1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
48 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
49 Free Software Foundation, Inc.
51 Permission is granted to copy, distribute and/or modify this document
52 under the terms of the GNU Free Documentation License, Version 1.1 or
53 any later version published by the Free Software Foundation; with the
54 Invariant Sections being ``Free Software'' and ``Free Software Needs
55 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
56 and with the Back-Cover Texts as in (a) below.
58 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
59 this GNU Manual. Buying copies from GNU Press supports the FSF in
60 developing GNU and promoting software freedom.''
64 This file documents the @sc{gnu} debugger @value{GDBN}.
66 This is the @value{EDITION} Edition, of @cite{Debugging with
67 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
68 @ifset VERSION_PACKAGE
69 @value{VERSION_PACKAGE}
71 Version @value{GDBVN}.
77 @title Debugging with @value{GDBN}
78 @subtitle The @sc{gnu} Source-Level Debugger
80 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
81 @ifset VERSION_PACKAGE
83 @subtitle @value{VERSION_PACKAGE}
85 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
89 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
90 \hfill {\it Debugging with @value{GDBN}}\par
91 \hfill \TeX{}info \texinfoversion\par
95 @vskip 0pt plus 1filll
96 Published by the Free Software Foundation @*
97 51 Franklin Street, Fifth Floor,
98 Boston, MA 02110-1301, USA@*
103 This edition of the GDB manual is dedicated to the memory of Fred
104 Fish. Fred was a long-standing contributor to GDB and to Free
105 software in general. We will miss him.
110 @node Top, Summary, (dir), (dir)
112 @top Debugging with @value{GDBN}
114 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
116 This is the @value{EDITION} Edition, for @value{GDBN}
117 @ifset VERSION_PACKAGE
118 @value{VERSION_PACKAGE}
120 Version @value{GDBVN}.
122 Copyright (C) 1988-2009 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Reverse Execution:: Running programs backward
137 * Stack:: Examining the stack
138 * Source:: Examining source files
139 * Data:: Examining data
140 * Macros:: Preprocessor Macros
141 * Tracepoints:: Debugging remote targets non-intrusively
142 * Overlays:: Debugging programs that use overlays
144 * Languages:: Using @value{GDBN} with different languages
146 * Symbols:: Examining the symbol table
147 * Altering:: Altering execution
148 * GDB Files:: @value{GDBN} files
149 * Targets:: Specifying a debugging target
150 * Remote Debugging:: Debugging remote programs
151 * Configurations:: Configuration-specific information
152 * Controlling GDB:: Controlling @value{GDBN}
153 * Extending GDB:: Extending @value{GDBN}
154 * Interpreters:: Command Interpreters
155 * TUI:: @value{GDBN} Text User Interface
156 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
157 * GDB/MI:: @value{GDBN}'s Machine Interface.
158 * Annotations:: @value{GDBN}'s annotation interface.
160 * GDB Bugs:: Reporting bugs in @value{GDBN}
162 * Command Line Editing:: Command Line Editing
163 * Using History Interactively:: Using History Interactively
164 * Formatting Documentation:: How to format and print @value{GDBN} documentation
165 * Installing GDB:: Installing GDB
166 * Maintenance Commands:: Maintenance Commands
167 * Remote Protocol:: GDB Remote Serial Protocol
168 * Agent Expressions:: The GDB Agent Expression Mechanism
169 * Target Descriptions:: How targets can describe themselves to
171 * Operating System Information:: Getting additional information from
173 * Copying:: GNU General Public License says
174 how you can copy and share GDB
175 * GNU Free Documentation License:: The license for this documentation
184 @unnumbered Summary of @value{GDBN}
186 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
187 going on ``inside'' another program while it executes---or what another
188 program was doing at the moment it crashed.
190 @value{GDBN} can do four main kinds of things (plus other things in support of
191 these) to help you catch bugs in the act:
195 Start your program, specifying anything that might affect its behavior.
198 Make your program stop on specified conditions.
201 Examine what has happened, when your program has stopped.
204 Change things in your program, so you can experiment with correcting the
205 effects of one bug and go on to learn about another.
208 You can use @value{GDBN} to debug programs written in C and C@t{++}.
209 For more information, see @ref{Supported Languages,,Supported Languages}.
210 For more information, see @ref{C,,C and C++}.
213 Support for Modula-2 is partial. For information on Modula-2, see
214 @ref{Modula-2,,Modula-2}.
217 Debugging Pascal programs which use sets, subranges, file variables, or
218 nested functions does not currently work. @value{GDBN} does not support
219 entering expressions, printing values, or similar features using Pascal
223 @value{GDBN} can be used to debug programs written in Fortran, although
224 it may be necessary to refer to some variables with a trailing
227 @value{GDBN} can be used to debug programs written in Objective-C,
228 using either the Apple/NeXT or the GNU Objective-C runtime.
231 * Free Software:: Freely redistributable software
232 * Contributors:: Contributors to GDB
236 @unnumberedsec Free Software
238 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
239 General Public License
240 (GPL). The GPL gives you the freedom to copy or adapt a licensed
241 program---but every person getting a copy also gets with it the
242 freedom to modify that copy (which means that they must get access to
243 the source code), and the freedom to distribute further copies.
244 Typical software companies use copyrights to limit your freedoms; the
245 Free Software Foundation uses the GPL to preserve these freedoms.
247 Fundamentally, the General Public License is a license which says that
248 you have these freedoms and that you cannot take these freedoms away
251 @unnumberedsec Free Software Needs Free Documentation
253 The biggest deficiency in the free software community today is not in
254 the software---it is the lack of good free documentation that we can
255 include with the free software. Many of our most important
256 programs do not come with free reference manuals and free introductory
257 texts. Documentation is an essential part of any software package;
258 when an important free software package does not come with a free
259 manual and a free tutorial, that is a major gap. We have many such
262 Consider Perl, for instance. The tutorial manuals that people
263 normally use are non-free. How did this come about? Because the
264 authors of those manuals published them with restrictive terms---no
265 copying, no modification, source files not available---which exclude
266 them from the free software world.
268 That wasn't the first time this sort of thing happened, and it was far
269 from the last. Many times we have heard a GNU user eagerly describe a
270 manual that he is writing, his intended contribution to the community,
271 only to learn that he had ruined everything by signing a publication
272 contract to make it non-free.
274 Free documentation, like free software, is a matter of freedom, not
275 price. The problem with the non-free manual is not that publishers
276 charge a price for printed copies---that in itself is fine. (The Free
277 Software Foundation sells printed copies of manuals, too.) The
278 problem is the restrictions on the use of the manual. Free manuals
279 are available in source code form, and give you permission to copy and
280 modify. Non-free manuals do not allow this.
282 The criteria of freedom for a free manual are roughly the same as for
283 free software. Redistribution (including the normal kinds of
284 commercial redistribution) must be permitted, so that the manual can
285 accompany every copy of the program, both on-line and on paper.
287 Permission for modification of the technical content is crucial too.
288 When people modify the software, adding or changing features, if they
289 are conscientious they will change the manual too---so they can
290 provide accurate and clear documentation for the modified program. A
291 manual that leaves you no choice but to write a new manual to document
292 a changed version of the program is not really available to our
295 Some kinds of limits on the way modification is handled are
296 acceptable. For example, requirements to preserve the original
297 author's copyright notice, the distribution terms, or the list of
298 authors, are ok. It is also no problem to require modified versions
299 to include notice that they were modified. Even entire sections that
300 may not be deleted or changed are acceptable, as long as they deal
301 with nontechnical topics (like this one). These kinds of restrictions
302 are acceptable because they don't obstruct the community's normal use
305 However, it must be possible to modify all the @emph{technical}
306 content of the manual, and then distribute the result in all the usual
307 media, through all the usual channels. Otherwise, the restrictions
308 obstruct the use of the manual, it is not free, and we need another
309 manual to replace it.
311 Please spread the word about this issue. Our community continues to
312 lose manuals to proprietary publishing. If we spread the word that
313 free software needs free reference manuals and free tutorials, perhaps
314 the next person who wants to contribute by writing documentation will
315 realize, before it is too late, that only free manuals contribute to
316 the free software community.
318 If you are writing documentation, please insist on publishing it under
319 the GNU Free Documentation License or another free documentation
320 license. Remember that this decision requires your approval---you
321 don't have to let the publisher decide. Some commercial publishers
322 will use a free license if you insist, but they will not propose the
323 option; it is up to you to raise the issue and say firmly that this is
324 what you want. If the publisher you are dealing with refuses, please
325 try other publishers. If you're not sure whether a proposed license
326 is free, write to @email{licensing@@gnu.org}.
328 You can encourage commercial publishers to sell more free, copylefted
329 manuals and tutorials by buying them, and particularly by buying
330 copies from the publishers that paid for their writing or for major
331 improvements. Meanwhile, try to avoid buying non-free documentation
332 at all. Check the distribution terms of a manual before you buy it,
333 and insist that whoever seeks your business must respect your freedom.
334 Check the history of the book, and try to reward the publishers that
335 have paid or pay the authors to work on it.
337 The Free Software Foundation maintains a list of free documentation
338 published by other publishers, at
339 @url{http://www.fsf.org/doc/other-free-books.html}.
342 @unnumberedsec Contributors to @value{GDBN}
344 Richard Stallman was the original author of @value{GDBN}, and of many
345 other @sc{gnu} programs. Many others have contributed to its
346 development. This section attempts to credit major contributors. One
347 of the virtues of free software is that everyone is free to contribute
348 to it; with regret, we cannot actually acknowledge everyone here. The
349 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
350 blow-by-blow account.
352 Changes much prior to version 2.0 are lost in the mists of time.
355 @emph{Plea:} Additions to this section are particularly welcome. If you
356 or your friends (or enemies, to be evenhanded) have been unfairly
357 omitted from this list, we would like to add your names!
360 So that they may not regard their many labors as thankless, we
361 particularly thank those who shepherded @value{GDBN} through major
363 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
364 Jim Blandy (release 4.18);
365 Jason Molenda (release 4.17);
366 Stan Shebs (release 4.14);
367 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
368 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
369 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
370 Jim Kingdon (releases 3.5, 3.4, and 3.3);
371 and Randy Smith (releases 3.2, 3.1, and 3.0).
373 Richard Stallman, assisted at various times by Peter TerMaat, Chris
374 Hanson, and Richard Mlynarik, handled releases through 2.8.
376 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
377 in @value{GDBN}, with significant additional contributions from Per
378 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
379 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
380 much general update work leading to release 3.0).
382 @value{GDBN} uses the BFD subroutine library to examine multiple
383 object-file formats; BFD was a joint project of David V.
384 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
386 David Johnson wrote the original COFF support; Pace Willison did
387 the original support for encapsulated COFF.
389 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
391 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
392 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
394 Jean-Daniel Fekete contributed Sun 386i support.
395 Chris Hanson improved the HP9000 support.
396 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
397 David Johnson contributed Encore Umax support.
398 Jyrki Kuoppala contributed Altos 3068 support.
399 Jeff Law contributed HP PA and SOM support.
400 Keith Packard contributed NS32K support.
401 Doug Rabson contributed Acorn Risc Machine support.
402 Bob Rusk contributed Harris Nighthawk CX-UX support.
403 Chris Smith contributed Convex support (and Fortran debugging).
404 Jonathan Stone contributed Pyramid support.
405 Michael Tiemann contributed SPARC support.
406 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
407 Pace Willison contributed Intel 386 support.
408 Jay Vosburgh contributed Symmetry support.
409 Marko Mlinar contributed OpenRISC 1000 support.
411 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
413 Rich Schaefer and Peter Schauer helped with support of SunOS shared
416 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
417 about several machine instruction sets.
419 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
420 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
421 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
422 and RDI targets, respectively.
424 Brian Fox is the author of the readline libraries providing
425 command-line editing and command history.
427 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
428 Modula-2 support, and contributed the Languages chapter of this manual.
430 Fred Fish wrote most of the support for Unix System Vr4.
431 He also enhanced the command-completion support to cover C@t{++} overloaded
434 Hitachi America (now Renesas America), Ltd. sponsored the support for
435 H8/300, H8/500, and Super-H processors.
437 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
439 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
442 Toshiba sponsored the support for the TX39 Mips processor.
444 Matsushita sponsored the support for the MN10200 and MN10300 processors.
446 Fujitsu sponsored the support for SPARClite and FR30 processors.
448 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
451 Michael Snyder added support for tracepoints.
453 Stu Grossman wrote gdbserver.
455 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
456 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
458 The following people at the Hewlett-Packard Company contributed
459 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
460 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
461 compiler, and the Text User Interface (nee Terminal User Interface):
462 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
463 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
464 provided HP-specific information in this manual.
466 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
467 Robert Hoehne made significant contributions to the DJGPP port.
469 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
470 development since 1991. Cygnus engineers who have worked on @value{GDBN}
471 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
472 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
473 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
474 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
475 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
476 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
477 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
478 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
479 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
480 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
481 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
482 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
483 Zuhn have made contributions both large and small.
485 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
486 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
488 Jim Blandy added support for preprocessor macros, while working for Red
491 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
492 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
493 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
494 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
495 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
496 with the migration of old architectures to this new framework.
498 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
499 unwinder framework, this consisting of a fresh new design featuring
500 frame IDs, independent frame sniffers, and the sentinel frame. Mark
501 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
502 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
503 trad unwinders. The architecture-specific changes, each involving a
504 complete rewrite of the architecture's frame code, were carried out by
505 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
506 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
507 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
508 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
511 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
512 Tensilica, Inc.@: contributed support for Xtensa processors. Others
513 who have worked on the Xtensa port of @value{GDBN} in the past include
514 Steve Tjiang, John Newlin, and Scott Foehner.
517 @chapter A Sample @value{GDBN} Session
519 You can use this manual at your leisure to read all about @value{GDBN}.
520 However, a handful of commands are enough to get started using the
521 debugger. This chapter illustrates those commands.
524 In this sample session, we emphasize user input like this: @b{input},
525 to make it easier to pick out from the surrounding output.
528 @c FIXME: this example may not be appropriate for some configs, where
529 @c FIXME...primary interest is in remote use.
531 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
532 processor) exhibits the following bug: sometimes, when we change its
533 quote strings from the default, the commands used to capture one macro
534 definition within another stop working. In the following short @code{m4}
535 session, we define a macro @code{foo} which expands to @code{0000}; we
536 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
537 same thing. However, when we change the open quote string to
538 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
539 procedure fails to define a new synonym @code{baz}:
548 @b{define(bar,defn(`foo'))}
552 @b{changequote(<QUOTE>,<UNQUOTE>)}
554 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
557 m4: End of input: 0: fatal error: EOF in string
561 Let us use @value{GDBN} to try to see what is going on.
564 $ @b{@value{GDBP} m4}
565 @c FIXME: this falsifies the exact text played out, to permit smallbook
566 @c FIXME... format to come out better.
567 @value{GDBN} is free software and you are welcome to distribute copies
568 of it under certain conditions; type "show copying" to see
570 There is absolutely no warranty for @value{GDBN}; type "show warranty"
573 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
578 @value{GDBN} reads only enough symbol data to know where to find the
579 rest when needed; as a result, the first prompt comes up very quickly.
580 We now tell @value{GDBN} to use a narrower display width than usual, so
581 that examples fit in this manual.
584 (@value{GDBP}) @b{set width 70}
588 We need to see how the @code{m4} built-in @code{changequote} works.
589 Having looked at the source, we know the relevant subroutine is
590 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
591 @code{break} command.
594 (@value{GDBP}) @b{break m4_changequote}
595 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
599 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
600 control; as long as control does not reach the @code{m4_changequote}
601 subroutine, the program runs as usual:
604 (@value{GDBP}) @b{run}
605 Starting program: /work/Editorial/gdb/gnu/m4/m4
613 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
614 suspends execution of @code{m4}, displaying information about the
615 context where it stops.
618 @b{changequote(<QUOTE>,<UNQUOTE>)}
620 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
622 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
626 Now we use the command @code{n} (@code{next}) to advance execution to
627 the next line of the current function.
631 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
636 @code{set_quotes} looks like a promising subroutine. We can go into it
637 by using the command @code{s} (@code{step}) instead of @code{next}.
638 @code{step} goes to the next line to be executed in @emph{any}
639 subroutine, so it steps into @code{set_quotes}.
643 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
645 530 if (lquote != def_lquote)
649 The display that shows the subroutine where @code{m4} is now
650 suspended (and its arguments) is called a stack frame display. It
651 shows a summary of the stack. We can use the @code{backtrace}
652 command (which can also be spelled @code{bt}), to see where we are
653 in the stack as a whole: the @code{backtrace} command displays a
654 stack frame for each active subroutine.
657 (@value{GDBP}) @b{bt}
658 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
660 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
662 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
663 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
665 #4 0x79dc in expand_input () at macro.c:40
666 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
670 We step through a few more lines to see what happens. The first two
671 times, we can use @samp{s}; the next two times we use @code{n} to avoid
672 falling into the @code{xstrdup} subroutine.
676 0x3b5c 532 if (rquote != def_rquote)
678 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
679 def_lquote : xstrdup(lq);
681 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
684 538 len_lquote = strlen(rquote);
688 The last line displayed looks a little odd; we can examine the variables
689 @code{lquote} and @code{rquote} to see if they are in fact the new left
690 and right quotes we specified. We use the command @code{p}
691 (@code{print}) to see their values.
694 (@value{GDBP}) @b{p lquote}
695 $1 = 0x35d40 "<QUOTE>"
696 (@value{GDBP}) @b{p rquote}
697 $2 = 0x35d50 "<UNQUOTE>"
701 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
702 To look at some context, we can display ten lines of source
703 surrounding the current line with the @code{l} (@code{list}) command.
709 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
711 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
714 538 len_lquote = strlen(rquote);
715 539 len_rquote = strlen(lquote);
722 Let us step past the two lines that set @code{len_lquote} and
723 @code{len_rquote}, and then examine the values of those variables.
727 539 len_rquote = strlen(lquote);
730 (@value{GDBP}) @b{p len_lquote}
732 (@value{GDBP}) @b{p len_rquote}
737 That certainly looks wrong, assuming @code{len_lquote} and
738 @code{len_rquote} are meant to be the lengths of @code{lquote} and
739 @code{rquote} respectively. We can set them to better values using
740 the @code{p} command, since it can print the value of
741 any expression---and that expression can include subroutine calls and
745 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
747 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
752 Is that enough to fix the problem of using the new quotes with the
753 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
754 executing with the @code{c} (@code{continue}) command, and then try the
755 example that caused trouble initially:
761 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
768 Success! The new quotes now work just as well as the default ones. The
769 problem seems to have been just the two typos defining the wrong
770 lengths. We allow @code{m4} exit by giving it an EOF as input:
774 Program exited normally.
778 The message @samp{Program exited normally.} is from @value{GDBN}; it
779 indicates @code{m4} has finished executing. We can end our @value{GDBN}
780 session with the @value{GDBN} @code{quit} command.
783 (@value{GDBP}) @b{quit}
787 @chapter Getting In and Out of @value{GDBN}
789 This chapter discusses how to start @value{GDBN}, and how to get out of it.
793 type @samp{@value{GDBP}} to start @value{GDBN}.
795 type @kbd{quit} or @kbd{Ctrl-d} to exit.
799 * Invoking GDB:: How to start @value{GDBN}
800 * Quitting GDB:: How to quit @value{GDBN}
801 * Shell Commands:: How to use shell commands inside @value{GDBN}
802 * Logging Output:: How to log @value{GDBN}'s output to a file
806 @section Invoking @value{GDBN}
808 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
809 @value{GDBN} reads commands from the terminal until you tell it to exit.
811 You can also run @code{@value{GDBP}} with a variety of arguments and options,
812 to specify more of your debugging environment at the outset.
814 The command-line options described here are designed
815 to cover a variety of situations; in some environments, some of these
816 options may effectively be unavailable.
818 The most usual way to start @value{GDBN} is with one argument,
819 specifying an executable program:
822 @value{GDBP} @var{program}
826 You can also start with both an executable program and a core file
830 @value{GDBP} @var{program} @var{core}
833 You can, instead, specify a process ID as a second argument, if you want
834 to debug a running process:
837 @value{GDBP} @var{program} 1234
841 would attach @value{GDBN} to process @code{1234} (unless you also have a file
842 named @file{1234}; @value{GDBN} does check for a core file first).
844 Taking advantage of the second command-line argument requires a fairly
845 complete operating system; when you use @value{GDBN} as a remote
846 debugger attached to a bare board, there may not be any notion of
847 ``process'', and there is often no way to get a core dump. @value{GDBN}
848 will warn you if it is unable to attach or to read core dumps.
850 You can optionally have @code{@value{GDBP}} pass any arguments after the
851 executable file to the inferior using @code{--args}. This option stops
854 @value{GDBP} --args gcc -O2 -c foo.c
856 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
857 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
859 You can run @code{@value{GDBP}} without printing the front material, which describes
860 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
867 You can further control how @value{GDBN} starts up by using command-line
868 options. @value{GDBN} itself can remind you of the options available.
878 to display all available options and briefly describe their use
879 (@samp{@value{GDBP} -h} is a shorter equivalent).
881 All options and command line arguments you give are processed
882 in sequential order. The order makes a difference when the
883 @samp{-x} option is used.
887 * File Options:: Choosing files
888 * Mode Options:: Choosing modes
889 * Startup:: What @value{GDBN} does during startup
893 @subsection Choosing Files
895 When @value{GDBN} starts, it reads any arguments other than options as
896 specifying an executable file and core file (or process ID). This is
897 the same as if the arguments were specified by the @samp{-se} and
898 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
899 first argument that does not have an associated option flag as
900 equivalent to the @samp{-se} option followed by that argument; and the
901 second argument that does not have an associated option flag, if any, as
902 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
903 If the second argument begins with a decimal digit, @value{GDBN} will
904 first attempt to attach to it as a process, and if that fails, attempt
905 to open it as a corefile. If you have a corefile whose name begins with
906 a digit, you can prevent @value{GDBN} from treating it as a pid by
907 prefixing it with @file{./}, e.g.@: @file{./12345}.
909 If @value{GDBN} has not been configured to included core file support,
910 such as for most embedded targets, then it will complain about a second
911 argument and ignore it.
913 Many options have both long and short forms; both are shown in the
914 following list. @value{GDBN} also recognizes the long forms if you truncate
915 them, so long as enough of the option is present to be unambiguous.
916 (If you prefer, you can flag option arguments with @samp{--} rather
917 than @samp{-}, though we illustrate the more usual convention.)
919 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
920 @c way, both those who look for -foo and --foo in the index, will find
924 @item -symbols @var{file}
926 @cindex @code{--symbols}
928 Read symbol table from file @var{file}.
930 @item -exec @var{file}
932 @cindex @code{--exec}
934 Use file @var{file} as the executable file to execute when appropriate,
935 and for examining pure data in conjunction with a core dump.
939 Read symbol table from file @var{file} and use it as the executable
942 @item -core @var{file}
944 @cindex @code{--core}
946 Use file @var{file} as a core dump to examine.
948 @item -pid @var{number}
949 @itemx -p @var{number}
952 Connect to process ID @var{number}, as with the @code{attach} command.
954 @item -command @var{file}
956 @cindex @code{--command}
958 Execute @value{GDBN} commands from file @var{file}. @xref{Command
959 Files,, Command files}.
961 @item -eval-command @var{command}
962 @itemx -ex @var{command}
963 @cindex @code{--eval-command}
965 Execute a single @value{GDBN} command.
967 This option may be used multiple times to call multiple commands. It may
968 also be interleaved with @samp{-command} as required.
971 @value{GDBP} -ex 'target sim' -ex 'load' \
972 -x setbreakpoints -ex 'run' a.out
975 @item -directory @var{directory}
976 @itemx -d @var{directory}
977 @cindex @code{--directory}
979 Add @var{directory} to the path to search for source and script files.
983 @cindex @code{--readnow}
985 Read each symbol file's entire symbol table immediately, rather than
986 the default, which is to read it incrementally as it is needed.
987 This makes startup slower, but makes future operations faster.
992 @subsection Choosing Modes
994 You can run @value{GDBN} in various alternative modes---for example, in
995 batch mode or quiet mode.
1002 Do not execute commands found in any initialization files. Normally,
1003 @value{GDBN} executes the commands in these files after all the command
1004 options and arguments have been processed. @xref{Command Files,,Command
1010 @cindex @code{--quiet}
1011 @cindex @code{--silent}
1013 ``Quiet''. Do not print the introductory and copyright messages. These
1014 messages are also suppressed in batch mode.
1017 @cindex @code{--batch}
1018 Run in batch mode. Exit with status @code{0} after processing all the
1019 command files specified with @samp{-x} (and all commands from
1020 initialization files, if not inhibited with @samp{-n}). Exit with
1021 nonzero status if an error occurs in executing the @value{GDBN} commands
1022 in the command files.
1024 Batch mode may be useful for running @value{GDBN} as a filter, for
1025 example to download and run a program on another computer; in order to
1026 make this more useful, the message
1029 Program exited normally.
1033 (which is ordinarily issued whenever a program running under
1034 @value{GDBN} control terminates) is not issued when running in batch
1038 @cindex @code{--batch-silent}
1039 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1040 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1041 unaffected). This is much quieter than @samp{-silent} and would be useless
1042 for an interactive session.
1044 This is particularly useful when using targets that give @samp{Loading section}
1045 messages, for example.
1047 Note that targets that give their output via @value{GDBN}, as opposed to
1048 writing directly to @code{stdout}, will also be made silent.
1050 @item -return-child-result
1051 @cindex @code{--return-child-result}
1052 The return code from @value{GDBN} will be the return code from the child
1053 process (the process being debugged), with the following exceptions:
1057 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1058 internal error. In this case the exit code is the same as it would have been
1059 without @samp{-return-child-result}.
1061 The user quits with an explicit value. E.g., @samp{quit 1}.
1063 The child process never runs, or is not allowed to terminate, in which case
1064 the exit code will be -1.
1067 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1068 when @value{GDBN} is being used as a remote program loader or simulator
1073 @cindex @code{--nowindows}
1075 ``No windows''. If @value{GDBN} comes with a graphical user interface
1076 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1077 interface. If no GUI is available, this option has no effect.
1081 @cindex @code{--windows}
1083 If @value{GDBN} includes a GUI, then this option requires it to be
1086 @item -cd @var{directory}
1088 Run @value{GDBN} using @var{directory} as its working directory,
1089 instead of the current directory.
1093 @cindex @code{--fullname}
1095 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1096 subprocess. It tells @value{GDBN} to output the full file name and line
1097 number in a standard, recognizable fashion each time a stack frame is
1098 displayed (which includes each time your program stops). This
1099 recognizable format looks like two @samp{\032} characters, followed by
1100 the file name, line number and character position separated by colons,
1101 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1102 @samp{\032} characters as a signal to display the source code for the
1106 @cindex @code{--epoch}
1107 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1108 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1109 routines so as to allow Epoch to display values of expressions in a
1112 @item -annotate @var{level}
1113 @cindex @code{--annotate}
1114 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1115 effect is identical to using @samp{set annotate @var{level}}
1116 (@pxref{Annotations}). The annotation @var{level} controls how much
1117 information @value{GDBN} prints together with its prompt, values of
1118 expressions, source lines, and other types of output. Level 0 is the
1119 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1120 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1121 that control @value{GDBN}, and level 2 has been deprecated.
1123 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1127 @cindex @code{--args}
1128 Change interpretation of command line so that arguments following the
1129 executable file are passed as command line arguments to the inferior.
1130 This option stops option processing.
1132 @item -baud @var{bps}
1134 @cindex @code{--baud}
1136 Set the line speed (baud rate or bits per second) of any serial
1137 interface used by @value{GDBN} for remote debugging.
1139 @item -l @var{timeout}
1141 Set the timeout (in seconds) of any communication used by @value{GDBN}
1142 for remote debugging.
1144 @item -tty @var{device}
1145 @itemx -t @var{device}
1146 @cindex @code{--tty}
1148 Run using @var{device} for your program's standard input and output.
1149 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1151 @c resolve the situation of these eventually
1153 @cindex @code{--tui}
1154 Activate the @dfn{Text User Interface} when starting. The Text User
1155 Interface manages several text windows on the terminal, showing
1156 source, assembly, registers and @value{GDBN} command outputs
1157 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1158 Text User Interface can be enabled by invoking the program
1159 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1160 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1163 @c @cindex @code{--xdb}
1164 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1165 @c For information, see the file @file{xdb_trans.html}, which is usually
1166 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1169 @item -interpreter @var{interp}
1170 @cindex @code{--interpreter}
1171 Use the interpreter @var{interp} for interface with the controlling
1172 program or device. This option is meant to be set by programs which
1173 communicate with @value{GDBN} using it as a back end.
1174 @xref{Interpreters, , Command Interpreters}.
1176 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1177 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1178 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1179 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1180 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1181 @sc{gdb/mi} interfaces are no longer supported.
1184 @cindex @code{--write}
1185 Open the executable and core files for both reading and writing. This
1186 is equivalent to the @samp{set write on} command inside @value{GDBN}
1190 @cindex @code{--statistics}
1191 This option causes @value{GDBN} to print statistics about time and
1192 memory usage after it completes each command and returns to the prompt.
1195 @cindex @code{--version}
1196 This option causes @value{GDBN} to print its version number and
1197 no-warranty blurb, and exit.
1202 @subsection What @value{GDBN} Does During Startup
1203 @cindex @value{GDBN} startup
1205 Here's the description of what @value{GDBN} does during session startup:
1209 Sets up the command interpreter as specified by the command line
1210 (@pxref{Mode Options, interpreter}).
1214 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1215 used when building @value{GDBN}; @pxref{System-wide configuration,
1216 ,System-wide configuration and settings}) and executes all the commands in
1220 Reads the init file (if any) in your home directory@footnote{On
1221 DOS/Windows systems, the home directory is the one pointed to by the
1222 @code{HOME} environment variable.} and executes all the commands in
1226 Processes command line options and operands.
1229 Reads and executes the commands from init file (if any) in the current
1230 working directory. This is only done if the current directory is
1231 different from your home directory. Thus, you can have more than one
1232 init file, one generic in your home directory, and another, specific
1233 to the program you are debugging, in the directory where you invoke
1237 Reads command files specified by the @samp{-x} option. @xref{Command
1238 Files}, for more details about @value{GDBN} command files.
1241 Reads the command history recorded in the @dfn{history file}.
1242 @xref{Command History}, for more details about the command history and the
1243 files where @value{GDBN} records it.
1246 Init files use the same syntax as @dfn{command files} (@pxref{Command
1247 Files}) and are processed by @value{GDBN} in the same way. The init
1248 file in your home directory can set options (such as @samp{set
1249 complaints}) that affect subsequent processing of command line options
1250 and operands. Init files are not executed if you use the @samp{-nx}
1251 option (@pxref{Mode Options, ,Choosing Modes}).
1253 To display the list of init files loaded by gdb at startup, you
1254 can use @kbd{gdb --help}.
1256 @cindex init file name
1257 @cindex @file{.gdbinit}
1258 @cindex @file{gdb.ini}
1259 The @value{GDBN} init files are normally called @file{.gdbinit}.
1260 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1261 the limitations of file names imposed by DOS filesystems. The Windows
1262 ports of @value{GDBN} use the standard name, but if they find a
1263 @file{gdb.ini} file, they warn you about that and suggest to rename
1264 the file to the standard name.
1268 @section Quitting @value{GDBN}
1269 @cindex exiting @value{GDBN}
1270 @cindex leaving @value{GDBN}
1273 @kindex quit @r{[}@var{expression}@r{]}
1274 @kindex q @r{(@code{quit})}
1275 @item quit @r{[}@var{expression}@r{]}
1277 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1278 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1279 do not supply @var{expression}, @value{GDBN} will terminate normally;
1280 otherwise it will terminate using the result of @var{expression} as the
1285 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1286 terminates the action of any @value{GDBN} command that is in progress and
1287 returns to @value{GDBN} command level. It is safe to type the interrupt
1288 character at any time because @value{GDBN} does not allow it to take effect
1289 until a time when it is safe.
1291 If you have been using @value{GDBN} to control an attached process or
1292 device, you can release it with the @code{detach} command
1293 (@pxref{Attach, ,Debugging an Already-running Process}).
1295 @node Shell Commands
1296 @section Shell Commands
1298 If you need to execute occasional shell commands during your
1299 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1300 just use the @code{shell} command.
1304 @cindex shell escape
1305 @item shell @var{command string}
1306 Invoke a standard shell to execute @var{command string}.
1307 If it exists, the environment variable @code{SHELL} determines which
1308 shell to run. Otherwise @value{GDBN} uses the default shell
1309 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1312 The utility @code{make} is often needed in development environments.
1313 You do not have to use the @code{shell} command for this purpose in
1318 @cindex calling make
1319 @item make @var{make-args}
1320 Execute the @code{make} program with the specified
1321 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1324 @node Logging Output
1325 @section Logging Output
1326 @cindex logging @value{GDBN} output
1327 @cindex save @value{GDBN} output to a file
1329 You may want to save the output of @value{GDBN} commands to a file.
1330 There are several commands to control @value{GDBN}'s logging.
1334 @item set logging on
1336 @item set logging off
1338 @cindex logging file name
1339 @item set logging file @var{file}
1340 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1341 @item set logging overwrite [on|off]
1342 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1343 you want @code{set logging on} to overwrite the logfile instead.
1344 @item set logging redirect [on|off]
1345 By default, @value{GDBN} output will go to both the terminal and the logfile.
1346 Set @code{redirect} if you want output to go only to the log file.
1347 @kindex show logging
1349 Show the current values of the logging settings.
1353 @chapter @value{GDBN} Commands
1355 You can abbreviate a @value{GDBN} command to the first few letters of the command
1356 name, if that abbreviation is unambiguous; and you can repeat certain
1357 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1358 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1359 show you the alternatives available, if there is more than one possibility).
1362 * Command Syntax:: How to give commands to @value{GDBN}
1363 * Completion:: Command completion
1364 * Help:: How to ask @value{GDBN} for help
1367 @node Command Syntax
1368 @section Command Syntax
1370 A @value{GDBN} command is a single line of input. There is no limit on
1371 how long it can be. It starts with a command name, which is followed by
1372 arguments whose meaning depends on the command name. For example, the
1373 command @code{step} accepts an argument which is the number of times to
1374 step, as in @samp{step 5}. You can also use the @code{step} command
1375 with no arguments. Some commands do not allow any arguments.
1377 @cindex abbreviation
1378 @value{GDBN} command names may always be truncated if that abbreviation is
1379 unambiguous. Other possible command abbreviations are listed in the
1380 documentation for individual commands. In some cases, even ambiguous
1381 abbreviations are allowed; for example, @code{s} is specially defined as
1382 equivalent to @code{step} even though there are other commands whose
1383 names start with @code{s}. You can test abbreviations by using them as
1384 arguments to the @code{help} command.
1386 @cindex repeating commands
1387 @kindex RET @r{(repeat last command)}
1388 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1389 repeat the previous command. Certain commands (for example, @code{run})
1390 will not repeat this way; these are commands whose unintentional
1391 repetition might cause trouble and which you are unlikely to want to
1392 repeat. User-defined commands can disable this feature; see
1393 @ref{Define, dont-repeat}.
1395 The @code{list} and @code{x} commands, when you repeat them with
1396 @key{RET}, construct new arguments rather than repeating
1397 exactly as typed. This permits easy scanning of source or memory.
1399 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1400 output, in a way similar to the common utility @code{more}
1401 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1402 @key{RET} too many in this situation, @value{GDBN} disables command
1403 repetition after any command that generates this sort of display.
1405 @kindex # @r{(a comment)}
1407 Any text from a @kbd{#} to the end of the line is a comment; it does
1408 nothing. This is useful mainly in command files (@pxref{Command
1409 Files,,Command Files}).
1411 @cindex repeating command sequences
1412 @kindex Ctrl-o @r{(operate-and-get-next)}
1413 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1414 commands. This command accepts the current line, like @key{RET}, and
1415 then fetches the next line relative to the current line from the history
1419 @section Command Completion
1422 @cindex word completion
1423 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1424 only one possibility; it can also show you what the valid possibilities
1425 are for the next word in a command, at any time. This works for @value{GDBN}
1426 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1428 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1429 of a word. If there is only one possibility, @value{GDBN} fills in the
1430 word, and waits for you to finish the command (or press @key{RET} to
1431 enter it). For example, if you type
1433 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1434 @c complete accuracy in these examples; space introduced for clarity.
1435 @c If texinfo enhancements make it unnecessary, it would be nice to
1436 @c replace " @key" by "@key" in the following...
1438 (@value{GDBP}) info bre @key{TAB}
1442 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1443 the only @code{info} subcommand beginning with @samp{bre}:
1446 (@value{GDBP}) info breakpoints
1450 You can either press @key{RET} at this point, to run the @code{info
1451 breakpoints} command, or backspace and enter something else, if
1452 @samp{breakpoints} does not look like the command you expected. (If you
1453 were sure you wanted @code{info breakpoints} in the first place, you
1454 might as well just type @key{RET} immediately after @samp{info bre},
1455 to exploit command abbreviations rather than command completion).
