine (the debugging
14498 @dfn{target} machine), you must first arrange for all the usual
14499 prerequisites for the program to run by itself. For example, for a C
14504 A startup routine to set up the C runtime environment; these usually
14505 have a name like @file{crt0}. The startup routine may be supplied by
14506 your hardware supplier, or you may have to write your own.
14509 A C subroutine library to support your program's
14510 subroutine calls, notably managing input and output.
14513 A way of getting your program to the other machine---for example, a
14514 download program. These are often supplied by the hardware
14515 manufacturer, but you may have to write your own from hardware
14519 The next step is to arrange for your program to use a serial port to
14520 communicate with the machine where @value{GDBN} is running (the @dfn{host}
14521 machine). In general terms, the scheme looks like this:
14525 @value{GDBN} already understands how to use this protocol; when everything
14526 else is set up, you can simply use the @samp{target remote} command
14527 (@pxref{Targets,,Specifying a Debugging Target}).
14529 @item On the target,
14530 you must link with your program a few special-purpose subroutines that
14531 implement the @value{GDBN} remote serial protocol. The file containing these
14532 subroutines is called a @dfn{debugging stub}.
14534 On certain remote targets, you can use an auxiliary program
14535 @code{gdbserver} instead of linking a stub into your program.
14536 @xref{Server,,Using the @code{gdbserver} Program}, for details.
14539 The debugging stub is specific to the architecture of the remote
14540 machine; for example, use @file{sparc-stub.c} to debug programs on
14543 @cindex remote serial stub list
14544 These working remote stubs are distributed with @value{GDBN}:
14549 @cindex @file{i386-stub.c}
14552 For Intel 386 and compatible architectures.
14555 @cindex @file{m68k-stub.c}
14556 @cindex Motorola 680x0
14558 For Motorola 680x0 architectures.
14561 @cindex @file{sh-stub.c}
14564 For Renesas SH architectures.
14567 @cindex @file{sparc-stub.c}
14569 For @sc{sparc} architectures.
14571 @item sparcl-stub.c
14572 @cindex @file{sparcl-stub.c}
14575 For Fujitsu @sc{sparclite} architectures.
14579 The @file{README} file in the @value{GDBN} distribution may list other
14580 recently added stubs.
14583 * Stub Contents:: What the stub can do for you
14584 * Bootstrapping:: What you must do for the stub
14585 * Debug Session:: Putting it all together
14588 @node Stub Contents
14589 @subsection What the Stub Can Do for You
14591 @cindex remote serial stub
14592 The debugging stub for your architecture supplies these three
14596 @item set_debug_traps
14597 @findex set_debug_traps
14598 @cindex remote serial stub, initialization
14599 This routine arranges for @code{handle_exception} to run when your
14600 program stops. You must call this subroutine explicitly near the
14601 beginning of your program.
14603 @item handle_exception
14604 @findex handle_exception
14605 @cindex remote serial stub, main routine
14606 This is the central workhorse, but your program never calls it
14607 explicitly---the setup code arranges for @code{handle_exception} to
14608 run when a trap is triggered.
14610 @code{handle_exception} takes control when your program stops during
14611 execution (for example, on a breakpoint), and mediates communications
14612 with @value{GDBN} on the host machine. This is where the communications
14613 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
14614 representative on the target machine. It begins by sending summary
14615 information on the state of your program, then continues to execute,
14616 retrieving and transmitting any information @value{GDBN} needs, until you
14617 execute a @value{GDBN} command that makes your program resume; at that point,
14618 @code{handle_exception} returns control to your own code on the target
14622 @cindex @code{breakpoint} subroutine, remote
14623 Use this auxiliary subroutine to make your program contain a
14624 breakpoint. Depending on the particular situation, this may be the only
14625 way for @value{GDBN} to get control. For instance, if your target
14626 machine has some sort of interrupt button, you won't need to call this;
14627 pressing the interrupt button transfers control to
14628 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
14629 simply receiving characters on the serial port may also trigger a trap;
14630 again, in that situation, you don't need to call @code{breakpoint} from
14631 your own program---simply running @samp{target remote} from the host
14632 @value{GDBN} session gets control.
14634 Call @code{breakpoint} if none of these is true, or if you simply want
14635 to make certain your program stops at a predetermined point for the
14636 start of your debugging session.
14639 @node Bootstrapping
14640 @subsection What You Must Do for the Stub
14642 @cindex remote stub, support routines
14643 The debugging stubs that come with @value{GDBN} are set up for a particular
14644 chip architecture, but they have no information about the rest of your
14645 debugging target machine.
14647 First of all you need to tell the stub how to communicate with the
14651 @item int getDebugChar()
14652 @findex getDebugChar
14653 Write this subroutine to read a single character from the serial port.
14654 It may be identical to @code{getchar} for your target system; a
14655 different name is used to allow you to distinguish the two if you wish.
14657 @item void putDebugChar(int)
14658 @findex putDebugChar
14659 Write this subroutine to write a single character to the serial port.
14660 It may be identical to @code{putchar} for your target system; a
14661 different name is used to allow you to distinguish the two if you wish.
14664 @cindex control C, and remote debugging
14665 @cindex interrupting remote targets
14666 If you want @value{GDBN} to be able to stop your program while it is
14667 running, you need to use an interrupt-driven serial driver, and arrange
14668 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
14669 character). That is the character which @value{GDBN} uses to tell the
14670 remote system to stop.
14672 Getting the debugging target to return the proper status to @value{GDBN}
14673 probably requires changes to the standard stub; one quick and dirty way
14674 is to just execute a breakpoint instruction (the ``dirty'' part is that
14675 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
14677 Other routines you need to supply are:
14680 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
14681 @findex exceptionHandler
14682 Write this function to install @var{exception_address} in the exception
14683 handling tables. You need to do this because the stub does not have any
14684 way of knowing what the exception handling tables on your target system
14685 are like (for example, the processor's table might be in @sc{rom},
14686 containing entries which point to a table in @sc{ram}).
14687 @var{exception_number} is the exception number which should be changed;
14688 its meaning is architecture-dependent (for example, different numbers
14689 might represent divide by zero, misaligned access, etc). When this
14690 exception occurs, control should be transferred directly to
14691 @var{exception_address}, and the processor state (stack, registers,
14692 and so on) should be just as it is when a processor exception occurs. So if
14693 you want to use a jump instruction to reach @var{exception_address}, it
14694 should be a simple jump, not a jump to subroutine.
14696 For the 386, @var{exception_address} should be installed as an interrupt
14697 gate so that interrupts are masked while the handler runs. The gate
14698 should be at privilege level 0 (the most privileged level). The
14699 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
14700 help from @code{exceptionHandler}.
14702 @item void flush_i_cache()
14703 @findex flush_i_cache
14704 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
14705 instruction cache, if any, on your target machine. If there is no
14706 instruction cache, this subroutine may be a no-op.
14708 On target machines that have instruction caches, @value{GDBN} requires this
14709 function to make certain that the state of your program is stable.
14713 You must also make sure this library routine is available:
14716 @item void *memset(void *, int, int)
14718 This is the standard library function @code{memset} that sets an area of
14719 memory to a known value. If you have one of the free versions of
14720 @code{libc.a}, @code{memset} can be found there; otherwise, you must
14721 either obtain it from your hardware manufacturer, or write your own.
14724 If you do not use the GNU C compiler, you may need other standard
14725 library subroutines as well; this varies from one stub to another,
14726 but in general the stubs are likely to use any of the common library
14727 subroutines which @code{@value{NGCC}} generates as inline code.
14730 @node Debug Session
14731 @subsection Putting it All Together
14733 @cindex remote serial debugging summary
14734 In summary, when your program is ready to debug, you must follow these
14739 Make sure you have defined the supporting low-level routines
14740 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
14742 @code{getDebugChar}, @code{putDebugChar},
14743 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
14747 Insert these lines near the top of your program:
14755 For the 680x0 stub only, you need to provide a variable called
14756 @code{exceptionHook}. Normally you just use:
14759 void (*exceptionHook)() = 0;
14763 but if before calling @code{set_debug_traps}, you set it to point to a
14764 function in your program, that function is called when
14765 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
14766 error). The function indicated by @code{exceptionHook} is called with
14767 one parameter: an @code{int} which is the exception number.
14770 Compile and link together: your program, the @value{GDBN} debugging stub for
14771 your target architecture, and the supporting subroutines.
14774 Make sure you have a serial connection between your target machine and
14775 the @value{GDBN} host, and identify the serial port on the host.
14778 @c The "remote" target now provides a `load' command, so we should
14779 @c document that. FIXME.
14780 Download your program to your target machine (or get it there by
14781 whatever means the manufacturer provides), and start it.
14784 Start @value{GDBN} on the host, and connect to the target
14785 (@pxref{Connecting,,Connecting to a Remote Target}).
14789 @node Configurations
14790 @chapter Configuration-Specific Information
14792 While nearly all @value{GDBN} commands are available for all native and
14793 cross versions of the debugger, there are some exceptions. This chapter
14794 describes things that are only available in certain configurations.
14796 There are three major categories of configurations: native
14797 configurations, where the host and target are the same, embedded
14798 operating system configurations, which are usually the same for several
14799 different processor architectures, and bare embedded processors, which
14800 are quite different from each other.
14805 * Embedded Processors::
14812 This section describes details specific to particular native
14817 * BSD libkvm Interface:: Debugging BSD kernel memory images
14818 * SVR4 Process Information:: SVR4 process information
14819 * DJGPP Native:: Features specific to the DJGPP port
14820 * Cygwin Native:: Features specific to the Cygwin port
14821 * Hurd Native:: Features specific to @sc{gnu} Hurd
14822 * Neutrino:: Features specific to QNX Neutrino
14823 * Darwin:: Features specific to Darwin
14829 On HP-UX systems, if you refer to a function or variable name that
14830 begins with a dollar sign, @value{GDBN} searches for a user or system
14831 name first, before it searches for a convenience variable.
14834 @node BSD libkvm Interface
14835 @subsection BSD libkvm Interface
14838 @cindex kernel memory image
14839 @cindex kernel crash dump
14841 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14842 interface that provides a uniform interface for accessing kernel virtual
14843 memory images, including live systems and crash dumps. @value{GDBN}
14844 uses this interface to allow you to debug live kernels and kernel crash
14845 dumps on many native BSD configurations. This is implemented as a
14846 special @code{kvm} debugging target. For debugging a live system, load
14847 the currently running kernel into @value{GDBN} and connect to the
14851 (@value{GDBP}) @b{target kvm}
14854 For debugging crash dumps, provide the file name of the crash dump as an
14858 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14861 Once connected to the @code{kvm} target, the following commands are
14867 Set current context from the @dfn{Process Control Block} (PCB) address.
14870 Set current context from proc address. This command isn't available on
14871 modern FreeBSD systems.
14874 @node SVR4 Process Information
14875 @subsection SVR4 Process Information
14877 @cindex examine process image
14878 @cindex process info via @file{/proc}
14880 Many versions of SVR4 and compatible systems provide a facility called
14881 @samp{/proc} that can be used to examine the image of a running
14882 process using file-system subroutines. If @value{GDBN} is configured
14883 for an operating system with this facility, the command @code{info
14884 proc} is available to report information about the process running
14885 your program, or about any process running on your system. @code{info
14886 proc} works only on SVR4 systems that include the @code{procfs} code.
14887 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14888 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14894 @itemx info proc @var{process-id}
14895 Summarize available information about any running process. If a
14896 process ID is specified by @var{process-id}, display information about
14897 that process; otherwise display information about the program being
14898 debugged. The summary includes the debugged process ID, the command
14899 line used to invoke it, its current working directory, and its
14900 executable file's absolute file name.
14902 On some systems, @var{process-id} can be of the form
14903 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14904 within a process. If the optional @var{pid} part is missing, it means
14905 a thread from the process being debugged (the leading @samp{/} still
14906 needs to be present, or else @value{GDBN} will interpret the number as
14907 a process ID rather than a thread ID).
14909 @item info proc mappings
14910 @cindex memory address space mappings
14911 Report the memory address space ranges accessible in the program, with
14912 information on whether the process has read, write, or execute access
14913 rights to each range. On @sc{gnu}/Linux systems, each memory range
14914 includes the object file which is mapped to that range, instead of the
14915 memory access rights to that range.
14917 @item info proc stat
14918 @itemx info proc status
14919 @cindex process detailed status information
14920 These subcommands are specific to @sc{gnu}/Linux systems. They show
14921 the process-related information, including the user ID and group ID;
14922 how many threads are there in the process; its virtual memory usage;
14923 the signals that are pending, blocked, and ignored; its TTY; its
14924 consumption of system and user time; its stack size; its @samp{nice}
14925 value; etc. For more information, see the @samp{proc} man page
14926 (type @kbd{man 5 proc} from your shell prompt).
14928 @item info proc all
14929 Show all the information about the process described under all of the
14930 above @code{info proc} subcommands.
14933 @comment These sub-options of 'info proc' were not included when
14934 @comment procfs.c was re-written. Keep their descriptions around
14935 @comment against the day when someone finds the time to put them back in.
14936 @kindex info proc times
14937 @item info proc times
14938 Starting time, user CPU time, and system CPU time for your program and
14941 @kindex info proc id
14943 Report on the process IDs related to your program: its own process ID,
14944 the ID of its parent, the process group ID, and the session ID.
14947 @item set procfs-trace
14948 @kindex set procfs-trace
14949 @cindex @code{procfs} API calls
14950 This command enables and disables tracing of @code{procfs} API calls.
14952 @item show procfs-trace
14953 @kindex show procfs-trace
14954 Show the current state of @code{procfs} API call tracing.
14956 @item set procfs-file @var{file}
14957 @kindex set procfs-file
14958 Tell @value{GDBN} to write @code{procfs} API trace to the named
14959 @var{file}. @value{GDBN} appends the trace info to the previous
14960 contents of the file. The default is to display the trace on the
14963 @item show procfs-file
14964 @kindex show procfs-file
14965 Show the file to which @code{procfs} API trace is written.
14967 @item proc-trace-entry
14968 @itemx proc-trace-exit
14969 @itemx proc-untrace-entry
14970 @itemx proc-untrace-exit
14971 @kindex proc-trace-entry
14972 @kindex proc-trace-exit
14973 @kindex proc-untrace-entry
14974 @kindex proc-untrace-exit
14975 These commands enable and disable tracing of entries into and exits
14976 from the @code{syscall} interface.
14979 @kindex info pidlist
14980 @cindex process list, QNX Neutrino
14981 For QNX Neutrino only, this command displays the list of all the
14982 processes and all the threads within each process.
14985 @kindex info meminfo
14986 @cindex mapinfo list, QNX Neutrino
14987 For QNX Neutrino only, this command displays the list of all mapinfos.
14991 @subsection Features for Debugging @sc{djgpp} Programs
14992 @cindex @sc{djgpp} debugging
14993 @cindex native @sc{djgpp} debugging
14994 @cindex MS-DOS-specific commands
14997 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
14998 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
14999 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
15000 top of real-mode DOS systems and their emulations.
15002 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
15003 defines a few commands specific to the @sc{djgpp} port. This
15004 subsection describes those commands.
15009 This is a prefix of @sc{djgpp}-specific commands which print
15010 information about the target system and important OS structures.
15013 @cindex MS-DOS system info
15014 @cindex free memory information (MS-DOS)
15015 @item info dos sysinfo
15016 This command displays assorted information about the underlying
15017 platform: the CPU type and features, the OS version and flavor, the
15018 DPMI version, and the available conventional and DPMI memory.
15023 @cindex segment descriptor tables
15024 @cindex descriptor tables display
15026 @itemx info dos ldt
15027 @itemx info dos idt
15028 These 3 commands display entries from, respectively, Global, Local,
15029 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
15030 tables are data structures which store a descriptor for each segment
15031 that is currently in use. The segment's selector is an index into a
15032 descriptor table; the table entry for that index holds the
15033 descriptor's base address and limit, and its attributes and access
15036 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
15037 segment (used for both data and the stack), and a DOS segment (which
15038 allows access to DOS/BIOS data structures and absolute addresses in
15039 conventional memory). However, the DPMI host will usually define
15040 additional segments in order to support the DPMI environment.
15042 @cindex garbled pointers
15043 These commands allow to display entries from the descriptor tables.
15044 Without an argument, all entries from the specified table are
15045 displayed. An argument, which should be an integer expression, means
15046 display a single entry whose index is given by the argument. For
15047 example, here's a convenient way to display information about the
15048 debugged program's data segment:
15051 @exdent @code{(@value{GDBP}) info dos ldt $ds}
15052 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
15056 This comes in handy when you want to see whether a pointer is outside
15057 the data segment's limit (i.e.@: @dfn{garbled}).
15059 @cindex page tables display (MS-DOS)
15061 @itemx info dos pte
15062 These two commands display entries from, respectively, the Page
15063 Directory and the Page Tables. Page Directories and Page Tables are
15064 data structures which control how virtual memory addresses are mapped
15065 into physical addresses. A Page Table includes an entry for every
15066 page of memory that is mapped into the program's address space; there
15067 may be several Page Tables, each one holding up to 4096 entries. A
15068 Page Directory has up to 4096 entries, one each for every Page Table
15069 that is currently in use.
15071 Without an argument, @kbd{info dos pde} displays the entire Page
15072 Directory, and @kbd{info dos pte} displays all the entries in all of
15073 the Page Tables. An argument, an integer expression, given to the
15074 @kbd{info dos pde} command means display only that entry from the Page
15075 Directory table. An argument given to the @kbd{info dos pte} command
15076 means display entries from a single Page Table, the one pointed to by
15077 the specified entry in the Page Directory.
15079 @cindex direct memory access (DMA) on MS-DOS
15080 These commands are useful when your program uses @dfn{DMA} (Direct
15081 Memory Access), which needs physical addresses to program the DMA
15084 These commands are supported only with some DPMI servers.
15086 @cindex physical address from linear address
15087 @item info dos address-pte @var{addr}
15088 This command displays the Page Table entry for a specified linear
15089 address. The argument @var{addr} is a linear address which should
15090 already have the appropriate segment's base address added to it,
15091 because this command accepts addresses which may belong to @emph{any}
15092 segment. For example, here's how to display the Page Table entry for
15093 the page where a variable @code{i} is stored:
15096 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
15097 @exdent @code{Page Table entry for address 0x11a00d30:}
15098 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
15102 This says that @code{i} is stored at offset @code{0xd30} from the page
15103 whose physical base address is @code{0x02698000}, and shows all the
15104 attributes of that page.
15106 Note that you must cast the addresses of variables to a @code{char *},
15107 since otherwise the value of @code{__djgpp_base_address}, the base
15108 address of all variables and functions in a @sc{djgpp} program, will
15109 be added using the rules of C pointer arithmetics: if @code{i} is
15110 declared an @code{int}, @value{GDBN} will add 4 times the value of
15111 @code{__djgpp_base_address} to the address of @code{i}.
15113 Here's another example, it displays the Page Table entry for the
15117 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
15118 @exdent @code{Page Table entry for address 0x29110:}
15119 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
15123 (The @code{+ 3} offset is because the transfer buffer's address is the
15124 3rd member of the @code{_go32_info_block} structure.) The output
15125 clearly shows that this DPMI server maps the addresses in conventional
15126 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
15127 linear (@code{0x29110}) addresses are identical.
15129 This command is supported only with some DPMI servers.
15132 @cindex DOS serial data link, remote debugging
15133 In addition to native debugging, the DJGPP port supports remote
15134 debugging via a serial data link. The following commands are specific
15135 to remote serial debugging in the DJGPP port of @value{GDBN}.
15138 @kindex set com1base
15139 @kindex set com1irq
15140 @kindex set com2base
15141 @kindex set com2irq
15142 @kindex set com3base
15143 @kindex set com3irq
15144 @kindex set com4base
15145 @kindex set com4irq
15146 @item set com1base @var{addr}
15147 This command sets the base I/O port address of the @file{COM1} serial
15150 @item set com1irq @var{irq}
15151 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
15152 for the @file{COM1} serial port.
15154 There are similar commands @samp{set com2base}, @samp{set com3irq},
15155 etc.@: for setting the port address and the @code{IRQ} lines for the
15158 @kindex show com1base
15159 @kindex show com1irq
15160 @kindex show com2base
15161 @kindex show com2irq
15162 @kindex show com3base
15163 @kindex show com3irq
15164 @kindex show com4base
15165 @kindex show com4irq
15166 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
15167 display the current settings of the base address and the @code{IRQ}
15168 lines used by the COM ports.
15171 @kindex info serial
15172 @cindex DOS serial port status
15173 This command prints the status of the 4 DOS serial ports. For each
15174 port, it prints whether it's active or not, its I/O base address and
15175 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
15176 counts of various errors encountered so far.
15180 @node Cygwin Native
15181 @subsection Features for Debugging MS Windows PE Executables
15182 @cindex MS Windows debugging
15183 @cindex native Cygwin debugging
15184 @cindex Cygwin-specific commands
15186 @value{GDBN} supports native debugging of MS Windows programs, including
15187 DLLs with and without symbolic debugging information. There are various
15188 additional Cygwin-specific commands, described in this section.
15189 Working with DLLs that have no debugging symbols is described in
15190 @ref{Non-debug DLL Symbols}.
15195 This is a prefix of MS Windows-specific commands which print
15196 information about the target system and important OS structures.
15198 @item info w32 selector
15199 This command displays information returned by
15200 the Win32 API @code{GetThreadSelectorEntry} function.
15201 It takes an optional argument that is evaluated to
15202 a long value to give the information about this given selector.
15203 Without argument, this command displays information
15204 about the six segment registers.
15208 This is a Cygwin-specific alias of @code{info shared}.
15210 @kindex dll-symbols
15212 This command loads symbols from a dll similarly to
15213 add-sym command but without the need to specify a base address.
15215 @kindex set cygwin-exceptions
15216 @cindex debugging the Cygwin DLL
15217 @cindex Cygwin DLL, debugging
15218 @item set cygwin-exceptions @var{mode}
15219 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
15220 happen inside the Cygwin DLL. If @var{mode} is @code{off},
15221 @value{GDBN} will delay recognition of exceptions, and may ignore some
15222 exceptions which seem to be caused by internal Cygwin DLL
15223 ``bookkeeping''. This option is meant primarily for debugging the
15224 Cygwin DLL itself; the default value is @code{off} to avoid annoying
15225 @value{GDBN} users with false @code{SIGSEGV} signals.
15227 @kindex show cygwin-exceptions
15228 @item show cygwin-exceptions
15229 Displays whether @value{GDBN} will break on exceptions that happen
15230 inside the Cygwin DLL itself.
15232 @kindex set new-console
15233 @item set new-console @var{mode}
15234 If @var{mode} is @code{on} the debuggee will
15235 be started in a new console on next start.
15236 If @var{mode} is @code{off}i, the debuggee will
15237 be started in the same console as the debugger.
15239 @kindex show new-console
15240 @item show new-console
15241 Displays whether a new console is used
15242 when the debuggee is started.
15244 @kindex set new-group
15245 @item set new-group @var{mode}
15246 This boolean value controls whether the debuggee should
15247 start a new group or stay in the same group as the debugger.
15248 This affects the way the Windows OS handles
15251 @kindex show new-group
15252 @item show new-group
15253 Displays current value of new-group boolean.
15255 @kindex set debugevents
15256 @item set debugevents
15257 This boolean value adds debug output concerning kernel events related
15258 to the debuggee seen by the debugger. This includes events that
15259 signal thread and process creation and exit, DLL loading and
15260 unloading, console interrupts, and debugging messages produced by the
15261 Windows @code{OutputDebugString} API call.
15263 @kindex set debugexec
15264 @item set debugexec
15265 This boolean value adds debug output concerning execute events
15266 (such as resume thread) seen by the debugger.
15268 @kindex set debugexceptions
15269 @item set debugexceptions
15270 This boolean value adds debug output concerning exceptions in the
15271 debuggee seen by the debugger.
15273 @kindex set debugmemory
15274 @item set debugmemory
15275 This boolean value adds debug output concerning debuggee memory reads
15276 and writes by the debugger.
15280 This boolean values specifies whether the debuggee is called
15281 via a shell or directly (default value is on).
15285 Displays if the debuggee will be started with a shell.
15290 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
15293 @node Non-debug DLL Symbols
15294 @subsubsection Support for DLLs without Debugging Symbols
15295 @cindex DLLs with no debugging symbols
15296 @cindex Minimal symbols and DLLs
15298 Very often on windows, some of the DLLs that your program relies on do
15299 not include symbolic debugging information (for example,
15300 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
15301 symbols in a DLL, it relies on the minimal amount of symbolic
15302 information contained in the DLL's export table. This section
15303 describes working with such symbols, known internally to @value{GDBN} as
15304 ``minimal symbols''.
15306 Note that before the debugged program has started execution, no DLLs
15307 will have been loaded. The easiest way around this problem is simply to
15308 start the program --- either by setting a breakpoint or letting the
15309 program run once to completion. It is also possible to force
15310 @value{GDBN} to load a particular DLL before starting the executable ---
15311 see the shared library information in @ref{Files}, or the
15312 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
15313 explicitly loading symbols from a DLL with no debugging information will
15314 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
15315 which may adversely affect symbol lookup performance.
15317 @subsubsection DLL Name Prefixes
15319 In keeping with the naming conventions used by the Microsoft debugging
15320 tools, DLL export symbols are made available with a prefix based on the
15321 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
15322 also entered into the symbol table, so @code{CreateFileA} is often
15323 sufficient. In some cases there will be name clashes within a program
15324 (particularly if the executable itself includes full debugging symbols)
15325 necessitating the use of the fully qualified name when referring to the
15326 contents of the DLL. Use single-quotes around the name to avoid the
15327 exclamation mark (``!'') being interpreted as a language operator.
15329 Note that the internal name of the DLL may be all upper-case, even
15330 though the file name of the DLL is lower-case, or vice-versa. Since
15331 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
15332 some confusion. If in doubt, try the @code{info functions} and
15333 @code{info variables} commands or even @code{maint print msymbols}
15334 (@pxref{Symbols}). Here's an example:
15337 (@value{GDBP}) info function CreateFileA
15338 All functions matching regular expression "CreateFileA":
15340 Non-debugging symbols:
15341 0x77e885f4 CreateFileA
15342 0x77e885f4 KERNEL32!CreateFileA
15346 (@value{GDBP}) info function !
15347 All functions matching regular expression "!":
15349 Non-debugging symbols:
15350 0x6100114c cygwin1!__assert
15351 0x61004034 cygwin1!_dll_crt0@@0
15352 0x61004240 cygwin1!dll_crt0(per_process *)
15356 @subsubsection Working with Minimal Symbols
15358 Symbols extracted from a DLL's export table do not contain very much
15359 type information. All that @value{GDBN} can do is guess whether a symbol
15360 refers to a function or variable depending on the linker section that
15361 contains the symbol. Also note that the actual contents of the memory
15362 contained in a DLL are not available unless the program is running. This
15363 means that you cannot examine the contents of a variable or disassemble
15364 a function within a DLL without a running program.
15366 Variables are generally treated as pointers and dereferenced
15367 automatically. For this reason, it is often necessary to prefix a
15368 variable name with the address-of operator (``&'') and provide explicit
15369 type information in the command. Here's an example of the type of
15373 (@value{GDBP}) print 'cygwin1!__argv'
15378 (@value{GDBP}) x 'cygwin1!__argv'
15379 0x10021610: "\230y\""
15382 And two possible solutions:
15385 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
15386 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
15390 (@value{GDBP}) x/2x &'cygwin1!__argv'
15391 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
15392 (@value{GDBP}) x/x 0x10021608
15393 0x10021608: 0x0022fd98
15394 (@value{GDBP}) x/s 0x0022fd98
15395 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
15398 Setting a break point within a DLL is possible even before the program
15399 starts execution. However, under these circumstances, @value{GDBN} can't
15400 examine the initial instructions of the function in order to skip the
15401 function's frame set-up code. You can work around this by using ``*&''
15402 to set the breakpoint at a raw memory address:
15405 (@value{GDBP}) break *&'python22!PyOS_Readline'
15406 Breakpoint 1 at 0x1e04eff0
15409 The author of these extensions is not entirely convinced that setting a
15410 break point within a shared DLL like @file{kernel32.dll} is completely
15414 @subsection Commands Specific to @sc{gnu} Hurd Systems
15415 @cindex @sc{gnu} Hurd debugging
15417 This subsection describes @value{GDBN} commands specific to the
15418 @sc{gnu} Hurd native debugging.
15423 @kindex set signals@r{, Hurd command}
15424 @kindex set sigs@r{, Hurd command}
15425 This command toggles the state of inferior signal interception by
15426 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
15427 affected by this command. @code{sigs} is a shorthand alias for
15432 @kindex show signals@r{, Hurd command}
15433 @kindex show sigs@r{, Hurd command}
15434 Show the current state of intercepting inferior's signals.
15436 @item set signal-thread
15437 @itemx set sigthread
15438 @kindex set signal-thread
15439 @kindex set sigthread
15440 This command tells @value{GDBN} which thread is the @code{libc} signal
15441 thread. That thread is run when a signal is delivered to a running
15442 process. @code{set sigthread} is the shorthand alias of @code{set
15445 @item show signal-thread
15446 @itemx show sigthread
15447 @kindex show signal-thread
15448 @kindex show sigthread
15449 These two commands show which thread will run when the inferior is
15450 delivered a signal.
15453 @kindex set stopped@r{, Hurd command}
15454 This commands tells @value{GDBN} that the inferior process is stopped,
15455 as with the @code{SIGSTOP} signal. The stopped process can be
15456 continued by delivering a signal to it.
15459 @kindex show stopped@r{, Hurd command}
15460 This command shows whether @value{GDBN} thinks the debuggee is
15463 @item set exceptions
15464 @kindex set exceptions@r{, Hurd command}
15465 Use this command to turn off trapping of exceptions in the inferior.
15466 When exception trapping is off, neither breakpoints nor
15467 single-stepping will work. To restore the default, set exception
15470 @item show exceptions
15471 @kindex show exceptions@r{, Hurd command}
15472 Show the current state of trapping exceptions in the inferior.
15474 @item set task pause
15475 @kindex set task@r{, Hurd commands}
15476 @cindex task attributes (@sc{gnu} Hurd)
15477 @cindex pause current task (@sc{gnu} Hurd)
15478 This command toggles task suspension when @value{GDBN} has control.
15479 Setting it to on takes effect immediately, and the task is suspended
15480 whenever @value{GDBN} gets control. Setting it to off will take
15481 effect the next time the inferior is continued. If this option is set
15482 to off, you can use @code{set thread default pause on} or @code{set
15483 thread pause on} (see below) to pause individual threads.
15485 @item show task pause
15486 @kindex show task@r{, Hurd commands}
15487 Show the current state of task suspension.
15489 @item set task detach-suspend-count
15490 @cindex task suspend count
15491 @cindex detach from task, @sc{gnu} Hurd
15492 This command sets the suspend count the task will be left with when
15493 @value{GDBN} detaches from it.
15495 @item show task detach-suspend-count
15496 Show the suspend count the task will be left with when detaching.
15498 @item set task exception-port
15499 @itemx set task excp
15500 @cindex task exception port, @sc{gnu} Hurd
15501 This command sets the task exception port to which @value{GDBN} will
15502 forward exceptions. The argument should be the value of the @dfn{send
15503 rights} of the task. @code{set task excp} is a shorthand alias.
15505 @item set noninvasive
15506 @cindex noninvasive task options
15507 This command switches @value{GDBN} to a mode that is the least
15508 invasive as far as interfering with the inferior is concerned. This
15509 is the same as using @code{set task pause}, @code{set exceptions}, and
15510 @code{set signals} to values opposite to the defaults.
15512 @item info send-rights
15513 @itemx info receive-rights
15514 @itemx info port-rights
15515 @itemx info port-sets
15516 @itemx info dead-names
15519 @cindex send rights, @sc{gnu} Hurd
15520 @cindex receive rights, @sc{gnu} Hurd
15521 @cindex port rights, @sc{gnu} Hurd
15522 @cindex port sets, @sc{gnu} Hurd
15523 @cindex dead names, @sc{gnu} Hurd
15524 These commands display information about, respectively, send rights,
15525 receive rights, port rights, port sets, and dead names of a task.
15526 There are also shorthand aliases: @code{info ports} for @code{info
15527 port-rights} and @code{info psets} for @code{info port-sets}.
15529 @item set thread pause
15530 @kindex set thread@r{, Hurd command}
15531 @cindex thread properties, @sc{gnu} Hurd
15532 @cindex pause current thread (@sc{gnu} Hurd)
15533 This command toggles current thread suspension when @value{GDBN} has
15534 control. Setting it to on takes effect immediately, and the current
15535 thread is suspended whenever @value{GDBN} gets control. Setting it to
15536 off will take effect the next time the inferior is continued.
15537 Normally, this command has no effect, since when @value{GDBN} has
15538 control, the whole task is suspended. However, if you used @code{set
15539 task pause off} (see above), this command comes in handy to suspend
15540 only the current thread.
15542 @item show thread pause
15543 @kindex show thread@r{, Hurd command}
15544 This command shows the state of current thread suspension.
15546 @item set thread run
15547 This command sets whether the current thread is allowed to run.
15549 @item show thread run
15550 Show whether the current thread is allowed to run.
15552 @item set thread detach-suspend-count
15553 @cindex thread suspend count, @sc{gnu} Hurd
15554 @cindex detach from thread, @sc{gnu} Hurd
15555 This command sets the suspend count @value{GDBN} will leave on a
15556 thread when detaching. This number is relative to the suspend count
15557 found by @value{GDBN} when it notices the thread; use @code{set thread
15558 takeover-suspend-count} to force it to an absolute value.
15560 @item show thread detach-suspend-count
15561 Show the suspend count @value{GDBN} will leave on the thread when
15564 @item set thread exception-port
15565 @itemx set thread excp
15566 Set the thread exception port to which to forward exceptions. This
15567 overrides the port set by @code{set task exception-port} (see above).
15568 @code{set thread excp} is the shorthand alias.
15570 @item set thread takeover-suspend-count
15571 Normally, @value{GDBN}'s thread suspend counts are relative to the
15572 value @value{GDBN} finds when it notices each thread. This command
15573 changes the suspend counts to be absolute instead.
15575 @item set thread default
15576 @itemx show thread default
15577 @cindex thread default settings, @sc{gnu} Hurd
15578 Each of the above @code{set thread} commands has a @code{set thread
15579 default} counterpart (e.g., @code{set thread default pause}, @code{set
15580 thread default exception-port}, etc.). The @code{thread default}
15581 variety of commands sets the default thread properties for all
15582 threads; you can then change the properties of individual threads with
15583 the non-default commands.
15588 @subsection QNX Neutrino
15589 @cindex QNX Neutrino
15591 @value{GDBN} provides the following commands specific to the QNX
15595 @item set debug nto-debug
15596 @kindex set debug nto-debug
15597 When set to on, enables debugging messages specific to the QNX
15600 @item show debug nto-debug
15601 @kindex show debug nto-debug
15602 Show the current state of QNX Neutrino messages.
15609 @value{GDBN} provides the following commands specific to the Darwin target:
15612 @item set debug darwin @var{num}
15613 @kindex set debug darwin
15614 When set to a non zero value, enables debugging messages specific to
15615 the Darwin support. Higher values produce more verbose output.
15617 @item show debug darwin
15618 @kindex show debug darwin
15619 Show the current state of Darwin messages.
15621 @item set debug mach-o @var{num}
15622 @kindex set debug mach-o
15623 When set to a non zero value, enables debugging messages while
15624 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
15625 file format used on Darwin for object and executable files.) Higher
15626 values produce more verbose output. This is a command to diagnose
15627 problems internal to @value{GDBN} and should not be needed in normal
15630 @item show debug mach-o
15631 @kindex show debug mach-o
15632 Show the current state of Mach-O file messages.
15634 @item set mach-exceptions on
15635 @itemx set mach-exceptions off
15636 @kindex set mach-exceptions
15637 On Darwin, faults are first reported as a Mach exception and are then
15638 mapped to a Posix signal. Use this command to turn on trapping of
15639 Mach exceptions in the inferior. This might be sometimes useful to
15640 better understand the cause of a fault. The default is off.
15642 @item show mach-exceptions
15643 @kindex show mach-exceptions
15644 Show the current state of exceptions trapping.
15649 @section Embedded Operating Systems
15651 This section describes configurations involving the debugging of
15652 embedded operating systems that are available for several different
15656 * VxWorks:: Using @value{GDBN} with VxWorks
15659 @value{GDBN} includes the ability to debug programs running on
15660 various real-time operating systems.
15663 @subsection Using @value{GDBN} with VxWorks
15669 @kindex target vxworks
15670 @item target vxworks @var{machinename}
15671 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
15672 is the target system's machine name or IP address.
15676 On VxWorks, @code{load} links @var{filename} dynamically on the
15677 current target system as well as adding its symbols in @value{GDBN}.
15679 @value{GDBN} enables developers to spawn and debug tasks running on networked
15680 VxWorks targets from a Unix host. Already-running tasks spawned from
15681 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
15682 both the Unix host and on the VxWorks target. The program
15683 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
15684 installed with the name @code{vxgdb}, to distinguish it from a
15685 @value{GDBN} for debugging programs on the host itself.)
15688 @item VxWorks-timeout @var{args}
15689 @kindex vxworks-timeout
15690 All VxWorks-based targets now support the option @code{vxworks-timeout}.
15691 This option is set by the user, and @var{args} represents the number of
15692 seconds @value{GDBN} waits for responses to rpc's. You might use this if
15693 your VxWorks target is a slow software simulator or is on the far side
15694 of a thin network line.
15697 The following information on connecting to VxWorks was current when
15698 this manual was produced; newer releases of VxWorks may use revised
15701 @findex INCLUDE_RDB
15702 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
15703 to include the remote debugging interface routines in the VxWorks
15704 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
15705 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
15706 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
15707 source debugging task @code{tRdbTask} when VxWorks is booted. For more
15708 information on configuring and remaking VxWorks, see the manufacturer's
15710 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
15712 Once you have included @file{rdb.a} in your VxWorks system image and set
15713 your Unix execution search path to find @value{GDBN}, you are ready to
15714 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
15715 @code{vxgdb}, depending on your installation).
15717 @value{GDBN} comes up showing the prompt:
15724 * VxWorks Connection:: Connecting to VxWorks
15725 * VxWorks Download:: VxWorks download
15726 * VxWorks Attach:: Running tasks
15729 @node VxWorks Connection
15730 @subsubsection Connecting to VxWorks
15732 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
15733 network. To connect to a target whose host name is ``@code{tt}'', type:
15736 (vxgdb) target vxworks tt
15740 @value{GDBN} displays messages like these:
15743 Attaching remote machine across net...
15748 @value{GDBN} then attempts to read the symbol tables of any object modules
15749 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
15750 these files by searching the directories listed in the command search
15751 path (@pxref{Environment, ,Your Program's Environment}); if it fails
15752 to find an object file, it displays a message such as:
15755 prog.o: No such file or directory.
15758 When this happens, add the appropriate directory to the search path with
15759 the @value{GDBN} command @code{path}, and execute the @code{target}
15762 @node VxWorks Download
15763 @subsubsection VxWorks Download
15765 @cindex download to VxWorks
15766 If you have connected to the VxWorks target and you want to debug an
15767 object that has not yet been loaded, you can use the @value{GDBN}
15768 @code{load} command to download a file from Unix to VxWorks
15769 incrementally. The object file given as an argument to the @code{load}
15770 command is actually opened twice: first by the VxWorks target in order
15771 to download the code, then by @value{GDBN} in order to read the symbol
15772 table. This can lead to problems if the current working directories on
15773 the two systems differ. If both systems have NFS mounted the same
15774 filesystems, you can avoid these problems by using absolute paths.
15775 Otherwise, it is simplest to set the working directory on both systems
15776 to the directory in which the object file resides, and then to reference
15777 the file by its name, without any path. For instance, a program
15778 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
15779 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
15780 program, type this on VxWorks:
15783 -> cd "@var{vxpath}/vw/demo/rdb"
15787 Then, in @value{GDBN}, type:
15790 (vxgdb) cd @var{hostpath}/vw/demo/rdb
15791 (vxgdb) load prog.o
15794 @value{GDBN} displays a response similar to this:
15797 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
15800 You can also use the @code{load} command to reload an object module
15801 after editing and recompiling the corresponding source file. Note that
15802 this makes @value{GDBN} delete all currently-defined breakpoints,
15803 auto-displays, and convenience variables, and to clear the value
15804 history. (This is necessary in order to preserve the integrity of
15805 debugger's data structures that reference the target system's symbol
15808 @node VxWorks Attach
15809 @subsubsection Running Tasks
15811 @cindex running VxWorks tasks
15812 You can also attach to an existing task using the @code{attach} command as
15816 (vxgdb) attach @var{task}
15820 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
15821 or suspended when you attach to it. Running tasks are suspended at
15822 the time of attachment.
15824 @node Embedded Processors
15825 @section Embedded Processors
15827 This section goes into details specific to particular embedded
15830 @cindex send command to simulator
15831 Whenever a specific embedded processor has a simulator, @value{GDBN}
15832 allows to send an arbitrary command to the simulator.
15835 @item sim @var{command}
15836 @kindex sim@r{, a command}
15837 Send an arbitrary @var{command} string to the simulator. Consult the
15838 documentation for the specific simulator in use for information about
15839 acceptable commands.
15845 * M32R/D:: Renesas M32R/D
15846 * M68K:: Motorola M68K
15847 * MIPS Embedded:: MIPS Embedded
15848 * OpenRISC 1000:: OpenRisc 1000
15849 * PA:: HP PA Embedded
15850 * PowerPC Embedded:: PowerPC Embedded
15851 * Sparclet:: Tsqware Sparclet
15852 * Sparclite:: Fujitsu Sparclite
15853 * Z8000:: Zilog Z8000
15856 * Super-H:: Renesas Super-H
15865 @item target rdi @var{dev}
15866 ARM Angel monitor, via RDI library interface to ADP protocol. You may
15867 use this target to communicate with both boards running the Angel
15868 monitor, or with the EmbeddedICE JTAG debug device.
15871 @item target rdp @var{dev}
15876 @value{GDBN} provides the following ARM-specific commands:
15879 @item set arm disassembler
15881 This commands selects from a list of disassembly styles. The
15882 @code{"std"} style is the standard style.
15884 @item show arm disassembler
15886 Show the current disassembly style.
15888 @item set arm apcs32
15889 @cindex ARM 32-bit mode
15890 This command toggles ARM operation mode between 32-bit and 26-bit.
15892 @item show arm apcs32
15893 Display the current usage of the ARM 32-bit mode.
15895 @item set arm fpu @var{fputype}
15896 This command sets the ARM floating-point unit (FPU) type. The
15897 argument @var{fputype} can be one of these:
15901 Determine the FPU type by querying the OS ABI.
15903 Software FPU, with mixed-endian doubles on little-endian ARM
15906 GCC-compiled FPA co-processor.
15908 Software FPU with pure-endian doubles.
15914 Show the current type of the FPU.
15917 This command forces @value{GDBN} to use the specified ABI.
15920 Show the currently used ABI.
15922 @item set arm fallback-mode (arm|thumb|auto)
15923 @value{GDBN} uses the symbol table, when available, to determine
15924 whether instructions are ARM or Thumb. This command controls
15925 @value{GDBN}'s default behavior when the symbol table is not
15926 available. The default is @samp{auto}, which causes @value{GDBN} to
15927 use the current execution mode (from the @code{T} bit in the @code{CPSR}
15930 @item show arm fallback-mode
15931 Show the current fallback instruction mode.
15933 @item set arm force-mode (arm|thumb|auto)
15934 This command overrides use of the symbol table to determine whether
15935 instructions are ARM or Thumb. The default is @samp{auto}, which
15936 causes @value{GDBN} to use the symbol table and then the setting
15937 of @samp{set arm fallback-mode}.
15939 @item show arm force-mode
15940 Show the current forced instruction mode.
15942 @item set debug arm
15943 Toggle whether to display ARM-specific debugging messages from the ARM
15944 target support subsystem.
15946 @item show debug arm
15947 Show whether ARM-specific debugging messages are enabled.
15950 The following commands are available when an ARM target is debugged
15951 using the RDI interface:
15954 @item rdilogfile @r{[}@var{file}@r{]}
15956 @cindex ADP (Angel Debugger Protocol) logging
15957 Set the filename for the ADP (Angel Debugger Protocol) packet log.
15958 With an argument, sets the log file to the specified @var{file}. With
15959 no argument, show the current log file name. The default log file is
15962 @item rdilogenable @r{[}@var{arg}@r{]}
15963 @kindex rdilogenable
15964 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
15965 enables logging, with an argument 0 or @code{"no"} disables it. With
15966 no arguments displays the current setting. When logging is enabled,
15967 ADP packets exchanged between @value{GDBN} and the RDI target device
15968 are logged to a file.
15970 @item set rdiromatzero
15971 @kindex set rdiromatzero
15972 @cindex ROM at zero address, RDI
15973 Tell @value{GDBN} whether the target has ROM at address 0. If on,
15974 vector catching is disabled, so that zero address can be used. If off
15975 (the default), vector catching is enabled. For this command to take
15976 effect, it needs to be invoked prior to the @code{target rdi} command.
15978 @item show rdiromatzero
15979 @kindex show rdiromatzero
15980 Show the current setting of ROM at zero address.
15982 @item set rdiheartbeat
15983 @kindex set rdiheartbeat
15984 @cindex RDI heartbeat
15985 Enable or disable RDI heartbeat packets. It is not recommended to
15986 turn on this option, since it confuses ARM and EPI JTAG interface, as
15987 well as the Angel monitor.
15989 @item show rdiheartbeat
15990 @kindex show rdiheartbeat
15991 Show the setting of RDI heartbeat packets.
15996 @subsection Renesas M32R/D and M32R/SDI
15999 @kindex target m32r
16000 @item target m32r @var{dev}
16001 Renesas M32R/D ROM monitor.
16003 @kindex target m32rsdi
16004 @item target m32rsdi @var{dev}
16005 Renesas M32R SDI server, connected via parallel port to the board.
16008 The following @value{GDBN} commands are specific to the M32R monitor:
16011 @item set download-path @var{path}
16012 @kindex set download-path
16013 @cindex find downloadable @sc{srec} files (M32R)
16014 Set the default path for finding downloadable @sc{srec} files.
16016 @item show download-path
16017 @kindex show download-path
16018 Show the default path for downloadable @sc{srec} files.
16020 @item set board-address @var{addr}
16021 @kindex set board-address
16022 @cindex M32-EVA target board address
16023 Set the IP address for the M32R-EVA target board.
16025 @item show board-address
16026 @kindex show board-address
16027 Show the current IP address of the target board.
16029 @item set server-address @var{addr}
16030 @kindex set server-address
16031 @cindex download server address (M32R)
16032 Set the IP address for the download server, which is the @value{GDBN}'s
16035 @item show server-address
16036 @kindex show server-address
16037 Display the IP address of the download server.
16039 @item upload @r{[}@var{file}@r{]}
16040 @kindex upload@r{, M32R}
16041 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
16042 upload capability. If no @var{file} argument is given, the current
16043 executable file is uploaded.
16045 @item tload @r{[}@var{file}@r{]}
16046 @kindex tload@r{, M32R}
16047 Test the @code{upload} command.
16050 The following commands are available for M32R/SDI:
16055 @cindex reset SDI connection, M32R
16056 This command resets the SDI connection.
16060 This command shows the SDI connection status.
16063 @kindex debug_chaos
16064 @cindex M32R/Chaos debugging
16065 Instructs the remote that M32R/Chaos debugging is to be used.
16067 @item use_debug_dma
16068 @kindex use_debug_dma
16069 Instructs the remote to use the DEBUG_DMA method of accessing memory.
16072 @kindex use_mon_code
16073 Instructs the remote to use the MON_CODE method of accessing memory.
16076 @kindex use_ib_break
16077 Instructs the remote to set breakpoints by IB break.
16079 @item use_dbt_break
16080 @kindex use_dbt_break
16081 Instructs the remote to set breakpoints by DBT.
16087 The Motorola m68k configuration includes ColdFire support, and a
16088 target command for the following ROM monitor.
16092 @kindex target dbug
16093 @item target dbug @var{dev}
16094 dBUG ROM monitor for Motorola ColdFire.
16098 @node MIPS Embedded
16099 @subsection MIPS Embedded
16101 @cindex MIPS boards
16102 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
16103 MIPS board attached to a serial line. This is available when
16104 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
16107 Use these @value{GDBN} commands to specify the connection to your target board:
16110 @item target mips @var{port}
16111 @kindex target mips @var{port}
16112 To run a program on the board, start up @code{@value{GDBP}} with the
16113 name of your program as the argument. To connect to the board, use the
16114 command @samp{target mips @var{port}}, where @var{port} is the name of
16115 the serial port connected to the board. If the program has not already
16116 been downloaded to the board, you may use the @code{load} command to
16117 download it. You can then use all the usual @value{GDBN} commands.
16119 For example, this sequence connects to the target board through a serial
16120 port, and loads and runs a program called @var{prog} through the
16124 host$ @value{GDBP} @var{prog}
16125 @value{GDBN} is free software and @dots{}
16126 (@value{GDBP}) target mips /dev/ttyb
16127 (@value{GDBP}) load @var{prog}
16131 @item target mips @var{hostname}:@var{portnumber}
16132 On some @value{GDBN} host configurations, you can specify a TCP
16133 connection (for instance, to a serial line managed by a terminal
16134 concentrator) instead of a serial port, using the syntax
16135 @samp{@var{hostname}:@var{portnumber}}.
16137 @item target pmon @var{port}
16138 @kindex target pmon @var{port}
16141 @item target ddb @var{port}
16142 @kindex target ddb @var{port}
16143 NEC's DDB variant of PMON for Vr4300.
16145 @item target lsi @var{port}
16146 @kindex target lsi @var{port}
16147 LSI variant of PMON.
16149 @kindex target r3900
16150 @item target r3900 @var{dev}
16151 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
16153 @kindex target array
16154 @item target array @var{dev}
16155 Array Tech LSI33K RAID controller board.
16161 @value{GDBN} also supports these special commands for MIPS targets:
16164 @item set mipsfpu double
16165 @itemx set mipsfpu single
16166 @itemx set mipsfpu none
16167 @itemx set mipsfpu auto
16168 @itemx show mipsfpu
16169 @kindex set mipsfpu
16170 @kindex show mipsfpu
16171 @cindex MIPS remote floating point
16172 @cindex floating point, MIPS remote
16173 If your target board does not support the MIPS floating point
16174 coprocessor, you should use the command @samp{set mipsfpu none} (if you
16175 need this, you may wish to put the command in your @value{GDBN} init
16176 file). This tells @value{GDBN} how to find the return value of
16177 functions which return floating point values. It also allows
16178 @value{GDBN} to avoid saving the floating point registers when calling
16179 functions on the board. If you are using a floating point coprocessor
16180 with only single precision floating point support, as on the @sc{r4650}
16181 processor, use the command @samp{set mipsfpu single}. The default
16182 double precision floating point coprocessor may be selected using
16183 @samp{set mipsfpu double}.