1457 If there is more than one possibility for the next word when you press
1458 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1459 characters and try again, or just press @key{TAB} a second time;
1460 @value{GDBN} displays all the possible completions for that word. For
1461 example, you might want to set a breakpoint on a subroutine whose name
1462 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1463 just sounds the bell. Typing @key{TAB} again displays all the
1464 function names in your program that begin with those characters, for
1468 (@value{GDBP}) b make_ @key{TAB}
1469 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1470 make_a_section_from_file make_environ
1471 make_abs_section make_function_type
1472 make_blockvector make_pointer_type
1473 make_cleanup make_reference_type
1474 make_command make_symbol_completion_list
1475 (@value{GDBP}) b make_
1479 After displaying the available possibilities, @value{GDBN} copies your
1480 partial input (@samp{b make_} in the example) so you can finish the
1483 If you just want to see the list of alternatives in the first place, you
1484 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1485 means @kbd{@key{META} ?}. You can type this either by holding down a
1486 key designated as the @key{META} shift on your keyboard (if there is
1487 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1489 @cindex quotes in commands
1490 @cindex completion of quoted strings
1491 Sometimes the string you need, while logically a ``word'', may contain
1492 parentheses or other characters that @value{GDBN} normally excludes from
1493 its notion of a word. To permit word completion to work in this
1494 situation, you may enclose words in @code{'} (single quote marks) in
1495 @value{GDBN} commands.
1497 The most likely situation where you might need this is in typing the
1498 name of a C@t{++} function. This is because C@t{++} allows function
1499 overloading (multiple definitions of the same function, distinguished
1500 by argument type). For example, when you want to set a breakpoint you
1501 may need to distinguish whether you mean the version of @code{name}
1502 that takes an @code{int} parameter, @code{name(int)}, or the version
1503 that takes a @code{float} parameter, @code{name(float)}. To use the
1504 word-completion facilities in this situation, type a single quote
1505 @code{'} at the beginning of the function name. This alerts
1506 @value{GDBN} that it may need to consider more information than usual
1507 when you press @key{TAB} or @kbd{M-?} to request word completion:
1510 (@value{GDBP}) b 'bubble( @kbd{M-?}
1511 bubble(double,double) bubble(int,int)
1512 (@value{GDBP}) b 'bubble(
1515 In some cases, @value{GDBN} can tell that completing a name requires using
1516 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1517 completing as much as it can) if you do not type the quote in the first
1521 (@value{GDBP}) b bub @key{TAB}
1522 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1523 (@value{GDBP}) b 'bubble(
1527 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1528 you have not yet started typing the argument list when you ask for
1529 completion on an overloaded symbol.
1531 For more information about overloaded functions, see @ref{C Plus Plus
1532 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1533 overload-resolution off} to disable overload resolution;
1534 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1536 @cindex completion of structure field names
1537 @cindex structure field name completion
1538 @cindex completion of union field names
1539 @cindex union field name completion
1540 When completing in an expression which looks up a field in a
1541 structure, @value{GDBN} also tries@footnote{The completer can be
1542 confused by certain kinds of invalid expressions. Also, it only
1543 examines the static type of the expression, not the dynamic type.} to
1544 limit completions to the field names available in the type of the
1548 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1549 magic to_delete to_fputs to_put to_rewind
1550 to_data to_flush to_isatty to_read to_write
1554 This is because the @code{gdb_stdout} is a variable of the type
1555 @code{struct ui_file} that is defined in @value{GDBN} sources as
1562 ui_file_flush_ftype *to_flush;
1563 ui_file_write_ftype *to_write;
1564 ui_file_fputs_ftype *to_fputs;
1565 ui_file_read_ftype *to_read;
1566 ui_file_delete_ftype *to_delete;
1567 ui_file_isatty_ftype *to_isatty;
1568 ui_file_rewind_ftype *to_rewind;
1569 ui_file_put_ftype *to_put;
1576 @section Getting Help
1577 @cindex online documentation
1580 You can always ask @value{GDBN} itself for information on its commands,
1581 using the command @code{help}.
1584 @kindex h @r{(@code{help})}
1587 You can use @code{help} (abbreviated @code{h}) with no arguments to
1588 display a short list of named classes of commands:
1592 List of classes of commands:
1594 aliases -- Aliases of other commands
1595 breakpoints -- Making program stop at certain points
1596 data -- Examining data
1597 files -- Specifying and examining files
1598 internals -- Maintenance commands
1599 obscure -- Obscure features
1600 running -- Running the program
1601 stack -- Examining the stack
1602 status -- Status inquiries
1603 support -- Support facilities
1604 tracepoints -- Tracing of program execution without
1605 stopping the program
1606 user-defined -- User-defined commands
1608 Type "help" followed by a class name for a list of
1609 commands in that class.
1610 Type "help" followed by command name for full
1612 Command name abbreviations are allowed if unambiguous.
1615 @c the above line break eliminates huge line overfull...
1617 @item help @var{class}
1618 Using one of the general help classes as an argument, you can get a
1619 list of the individual commands in that class. For example, here is the
1620 help display for the class @code{status}:
1623 (@value{GDBP}) help status
1628 @c Line break in "show" line falsifies real output, but needed
1629 @c to fit in smallbook page size.
1630 info -- Generic command for showing things
1631 about the program being debugged
1632 show -- Generic command for showing things
1635 Type "help" followed by command name for full
1637 Command name abbreviations are allowed if unambiguous.
1641 @item help @var{command}
1642 With a command name as @code{help} argument, @value{GDBN} displays a
1643 short paragraph on how to use that command.
1646 @item apropos @var{args}
1647 The @code{apropos} command searches through all of the @value{GDBN}
1648 commands, and their documentation, for the regular expression specified in
1649 @var{args}. It prints out all matches found. For example:
1660 set symbol-reloading -- Set dynamic symbol table reloading
1661 multiple times in one run
1662 show symbol-reloading -- Show dynamic symbol table reloading
1663 multiple times in one run
1668 @item complete @var{args}
1669 The @code{complete @var{args}} command lists all the possible completions
1670 for the beginning of a command. Use @var{args} to specify the beginning of the
1671 command you want completed. For example:
1677 @noindent results in:
1688 @noindent This is intended for use by @sc{gnu} Emacs.
1691 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1692 and @code{show} to inquire about the state of your program, or the state
1693 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1694 manual introduces each of them in the appropriate context. The listings
1695 under @code{info} and under @code{show} in the Index point to
1696 all the sub-commands. @xref{Index}.
1701 @kindex i @r{(@code{info})}
1703 This command (abbreviated @code{i}) is for describing the state of your
1704 program. For example, you can show the arguments passed to a function
1705 with @code{info args}, list the registers currently in use with @code{info
1706 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1707 You can get a complete list of the @code{info} sub-commands with
1708 @w{@code{help info}}.
1712 You can assign the result of an expression to an environment variable with
1713 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1714 @code{set prompt $}.
1718 In contrast to @code{info}, @code{show} is for describing the state of
1719 @value{GDBN} itself.
1720 You can change most of the things you can @code{show}, by using the
1721 related command @code{set}; for example, you can control what number
1722 system is used for displays with @code{set radix}, or simply inquire
1723 which is currently in use with @code{show radix}.
1726 To display all the settable parameters and their current
1727 values, you can use @code{show} with no arguments; you may also use
1728 @code{info set}. Both commands produce the same display.
1729 @c FIXME: "info set" violates the rule that "info" is for state of
1730 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1731 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1735 Here are three miscellaneous @code{show} subcommands, all of which are
1736 exceptional in lacking corresponding @code{set} commands:
1739 @kindex show version
1740 @cindex @value{GDBN} version number
1742 Show what version of @value{GDBN} is running. You should include this
1743 information in @value{GDBN} bug-reports. If multiple versions of
1744 @value{GDBN} are in use at your site, you may need to determine which
1745 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1746 commands are introduced, and old ones may wither away. Also, many
1747 system vendors ship variant versions of @value{GDBN}, and there are
1748 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1749 The version number is the same as the one announced when you start
1752 @kindex show copying
1753 @kindex info copying
1754 @cindex display @value{GDBN} copyright
1757 Display information about permission for copying @value{GDBN}.
1759 @kindex show warranty
1760 @kindex info warranty
1762 @itemx info warranty
1763 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1764 if your version of @value{GDBN} comes with one.
1769 @chapter Running Programs Under @value{GDBN}
1771 When you run a program under @value{GDBN}, you must first generate
1772 debugging information when you compile it.
1774 You may start @value{GDBN} with its arguments, if any, in an environment
1775 of your choice. If you are doing native debugging, you may redirect
1776 your program's input and output, debug an already running process, or
1777 kill a child process.
1780 * Compilation:: Compiling for debugging
1781 * Starting:: Starting your program
1782 * Arguments:: Your program's arguments
1783 * Environment:: Your program's environment
1785 * Working Directory:: Your program's working directory
1786 * Input/Output:: Your program's input and output
1787 * Attach:: Debugging an already-running process
1788 * Kill Process:: Killing the child process
1790 * Inferiors:: Debugging multiple inferiors
1791 * Threads:: Debugging programs with multiple threads
1792 * Processes:: Debugging programs with multiple processes
1793 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1797 @section Compiling for Debugging
1799 In order to debug a program effectively, you need to generate
1800 debugging information when you compile it. This debugging information
1801 is stored in the object file; it describes the data type of each
1802 variable or function and the correspondence between source line numbers
1803 and addresses in the executable code.
1805 To request debugging information, specify the @samp{-g} option when you run
1808 Programs that are to be shipped to your customers are compiled with
1809 optimizations, using the @samp{-O} compiler option. However, many
1810 compilers are unable to handle the @samp{-g} and @samp{-O} options
1811 together. Using those compilers, you cannot generate optimized
1812 executables containing debugging information.
1814 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1815 without @samp{-O}, making it possible to debug optimized code. We
1816 recommend that you @emph{always} use @samp{-g} whenever you compile a
1817 program. You may think your program is correct, but there is no sense
1818 in pushing your luck.
1820 @cindex optimized code, debugging
1821 @cindex debugging optimized code
1822 When you debug a program compiled with @samp{-g -O}, remember that the
1823 optimizer is rearranging your code; the debugger shows you what is
1824 really there. Do not be too surprised when the execution path does not
1825 exactly match your source file! An extreme example: if you define a
1826 variable, but never use it, @value{GDBN} never sees that
1827 variable---because the compiler optimizes it out of existence.
1829 Some things do not work as well with @samp{-g -O} as with just
1830 @samp{-g}, particularly on machines with instruction scheduling. If in
1831 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1832 please report it to us as a bug (including a test case!).
1833 @xref{Variables}, for more information about debugging optimized code.
1835 Older versions of the @sc{gnu} C compiler permitted a variant option
1836 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1837 format; if your @sc{gnu} C compiler has this option, do not use it.
1839 @value{GDBN} knows about preprocessor macros and can show you their
1840 expansion (@pxref{Macros}). Most compilers do not include information
1841 about preprocessor macros in the debugging information if you specify
1842 the @option{-g} flag alone, because this information is rather large.
1843 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1844 provides macro information if you specify the options
1845 @option{-gdwarf-2} and @option{-g3}; the former option requests
1846 debugging information in the Dwarf 2 format, and the latter requests
1847 ``extra information''. In the future, we hope to find more compact
1848 ways to represent macro information, so that it can be included with
1853 @section Starting your Program
1859 @kindex r @r{(@code{run})}
1862 Use the @code{run} command to start your program under @value{GDBN}.
1863 You must first specify the program name (except on VxWorks) with an
1864 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1865 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1866 (@pxref{Files, ,Commands to Specify Files}).
1870 If you are running your program in an execution environment that
1871 supports processes, @code{run} creates an inferior process and makes
1872 that process run your program. In some environments without processes,
1873 @code{run} jumps to the start of your program. Other targets,
1874 like @samp{remote}, are always running. If you get an error
1875 message like this one:
1878 The "remote" target does not support "run".
1879 Try "help target" or "continue".
1883 then use @code{continue} to run your program. You may need @code{load}
1884 first (@pxref{load}).
1886 The execution of a program is affected by certain information it
1887 receives from its superior. @value{GDBN} provides ways to specify this
1888 information, which you must do @emph{before} starting your program. (You
1889 can change it after starting your program, but such changes only affect
1890 your program the next time you start it.) This information may be
1891 divided into four categories:
1894 @item The @emph{arguments.}
1895 Specify the arguments to give your program as the arguments of the
1896 @code{run} command. If a shell is available on your target, the shell
1897 is used to pass the arguments, so that you may use normal conventions
1898 (such as wildcard expansion or variable substitution) in describing
1900 In Unix systems, you can control which shell is used with the
1901 @code{SHELL} environment variable.
1902 @xref{Arguments, ,Your Program's Arguments}.
1904 @item The @emph{environment.}
1905 Your program normally inherits its environment from @value{GDBN}, but you can
1906 use the @value{GDBN} commands @code{set environment} and @code{unset
1907 environment} to change parts of the environment that affect
1908 your program. @xref{Environment, ,Your Program's Environment}.
1910 @item The @emph{working directory.}
1911 Your program inherits its working directory from @value{GDBN}. You can set
1912 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1913 @xref{Working Directory, ,Your Program's Working Directory}.
1915 @item The @emph{standard input and output.}
1916 Your program normally uses the same device for standard input and
1917 standard output as @value{GDBN} is using. You can redirect input and output
1918 in the @code{run} command line, or you can use the @code{tty} command to
1919 set a different device for your program.
1920 @xref{Input/Output, ,Your Program's Input and Output}.
1923 @emph{Warning:} While input and output redirection work, you cannot use
1924 pipes to pass the output of the program you are debugging to another
1925 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1929 When you issue the @code{run} command, your program begins to execute
1930 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1931 of how to arrange for your program to stop. Once your program has
1932 stopped, you may call functions in your program, using the @code{print}
1933 or @code{call} commands. @xref{Data, ,Examining Data}.
1935 If the modification time of your symbol file has changed since the last
1936 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1937 table, and reads it again. When it does this, @value{GDBN} tries to retain
1938 your current breakpoints.
1943 @cindex run to main procedure
1944 The name of the main procedure can vary from language to language.
1945 With C or C@t{++}, the main procedure name is always @code{main}, but
1946 other languages such as Ada do not require a specific name for their
1947 main procedure. The debugger provides a convenient way to start the
1948 execution of the program and to stop at the beginning of the main
1949 procedure, depending on the language used.
1951 The @samp{start} command does the equivalent of setting a temporary
1952 breakpoint at the beginning of the main procedure and then invoking
1953 the @samp{run} command.
1955 @cindex elaboration phase
1956 Some programs contain an @dfn{elaboration} phase where some startup code is
1957 executed before the main procedure is called. This depends on the
1958 languages used to write your program. In C@t{++}, for instance,
1959 constructors for static and global objects are executed before
1960 @code{main} is called. It is therefore possible that the debugger stops
1961 before reaching the main procedure. However, the temporary breakpoint
1962 will remain to halt execution.
1964 Specify the arguments to give to your program as arguments to the
1965 @samp{start} command. These arguments will be given verbatim to the
1966 underlying @samp{run} command. Note that the same arguments will be
1967 reused if no argument is provided during subsequent calls to
1968 @samp{start} or @samp{run}.
1970 It is sometimes necessary to debug the program during elaboration. In
1971 these cases, using the @code{start} command would stop the execution of
1972 your program too late, as the program would have already completed the
1973 elaboration phase. Under these circumstances, insert breakpoints in your
1974 elaboration code before running your program.
1976 @kindex set exec-wrapper
1977 @item set exec-wrapper @var{wrapper}
1978 @itemx show exec-wrapper
1979 @itemx unset exec-wrapper
1980 When @samp{exec-wrapper} is set, the specified wrapper is used to
1981 launch programs for debugging. @value{GDBN} starts your program
1982 with a shell command of the form @kbd{exec @var{wrapper}
1983 @var{program}}. Quoting is added to @var{program} and its
1984 arguments, but not to @var{wrapper}, so you should add quotes if
1985 appropriate for your shell. The wrapper runs until it executes
1986 your program, and then @value{GDBN} takes control.
1988 You can use any program that eventually calls @code{execve} with
1989 its arguments as a wrapper. Several standard Unix utilities do
1990 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1991 with @code{exec "$@@"} will also work.
1993 For example, you can use @code{env} to pass an environment variable to
1994 the debugged program, without setting the variable in your shell's
1998 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2002 This command is available when debugging locally on most targets, excluding
2003 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2005 @kindex set disable-randomization
2006 @item set disable-randomization
2007 @itemx set disable-randomization on
2008 This option (enabled by default in @value{GDBN}) will turn off the native
2009 randomization of the virtual address space of the started program. This option
2010 is useful for multiple debugging sessions to make the execution better
2011 reproducible and memory addresses reusable across debugging sessions.
2013 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2017 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2020 @item set disable-randomization off
2021 Leave the behavior of the started executable unchanged. Some bugs rear their
2022 ugly heads only when the program is loaded at certain addresses. If your bug
2023 disappears when you run the program under @value{GDBN}, that might be because
2024 @value{GDBN} by default disables the address randomization on platforms, such
2025 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2026 disable-randomization off} to try to reproduce such elusive bugs.
2028 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2029 It protects the programs against some kinds of security attacks. In these
2030 cases the attacker needs to know the exact location of a concrete executable
2031 code. Randomizing its location makes it impossible to inject jumps misusing
2032 a code at its expected addresses.
2034 Prelinking shared libraries provides a startup performance advantage but it
2035 makes addresses in these libraries predictable for privileged processes by
2036 having just unprivileged access at the target system. Reading the shared
2037 library binary gives enough information for assembling the malicious code
2038 misusing it. Still even a prelinked shared library can get loaded at a new
2039 random address just requiring the regular relocation process during the
2040 startup. Shared libraries not already prelinked are always loaded at
2041 a randomly chosen address.
2043 Position independent executables (PIE) contain position independent code
2044 similar to the shared libraries and therefore such executables get loaded at
2045 a randomly chosen address upon startup. PIE executables always load even
2046 already prelinked shared libraries at a random address. You can build such
2047 executable using @command{gcc -fPIE -pie}.
2049 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2050 (as long as the randomization is enabled).
2052 @item show disable-randomization
2053 Show the current setting of the explicit disable of the native randomization of
2054 the virtual address space of the started program.
2059 @section Your Program's Arguments
2061 @cindex arguments (to your program)
2062 The arguments to your program can be specified by the arguments of the
2064 They are passed to a shell, which expands wildcard characters and
2065 performs redirection of I/O, and thence to your program. Your
2066 @code{SHELL} environment variable (if it exists) specifies what shell
2067 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2068 the default shell (@file{/bin/sh} on Unix).
2070 On non-Unix systems, the program is usually invoked directly by
2071 @value{GDBN}, which emulates I/O redirection via the appropriate system
2072 calls, and the wildcard characters are expanded by the startup code of
2073 the program, not by the shell.
2075 @code{run} with no arguments uses the same arguments used by the previous
2076 @code{run}, or those set by the @code{set args} command.
2081 Specify the arguments to be used the next time your program is run. If
2082 @code{set args} has no arguments, @code{run} executes your program
2083 with no arguments. Once you have run your program with arguments,
2084 using @code{set args} before the next @code{run} is the only way to run
2085 it again without arguments.
2089 Show the arguments to give your program when it is started.
2093 @section Your Program's Environment
2095 @cindex environment (of your program)
2096 The @dfn{environment} consists of a set of environment variables and
2097 their values. Environment variables conventionally record such things as
2098 your user name, your home directory, your terminal type, and your search
2099 path for programs to run. Usually you set up environment variables with
2100 the shell and they are inherited by all the other programs you run. When
2101 debugging, it can be useful to try running your program with a modified
2102 environment without having to start @value{GDBN} over again.
2106 @item path @var{directory}
2107 Add @var{directory} to the front of the @code{PATH} environment variable
2108 (the search path for executables) that will be passed to your program.
2109 The value of @code{PATH} used by @value{GDBN} does not change.
2110 You may specify several directory names, separated by whitespace or by a
2111 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2112 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2113 is moved to the front, so it is searched sooner.
2115 You can use the string @samp{$cwd} to refer to whatever is the current
2116 working directory at the time @value{GDBN} searches the path. If you
2117 use @samp{.} instead, it refers to the directory where you executed the
2118 @code{path} command. @value{GDBN} replaces @samp{.} in the
2119 @var{directory} argument (with the current path) before adding
2120 @var{directory} to the search path.
2121 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2122 @c document that, since repeating it would be a no-op.
2126 Display the list of search paths for executables (the @code{PATH}
2127 environment variable).
2129 @kindex show environment
2130 @item show environment @r{[}@var{varname}@r{]}
2131 Print the value of environment variable @var{varname} to be given to
2132 your program when it starts. If you do not supply @var{varname},
2133 print the names and values of all environment variables to be given to
2134 your program. You can abbreviate @code{environment} as @code{env}.
2136 @kindex set environment
2137 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2138 Set environment variable @var{varname} to @var{value}. The value
2139 changes for your program only, not for @value{GDBN} itself. @var{value} may
2140 be any string; the values of environment variables are just strings, and
2141 any interpretation is supplied by your program itself. The @var{value}
2142 parameter is optional; if it is eliminated, the variable is set to a
2144 @c "any string" here does not include leading, trailing
2145 @c blanks. Gnu asks: does anyone care?
2147 For example, this command:
2154 tells the debugged program, when subsequently run, that its user is named
2155 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2156 are not actually required.)
2158 @kindex unset environment
2159 @item unset environment @var{varname}
2160 Remove variable @var{varname} from the environment to be passed to your
2161 program. This is different from @samp{set env @var{varname} =};
2162 @code{unset environment} removes the variable from the environment,
2163 rather than assigning it an empty value.
2166 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2168 by your @code{SHELL} environment variable if it exists (or
2169 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2170 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2171 @file{.bashrc} for BASH---any variables you set in that file affect
2172 your program. You may wish to move setting of environment variables to
2173 files that are only run when you sign on, such as @file{.login} or
2176 @node Working Directory
2177 @section Your Program's Working Directory
2179 @cindex working directory (of your program)
2180 Each time you start your program with @code{run}, it inherits its
2181 working directory from the current working directory of @value{GDBN}.
2182 The @value{GDBN} working directory is initially whatever it inherited
2183 from its parent process (typically the shell), but you can specify a new
2184 working directory in @value{GDBN} with the @code{cd} command.
2186 The @value{GDBN} working directory also serves as a default for the commands
2187 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2192 @cindex change working directory
2193 @item cd @var{directory}
2194 Set the @value{GDBN} working directory to @var{directory}.
2198 Print the @value{GDBN} working directory.
2201 It is generally impossible to find the current working directory of
2202 the process being debugged (since a program can change its directory
2203 during its run). If you work on a system where @value{GDBN} is
2204 configured with the @file{/proc} support, you can use the @code{info
2205 proc} command (@pxref{SVR4 Process Information}) to find out the
2206 current working directory of the debuggee.
2209 @section Your Program's Input and Output
2214 By default, the program you run under @value{GDBN} does input and output to
2215 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2216 to its own terminal modes to interact with you, but it records the terminal
2217 modes your program was using and switches back to them when you continue
2218 running your program.
2221 @kindex info terminal
2223 Displays information recorded by @value{GDBN} about the terminal modes your
2227 You can redirect your program's input and/or output using shell
2228 redirection with the @code{run} command. For example,
2235 starts your program, diverting its output to the file @file{outfile}.
2238 @cindex controlling terminal
2239 Another way to specify where your program should do input and output is
2240 with the @code{tty} command. This command accepts a file name as
2241 argument, and causes this file to be the default for future @code{run}
2242 commands. It also resets the controlling terminal for the child
2243 process, for future @code{run} commands. For example,
2250 directs that processes started with subsequent @code{run} commands
2251 default to do input and output on the terminal @file{/dev/ttyb} and have
2252 that as their controlling terminal.
2254 An explicit redirection in @code{run} overrides the @code{tty} command's
2255 effect on the input/output device, but not its effect on the controlling
2258 When you use the @code{tty} command or redirect input in the @code{run}
2259 command, only the input @emph{for your program} is affected. The input
2260 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2261 for @code{set inferior-tty}.
2263 @cindex inferior tty
2264 @cindex set inferior controlling terminal
2265 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2266 display the name of the terminal that will be used for future runs of your
2270 @item set inferior-tty /dev/ttyb
2271 @kindex set inferior-tty
2272 Set the tty for the program being debugged to /dev/ttyb.
2274 @item show inferior-tty
2275 @kindex show inferior-tty
2276 Show the current tty for the program being debugged.
2280 @section Debugging an Already-running Process
2285 @item attach @var{process-id}
2286 This command attaches to a running process---one that was started
2287 outside @value{GDBN}. (@code{info files} shows your active
2288 targets.) The command takes as argument a process ID. The usual way to
2289 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2290 or with the @samp{jobs -l} shell command.
2292 @code{attach} does not repeat if you press @key{RET} a second time after
2293 executing the command.
2296 To use @code{attach}, your program must be running in an environment
2297 which supports processes; for example, @code{attach} does not work for
2298 programs on bare-board targets that lack an operating system. You must
2299 also have permission to send the process a signal.
2301 When you use @code{attach}, the debugger finds the program running in
2302 the process first by looking in the current working directory, then (if
2303 the program is not found) by using the source file search path
2304 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2305 the @code{file} command to load the program. @xref{Files, ,Commands to
2308 The first thing @value{GDBN} does after arranging to debug the specified
2309 process is to stop it. You can examine and modify an attached process
2310 with all the @value{GDBN} commands that are ordinarily available when
2311 you start processes with @code{run}. You can insert breakpoints; you
2312 can step and continue; you can modify storage. If you would rather the
2313 process continue running, you may use the @code{continue} command after
2314 attaching @value{GDBN} to the process.
2319 When you have finished debugging the attached process, you can use the
2320 @code{detach} command to release it from @value{GDBN} control. Detaching
2321 the process continues its execution. After the @code{detach} command,
2322 that process and @value{GDBN} become completely independent once more, and you
2323 are ready to @code{attach} another process or start one with @code{run}.
2324 @code{detach} does not repeat if you press @key{RET} again after
2325 executing the command.
2328 If you exit @value{GDBN} while you have an attached process, you detach
2329 that process. If you use the @code{run} command, you kill that process.
2330 By default, @value{GDBN} asks for confirmation if you try to do either of these
2331 things; you can control whether or not you need to confirm by using the
2332 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2336 @section Killing the Child Process
2341 Kill the child process in which your program is running under @value{GDBN}.
2344 This command is useful if you wish to debug a core dump instead of a
2345 running process. @value{GDBN} ignores any core dump file while your program
2348 On some operating systems, a program cannot be executed outside @value{GDBN}
2349 while you have breakpoints set on it inside @value{GDBN}. You can use the
2350 @code{kill} command in this situation to permit running your program
2351 outside the debugger.
2353 The @code{kill} command is also useful if you wish to recompile and
2354 relink your program, since on many systems it is impossible to modify an
2355 executable file while it is running in a process. In this case, when you
2356 next type @code{run}, @value{GDBN} notices that the file has changed, and
2357 reads the symbol table again (while trying to preserve your current
2358 breakpoint settings).
2361 @section Debugging Multiple Inferiors
2363 Some @value{GDBN} targets are able to run multiple processes created
2364 from a single executable. This can happen, for instance, with an
2365 embedded system reporting back several processes via the remote
2369 @value{GDBN} represents the state of each program execution with an
2370 object called an @dfn{inferior}. An inferior typically corresponds to
2371 a process, but is more general and applies also to targets that do not
2372 have processes. Inferiors may be created before a process runs, and
2373 may (in future) be retained after a process exits. Each run of an
2374 executable creates a new inferior, as does each attachment to an
2375 existing process. Inferiors have unique identifiers that are
2376 different from process ids, and may optionally be named as well.
2377 Usually each inferior will also have its own distinct address space,
2378 although some embedded targets may have several inferiors running in
2379 different parts of a single space.
2381 Each inferior may in turn have multiple threads running in it.
2383 To find out what inferiors exist at any moment, use @code{info inferiors}:
2386 @kindex info inferiors
2387 @item info inferiors
2388 Print a list of all inferiors currently being managed by @value{GDBN}.
2390 @kindex set print inferior-events
2391 @cindex print messages on inferior start and exit
2392 @item set print inferior-events
2393 @itemx set print inferior-events on
2394 @itemx set print inferior-events off
2395 The @code{set print inferior-events} command allows you to enable or
2396 disable printing of messages when @value{GDBN} notices that new
2397 inferiors have started or that inferiors have exited or have been
2398 detached. By default, these messages will not be printed.
2400 @kindex show print inferior-events
2401 @item show print inferior-events
2402 Show whether messages will be printed when @value{GDBN} detects that
2403 inferiors have started, exited or have been detached.
2407 @section Debugging Programs with Multiple Threads
2409 @cindex threads of execution
2410 @cindex multiple threads
2411 @cindex switching threads
2412 In some operating systems, such as HP-UX and Solaris, a single program
2413 may have more than one @dfn{thread} of execution. The precise semantics
2414 of threads differ from one operating system to another, but in general
2415 the threads of a single program are akin to multiple processes---except
2416 that they share one address space (that is, they can all examine and
2417 modify the same variables). On the other hand, each thread has its own
2418 registers and execution stack, and perhaps private memory.
2420 @value{GDBN} provides these facilities for debugging multi-thread
2424 @item automatic notification of new threads
2425 @item @samp{thread @var{threadno}}, a command to switch among threads
2426 @item @samp{info threads}, a command to inquire about existing threads
2427 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2428 a command to apply a command to a list of threads
2429 @item thread-specific breakpoints
2430 @item @samp{set print thread-events}, which controls printing of
2431 messages on thread start and exit.
2435 @emph{Warning:} These facilities are not yet available on every
2436 @value{GDBN} configuration where the operating system supports threads.
2437 If your @value{GDBN} does not support threads, these commands have no
2438 effect. For example, a system without thread support shows no output
2439 from @samp{info threads}, and always rejects the @code{thread} command,
2443 (@value{GDBP}) info threads
2444 (@value{GDBP}) thread 1
2445 Thread ID 1 not known. Use the "info threads" command to
2446 see the IDs of currently known threads.
2448 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2449 @c doesn't support threads"?
2452 @cindex focus of debugging
2453 @cindex current thread
2454 The @value{GDBN} thread debugging facility allows you to observe all
2455 threads while your program runs---but whenever @value{GDBN} takes
2456 control, one thread in particular is always the focus of debugging.
2457 This thread is called the @dfn{current thread}. Debugging commands show
2458 program information from the perspective of the current thread.
2460 @cindex @code{New} @var{systag} message
2461 @cindex thread identifier (system)
2462 @c FIXME-implementors!! It would be more helpful if the [New...] message
2463 @c included GDB's numeric thread handle, so you could just go to that
2464 @c thread without first checking `info threads'.
2465 Whenever @value{GDBN} detects a new thread in your program, it displays
2466 the target system's identification for the thread with a message in the
2467 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2468 whose form varies depending on the particular system. For example, on
2469 @sc{gnu}/Linux, you might see
2472 [New Thread 46912507313328 (LWP 25582)]
2476 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2477 the @var{systag} is simply something like @samp{process 368}, with no
2480 @c FIXME!! (1) Does the [New...] message appear even for the very first
2481 @c thread of a program, or does it only appear for the
2482 @c second---i.e.@: when it becomes obvious we have a multithread
2484 @c (2) *Is* there necessarily a first thread always? Or do some
2485 @c multithread systems permit starting a program with multiple
2486 @c threads ab initio?
2488 @cindex thread number
2489 @cindex thread identifier (GDB)
2490 For debugging purposes, @value{GDBN} associates its own thread
2491 number---always a single integer---with each thread in your program.
2494 @kindex info threads
2496 Display a summary of all threads currently in your
2497 program. @value{GDBN} displays for each thread (in this order):
2501 the thread number assigned by @value{GDBN}
2504 the target system's thread identifier (@var{systag})
2507 the current stack frame summary for that thread
2511 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2512 indicates the current thread.
2516 @c end table here to get a little more width for example
2519 (@value{GDBP}) info threads
2520 3 process 35 thread 27 0x34e5 in sigpause ()
2521 2 process 35 thread 23 0x34e5 in sigpause ()
2522 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2528 @cindex debugging multithreaded programs (on HP-UX)
2529 @cindex thread identifier (GDB), on HP-UX
2530 For debugging purposes, @value{GDBN} associates its own thread
2531 number---a small integer assigned in thread-creation order---with each
2532 thread in your program.
2534 @cindex @code{New} @var{systag} message, on HP-UX
2535 @cindex thread identifier (system), on HP-UX
2536 @c FIXME-implementors!! It would be more helpful if the [New...] message
2537 @c included GDB's numeric thread handle, so you could just go to that
2538 @c thread without first checking `info threads'.
2539 Whenever @value{GDBN} detects a new thread in your program, it displays
2540 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2541 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2542 whose form varies depending on the particular system. For example, on
2546 [New thread 2 (system thread 26594)]
2550 when @value{GDBN} notices a new thread.
2553 @kindex info threads (HP-UX)
2555 Display a summary of all threads currently in your
2556 program. @value{GDBN} displays for each thread (in this order):
2559 @item the thread number assigned by @value{GDBN}
2561 @item the target system's thread identifier (@var{systag})
2563 @item the current stack frame summary for that thread
2567 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2568 indicates the current thread.
2572 @c end table here to get a little more width for example
2575 (@value{GDBP}) info threads
2576 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2578 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2579 from /usr/lib/libc.2
2580 1 system thread 27905 0x7b003498 in _brk () \@*
2581 from /usr/lib/libc.2
2584 On Solaris, you can display more information about user threads with a
2585 Solaris-specific command:
2588 @item maint info sol-threads
2589 @kindex maint info sol-threads
2590 @cindex thread info (Solaris)
2591 Display info on Solaris user threads.
2595 @kindex thread @var{threadno}
2596 @item thread @var{threadno}
2597 Make thread number @var{threadno} the current thread. The command
2598 argument @var{threadno} is the internal @value{GDBN} thread number, as
2599 shown in the first field of the @samp{info threads} display.
2600 @value{GDBN} responds by displaying the system identifier of the thread
2601 you selected, and its current stack frame summary:
2604 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2605 (@value{GDBP}) thread 2
2606 [Switching to process 35 thread 23]
2607 0x34e5 in sigpause ()
2611 As with the @samp{[New @dots{}]} message, the form of the text after
2612 @samp{Switching to} depends on your system's conventions for identifying
2615 @kindex thread apply
2616 @cindex apply command to several threads
2617 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2618 The @code{thread apply} command allows you to apply the named
2619 @var{command} to one or more threads. Specify the numbers of the
2620 threads that you want affected with the command argument
2621 @var{threadno}. It can be a single thread number, one of the numbers
2622 shown in the first field of the @samp{info threads} display; or it
2623 could be a range of thread numbers, as in @code{2-4}. To apply a
2624 command to all threads, type @kbd{thread apply all @var{command}}.
2626 @kindex set print thread-events
2627 @cindex print messages on thread start and exit
2628 @item set print thread-events
2629 @itemx set print thread-events on
2630 @itemx set print thread-events off
2631 The @code{set print thread-events} command allows you to enable or
2632 disable printing of messages when @value{GDBN} notices that new threads have
2633 started or that threads have exited. By default, these messages will
2634 be printed if detection of these events is supported by the target.
2635 Note that these messages cannot be disabled on all targets.
2637 @kindex show print thread-events
2638 @item show print thread-events
2639 Show whether messages will be printed when @value{GDBN} detects that threads
2640 have started and exited.
2643 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2644 more information about how @value{GDBN} behaves when you stop and start
2645 programs with multiple threads.
2647 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2648 watchpoints in programs with multiple threads.
2651 @section Debugging Programs with Multiple Processes
2653 @cindex fork, debugging programs which call
2654 @cindex multiple processes
2655 @cindex processes, multiple
2656 On most systems, @value{GDBN} has no special support for debugging
2657 programs which create additional processes using the @code{fork}
2658 function. When a program forks, @value{GDBN} will continue to debug the
2659 parent process and the child process will run unimpeded. If you have
2660 set a breakpoint in any code which the child then executes, the child
2661 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2662 will cause it to terminate.
2664 However, if you want to debug the child process there is a workaround
2665 which isn't too painful. Put a call to @code{sleep} in the code which
2666 the child process executes after the fork. It may be useful to sleep
2667 only if a certain environment variable is set, or a certain file exists,
2668 so that the delay need not occur when you don't want to run @value{GDBN}
2669 on the child. While the child is sleeping, use the @code{ps} program to
2670 get its process ID. Then tell @value{GDBN} (a new invocation of
2671 @value{GDBN} if you are also debugging the parent process) to attach to
2672 the child process (@pxref{Attach}). From that point on you can debug
2673 the child process just like any other process which you attached to.
2675 On some systems, @value{GDBN} provides support for debugging programs that
2676 create additional processes using the @code{fork} or @code{vfork} functions.