16185 In previous versions the only choices were double precision or no
16186 floating point, so @samp{set mipsfpu on} will select double precision
16187 and @samp{set mipsfpu off} will select no floating point.
16189 As usual, you can inquire about the @code{mipsfpu} variable with
16190 @samp{show mipsfpu}.
16192 @item set timeout @var{seconds}
16193 @itemx set retransmit-timeout @var{seconds}
16194 @itemx show timeout
16195 @itemx show retransmit-timeout
16196 @cindex @code{timeout}, MIPS protocol
16197 @cindex @code{retransmit-timeout}, MIPS protocol
16198 @kindex set timeout
16199 @kindex show timeout
16200 @kindex set retransmit-timeout
16201 @kindex show retransmit-timeout
16202 You can control the timeout used while waiting for a packet, in the MIPS
16203 remote protocol, with the @code{set timeout @var{seconds}} command. The
16204 default is 5 seconds. Similarly, you can control the timeout used while
16205 waiting for an acknowledgment of a packet with the @code{set
16206 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
16207 You can inspect both values with @code{show timeout} and @code{show
16208 retransmit-timeout}. (These commands are @emph{only} available when
16209 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
16211 The timeout set by @code{set timeout} does not apply when @value{GDBN}
16212 is waiting for your program to stop. In that case, @value{GDBN} waits
16213 forever because it has no way of knowing how long the program is going
16214 to run before stopping.
16216 @item set syn-garbage-limit @var{num}
16217 @kindex set syn-garbage-limit@r{, MIPS remote}
16218 @cindex synchronize with remote MIPS target
16219 Limit the maximum number of characters @value{GDBN} should ignore when
16220 it tries to synchronize with the remote target. The default is 10
16221 characters. Setting the limit to -1 means there's no limit.
16223 @item show syn-garbage-limit
16224 @kindex show syn-garbage-limit@r{, MIPS remote}
16225 Show the current limit on the number of characters to ignore when
16226 trying to synchronize with the remote system.
16228 @item set monitor-prompt @var{prompt}
16229 @kindex set monitor-prompt@r{, MIPS remote}
16230 @cindex remote monitor prompt
16231 Tell @value{GDBN} to expect the specified @var{prompt} string from the
16232 remote monitor. The default depends on the target:
16242 @item show monitor-prompt
16243 @kindex show monitor-prompt@r{, MIPS remote}
16244 Show the current strings @value{GDBN} expects as the prompt from the
16247 @item set monitor-warnings
16248 @kindex set monitor-warnings@r{, MIPS remote}
16249 Enable or disable monitor warnings about hardware breakpoints. This
16250 has effect only for the @code{lsi} target. When on, @value{GDBN} will
16251 display warning messages whose codes are returned by the @code{lsi}
16252 PMON monitor for breakpoint commands.
16254 @item show monitor-warnings
16255 @kindex show monitor-warnings@r{, MIPS remote}
16256 Show the current setting of printing monitor warnings.
16258 @item pmon @var{command}
16259 @kindex pmon@r{, MIPS remote}
16260 @cindex send PMON command
16261 This command allows sending an arbitrary @var{command} string to the
16262 monitor. The monitor must be in debug mode for this to work.
16265 @node OpenRISC 1000
16266 @subsection OpenRISC 1000
16267 @cindex OpenRISC 1000
16269 @cindex or1k boards
16270 See OR1k Architecture document (@uref{www.opencores.org}) for more information
16271 about platform and commands.
16275 @kindex target jtag
16276 @item target jtag jtag://@var{host}:@var{port}
16278 Connects to remote JTAG server.
16279 JTAG remote server can be either an or1ksim or JTAG server,
16280 connected via parallel port to the board.
16282 Example: @code{target jtag jtag://localhost:9999}
16285 @item or1ksim @var{command}
16286 If connected to @code{or1ksim} OpenRISC 1000 Architectural
16287 Simulator, proprietary commands can be executed.
16289 @kindex info or1k spr
16290 @item info or1k spr
16291 Displays spr groups.
16293 @item info or1k spr @var{group}
16294 @itemx info or1k spr @var{groupno}
16295 Displays register names in selected group.
16297 @item info or1k spr @var{group} @var{register}
16298 @itemx info or1k spr @var{register}
16299 @itemx info or1k spr @var{groupno} @var{registerno}
16300 @itemx info or1k spr @var{registerno}
16301 Shows information about specified spr register.
16304 @item spr @var{group} @var{register} @var{value}
16305 @itemx spr @var{register @var{value}}
16306 @itemx spr @var{groupno} @var{registerno @var{value}}
16307 @itemx spr @var{registerno @var{value}}
16308 Writes @var{value} to specified spr register.
16311 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
16312 It is very similar to @value{GDBN} trace, except it does not interfere with normal
16313 program execution and is thus much faster. Hardware breakpoints/watchpoint
16314 triggers can be set using:
16317 Load effective address/data
16319 Store effective address/data
16321 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
16326 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
16327 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
16329 @code{htrace} commands:
16330 @cindex OpenRISC 1000 htrace
16333 @item hwatch @var{conditional}
16334 Set hardware watchpoint on combination of Load/Store Effective Address(es)
16335 or Data. For example:
16337 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16339 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16343 Display information about current HW trace configuration.
16345 @item htrace trigger @var{conditional}
16346 Set starting criteria for HW trace.
16348 @item htrace qualifier @var{conditional}
16349 Set acquisition qualifier for HW trace.
16351 @item htrace stop @var{conditional}
16352 Set HW trace stopping criteria.
16354 @item htrace record [@var{data}]*
16355 Selects the data to be recorded, when qualifier is met and HW trace was
16358 @item htrace enable
16359 @itemx htrace disable
16360 Enables/disables the HW trace.
16362 @item htrace rewind [@var{filename}]
16363 Clears currently recorded trace data.
16365 If filename is specified, new trace file is made and any newly collected data
16366 will be written there.
16368 @item htrace print [@var{start} [@var{len}]]
16369 Prints trace buffer, using current record configuration.
16371 @item htrace mode continuous
16372 Set continuous trace mode.
16374 @item htrace mode suspend
16375 Set suspend trace mode.
16379 @node PowerPC Embedded
16380 @subsection PowerPC Embedded
16382 @value{GDBN} provides the following PowerPC-specific commands:
16385 @kindex set powerpc
16386 @item set powerpc soft-float
16387 @itemx show powerpc soft-float
16388 Force @value{GDBN} to use (or not use) a software floating point calling
16389 convention. By default, @value{GDBN} selects the calling convention based
16390 on the selected architecture and the provided executable file.
16392 @item set powerpc vector-abi
16393 @itemx show powerpc vector-abi
16394 Force @value{GDBN} to use the specified calling convention for vector
16395 arguments and return values. The valid options are @samp{auto};
16396 @samp{generic}, to avoid vector registers even if they are present;
16397 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
16398 registers. By default, @value{GDBN} selects the calling convention
16399 based on the selected architecture and the provided executable file.
16401 @kindex target dink32
16402 @item target dink32 @var{dev}
16403 DINK32 ROM monitor.
16405 @kindex target ppcbug
16406 @item target ppcbug @var{dev}
16407 @kindex target ppcbug1
16408 @item target ppcbug1 @var{dev}
16409 PPCBUG ROM monitor for PowerPC.
16412 @item target sds @var{dev}
16413 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
16416 @cindex SDS protocol
16417 The following commands specific to the SDS protocol are supported
16421 @item set sdstimeout @var{nsec}
16422 @kindex set sdstimeout
16423 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
16424 default is 2 seconds.
16426 @item show sdstimeout
16427 @kindex show sdstimeout
16428 Show the current value of the SDS timeout.
16430 @item sds @var{command}
16431 @kindex sds@r{, a command}
16432 Send the specified @var{command} string to the SDS monitor.
16437 @subsection HP PA Embedded
16441 @kindex target op50n
16442 @item target op50n @var{dev}
16443 OP50N monitor, running on an OKI HPPA board.
16445 @kindex target w89k
16446 @item target w89k @var{dev}
16447 W89K monitor, running on a Winbond HPPA board.
16452 @subsection Tsqware Sparclet
16456 @value{GDBN} enables developers to debug tasks running on
16457 Sparclet targets from a Unix host.
16458 @value{GDBN} uses code that runs on
16459 both the Unix host and on the Sparclet target. The program
16460 @code{@value{GDBP}} is installed and executed on the Unix host.
16463 @item remotetimeout @var{args}
16464 @kindex remotetimeout
16465 @value{GDBN} supports the option @code{remotetimeout}.
16466 This option is set by the user, and @var{args} represents the number of
16467 seconds @value{GDBN} waits for responses.
16470 @cindex compiling, on Sparclet
16471 When compiling for debugging, include the options @samp{-g} to get debug
16472 information and @samp{-Ttext} to relocate the program to where you wish to
16473 load it on the target. You may also want to add the options @samp{-n} or
16474 @samp{-N} in order to reduce the size of the sections. Example:
16477 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
16480 You can use @code{objdump} to verify that the addresses are what you intended:
16483 sparclet-aout-objdump --headers --syms prog
16486 @cindex running, on Sparclet
16488 your Unix execution search path to find @value{GDBN}, you are ready to
16489 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
16490 (or @code{sparclet-aout-gdb}, depending on your installation).
16492 @value{GDBN} comes up showing the prompt:
16499 * Sparclet File:: Setting the file to debug
16500 * Sparclet Connection:: Connecting to Sparclet
16501 * Sparclet Download:: Sparclet download
16502 * Sparclet Execution:: Running and debugging
16505 @node Sparclet File
16506 @subsubsection Setting File to Debug
16508 The @value{GDBN} command @code{file} lets you choose with program to debug.
16511 (gdbslet) file prog
16515 @value{GDBN} then attempts to read the symbol table of @file{prog}.
16516 @value{GDBN} locates
16517 the file by searching the directories listed in the command search
16519 If the file was compiled with debug information (option @samp{-g}), source
16520 files will be searched as well.
16521 @value{GDBN} locates
16522 the source files by searching the directories listed in the directory search
16523 path (@pxref{Environment, ,Your Program's Environment}).
16525 to find a file, it displays a message such as:
16528 prog: No such file or directory.
16531 When this happens, add the appropriate directories to the search paths with
16532 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
16533 @code{target} command again.
16535 @node Sparclet Connection
16536 @subsubsection Connecting to Sparclet
16538 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
16539 To connect to a target on serial port ``@code{ttya}'', type:
16542 (gdbslet) target sparclet /dev/ttya
16543 Remote target sparclet connected to /dev/ttya
16544 main () at ../prog.c:3
16548 @value{GDBN} displays messages like these:
16554 @node Sparclet Download
16555 @subsubsection Sparclet Download
16557 @cindex download to Sparclet
16558 Once connected to the Sparclet target,
16559 you can use the @value{GDBN}
16560 @code{load} command to download the file from the host to the target.
16561 The file name and load offset should be given as arguments to the @code{load}
16563 Since the file format is aout, the program must be loaded to the starting
16564 address. You can use @code{objdump} to find out what this value is. The load
16565 offset is an offset which is added to the VMA (virtual memory address)
16566 of each of the file's sections.
16567 For instance, if the program
16568 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
16569 and bss at 0x12010170, in @value{GDBN}, type:
16572 (gdbslet) load prog 0x12010000
16573 Loading section .text, size 0xdb0 vma 0x12010000
16576 If the code is loaded at a different address then what the program was linked
16577 to, you may need to use the @code{section} and @code{add-symbol-file} commands
16578 to tell @value{GDBN} where to map the symbol table.
16580 @node Sparclet Execution
16581 @subsubsection Running and Debugging
16583 @cindex running and debugging Sparclet programs
16584 You can now begin debugging the task using @value{GDBN}'s execution control
16585 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
16586 manual for the list of commands.
16590 Breakpoint 1 at 0x12010000: file prog.c, line 3.
16592 Starting program: prog
16593 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
16594 3 char *symarg = 0;
16596 4 char *execarg = "hello!";
16601 @subsection Fujitsu Sparclite
16605 @kindex target sparclite
16606 @item target sparclite @var{dev}
16607 Fujitsu sparclite boards, used only for the purpose of loading.
16608 You must use an additional command to debug the program.
16609 For example: target remote @var{dev} using @value{GDBN} standard
16615 @subsection Zilog Z8000
16618 @cindex simulator, Z8000
16619 @cindex Zilog Z8000 simulator
16621 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
16624 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
16625 unsegmented variant of the Z8000 architecture) or the Z8001 (the
16626 segmented variant). The simulator recognizes which architecture is
16627 appropriate by inspecting the object code.
16630 @item target sim @var{args}
16632 @kindex target sim@r{, with Z8000}
16633 Debug programs on a simulated CPU. If the simulator supports setup
16634 options, specify them via @var{args}.
16638 After specifying this target, you can debug programs for the simulated
16639 CPU in the same style as programs for your host computer; use the
16640 @code{file} command to load a new program image, the @code{run} command
16641 to run your program, and so on.
16643 As well as making available all the usual machine registers
16644 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
16645 additional items of information as specially named registers:
16650 Counts clock-ticks in the simulator.
16653 Counts instructions run in the simulator.
16656 Execution time in 60ths of a second.
16660 You can refer to these values in @value{GDBN} expressions with the usual
16661 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
16662 conditional breakpoint that suspends only after at least 5000
16663 simulated clock ticks.
16666 @subsection Atmel AVR
16669 When configured for debugging the Atmel AVR, @value{GDBN} supports the
16670 following AVR-specific commands:
16673 @item info io_registers
16674 @kindex info io_registers@r{, AVR}
16675 @cindex I/O registers (Atmel AVR)
16676 This command displays information about the AVR I/O registers. For
16677 each register, @value{GDBN} prints its number and value.
16684 When configured for debugging CRIS, @value{GDBN} provides the
16685 following CRIS-specific commands:
16688 @item set cris-version @var{ver}
16689 @cindex CRIS version
16690 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
16691 The CRIS version affects register names and sizes. This command is useful in
16692 case autodetection of the CRIS version fails.
16694 @item show cris-version
16695 Show the current CRIS version.
16697 @item set cris-dwarf2-cfi
16698 @cindex DWARF-2 CFI and CRIS
16699 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
16700 Change to @samp{off} when using @code{gcc-cris} whose version is below
16703 @item show cris-dwarf2-cfi
16704 Show the current state of using DWARF-2 CFI.
16706 @item set cris-mode @var{mode}
16708 Set the current CRIS mode to @var{mode}. It should only be changed when
16709 debugging in guru mode, in which case it should be set to
16710 @samp{guru} (the default is @samp{normal}).
16712 @item show cris-mode
16713 Show the current CRIS mode.
16717 @subsection Renesas Super-H
16720 For the Renesas Super-H processor, @value{GDBN} provides these
16725 @kindex regs@r{, Super-H}
16726 Show the values of all Super-H registers.
16728 @item set sh calling-convention @var{convention}
16729 @kindex set sh calling-convention
16730 Set the calling-convention used when calling functions from @value{GDBN}.
16731 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
16732 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
16733 convention. If the DWARF-2 information of the called function specifies
16734 that the function follows the Renesas calling convention, the function
16735 is called using the Renesas calling convention. If the calling convention
16736 is set to @samp{renesas}, the Renesas calling convention is always used,
16737 regardless of the DWARF-2 information. This can be used to override the
16738 default of @samp{gcc} if debug information is missing, or the compiler
16739 does not emit the DWARF-2 calling convention entry for a function.
16741 @item show sh calling-convention
16742 @kindex show sh calling-convention
16743 Show the current calling convention setting.
16748 @node Architectures
16749 @section Architectures
16751 This section describes characteristics of architectures that affect
16752 all uses of @value{GDBN} with the architecture, both native and cross.
16759 * HPPA:: HP PA architecture
16760 * SPU:: Cell Broadband Engine SPU architecture
16765 @subsection x86 Architecture-specific Issues
16768 @item set struct-convention @var{mode}
16769 @kindex set struct-convention
16770 @cindex struct return convention
16771 @cindex struct/union returned in registers
16772 Set the convention used by the inferior to return @code{struct}s and
16773 @code{union}s from functions to @var{mode}. Possible values of
16774 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
16775 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
16776 are returned on the stack, while @code{"reg"} means that a
16777 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
16778 be returned in a register.
16780 @item show struct-convention
16781 @kindex show struct-convention
16782 Show the current setting of the convention to return @code{struct}s
16791 @kindex set rstack_high_address
16792 @cindex AMD 29K register stack
16793 @cindex register stack, AMD29K
16794 @item set rstack_high_address @var{address}
16795 On AMD 29000 family processors, registers are saved in a separate
16796 @dfn{register stack}. There is no way for @value{GDBN} to determine the
16797 extent of this stack. Normally, @value{GDBN} just assumes that the
16798 stack is ``large enough''. This may result in @value{GDBN} referencing
16799 memory locations that do not exist. If necessary, you can get around
16800 this problem by specifying the ending address of the register stack with
16801 the @code{set rstack_high_address} command. The argument should be an
16802 address, which you probably want to precede with @samp{0x} to specify in
16805 @kindex show rstack_high_address
16806 @item show rstack_high_address
16807 Display the current limit of the register stack, on AMD 29000 family
16815 See the following section.
16820 @cindex stack on Alpha
16821 @cindex stack on MIPS
16822 @cindex Alpha stack
16824 Alpha- and MIPS-based computers use an unusual stack frame, which
16825 sometimes requires @value{GDBN} to search backward in the object code to
16826 find the beginning of a function.
16828 @cindex response time, MIPS debugging
16829 To improve response time (especially for embedded applications, where
16830 @value{GDBN} may be restricted to a slow serial line for this search)
16831 you may want to limit the size of this search, using one of these
16835 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
16836 @item set heuristic-fence-post @var{limit}
16837 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
16838 search for the beginning of a function. A value of @var{0} (the
16839 default) means there is no limit. However, except for @var{0}, the
16840 larger the limit the more bytes @code{heuristic-fence-post} must search
16841 and therefore the longer it takes to run. You should only need to use
16842 this command when debugging a stripped executable.
16844 @item show heuristic-fence-post
16845 Display the current limit.
16849 These commands are available @emph{only} when @value{GDBN} is configured
16850 for debugging programs on Alpha or MIPS processors.
16852 Several MIPS-specific commands are available when debugging MIPS
16856 @item set mips abi @var{arg}
16857 @kindex set mips abi
16858 @cindex set ABI for MIPS
16859 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
16860 values of @var{arg} are:
16864 The default ABI associated with the current binary (this is the
16875 @item show mips abi
16876 @kindex show mips abi
16877 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
16880 @itemx show mipsfpu
16881 @xref{MIPS Embedded, set mipsfpu}.
16883 @item set mips mask-address @var{arg}
16884 @kindex set mips mask-address
16885 @cindex MIPS addresses, masking
16886 This command determines whether the most-significant 32 bits of 64-bit
16887 MIPS addresses are masked off. The argument @var{arg} can be
16888 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
16889 setting, which lets @value{GDBN} determine the correct value.
16891 @item show mips mask-address
16892 @kindex show mips mask-address
16893 Show whether the upper 32 bits of MIPS addresses are masked off or
16896 @item set remote-mips64-transfers-32bit-regs
16897 @kindex set remote-mips64-transfers-32bit-regs
16898 This command controls compatibility with 64-bit MIPS targets that
16899 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16900 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16901 and 64 bits for other registers, set this option to @samp{on}.
16903 @item show remote-mips64-transfers-32bit-regs
16904 @kindex show remote-mips64-transfers-32bit-regs
16905 Show the current setting of compatibility with older MIPS 64 targets.
16907 @item set debug mips
16908 @kindex set debug mips
16909 This command turns on and off debugging messages for the MIPS-specific
16910 target code in @value{GDBN}.
16912 @item show debug mips
16913 @kindex show debug mips
16914 Show the current setting of MIPS debugging messages.
16920 @cindex HPPA support
16922 When @value{GDBN} is debugging the HP PA architecture, it provides the
16923 following special commands:
16926 @item set debug hppa
16927 @kindex set debug hppa
16928 This command determines whether HPPA architecture-specific debugging
16929 messages are to be displayed.
16931 @item show debug hppa
16932 Show whether HPPA debugging messages are displayed.
16934 @item maint print unwind @var{address}
16935 @kindex maint print unwind@r{, HPPA}
16936 This command displays the contents of the unwind table entry at the
16937 given @var{address}.
16943 @subsection Cell Broadband Engine SPU architecture
16944 @cindex Cell Broadband Engine
16947 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
16948 it provides the following special commands:
16951 @item info spu event
16953 Display SPU event facility status. Shows current event mask
16954 and pending event status.
16956 @item info spu signal
16957 Display SPU signal notification facility status. Shows pending
16958 signal-control word and signal notification mode of both signal
16959 notification channels.
16961 @item info spu mailbox
16962 Display SPU mailbox facility status. Shows all pending entries,
16963 in order of processing, in each of the SPU Write Outbound,
16964 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
16967 Display MFC DMA status. Shows all pending commands in the MFC
16968 DMA queue. For each entry, opcode, tag, class IDs, effective
16969 and local store addresses and transfer size are shown.
16971 @item info spu proxydma
16972 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
16973 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
16974 and local store addresses and transfer size are shown.
16979 @subsection PowerPC
16980 @cindex PowerPC architecture
16982 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
16983 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
16984 numbers stored in the floating point registers. These values must be stored
16985 in two consecutive registers, always starting at an even register like
16986 @code{f0} or @code{f2}.
16988 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
16989 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
16990 @code{f2} and @code{f3} for @code{$dl1} and so on.
16992 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
16993 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
16996 @node Controlling GDB
16997 @chapter Controlling @value{GDBN}
16999 You can alter the way @value{GDBN} interacts with you by using the
17000 @code{set} command. For commands controlling how @value{GDBN} displays
17001 data, see @ref{Print Settings, ,Print Settings}. Other settings are
17006 * Editing:: Command editing
17007 * Command History:: Command history
17008 * Screen Size:: Screen size
17009 * Numbers:: Numbers
17010 * ABI:: Configuring the current ABI
17011 * Messages/Warnings:: Optional warnings and messages
17012 * Debugging Output:: Optional messages about internal happenings
17020 @value{GDBN} indicates its readiness to read a command by printing a string
17021 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
17022 can change the prompt string with the @code{set prompt} command. For
17023 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
17024 the prompt in one of the @value{GDBN} sessions so that you can always tell
17025 which one you are talking to.
17027 @emph{Note:} @code{set prompt} does not add a space for you after the
17028 prompt you set. This allows you to set a prompt which ends in a space
17029 or a prompt that does not.
17033 @item set prompt @var{newprompt}
17034 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
17036 @kindex show prompt
17038 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
17042 @section Command Editing
17044 @cindex command line editing
17046 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
17047 @sc{gnu} library provides consistent behavior for programs which provide a
17048 command line interface to the user. Advantages are @sc{gnu} Emacs-style
17049 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
17050 substitution, and a storage and recall of command history across
17051 debugging sessions.
17053 You may control the behavior of command line editing in @value{GDBN} with the
17054 command @code{set}.
17057 @kindex set editing
17060 @itemx set editing on
17061 Enable command line editing (enabled by default).
17063 @item set editing off
17064 Disable command line editing.
17066 @kindex show editing
17068 Show whether command line editing is enabled.
17071 @xref{Command Line Editing}, for more details about the Readline
17072 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
17073 encouraged to read that chapter.
17075 @node Command History
17076 @section Command History
17077 @cindex command history
17079 @value{GDBN} can keep track of the commands you type during your
17080 debugging sessions, so that you can be certain of precisely what
17081 happened. Use these commands to manage the @value{GDBN} command
17084 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
17085 package, to provide the history facility. @xref{Using History
17086 Interactively}, for the detailed description of the History library.
17088 To issue a command to @value{GDBN} without affecting certain aspects of
17089 the state which is seen by users, prefix it with @samp{server }
17090 (@pxref{Server Prefix}). This
17091 means that this command will not affect the command history, nor will it
17092 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
17093 pressed on a line by itself.
17095 @cindex @code{server}, command prefix
17096 The server prefix does not affect the recording of values into the value
17097 history; to print a value without recording it into the value history,
17098 use the @code{output} command instead of the @code{print} command.
17100 Here is the description of @value{GDBN} commands related to command
17104 @cindex history substitution
17105 @cindex history file
17106 @kindex set history filename
17107 @cindex @env{GDBHISTFILE}, environment variable
17108 @item set history filename @var{fname}
17109 Set the name of the @value{GDBN} command history file to @var{fname}.
17110 This is the file where @value{GDBN} reads an initial command history
17111 list, and where it writes the command history from this session when it
17112 exits. You can access this list through history expansion or through
17113 the history command editing characters listed below. This file defaults
17114 to the value of the environment variable @code{GDBHISTFILE}, or to
17115 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
17118 @cindex save command history
17119 @kindex set history save
17120 @item set history save
17121 @itemx set history save on
17122 Record command history in a file, whose name may be specified with the
17123 @code{set history filename} command. By default, this option is disabled.
17125 @item set history save off
17126 Stop recording command history in a file.
17128 @cindex history size
17129 @kindex set history size
17130 @cindex @env{HISTSIZE}, environment variable
17131 @item set history size @var{size}
17132 Set the number of commands which @value{GDBN} keeps in its history list.
17133 This defaults to the value of the environment variable
17134 @code{HISTSIZE}, or to 256 if this variable is not set.
17137 History expansion assigns special meaning to the character @kbd{!}.
17138 @xref{Event Designators}, for more details.
17140 @cindex history expansion, turn on/off
17141 Since @kbd{!} is also the logical not operator in C, history expansion
17142 is off by default. If you decide to enable history expansion with the
17143 @code{set history expansion on} command, you may sometimes need to
17144 follow @kbd{!} (when it is used as logical not, in an expression) with
17145 a space or a tab to prevent it from being expanded. The readline
17146 history facilities do not attempt substitution on the strings
17147 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
17149 The commands to control history expansion are:
17152 @item set history expansion on
17153 @itemx set history expansion
17154 @kindex set history expansion
17155 Enable history expansion. History expansion is off by default.
17157 @item set history expansion off
17158 Disable history expansion.
17161 @kindex show history
17163 @itemx show history filename
17164 @itemx show history save
17165 @itemx show history size
17166 @itemx show history expansion
17167 These commands display the state of the @value{GDBN} history parameters.
17168 @code{show history} by itself displays all four states.
17173 @kindex show commands
17174 @cindex show last commands
17175 @cindex display command history
17176 @item show commands
17177 Display the last ten commands in the command history.
17179 @item show commands @var{n}
17180 Print ten commands centered on command number @var{n}.
17182 @item show commands +
17183 Print ten commands just after the commands last printed.
17187 @section Screen Size
17188 @cindex size of screen
17189 @cindex pauses in output
17191 Certain commands to @value{GDBN} may produce large amounts of
17192 information output to the screen. To help you read all of it,
17193 @value{GDBN} pauses and asks you for input at the end of each page of
17194 output. Type @key{RET} when you want to continue the output, or @kbd{q}
17195 to discard the remaining output. Also, the screen width setting
17196 determines when to wrap lines of output. Depending on what is being
17197 printed, @value{GDBN} tries to break the line at a readable place,
17198 rather than simply letting it overflow onto the following line.
17200 Normally @value{GDBN} knows the size of the screen from the terminal
17201 driver software. For example, on Unix @value{GDBN} uses the termcap data base
17202 together with the value of the @code{TERM} environment variable and the
17203 @code{stty rows} and @code{stty cols} settings. If this is not correct,
17204 you can override it with the @code{set height} and @code{set
17211 @kindex show height
17212 @item set height @var{lpp}
17214 @itemx set width @var{cpl}
17216 These @code{set} commands specify a screen height of @var{lpp} lines and
17217 a screen width of @var{cpl} characters. The associated @code{show}
17218 commands display the current settings.
17220 If you specify a height of zero lines, @value{GDBN} does not pause during
17221 output no matter how long the output is. This is useful if output is to a
17222 file or to an editor buffer.
17224 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
17225 from wrapping its output.
17227 @item set pagination on
17228 @itemx set pagination off
17229 @kindex set pagination
17230 Turn the output pagination on or off; the default is on. Turning
17231 pagination off is the alternative to @code{set height 0}.
17233 @item show pagination
17234 @kindex show pagination
17235 Show the current pagination mode.
17240 @cindex number representation
17241 @cindex entering numbers
17243 You can always enter numbers in octal, decimal, or hexadecimal in
17244 @value{GDBN} by the usual conventions: octal numbers begin with
17245 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
17246 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
17247 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
17248 10; likewise, the default display for numbers---when no particular
17249 format is specified---is base 10. You can change the default base for
17250 both input and output with the commands described below.
17253 @kindex set input-radix
17254 @item set input-radix @var{base}
17255 Set the default base for numeric input. Supported choices
17256 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17257 specified either unambiguously or using the current input radix; for
17261 set input-radix 012
17262 set input-radix 10.
17263 set input-radix 0xa
17267 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
17268 leaves the input radix unchanged, no matter what it was, since
17269 @samp{10}, being without any leading or trailing signs of its base, is
17270 interpreted in the current radix. Thus, if the current radix is 16,
17271 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
17274 @kindex set output-radix
17275 @item set output-radix @var{base}
17276 Set the default base for numeric display. Supported choices
17277 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17278 specified either unambiguously or using the current input radix.
17280 @kindex show input-radix
17281 @item show input-radix
17282 Display the current default base for numeric input.
17284 @kindex show output-radix
17285 @item show output-radix
17286 Display the current default base for numeric display.
17288 @item set radix @r{[}@var{base}@r{]}
17292 These commands set and show the default base for both input and output
17293 of numbers. @code{set radix} sets the radix of input and output to
17294 the same base; without an argument, it resets the radix back to its
17295 default value of 10.
17300 @section Configuring the Current ABI
17302 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
17303 application automatically. However, sometimes you need to override its
17304 conclusions. Use these commands to manage @value{GDBN}'s view of the
17311 One @value{GDBN} configuration can debug binaries for multiple operating
17312 system targets, either via remote debugging or native emulation.
17313 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
17314 but you can override its conclusion using the @code{set osabi} command.
17315 One example where this is useful is in debugging of binaries which use
17316 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
17317 not have the same identifying marks that the standard C library for your
17322 Show the OS ABI currently in use.
17325 With no argument, show the list of registered available OS ABI's.
17327 @item set osabi @var{abi}
17328 Set the current OS ABI to @var{abi}.
17331 @cindex float promotion
17333 Generally, the way that an argument of type @code{float} is passed to a
17334 function depends on whether the function is prototyped. For a prototyped
17335 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
17336 according to the architecture's convention for @code{float}. For unprototyped
17337 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
17338 @code{double} and then passed.
17340 Unfortunately, some forms of debug information do not reliably indicate whether
17341 a function is prototyped. If @value{GDBN} calls a function that is not marked
17342 as prototyped, it consults @kbd{set coerce-float-to-double}.
17345 @kindex set coerce-float-to-double
17346 @item set coerce-float-to-double
17347 @itemx set coerce-float-to-double on
17348 Arguments of type @code{float} will be promoted to @code{double} when passed
17349 to an unprototyped function. This is the default setting.
17351 @item set coerce-float-to-double off
17352 Arguments of type @code{float} will be passed directly to unprototyped
17355 @kindex show coerce-float-to-double
17356 @item show coerce-float-to-double
17357 Show the current setting of promoting @code{float} to @code{double}.
17361 @kindex show cp-abi
17362 @value{GDBN} needs to know the ABI used for your program's C@t{++}
17363 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
17364 used to build your application. @value{GDBN} only fully supports
17365 programs with a single C@t{++} ABI; if your program contains code using
17366 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
17367 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
17368 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
17369 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
17370 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
17371 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
17376 Show the C@t{++} ABI currently in use.
17379 With no argument, show the list of supported C@t{++} ABI's.
17381 @item set cp-abi @var{abi}
17382 @itemx set cp-abi auto
17383 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
17386 @node Messages/Warnings
17387 @section Optional Warnings and Messages
17389 @cindex verbose operation
17390 @cindex optional warnings
17391 By default, @value{GDBN} is silent about its inner workings. If you are
17392 running on a slow machine, you may want to use the @code{set verbose}
17393 command. This makes @value{GDBN} tell you when it does a lengthy
17394 internal operation, so you will not think it has crashed.
17396 Currently, the messages controlled by @code{set verbose} are those
17397 which announce that the symbol table for a source file is being read;
17398 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
17401 @kindex set verbose
17402 @item set verbose on
17403 Enables @value{GDBN} output of certain informational messages.
17405 @item set verbose off
17406 Disables @value{GDBN} output of certain informational messages.
17408 @kindex show verbose
17410 Displays whether @code{set verbose} is on or off.
17413 By default, if @value{GDBN} encounters bugs in the symbol table of an
17414 object file, it is silent; but if you are debugging a compiler, you may
17415 find this information useful (@pxref{Symbol Errors, ,Errors Reading
17420 @kindex set complaints
17421 @item set complaints @var{limit}
17422 Permits @value{GDBN} to output @var{limit} complaints about each type of
17423 unusual symbols before becoming silent about the problem. Set
17424 @var{limit} to zero to suppress all complaints; set it to a large number
17425 to prevent complaints from being suppressed.
17427 @kindex show complaints
17428 @item show complaints
17429 Displays how many symbol complaints @value{GDBN} is permitted to produce.
17433 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
17434 lot of stupid questions to confirm certain commands. For example, if
17435 you try to run a program which is already running:
17439 The program being debugged has been started already.
17440 Start it from the beginning? (y or n)
17443 If you are willing to unflinchingly face the consequences of your own
17444 commands, you can disable this ``feature'':
17448 @kindex set confirm
17450 @cindex confirmation
17451 @cindex stupid questions
17452 @item set confirm off
17453 Disables confirmation requests.
17455 @item set confirm on
17456 Enables confirmation requests (the default).
17458 @kindex show confirm
17460 Displays state of confirmation requests.
17464 @cindex command tracing
17465 If you need to debug user-defined commands or sourced files you may find it
17466 useful to enable @dfn{command tracing}. In this mode each command will be
17467 printed as it is executed, prefixed with one or more @samp{+} symbols, the
17468 quantity denoting the call depth of each command.
17471 @kindex set trace-commands
17472 @cindex command scripts, debugging
17473 @item set trace-commands on
17474 Enable command tracing.
17475 @item set trace-commands off
17476 Disable command tracing.
17477 @item show trace-commands
17478 Display the current state of command tracing.
17481 @node Debugging Output
17482 @section Optional Messages about Internal Happenings
17483 @cindex optional debugging messages
17485 @value{GDBN} has commands that enable optional debugging messages from
17486 various @value{GDBN} subsystems; normally these commands are of
17487 interest to @value{GDBN} maintainers, or when reporting a bug. This
17488 section documents those commands.
17491 @kindex set exec-done-display
17492 @item set exec-done-display
17493 Turns on or off the notification of asynchronous commands'
17494 completion. When on, @value{GDBN} will print a message when an
17495 asynchronous command finishes its execution. The default is off.
17496 @kindex show exec-done-display
17497 @item show exec-done-display
17498 Displays the current setting of asynchronous command completion
17501 @cindex gdbarch debugging info
17502 @cindex architecture debugging info
17503 @item set debug arch
17504 Turns on or off display of gdbarch debugging info. The default is off
17506 @item show debug arch
17507 Displays the current state of displaying gdbarch debugging info.
17508 @item set debug aix-thread
17509 @cindex AIX threads
17510 Display debugging messages about inner workings of the AIX thread
17512 @item show debug aix-thread
17513 Show the current state of AIX thread debugging info display.
17514 @item set debug dwarf2-die
17515 @cindex DWARF2 DIEs
17516 Dump DWARF2 DIEs after they are read in.
17517 The value is the number of nesting levels to print.
17518 A value of zero turns off the display.
17519 @item show debug dwarf2-die
17520 Show the current state of DWARF2 DIE debugging.
17521 @item set debug displaced
17522 @cindex displaced stepping debugging info
17523 Turns on or off display of @value{GDBN} debugging info for the
17524 displaced stepping support. The default is off.
17525 @item show debug displaced
17526 Displays the current state of displaying @value{GDBN} debugging info
17527 related to displaced stepping.
17528 @item set debug event
17529 @cindex event debugging info
17530 Turns on or off display of @value{GDBN} event debugging info. The
17532 @item show debug event
17533 Displays the current state of displaying @value{GDBN} event debugging
17535 @item set debug expression
17536 @cindex expression debugging info
17537 Turns on or off display of debugging info about @value{GDBN}
17538 expression parsing. The default is off.
17539 @item show debug expression
17540 Displays the current state of displaying debugging info about
17541 @value{GDBN} expression parsing.
17542 @item set debug frame
17543 @cindex frame debugging info
17544 Turns on or off display of @value{GDBN} frame debugging info. The
17546 @item show debug frame
17547 Displays the current state of displaying @value{GDBN} frame debugging
17549 @item set debug infrun
17550 @cindex inferior debugging info
17551 Turns on or off display of @value{GDBN} debugging info for running the inferior.
17552 The default is off. @file{infrun.c} contains GDB's runtime state machine used
17553 for implementing operations such as single-stepping the inferior.
17554 @item show debug infrun
17555 Displays the current state of @value{GDBN} inferior debugging.
17556 @item set debug lin-lwp
17557 @cindex @sc{gnu}/Linux LWP debug messages
17558 @cindex Linux lightweight processes
17559 Turns on or off debugging messages from the Linux LWP debug support.
17560 @item show debug lin-lwp
17561 Show the current state of Linux LWP debugging messages.
17562 @item set debug lin-lwp-async
17563 @cindex @sc{gnu}/Linux LWP async debug messages
17564 @cindex Linux lightweight processes
17565 Turns on or off debugging messages from the Linux LWP async debug support.
17566 @item show debug lin-lwp-async
17567 Show the current state of Linux LWP async debugging messages.
17568 @item set debug observer
17569 @cindex observer debugging info
17570 Turns on or off display of @value{GDBN} observer debugging. This
17571 includes info such as the notification of observable events.
17572 @item show debug observer
17573 Displays the current state of observer debugging.
17574 @item set debug overload
17575 @cindex C@t{++} overload debugging info
17576 Turns on or off display of @value{GDBN} C@t{++} overload debugging
17577 info. This includes info such as ranking of functions, etc. The default
17579 @item show debug overload
17580 Displays the current state of displaying @value{GDBN} C@t{++} overload
17582 @cindex packets, reporting on stdout
17583 @cindex serial connections, debugging
17584 @cindex debug remote protocol
17585 @cindex remote protocol debugging
17586 @cindex display remote packets
17587 @item set debug remote
17588 Turns on or off display of reports on all packets sent back and forth across
17589 the serial line to the remote machine. The info is printed on the
17590 @value{GDBN} standard output stream. The default is off.
17591 @item show debug remote
17592 Displays the state of display of remote packets.
17593 @item set debug serial
17594 Turns on or off display of @value{GDBN} serial debugging info. The
17596 @item show debug serial
17597 Displays the current state of displaying @value{GDBN} serial debugging
17599 @item set debug solib-frv
17600 @cindex FR-V shared-library debugging
17601 Turns on or off debugging messages for FR-V shared-library code.
17602 @item show debug solib-frv
17603 Display the current state of FR-V shared-library code debugging
17605 @item set debug target
17606 @cindex target debugging info
17607 Turns on or off display of @value{GDBN} target debugging info. This info
17608 includes what is going on at the target level of GDB, as it happens. The
17609 default is 0. Set it to 1 to track events, and to 2 to also track the
17610 value of large memory transfers. Changes to this flag do not take effect
17611 until the next time you connect to a target or use the @code{run} command.
17612 @item show debug target
17613 Displays the current state of displaying @value{GDBN} target debugging
17615 @item set debug timestamp
17616 @cindex timestampping debugging info
17617 Turns on or off display of timestamps with @value{GDBN} debugging info.
17618 When enabled, seconds and microseconds are displayed before each debugging
17620 @item show debug timestamp
17621 Displays the current state of displaying timestamps with @value{GDBN}
17623 @item set debugvarobj
17624 @cindex variable object debugging info
17625 Turns on or off display of @value{GDBN} variable object debugging
17626 info. The default is off.
17627 @item show debugvarobj
17628 Displays the current state of displaying @value{GDBN} variable object
17630 @item set debug xml
17631 @cindex XML parser debugging
17632 Turns on or off debugging messages for built-in XML parsers.
17633 @item show debug xml
17634 Displays the current state of XML debugging messages.
17637 @node Extending GDB
17638 @chapter Extending @value{GDBN}
17639 @cindex extending GDB
17641 @value{GDBN} provides two mechanisms for extension. The first is based
17642 on composition of @value{GDBN} commands, and the second is based on the
17643 Python scripting language.
17646 * Sequences:: Canned Sequences of Commands
17647 * Python:: Scripting @value{GDBN} using Python
17651 @section Canned Sequences of Commands
17653 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
17654 Command Lists}), @value{GDBN} provides two ways to store sequences of
17655 commands for execution as a unit: user-defined commands and command
17659 * Define:: How to define your own commands
17660 * Hooks:: Hooks for user-defined commands
17661 * Command Files:: How to write scripts of commands to be stored in a file
17662 * Output:: Commands for controlled output
17666 @subsection User-defined Commands
17668 @cindex user-defined command
17669 @cindex arguments, to user-defined commands
17670 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
17671 which you assign a new name as a command. This is done with the
17672 @code{define} command. User commands may accept up to 10 arguments
17673 separated by whitespace. Arguments are accessed within the user command
17674 via @code{$arg0@dots{}$arg9}. A trivial example:
17678 print $arg0 + $arg1 + $arg2
17683 To execute the command use:
17690 This defines the command @code{adder}, which prints the sum of
17691 its three arguments. Note the arguments are text substitutions, so they may
17692 reference variables, use complex expressions, or even perform inferior
17695 @cindex argument count in user-defined commands
17696 @cindex how many arguments (user-defined commands)
17697 In addition, @code{$argc} may be used to find out how many arguments have
17698 been passed. This expands to a number in the range 0@dots{}10.
17703 print $arg0 + $arg1
17706 print $arg0 + $arg1 + $arg2
17714 @item define @var{commandname}
17715 Define a command named @var{commandname}. If there is already a command
17716 by that name, you are asked to confirm that you want to redefine it.
17717 @var{commandname} may be a bare command name consisting of letters,
17718 numbers, dashes, and underscores. It may also start with any predefined
17719 prefix command. For example, @samp{define target my-target} creates
17720 a user-defined @samp{target my-target} command.
17722 The definition of the command is made up of other @value{GDBN} command lines,
17723 which are given following the @code{define} command. The end of these
17724 commands is marked by a line containing @code{end}.
17727 @kindex end@r{ (user-defined commands)}
17728 @item document @var{commandname}
17729 Document the user-defined command @var{commandname}, so that it can be
17730 accessed by @code{help}. The command @var{commandname} must already be
17731 defined. This command reads lines of documentation just as @code{define}
17732 reads the lines of the command definition, ending with @code{end}.
17733 After the @code{document} command is finished, @code{help} on command
17734 @var{commandname} displays the documentation you have written.
17736 You may use the @code{document} command again to change the
17737 documentation of a command. Redefining the command with @code{define}
17738 does not change the documentation.
17740 @kindex dont-repeat
17741 @cindex don't repeat command
17743 Used inside a user-defined command, this tells @value{GDBN} that this
17744 command should not be repeated when the user hits @key{RET}
17745 (@pxref{Command Syntax, repeat last command}).
17747 @kindex help user-defined
17748 @item help user-defined
17749 List all user-defined commands, with the first line of the documentation
17754 @itemx show user @var{commandname}
17755 Display the @value{GDBN} commands used to define @var{commandname} (but
17756 not its documentation). If no @var{commandname} is given, display the
17757 definitions for all user-defined commands.
17759 @cindex infinite recursion in user-defined commands
17760 @kindex show max-user-call-depth
17761 @kindex set max-user-call-depth
17762 @item show max-user-call-depth
17763 @itemx set max-user-call-depth
17764 The value of @code{max-user-call-depth} controls how many recursion
17765 levels are allowed in user-defined commands before @value{GDBN} suspects an
17766 infinite recursion and aborts the command.
17769 In addition to the above commands, user-defined commands frequently
17770 use control flow commands, described in @ref{Command Files}.
17772 When user-defined commands are executed, the
17773 commands of the definition are not printed. An error in any command
17774 stops execution of the user-defined command.
17776 If used interactively, commands that would ask for confirmation proceed
17777 without asking when used inside a user-defined command. Many @value{GDBN}
17778 commands that normally print messages to say what they are doing omit the
17779 messages when used in a user-defined command.
17782 @subsection User-defined Command Hooks
17783 @cindex command hooks
17784 @cindex hooks, for commands
17785 @cindex hooks, pre-command
17788 You may define @dfn{hooks}, which are a special kind of user-defined
17789 command. Whenever you run the command @samp{foo}, if the user-defined
17790 command @samp{hook-foo} exists, it is executed (with no arguments)
17791 before that command.
17793 @cindex hooks, post-command
17795 A hook may also be defined which is run after the command you executed.
17796 Whenever you run the command @samp{foo}, if the user-defined command
17797 @samp{hookpost-foo} exists, it is executed (with no arguments) after
17798 that command. Post-execution hooks may exist simultaneously with
17799 pre-execution hooks, for the same command.
17801 It is valid for a hook to call the command which it hooks. If this
17802 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
17804 @c It would be nice if hookpost could be passed a parameter indicating
17805 @c if the command it hooks executed properly or not. FIXME!
17807 @kindex stop@r{, a pseudo-command}
17808 In addition, a pseudo-command, @samp{stop} exists. Defining
17809 (@samp{hook-stop}) makes the associated commands execute every time
17810 execution stops in your program: before breakpoint commands are run,
17811 displays are printed, or the stack frame is printed.
17813 For example, to ignore @code{SIGALRM} signals while
17814 single-stepping, but treat them normally during normal execution,
17819 handle SIGALRM nopass
17823 handle SIGALRM pass
17826 define hook-continue
17827 handle SIGALRM pass
17831 As a further example, to hook at the beginning and end of the @code{echo}
17832 command, and to add extra text to the beginning and end of the message,
17840 define hookpost-echo
17844 (@value{GDBP}) echo Hello World
17845 <<<---Hello World--->>>
17850 You can define a hook for any single-word command in @value{GDBN}, but
17851 not for command aliases; you should define a hook for the basic command
17852 name, e.g.@: @code{backtrace} rather than @code{bt}.
17853 @c FIXME! So how does Joe User discover whether a command is an alias
17855 You can hook a multi-word command by adding @code{hook-} or
17856 @code{hookpost-} to the last word of the command, e.g.@:
17857 @samp{define target hook-remote} to add a hook to @samp{target remote}.
17859 If an error occurs during the execution of your hook, execution of
17860 @value{GDBN} commands stops and @value{GDBN} issues a prompt
17861 (before the command that you actually typed had a chance to run).
17863 If you try to define a hook which does not match any known command, you
17864 get a warning from the @code{define} command.
17866 @node Command Files
17867 @subsection Command Files
17869 @cindex command files
17870 @cindex scripting commands
17871 A command file for @value{GDBN} is a text file made of lines that are
17872 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
17873 also be included. An empty line in a command file does nothing; it
17874 does not mean to repeat the last command, as it would from the
17877 You can request the execution of a command file with the @code{source}
17882 @cindex execute commands from a file
17883 @item source [@code{-v}] @var{filename}
17884 Execute the command file @var{filename}.
17887 The lines in a command file are generally executed sequentially,
17888 unless the order of execution is changed by one of the
17889 @emph{flow-control commands} described below. The commands are not
17890 printed as they are executed. An error in any command terminates
17891 execution of the command file and control is returned to the console.
17893 @value{GDBN} searches for @var{filename} in the current directory and then
17894 on the search path (specified with the @samp{directory} command).
17896 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
17897 each command as it is executed. The option must be given before
17898 @var{filename}, and is interpreted as part of the filename anywhere else.
17900 Commands that would ask for confirmation if used interactively proceed
17901 without asking when used in a command file. Many @value{GDBN} commands that
17902 normally print messages to say what they are doing omit the messages
17903 when called from command files.
17905 @value{GDBN} also accepts command input from standard input. In this
17906 mode, normal output goes to standard output and error output goes to
17907 standard error. Errors in a command file supplied on standard input do
17908 not terminate execution of the command file---execution continues with
17912 gdb < cmds > log 2>&1
17915 (The syntax above will vary depending on the shell used.) This example
17916 will execute commands from the file @file{cmds}. All output and errors
17917 would be directed to @file{log}.
17919 Since commands stored on command files tend to be more general than
17920 commands typed interactively, they frequently need to deal with
17921 complicated situations, such as different or unexpected values of
17922 variables and symbols, changes in how the program being debugged is
17923 built, etc. @value{GDBN} provides a set of flow-control commands to
17924 deal with these complexities. Using these commands, you can write
17925 complex scripts that loop over data structures, execute commands
17926 conditionally, etc.
17933 This command allows to include in your script conditionally executed
17934 commands. The @code{if} command takes a single argument, which is an
17935 expression to evaluate. It is followed by a series of commands that
17936 are executed only if the expression is true (its value is nonzero).
17937 There can then optionally be an @code{else} line, followed by a series
17938 of commands that are only executed if the expression was false. The
17939 end of the list is marked by a line containing @code{end}.
17943 This command allows to write loops. Its syntax is similar to
17944 @code{if}: the command takes a single argument, which is an expression
17945 to evaluate, and must be followed by the commands to execute, one per
17946 line, terminated by an @code{end}. These commands are called the
17947 @dfn{body} of the loop. The commands in the body of @code{while} are
17948 executed repeatedly as long as the expression evaluates to true.
17952 This command exits the @code{while} loop in whose body it is included.
17953 Execution of the script continues after that @code{while}s @code{end}
17956 @kindex loop_continue
17957 @item loop_continue
17958 This command skips the execution of the rest of the body of commands
17959 in the @code{while} loop in whose body it is included. Execution
17960 branches to the beginning of the @code{while} loop, where it evaluates
17961 the controlling expression.
17963 @kindex end@r{ (if/else/while commands)}
17965 Terminate the block of commands that are the body of @code{if},
17966 @code{else}, or @code{while} flow-control commands.
17971 @subsection Commands for Controlled Output
17973 During the execution of a command file or a user-defined command, normal
17974 @value{GDBN} output is suppressed; the only output that appears is what is
17975 explicitly printed by the commands in the definition. This section
17976 describes three commands useful for generating exactly the output you
17981 @item echo @var{text}
17982 @c I do not consider backslash-space a standard C escape sequence
17983 @c because it is not in ANSI.