2677 Currently, the only platforms with this feature are HP-UX (11.x and later
2678 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2680 By default, when a program forks, @value{GDBN} will continue to debug
2681 the parent process and the child process will run unimpeded.
2683 If you want to follow the child process instead of the parent process,
2684 use the command @w{@code{set follow-fork-mode}}.
2687 @kindex set follow-fork-mode
2688 @item set follow-fork-mode @var{mode}
2689 Set the debugger response to a program call of @code{fork} or
2690 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2691 process. The @var{mode} argument can be:
2695 The original process is debugged after a fork. The child process runs
2696 unimpeded. This is the default.
2699 The new process is debugged after a fork. The parent process runs
2704 @kindex show follow-fork-mode
2705 @item show follow-fork-mode
2706 Display the current debugger response to a @code{fork} or @code{vfork} call.
2709 @cindex debugging multiple processes
2710 On Linux, if you want to debug both the parent and child processes, use the
2711 command @w{@code{set detach-on-fork}}.
2714 @kindex set detach-on-fork
2715 @item set detach-on-fork @var{mode}
2716 Tells gdb whether to detach one of the processes after a fork, or
2717 retain debugger control over them both.
2721 The child process (or parent process, depending on the value of
2722 @code{follow-fork-mode}) will be detached and allowed to run
2723 independently. This is the default.
2726 Both processes will be held under the control of @value{GDBN}.
2727 One process (child or parent, depending on the value of
2728 @code{follow-fork-mode}) is debugged as usual, while the other
2733 @kindex show detach-on-fork
2734 @item show detach-on-fork
2735 Show whether detach-on-fork mode is on/off.
2738 If you choose to set @samp{detach-on-fork} mode off, then
2739 @value{GDBN} will retain control of all forked processes (including
2740 nested forks). You can list the forked processes under the control of
2741 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2742 from one fork to another by using the @w{@code{fork}} command.
2747 Print a list of all forked processes under the control of @value{GDBN}.
2748 The listing will include a fork id, a process id, and the current
2749 position (program counter) of the process.
2751 @kindex fork @var{fork-id}
2752 @item fork @var{fork-id}
2753 Make fork number @var{fork-id} the current process. The argument
2754 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2755 as shown in the first field of the @samp{info forks} display.
2757 @kindex process @var{process-id}
2758 @item process @var{process-id}
2759 Make process number @var{process-id} the current process. The
2760 argument @var{process-id} must be one that is listed in the output of
2765 To quit debugging one of the forked processes, you can either detach
2766 from it by using the @w{@code{detach fork}} command (allowing it to
2767 run independently), or delete (and kill) it using the
2768 @w{@code{delete fork}} command.
2771 @kindex detach fork @var{fork-id}
2772 @item detach fork @var{fork-id}
2773 Detach from the process identified by @value{GDBN} fork number
2774 @var{fork-id}, and remove it from the fork list. The process will be
2775 allowed to run independently.
2777 @kindex delete fork @var{fork-id}
2778 @item delete fork @var{fork-id}
2779 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2780 and remove it from the fork list.
2784 If you ask to debug a child process and a @code{vfork} is followed by an
2785 @code{exec}, @value{GDBN} executes the new target up to the first
2786 breakpoint in the new target. If you have a breakpoint set on
2787 @code{main} in your original program, the breakpoint will also be set on
2788 the child process's @code{main}.
2790 When a child process is spawned by @code{vfork}, you cannot debug the
2791 child or parent until an @code{exec} call completes.
2793 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2794 call executes, the new target restarts. To restart the parent process,
2795 use the @code{file} command with the parent executable name as its
2798 You can use the @code{catch} command to make @value{GDBN} stop whenever
2799 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2800 Catchpoints, ,Setting Catchpoints}.
2802 @node Checkpoint/Restart
2803 @section Setting a @emph{Bookmark} to Return to Later
2808 @cindex snapshot of a process
2809 @cindex rewind program state
2811 On certain operating systems@footnote{Currently, only
2812 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2813 program's state, called a @dfn{checkpoint}, and come back to it
2816 Returning to a checkpoint effectively undoes everything that has
2817 happened in the program since the @code{checkpoint} was saved. This
2818 includes changes in memory, registers, and even (within some limits)
2819 system state. Effectively, it is like going back in time to the
2820 moment when the checkpoint was saved.
2822 Thus, if you're stepping thru a program and you think you're
2823 getting close to the point where things go wrong, you can save
2824 a checkpoint. Then, if you accidentally go too far and miss
2825 the critical statement, instead of having to restart your program
2826 from the beginning, you can just go back to the checkpoint and
2827 start again from there.
2829 This can be especially useful if it takes a lot of time or
2830 steps to reach the point where you think the bug occurs.
2832 To use the @code{checkpoint}/@code{restart} method of debugging:
2837 Save a snapshot of the debugged program's current execution state.
2838 The @code{checkpoint} command takes no arguments, but each checkpoint
2839 is assigned a small integer id, similar to a breakpoint id.
2841 @kindex info checkpoints
2842 @item info checkpoints
2843 List the checkpoints that have been saved in the current debugging
2844 session. For each checkpoint, the following information will be
2851 @item Source line, or label
2854 @kindex restart @var{checkpoint-id}
2855 @item restart @var{checkpoint-id}
2856 Restore the program state that was saved as checkpoint number
2857 @var{checkpoint-id}. All program variables, registers, stack frames
2858 etc.@: will be returned to the values that they had when the checkpoint
2859 was saved. In essence, gdb will ``wind back the clock'' to the point
2860 in time when the checkpoint was saved.
2862 Note that breakpoints, @value{GDBN} variables, command history etc.
2863 are not affected by restoring a checkpoint. In general, a checkpoint
2864 only restores things that reside in the program being debugged, not in
2867 @kindex delete checkpoint @var{checkpoint-id}
2868 @item delete checkpoint @var{checkpoint-id}
2869 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2873 Returning to a previously saved checkpoint will restore the user state
2874 of the program being debugged, plus a significant subset of the system
2875 (OS) state, including file pointers. It won't ``un-write'' data from
2876 a file, but it will rewind the file pointer to the previous location,
2877 so that the previously written data can be overwritten. For files
2878 opened in read mode, the pointer will also be restored so that the
2879 previously read data can be read again.
2881 Of course, characters that have been sent to a printer (or other
2882 external device) cannot be ``snatched back'', and characters received
2883 from eg.@: a serial device can be removed from internal program buffers,
2884 but they cannot be ``pushed back'' into the serial pipeline, ready to
2885 be received again. Similarly, the actual contents of files that have
2886 been changed cannot be restored (at this time).
2888 However, within those constraints, you actually can ``rewind'' your
2889 program to a previously saved point in time, and begin debugging it
2890 again --- and you can change the course of events so as to debug a
2891 different execution path this time.
2893 @cindex checkpoints and process id
2894 Finally, there is one bit of internal program state that will be
2895 different when you return to a checkpoint --- the program's process
2896 id. Each checkpoint will have a unique process id (or @var{pid}),
2897 and each will be different from the program's original @var{pid}.
2898 If your program has saved a local copy of its process id, this could
2899 potentially pose a problem.
2901 @subsection A Non-obvious Benefit of Using Checkpoints
2903 On some systems such as @sc{gnu}/Linux, address space randomization
2904 is performed on new processes for security reasons. This makes it
2905 difficult or impossible to set a breakpoint, or watchpoint, on an
2906 absolute address if you have to restart the program, since the
2907 absolute location of a symbol will change from one execution to the
2910 A checkpoint, however, is an @emph{identical} copy of a process.
2911 Therefore if you create a checkpoint at (eg.@:) the start of main,
2912 and simply return to that checkpoint instead of restarting the
2913 process, you can avoid the effects of address randomization and
2914 your symbols will all stay in the same place.
2917 @chapter Stopping and Continuing
2919 The principal purposes of using a debugger are so that you can stop your
2920 program before it terminates; or so that, if your program runs into
2921 trouble, you can investigate and find out why.
2923 Inside @value{GDBN}, your program may stop for any of several reasons,
2924 such as a signal, a breakpoint, or reaching a new line after a
2925 @value{GDBN} command such as @code{step}. You may then examine and
2926 change variables, set new breakpoints or remove old ones, and then
2927 continue execution. Usually, the messages shown by @value{GDBN} provide
2928 ample explanation of the status of your program---but you can also
2929 explicitly request this information at any time.
2932 @kindex info program
2934 Display information about the status of your program: whether it is
2935 running or not, what process it is, and why it stopped.
2939 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2940 * Continuing and Stepping:: Resuming execution
2942 * Thread Stops:: Stopping and starting multi-thread programs
2946 @section Breakpoints, Watchpoints, and Catchpoints
2949 A @dfn{breakpoint} makes your program stop whenever a certain point in
2950 the program is reached. For each breakpoint, you can add conditions to
2951 control in finer detail whether your program stops. You can set
2952 breakpoints with the @code{break} command and its variants (@pxref{Set
2953 Breaks, ,Setting Breakpoints}), to specify the place where your program
2954 should stop by line number, function name or exact address in the
2957 On some systems, you can set breakpoints in shared libraries before
2958 the executable is run. There is a minor limitation on HP-UX systems:
2959 you must wait until the executable is run in order to set breakpoints
2960 in shared library routines that are not called directly by the program
2961 (for example, routines that are arguments in a @code{pthread_create}
2965 @cindex data breakpoints
2966 @cindex memory tracing
2967 @cindex breakpoint on memory address
2968 @cindex breakpoint on variable modification
2969 A @dfn{watchpoint} is a special breakpoint that stops your program
2970 when the value of an expression changes. The expression may be a value
2971 of a variable, or it could involve values of one or more variables
2972 combined by operators, such as @samp{a + b}. This is sometimes called
2973 @dfn{data breakpoints}. You must use a different command to set
2974 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2975 from that, you can manage a watchpoint like any other breakpoint: you
2976 enable, disable, and delete both breakpoints and watchpoints using the
2979 You can arrange to have values from your program displayed automatically
2980 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2984 @cindex breakpoint on events
2985 A @dfn{catchpoint} is another special breakpoint that stops your program
2986 when a certain kind of event occurs, such as the throwing of a C@t{++}
2987 exception or the loading of a library. As with watchpoints, you use a
2988 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2989 Catchpoints}), but aside from that, you can manage a catchpoint like any
2990 other breakpoint. (To stop when your program receives a signal, use the
2991 @code{handle} command; see @ref{Signals, ,Signals}.)
2993 @cindex breakpoint numbers
2994 @cindex numbers for breakpoints
2995 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2996 catchpoint when you create it; these numbers are successive integers
2997 starting with one. In many of the commands for controlling various
2998 features of breakpoints you use the breakpoint number to say which
2999 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3000 @dfn{disabled}; if disabled, it has no effect on your program until you
3003 @cindex breakpoint ranges
3004 @cindex ranges of breakpoints
3005 Some @value{GDBN} commands accept a range of breakpoints on which to
3006 operate. A breakpoint range is either a single breakpoint number, like
3007 @samp{5}, or two such numbers, in increasing order, separated by a
3008 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3009 all breakpoints in that range are operated on.
3012 * Set Breaks:: Setting breakpoints
3013 * Set Watchpoints:: Setting watchpoints
3014 * Set Catchpoints:: Setting catchpoints
3015 * Delete Breaks:: Deleting breakpoints
3016 * Disabling:: Disabling breakpoints
3017 * Conditions:: Break conditions
3018 * Break Commands:: Breakpoint command lists
3019 * Error in Breakpoints:: ``Cannot insert breakpoints''
3020 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3024 @subsection Setting Breakpoints
3026 @c FIXME LMB what does GDB do if no code on line of breakpt?
3027 @c consider in particular declaration with/without initialization.
3029 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3032 @kindex b @r{(@code{break})}
3033 @vindex $bpnum@r{, convenience variable}
3034 @cindex latest breakpoint
3035 Breakpoints are set with the @code{break} command (abbreviated
3036 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3037 number of the breakpoint you've set most recently; see @ref{Convenience
3038 Vars,, Convenience Variables}, for a discussion of what you can do with
3039 convenience variables.
3042 @item break @var{location}
3043 Set a breakpoint at the given @var{location}, which can specify a
3044 function name, a line number, or an address of an instruction.
3045 (@xref{Specify Location}, for a list of all the possible ways to
3046 specify a @var{location}.) The breakpoint will stop your program just
3047 before it executes any of the code in the specified @var{location}.
3049 When using source languages that permit overloading of symbols, such as
3050 C@t{++}, a function name may refer to more than one possible place to break.
3051 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3054 It is also possible to insert a breakpoint that will stop the program
3055 only if a specific thread or a specific task hits that breakpoint.
3056 @xref{Thread-Specific Breakpoints} and @ref{Ada Tasks} for more
3057 information about this feature.
3060 When called without any arguments, @code{break} sets a breakpoint at
3061 the next instruction to be executed in the selected stack frame
3062 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3063 innermost, this makes your program stop as soon as control
3064 returns to that frame. This is similar to the effect of a
3065 @code{finish} command in the frame inside the selected frame---except
3066 that @code{finish} does not leave an active breakpoint. If you use
3067 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3068 the next time it reaches the current location; this may be useful
3071 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3072 least one instruction has been executed. If it did not do this, you
3073 would be unable to proceed past a breakpoint without first disabling the
3074 breakpoint. This rule applies whether or not the breakpoint already
3075 existed when your program stopped.
3077 @item break @dots{} if @var{cond}
3078 Set a breakpoint with condition @var{cond}; evaluate the expression
3079 @var{cond} each time the breakpoint is reached, and stop only if the
3080 value is nonzero---that is, if @var{cond} evaluates as true.
3081 @samp{@dots{}} stands for one of the possible arguments described
3082 above (or no argument) specifying where to break. @xref{Conditions,
3083 ,Break Conditions}, for more information on breakpoint conditions.
3086 @item tbreak @var{args}
3087 Set a breakpoint enabled only for one stop. @var{args} are the
3088 same as for the @code{break} command, and the breakpoint is set in the same
3089 way, but the breakpoint is automatically deleted after the first time your
3090 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3093 @cindex hardware breakpoints
3094 @item hbreak @var{args}
3095 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3096 @code{break} command and the breakpoint is set in the same way, but the
3097 breakpoint requires hardware support and some target hardware may not
3098 have this support. The main purpose of this is EPROM/ROM code
3099 debugging, so you can set a breakpoint at an instruction without
3100 changing the instruction. This can be used with the new trap-generation
3101 provided by SPARClite DSU and most x86-based targets. These targets
3102 will generate traps when a program accesses some data or instruction
3103 address that is assigned to the debug registers. However the hardware
3104 breakpoint registers can take a limited number of breakpoints. For
3105 example, on the DSU, only two data breakpoints can be set at a time, and
3106 @value{GDBN} will reject this command if more than two are used. Delete
3107 or disable unused hardware breakpoints before setting new ones
3108 (@pxref{Disabling, ,Disabling Breakpoints}).
3109 @xref{Conditions, ,Break Conditions}.
3110 For remote targets, you can restrict the number of hardware
3111 breakpoints @value{GDBN} will use, see @ref{set remote
3112 hardware-breakpoint-limit}.
3115 @item thbreak @var{args}
3116 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3117 are the same as for the @code{hbreak} command and the breakpoint is set in
3118 the same way. However, like the @code{tbreak} command,
3119 the breakpoint is automatically deleted after the
3120 first time your program stops there. Also, like the @code{hbreak}
3121 command, the breakpoint requires hardware support and some target hardware
3122 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3123 See also @ref{Conditions, ,Break Conditions}.
3126 @cindex regular expression
3127 @cindex breakpoints in functions matching a regexp
3128 @cindex set breakpoints in many functions
3129 @item rbreak @var{regex}
3130 Set breakpoints on all functions matching the regular expression
3131 @var{regex}. This command sets an unconditional breakpoint on all
3132 matches, printing a list of all breakpoints it set. Once these
3133 breakpoints are set, they are treated just like the breakpoints set with
3134 the @code{break} command. You can delete them, disable them, or make
3135 them conditional the same way as any other breakpoint.
3137 The syntax of the regular expression is the standard one used with tools
3138 like @file{grep}. Note that this is different from the syntax used by
3139 shells, so for instance @code{foo*} matches all functions that include
3140 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3141 @code{.*} leading and trailing the regular expression you supply, so to
3142 match only functions that begin with @code{foo}, use @code{^foo}.
3144 @cindex non-member C@t{++} functions, set breakpoint in
3145 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3146 breakpoints on overloaded functions that are not members of any special
3149 @cindex set breakpoints on all functions
3150 The @code{rbreak} command can be used to set breakpoints in
3151 @strong{all} the functions in a program, like this:
3154 (@value{GDBP}) rbreak .
3157 @kindex info breakpoints
3158 @cindex @code{$_} and @code{info breakpoints}
3159 @item info breakpoints @r{[}@var{n}@r{]}
3160 @itemx info break @r{[}@var{n}@r{]}
3161 @itemx info watchpoints @r{[}@var{n}@r{]}
3162 Print a table of all breakpoints, watchpoints, and catchpoints set and
3163 not deleted. Optional argument @var{n} means print information only
3164 about the specified breakpoint (or watchpoint or catchpoint). For
3165 each breakpoint, following columns are printed:
3168 @item Breakpoint Numbers
3170 Breakpoint, watchpoint, or catchpoint.
3172 Whether the breakpoint is marked to be disabled or deleted when hit.
3173 @item Enabled or Disabled
3174 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3175 that are not enabled.
3177 Where the breakpoint is in your program, as a memory address. For a
3178 pending breakpoint whose address is not yet known, this field will
3179 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3180 library that has the symbol or line referred by breakpoint is loaded.
3181 See below for details. A breakpoint with several locations will
3182 have @samp{<MULTIPLE>} in this field---see below for details.
3184 Where the breakpoint is in the source for your program, as a file and
3185 line number. For a pending breakpoint, the original string passed to
3186 the breakpoint command will be listed as it cannot be resolved until
3187 the appropriate shared library is loaded in the future.
3191 If a breakpoint is conditional, @code{info break} shows the condition on
3192 the line following the affected breakpoint; breakpoint commands, if any,
3193 are listed after that. A pending breakpoint is allowed to have a condition
3194 specified for it. The condition is not parsed for validity until a shared
3195 library is loaded that allows the pending breakpoint to resolve to a
3199 @code{info break} with a breakpoint
3200 number @var{n} as argument lists only that breakpoint. The
3201 convenience variable @code{$_} and the default examining-address for
3202 the @code{x} command are set to the address of the last breakpoint
3203 listed (@pxref{Memory, ,Examining Memory}).
3206 @code{info break} displays a count of the number of times the breakpoint
3207 has been hit. This is especially useful in conjunction with the
3208 @code{ignore} command. You can ignore a large number of breakpoint
3209 hits, look at the breakpoint info to see how many times the breakpoint
3210 was hit, and then run again, ignoring one less than that number. This
3211 will get you quickly to the last hit of that breakpoint.
3214 @value{GDBN} allows you to set any number of breakpoints at the same place in
3215 your program. There is nothing silly or meaningless about this. When
3216 the breakpoints are conditional, this is even useful
3217 (@pxref{Conditions, ,Break Conditions}).
3219 @cindex multiple locations, breakpoints
3220 @cindex breakpoints, multiple locations
3221 It is possible that a breakpoint corresponds to several locations
3222 in your program. Examples of this situation are:
3226 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3227 instances of the function body, used in different cases.
3230 For a C@t{++} template function, a given line in the function can
3231 correspond to any number of instantiations.
3234 For an inlined function, a given source line can correspond to
3235 several places where that function is inlined.
3238 In all those cases, @value{GDBN} will insert a breakpoint at all
3239 the relevant locations@footnote{
3240 As of this writing, multiple-location breakpoints work only if there's
3241 line number information for all the locations. This means that they
3242 will generally not work in system libraries, unless you have debug
3243 info with line numbers for them.}.
3245 A breakpoint with multiple locations is displayed in the breakpoint
3246 table using several rows---one header row, followed by one row for
3247 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3248 address column. The rows for individual locations contain the actual
3249 addresses for locations, and show the functions to which those
3250 locations belong. The number column for a location is of the form
3251 @var{breakpoint-number}.@var{location-number}.
3256 Num Type Disp Enb Address What
3257 1 breakpoint keep y <MULTIPLE>
3259 breakpoint already hit 1 time
3260 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3261 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3264 Each location can be individually enabled or disabled by passing
3265 @var{breakpoint-number}.@var{location-number} as argument to the
3266 @code{enable} and @code{disable} commands. Note that you cannot
3267 delete the individual locations from the list, you can only delete the
3268 entire list of locations that belong to their parent breakpoint (with
3269 the @kbd{delete @var{num}} command, where @var{num} is the number of
3270 the parent breakpoint, 1 in the above example). Disabling or enabling
3271 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3272 that belong to that breakpoint.
3274 @cindex pending breakpoints
3275 It's quite common to have a breakpoint inside a shared library.
3276 Shared libraries can be loaded and unloaded explicitly,
3277 and possibly repeatedly, as the program is executed. To support
3278 this use case, @value{GDBN} updates breakpoint locations whenever
3279 any shared library is loaded or unloaded. Typically, you would
3280 set a breakpoint in a shared library at the beginning of your
3281 debugging session, when the library is not loaded, and when the
3282 symbols from the library are not available. When you try to set
3283 breakpoint, @value{GDBN} will ask you if you want to set
3284 a so called @dfn{pending breakpoint}---breakpoint whose address
3285 is not yet resolved.
3287 After the program is run, whenever a new shared library is loaded,
3288 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3289 shared library contains the symbol or line referred to by some
3290 pending breakpoint, that breakpoint is resolved and becomes an
3291 ordinary breakpoint. When a library is unloaded, all breakpoints
3292 that refer to its symbols or source lines become pending again.
3294 This logic works for breakpoints with multiple locations, too. For
3295 example, if you have a breakpoint in a C@t{++} template function, and
3296 a newly loaded shared library has an instantiation of that template,
3297 a new location is added to the list of locations for the breakpoint.
3299 Except for having unresolved address, pending breakpoints do not
3300 differ from regular breakpoints. You can set conditions or commands,
3301 enable and disable them and perform other breakpoint operations.
3303 @value{GDBN} provides some additional commands for controlling what
3304 happens when the @samp{break} command cannot resolve breakpoint
3305 address specification to an address:
3307 @kindex set breakpoint pending
3308 @kindex show breakpoint pending
3310 @item set breakpoint pending auto
3311 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3312 location, it queries you whether a pending breakpoint should be created.
3314 @item set breakpoint pending on
3315 This indicates that an unrecognized breakpoint location should automatically
3316 result in a pending breakpoint being created.
3318 @item set breakpoint pending off
3319 This indicates that pending breakpoints are not to be created. Any
3320 unrecognized breakpoint location results in an error. This setting does
3321 not affect any pending breakpoints previously created.
3323 @item show breakpoint pending
3324 Show the current behavior setting for creating pending breakpoints.
3327 The settings above only affect the @code{break} command and its
3328 variants. Once breakpoint is set, it will be automatically updated
3329 as shared libraries are loaded and unloaded.
3331 @cindex automatic hardware breakpoints
3332 For some targets, @value{GDBN} can automatically decide if hardware or
3333 software breakpoints should be used, depending on whether the
3334 breakpoint address is read-only or read-write. This applies to
3335 breakpoints set with the @code{break} command as well as to internal
3336 breakpoints set by commands like @code{next} and @code{finish}. For
3337 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3340 You can control this automatic behaviour with the following commands::
3342 @kindex set breakpoint auto-hw
3343 @kindex show breakpoint auto-hw
3345 @item set breakpoint auto-hw on
3346 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3347 will try to use the target memory map to decide if software or hardware
3348 breakpoint must be used.
3350 @item set breakpoint auto-hw off
3351 This indicates @value{GDBN} should not automatically select breakpoint
3352 type. If the target provides a memory map, @value{GDBN} will warn when
3353 trying to set software breakpoint at a read-only address.
3356 @value{GDBN} normally implements breakpoints by replacing the program code
3357 at the breakpoint address with a special instruction, which, when
3358 executed, given control to the debugger. By default, the program
3359 code is so modified only when the program is resumed. As soon as
3360 the program stops, @value{GDBN} restores the original instructions. This
3361 behaviour guards against leaving breakpoints inserted in the
3362 target should gdb abrubptly disconnect. However, with slow remote
3363 targets, inserting and removing breakpoint can reduce the performance.
3364 This behavior can be controlled with the following commands::
3366 @kindex set breakpoint always-inserted
3367 @kindex show breakpoint always-inserted
3369 @item set breakpoint always-inserted off
3370 All breakpoints, including newly added by the user, are inserted in
3371 the target only when the target is resumed. All breakpoints are
3372 removed from the target when it stops.
3374 @item set breakpoint always-inserted on
3375 Causes all breakpoints to be inserted in the target at all times. If
3376 the user adds a new breakpoint, or changes an existing breakpoint, the
3377 breakpoints in the target are updated immediately. A breakpoint is
3378 removed from the target only when breakpoint itself is removed.
3380 @cindex non-stop mode, and @code{breakpoint always-inserted}
3381 @item set breakpoint always-inserted auto
3382 This is the default mode. If @value{GDBN} is controlling the inferior
3383 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3384 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3385 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3386 @code{breakpoint always-inserted} mode is off.
3389 @cindex negative breakpoint numbers
3390 @cindex internal @value{GDBN} breakpoints
3391 @value{GDBN} itself sometimes sets breakpoints in your program for
3392 special purposes, such as proper handling of @code{longjmp} (in C
3393 programs). These internal breakpoints are assigned negative numbers,
3394 starting with @code{-1}; @samp{info breakpoints} does not display them.
3395 You can see these breakpoints with the @value{GDBN} maintenance command
3396 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3399 @node Set Watchpoints
3400 @subsection Setting Watchpoints
3402 @cindex setting watchpoints
3403 You can use a watchpoint to stop execution whenever the value of an
3404 expression changes, without having to predict a particular place where
3405 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3406 The expression may be as simple as the value of a single variable, or
3407 as complex as many variables combined by operators. Examples include:
3411 A reference to the value of a single variable.
3414 An address cast to an appropriate data type. For example,
3415 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3416 address (assuming an @code{int} occupies 4 bytes).
3419 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3420 expression can use any operators valid in the program's native
3421 language (@pxref{Languages}).
3424 You can set a watchpoint on an expression even if the expression can
3425 not be evaluated yet. For instance, you can set a watchpoint on
3426 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3427 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3428 the expression produces a valid value. If the expression becomes
3429 valid in some other way than changing a variable (e.g.@: if the memory
3430 pointed to by @samp{*global_ptr} becomes readable as the result of a
3431 @code{malloc} call), @value{GDBN} may not stop until the next time
3432 the expression changes.
3434 @cindex software watchpoints
3435 @cindex hardware watchpoints
3436 Depending on your system, watchpoints may be implemented in software or
3437 hardware. @value{GDBN} does software watchpointing by single-stepping your
3438 program and testing the variable's value each time, which is hundreds of
3439 times slower than normal execution. (But this may still be worth it, to
3440 catch errors where you have no clue what part of your program is the
3443 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3444 x86-based targets, @value{GDBN} includes support for hardware
3445 watchpoints, which do not slow down the running of your program.
3449 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3450 Set a watchpoint for an expression. @value{GDBN} will break when the
3451 expression @var{expr} is written into by the program and its value
3452 changes. The simplest (and the most popular) use of this command is
3453 to watch the value of a single variable:
3456 (@value{GDBP}) watch foo
3459 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3460 clause, @value{GDBN} breaks only when the thread identified by
3461 @var{threadnum} changes the value of @var{expr}. If any other threads
3462 change the value of @var{expr}, @value{GDBN} will not break. Note
3463 that watchpoints restricted to a single thread in this way only work
3464 with Hardware Watchpoints.
3467 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3468 Set a watchpoint that will break when the value of @var{expr} is read
3472 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3473 Set a watchpoint that will break when @var{expr} is either read from
3474 or written into by the program.
3476 @kindex info watchpoints @r{[}@var{n}@r{]}
3477 @item info watchpoints
3478 This command prints a list of watchpoints, breakpoints, and catchpoints;
3479 it is the same as @code{info break} (@pxref{Set Breaks}).
3482 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3483 watchpoints execute very quickly, and the debugger reports a change in
3484 value at the exact instruction where the change occurs. If @value{GDBN}
3485 cannot set a hardware watchpoint, it sets a software watchpoint, which
3486 executes more slowly and reports the change in value at the next
3487 @emph{statement}, not the instruction, after the change occurs.
3489 @cindex use only software watchpoints
3490 You can force @value{GDBN} to use only software watchpoints with the
3491 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3492 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3493 the underlying system supports them. (Note that hardware-assisted
3494 watchpoints that were set @emph{before} setting
3495 @code{can-use-hw-watchpoints} to zero will still use the hardware
3496 mechanism of watching expression values.)
3499 @item set can-use-hw-watchpoints
3500 @kindex set can-use-hw-watchpoints
3501 Set whether or not to use hardware watchpoints.
3503 @item show can-use-hw-watchpoints
3504 @kindex show can-use-hw-watchpoints
3505 Show the current mode of using hardware watchpoints.
3508 For remote targets, you can restrict the number of hardware
3509 watchpoints @value{GDBN} will use, see @ref{set remote
3510 hardware-breakpoint-limit}.
3512 When you issue the @code{watch} command, @value{GDBN} reports
3515 Hardware watchpoint @var{num}: @var{expr}
3519 if it was able to set a hardware watchpoint.
3521 Currently, the @code{awatch} and @code{rwatch} commands can only set
3522 hardware watchpoints, because accesses to data that don't change the
3523 value of the watched expression cannot be detected without examining
3524 every instruction as it is being executed, and @value{GDBN} does not do
3525 that currently. If @value{GDBN} finds that it is unable to set a
3526 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3527 will print a message like this:
3530 Expression cannot be implemented with read/access watchpoint.
3533 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3534 data type of the watched expression is wider than what a hardware
3535 watchpoint on the target machine can handle. For example, some systems
3536 can only watch regions that are up to 4 bytes wide; on such systems you
3537 cannot set hardware watchpoints for an expression that yields a
3538 double-precision floating-point number (which is typically 8 bytes
3539 wide). As a work-around, it might be possible to break the large region
3540 into a series of smaller ones and watch them with separate watchpoints.
3542 If you set too many hardware watchpoints, @value{GDBN} might be unable
3543 to insert all of them when you resume the execution of your program.
3544 Since the precise number of active watchpoints is unknown until such
3545 time as the program is about to be resumed, @value{GDBN} might not be
3546 able to warn you about this when you set the watchpoints, and the
3547 warning will be printed only when the program is resumed:
3550 Hardware watchpoint @var{num}: Could not insert watchpoint
3554 If this happens, delete or disable some of the watchpoints.
3556 Watching complex expressions that reference many variables can also
3557 exhaust the resources available for hardware-assisted watchpoints.
3558 That's because @value{GDBN} needs to watch every variable in the
3559 expression with separately allocated resources.
3561 If you call a function interactively using @code{print} or @code{call},
3562 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3563 kind of breakpoint or the call completes.
3565 @value{GDBN} automatically deletes watchpoints that watch local
3566 (automatic) variables, or expressions that involve such variables, when
3567 they go out of scope, that is, when the execution leaves the block in
3568 which these variables were defined. In particular, when the program
3569 being debugged terminates, @emph{all} local variables go out of scope,
3570 and so only watchpoints that watch global variables remain set. If you
3571 rerun the program, you will need to set all such watchpoints again. One
3572 way of doing that would be to set a code breakpoint at the entry to the
3573 @code{main} function and when it breaks, set all the watchpoints.
3575 @cindex watchpoints and threads
3576 @cindex threads and watchpoints
3577 In multi-threaded programs, watchpoints will detect changes to the
3578 watched expression from every thread.
3581 @emph{Warning:} In multi-threaded programs, software watchpoints
3582 have only limited usefulness. If @value{GDBN} creates a software
3583 watchpoint, it can only watch the value of an expression @emph{in a
3584 single thread}. If you are confident that the expression can only
3585 change due to the current thread's activity (and if you are also
3586 confident that no other thread can become current), then you can use
3587 software watchpoints as usual. However, @value{GDBN} may not notice
3588 when a non-current thread's activity changes the expression. (Hardware
3589 watchpoints, in contrast, watch an expression in all threads.)
3592 @xref{set remote hardware-watchpoint-limit}.
3594 @node Set Catchpoints
3595 @subsection Setting Catchpoints
3596 @cindex catchpoints, setting
3597 @cindex exception handlers
3598 @cindex event handling
3600 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3601 kinds of program events, such as C@t{++} exceptions or the loading of a
3602 shared library. Use the @code{catch} command to set a catchpoint.
3606 @item catch @var{event}
3607 Stop when @var{event} occurs. @var{event} can be any of the following:
3610 @cindex stop on C@t{++} exceptions
3611 The throwing of a C@t{++} exception.
3614 The catching of a C@t{++} exception.
3617 @cindex Ada exception catching
3618 @cindex catch Ada exceptions
3619 An Ada exception being raised. If an exception name is specified
3620 at the end of the command (eg @code{catch exception Program_Error}),
3621 the debugger will stop only when this specific exception is raised.
3622 Otherwise, the debugger stops execution when any Ada exception is raised.
3624 When inserting an exception catchpoint on a user-defined exception whose
3625 name is identical to one of the exceptions defined by the language, the
3626 fully qualified name must be used as the exception name. Otherwise,
3627 @value{GDBN} will assume that it should stop on the pre-defined exception
3628 rather than the user-defined one. For instance, assuming an exception
3629 called @code{Constraint_Error} is defined in package @code{Pck}, then
3630 the command to use to catch such exceptions is @kbd{catch exception
3631 Pck.Constraint_Error}.
3633 @item exception unhandled
3634 An exception that was raised but is not handled by the program.
3637 A failed Ada assertion.
3640 @cindex break on fork/exec
3641 A call to @code{exec}. This is currently only available for HP-UX
3645 A call to @code{fork}. This is currently only available for HP-UX
3649 A call to @code{vfork}. This is currently only available for HP-UX
3654 @item tcatch @var{event}
3655 Set a catchpoint that is enabled only for one stop. The catchpoint is
3656 automatically deleted after the first time the event is caught.
3660 Use the @code{info break} command to list the current catchpoints.
3662 There are currently some limitations to C@t{++} exception handling
3663 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3667 If you call a function interactively, @value{GDBN} normally returns
3668 control to you when the function has finished executing. If the call
3669 raises an exception, however, the call may bypass the mechanism that
3670 returns control to you and cause your program either to abort or to
3671 simply continue running until it hits a breakpoint, catches a signal
3672 that @value{GDBN} is listening for, or exits. This is the case even if
3673 you set a catchpoint for the exception; catchpoints on exceptions are
3674 disabled within interactive calls.
3677 You cannot raise an exception interactively.
3680 You cannot install an exception handler interactively.
3683 @cindex raise exceptions
3684 Sometimes @code{catch} is not the best way to debug exception handling:
3685 if you need to know exactly where an exception is raised, it is better to
3686 stop @emph{before} the exception handler is called, since that way you
3687 can see the stack before any unwinding takes place. If you set a
3688 breakpoint in an exception handler instead, it may not be easy to find
3689 out where the exception was raised.
3691 To stop just before an exception handler is called, you need some
3692 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3693 raised by calling a library function named @code{__raise_exception}
3694 which has the following ANSI C interface:
3697 /* @var{addr} is where the exception identifier is stored.
3698 @var{id} is the exception identifier. */
3699 void __raise_exception (void **addr, void *id);
3703 To make the debugger catch all exceptions before any stack
3704 unwinding takes place, set a breakpoint on @code{__raise_exception}
3705 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3707 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3708 that depends on the value of @var{id}, you can stop your program when
3709 a specific exception is raised. You can use multiple conditional
3710 breakpoints to stop your program when any of a number of exceptions are
3715 @subsection Deleting Breakpoints
3717 @cindex clearing breakpoints, watchpoints, catchpoints
3718 @cindex deleting breakpoints, watchpoints, catchpoints
3719 It is often necessary to eliminate a breakpoint, watchpoint, or
3720 catchpoint once it has done its job and you no longer want your program
3721 to stop there. This is called @dfn{deleting} the breakpoint. A
3722 breakpoint that has been deleted no longer exists; it is forgotten.
3724 With the @code{clear} command you can delete breakpoints according to
3725 where they are in your program. With the @code{delete} command you can
3726 delete individual breakpoints, watchpoints, or catchpoints by specifying
3727 their breakpoint numbers.
3729 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3730 automatically ignores breakpoints on the first instruction to be executed
3731 when you continue execution without changing the execution address.
3736 Delete any breakpoints at the next instruction to be executed in the
3737 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3738 the innermost frame is selected, this is a good way to delete a
3739 breakpoint where your program just stopped.
3741 @item clear @var{location}
3742 Delete any breakpoints set at the specified @var{location}.
3743 @xref{Specify Location}, for the various forms of @var{location}; the
3744 most useful ones are listed below:
3747 @item clear @var{function}
3748 @itemx clear @var{filename}:@var{function}
3749 Delete any breakpoints set at entry to the named @var{function}.
3751 @item clear @var{linenum}
3752 @itemx clear @var{filename}:@var{linenum}
3753 Delete any breakpoints set at or within the code of the specified
3754 @var{linenum} of the specified @var{filename}.