17984 Print @var{text}. Nonprinting characters can be included in
17985 @var{text} using C escape sequences, such as @samp{\n} to print a
17986 newline. @strong{No newline is printed unless you specify one.}
17987 In addition to the standard C escape sequences, a backslash followed
17988 by a space stands for a space. This is useful for displaying a
17989 string with spaces at the beginning or the end, since leading and
17990 trailing spaces are otherwise trimmed from all arguments.
17991 To print @samp{@w{ }and foo =@w{ }}, use the command
17992 @samp{echo \@w{ }and foo = \@w{ }}.
17994 A backslash at the end of @var{text} can be used, as in C, to continue
17995 the command onto subsequent lines. For example,
17998 echo This is some text\n\
17999 which is continued\n\
18000 onto several lines.\n
18003 produces the same output as
18006 echo This is some text\n
18007 echo which is continued\n
18008 echo onto several lines.\n
18012 @item output @var{expression}
18013 Print the value of @var{expression} and nothing but that value: no
18014 newlines, no @samp{$@var{nn} = }. The value is not entered in the
18015 value history either. @xref{Expressions, ,Expressions}, for more information
18018 @item output/@var{fmt} @var{expression}
18019 Print the value of @var{expression} in format @var{fmt}. You can use
18020 the same formats as for @code{print}. @xref{Output Formats,,Output
18021 Formats}, for more information.
18024 @item printf @var{template}, @var{expressions}@dots{}
18025 Print the values of one or more @var{expressions} under the control of
18026 the string @var{template}. To print several values, make
18027 @var{expressions} be a comma-separated list of individual expressions,
18028 which may be either numbers or pointers. Their values are printed as
18029 specified by @var{template}, exactly as a C program would do by
18030 executing the code below:
18033 printf (@var{template}, @var{expressions}@dots{});
18036 As in @code{C} @code{printf}, ordinary characters in @var{template}
18037 are printed verbatim, while @dfn{conversion specification} introduced
18038 by the @samp{%} character cause subsequent @var{expressions} to be
18039 evaluated, their values converted and formatted according to type and
18040 style information encoded in the conversion specifications, and then
18043 For example, you can print two values in hex like this:
18046 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
18049 @code{printf} supports all the standard @code{C} conversion
18050 specifications, including the flags and modifiers between the @samp{%}
18051 character and the conversion letter, with the following exceptions:
18055 The argument-ordering modifiers, such as @samp{2$}, are not supported.
18058 The modifier @samp{*} is not supported for specifying precision or
18062 The @samp{'} flag (for separation of digits into groups according to
18063 @code{LC_NUMERIC'}) is not supported.
18066 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
18070 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
18073 The conversion letters @samp{a} and @samp{A} are not supported.
18077 Note that the @samp{ll} type modifier is supported only if the
18078 underlying @code{C} implementation used to build @value{GDBN} supports
18079 the @code{long long int} type, and the @samp{L} type modifier is
18080 supported only if @code{long double} type is available.
18082 As in @code{C}, @code{printf} supports simple backslash-escape
18083 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
18084 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
18085 single character. Octal and hexadecimal escape sequences are not
18088 Additionally, @code{printf} supports conversion specifications for DFP
18089 (@dfn{Decimal Floating Point}) types using the following length modifiers
18090 together with a floating point specifier.
18095 @samp{H} for printing @code{Decimal32} types.
18098 @samp{D} for printing @code{Decimal64} types.
18101 @samp{DD} for printing @code{Decimal128} types.
18104 If the underlying @code{C} implementation used to build @value{GDBN} has
18105 support for the three length modifiers for DFP types, other modifiers
18106 such as width and precision will also be available for @value{GDBN} to use.
18108 In case there is no such @code{C} support, no additional modifiers will be
18109 available and the value will be printed in the standard way.
18111 Here's an example of printing DFP types using the above conversion letters:
18113 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
18119 @section Scripting @value{GDBN} using Python
18120 @cindex python scripting
18121 @cindex scripting with python
18123 You can script @value{GDBN} using the @uref{http://www.python.org/,
18124 Python programming language}. This feature is available only if
18125 @value{GDBN} was configured using @option{--with-python}.
18128 * Python Commands:: Accessing Python from @value{GDBN}.
18129 * Python API:: Accessing @value{GDBN} from Python.
18132 @node Python Commands
18133 @subsection Python Commands
18134 @cindex python commands
18135 @cindex commands to access python
18137 @value{GDBN} provides one command for accessing the Python interpreter,
18138 and one related setting:
18142 @item python @r{[}@var{code}@r{]}
18143 The @code{python} command can be used to evaluate Python code.
18145 If given an argument, the @code{python} command will evaluate the
18146 argument as a Python command. For example:
18149 (@value{GDBP}) python print 23
18153 If you do not provide an argument to @code{python}, it will act as a
18154 multi-line command, like @code{define}. In this case, the Python
18155 script is made up of subsequent command lines, given after the
18156 @code{python} command. This command list is terminated using a line
18157 containing @code{end}. For example:
18160 (@value{GDBP}) python
18162 End with a line saying just "end".
18168 @kindex maint set python print-stack
18169 @item maint set python print-stack
18170 By default, @value{GDBN} will print a stack trace when an error occurs
18171 in a Python script. This can be controlled using @code{maint set
18172 python print-stack}: if @code{on}, the default, then Python stack
18173 printing is enabled; if @code{off}, then Python stack printing is
18178 @subsection Python API
18180 @cindex programming in python
18182 @cindex python stdout
18183 @cindex python pagination
18184 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
18185 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
18186 A Python program which outputs to one of these streams may have its
18187 output interrupted by the user (@pxref{Screen Size}). In this
18188 situation, a Python @code{KeyboardInterrupt} exception is thrown.
18191 * Basic Python:: Basic Python Functions.
18192 * Exception Handling::
18193 * Values From Inferior::
18194 * Commands In Python:: Implementing new commands in Python.
18195 * Functions In Python:: Writing new convenience functions.
18199 @subsubsection Basic Python
18201 @cindex python functions
18202 @cindex python module
18204 @value{GDBN} introduces a new Python module, named @code{gdb}. All
18205 methods and classes added by @value{GDBN} are placed in this module.
18206 @value{GDBN} automatically @code{import}s the @code{gdb} module for
18207 use in all scripts evaluated by the @code{python} command.
18209 @findex gdb.execute
18210 @defun execute command [from_tty]
18211 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
18212 If a GDB exception happens while @var{command} runs, it is
18213 translated as described in @ref{Exception Handling,,Exception Handling}.
18214 If no exceptions occur, this function returns @code{None}.
18216 @var{from_tty} specifies whether @value{GDBN} ought to consider this
18217 command as having originated from the user invoking it interactively.
18218 It must be a boolean value. If omitted, it defaults to @code{False}.
18221 @findex gdb.get_parameter
18222 @defun get_parameter parameter
18223 Return the value of a @value{GDBN} parameter. @var{parameter} is a
18224 string naming the parameter to look up; @var{parameter} may contain
18225 spaces if the parameter has a multi-part name. For example,
18226 @samp{print object} is a valid parameter name.
18228 If the named parameter does not exist, this function throws a
18229 @code{RuntimeError}. Otherwise, the parameter's value is converted to
18230 a Python value of the appropriate type, and returned.
18233 @findex gdb.history
18234 @defun history number
18235 Return a value from @value{GDBN}'s value history (@pxref{Value
18236 History}). @var{number} indicates which history element to return.
18237 If @var{number} is negative, then @value{GDBN} will take its absolute value
18238 and count backward from the last element (i.e., the most recent element) to
18239 find the value to return. If @var{number} is zero, then @value{GDBN} will
18240 return the most recent element. If the element specified by @var{number}
18241 doesn't exist in the value history, a @code{RuntimeError} exception will be
18244 If no exception is raised, the return value is always an instance of
18245 @code{gdb.Value} (@pxref{Values From Inferior}).
18249 @defun write string
18250 Print a string to @value{GDBN}'s paginated standard output stream.
18251 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
18252 call this function.
18257 Flush @value{GDBN}'s paginated standard output stream. Flushing
18258 @code{sys.stdout} or @code{sys.stderr} will automatically call this
18262 @node Exception Handling
18263 @subsubsection Exception Handling
18264 @cindex python exceptions
18265 @cindex exceptions, python
18267 When executing the @code{python} command, Python exceptions
18268 uncaught within the Python code are translated to calls to
18269 @value{GDBN} error-reporting mechanism. If the command that called
18270 @code{python} does not handle the error, @value{GDBN} will
18271 terminate it and print an error message containing the Python
18272 exception name, the associated value, and the Python call stack
18273 backtrace at the point where the exception was raised. Example:
18276 (@value{GDBP}) python print foo
18277 Traceback (most recent call last):
18278 File "<string>", line 1, in <module>
18279 NameError: name 'foo' is not defined
18282 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
18283 code are converted to Python @code{RuntimeError} exceptions. User
18284 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
18285 prompt) is translated to a Python @code{KeyboardInterrupt}
18286 exception. If you catch these exceptions in your Python code, your
18287 exception handler will see @code{RuntimeError} or
18288 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
18289 message as its value, and the Python call stack backtrace at the
18290 Python statement closest to where the @value{GDBN} error occured as the
18293 @node Values From Inferior
18294 @subsubsection Values From Inferior
18295 @cindex values from inferior, with Python
18296 @cindex python, working with values from inferior
18298 @cindex @code{gdb.Value}
18299 @value{GDBN} provides values it obtains from the inferior program in
18300 an object of type @code{gdb.Value}. @value{GDBN} uses this object
18301 for its internal bookkeeping of the inferior's values, and for
18302 fetching values when necessary.
18304 Inferior values that are simple scalars can be used directly in
18305 Python expressions that are valid for the value's data type. Here's
18306 an example for an integer or floating-point value @code{some_val}:
18313 As result of this, @code{bar} will also be a @code{gdb.Value} object
18314 whose values are of the same type as those of @code{some_val}.
18316 Inferior values that are structures or instances of some class can
18317 be accessed using the Python @dfn{dictionary syntax}. For example, if
18318 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
18319 can access its @code{foo} element with:
18322 bar = some_val['foo']
18325 Again, @code{bar} will also be a @code{gdb.Value} object.
18327 For pointer data types, @code{gdb.Value} provides a method for
18328 dereferencing the pointer to obtain the object it points to.
18330 @defmethod Value dereference
18331 This method returns a new @code{gdb.Value} object whose contents is
18332 the object pointed to by the pointer. For example, if @code{foo} is
18333 a C pointer to an @code{int}, declared in your C program as
18340 then you can use the corresponding @code{gdb.Value} to access what
18341 @code{foo} points to like this:
18344 bar = foo.dereference ()
18347 The result @code{bar} will be a @code{gdb.Value} object holding the
18348 value pointed to by @code{foo}.
18351 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]}
18352 If this @code{gdb.Value} represents a string, then this method
18353 converts the contents to a Python string. Otherwise, this method will
18354 throw an exception.
18356 Strings are recognized in a language-specific way; whether a given
18357 @code{gdb.Value} represents a string is determined by the current
18360 For C-like languages, a value is a string if it is a pointer to or an
18361 array of characters or ints. The string is assumed to be terminated
18362 by a zero of the appropriate width.
18364 If the optional @var{encoding} argument is given, it must be a string
18365 naming the encoding of the string in the @code{gdb.Value}, such as
18366 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
18367 the same encodings as the corresponding argument to Python's
18368 @code{string.decode} method, and the Python codec machinery will be used
18369 to convert the string. If @var{encoding} is not given, or if
18370 @var{encoding} is the empty string, then either the @code{target-charset}
18371 (@pxref{Character Sets}) will be used, or a language-specific encoding
18372 will be used, if the current language is able to supply one.
18374 The optional @var{errors} argument is the same as the corresponding
18375 argument to Python's @code{string.decode} method.
18378 @node Commands In Python
18379 @subsubsection Commands In Python
18381 @cindex commands in python
18382 @cindex python commands
18383 You can implement new @value{GDBN} CLI commands in Python. A CLI
18384 command is implemented using an instance of the @code{gdb.Command}
18385 class, most commonly using a subclass.
18387 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
18388 The object initializer for @code{Command} registers the new command
18389 with @value{GDBN}. This initializer is normally invoked from the
18390 subclass' own @code{__init__} method.
18392 @var{name} is the name of the command. If @var{name} consists of
18393 multiple words, then the initial words are looked for as prefix
18394 commands. In this case, if one of the prefix commands does not exist,
18395 an exception is raised.
18397 There is no support for multi-line commands.
18399 @var{command_class} should be one of the @samp{COMMAND_} constants
18400 defined below. This argument tells @value{GDBN} how to categorize the
18401 new command in the help system.
18403 @var{completer_class} is an optional argument. If given, it should be
18404 one of the @samp{COMPLETE_} constants defined below. This argument
18405 tells @value{GDBN} how to perform completion for this command. If not
18406 given, @value{GDBN} will attempt to complete using the object's
18407 @code{complete} method (see below); if no such method is found, an
18408 error will occur when completion is attempted.
18410 @var{prefix} is an optional argument. If @code{True}, then the new
18411 command is a prefix command; sub-commands of this command may be
18414 The help text for the new command is taken from the Python
18415 documentation string for the command's class, if there is one. If no
18416 documentation string is provided, the default value ``This command is
18417 not documented.'' is used.
18420 @cindex don't repeat Python command
18421 @defmethod Command dont_repeat
18422 By default, a @value{GDBN} command is repeated when the user enters a
18423 blank line at the command prompt. A command can suppress this
18424 behavior by invoking the @code{dont_repeat} method. This is similar
18425 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
18428 @defmethod Command invoke argument from_tty
18429 This method is called by @value{GDBN} when this command is invoked.
18431 @var{argument} is a string. It is the argument to the command, after
18432 leading and trailing whitespace has been stripped.
18434 @var{from_tty} is a boolean argument. When true, this means that the
18435 command was entered by the user at the terminal; when false it means
18436 that the command came from elsewhere.
18438 If this method throws an exception, it is turned into a @value{GDBN}
18439 @code{error} call. Otherwise, the return value is ignored.
18442 @cindex completion of Python commands
18443 @defmethod Command complete text word
18444 This method is called by @value{GDBN} when the user attempts
18445 completion on this command. All forms of completion are handled by
18446 this method, that is, the @key{TAB} and @key{M-?} key bindings
18447 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
18450 The arguments @var{text} and @var{word} are both strings. @var{text}
18451 holds the complete command line up to the cursor's location.
18452 @var{word} holds the last word of the command line; this is computed
18453 using a word-breaking heuristic.
18455 The @code{complete} method can return several values:
18458 If the return value is a sequence, the contents of the sequence are
18459 used as the completions. It is up to @code{complete} to ensure that the
18460 contents actually do complete the word. A zero-length sequence is
18461 allowed, it means that there were no completions available. Only
18462 string elements of the sequence are used; other elements in the
18463 sequence are ignored.
18466 If the return value is one of the @samp{COMPLETE_} constants defined
18467 below, then the corresponding @value{GDBN}-internal completion
18468 function is invoked, and its result is used.
18471 All other results are treated as though there were no available
18476 When a new command is registered, it must be declared as a member of
18477 some general class of commands. This is used to classify top-level
18478 commands in the on-line help system; note that prefix commands are not
18479 listed under their own category but rather that of their top-level
18480 command. The available classifications are represented by constants
18481 defined in the @code{gdb} module:
18484 @findex COMMAND_NONE
18485 @findex gdb.COMMAND_NONE
18487 The command does not belong to any particular class. A command in
18488 this category will not be displayed in any of the help categories.
18490 @findex COMMAND_RUNNING
18491 @findex gdb.COMMAND_RUNNING
18492 @item COMMAND_RUNNING
18493 The command is related to running the inferior. For example,
18494 @code{start}, @code{step}, and @code{continue} are in this category.
18495 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
18496 commands in this category.
18498 @findex COMMAND_DATA
18499 @findex gdb.COMMAND_DATA
18501 The command is related to data or variables. For example,
18502 @code{call}, @code{find}, and @code{print} are in this category. Type
18503 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
18506 @findex COMMAND_STACK
18507 @findex gdb.COMMAND_STACK
18508 @item COMMAND_STACK
18509 The command has to do with manipulation of the stack. For example,
18510 @code{backtrace}, @code{frame}, and @code{return} are in this
18511 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
18512 list of commands in this category.
18514 @findex COMMAND_FILES
18515 @findex gdb.COMMAND_FILES
18516 @item COMMAND_FILES
18517 This class is used for file-related commands. For example,
18518 @code{file}, @code{list} and @code{section} are in this category.
18519 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
18520 commands in this category.
18522 @findex COMMAND_SUPPORT
18523 @findex gdb.COMMAND_SUPPORT
18524 @item COMMAND_SUPPORT
18525 This should be used for ``support facilities'', generally meaning
18526 things that are useful to the user when interacting with @value{GDBN},
18527 but not related to the state of the inferior. For example,
18528 @code{help}, @code{make}, and @code{shell} are in this category. Type
18529 @kbd{help support} at the @value{GDBN} prompt to see a list of
18530 commands in this category.
18532 @findex COMMAND_STATUS
18533 @findex gdb.COMMAND_STATUS
18534 @item COMMAND_STATUS
18535 The command is an @samp{info}-related command, that is, related to the
18536 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
18537 and @code{show} are in this category. Type @kbd{help status} at the
18538 @value{GDBN} prompt to see a list of commands in this category.
18540 @findex COMMAND_BREAKPOINTS
18541 @findex gdb.COMMAND_BREAKPOINTS
18542 @item COMMAND_BREAKPOINTS
18543 The command has to do with breakpoints. For example, @code{break},
18544 @code{clear}, and @code{delete} are in this category. Type @kbd{help
18545 breakpoints} at the @value{GDBN} prompt to see a list of commands in
18548 @findex COMMAND_TRACEPOINTS
18549 @findex gdb.COMMAND_TRACEPOINTS
18550 @item COMMAND_TRACEPOINTS
18551 The command has to do with tracepoints. For example, @code{trace},
18552 @code{actions}, and @code{tfind} are in this category. Type
18553 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
18554 commands in this category.
18556 @findex COMMAND_OBSCURE
18557 @findex gdb.COMMAND_OBSCURE
18558 @item COMMAND_OBSCURE
18559 The command is only used in unusual circumstances, or is not of
18560 general interest to users. For example, @code{checkpoint},
18561 @code{fork}, and @code{stop} are in this category. Type @kbd{help
18562 obscure} at the @value{GDBN} prompt to see a list of commands in this
18565 @findex COMMAND_MAINTENANCE
18566 @findex gdb.COMMAND_MAINTENANCE
18567 @item COMMAND_MAINTENANCE
18568 The command is only useful to @value{GDBN} maintainers. The
18569 @code{maintenance} and @code{flushregs} commands are in this category.
18570 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
18571 commands in this category.
18574 A new command can use a predefined completion function, either by
18575 specifying it via an argument at initialization, or by returning it
18576 from the @code{complete} method. These predefined completion
18577 constants are all defined in the @code{gdb} module:
18580 @findex COMPLETE_NONE
18581 @findex gdb.COMPLETE_NONE
18582 @item COMPLETE_NONE
18583 This constant means that no completion should be done.
18585 @findex COMPLETE_FILENAME
18586 @findex gdb.COMPLETE_FILENAME
18587 @item COMPLETE_FILENAME
18588 This constant means that filename completion should be performed.
18590 @findex COMPLETE_LOCATION
18591 @findex gdb.COMPLETE_LOCATION
18592 @item COMPLETE_LOCATION
18593 This constant means that location completion should be done.
18594 @xref{Specify Location}.
18596 @findex COMPLETE_COMMAND
18597 @findex gdb.COMPLETE_COMMAND
18598 @item COMPLETE_COMMAND
18599 This constant means that completion should examine @value{GDBN}
18602 @findex COMPLETE_SYMBOL
18603 @findex gdb.COMPLETE_SYMBOL
18604 @item COMPLETE_SYMBOL
18605 This constant means that completion should be done using symbol names
18609 The following code snippet shows how a trivial CLI command can be
18610 implemented in Python:
18613 class HelloWorld (gdb.Command):
18614 """Greet the whole world."""
18616 def __init__ (self):
18617 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
18619 def invoke (self, arg, from_tty):
18620 print "Hello, World!"
18625 The last line instantiates the class, and is necessary to trigger the
18626 registration of the command with @value{GDBN}. Depending on how the
18627 Python code is read into @value{GDBN}, you may need to import the
18628 @code{gdb} module explicitly.
18630 @node Functions In Python
18631 @subsubsection Writing new convenience functions
18633 @cindex writing convenience functions
18634 @cindex convenience functions in python
18635 @cindex python convenience functions
18636 @tindex gdb.Function
18638 You can implement new convenience functions (@pxref{Convenience Vars})
18639 in Python. A convenience function is an instance of a subclass of the
18640 class @code{gdb.Function}.
18642 @defmethod Function __init__ name
18643 The initializer for @code{Function} registers the new function with
18644 @value{GDBN}. The argument @var{name} is the name of the function,
18645 a string. The function will be visible to the user as a convenience
18646 variable of type @code{internal function}, whose name is the same as
18647 the given @var{name}.
18649 The documentation for the new function is taken from the documentation
18650 string for the new class.
18653 @defmethod Function invoke @var{*args}
18654 When a convenience function is evaluated, its arguments are converted
18655 to instances of @code{gdb.Value}, and then the function's
18656 @code{invoke} method is called. Note that @value{GDBN} does not
18657 predetermine the arity of convenience functions. Instead, all
18658 available arguments are passed to @code{invoke}, following the
18659 standard Python calling convention. In particular, a convenience
18660 function can have default values for parameters without ill effect.
18662 The return value of this method is used as its value in the enclosing
18663 expression. If an ordinary Python value is returned, it is converted
18664 to a @code{gdb.Value} following the usual rules.
18667 The following code snippet shows how a trivial convenience function can
18668 be implemented in Python:
18671 class Greet (gdb.Function):
18672 """Return string to greet someone.
18673 Takes a name as argument."""
18675 def __init__ (self):
18676 super (Greet, self).__init__ ("greet")
18678 def invoke (self, name):
18679 return "Hello, %s!" % name.string ()
18684 The last line instantiates the class, and is necessary to trigger the
18685 registration of the function with @value{GDBN}. Depending on how the
18686 Python code is read into @value{GDBN}, you may need to import the
18687 @code{gdb} module explicitly.
18690 @chapter Command Interpreters
18691 @cindex command interpreters
18693 @value{GDBN} supports multiple command interpreters, and some command
18694 infrastructure to allow users or user interface writers to switch
18695 between interpreters or run commands in other interpreters.
18697 @value{GDBN} currently supports two command interpreters, the console
18698 interpreter (sometimes called the command-line interpreter or @sc{cli})
18699 and the machine interface interpreter (or @sc{gdb/mi}). This manual
18700 describes both of these interfaces in great detail.
18702 By default, @value{GDBN} will start with the console interpreter.
18703 However, the user may choose to start @value{GDBN} with another
18704 interpreter by specifying the @option{-i} or @option{--interpreter}
18705 startup options. Defined interpreters include:
18709 @cindex console interpreter
18710 The traditional console or command-line interpreter. This is the most often
18711 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
18712 @value{GDBN} will use this interpreter.
18715 @cindex mi interpreter
18716 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
18717 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
18718 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
18722 @cindex mi2 interpreter
18723 The current @sc{gdb/mi} interface.
18726 @cindex mi1 interpreter
18727 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
18731 @cindex invoke another interpreter
18732 The interpreter being used by @value{GDBN} may not be dynamically
18733 switched at runtime. Although possible, this could lead to a very
18734 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
18735 enters the command "interpreter-set console" in a console view,
18736 @value{GDBN} would switch to using the console interpreter, rendering
18737 the IDE inoperable!
18739 @kindex interpreter-exec
18740 Although you may only choose a single interpreter at startup, you may execute
18741 commands in any interpreter from the current interpreter using the appropriate
18742 command. If you are running the console interpreter, simply use the
18743 @code{interpreter-exec} command:
18746 interpreter-exec mi "-data-list-register-names"
18749 @sc{gdb/mi} has a similar command, although it is only available in versions of
18750 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
18753 @chapter @value{GDBN} Text User Interface
18755 @cindex Text User Interface
18758 * TUI Overview:: TUI overview
18759 * TUI Keys:: TUI key bindings
18760 * TUI Single Key Mode:: TUI single key mode
18761 * TUI Commands:: TUI-specific commands
18762 * TUI Configuration:: TUI configuration variables
18765 The @value{GDBN} Text User Interface (TUI) is a terminal
18766 interface which uses the @code{curses} library to show the source
18767 file, the assembly output, the program registers and @value{GDBN}
18768 commands in separate text windows. The TUI mode is supported only
18769 on platforms where a suitable version of the @code{curses} library
18772 @pindex @value{GDBTUI}
18773 The TUI mode is enabled by default when you invoke @value{GDBN} as
18774 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
18775 You can also switch in and out of TUI mode while @value{GDBN} runs by
18776 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
18777 @xref{TUI Keys, ,TUI Key Bindings}.
18780 @section TUI Overview
18782 In TUI mode, @value{GDBN} can display several text windows:
18786 This window is the @value{GDBN} command window with the @value{GDBN}
18787 prompt and the @value{GDBN} output. The @value{GDBN} input is still
18788 managed using readline.
18791 The source window shows the source file of the program. The current
18792 line and active breakpoints are displayed in this window.
18795 The assembly window shows the disassembly output of the program.
18798 This window shows the processor registers. Registers are highlighted
18799 when their values change.
18802 The source and assembly windows show the current program position
18803 by highlighting the current line and marking it with a @samp{>} marker.
18804 Breakpoints are indicated with two markers. The first marker
18805 indicates the breakpoint type:
18809 Breakpoint which was hit at least once.
18812 Breakpoint which was never hit.
18815 Hardware breakpoint which was hit at least once.
18818 Hardware breakpoint which was never hit.
18821 The second marker indicates whether the breakpoint is enabled or not:
18825 Breakpoint is enabled.
18828 Breakpoint is disabled.
18831 The source, assembly and register windows are updated when the current
18832 thread changes, when the frame changes, or when the program counter
18835 These windows are not all visible at the same time. The command
18836 window is always visible. The others can be arranged in several
18847 source and assembly,
18850 source and registers, or
18853 assembly and registers.
18856 A status line above the command window shows the following information:
18860 Indicates the current @value{GDBN} target.
18861 (@pxref{Targets, ,Specifying a Debugging Target}).
18864 Gives the current process or thread number.
18865 When no process is being debugged, this field is set to @code{No process}.
18868 Gives the current function name for the selected frame.
18869 The name is demangled if demangling is turned on (@pxref{Print Settings}).
18870 When there is no symbol corresponding to the current program counter,
18871 the string @code{??} is displayed.
18874 Indicates the current line number for the selected frame.
18875 When the current line number is not known, the string @code{??} is displayed.
18878 Indicates the current program counter address.
18882 @section TUI Key Bindings
18883 @cindex TUI key bindings
18885 The TUI installs several key bindings in the readline keymaps
18886 (@pxref{Command Line Editing}). The following key bindings
18887 are installed for both TUI mode and the @value{GDBN} standard mode.
18896 Enter or leave the TUI mode. When leaving the TUI mode,
18897 the curses window management stops and @value{GDBN} operates using
18898 its standard mode, writing on the terminal directly. When reentering
18899 the TUI mode, control is given back to the curses windows.
18900 The screen is then refreshed.
18904 Use a TUI layout with only one window. The layout will
18905 either be @samp{source} or @samp{assembly}. When the TUI mode
18906 is not active, it will switch to the TUI mode.
18908 Think of this key binding as the Emacs @kbd{C-x 1} binding.
18912 Use a TUI layout with at least two windows. When the current
18913 layout already has two windows, the next layout with two windows is used.
18914 When a new layout is chosen, one window will always be common to the
18915 previous layout and the new one.
18917 Think of it as the Emacs @kbd{C-x 2} binding.
18921 Change the active window. The TUI associates several key bindings
18922 (like scrolling and arrow keys) with the active window. This command
18923 gives the focus to the next TUI window.
18925 Think of it as the Emacs @kbd{C-x o} binding.
18929 Switch in and out of the TUI SingleKey mode that binds single
18930 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
18933 The following key bindings only work in the TUI mode:
18938 Scroll the active window one page up.
18942 Scroll the active window one page down.
18946 Scroll the active window one line up.
18950 Scroll the active window one line down.
18954 Scroll the active window one column left.
18958 Scroll the active window one column right.
18962 Refresh the screen.
18965 Because the arrow keys scroll the active window in the TUI mode, they
18966 are not available for their normal use by readline unless the command
18967 window has the focus. When another window is active, you must use
18968 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
18969 and @kbd{C-f} to control the command window.
18971 @node TUI Single Key Mode
18972 @section TUI Single Key Mode
18973 @cindex TUI single key mode
18975 The TUI also provides a @dfn{SingleKey} mode, which binds several
18976 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
18977 switch into this mode, where the following key bindings are used:
18980 @kindex c @r{(SingleKey TUI key)}
18984 @kindex d @r{(SingleKey TUI key)}
18988 @kindex f @r{(SingleKey TUI key)}
18992 @kindex n @r{(SingleKey TUI key)}
18996 @kindex q @r{(SingleKey TUI key)}
18998 exit the SingleKey mode.
19000 @kindex r @r{(SingleKey TUI key)}
19004 @kindex s @r{(SingleKey TUI key)}
19008 @kindex u @r{(SingleKey TUI key)}
19012 @kindex v @r{(SingleKey TUI key)}
19016 @kindex w @r{(SingleKey TUI key)}
19021 Other keys temporarily switch to the @value{GDBN} command prompt.
19022 The key that was pressed is inserted in the editing buffer so that
19023 it is possible to type most @value{GDBN} commands without interaction
19024 with the TUI SingleKey mode. Once the command is entered the TUI
19025 SingleKey mode is restored. The only way to permanently leave
19026 this mode is by typing @kbd{q} or @kbd{C-x s}.
19030 @section TUI-specific Commands
19031 @cindex TUI commands
19033 The TUI has specific commands to control the text windows.
19034 These commands are always available, even when @value{GDBN} is not in
19035 the TUI mode. When @value{GDBN} is in the standard mode, most
19036 of these commands will automatically switch to the TUI mode.
19041 List and give the size of all displayed windows.
19045 Display the next layout.
19048 Display the previous layout.
19051 Display the source window only.
19054 Display the assembly window only.
19057 Display the source and assembly window.
19060 Display the register window together with the source or assembly window.
19064 Make the next window active for scrolling.
19067 Make the previous window active for scrolling.
19070 Make the source window active for scrolling.
19073 Make the assembly window active for scrolling.
19076 Make the register window active for scrolling.
19079 Make the command window active for scrolling.
19083 Refresh the screen. This is similar to typing @kbd{C-L}.
19085 @item tui reg float
19087 Show the floating point registers in the register window.
19089 @item tui reg general
19090 Show the general registers in the register window.
19093 Show the next register group. The list of register groups as well as
19094 their order is target specific. The predefined register groups are the
19095 following: @code{general}, @code{float}, @code{system}, @code{vector},
19096 @code{all}, @code{save}, @code{restore}.
19098 @item tui reg system
19099 Show the system registers in the register window.
19103 Update the source window and the current execution point.
19105 @item winheight @var{name} +@var{count}
19106 @itemx winheight @var{name} -@var{count}
19108 Change the height of the window @var{name} by @var{count}
19109 lines. Positive counts increase the height, while negative counts
19112 @item tabset @var{nchars}
19114 Set the width of tab stops to be @var{nchars} characters.
19117 @node TUI Configuration
19118 @section TUI Configuration Variables
19119 @cindex TUI configuration variables
19121 Several configuration variables control the appearance of TUI windows.
19124 @item set tui border-kind @var{kind}
19125 @kindex set tui border-kind
19126 Select the border appearance for the source, assembly and register windows.
19127 The possible values are the following:
19130 Use a space character to draw the border.
19133 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
19136 Use the Alternate Character Set to draw the border. The border is
19137 drawn using character line graphics if the terminal supports them.
19140 @item set tui border-mode @var{mode}
19141 @kindex set tui border-mode
19142 @itemx set tui active-border-mode @var{mode}
19143 @kindex set tui active-border-mode
19144 Select the display attributes for the borders of the inactive windows
19145 or the active window. The @var{mode} can be one of the following:
19148 Use normal attributes to display the border.
19154 Use reverse video mode.
19157 Use half bright mode.
19159 @item half-standout
19160 Use half bright and standout mode.
19163 Use extra bright or bold mode.
19165 @item bold-standout
19166 Use extra bright or bold and standout mode.
19171 @chapter Using @value{GDBN} under @sc{gnu} Emacs
19174 @cindex @sc{gnu} Emacs
19175 A special interface allows you to use @sc{gnu} Emacs to view (and
19176 edit) the source files for the program you are debugging with
19179 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
19180 executable file you want to debug as an argument. This command starts
19181 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
19182 created Emacs buffer.
19183 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
19185 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
19190 All ``terminal'' input and output goes through an Emacs buffer, called
19193 This applies both to @value{GDBN} commands and their output, and to the input
19194 and output done by the program you are debugging.
19196 This is useful because it means that you can copy the text of previous
19197 commands and input them again; you can even use parts of the output
19200 All the facilities of Emacs' Shell mode are available for interacting
19201 with your program. In particular, you can send signals the usual
19202 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
19206 @value{GDBN} displays source code through Emacs.
19208 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
19209 source file for that frame and puts an arrow (@samp{=>}) at the
19210 left margin of the current line. Emacs uses a separate buffer for
19211 source display, and splits the screen to show both your @value{GDBN} session
19214 Explicit @value{GDBN} @code{list} or search commands still produce output as
19215 usual, but you probably have no reason to use them from Emacs.
19218 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
19219 a graphical mode, enabled by default, which provides further buffers
19220 that can control the execution and describe the state of your program.
19221 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
19223 If you specify an absolute file name when prompted for the @kbd{M-x
19224 gdb} argument, then Emacs sets your current working directory to where
19225 your program resides. If you only specify the file name, then Emacs
19226 sets your current working directory to to the directory associated
19227 with the previous buffer. In this case, @value{GDBN} may find your
19228 program by searching your environment's @code{PATH} variable, but on
19229 some operating systems it might not find the source. So, although the
19230 @value{GDBN} input and output session proceeds normally, the auxiliary
19231 buffer does not display the current source and line of execution.
19233 The initial working directory of @value{GDBN} is printed on the top
19234 line of the GUD buffer and this serves as a default for the commands
19235 that specify files for @value{GDBN} to operate on. @xref{Files,
19236 ,Commands to Specify Files}.
19238 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
19239 need to call @value{GDBN} by a different name (for example, if you
19240 keep several configurations around, with different names) you can
19241 customize the Emacs variable @code{gud-gdb-command-name} to run the
19244 In the GUD buffer, you can use these special Emacs commands in
19245 addition to the standard Shell mode commands:
19249 Describe the features of Emacs' GUD Mode.
19252 Execute to another source line, like the @value{GDBN} @code{step} command; also
19253 update the display window to show the current file and location.
19256 Execute to next source line in this function, skipping all function
19257 calls, like the @value{GDBN} @code{next} command. Then update the display window
19258 to show the current file and location.
19261 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
19262 display window accordingly.
19265 Execute until exit from the selected stack frame, like the @value{GDBN}
19266 @code{finish} command.
19269 Continue execution of your program, like the @value{GDBN} @code{continue}
19273 Go up the number of frames indicated by the numeric argument
19274 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
19275 like the @value{GDBN} @code{up} command.
19278 Go down the number of frames indicated by the numeric argument, like the
19279 @value{GDBN} @code{down} command.
19282 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
19283 tells @value{GDBN} to set a breakpoint on the source line point is on.
19285 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
19286 separate frame which shows a backtrace when the GUD buffer is current.
19287 Move point to any frame in the stack and type @key{RET} to make it
19288 become the current frame and display the associated source in the
19289 source buffer. Alternatively, click @kbd{Mouse-2} to make the
19290 selected frame become the current one. In graphical mode, the
19291 speedbar displays watch expressions.
19293 If you accidentally delete the source-display buffer, an easy way to get
19294 it back is to type the command @code{f} in the @value{GDBN} buffer, to
19295 request a frame display; when you run under Emacs, this recreates
19296 the source buffer if necessary to show you the context of the current
19299 The source files displayed in Emacs are in ordinary Emacs buffers
19300 which are visiting the source files in the usual way. You can edit
19301 the files with these buffers if you wish; but keep in mind that @value{GDBN}
19302 communicates with Emacs in terms of line numbers. If you add or
19303 delete lines from the text, the line numbers that @value{GDBN} knows cease
19304 to correspond properly with the code.
19306 A more detailed description of Emacs' interaction with @value{GDBN} is
19307 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
19310 @c The following dropped because Epoch is nonstandard. Reactivate
19311 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
19313 @kindex Emacs Epoch environment
19317 Version 18 of @sc{gnu} Emacs has a built-in window system
19318 called the @code{epoch}
19319 environment. Users of this environment can use a new command,
19320 @code{inspect} which performs identically to @code{print} except that
19321 each value is printed in its own window.
19326 @chapter The @sc{gdb/mi} Interface
19328 @unnumberedsec Function and Purpose
19330 @cindex @sc{gdb/mi}, its purpose
19331 @sc{gdb/mi} is a line based machine oriented text interface to
19332 @value{GDBN} and is activated by specifying using the
19333 @option{--interpreter} command line option (@pxref{Mode Options}). It
19334 is specifically intended to support the development of systems which
19335 use the debugger as just one small component of a larger system.
19337 This chapter is a specification of the @sc{gdb/mi} interface. It is written
19338 in the form of a reference manual.
19340 Note that @sc{gdb/mi} is still under construction, so some of the
19341 features described below are incomplete and subject to change
19342 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
19344 @unnumberedsec Notation and Terminology
19346 @cindex notational conventions, for @sc{gdb/mi}
19347 This chapter uses the following notation:
19351 @code{|} separates two alternatives.
19354 @code{[ @var{something} ]} indicates that @var{something} is optional:
19355 it may or may not be given.
19358 @code{( @var{group} )*} means that @var{group} inside the parentheses
19359 may repeat zero or more times.
19362 @code{( @var{group} )+} means that @var{group} inside the parentheses
19363 may repeat one or more times.
19366 @code{"@var{string}"} means a literal @var{string}.
19370 @heading Dependencies
19374 * GDB/MI General Design::
19375 * GDB/MI Command Syntax::
19376 * GDB/MI Compatibility with CLI::
19377 * GDB/MI Development and Front Ends::
19378 * GDB/MI Output Records::
19379 * GDB/MI Simple Examples::
19380 * GDB/MI Command Description Format::
19381 * GDB/MI Breakpoint Commands::
19382 * GDB/MI Program Context::
19383 * GDB/MI Thread Commands::
19384 * GDB/MI Program Execution::
19385 * GDB/MI Stack Manipulation::
19386 * GDB/MI Variable Objects::
19387 * GDB/MI Data Manipulation::
19388 * GDB/MI Tracepoint Commands::
19389 * GDB/MI Symbol Query::
19390 * GDB/MI File Commands::
19392 * GDB/MI Kod Commands::
19393 * GDB/MI Memory Overlay Commands::
19394 * GDB/MI Signal Handling Commands::
19396 * GDB/MI Target Manipulation::
19397 * GDB/MI File Transfer Commands::
19398 * GDB/MI Miscellaneous Commands::
19401 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19402 @node GDB/MI General Design
19403 @section @sc{gdb/mi} General Design
19404 @cindex GDB/MI General Design
19406 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
19407 parts---commands sent to @value{GDBN}, responses to those commands
19408 and notifications. Each command results in exactly one response,
19409 indicating either successful completion of the command, or an error.
19410 For the commands that do not resume the target, the response contains the
19411 requested information. For the commands that resume the target, the
19412 response only indicates whether the target was successfully resumed.
19413 Notifications is the mechanism for reporting changes in the state of the
19414 target, or in @value{GDBN} state, that cannot conveniently be associated with
19415 a command and reported as part of that command response.
19417 The important examples of notifications are:
19421 Exec notifications. These are used to report changes in
19422 target state---when a target is resumed, or stopped. It would not
19423 be feasible to include this information in response of resuming
19424 commands, because one resume commands can result in multiple events in
19425 different threads. Also, quite some time may pass before any event
19426 happens in the target, while a frontend needs to know whether the resuming
19427 command itself was successfully executed.
19430 Console output, and status notifications. Console output
19431 notifications are used to report output of CLI commands, as well as
19432 diagnostics for other commands. Status notifications are used to
19433 report the progress of a long-running operation. Naturally, including
19434 this information in command response would mean no output is produced
19435 until the command is finished, which is undesirable.
19438 General notifications. Commands may have various side effects on
19439 the @value{GDBN} or target state beyond their official purpose. For example,
19440 a command may change the selected thread. Although such changes can
19441 be included in command response, using notification allows for more
19442 orthogonal frontend design.
19446 There's no guarantee that whenever an MI command reports an error,
19447 @value{GDBN} or the target are in any specific state, and especially,
19448 the state is not reverted to the state before the MI command was
19449 processed. Therefore, whenever an MI command results in an error,
19450 we recommend that the frontend refreshes all the information shown in
19451 the user interface.
19453 @subsection Context management
19455 In most cases when @value{GDBN} accesses the target, this access is
19456 done in context of a specific thread and frame (@pxref{Frames}).
19457 Often, even when accessing global data, the target requires that a thread
19458 be specified. The CLI interface maintains the selected thread and frame,
19459 and supplies them to target on each command. This is convenient,
19460 because a command line user would not want to specify that information
19461 explicitly on each command, and because user interacts with
19462 @value{GDBN} via a single terminal, so no confusion is possible as
19463 to what thread and frame are the current ones.
19465 In the case of MI, the concept of selected thread and frame is less
19466 useful. First, a frontend can easily remember this information
19467 itself. Second, a graphical frontend can have more than one window,
19468 each one used for debugging a different thread, and the frontend might
19469 want to access additional threads for internal purposes. This
19470 increases the risk that by relying on implicitly selected thread, the
19471 frontend may be operating on a wrong one. Therefore, each MI command
19472 should explicitly specify which thread and frame to operate on. To
19473 make it possible, each MI command accepts the @samp{--thread} and
19474 @samp{--frame} options, the value to each is @value{GDBN} identifier
19475 for thread and frame to operate on.
19477 Usually, each top-level window in a frontend allows the user to select
19478 a thread and a frame, and remembers the user selection for further
19479 operations. However, in some cases @value{GDBN} may suggest that the
19480 current thread be changed. For example, when stopping on a breakpoint
19481 it is reasonable to switch to the thread where breakpoint is hit. For
19482 another example, if the user issues the CLI @samp{thread} command via
19483 the frontend, it is desirable to change the frontend's selected thread to the
19484 one specified by user. @value{GDBN} communicates the suggestion to
19485 change current thread using the @samp{=thread-selected} notification.
19486 No such notification is available for the selected frame at the moment.
19488 Note that historically, MI shares the selected thread with CLI, so
19489 frontends used the @code{-thread-select} to execute commands in the
19490 right context. However, getting this to work right is cumbersome. The
19491 simplest way is for frontend to emit @code{-thread-select} command
19492 before every command. This doubles the number of commands that need
19493 to be sent. The alternative approach is to suppress @code{-thread-select}
19494 if the selected thread in @value{GDBN} is supposed to be identical to the
19495 thread the frontend wants to operate on. However, getting this
19496 optimization right can be tricky. In particular, if the frontend
19497 sends several commands to @value{GDBN}, and one of the commands changes the
19498 selected thread, then the behaviour of subsequent commands will
19499 change. So, a frontend should either wait for response from such
19500 problematic commands, or explicitly add @code{-thread-select} for
19501 all subsequent commands. No frontend is known to do this exactly
19502 right, so it is suggested to just always pass the @samp{--thread} and
19503 @samp{--frame} options.
19505 @subsection Asynchronous command execution and non-stop mode
19507 On some targets, @value{GDBN} is capable of processing MI commands
19508 even while the target is running. This is called @dfn{asynchronous
19509 command execution} (@pxref{Background Execution}). The frontend may
19510 specify a preferrence for asynchronous execution using the
19511 @code{-gdb-set target-async 1} command, which should be emitted before
19512 either running the executable or attaching to the target. After the
19513 frontend has started the executable or attached to the target, it can
19514 find if asynchronous execution is enabled using the
19515 @code{-list-target-features} command.
19517 Even if @value{GDBN} can accept a command while target is running,
19518 many commands that access the target do not work when the target is
19519 running. Therefore, asynchronous command execution is most useful
19520 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
19521 it is possible to examine the state of one thread, while other threads
19524 When a given thread is running, MI commands that try to access the
19525 target in the context of that thread may not work, or may work only on
19526 some targets. In particular, commands that try to operate on thread's
19527 stack will not work, on any target. Commands that read memory, or
19528 modify breakpoints, may work or not work, depending on the target. Note
19529 that even commands that operate on global state, such as @code{print},
19530 @code{set}, and breakpoint commands, still access the target in the
19531 context of a specific thread, so frontend should try to find a
19532 stopped thread and perform the operation on that thread (using the
19533 @samp{--thread} option).
19535 Which commands will work in the context of a running thread is
19536 highly target dependent. However, the two commands
19537 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
19538 to find the state of a thread, will always work.
19540 @subsection Thread groups
19541 @value{GDBN} may be used to debug several processes at the same time.
19542 On some platfroms, @value{GDBN} may support debugging of several
19543 hardware systems, each one having several cores with several different
19544 processes running on each core. This section describes the MI
19545 mechanism to support such debugging scenarios.
19547 The key observation is that regardless of the structure of the
19548 target, MI can have a global list of threads, because most commands that
19549 accept the @samp{--thread} option do not need to know what process that
19550 thread belongs to. Therefore, it is not necessary to introduce
19551 neither additional @samp{--process} option, nor an notion of the
19552 current process in the MI interface. The only strictly new feature
19553 that is required is the ability to find how the threads are grouped
19556 To allow the user to discover such grouping, and to support arbitrary
19557 hierarchy of machines/cores/processes, MI introduces the concept of a
19558 @dfn{thread group}. Thread group is a collection of threads and other
19559 thread groups. A thread group always has a string identifier, a type,
19560 and may have additional attributes specific to the type. A new
19561 command, @code{-list-thread-groups}, returns the list of top-level
19562 thread groups, which correspond to processes that @value{GDBN} is
19563 debugging at the moment. By passing an identifier of a thread group
19564 to the @code{-list-thread-groups} command, it is possible to obtain
19565 the members of specific thread group.
19567 To allow the user to easily discover processes, and other objects, he
19568 wishes to debug, a concept of @dfn{available thread group} is
19569 introduced. Available thread group is an thread group that
19570 @value{GDBN} is not debugging, but that can be attached to, using the
19571 @code{-target-attach} command. The list of available top-level thread
19572 groups can be obtained using @samp{-list-thread-groups --available}.
19573 In general, the content of a thread group may be only retrieved only
19574 after attaching to that thread group.
19576 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19577 @node GDB/MI Command Syntax
19578 @section @sc{gdb/mi} Command Syntax
19581 * GDB/MI Input Syntax::
19582 * GDB/MI Output Syntax::
19585 @node GDB/MI Input Syntax
19586 @subsection @sc{gdb/mi} Input Syntax
19588 @cindex input syntax for @sc{gdb/mi}
19589 @cindex @sc{gdb/mi}, input syntax
19591 @item @var{command} @expansion{}
19592 @code{@var{cli-command} | @var{mi-command}}
19594 @item @var{cli-command} @expansion{}
19595 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
19596 @var{cli-command} is any existing @value{GDBN} CLI command.
19598 @item @var{mi-command} @expansion{}
19599 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
19600 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
19602 @item @var{token} @expansion{}
19603 "any sequence of digits"
19605 @item @var{option} @expansion{}
19606 @code{"-" @var{parameter} [ " " @var{parameter} ]}
19608 @item @var{parameter} @expansion{}
19609 @code{@var{non-blank-sequence} | @var{c-string}}
19611 @item @var{operation} @expansion{}
19612 @emph{any of the operations described in this chapter}
19614 @item @var{non-blank-sequence} @expansion{}
19615 @emph{anything, provided it doesn't contain special characters such as
19616 "-", @var{nl}, """ and of course " "}
19618 @item @var{c-string} @expansion{}
19619 @code{""" @var{seven-bit-iso-c-string-content} """}
19621 @item @var{nl} @expansion{}
19630 The CLI commands are still handled by the @sc{mi} interpreter; their
19631 output is described below.
19634 The @code{@var{token}}, when present, is passed back when the command
19638 Some @sc{mi} commands accept optional arguments as part of the parameter
19639 list. Each option is identified by a leading @samp{-} (dash) and may be
19640 followed by an optional argument parameter. Options occur first in the
19641 parameter list and can be delimited from normal parameters using
19642 @samp{--} (this is useful when some parameters begin with a dash).
19649 We want easy access to the existing CLI syntax (for debugging).
19652 We want it to be easy to spot a @sc{mi} operation.
19655 @node GDB/MI Output Syntax
19656 @subsection @sc{gdb/mi} Output Syntax
19658 @cindex output syntax of @sc{gdb/mi}
19659 @cindex @sc{gdb/mi}, output syntax
19660 The output from @sc{gdb/mi} consists of zero or more out-of-band records
19661 followed, optionally, by a single result record. This result record
19662 is for the most recent command. The sequence of output records is
19663 terminated by @samp{(gdb)}.
19665 If an input command was prefixed with a @code{@var{token}} then the
19666 corresponding output for that command will also be prefixed by that same
19670 @item @var{output} @expansion{}
19671 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
19673 @item @var{result-record} @expansion{}
19674 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
19676 @item @var{out-of-band-record} @expansion{}
19677 @code{@var{async-record} | @var{stream-record}}
19679 @item @var{async-record} @expansion{}
19680 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
19682 @item @var{exec-async-output} @expansion{}
19683 @code{[ @var{token} ] "*" @var{async-output}}
19685 @item @var{status-async-output} @expansion{}
19686 @code{[ @var{token} ] "+" @var{async-output}}
19688 @item @var{notify-async-output} @expansion{}
19689 @code{[ @var{token} ] "=" @var{async-output}}
19691 @item @var{async-output} @expansion{}
19692 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
19694 @item @var{result-class} @expansion{}
19695 @code{"done" | "running" | "connected" | "error" | "exit"}
19697 @item @var{async-class} @expansion{}
19698 @code{"stopped" | @var{others}} (where @var{others} will be added
19699 depending on the needs---this is still in development).
19701 @item @var{result} @expansion{}
19702 @code{ @var{variable} "=" @var{value}}
19704 @item @var{variable} @expansion{}
19705 @code{ @var{string} }
19707 @item @var{value} @expansion{}
19708 @code{ @var{const} | @var{tuple} | @var{list} }
19710 @item @var{const} @expansion{}
19711 @code{@var{c-string}}
19713 @item @var{tuple} @expansion{}
19714 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
19716 @item @var{list} @expansion{}
19717 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
19718 @var{result} ( "," @var{result} )* "]" }
19720 @item @var{stream-record} @expansion{}
19721 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
19723 @item @var{console-stream-output} @expansion{}
19724 @code{"~" @var{c-string}}
19726 @item @var{target-stream-output} @expansion{}
19727 @code{"@@" @var{c-string}}
19729 @item @var{log-stream-output} @expansion{}
19730 @code{"&" @var{c-string}}
19732 @item @var{nl} @expansion{}
19735 @item @var{token} @expansion{}
19736 @emph{any sequence of digits}.
19744 All output sequences end in a single line containing a period.
19747 The @code{@var{token}} is from the corresponding request. Note that
19748 for all async output, while the token is allowed by the grammar and
19749 may be output by future versions of @value{GDBN} for select async
19750 output messages, it is generally omitted. Frontends should treat
19751 all async output as reporting general changes in the state of the
19752 target and there should be no need to associate async output to any
19756 @cindex status output in @sc{gdb/mi}
19757 @var{status-async-output} contains on-going status information about the
19758 progress of a slow operation. It can be discarded. All status output is
19759 prefixed by @samp{+}.
19762 @cindex async output in @sc{gdb/mi}
19763 @var{exec-async-output} contains asynchronous state change on the target
19764 (stopped, started, disappeared). All async output is prefixed by
19768 @cindex notify output in @sc{gdb/mi}
19769 @var{notify-async-output} contains supplementary information that the
19770 client should handle (e.g., a new breakpoint information). All notify
19771 output is prefixed by @samp{=}.
19774 @cindex console output in @sc{gdb/mi}
19775 @var{console-stream-output} is output that should be displayed as is in the
19776 console. It is the textual response to a CLI command. All the console
19777 output is prefixed by @samp{~}.
19780 @cindex target output in @sc{gdb/mi}
19781 @var{target-stream-output} is the output produced by the target program.
19782 All the target output is prefixed by @samp{@@}.
19785 @cindex log output in @sc{gdb/mi}
19786 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
19787 instance messages that should be displayed as part of an error log. All
19788 the log output is prefixed by @samp{&}.
19791 @cindex list output in @sc{gdb/mi}
19792 New @sc{gdb/mi} commands should only output @var{lists} containing
19798 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
19799 details about the various output records.
19801 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19802 @node GDB/MI Compatibility with CLI
19803 @section @sc{gdb/mi} Compatibility with CLI
19805 @cindex compatibility, @sc{gdb/mi} and CLI
19806 @cindex @sc{gdb/mi}, compatibility with CLI
19808 For the developers convenience CLI commands can be entered directly,
19809 but there may be some unexpected behaviour. For example, commands
19810 that query the user will behave as if the user replied yes, breakpoint
19811 command lists are not executed and some CLI commands, such as
19812 @code{if}, @code{when} and @code{define}, prompt for further input with
19813 @samp{>}, which is not valid MI output.
19815 This feature may be removed at some stage in the future and it is
19816 recommended that front ends use the @code{-interpreter-exec} command
19817 (@pxref{-interpreter-exec}).
19819 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19820 @node GDB/MI Development and Front Ends
19821 @section @sc{gdb/mi} Development and Front Ends
19822 @cindex @sc{gdb/mi} development
19824 The application which takes the MI output and presents the state of the
19825 program being debugged to the user is called a @dfn{front end}.
19827 Although @sc{gdb/mi} is still incomplete, it is currently being used
19828 by a variety of front ends to @value{GDBN}. This makes it difficult
19829 to introduce new functionality without breaking existing usage. This
19830 section tries to minimize the problems by describing how the protocol
19833 Some changes in MI need not break a carefully designed front end, and
19834 for these the MI version will remain unchanged. The following is a
19835 list of changes that may occur within one level, so front ends should
19836 parse MI output in a way that can handle them:
19840 New MI commands may be added.
19843 New fields may be added to the output of any MI command.
19846 The range of values for fields with specified values, e.g.,
19847 @code{in_scope} (@pxref{-var-update}) may be extended.
19849 @c The format of field's content e.g type prefix, may change so parse it
19850 @c at your own risk. Yes, in general?
19852 @c The order of fields may change? Shouldn't really matter but it might
19853 @c resolve inconsistencies.
19856 If the changes are likely to break front ends, the MI version level
19857 will be increased by one. This will allow the front end to parse the
19858 output according to the MI version. Apart from mi0, new versions of
19859 @value{GDBN} will not support old versions of MI and it will be the
19860 responsibility of the front end to work with the new one.
19862 @c Starting with mi3, add a new command -mi-version that prints the MI
19865 The best way to avoid unexpected changes in MI that might break your front
19866 end is to make your project known to @value{GDBN} developers and
19867 follow development on @email{gdb@@sourceware.org} and
19868 @email{gdb-patches@@sourceware.org}.
19869 @cindex mailing lists
19871 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19872 @node GDB/MI Output Records
19873 @section @sc{gdb/mi} Output Records
19876 * GDB/MI Result Records::
19877 * GDB/MI Stream Records::
19878 * GDB/MI Async Records::
19879 * GDB/MI Frame Information::
19882 @node GDB/MI Result Records
19883 @subsection @sc{gdb/mi} Result Records
19885 @cindex result records in @sc{gdb/mi}
19886 @cindex @sc{gdb/mi}, result records
19887 In addition to a number of out-of-band notifications, the response to a
19888 @sc{gdb/mi} command includes one of the following result indications:
19892 @item "^done" [ "," @var{results} ]
19893 The synchronous operation was successful, @code{@var{results}} are the return
19898 @c Is this one correct? Should it be an out-of-band notification?
19899 The asynchronous operation was successfully started. The target is
19904 @value{GDBN} has connected to a remote target.
19906 @item "^error" "," @var{c-string}
19908 The operation failed. The @code{@var{c-string}} contains the corresponding
19913 @value{GDBN} has terminated.
19917 @node GDB/MI Stream Records
19918 @subsection @sc{gdb/mi} Stream Records
19920 @cindex @sc{gdb/mi}, stream records
19921 @cindex stream records in @sc{gdb/mi}
19922 @value{GDBN} internally maintains a number of output streams: the console, the
19923 target, and the log. The output intended for each of these streams is
19924 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
19926 Each stream record begins with a unique @dfn{prefix character} which
19927 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
19928 Syntax}). In addition to the prefix, each stream record contains a
19929 @code{@var{string-output}}. This is either raw text (with an implicit new
19930 line) or a quoted C string (which does not contain an implicit newline).
19933 @item "~" @var{string-output}
19934 The console output stream contains text that should be displayed in the
19935 CLI console window. It contains the textual responses to CLI commands.
19937 @item "@@" @var{string-output}
19938 The target output stream contains any textual output from the running
19939 target. This is only present when GDB's event loop is truly
19940 asynchronous, which is currently only the case for remote targets.
19942 @item "&" @var{string-output}
19943 The log stream contains debugging messages being produced by @value{GDBN}'s
19947 @node GDB/MI Async Records
19948 @subsection @sc{gdb/mi} Async Records
19950 @cindex async records in @sc{gdb/mi}
19951 @cindex @sc{gdb/mi}, async records
19952 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
19953 additional changes that have occurred. Those changes can either be a
19954 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
19955 target activity (e.g., target stopped).
19957 The following is the list of possible async records:
19961 @item *running,thread-id="@var{thread}"
19962 The target is now running. The @var{thread} field tells which
19963 specific thread is now running, and can be @samp{all} if all threads
19964 are running. The frontend should assume that no interaction with a
19965 running thread is possible after this notification is produced.
19966 The frontend should not assume that this notification is output
19967 only once for any command. @value{GDBN} may emit this notification
19968 several times, either for different threads, because it cannot resume
19969 all threads together, or even for a single thread, if the thread must
19970 be stepped though some code before letting it run freely.
19972 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}"
19973 The target has stopped. The @var{reason} field can have one of the
19977 @item breakpoint-hit
19978 A breakpoint was reached.
19979 @item watchpoint-trigger
19980 A watchpoint was triggered.
19981 @item read-watchpoint-trigger
19982 A read watchpoint was triggered.
19983 @item access-watchpoint-trigger
19984 An access watchpoint was triggered.
19985 @item function-finished
19986 An -exec-finish or similar CLI command was accomplished.
19987 @item location-reached
19988 An -exec-until or similar CLI command was accomplished.
19989 @item watchpoint-scope
19990 A watchpoint has gone out of scope.
19991 @item end-stepping-range
19992 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
19993 similar CLI command was accomplished.
19994 @item exited-signalled
19995 The inferior exited because of a signal.
19997 The inferior exited.
19998 @item exited-normally
19999 The inferior exited normally.
20000 @item signal-received
20001 A signal was received by the inferior.
20004 The @var{id} field identifies the thread that directly caused the stop
20005 -- for example by hitting a breakpoint. Depending on whether all-stop
20006 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
20007 stop all threads, or only the thread that directly triggered the stop.
20008 If all threads are stopped, the @var{stopped} field will have the
20009 value of @code{"all"}. Otherwise, the value of the @var{stopped}
20010 field will be a list of thread identifiers. Presently, this list will
20011 always include a single thread, but frontend should be prepared to see
20012 several threads in the list.
20014 @item =thread-group-created,id="@var{id}"
20015 @itemx =thread-group-exited,id="@var{id}"
20016 A thread thread group either was attached to, or has exited/detached
20017 from. The @var{id} field contains the @value{GDBN} identifier of the
20020 @item =thread-created,id="@var{id}",group-id="@var{gid}"
20021 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
20022 A thread either was created, or has exited. The @var{id} field
20023 contains the @value{GDBN} identifier of the thread. The @var{gid}
20024 field identifies the thread group this thread belongs to.
20026 @item =thread-selected,id="@var{id}"
20027 Informs that the selected thread was changed as result of the last
20028 command. This notification is not emitted as result of @code{-thread-select}
20029 command but is emitted whenever an MI command that is not documented
20030 to change the selected thread actually changes it. In particular,
20031 invoking, directly or indirectly (via user-defined command), the CLI
20032 @code{thread} command, will generate this notification.
20034 We suggest that in response to this notification, front ends
20035 highlight the selected thread and cause subsequent commands to apply to
20038 @item =library-loaded,...
20039 Reports that a new library file was loaded by the program. This
20040 notification has 4 fields---@var{id}, @var{target-name},
20041 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
20042 opaque identifier of the library. For remote debugging case,
20043 @var{target-name} and @var{host-name} fields give the name of the
20044 library file on the target, and on the host respectively. For native
20045 debugging, both those fields have the same value. The
20046 @var{symbols-loaded} field reports if the debug symbols for this
20047 library are loaded.
20049 @item =library-unloaded,...
20050 Reports that a library was unloaded by the program. This notification
20051 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
20052 the same meaning as for the @code{=library-loaded} notification
20056 @node GDB/MI Frame Information
20057 @subsection @sc{gdb/mi} Frame Information
20059 Response from many MI commands includes an information about stack
20060 frame. This information is a tuple that may have the following
20065 The level of the stack frame. The innermost frame has the level of
20066 zero. This field is always present.
20069 The name of the function corresponding to the frame. This field may
20070 be absent if @value{GDBN} is unable to determine the function name.
20073 The code address for the frame. This field is always present.
20076 The name of the source files that correspond to the frame's code
20077 address. This field may be absent.
20080 The source line corresponding to the frames' code address. This field
20084 The name of the binary file (either executable or shared library) the
20085 corresponds to the frame's code address. This field may be absent.
20090 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20091 @node GDB/MI Simple Examples
20092 @section Simple Examples of @sc{gdb/mi} Interaction
20093 @cindex @sc{gdb/mi}, simple examples
20095 This subsection presents several simple examples of interaction using
20096 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
20097 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
20098 the output received from @sc{gdb/mi}.
20100 Note the line breaks shown in the examples are here only for
20101 readability, they don't appear in the real output.
20103 @subheading Setting a Breakpoint
20105 Setting a breakpoint generates synchronous output which contains detailed
20106 information of the breakpoint.
20109 -> -break-insert main
20110 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20111 enabled="y",addr="0x08048564",func="main",file="myprog.c",
20112 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
20116 @subheading Program Execution
20118 Program execution generates asynchronous records and MI gives the
20119 reason that execution stopped.
20125 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
20126 frame=@{addr="0x08048564",func="main",
20127 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
20128 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
20133 <- *stopped,reason="exited-normally"
20137 @subheading Quitting @value{GDBN}
20139 Quitting @value{GDBN} just prints the result class @samp{^exit}.
20147 @subheading A Bad Command
20149 Here's what happens if you pass a non-existent command:
20153 <- ^error,msg="Undefined MI command: rubbish"
20158 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20159 @node GDB/MI Command Description Format
20160 @section @sc{gdb/mi} Command Description Format
20162 The remaining sections describe blocks of commands. Each block of
20163 commands is laid out in a fashion similar to this section.
20165 @subheading Motivation
20167 The motivation for this collection of commands.
20169 @subheading Introduction
20171 A brief introduction to this collection of commands as a whole.
20173 @subheading Commands
20175 For each command in the block, the following is described:
20177 @subsubheading Synopsis
20180 -command @var{args}@dots{}
20183 @subsubheading Result
20185 @subsubheading @value{GDBN} Command
20187 The corresponding @value{GDBN} CLI command(s), if any.
20189 @subsubheading Example
20191 Example(s) formatted for readability. Some of the described commands have
20192 not been implemented yet and these are labeled N.A.@: (not available).
20195 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20196 @node GDB/MI Breakpoint Commands
20197 @section @sc{gdb/mi} Breakpoint Commands
20199 @cindex breakpoint commands for @sc{gdb/mi}
20200 @cindex @sc{gdb/mi}, breakpoint commands
20201 This section documents @sc{gdb/mi} commands for manipulating
20204 @subheading The @code{-break-after} Command
20205 @findex -break-after
20207 @subsubheading Synopsis
20210 -break-after @var{number} @var{count}
20213 The breakpoint number @var{number} is not in effect until it has been
20214 hit @var{count} times. To see how this is reflected in the output of
20215 the @samp{-break-list} command, see the description of the
20216 @samp{-break-list} command below.
20218 @subsubheading @value{GDBN} Command
20220 The corresponding @value{GDBN} command is @samp{ignore}.
20222 @subsubheading Example
20227 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20228 enabled="y",addr="0x000100d0",func="main",file="hello.c",
20229 fullname="/home/foo/hello.c",line="5",times="0"@}
20236 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20237 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20238 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20239 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20240 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20241 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20242 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20243 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20244 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20245 line="5",times="0",ignore="3"@}]@}
20250 @subheading The @code{-break-catch} Command
20251 @findex -break-catch
20253 @subheading The @code{-break-commands} Command
20254 @findex -break-commands
20258 @subheading The @code{-break-condition} Command
20259 @findex -break-condition
20261 @subsubheading Synopsis
20264 -break-condition @var{number} @var{expr}
20267 Breakpoint @var{number} will stop the program only if the condition in
20268 @var{expr} is true. The condition becomes part of the
20269 @samp{-break-list} output (see the description of the @samp{-break-list}
20272 @subsubheading @value{GDBN} Command
20274 The corresponding @value{GDBN} command is @samp{condition}.
20276 @subsubheading Example
20280 -break-condition 1 1
20284 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20285 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20286 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20287 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20288 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20289 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20290 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20291 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20292 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20293 line="5",cond="1",times="0",ignore="3"@}]@}
20297 @subheading The @code{-break-delete} Command
20298 @findex -break-delete
20300 @subsubheading Synopsis
20303 -break-delete ( @var{breakpoint} )+
20306 Delete the breakpoint(s) whose number(s) are specified in the argument
20307 list. This is obviously reflected in the breakpoint list.
20309 @subsubheading @value{GDBN} Command
20311 The corresponding @value{GDBN} command is @samp{delete}.
20313 @subsubheading Example
20321 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20322 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20323 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20324 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20325 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20326 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20327 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20332 @subheading The @code{-break-disable} Command
20333 @findex -break-disable
20335 @subsubheading Synopsis
20338 -break-disable ( @var{breakpoint} )+
20341 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
20342 break list is now set to @samp{n} for the named @var{breakpoint}(s).
20344 @subsubheading @value{GDBN} Command
20346 The corresponding @value{GDBN} command is @samp{disable}.
20348 @subsubheading Example
20356 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20357 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20358 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20359 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20360 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20361 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20362 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20363 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
20364 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20365 line="5",times="0"@}]@}
20369 @subheading The @code{-break-enable} Command
20370 @findex -break-enable
20372 @subsubheading Synopsis
20375 -break-enable ( @var{breakpoint} )+
20378 Enable (previously disabled) @var{breakpoint}(s).
20380 @subsubheading @value{GDBN} Command
20382 The corresponding @value{GDBN} command is @samp{enable}.
20384 @subsubheading Example
20392 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20393 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20394 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20395 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20396 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20397 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20398 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20399 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20400 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20401 line="5",times="0"@}]@}
20405 @subheading The @code{-break-info} Command
20406 @findex -break-info
20408 @subsubheading Synopsis
20411 -break-info @var{breakpoint}
20415 Get information about a single breakpoint.
20417 @subsubheading @value{GDBN} Command
20419 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
20421 @subsubheading Example
20424 @subheading The @code{-break-insert} Command
20425 @findex -break-insert
20427 @subsubheading Synopsis
20430 -break-insert [ -t ] [ -h ] [ -f ] [ -d ]
20431 [ -c @var{condition} ] [ -i @var{ignore-count} ]
20432 [ -p @var{thread} ] [ @var{location} ]
20436 If specified, @var{location}, can be one of:
20443 @item filename:linenum
20444 @item filename:function
20448 The possible optional parameters of this command are:
20452 Insert a temporary breakpoint.
20454 Insert a hardware breakpoint.
20455 @item -c @var{condition}
20456 Make the breakpoint conditional on @var{condition}.
20457 @item -i @var{ignore-count}
20458 Initialize the @var{ignore-count}.
20460 If @var{location} cannot be parsed (for example if it
20461 refers to unknown files or functions), create a pending
20462 breakpoint. Without this flag, @value{GDBN} will report
20463 an error, and won't create a breakpoint, if @var{location}
20466 Create a disabled breakpoint.
20469 @subsubheading Result
20471 The result is in the form:
20474 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
20475 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
20476 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
20477 times="@var{times}"@}
20481 where @var{number} is the @value{GDBN} number for this breakpoint,
20482 @var{funcname} is the name of the function where the breakpoint was
20483 inserted, @var{filename} is the name of the source file which contains
20484 this function, @var{lineno} is the source line number within that file
20485 and @var{times} the number of times that the breakpoint has been hit
20486 (always 0 for -break-insert but may be greater for -break-info or -break-list
20487 which use the same output).
20489 Note: this format is open to change.
20490 @c An out-of-band breakpoint instead of part of the result?
20492 @subsubheading @value{GDBN} Command
20494 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
20495 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
20497 @subsubheading Example
20502 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
20503 fullname="/home/foo/recursive2.c,line="4",times="0"@}
20505 -break-insert -t foo
20506 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
20507 fullname="/home/foo/recursive2.c,line="11",times="0"@}
20510 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20511 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20512 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20513 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20514 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20515 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20516 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20517 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20518 addr="0x0001072c", func="main",file="recursive2.c",
20519 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
20520 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
20521 addr="0x00010774",func="foo",file="recursive2.c",
20522 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
20524 -break-insert -r foo.*
20525 ~int foo(int, int);
20526 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
20527 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
20531 @subheading The @code{-break-list} Command
20532 @findex -break-list
20534 @subsubheading Synopsis
20540 Displays the list of inserted breakpoints, showing the following fields:
20544 number of the breakpoint
20546 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
20548 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
20551 is the breakpoint enabled or no: @samp{y} or @samp{n}
20553 memory location at which the breakpoint is set
20555 logical location of the breakpoint, expressed by function name, file
20558 number of times the breakpoint has been hit
20561 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
20562 @code{body} field is an empty list.
20564 @subsubheading @value{GDBN} Command
20566 The corresponding @value{GDBN} command is @samp{info break}.
20568 @subsubheading Example
20573 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20574 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20575 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20576 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20577 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20578 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20579 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20580 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20581 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
20582 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20583 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
20584 line="13",times="0"@}]@}
20588 Here's an example of the result when there are no breakpoints:
20593 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20594 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20595 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20596 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20597 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20598 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20599 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20604 @subheading The @code{-break-watch} Command
20605 @findex -break-watch
20607 @subsubheading Synopsis
20610 -break-watch [ -a | -r ]
20613 Create a watchpoint. With the @samp{-a} option it will create an
20614 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
20615 read from or on a write to the memory location. With the @samp{-r}
20616 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
20617 trigger only when the memory location is accessed for reading. Without
20618 either of the options, the watchpoint created is a regular watchpoint,
20619 i.e., it will trigger when the memory location is accessed for writing.
20620 @xref{Set Watchpoints, , Setting Watchpoints}.
20622 Note that @samp{-break-list} will report a single list of watchpoints and
20623 breakpoints inserted.
20625 @subsubheading @value{GDBN} Command
20627 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
20630 @subsubheading Example
20632 Setting a watchpoint on a variable in the @code{main} function:
20637 ^done,wpt=@{number="2",exp="x"@}
20642 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
20643 value=@{old="-268439212",new="55"@},
20644 frame=@{func="main",args=[],file="recursive2.c",
20645 fullname="/home/foo/bar/recursive2.c",line="5"@}
20649 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
20650 the program execution twice: first for the variable changing value, then
20651 for the watchpoint going out of scope.
20656 ^done,wpt=@{number="5",exp="C"@}
20661 *stopped,reason="watchpoint-trigger",
20662 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
20663 frame=@{func="callee4",args=[],
20664 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20665 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20670 *stopped,reason="watchpoint-scope",wpnum="5",
20671 frame=@{func="callee3",args=[@{name="strarg",
20672 value="0x11940 \"A string argument.\""@}],
20673 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20674 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20678 Listing breakpoints and watchpoints, at different points in the program
20679 execution. Note that once the watchpoint goes out of scope, it is
20685 ^done,wpt=@{number="2",exp="C"@}
20688 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20689 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20690 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20691 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20692 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20693 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20694 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20695 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20696 addr="0x00010734",func="callee4",
20697 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20698 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
20699 bkpt=@{number="2",type="watchpoint",disp="keep",
20700 enabled="y",addr="",what="C",times="0"@}]@}
20705 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
20706 value=@{old="-276895068",new="3"@},
20707 frame=@{func="callee4",args=[],
20708 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20709 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20712 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20713 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20714 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20715 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20716 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20717 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20718 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20719 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20720 addr="0x00010734",func="callee4",
20721 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20722 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
20723 bkpt=@{number="2",type="watchpoint",disp="keep",
20724 enabled="y",addr="",what="C",times="-5"@}]@}
20728 ^done,reason="watchpoint-scope",wpnum="2",
20729 frame=@{func="callee3",args=[@{name="strarg",
20730 value="0x11940 \"A string argument.\""@}],
20731 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20732 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20735 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20736 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20737 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20738 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20739 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20740 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20741 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20742 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20743 addr="0x00010734",func="callee4",
20744 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20745 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
20750 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20751 @node GDB/MI Program Context
20752 @section @sc{gdb/mi} Program Context
20754 @subheading The @code{-exec-arguments} Command
20755 @findex -exec-arguments
20758 @subsubheading Synopsis
20761 -exec-arguments @var{args}
20764 Set the inferior program arguments, to be used in the next
20767 @subsubheading @value{GDBN} Command
20769 The corresponding @value{GDBN} command is @samp{set args}.
20771 @subsubheading Example
20775 -exec-arguments -v word
20781 @subheading The @code{-exec-show-arguments} Command
20782 @findex -exec-show-arguments
20784 @subsubheading Synopsis
20787 -exec-show-arguments
20790 Print the arguments of the program.
20792 @subsubheading @value{GDBN} Command
20794 The corresponding @value{GDBN} command is @samp{show args}.
20796 @subsubheading Example
20800 @subheading The @code{-environment-cd} Command
20801 @findex -environment-cd
20803 @subsubheading Synopsis
20806 -environment-cd @var{pathdir}
20809 Set @value{GDBN}'s working directory.
20811 @subsubheading @value{GDBN} Command
20813 The corresponding @value{GDBN} command is @samp{cd}.
20815 @subsubheading Example
20819 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20825 @subheading The @code{-environment-directory} Command
20826 @findex -environment-directory
20828 @subsubheading Synopsis
20831 -environment-directory [ -r ] [ @var{pathdir} ]+
20834 Add directories @var{pathdir} to beginning of search path for source files.
20835 If the @samp{-r} option is used, the search path is reset to the default
20836 search path. If directories @var{pathdir} are supplied in addition to the
20837 @samp{-r} option, the search path is first reset and then addition
20839 Multiple directories may be specified, separated by blanks. Specifying
20840 multiple directories in a single command
20841 results in the directories added to the beginning of the
20842 search path in the same order they were presented in the command.
20843 If blanks are needed as
20844 part of a directory name, double-quotes should be used around
20845 the name. In the command output, the path will show up separated
20846 by the system directory-separator character. The directory-separator
20847 character must not be used
20848 in any directory name.
20849 If no directories are specified, the current search path is displayed.
20851 @subsubheading @value{GDBN} Command
20853 The corresponding @value{GDBN} command is @samp{dir}.
20855 @subsubheading Example
20859 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20860 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
20862 -environment-directory ""
20863 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
20865 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
20866 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
20868 -environment-directory -r
20869 ^done,source-path="$cdir:$cwd"
20874 @subheading The @code{-environment-path} Command
20875 @findex -environment-path
20877 @subsubheading Synopsis
20880 -environment-path [ -r ] [ @var{pathdir} ]+
20883 Add directories @var{pathdir} to beginning of search path for object files.
20884 If the @samp{-r} option is used, the search path is reset to the original
20885 search path that existed at gdb start-up. If directories @var{pathdir} are
20886 supplied in addition to the
20887 @samp{-r} option, the search path is first reset and then addition
20889 Multiple directories may be specified, separated by blanks. Specifying
20890 multiple directories in a single command
20891 results in the directories added to the beginning of the
20892 search path in the same order they were presented in the command.
20893 If blanks are needed as
20894 part of a directory name, double-quotes should be used around
20895 the name. In the command output, the path will show up separated
20896 by the system directory-separator character. The directory-separator
20897 character must not be used
20898 in any directory name.
20899 If no directories are specified, the current path is displayed.
20902 @subsubheading @value{GDBN} Command
20904 The corresponding @value{GDBN} command is @samp{path}.
20906 @subsubheading Example
20911 ^done,path="/usr/bin"
20913 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
20914 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
20916 -environment-path -r /usr/local/bin
20917 ^done,path="/usr/local/bin:/usr/bin"
20922 @subheading The @code{-environment-pwd} Command
20923 @findex -environment-pwd
20925 @subsubheading Synopsis
20931 Show the current working directory.
20933 @subsubheading @value{GDBN} Command
20935 The corresponding @value{GDBN} command is @samp{pwd}.
20937 @subsubheading Example
20942 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
20946 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20947 @node GDB/MI Thread Commands
20948 @section @sc{gdb/mi} Thread Commands
20951 @subheading The @code{-thread-info} Command
20952 @findex -thread-info
20954 @subsubheading Synopsis
20957 -thread-info [ @var{thread-id} ]
20960 Reports information about either a specific thread, if
20961 the @var{thread-id} parameter is present, or about all
20962 threads. When printing information about all threads,
20963 also reports the current thread.
20965 @subsubheading @value{GDBN} Command
20967 The @samp{info thread} command prints the same information
20970 @subsubheading Example
20975 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
20976 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
20977 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
20978 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
20979 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
20980 current-thread-id="1"
20984 The @samp{state} field may have the following values:
20988 The thread is stopped. Frame information is available for stopped
20992 The thread is running. There's no frame information for running
20997 @subheading The @code{-thread-list-ids} Command
20998 @findex -thread-list-ids
21000 @subsubheading Synopsis
21006 Produces a list of the currently known @value{GDBN} thread ids. At the
21007 end of the list it also prints the total number of such threads.
21009 This command is retained for historical reasons, the
21010 @code{-thread-info} command should be used instead.
21012 @subsubheading @value{GDBN} Command
21014 Part of @samp{info threads} supplies the same information.
21016 @subsubheading Example
21021 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
21022 current-thread-id="1",number-of-threads="3"
21027 @subheading The @code{-thread-select} Command
21028 @findex -thread-select
21030 @subsubheading Synopsis
21033 -thread-select @var{threadnum}
21036 Make @var{threadnum} the current thread. It prints the number of the new
21037 current thread, and the topmost frame for that thread.
21039 This command is deprecated in favor of explicitly using the
21040 @samp{--thread} option to each command.
21042 @subsubheading @value{GDBN} Command
21044 The corresponding @value{GDBN} command is @samp{thread}.
21046 @subsubheading Example
21053 *stopped,reason="end-stepping-range",thread-id="2",line="187",
21054 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
21058 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
21059 number-of-threads="3"
21062 ^done,new-thread-id="3",
21063 frame=@{level="0",func="vprintf",
21064 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
21065 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
21069 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21070 @node GDB/MI Program Execution
21071 @section @sc{gdb/mi} Program Execution
21073 These are the asynchronous commands which generate the out-of-band
21074 record @samp{*stopped}. Currently @value{GDBN} only really executes
21075 asynchronously with remote targets and this interaction is mimicked in
21078 @subheading The @code{-exec-continue} Command
21079 @findex -exec-continue
21081 @subsubheading Synopsis
21084 -exec-continue [--all|--thread-group N]
21087 Resumes the execution of the inferior program until a breakpoint is
21088 encountered, or until the inferior exits. In all-stop mode
21089 (@pxref{All-Stop Mode}), may resume only one thread, or all threads,
21090 depending on the value of the @samp{scheduler-locking} variable. In
21091 non-stop mode (@pxref{Non-Stop Mode}), if the @samp{--all} is not
21092 specified, only the thread specified with the @samp{--thread} option
21093 (or current thread, if no @samp{--thread} is provided) is resumed. If
21094 @samp{--all} is specified, all threads will be resumed. The
21095 @samp{--all} option is ignored in all-stop mode. If the
21096 @samp{--thread-group} options is specified, then all threads in that
21097 thread group are resumed.
21099 @subsubheading @value{GDBN} Command
21101 The corresponding @value{GDBN} corresponding is @samp{continue}.
21103 @subsubheading Example
21110 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
21111 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
21117 @subheading The @code{-exec-finish} Command
21118 @findex -exec-finish
21120 @subsubheading Synopsis
21126 Resumes the execution of the inferior program until the current
21127 function is exited. Displays the results returned by the function.
21129 @subsubheading @value{GDBN} Command
21131 The corresponding @value{GDBN} command is @samp{finish}.
21133 @subsubheading Example
21135 Function returning @code{void}.
21142 *stopped,reason="function-finished",frame=@{func="main",args=[],
21143 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
21147 Function returning other than @code{void}. The name of the internal
21148 @value{GDBN} variable storing the result is printed, together with the
21155 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
21156 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
21157 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21158 gdb-result-var="$1",return-value="0"
21163 @subheading The @code{-exec-interrupt} Command
21164 @findex -exec-interrupt
21166 @subsubheading Synopsis
21169 -exec-interrupt [--all|--thread-group N]
21172 Interrupts the background execution of the target. Note how the token
21173 associated with the stop message is the one for the execution command
21174 that has been interrupted. The token for the interrupt itself only
21175 appears in the @samp{^done} output. If the user is trying to
21176 interrupt a non-running program, an error message will be printed.
21178 Note that when asynchronous execution is enabled, this command is
21179 asynchronous just like other execution commands. That is, first the
21180 @samp{^done} response will be printed, and the target stop will be
21181 reported after that using the @samp{*stopped} notification.
21183 In non-stop mode, only the context thread is interrupted by default.
21184 All threads will be interrupted if the @samp{--all} option is
21185 specified. If the @samp{--thread-group} option is specified, all
21186 threads in that group will be interrupted.
21188 @subsubheading @value{GDBN} Command
21190 The corresponding @value{GDBN} command is @samp{interrupt}.
21192 @subsubheading Example
21203 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
21204 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
21205 fullname="/home/foo/bar/try.c",line="13"@}
21210 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
21215 @subheading The @code{-exec-next} Command
21218 @subsubheading Synopsis
21224 Resumes execution of the inferior program, stopping when the beginning
21225 of the next source line is reached.
21227 @subsubheading @value{GDBN} Command
21229 The corresponding @value{GDBN} command is @samp{next}.
21231 @subsubheading Example
21237 *stopped,reason="end-stepping-range",line="8",file="hello.c"
21242 @subheading The @code{-exec-next-instruction} Command
21243 @findex -exec-next-instruction
21245 @subsubheading Synopsis
21248 -exec-next-instruction
21251 Executes one machine instruction. If the instruction is a function
21252 call, continues until the function returns. If the program stops at an
21253 instruction in the middle of a source line, the address will be
21256 @subsubheading @value{GDBN} Command
21258 The corresponding @value{GDBN} command is @samp{nexti}.
21260 @subsubheading Example
21264 -exec-next-instruction
21268 *stopped,reason="end-stepping-range",
21269 addr="0x000100d4",line="5",file="hello.c"
21274 @subheading The @code{-exec-return} Command
21275 @findex -exec-return
21277 @subsubheading Synopsis
21283 Makes current function return immediately. Doesn't execute the inferior.
21284 Displays the new current frame.
21286 @subsubheading @value{GDBN} Command
21288 The corresponding @value{GDBN} command is @samp{return}.
21290 @subsubheading Example
21294 200-break-insert callee4
21295 200^done,bkpt=@{number="1",addr="0x00010734",
21296 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21301 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21302 frame=@{func="callee4",args=[],
21303 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21304 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21310 111^done,frame=@{level="0",func="callee3",
21311 args=[@{name="strarg",
21312 value="0x11940 \"A string argument.\""@}],
21313 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21314 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
21319 @subheading The @code{-exec-run} Command
21322 @subsubheading Synopsis
21328 Starts execution of the inferior from the beginning. The inferior
21329 executes until either a breakpoint is encountered or the program
21330 exits. In the latter case the output will include an exit code, if
21331 the program has exited exceptionally.
21333 @subsubheading @value{GDBN} Command
21335 The corresponding @value{GDBN} command is @samp{run}.
21337 @subsubheading Examples
21342 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
21347 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21348 frame=@{func="main",args=[],file="recursive2.c",
21349 fullname="/home/foo/bar/recursive2.c",line="4"@}
21354 Program exited normally:
21362 *stopped,reason="exited-normally"
21367 Program exited exceptionally:
21375 *stopped,reason="exited",exit-code="01"
21379 Another way the program can terminate is if it receives a signal such as
21380 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
21384 *stopped,reason="exited-signalled",signal-name="SIGINT",
21385 signal-meaning="Interrupt"
21389 @c @subheading -exec-signal
21392 @subheading The @code{-exec-step} Command
21395 @subsubheading Synopsis
21401 Resumes execution of the inferior program, stopping when the beginning
21402 of the next source line is reached, if the next source line is not a
21403 function call. If it is, stop at the first instruction of the called
21406 @subsubheading @value{GDBN} Command
21408 The corresponding @value{GDBN} command is @samp{step}.
21410 @subsubheading Example
21412 Stepping into a function:
21418 *stopped,reason="end-stepping-range",
21419 frame=@{func="foo",args=[@{name="a",value="10"@},
21420 @{name="b",value="0"@}],file="recursive2.c",
21421 fullname="/home/foo/bar/recursive2.c",line="11"@}
21431 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
21436 @subheading The @code{-exec-step-instruction} Command
21437 @findex -exec-step-instruction
21439 @subsubheading Synopsis
21442 -exec-step-instruction
21445 Resumes the inferior which executes one machine instruction. The
21446 output, once @value{GDBN} has stopped, will vary depending on whether
21447 we have stopped in the middle of a source line or not. In the former
21448 case, the address at which the program stopped will be printed as
21451 @subsubheading @value{GDBN} Command
21453 The corresponding @value{GDBN} command is @samp{stepi}.
21455 @subsubheading Example
21459 -exec-step-instruction
21463 *stopped,reason="end-stepping-range",
21464 frame=@{func="foo",args=[],file="try.c",
21465 fullname="/home/foo/bar/try.c",line="10"@}
21467 -exec-step-instruction
21471 *stopped,reason="end-stepping-range",
21472 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
21473 fullname="/home/foo/bar/try.c",line="10"@}
21478 @subheading The @code{-exec-until} Command
21479 @findex -exec-until
21481 @subsubheading Synopsis
21484 -exec-until [ @var{location} ]
21487 Executes the inferior until the @var{location} specified in the
21488 argument is reached. If there is no argument, the inferior executes
21489 until a source line greater than the current one is reached. The
21490 reason for stopping in this case will be @samp{location-reached}.
21492 @subsubheading @value{GDBN} Command
21494 The corresponding @value{GDBN} command is @samp{until}.
21496 @subsubheading Example
21500 -exec-until recursive2.c:6
21504 *stopped,reason="location-reached",frame=@{func="main",args=[],
21505 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
21510 @subheading -file-clear
21511 Is this going away????
21514 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21515 @node GDB/MI Stack Manipulation
21516 @section @sc{gdb/mi} Stack Manipulation Commands
21519 @subheading The @code{-stack-info-frame} Command
21520 @findex -stack-info-frame
21522 @subsubheading Synopsis
21528 Get info on the selected frame.
21530 @subsubheading @value{GDBN} Command
21532 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
21533 (without arguments).
21535 @subsubheading Example
21540 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
21541 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21542 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
21546 @subheading The @code{-stack-info-depth} Command
21547 @findex -stack-info-depth
21549 @subsubheading Synopsis
21552 -stack-info-depth [ @var{max-depth} ]
21555 Return the depth of the stack. If the integer argument @var{max-depth}
21556 is specified, do not count beyond @var{max-depth} frames.
21558 @subsubheading @value{GDBN} Command
21560 There's no equivalent @value{GDBN} command.
21562 @subsubheading Example
21564 For a stack with frame levels 0 through 11:
21571 -stack-info-depth 4
21574 -stack-info-depth 12
21577 -stack-info-depth 11
21580 -stack-info-depth 13
21585 @subheading The @code{-stack-list-arguments} Command
21586 @findex -stack-list-arguments
21588 @subsubheading Synopsis
21591 -stack-list-arguments @var{show-values}
21592 [ @var{low-frame} @var{high-frame} ]
21595 Display a list of the arguments for the frames between @var{low-frame}
21596 and @var{high-frame} (inclusive). If @var{low-frame} and
21597 @var{high-frame} are not provided, list the arguments for the whole
21598 call stack. If the two arguments are equal, show the single frame
21599 at the corresponding level. It is an error if @var{low-frame} is
21600 larger than the actual number of frames. On the other hand,
21601 @var{high-frame} may be larger than the actual number of frames, in
21602 which case only existing frames will be returned.
21604 The @var{show-values} argument must have a value of 0 or 1. A value of
21605 0 means that only the names of the arguments are listed, a value of 1
21606 means that both names and values of the arguments are printed.
21608 @subsubheading @value{GDBN} Command
21610 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
21611 @samp{gdb_get_args} command which partially overlaps with the
21612 functionality of @samp{-stack-list-arguments}.
21614 @subsubheading Example
21621 frame=@{level="0",addr="0x00010734",func="callee4",
21622 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21623 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
21624 frame=@{level="1",addr="0x0001076c",func="callee3",
21625 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21626 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
21627 frame=@{level="2",addr="0x0001078c",func="callee2",
21628 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21629 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
21630 frame=@{level="3",addr="0x000107b4",func="callee1",
21631 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21632 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
21633 frame=@{level="4",addr="0x000107e0",func="main",
21634 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21635 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
21637 -stack-list-arguments 0
21640 frame=@{level="0",args=[]@},
21641 frame=@{level="1",args=[name="strarg"]@},
21642 frame=@{level="2",args=[name="intarg",name="strarg"]@},
21643 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
21644 frame=@{level="4",args=[]@}]
21646 -stack-list-arguments 1
21649 frame=@{level="0",args=[]@},
21651 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21652 frame=@{level="2",args=[
21653 @{name="intarg",value="2"@},
21654 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21655 @{frame=@{level="3",args=[
21656 @{name="intarg",value="2"@},
21657 @{name="strarg",value="0x11940 \"A string argument.\""@},
21658 @{name="fltarg",value="3.5"@}]@},
21659 frame=@{level="4",args=[]@}]
21661 -stack-list-arguments 0 2 2
21662 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
21664 -stack-list-arguments 1 2 2
21665 ^done,stack-args=[frame=@{level="2",
21666 args=[@{name="intarg",value="2"@},
21667 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
21671 @c @subheading -stack-list-exception-handlers
21674 @subheading The @code{-stack-list-frames} Command
21675 @findex -stack-list-frames
21677 @subsubheading Synopsis
21680 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
21683 List the frames currently on the stack. For each frame it displays the
21688 The frame number, 0 being the topmost frame, i.e., the innermost function.
21690 The @code{$pc} value for that frame.
21694 File name of the source file where the function lives.
21696 Line number corresponding to the @code{$pc}.
21699 If invoked without arguments, this command prints a backtrace for the
21700 whole stack. If given two integer arguments, it shows the frames whose
21701 levels are between the two arguments (inclusive). If the two arguments
21702 are equal, it shows the single frame at the corresponding level. It is
21703 an error if @var{low-frame} is larger than the actual number of
21704 frames. On the other hand, @var{high-frame} may be larger than the
21705 actual number of frames, in which case only existing frames will be returned.
21707 @subsubheading @value{GDBN} Command
21709 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
21711 @subsubheading Example
21713 Full stack backtrace:
21719 [frame=@{level="0",addr="0x0001076c",func="foo",
21720 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
21721 frame=@{level="1",addr="0x000107a4",func="foo",
21722 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21723 frame=@{level="2",addr="0x000107a4",func="foo",
21724 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21725 frame=@{level="3",addr="0x000107a4",func="foo",
21726 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21727 frame=@{level="4",addr="0x000107a4",func="foo",
21728 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21729 frame=@{level="5",addr="0x000107a4",func="foo",
21730 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21731 frame=@{level="6",addr="0x000107a4",func="foo",
21732 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21733 frame=@{level="7",addr="0x000107a4",func="foo",
21734 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21735 frame=@{level="8",addr="0x000107a4",func="foo",
21736 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21737 frame=@{level="9",addr="0x000107a4",func="foo",
21738 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21739 frame=@{level="10",addr="0x000107a4",func="foo",
21740 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21741 frame=@{level="11",addr="0x00010738",func="main",
21742 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
21746 Show frames between @var{low_frame} and @var{high_frame}:
21750 -stack-list-frames 3 5
21752 [frame=@{level="3",addr="0x000107a4",func="foo",
21753 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21754 frame=@{level="4",addr="0x000107a4",func="foo",
21755 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21756 frame=@{level="5",addr="0x000107a4",func="foo",
21757 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21761 Show a single frame:
21765 -stack-list-frames 3 3
21767 [frame=@{level="3",addr="0x000107a4",func="foo",
21768 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21773 @subheading The @code{-stack-list-locals} Command
21774 @findex -stack-list-locals
21776 @subsubheading Synopsis
21779 -stack-list-locals @var{print-values}
21782 Display the local variable names for the selected frame. If
21783 @var{print-values} is 0 or @code{--no-values}, print only the names of
21784 the variables; if it is 1 or @code{--all-values}, print also their
21785 values; and if it is 2 or @code{--simple-values}, print the name,
21786 type and value for simple data types and the name and type for arrays,
21787 structures and unions. In this last case, a frontend can immediately
21788 display the value of simple data types and create variable objects for
21789 other data types when the user wishes to explore their values in
21792 @subsubheading @value{GDBN} Command
21794 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
21796 @subsubheading Example
21800 -stack-list-locals 0
21801 ^done,locals=[name="A",name="B",name="C"]
21803 -stack-list-locals --all-values
21804 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
21805 @{name="C",value="@{1, 2, 3@}"@}]
21806 -stack-list-locals --simple-values
21807 ^done,locals=[@{name="A",type="int",value="1"@},
21808 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
21813 @subheading The @code{-stack-select-frame} Command
21814 @findex -stack-select-frame
21816 @subsubheading Synopsis
21819 -stack-select-frame @var{framenum}
21822 Change the selected frame. Select a different frame @var{framenum} on
21825 This command in deprecated in favor of passing the @samp{--frame}
21826 option to every command.
21828 @subsubheading @value{GDBN} Command
21830 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
21831 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
21833 @subsubheading Example
21837 -stack-select-frame 2
21842 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21843 @node GDB/MI Variable Objects
21844 @section @sc{gdb/mi} Variable Objects
21848 @subheading Motivation for Variable Objects in @sc{gdb/mi}
21850 For the implementation of a variable debugger window (locals, watched
21851 expressions, etc.), we are proposing the adaptation of the existing code
21852 used by @code{Insight}.
21854 The two main reasons for that are:
21858 It has been proven in practice (it is already on its second generation).
21861 It will shorten development time (needless to say how important it is
21865 The original interface was designed to be used by Tcl code, so it was
21866 slightly changed so it could be used through @sc{gdb/mi}. This section
21867 describes the @sc{gdb/mi} operations that will be available and gives some
21868 hints about their use.
21870 @emph{Note}: In addition to the set of operations described here, we
21871 expect the @sc{gui} implementation of a variable window to require, at
21872 least, the following operations:
21875 @item @code{-gdb-show} @code{output-radix}
21876 @item @code{-stack-list-arguments}
21877 @item @code{-stack-list-locals}
21878 @item @code{-stack-select-frame}
21883 @subheading Introduction to Variable Objects
21885 @cindex variable objects in @sc{gdb/mi}
21887 Variable objects are "object-oriented" MI interface for examining and
21888 changing values of expressions. Unlike some other MI interfaces that
21889 work with expressions, variable objects are specifically designed for
21890 simple and efficient presentation in the frontend. A variable object
21891 is identified by string name. When a variable object is created, the
21892 frontend specifies the expression for that variable object. The
21893 expression can be a simple variable, or it can be an arbitrary complex
21894 expression, and can even involve CPU registers. After creating a
21895 variable object, the frontend can invoke other variable object
21896 operations---for example to obtain or change the value of a variable
21897 object, or to change display format.
21899 Variable objects have hierarchical tree structure. Any variable object
21900 that corresponds to a composite type, such as structure in C, has
21901 a number of child variable objects, for example corresponding to each
21902 element of a structure. A child variable object can itself have
21903 children, recursively. Recursion ends when we reach
21904 leaf variable objects, which always have built-in types. Child variable
21905 objects are created only by explicit request, so if a frontend
21906 is not interested in the children of a particular variable object, no
21907 child will be created.
21909 For a leaf variable object it is possible to obtain its value as a
21910 string, or set the value from a string. String value can be also
21911 obtained for a non-leaf variable object, but it's generally a string
21912 that only indicates the type of the object, and does not list its
21913 contents. Assignment to a non-leaf variable object is not allowed.
21915 A frontend does not need to read the values of all variable objects each time
21916 the program stops. Instead, MI provides an update command that lists all
21917 variable objects whose values has changed since the last update
21918 operation. This considerably reduces the amount of data that must
21919 be transferred to the frontend. As noted above, children variable
21920 objects are created on demand, and only leaf variable objects have a
21921 real value. As result, gdb will read target memory only for leaf
21922 variables that frontend has created.
21924 The automatic update is not always desirable. For example, a frontend
21925 might want to keep a value of some expression for future reference,
21926 and never update it. For another example, fetching memory is
21927 relatively slow for embedded targets, so a frontend might want
21928 to disable automatic update for the variables that are either not
21929 visible on the screen, or ``closed''. This is possible using so
21930 called ``frozen variable objects''. Such variable objects are never
21931 implicitly updated.
21933 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
21934 fixed variable object, the expression is parsed when the variable
21935 object is created, including associating identifiers to specific
21936 variables. The meaning of expression never changes. For a floating
21937 variable object the values of variables whose names appear in the
21938 expressions are re-evaluated every time in the context of the current
21939 frame. Consider this example:
21944 struct work_state state;
21951 If a fixed variable object for the @code{state} variable is created in
21952 this function, and we enter the recursive call, the the variable
21953 object will report the value of @code{state} in the top-level
21954 @code{do_work} invocation. On the other hand, a floating variable
21955 object will report the value of @code{state} in the current frame.
21957 If an expression specified when creating a fixed variable object
21958 refers to a local variable, the variable object becomes bound to the
21959 thread and frame in which the variable object is created. When such
21960 variable object is updated, @value{GDBN} makes sure that the
21961 thread/frame combination the variable object is bound to still exists,
21962 and re-evaluates the variable object in context of that thread/frame.
21964 The following is the complete set of @sc{gdb/mi} operations defined to
21965 access this functionality:
21967 @multitable @columnfractions .4 .6
21968 @item @strong{Operation}
21969 @tab @strong{Description}
21971 @item @code{-var-create}
21972 @tab create a variable object
21973 @item @code{-var-delete}
21974 @tab delete the variable object and/or its children
21975 @item @code{-var-set-format}
21976 @tab set the display format of this variable
21977 @item @code{-var-show-format}
21978 @tab show the display format of this variable
21979 @item @code{-var-info-num-children}
21980 @tab tells how many children this object has
21981 @item @code{-var-list-children}
21982 @tab return a list of the object's children
21983 @item @code{-var-info-type}
21984 @tab show the type of this variable object
21985 @item @code{-var-info-expression}
21986 @tab print parent-relative expression that this variable object represents
21987 @item @code{-var-info-path-expression}
21988 @tab print full expression that this variable object represents
21989 @item @code{-var-show-attributes}
21990 @tab is this variable editable? does it exist here?
21991 @item @code{-var-evaluate-expression}
21992 @tab get the value of this variable
21993 @item @code{-var-assign}
21994 @tab set the value of this variable
21995 @item @code{-var-update}
21996 @tab update the variable and its children
21997 @item @code{-var-set-frozen}
21998 @tab set frozeness attribute
22001 In the next subsection we describe each operation in detail and suggest
22002 how it can be used.
22004 @subheading Description And Use of Operations on Variable Objects
22006 @subheading The @code{-var-create} Command
22007 @findex -var-create
22009 @subsubheading Synopsis
22012 -var-create @{@var{name} | "-"@}
22013 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
22016 This operation creates a variable object, which allows the monitoring of
22017 a variable, the result of an expression, a memory cell or a CPU
22020 The @var{name} parameter is the string by which the object can be
22021 referenced. It must be unique. If @samp{-} is specified, the varobj
22022 system will generate a string ``varNNNNNN'' automatically. It will be
22023 unique provided that one does not specify @var{name} of that format.
22024 The command fails if a duplicate name is found.
22026 The frame under which the expression should be evaluated can be
22027 specified by @var{frame-addr}. A @samp{*} indicates that the current
22028 frame should be used. A @samp{@@} indicates that a floating variable
22029 object must be created.