3757 @cindex delete breakpoints
3759 @kindex d @r{(@code{delete})}
3760 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3761 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3762 ranges specified as arguments. If no argument is specified, delete all
3763 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3764 confirm off}). You can abbreviate this command as @code{d}.
3768 @subsection Disabling Breakpoints
3770 @cindex enable/disable a breakpoint
3771 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3772 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3773 it had been deleted, but remembers the information on the breakpoint so
3774 that you can @dfn{enable} it again later.
3776 You disable and enable breakpoints, watchpoints, and catchpoints with
3777 the @code{enable} and @code{disable} commands, optionally specifying one
3778 or more breakpoint numbers as arguments. Use @code{info break} or
3779 @code{info watch} to print a list of breakpoints, watchpoints, and
3780 catchpoints if you do not know which numbers to use.
3782 Disabling and enabling a breakpoint that has multiple locations
3783 affects all of its locations.
3785 A breakpoint, watchpoint, or catchpoint can have any of four different
3786 states of enablement:
3790 Enabled. The breakpoint stops your program. A breakpoint set
3791 with the @code{break} command starts out in this state.
3793 Disabled. The breakpoint has no effect on your program.
3795 Enabled once. The breakpoint stops your program, but then becomes
3798 Enabled for deletion. The breakpoint stops your program, but
3799 immediately after it does so it is deleted permanently. A breakpoint
3800 set with the @code{tbreak} command starts out in this state.
3803 You can use the following commands to enable or disable breakpoints,
3804 watchpoints, and catchpoints:
3808 @kindex dis @r{(@code{disable})}
3809 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3810 Disable the specified breakpoints---or all breakpoints, if none are
3811 listed. A disabled breakpoint has no effect but is not forgotten. All
3812 options such as ignore-counts, conditions and commands are remembered in
3813 case the breakpoint is enabled again later. You may abbreviate
3814 @code{disable} as @code{dis}.
3817 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3818 Enable the specified breakpoints (or all defined breakpoints). They
3819 become effective once again in stopping your program.
3821 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3822 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3823 of these breakpoints immediately after stopping your program.
3825 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3826 Enable the specified breakpoints to work once, then die. @value{GDBN}
3827 deletes any of these breakpoints as soon as your program stops there.
3828 Breakpoints set by the @code{tbreak} command start out in this state.
3831 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3832 @c confusing: tbreak is also initially enabled.
3833 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3834 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3835 subsequently, they become disabled or enabled only when you use one of
3836 the commands above. (The command @code{until} can set and delete a
3837 breakpoint of its own, but it does not change the state of your other
3838 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3842 @subsection Break Conditions
3843 @cindex conditional breakpoints
3844 @cindex breakpoint conditions
3846 @c FIXME what is scope of break condition expr? Context where wanted?
3847 @c in particular for a watchpoint?
3848 The simplest sort of breakpoint breaks every time your program reaches a
3849 specified place. You can also specify a @dfn{condition} for a
3850 breakpoint. A condition is just a Boolean expression in your
3851 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3852 a condition evaluates the expression each time your program reaches it,
3853 and your program stops only if the condition is @emph{true}.
3855 This is the converse of using assertions for program validation; in that
3856 situation, you want to stop when the assertion is violated---that is,
3857 when the condition is false. In C, if you want to test an assertion expressed
3858 by the condition @var{assert}, you should set the condition
3859 @samp{! @var{assert}} on the appropriate breakpoint.
3861 Conditions are also accepted for watchpoints; you may not need them,
3862 since a watchpoint is inspecting the value of an expression anyhow---but
3863 it might be simpler, say, to just set a watchpoint on a variable name,
3864 and specify a condition that tests whether the new value is an interesting
3867 Break conditions can have side effects, and may even call functions in
3868 your program. This can be useful, for example, to activate functions
3869 that log program progress, or to use your own print functions to
3870 format special data structures. The effects are completely predictable
3871 unless there is another enabled breakpoint at the same address. (In
3872 that case, @value{GDBN} might see the other breakpoint first and stop your
3873 program without checking the condition of this one.) Note that
3874 breakpoint commands are usually more convenient and flexible than break
3876 purpose of performing side effects when a breakpoint is reached
3877 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3879 Break conditions can be specified when a breakpoint is set, by using
3880 @samp{if} in the arguments to the @code{break} command. @xref{Set
3881 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3882 with the @code{condition} command.
3884 You can also use the @code{if} keyword with the @code{watch} command.
3885 The @code{catch} command does not recognize the @code{if} keyword;
3886 @code{condition} is the only way to impose a further condition on a
3891 @item condition @var{bnum} @var{expression}
3892 Specify @var{expression} as the break condition for breakpoint,
3893 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3894 breakpoint @var{bnum} stops your program only if the value of
3895 @var{expression} is true (nonzero, in C). When you use
3896 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3897 syntactic correctness, and to determine whether symbols in it have
3898 referents in the context of your breakpoint. If @var{expression} uses
3899 symbols not referenced in the context of the breakpoint, @value{GDBN}
3900 prints an error message:
3903 No symbol "foo" in current context.
3908 not actually evaluate @var{expression} at the time the @code{condition}
3909 command (or a command that sets a breakpoint with a condition, like
3910 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3912 @item condition @var{bnum}
3913 Remove the condition from breakpoint number @var{bnum}. It becomes
3914 an ordinary unconditional breakpoint.
3917 @cindex ignore count (of breakpoint)
3918 A special case of a breakpoint condition is to stop only when the
3919 breakpoint has been reached a certain number of times. This is so
3920 useful that there is a special way to do it, using the @dfn{ignore
3921 count} of the breakpoint. Every breakpoint has an ignore count, which
3922 is an integer. Most of the time, the ignore count is zero, and
3923 therefore has no effect. But if your program reaches a breakpoint whose
3924 ignore count is positive, then instead of stopping, it just decrements
3925 the ignore count by one and continues. As a result, if the ignore count
3926 value is @var{n}, the breakpoint does not stop the next @var{n} times
3927 your program reaches it.
3931 @item ignore @var{bnum} @var{count}
3932 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3933 The next @var{count} times the breakpoint is reached, your program's
3934 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3937 To make the breakpoint stop the next time it is reached, specify
3940 When you use @code{continue} to resume execution of your program from a
3941 breakpoint, you can specify an ignore count directly as an argument to
3942 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3943 Stepping,,Continuing and Stepping}.
3945 If a breakpoint has a positive ignore count and a condition, the
3946 condition is not checked. Once the ignore count reaches zero,
3947 @value{GDBN} resumes checking the condition.
3949 You could achieve the effect of the ignore count with a condition such
3950 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3951 is decremented each time. @xref{Convenience Vars, ,Convenience
3955 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3958 @node Break Commands
3959 @subsection Breakpoint Command Lists
3961 @cindex breakpoint commands
3962 You can give any breakpoint (or watchpoint or catchpoint) a series of
3963 commands to execute when your program stops due to that breakpoint. For
3964 example, you might want to print the values of certain expressions, or
3965 enable other breakpoints.
3969 @kindex end@r{ (breakpoint commands)}
3970 @item commands @r{[}@var{bnum}@r{]}
3971 @itemx @dots{} @var{command-list} @dots{}
3973 Specify a list of commands for breakpoint number @var{bnum}. The commands
3974 themselves appear on the following lines. Type a line containing just
3975 @code{end} to terminate the commands.
3977 To remove all commands from a breakpoint, type @code{commands} and
3978 follow it immediately with @code{end}; that is, give no commands.
3980 With no @var{bnum} argument, @code{commands} refers to the last
3981 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3982 recently encountered).
3985 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3986 disabled within a @var{command-list}.
3988 You can use breakpoint commands to start your program up again. Simply
3989 use the @code{continue} command, or @code{step}, or any other command
3990 that resumes execution.
3992 Any other commands in the command list, after a command that resumes
3993 execution, are ignored. This is because any time you resume execution
3994 (even with a simple @code{next} or @code{step}), you may encounter
3995 another breakpoint---which could have its own command list, leading to
3996 ambiguities about which list to execute.
3999 If the first command you specify in a command list is @code{silent}, the
4000 usual message about stopping at a breakpoint is not printed. This may
4001 be desirable for breakpoints that are to print a specific message and
4002 then continue. If none of the remaining commands print anything, you
4003 see no sign that the breakpoint was reached. @code{silent} is
4004 meaningful only at the beginning of a breakpoint command list.
4006 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4007 print precisely controlled output, and are often useful in silent
4008 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4010 For example, here is how you could use breakpoint commands to print the
4011 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4017 printf "x is %d\n",x
4022 One application for breakpoint commands is to compensate for one bug so
4023 you can test for another. Put a breakpoint just after the erroneous line
4024 of code, give it a condition to detect the case in which something
4025 erroneous has been done, and give it commands to assign correct values
4026 to any variables that need them. End with the @code{continue} command
4027 so that your program does not stop, and start with the @code{silent}
4028 command so that no output is produced. Here is an example:
4039 @c @ifclear BARETARGET
4040 @node Error in Breakpoints
4041 @subsection ``Cannot insert breakpoints''
4043 If you request too many active hardware-assisted breakpoints and
4044 watchpoints, you will see this error message:
4046 @c FIXME: the precise wording of this message may change; the relevant
4047 @c source change is not committed yet (Sep 3, 1999).
4049 Stopped; cannot insert breakpoints.
4050 You may have requested too many hardware breakpoints and watchpoints.
4054 This message is printed when you attempt to resume the program, since
4055 only then @value{GDBN} knows exactly how many hardware breakpoints and
4056 watchpoints it needs to insert.
4058 When this message is printed, you need to disable or remove some of the
4059 hardware-assisted breakpoints and watchpoints, and then continue.
4061 @node Breakpoint-related Warnings
4062 @subsection ``Breakpoint address adjusted...''
4063 @cindex breakpoint address adjusted
4065 Some processor architectures place constraints on the addresses at
4066 which breakpoints may be placed. For architectures thus constrained,
4067 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4068 with the constraints dictated by the architecture.
4070 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4071 a VLIW architecture in which a number of RISC-like instructions may be
4072 bundled together for parallel execution. The FR-V architecture
4073 constrains the location of a breakpoint instruction within such a
4074 bundle to the instruction with the lowest address. @value{GDBN}
4075 honors this constraint by adjusting a breakpoint's address to the
4076 first in the bundle.
4078 It is not uncommon for optimized code to have bundles which contain
4079 instructions from different source statements, thus it may happen that
4080 a breakpoint's address will be adjusted from one source statement to
4081 another. Since this adjustment may significantly alter @value{GDBN}'s
4082 breakpoint related behavior from what the user expects, a warning is
4083 printed when the breakpoint is first set and also when the breakpoint
4086 A warning like the one below is printed when setting a breakpoint
4087 that's been subject to address adjustment:
4090 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4093 Such warnings are printed both for user settable and @value{GDBN}'s
4094 internal breakpoints. If you see one of these warnings, you should
4095 verify that a breakpoint set at the adjusted address will have the
4096 desired affect. If not, the breakpoint in question may be removed and
4097 other breakpoints may be set which will have the desired behavior.
4098 E.g., it may be sufficient to place the breakpoint at a later
4099 instruction. A conditional breakpoint may also be useful in some
4100 cases to prevent the breakpoint from triggering too often.
4102 @value{GDBN} will also issue a warning when stopping at one of these
4103 adjusted breakpoints:
4106 warning: Breakpoint 1 address previously adjusted from 0x00010414
4110 When this warning is encountered, it may be too late to take remedial
4111 action except in cases where the breakpoint is hit earlier or more
4112 frequently than expected.
4114 @node Continuing and Stepping
4115 @section Continuing and Stepping
4119 @cindex resuming execution
4120 @dfn{Continuing} means resuming program execution until your program
4121 completes normally. In contrast, @dfn{stepping} means executing just
4122 one more ``step'' of your program, where ``step'' may mean either one
4123 line of source code, or one machine instruction (depending on what
4124 particular command you use). Either when continuing or when stepping,
4125 your program may stop even sooner, due to a breakpoint or a signal. (If
4126 it stops due to a signal, you may want to use @code{handle}, or use
4127 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4131 @kindex c @r{(@code{continue})}
4132 @kindex fg @r{(resume foreground execution)}
4133 @item continue @r{[}@var{ignore-count}@r{]}
4134 @itemx c @r{[}@var{ignore-count}@r{]}
4135 @itemx fg @r{[}@var{ignore-count}@r{]}
4136 Resume program execution, at the address where your program last stopped;
4137 any breakpoints set at that address are bypassed. The optional argument
4138 @var{ignore-count} allows you to specify a further number of times to
4139 ignore a breakpoint at this location; its effect is like that of
4140 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4142 The argument @var{ignore-count} is meaningful only when your program
4143 stopped due to a breakpoint. At other times, the argument to
4144 @code{continue} is ignored.
4146 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4147 debugged program is deemed to be the foreground program) are provided
4148 purely for convenience, and have exactly the same behavior as
4152 To resume execution at a different place, you can use @code{return}
4153 (@pxref{Returning, ,Returning from a Function}) to go back to the
4154 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4155 Different Address}) to go to an arbitrary location in your program.
4157 A typical technique for using stepping is to set a breakpoint
4158 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4159 beginning of the function or the section of your program where a problem
4160 is believed to lie, run your program until it stops at that breakpoint,
4161 and then step through the suspect area, examining the variables that are
4162 interesting, until you see the problem happen.
4166 @kindex s @r{(@code{step})}
4168 Continue running your program until control reaches a different source
4169 line, then stop it and return control to @value{GDBN}. This command is
4170 abbreviated @code{s}.
4173 @c "without debugging information" is imprecise; actually "without line
4174 @c numbers in the debugging information". (gcc -g1 has debugging info but
4175 @c not line numbers). But it seems complex to try to make that
4176 @c distinction here.
4177 @emph{Warning:} If you use the @code{step} command while control is
4178 within a function that was compiled without debugging information,
4179 execution proceeds until control reaches a function that does have
4180 debugging information. Likewise, it will not step into a function which
4181 is compiled without debugging information. To step through functions
4182 without debugging information, use the @code{stepi} command, described
4186 The @code{step} command only stops at the first instruction of a source
4187 line. This prevents the multiple stops that could otherwise occur in
4188 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4189 to stop if a function that has debugging information is called within
4190 the line. In other words, @code{step} @emph{steps inside} any functions
4191 called within the line.
4193 Also, the @code{step} command only enters a function if there is line
4194 number information for the function. Otherwise it acts like the
4195 @code{next} command. This avoids problems when using @code{cc -gl}
4196 on MIPS machines. Previously, @code{step} entered subroutines if there
4197 was any debugging information about the routine.
4199 @item step @var{count}
4200 Continue running as in @code{step}, but do so @var{count} times. If a
4201 breakpoint is reached, or a signal not related to stepping occurs before
4202 @var{count} steps, stepping stops right away.
4205 @kindex n @r{(@code{next})}
4206 @item next @r{[}@var{count}@r{]}
4207 Continue to the next source line in the current (innermost) stack frame.
4208 This is similar to @code{step}, but function calls that appear within
4209 the line of code are executed without stopping. Execution stops when
4210 control reaches a different line of code at the original stack level
4211 that was executing when you gave the @code{next} command. This command
4212 is abbreviated @code{n}.
4214 An argument @var{count} is a repeat count, as for @code{step}.
4217 @c FIX ME!! Do we delete this, or is there a way it fits in with
4218 @c the following paragraph? --- Vctoria
4220 @c @code{next} within a function that lacks debugging information acts like
4221 @c @code{step}, but any function calls appearing within the code of the
4222 @c function are executed without stopping.
4224 The @code{next} command only stops at the first instruction of a
4225 source line. This prevents multiple stops that could otherwise occur in
4226 @code{switch} statements, @code{for} loops, etc.
4228 @kindex set step-mode
4230 @cindex functions without line info, and stepping
4231 @cindex stepping into functions with no line info
4232 @itemx set step-mode on
4233 The @code{set step-mode on} command causes the @code{step} command to
4234 stop at the first instruction of a function which contains no debug line
4235 information rather than stepping over it.
4237 This is useful in cases where you may be interested in inspecting the
4238 machine instructions of a function which has no symbolic info and do not
4239 want @value{GDBN} to automatically skip over this function.
4241 @item set step-mode off
4242 Causes the @code{step} command to step over any functions which contains no
4243 debug information. This is the default.
4245 @item show step-mode
4246 Show whether @value{GDBN} will stop in or step over functions without
4247 source line debug information.
4250 @kindex fin @r{(@code{finish})}
4252 Continue running until just after function in the selected stack frame
4253 returns. Print the returned value (if any). This command can be
4254 abbreviated as @code{fin}.
4256 Contrast this with the @code{return} command (@pxref{Returning,
4257 ,Returning from a Function}).
4260 @kindex u @r{(@code{until})}
4261 @cindex run until specified location
4264 Continue running until a source line past the current line, in the
4265 current stack frame, is reached. This command is used to avoid single
4266 stepping through a loop more than once. It is like the @code{next}
4267 command, except that when @code{until} encounters a jump, it
4268 automatically continues execution until the program counter is greater
4269 than the address of the jump.
4271 This means that when you reach the end of a loop after single stepping
4272 though it, @code{until} makes your program continue execution until it
4273 exits the loop. In contrast, a @code{next} command at the end of a loop
4274 simply steps back to the beginning of the loop, which forces you to step
4275 through the next iteration.
4277 @code{until} always stops your program if it attempts to exit the current
4280 @code{until} may produce somewhat counterintuitive results if the order
4281 of machine code does not match the order of the source lines. For
4282 example, in the following excerpt from a debugging session, the @code{f}
4283 (@code{frame}) command shows that execution is stopped at line
4284 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4288 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4290 (@value{GDBP}) until
4291 195 for ( ; argc > 0; NEXTARG) @{
4294 This happened because, for execution efficiency, the compiler had
4295 generated code for the loop closure test at the end, rather than the
4296 start, of the loop---even though the test in a C @code{for}-loop is
4297 written before the body of the loop. The @code{until} command appeared
4298 to step back to the beginning of the loop when it advanced to this
4299 expression; however, it has not really gone to an earlier
4300 statement---not in terms of the actual machine code.
4302 @code{until} with no argument works by means of single
4303 instruction stepping, and hence is slower than @code{until} with an
4306 @item until @var{location}
4307 @itemx u @var{location}
4308 Continue running your program until either the specified location is
4309 reached, or the current stack frame returns. @var{location} is any of
4310 the forms described in @ref{Specify Location}.
4311 This form of the command uses temporary breakpoints, and
4312 hence is quicker than @code{until} without an argument. The specified
4313 location is actually reached only if it is in the current frame. This
4314 implies that @code{until} can be used to skip over recursive function
4315 invocations. For instance in the code below, if the current location is
4316 line @code{96}, issuing @code{until 99} will execute the program up to
4317 line @code{99} in the same invocation of factorial, i.e., after the inner
4318 invocations have returned.
4321 94 int factorial (int value)
4323 96 if (value > 1) @{
4324 97 value *= factorial (value - 1);
4331 @kindex advance @var{location}
4332 @itemx advance @var{location}
4333 Continue running the program up to the given @var{location}. An argument is
4334 required, which should be of one of the forms described in
4335 @ref{Specify Location}.
4336 Execution will also stop upon exit from the current stack
4337 frame. This command is similar to @code{until}, but @code{advance} will
4338 not skip over recursive function calls, and the target location doesn't
4339 have to be in the same frame as the current one.
4343 @kindex si @r{(@code{stepi})}
4345 @itemx stepi @var{arg}
4347 Execute one machine instruction, then stop and return to the debugger.
4349 It is often useful to do @samp{display/i $pc} when stepping by machine
4350 instructions. This makes @value{GDBN} automatically display the next
4351 instruction to be executed, each time your program stops. @xref{Auto
4352 Display,, Automatic Display}.
4354 An argument is a repeat count, as in @code{step}.
4358 @kindex ni @r{(@code{nexti})}
4360 @itemx nexti @var{arg}
4362 Execute one machine instruction, but if it is a function call,
4363 proceed until the function returns.
4365 An argument is a repeat count, as in @code{next}.
4372 A signal is an asynchronous event that can happen in a program. The
4373 operating system defines the possible kinds of signals, and gives each
4374 kind a name and a number. For example, in Unix @code{SIGINT} is the
4375 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4376 @code{SIGSEGV} is the signal a program gets from referencing a place in
4377 memory far away from all the areas in use; @code{SIGALRM} occurs when
4378 the alarm clock timer goes off (which happens only if your program has
4379 requested an alarm).
4381 @cindex fatal signals
4382 Some signals, including @code{SIGALRM}, are a normal part of the
4383 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4384 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4385 program has not specified in advance some other way to handle the signal.
4386 @code{SIGINT} does not indicate an error in your program, but it is normally
4387 fatal so it can carry out the purpose of the interrupt: to kill the program.
4389 @value{GDBN} has the ability to detect any occurrence of a signal in your
4390 program. You can tell @value{GDBN} in advance what to do for each kind of
4393 @cindex handling signals
4394 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4395 @code{SIGALRM} be silently passed to your program
4396 (so as not to interfere with their role in the program's functioning)
4397 but to stop your program immediately whenever an error signal happens.
4398 You can change these settings with the @code{handle} command.
4401 @kindex info signals
4405 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4406 handle each one. You can use this to see the signal numbers of all
4407 the defined types of signals.
4409 @item info signals @var{sig}
4410 Similar, but print information only about the specified signal number.
4412 @code{info handle} is an alias for @code{info signals}.
4415 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4416 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4417 can be the number of a signal or its name (with or without the
4418 @samp{SIG} at the beginning); a list of signal numbers of the form
4419 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4420 known signals. Optional arguments @var{keywords}, described below,
4421 say what change to make.
4425 The keywords allowed by the @code{handle} command can be abbreviated.
4426 Their full names are:
4430 @value{GDBN} should not stop your program when this signal happens. It may
4431 still print a message telling you that the signal has come in.
4434 @value{GDBN} should stop your program when this signal happens. This implies
4435 the @code{print} keyword as well.
4438 @value{GDBN} should print a message when this signal happens.
4441 @value{GDBN} should not mention the occurrence of the signal at all. This
4442 implies the @code{nostop} keyword as well.
4446 @value{GDBN} should allow your program to see this signal; your program
4447 can handle the signal, or else it may terminate if the signal is fatal
4448 and not handled. @code{pass} and @code{noignore} are synonyms.
4452 @value{GDBN} should not allow your program to see this signal.
4453 @code{nopass} and @code{ignore} are synonyms.
4457 When a signal stops your program, the signal is not visible to the
4459 continue. Your program sees the signal then, if @code{pass} is in
4460 effect for the signal in question @emph{at that time}. In other words,
4461 after @value{GDBN} reports a signal, you can use the @code{handle}
4462 command with @code{pass} or @code{nopass} to control whether your
4463 program sees that signal when you continue.
4465 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4466 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4467 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4470 You can also use the @code{signal} command to prevent your program from
4471 seeing a signal, or cause it to see a signal it normally would not see,
4472 or to give it any signal at any time. For example, if your program stopped
4473 due to some sort of memory reference error, you might store correct
4474 values into the erroneous variables and continue, hoping to see more
4475 execution; but your program would probably terminate immediately as
4476 a result of the fatal signal once it saw the signal. To prevent this,
4477 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4480 @cindex extra signal information
4481 @anchor{extra signal information}
4483 On some targets, @value{GDBN} can inspect extra signal information
4484 associated with the intercepted signal, before it is actually
4485 delivered to the program being debugged. This information is exported
4486 by the convenience variable @code{$_siginfo}, and consists of data
4487 that is passed by the kernel to the signal handler at the time of the
4488 receipt of a signal. The data type of the information itself is
4489 target dependent. You can see the data type using the @code{ptype
4490 $_siginfo} command. On Unix systems, it typically corresponds to the
4491 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4494 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4495 referenced address that raised a segmentation fault.
4499 (@value{GDBP}) continue
4500 Program received signal SIGSEGV, Segmentation fault.
4501 0x0000000000400766 in main ()
4503 (@value{GDBP}) ptype $_siginfo
4510 struct @{...@} _kill;
4511 struct @{...@} _timer;
4513 struct @{...@} _sigchld;
4514 struct @{...@} _sigfault;
4515 struct @{...@} _sigpoll;
4518 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4522 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4523 $1 = (void *) 0x7ffff7ff7000
4527 Depending on target support, @code{$_siginfo} may also be writable.
4530 @section Stopping and Starting Multi-thread Programs
4532 @cindex stopped threads
4533 @cindex threads, stopped
4535 @cindex continuing threads
4536 @cindex threads, continuing
4538 @value{GDBN} supports debugging programs with multiple threads
4539 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4540 are two modes of controlling execution of your program within the
4541 debugger. In the default mode, referred to as @dfn{all-stop mode},
4542 when any thread in your program stops (for example, at a breakpoint
4543 or while being stepped), all other threads in the program are also stopped by
4544 @value{GDBN}. On some targets, @value{GDBN} also supports
4545 @dfn{non-stop mode}, in which other threads can continue to run freely while
4546 you examine the stopped thread in the debugger.
4549 * All-Stop Mode:: All threads stop when GDB takes control
4550 * Non-Stop Mode:: Other threads continue to execute
4551 * Background Execution:: Running your program asynchronously
4552 * Thread-Specific Breakpoints:: Controlling breakpoints
4553 * Interrupted System Calls:: GDB may interfere with system calls
4557 @subsection All-Stop Mode
4559 @cindex all-stop mode
4561 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4562 @emph{all} threads of execution stop, not just the current thread. This
4563 allows you to examine the overall state of the program, including
4564 switching between threads, without worrying that things may change
4567 Conversely, whenever you restart the program, @emph{all} threads start
4568 executing. @emph{This is true even when single-stepping} with commands
4569 like @code{step} or @code{next}.
4571 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4572 Since thread scheduling is up to your debugging target's operating
4573 system (not controlled by @value{GDBN}), other threads may
4574 execute more than one statement while the current thread completes a
4575 single step. Moreover, in general other threads stop in the middle of a
4576 statement, rather than at a clean statement boundary, when the program
4579 You might even find your program stopped in another thread after
4580 continuing or even single-stepping. This happens whenever some other
4581 thread runs into a breakpoint, a signal, or an exception before the
4582 first thread completes whatever you requested.
4584 @cindex automatic thread selection
4585 @cindex switching threads automatically
4586 @cindex threads, automatic switching
4587 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4588 signal, it automatically selects the thread where that breakpoint or
4589 signal happened. @value{GDBN} alerts you to the context switch with a
4590 message such as @samp{[Switching to Thread @var{n}]} to identify the
4593 On some OSes, you can modify @value{GDBN}'s default behavior by
4594 locking the OS scheduler to allow only a single thread to run.
4597 @item set scheduler-locking @var{mode}
4598 @cindex scheduler locking mode
4599 @cindex lock scheduler
4600 Set the scheduler locking mode. If it is @code{off}, then there is no
4601 locking and any thread may run at any time. If @code{on}, then only the
4602 current thread may run when the inferior is resumed. The @code{step}
4603 mode optimizes for single-stepping; it prevents other threads
4604 from preempting the current thread while you are stepping, so that
4605 the focus of debugging does not change unexpectedly.
4606 Other threads only rarely (or never) get a chance to run
4607 when you step. They are more likely to run when you @samp{next} over a
4608 function call, and they are completely free to run when you use commands
4609 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4610 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4611 the current thread away from the thread that you are debugging.
4613 @item show scheduler-locking
4614 Display the current scheduler locking mode.
4618 @subsection Non-Stop Mode
4620 @cindex non-stop mode
4622 @c This section is really only a place-holder, and needs to be expanded
4623 @c with more details.
4625 For some multi-threaded targets, @value{GDBN} supports an optional
4626 mode of operation in which you can examine stopped program threads in
4627 the debugger while other threads continue to execute freely. This
4628 minimizes intrusion when debugging live systems, such as programs
4629 where some threads have real-time constraints or must continue to
4630 respond to external events. This is referred to as @dfn{non-stop} mode.
4632 In non-stop mode, when a thread stops to report a debugging event,
4633 @emph{only} that thread is stopped; @value{GDBN} does not stop other
4634 threads as well, in contrast to the all-stop mode behavior. Additionally,
4635 execution commands such as @code{continue} and @code{step} apply by default
4636 only to the current thread in non-stop mode, rather than all threads as
4637 in all-stop mode. This allows you to control threads explicitly in
4638 ways that are not possible in all-stop mode --- for example, stepping
4639 one thread while allowing others to run freely, stepping
4640 one thread while holding all others stopped, or stepping several threads
4641 independently and simultaneously.
4643 To enter non-stop mode, use this sequence of commands before you run
4644 or attach to your program:
4647 # Enable the async interface.
4650 # If using the CLI, pagination breaks non-stop.
4653 # Finally, turn it on!
4657 You can use these commands to manipulate the non-stop mode setting:
4660 @kindex set non-stop
4661 @item set non-stop on
4662 Enable selection of non-stop mode.
4663 @item set non-stop off
4664 Disable selection of non-stop mode.
4665 @kindex show non-stop
4667 Show the current non-stop enablement setting.
4670 Note these commands only reflect whether non-stop mode is enabled,
4671 not whether the currently-executing program is being run in non-stop mode.
4672 In particular, the @code{set non-stop} preference is only consulted when
4673 @value{GDBN} starts or connects to the target program, and it is generally
4674 not possible to switch modes once debugging has started. Furthermore,
4675 since not all targets support non-stop mode, even when you have enabled
4676 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
4679 In non-stop mode, all execution commands apply only to the current thread
4680 by default. That is, @code{continue} only continues one thread.
4681 To continue all threads, issue @code{continue -a} or @code{c -a}.
4683 You can use @value{GDBN}'s background execution commands
4684 (@pxref{Background Execution}) to run some threads in the background
4685 while you continue to examine or step others from @value{GDBN}.
4686 The MI execution commands (@pxref{GDB/MI Program Execution}) are
4687 always executed asynchronously in non-stop mode.
4689 Suspending execution is done with the @code{interrupt} command when
4690 running in the background, or @kbd{Ctrl-c} during foreground execution.
4691 In all-stop mode, this stops the whole process;
4692 but in non-stop mode the interrupt applies only to the current thread.
4693 To stop the whole program, use @code{interrupt -a}.
4695 Other execution commands do not currently support the @code{-a} option.
4697 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
4698 that thread current, as it does in all-stop mode. This is because the
4699 thread stop notifications are asynchronous with respect to @value{GDBN}'s
4700 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
4701 changed to a different thread just as you entered a command to operate on the
4702 previously current thread.
4704 @node Background Execution
4705 @subsection Background Execution
4707 @cindex foreground execution
4708 @cindex background execution
4709 @cindex asynchronous execution
4710 @cindex execution, foreground, background and asynchronous
4712 @value{GDBN}'s execution commands have two variants: the normal
4713 foreground (synchronous) behavior, and a background
4714 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
4715 the program to report that some thread has stopped before prompting for
4716 another command. In background execution, @value{GDBN} immediately gives
4717 a command prompt so that you can issue other commands while your program runs.
4719 You need to explicitly enable asynchronous mode before you can use
4720 background execution commands. You can use these commands to
4721 manipulate the asynchronous mode setting:
4724 @kindex set target-async
4725 @item set target-async on
4726 Enable asynchronous mode.
4727 @item set target-async off
4728 Disable asynchronous mode.
4729 @kindex show target-async
4730 @item show target-async
4731 Show the current target-async setting.
4734 If the target doesn't support async mode, @value{GDBN} issues an error
4735 message if you attempt to use the background execution commands.
4737 To specify background execution, add a @code{&} to the command. For example,
4738 the background form of the @code{continue} command is @code{continue&}, or
4739 just @code{c&}. The execution commands that accept background execution
4745 @xref{Starting, , Starting your Program}.
4749 @xref{Attach, , Debugging an Already-running Process}.
4753 @xref{Continuing and Stepping, step}.
4757 @xref{Continuing and Stepping, stepi}.
4761 @xref{Continuing and Stepping, next}.
4765 @xref{Continuing and Stepping, nexti}.
4769 @xref{Continuing and Stepping, continue}.
4773 @xref{Continuing and Stepping, finish}.
4777 @xref{Continuing and Stepping, until}.
4781 Background execution is especially useful in conjunction with non-stop
4782 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
4783 However, you can also use these commands in the normal all-stop mode with
4784 the restriction that you cannot issue another execution command until the
4785 previous one finishes. Examples of commands that are valid in all-stop
4786 mode while the program is running include @code{help} and @code{info break}.
4788 You can interrupt your program while it is running in the background by
4789 using the @code{interrupt} command.
4796 Suspend execution of the running program. In all-stop mode,
4797 @code{interrupt} stops the whole process, but in non-stop mode, it stops
4798 only the current thread. To stop the whole program in non-stop mode,
4799 use @code{interrupt -a}.
4802 @node Thread-Specific Breakpoints
4803 @subsection Thread-Specific Breakpoints
4805 When your program has multiple threads (@pxref{Threads,, Debugging
4806 Programs with Multiple Threads}), you can choose whether to set
4807 breakpoints on all threads, or on a particular thread.
4810 @cindex breakpoints and threads
4811 @cindex thread breakpoints
4812 @kindex break @dots{} thread @var{threadno}
4813 @item break @var{linespec} thread @var{threadno}
4814 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4815 @var{linespec} specifies source lines; there are several ways of
4816 writing them (@pxref{Specify Location}), but the effect is always to
4817 specify some source line.
4819 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4820 to specify that you only want @value{GDBN} to stop the program when a
4821 particular thread reaches this breakpoint. @var{threadno} is one of the
4822 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4823 column of the @samp{info threads} display.
4825 If you do not specify @samp{thread @var{threadno}} when you set a
4826 breakpoint, the breakpoint applies to @emph{all} threads of your
4829 You can use the @code{thread} qualifier on conditional breakpoints as
4830 well; in this case, place @samp{thread @var{threadno}} before the
4831 breakpoint condition, like this:
4834 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4839 @node Interrupted System Calls
4840 @subsection Interrupted System Calls
4842 @cindex thread breakpoints and system calls
4843 @cindex system calls and thread breakpoints
4844 @cindex premature return from system calls
4845 There is an unfortunate side effect when using @value{GDBN} to debug
4846 multi-threaded programs. If one thread stops for a
4847 breakpoint, or for some other reason, and another thread is blocked in a
4848 system call, then the system call may return prematurely. This is a
4849 consequence of the interaction between multiple threads and the signals
4850 that @value{GDBN} uses to implement breakpoints and other events that
4853 To handle this problem, your program should check the return value of
4854 each system call and react appropriately. This is good programming
4857 For example, do not write code like this:
4863 The call to @code{sleep} will return early if a different thread stops
4864 at a breakpoint or for some other reason.
4866 Instead, write this:
4871 unslept = sleep (unslept);
4874 A system call is allowed to return early, so the system is still
4875 conforming to its specification. But @value{GDBN} does cause your
4876 multi-threaded program to behave differently than it would without
4879 Also, @value{GDBN} uses internal breakpoints in the thread library to
4880 monitor certain events such as thread creation and thread destruction.
4881 When such an event happens, a system call in another thread may return
4882 prematurely, even though your program does not appear to stop.
4885 @node Reverse Execution
4886 @chapter Running programs backward
4887 @cindex reverse execution
4888 @cindex running programs backward
4890 When you are debugging a program, it is not unusual to realize that
4891 you have gone too far, and some event of interest has already happened.
4892 If the target environment supports it, @value{GDBN} can allow you to
4893 ``rewind'' the program by running it backward.
4895 A target environment that supports reverse execution should be able
4896 to ``undo'' the changes in machine state that have taken place as the
4897 program was executing normally. Variables, registers etc.@: should
4898 revert to their previous values. Obviously this requires a great
4899 deal of sophistication on the part of the target environment; not
4900 all target environments can support reverse execution.
4902 When a program is executed in reverse, the instructions that
4903 have most recently been executed are ``un-executed'', in reverse
4904 order. The program counter runs backward, following the previous
4905 thread of execution in reverse. As each instruction is ``un-executed'',
4906 the values of memory and/or registers that were changed by that
4907 instruction are reverted to their previous states. After executing
4908 a piece of source code in reverse, all side effects of that code
4909 should be ``undone'', and all variables should be returned to their
4910 prior values@footnote{
4911 Note that some side effects are easier to undo than others. For instance,
4912 memory and registers are relatively easy, but device I/O is hard. Some
4913 targets may be able undo things like device I/O, and some may not.
4915 The contract between @value{GDBN} and the reverse executing target
4916 requires only that the target do something reasonable when
4917 @value{GDBN} tells it to execute backwards, and then report the
4918 results back to @value{GDBN}. Whatever the target reports back to
4919 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
4920 assumes that the memory and registers that the target reports are in a
4921 consistant state, but @value{GDBN} accepts whatever it is given.
4924 If you are debugging in a target environment that supports
4925 reverse execution, @value{GDBN} provides the following commands.
4928 @kindex reverse-continue
4929 @kindex rc @r{(@code{reverse-continue})}
4930 @item reverse-continue @r{[}@var{ignore-count}@r{]}
4931 @itemx rc @r{[}@var{ignore-count}@r{]}
4932 Beginning at the point where your program last stopped, start executing
4933 in reverse. Reverse execution will stop for breakpoints and synchronous
4934 exceptions (signals), just like normal execution. Behavior of
4935 asynchronous signals depends on the target environment.
4937 @kindex reverse-step
4938 @kindex rs @r{(@code{step})}
4939 @item reverse-step @r{[}@var{count}@r{]}
4940 Run the program backward until control reaches the start of a
4941 different source line; then stop it, and return control to @value{GDBN}.
4943 Like the @code{step} command, @code{reverse-step} will only stop
4944 at the beginning of a source line. It ``un-executes'' the previously
4945 executed source line. If the previous source line included calls to
4946 debuggable functions, @code{reverse-step} will step (backward) into
4947 the called function, stopping at the beginning of the @emph{last}
4948 statement in the called function (typically a return statement).
4950 Also, as with the @code{step} command, if non-debuggable functions are
4951 called, @code{reverse-step} will run thru them backward without stopping.
4953 @kindex reverse-stepi
4954 @kindex rsi @r{(@code{reverse-stepi})}
4955 @item reverse-stepi @r{[}@var{count}@r{]}
4956 Reverse-execute one machine instruction. Note that the instruction
4957 to be reverse-executed is @emph{not} the one pointed to by the program
4958 counter, but the instruction executed prior to that one. For instance,
4959 if the last instruction was a jump, @code{reverse-stepi} will take you
4960 back from the destination of the jump to the jump instruction itself.
4962 @kindex reverse-next
4963 @kindex rn @r{(@code{reverse-next})}
4964 @item reverse-next @r{[}@var{count}@r{]}
4965 Run backward to the beginning of the previous line executed in
4966 the current (innermost) stack frame. If the line contains function
4967 calls, they will be ``un-executed'' without stopping. Starting from
4968 the first line of a function, @code{reverse-next} will take you back
4969 to the caller of that function, @emph{before} the function was called,
4970 just as the normal @code{next} command would take you from the last
4971 line of a function back to its return to its caller
4972 @footnote{Unles the code is too heavily optimized.}.
4974 @kindex reverse-nexti
4975 @kindex rni @r{(@code{reverse-nexti})}
4976 @item reverse-nexti @r{[}@var{count}@r{]}
4977 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
4978 in reverse, except that called functions are ``un-executed'' atomically.
4979 That is, if the previously executed instruction was a return from
4980 another instruction, @code{reverse-nexti} will continue to execute
4981 in reverse until the call to that function (from the current stack
4984 @kindex reverse-finish
4985 @item reverse-finish
4986 Just as the @code{finish} command takes you to the point where the
4987 current function returns, @code{reverse-finish} takes you to the point
4988 where it was called. Instead of ending up at the end of the current
4989 function invocation, you end up at the beginning.
4991 @kindex set exec-direction
4992 @item set exec-direction
4993 Set the direction of target execution.
4994 @itemx set exec-direction reverse
4995 @cindex execute forward or backward in time
4996 @value{GDBN} will perform all execution commands in reverse, until the
4997 exec-direction mode is changed to ``forward''. Affected commands include
4998 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
4999 command cannot be used in reverse mode.
5000 @item set exec-direction forward
5001 @value{GDBN} will perform all execution commands in the normal fashion.
5002 This is the default.
5007 @chapter Examining the Stack
5009 When your program has stopped, the first thing you need to know is where it
5010 stopped and how it got there.
5013 Each time your program performs a function call, information about the call
5015 That information includes the location of the call in your program,
5016 the arguments of the call,
5017 and the local variables of the function being called.
5018 The information is saved in a block of data called a @dfn{stack frame}.
5019 The stack frames are allocated in a region of memory called the @dfn{call
5022 When your program stops, the @value{GDBN} commands for examining the
5023 stack allow you to see all of this information.
5025 @cindex selected frame
5026 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5027 @value{GDBN} commands refer implicitly to the selected frame. In
5028 particular, whenever you ask @value{GDBN} for the value of a variable in
5029 your program, the value is found in the selected frame. There are
5030 special @value{GDBN} commands to select whichever frame you are
5031 interested in. @xref{Selection, ,Selecting a Frame}.
5033 When your program stops, @value{GDBN} automatically selects the
5034 currently executing frame and describes it briefly, similar to the
5035 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5038 * Frames:: Stack frames
5039 * Backtrace:: Backtraces
5040 * Selection:: Selecting a frame
5041 * Frame Info:: Information on a frame
5046 @section Stack Frames
5048 @cindex frame, definition
5050 The call stack is divided up into contiguous pieces called @dfn{stack
5051 frames}, or @dfn{frames} for short; each frame is the data associated
5052 with one call to one function. The frame contains the arguments given
5053 to the function, the function's local variables, and the address at
5054 which the function is executing.
5056 @cindex initial frame
5057 @cindex outermost frame
5058 @cindex innermost frame
5059 When your program is started, the stack has only one frame, that of the
5060 function @code{main}. This is called the @dfn{initial} frame or the
5061 @dfn{outermost} frame. Each time a function is called, a new frame is
5062 made. Each time a function returns, the frame for that function invocation
5063 is eliminated. If a function is recursive, there can be many frames for
5064 the same function. The frame for the function in which execution is
5065 actually occurring is called the @dfn{innermost} frame. This is the most
5066 recently created of all the stack frames that still exist.
5068 @cindex frame pointer
5069 Inside your program, stack frames are identified by their addresses. A
5070 stack frame consists of many bytes, each of which has its own address; each
5071 kind of computer has a convention for choosing one byte whose
5072 address serves as the address of the frame. Usually this address is kept
5073 in a register called the @dfn{frame pointer register}
5074 (@pxref{Registers, $fp}) while execution is going on in that frame.
5076 @cindex frame number
5077 @value{GDBN} assigns numbers to all existing stack frames, starting with
5078 zero for the innermost frame, one for the frame that called it,
5079 and so on upward. These numbers do not really exist in your program;
5080 they are assigned by @value{GDBN} to give you a way of designating stack
5081 frames in @value{GDBN} commands.
5083 @c The -fomit-frame-pointer below perennially causes hbox overflow
5084 @c underflow problems.
5085 @cindex frameless execution
5086 Some compilers provide a way to compile functions so that they operate
5087 without stack frames. (For example, the @value{NGCC} option
5089 @samp{-fomit-frame-pointer}
5091 generates functions without a frame.)
5092 This is occasionally done with heavily used library functions to save
5093 the frame setup time. @value{GDBN} has limited facilities for dealing
5094 with these function invocations. If the innermost function invocation
5095 has no stack frame, @value{GDBN} nevertheless regards it as though
5096 it had a separate frame, which is numbered zero as usual, allowing
5097 correct tracing of the function call chain. However, @value{GDBN} has
5098 no provision for frameless functions elsewhere in the stack.
5101 @kindex frame@r{, command}
5102 @cindex current stack frame
5103 @item frame @var{args}
5104 The @code{frame} command allows you to move from one stack frame to another,
5105 and to print the stack frame you select. @var{args} may be either the
5106 address of the frame or the stack frame number. Without an argument,
5107 @code{frame} prints the current stack frame.
5109 @kindex select-frame
5110 @cindex selecting frame silently
5112 The @code{select-frame} command allows you to move from one stack frame
5113 to another without printing the frame. This is the silent version of
5121 @cindex call stack traces
5122 A backtrace is a summary of how your program got where it is. It shows one
5123 line per frame, for many frames, starting with the currently executing
5124 frame (frame zero), followed by its caller (frame one), and on up the
5129 @kindex bt @r{(@code{backtrace})}
5132 Print a backtrace of the entire stack: one line per frame for all
5133 frames in the stack.
5135 You can stop the backtrace at any time by typing the system interrupt
5136 character, normally @kbd{Ctrl-c}.
5138 @item backtrace @var{n}
5140 Similar, but print only the innermost @var{n} frames.
5142 @item backtrace -@var{n}
5144 Similar, but print only the outermost @var{n} frames.
5146 @item backtrace full
5148 @itemx bt full @var{n}
5149 @itemx bt full -@var{n}
5150 Print the values of the local variables also. @var{n} specifies the
5151 number of frames to print, as described above.
5156 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5157 are additional aliases for @code{backtrace}.
5159 @cindex multiple threads, backtrace
5160 In a multi-threaded program, @value{GDBN} by default shows the
5161 backtrace only for the current thread. To display the backtrace for
5162 several or all of the threads, use the command @code{thread apply}
5163 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5164 apply all backtrace}, @value{GDBN} will display the backtrace for all
5165 the threads; this is handy when you debug a core dump of a
5166 multi-threaded program.
5168 Each line in the backtrace shows the frame number and the function name.
5169 The program counter value is also shown---unless you use @code{set
5170 print address off}. The backtrace also shows the source file name and
5171 line number, as well as the arguments to the function. The program
5172 counter value is omitted if it is at the beginning of the code for that
5175 Here is an example of a backtrace. It was made with the command
5176 @samp{bt 3}, so it shows the innermost three frames.
5180 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5182 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5183 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5185 (More stack frames follow...)
5190 The display for frame zero does not begin with a program counter
5191 value, indicating that your program has stopped at the beginning of the
5192 code for line @code{993} of @code{builtin.c}.
5195 The value of parameter @code{data} in frame 1 has been replaced by
5196 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5197 only if it is a scalar (integer, pointer, enumeration, etc). See command
5198 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5199 on how to configure the way function parameter values are printed.
5201 @cindex value optimized out, in backtrace
5202 @cindex function call arguments, optimized out
5203 If your program was compiled with optimizations, some compilers will
5204 optimize away arguments passed to functions if those arguments are
5205 never used after the call. Such optimizations generate code that
5206 passes arguments through registers, but doesn't store those arguments
5207 in the stack frame. @value{GDBN} has no way of displaying such
5208 arguments in stack frames other than the innermost one. Here's what
5209 such a backtrace might look like:
5213 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5215 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5216 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5218 (More stack frames follow...)
5223 The values of arguments that were not saved in their stack frames are
5224 shown as @samp{<value optimized out>}.
5226 If you need to display the values of such optimized-out arguments,
5227 either deduce that from other variables whose values depend on the one
5228 you are interested in, or recompile without optimizations.
5230 @cindex backtrace beyond @code{main} function
5231 @cindex program entry point
5232 @cindex startup code, and backtrace
5233 Most programs have a standard user entry point---a place where system
5234 libraries and startup code transition into user code. For C this is
5235 @code{main}@footnote{
5236 Note that embedded programs (the so-called ``free-standing''
5237 environment) are not required to have a @code{main} function as the
5238 entry point. They could even have multiple entry points.}.
5239 When @value{GDBN} finds the entry function in a backtrace
5240 it will terminate the backtrace, to avoid tracing into highly
5241 system-specific (and generally uninteresting) code.
5243 If you need to examine the startup code, or limit the number of levels
5244 in a backtrace, you can change this behavior:
5247 @item set backtrace past-main
5248 @itemx set backtrace past-main on
5249 @kindex set backtrace
5250 Backtraces will continue past the user entry point.
5252 @item set backtrace past-main off
5253 Backtraces will stop when they encounter the user entry point. This is the
5256 @item show backtrace past-main
5257 @kindex show backtrace
5258 Display the current user entry point backtrace policy.
5260 @item set backtrace past-entry
5261 @itemx set backtrace past-entry on
5262 Backtraces will continue past the internal entry point of an application.
5263 This entry point is encoded by the linker when the application is built,
5264 and is likely before the user entry point @code{main} (or equivalent) is called.
5266 @item set backtrace past-entry off
5267 Backtraces will stop when they encounter the internal entry point of an
5268 application. This is the default.
5270 @item show backtrace past-entry
5271 Display the current internal entry point backtrace policy.
5273 @item set backtrace limit @var{n}
5274 @itemx set backtrace limit 0
5275 @cindex backtrace limit
5276 Limit the backtrace to @var{n} levels. A value of zero means
5279 @item show backtrace limit
5280 Display the current limit on backtrace levels.
5284 @section Selecting a Frame
5286 Most commands for examining the stack and other data in your program work on
5287 whichever stack frame is selected at the moment. Here are the commands for
5288 selecting a stack frame; all of them finish by printing a brief description
5289 of the stack frame just selected.
5292 @kindex frame@r{, selecting}
5293 @kindex f @r{(@code{frame})}
5296 Select frame number @var{n}. Recall that frame zero is the innermost
5297 (currently executing) frame, frame one is the frame that called the
5298 innermost one, and so on. The highest-numbered frame is the one for
5301 @item frame @var{addr}
5303 Select the frame at address @var{addr}. This is useful mainly if the
5304 chaining of stack frames has been damaged by a bug, making it
5305 impossible for @value{GDBN} to assign numbers properly to all frames. In
5306 addition, this can be useful when your program has multiple stacks and
5307 switches between them.
5309 On the SPARC architecture, @code{frame} needs two addresses to
5310 select an arbitrary frame: a frame pointer and a stack pointer.
5312 On the MIPS and Alpha architecture, it needs two addresses: a stack
5313 pointer and a program counter.
5315 On the 29k architecture, it needs three addresses: a register stack
5316 pointer, a program counter, and a memory stack pointer.
5320 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5321 advances toward the outermost frame, to higher frame numbers, to frames
5322 that have existed longer. @var{n} defaults to one.
5325 @kindex do @r{(@code{down})}
5327 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5328 advances toward the innermost frame, to lower frame numbers, to frames
5329 that were created more recently. @var{n} defaults to one. You may
5330 abbreviate @code{down} as @code{do}.
5333 All of these commands end by printing two lines of output describing the
5334 frame. The first line shows the frame number, the function name, the
5335 arguments, and the source file and line number of execution in that
5336 frame. The second line shows the text of that source line.
5344 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5346 10 read_input_file (argv[i]);
5350 After such a printout, the @code{list} command with no arguments
5351 prints ten lines centered on the point of execution in the frame.
5352 You can also edit the program at the point of execution with your favorite
5353 editing program by typing @code{edit}.
5354 @xref{List, ,Printing Source Lines},
5358 @kindex down-silently
5360 @item up-silently @var{n}
5361 @itemx down-silently @var{n}
5362 These two commands are variants of @code{up} and @code{down},
5363 respectively; they differ in that they do their work silently, without
5364 causing display of the new frame. They are intended primarily for use
5365 in @value{GDBN} command scripts, where the output might be unnecessary and
5370 @section Information About a Frame
5372 There are several other commands to print information about the selected
5378 When used without any argument, this command does not change which
5379 frame is selected, but prints a brief description of the currently
5380 selected stack frame. It can be abbreviated @code{f}. With an
5381 argument, this command is used to select a stack frame.
5382 @xref{Selection, ,Selecting a Frame}.
5385 @kindex info f @r{(@code{info frame})}
5388 This command prints a verbose description of the selected stack frame,
5393 the address of the frame
5395 the address of the next frame down (called by this frame)
5397 the address of the next frame up (caller of this frame)
5399 the language in which the source code corresponding to this frame is written
5401 the address of the frame's arguments
5403 the address of the frame's local variables
5405 the program counter saved in it (the address of execution in the caller frame)
5407 which registers were saved in the frame
5410 @noindent The verbose description is useful when
5411 something has gone wrong that has made the stack format fail to fit
5412 the usual conventions.
5414 @item info frame @var{addr}
5415 @itemx info f @var{addr}
5416 Print a verbose description of the frame at address @var{addr}, without
5417 selecting that frame. The selected frame remains unchanged by this
5418 command. This requires the same kind of address (more than one for some
5419 architectures) that you specify in the @code{frame} command.
5420 @xref{Selection, ,Selecting a Frame}.
5424 Print the arguments of the selected frame, each on a separate line.
5428 Print the local variables of the selected frame, each on a separate
5429 line. These are all variables (declared either static or automatic)
5430 accessible at the point of execution of the selected frame.
5433 @cindex catch exceptions, list active handlers
5434 @cindex exception handlers, how to list
5436 Print a list of all the exception handlers that are active in the
5437 current stack frame at the current point of execution. To see other
5438 exception handlers, visit the associated frame (using the @code{up},
5439 @code{down}, or @code{frame} commands); then type @code{info catch}.
5440 @xref{Set Catchpoints, , Setting Catchpoints}.
5446 @chapter Examining Source Files
5448 @value{GDBN} can print parts of your program's source, since the debugging
5449 information recorded in the program tells @value{GDBN} what source files were
5450 used to build it. When your program stops, @value{GDBN} spontaneously prints
5451 the line where it stopped. Likewise, when you select a stack frame
5452 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5453 execution in that frame has stopped. You can print other portions of
5454 source files by explicit command.
5456 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5457 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5458 @value{GDBN} under @sc{gnu} Emacs}.
5461 * List:: Printing source lines
5462 * Specify Location:: How to specify code locations
5463 * Edit:: Editing source files
5464 * Search:: Searching source files
5465 * Source Path:: Specifying source directories
5466 * Machine Code:: Source and machine code
5470 @section Printing Source Lines
5473 @kindex l @r{(@code{list})}
5474 To print lines from a source file, use the @code{list} command
5475 (abbreviated @code{l}). By default, ten lines are printed.
5476 There are several ways to specify what part of the file you want to
5477 print; see @ref{Specify Location}, for the full list.
5479 Here are the forms of the @code{list} command most commonly used:
5482 @item list @var{linenum}
5483 Print lines centered around line number @var{linenum} in the
5484 current source file.
5486 @item list @var{function}
5487 Print lines centered around the beginning of function
5491 Print more lines. If the last lines printed were printed with a
5492 @code{list} command, this prints lines following the last lines
5493 printed; however, if the last line printed was a solitary line printed
5494 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5495 Stack}), this prints lines centered around that line.
5498 Print lines just before the lines last printed.
5501 @cindex @code{list}, how many lines to display
5502 By default, @value{GDBN} prints ten source lines with any of these forms of
5503 the @code{list} command. You can change this using @code{set listsize}:
5506 @kindex set listsize
5507 @item set listsize @var{count}
5508 Make the @code{list} command display @var{count} source lines (unless
5509 the @code{list} argument explicitly specifies some other number).
5511 @kindex show listsize
5513 Display the number of lines that @code{list} prints.
5516 Repeating a @code{list} command with @key{RET} discards the argument,
5517 so it is equivalent to typing just @code{list}. This is more useful
5518 than listing the same lines again. An exception is made for an
5519 argument of @samp{-}; that argument is preserved in repetition so that
5520 each repetition moves up in the source file.
5522 In general, the @code{list} command expects you to supply zero, one or two
5523 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5524 of writing them (@pxref{Specify Location}), but the effect is always
5525 to specify some source line.
5527 Here is a complete description of the possible arguments for @code{list}:
5530 @item list @var{linespec}
5531 Print lines centered around the line specified by @var{linespec}.
5533 @item list @var{first},@var{last}
5534 Print lines from @var{first} to @var{last}. Both arguments are
5535 linespecs. When a @code{list} command has two linespecs, and the
5536 source file of the second linespec is omitted, this refers to
5537 the same source file as the first linespec.
5539 @item list ,@var{last}
5540 Print lines ending with @var{last}.
5542 @item list @var{first},
5543 Print lines starting with @var{first}.
5546 Print lines just after the lines last printed.
5549 Print lines just before the lines last printed.
5552 As described in the preceding table.
5555 @node Specify Location
5556 @section Specifying a Location
5557 @cindex specifying location
5560 Several @value{GDBN} commands accept arguments that specify a location
5561 of your program's code. Since @value{GDBN} is a source-level
5562 debugger, a location usually specifies some line in the source code;
5563 for that reason, locations are also known as @dfn{linespecs}.
5565 Here are all the different ways of specifying a code location that
5566 @value{GDBN} understands:
5570 Specifies the line number @var{linenum} of the current source file.
5573 @itemx +@var{offset}
5574 Specifies the line @var{offset} lines before or after the @dfn{current
5575 line}. For the @code{list} command, the current line is the last one
5576 printed; for the breakpoint commands, this is the line at which
5577 execution stopped in the currently selected @dfn{stack frame}
5578 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5579 used as the second of the two linespecs in a @code{list} command,
5580 this specifies the line @var{offset} lines up or down from the first
5583 @item @var{filename}:@var{linenum}
5584 Specifies the line @var{linenum} in the source file @var{filename}.
5586 @item @var{function}
5587 Specifies the line that begins the body of the function @var{function}.
5588 For example, in C, this is the line with the open brace.
5590 @item @var{filename}:@var{function}
5591 Specifies the line that begins the body of the function @var{function}
5592 in the file @var{filename}. You only need the file name with a
5593 function name to avoid ambiguity when there are identically named
5594 functions in different source files.
5596 @item *@var{address}
5597 Specifies the program address @var{address}. For line-oriented
5598 commands, such as @code{list} and @code{edit}, this specifies a source
5599 line that contains @var{address}. For @code{break} and other
5600 breakpoint oriented commands, this can be used to set breakpoints in
5601 parts of your program which do not have debugging information or
5604 Here @var{address} may be any expression valid in the current working
5605 language (@pxref{Languages, working language}) that specifies a code
5606 address. In addition, as a convenience, @value{GDBN} extends the
5607 semantics of expressions used in locations to cover the situations
5608 that frequently happen during debugging. Here are the various forms
5612 @item @var{expression}
5613 Any expression valid in the current working language.
5615 @item @var{funcaddr}
5616 An address of a function or procedure derived from its name. In C,
5617 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5618 simply the function's name @var{function} (and actually a special case
5619 of a valid expression). In Pascal and Modula-2, this is
5620 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5621 (although the Pascal form also works).
5623 This form specifies the address of the function's first instruction,
5624 before the stack frame and arguments have been set up.
5626 @item '@var{filename}'::@var{funcaddr}
5627 Like @var{funcaddr} above, but also specifies the name of the source
5628 file explicitly. This is useful if the name of the function does not
5629 specify the function unambiguously, e.g., if there are several
5630 functions with identical names in different source files.
5637 @section Editing Source Files
5638 @cindex editing source files
5641 @kindex e @r{(@code{edit})}
5642 To edit the lines in a source file, use the @code{edit} command.
5643 The editing program of your choice
5644 is invoked with the current line set to
5645 the active line in the program.
5646 Alternatively, there are several ways to specify what part of the file you
5647 want to print if you want to see other parts of the program:
5650 @item edit @var{location}
5651 Edit the source file specified by @code{location}. Editing starts at
5652 that @var{location}, e.g., at the specified source line of the
5653 specified file. @xref{Specify Location}, for all the possible forms
5654 of the @var{location} argument; here are the forms of the @code{edit}
5655 command most commonly used:
5658 @item edit @var{number}
5659 Edit the current source file with @var{number} as the active line number.
5661 @item edit @var{function}
5662 Edit the file containing @var{function} at the beginning of its definition.
5667 @subsection Choosing your Editor
5668 You can customize @value{GDBN} to use any editor you want
5670 The only restriction is that your editor (say @code{ex}), recognizes the
5671 following command-line syntax:
5673 ex +@var{number} file
5675 The optional numeric value +@var{number} specifies the number of the line in
5676 the file where to start editing.}.
5677 By default, it is @file{@value{EDITOR}}, but you can change this
5678 by setting the environment variable @code{EDITOR} before using
5679 @value{GDBN}. For example, to configure @value{GDBN} to use the
5680 @code{vi} editor, you could use these commands with the @code{sh} shell:
5686 or in the @code{csh} shell,
5688 setenv EDITOR /usr/bin/vi
5693 @section Searching Source Files
5694 @cindex searching source files
5696 There are two commands for searching through the current source file for a
5701 @kindex forward-search
5702 @item forward-search @var{regexp}
5703 @itemx search @var{regexp}
5704 The command @samp{forward-search @var{regexp}} checks each line,
5705 starting with the one following the last line listed, for a match for
5706 @var{regexp}. It lists the line that is found. You can use the
5707 synonym @samp{search @var{regexp}} or abbreviate the command name as
5710 @kindex reverse-search
5711 @item reverse-search @var{regexp}
5712 The command @samp{reverse-search @var{regexp}} checks each line, starting
5713 with the one before the last line listed and going backward, for a match
5714 for @var{regexp}. It lists the line that is found. You can abbreviate
5715 this command as @code{rev}.
5719 @section Specifying Source Directories
5722 @cindex directories for source files
5723 Executable programs sometimes do not record the directories of the source
5724 files from which they were compiled, just the names. Even when they do,
5725 the directories could be moved between the compilation and your debugging
5726 session. @value{GDBN} has a list of directories to search for source files;
5727 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5728 it tries all the directories in the list, in the order they are present
5729 in the list, until it finds a file with the desired name.
5731 For example, suppose an executable references the file
5732 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5733 @file{/mnt/cross}. The file is first looked up literally; if this
5734 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5735 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5736 message is printed. @value{GDBN} does not look up the parts of the
5737 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5738 Likewise, the subdirectories of the source path are not searched: if
5739 the source path is @file{/mnt/cross}, and the binary refers to
5740 @file{foo.c}, @value{GDBN} would not find it under
5741 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5743 Plain file names, relative file names with leading directories, file
5744 names containing dots, etc.@: are all treated as described above; for
5745 instance, if the source path is @file{/mnt/cross}, and the source file
5746 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5747 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5748 that---@file{/mnt/cross/foo.c}.
5750 Note that the executable search path is @emph{not} used to locate the
5753 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5754 any information it has cached about where source files are found and where
5755 each line is in the file.
5759 When you start @value{GDBN}, its source path includes only @samp{cdir}
5760 and @samp{cwd}, in that order.
5761 To add other directories, use the @code{directory} command.
5763 The search path is used to find both program source files and @value{GDBN}
5764 script files (read using the @samp{-command} option and @samp{source} command).
5766 In addition to the source path, @value{GDBN} provides a set of commands
5767 that manage a list of source path substitution rules. A @dfn{substitution
5768 rule} specifies how to rewrite source directories stored in the program's
5769 debug information in case the sources were moved to a different
5770 directory between compilation and debugging. A rule is made of
5771 two strings, the first specifying what needs to be rewritten in
5772 the path, and the second specifying how it should be rewritten.
5773 In @ref{set substitute-path}, we name these two parts @var{from} and
5774 @var{to} respectively. @value{GDBN} does a simple string replacement
5775 of @var{from} with @var{to} at the start of the directory part of the
5776 source file name, and uses that result instead of the original file
5777 name to look up the sources.
5779 Using the previous example, suppose the @file{foo-1.0} tree has been
5780 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5781 @value{GDBN} to replace @file{/usr/src} in all source path names with
5782 @file{/mnt/cross}. The first lookup will then be
5783 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5784 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5785 substitution rule, use the @code{set substitute-path} command
5786 (@pxref{set substitute-path}).
5788 To avoid unexpected substitution results, a rule is applied only if the
5789 @var{from} part of the directory name ends at a directory separator.
5790 For instance, a rule substituting @file{/usr/source} into
5791 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5792 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5793 is applied only at the beginning of the directory name, this rule will
5794 not be applied to @file{/root/usr/source/baz.c} either.
5796 In many cases, you can achieve the same result using the @code{directory}
5797 command. However, @code{set substitute-path} can be more efficient in
5798 the case where the sources are organized in a complex tree with multiple
5799 subdirectories. With the @code{directory} command, you need to add each
5800 subdirectory of your project. If you moved the entire tree while
5801 preserving its internal organization, then @code{set substitute-path}
5802 allows you to direct the debugger to all the sources with one single
5805 @code{set substitute-path} is also more than just a shortcut command.
5806 The source path is only used if the file at the original location no
5807 longer exists. On the other hand, @code{set substitute-path} modifies
5808 the debugger behavior to look at the rewritten location instead. So, if
5809 for any reason a source file that is not relevant to your executable is
5810 located at the original location, a substitution rule is the only
5811 method available to point @value{GDBN} at the new location.
5814 @item directory @var{dirname} @dots{}
5815 @item dir @var{dirname} @dots{}
5816 Add directory @var{dirname} to the front of the source path. Several
5817 directory names may be given to this command, separated by @samp{:}
5818 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5819 part of absolute file names) or
5820 whitespace. You may specify a directory that is already in the source
5821 path; this moves it forward, so @value{GDBN} searches it sooner.
5825 @vindex $cdir@r{, convenience variable}
5826 @vindex $cwd@r{, convenience variable}
5827 @cindex compilation directory
5828 @cindex current directory
5829 @cindex working directory
5830 @cindex directory, current
5831 @cindex directory, compilation
5832 You can use the string @samp{$cdir} to refer to the compilation
5833 directory (if one is recorded), and @samp{$cwd} to refer to the current
5834 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5835 tracks the current working directory as it changes during your @value{GDBN}
5836 session, while the latter is immediately expanded to the current
5837 directory at the time you add an entry to the source path.
5840 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5842 @c RET-repeat for @code{directory} is explicitly disabled, but since
5843 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5845 @item show directories
5846 @kindex show directories
5847 Print the source path: show which directories it contains.
5849 @anchor{set substitute-path}
5850 @item set substitute-path @var{from} @var{to}
5851 @kindex set substitute-path
5852 Define a source path substitution rule, and add it at the end of the
5853 current list of existing substitution rules. If a rule with the same
5854 @var{from} was already defined, then the old rule is also deleted.
5856 For example, if the file @file{/foo/bar/baz.c} was moved to
5857 @file{/mnt/cross/baz.c}, then the command
5860 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5864 will tell @value{GDBN} to replace @samp{/usr/src} with
5865 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5866 @file{baz.c} even though it was moved.
5868 In the case when more than one substitution rule have been defined,
5869 the rules are evaluated one by one in the order where they have been
5870 defined. The first one matching, if any, is selected to perform
5873 For instance, if we had entered the following commands:
5876 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5877 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5881 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5882 @file{/mnt/include/defs.h} by using the first rule. However, it would
5883 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5884 @file{/mnt/src/lib/foo.c}.
5887 @item unset substitute-path [path]
5888 @kindex unset substitute-path
5889 If a path is specified, search the current list of substitution rules
5890 for a rule that would rewrite that path. Delete that rule if found.
5891 A warning is emitted by the debugger if no rule could be found.
5893 If no path is specified, then all substitution rules are deleted.
5895 @item show substitute-path [path]
5896 @kindex show substitute-path
5897 If a path is specified, then print the source path substitution rule
5898 which would rewrite that path, if any.
5900 If no path is specified, then print all existing source path substitution
5905 If your source path is cluttered with directories that are no longer of
5906 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5907 versions of source. You can correct the situation as follows:
5911 Use @code{directory} with no argument to reset the source path to its default value.
5914 Use @code{directory} with suitable arguments to reinstall the
5915 directories you want in the source path. You can add all the
5916 directories in one command.
5920 @section Source and Machine Code
5921 @cindex source line and its code address
5923 You can use the command @code{info line} to map source lines to program
5924 addresses (and vice versa), and the command @code{disassemble} to display
5925 a range of addresses as machine instructions. You can use the command
5926 @code{set disassemble-next-line} to set whether to disassemble next
5927 source line when execution stops. When run under @sc{gnu} Emacs
5928 mode, the @code{info line} command causes the arrow to point to the
5929 line specified. Also, @code{info line} prints addresses in symbolic form as
5934 @item info line @var{linespec}
5935 Print the starting and ending addresses of the compiled code for
5936 source line @var{linespec}. You can specify source lines in any of
5937 the ways documented in @ref{Specify Location}.
5940 For example, we can use @code{info line} to discover the location of
5941 the object code for the first line of function
5942 @code{m4_changequote}:
5944 @c FIXME: I think this example should also show the addresses in
5945 @c symbolic form, as they usually would be displayed.
5947 (@value{GDBP}) info line m4_changequote
5948 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5952 @cindex code address and its source line
5953 We can also inquire (using @code{*@var{addr}} as the form for
5954 @var{linespec}) what source line covers a particular address:
5956 (@value{GDBP}) info line *0x63ff
5957 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5960 @cindex @code{$_} and @code{info line}
5961 @cindex @code{x} command, default address
5962 @kindex x@r{(examine), and} info line
5963 After @code{info line}, the default address for the @code{x} command
5964 is changed to the starting address of the line, so that @samp{x/i} is
5965 sufficient to begin examining the machine code (@pxref{Memory,
5966 ,Examining Memory}). Also, this address is saved as the value of the
5967 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5972 @cindex assembly instructions
5973 @cindex instructions, assembly
5974 @cindex machine instructions
5975 @cindex listing machine instructions
5977 @itemx disassemble /m
5978 This specialized command dumps a range of memory as machine
5979 instructions. It can also print mixed source+disassembly by specifying
5980 the @code{/m} modifier.
5981 The default memory range is the function surrounding the
5982 program counter of the selected frame. A single argument to this
5983 command is a program counter value; @value{GDBN} dumps the function
5984 surrounding this value. Two arguments specify a range of addresses
5985 (first inclusive, second exclusive) to dump.
5988 The following example shows the disassembly of a range of addresses of
5989 HP PA-RISC 2.0 code:
5992 (@value{GDBP}) disas 0x32c4 0x32e4
5993 Dump of assembler code from 0x32c4 to 0x32e4:
5994 0x32c4 <main+204>: addil 0,dp
5995 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5996 0x32cc <main+212>: ldil 0x3000,r31
5997 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5998 0x32d4 <main+220>: ldo 0(r31),rp
5999 0x32d8 <main+224>: addil -0x800,dp
6000 0x32dc <main+228>: ldo 0x588(r1),r26
6001 0x32e0 <main+232>: ldil 0x3000,r31
6002 End of assembler dump.
6005 Here is an example showing mixed source+assembly for Intel x86:
6008 (@value{GDBP}) disas /m main
6009 Dump of assembler code for function main:
6011 0x08048330 <main+0>: push %ebp
6012 0x08048331 <main+1>: mov %esp,%ebp
6013 0x08048333 <main+3>: sub $0x8,%esp
6014 0x08048336 <main+6>: and $0xfffffff0,%esp
6015 0x08048339 <main+9>: sub $0x10,%esp
6017 6 printf ("Hello.\n");
6018 0x0804833c <main+12>: movl $0x8048440,(%esp)
6019 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
6023 0x08048348 <main+24>: mov $0x0,%eax
6024 0x0804834d <main+29>: leave
6025 0x0804834e <main+30>: ret
6027 End of assembler dump.
6030 Some architectures have more than one commonly-used set of instruction
6031 mnemonics or other syntax.
6033 For programs that were dynamically linked and use shared libraries,
6034 instructions that call functions or branch to locations in the shared
6035 libraries might show a seemingly bogus location---it's actually a
6036 location of the relocation table. On some architectures, @value{GDBN}
6037 might be able to resolve these to actual function names.
6040 @kindex set disassembly-flavor
6041 @cindex Intel disassembly flavor
6042 @cindex AT&T disassembly flavor
6043 @item set disassembly-flavor @var{instruction-set}
6044 Select the instruction set to use when disassembling the
6045 program via the @code{disassemble} or @code{x/i} commands.
6047 Currently this command is only defined for the Intel x86 family. You
6048 can set @var{instruction-set} to either @code{intel} or @code{att}.
6049 The default is @code{att}, the AT&T flavor used by default by Unix
6050 assemblers for x86-based targets.
6052 @kindex show disassembly-flavor
6053 @item show disassembly-flavor
6054 Show the current setting of the disassembly flavor.
6058 @kindex set disassemble-next-line
6059 @kindex show disassemble-next-line
6060 @item set disassemble-next-line
6061 @itemx show disassemble-next-line
6062 Control whether or not @value{GDBN} will disassemble next source line
6063 when execution stops. If ON, GDB will display disassembly of the next
6064 source line when execution of the program being debugged stops.
6065 If AUTO (which is the default), or there's no line info to determine
6066 the source line of the next instruction, display disassembly of next
6067 instruction instead.
6072 @chapter Examining Data
6074 @cindex printing data
6075 @cindex examining data
6078 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6079 @c document because it is nonstandard... Under Epoch it displays in a
6080 @c different window or something like that.
6081 The usual way to examine data in your program is with the @code{print}
6082 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6083 evaluates and prints the value of an expression of the language your
6084 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6085 Different Languages}).
6088 @item print @var{expr}
6089 @itemx print /@var{f} @var{expr}
6090 @var{expr} is an expression (in the source language). By default the
6091 value of @var{expr} is printed in a format appropriate to its data type;
6092 you can choose a different format by specifying @samp{/@var{f}}, where
6093 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6097 @itemx print /@var{f}
6098 @cindex reprint the last value
6099 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6100 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6101 conveniently inspect the same value in an alternative format.
6104 A more low-level way of examining data is with the @code{x} command.
6105 It examines data in memory at a specified address and prints it in a
6106 specified format. @xref{Memory, ,Examining Memory}.