22031 @var{expression} is any expression valid on the current language set (must not
22032 begin with a @samp{*}), or one of the following:
22036 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
22039 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
22042 @samp{$@var{regname}} --- a CPU register name
22045 @subsubheading Result
22047 This operation returns the name, number of children and the type of the
22048 object created. Type is returned as a string as the ones generated by
22049 the @value{GDBN} CLI. If a fixed variable object is bound to a
22050 specific thread, the thread is is also printed:
22053 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}"
22057 @subheading The @code{-var-delete} Command
22058 @findex -var-delete
22060 @subsubheading Synopsis
22063 -var-delete [ -c ] @var{name}
22066 Deletes a previously created variable object and all of its children.
22067 With the @samp{-c} option, just deletes the children.
22069 Returns an error if the object @var{name} is not found.
22072 @subheading The @code{-var-set-format} Command
22073 @findex -var-set-format
22075 @subsubheading Synopsis
22078 -var-set-format @var{name} @var{format-spec}
22081 Sets the output format for the value of the object @var{name} to be
22084 @anchor{-var-set-format}
22085 The syntax for the @var{format-spec} is as follows:
22088 @var{format-spec} @expansion{}
22089 @{binary | decimal | hexadecimal | octal | natural@}
22092 The natural format is the default format choosen automatically
22093 based on the variable type (like decimal for an @code{int}, hex
22094 for pointers, etc.).
22096 For a variable with children, the format is set only on the
22097 variable itself, and the children are not affected.
22099 @subheading The @code{-var-show-format} Command
22100 @findex -var-show-format
22102 @subsubheading Synopsis
22105 -var-show-format @var{name}
22108 Returns the format used to display the value of the object @var{name}.
22111 @var{format} @expansion{}
22116 @subheading The @code{-var-info-num-children} Command
22117 @findex -var-info-num-children
22119 @subsubheading Synopsis
22122 -var-info-num-children @var{name}
22125 Returns the number of children of a variable object @var{name}:
22132 @subheading The @code{-var-list-children} Command
22133 @findex -var-list-children
22135 @subsubheading Synopsis
22138 -var-list-children [@var{print-values}] @var{name}
22140 @anchor{-var-list-children}
22142 Return a list of the children of the specified variable object and
22143 create variable objects for them, if they do not already exist. With
22144 a single argument or if @var{print-values} has a value for of 0 or
22145 @code{--no-values}, print only the names of the variables; if
22146 @var{print-values} is 1 or @code{--all-values}, also print their
22147 values; and if it is 2 or @code{--simple-values} print the name and
22148 value for simple data types and just the name for arrays, structures
22151 @subsubheading Example
22155 -var-list-children n
22156 ^done,numchild=@var{n},children=[@{name=@var{name},
22157 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
22159 -var-list-children --all-values n
22160 ^done,numchild=@var{n},children=[@{name=@var{name},
22161 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
22165 @subheading The @code{-var-info-type} Command
22166 @findex -var-info-type
22168 @subsubheading Synopsis
22171 -var-info-type @var{name}
22174 Returns the type of the specified variable @var{name}. The type is
22175 returned as a string in the same format as it is output by the
22179 type=@var{typename}
22183 @subheading The @code{-var-info-expression} Command
22184 @findex -var-info-expression
22186 @subsubheading Synopsis
22189 -var-info-expression @var{name}
22192 Returns a string that is suitable for presenting this
22193 variable object in user interface. The string is generally
22194 not valid expression in the current language, and cannot be evaluated.
22196 For example, if @code{a} is an array, and variable object
22197 @code{A} was created for @code{a}, then we'll get this output:
22200 (gdb) -var-info-expression A.1
22201 ^done,lang="C",exp="1"
22205 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
22207 Note that the output of the @code{-var-list-children} command also
22208 includes those expressions, so the @code{-var-info-expression} command
22211 @subheading The @code{-var-info-path-expression} Command
22212 @findex -var-info-path-expression
22214 @subsubheading Synopsis
22217 -var-info-path-expression @var{name}
22220 Returns an expression that can be evaluated in the current
22221 context and will yield the same value that a variable object has.
22222 Compare this with the @code{-var-info-expression} command, which
22223 result can be used only for UI presentation. Typical use of
22224 the @code{-var-info-path-expression} command is creating a
22225 watchpoint from a variable object.
22227 For example, suppose @code{C} is a C@t{++} class, derived from class
22228 @code{Base}, and that the @code{Base} class has a member called
22229 @code{m_size}. Assume a variable @code{c} is has the type of
22230 @code{C} and a variable object @code{C} was created for variable
22231 @code{c}. Then, we'll get this output:
22233 (gdb) -var-info-path-expression C.Base.public.m_size
22234 ^done,path_expr=((Base)c).m_size)
22237 @subheading The @code{-var-show-attributes} Command
22238 @findex -var-show-attributes
22240 @subsubheading Synopsis
22243 -var-show-attributes @var{name}
22246 List attributes of the specified variable object @var{name}:
22249 status=@var{attr} [ ( ,@var{attr} )* ]
22253 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
22255 @subheading The @code{-var-evaluate-expression} Command
22256 @findex -var-evaluate-expression
22258 @subsubheading Synopsis
22261 -var-evaluate-expression [-f @var{format-spec}] @var{name}
22264 Evaluates the expression that is represented by the specified variable
22265 object and returns its value as a string. The format of the string
22266 can be specified with the @samp{-f} option. The possible values of
22267 this option are the same as for @code{-var-set-format}
22268 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
22269 the current display format will be used. The current display format
22270 can be changed using the @code{-var-set-format} command.
22276 Note that one must invoke @code{-var-list-children} for a variable
22277 before the value of a child variable can be evaluated.
22279 @subheading The @code{-var-assign} Command
22280 @findex -var-assign
22282 @subsubheading Synopsis
22285 -var-assign @var{name} @var{expression}
22288 Assigns the value of @var{expression} to the variable object specified
22289 by @var{name}. The object must be @samp{editable}. If the variable's
22290 value is altered by the assign, the variable will show up in any
22291 subsequent @code{-var-update} list.
22293 @subsubheading Example
22301 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
22305 @subheading The @code{-var-update} Command
22306 @findex -var-update
22308 @subsubheading Synopsis
22311 -var-update [@var{print-values}] @{@var{name} | "*"@}
22314 Reevaluate the expressions corresponding to the variable object
22315 @var{name} and all its direct and indirect children, and return the
22316 list of variable objects whose values have changed; @var{name} must
22317 be a root variable object. Here, ``changed'' means that the result of
22318 @code{-var-evaluate-expression} before and after the
22319 @code{-var-update} is different. If @samp{*} is used as the variable
22320 object names, all existing variable objects are updated, except
22321 for frozen ones (@pxref{-var-set-frozen}). The option
22322 @var{print-values} determines whether both names and values, or just
22323 names are printed. The possible values of this option are the same
22324 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
22325 recommended to use the @samp{--all-values} option, to reduce the
22326 number of MI commands needed on each program stop.
22328 With the @samp{*} parameter, if a variable object is bound to a
22329 currently running thread, it will not be updated, without any
22332 @subsubheading Example
22339 -var-update --all-values var1
22340 ^done,changelist=[@{name="var1",value="3",in_scope="true",
22341 type_changed="false"@}]
22345 @anchor{-var-update}
22346 The field in_scope may take three values:
22350 The variable object's current value is valid.
22353 The variable object does not currently hold a valid value but it may
22354 hold one in the future if its associated expression comes back into
22358 The variable object no longer holds a valid value.
22359 This can occur when the executable file being debugged has changed,
22360 either through recompilation or by using the @value{GDBN} @code{file}
22361 command. The front end should normally choose to delete these variable
22365 In the future new values may be added to this list so the front should
22366 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
22368 @subheading The @code{-var-set-frozen} Command
22369 @findex -var-set-frozen
22370 @anchor{-var-set-frozen}
22372 @subsubheading Synopsis
22375 -var-set-frozen @var{name} @var{flag}
22378 Set the frozenness flag on the variable object @var{name}. The
22379 @var{flag} parameter should be either @samp{1} to make the variable
22380 frozen or @samp{0} to make it unfrozen. If a variable object is
22381 frozen, then neither itself, nor any of its children, are
22382 implicitly updated by @code{-var-update} of
22383 a parent variable or by @code{-var-update *}. Only
22384 @code{-var-update} of the variable itself will update its value and
22385 values of its children. After a variable object is unfrozen, it is
22386 implicitly updated by all subsequent @code{-var-update} operations.
22387 Unfreezing a variable does not update it, only subsequent
22388 @code{-var-update} does.
22390 @subsubheading Example
22394 -var-set-frozen V 1
22400 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22401 @node GDB/MI Data Manipulation
22402 @section @sc{gdb/mi} Data Manipulation
22404 @cindex data manipulation, in @sc{gdb/mi}
22405 @cindex @sc{gdb/mi}, data manipulation
22406 This section describes the @sc{gdb/mi} commands that manipulate data:
22407 examine memory and registers, evaluate expressions, etc.
22409 @c REMOVED FROM THE INTERFACE.
22410 @c @subheading -data-assign
22411 @c Change the value of a program variable. Plenty of side effects.
22412 @c @subsubheading GDB Command
22414 @c @subsubheading Example
22417 @subheading The @code{-data-disassemble} Command
22418 @findex -data-disassemble
22420 @subsubheading Synopsis
22424 [ -s @var{start-addr} -e @var{end-addr} ]
22425 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
22433 @item @var{start-addr}
22434 is the beginning address (or @code{$pc})
22435 @item @var{end-addr}
22437 @item @var{filename}
22438 is the name of the file to disassemble
22439 @item @var{linenum}
22440 is the line number to disassemble around
22442 is the number of disassembly lines to be produced. If it is -1,
22443 the whole function will be disassembled, in case no @var{end-addr} is
22444 specified. If @var{end-addr} is specified as a non-zero value, and
22445 @var{lines} is lower than the number of disassembly lines between
22446 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
22447 displayed; if @var{lines} is higher than the number of lines between
22448 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
22451 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
22455 @subsubheading Result
22457 The output for each instruction is composed of four fields:
22466 Note that whatever included in the instruction field, is not manipulated
22467 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
22469 @subsubheading @value{GDBN} Command
22471 There's no direct mapping from this command to the CLI.
22473 @subsubheading Example
22475 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
22479 -data-disassemble -s $pc -e "$pc + 20" -- 0
22482 @{address="0x000107c0",func-name="main",offset="4",
22483 inst="mov 2, %o0"@},
22484 @{address="0x000107c4",func-name="main",offset="8",
22485 inst="sethi %hi(0x11800), %o2"@},
22486 @{address="0x000107c8",func-name="main",offset="12",
22487 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
22488 @{address="0x000107cc",func-name="main",offset="16",
22489 inst="sethi %hi(0x11800), %o2"@},
22490 @{address="0x000107d0",func-name="main",offset="20",
22491 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
22495 Disassemble the whole @code{main} function. Line 32 is part of
22499 -data-disassemble -f basics.c -l 32 -- 0
22501 @{address="0x000107bc",func-name="main",offset="0",
22502 inst="save %sp, -112, %sp"@},
22503 @{address="0x000107c0",func-name="main",offset="4",
22504 inst="mov 2, %o0"@},
22505 @{address="0x000107c4",func-name="main",offset="8",
22506 inst="sethi %hi(0x11800), %o2"@},
22508 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
22509 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
22513 Disassemble 3 instructions from the start of @code{main}:
22517 -data-disassemble -f basics.c -l 32 -n 3 -- 0
22519 @{address="0x000107bc",func-name="main",offset="0",
22520 inst="save %sp, -112, %sp"@},
22521 @{address="0x000107c0",func-name="main",offset="4",
22522 inst="mov 2, %o0"@},
22523 @{address="0x000107c4",func-name="main",offset="8",
22524 inst="sethi %hi(0x11800), %o2"@}]
22528 Disassemble 3 instructions from the start of @code{main} in mixed mode:
22532 -data-disassemble -f basics.c -l 32 -n 3 -- 1
22534 src_and_asm_line=@{line="31",
22535 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22536 testsuite/gdb.mi/basics.c",line_asm_insn=[
22537 @{address="0x000107bc",func-name="main",offset="0",
22538 inst="save %sp, -112, %sp"@}]@},
22539 src_and_asm_line=@{line="32",
22540 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22541 testsuite/gdb.mi/basics.c",line_asm_insn=[
22542 @{address="0x000107c0",func-name="main",offset="4",
22543 inst="mov 2, %o0"@},
22544 @{address="0x000107c4",func-name="main",offset="8",
22545 inst="sethi %hi(0x11800), %o2"@}]@}]
22550 @subheading The @code{-data-evaluate-expression} Command
22551 @findex -data-evaluate-expression
22553 @subsubheading Synopsis
22556 -data-evaluate-expression @var{expr}
22559 Evaluate @var{expr} as an expression. The expression could contain an
22560 inferior function call. The function call will execute synchronously.
22561 If the expression contains spaces, it must be enclosed in double quotes.
22563 @subsubheading @value{GDBN} Command
22565 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
22566 @samp{call}. In @code{gdbtk} only, there's a corresponding
22567 @samp{gdb_eval} command.
22569 @subsubheading Example
22571 In the following example, the numbers that precede the commands are the
22572 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
22573 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
22577 211-data-evaluate-expression A
22580 311-data-evaluate-expression &A
22581 311^done,value="0xefffeb7c"
22583 411-data-evaluate-expression A+3
22586 511-data-evaluate-expression "A + 3"
22592 @subheading The @code{-data-list-changed-registers} Command
22593 @findex -data-list-changed-registers
22595 @subsubheading Synopsis
22598 -data-list-changed-registers
22601 Display a list of the registers that have changed.
22603 @subsubheading @value{GDBN} Command
22605 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
22606 has the corresponding command @samp{gdb_changed_register_list}.
22608 @subsubheading Example
22610 On a PPC MBX board:
22618 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
22619 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
22622 -data-list-changed-registers
22623 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
22624 "10","11","13","14","15","16","17","18","19","20","21","22","23",
22625 "24","25","26","27","28","30","31","64","65","66","67","69"]
22630 @subheading The @code{-data-list-register-names} Command
22631 @findex -data-list-register-names
22633 @subsubheading Synopsis
22636 -data-list-register-names [ ( @var{regno} )+ ]
22639 Show a list of register names for the current target. If no arguments
22640 are given, it shows a list of the names of all the registers. If
22641 integer numbers are given as arguments, it will print a list of the
22642 names of the registers corresponding to the arguments. To ensure
22643 consistency between a register name and its number, the output list may
22644 include empty register names.
22646 @subsubheading @value{GDBN} Command
22648 @value{GDBN} does not have a command which corresponds to
22649 @samp{-data-list-register-names}. In @code{gdbtk} there is a
22650 corresponding command @samp{gdb_regnames}.
22652 @subsubheading Example
22654 For the PPC MBX board:
22657 -data-list-register-names
22658 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
22659 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
22660 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
22661 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
22662 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
22663 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
22664 "", "pc","ps","cr","lr","ctr","xer"]
22666 -data-list-register-names 1 2 3
22667 ^done,register-names=["r1","r2","r3"]
22671 @subheading The @code{-data-list-register-values} Command
22672 @findex -data-list-register-values
22674 @subsubheading Synopsis
22677 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
22680 Display the registers' contents. @var{fmt} is the format according to
22681 which the registers' contents are to be returned, followed by an optional
22682 list of numbers specifying the registers to display. A missing list of
22683 numbers indicates that the contents of all the registers must be returned.
22685 Allowed formats for @var{fmt} are:
22702 @subsubheading @value{GDBN} Command
22704 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
22705 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
22707 @subsubheading Example
22709 For a PPC MBX board (note: line breaks are for readability only, they
22710 don't appear in the actual output):
22714 -data-list-register-values r 64 65
22715 ^done,register-values=[@{number="64",value="0xfe00a300"@},
22716 @{number="65",value="0x00029002"@}]
22718 -data-list-register-values x
22719 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
22720 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
22721 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
22722 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
22723 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
22724 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
22725 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
22726 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
22727 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
22728 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
22729 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
22730 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
22731 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
22732 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
22733 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
22734 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
22735 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
22736 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
22737 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
22738 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
22739 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
22740 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
22741 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
22742 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
22743 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
22744 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
22745 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
22746 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
22747 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
22748 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
22749 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
22750 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
22751 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
22752 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
22753 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
22754 @{number="69",value="0x20002b03"@}]
22759 @subheading The @code{-data-read-memory} Command
22760 @findex -data-read-memory
22762 @subsubheading Synopsis
22765 -data-read-memory [ -o @var{byte-offset} ]
22766 @var{address} @var{word-format} @var{word-size}
22767 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
22774 @item @var{address}
22775 An expression specifying the address of the first memory word to be
22776 read. Complex expressions containing embedded white space should be
22777 quoted using the C convention.
22779 @item @var{word-format}
22780 The format to be used to print the memory words. The notation is the
22781 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
22784 @item @var{word-size}
22785 The size of each memory word in bytes.
22787 @item @var{nr-rows}
22788 The number of rows in the output table.
22790 @item @var{nr-cols}
22791 The number of columns in the output table.
22794 If present, indicates that each row should include an @sc{ascii} dump. The
22795 value of @var{aschar} is used as a padding character when a byte is not a
22796 member of the printable @sc{ascii} character set (printable @sc{ascii}
22797 characters are those whose code is between 32 and 126, inclusively).
22799 @item @var{byte-offset}
22800 An offset to add to the @var{address} before fetching memory.
22803 This command displays memory contents as a table of @var{nr-rows} by
22804 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
22805 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
22806 (returned as @samp{total-bytes}). Should less than the requested number
22807 of bytes be returned by the target, the missing words are identified
22808 using @samp{N/A}. The number of bytes read from the target is returned
22809 in @samp{nr-bytes} and the starting address used to read memory in
22812 The address of the next/previous row or page is available in
22813 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
22816 @subsubheading @value{GDBN} Command
22818 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
22819 @samp{gdb_get_mem} memory read command.
22821 @subsubheading Example
22823 Read six bytes of memory starting at @code{bytes+6} but then offset by
22824 @code{-6} bytes. Format as three rows of two columns. One byte per
22825 word. Display each word in hex.
22829 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
22830 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
22831 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
22832 prev-page="0x0000138a",memory=[
22833 @{addr="0x00001390",data=["0x00","0x01"]@},
22834 @{addr="0x00001392",data=["0x02","0x03"]@},
22835 @{addr="0x00001394",data=["0x04","0x05"]@}]
22839 Read two bytes of memory starting at address @code{shorts + 64} and
22840 display as a single word formatted in decimal.
22844 5-data-read-memory shorts+64 d 2 1 1
22845 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
22846 next-row="0x00001512",prev-row="0x0000150e",
22847 next-page="0x00001512",prev-page="0x0000150e",memory=[
22848 @{addr="0x00001510",data=["128"]@}]
22852 Read thirty two bytes of memory starting at @code{bytes+16} and format
22853 as eight rows of four columns. Include a string encoding with @samp{x}
22854 used as the non-printable character.
22858 4-data-read-memory bytes+16 x 1 8 4 x
22859 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
22860 next-row="0x000013c0",prev-row="0x0000139c",
22861 next-page="0x000013c0",prev-page="0x00001380",memory=[
22862 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
22863 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
22864 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
22865 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
22866 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
22867 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
22868 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
22869 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
22873 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22874 @node GDB/MI Tracepoint Commands
22875 @section @sc{gdb/mi} Tracepoint Commands
22877 The tracepoint commands are not yet implemented.
22879 @c @subheading -trace-actions
22881 @c @subheading -trace-delete
22883 @c @subheading -trace-disable
22885 @c @subheading -trace-dump
22887 @c @subheading -trace-enable
22889 @c @subheading -trace-exists
22891 @c @subheading -trace-find
22893 @c @subheading -trace-frame-number
22895 @c @subheading -trace-info
22897 @c @subheading -trace-insert
22899 @c @subheading -trace-list
22901 @c @subheading -trace-pass-count
22903 @c @subheading -trace-save
22905 @c @subheading -trace-start
22907 @c @subheading -trace-stop
22910 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22911 @node GDB/MI Symbol Query
22912 @section @sc{gdb/mi} Symbol Query Commands
22915 @subheading The @code{-symbol-info-address} Command
22916 @findex -symbol-info-address
22918 @subsubheading Synopsis
22921 -symbol-info-address @var{symbol}
22924 Describe where @var{symbol} is stored.
22926 @subsubheading @value{GDBN} Command
22928 The corresponding @value{GDBN} command is @samp{info address}.
22930 @subsubheading Example
22934 @subheading The @code{-symbol-info-file} Command
22935 @findex -symbol-info-file
22937 @subsubheading Synopsis
22943 Show the file for the symbol.
22945 @subsubheading @value{GDBN} Command
22947 There's no equivalent @value{GDBN} command. @code{gdbtk} has
22948 @samp{gdb_find_file}.
22950 @subsubheading Example
22954 @subheading The @code{-symbol-info-function} Command
22955 @findex -symbol-info-function
22957 @subsubheading Synopsis
22960 -symbol-info-function
22963 Show which function the symbol lives in.
22965 @subsubheading @value{GDBN} Command
22967 @samp{gdb_get_function} in @code{gdbtk}.
22969 @subsubheading Example
22973 @subheading The @code{-symbol-info-line} Command
22974 @findex -symbol-info-line
22976 @subsubheading Synopsis
22982 Show the core addresses of the code for a source line.
22984 @subsubheading @value{GDBN} Command
22986 The corresponding @value{GDBN} command is @samp{info line}.
22987 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
22989 @subsubheading Example
22993 @subheading The @code{-symbol-info-symbol} Command
22994 @findex -symbol-info-symbol
22996 @subsubheading Synopsis
22999 -symbol-info-symbol @var{addr}
23002 Describe what symbol is at location @var{addr}.
23004 @subsubheading @value{GDBN} Command
23006 The corresponding @value{GDBN} command is @samp{info symbol}.
23008 @subsubheading Example
23012 @subheading The @code{-symbol-list-functions} Command
23013 @findex -symbol-list-functions
23015 @subsubheading Synopsis
23018 -symbol-list-functions
23021 List the functions in the executable.
23023 @subsubheading @value{GDBN} Command
23025 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
23026 @samp{gdb_search} in @code{gdbtk}.
23028 @subsubheading Example
23032 @subheading The @code{-symbol-list-lines} Command
23033 @findex -symbol-list-lines
23035 @subsubheading Synopsis
23038 -symbol-list-lines @var{filename}
23041 Print the list of lines that contain code and their associated program
23042 addresses for the given source filename. The entries are sorted in
23043 ascending PC order.
23045 @subsubheading @value{GDBN} Command
23047 There is no corresponding @value{GDBN} command.
23049 @subsubheading Example
23052 -symbol-list-lines basics.c
23053 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
23058 @subheading The @code{-symbol-list-types} Command
23059 @findex -symbol-list-types
23061 @subsubheading Synopsis
23067 List all the type names.
23069 @subsubheading @value{GDBN} Command
23071 The corresponding commands are @samp{info types} in @value{GDBN},
23072 @samp{gdb_search} in @code{gdbtk}.
23074 @subsubheading Example
23078 @subheading The @code{-symbol-list-variables} Command
23079 @findex -symbol-list-variables
23081 @subsubheading Synopsis
23084 -symbol-list-variables
23087 List all the global and static variable names.
23089 @subsubheading @value{GDBN} Command
23091 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
23093 @subsubheading Example
23097 @subheading The @code{-symbol-locate} Command
23098 @findex -symbol-locate
23100 @subsubheading Synopsis
23106 @subsubheading @value{GDBN} Command
23108 @samp{gdb_loc} in @code{gdbtk}.
23110 @subsubheading Example
23114 @subheading The @code{-symbol-type} Command
23115 @findex -symbol-type
23117 @subsubheading Synopsis
23120 -symbol-type @var{variable}
23123 Show type of @var{variable}.
23125 @subsubheading @value{GDBN} Command
23127 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
23128 @samp{gdb_obj_variable}.
23130 @subsubheading Example
23134 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23135 @node GDB/MI File Commands
23136 @section @sc{gdb/mi} File Commands
23138 This section describes the GDB/MI commands to specify executable file names
23139 and to read in and obtain symbol table information.
23141 @subheading The @code{-file-exec-and-symbols} Command
23142 @findex -file-exec-and-symbols
23144 @subsubheading Synopsis
23147 -file-exec-and-symbols @var{file}
23150 Specify the executable file to be debugged. This file is the one from
23151 which the symbol table is also read. If no file is specified, the
23152 command clears the executable and symbol information. If breakpoints
23153 are set when using this command with no arguments, @value{GDBN} will produce
23154 error messages. Otherwise, no output is produced, except a completion
23157 @subsubheading @value{GDBN} Command
23159 The corresponding @value{GDBN} command is @samp{file}.
23161 @subsubheading Example
23165 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23171 @subheading The @code{-file-exec-file} Command
23172 @findex -file-exec-file
23174 @subsubheading Synopsis
23177 -file-exec-file @var{file}
23180 Specify the executable file to be debugged. Unlike
23181 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
23182 from this file. If used without argument, @value{GDBN} clears the information
23183 about the executable file. No output is produced, except a completion
23186 @subsubheading @value{GDBN} Command
23188 The corresponding @value{GDBN} command is @samp{exec-file}.
23190 @subsubheading Example
23194 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23200 @subheading The @code{-file-list-exec-sections} Command
23201 @findex -file-list-exec-sections
23203 @subsubheading Synopsis
23206 -file-list-exec-sections
23209 List the sections of the current executable file.
23211 @subsubheading @value{GDBN} Command
23213 The @value{GDBN} command @samp{info file} shows, among the rest, the same
23214 information as this command. @code{gdbtk} has a corresponding command
23215 @samp{gdb_load_info}.
23217 @subsubheading Example
23221 @subheading The @code{-file-list-exec-source-file} Command
23222 @findex -file-list-exec-source-file
23224 @subsubheading Synopsis
23227 -file-list-exec-source-file
23230 List the line number, the current source file, and the absolute path
23231 to the current source file for the current executable. The macro
23232 information field has a value of @samp{1} or @samp{0} depending on
23233 whether or not the file includes preprocessor macro information.
23235 @subsubheading @value{GDBN} Command
23237 The @value{GDBN} equivalent is @samp{info source}
23239 @subsubheading Example
23243 123-file-list-exec-source-file
23244 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
23249 @subheading The @code{-file-list-exec-source-files} Command
23250 @findex -file-list-exec-source-files
23252 @subsubheading Synopsis
23255 -file-list-exec-source-files
23258 List the source files for the current executable.
23260 It will always output the filename, but only when @value{GDBN} can find
23261 the absolute file name of a source file, will it output the fullname.
23263 @subsubheading @value{GDBN} Command
23265 The @value{GDBN} equivalent is @samp{info sources}.
23266 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
23268 @subsubheading Example
23271 -file-list-exec-source-files
23273 @{file=foo.c,fullname=/home/foo.c@},
23274 @{file=/home/bar.c,fullname=/home/bar.c@},
23275 @{file=gdb_could_not_find_fullpath.c@}]
23279 @subheading The @code{-file-list-shared-libraries} Command
23280 @findex -file-list-shared-libraries
23282 @subsubheading Synopsis
23285 -file-list-shared-libraries
23288 List the shared libraries in the program.
23290 @subsubheading @value{GDBN} Command
23292 The corresponding @value{GDBN} command is @samp{info shared}.
23294 @subsubheading Example
23298 @subheading The @code{-file-list-symbol-files} Command
23299 @findex -file-list-symbol-files
23301 @subsubheading Synopsis
23304 -file-list-symbol-files
23309 @subsubheading @value{GDBN} Command
23311 The corresponding @value{GDBN} command is @samp{info file} (part of it).
23313 @subsubheading Example
23317 @subheading The @code{-file-symbol-file} Command
23318 @findex -file-symbol-file
23320 @subsubheading Synopsis
23323 -file-symbol-file @var{file}
23326 Read symbol table info from the specified @var{file} argument. When
23327 used without arguments, clears @value{GDBN}'s symbol table info. No output is
23328 produced, except for a completion notification.
23330 @subsubheading @value{GDBN} Command
23332 The corresponding @value{GDBN} command is @samp{symbol-file}.
23334 @subsubheading Example
23338 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23344 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23345 @node GDB/MI Memory Overlay Commands
23346 @section @sc{gdb/mi} Memory Overlay Commands
23348 The memory overlay commands are not implemented.
23350 @c @subheading -overlay-auto
23352 @c @subheading -overlay-list-mapping-state
23354 @c @subheading -overlay-list-overlays
23356 @c @subheading -overlay-map
23358 @c @subheading -overlay-off
23360 @c @subheading -overlay-on
23362 @c @subheading -overlay-unmap
23364 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23365 @node GDB/MI Signal Handling Commands
23366 @section @sc{gdb/mi} Signal Handling Commands
23368 Signal handling commands are not implemented.
23370 @c @subheading -signal-handle
23372 @c @subheading -signal-list-handle-actions
23374 @c @subheading -signal-list-signal-types
23378 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23379 @node GDB/MI Target Manipulation
23380 @section @sc{gdb/mi} Target Manipulation Commands
23383 @subheading The @code{-target-attach} Command
23384 @findex -target-attach
23386 @subsubheading Synopsis
23389 -target-attach @var{pid} | @var{gid} | @var{file}
23392 Attach to a process @var{pid} or a file @var{file} outside of
23393 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
23394 group, the id previously returned by
23395 @samp{-list-thread-groups --available} must be used.
23397 @subsubheading @value{GDBN} Command
23399 The corresponding @value{GDBN} command is @samp{attach}.
23401 @subsubheading Example
23405 =thread-created,id="1"
23406 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
23411 @subheading The @code{-target-compare-sections} Command
23412 @findex -target-compare-sections
23414 @subsubheading Synopsis
23417 -target-compare-sections [ @var{section} ]
23420 Compare data of section @var{section} on target to the exec file.
23421 Without the argument, all sections are compared.
23423 @subsubheading @value{GDBN} Command
23425 The @value{GDBN} equivalent is @samp{compare-sections}.
23427 @subsubheading Example
23431 @subheading The @code{-target-detach} Command
23432 @findex -target-detach
23434 @subsubheading Synopsis
23437 -target-detach [ @var{pid} | @var{gid} ]
23440 Detach from the remote target which normally resumes its execution.
23441 If either @var{pid} or @var{gid} is specified, detaches from either
23442 the specified process, or specified thread group. There's no output.
23444 @subsubheading @value{GDBN} Command
23446 The corresponding @value{GDBN} command is @samp{detach}.
23448 @subsubheading Example
23458 @subheading The @code{-target-disconnect} Command
23459 @findex -target-disconnect
23461 @subsubheading Synopsis
23467 Disconnect from the remote target. There's no output and the target is
23468 generally not resumed.
23470 @subsubheading @value{GDBN} Command
23472 The corresponding @value{GDBN} command is @samp{disconnect}.
23474 @subsubheading Example
23484 @subheading The @code{-target-download} Command
23485 @findex -target-download
23487 @subsubheading Synopsis
23493 Loads the executable onto the remote target.
23494 It prints out an update message every half second, which includes the fields:
23498 The name of the section.
23500 The size of what has been sent so far for that section.
23502 The size of the section.
23504 The total size of what was sent so far (the current and the previous sections).
23506 The size of the overall executable to download.
23510 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
23511 @sc{gdb/mi} Output Syntax}).
23513 In addition, it prints the name and size of the sections, as they are
23514 downloaded. These messages include the following fields:
23518 The name of the section.
23520 The size of the section.
23522 The size of the overall executable to download.
23526 At the end, a summary is printed.
23528 @subsubheading @value{GDBN} Command
23530 The corresponding @value{GDBN} command is @samp{load}.
23532 @subsubheading Example
23534 Note: each status message appears on a single line. Here the messages
23535 have been broken down so that they can fit onto a page.
23540 +download,@{section=".text",section-size="6668",total-size="9880"@}
23541 +download,@{section=".text",section-sent="512",section-size="6668",
23542 total-sent="512",total-size="9880"@}
23543 +download,@{section=".text",section-sent="1024",section-size="6668",
23544 total-sent="1024",total-size="9880"@}
23545 +download,@{section=".text",section-sent="1536",section-size="6668",
23546 total-sent="1536",total-size="9880"@}
23547 +download,@{section=".text",section-sent="2048",section-size="6668",
23548 total-sent="2048",total-size="9880"@}
23549 +download,@{section=".text",section-sent="2560",section-size="6668",
23550 total-sent="2560",total-size="9880"@}
23551 +download,@{section=".text",section-sent="3072",section-size="6668",
23552 total-sent="3072",total-size="9880"@}
23553 +download,@{section=".text",section-sent="3584",section-size="6668",
23554 total-sent="3584",total-size="9880"@}
23555 +download,@{section=".text",section-sent="4096",section-size="6668",
23556 total-sent="4096",total-size="9880"@}
23557 +download,@{section=".text",section-sent="4608",section-size="6668",
23558 total-sent="4608",total-size="9880"@}
23559 +download,@{section=".text",section-sent="5120",section-size="6668",
23560 total-sent="5120",total-size="9880"@}
23561 +download,@{section=".text",section-sent="5632",section-size="6668",
23562 total-sent="5632",total-size="9880"@}
23563 +download,@{section=".text",section-sent="6144",section-size="6668",
23564 total-sent="6144",total-size="9880"@}
23565 +download,@{section=".text",section-sent="6656",section-size="6668",
23566 total-sent="6656",total-size="9880"@}
23567 +download,@{section=".init",section-size="28",total-size="9880"@}
23568 +download,@{section=".fini",section-size="28",total-size="9880"@}
23569 +download,@{section=".data",section-size="3156",total-size="9880"@}
23570 +download,@{section=".data",section-sent="512",section-size="3156",
23571 total-sent="7236",total-size="9880"@}
23572 +download,@{section=".data",section-sent="1024",section-size="3156",
23573 total-sent="7748",total-size="9880"@}
23574 +download,@{section=".data",section-sent="1536",section-size="3156",
23575 total-sent="8260",total-size="9880"@}
23576 +download,@{section=".data",section-sent="2048",section-size="3156",
23577 total-sent="8772",total-size="9880"@}
23578 +download,@{section=".data",section-sent="2560",section-size="3156",
23579 total-sent="9284",total-size="9880"@}
23580 +download,@{section=".data",section-sent="3072",section-size="3156",
23581 total-sent="9796",total-size="9880"@}
23582 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
23588 @subheading The @code{-target-exec-status} Command
23589 @findex -target-exec-status
23591 @subsubheading Synopsis
23594 -target-exec-status
23597 Provide information on the state of the target (whether it is running or
23598 not, for instance).
23600 @subsubheading @value{GDBN} Command
23602 There's no equivalent @value{GDBN} command.
23604 @subsubheading Example
23608 @subheading The @code{-target-list-available-targets} Command
23609 @findex -target-list-available-targets
23611 @subsubheading Synopsis
23614 -target-list-available-targets
23617 List the possible targets to connect to.
23619 @subsubheading @value{GDBN} Command
23621 The corresponding @value{GDBN} command is @samp{help target}.
23623 @subsubheading Example
23627 @subheading The @code{-target-list-current-targets} Command
23628 @findex -target-list-current-targets
23630 @subsubheading Synopsis
23633 -target-list-current-targets
23636 Describe the current target.
23638 @subsubheading @value{GDBN} Command
23640 The corresponding information is printed by @samp{info file} (among
23643 @subsubheading Example
23647 @subheading The @code{-target-list-parameters} Command
23648 @findex -target-list-parameters
23650 @subsubheading Synopsis
23653 -target-list-parameters
23658 @subsubheading @value{GDBN} Command
23662 @subsubheading Example
23666 @subheading The @code{-target-select} Command
23667 @findex -target-select
23669 @subsubheading Synopsis
23672 -target-select @var{type} @var{parameters @dots{}}
23675 Connect @value{GDBN} to the remote target. This command takes two args:
23679 The type of target, for instance @samp{remote}, etc.
23680 @item @var{parameters}
23681 Device names, host names and the like. @xref{Target Commands, ,
23682 Commands for Managing Targets}, for more details.
23685 The output is a connection notification, followed by the address at
23686 which the target program is, in the following form:
23689 ^connected,addr="@var{address}",func="@var{function name}",
23690 args=[@var{arg list}]
23693 @subsubheading @value{GDBN} Command
23695 The corresponding @value{GDBN} command is @samp{target}.
23697 @subsubheading Example
23701 -target-select remote /dev/ttya
23702 ^connected,addr="0xfe00a300",func="??",args=[]
23706 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23707 @node GDB/MI File Transfer Commands
23708 @section @sc{gdb/mi} File Transfer Commands
23711 @subheading The @code{-target-file-put} Command
23712 @findex -target-file-put
23714 @subsubheading Synopsis
23717 -target-file-put @var{hostfile} @var{targetfile}
23720 Copy file @var{hostfile} from the host system (the machine running
23721 @value{GDBN}) to @var{targetfile} on the target system.
23723 @subsubheading @value{GDBN} Command
23725 The corresponding @value{GDBN} command is @samp{remote put}.
23727 @subsubheading Example
23731 -target-file-put localfile remotefile
23737 @subheading The @code{-target-file-get} Command
23738 @findex -target-file-get
23740 @subsubheading Synopsis
23743 -target-file-get @var{targetfile} @var{hostfile}
23746 Copy file @var{targetfile} from the target system to @var{hostfile}
23747 on the host system.
23749 @subsubheading @value{GDBN} Command
23751 The corresponding @value{GDBN} command is @samp{remote get}.
23753 @subsubheading Example
23757 -target-file-get remotefile localfile
23763 @subheading The @code{-target-file-delete} Command
23764 @findex -target-file-delete
23766 @subsubheading Synopsis
23769 -target-file-delete @var{targetfile}
23772 Delete @var{targetfile} from the target system.
23774 @subsubheading @value{GDBN} Command
23776 The corresponding @value{GDBN} command is @samp{remote delete}.
23778 @subsubheading Example
23782 -target-file-delete remotefile
23788 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23789 @node GDB/MI Miscellaneous Commands
23790 @section Miscellaneous @sc{gdb/mi} Commands
23792 @c @subheading -gdb-complete
23794 @subheading The @code{-gdb-exit} Command
23797 @subsubheading Synopsis
23803 Exit @value{GDBN} immediately.
23805 @subsubheading @value{GDBN} Command
23807 Approximately corresponds to @samp{quit}.
23809 @subsubheading Example
23818 @subheading The @code{-exec-abort} Command
23819 @findex -exec-abort
23821 @subsubheading Synopsis
23827 Kill the inferior running program.
23829 @subsubheading @value{GDBN} Command
23831 The corresponding @value{GDBN} command is @samp{kill}.
23833 @subsubheading Example
23837 @subheading The @code{-gdb-set} Command
23840 @subsubheading Synopsis
23846 Set an internal @value{GDBN} variable.
23847 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
23849 @subsubheading @value{GDBN} Command
23851 The corresponding @value{GDBN} command is @samp{set}.
23853 @subsubheading Example
23863 @subheading The @code{-gdb-show} Command
23866 @subsubheading Synopsis
23872 Show the current value of a @value{GDBN} variable.
23874 @subsubheading @value{GDBN} Command
23876 The corresponding @value{GDBN} command is @samp{show}.
23878 @subsubheading Example
23887 @c @subheading -gdb-source
23890 @subheading The @code{-gdb-version} Command
23891 @findex -gdb-version
23893 @subsubheading Synopsis
23899 Show version information for @value{GDBN}. Used mostly in testing.
23901 @subsubheading @value{GDBN} Command
23903 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
23904 default shows this information when you start an interactive session.
23906 @subsubheading Example
23908 @c This example modifies the actual output from GDB to avoid overfull
23914 ~Copyright 2000 Free Software Foundation, Inc.
23915 ~GDB is free software, covered by the GNU General Public License, and
23916 ~you are welcome to change it and/or distribute copies of it under
23917 ~ certain conditions.
23918 ~Type "show copying" to see the conditions.
23919 ~There is absolutely no warranty for GDB. Type "show warranty" for
23921 ~This GDB was configured as
23922 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
23927 @subheading The @code{-list-features} Command
23928 @findex -list-features
23930 Returns a list of particular features of the MI protocol that
23931 this version of gdb implements. A feature can be a command,
23932 or a new field in an output of some command, or even an
23933 important bugfix. While a frontend can sometimes detect presence
23934 of a feature at runtime, it is easier to perform detection at debugger
23937 The command returns a list of strings, with each string naming an
23938 available feature. Each returned string is just a name, it does not
23939 have any internal structure. The list of possible feature names
23945 (gdb) -list-features
23946 ^done,result=["feature1","feature2"]
23949 The current list of features is:
23952 @item frozen-varobjs
23953 Indicates presence of the @code{-var-set-frozen} command, as well
23954 as possible presense of the @code{frozen} field in the output
23955 of @code{-varobj-create}.
23956 @item pending-breakpoints
23957 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
23959 Indicates presence of the @code{-thread-info} command.
23963 @subheading The @code{-list-target-features} Command
23964 @findex -list-target-features
23966 Returns a list of particular features that are supported by the
23967 target. Those features affect the permitted MI commands, but
23968 unlike the features reported by the @code{-list-features} command, the
23969 features depend on which target GDB is using at the moment. Whenever
23970 a target can change, due to commands such as @code{-target-select},
23971 @code{-target-attach} or @code{-exec-run}, the list of target features
23972 may change, and the frontend should obtain it again.
23976 (gdb) -list-features
23977 ^done,result=["async"]
23980 The current list of features is:
23984 Indicates that the target is capable of asynchronous command
23985 execution, which means that @value{GDBN} will accept further commands
23986 while the target is running.
23990 @subheading The @code{-list-thread-groups} Command
23991 @findex -list-thread-groups
23993 @subheading Synopsis
23996 -list-thread-groups [ --available ] [ @var{group} ]
23999 When used without the @var{group} parameter, lists top-level thread
24000 groups that are being debugged. When used with the @var{group}
24001 parameter, the children of the specified group are listed. The
24002 children can be either threads, or other groups. At present,
24003 @value{GDBN} will not report both threads and groups as children at
24004 the same time, but it may change in future.
24006 With the @samp{--available} option, instead of reporting groups that
24007 are been debugged, GDB will report all thread groups available on the
24008 target. Using the @samp{--available} option together with @var{group}
24011 @subheading Example
24015 -list-thread-groups
24016 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
24017 -list-thread-groups 17
24018 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
24019 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
24020 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
24021 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
24022 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
24025 @subheading The @code{-interpreter-exec} Command
24026 @findex -interpreter-exec
24028 @subheading Synopsis
24031 -interpreter-exec @var{interpreter} @var{command}
24033 @anchor{-interpreter-exec}
24035 Execute the specified @var{command} in the given @var{interpreter}.
24037 @subheading @value{GDBN} Command
24039 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
24041 @subheading Example
24045 -interpreter-exec console "break main"
24046 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
24047 &"During symbol reading, bad structure-type format.\n"
24048 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
24053 @subheading The @code{-inferior-tty-set} Command
24054 @findex -inferior-tty-set
24056 @subheading Synopsis
24059 -inferior-tty-set /dev/pts/1
24062 Set terminal for future runs of the program being debugged.
24064 @subheading @value{GDBN} Command
24066 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
24068 @subheading Example
24072 -inferior-tty-set /dev/pts/1
24077 @subheading The @code{-inferior-tty-show} Command
24078 @findex -inferior-tty-show
24080 @subheading Synopsis
24086 Show terminal for future runs of program being debugged.
24088 @subheading @value{GDBN} Command
24090 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
24092 @subheading Example
24096 -inferior-tty-set /dev/pts/1
24100 ^done,inferior_tty_terminal="/dev/pts/1"
24104 @subheading The @code{-enable-timings} Command
24105 @findex -enable-timings
24107 @subheading Synopsis
24110 -enable-timings [yes | no]
24113 Toggle the printing of the wallclock, user and system times for an MI
24114 command as a field in its output. This command is to help frontend
24115 developers optimize the performance of their code. No argument is
24116 equivalent to @samp{yes}.
24118 @subheading @value{GDBN} Command
24122 @subheading Example
24130 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24131 addr="0x080484ed",func="main",file="myprog.c",
24132 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
24133 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
24141 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24142 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
24143 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
24144 fullname="/home/nickrob/myprog.c",line="73"@}
24149 @chapter @value{GDBN} Annotations
24151 This chapter describes annotations in @value{GDBN}. Annotations were
24152 designed to interface @value{GDBN} to graphical user interfaces or other
24153 similar programs which want to interact with @value{GDBN} at a
24154 relatively high level.
24156 The annotation mechanism has largely been superseded by @sc{gdb/mi}
24160 This is Edition @value{EDITION}, @value{DATE}.
24164 * Annotations Overview:: What annotations are; the general syntax.
24165 * Server Prefix:: Issuing a command without affecting user state.
24166 * Prompting:: Annotations marking @value{GDBN}'s need for input.
24167 * Errors:: Annotations for error messages.
24168 * Invalidation:: Some annotations describe things now invalid.
24169 * Annotations for Running::
24170 Whether the program is running, how it stopped, etc.
24171 * Source Annotations:: Annotations describing source code.
24174 @node Annotations Overview
24175 @section What is an Annotation?
24176 @cindex annotations
24178 Annotations start with a newline character, two @samp{control-z}
24179 characters, and the name of the annotation. If there is no additional
24180 information associated with this annotation, the name of the annotation
24181 is followed immediately by a newline. If there is additional
24182 information, the name of the annotation is followed by a space, the
24183 additional information, and a newline. The additional information
24184 cannot contain newline characters.
24186 Any output not beginning with a newline and two @samp{control-z}
24187 characters denotes literal output from @value{GDBN}. Currently there is
24188 no need for @value{GDBN} to output a newline followed by two
24189 @samp{control-z} characters, but if there was such a need, the
24190 annotations could be extended with an @samp{escape} annotation which
24191 means those three characters as output.
24193 The annotation @var{level}, which is specified using the
24194 @option{--annotate} command line option (@pxref{Mode Options}), controls
24195 how much information @value{GDBN} prints together with its prompt,
24196 values of expressions, source lines, and other types of output. Level 0
24197 is for no annotations, level 1 is for use when @value{GDBN} is run as a
24198 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
24199 for programs that control @value{GDBN}, and level 2 annotations have
24200 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
24201 Interface, annotate, GDB's Obsolete Annotations}).
24204 @kindex set annotate
24205 @item set annotate @var{level}
24206 The @value{GDBN} command @code{set annotate} sets the level of
24207 annotations to the specified @var{level}.
24209 @item show annotate
24210 @kindex show annotate
24211 Show the current annotation level.
24214 This chapter describes level 3 annotations.
24216 A simple example of starting up @value{GDBN} with annotations is:
24219 $ @kbd{gdb --annotate=3}
24221 Copyright 2003 Free Software Foundation, Inc.
24222 GDB is free software, covered by the GNU General Public License,
24223 and you are welcome to change it and/or distribute copies of it
24224 under certain conditions.
24225 Type "show copying" to see the conditions.
24226 There is absolutely no warranty for GDB. Type "show warranty"
24228 This GDB was configured as "i386-pc-linux-gnu"
24239 Here @samp{quit} is input to @value{GDBN}; the rest is output from
24240 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
24241 denotes a @samp{control-z} character) are annotations; the rest is
24242 output from @value{GDBN}.
24244 @node Server Prefix
24245 @section The Server Prefix
24246 @cindex server prefix
24248 If you prefix a command with @samp{server } then it will not affect
24249 the command history, nor will it affect @value{GDBN}'s notion of which
24250 command to repeat if @key{RET} is pressed on a line by itself. This
24251 means that commands can be run behind a user's back by a front-end in
24252 a transparent manner.
24254 The server prefix does not affect the recording of values into the value
24255 history; to print a value without recording it into the value history,
24256 use the @code{output} command instead of the @code{print} command.
24259 @section Annotation for @value{GDBN} Input
24261 @cindex annotations for prompts
24262 When @value{GDBN} prompts for input, it annotates this fact so it is possible
24263 to know when to send output, when the output from a given command is
24266 Different kinds of input each have a different @dfn{input type}. Each
24267 input type has three annotations: a @code{pre-} annotation, which
24268 denotes the beginning of any prompt which is being output, a plain
24269 annotation, which denotes the end of the prompt, and then a @code{post-}
24270 annotation which denotes the end of any echo which may (or may not) be
24271 associated with the input. For example, the @code{prompt} input type
24272 features the following annotations:
24280 The input types are
24283 @findex pre-prompt annotation
24284 @findex prompt annotation
24285 @findex post-prompt annotation
24287 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
24289 @findex pre-commands annotation
24290 @findex commands annotation
24291 @findex post-commands annotation
24293 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
24294 command. The annotations are repeated for each command which is input.
24296 @findex pre-overload-choice annotation
24297 @findex overload-choice annotation
24298 @findex post-overload-choice annotation
24299 @item overload-choice
24300 When @value{GDBN} wants the user to select between various overloaded functions.
24302 @findex pre-query annotation
24303 @findex query annotation
24304 @findex post-query annotation
24306 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
24308 @findex pre-prompt-for-continue annotation
24309 @findex prompt-for-continue annotation
24310 @findex post-prompt-for-continue annotation
24311 @item prompt-for-continue
24312 When @value{GDBN} is asking the user to press return to continue. Note: Don't
24313 expect this to work well; instead use @code{set height 0} to disable
24314 prompting. This is because the counting of lines is buggy in the
24315 presence of annotations.
24320 @cindex annotations for errors, warnings and interrupts
24322 @findex quit annotation
24327 This annotation occurs right before @value{GDBN} responds to an interrupt.
24329 @findex error annotation
24334 This annotation occurs right before @value{GDBN} responds to an error.
24336 Quit and error annotations indicate that any annotations which @value{GDBN} was
24337 in the middle of may end abruptly. For example, if a
24338 @code{value-history-begin} annotation is followed by a @code{error}, one
24339 cannot expect to receive the matching @code{value-history-end}. One
24340 cannot expect not to receive it either, however; an error annotation
24341 does not necessarily mean that @value{GDBN} is immediately returning all the way
24344 @findex error-begin annotation
24345 A quit or error annotation may be preceded by
24351 Any output between that and the quit or error annotation is the error
24354 Warning messages are not yet annotated.
24355 @c If we want to change that, need to fix warning(), type_error(),
24356 @c range_error(), and possibly other places.
24359 @section Invalidation Notices
24361 @cindex annotations for invalidation messages
24362 The following annotations say that certain pieces of state may have
24366 @findex frames-invalid annotation
24367 @item ^Z^Zframes-invalid
24369 The frames (for example, output from the @code{backtrace} command) may
24372 @findex breakpoints-invalid annotation
24373 @item ^Z^Zbreakpoints-invalid
24375 The breakpoints may have changed. For example, the user just added or
24376 deleted a breakpoint.