6108 If you are interested in information about types, or about how the
6109 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6110 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6114 * Expressions:: Expressions
6115 * Ambiguous Expressions:: Ambiguous Expressions
6116 * Variables:: Program variables
6117 * Arrays:: Artificial arrays
6118 * Output Formats:: Output formats
6119 * Memory:: Examining memory
6120 * Auto Display:: Automatic display
6121 * Print Settings:: Print settings
6122 * Value History:: Value history
6123 * Convenience Vars:: Convenience variables
6124 * Registers:: Registers
6125 * Floating Point Hardware:: Floating point hardware
6126 * Vector Unit:: Vector Unit
6127 * OS Information:: Auxiliary data provided by operating system
6128 * Memory Region Attributes:: Memory region attributes
6129 * Dump/Restore Files:: Copy between memory and a file
6130 * Core File Generation:: Cause a program dump its core
6131 * Character Sets:: Debugging programs that use a different
6132 character set than GDB does
6133 * Caching Remote Data:: Data caching for remote targets
6134 * Searching Memory:: Searching memory for a sequence of bytes
6138 @section Expressions
6141 @code{print} and many other @value{GDBN} commands accept an expression and
6142 compute its value. Any kind of constant, variable or operator defined
6143 by the programming language you are using is valid in an expression in
6144 @value{GDBN}. This includes conditional expressions, function calls,
6145 casts, and string constants. It also includes preprocessor macros, if
6146 you compiled your program to include this information; see
6149 @cindex arrays in expressions
6150 @value{GDBN} supports array constants in expressions input by
6151 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6152 you can use the command @code{print @{1, 2, 3@}} to create an array
6153 of three integers. If you pass an array to a function or assign it
6154 to a program variable, @value{GDBN} copies the array to memory that
6155 is @code{malloc}ed in the target program.
6157 Because C is so widespread, most of the expressions shown in examples in
6158 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6159 Languages}, for information on how to use expressions in other
6162 In this section, we discuss operators that you can use in @value{GDBN}
6163 expressions regardless of your programming language.
6165 @cindex casts, in expressions
6166 Casts are supported in all languages, not just in C, because it is so
6167 useful to cast a number into a pointer in order to examine a structure
6168 at that address in memory.
6169 @c FIXME: casts supported---Mod2 true?
6171 @value{GDBN} supports these operators, in addition to those common
6172 to programming languages:
6176 @samp{@@} is a binary operator for treating parts of memory as arrays.
6177 @xref{Arrays, ,Artificial Arrays}, for more information.
6180 @samp{::} allows you to specify a variable in terms of the file or
6181 function where it is defined. @xref{Variables, ,Program Variables}.
6183 @cindex @{@var{type}@}
6184 @cindex type casting memory
6185 @cindex memory, viewing as typed object
6186 @cindex casts, to view memory
6187 @item @{@var{type}@} @var{addr}
6188 Refers to an object of type @var{type} stored at address @var{addr} in
6189 memory. @var{addr} may be any expression whose value is an integer or
6190 pointer (but parentheses are required around binary operators, just as in
6191 a cast). This construct is allowed regardless of what kind of data is
6192 normally supposed to reside at @var{addr}.
6195 @node Ambiguous Expressions
6196 @section Ambiguous Expressions
6197 @cindex ambiguous expressions
6199 Expressions can sometimes contain some ambiguous elements. For instance,
6200 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6201 a single function name to be defined several times, for application in
6202 different contexts. This is called @dfn{overloading}. Another example
6203 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6204 templates and is typically instantiated several times, resulting in
6205 the same function name being defined in different contexts.
6207 In some cases and depending on the language, it is possible to adjust
6208 the expression to remove the ambiguity. For instance in C@t{++}, you
6209 can specify the signature of the function you want to break on, as in
6210 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6211 qualified name of your function often makes the expression unambiguous
6214 When an ambiguity that needs to be resolved is detected, the debugger
6215 has the capability to display a menu of numbered choices for each
6216 possibility, and then waits for the selection with the prompt @samp{>}.
6217 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6218 aborts the current command. If the command in which the expression was
6219 used allows more than one choice to be selected, the next option in the
6220 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6223 For example, the following session excerpt shows an attempt to set a
6224 breakpoint at the overloaded symbol @code{String::after}.
6225 We choose three particular definitions of that function name:
6227 @c FIXME! This is likely to change to show arg type lists, at least
6230 (@value{GDBP}) b String::after
6233 [2] file:String.cc; line number:867
6234 [3] file:String.cc; line number:860
6235 [4] file:String.cc; line number:875
6236 [5] file:String.cc; line number:853
6237 [6] file:String.cc; line number:846
6238 [7] file:String.cc; line number:735
6240 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6241 Breakpoint 2 at 0xb344: file String.cc, line 875.
6242 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6243 Multiple breakpoints were set.
6244 Use the "delete" command to delete unwanted
6251 @kindex set multiple-symbols
6252 @item set multiple-symbols @var{mode}
6253 @cindex multiple-symbols menu
6255 This option allows you to adjust the debugger behavior when an expression
6258 By default, @var{mode} is set to @code{all}. If the command with which
6259 the expression is used allows more than one choice, then @value{GDBN}
6260 automatically selects all possible choices. For instance, inserting
6261 a breakpoint on a function using an ambiguous name results in a breakpoint
6262 inserted on each possible match. However, if a unique choice must be made,
6263 then @value{GDBN} uses the menu to help you disambiguate the expression.
6264 For instance, printing the address of an overloaded function will result
6265 in the use of the menu.
6267 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6268 when an ambiguity is detected.
6270 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6271 an error due to the ambiguity and the command is aborted.
6273 @kindex show multiple-symbols
6274 @item show multiple-symbols
6275 Show the current value of the @code{multiple-symbols} setting.
6279 @section Program Variables
6281 The most common kind of expression to use is the name of a variable
6284 Variables in expressions are understood in the selected stack frame
6285 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6289 global (or file-static)
6296 visible according to the scope rules of the
6297 programming language from the point of execution in that frame
6300 @noindent This means that in the function
6315 you can examine and use the variable @code{a} whenever your program is
6316 executing within the function @code{foo}, but you can only use or
6317 examine the variable @code{b} while your program is executing inside
6318 the block where @code{b} is declared.
6320 @cindex variable name conflict
6321 There is an exception: you can refer to a variable or function whose
6322 scope is a single source file even if the current execution point is not
6323 in this file. But it is possible to have more than one such variable or
6324 function with the same name (in different source files). If that
6325 happens, referring to that name has unpredictable effects. If you wish,
6326 you can specify a static variable in a particular function or file,
6327 using the colon-colon (@code{::}) notation:
6329 @cindex colon-colon, context for variables/functions
6331 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6332 @cindex @code{::}, context for variables/functions
6335 @var{file}::@var{variable}
6336 @var{function}::@var{variable}
6340 Here @var{file} or @var{function} is the name of the context for the
6341 static @var{variable}. In the case of file names, you can use quotes to
6342 make sure @value{GDBN} parses the file name as a single word---for example,
6343 to print a global value of @code{x} defined in @file{f2.c}:
6346 (@value{GDBP}) p 'f2.c'::x
6349 @cindex C@t{++} scope resolution
6350 This use of @samp{::} is very rarely in conflict with the very similar
6351 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6352 scope resolution operator in @value{GDBN} expressions.
6353 @c FIXME: Um, so what happens in one of those rare cases where it's in
6356 @cindex wrong values
6357 @cindex variable values, wrong
6358 @cindex function entry/exit, wrong values of variables
6359 @cindex optimized code, wrong values of variables
6361 @emph{Warning:} Occasionally, a local variable may appear to have the
6362 wrong value at certain points in a function---just after entry to a new
6363 scope, and just before exit.
6365 You may see this problem when you are stepping by machine instructions.
6366 This is because, on most machines, it takes more than one instruction to
6367 set up a stack frame (including local variable definitions); if you are
6368 stepping by machine instructions, variables may appear to have the wrong
6369 values until the stack frame is completely built. On exit, it usually
6370 also takes more than one machine instruction to destroy a stack frame;
6371 after you begin stepping through that group of instructions, local
6372 variable definitions may be gone.
6374 This may also happen when the compiler does significant optimizations.
6375 To be sure of always seeing accurate values, turn off all optimization
6378 @cindex ``No symbol "foo" in current context''
6379 Another possible effect of compiler optimizations is to optimize
6380 unused variables out of existence, or assign variables to registers (as
6381 opposed to memory addresses). Depending on the support for such cases
6382 offered by the debug info format used by the compiler, @value{GDBN}
6383 might not be able to display values for such local variables. If that
6384 happens, @value{GDBN} will print a message like this:
6387 No symbol "foo" in current context.
6390 To solve such problems, either recompile without optimizations, or use a
6391 different debug info format, if the compiler supports several such
6392 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6393 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6394 produces debug info in a format that is superior to formats such as
6395 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6396 an effective form for debug info. @xref{Debugging Options,,Options
6397 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6398 Compiler Collection (GCC)}.
6399 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6400 that are best suited to C@t{++} programs.
6402 If you ask to print an object whose contents are unknown to
6403 @value{GDBN}, e.g., because its data type is not completely specified
6404 by the debug information, @value{GDBN} will say @samp{<incomplete
6405 type>}. @xref{Symbols, incomplete type}, for more about this.
6407 Strings are identified as arrays of @code{char} values without specified
6408 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6409 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6410 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6411 defines literal string type @code{"char"} as @code{char} without a sign.
6416 signed char var1[] = "A";
6419 You get during debugging
6424 $2 = @{65 'A', 0 '\0'@}
6428 @section Artificial Arrays
6430 @cindex artificial array
6432 @kindex @@@r{, referencing memory as an array}
6433 It is often useful to print out several successive objects of the
6434 same type in memory; a section of an array, or an array of
6435 dynamically determined size for which only a pointer exists in the
6438 You can do this by referring to a contiguous span of memory as an
6439 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6440 operand of @samp{@@} should be the first element of the desired array
6441 and be an individual object. The right operand should be the desired length
6442 of the array. The result is an array value whose elements are all of
6443 the type of the left argument. The first element is actually the left
6444 argument; the second element comes from bytes of memory immediately
6445 following those that hold the first element, and so on. Here is an
6446 example. If a program says
6449 int *array = (int *) malloc (len * sizeof (int));
6453 you can print the contents of @code{array} with
6459 The left operand of @samp{@@} must reside in memory. Array values made
6460 with @samp{@@} in this way behave just like other arrays in terms of
6461 subscripting, and are coerced to pointers when used in expressions.
6462 Artificial arrays most often appear in expressions via the value history
6463 (@pxref{Value History, ,Value History}), after printing one out.
6465 Another way to create an artificial array is to use a cast.
6466 This re-interprets a value as if it were an array.
6467 The value need not be in memory:
6469 (@value{GDBP}) p/x (short[2])0x12345678
6470 $1 = @{0x1234, 0x5678@}
6473 As a convenience, if you leave the array length out (as in
6474 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6475 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6477 (@value{GDBP}) p/x (short[])0x12345678
6478 $2 = @{0x1234, 0x5678@}
6481 Sometimes the artificial array mechanism is not quite enough; in
6482 moderately complex data structures, the elements of interest may not
6483 actually be adjacent---for example, if you are interested in the values
6484 of pointers in an array. One useful work-around in this situation is
6485 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6486 Variables}) as a counter in an expression that prints the first
6487 interesting value, and then repeat that expression via @key{RET}. For
6488 instance, suppose you have an array @code{dtab} of pointers to
6489 structures, and you are interested in the values of a field @code{fv}
6490 in each structure. Here is an example of what you might type:
6500 @node Output Formats
6501 @section Output Formats
6503 @cindex formatted output
6504 @cindex output formats
6505 By default, @value{GDBN} prints a value according to its data type. Sometimes
6506 this is not what you want. For example, you might want to print a number
6507 in hex, or a pointer in decimal. Or you might want to view data in memory
6508 at a certain address as a character string or as an instruction. To do
6509 these things, specify an @dfn{output format} when you print a value.
6511 The simplest use of output formats is to say how to print a value
6512 already computed. This is done by starting the arguments of the
6513 @code{print} command with a slash and a format letter. The format
6514 letters supported are:
6518 Regard the bits of the value as an integer, and print the integer in
6522 Print as integer in signed decimal.
6525 Print as integer in unsigned decimal.
6528 Print as integer in octal.
6531 Print as integer in binary. The letter @samp{t} stands for ``two''.
6532 @footnote{@samp{b} cannot be used because these format letters are also
6533 used with the @code{x} command, where @samp{b} stands for ``byte'';
6534 see @ref{Memory,,Examining Memory}.}
6537 @cindex unknown address, locating
6538 @cindex locate address
6539 Print as an address, both absolute in hexadecimal and as an offset from
6540 the nearest preceding symbol. You can use this format used to discover
6541 where (in what function) an unknown address is located:
6544 (@value{GDBP}) p/a 0x54320
6545 $3 = 0x54320 <_initialize_vx+396>
6549 The command @code{info symbol 0x54320} yields similar results.
6550 @xref{Symbols, info symbol}.
6553 Regard as an integer and print it as a character constant. This
6554 prints both the numerical value and its character representation. The
6555 character representation is replaced with the octal escape @samp{\nnn}
6556 for characters outside the 7-bit @sc{ascii} range.
6558 Without this format, @value{GDBN} displays @code{char},
6559 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6560 constants. Single-byte members of vectors are displayed as integer
6564 Regard the bits of the value as a floating point number and print
6565 using typical floating point syntax.
6568 @cindex printing strings
6569 @cindex printing byte arrays
6570 Regard as a string, if possible. With this format, pointers to single-byte
6571 data are displayed as null-terminated strings and arrays of single-byte data
6572 are displayed as fixed-length strings. Other values are displayed in their
6575 Without this format, @value{GDBN} displays pointers to and arrays of
6576 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6577 strings. Single-byte members of a vector are displayed as an integer
6581 For example, to print the program counter in hex (@pxref{Registers}), type
6588 Note that no space is required before the slash; this is because command
6589 names in @value{GDBN} cannot contain a slash.
6591 To reprint the last value in the value history with a different format,
6592 you can use the @code{print} command with just a format and no
6593 expression. For example, @samp{p/x} reprints the last value in hex.
6596 @section Examining Memory
6598 You can use the command @code{x} (for ``examine'') to examine memory in
6599 any of several formats, independently of your program's data types.
6601 @cindex examining memory
6603 @kindex x @r{(examine memory)}
6604 @item x/@var{nfu} @var{addr}
6607 Use the @code{x} command to examine memory.
6610 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6611 much memory to display and how to format it; @var{addr} is an
6612 expression giving the address where you want to start displaying memory.
6613 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6614 Several commands set convenient defaults for @var{addr}.
6617 @item @var{n}, the repeat count
6618 The repeat count is a decimal integer; the default is 1. It specifies
6619 how much memory (counting by units @var{u}) to display.
6620 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6623 @item @var{f}, the display format
6624 The display format is one of the formats used by @code{print}
6625 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6626 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6627 The default is @samp{x} (hexadecimal) initially. The default changes
6628 each time you use either @code{x} or @code{print}.
6630 @item @var{u}, the unit size
6631 The unit size is any of
6637 Halfwords (two bytes).
6639 Words (four bytes). This is the initial default.
6641 Giant words (eight bytes).
6644 Each time you specify a unit size with @code{x}, that size becomes the
6645 default unit the next time you use @code{x}. (For the @samp{s} and
6646 @samp{i} formats, the unit size is ignored and is normally not written.)
6648 @item @var{addr}, starting display address
6649 @var{addr} is the address where you want @value{GDBN} to begin displaying
6650 memory. The expression need not have a pointer value (though it may);
6651 it is always interpreted as an integer address of a byte of memory.
6652 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6653 @var{addr} is usually just after the last address examined---but several
6654 other commands also set the default address: @code{info breakpoints} (to
6655 the address of the last breakpoint listed), @code{info line} (to the
6656 starting address of a line), and @code{print} (if you use it to display
6657 a value from memory).
6660 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6661 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6662 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6663 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6664 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6666 Since the letters indicating unit sizes are all distinct from the
6667 letters specifying output formats, you do not have to remember whether
6668 unit size or format comes first; either order works. The output
6669 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6670 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6672 Even though the unit size @var{u} is ignored for the formats @samp{s}
6673 and @samp{i}, you might still want to use a count @var{n}; for example,
6674 @samp{3i} specifies that you want to see three machine instructions,
6675 including any operands. For convenience, especially when used with
6676 the @code{display} command, the @samp{i} format also prints branch delay
6677 slot instructions, if any, beyond the count specified, which immediately
6678 follow the last instruction that is within the count. The command
6679 @code{disassemble} gives an alternative way of inspecting machine
6680 instructions; see @ref{Machine Code,,Source and Machine Code}.
6682 All the defaults for the arguments to @code{x} are designed to make it
6683 easy to continue scanning memory with minimal specifications each time
6684 you use @code{x}. For example, after you have inspected three machine
6685 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6686 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6687 the repeat count @var{n} is used again; the other arguments default as
6688 for successive uses of @code{x}.
6690 @cindex @code{$_}, @code{$__}, and value history
6691 The addresses and contents printed by the @code{x} command are not saved
6692 in the value history because there is often too much of them and they
6693 would get in the way. Instead, @value{GDBN} makes these values available for
6694 subsequent use in expressions as values of the convenience variables
6695 @code{$_} and @code{$__}. After an @code{x} command, the last address
6696 examined is available for use in expressions in the convenience variable
6697 @code{$_}. The contents of that address, as examined, are available in
6698 the convenience variable @code{$__}.
6700 If the @code{x} command has a repeat count, the address and contents saved
6701 are from the last memory unit printed; this is not the same as the last
6702 address printed if several units were printed on the last line of output.
6704 @cindex remote memory comparison
6705 @cindex verify remote memory image
6706 When you are debugging a program running on a remote target machine
6707 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6708 remote machine's memory against the executable file you downloaded to
6709 the target. The @code{compare-sections} command is provided for such
6713 @kindex compare-sections
6714 @item compare-sections @r{[}@var{section-name}@r{]}
6715 Compare the data of a loadable section @var{section-name} in the
6716 executable file of the program being debugged with the same section in
6717 the remote machine's memory, and report any mismatches. With no
6718 arguments, compares all loadable sections. This command's
6719 availability depends on the target's support for the @code{"qCRC"}
6724 @section Automatic Display
6725 @cindex automatic display
6726 @cindex display of expressions
6728 If you find that you want to print the value of an expression frequently
6729 (to see how it changes), you might want to add it to the @dfn{automatic
6730 display list} so that @value{GDBN} prints its value each time your program stops.
6731 Each expression added to the list is given a number to identify it;
6732 to remove an expression from the list, you specify that number.
6733 The automatic display looks like this:
6737 3: bar[5] = (struct hack *) 0x3804
6741 This display shows item numbers, expressions and their current values. As with
6742 displays you request manually using @code{x} or @code{print}, you can
6743 specify the output format you prefer; in fact, @code{display} decides
6744 whether to use @code{print} or @code{x} depending your format
6745 specification---it uses @code{x} if you specify either the @samp{i}
6746 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6750 @item display @var{expr}
6751 Add the expression @var{expr} to the list of expressions to display
6752 each time your program stops. @xref{Expressions, ,Expressions}.
6754 @code{display} does not repeat if you press @key{RET} again after using it.
6756 @item display/@var{fmt} @var{expr}
6757 For @var{fmt} specifying only a display format and not a size or
6758 count, add the expression @var{expr} to the auto-display list but
6759 arrange to display it each time in the specified format @var{fmt}.
6760 @xref{Output Formats,,Output Formats}.
6762 @item display/@var{fmt} @var{addr}
6763 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6764 number of units, add the expression @var{addr} as a memory address to
6765 be examined each time your program stops. Examining means in effect
6766 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6769 For example, @samp{display/i $pc} can be helpful, to see the machine
6770 instruction about to be executed each time execution stops (@samp{$pc}
6771 is a common name for the program counter; @pxref{Registers, ,Registers}).
6774 @kindex delete display
6776 @item undisplay @var{dnums}@dots{}
6777 @itemx delete display @var{dnums}@dots{}
6778 Remove item numbers @var{dnums} from the list of expressions to display.
6780 @code{undisplay} does not repeat if you press @key{RET} after using it.
6781 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6783 @kindex disable display
6784 @item disable display @var{dnums}@dots{}
6785 Disable the display of item numbers @var{dnums}. A disabled display
6786 item is not printed automatically, but is not forgotten. It may be
6787 enabled again later.
6789 @kindex enable display
6790 @item enable display @var{dnums}@dots{}
6791 Enable display of item numbers @var{dnums}. It becomes effective once
6792 again in auto display of its expression, until you specify otherwise.
6795 Display the current values of the expressions on the list, just as is
6796 done when your program stops.
6798 @kindex info display
6800 Print the list of expressions previously set up to display
6801 automatically, each one with its item number, but without showing the
6802 values. This includes disabled expressions, which are marked as such.
6803 It also includes expressions which would not be displayed right now
6804 because they refer to automatic variables not currently available.
6807 @cindex display disabled out of scope
6808 If a display expression refers to local variables, then it does not make
6809 sense outside the lexical context for which it was set up. Such an
6810 expression is disabled when execution enters a context where one of its
6811 variables is not defined. For example, if you give the command
6812 @code{display last_char} while inside a function with an argument
6813 @code{last_char}, @value{GDBN} displays this argument while your program
6814 continues to stop inside that function. When it stops elsewhere---where
6815 there is no variable @code{last_char}---the display is disabled
6816 automatically. The next time your program stops where @code{last_char}
6817 is meaningful, you can enable the display expression once again.
6819 @node Print Settings
6820 @section Print Settings
6822 @cindex format options
6823 @cindex print settings
6824 @value{GDBN} provides the following ways to control how arrays, structures,
6825 and symbols are printed.
6828 These settings are useful for debugging programs in any language:
6832 @item set print address
6833 @itemx set print address on
6834 @cindex print/don't print memory addresses
6835 @value{GDBN} prints memory addresses showing the location of stack
6836 traces, structure values, pointer values, breakpoints, and so forth,
6837 even when it also displays the contents of those addresses. The default
6838 is @code{on}. For example, this is what a stack frame display looks like with
6839 @code{set print address on}:
6844 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6846 530 if (lquote != def_lquote)
6850 @item set print address off
6851 Do not print addresses when displaying their contents. For example,
6852 this is the same stack frame displayed with @code{set print address off}:
6856 (@value{GDBP}) set print addr off
6858 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6859 530 if (lquote != def_lquote)
6863 You can use @samp{set print address off} to eliminate all machine
6864 dependent displays from the @value{GDBN} interface. For example, with
6865 @code{print address off}, you should get the same text for backtraces on
6866 all machines---whether or not they involve pointer arguments.
6869 @item show print address
6870 Show whether or not addresses are to be printed.
6873 When @value{GDBN} prints a symbolic address, it normally prints the
6874 closest earlier symbol plus an offset. If that symbol does not uniquely
6875 identify the address (for example, it is a name whose scope is a single
6876 source file), you may need to clarify. One way to do this is with
6877 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6878 you can set @value{GDBN} to print the source file and line number when
6879 it prints a symbolic address:
6882 @item set print symbol-filename on
6883 @cindex source file and line of a symbol
6884 @cindex symbol, source file and line
6885 Tell @value{GDBN} to print the source file name and line number of a
6886 symbol in the symbolic form of an address.
6888 @item set print symbol-filename off
6889 Do not print source file name and line number of a symbol. This is the
6892 @item show print symbol-filename
6893 Show whether or not @value{GDBN} will print the source file name and
6894 line number of a symbol in the symbolic form of an address.
6897 Another situation where it is helpful to show symbol filenames and line
6898 numbers is when disassembling code; @value{GDBN} shows you the line
6899 number and source file that corresponds to each instruction.
6901 Also, you may wish to see the symbolic form only if the address being
6902 printed is reasonably close to the closest earlier symbol:
6905 @item set print max-symbolic-offset @var{max-offset}
6906 @cindex maximum value for offset of closest symbol
6907 Tell @value{GDBN} to only display the symbolic form of an address if the
6908 offset between the closest earlier symbol and the address is less than
6909 @var{max-offset}. The default is 0, which tells @value{GDBN}
6910 to always print the symbolic form of an address if any symbol precedes it.
6912 @item show print max-symbolic-offset
6913 Ask how large the maximum offset is that @value{GDBN} prints in a
6917 @cindex wild pointer, interpreting
6918 @cindex pointer, finding referent
6919 If you have a pointer and you are not sure where it points, try
6920 @samp{set print symbol-filename on}. Then you can determine the name
6921 and source file location of the variable where it points, using
6922 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6923 For example, here @value{GDBN} shows that a variable @code{ptt} points
6924 at another variable @code{t}, defined in @file{hi2.c}:
6927 (@value{GDBP}) set print symbol-filename on
6928 (@value{GDBP}) p/a ptt
6929 $4 = 0xe008 <t in hi2.c>
6933 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6934 does not show the symbol name and filename of the referent, even with
6935 the appropriate @code{set print} options turned on.
6938 Other settings control how different kinds of objects are printed:
6941 @item set print array
6942 @itemx set print array on
6943 @cindex pretty print arrays
6944 Pretty print arrays. This format is more convenient to read,
6945 but uses more space. The default is off.
6947 @item set print array off
6948 Return to compressed format for arrays.
6950 @item show print array
6951 Show whether compressed or pretty format is selected for displaying
6954 @cindex print array indexes
6955 @item set print array-indexes
6956 @itemx set print array-indexes on
6957 Print the index of each element when displaying arrays. May be more
6958 convenient to locate a given element in the array or quickly find the
6959 index of a given element in that printed array. The default is off.
6961 @item set print array-indexes off
6962 Stop printing element indexes when displaying arrays.
6964 @item show print array-indexes
6965 Show whether the index of each element is printed when displaying
6968 @item set print elements @var{number-of-elements}
6969 @cindex number of array elements to print
6970 @cindex limit on number of printed array elements
6971 Set a limit on how many elements of an array @value{GDBN} will print.
6972 If @value{GDBN} is printing a large array, it stops printing after it has
6973 printed the number of elements set by the @code{set print elements} command.
6974 This limit also applies to the display of strings.
6975 When @value{GDBN} starts, this limit is set to 200.
6976 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6978 @item show print elements
6979 Display the number of elements of a large array that @value{GDBN} will print.
6980 If the number is 0, then the printing is unlimited.
6982 @item set print frame-arguments @var{value}
6983 @kindex set print frame-arguments
6984 @cindex printing frame argument values
6985 @cindex print all frame argument values
6986 @cindex print frame argument values for scalars only
6987 @cindex do not print frame argument values
6988 This command allows to control how the values of arguments are printed
6989 when the debugger prints a frame (@pxref{Frames}). The possible
6994 The values of all arguments are printed.
6997 Print the value of an argument only if it is a scalar. The value of more
6998 complex arguments such as arrays, structures, unions, etc, is replaced
6999 by @code{@dots{}}. This is the default. Here is an example where
7000 only scalar arguments are shown:
7003 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7008 None of the argument values are printed. Instead, the value of each argument
7009 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7012 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7017 By default, only scalar arguments are printed. This command can be used
7018 to configure the debugger to print the value of all arguments, regardless
7019 of their type. However, it is often advantageous to not print the value
7020 of more complex parameters. For instance, it reduces the amount of
7021 information printed in each frame, making the backtrace more readable.
7022 Also, it improves performance when displaying Ada frames, because
7023 the computation of large arguments can sometimes be CPU-intensive,
7024 especially in large applications. Setting @code{print frame-arguments}
7025 to @code{scalars} (the default) or @code{none} avoids this computation,
7026 thus speeding up the display of each Ada frame.
7028 @item show print frame-arguments
7029 Show how the value of arguments should be displayed when printing a frame.
7031 @item set print repeats
7032 @cindex repeated array elements
7033 Set the threshold for suppressing display of repeated array
7034 elements. When the number of consecutive identical elements of an
7035 array exceeds the threshold, @value{GDBN} prints the string
7036 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7037 identical repetitions, instead of displaying the identical elements
7038 themselves. Setting the threshold to zero will cause all elements to
7039 be individually printed. The default threshold is 10.
7041 @item show print repeats
7042 Display the current threshold for printing repeated identical
7045 @item set print null-stop
7046 @cindex @sc{null} elements in arrays
7047 Cause @value{GDBN} to stop printing the characters of an array when the first
7048 @sc{null} is encountered. This is useful when large arrays actually
7049 contain only short strings.
7052 @item show print null-stop
7053 Show whether @value{GDBN} stops printing an array on the first
7054 @sc{null} character.
7056 @item set print pretty on
7057 @cindex print structures in indented form
7058 @cindex indentation in structure display
7059 Cause @value{GDBN} to print structures in an indented format with one member
7060 per line, like this:
7075 @item set print pretty off
7076 Cause @value{GDBN} to print structures in a compact format, like this:
7080 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7081 meat = 0x54 "Pork"@}
7086 This is the default format.
7088 @item show print pretty
7089 Show which format @value{GDBN} is using to print structures.
7091 @item set print sevenbit-strings on
7092 @cindex eight-bit characters in strings
7093 @cindex octal escapes in strings
7094 Print using only seven-bit characters; if this option is set,
7095 @value{GDBN} displays any eight-bit characters (in strings or
7096 character values) using the notation @code{\}@var{nnn}. This setting is
7097 best if you are working in English (@sc{ascii}) and you use the
7098 high-order bit of characters as a marker or ``meta'' bit.
7100 @item set print sevenbit-strings off
7101 Print full eight-bit characters. This allows the use of more
7102 international character sets, and is the default.
7104 @item show print sevenbit-strings
7105 Show whether or not @value{GDBN} is printing only seven-bit characters.
7107 @item set print union on
7108 @cindex unions in structures, printing
7109 Tell @value{GDBN} to print unions which are contained in structures
7110 and other unions. This is the default setting.
7112 @item set print union off
7113 Tell @value{GDBN} not to print unions which are contained in
7114 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7117 @item show print union
7118 Ask @value{GDBN} whether or not it will print unions which are contained in
7119 structures and other unions.
7121 For example, given the declarations
7124 typedef enum @{Tree, Bug@} Species;
7125 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7126 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7137 struct thing foo = @{Tree, @{Acorn@}@};
7141 with @code{set print union on} in effect @samp{p foo} would print
7144 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7148 and with @code{set print union off} in effect it would print
7151 $1 = @{it = Tree, form = @{...@}@}
7155 @code{set print union} affects programs written in C-like languages
7161 These settings are of interest when debugging C@t{++} programs:
7164 @cindex demangling C@t{++} names
7165 @item set print demangle
7166 @itemx set print demangle on
7167 Print C@t{++} names in their source form rather than in the encoded
7168 (``mangled'') form passed to the assembler and linker for type-safe
7169 linkage. The default is on.
7171 @item show print demangle
7172 Show whether C@t{++} names are printed in mangled or demangled form.
7174 @item set print asm-demangle
7175 @itemx set print asm-demangle on
7176 Print C@t{++} names in their source form rather than their mangled form, even
7177 in assembler code printouts such as instruction disassemblies.
7180 @item show print asm-demangle
7181 Show whether C@t{++} names in assembly listings are printed in mangled
7184 @cindex C@t{++} symbol decoding style
7185 @cindex symbol decoding style, C@t{++}
7186 @kindex set demangle-style
7187 @item set demangle-style @var{style}
7188 Choose among several encoding schemes used by different compilers to
7189 represent C@t{++} names. The choices for @var{style} are currently:
7193 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7196 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7197 This is the default.
7200 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7203 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7206 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7207 @strong{Warning:} this setting alone is not sufficient to allow
7208 debugging @code{cfront}-generated executables. @value{GDBN} would
7209 require further enhancement to permit that.
7212 If you omit @var{style}, you will see a list of possible formats.
7214 @item show demangle-style
7215 Display the encoding style currently in use for decoding C@t{++} symbols.
7217 @item set print object
7218 @itemx set print object on
7219 @cindex derived type of an object, printing
7220 @cindex display derived types
7221 When displaying a pointer to an object, identify the @emph{actual}
7222 (derived) type of the object rather than the @emph{declared} type, using
7223 the virtual function table.
7225 @item set print object off
7226 Display only the declared type of objects, without reference to the
7227 virtual function table. This is the default setting.
7229 @item show print object
7230 Show whether actual, or declared, object types are displayed.
7232 @item set print static-members
7233 @itemx set print static-members on
7234 @cindex static members of C@t{++} objects
7235 Print static members when displaying a C@t{++} object. The default is on.
7237 @item set print static-members off
7238 Do not print static members when displaying a C@t{++} object.
7240 @item show print static-members
7241 Show whether C@t{++} static members are printed or not.
7243 @item set print pascal_static-members
7244 @itemx set print pascal_static-members on
7245 @cindex static members of Pascal objects
7246 @cindex Pascal objects, static members display
7247 Print static members when displaying a Pascal object. The default is on.
7249 @item set print pascal_static-members off
7250 Do not print static members when displaying a Pascal object.
7252 @item show print pascal_static-members
7253 Show whether Pascal static members are printed or not.
7255 @c These don't work with HP ANSI C++ yet.
7256 @item set print vtbl
7257 @itemx set print vtbl on
7258 @cindex pretty print C@t{++} virtual function tables
7259 @cindex virtual functions (C@t{++}) display
7260 @cindex VTBL display
7261 Pretty print C@t{++} virtual function tables. The default is off.
7262 (The @code{vtbl} commands do not work on programs compiled with the HP
7263 ANSI C@t{++} compiler (@code{aCC}).)
7265 @item set print vtbl off
7266 Do not pretty print C@t{++} virtual function tables.
7268 @item show print vtbl
7269 Show whether C@t{++} virtual function tables are pretty printed, or not.
7273 @section Value History
7275 @cindex value history
7276 @cindex history of values printed by @value{GDBN}
7277 Values printed by the @code{print} command are saved in the @value{GDBN}
7278 @dfn{value history}. This allows you to refer to them in other expressions.
7279 Values are kept until the symbol table is re-read or discarded
7280 (for example with the @code{file} or @code{symbol-file} commands).
7281 When the symbol table changes, the value history is discarded,
7282 since the values may contain pointers back to the types defined in the
7287 @cindex history number
7288 The values printed are given @dfn{history numbers} by which you can
7289 refer to them. These are successive integers starting with one.
7290 @code{print} shows you the history number assigned to a value by
7291 printing @samp{$@var{num} = } before the value; here @var{num} is the
7294 To refer to any previous value, use @samp{$} followed by the value's
7295 history number. The way @code{print} labels its output is designed to
7296 remind you of this. Just @code{$} refers to the most recent value in
7297 the history, and @code{$$} refers to the value before that.
7298 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7299 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7300 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7302 For example, suppose you have just printed a pointer to a structure and
7303 want to see the contents of the structure. It suffices to type
7309 If you have a chain of structures where the component @code{next} points
7310 to the next one, you can print the contents of the next one with this:
7317 You can print successive links in the chain by repeating this
7318 command---which you can do by just typing @key{RET}.
7320 Note that the history records values, not expressions. If the value of
7321 @code{x} is 4 and you type these commands:
7329 then the value recorded in the value history by the @code{print} command
7330 remains 4 even though the value of @code{x} has changed.
7335 Print the last ten values in the value history, with their item numbers.
7336 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7337 values} does not change the history.
7339 @item show values @var{n}
7340 Print ten history values centered on history item number @var{n}.
7343 Print ten history values just after the values last printed. If no more
7344 values are available, @code{show values +} produces no display.
7347 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7348 same effect as @samp{show values +}.
7350 @node Convenience Vars
7351 @section Convenience Variables
7353 @cindex convenience variables
7354 @cindex user-defined variables
7355 @value{GDBN} provides @dfn{convenience variables} that you can use within
7356 @value{GDBN} to hold on to a value and refer to it later. These variables
7357 exist entirely within @value{GDBN}; they are not part of your program, and
7358 setting a convenience variable has no direct effect on further execution
7359 of your program. That is why you can use them freely.
7361 Convenience variables are prefixed with @samp{$}. Any name preceded by
7362 @samp{$} can be used for a convenience variable, unless it is one of
7363 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7364 (Value history references, in contrast, are @emph{numbers} preceded
7365 by @samp{$}. @xref{Value History, ,Value History}.)
7367 You can save a value in a convenience variable with an assignment
7368 expression, just as you would set a variable in your program.
7372 set $foo = *object_ptr
7376 would save in @code{$foo} the value contained in the object pointed to by
7379 Using a convenience variable for the first time creates it, but its
7380 value is @code{void} until you assign a new value. You can alter the
7381 value with another assignment at any time.
7383 Convenience variables have no fixed types. You can assign a convenience
7384 variable any type of value, including structures and arrays, even if
7385 that variable already has a value of a different type. The convenience
7386 variable, when used as an expression, has the type of its current value.
7389 @kindex show convenience
7390 @cindex show all user variables
7391 @item show convenience
7392 Print a list of convenience variables used so far, and their values.
7393 Abbreviated @code{show conv}.
7395 @kindex init-if-undefined
7396 @cindex convenience variables, initializing
7397 @item init-if-undefined $@var{variable} = @var{expression}
7398 Set a convenience variable if it has not already been set. This is useful
7399 for user-defined commands that keep some state. It is similar, in concept,
7400 to using local static variables with initializers in C (except that
7401 convenience variables are global). It can also be used to allow users to
7402 override default values used in a command script.