24379 @node Annotations for Running
24380 @section Running the Program
24381 @cindex annotations for running programs
24383 @findex starting annotation
24384 @findex stopping annotation
24385 When the program starts executing due to a @value{GDBN} command such as
24386 @code{step} or @code{continue},
24392 is output. When the program stops,
24398 is output. Before the @code{stopped} annotation, a variety of
24399 annotations describe how the program stopped.
24402 @findex exited annotation
24403 @item ^Z^Zexited @var{exit-status}
24404 The program exited, and @var{exit-status} is the exit status (zero for
24405 successful exit, otherwise nonzero).
24407 @findex signalled annotation
24408 @findex signal-name annotation
24409 @findex signal-name-end annotation
24410 @findex signal-string annotation
24411 @findex signal-string-end annotation
24412 @item ^Z^Zsignalled
24413 The program exited with a signal. After the @code{^Z^Zsignalled}, the
24414 annotation continues:
24420 ^Z^Zsignal-name-end
24424 ^Z^Zsignal-string-end
24429 where @var{name} is the name of the signal, such as @code{SIGILL} or
24430 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
24431 as @code{Illegal Instruction} or @code{Segmentation fault}.
24432 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
24433 user's benefit and have no particular format.
24435 @findex signal annotation
24437 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
24438 just saying that the program received the signal, not that it was
24439 terminated with it.
24441 @findex breakpoint annotation
24442 @item ^Z^Zbreakpoint @var{number}
24443 The program hit breakpoint number @var{number}.
24445 @findex watchpoint annotation
24446 @item ^Z^Zwatchpoint @var{number}
24447 The program hit watchpoint number @var{number}.
24450 @node Source Annotations
24451 @section Displaying Source
24452 @cindex annotations for source display
24454 @findex source annotation
24455 The following annotation is used instead of displaying source code:
24458 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
24461 where @var{filename} is an absolute file name indicating which source
24462 file, @var{line} is the line number within that file (where 1 is the
24463 first line in the file), @var{character} is the character position
24464 within the file (where 0 is the first character in the file) (for most
24465 debug formats this will necessarily point to the beginning of a line),
24466 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
24467 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
24468 @var{addr} is the address in the target program associated with the
24469 source which is being displayed. @var{addr} is in the form @samp{0x}
24470 followed by one or more lowercase hex digits (note that this does not
24471 depend on the language).
24474 @chapter Reporting Bugs in @value{GDBN}
24475 @cindex bugs in @value{GDBN}
24476 @cindex reporting bugs in @value{GDBN}
24478 Your bug reports play an essential role in making @value{GDBN} reliable.
24480 Reporting a bug may help you by bringing a solution to your problem, or it
24481 may not. But in any case the principal function of a bug report is to help
24482 the entire community by making the next version of @value{GDBN} work better. Bug
24483 reports are your contribution to the maintenance of @value{GDBN}.
24485 In order for a bug report to serve its purpose, you must include the
24486 information that enables us to fix the bug.
24489 * Bug Criteria:: Have you found a bug?
24490 * Bug Reporting:: How to report bugs
24494 @section Have You Found a Bug?
24495 @cindex bug criteria
24497 If you are not sure whether you have found a bug, here are some guidelines:
24500 @cindex fatal signal
24501 @cindex debugger crash
24502 @cindex crash of debugger
24504 If the debugger gets a fatal signal, for any input whatever, that is a
24505 @value{GDBN} bug. Reliable debuggers never crash.
24507 @cindex error on valid input
24509 If @value{GDBN} produces an error message for valid input, that is a
24510 bug. (Note that if you're cross debugging, the problem may also be
24511 somewhere in the connection to the target.)
24513 @cindex invalid input
24515 If @value{GDBN} does not produce an error message for invalid input,
24516 that is a bug. However, you should note that your idea of
24517 ``invalid input'' might be our idea of ``an extension'' or ``support
24518 for traditional practice''.
24521 If you are an experienced user of debugging tools, your suggestions
24522 for improvement of @value{GDBN} are welcome in any case.
24525 @node Bug Reporting
24526 @section How to Report Bugs
24527 @cindex bug reports
24528 @cindex @value{GDBN} bugs, reporting
24530 A number of companies and individuals offer support for @sc{gnu} products.
24531 If you obtained @value{GDBN} from a support organization, we recommend you
24532 contact that organization first.
24534 You can find contact information for many support companies and
24535 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
24537 @c should add a web page ref...
24540 @ifset BUGURL_DEFAULT
24541 In any event, we also recommend that you submit bug reports for
24542 @value{GDBN}. The preferred method is to submit them directly using
24543 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
24544 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
24547 @strong{Do not send bug reports to @samp{info-gdb}, or to
24548 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
24549 not want to receive bug reports. Those that do have arranged to receive
24552 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
24553 serves as a repeater. The mailing list and the newsgroup carry exactly
24554 the same messages. Often people think of posting bug reports to the
24555 newsgroup instead of mailing them. This appears to work, but it has one
24556 problem which can be crucial: a newsgroup posting often lacks a mail
24557 path back to the sender. Thus, if we need to ask for more information,
24558 we may be unable to reach you. For this reason, it is better to send
24559 bug reports to the mailing list.
24561 @ifclear BUGURL_DEFAULT
24562 In any event, we also recommend that you submit bug reports for
24563 @value{GDBN} to @value{BUGURL}.
24567 The fundamental principle of reporting bugs usefully is this:
24568 @strong{report all the facts}. If you are not sure whether to state a
24569 fact or leave it out, state it!
24571 Often people omit facts because they think they know what causes the
24572 problem and assume that some details do not matter. Thus, you might
24573 assume that the name of the variable you use in an example does not matter.
24574 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
24575 stray memory reference which happens to fetch from the location where that
24576 name is stored in memory; perhaps, if the name were different, the contents
24577 of that location would fool the debugger into doing the right thing despite
24578 the bug. Play it safe and give a specific, complete example. That is the
24579 easiest thing for you to do, and the most helpful.
24581 Keep in mind that the purpose of a bug report is to enable us to fix the
24582 bug. It may be that the bug has been reported previously, but neither
24583 you nor we can know that unless your bug report is complete and
24586 Sometimes people give a few sketchy facts and ask, ``Does this ring a
24587 bell?'' Those bug reports are useless, and we urge everyone to
24588 @emph{refuse to respond to them} except to chide the sender to report
24591 To enable us to fix the bug, you should include all these things:
24595 The version of @value{GDBN}. @value{GDBN} announces it if you start
24596 with no arguments; you can also print it at any time using @code{show
24599 Without this, we will not know whether there is any point in looking for
24600 the bug in the current version of @value{GDBN}.
24603 The type of machine you are using, and the operating system name and
24607 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
24608 ``@value{GCC}--2.8.1''.
24611 What compiler (and its version) was used to compile the program you are
24612 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
24613 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
24614 to get this information; for other compilers, see the documentation for
24618 The command arguments you gave the compiler to compile your example and
24619 observe the bug. For example, did you use @samp{-O}? To guarantee
24620 you will not omit something important, list them all. A copy of the
24621 Makefile (or the output from make) is sufficient.
24623 If we were to try to guess the arguments, we would probably guess wrong
24624 and then we might not encounter the bug.
24627 A complete input script, and all necessary source files, that will
24631 A description of what behavior you observe that you believe is
24632 incorrect. For example, ``It gets a fatal signal.''
24634 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
24635 will certainly notice it. But if the bug is incorrect output, we might
24636 not notice unless it is glaringly wrong. You might as well not give us
24637 a chance to make a mistake.
24639 Even if the problem you experience is a fatal signal, you should still
24640 say so explicitly. Suppose something strange is going on, such as, your
24641 copy of @value{GDBN} is out of synch, or you have encountered a bug in
24642 the C library on your system. (This has happened!) Your copy might
24643 crash and ours would not. If you told us to expect a crash, then when
24644 ours fails to crash, we would know that the bug was not happening for
24645 us. If you had not told us to expect a crash, then we would not be able
24646 to draw any conclusion from our observations.
24649 @cindex recording a session script
24650 To collect all this information, you can use a session recording program
24651 such as @command{script}, which is available on many Unix systems.
24652 Just run your @value{GDBN} session inside @command{script} and then
24653 include the @file{typescript} file with your bug report.
24655 Another way to record a @value{GDBN} session is to run @value{GDBN}
24656 inside Emacs and then save the entire buffer to a file.
24659 If you wish to suggest changes to the @value{GDBN} source, send us context
24660 diffs. If you even discuss something in the @value{GDBN} source, refer to
24661 it by context, not by line number.
24663 The line numbers in our development sources will not match those in your
24664 sources. Your line numbers would convey no useful information to us.
24668 Here are some things that are not necessary:
24672 A description of the envelope of the bug.
24674 Often people who encounter a bug spend a lot of time investigating
24675 which changes to the input file will make the bug go away and which
24676 changes will not affect it.
24678 This is often time consuming and not very useful, because the way we
24679 will find the bug is by running a single example under the debugger
24680 with breakpoints, not by pure deduction from a series of examples.
24681 We recommend that you save your time for something else.
24683 Of course, if you can find a simpler example to report @emph{instead}
24684 of the original one, that is a convenience for us. Errors in the
24685 output will be easier to spot, running under the debugger will take
24686 less time, and so on.
24688 However, simplification is not vital; if you do not want to do this,
24689 report the bug anyway and send us the entire test case you used.
24692 A patch for the bug.
24694 A patch for the bug does help us if it is a good one. But do not omit
24695 the necessary information, such as the test case, on the assumption that
24696 a patch is all we need. We might see problems with your patch and decide
24697 to fix the problem another way, or we might not understand it at all.
24699 Sometimes with a program as complicated as @value{GDBN} it is very hard to
24700 construct an example that will make the program follow a certain path
24701 through the code. If you do not send us the example, we will not be able
24702 to construct one, so we will not be able to verify that the bug is fixed.
24704 And if we cannot understand what bug you are trying to fix, or why your
24705 patch should be an improvement, we will not install it. A test case will
24706 help us to understand.
24709 A guess about what the bug is or what it depends on.
24711 Such guesses are usually wrong. Even we cannot guess right about such
24712 things without first using the debugger to find the facts.
24715 @c The readline documentation is distributed with the readline code
24716 @c and consists of the two following files:
24718 @c inc-hist.texinfo
24719 @c Use -I with makeinfo to point to the appropriate directory,
24720 @c environment var TEXINPUTS with TeX.
24721 @include rluser.texi
24722 @include inc-hist.texinfo
24725 @node Formatting Documentation
24726 @appendix Formatting Documentation
24728 @cindex @value{GDBN} reference card
24729 @cindex reference card
24730 The @value{GDBN} 4 release includes an already-formatted reference card, ready
24731 for printing with PostScript or Ghostscript, in the @file{gdb}
24732 subdirectory of the main source directory@footnote{In
24733 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
24734 release.}. If you can use PostScript or Ghostscript with your printer,
24735 you can print the reference card immediately with @file{refcard.ps}.
24737 The release also includes the source for the reference card. You
24738 can format it, using @TeX{}, by typing:
24744 The @value{GDBN} reference card is designed to print in @dfn{landscape}
24745 mode on US ``letter'' size paper;
24746 that is, on a sheet 11 inches wide by 8.5 inches
24747 high. You will need to specify this form of printing as an option to
24748 your @sc{dvi} output program.
24750 @cindex documentation
24752 All the documentation for @value{GDBN} comes as part of the machine-readable
24753 distribution. The documentation is written in Texinfo format, which is
24754 a documentation system that uses a single source file to produce both
24755 on-line information and a printed manual. You can use one of the Info
24756 formatting commands to create the on-line version of the documentation
24757 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
24759 @value{GDBN} includes an already formatted copy of the on-line Info
24760 version of this manual in the @file{gdb} subdirectory. The main Info
24761 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
24762 subordinate files matching @samp{gdb.info*} in the same directory. If
24763 necessary, you can print out these files, or read them with any editor;
24764 but they are easier to read using the @code{info} subsystem in @sc{gnu}
24765 Emacs or the standalone @code{info} program, available as part of the
24766 @sc{gnu} Texinfo distribution.
24768 If you want to format these Info files yourself, you need one of the
24769 Info formatting programs, such as @code{texinfo-format-buffer} or
24772 If you have @code{makeinfo} installed, and are in the top level
24773 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
24774 version @value{GDBVN}), you can make the Info file by typing:
24781 If you want to typeset and print copies of this manual, you need @TeX{},
24782 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
24783 Texinfo definitions file.
24785 @TeX{} is a typesetting program; it does not print files directly, but
24786 produces output files called @sc{dvi} files. To print a typeset
24787 document, you need a program to print @sc{dvi} files. If your system
24788 has @TeX{} installed, chances are it has such a program. The precise
24789 command to use depends on your system; @kbd{lpr -d} is common; another
24790 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
24791 require a file name without any extension or a @samp{.dvi} extension.
24793 @TeX{} also requires a macro definitions file called
24794 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
24795 written in Texinfo format. On its own, @TeX{} cannot either read or
24796 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
24797 and is located in the @file{gdb-@var{version-number}/texinfo}
24800 If you have @TeX{} and a @sc{dvi} printer program installed, you can
24801 typeset and print this manual. First switch to the @file{gdb}
24802 subdirectory of the main source directory (for example, to
24803 @file{gdb-@value{GDBVN}/gdb}) and type:
24809 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
24811 @node Installing GDB
24812 @appendix Installing @value{GDBN}
24813 @cindex installation
24816 * Requirements:: Requirements for building @value{GDBN}
24817 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
24818 * Separate Objdir:: Compiling @value{GDBN} in another directory
24819 * Config Names:: Specifying names for hosts and targets
24820 * Configure Options:: Summary of options for configure
24821 * System-wide configuration:: Having a system-wide init file
24825 @section Requirements for Building @value{GDBN}
24826 @cindex building @value{GDBN}, requirements for
24828 Building @value{GDBN} requires various tools and packages to be available.
24829 Other packages will be used only if they are found.
24831 @heading Tools/Packages Necessary for Building @value{GDBN}
24833 @item ISO C90 compiler
24834 @value{GDBN} is written in ISO C90. It should be buildable with any
24835 working C90 compiler, e.g.@: GCC.
24839 @heading Tools/Packages Optional for Building @value{GDBN}
24843 @value{GDBN} can use the Expat XML parsing library. This library may be
24844 included with your operating system distribution; if it is not, you
24845 can get the latest version from @url{http://expat.sourceforge.net}.
24846 The @file{configure} script will search for this library in several
24847 standard locations; if it is installed in an unusual path, you can
24848 use the @option{--with-libexpat-prefix} option to specify its location.
24854 Remote protocol memory maps (@pxref{Memory Map Format})
24856 Target descriptions (@pxref{Target Descriptions})
24858 Remote shared library lists (@pxref{Library List Format})
24860 MS-Windows shared libraries (@pxref{Shared Libraries})
24864 @cindex compressed debug sections
24865 @value{GDBN} will use the @samp{zlib} library, if available, to read
24866 compressed debug sections. Some linkers, such as GNU gold, are capable
24867 of producing binaries with compressed debug sections. If @value{GDBN}
24868 is compiled with @samp{zlib}, it will be able to read the debug
24869 information in such binaries.
24871 The @samp{zlib} library is likely included with your operating system
24872 distribution; if it is not, you can get the latest version from
24873 @url{http://zlib.net}.
24876 @value{GDBN}'s features related to character sets (@pxref{Character
24877 Sets}) require a functioning @code{iconv} implementation. If you are
24878 on a GNU system, then this is provided by the GNU C Library. Some
24879 other systems also provide a working @code{iconv}.
24881 On systems with @code{iconv}, you can install GNU Libiconv. If you
24882 have previously installed Libiconv, you can use the
24883 @option{--with-libiconv-prefix} option to configure.
24885 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
24886 arrange to build Libiconv if a directory named @file{libiconv} appears
24887 in the top-most source directory. If Libiconv is built this way, and
24888 if the operating system does not provide a suitable @code{iconv}
24889 implementation, then the just-built library will automatically be used
24890 by @value{GDBN}. One easy way to set this up is to download GNU
24891 Libiconv, unpack it, and then rename the directory holding the
24892 Libiconv source code to @samp{libiconv}.
24895 @node Running Configure
24896 @section Invoking the @value{GDBN} @file{configure} Script
24897 @cindex configuring @value{GDBN}
24898 @value{GDBN} comes with a @file{configure} script that automates the process
24899 of preparing @value{GDBN} for installation; you can then use @code{make} to
24900 build the @code{gdb} program.
24902 @c irrelevant in info file; it's as current as the code it lives with.
24903 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
24904 look at the @file{README} file in the sources; we may have improved the
24905 installation procedures since publishing this manual.}
24908 The @value{GDBN} distribution includes all the source code you need for
24909 @value{GDBN} in a single directory, whose name is usually composed by
24910 appending the version number to @samp{gdb}.
24912 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
24913 @file{gdb-@value{GDBVN}} directory. That directory contains:
24916 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
24917 script for configuring @value{GDBN} and all its supporting libraries
24919 @item gdb-@value{GDBVN}/gdb
24920 the source specific to @value{GDBN} itself
24922 @item gdb-@value{GDBVN}/bfd
24923 source for the Binary File Descriptor library
24925 @item gdb-@value{GDBVN}/include
24926 @sc{gnu} include files
24928 @item gdb-@value{GDBVN}/libiberty
24929 source for the @samp{-liberty} free software library
24931 @item gdb-@value{GDBVN}/opcodes
24932 source for the library of opcode tables and disassemblers
24934 @item gdb-@value{GDBVN}/readline
24935 source for the @sc{gnu} command-line interface
24937 @item gdb-@value{GDBVN}/glob
24938 source for the @sc{gnu} filename pattern-matching subroutine
24940 @item gdb-@value{GDBVN}/mmalloc
24941 source for the @sc{gnu} memory-mapped malloc package
24944 The simplest way to configure and build @value{GDBN} is to run @file{configure}
24945 from the @file{gdb-@var{version-number}} source directory, which in
24946 this example is the @file{gdb-@value{GDBVN}} directory.
24948 First switch to the @file{gdb-@var{version-number}} source directory
24949 if you are not already in it; then run @file{configure}. Pass the
24950 identifier for the platform on which @value{GDBN} will run as an
24956 cd gdb-@value{GDBVN}
24957 ./configure @var{host}
24962 where @var{host} is an identifier such as @samp{sun4} or
24963 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
24964 (You can often leave off @var{host}; @file{configure} tries to guess the
24965 correct value by examining your system.)
24967 Running @samp{configure @var{host}} and then running @code{make} builds the
24968 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
24969 libraries, then @code{gdb} itself. The configured source files, and the
24970 binaries, are left in the corresponding source directories.
24973 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
24974 system does not recognize this automatically when you run a different
24975 shell, you may need to run @code{sh} on it explicitly:
24978 sh configure @var{host}
24981 If you run @file{configure} from a directory that contains source
24982 directories for multiple libraries or programs, such as the
24983 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
24985 creates configuration files for every directory level underneath (unless
24986 you tell it not to, with the @samp{--norecursion} option).
24988 You should run the @file{configure} script from the top directory in the
24989 source tree, the @file{gdb-@var{version-number}} directory. If you run
24990 @file{configure} from one of the subdirectories, you will configure only
24991 that subdirectory. That is usually not what you want. In particular,
24992 if you run the first @file{configure} from the @file{gdb} subdirectory
24993 of the @file{gdb-@var{version-number}} directory, you will omit the
24994 configuration of @file{bfd}, @file{readline}, and other sibling
24995 directories of the @file{gdb} subdirectory. This leads to build errors
24996 about missing include files such as @file{bfd/bfd.h}.
24998 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
24999 However, you should make sure that the shell on your path (named by
25000 the @samp{SHELL} environment variable) is publicly readable. Remember
25001 that @value{GDBN} uses the shell to start your program---some systems refuse to
25002 let @value{GDBN} debug child processes whose programs are not readable.
25004 @node Separate Objdir
25005 @section Compiling @value{GDBN} in Another Directory
25007 If you want to run @value{GDBN} versions for several host or target machines,
25008 you need a different @code{gdb} compiled for each combination of
25009 host and target. @file{configure} is designed to make this easy by
25010 allowing you to generate each configuration in a separate subdirectory,
25011 rather than in the source directory. If your @code{make} program
25012 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
25013 @code{make} in each of these directories builds the @code{gdb}
25014 program specified there.
25016 To build @code{gdb} in a separate directory, run @file{configure}
25017 with the @samp{--srcdir} option to specify where to find the source.
25018 (You also need to specify a path to find @file{configure}
25019 itself from your working directory. If the path to @file{configure}
25020 would be the same as the argument to @samp{--srcdir}, you can leave out
25021 the @samp{--srcdir} option; it is assumed.)
25023 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
25024 separate directory for a Sun 4 like this:
25028 cd gdb-@value{GDBVN}
25031 ../gdb-@value{GDBVN}/configure sun4
25036 When @file{configure} builds a configuration using a remote source
25037 directory, it creates a tree for the binaries with the same structure
25038 (and using the same names) as the tree under the source directory. In
25039 the example, you'd find the Sun 4 library @file{libiberty.a} in the
25040 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
25041 @file{gdb-sun4/gdb}.
25043 Make sure that your path to the @file{configure} script has just one
25044 instance of @file{gdb} in it. If your path to @file{configure} looks
25045 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
25046 one subdirectory of @value{GDBN}, not the whole package. This leads to
25047 build errors about missing include files such as @file{bfd/bfd.h}.
25049 One popular reason to build several @value{GDBN} configurations in separate
25050 directories is to configure @value{GDBN} for cross-compiling (where
25051 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
25052 programs that run on another machine---the @dfn{target}).
25053 You specify a cross-debugging target by
25054 giving the @samp{--target=@var{target}} option to @file{configure}.
25056 When you run @code{make} to build a program or library, you must run
25057 it in a configured directory---whatever directory you were in when you
25058 called @file{configure} (or one of its subdirectories).
25060 The @code{Makefile} that @file{configure} generates in each source
25061 directory also runs recursively. If you type @code{make} in a source
25062 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
25063 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
25064 will build all the required libraries, and then build GDB.
25066 When you have multiple hosts or targets configured in separate
25067 directories, you can run @code{make} on them in parallel (for example,
25068 if they are NFS-mounted on each of the hosts); they will not interfere
25072 @section Specifying Names for Hosts and Targets
25074 The specifications used for hosts and targets in the @file{configure}
25075 script are based on a three-part naming scheme, but some short predefined
25076 aliases are also supported. The full naming scheme encodes three pieces
25077 of information in the following pattern:
25080 @var{architecture}-@var{vendor}-@var{os}
25083 For example, you can use the alias @code{sun4} as a @var{host} argument,
25084 or as the value for @var{target} in a @code{--target=@var{target}}
25085 option. The equivalent full name is @samp{sparc-sun-sunos4}.
25087 The @file{configure} script accompanying @value{GDBN} does not provide
25088 any query facility to list all supported host and target names or
25089 aliases. @file{configure} calls the Bourne shell script
25090 @code{config.sub} to map abbreviations to full names; you can read the
25091 script, if you wish, or you can use it to test your guesses on
25092 abbreviations---for example:
25095 % sh config.sub i386-linux
25097 % sh config.sub alpha-linux
25098 alpha-unknown-linux-gnu
25099 % sh config.sub hp9k700
25101 % sh config.sub sun4
25102 sparc-sun-sunos4.1.1
25103 % sh config.sub sun3
25104 m68k-sun-sunos4.1.1
25105 % sh config.sub i986v
25106 Invalid configuration `i986v': machine `i986v' not recognized
25110 @code{config.sub} is also distributed in the @value{GDBN} source
25111 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
25113 @node Configure Options
25114 @section @file{configure} Options
25116 Here is a summary of the @file{configure} options and arguments that
25117 are most often useful for building @value{GDBN}. @file{configure} also has
25118 several other options not listed here. @inforef{What Configure
25119 Does,,configure.info}, for a full explanation of @file{configure}.
25122 configure @r{[}--help@r{]}
25123 @r{[}--prefix=@var{dir}@r{]}
25124 @r{[}--exec-prefix=@var{dir}@r{]}
25125 @r{[}--srcdir=@var{dirname}@r{]}
25126 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
25127 @r{[}--target=@var{target}@r{]}
25132 You may introduce options with a single @samp{-} rather than
25133 @samp{--} if you prefer; but you may abbreviate option names if you use
25138 Display a quick summary of how to invoke @file{configure}.
25140 @item --prefix=@var{dir}
25141 Configure the source to install programs and files under directory
25144 @item --exec-prefix=@var{dir}
25145 Configure the source to install programs under directory
25148 @c avoid splitting the warning from the explanation:
25150 @item --srcdir=@var{dirname}
25151 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
25152 @code{make} that implements the @code{VPATH} feature.}@*
25153 Use this option to make configurations in directories separate from the
25154 @value{GDBN} source directories. Among other things, you can use this to
25155 build (or maintain) several configurations simultaneously, in separate
25156 directories. @file{configure} writes configuration-specific files in
25157 the current directory, but arranges for them to use the source in the
25158 directory @var{dirname}. @file{configure} creates directories under
25159 the working directory in parallel to the source directories below
25162 @item --norecursion
25163 Configure only the directory level where @file{configure} is executed; do not
25164 propagate configuration to subdirectories.
25166 @item --target=@var{target}
25167 Configure @value{GDBN} for cross-debugging programs running on the specified
25168 @var{target}. Without this option, @value{GDBN} is configured to debug
25169 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
25171 There is no convenient way to generate a list of all available targets.
25173 @item @var{host} @dots{}
25174 Configure @value{GDBN} to run on the specified @var{host}.
25176 There is no convenient way to generate a list of all available hosts.
25179 There are many other options available as well, but they are generally
25180 needed for special purposes only.
25182 @node System-wide configuration
25183 @section System-wide configuration and settings
25184 @cindex system-wide init file
25186 @value{GDBN} can be configured to have a system-wide init file;
25187 this file will be read and executed at startup (@pxref{Startup, , What
25188 @value{GDBN} does during startup}).
25190 Here is the corresponding configure option:
25193 @item --with-system-gdbinit=@var{file}
25194 Specify that the default location of the system-wide init file is
25198 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
25199 it may be subject to relocation. Two possible cases:
25203 If the default location of this init file contains @file{$prefix},
25204 it will be subject to relocation. Suppose that the configure options
25205 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
25206 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
25207 init file is looked for as @file{$install/etc/gdbinit} instead of
25208 @file{$prefix/etc/gdbinit}.
25211 By contrast, if the default location does not contain the prefix,
25212 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
25213 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
25214 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
25215 wherever @value{GDBN} is installed.
25218 @node Maintenance Commands
25219 @appendix Maintenance Commands
25220 @cindex maintenance commands
25221 @cindex internal commands
25223 In addition to commands intended for @value{GDBN} users, @value{GDBN}
25224 includes a number of commands intended for @value{GDBN} developers,
25225 that are not documented elsewhere in this manual. These commands are
25226 provided here for reference. (For commands that turn on debugging
25227 messages, see @ref{Debugging Output}.)
25230 @kindex maint agent
25231 @item maint agent @var{expression}
25232 Translate the given @var{expression} into remote agent bytecodes.
25233 This command is useful for debugging the Agent Expression mechanism
25234 (@pxref{Agent Expressions}).
25236 @kindex maint info breakpoints
25237 @item @anchor{maint info breakpoints}maint info breakpoints
25238 Using the same format as @samp{info breakpoints}, display both the
25239 breakpoints you've set explicitly, and those @value{GDBN} is using for
25240 internal purposes. Internal breakpoints are shown with negative
25241 breakpoint numbers. The type column identifies what kind of breakpoint
25246 Normal, explicitly set breakpoint.
25249 Normal, explicitly set watchpoint.
25252 Internal breakpoint, used to handle correctly stepping through
25253 @code{longjmp} calls.
25255 @item longjmp resume
25256 Internal breakpoint at the target of a @code{longjmp}.
25259 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
25262 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
25265 Shared library events.
25269 @kindex set displaced-stepping
25270 @kindex show displaced-stepping
25271 @cindex displaced stepping support
25272 @cindex out-of-line single-stepping
25273 @item set displaced-stepping
25274 @itemx show displaced-stepping
25275 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
25276 if the target supports it. Displaced stepping is a way to single-step
25277 over breakpoints without removing them from the inferior, by executing
25278 an out-of-line copy of the instruction that was originally at the
25279 breakpoint location. It is also known as out-of-line single-stepping.
25282 @item set displaced-stepping on
25283 If the target architecture supports it, @value{GDBN} will use
25284 displaced stepping to step over breakpoints.
25286 @item set displaced-stepping off
25287 @value{GDBN} will not use displaced stepping to step over breakpoints,
25288 even if such is supported by the target architecture.
25290 @cindex non-stop mode, and @samp{set displaced-stepping}
25291 @item set displaced-stepping auto
25292 This is the default mode. @value{GDBN} will use displaced stepping
25293 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
25294 architecture supports displaced stepping.
25297 @kindex maint check-symtabs
25298 @item maint check-symtabs
25299 Check the consistency of psymtabs and symtabs.
25301 @kindex maint cplus first_component
25302 @item maint cplus first_component @var{name}
25303 Print the first C@t{++} class/namespace component of @var{name}.
25305 @kindex maint cplus namespace
25306 @item maint cplus namespace
25307 Print the list of possible C@t{++} namespaces.
25309 @kindex maint demangle
25310 @item maint demangle @var{name}
25311 Demangle a C@t{++} or Objective-C mangled @var{name}.
25313 @kindex maint deprecate
25314 @kindex maint undeprecate
25315 @cindex deprecated commands
25316 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
25317 @itemx maint undeprecate @var{command}
25318 Deprecate or undeprecate the named @var{command}. Deprecated commands
25319 cause @value{GDBN} to issue a warning when you use them. The optional
25320 argument @var{replacement} says which newer command should be used in
25321 favor of the deprecated one; if it is given, @value{GDBN} will mention
25322 the replacement as part of the warning.
25324 @kindex maint dump-me
25325 @item maint dump-me
25326 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
25327 Cause a fatal signal in the debugger and force it to dump its core.
25328 This is supported only on systems which support aborting a program
25329 with the @code{SIGQUIT} signal.
25331 @kindex maint internal-error
25332 @kindex maint internal-warning
25333 @item maint internal-error @r{[}@var{message-text}@r{]}
25334 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
25335 Cause @value{GDBN} to call the internal function @code{internal_error}
25336 or @code{internal_warning} and hence behave as though an internal error
25337 or internal warning has been detected. In addition to reporting the
25338 internal problem, these functions give the user the opportunity to
25339 either quit @value{GDBN} or create a core file of the current
25340 @value{GDBN} session.
25342 These commands take an optional parameter @var{message-text} that is
25343 used as the text of the error or warning message.
25345 Here's an example of using @code{internal-error}:
25348 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
25349 @dots{}/maint.c:121: internal-error: testing, 1, 2
25350 A problem internal to GDB has been detected. Further
25351 debugging may prove unreliable.
25352 Quit this debugging session? (y or n) @kbd{n}
25353 Create a core file? (y or n) @kbd{n}
25357 @cindex @value{GDBN} internal error
25358 @cindex internal errors, control of @value{GDBN} behavior
25360 @kindex maint set internal-error
25361 @kindex maint show internal-error
25362 @kindex maint set internal-warning
25363 @kindex maint show internal-warning
25364 @item maint set internal-error @var{action} [ask|yes|no]
25365 @itemx maint show internal-error @var{action}
25366 @itemx maint set internal-warning @var{action} [ask|yes|no]
25367 @itemx maint show internal-warning @var{action}
25368 When @value{GDBN} reports an internal problem (error or warning) it
25369 gives the user the opportunity to both quit @value{GDBN} and create a
25370 core file of the current @value{GDBN} session. These commands let you
25371 override the default behaviour for each particular @var{action},
25372 described in the table below.
25376 You can specify that @value{GDBN} should always (yes) or never (no)
25377 quit. The default is to ask the user what to do.
25380 You can specify that @value{GDBN} should always (yes) or never (no)
25381 create a core file. The default is to ask the user what to do.
25384 @kindex maint packet
25385 @item maint packet @var{text}
25386 If @value{GDBN} is talking to an inferior via the serial protocol,
25387 then this command sends the string @var{text} to the inferior, and
25388 displays the response packet. @value{GDBN} supplies the initial
25389 @samp{$} character, the terminating @samp{#} character, and the
25392 @kindex maint print architecture
25393 @item maint print architecture @r{[}@var{file}@r{]}
25394 Print the entire architecture configuration. The optional argument
25395 @var{file} names the file where the output goes.
25397 @kindex maint print c-tdesc
25398 @item maint print c-tdesc
25399 Print the current target description (@pxref{Target Descriptions}) as
25400 a C source file. The created source file can be used in @value{GDBN}
25401 when an XML parser is not available to parse the description.
25403 @kindex maint print dummy-frames
25404 @item maint print dummy-frames
25405 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
25408 (@value{GDBP}) @kbd{b add}
25410 (@value{GDBP}) @kbd{print add(2,3)}
25411 Breakpoint 2, add (a=2, b=3) at @dots{}
25413 The program being debugged stopped while in a function called from GDB.
25415 (@value{GDBP}) @kbd{maint print dummy-frames}
25416 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
25417 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
25418 call_lo=0x01014000 call_hi=0x01014001
25422 Takes an optional file parameter.
25424 @kindex maint print registers
25425 @kindex maint print raw-registers
25426 @kindex maint print cooked-registers
25427 @kindex maint print register-groups
25428 @item maint print registers @r{[}@var{file}@r{]}
25429 @itemx maint print raw-registers @r{[}@var{file}@r{]}
25430 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
25431 @itemx maint print register-groups @r{[}@var{file}@r{]}
25432 Print @value{GDBN}'s internal register data structures.
25434 The command @code{maint print raw-registers} includes the contents of
25435 the raw register cache; the command @code{maint print cooked-registers}
25436 includes the (cooked) value of all registers; and the command
25437 @code{maint print register-groups} includes the groups that each
25438 register is a member of. @xref{Registers,, Registers, gdbint,
25439 @value{GDBN} Internals}.
25441 These commands take an optional parameter, a file name to which to
25442 write the information.
25444 @kindex maint print reggroups
25445 @item maint print reggroups @r{[}@var{file}@r{]}
25446 Print @value{GDBN}'s internal register group data structures. The
25447 optional argument @var{file} tells to what file to write the
25450 The register groups info looks like this:
25453 (@value{GDBP}) @kbd{maint print reggroups}
25466 This command forces @value{GDBN} to flush its internal register cache.
25468 @kindex maint print objfiles
25469 @cindex info for known object files
25470 @item maint print objfiles
25471 Print a dump of all known object files. For each object file, this
25472 command prints its name, address in memory, and all of its psymtabs
25475 @kindex maint print statistics
25476 @cindex bcache statistics
25477 @item maint print statistics
25478 This command prints, for each object file in the program, various data
25479 about that object file followed by the byte cache (@dfn{bcache})
25480 statistics for the object file. The objfile data includes the number
25481 of minimal, partial, full, and stabs symbols, the number of types
25482 defined by the objfile, the number of as yet unexpanded psym tables,
25483 the number of line tables and string tables, and the amount of memory
25484 used by the various tables. The bcache statistics include the counts,
25485 sizes, and counts of duplicates of all and unique objects, max,
25486 average, and median entry size, total memory used and its overhead and
25487 savings, and various measures of the hash table size and chain
25490 @kindex maint print target-stack
25491 @cindex target stack description
25492 @item maint print target-stack
25493 A @dfn{target} is an interface between the debugger and a particular
25494 kind of file or process. Targets can be stacked in @dfn{strata},
25495 so that more than one target can potentially respond to a request.
25496 In particular, memory accesses will walk down the stack of targets
25497 until they find a target that is interested in handling that particular
25500 This command prints a short description of each layer that was pushed on
25501 the @dfn{target stack}, starting from the top layer down to the bottom one.
25503 @kindex maint print type
25504 @cindex type chain of a data type
25505 @item maint print type @var{expr}
25506 Print the type chain for a type specified by @var{expr}. The argument
25507 can be either a type name or a symbol. If it is a symbol, the type of
25508 that symbol is described. The type chain produced by this command is
25509 a recursive definition of the data type as stored in @value{GDBN}'s
25510 data structures, including its flags and contained types.
25512 @kindex maint set dwarf2 max-cache-age
25513 @kindex maint show dwarf2 max-cache-age
25514 @item maint set dwarf2 max-cache-age
25515 @itemx maint show dwarf2 max-cache-age
25516 Control the DWARF 2 compilation unit cache.
25518 @cindex DWARF 2 compilation units cache
25519 In object files with inter-compilation-unit references, such as those
25520 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
25521 reader needs to frequently refer to previously read compilation units.
25522 This setting controls how long a compilation unit will remain in the
25523 cache if it is not referenced. A higher limit means that cached
25524 compilation units will be stored in memory longer, and more total
25525 memory will be used. Setting it to zero disables caching, which will
25526 slow down @value{GDBN} startup, but reduce memory consumption.
25528 @kindex maint set profile
25529 @kindex maint show profile
25530 @cindex profiling GDB
25531 @item maint set profile
25532 @itemx maint show profile
25533 Control profiling of @value{GDBN}.
25535 Profiling will be disabled until you use the @samp{maint set profile}
25536 command to enable it. When you enable profiling, the system will begin
25537 collecting timing and execution count data; when you disable profiling or
25538 exit @value{GDBN}, the results will be written to a log file. Remember that
25539 if you use profiling, @value{GDBN} will overwrite the profiling log file
25540 (often called @file{gmon.out}). If you have a record of important profiling
25541 data in a @file{gmon.out} file, be sure to move it to a safe location.
25543 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
25544 compiled with the @samp{-pg} compiler option.
25546 @kindex maint show-debug-regs
25547 @cindex x86 hardware debug registers
25548 @item maint show-debug-regs
25549 Control whether to show variables that mirror the x86 hardware debug
25550 registers. Use @code{ON} to enable, @code{OFF} to disable. If
25551 enabled, the debug registers values are shown when @value{GDBN} inserts or
25552 removes a hardware breakpoint or watchpoint, and when the inferior
25553 triggers a hardware-assisted breakpoint or watchpoint.
25555 @kindex maint space
25556 @cindex memory used by commands
25558 Control whether to display memory usage for each command. If set to a
25559 nonzero value, @value{GDBN} will display how much memory each command
25560 took, following the command's own output. This can also be requested
25561 by invoking @value{GDBN} with the @option{--statistics} command-line
25562 switch (@pxref{Mode Options}).
25565 @cindex time of command execution
25567 Control whether to display the execution time for each command. If
25568 set to a nonzero value, @value{GDBN} will display how much time it
25569 took to execute each command, following the command's own output.
25570 The time is not printed for the commands that run the target, since
25571 there's no mechanism currently to compute how much time was spend
25572 by @value{GDBN} and how much time was spend by the program been debugged.
25573 it's not possibly currently
25574 This can also be requested by invoking @value{GDBN} with the
25575 @option{--statistics} command-line switch (@pxref{Mode Options}).
25577 @kindex maint translate-address
25578 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
25579 Find the symbol stored at the location specified by the address
25580 @var{addr} and an optional section name @var{section}. If found,
25581 @value{GDBN} prints the name of the closest symbol and an offset from
25582 the symbol's location to the specified address. This is similar to
25583 the @code{info address} command (@pxref{Symbols}), except that this
25584 command also allows to find symbols in other sections.
25586 If section was not specified, the section in which the symbol was found
25587 is also printed. For dynamically linked executables, the name of
25588 executable or shared library containing the symbol is printed as well.
25592 The following command is useful for non-interactive invocations of
25593 @value{GDBN}, such as in the test suite.
25596 @item set watchdog @var{nsec}
25597 @kindex set watchdog
25598 @cindex watchdog timer
25599 @cindex timeout for commands
25600 Set the maximum number of seconds @value{GDBN} will wait for the
25601 target operation to finish. If this time expires, @value{GDBN}
25602 reports and error and the command is aborted.
25604 @item show watchdog
25605 Show the current setting of the target wait timeout.
25608 @node Remote Protocol
25609 @appendix @value{GDBN} Remote Serial Protocol
25614 * Stop Reply Packets::
25615 * General Query Packets::
25616 * Register Packet Format::
25617 * Tracepoint Packets::
25618 * Host I/O Packets::
25620 * Notification Packets::
25621 * Remote Non-Stop::
25622 * Packet Acknowledgment::
25624 * File-I/O Remote Protocol Extension::
25625 * Library List Format::
25626 * Memory Map Format::
25632 There may be occasions when you need to know something about the
25633 protocol---for example, if there is only one serial port to your target
25634 machine, you might want your program to do something special if it
25635 recognizes a packet meant for @value{GDBN}.
25637 In the examples below, @samp{->} and @samp{<-} are used to indicate
25638 transmitted and received data, respectively.
25640 @cindex protocol, @value{GDBN} remote serial
25641 @cindex serial protocol, @value{GDBN} remote
25642 @cindex remote serial protocol
25643 All @value{GDBN} commands and responses (other than acknowledgments
25644 and notifications, see @ref{Notification Packets}) are sent as a
25645 @var{packet}. A @var{packet} is introduced with the character
25646 @samp{$}, the actual @var{packet-data}, and the terminating character
25647 @samp{#} followed by a two-digit @var{checksum}:
25650 @code{$}@var{packet-data}@code{#}@var{checksum}
25654 @cindex checksum, for @value{GDBN} remote
25656 The two-digit @var{checksum} is computed as the modulo 256 sum of all
25657 characters between the leading @samp{$} and the trailing @samp{#} (an
25658 eight bit unsigned checksum).
25660 Implementors should note that prior to @value{GDBN} 5.0 the protocol
25661 specification also included an optional two-digit @var{sequence-id}:
25664 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
25667 @cindex sequence-id, for @value{GDBN} remote
25669 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
25670 has never output @var{sequence-id}s. Stubs that handle packets added
25671 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
25673 When either the host or the target machine receives a packet, the first
25674 response expected is an acknowledgment: either @samp{+} (to indicate
25675 the package was received correctly) or @samp{-} (to request
25679 -> @code{$}@var{packet-data}@code{#}@var{checksum}
25684 The @samp{+}/@samp{-} acknowledgments can be disabled
25685 once a connection is established.
25686 @xref{Packet Acknowledgment}, for details.
25688 The host (@value{GDBN}) sends @var{command}s, and the target (the
25689 debugging stub incorporated in your program) sends a @var{response}. In
25690 the case of step and continue @var{command}s, the response is only sent
25691 when the operation has completed, and the target has again stopped all
25692 threads in all attached processes. This is the default all-stop mode
25693 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
25694 execution mode; see @ref{Remote Non-Stop}, for details.
25696 @var{packet-data} consists of a sequence of characters with the
25697 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
25700 @cindex remote protocol, field separator
25701 Fields within the packet should be separated using @samp{,} @samp{;} or
25702 @samp{:}. Except where otherwise noted all numbers are represented in
25703 @sc{hex} with leading zeros suppressed.
25705 Implementors should note that prior to @value{GDBN} 5.0, the character
25706 @samp{:} could not appear as the third character in a packet (as it
25707 would potentially conflict with the @var{sequence-id}).
25709 @cindex remote protocol, binary data
25710 @anchor{Binary Data}
25711 Binary data in most packets is encoded either as two hexadecimal
25712 digits per byte of binary data. This allowed the traditional remote
25713 protocol to work over connections which were only seven-bit clean.
25714 Some packets designed more recently assume an eight-bit clean
25715 connection, and use a more efficient encoding to send and receive
25718 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
25719 as an escape character. Any escaped byte is transmitted as the escape
25720 character followed by the original character XORed with @code{0x20}.
25721 For example, the byte @code{0x7d} would be transmitted as the two
25722 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
25723 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
25724 @samp{@}}) must always be escaped. Responses sent by the stub
25725 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
25726 is not interpreted as the start of a run-length encoded sequence
25729 Response @var{data} can be run-length encoded to save space.
25730 Run-length encoding replaces runs of identical characters with one
25731 instance of the repeated character, followed by a @samp{*} and a
25732 repeat count. The repeat count is itself sent encoded, to avoid
25733 binary characters in @var{data}: a value of @var{n} is sent as
25734 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
25735 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
25736 code 32) for a repeat count of 3. (This is because run-length
25737 encoding starts to win for counts 3 or more.) Thus, for example,
25738 @samp{0* } is a run-length encoding of ``0000'': the space character
25739 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
25742 The printable characters @samp{#} and @samp{$} or with a numeric value
25743 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
25744 seven repeats (@samp{$}) can be expanded using a repeat count of only
25745 five (@samp{"}). For example, @samp{00000000} can be encoded as
25748 The error response returned for some packets includes a two character
25749 error number. That number is not well defined.
25751 @cindex empty response, for unsupported packets
25752 For any @var{command} not supported by the stub, an empty response
25753 (@samp{$#00}) should be returned. That way it is possible to extend the
25754 protocol. A newer @value{GDBN} can tell if a packet is supported based
25757 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
25758 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
25764 The following table provides a complete list of all currently defined
25765 @var{command}s and their corresponding response @var{data}.
25766 @xref{File-I/O Remote Protocol Extension}, for details about the File
25767 I/O extension of the remote protocol.
25769 Each packet's description has a template showing the packet's overall
25770 syntax, followed by an explanation of the packet's meaning. We
25771 include spaces in some of the templates for clarity; these are not
25772 part of the packet's syntax. No @value{GDBN} packet uses spaces to
25773 separate its components. For example, a template like @samp{foo
25774 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
25775 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
25776 @var{baz}. @value{GDBN} does not transmit a space character between the
25777 @samp{foo} and the @var{bar}, or between the @var{bar} and the
25780 @cindex @var{thread-id}, in remote protocol
25781 @anchor{thread-id syntax}
25782 Several packets and replies include a @var{thread-id} field to identify
25783 a thread. Normally these are positive numbers with a target-specific
25784 interpretation, formatted as big-endian hex strings. A @var{thread-id}
25785 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
25788 In addition, the remote protocol supports a multiprocess feature in
25789 which the @var{thread-id} syntax is extended to optionally include both
25790 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
25791 The @var{pid} (process) and @var{tid} (thread) components each have the
25792 format described above: a positive number with target-specific
25793 interpretation formatted as a big-endian hex string, literal @samp{-1}
25794 to indicate all processes or threads (respectively), or @samp{0} to
25795 indicate an arbitrary process or thread. Specifying just a process, as
25796 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
25797 error to specify all processes but a specific thread, such as
25798 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
25799 for those packets and replies explicitly documented to include a process
25800 ID, rather than a @var{thread-id}.
25802 The multiprocess @var{thread-id} syntax extensions are only used if both
25803 @value{GDBN} and the stub report support for the @samp{multiprocess}
25804 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
25807 Note that all packet forms beginning with an upper- or lower-case
25808 letter, other than those described here, are reserved for future use.
25810 Here are the packet descriptions.
25815 @cindex @samp{!} packet
25816 @anchor{extended mode}
25817 Enable extended mode. In extended mode, the remote server is made
25818 persistent. The @samp{R} packet is used to restart the program being
25824 The remote target both supports and has enabled extended mode.
25828 @cindex @samp{?} packet
25829 Indicate the reason the target halted. The reply is the same as for
25830 step and continue. This packet has a special interpretation when the
25831 target is in non-stop mode; see @ref{Remote Non-Stop}.
25834 @xref{Stop Reply Packets}, for the reply specifications.
25836 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
25837 @cindex @samp{A} packet
25838 Initialized @code{argv[]} array passed into program. @var{arglen}
25839 specifies the number of bytes in the hex encoded byte stream
25840 @var{arg}. See @code{gdbserver} for more details.
25845 The arguments were set.
25851 @cindex @samp{b} packet
25852 (Don't use this packet; its behavior is not well-defined.)
25853 Change the serial line speed to @var{baud}.
25855 JTC: @emph{When does the transport layer state change? When it's
25856 received, or after the ACK is transmitted. In either case, there are
25857 problems if the command or the acknowledgment packet is dropped.}
25859 Stan: @emph{If people really wanted to add something like this, and get
25860 it working for the first time, they ought to modify ser-unix.c to send
25861 some kind of out-of-band message to a specially-setup stub and have the
25862 switch happen "in between" packets, so that from remote protocol's point
25863 of view, nothing actually happened.}
25865 @item B @var{addr},@var{mode}
25866 @cindex @samp{B} packet
25867 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
25868 breakpoint at @var{addr}.
25870 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
25871 (@pxref{insert breakpoint or watchpoint packet}).
25874 @cindex @samp{bc} packet
25875 Backward continue. Execute the target system in reverse. No parameter.
25876 @xref{Reverse Execution}, for more information.
25879 @xref{Stop Reply Packets}, for the reply specifications.
25882 @cindex @samp{bs} packet
25883 Backward single step. Execute one instruction in reverse. No parameter.
25884 @xref{Reverse Execution}, for more information.
25887 @xref{Stop Reply Packets}, for the reply specifications.
25889 @item c @r{[}@var{addr}@r{]}
25890 @cindex @samp{c} packet
25891 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
25892 resume at current address.
25895 @xref{Stop Reply Packets}, for the reply specifications.
25897 @item C @var{sig}@r{[};@var{addr}@r{]}
25898 @cindex @samp{C} packet
25899 Continue with signal @var{sig} (hex signal number). If
25900 @samp{;@var{addr}} is omitted, resume at same address.
25903 @xref{Stop Reply Packets}, for the reply specifications.
25906 @cindex @samp{d} packet
25909 Don't use this packet; instead, define a general set packet
25910 (@pxref{General Query Packets}).
25914 @cindex @samp{D} packet
25915 The first form of the packet is used to detach @value{GDBN} from the
25916 remote system. It is sent to the remote target
25917 before @value{GDBN} disconnects via the @code{detach} command.
25919 The second form, including a process ID, is used when multiprocess
25920 protocol extensions are enabled (@pxref{multiprocess extensions}), to
25921 detach only a specific process. The @var{pid} is specified as a
25922 big-endian hex string.
25932 @item F @var{RC},@var{EE},@var{CF};@var{XX}
25933 @cindex @samp{F} packet
25934 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
25935 This is part of the File-I/O protocol extension. @xref{File-I/O
25936 Remote Protocol Extension}, for the specification.
25939 @anchor{read registers packet}
25940 @cindex @samp{g} packet
25941 Read general registers.
25945 @item @var{XX@dots{}}
25946 Each byte of register data is described by two hex digits. The bytes
25947 with the register are transmitted in target byte order. The size of
25948 each register and their position within the @samp{g} packet are
25949 determined by the @value{GDBN} internal gdbarch functions
25950 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
25951 specification of several standard @samp{g} packets is specified below.
25956 @item G @var{XX@dots{}}
25957 @cindex @samp{G} packet
25958 Write general registers. @xref{read registers packet}, for a
25959 description of the @var{XX@dots{}} data.