7404 If the variable is already defined then the expression is not evaluated so
7405 any side-effects do not occur.
7408 One of the ways to use a convenience variable is as a counter to be
7409 incremented or a pointer to be advanced. For example, to print
7410 a field from successive elements of an array of structures:
7414 print bar[$i++]->contents
7418 Repeat that command by typing @key{RET}.
7420 Some convenience variables are created automatically by @value{GDBN} and given
7421 values likely to be useful.
7424 @vindex $_@r{, convenience variable}
7426 The variable @code{$_} is automatically set by the @code{x} command to
7427 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7428 commands which provide a default address for @code{x} to examine also
7429 set @code{$_} to that address; these commands include @code{info line}
7430 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7431 except when set by the @code{x} command, in which case it is a pointer
7432 to the type of @code{$__}.
7434 @vindex $__@r{, convenience variable}
7436 The variable @code{$__} is automatically set by the @code{x} command
7437 to the value found in the last address examined. Its type is chosen
7438 to match the format in which the data was printed.
7441 @vindex $_exitcode@r{, convenience variable}
7442 The variable @code{$_exitcode} is automatically set to the exit code when
7443 the program being debugged terminates.
7446 @vindex $_siginfo@r{, convenience variable}
7447 The variable @code{$_siginfo} is bound to extra signal information
7448 inspection (@pxref{extra signal information}).
7451 On HP-UX systems, if you refer to a function or variable name that
7452 begins with a dollar sign, @value{GDBN} searches for a user or system
7453 name first, before it searches for a convenience variable.
7455 @cindex convenience functions
7456 @value{GDBN} also supplies some @dfn{convenience functions}. These
7457 have a syntax similar to convenience variables. A convenience
7458 function can be used in an expression just like an ordinary function;
7459 however, a convenience function is implemented internally to
7464 @kindex help function
7465 @cindex show all convenience functions
7466 Print a list of all convenience functions.
7473 You can refer to machine register contents, in expressions, as variables
7474 with names starting with @samp{$}. The names of registers are different
7475 for each machine; use @code{info registers} to see the names used on
7479 @kindex info registers
7480 @item info registers
7481 Print the names and values of all registers except floating-point
7482 and vector registers (in the selected stack frame).
7484 @kindex info all-registers
7485 @cindex floating point registers
7486 @item info all-registers
7487 Print the names and values of all registers, including floating-point
7488 and vector registers (in the selected stack frame).
7490 @item info registers @var{regname} @dots{}
7491 Print the @dfn{relativized} value of each specified register @var{regname}.
7492 As discussed in detail below, register values are normally relative to
7493 the selected stack frame. @var{regname} may be any register name valid on
7494 the machine you are using, with or without the initial @samp{$}.
7497 @cindex stack pointer register
7498 @cindex program counter register
7499 @cindex process status register
7500 @cindex frame pointer register
7501 @cindex standard registers
7502 @value{GDBN} has four ``standard'' register names that are available (in
7503 expressions) on most machines---whenever they do not conflict with an
7504 architecture's canonical mnemonics for registers. The register names
7505 @code{$pc} and @code{$sp} are used for the program counter register and
7506 the stack pointer. @code{$fp} is used for a register that contains a
7507 pointer to the current stack frame, and @code{$ps} is used for a
7508 register that contains the processor status. For example,
7509 you could print the program counter in hex with
7516 or print the instruction to be executed next with
7523 or add four to the stack pointer@footnote{This is a way of removing
7524 one word from the stack, on machines where stacks grow downward in
7525 memory (most machines, nowadays). This assumes that the innermost
7526 stack frame is selected; setting @code{$sp} is not allowed when other
7527 stack frames are selected. To pop entire frames off the stack,
7528 regardless of machine architecture, use @code{return};
7529 see @ref{Returning, ,Returning from a Function}.} with
7535 Whenever possible, these four standard register names are available on
7536 your machine even though the machine has different canonical mnemonics,
7537 so long as there is no conflict. The @code{info registers} command
7538 shows the canonical names. For example, on the SPARC, @code{info
7539 registers} displays the processor status register as @code{$psr} but you
7540 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7541 is an alias for the @sc{eflags} register.
7543 @value{GDBN} always considers the contents of an ordinary register as an
7544 integer when the register is examined in this way. Some machines have
7545 special registers which can hold nothing but floating point; these
7546 registers are considered to have floating point values. There is no way
7547 to refer to the contents of an ordinary register as floating point value
7548 (although you can @emph{print} it as a floating point value with
7549 @samp{print/f $@var{regname}}).
7551 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7552 means that the data format in which the register contents are saved by
7553 the operating system is not the same one that your program normally
7554 sees. For example, the registers of the 68881 floating point
7555 coprocessor are always saved in ``extended'' (raw) format, but all C
7556 programs expect to work with ``double'' (virtual) format. In such
7557 cases, @value{GDBN} normally works with the virtual format only (the format
7558 that makes sense for your program), but the @code{info registers} command
7559 prints the data in both formats.
7561 @cindex SSE registers (x86)
7562 @cindex MMX registers (x86)
7563 Some machines have special registers whose contents can be interpreted
7564 in several different ways. For example, modern x86-based machines
7565 have SSE and MMX registers that can hold several values packed
7566 together in several different formats. @value{GDBN} refers to such
7567 registers in @code{struct} notation:
7570 (@value{GDBP}) print $xmm1
7572 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7573 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7574 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7575 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7576 v4_int32 = @{0, 20657912, 11, 13@},
7577 v2_int64 = @{88725056443645952, 55834574859@},
7578 uint128 = 0x0000000d0000000b013b36f800000000
7583 To set values of such registers, you need to tell @value{GDBN} which
7584 view of the register you wish to change, as if you were assigning
7585 value to a @code{struct} member:
7588 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7591 Normally, register values are relative to the selected stack frame
7592 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7593 value that the register would contain if all stack frames farther in
7594 were exited and their saved registers restored. In order to see the
7595 true contents of hardware registers, you must select the innermost
7596 frame (with @samp{frame 0}).
7598 However, @value{GDBN} must deduce where registers are saved, from the machine
7599 code generated by your compiler. If some registers are not saved, or if
7600 @value{GDBN} is unable to locate the saved registers, the selected stack
7601 frame makes no difference.
7603 @node Floating Point Hardware
7604 @section Floating Point Hardware
7605 @cindex floating point
7607 Depending on the configuration, @value{GDBN} may be able to give
7608 you more information about the status of the floating point hardware.
7613 Display hardware-dependent information about the floating
7614 point unit. The exact contents and layout vary depending on the
7615 floating point chip. Currently, @samp{info float} is supported on
7616 the ARM and x86 machines.
7620 @section Vector Unit
7623 Depending on the configuration, @value{GDBN} may be able to give you
7624 more information about the status of the vector unit.
7629 Display information about the vector unit. The exact contents and
7630 layout vary depending on the hardware.
7633 @node OS Information
7634 @section Operating System Auxiliary Information
7635 @cindex OS information
7637 @value{GDBN} provides interfaces to useful OS facilities that can help
7638 you debug your program.
7640 @cindex @code{ptrace} system call
7641 @cindex @code{struct user} contents
7642 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7643 machines), it interfaces with the inferior via the @code{ptrace}
7644 system call. The operating system creates a special sata structure,
7645 called @code{struct user}, for this interface. You can use the
7646 command @code{info udot} to display the contents of this data
7652 Display the contents of the @code{struct user} maintained by the OS
7653 kernel for the program being debugged. @value{GDBN} displays the
7654 contents of @code{struct user} as a list of hex numbers, similar to
7655 the @code{examine} command.
7658 @cindex auxiliary vector
7659 @cindex vector, auxiliary
7660 Some operating systems supply an @dfn{auxiliary vector} to programs at
7661 startup. This is akin to the arguments and environment that you
7662 specify for a program, but contains a system-dependent variety of
7663 binary values that tell system libraries important details about the
7664 hardware, operating system, and process. Each value's purpose is
7665 identified by an integer tag; the meanings are well-known but system-specific.
7666 Depending on the configuration and operating system facilities,
7667 @value{GDBN} may be able to show you this information. For remote
7668 targets, this functionality may further depend on the remote stub's
7669 support of the @samp{qXfer:auxv:read} packet, see
7670 @ref{qXfer auxiliary vector read}.
7675 Display the auxiliary vector of the inferior, which can be either a
7676 live process or a core dump file. @value{GDBN} prints each tag value
7677 numerically, and also shows names and text descriptions for recognized
7678 tags. Some values in the vector are numbers, some bit masks, and some
7679 pointers to strings or other data. @value{GDBN} displays each value in the
7680 most appropriate form for a recognized tag, and in hexadecimal for
7681 an unrecognized tag.
7684 On some targets, @value{GDBN} can access operating-system-specific information
7685 and display it to user, without interpretation. For remote targets,
7686 this functionality depends on the remote stub's support of the
7687 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
7690 @kindex info os processes
7691 @item info os processes
7692 Display the list of processes on the target. For each process,
7693 @value{GDBN} prints the process identifier, the name of the user, and
7694 the command corresponding to the process.
7697 @node Memory Region Attributes
7698 @section Memory Region Attributes
7699 @cindex memory region attributes
7701 @dfn{Memory region attributes} allow you to describe special handling
7702 required by regions of your target's memory. @value{GDBN} uses
7703 attributes to determine whether to allow certain types of memory
7704 accesses; whether to use specific width accesses; and whether to cache
7705 target memory. By default the description of memory regions is
7706 fetched from the target (if the current target supports this), but the
7707 user can override the fetched regions.
7709 Defined memory regions can be individually enabled and disabled. When a
7710 memory region is disabled, @value{GDBN} uses the default attributes when
7711 accessing memory in that region. Similarly, if no memory regions have
7712 been defined, @value{GDBN} uses the default attributes when accessing
7715 When a memory region is defined, it is given a number to identify it;
7716 to enable, disable, or remove a memory region, you specify that number.
7720 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7721 Define a memory region bounded by @var{lower} and @var{upper} with
7722 attributes @var{attributes}@dots{}, and add it to the list of regions
7723 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7724 case: it is treated as the target's maximum memory address.
7725 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7728 Discard any user changes to the memory regions and use target-supplied
7729 regions, if available, or no regions if the target does not support.
7732 @item delete mem @var{nums}@dots{}
7733 Remove memory regions @var{nums}@dots{} from the list of regions
7734 monitored by @value{GDBN}.
7737 @item disable mem @var{nums}@dots{}
7738 Disable monitoring of memory regions @var{nums}@dots{}.
7739 A disabled memory region is not forgotten.
7740 It may be enabled again later.
7743 @item enable mem @var{nums}@dots{}
7744 Enable monitoring of memory regions @var{nums}@dots{}.
7748 Print a table of all defined memory regions, with the following columns
7752 @item Memory Region Number
7753 @item Enabled or Disabled.
7754 Enabled memory regions are marked with @samp{y}.
7755 Disabled memory regions are marked with @samp{n}.
7758 The address defining the inclusive lower bound of the memory region.
7761 The address defining the exclusive upper bound of the memory region.
7764 The list of attributes set for this memory region.
7769 @subsection Attributes
7771 @subsubsection Memory Access Mode
7772 The access mode attributes set whether @value{GDBN} may make read or
7773 write accesses to a memory region.
7775 While these attributes prevent @value{GDBN} from performing invalid
7776 memory accesses, they do nothing to prevent the target system, I/O DMA,
7777 etc.@: from accessing memory.
7781 Memory is read only.
7783 Memory is write only.
7785 Memory is read/write. This is the default.
7788 @subsubsection Memory Access Size
7789 The access size attribute tells @value{GDBN} to use specific sized
7790 accesses in the memory region. Often memory mapped device registers
7791 require specific sized accesses. If no access size attribute is
7792 specified, @value{GDBN} may use accesses of any size.
7796 Use 8 bit memory accesses.
7798 Use 16 bit memory accesses.
7800 Use 32 bit memory accesses.
7802 Use 64 bit memory accesses.
7805 @c @subsubsection Hardware/Software Breakpoints
7806 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7807 @c will use hardware or software breakpoints for the internal breakpoints
7808 @c used by the step, next, finish, until, etc. commands.
7812 @c Always use hardware breakpoints
7813 @c @item swbreak (default)
7816 @subsubsection Data Cache
7817 The data cache attributes set whether @value{GDBN} will cache target
7818 memory. While this generally improves performance by reducing debug
7819 protocol overhead, it can lead to incorrect results because @value{GDBN}
7820 does not know about volatile variables or memory mapped device
7825 Enable @value{GDBN} to cache target memory.
7827 Disable @value{GDBN} from caching target memory. This is the default.
7830 @subsection Memory Access Checking
7831 @value{GDBN} can be instructed to refuse accesses to memory that is
7832 not explicitly described. This can be useful if accessing such
7833 regions has undesired effects for a specific target, or to provide
7834 better error checking. The following commands control this behaviour.
7837 @kindex set mem inaccessible-by-default
7838 @item set mem inaccessible-by-default [on|off]
7839 If @code{on} is specified, make @value{GDBN} treat memory not
7840 explicitly described by the memory ranges as non-existent and refuse accesses
7841 to such memory. The checks are only performed if there's at least one
7842 memory range defined. If @code{off} is specified, make @value{GDBN}
7843 treat the memory not explicitly described by the memory ranges as RAM.
7844 The default value is @code{on}.
7845 @kindex show mem inaccessible-by-default
7846 @item show mem inaccessible-by-default
7847 Show the current handling of accesses to unknown memory.
7851 @c @subsubsection Memory Write Verification
7852 @c The memory write verification attributes set whether @value{GDBN}
7853 @c will re-reads data after each write to verify the write was successful.
7857 @c @item noverify (default)
7860 @node Dump/Restore Files
7861 @section Copy Between Memory and a File
7862 @cindex dump/restore files
7863 @cindex append data to a file
7864 @cindex dump data to a file
7865 @cindex restore data from a file
7867 You can use the commands @code{dump}, @code{append}, and
7868 @code{restore} to copy data between target memory and a file. The
7869 @code{dump} and @code{append} commands write data to a file, and the
7870 @code{restore} command reads data from a file back into the inferior's
7871 memory. Files may be in binary, Motorola S-record, Intel hex, or
7872 Tektronix Hex format; however, @value{GDBN} can only append to binary
7878 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7879 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7880 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7881 or the value of @var{expr}, to @var{filename} in the given format.
7883 The @var{format} parameter may be any one of:
7890 Motorola S-record format.
7892 Tektronix Hex format.
7895 @value{GDBN} uses the same definitions of these formats as the
7896 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7897 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7901 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7902 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7903 Append the contents of memory from @var{start_addr} to @var{end_addr},
7904 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7905 (@value{GDBN} can only append data to files in raw binary form.)
7908 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7909 Restore the contents of file @var{filename} into memory. The
7910 @code{restore} command can automatically recognize any known @sc{bfd}
7911 file format, except for raw binary. To restore a raw binary file you
7912 must specify the optional keyword @code{binary} after the filename.
7914 If @var{bias} is non-zero, its value will be added to the addresses
7915 contained in the file. Binary files always start at address zero, so
7916 they will be restored at address @var{bias}. Other bfd files have
7917 a built-in location; they will be restored at offset @var{bias}
7920 If @var{start} and/or @var{end} are non-zero, then only data between
7921 file offset @var{start} and file offset @var{end} will be restored.
7922 These offsets are relative to the addresses in the file, before
7923 the @var{bias} argument is applied.
7927 @node Core File Generation
7928 @section How to Produce a Core File from Your Program
7929 @cindex dump core from inferior
7931 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7932 image of a running process and its process status (register values
7933 etc.). Its primary use is post-mortem debugging of a program that
7934 crashed while it ran outside a debugger. A program that crashes
7935 automatically produces a core file, unless this feature is disabled by
7936 the user. @xref{Files}, for information on invoking @value{GDBN} in
7937 the post-mortem debugging mode.
7939 Occasionally, you may wish to produce a core file of the program you
7940 are debugging in order to preserve a snapshot of its state.
7941 @value{GDBN} has a special command for that.
7945 @kindex generate-core-file
7946 @item generate-core-file [@var{file}]
7947 @itemx gcore [@var{file}]
7948 Produce a core dump of the inferior process. The optional argument
7949 @var{file} specifies the file name where to put the core dump. If not
7950 specified, the file name defaults to @file{core.@var{pid}}, where
7951 @var{pid} is the inferior process ID.
7953 Note that this command is implemented only for some systems (as of
7954 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7957 @node Character Sets
7958 @section Character Sets
7959 @cindex character sets
7961 @cindex translating between character sets
7962 @cindex host character set
7963 @cindex target character set
7965 If the program you are debugging uses a different character set to
7966 represent characters and strings than the one @value{GDBN} uses itself,
7967 @value{GDBN} can automatically translate between the character sets for
7968 you. The character set @value{GDBN} uses we call the @dfn{host
7969 character set}; the one the inferior program uses we call the
7970 @dfn{target character set}.
7972 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7973 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7974 remote protocol (@pxref{Remote Debugging}) to debug a program
7975 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7976 then the host character set is Latin-1, and the target character set is
7977 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7978 target-charset EBCDIC-US}, then @value{GDBN} translates between
7979 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7980 character and string literals in expressions.
7982 @value{GDBN} has no way to automatically recognize which character set
7983 the inferior program uses; you must tell it, using the @code{set
7984 target-charset} command, described below.
7986 Here are the commands for controlling @value{GDBN}'s character set
7990 @item set target-charset @var{charset}
7991 @kindex set target-charset
7992 Set the current target character set to @var{charset}. To display the
7993 list of supported target character sets, type
7994 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
7996 @item set host-charset @var{charset}
7997 @kindex set host-charset
7998 Set the current host character set to @var{charset}.
8000 By default, @value{GDBN} uses a host character set appropriate to the
8001 system it is running on; you can override that default using the
8002 @code{set host-charset} command.
8004 @value{GDBN} can only use certain character sets as its host character
8005 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8006 @value{GDBN} will list the host character sets it supports.
8008 @item set charset @var{charset}
8010 Set the current host and target character sets to @var{charset}. As
8011 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8012 @value{GDBN} will list the names of the character sets that can be used
8013 for both host and target.
8016 @kindex show charset
8017 Show the names of the current host and target character sets.
8019 @item show host-charset
8020 @kindex show host-charset
8021 Show the name of the current host character set.
8023 @item show target-charset
8024 @kindex show target-charset
8025 Show the name of the current target character set.
8027 @item set target-wide-charset @var{charset}
8028 @kindex set target-wide-charset
8029 Set the current target's wide character set to @var{charset}. This is
8030 the character set used by the target's @code{wchar_t} type. To
8031 display the list of supported wide character sets, type
8032 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8034 @item show target-wide-charset
8035 @kindex show target-wide-charset
8036 Show the name of the current target's wide character set.
8039 Here is an example of @value{GDBN}'s character set support in action.
8040 Assume that the following source code has been placed in the file
8041 @file{charset-test.c}:
8047 = @{72, 101, 108, 108, 111, 44, 32, 119,
8048 111, 114, 108, 100, 33, 10, 0@};
8049 char ibm1047_hello[]
8050 = @{200, 133, 147, 147, 150, 107, 64, 166,
8051 150, 153, 147, 132, 90, 37, 0@};
8055 printf ("Hello, world!\n");
8059 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8060 containing the string @samp{Hello, world!} followed by a newline,
8061 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8063 We compile the program, and invoke the debugger on it:
8066 $ gcc -g charset-test.c -o charset-test
8067 $ gdb -nw charset-test
8068 GNU gdb 2001-12-19-cvs
8069 Copyright 2001 Free Software Foundation, Inc.
8074 We can use the @code{show charset} command to see what character sets
8075 @value{GDBN} is currently using to interpret and display characters and
8079 (@value{GDBP}) show charset
8080 The current host and target character set is `ISO-8859-1'.
8084 For the sake of printing this manual, let's use @sc{ascii} as our
8085 initial character set:
8087 (@value{GDBP}) set charset ASCII
8088 (@value{GDBP}) show charset
8089 The current host and target character set is `ASCII'.
8093 Let's assume that @sc{ascii} is indeed the correct character set for our
8094 host system --- in other words, let's assume that if @value{GDBN} prints
8095 characters using the @sc{ascii} character set, our terminal will display
8096 them properly. Since our current target character set is also
8097 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8100 (@value{GDBP}) print ascii_hello
8101 $1 = 0x401698 "Hello, world!\n"
8102 (@value{GDBP}) print ascii_hello[0]
8107 @value{GDBN} uses the target character set for character and string
8108 literals you use in expressions:
8111 (@value{GDBP}) print '+'
8116 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8119 @value{GDBN} relies on the user to tell it which character set the
8120 target program uses. If we print @code{ibm1047_hello} while our target
8121 character set is still @sc{ascii}, we get jibberish:
8124 (@value{GDBP}) print ibm1047_hello
8125 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8126 (@value{GDBP}) print ibm1047_hello[0]
8131 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8132 @value{GDBN} tells us the character sets it supports:
8135 (@value{GDBP}) set target-charset
8136 ASCII EBCDIC-US IBM1047 ISO-8859-1
8137 (@value{GDBP}) set target-charset
8140 We can select @sc{ibm1047} as our target character set, and examine the
8141 program's strings again. Now the @sc{ascii} string is wrong, but
8142 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8143 target character set, @sc{ibm1047}, to the host character set,
8144 @sc{ascii}, and they display correctly:
8147 (@value{GDBP}) set target-charset IBM1047
8148 (@value{GDBP}) show charset
8149 The current host character set is `ASCII'.
8150 The current target character set is `IBM1047'.
8151 (@value{GDBP}) print ascii_hello
8152 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8153 (@value{GDBP}) print ascii_hello[0]
8155 (@value{GDBP}) print ibm1047_hello
8156 $8 = 0x4016a8 "Hello, world!\n"
8157 (@value{GDBP}) print ibm1047_hello[0]
8162 As above, @value{GDBN} uses the target character set for character and
8163 string literals you use in expressions:
8166 (@value{GDBP}) print '+'
8171 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8174 @node Caching Remote Data
8175 @section Caching Data of Remote Targets
8176 @cindex caching data of remote targets
8178 @value{GDBN} can cache data exchanged between the debugger and a
8179 remote target (@pxref{Remote Debugging}). Such caching generally improves
8180 performance, because it reduces the overhead of the remote protocol by
8181 bundling memory reads and writes into large chunks. Unfortunately,
8182 @value{GDBN} does not currently know anything about volatile
8183 registers, and thus data caching will produce incorrect results when
8184 volatile registers are in use.
8187 @kindex set remotecache
8188 @item set remotecache on
8189 @itemx set remotecache off
8190 Set caching state for remote targets. When @code{ON}, use data
8191 caching. By default, this option is @code{OFF}.
8193 @kindex show remotecache
8194 @item show remotecache
8195 Show the current state of data caching for remote targets.
8199 Print the information about the data cache performance. The
8200 information displayed includes: the dcache width and depth; and for
8201 each cache line, how many times it was referenced, and its data and
8202 state (invalid, dirty, valid). This command is useful for debugging
8203 the data cache operation.
8206 @node Searching Memory
8207 @section Search Memory
8208 @cindex searching memory
8210 Memory can be searched for a particular sequence of bytes with the
8211 @code{find} command.
8215 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8216 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8217 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8218 etc. The search begins at address @var{start_addr} and continues for either
8219 @var{len} bytes or through to @var{end_addr} inclusive.
8222 @var{s} and @var{n} are optional parameters.
8223 They may be specified in either order, apart or together.
8226 @item @var{s}, search query size
8227 The size of each search query value.
8233 halfwords (two bytes)
8237 giant words (eight bytes)
8240 All values are interpreted in the current language.
8241 This means, for example, that if the current source language is C/C@t{++}
8242 then searching for the string ``hello'' includes the trailing '\0'.
8244 If the value size is not specified, it is taken from the
8245 value's type in the current language.
8246 This is useful when one wants to specify the search
8247 pattern as a mixture of types.
8248 Note that this means, for example, that in the case of C-like languages
8249 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8250 which is typically four bytes.
8252 @item @var{n}, maximum number of finds
8253 The maximum number of matches to print. The default is to print all finds.
8256 You can use strings as search values. Quote them with double-quotes
8258 The string value is copied into the search pattern byte by byte,
8259 regardless of the endianness of the target and the size specification.
8261 The address of each match found is printed as well as a count of the
8262 number of matches found.
8264 The address of the last value found is stored in convenience variable
8266 A count of the number of matches is stored in @samp{$numfound}.
8268 For example, if stopped at the @code{printf} in this function:
8274 static char hello[] = "hello-hello";
8275 static struct @{ char c; short s; int i; @}
8276 __attribute__ ((packed)) mixed
8277 = @{ 'c', 0x1234, 0x87654321 @};
8278 printf ("%s\n", hello);
8283 you get during debugging:
8286 (gdb) find &hello[0], +sizeof(hello), "hello"
8287 0x804956d <hello.1620+6>
8289 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8290 0x8049567 <hello.1620>
8291 0x804956d <hello.1620+6>
8293 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8294 0x8049567 <hello.1620>
8296 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8297 0x8049560 <mixed.1625>
8299 (gdb) print $numfound
8302 $2 = (void *) 0x8049560
8306 @chapter C Preprocessor Macros
8308 Some languages, such as C and C@t{++}, provide a way to define and invoke
8309 ``preprocessor macros'' which expand into strings of tokens.
8310 @value{GDBN} can evaluate expressions containing macro invocations, show
8311 the result of macro expansion, and show a macro's definition, including
8312 where it was defined.
8314 You may need to compile your program specially to provide @value{GDBN}
8315 with information about preprocessor macros. Most compilers do not
8316 include macros in their debugging information, even when you compile
8317 with the @option{-g} flag. @xref{Compilation}.
8319 A program may define a macro at one point, remove that definition later,
8320 and then provide a different definition after that. Thus, at different
8321 points in the program, a macro may have different definitions, or have
8322 no definition at all. If there is a current stack frame, @value{GDBN}
8323 uses the macros in scope at that frame's source code line. Otherwise,
8324 @value{GDBN} uses the macros in scope at the current listing location;
8327 Whenever @value{GDBN} evaluates an expression, it always expands any
8328 macro invocations present in the expression. @value{GDBN} also provides
8329 the following commands for working with macros explicitly.
8333 @kindex macro expand
8334 @cindex macro expansion, showing the results of preprocessor
8335 @cindex preprocessor macro expansion, showing the results of
8336 @cindex expanding preprocessor macros
8337 @item macro expand @var{expression}
8338 @itemx macro exp @var{expression}
8339 Show the results of expanding all preprocessor macro invocations in
8340 @var{expression}. Since @value{GDBN} simply expands macros, but does
8341 not parse the result, @var{expression} need not be a valid expression;
8342 it can be any string of tokens.
8345 @item macro expand-once @var{expression}
8346 @itemx macro exp1 @var{expression}
8347 @cindex expand macro once
8348 @i{(This command is not yet implemented.)} Show the results of
8349 expanding those preprocessor macro invocations that appear explicitly in
8350 @var{expression}. Macro invocations appearing in that expansion are
8351 left unchanged. This command allows you to see the effect of a
8352 particular macro more clearly, without being confused by further
8353 expansions. Since @value{GDBN} simply expands macros, but does not
8354 parse the result, @var{expression} need not be a valid expression; it
8355 can be any string of tokens.
8358 @cindex macro definition, showing
8359 @cindex definition, showing a macro's
8360 @item info macro @var{macro}
8361 Show the definition of the macro named @var{macro}, and describe the
8362 source location where that definition was established.
8364 @kindex macro define
8365 @cindex user-defined macros
8366 @cindex defining macros interactively
8367 @cindex macros, user-defined
8368 @item macro define @var{macro} @var{replacement-list}
8369 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8370 Introduce a definition for a preprocessor macro named @var{macro},
8371 invocations of which are replaced by the tokens given in
8372 @var{replacement-list}. The first form of this command defines an
8373 ``object-like'' macro, which takes no arguments; the second form
8374 defines a ``function-like'' macro, which takes the arguments given in
8377 A definition introduced by this command is in scope in every
8378 expression evaluated in @value{GDBN}, until it is removed with the
8379 @code{macro undef} command, described below. The definition overrides
8380 all definitions for @var{macro} present in the program being debugged,
8381 as well as any previous user-supplied definition.
8384 @item macro undef @var{macro}
8385 Remove any user-supplied definition for the macro named @var{macro}.
8386 This command only affects definitions provided with the @code{macro
8387 define} command, described above; it cannot remove definitions present
8388 in the program being debugged.
8392 List all the macros defined using the @code{macro define} command.
8395 @cindex macros, example of debugging with
8396 Here is a transcript showing the above commands in action. First, we
8397 show our source files:
8405 #define ADD(x) (M + x)
8410 printf ("Hello, world!\n");
8412 printf ("We're so creative.\n");
8414 printf ("Goodbye, world!\n");
8421 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8422 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8423 compiler includes information about preprocessor macros in the debugging
8427 $ gcc -gdwarf-2 -g3 sample.c -o sample
8431 Now, we start @value{GDBN} on our sample program:
8435 GNU gdb 2002-05-06-cvs
8436 Copyright 2002 Free Software Foundation, Inc.
8437 GDB is free software, @dots{}
8441 We can expand macros and examine their definitions, even when the
8442 program is not running. @value{GDBN} uses the current listing position
8443 to decide which macro definitions are in scope:
8446 (@value{GDBP}) list main
8449 5 #define ADD(x) (M + x)
8454 10 printf ("Hello, world!\n");
8456 12 printf ("We're so creative.\n");
8457 (@value{GDBP}) info macro ADD
8458 Defined at /home/jimb/gdb/macros/play/sample.c:5
8459 #define ADD(x) (M + x)
8460 (@value{GDBP}) info macro Q
8461 Defined at /home/jimb/gdb/macros/play/sample.h:1
8462 included at /home/jimb/gdb/macros/play/sample.c:2
8464 (@value{GDBP}) macro expand ADD(1)
8465 expands to: (42 + 1)
8466 (@value{GDBP}) macro expand-once ADD(1)
8467 expands to: once (M + 1)
8471 In the example above, note that @code{macro expand-once} expands only
8472 the macro invocation explicit in the original text --- the invocation of
8473 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8474 which was introduced by @code{ADD}.
8476 Once the program is running, @value{GDBN} uses the macro definitions in
8477 force at the source line of the current stack frame:
8480 (@value{GDBP}) break main
8481 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8483 Starting program: /home/jimb/gdb/macros/play/sample
8485 Breakpoint 1, main () at sample.c:10
8486 10 printf ("Hello, world!\n");
8490 At line 10, the definition of the macro @code{N} at line 9 is in force:
8493 (@value{GDBP}) info macro N
8494 Defined at /home/jimb/gdb/macros/play/sample.c:9
8496 (@value{GDBP}) macro expand N Q M
8498 (@value{GDBP}) print N Q M
8503 As we step over directives that remove @code{N}'s definition, and then
8504 give it a new definition, @value{GDBN} finds the definition (or lack
8505 thereof) in force at each point:
8510 12 printf ("We're so creative.\n");
8511 (@value{GDBP}) info macro N
8512 The symbol `N' has no definition as a C/C++ preprocessor macro
8513 at /home/jimb/gdb/macros/play/sample.c:12
8516 14 printf ("Goodbye, world!\n");
8517 (@value{GDBP}) info macro N
8518 Defined at /home/jimb/gdb/macros/play/sample.c:13
8520 (@value{GDBP}) macro expand N Q M
8521 expands to: 1729 < 42
8522 (@value{GDBP}) print N Q M
8529 @chapter Tracepoints
8530 @c This chapter is based on the documentation written by Michael
8531 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8534 In some applications, it is not feasible for the debugger to interrupt
8535 the program's execution long enough for the developer to learn
8536 anything helpful about its behavior. If the program's correctness
8537 depends on its real-time behavior, delays introduced by a debugger
8538 might cause the program to change its behavior drastically, or perhaps
8539 fail, even when the code itself is correct. It is useful to be able
8540 to observe the program's behavior without interrupting it.
8542 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8543 specify locations in the program, called @dfn{tracepoints}, and
8544 arbitrary expressions to evaluate when those tracepoints are reached.
8545 Later, using the @code{tfind} command, you can examine the values
8546 those expressions had when the program hit the tracepoints. The
8547 expressions may also denote objects in memory---structures or arrays,
8548 for example---whose values @value{GDBN} should record; while visiting
8549 a particular tracepoint, you may inspect those objects as if they were
8550 in memory at that moment. However, because @value{GDBN} records these
8551 values without interacting with you, it can do so quickly and
8552 unobtrusively, hopefully not disturbing the program's behavior.
8554 The tracepoint facility is currently available only for remote
8555 targets. @xref{Targets}. In addition, your remote target must know
8556 how to collect trace data. This functionality is implemented in the
8557 remote stub; however, none of the stubs distributed with @value{GDBN}
8558 support tracepoints as of this writing. The format of the remote
8559 packets used to implement tracepoints are described in @ref{Tracepoint
8562 This chapter describes the tracepoint commands and features.
8566 * Analyze Collected Data::
8567 * Tracepoint Variables::
8570 @node Set Tracepoints
8571 @section Commands to Set Tracepoints
8573 Before running such a @dfn{trace experiment}, an arbitrary number of
8574 tracepoints can be set. A tracepoint is actually a special type of
8575 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
8576 standard breakpoint commands. For instance, as with breakpoints,
8577 tracepoint numbers are successive integers starting from one, and many
8578 of the commands associated with tracepoints take the tracepoint number
8579 as their argument, to identify which tracepoint to work on.
8581 For each tracepoint, you can specify, in advance, some arbitrary set
8582 of data that you want the target to collect in the trace buffer when
8583 it hits that tracepoint. The collected data can include registers,
8584 local variables, or global data. Later, you can use @value{GDBN}
8585 commands to examine the values these data had at the time the
8588 Tracepoints do not support every breakpoint feature. Conditional
8589 expressions and ignore counts on tracepoints have no effect, and
8590 tracepoints cannot run @value{GDBN} commands when they are
8591 hit. Tracepoints may not be thread-specific either.
8593 This section describes commands to set tracepoints and associated
8594 conditions and actions.
8597 * Create and Delete Tracepoints::
8598 * Enable and Disable Tracepoints::
8599 * Tracepoint Passcounts::
8600 * Tracepoint Actions::
8601 * Listing Tracepoints::
8602 * Starting and Stopping Trace Experiments::
8605 @node Create and Delete Tracepoints
8606 @subsection Create and Delete Tracepoints
8609 @cindex set tracepoint
8611 @item trace @var{location}
8612 The @code{trace} command is very similar to the @code{break} command.
8613 Its argument @var{location} can be a source line, a function name, or
8614 an address in the target program. @xref{Specify Location}. The
8615 @code{trace} command defines a tracepoint, which is a point in the
8616 target program where the debugger will briefly stop, collect some
8617 data, and then allow the program to continue. Setting a tracepoint or
8618 changing its actions doesn't take effect until the next @code{tstart}
8619 command, and once a trace experiment is running, further changes will
8620 not have any effect until the next trace experiment starts.
8622 Here are some examples of using the @code{trace} command:
8625 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8627 (@value{GDBP}) @b{trace +2} // 2 lines forward
8629 (@value{GDBP}) @b{trace my_function} // first source line of function
8631 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8633 (@value{GDBP}) @b{trace *0x2117c4} // an address
8637 You can abbreviate @code{trace} as @code{tr}.
8640 @cindex last tracepoint number
8641 @cindex recent tracepoint number
8642 @cindex tracepoint number
8643 The convenience variable @code{$tpnum} records the tracepoint number
8644 of the most recently set tracepoint.
8646 @kindex delete tracepoint
8647 @cindex tracepoint deletion
8648 @item delete tracepoint @r{[}@var{num}@r{]}
8649 Permanently delete one or more tracepoints. With no argument, the
8650 default is to delete all tracepoints. Note that the regular
8651 @code{delete} command can remove tracepoints also.
8656 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8658 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8662 You can abbreviate this command as @code{del tr}.
8665 @node Enable and Disable Tracepoints
8666 @subsection Enable and Disable Tracepoints
8668 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
8671 @kindex disable tracepoint
8672 @item disable tracepoint @r{[}@var{num}@r{]}
8673 Disable tracepoint @var{num}, or all tracepoints if no argument
8674 @var{num} is given. A disabled tracepoint will have no effect during
8675 the next trace experiment, but it is not forgotten. You can re-enable
8676 a disabled tracepoint using the @code{enable tracepoint} command.