25969 @item H @var{c} @var{thread-id}
25970 @cindex @samp{H} packet
25971 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
25972 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
25973 should be @samp{c} for step and continue operations, @samp{g} for other
25974 operations. The thread designator @var{thread-id} has the format and
25975 interpretation described in @ref{thread-id syntax}.
25986 @c 'H': How restrictive (or permissive) is the thread model. If a
25987 @c thread is selected and stopped, are other threads allowed
25988 @c to continue to execute? As I mentioned above, I think the
25989 @c semantics of each command when a thread is selected must be
25990 @c described. For example:
25992 @c 'g': If the stub supports threads and a specific thread is
25993 @c selected, returns the register block from that thread;
25994 @c otherwise returns current registers.
25996 @c 'G' If the stub supports threads and a specific thread is
25997 @c selected, sets the registers of the register block of
25998 @c that thread; otherwise sets current registers.
26000 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
26001 @anchor{cycle step packet}
26002 @cindex @samp{i} packet
26003 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
26004 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
26005 step starting at that address.
26008 @cindex @samp{I} packet
26009 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
26013 @cindex @samp{k} packet
26016 FIXME: @emph{There is no description of how to operate when a specific
26017 thread context has been selected (i.e.@: does 'k' kill only that
26020 @item m @var{addr},@var{length}
26021 @cindex @samp{m} packet
26022 Read @var{length} bytes of memory starting at address @var{addr}.
26023 Note that @var{addr} may not be aligned to any particular boundary.
26025 The stub need not use any particular size or alignment when gathering
26026 data from memory for the response; even if @var{addr} is word-aligned
26027 and @var{length} is a multiple of the word size, the stub is free to
26028 use byte accesses, or not. For this reason, this packet may not be
26029 suitable for accessing memory-mapped I/O devices.
26030 @cindex alignment of remote memory accesses
26031 @cindex size of remote memory accesses
26032 @cindex memory, alignment and size of remote accesses
26036 @item @var{XX@dots{}}
26037 Memory contents; each byte is transmitted as a two-digit hexadecimal
26038 number. The reply may contain fewer bytes than requested if the
26039 server was able to read only part of the region of memory.
26044 @item M @var{addr},@var{length}:@var{XX@dots{}}
26045 @cindex @samp{M} packet
26046 Write @var{length} bytes of memory starting at address @var{addr}.
26047 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
26048 hexadecimal number.
26055 for an error (this includes the case where only part of the data was
26060 @cindex @samp{p} packet
26061 Read the value of register @var{n}; @var{n} is in hex.
26062 @xref{read registers packet}, for a description of how the returned
26063 register value is encoded.
26067 @item @var{XX@dots{}}
26068 the register's value
26072 Indicating an unrecognized @var{query}.
26075 @item P @var{n@dots{}}=@var{r@dots{}}
26076 @anchor{write register packet}
26077 @cindex @samp{P} packet
26078 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
26079 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
26080 digits for each byte in the register (target byte order).
26090 @item q @var{name} @var{params}@dots{}
26091 @itemx Q @var{name} @var{params}@dots{}
26092 @cindex @samp{q} packet
26093 @cindex @samp{Q} packet
26094 General query (@samp{q}) and set (@samp{Q}). These packets are
26095 described fully in @ref{General Query Packets}.
26098 @cindex @samp{r} packet
26099 Reset the entire system.
26101 Don't use this packet; use the @samp{R} packet instead.
26104 @cindex @samp{R} packet
26105 Restart the program being debugged. @var{XX}, while needed, is ignored.
26106 This packet is only available in extended mode (@pxref{extended mode}).
26108 The @samp{R} packet has no reply.
26110 @item s @r{[}@var{addr}@r{]}
26111 @cindex @samp{s} packet
26112 Single step. @var{addr} is the address at which to resume. If
26113 @var{addr} is omitted, resume at same address.
26116 @xref{Stop Reply Packets}, for the reply specifications.
26118 @item S @var{sig}@r{[};@var{addr}@r{]}
26119 @anchor{step with signal packet}
26120 @cindex @samp{S} packet
26121 Step with signal. This is analogous to the @samp{C} packet, but
26122 requests a single-step, rather than a normal resumption of execution.
26125 @xref{Stop Reply Packets}, for the reply specifications.
26127 @item t @var{addr}:@var{PP},@var{MM}
26128 @cindex @samp{t} packet
26129 Search backwards starting at address @var{addr} for a match with pattern
26130 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
26131 @var{addr} must be at least 3 digits.
26133 @item T @var{thread-id}
26134 @cindex @samp{T} packet
26135 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
26140 thread is still alive
26146 Packets starting with @samp{v} are identified by a multi-letter name,
26147 up to the first @samp{;} or @samp{?} (or the end of the packet).
26149 @item vAttach;@var{pid}
26150 @cindex @samp{vAttach} packet
26151 Attach to a new process with the specified process ID @var{pid}.
26152 The process ID is a
26153 hexadecimal integer identifying the process. In all-stop mode, all
26154 threads in the attached process are stopped; in non-stop mode, it may be
26155 attached without being stopped if that is supported by the target.
26157 @c In non-stop mode, on a successful vAttach, the stub should set the
26158 @c current thread to a thread of the newly-attached process. After
26159 @c attaching, GDB queries for the attached process's thread ID with qC.
26160 @c Also note that, from a user perspective, whether or not the
26161 @c target is stopped on attach in non-stop mode depends on whether you
26162 @c use the foreground or background version of the attach command, not
26163 @c on what vAttach does; GDB does the right thing with respect to either
26164 @c stopping or restarting threads.
26166 This packet is only available in extended mode (@pxref{extended mode}).
26172 @item @r{Any stop packet}
26173 for success in all-stop mode (@pxref{Stop Reply Packets})
26175 for success in non-stop mode (@pxref{Remote Non-Stop})
26178 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
26179 @cindex @samp{vCont} packet
26180 Resume the inferior, specifying different actions for each thread.
26181 If an action is specified with no @var{thread-id}, then it is applied to any
26182 threads that don't have a specific action specified; if no default action is
26183 specified then other threads should remain stopped in all-stop mode and
26184 in their current state in non-stop mode.
26185 Specifying multiple
26186 default actions is an error; specifying no actions is also an error.
26187 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
26189 Currently supported actions are:
26195 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
26199 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
26203 Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
26206 The optional argument @var{addr} normally associated with the
26207 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
26208 not supported in @samp{vCont}.
26210 The @samp{t} and @samp{T} actions are only relevant in non-stop mode
26211 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
26212 A stop reply should be generated for any affected thread not already stopped.
26213 When a thread is stopped by means of a @samp{t} action,
26214 the corresponding stop reply should indicate that the thread has stopped with
26215 signal @samp{0}, regardless of whether the target uses some other signal
26216 as an implementation detail.
26219 @xref{Stop Reply Packets}, for the reply specifications.
26222 @cindex @samp{vCont?} packet
26223 Request a list of actions supported by the @samp{vCont} packet.
26227 @item vCont@r{[};@var{action}@dots{}@r{]}
26228 The @samp{vCont} packet is supported. Each @var{action} is a supported
26229 command in the @samp{vCont} packet.
26231 The @samp{vCont} packet is not supported.
26234 @item vFile:@var{operation}:@var{parameter}@dots{}
26235 @cindex @samp{vFile} packet
26236 Perform a file operation on the target system. For details,
26237 see @ref{Host I/O Packets}.
26239 @item vFlashErase:@var{addr},@var{length}
26240 @cindex @samp{vFlashErase} packet
26241 Direct the stub to erase @var{length} bytes of flash starting at
26242 @var{addr}. The region may enclose any number of flash blocks, but
26243 its start and end must fall on block boundaries, as indicated by the
26244 flash block size appearing in the memory map (@pxref{Memory Map
26245 Format}). @value{GDBN} groups flash memory programming operations
26246 together, and sends a @samp{vFlashDone} request after each group; the
26247 stub is allowed to delay erase operation until the @samp{vFlashDone}
26248 packet is received.
26250 The stub must support @samp{vCont} if it reports support for
26251 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
26252 this case @samp{vCont} actions can be specified to apply to all threads
26253 in a process by using the @samp{p@var{pid}.-1} form of the
26264 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
26265 @cindex @samp{vFlashWrite} packet
26266 Direct the stub to write data to flash address @var{addr}. The data
26267 is passed in binary form using the same encoding as for the @samp{X}
26268 packet (@pxref{Binary Data}). The memory ranges specified by
26269 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
26270 not overlap, and must appear in order of increasing addresses
26271 (although @samp{vFlashErase} packets for higher addresses may already
26272 have been received; the ordering is guaranteed only between
26273 @samp{vFlashWrite} packets). If a packet writes to an address that was
26274 neither erased by a preceding @samp{vFlashErase} packet nor by some other
26275 target-specific method, the results are unpredictable.
26283 for vFlashWrite addressing non-flash memory
26289 @cindex @samp{vFlashDone} packet
26290 Indicate to the stub that flash programming operation is finished.
26291 The stub is permitted to delay or batch the effects of a group of
26292 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
26293 @samp{vFlashDone} packet is received. The contents of the affected
26294 regions of flash memory are unpredictable until the @samp{vFlashDone}
26295 request is completed.
26297 @item vKill;@var{pid}
26298 @cindex @samp{vKill} packet
26299 Kill the process with the specified process ID. @var{pid} is a
26300 hexadecimal integer identifying the process. This packet is used in
26301 preference to @samp{k} when multiprocess protocol extensions are
26302 supported; see @ref{multiprocess extensions}.
26312 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
26313 @cindex @samp{vRun} packet
26314 Run the program @var{filename}, passing it each @var{argument} on its
26315 command line. The file and arguments are hex-encoded strings. If
26316 @var{filename} is an empty string, the stub may use a default program
26317 (e.g.@: the last program run). The program is created in the stopped
26320 @c FIXME: What about non-stop mode?
26322 This packet is only available in extended mode (@pxref{extended mode}).
26328 @item @r{Any stop packet}
26329 for success (@pxref{Stop Reply Packets})
26333 @anchor{vStopped packet}
26334 @cindex @samp{vStopped} packet
26336 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
26337 reply and prompt for the stub to report another one.
26341 @item @r{Any stop packet}
26342 if there is another unreported stop event (@pxref{Stop Reply Packets})
26344 if there are no unreported stop events
26347 @item X @var{addr},@var{length}:@var{XX@dots{}}
26349 @cindex @samp{X} packet
26350 Write data to memory, where the data is transmitted in binary.
26351 @var{addr} is address, @var{length} is number of bytes,
26352 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
26362 @item z @var{type},@var{addr},@var{length}
26363 @itemx Z @var{type},@var{addr},@var{length}
26364 @anchor{insert breakpoint or watchpoint packet}
26365 @cindex @samp{z} packet
26366 @cindex @samp{Z} packets
26367 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
26368 watchpoint starting at address @var{address} and covering the next
26369 @var{length} bytes.
26371 Each breakpoint and watchpoint packet @var{type} is documented
26374 @emph{Implementation notes: A remote target shall return an empty string
26375 for an unrecognized breakpoint or watchpoint packet @var{type}. A
26376 remote target shall support either both or neither of a given
26377 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
26378 avoid potential problems with duplicate packets, the operations should
26379 be implemented in an idempotent way.}
26381 @item z0,@var{addr},@var{length}
26382 @itemx Z0,@var{addr},@var{length}
26383 @cindex @samp{z0} packet
26384 @cindex @samp{Z0} packet
26385 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
26386 @var{addr} of size @var{length}.
26388 A memory breakpoint is implemented by replacing the instruction at
26389 @var{addr} with a software breakpoint or trap instruction. The
26390 @var{length} is used by targets that indicates the size of the
26391 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
26392 @sc{mips} can insert either a 2 or 4 byte breakpoint).
26394 @emph{Implementation note: It is possible for a target to copy or move
26395 code that contains memory breakpoints (e.g., when implementing
26396 overlays). The behavior of this packet, in the presence of such a
26397 target, is not defined.}
26409 @item z1,@var{addr},@var{length}
26410 @itemx Z1,@var{addr},@var{length}
26411 @cindex @samp{z1} packet
26412 @cindex @samp{Z1} packet
26413 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
26414 address @var{addr} of size @var{length}.
26416 A hardware breakpoint is implemented using a mechanism that is not
26417 dependant on being able to modify the target's memory.
26419 @emph{Implementation note: A hardware breakpoint is not affected by code
26432 @item z2,@var{addr},@var{length}
26433 @itemx Z2,@var{addr},@var{length}
26434 @cindex @samp{z2} packet
26435 @cindex @samp{Z2} packet
26436 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
26448 @item z3,@var{addr},@var{length}
26449 @itemx Z3,@var{addr},@var{length}
26450 @cindex @samp{z3} packet
26451 @cindex @samp{Z3} packet
26452 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
26464 @item z4,@var{addr},@var{length}
26465 @itemx Z4,@var{addr},@var{length}
26466 @cindex @samp{z4} packet
26467 @cindex @samp{Z4} packet
26468 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
26482 @node Stop Reply Packets
26483 @section Stop Reply Packets
26484 @cindex stop reply packets
26486 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
26487 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
26488 receive any of the below as a reply. Except for @samp{?}
26489 and @samp{vStopped}, that reply is only returned
26490 when the target halts. In the below the exact meaning of @dfn{signal
26491 number} is defined by the header @file{include/gdb/signals.h} in the
26492 @value{GDBN} source code.
26494 As in the description of request packets, we include spaces in the
26495 reply templates for clarity; these are not part of the reply packet's
26496 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
26502 The program received signal number @var{AA} (a two-digit hexadecimal
26503 number). This is equivalent to a @samp{T} response with no
26504 @var{n}:@var{r} pairs.
26506 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
26507 @cindex @samp{T} packet reply
26508 The program received signal number @var{AA} (a two-digit hexadecimal
26509 number). This is equivalent to an @samp{S} response, except that the
26510 @samp{@var{n}:@var{r}} pairs can carry values of important registers
26511 and other information directly in the stop reply packet, reducing
26512 round-trip latency. Single-step and breakpoint traps are reported
26513 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
26517 If @var{n} is a hexadecimal number, it is a register number, and the
26518 corresponding @var{r} gives that register's value. @var{r} is a
26519 series of bytes in target byte order, with each byte given by a
26520 two-digit hex number.
26523 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
26524 the stopped thread, as specified in @ref{thread-id syntax}.
26527 If @var{n} is a recognized @dfn{stop reason}, it describes a more
26528 specific event that stopped the target. The currently defined stop
26529 reasons are listed below. @var{aa} should be @samp{05}, the trap
26530 signal. At most one stop reason should be present.
26533 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
26534 and go on to the next; this allows us to extend the protocol in the
26538 The currently defined stop reasons are:
26544 The packet indicates a watchpoint hit, and @var{r} is the data address, in
26547 @cindex shared library events, remote reply
26549 The packet indicates that the loaded libraries have changed.
26550 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
26551 list of loaded libraries. @var{r} is ignored.
26553 @cindex replay log events, remote reply
26555 The packet indicates that the target cannot continue replaying
26556 logged execution events, because it has reached the end (or the
26557 beginning when executing backward) of the log. The value of @var{r}
26558 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
26559 for more information.
26565 @itemx W @var{AA} ; process:@var{pid}
26566 The process exited, and @var{AA} is the exit status. This is only
26567 applicable to certain targets.
26569 The second form of the response, including the process ID of the exited
26570 process, can be used only when @value{GDBN} has reported support for
26571 multiprocess protocol extensions; see @ref{multiprocess extensions}.
26572 The @var{pid} is formatted as a big-endian hex string.
26575 @itemx X @var{AA} ; process:@var{pid}
26576 The process terminated with signal @var{AA}.
26578 The second form of the response, including the process ID of the
26579 terminated process, can be used only when @value{GDBN} has reported
26580 support for multiprocess protocol extensions; see @ref{multiprocess
26581 extensions}. The @var{pid} is formatted as a big-endian hex string.
26583 @item O @var{XX}@dots{}
26584 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
26585 written as the program's console output. This can happen at any time
26586 while the program is running and the debugger should continue to wait
26587 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
26589 @item F @var{call-id},@var{parameter}@dots{}
26590 @var{call-id} is the identifier which says which host system call should
26591 be called. This is just the name of the function. Translation into the
26592 correct system call is only applicable as it's defined in @value{GDBN}.
26593 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
26596 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
26597 this very system call.
26599 The target replies with this packet when it expects @value{GDBN} to
26600 call a host system call on behalf of the target. @value{GDBN} replies
26601 with an appropriate @samp{F} packet and keeps up waiting for the next
26602 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
26603 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
26604 Protocol Extension}, for more details.
26608 @node General Query Packets
26609 @section General Query Packets
26610 @cindex remote query requests
26612 Packets starting with @samp{q} are @dfn{general query packets};
26613 packets starting with @samp{Q} are @dfn{general set packets}. General
26614 query and set packets are a semi-unified form for retrieving and
26615 sending information to and from the stub.
26617 The initial letter of a query or set packet is followed by a name
26618 indicating what sort of thing the packet applies to. For example,
26619 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
26620 definitions with the stub. These packet names follow some
26625 The name must not contain commas, colons or semicolons.
26627 Most @value{GDBN} query and set packets have a leading upper case
26630 The names of custom vendor packets should use a company prefix, in
26631 lower case, followed by a period. For example, packets designed at
26632 the Acme Corporation might begin with @samp{qacme.foo} (for querying
26633 foos) or @samp{Qacme.bar} (for setting bars).
26636 The name of a query or set packet should be separated from any
26637 parameters by a @samp{:}; the parameters themselves should be
26638 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
26639 full packet name, and check for a separator or the end of the packet,
26640 in case two packet names share a common prefix. New packets should not begin
26641 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
26642 packets predate these conventions, and have arguments without any terminator
26643 for the packet name; we suspect they are in widespread use in places that
26644 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
26645 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
26648 Like the descriptions of the other packets, each description here
26649 has a template showing the packet's overall syntax, followed by an
26650 explanation of the packet's meaning. We include spaces in some of the
26651 templates for clarity; these are not part of the packet's syntax. No
26652 @value{GDBN} packet uses spaces to separate its components.
26654 Here are the currently defined query and set packets:
26659 @cindex current thread, remote request
26660 @cindex @samp{qC} packet
26661 Return the current thread ID.
26665 @item QC @var{thread-id}
26666 Where @var{thread-id} is a thread ID as documented in
26667 @ref{thread-id syntax}.
26668 @item @r{(anything else)}
26669 Any other reply implies the old thread ID.
26672 @item qCRC:@var{addr},@var{length}
26673 @cindex CRC of memory block, remote request
26674 @cindex @samp{qCRC} packet
26675 Compute the CRC checksum of a block of memory.
26679 An error (such as memory fault)
26680 @item C @var{crc32}
26681 The specified memory region's checksum is @var{crc32}.
26685 @itemx qsThreadInfo
26686 @cindex list active threads, remote request
26687 @cindex @samp{qfThreadInfo} packet
26688 @cindex @samp{qsThreadInfo} packet
26689 Obtain a list of all active thread IDs from the target (OS). Since there
26690 may be too many active threads to fit into one reply packet, this query
26691 works iteratively: it may require more than one query/reply sequence to
26692 obtain the entire list of threads. The first query of the sequence will
26693 be the @samp{qfThreadInfo} query; subsequent queries in the
26694 sequence will be the @samp{qsThreadInfo} query.
26696 NOTE: This packet replaces the @samp{qL} query (see below).
26700 @item m @var{thread-id}
26702 @item m @var{thread-id},@var{thread-id}@dots{}
26703 a comma-separated list of thread IDs
26705 (lower case letter @samp{L}) denotes end of list.
26708 In response to each query, the target will reply with a list of one or
26709 more thread IDs, separated by commas.
26710 @value{GDBN} will respond to each reply with a request for more thread
26711 ids (using the @samp{qs} form of the query), until the target responds
26712 with @samp{l} (lower-case el, for @dfn{last}).
26713 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
26716 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
26717 @cindex get thread-local storage address, remote request
26718 @cindex @samp{qGetTLSAddr} packet
26719 Fetch the address associated with thread local storage specified
26720 by @var{thread-id}, @var{offset}, and @var{lm}.
26722 @var{thread-id} is the thread ID associated with the
26723 thread for which to fetch the TLS address. @xref{thread-id syntax}.
26725 @var{offset} is the (big endian, hex encoded) offset associated with the
26726 thread local variable. (This offset is obtained from the debug
26727 information associated with the variable.)
26729 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
26730 the load module associated with the thread local storage. For example,
26731 a @sc{gnu}/Linux system will pass the link map address of the shared
26732 object associated with the thread local storage under consideration.
26733 Other operating environments may choose to represent the load module
26734 differently, so the precise meaning of this parameter will vary.
26738 @item @var{XX}@dots{}
26739 Hex encoded (big endian) bytes representing the address of the thread
26740 local storage requested.
26743 An error occurred. @var{nn} are hex digits.
26746 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
26749 @item qL @var{startflag} @var{threadcount} @var{nextthread}
26750 Obtain thread information from RTOS. Where: @var{startflag} (one hex
26751 digit) is one to indicate the first query and zero to indicate a
26752 subsequent query; @var{threadcount} (two hex digits) is the maximum
26753 number of threads the response packet can contain; and @var{nextthread}
26754 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
26755 returned in the response as @var{argthread}.
26757 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
26761 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
26762 Where: @var{count} (two hex digits) is the number of threads being
26763 returned; @var{done} (one hex digit) is zero to indicate more threads
26764 and one indicates no further threads; @var{argthreadid} (eight hex
26765 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
26766 is a sequence of thread IDs from the target. @var{threadid} (eight hex
26767 digits). See @code{remote.c:parse_threadlist_response()}.
26771 @cindex section offsets, remote request
26772 @cindex @samp{qOffsets} packet
26773 Get section offsets that the target used when relocating the downloaded
26778 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
26779 Relocate the @code{Text} section by @var{xxx} from its original address.
26780 Relocate the @code{Data} section by @var{yyy} from its original address.
26781 If the object file format provides segment information (e.g.@: @sc{elf}
26782 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
26783 segments by the supplied offsets.
26785 @emph{Note: while a @code{Bss} offset may be included in the response,
26786 @value{GDBN} ignores this and instead applies the @code{Data} offset
26787 to the @code{Bss} section.}
26789 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
26790 Relocate the first segment of the object file, which conventionally
26791 contains program code, to a starting address of @var{xxx}. If
26792 @samp{DataSeg} is specified, relocate the second segment, which
26793 conventionally contains modifiable data, to a starting address of
26794 @var{yyy}. @value{GDBN} will report an error if the object file
26795 does not contain segment information, or does not contain at least
26796 as many segments as mentioned in the reply. Extra segments are
26797 kept at fixed offsets relative to the last relocated segment.
26800 @item qP @var{mode} @var{thread-id}
26801 @cindex thread information, remote request
26802 @cindex @samp{qP} packet
26803 Returns information on @var{thread-id}. Where: @var{mode} is a hex
26804 encoded 32 bit mode; @var{thread-id} is a thread ID
26805 (@pxref{thread-id syntax}).
26807 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
26810 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
26814 @cindex non-stop mode, remote request
26815 @cindex @samp{QNonStop} packet
26817 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
26818 @xref{Remote Non-Stop}, for more information.
26823 The request succeeded.
26826 An error occurred. @var{nn} are hex digits.
26829 An empty reply indicates that @samp{QNonStop} is not supported by
26833 This packet is not probed by default; the remote stub must request it,
26834 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26835 Use of this packet is controlled by the @code{set non-stop} command;
26836 @pxref{Non-Stop Mode}.
26838 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
26839 @cindex pass signals to inferior, remote request
26840 @cindex @samp{QPassSignals} packet
26841 @anchor{QPassSignals}
26842 Each listed @var{signal} should be passed directly to the inferior process.
26843 Signals are numbered identically to continue packets and stop replies
26844 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
26845 strictly greater than the previous item. These signals do not need to stop
26846 the inferior, or be reported to @value{GDBN}. All other signals should be
26847 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
26848 combine; any earlier @samp{QPassSignals} list is completely replaced by the
26849 new list. This packet improves performance when using @samp{handle
26850 @var{signal} nostop noprint pass}.
26855 The request succeeded.
26858 An error occurred. @var{nn} are hex digits.
26861 An empty reply indicates that @samp{QPassSignals} is not supported by
26865 Use of this packet is controlled by the @code{set remote pass-signals}
26866 command (@pxref{Remote Configuration, set remote pass-signals}).
26867 This packet is not probed by default; the remote stub must request it,
26868 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26870 @item qRcmd,@var{command}
26871 @cindex execute remote command, remote request
26872 @cindex @samp{qRcmd} packet
26873 @var{command} (hex encoded) is passed to the local interpreter for
26874 execution. Invalid commands should be reported using the output
26875 string. Before the final result packet, the target may also respond
26876 with a number of intermediate @samp{O@var{output}} console output
26877 packets. @emph{Implementors should note that providing access to a
26878 stubs's interpreter may have security implications}.
26883 A command response with no output.
26885 A command response with the hex encoded output string @var{OUTPUT}.
26887 Indicate a badly formed request.
26889 An empty reply indicates that @samp{qRcmd} is not recognized.
26892 (Note that the @code{qRcmd} packet's name is separated from the
26893 command by a @samp{,}, not a @samp{:}, contrary to the naming
26894 conventions above. Please don't use this packet as a model for new
26897 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
26898 @cindex searching memory, in remote debugging
26899 @cindex @samp{qSearch:memory} packet
26900 @anchor{qSearch memory}
26901 Search @var{length} bytes at @var{address} for @var{search-pattern}.
26902 @var{address} and @var{length} are encoded in hex.
26903 @var{search-pattern} is a sequence of bytes, hex encoded.
26908 The pattern was not found.
26910 The pattern was found at @var{address}.
26912 A badly formed request or an error was encountered while searching memory.
26914 An empty reply indicates that @samp{qSearch:memory} is not recognized.
26917 @item QStartNoAckMode
26918 @cindex @samp{QStartNoAckMode} packet
26919 @anchor{QStartNoAckMode}
26920 Request that the remote stub disable the normal @samp{+}/@samp{-}
26921 protocol acknowledgments (@pxref{Packet Acknowledgment}).
26926 The stub has switched to no-acknowledgment mode.
26927 @value{GDBN} acknowledges this reponse,
26928 but neither the stub nor @value{GDBN} shall send or expect further
26929 @samp{+}/@samp{-} acknowledgments in the current connection.
26931 An empty reply indicates that the stub does not support no-acknowledgment mode.
26934 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
26935 @cindex supported packets, remote query
26936 @cindex features of the remote protocol
26937 @cindex @samp{qSupported} packet
26938 @anchor{qSupported}
26939 Tell the remote stub about features supported by @value{GDBN}, and
26940 query the stub for features it supports. This packet allows
26941 @value{GDBN} and the remote stub to take advantage of each others'
26942 features. @samp{qSupported} also consolidates multiple feature probes
26943 at startup, to improve @value{GDBN} performance---a single larger
26944 packet performs better than multiple smaller probe packets on
26945 high-latency links. Some features may enable behavior which must not
26946 be on by default, e.g.@: because it would confuse older clients or
26947 stubs. Other features may describe packets which could be
26948 automatically probed for, but are not. These features must be
26949 reported before @value{GDBN} will use them. This ``default
26950 unsupported'' behavior is not appropriate for all packets, but it
26951 helps to keep the initial connection time under control with new
26952 versions of @value{GDBN} which support increasing numbers of packets.
26956 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
26957 The stub supports or does not support each returned @var{stubfeature},
26958 depending on the form of each @var{stubfeature} (see below for the
26961 An empty reply indicates that @samp{qSupported} is not recognized,
26962 or that no features needed to be reported to @value{GDBN}.
26965 The allowed forms for each feature (either a @var{gdbfeature} in the
26966 @samp{qSupported} packet, or a @var{stubfeature} in the response)
26970 @item @var{name}=@var{value}
26971 The remote protocol feature @var{name} is supported, and associated
26972 with the specified @var{value}. The format of @var{value} depends
26973 on the feature, but it must not include a semicolon.
26975 The remote protocol feature @var{name} is supported, and does not
26976 need an associated value.
26978 The remote protocol feature @var{name} is not supported.
26980 The remote protocol feature @var{name} may be supported, and
26981 @value{GDBN} should auto-detect support in some other way when it is
26982 needed. This form will not be used for @var{gdbfeature} notifications,
26983 but may be used for @var{stubfeature} responses.
26986 Whenever the stub receives a @samp{qSupported} request, the
26987 supplied set of @value{GDBN} features should override any previous
26988 request. This allows @value{GDBN} to put the stub in a known
26989 state, even if the stub had previously been communicating with
26990 a different version of @value{GDBN}.
26992 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
26997 This feature indicates whether @value{GDBN} supports multiprocess
26998 extensions to the remote protocol. @value{GDBN} does not use such
26999 extensions unless the stub also reports that it supports them by
27000 including @samp{multiprocess+} in its @samp{qSupported} reply.
27001 @xref{multiprocess extensions}, for details.
27004 Stubs should ignore any unknown values for
27005 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
27006 packet supports receiving packets of unlimited length (earlier
27007 versions of @value{GDBN} may reject overly long responses). Additional values
27008 for @var{gdbfeature} may be defined in the future to let the stub take
27009 advantage of new features in @value{GDBN}, e.g.@: incompatible
27010 improvements in the remote protocol---the @samp{multiprocess} feature is
27011 an example of such a feature. The stub's reply should be independent
27012 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
27013 describes all the features it supports, and then the stub replies with
27014 all the features it supports.
27016 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
27017 responses, as long as each response uses one of the standard forms.
27019 Some features are flags. A stub which supports a flag feature
27020 should respond with a @samp{+} form response. Other features
27021 require values, and the stub should respond with an @samp{=}
27024 Each feature has a default value, which @value{GDBN} will use if
27025 @samp{qSupported} is not available or if the feature is not mentioned
27026 in the @samp{qSupported} response. The default values are fixed; a
27027 stub is free to omit any feature responses that match the defaults.
27029 Not all features can be probed, but for those which can, the probing
27030 mechanism is useful: in some cases, a stub's internal
27031 architecture may not allow the protocol layer to know some information
27032 about the underlying target in advance. This is especially common in
27033 stubs which may be configured for multiple targets.
27035 These are the currently defined stub features and their properties:
27037 @multitable @columnfractions 0.35 0.2 0.12 0.2
27038 @c NOTE: The first row should be @headitem, but we do not yet require
27039 @c a new enough version of Texinfo (4.7) to use @headitem.
27041 @tab Value Required
27045 @item @samp{PacketSize}
27050 @item @samp{qXfer:auxv:read}
27055 @item @samp{qXfer:features:read}
27060 @item @samp{qXfer:libraries:read}
27065 @item @samp{qXfer:memory-map:read}
27070 @item @samp{qXfer:spu:read}
27075 @item @samp{qXfer:spu:write}
27080 @item @samp{qXfer:siginfo:read}
27085 @item @samp{qXfer:siginfo:write}
27090 @item @samp{QNonStop}
27095 @item @samp{QPassSignals}
27100 @item @samp{QStartNoAckMode}
27105 @item @samp{multiprocess}
27112 These are the currently defined stub features, in more detail:
27115 @cindex packet size, remote protocol
27116 @item PacketSize=@var{bytes}
27117 The remote stub can accept packets up to at least @var{bytes} in
27118 length. @value{GDBN} will send packets up to this size for bulk
27119 transfers, and will never send larger packets. This is a limit on the
27120 data characters in the packet, including the frame and checksum.
27121 There is no trailing NUL byte in a remote protocol packet; if the stub
27122 stores packets in a NUL-terminated format, it should allow an extra
27123 byte in its buffer for the NUL. If this stub feature is not supported,
27124 @value{GDBN} guesses based on the size of the @samp{g} packet response.
27126 @item qXfer:auxv:read
27127 The remote stub understands the @samp{qXfer:auxv:read} packet
27128 (@pxref{qXfer auxiliary vector read}).
27130 @item qXfer:features:read
27131 The remote stub understands the @samp{qXfer:features:read} packet
27132 (@pxref{qXfer target description read}).
27134 @item qXfer:libraries:read
27135 The remote stub understands the @samp{qXfer:libraries:read} packet
27136 (@pxref{qXfer library list read}).
27138 @item qXfer:memory-map:read
27139 The remote stub understands the @samp{qXfer:memory-map:read} packet
27140 (@pxref{qXfer memory map read}).
27142 @item qXfer:spu:read
27143 The remote stub understands the @samp{qXfer:spu:read} packet
27144 (@pxref{qXfer spu read}).
27146 @item qXfer:spu:write
27147 The remote stub understands the @samp{qXfer:spu:write} packet
27148 (@pxref{qXfer spu write}).
27150 @item qXfer:siginfo:read
27151 The remote stub understands the @samp{qXfer:siginfo:read} packet
27152 (@pxref{qXfer siginfo read}).
27154 @item qXfer:siginfo:write
27155 The remote stub understands the @samp{qXfer:siginfo:write} packet
27156 (@pxref{qXfer siginfo write}).
27159 The remote stub understands the @samp{QNonStop} packet
27160 (@pxref{QNonStop}).
27163 The remote stub understands the @samp{QPassSignals} packet
27164 (@pxref{QPassSignals}).
27166 @item QStartNoAckMode
27167 The remote stub understands the @samp{QStartNoAckMode} packet and
27168 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
27171 @anchor{multiprocess extensions}
27172 @cindex multiprocess extensions, in remote protocol
27173 The remote stub understands the multiprocess extensions to the remote
27174 protocol syntax. The multiprocess extensions affect the syntax of
27175 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
27176 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
27177 replies. Note that reporting this feature indicates support for the
27178 syntactic extensions only, not that the stub necessarily supports
27179 debugging of more than one process at a time. The stub must not use
27180 multiprocess extensions in packet replies unless @value{GDBN} has also
27181 indicated it supports them in its @samp{qSupported} request.
27183 @item qXfer:osdata:read
27184 The remote stub understands the @samp{qXfer:osdata:read} packet
27185 ((@pxref{qXfer osdata read}).
27190 @cindex symbol lookup, remote request
27191 @cindex @samp{qSymbol} packet
27192 Notify the target that @value{GDBN} is prepared to serve symbol lookup
27193 requests. Accept requests from the target for the values of symbols.
27198 The target does not need to look up any (more) symbols.
27199 @item qSymbol:@var{sym_name}
27200 The target requests the value of symbol @var{sym_name} (hex encoded).
27201 @value{GDBN} may provide the value by using the
27202 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
27206 @item qSymbol:@var{sym_value}:@var{sym_name}
27207 Set the value of @var{sym_name} to @var{sym_value}.
27209 @var{sym_name} (hex encoded) is the name of a symbol whose value the
27210 target has previously requested.
27212 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
27213 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
27219 The target does not need to look up any (more) symbols.
27220 @item qSymbol:@var{sym_name}
27221 The target requests the value of a new symbol @var{sym_name} (hex
27222 encoded). @value{GDBN} will continue to supply the values of symbols
27223 (if available), until the target ceases to request them.
27228 @xref{Tracepoint Packets}.
27230 @item qThreadExtraInfo,@var{thread-id}
27231 @cindex thread attributes info, remote request
27232 @cindex @samp{qThreadExtraInfo} packet
27233 Obtain a printable string description of a thread's attributes from
27234 the target OS. @var{thread-id} is a thread ID;
27235 see @ref{thread-id syntax}. This
27236 string may contain anything that the target OS thinks is interesting
27237 for @value{GDBN} to tell the user about the thread. The string is
27238 displayed in @value{GDBN}'s @code{info threads} display. Some
27239 examples of possible thread extra info strings are @samp{Runnable}, or
27240 @samp{Blocked on Mutex}.
27244 @item @var{XX}@dots{}
27245 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
27246 comprising the printable string containing the extra information about
27247 the thread's attributes.
27250 (Note that the @code{qThreadExtraInfo} packet's name is separated from
27251 the command by a @samp{,}, not a @samp{:}, contrary to the naming
27252 conventions above. Please don't use this packet as a model for new
27260 @xref{Tracepoint Packets}.
27262 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
27263 @cindex read special object, remote request
27264 @cindex @samp{qXfer} packet
27265 @anchor{qXfer read}
27266 Read uninterpreted bytes from the target's special data area
27267 identified by the keyword @var{object}. Request @var{length} bytes
27268 starting at @var{offset} bytes into the data. The content and
27269 encoding of @var{annex} is specific to @var{object}; it can supply
27270 additional details about what data to access.
27272 Here are the specific requests of this form defined so far. All
27273 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
27274 formats, listed below.
27277 @item qXfer:auxv:read::@var{offset},@var{length}
27278 @anchor{qXfer auxiliary vector read}
27279 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
27280 auxiliary vector}. Note @var{annex} must be empty.
27282 This packet is not probed by default; the remote stub must request it,
27283 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27285 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
27286 @anchor{qXfer target description read}
27287 Access the @dfn{target description}. @xref{Target Descriptions}. The
27288 annex specifies which XML document to access. The main description is
27289 always loaded from the @samp{target.xml} annex.
27291 This packet is not probed by default; the remote stub must request it,
27292 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27294 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
27295 @anchor{qXfer library list read}
27296 Access the target's list of loaded libraries. @xref{Library List Format}.
27297 The annex part of the generic @samp{qXfer} packet must be empty
27298 (@pxref{qXfer read}).
27300 Targets which maintain a list of libraries in the program's memory do
27301 not need to implement this packet; it is designed for platforms where
27302 the operating system manages the list of loaded libraries.
27304 This packet is not probed by default; the remote stub must request it,
27305 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27307 @item qXfer:memory-map:read::@var{offset},@var{length}
27308 @anchor{qXfer memory map read}
27309 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
27310 annex part of the generic @samp{qXfer} packet must be empty
27311 (@pxref{qXfer read}).
27313 This packet is not probed by default; the remote stub must request it,
27314 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27316 @item qXfer:siginfo:read::@var{offset},@var{length}
27317 @anchor{qXfer siginfo read}
27318 Read contents of the extra signal information on the target
27319 system. The annex part of the generic @samp{qXfer} packet must be
27320 empty (@pxref{qXfer read}).
27322 This packet is not probed by default; the remote stub must request it,
27323 by supplying an appropriate @samp{qSupported} response
27324 (@pxref{qSupported}).
27326 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
27327 @anchor{qXfer spu read}
27328 Read contents of an @code{spufs} file on the target system. The
27329 annex specifies which file to read; it must be of the form
27330 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27331 in the target process, and @var{name} identifes the @code{spufs} file
27332 in that context to be accessed.
27334 This packet is not probed by default; the remote stub must request it,
27335 by supplying an appropriate @samp{qSupported} response
27336 (@pxref{qSupported}).
27338 @item qXfer:osdata:read::@var{offset},@var{length}
27339 @anchor{qXfer osdata read}
27340 Access the target's @dfn{operating system information}.
27341 @xref{Operating System Information}.
27348 Data @var{data} (@pxref{Binary Data}) has been read from the
27349 target. There may be more data at a higher address (although
27350 it is permitted to return @samp{m} even for the last valid
27351 block of data, as long as at least one byte of data was read).
27352 @var{data} may have fewer bytes than the @var{length} in the
27356 Data @var{data} (@pxref{Binary Data}) has been read from the target.
27357 There is no more data to be read. @var{data} may have fewer bytes
27358 than the @var{length} in the request.
27361 The @var{offset} in the request is at the end of the data.
27362 There is no more data to be read.
27365 The request was malformed, or @var{annex} was invalid.
27368 The offset was invalid, or there was an error encountered reading the data.
27369 @var{nn} is a hex-encoded @code{errno} value.
27372 An empty reply indicates the @var{object} string was not recognized by
27373 the stub, or that the object does not support reading.
27376 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
27377 @cindex write data into object, remote request
27378 @anchor{qXfer write}
27379 Write uninterpreted bytes into the target's special data area
27380 identified by the keyword @var{object}, starting at @var{offset} bytes
27381 into the data. @var{data}@dots{} is the binary-encoded data
27382 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
27383 is specific to @var{object}; it can supply additional details about what data
27386 Here are the specific requests of this form defined so far. All
27387 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
27388 formats, listed below.
27391 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
27392 @anchor{qXfer siginfo write}
27393 Write @var{data} to the extra signal information on the target system.
27394 The annex part of the generic @samp{qXfer} packet must be
27395 empty (@pxref{qXfer write}).
27397 This packet is not probed by default; the remote stub must request it,
27398 by supplying an appropriate @samp{qSupported} response
27399 (@pxref{qSupported}).
27401 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
27402 @anchor{qXfer spu write}
27403 Write @var{data} to an @code{spufs} file on the target system. The
27404 annex specifies which file to write; it must be of the form
27405 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27406 in the target process, and @var{name} identifes the @code{spufs} file
27407 in that context to be accessed.
27409 This packet is not probed by default; the remote stub must request it,
27410 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27416 @var{nn} (hex encoded) is the number of bytes written.
27417 This may be fewer bytes than supplied in the request.
27420 The request was malformed, or @var{annex} was invalid.
27423 The offset was invalid, or there was an error encountered writing the data.
27424 @var{nn} is a hex-encoded @code{errno} value.
27427 An empty reply indicates the @var{object} string was not
27428 recognized by the stub, or that the object does not support writing.
27431 @item qXfer:@var{object}:@var{operation}:@dots{}
27432 Requests of this form may be added in the future. When a stub does
27433 not recognize the @var{object} keyword, or its support for
27434 @var{object} does not recognize the @var{operation} keyword, the stub
27435 must respond with an empty packet.
27437 @item qAttached:@var{pid}
27438 @cindex query attached, remote request
27439 @cindex @samp{qAttached} packet
27440 Return an indication of whether the remote server attached to an
27441 existing process or created a new process. When the multiprocess
27442 protocol extensions are supported (@pxref{multiprocess extensions}),
27443 @var{pid} is an integer in hexadecimal format identifying the target
27444 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
27445 the query packet will be simplified as @samp{qAttached}.
27447 This query is used, for example, to know whether the remote process
27448 should be detached or killed when a @value{GDBN} session is ended with
27449 the @code{quit} command.
27454 The remote server attached to an existing process.
27456 The remote server created a new process.
27458 A badly formed request or an error was encountered.
27463 @node Register Packet Format
27464 @section Register Packet Format
27466 The following @code{g}/@code{G} packets have previously been defined.
27467 In the below, some thirty-two bit registers are transferred as
27468 sixty-four bits. Those registers should be zero/sign extended (which?)
27469 to fill the space allocated. Register bytes are transferred in target
27470 byte order. The two nibbles within a register byte are transferred
27471 most-significant - least-significant.
27477 All registers are transferred as thirty-two bit quantities in the order:
27478 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
27479 registers; fsr; fir; fp.
27483 All registers are transferred as sixty-four bit quantities (including
27484 thirty-two bit registers such as @code{sr}). The ordering is the same
27489 @node Tracepoint Packets
27490 @section Tracepoint Packets
27491 @cindex tracepoint packets
27492 @cindex packets, tracepoint
27494 Here we describe the packets @value{GDBN} uses to implement
27495 tracepoints (@pxref{Tracepoints}).
27499 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
27500 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
27501 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
27502 the tracepoint is disabled. @var{step} is the tracepoint's step
27503 count, and @var{pass} is its pass count. If the trailing @samp{-} is
27504 present, further @samp{QTDP} packets will follow to specify this
27505 tracepoint's actions.
27510 The packet was understood and carried out.
27512 The packet was not recognized.
27515 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
27516 Define actions to be taken when a tracepoint is hit. @var{n} and
27517 @var{addr} must be the same as in the initial @samp{QTDP} packet for
27518 this tracepoint. This packet may only be sent immediately after
27519 another @samp{QTDP} packet that ended with a @samp{-}. If the
27520 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
27521 specifying more actions for this tracepoint.
27523 In the series of action packets for a given tracepoint, at most one
27524 can have an @samp{S} before its first @var{action}. If such a packet
27525 is sent, it and the following packets define ``while-stepping''
27526 actions. Any prior packets define ordinary actions --- that is, those
27527 taken when the tracepoint is first hit. If no action packet has an
27528 @samp{S}, then all the packets in the series specify ordinary
27529 tracepoint actions.
27531 The @samp{@var{action}@dots{}} portion of the packet is a series of
27532 actions, concatenated without separators. Each action has one of the
27538 Collect the registers whose bits are set in @var{mask}. @var{mask} is
27539 a hexadecimal number whose @var{i}'th bit is set if register number
27540 @var{i} should be collected. (The least significant bit is numbered
27541 zero.) Note that @var{mask} may be any number of digits long; it may
27542 not fit in a 32-bit word.
27544 @item M @var{basereg},@var{offset},@var{len}
27545 Collect @var{len} bytes of memory starting at the address in register
27546 number @var{basereg}, plus @var{offset}. If @var{basereg} is
27547 @samp{-1}, then the range has a fixed address: @var{offset} is the
27548 address of the lowest byte to collect. The @var{basereg},
27549 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
27550 values (the @samp{-1} value for @var{basereg} is a special case).
27552 @item X @var{len},@var{expr}
27553 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
27554 it directs. @var{expr} is an agent expression, as described in
27555 @ref{Agent Expressions}. Each byte of the expression is encoded as a
27556 two-digit hex number in the packet; @var{len} is the number of bytes
27557 in the expression (and thus one-half the number of hex digits in the
27562 Any number of actions may be packed together in a single @samp{QTDP}
27563 packet, as long as the packet does not exceed the maximum packet
27564 length (400 bytes, for many stubs). There may be only one @samp{R}
27565 action per tracepoint, and it must precede any @samp{M} or @samp{X}
27566 actions. Any registers referred to by @samp{M} and @samp{X} actions
27567 must be collected by a preceding @samp{R} action. (The
27568 ``while-stepping'' actions are treated as if they were attached to a
27569 separate tracepoint, as far as these restrictions are concerned.)
27574 The packet was understood and carried out.
27576 The packet was not recognized.
27579 @item QTFrame:@var{n}
27580 Select the @var{n}'th tracepoint frame from the buffer, and use the
27581 register and memory contents recorded there to answer subsequent
27582 request packets from @value{GDBN}.
27584 A successful reply from the stub indicates that the stub has found the
27585 requested frame. The response is a series of parts, concatenated
27586 without separators, describing the frame we selected. Each part has
27587 one of the following forms:
27591 The selected frame is number @var{n} in the trace frame buffer;
27592 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
27593 was no frame matching the criteria in the request packet.
27596 The selected trace frame records a hit of tracepoint number @var{t};
27597 @var{t} is a hexadecimal number.
27601 @item QTFrame:pc:@var{addr}
27602 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27603 currently selected frame whose PC is @var{addr};
27604 @var{addr} is a hexadecimal number.
27606 @item QTFrame:tdp:@var{t}
27607 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27608 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
27609 is a hexadecimal number.
27611 @item QTFrame:range:@var{start}:@var{end}
27612 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27613 currently selected frame whose PC is between @var{start} (inclusive)
27614 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
27617 @item QTFrame:outside:@var{start}:@var{end}
27618 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
27619 frame @emph{outside} the given range of addresses.
27622 Begin the tracepoint experiment. Begin collecting data from tracepoint
27623 hits in the trace frame buffer.
27626 End the tracepoint experiment. Stop collecting trace frames.
27629 Clear the table of tracepoints, and empty the trace frame buffer.
27631 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
27632 Establish the given ranges of memory as ``transparent''. The stub
27633 will answer requests for these ranges from memory's current contents,
27634 if they were not collected as part of the tracepoint hit.
27636 @value{GDBN} uses this to mark read-only regions of memory, like those
27637 containing program code. Since these areas never change, they should
27638 still have the same contents they did when the tracepoint was hit, so
27639 there's no reason for the stub to refuse to provide their contents.
27642 Ask the stub if there is a trace experiment running right now.
27647 There is no trace experiment running.
27649 There is a trace experiment running.
27655 @node Host I/O Packets
27656 @section Host I/O Packets
27657 @cindex Host I/O, remote protocol
27658 @cindex file transfer, remote protocol
27660 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
27661 operations on the far side of a remote link. For example, Host I/O is
27662 used to upload and download files to a remote target with its own
27663 filesystem. Host I/O uses the same constant values and data structure
27664 layout as the target-initiated File-I/O protocol. However, the
27665 Host I/O packets are structured differently. The target-initiated
27666 protocol relies on target memory to store parameters and buffers.
27667 Host I/O requests are initiated by @value{GDBN}, and the
27668 target's memory is not involved. @xref{File-I/O Remote Protocol
27669 Extension}, for more details on the target-initiated protocol.
27671 The Host I/O request packets all encode a single operation along with
27672 its arguments. They have this format:
27676 @item vFile:@var{operation}: @var{parameter}@dots{}
27677 @var{operation} is the name of the particular request; the target
27678 should compare the entire packet name up to the second colon when checking
27679 for a supported operation. The format of @var{parameter} depends on
27680 the operation. Numbers are always passed in hexadecimal. Negative
27681 numbers have an explicit minus sign (i.e.@: two's complement is not
27682 used). Strings (e.g.@: filenames) are encoded as a series of
27683 hexadecimal bytes. The last argument to a system call may be a
27684 buffer of escaped binary data (@pxref{Binary Data}).
27688 The valid responses to Host I/O packets are:
27692 @item F @var{result} [, @var{errno}] [; @var{attachment}]
27693 @var{result} is the integer value returned by this operation, usually
27694 non-negative for success and -1 for errors. If an error has occured,
27695 @var{errno} will be included in the result. @var{errno} will have a
27696 value defined by the File-I/O protocol (@pxref{Errno Values}). For
27697 operations which return data, @var{attachment} supplies the data as a
27698 binary buffer. Binary buffers in response packets are escaped in the
27699 normal way (@pxref{Binary Data}). See the individual packet
27700 documentation for the interpretation of @var{result} and
27704 An empty response indicates that this operation is not recognized.
27708 These are the supported Host I/O operations:
27711 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
27712 Open a file at @var{pathname} and return a file descriptor for it, or
27713 return -1 if an error occurs. @var{pathname} is a string,
27714 @var{flags} is an integer indicating a mask of open flags
27715 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
27716 of mode bits to use if the file is created (@pxref{mode_t Values}).
27717 @xref{open}, for details of the open flags and mode values.
27719 @item vFile:close: @var{fd}
27720 Close the open file corresponding to @var{fd} and return 0, or
27721 -1 if an error occurs.
27723 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
27724 Read data from the open file corresponding to @var{fd}. Up to
27725 @var{count} bytes will be read from the file, starting at @var{offset}
27726 relative to the start of the file. The target may read fewer bytes;
27727 common reasons include packet size limits and an end-of-file
27728 condition. The number of bytes read is returned. Zero should only be
27729 returned for a successful read at the end of the file, or if
27730 @var{count} was zero.
27732 The data read should be returned as a binary attachment on success.
27733 If zero bytes were read, the response should include an empty binary
27734 attachment (i.e.@: a trailing semicolon). The return value is the
27735 number of target bytes read; the binary attachment may be longer if
27736 some characters were escaped.
27738 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
27739 Write @var{data} (a binary buffer) to the open file corresponding
27740 to @var{fd}. Start the write at @var{offset} from the start of the
27741 file. Unlike many @code{write} system calls, there is no
27742 separate @var{count} argument; the length of @var{data} in the
27743 packet is used. @samp{vFile:write} returns the number of bytes written,
27744 which may be shorter than the length of @var{data}, or -1 if an
27747 @item vFile:unlink: @var{pathname}
27748 Delete the file at @var{pathname} on the target. Return 0,
27749 or -1 if an error occurs. @var{pathname} is a string.
27754 @section Interrupts
27755 @cindex interrupts (remote protocol)
27757 When a program on the remote target is running, @value{GDBN} may
27758 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
27759 control of which is specified via @value{GDBN}'s @samp{remotebreak}
27760 setting (@pxref{set remotebreak}).
27762 The precise meaning of @code{BREAK} is defined by the transport
27763 mechanism and may, in fact, be undefined. @value{GDBN} does not
27764 currently define a @code{BREAK} mechanism for any of the network
27765 interfaces except for TCP, in which case @value{GDBN} sends the
27766 @code{telnet} BREAK sequence.
27768 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
27769 transport mechanisms. It is represented by sending the single byte
27770 @code{0x03} without any of the usual packet overhead described in
27771 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
27772 transmitted as part of a packet, it is considered to be packet data
27773 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
27774 (@pxref{X packet}), used for binary downloads, may include an unescaped
27775 @code{0x03} as part of its packet.
27777 Stubs are not required to recognize these interrupt mechanisms and the
27778 precise meaning associated with receipt of the interrupt is
27779 implementation defined. If the target supports debugging of multiple
27780 threads and/or processes, it should attempt to interrupt all
27781 currently-executing threads and processes.
27782 If the stub is successful at interrupting the
27783 running program, it should send one of the stop
27784 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
27785 of successfully stopping the program in all-stop mode, and a stop reply
27786 for each stopped thread in non-stop mode.
27787 Interrupts received while the
27788 program is stopped are discarded.
27790 @node Notification Packets
27791 @section Notification Packets
27792 @cindex notification packets
27793 @cindex packets, notification
27795 The @value{GDBN} remote serial protocol includes @dfn{notifications},
27796 packets that require no acknowledgment. Both the GDB and the stub
27797 may send notifications (although the only notifications defined at
27798 present are sent by the stub). Notifications carry information
27799 without incurring the round-trip latency of an acknowledgment, and so
27800 are useful for low-impact communications where occasional packet loss
27803 A notification packet has the form @samp{% @var{data} #
27804 @var{checksum}}, where @var{data} is the content of the notification,
27805 and @var{checksum} is a checksum of @var{data}, computed and formatted
27806 as for ordinary @value{GDBN} packets. A notification's @var{data}
27807 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
27808 receiving a notification, the recipient sends no @samp{+} or @samp{-}
27809 to acknowledge the notification's receipt or to report its corruption.
27811 Every notification's @var{data} begins with a name, which contains no
27812 colon characters, followed by a colon character.
27814 Recipients should silently ignore corrupted notifications and
27815 notifications they do not understand. Recipients should restart
27816 timeout periods on receipt of a well-formed notification, whether or
27817 not they understand it.
27819 Senders should only send the notifications described here when this
27820 protocol description specifies that they are permitted. In the
27821 future, we may extend the protocol to permit existing notifications in
27822 new contexts; this rule helps older senders avoid confusing newer
27825 (Older versions of @value{GDBN} ignore bytes received until they see
27826 the @samp{$} byte that begins an ordinary packet, so new stubs may
27827 transmit notifications without fear of confusing older clients. There
27828 are no notifications defined for @value{GDBN} to send at the moment, but we
27829 assume that most older stubs would ignore them, as well.)
27831 The following notification packets from the stub to @value{GDBN} are
27835 @item Stop: @var{reply}
27836 Report an asynchronous stop event in non-stop mode.
27837 The @var{reply} has the form of a stop reply, as
27838 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
27839 for information on how these notifications are acknowledged by
27843 @node Remote Non-Stop
27844 @section Remote Protocol Support for Non-Stop Mode
27846 @value{GDBN}'s remote protocol supports non-stop debugging of
27847 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
27848 supports non-stop mode, it should report that to @value{GDBN} by including
27849 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
27851 @value{GDBN} typically sends a @samp{QNonStop} packet only when
27852 establishing a new connection with the stub. Entering non-stop mode
27853 does not alter the state of any currently-running threads, but targets
27854 must stop all threads in any already-attached processes when entering
27855 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
27856 probe the target state after a mode change.
27858 In non-stop mode, when an attached process encounters an event that
27859 would otherwise be reported with a stop reply, it uses the
27860 asynchronous notification mechanism (@pxref{Notification Packets}) to
27861 inform @value{GDBN}. In contrast to all-stop mode, where all threads
27862 in all processes are stopped when a stop reply is sent, in non-stop
27863 mode only the thread reporting the stop event is stopped. That is,
27864 when reporting a @samp{S} or @samp{T} response to indicate completion
27865 of a step operation, hitting a breakpoint, or a fault, only the
27866 affected thread is stopped; any other still-running threads continue
27867 to run. When reporting a @samp{W} or @samp{X} response, all running
27868 threads belonging to other attached processes continue to run.
27870 Only one stop reply notification at a time may be pending; if
27871 additional stop events occur before @value{GDBN} has acknowledged the
27872 previous notification, they must be queued by the stub for later
27873 synchronous transmission in response to @samp{vStopped} packets from
27874 @value{GDBN}. Because the notification mechanism is unreliable,
27875 the stub is permitted to resend a stop reply notification
27876 if it believes @value{GDBN} may not have received it. @value{GDBN}
27877 ignores additional stop reply notifications received before it has
27878 finished processing a previous notification and the stub has completed
27879 sending any queued stop events.
27881 Otherwise, @value{GDBN} must be prepared to receive a stop reply
27882 notification at any time. Specifically, they may appear when
27883 @value{GDBN} is not otherwise reading input from the stub, or when
27884 @value{GDBN} is expecting to read a normal synchronous response or a
27885 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
27886 Notification packets are distinct from any other communication from
27887 the stub so there is no ambiguity.
27889 After receiving a stop reply notification, @value{GDBN} shall
27890 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
27891 as a regular, synchronous request to the stub. Such acknowledgment
27892 is not required to happen immediately, as @value{GDBN} is permitted to
27893 send other, unrelated packets to the stub first, which the stub should
27896 Upon receiving a @samp{vStopped} packet, if the stub has other queued
27897 stop events to report to @value{GDBN}, it shall respond by sending a
27898 normal stop reply response. @value{GDBN} shall then send another
27899 @samp{vStopped} packet to solicit further responses; again, it is
27900 permitted to send other, unrelated packets as well which the stub
27901 should process normally.
27903 If the stub receives a @samp{vStopped} packet and there are no
27904 additional stop events to report, the stub shall return an @samp{OK}
27905 response. At this point, if further stop events occur, the stub shall
27906 send a new stop reply notification, @value{GDBN} shall accept the
27907 notification, and the process shall be repeated.
27909 In non-stop mode, the target shall respond to the @samp{?} packet as
27910 follows. First, any incomplete stop reply notification/@samp{vStopped}
27911 sequence in progress is abandoned. The target must begin a new
27912 sequence reporting stop events for all stopped threads, whether or not
27913 it has previously reported those events to @value{GDBN}. The first
27914 stop reply is sent as a synchronous reply to the @samp{?} packet, and
27915 subsequent stop replies are sent as responses to @samp{vStopped} packets
27916 using the mechanism described above. The target must not send
27917 asynchronous stop reply notifications until the sequence is complete.
27918 If all threads are running when the target receives the @samp{?} packet,
27919 or if the target is not attached to any process, it shall respond
27922 @node Packet Acknowledgment
27923 @section Packet Acknowledgment
27925 @cindex acknowledgment, for @value{GDBN} remote
27926 @cindex packet acknowledgment, for @value{GDBN} remote
27927 By default, when either the host or the target machine receives a packet,
27928 the first response expected is an acknowledgment: either @samp{+} (to indicate
27929 the package was received correctly) or @samp{-} (to request retransmission).
27930 This mechanism allows the @value{GDBN} remote protocol to operate over
27931 unreliable transport mechanisms, such as a serial line.
27933 In cases where the transport mechanism is itself reliable (such as a pipe or
27934 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
27935 It may be desirable to disable them in that case to reduce communication
27936 overhead, or for other reasons. This can be accomplished by means of the
27937 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
27939 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
27940 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
27941 and response format still includes the normal checksum, as described in
27942 @ref{Overview}, but the checksum may be ignored by the receiver.
27944 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
27945 no-acknowledgment mode, it should report that to @value{GDBN}
27946 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
27947 @pxref{qSupported}.
27948 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
27949 disabled via the @code{set remote noack-packet off} command
27950 (@pxref{Remote Configuration}),
27951 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
27952 Only then may the stub actually turn off packet acknowledgments.
27953 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
27954 response, which can be safely ignored by the stub.
27956 Note that @code{set remote noack-packet} command only affects negotiation
27957 between @value{GDBN} and the stub when subsequent connections are made;
27958 it does not affect the protocol acknowledgment state for any current
27960 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
27961 new connection is established,
27962 there is also no protocol request to re-enable the acknowledgments
27963 for the current connection, once disabled.
27968 Example sequence of a target being re-started. Notice how the restart
27969 does not get any direct output:
27974 @emph{target restarts}
27977 <- @code{T001:1234123412341234}
27981 Example sequence of a target being stepped by a single instruction:
27984 -> @code{G1445@dots{}}
27989 <- @code{T001:1234123412341234}
27993 <- @code{1455@dots{}}
27997 @node File-I/O Remote Protocol Extension
27998 @section File-I/O Remote Protocol Extension
27999 @cindex File-I/O remote protocol extension
28002 * File-I/O Overview::
28003 * Protocol Basics::
28004 * The F Request Packet::
28005 * The F Reply Packet::
28006 * The Ctrl-C Message::
28008 * List of Supported Calls::
28009 * Protocol-specific Representation of Datatypes::
28011 * File-I/O Examples::
28014 @node File-I/O Overview
28015 @subsection File-I/O Overview
28016 @cindex file-i/o overview
28018 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
28019 target to use the host's file system and console I/O to perform various
28020 system calls. System calls on the target system are translated into a
28021 remote protocol packet to the host system, which then performs the needed
28022 actions and returns a response packet to the target system.
28023 This simulates file system operations even on targets that lack file systems.
28025 The protocol is defined to be independent of both the host and target systems.
28026 It uses its own internal representation of datatypes and values. Both
28027 @value{GDBN} and the target's @value{GDBN} stub are responsible for
28028 translating the system-dependent value representations into the internal
28029 protocol representations when data is transmitted.
28031 The communication is synchronous. A system call is possible only when
28032 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
28033 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
28034 the target is stopped to allow deterministic access to the target's
28035 memory. Therefore File-I/O is not interruptible by target signals. On
28036 the other hand, it is possible to interrupt File-I/O by a user interrupt
28037 (@samp{Ctrl-C}) within @value{GDBN}.
28039 The target's request to perform a host system call does not finish
28040 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
28041 after finishing the system call, the target returns to continuing the
28042 previous activity (continue, step). No additional continue or step
28043 request from @value{GDBN} is required.
28046 (@value{GDBP}) continue
28047 <- target requests 'system call X'
28048 target is stopped, @value{GDBN} executes system call
28049 -> @value{GDBN} returns result
28050 ... target continues, @value{GDBN} returns to wait for the target
28051 <- target hits breakpoint and sends a Txx packet
28054 The protocol only supports I/O on the console and to regular files on
28055 the host file system. Character or block special devices, pipes,
28056 named pipes, sockets or any other communication method on the host
28057 system are not supported by this protocol.
28059 File I/O is not supported in non-stop mode.
28061 @node Protocol Basics
28062 @subsection Protocol Basics
28063 @cindex protocol basics, file-i/o
28065 The File-I/O protocol uses the @code{F} packet as the request as well
28066 as reply packet. Since a File-I/O system call can only occur when
28067 @value{GDBN} is waiting for a response from the continuing or stepping target,
28068 the File-I/O request is a reply that @value{GDBN} has to expect as a result
28069 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
28070 This @code{F} packet contains all information needed to allow @value{GDBN}
28071 to call the appropriate host system call:
28075 A unique identifier for the requested system call.
28078 All parameters to the system call. Pointers are given as addresses
28079 in the target memory address space. Pointers to strings are given as
28080 pointer/length pair. Numerical values are given as they are.
28081 Numerical control flags are given in a protocol-specific representation.
28085 At this point, @value{GDBN} has to perform the following actions.
28089 If the parameters include pointer values to data needed as input to a
28090 system call, @value{GDBN} requests this data from the target with a
28091 standard @code{m} packet request. This additional communication has to be
28092 expected by the target implementation and is handled as any other @code{m}
28096 @value{GDBN} translates all value from protocol representation to host
28097 representation as needed. Datatypes are coerced into the host types.
28100 @value{GDBN} calls the system call.
28103 It then coerces datatypes back to protocol representation.
28106 If the system call is expected to return data in buffer space specified
28107 by pointer parameters to the call, the data is transmitted to the
28108 target using a @code{M} or @code{X} packet. This packet has to be expected
28109 by the target implementation and is handled as any other @code{M} or @code{X}
28114 Eventually @value{GDBN} replies with another @code{F} packet which contains all
28115 necessary information for the target to continue. This at least contains
28122 @code{errno}, if has been changed by the system call.
28129 After having done the needed type and value coercion, the target continues
28130 the latest continue or step action.
28132 @node The F Request Packet
28133 @subsection The @code{F} Request Packet
28134 @cindex file-i/o request packet
28135 @cindex @code{F} request packet
28137 The @code{F} request packet has the following format:
28140 @item F@var{call-id},@var{parameter@dots{}}
28142 @var{call-id} is the identifier to indicate the host system call to be called.
28143 This is just the name of the function.
28145 @var{parameter@dots{}} are the parameters to the system call.
28146 Parameters are hexadecimal integer values, either the actual values in case
28147 of scalar datatypes, pointers to target buffer space in case of compound
28148 datatypes and unspecified memory areas, or pointer/length pairs in case
28149 of string parameters. These are appended to the @var{call-id} as a
28150 comma-delimited list. All values are transmitted in ASCII
28151 string representation, pointer/length pairs separated by a slash.
28157 @node The F Reply Packet
28158 @subsection The @code{F} Reply Packet
28159 @cindex file-i/o reply packet
28160 @cindex @code{F} reply packet
28162 The @code{F} reply packet has the following format:
28166 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
28168 @var{retcode} is the return code of the system call as hexadecimal value.
28170 @var{errno} is the @code{errno} set by the call, in protocol-specific
28172 This parameter can be omitted if the call was successful.
28174 @var{Ctrl-C flag} is only sent if the user requested a break. In this
28175 case, @var{errno} must be sent as well, even if the call was successful.
28176 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
28183 or, if the call was interrupted before the host call has been performed:
28190 assuming 4 is the protocol-specific representation of @code{EINTR}.
28195 @node The Ctrl-C Message
28196 @subsection The @samp{Ctrl-C} Message
28197 @cindex ctrl-c message, in file-i/o protocol
28199 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
28200 reply packet (@pxref{The F Reply Packet}),
28201 the target should behave as if it had
28202 gotten a break message. The meaning for the target is ``system call
28203 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
28204 (as with a break message) and return to @value{GDBN} with a @code{T02}
28207 It's important for the target to know in which
28208 state the system call was interrupted. There are two possible cases:
28212 The system call hasn't been performed on the host yet.
28215 The system call on the host has been finished.
28219 These two states can be distinguished by the target by the value of the
28220 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
28221 call hasn't been performed. This is equivalent to the @code{EINTR} handling
28222 on POSIX systems. In any other case, the target may presume that the
28223 system call has been finished --- successfully or not --- and should behave
28224 as if the break message arrived right after the system call.
28226 @value{GDBN} must behave reliably. If the system call has not been called
28227 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
28228 @code{errno} in the packet. If the system call on the host has been finished
28229 before the user requests a break, the full action must be finished by
28230 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
28231 The @code{F} packet may only be sent when either nothing has happened
28232 or the full action has been completed.
28235 @subsection Console I/O
28236 @cindex console i/o as part of file-i/o
28238 By default and if not explicitly closed by the target system, the file
28239 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
28240 on the @value{GDBN} console is handled as any other file output operation
28241 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
28242 by @value{GDBN} so that after the target read request from file descriptor
28243 0 all following typing is buffered until either one of the following
28248 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
28250 system call is treated as finished.
28253 The user presses @key{RET}. This is treated as end of input with a trailing
28257 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
28258 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
28262 If the user has typed more characters than fit in the buffer given to
28263 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
28264 either another @code{read(0, @dots{})} is requested by the target, or debugging
28265 is stopped at the user's request.
28268 @node List of Supported Calls
28269 @subsection List of Supported Calls
28270 @cindex list of supported file-i/o calls
28287 @unnumberedsubsubsec open
28288 @cindex open, file-i/o system call
28293 int open(const char *pathname, int flags);
28294 int open(const char *pathname, int flags, mode_t mode);
28298 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
28301 @var{flags} is the bitwise @code{OR} of the following values:
28305 If the file does not exist it will be created. The host
28306 rules apply as far as file ownership and time stamps
28310 When used with @code{O_CREAT}, if the file already exists it is
28311 an error and open() fails.
28314 If the file already exists and the open mode allows
28315 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
28316 truncated to zero length.
28319 The file is opened in append mode.
28322 The file is opened for reading only.
28325 The file is opened for writing only.
28328 The file is opened for reading and writing.
28332 Other bits are silently ignored.
28336 @var{mode} is the bitwise @code{OR} of the following values:
28340 User has read permission.
28343 User has write permission.
28346 Group has read permission.
28349 Group has write permission.
28352 Others have read permission.
28355 Others have write permission.
28359 Other bits are silently ignored.
28362 @item Return value:
28363 @code{open} returns the new file descriptor or -1 if an error
28370 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
28373 @var{pathname} refers to a directory.
28376 The requested access is not allowed.
28379 @var{pathname} was too long.
28382 A directory component in @var{pathname} does not exist.
28385 @var{pathname} refers to a device, pipe, named pipe or socket.
28388 @var{pathname} refers to a file on a read-only filesystem and
28389 write access was requested.
28392 @var{pathname} is an invalid pointer value.
28395 No space on device to create the file.
28398 The process already has the maximum number of files open.
28401 The limit on the total number of files open on the system
28405 The call was interrupted by the user.
28411 @unnumberedsubsubsec close
28412 @cindex close, file-i/o system call
28421 @samp{Fclose,@var{fd}}
28423 @item Return value:
28424 @code{close} returns zero on success, or -1 if an error occurred.
28430 @var{fd} isn't a valid open file descriptor.
28433 The call was interrupted by the user.
28439 @unnumberedsubsubsec read
28440 @cindex read, file-i/o system call
28445 int read(int fd, void *buf, unsigned int count);
28449 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
28451 @item Return value:
28452 On success, the number of bytes read is returned.
28453 Zero indicates end of file. If count is zero, read
28454 returns zero as well. On error, -1 is returned.
28460 @var{fd} is not a valid file descriptor or is not open for
28464 @var{bufptr} is an invalid pointer value.
28467 The call was interrupted by the user.
28473 @unnumberedsubsubsec write
28474 @cindex write, file-i/o system call
28479 int write(int fd, const void *buf, unsigned int count);
28483 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
28485 @item Return value:
28486 On success, the number of bytes written are returned.
28487 Zero indicates nothing was written. On error, -1
28494 @var{fd} is not a valid file descriptor or is not open for
28498 @var{bufptr} is an invalid pointer value.
28501 An attempt was made to write a file that exceeds the
28502 host-specific maximum file size allowed.
28505 No space on device to write the data.
28508 The call was interrupted by the user.
28514 @unnumberedsubsubsec lseek
28515 @cindex lseek, file-i/o system call
28520 long lseek (int fd, long offset, int flag);
28524 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
28526 @var{flag} is one of:
28530 The offset is set to @var{offset} bytes.
28533 The offset is set to its current location plus @var{offset}
28537 The offset is set to the size of the file plus @var{offset}
28541 @item Return value:
28542 On success, the resulting unsigned offset in bytes from
28543 the beginning of the file is returned. Otherwise, a
28544 value of -1 is returned.
28550 @var{fd} is not a valid open file descriptor.
28553 @var{fd} is associated with the @value{GDBN} console.
28556 @var{flag} is not a proper value.
28559 The call was interrupted by the user.
28565 @unnumberedsubsubsec rename
28566 @cindex rename, file-i/o system call
28571 int rename(const char *oldpath, const char *newpath);
28575 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
28577 @item Return value:
28578 On success, zero is returned. On error, -1 is returned.
28584 @var{newpath} is an existing directory, but @var{oldpath} is not a
28588 @var{newpath} is a non-empty directory.
28591 @var{oldpath} or @var{newpath} is a directory that is in use by some
28595 An attempt was made to make a directory a subdirectory
28599 A component used as a directory in @var{oldpath} or new
28600 path is not a directory. Or @var{oldpath} is a directory
28601 and @var{newpath} exists but is not a directory.
28604 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
28607 No access to the file or the path of the file.
28611 @var{oldpath} or @var{newpath} was too long.
28614 A directory component in @var{oldpath} or @var{newpath} does not exist.
28617 The file is on a read-only filesystem.
28620 The device containing the file has no room for the new
28624 The call was interrupted by the user.
28630 @unnumberedsubsubsec unlink
28631 @cindex unlink, file-i/o system call
28636 int unlink(const char *pathname);
28640 @samp{Funlink,@var{pathnameptr}/@var{len}}
28642 @item Return value:
28643 On success, zero is returned. On error, -1 is returned.
28649 No access to the file or the path of the file.
28652 The system does not allow unlinking of directories.
28655 The file @var{pathname} cannot be unlinked because it's
28656 being used by another process.
28659 @var{pathnameptr} is an invalid pointer value.
28662 @var{pathname} was too long.
28665 A directory component in @var{pathname} does not exist.
28668 A component of the path is not a directory.
28671 The file is on a read-only filesystem.
28674 The call was interrupted by the user.
28680 @unnumberedsubsubsec stat/fstat
28681 @cindex fstat, file-i/o system call
28682 @cindex stat, file-i/o system call
28687 int stat(const char *pathname, struct stat *buf);
28688 int fstat(int fd, struct stat *buf);
28692 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
28693 @samp{Ffstat,@var{fd},@var{bufptr}}
28695 @item Return value:
28696 On success, zero is returned. On error, -1 is returned.
28702 @var{fd} is not a valid open file.
28705 A directory component in @var{pathname} does not exist or the
28706 path is an empty string.
28709 A component of the path is not a directory.
28712 @var{pathnameptr} is an invalid pointer value.
28715 No access to the file or the path of the file.
28718 @var{pathname} was too long.
28721 The call was interrupted by the user.
28727 @unnumberedsubsubsec gettimeofday
28728 @cindex gettimeofday, file-i/o system call
28733 int gettimeofday(struct timeval *tv, void *tz);
28737 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
28739 @item Return value:
28740 On success, 0 is returned, -1 otherwise.
28746 @var{tz} is a non-NULL pointer.
28749 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
28755 @unnumberedsubsubsec isatty
28756 @cindex isatty, file-i/o system call
28761 int isatty(int fd);
28765 @samp{Fisatty,@var{fd}}
28767 @item Return value:
28768 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
28774 The call was interrupted by the user.
28779 Note that the @code{isatty} call is treated as a special case: it returns
28780 1 to the target if the file descriptor is attached
28781 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
28782 would require implementing @code{ioctl} and would be more complex than
28787 @unnumberedsubsubsec system
28788 @cindex system, file-i/o system call
28793 int system(const char *command);
28797 @samp{Fsystem,@var{commandptr}/@var{len}}
28799 @item Return value:
28800 If @var{len} is zero, the return value indicates whether a shell is
28801 available. A zero return value indicates a shell is not available.
28802 For non-zero @var{len}, the value returned is -1 on error and the
28803 return status of the command otherwise. Only the exit status of the
28804 command is returned, which is extracted from the host's @code{system}
28805 return value by calling @code{WEXITSTATUS(retval)}. In case
28806 @file{/bin/sh} could not be executed, 127 is returned.
28812 The call was interrupted by the user.
28817 @value{GDBN} takes over the full task of calling the necessary host calls
28818 to perform the @code{system} call. The return value of @code{system} on
28819 the host is simplified before it's returned
28820 to the target. Any termination signal information from the child process
28821 is discarded, and the return value consists
28822 entirely of the exit status of the called command.
28824 Due to security concerns, the @code{system} call is by default refused
28825 by @value{GDBN}. The user has to allow this call explicitly with the
28826 @code{set remote system-call-allowed 1} command.
28829 @item set remote system-call-allowed
28830 @kindex set remote system-call-allowed
28831 Control whether to allow the @code{system} calls in the File I/O
28832 protocol for the remote target. The default is zero (disabled).
28834 @item show remote system-call-allowed
28835 @kindex show remote system-call-allowed
28836 Show whether the @code{system} calls are allowed in the File I/O
28840 @node Protocol-specific Representation of Datatypes
28841 @subsection Protocol-specific Representation of Datatypes
28842 @cindex protocol-specific representation of datatypes, in file-i/o protocol
28845 * Integral Datatypes::
28847 * Memory Transfer::
28852 @node Integral Datatypes
28853 @unnumberedsubsubsec Integral Datatypes
28854 @cindex integral datatypes, in file-i/o protocol
28856 The integral datatypes used in the system calls are @code{int},
28857 @code{unsigned int}, @code{long}, @code{unsigned long},
28858 @code{mode_t}, and @code{time_t}.
28860 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
28861 implemented as 32 bit values in this protocol.
28863 @code{long} and @code{unsigned long} are implemented as 64 bit types.
28865 @xref{Limits}, for corresponding MIN and MAX values (similar to those
28866 in @file{limits.h}) to allow range checking on host and target.
28868 @code{time_t} datatypes are defined as seconds since the Epoch.
28870 All integral datatypes transferred as part of a memory read or write of a
28871 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
28874 @node Pointer Values
28875 @unnumberedsubsubsec Pointer Values
28876 @cindex pointer values, in file-i/o protocol
28878 Pointers to target data are transmitted as they are. An exception
28879 is made for pointers to buffers for which the length isn't
28880 transmitted as part of the function call, namely strings. Strings
28881 are transmitted as a pointer/length pair, both as hex values, e.g.@:
28888 which is a pointer to data of length 18 bytes at position 0x1aaf.
28889 The length is defined as the full string length in bytes, including
28890 the trailing null byte. For example, the string @code{"hello world"}
28891 at address 0x123456 is transmitted as
28897 @node Memory Transfer
28898 @unnumberedsubsubsec Memory Transfer
28899 @cindex memory transfer, in file-i/o protocol
28901 Structured data which is transferred using a memory read or write (for
28902 example, a @code{struct stat}) is expected to be in a protocol-specific format
28903 with all scalar multibyte datatypes being big endian. Translation to
28904 this representation needs to be done both by the target before the @code{F}
28905 packet is sent, and by @value{GDBN} before
28906 it transfers memory to the target. Transferred pointers to structured
28907 data should point to the already-coerced data at any time.
28911 @unnumberedsubsubsec struct stat
28912 @cindex struct stat, in file-i/o protocol
28914 The buffer of type @code{struct stat} used by the target and @value{GDBN}
28915 is defined as follows:
28919 unsigned int st_dev; /* device */
28920 unsigned int st_ino; /* inode */
28921 mode_t st_mode; /* protection */
28922 unsigned int st_nlink; /* number of hard links */
28923 unsigned int st_uid; /* user ID of owner */
28924 unsigned int st_gid; /* group ID of owner */
28925 unsigned int st_rdev; /* device type (if inode device) */
28926 unsigned long st_size; /* total size, in bytes */
28927 unsigned long st_blksize; /* blocksize for filesystem I/O */
28928 unsigned long st_blocks; /* number of blocks allocated */
28929 time_t st_atime; /* time of last access */
28930 time_t st_mtime; /* time of last modification */
28931 time_t st_ctime; /* time of last change */
28935 The integral datatypes conform to the definitions given in the
28936 appropriate section (see @ref{Integral Datatypes}, for details) so this
28937 structure is of size 64 bytes.
28939 The values of several fields have a restricted meaning and/or
28945 A value of 0 represents a file, 1 the console.
28948 No valid meaning for the target. Transmitted unchanged.
28951 Valid mode bits are described in @ref{Constants}. Any other
28952 bits have currently no meaning for the target.
28957 No valid meaning for the target. Transmitted unchanged.
28962 These values have a host and file system dependent
28963 accuracy. Especially on Windows hosts, the file system may not
28964 support exact timing values.
28967 The target gets a @code{struct stat} of the above representation and is
28968 responsible for coercing it to the target representation before
28971 Note that due to size differences between the host, target, and protocol
28972 representations of @code{struct stat} members, these members could eventually
28973 get truncated on the target.
28975 @node struct timeval
28976 @unnumberedsubsubsec struct timeval
28977 @cindex struct timeval, in file-i/o protocol
28979 The buffer of type @code{struct timeval} used by the File-I/O protocol
28980 is defined as follows:
28984 time_t tv_sec; /* second */
28985 long tv_usec; /* microsecond */
28989 The integral datatypes conform to the definitions given in the
28990 appropriate section (see @ref{Integral Datatypes}, for details) so this
28991 structure is of size 8 bytes.
28994 @subsection Constants
28995 @cindex constants, in file-i/o protocol
28997 The following values are used for the constants inside of the
28998 protocol. @value{GDBN} and target are responsible for translating these
28999 values before and after the call as needed.
29010 @unnumberedsubsubsec Open Flags
29011 @cindex open flags, in file-i/o protocol
29013 All values are given in hexadecimal representation.
29025 @node mode_t Values
29026 @unnumberedsubsubsec mode_t Values
29027 @cindex mode_t values, in file-i/o protocol
29029 All values are given in octal representation.
29046 @unnumberedsubsubsec Errno Values
29047 @cindex errno values, in file-i/o protocol
29049 All values are given in decimal representation.
29074 @code{EUNKNOWN} is used as a fallback error value if a host system returns
29075 any error value not in the list of supported error numbers.
29078 @unnumberedsubsubsec Lseek Flags
29079 @cindex lseek flags, in file-i/o protocol
29088 @unnumberedsubsubsec Limits
29089 @cindex limits, in file-i/o protocol
29091 All values are given in decimal representation.
29094 INT_MIN -2147483648
29096 UINT_MAX 4294967295
29097 LONG_MIN -9223372036854775808
29098 LONG_MAX 9223372036854775807
29099 ULONG_MAX 18446744073709551615
29102 @node File-I/O Examples
29103 @subsection File-I/O Examples
29104 @cindex file-i/o examples
29106 Example sequence of a write call, file descriptor 3, buffer is at target
29107 address 0x1234, 6 bytes should be written:
29110 <- @code{Fwrite,3,1234,6}
29111 @emph{request memory read from target}
29114 @emph{return "6 bytes written"}
29118 Example sequence of a read call, file descriptor 3, buffer is at target
29119 address 0x1234, 6 bytes should be read:
29122 <- @code{Fread,3,1234,6}
29123 @emph{request memory write to target}
29124 -> @code{X1234,6:XXXXXX}
29125 @emph{return "6 bytes read"}
29129 Example sequence of a read call, call fails on the host due to invalid
29130 file descriptor (@code{EBADF}):
29133 <- @code{Fread,3,1234,6}
29137 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
29141 <- @code{Fread,3,1234,6}
29146 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
29150 <- @code{Fread,3,1234,6}
29151 -> @code{X1234,6:XXXXXX}
29155 @node Library List Format
29156 @section Library List Format
29157 @cindex library list format, remote protocol
29159 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
29160 same process as your application to manage libraries. In this case,
29161 @value{GDBN} can use the loader's symbol table and normal memory
29162 operations to maintain a list of shared libraries. On other
29163 platforms, the operating system manages loaded libraries.
29164 @value{GDBN} can not retrieve the list of currently loaded libraries
29165 through memory operations, so it uses the @samp{qXfer:libraries:read}
29166 packet (@pxref{qXfer library list read}) instead. The remote stub
29167 queries the target's operating system and reports which libraries
29170 The @samp{qXfer:libraries:read} packet returns an XML document which
29171 lists loaded libraries and their offsets. Each library has an
29172 associated name and one or more segment or section base addresses,
29173 which report where the library was loaded in memory.
29175 For the common case of libraries that are fully linked binaries, the
29176 library should have a list of segments. If the target supports
29177 dynamic linking of a relocatable object file, its library XML element
29178 should instead include a list of allocated sections. The segment or
29179 section bases are start addresses, not relocation offsets; they do not
29180 depend on the library's link-time base addresses.
29182 @value{GDBN} must be linked with the Expat library to support XML
29183 library lists. @xref{Expat}.
29185 A simple memory map, with one loaded library relocated by a single
29186 offset, looks like this:
29190 <library name="/lib/libc.so.6">
29191 <segment address="0x10000000"/>
29196 Another simple memory map, with one loaded library with three
29197 allocated sections (.text, .data, .bss), looks like this:
29201 <library name="sharedlib.o">
29202 <section address="0x10000000"/>
29203 <section address="0x20000000"/>
29204 <section address="0x30000000"/>
29209 The format of a library list is described by this DTD:
29212 <!-- library-list: Root element with versioning -->
29213 <!ELEMENT library-list (library)*>
29214 <!ATTLIST library-list version CDATA #FIXED "1.0">
29215 <!ELEMENT library (segment*, section*)>
29216 <!ATTLIST library name CDATA #REQUIRED>
29217 <!ELEMENT segment EMPTY>
29218 <!ATTLIST segment address CDATA #REQUIRED>
29219 <!ELEMENT section EMPTY>
29220 <!ATTLIST section address CDATA #REQUIRED>
29223 In addition, segments and section descriptors cannot be mixed within a
29224 single library element, and you must supply at least one segment or
29225 section for each library.
29227 @node Memory Map Format
29228 @section Memory Map Format
29229 @cindex memory map format
29231 To be able to write into flash memory, @value{GDBN} needs to obtain a
29232 memory map from the target. This section describes the format of the
29235 The memory map is obtained using the @samp{qXfer:memory-map:read}
29236 (@pxref{qXfer memory map read}) packet and is an XML document that
29237 lists memory regions.
29239 @value{GDBN} must be linked with the Expat library to support XML
29240 memory maps. @xref{Expat}.
29242 The top-level structure of the document is shown below:
29245 <?xml version="1.0"?>
29246 <!DOCTYPE memory-map
29247 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
29248 "http://sourceware.org/gdb/gdb-memory-map.dtd">
29254 Each region can be either:
29259 A region of RAM starting at @var{addr} and extending for @var{length}
29263 <memory type="ram" start="@var{addr}" length="@var{length}"/>
29268 A region of read-only memory:
29271 <memory type="rom" start="@var{addr}" length="@var{length}"/>
29276 A region of flash memory, with erasure blocks @var{blocksize}
29280 <memory type="flash" start="@var{addr}" length="@var{length}">
29281 <property name="blocksize">@var{blocksize}</property>
29287 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
29288 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
29289 packets to write to addresses in such ranges.
29291 The formal DTD for memory map format is given below:
29294 <!-- ................................................... -->
29295 <!-- Memory Map XML DTD ................................ -->
29296 <!-- File: memory-map.dtd .............................. -->
29297 <!-- .................................... .............. -->
29298 <!-- memory-map.dtd -->
29299 <!-- memory-map: Root element with versioning -->
29300 <!ELEMENT memory-map (memory | property)>
29301 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
29302 <!ELEMENT memory (property)>
29303 <!-- memory: Specifies a memory region,
29304 and its type, or device. -->
29305 <!ATTLIST memory type CDATA #REQUIRED
29306 start CDATA #REQUIRED
29307 length CDATA #REQUIRED
29308 device CDATA #IMPLIED>
29309 <!-- property: Generic attribute tag -->
29310 <!ELEMENT property (#PCDATA | property)*>
29311 <!ATTLIST property name CDATA #REQUIRED>
29314 @include agentexpr.texi
29316 @node Target Descriptions
29317 @appendix Target Descriptions
29318 @cindex target descriptions
29320 @strong{Warning:} target descriptions are still under active development,
29321 and the contents and format may change between @value{GDBN} releases.
29322 The format is expected to stabilize in the future.
29324 One of the challenges of using @value{GDBN} to debug embedded systems
29325 is that there are so many minor variants of each processor
29326 architecture in use. It is common practice for vendors to start with
29327 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
29328 and then make changes to adapt it to a particular market niche. Some
29329 architectures have hundreds of variants, available from dozens of
29330 vendors. This leads to a number of problems:
29334 With so many different customized processors, it is difficult for
29335 the @value{GDBN} maintainers to keep up with the changes.
29337 Since individual variants may have short lifetimes or limited
29338 audiences, it may not be worthwhile to carry information about every
29339 variant in the @value{GDBN} source tree.
29341 When @value{GDBN} does support the architecture of the embedded system
29342 at hand, the task of finding the correct architecture name to give the
29343 @command{set architecture} command can be error-prone.
29346 To address these problems, the @value{GDBN} remote protocol allows a
29347 target system to not only identify itself to @value{GDBN}, but to
29348 actually describe its own features. This lets @value{GDBN} support
29349 processor variants it has never seen before --- to the extent that the
29350 descriptions are accurate, and that @value{GDBN} understands them.
29352 @value{GDBN} must be linked with the Expat library to support XML
29353 target descriptions. @xref{Expat}.
29356 * Retrieving Descriptions:: How descriptions are fetched from a target.
29357 * Target Description Format:: The contents of a target description.
29358 * Predefined Target Types:: Standard types available for target
29360 * Standard Target Features:: Features @value{GDBN} knows about.
29363 @node Retrieving Descriptions
29364 @section Retrieving Descriptions
29366 Target descriptions can be read from the target automatically, or
29367 specified by the user manually. The default behavior is to read the
29368 description from the target. @value{GDBN} retrieves it via the remote
29369 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
29370 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
29371 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
29372 XML document, of the form described in @ref{Target Description
29375 Alternatively, you can specify a file to read for the target description.
29376 If a file is set, the target will not be queried. The commands to
29377 specify a file are:
29380 @cindex set tdesc filename
29381 @item set tdesc filename @var{path}
29382 Read the target description from @var{path}.
29384 @cindex unset tdesc filename
29385 @item unset tdesc filename
29386 Do not read the XML target description from a file. @value{GDBN}
29387 will use the description supplied by the current target.
29389 @cindex show tdesc filename
29390 @item show tdesc filename
29391 Show the filename to read for a target description, if any.
29395 @node Target Description Format
29396 @section Target Description Format
29397 @cindex target descriptions, XML format
29399 A target description annex is an @uref{http://www.w3.org/XML/, XML}
29400 document which complies with the Document Type Definition provided in
29401 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
29402 means you can use generally available tools like @command{xmllint} to
29403 check that your feature descriptions are well-formed and valid.
29404 However, to help people unfamiliar with XML write descriptions for
29405 their targets, we also describe the grammar here.
29407 Target descriptions can identify the architecture of the remote target
29408 and (for some architectures) provide information about custom register
29409 sets. @value{GDBN} can use this information to autoconfigure for your
29410 target, or to warn you if you connect to an unsupported target.
29412 Here is a simple target description:
29415 <target version="1.0">
29416 <architecture>i386:x86-64</architecture>
29421 This minimal description only says that the target uses
29422 the x86-64 architecture.
29424 A target description has the following overall form, with [ ] marking
29425 optional elements and @dots{} marking repeatable elements. The elements
29426 are explained further below.
29429 <?xml version="1.0"?>
29430 <!DOCTYPE target SYSTEM "gdb-target.dtd">
29431 <target version="1.0">
29432 @r{[}@var{architecture}@r{]}
29433 @r{[}@var{feature}@dots{}@r{]}
29438 The description is generally insensitive to whitespace and line
29439 breaks, under the usual common-sense rules. The XML version
29440 declaration and document type declaration can generally be omitted
29441 (@value{GDBN} does not require them), but specifying them may be
29442 useful for XML validation tools. The @samp{version} attribute for
29443 @samp{<target>} may also be omitted, but we recommend
29444 including it; if future versions of @value{GDBN} use an incompatible
29445 revision of @file{gdb-target.dtd}, they will detect and report
29446 the version mismatch.
29448 @subsection Inclusion
29449 @cindex target descriptions, inclusion
29452 @cindex <xi:include>
29455 It can sometimes be valuable to split a target description up into
29456 several different annexes, either for organizational purposes, or to
29457 share files between different possible target descriptions. You can
29458 divide a description into multiple files by replacing any element of
29459 the target description with an inclusion directive of the form:
29462 <xi:include href="@var{document}"/>
29466 When @value{GDBN} encounters an element of this form, it will retrieve
29467 the named XML @var{document}, and replace the inclusion directive with
29468 the contents of that document. If the current description was read
29469 using @samp{qXfer}, then so will be the included document;
29470 @var{document} will be interpreted as the name of an annex. If the
29471 current description was read from a file, @value{GDBN} will look for
29472 @var{document} as a file in the same directory where it found the
29473 original description.
29475 @subsection Architecture
29476 @cindex <architecture>
29478 An @samp{<architecture>} element has this form:
29481 <architecture>@var{arch}</architecture>
29484 @var{arch} is an architecture name from the same selection
29485 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
29486 Debugging Target}).
29488 @subsection Features
29491 Each @samp{<feature>} describes some logical portion of the target
29492 system. Features are currently used to describe available CPU
29493 registers and the types of their contents. A @samp{<feature>} element
29497 <feature name="@var{name}">
29498 @r{[}@var{type}@dots{}@r{]}
29504 Each feature's name should be unique within the description. The name
29505 of a feature does not matter unless @value{GDBN} has some special
29506 knowledge of the contents of that feature; if it does, the feature
29507 should have its standard name. @xref{Standard Target Features}.
29511 Any register's value is a collection of bits which @value{GDBN} must
29512 interpret. The default interpretation is a two's complement integer,
29513 but other types can be requested by name in the register description.
29514 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
29515 Target Types}), and the description can define additional composite types.
29517 Each type element must have an @samp{id} attribute, which gives
29518 a unique (within the containing @samp{<feature>}) name to the type.
29519 Types must be defined before they are used.
29522 Some targets offer vector registers, which can be treated as arrays
29523 of scalar elements. These types are written as @samp{<vector>} elements,
29524 specifying the array element type, @var{type}, and the number of elements,
29528 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
29532 If a register's value is usefully viewed in multiple ways, define it
29533 with a union type containing the useful representations. The
29534 @samp{<union>} element contains one or more @samp{<field>} elements,
29535 each of which has a @var{name} and a @var{type}:
29538 <union id="@var{id}">
29539 <field name="@var{name}" type="@var{type}"/>
29544 @subsection Registers
29547 Each register is represented as an element with this form:
29550 <reg name="@var{name}"
29551 bitsize="@var{size}"
29552 @r{[}regnum="@var{num}"@r{]}
29553 @r{[}save-restore="@var{save-restore}"@r{]}
29554 @r{[}type="@var{type}"@r{]}
29555 @r{[}group="@var{group}"@r{]}/>
29559 The components are as follows:
29564 The register's name; it must be unique within the target description.
29567 The register's size, in bits.
29570 The register's number. If omitted, a register's number is one greater
29571 than that of the previous register (either in the current feature or in
29572 a preceeding feature); the first register in the target description
29573 defaults to zero. This register number is used to read or write
29574 the register; e.g.@: it is used in the remote @code{p} and @code{P}
29575 packets, and registers appear in the @code{g} and @code{G} packets
29576 in order of increasing register number.
29579 Whether the register should be preserved across inferior function
29580 calls; this must be either @code{yes} or @code{no}. The default is
29581 @code{yes}, which is appropriate for most registers except for
29582 some system control registers; this is not related to the target's
29586 The type of the register. @var{type} may be a predefined type, a type
29587 defined in the current feature, or one of the special types @code{int}
29588 and @code{float}. @code{int} is an integer type of the correct size
29589 for @var{bitsize}, and @code{float} is a floating point type (in the
29590 architecture's normal floating point format) of the correct size for
29591 @var{bitsize}. The default is @code{int}.
29594 The register group to which this register belongs. @var{group} must
29595 be either @code{general}, @code{float}, or @code{vector}. If no
29596 @var{group} is specified, @value{GDBN} will not display the register
29597 in @code{info registers}.
29601 @node Predefined Target Types
29602 @section Predefined Target Types
29603 @cindex target descriptions, predefined types
29605 Type definitions in the self-description can build up composite types
29606 from basic building blocks, but can not define fundamental types. Instead,
29607 standard identifiers are provided by @value{GDBN} for the fundamental
29608 types. The currently supported types are:
29617 Signed integer types holding the specified number of bits.
29624 Unsigned integer types holding the specified number of bits.
29628 Pointers to unspecified code and data. The program counter and
29629 any dedicated return address register may be marked as code
29630 pointers; printing a code pointer converts it into a symbolic
29631 address. The stack pointer and any dedicated address registers
29632 may be marked as data pointers.
29635 Single precision IEEE floating point.
29638 Double precision IEEE floating point.
29641 The 12-byte extended precision format used by ARM FPA registers.
29645 @node Standard Target Features
29646 @section Standard Target Features
29647 @cindex target descriptions, standard features
29649 A target description must contain either no registers or all the
29650 target's registers. If the description contains no registers, then
29651 @value{GDBN} will assume a default register layout, selected based on
29652 the architecture. If the description contains any registers, the
29653 default layout will not be used; the standard registers must be
29654 described in the target description, in such a way that @value{GDBN}
29655 can recognize them.
29657 This is accomplished by giving specific names to feature elements
29658 which contain standard registers. @value{GDBN} will look for features
29659 with those names and verify that they contain the expected registers;
29660 if any known feature is missing required registers, or if any required
29661 feature is missing, @value{GDBN} will reject the target
29662 description. You can add additional registers to any of the
29663 standard features --- @value{GDBN} will display them just as if
29664 they were added to an unrecognized feature.
29666 This section lists the known features and their expected contents.
29667 Sample XML documents for these features are included in the
29668 @value{GDBN} source tree, in the directory @file{gdb/features}.
29670 Names recognized by @value{GDBN} should include the name of the
29671 company or organization which selected the name, and the overall
29672 architecture to which the feature applies; so e.g.@: the feature
29673 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
29675 The names of registers are not case sensitive for the purpose
29676 of recognizing standard features, but @value{GDBN} will only display
29677 registers using the capitalization used in the description.
29683 * PowerPC Features::
29688 @subsection ARM Features
29689 @cindex target descriptions, ARM features
29691 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
29692 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
29693 @samp{lr}, @samp{pc}, and @samp{cpsr}.
29695 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
29696 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
29698 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
29699 it should contain at least registers @samp{wR0} through @samp{wR15} and
29700 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
29701 @samp{wCSSF}, and @samp{wCASF} registers are optional.
29703 @node MIPS Features
29704 @subsection MIPS Features
29705 @cindex target descriptions, MIPS features
29707 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
29708 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
29709 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
29712 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
29713 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
29714 registers. They may be 32-bit or 64-bit depending on the target.
29716 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
29717 it may be optional in a future version of @value{GDBN}. It should
29718 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
29719 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
29721 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
29722 contain a single register, @samp{restart}, which is used by the
29723 Linux kernel to control restartable syscalls.
29725 @node M68K Features
29726 @subsection M68K Features
29727 @cindex target descriptions, M68K features
29730 @item @samp{org.gnu.gdb.m68k.core}
29731 @itemx @samp{org.gnu.gdb.coldfire.core}
29732 @itemx @samp{org.gnu.gdb.fido.core}
29733 One of those features must be always present.
29734 The feature that is present determines which flavor of m68k is
29735 used. The feature that is present should contain registers
29736 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
29737 @samp{sp}, @samp{ps} and @samp{pc}.
29739 @item @samp{org.gnu.gdb.coldfire.fp}
29740 This feature is optional. If present, it should contain registers
29741 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
29745 @node PowerPC Features
29746 @subsection PowerPC Features
29747 @cindex target descriptions, PowerPC features
29749 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
29750 targets. It should contain registers @samp{r0} through @samp{r31},
29751 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
29752 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
29754 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
29755 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
29757 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
29758 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
29761 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
29762 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
29763 will combine these registers with the floating point registers
29764 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
29765 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
29766 through @samp{vs63}, the set of vector registers for POWER7.
29768 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
29769 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
29770 @samp{spefscr}. SPE targets should provide 32-bit registers in
29771 @samp{org.gnu.gdb.power.core} and provide the upper halves in
29772 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
29773 these to present registers @samp{ev0} through @samp{ev31} to the
29776 @node Operating System Information
29777 @appendix Operating System Information
29778 @cindex operating system information
29784 Users of @value{GDBN} often wish to obtain information about the state of
29785 the operating system running on the target---for example the list of
29786 processes, or the list of open files. This section describes the
29787 mechanism that makes it possible. This mechanism is similar to the
29788 target features mechanism (@pxref{Target Descriptions}), but focuses
29789 on a different aspect of target.
29791 Operating system information is retrived from the target via the
29792 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
29793 read}). The object name in the request should be @samp{osdata}, and
29794 the @var{annex} identifies the data to be fetched.
29797 @appendixsection Process list
29798 @cindex operating system information, process list
29800 When requesting the process list, the @var{annex} field in the
29801 @samp{qXfer} request should be @samp{processes}. The returned data is
29802 an XML document. The formal syntax of this document is defined in
29803 @file{gdb/features/osdata.dtd}.
29805 An example document is:
29808 <?xml version="1.0"?>
29809 <!DOCTYPE target SYSTEM "osdata.dtd">
29810 <osdata type="processes">
29812 <column name="pid">1</column>
29813 <column name="user">root</column>
29814 <column name="command">/sbin/init</column>
29819 Each item should include a column whose name is @samp{pid}. The value
29820 of that column should identify the process on the target. The
29821 @samp{user} and @samp{command} columns are optional, and will be
29822 displayed by @value{GDBN}. Target may provide additional columns,
29823 which @value{GDBN} currently ignores.
29837 % I think something like @colophon should be in texinfo. In the
29839 \long\def\colophon{\hbox to0pt{}\vfill
29840 \centerline{The body of this manual is set in}
29841 \centerline{\fontname\tenrm,}
29842 \centerline{with headings in {\bf\fontname\tenbf}}
29843 \centerline{and examples in {\tt\fontname\tentt}.}
29844 \centerline{{\it\fontname\tenit\/},}
29845 \centerline{{\bf\fontname\tenbf}, and}
29846 \centerline{{\sl\fontname\tensl\/}}
29847 \centerline{are used for emphasis.}\vfill}
29849 % Blame: doc@cygnus.com, 1991.