8678 @kindex enable tracepoint
8679 @item enable tracepoint @r{[}@var{num}@r{]}
8680 Enable tracepoint @var{num}, or all tracepoints. The enabled
8681 tracepoints will become effective the next time a trace experiment is
8685 @node Tracepoint Passcounts
8686 @subsection Tracepoint Passcounts
8690 @cindex tracepoint pass count
8691 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8692 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8693 automatically stop a trace experiment. If a tracepoint's passcount is
8694 @var{n}, then the trace experiment will be automatically stopped on
8695 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8696 @var{num} is not specified, the @code{passcount} command sets the
8697 passcount of the most recently defined tracepoint. If no passcount is
8698 given, the trace experiment will run until stopped explicitly by the
8704 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8705 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8707 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8708 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8709 (@value{GDBP}) @b{trace foo}
8710 (@value{GDBP}) @b{pass 3}
8711 (@value{GDBP}) @b{trace bar}
8712 (@value{GDBP}) @b{pass 2}
8713 (@value{GDBP}) @b{trace baz}
8714 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8715 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8716 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8717 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8721 @node Tracepoint Actions
8722 @subsection Tracepoint Action Lists
8726 @cindex tracepoint actions
8727 @item actions @r{[}@var{num}@r{]}
8728 This command will prompt for a list of actions to be taken when the
8729 tracepoint is hit. If the tracepoint number @var{num} is not
8730 specified, this command sets the actions for the one that was most
8731 recently defined (so that you can define a tracepoint and then say
8732 @code{actions} without bothering about its number). You specify the
8733 actions themselves on the following lines, one action at a time, and
8734 terminate the actions list with a line containing just @code{end}. So
8735 far, the only defined actions are @code{collect} and
8736 @code{while-stepping}.
8738 @cindex remove actions from a tracepoint
8739 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8740 and follow it immediately with @samp{end}.
8743 (@value{GDBP}) @b{collect @var{data}} // collect some data
8745 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8747 (@value{GDBP}) @b{end} // signals the end of actions.
8750 In the following example, the action list begins with @code{collect}
8751 commands indicating the things to be collected when the tracepoint is
8752 hit. Then, in order to single-step and collect additional data
8753 following the tracepoint, a @code{while-stepping} command is used,
8754 followed by the list of things to be collected while stepping. The
8755 @code{while-stepping} command is terminated by its own separate
8756 @code{end} command. Lastly, the action list is terminated by an
8760 (@value{GDBP}) @b{trace foo}
8761 (@value{GDBP}) @b{actions}
8762 Enter actions for tracepoint 1, one per line:
8771 @kindex collect @r{(tracepoints)}
8772 @item collect @var{expr1}, @var{expr2}, @dots{}
8773 Collect values of the given expressions when the tracepoint is hit.
8774 This command accepts a comma-separated list of any valid expressions.
8775 In addition to global, static, or local variables, the following
8776 special arguments are supported:
8780 collect all registers
8783 collect all function arguments
8786 collect all local variables.
8789 You can give several consecutive @code{collect} commands, each one
8790 with a single argument, or one @code{collect} command with several
8791 arguments separated by commas: the effect is the same.
8793 The command @code{info scope} (@pxref{Symbols, info scope}) is
8794 particularly useful for figuring out what data to collect.
8796 @kindex while-stepping @r{(tracepoints)}
8797 @item while-stepping @var{n}
8798 Perform @var{n} single-step traces after the tracepoint, collecting
8799 new data at each step. The @code{while-stepping} command is
8800 followed by the list of what to collect while stepping (followed by
8801 its own @code{end} command):
8805 > collect $regs, myglobal
8811 You may abbreviate @code{while-stepping} as @code{ws} or
8815 @node Listing Tracepoints
8816 @subsection Listing Tracepoints
8819 @kindex info tracepoints
8821 @cindex information about tracepoints
8822 @item info tracepoints @r{[}@var{num}@r{]}
8823 Display information about the tracepoint @var{num}. If you don't
8824 specify a tracepoint number, displays information about all the
8825 tracepoints defined so far. The format is similar to that used for
8826 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
8827 command, simply restricting itself to tracepoints.
8829 A tracepoint's listing may include additional information specific to
8834 its passcount as given by the @code{passcount @var{n}} command
8836 its step count as given by the @code{while-stepping @var{n}} command
8838 its action list as given by the @code{actions} command. The actions
8839 are prefixed with an @samp{A} so as to distinguish them from commands.
8843 (@value{GDBP}) @b{info trace}
8844 Num Type Disp Enb Address What
8845 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
8849 A collect globfoo, $regs
8857 This command can be abbreviated @code{info tp}.
8860 @node Starting and Stopping Trace Experiments
8861 @subsection Starting and Stopping Trace Experiments
8865 @cindex start a new trace experiment
8866 @cindex collected data discarded
8868 This command takes no arguments. It starts the trace experiment, and
8869 begins collecting data. This has the side effect of discarding all
8870 the data collected in the trace buffer during the previous trace
8874 @cindex stop a running trace experiment
8876 This command takes no arguments. It ends the trace experiment, and
8877 stops collecting data.
8879 @strong{Note}: a trace experiment and data collection may stop
8880 automatically if any tracepoint's passcount is reached
8881 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8884 @cindex status of trace data collection
8885 @cindex trace experiment, status of
8887 This command displays the status of the current trace data
8891 Here is an example of the commands we described so far:
8894 (@value{GDBP}) @b{trace gdb_c_test}
8895 (@value{GDBP}) @b{actions}
8896 Enter actions for tracepoint #1, one per line.
8897 > collect $regs,$locals,$args
8902 (@value{GDBP}) @b{tstart}
8903 [time passes @dots{}]
8904 (@value{GDBP}) @b{tstop}
8908 @node Analyze Collected Data
8909 @section Using the Collected Data
8911 After the tracepoint experiment ends, you use @value{GDBN} commands
8912 for examining the trace data. The basic idea is that each tracepoint
8913 collects a trace @dfn{snapshot} every time it is hit and another
8914 snapshot every time it single-steps. All these snapshots are
8915 consecutively numbered from zero and go into a buffer, and you can
8916 examine them later. The way you examine them is to @dfn{focus} on a
8917 specific trace snapshot. When the remote stub is focused on a trace
8918 snapshot, it will respond to all @value{GDBN} requests for memory and
8919 registers by reading from the buffer which belongs to that snapshot,
8920 rather than from @emph{real} memory or registers of the program being
8921 debugged. This means that @strong{all} @value{GDBN} commands
8922 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8923 behave as if we were currently debugging the program state as it was
8924 when the tracepoint occurred. Any requests for data that are not in
8925 the buffer will fail.
8928 * tfind:: How to select a trace snapshot
8929 * tdump:: How to display all data for a snapshot
8930 * save-tracepoints:: How to save tracepoints for a future run
8934 @subsection @code{tfind @var{n}}
8937 @cindex select trace snapshot
8938 @cindex find trace snapshot
8939 The basic command for selecting a trace snapshot from the buffer is
8940 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8941 counting from zero. If no argument @var{n} is given, the next
8942 snapshot is selected.
8944 Here are the various forms of using the @code{tfind} command.
8948 Find the first snapshot in the buffer. This is a synonym for
8949 @code{tfind 0} (since 0 is the number of the first snapshot).
8952 Stop debugging trace snapshots, resume @emph{live} debugging.
8955 Same as @samp{tfind none}.
8958 No argument means find the next trace snapshot.
8961 Find the previous trace snapshot before the current one. This permits
8962 retracing earlier steps.
8964 @item tfind tracepoint @var{num}
8965 Find the next snapshot associated with tracepoint @var{num}. Search
8966 proceeds forward from the last examined trace snapshot. If no
8967 argument @var{num} is given, it means find the next snapshot collected
8968 for the same tracepoint as the current snapshot.
8970 @item tfind pc @var{addr}
8971 Find the next snapshot associated with the value @var{addr} of the
8972 program counter. Search proceeds forward from the last examined trace
8973 snapshot. If no argument @var{addr} is given, it means find the next
8974 snapshot with the same value of PC as the current snapshot.
8976 @item tfind outside @var{addr1}, @var{addr2}
8977 Find the next snapshot whose PC is outside the given range of
8980 @item tfind range @var{addr1}, @var{addr2}
8981 Find the next snapshot whose PC is between @var{addr1} and
8982 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8984 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8985 Find the next snapshot associated with the source line @var{n}. If
8986 the optional argument @var{file} is given, refer to line @var{n} in
8987 that source file. Search proceeds forward from the last examined
8988 trace snapshot. If no argument @var{n} is given, it means find the
8989 next line other than the one currently being examined; thus saying
8990 @code{tfind line} repeatedly can appear to have the same effect as
8991 stepping from line to line in a @emph{live} debugging session.
8994 The default arguments for the @code{tfind} commands are specifically
8995 designed to make it easy to scan through the trace buffer. For
8996 instance, @code{tfind} with no argument selects the next trace
8997 snapshot, and @code{tfind -} with no argument selects the previous
8998 trace snapshot. So, by giving one @code{tfind} command, and then
8999 simply hitting @key{RET} repeatedly you can examine all the trace
9000 snapshots in order. Or, by saying @code{tfind -} and then hitting
9001 @key{RET} repeatedly you can examine the snapshots in reverse order.
9002 The @code{tfind line} command with no argument selects the snapshot
9003 for the next source line executed. The @code{tfind pc} command with
9004 no argument selects the next snapshot with the same program counter
9005 (PC) as the current frame. The @code{tfind tracepoint} command with
9006 no argument selects the next trace snapshot collected by the same
9007 tracepoint as the current one.
9009 In addition to letting you scan through the trace buffer manually,
9010 these commands make it easy to construct @value{GDBN} scripts that
9011 scan through the trace buffer and print out whatever collected data
9012 you are interested in. Thus, if we want to examine the PC, FP, and SP
9013 registers from each trace frame in the buffer, we can say this:
9016 (@value{GDBP}) @b{tfind start}
9017 (@value{GDBP}) @b{while ($trace_frame != -1)}
9018 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
9019 $trace_frame, $pc, $sp, $fp
9023 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
9024 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
9025 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
9026 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
9027 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
9028 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
9029 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
9030 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
9031 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
9032 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
9033 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
9036 Or, if we want to examine the variable @code{X} at each source line in
9040 (@value{GDBP}) @b{tfind start}
9041 (@value{GDBP}) @b{while ($trace_frame != -1)}
9042 > printf "Frame %d, X == %d\n", $trace_frame, X
9052 @subsection @code{tdump}
9054 @cindex dump all data collected at tracepoint
9055 @cindex tracepoint data, display
9057 This command takes no arguments. It prints all the data collected at
9058 the current trace snapshot.
9061 (@value{GDBP}) @b{trace 444}
9062 (@value{GDBP}) @b{actions}
9063 Enter actions for tracepoint #2, one per line:
9064 > collect $regs, $locals, $args, gdb_long_test
9067 (@value{GDBP}) @b{tstart}
9069 (@value{GDBP}) @b{tfind line 444}
9070 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
9072 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
9074 (@value{GDBP}) @b{tdump}
9075 Data collected at tracepoint 2, trace frame 1:
9076 d0 0xc4aa0085 -995491707
9080 d4 0x71aea3d 119204413
9085 a1 0x3000668 50333288
9088 a4 0x3000698 50333336
9090 fp 0x30bf3c 0x30bf3c
9091 sp 0x30bf34 0x30bf34
9093 pc 0x20b2c8 0x20b2c8
9097 p = 0x20e5b4 "gdb-test"
9104 gdb_long_test = 17 '\021'
9109 @node save-tracepoints
9110 @subsection @code{save-tracepoints @var{filename}}
9111 @kindex save-tracepoints
9112 @cindex save tracepoints for future sessions
9114 This command saves all current tracepoint definitions together with
9115 their actions and passcounts, into a file @file{@var{filename}}
9116 suitable for use in a later debugging session. To read the saved
9117 tracepoint definitions, use the @code{source} command (@pxref{Command
9120 @node Tracepoint Variables
9121 @section Convenience Variables for Tracepoints
9122 @cindex tracepoint variables
9123 @cindex convenience variables for tracepoints
9126 @vindex $trace_frame
9127 @item (int) $trace_frame
9128 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9129 snapshot is selected.
9132 @item (int) $tracepoint
9133 The tracepoint for the current trace snapshot.
9136 @item (int) $trace_line
9137 The line number for the current trace snapshot.
9140 @item (char []) $trace_file
9141 The source file for the current trace snapshot.
9144 @item (char []) $trace_func
9145 The name of the function containing @code{$tracepoint}.
9148 Note: @code{$trace_file} is not suitable for use in @code{printf},
9149 use @code{output} instead.
9151 Here's a simple example of using these convenience variables for
9152 stepping through all the trace snapshots and printing some of their
9156 (@value{GDBP}) @b{tfind start}
9158 (@value{GDBP}) @b{while $trace_frame != -1}
9159 > output $trace_file
9160 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9166 @chapter Debugging Programs That Use Overlays
9169 If your program is too large to fit completely in your target system's
9170 memory, you can sometimes use @dfn{overlays} to work around this
9171 problem. @value{GDBN} provides some support for debugging programs that
9175 * How Overlays Work:: A general explanation of overlays.
9176 * Overlay Commands:: Managing overlays in @value{GDBN}.
9177 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9178 mapped by asking the inferior.
9179 * Overlay Sample Program:: A sample program using overlays.
9182 @node How Overlays Work
9183 @section How Overlays Work
9184 @cindex mapped overlays
9185 @cindex unmapped overlays
9186 @cindex load address, overlay's
9187 @cindex mapped address
9188 @cindex overlay area
9190 Suppose you have a computer whose instruction address space is only 64
9191 kilobytes long, but which has much more memory which can be accessed by
9192 other means: special instructions, segment registers, or memory
9193 management hardware, for example. Suppose further that you want to
9194 adapt a program which is larger than 64 kilobytes to run on this system.
9196 One solution is to identify modules of your program which are relatively
9197 independent, and need not call each other directly; call these modules
9198 @dfn{overlays}. Separate the overlays from the main program, and place
9199 their machine code in the larger memory. Place your main program in
9200 instruction memory, but leave at least enough space there to hold the
9201 largest overlay as well.
9203 Now, to call a function located in an overlay, you must first copy that
9204 overlay's machine code from the large memory into the space set aside
9205 for it in the instruction memory, and then jump to its entry point
9208 @c NB: In the below the mapped area's size is greater or equal to the
9209 @c size of all overlays. This is intentional to remind the developer
9210 @c that overlays don't necessarily need to be the same size.
9214 Data Instruction Larger
9215 Address Space Address Space Address Space
9216 +-----------+ +-----------+ +-----------+
9218 +-----------+ +-----------+ +-----------+<-- overlay 1
9219 | program | | main | .----| overlay 1 | load address
9220 | variables | | program | | +-----------+
9221 | and heap | | | | | |
9222 +-----------+ | | | +-----------+<-- overlay 2
9223 | | +-----------+ | | | load address
9224 +-----------+ | | | .-| overlay 2 |
9226 mapped --->+-----------+ | | +-----------+
9228 | overlay | <-' | | |
9229 | area | <---' +-----------+<-- overlay 3
9230 | | <---. | | load address
9231 +-----------+ `--| overlay 3 |
9238 @anchor{A code overlay}A code overlay
9242 The diagram (@pxref{A code overlay}) shows a system with separate data
9243 and instruction address spaces. To map an overlay, the program copies
9244 its code from the larger address space to the instruction address space.
9245 Since the overlays shown here all use the same mapped address, only one
9246 may be mapped at a time. For a system with a single address space for
9247 data and instructions, the diagram would be similar, except that the
9248 program variables and heap would share an address space with the main
9249 program and the overlay area.
9251 An overlay loaded into instruction memory and ready for use is called a
9252 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9253 instruction memory. An overlay not present (or only partially present)
9254 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9255 is its address in the larger memory. The mapped address is also called
9256 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9257 called the @dfn{load memory address}, or @dfn{LMA}.
9259 Unfortunately, overlays are not a completely transparent way to adapt a
9260 program to limited instruction memory. They introduce a new set of
9261 global constraints you must keep in mind as you design your program:
9266 Before calling or returning to a function in an overlay, your program
9267 must make sure that overlay is actually mapped. Otherwise, the call or
9268 return will transfer control to the right address, but in the wrong
9269 overlay, and your program will probably crash.
9272 If the process of mapping an overlay is expensive on your system, you
9273 will need to choose your overlays carefully to minimize their effect on
9274 your program's performance.
9277 The executable file you load onto your system must contain each
9278 overlay's instructions, appearing at the overlay's load address, not its
9279 mapped address. However, each overlay's instructions must be relocated
9280 and its symbols defined as if the overlay were at its mapped address.
9281 You can use GNU linker scripts to specify different load and relocation
9282 addresses for pieces of your program; see @ref{Overlay Description,,,
9283 ld.info, Using ld: the GNU linker}.
9286 The procedure for loading executable files onto your system must be able
9287 to load their contents into the larger address space as well as the
9288 instruction and data spaces.
9292 The overlay system described above is rather simple, and could be
9293 improved in many ways:
9298 If your system has suitable bank switch registers or memory management
9299 hardware, you could use those facilities to make an overlay's load area
9300 contents simply appear at their mapped address in instruction space.
9301 This would probably be faster than copying the overlay to its mapped
9302 area in the usual way.
9305 If your overlays are small enough, you could set aside more than one
9306 overlay area, and have more than one overlay mapped at a time.
9309 You can use overlays to manage data, as well as instructions. In
9310 general, data overlays are even less transparent to your design than
9311 code overlays: whereas code overlays only require care when you call or
9312 return to functions, data overlays require care every time you access
9313 the data. Also, if you change the contents of a data overlay, you
9314 must copy its contents back out to its load address before you can copy a
9315 different data overlay into the same mapped area.
9320 @node Overlay Commands
9321 @section Overlay Commands
9323 To use @value{GDBN}'s overlay support, each overlay in your program must
9324 correspond to a separate section of the executable file. The section's
9325 virtual memory address and load memory address must be the overlay's
9326 mapped and load addresses. Identifying overlays with sections allows
9327 @value{GDBN} to determine the appropriate address of a function or
9328 variable, depending on whether the overlay is mapped or not.
9330 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9331 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9336 Disable @value{GDBN}'s overlay support. When overlay support is
9337 disabled, @value{GDBN} assumes that all functions and variables are
9338 always present at their mapped addresses. By default, @value{GDBN}'s
9339 overlay support is disabled.
9341 @item overlay manual
9342 @cindex manual overlay debugging
9343 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9344 relies on you to tell it which overlays are mapped, and which are not,
9345 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9346 commands described below.
9348 @item overlay map-overlay @var{overlay}
9349 @itemx overlay map @var{overlay}
9350 @cindex map an overlay
9351 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9352 be the name of the object file section containing the overlay. When an
9353 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9354 functions and variables at their mapped addresses. @value{GDBN} assumes
9355 that any other overlays whose mapped ranges overlap that of
9356 @var{overlay} are now unmapped.
9358 @item overlay unmap-overlay @var{overlay}
9359 @itemx overlay unmap @var{overlay}
9360 @cindex unmap an overlay
9361 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9362 must be the name of the object file section containing the overlay.
9363 When an overlay is unmapped, @value{GDBN} assumes it can find the
9364 overlay's functions and variables at their load addresses.
9367 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9368 consults a data structure the overlay manager maintains in the inferior
9369 to see which overlays are mapped. For details, see @ref{Automatic
9372 @item overlay load-target
9374 @cindex reloading the overlay table
9375 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9376 re-reads the table @value{GDBN} automatically each time the inferior
9377 stops, so this command should only be necessary if you have changed the
9378 overlay mapping yourself using @value{GDBN}. This command is only
9379 useful when using automatic overlay debugging.
9381 @item overlay list-overlays
9383 @cindex listing mapped overlays
9384 Display a list of the overlays currently mapped, along with their mapped
9385 addresses, load addresses, and sizes.
9389 Normally, when @value{GDBN} prints a code address, it includes the name
9390 of the function the address falls in:
9393 (@value{GDBP}) print main
9394 $3 = @{int ()@} 0x11a0 <main>
9397 When overlay debugging is enabled, @value{GDBN} recognizes code in
9398 unmapped overlays, and prints the names of unmapped functions with
9399 asterisks around them. For example, if @code{foo} is a function in an
9400 unmapped overlay, @value{GDBN} prints it this way:
9403 (@value{GDBP}) overlay list
9404 No sections are mapped.
9405 (@value{GDBP}) print foo
9406 $5 = @{int (int)@} 0x100000 <*foo*>
9409 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9413 (@value{GDBP}) overlay list
9414 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9415 mapped at 0x1016 - 0x104a
9416 (@value{GDBP}) print foo
9417 $6 = @{int (int)@} 0x1016 <foo>
9420 When overlay debugging is enabled, @value{GDBN} can find the correct
9421 address for functions and variables in an overlay, whether or not the
9422 overlay is mapped. This allows most @value{GDBN} commands, like
9423 @code{break} and @code{disassemble}, to work normally, even on unmapped
9424 code. However, @value{GDBN}'s breakpoint support has some limitations:
9428 @cindex breakpoints in overlays
9429 @cindex overlays, setting breakpoints in
9430 You can set breakpoints in functions in unmapped overlays, as long as
9431 @value{GDBN} can write to the overlay at its load address.
9433 @value{GDBN} can not set hardware or simulator-based breakpoints in
9434 unmapped overlays. However, if you set a breakpoint at the end of your
9435 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9436 you are using manual overlay management), @value{GDBN} will re-set its
9437 breakpoints properly.
9441 @node Automatic Overlay Debugging
9442 @section Automatic Overlay Debugging
9443 @cindex automatic overlay debugging
9445 @value{GDBN} can automatically track which overlays are mapped and which
9446 are not, given some simple co-operation from the overlay manager in the
9447 inferior. If you enable automatic overlay debugging with the
9448 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
9449 looks in the inferior's memory for certain variables describing the
9450 current state of the overlays.
9452 Here are the variables your overlay manager must define to support
9453 @value{GDBN}'s automatic overlay debugging:
9457 @item @code{_ovly_table}:
9458 This variable must be an array of the following structures:
9463 /* The overlay's mapped address. */
9466 /* The size of the overlay, in bytes. */
9469 /* The overlay's load address. */
9472 /* Non-zero if the overlay is currently mapped;
9474 unsigned long mapped;
9478 @item @code{_novlys}:
9479 This variable must be a four-byte signed integer, holding the total
9480 number of elements in @code{_ovly_table}.
9484 To decide whether a particular overlay is mapped or not, @value{GDBN}
9485 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9486 @code{lma} members equal the VMA and LMA of the overlay's section in the
9487 executable file. When @value{GDBN} finds a matching entry, it consults
9488 the entry's @code{mapped} member to determine whether the overlay is
9491 In addition, your overlay manager may define a function called
9492 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9493 will silently set a breakpoint there. If the overlay manager then
9494 calls this function whenever it has changed the overlay table, this
9495 will enable @value{GDBN} to accurately keep track of which overlays
9496 are in program memory, and update any breakpoints that may be set
9497 in overlays. This will allow breakpoints to work even if the
9498 overlays are kept in ROM or other non-writable memory while they
9499 are not being executed.
9501 @node Overlay Sample Program
9502 @section Overlay Sample Program
9503 @cindex overlay example program
9505 When linking a program which uses overlays, you must place the overlays
9506 at their load addresses, while relocating them to run at their mapped
9507 addresses. To do this, you must write a linker script (@pxref{Overlay
9508 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9509 since linker scripts are specific to a particular host system, target
9510 architecture, and target memory layout, this manual cannot provide
9511 portable sample code demonstrating @value{GDBN}'s overlay support.
9513 However, the @value{GDBN} source distribution does contain an overlaid
9514 program, with linker scripts for a few systems, as part of its test
9515 suite. The program consists of the following files from
9516 @file{gdb/testsuite/gdb.base}:
9520 The main program file.
9522 A simple overlay manager, used by @file{overlays.c}.
9527 Overlay modules, loaded and used by @file{overlays.c}.
9530 Linker scripts for linking the test program on the @code{d10v-elf}
9531 and @code{m32r-elf} targets.
9534 You can build the test program using the @code{d10v-elf} GCC
9535 cross-compiler like this:
9538 $ d10v-elf-gcc -g -c overlays.c
9539 $ d10v-elf-gcc -g -c ovlymgr.c
9540 $ d10v-elf-gcc -g -c foo.c
9541 $ d10v-elf-gcc -g -c bar.c
9542 $ d10v-elf-gcc -g -c baz.c
9543 $ d10v-elf-gcc -g -c grbx.c
9544 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9545 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9548 The build process is identical for any other architecture, except that
9549 you must substitute the appropriate compiler and linker script for the
9550 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9554 @chapter Using @value{GDBN} with Different Languages
9557 Although programming languages generally have common aspects, they are
9558 rarely expressed in the same manner. For instance, in ANSI C,
9559 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9560 Modula-2, it is accomplished by @code{p^}. Values can also be
9561 represented (and displayed) differently. Hex numbers in C appear as
9562 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9564 @cindex working language
9565 Language-specific information is built into @value{GDBN} for some languages,
9566 allowing you to express operations like the above in your program's
9567 native language, and allowing @value{GDBN} to output values in a manner
9568 consistent with the syntax of your program's native language. The
9569 language you use to build expressions is called the @dfn{working
9573 * Setting:: Switching between source languages
9574 * Show:: Displaying the language
9575 * Checks:: Type and range checks
9576 * Supported Languages:: Supported languages
9577 * Unsupported Languages:: Unsupported languages
9581 @section Switching Between Source Languages
9583 There are two ways to control the working language---either have @value{GDBN}
9584 set it automatically, or select it manually yourself. You can use the
9585 @code{set language} command for either purpose. On startup, @value{GDBN}
9586 defaults to setting the language automatically. The working language is
9587 used to determine how expressions you type are interpreted, how values
9590 In addition to the working language, every source file that
9591 @value{GDBN} knows about has its own working language. For some object
9592 file formats, the compiler might indicate which language a particular
9593 source file is in. However, most of the time @value{GDBN} infers the
9594 language from the name of the file. The language of a source file
9595 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9596 show each frame appropriately for its own language. There is no way to
9597 set the language of a source file from within @value{GDBN}, but you can
9598 set the language associated with a filename extension. @xref{Show, ,
9599 Displaying the Language}.
9601 This is most commonly a problem when you use a program, such
9602 as @code{cfront} or @code{f2c}, that generates C but is written in
9603 another language. In that case, make the
9604 program use @code{#line} directives in its C output; that way
9605 @value{GDBN} will know the correct language of the source code of the original
9606 program, and will display that source code, not the generated C code.
9609 * Filenames:: Filename extensions and languages.
9610 * Manually:: Setting the working language manually
9611 * Automatically:: Having @value{GDBN} infer the source language
9615 @subsection List of Filename Extensions and Languages
9617 If a source file name ends in one of the following extensions, then
9618 @value{GDBN} infers that its language is the one indicated.
9639 Objective-C source file
9646 Modula-2 source file
9650 Assembler source file. This actually behaves almost like C, but
9651 @value{GDBN} does not skip over function prologues when stepping.
9654 In addition, you may set the language associated with a filename
9655 extension. @xref{Show, , Displaying the Language}.
9658 @subsection Setting the Working Language
9660 If you allow @value{GDBN} to set the language automatically,
9661 expressions are interpreted the same way in your debugging session and
9664 @kindex set language
9665 If you wish, you may set the language manually. To do this, issue the
9666 command @samp{set language @var{lang}}, where @var{lang} is the name of
9668 @code{c} or @code{modula-2}.
9669 For a list of the supported languages, type @samp{set language}.
9671 Setting the language manually prevents @value{GDBN} from updating the working
9672 language automatically. This can lead to confusion if you try
9673 to debug a program when the working language is not the same as the
9674 source language, when an expression is acceptable to both
9675 languages---but means different things. For instance, if the current
9676 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9684 might not have the effect you intended. In C, this means to add
9685 @code{b} and @code{c} and place the result in @code{a}. The result
9686 printed would be the value of @code{a}. In Modula-2, this means to compare
9687 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9690 @subsection Having @value{GDBN} Infer the Source Language
9692 To have @value{GDBN} set the working language automatically, use
9693 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9694 then infers the working language. That is, when your program stops in a
9695 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9696 working language to the language recorded for the function in that
9697 frame. If the language for a frame is unknown (that is, if the function
9698 or block corresponding to the frame was defined in a source file that
9699 does not have a recognized extension), the current working language is
9700 not changed, and @value{GDBN} issues a warning.
9702 This may not seem necessary for most programs, which are written
9703 entirely in one source language. However, program modules and libraries
9704 written in one source language can be used by a main program written in
9705 a different source language. Using @samp{set language auto} in this
9706 case frees you from having to set the working language manually.
9709 @section Displaying the Language
9711 The following commands help you find out which language is the
9712 working language, and also what language source files were written in.
9716 @kindex show language
9717 Display the current working language. This is the
9718 language you can use with commands such as @code{print} to
9719 build and compute expressions that may involve variables in your program.
9722 @kindex info frame@r{, show the source language}
9723 Display the source language for this frame. This language becomes the
9724 working language if you use an identifier from this frame.
9725 @xref{Frame Info, ,Information about a Frame}, to identify the other
9726 information listed here.
9729 @kindex info source@r{, show the source language}
9730 Display the source language of this source file.
9731 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9732 information listed here.
9735 In unusual circumstances, you may have source files with extensions
9736 not in the standard list. You can then set the extension associated
9737 with a language explicitly:
9740 @item set extension-language @var{ext} @var{language}
9741 @kindex set extension-language
9742 Tell @value{GDBN} that source files with extension @var{ext} are to be
9743 assumed as written in the source language @var{language}.
9745 @item info extensions
9746 @kindex info extensions
9747 List all the filename extensions and the associated languages.
9751 @section Type and Range Checking
9754 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9755 checking are included, but they do not yet have any effect. This
9756 section documents the intended facilities.
9758 @c FIXME remove warning when type/range code added
9760 Some languages are designed to guard you against making seemingly common
9761 errors through a series of compile- and run-time checks. These include
9762 checking the type of arguments to functions and operators, and making
9763 sure mathematical overflows are caught at run time. Checks such as
9764 these help to ensure a program's correctness once it has been compiled
9765 by eliminating type mismatches, and providing active checks for range
9766 errors when your program is running.
9768 @value{GDBN} can check for conditions like the above if you wish.
9769 Although @value{GDBN} does not check the statements in your program,
9770 it can check expressions entered directly into @value{GDBN} for
9771 evaluation via the @code{print} command, for example. As with the
9772 working language, @value{GDBN} can also decide whether or not to check
9773 automatically based on your program's source language.
9774 @xref{Supported Languages, ,Supported Languages}, for the default
9775 settings of supported languages.
9778 * Type Checking:: An overview of type checking
9779 * Range Checking:: An overview of range checking
9782 @cindex type checking
9783 @cindex checks, type
9785 @subsection An Overview of Type Checking
9787 Some languages, such as Modula-2, are strongly typed, meaning that the
9788 arguments to operators and functions have to be of the correct type,
9789 otherwise an error occurs. These checks prevent type mismatch
9790 errors from ever causing any run-time problems. For example,
9798 The second example fails because the @code{CARDINAL} 1 is not
9799 type-compatible with the @code{REAL} 2.3.
9801 For the expressions you use in @value{GDBN} commands, you can tell the
9802 @value{GDBN} type checker to skip checking;
9803 to treat any mismatches as errors and abandon the expression;
9804 or to only issue warnings when type mismatches occur,
9805 but evaluate the expression anyway. When you choose the last of
9806 these, @value{GDBN} evaluates expressions like the second example above, but
9807 also issues a warning.
9809 Even if you turn type checking off, there may be other reasons
9810 related to type that prevent @value{GDBN} from evaluating an expression.
9811 For instance, @value{GDBN} does not know how to add an @code{int} and
9812 a @code{struct foo}. These particular type errors have nothing to do
9813 with the language in use, and usually arise from expressions, such as
9814 the one described above, which make little sense to evaluate anyway.
9816 Each language defines to what degree it is strict about type. For
9817 instance, both Modula-2 and C require the arguments to arithmetical
9818 operators to be numbers. In C, enumerated types and pointers can be
9819 represented as numbers, so that they are valid arguments to mathematical
9820 operators. @xref{Supported Languages, ,Supported Languages}, for further
9821 details on specific languages.
9823 @value{GDBN} provides some additional commands for controlling the type checker:
9825 @kindex set check type
9826 @kindex show check type
9828 @item set check type auto
9829 Set type checking on or off based on the current working language.
9830 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9833 @item set check type on
9834 @itemx set check type off
9835 Set type checking on or off, overriding the default setting for the
9836 current working language. Issue a warning if the setting does not
9837 match the language default. If any type mismatches occur in
9838 evaluating an expression while type checking is on, @value{GDBN} prints a
9839 message and aborts evaluation of the expression.
9841 @item set check type warn
9842 Cause the type checker to issue warnings, but to always attempt to
9843 evaluate the expression. Evaluating the expression may still
9844 be impossible for other reasons. For example, @value{GDBN} cannot add
9845 numbers and structures.
9848 Show the current setting of the type checker, and whether or not @value{GDBN}
9849 is setting it automatically.
9852 @cindex range checking
9853 @cindex checks, range
9854 @node Range Checking
9855 @subsection An Overview of Range Checking
9857 In some languages (such as Modula-2), it is an error to exceed the
9858 bounds of a type; this is enforced with run-time checks. Such range
9859 checking is meant to ensure program correctness by making sure
9860 computations do not overflow, or indices on an array element access do
9861 not exceed the bounds of the array.
9863 For expressions you use in @value{GDBN} commands, you can tell
9864 @value{GDBN} to treat range errors in one of three ways: ignore them,
9865 always treat them as errors and abandon the expression, or issue
9866 warnings but evaluate the expression anyway.
9868 A range error can result from numerical overflow, from exceeding an
9869 array index bound, or when you type a constant that is not a member
9870 of any type. Some languages, however, do not treat overflows as an
9871 error. In many implementations of C, mathematical overflow causes the
9872 result to ``wrap around'' to lower values---for example, if @var{m} is
9873 the largest integer value, and @var{s} is the smallest, then
9876 @var{m} + 1 @result{} @var{s}
9879 This, too, is specific to individual languages, and in some cases
9880 specific to individual compilers or machines. @xref{Supported Languages, ,
9881 Supported Languages}, for further details on specific languages.
9883 @value{GDBN} provides some additional commands for controlling the range checker:
9885 @kindex set check range
9886 @kindex show check range
9888 @item set check range auto
9889 Set range checking on or off based on the current working language.
9890 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9893 @item set check range on
9894 @itemx set check range off
9895 Set range checking on or off, overriding the default setting for the
9896 current working language. A warning is issued if the setting does not
9897 match the language default. If a range error occurs and range checking is on,
9898 then a message is printed and evaluation of the expression is aborted.
9900 @item set check range warn
9901 Output messages when the @value{GDBN} range checker detects a range error,
9902 but attempt to evaluate the expression anyway. Evaluating the
9903 expression may still be impossible for other reasons, such as accessing
9904 memory that the process does not own (a typical example from many Unix
9908 Show the current setting of the range checker, and whether or not it is
9909 being set automatically by @value{GDBN}.
9912 @node Supported Languages
9913 @section Supported Languages
9915 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9916 assembly, Modula-2, and Ada.
9917 @c This is false ...
9918 Some @value{GDBN} features may be used in expressions regardless of the
9919 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9920 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9921 ,Expressions}) can be used with the constructs of any supported
9924 The following sections detail to what degree each source language is
9925 supported by @value{GDBN}. These sections are not meant to be language
9926 tutorials or references, but serve only as a reference guide to what the
9927 @value{GDBN} expression parser accepts, and what input and output
9928 formats should look like for different languages. There are many good
9929 books written on each of these languages; please look to these for a
9930 language reference or tutorial.
9934 * Objective-C:: Objective-C
9937 * Modula-2:: Modula-2
9942 @subsection C and C@t{++}
9944 @cindex C and C@t{++}
9945 @cindex expressions in C or C@t{++}
9947 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9948 to both languages. Whenever this is the case, we discuss those languages
9952 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9953 @cindex @sc{gnu} C@t{++}
9954 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9955 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9956 effectively, you must compile your C@t{++} programs with a supported
9957 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9958 compiler (@code{aCC}).
9960 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9961 format; if it doesn't work on your system, try the stabs+ debugging
9962 format. You can select those formats explicitly with the @code{g++}
9963 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9964 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9965 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9968 * C Operators:: C and C@t{++} operators
9969 * C Constants:: C and C@t{++} constants
9970 * C Plus Plus Expressions:: C@t{++} expressions
9971 * C Defaults:: Default settings for C and C@t{++}
9972 * C Checks:: C and C@t{++} type and range checks
9973 * Debugging C:: @value{GDBN} and C
9974 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9975 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9979 @subsubsection C and C@t{++} Operators
9981 @cindex C and C@t{++} operators
9983 Operators must be defined on values of specific types. For instance,
9984 @code{+} is defined on numbers, but not on structures. Operators are
9985 often defined on groups of types.
9987 For the purposes of C and C@t{++}, the following definitions hold:
9992 @emph{Integral types} include @code{int} with any of its storage-class
9993 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9996 @emph{Floating-point types} include @code{float}, @code{double}, and
9997 @code{long double} (if supported by the target platform).
10000 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
10003 @emph{Scalar types} include all of the above.
10008 The following operators are supported. They are listed here
10009 in order of increasing precedence:
10013 The comma or sequencing operator. Expressions in a comma-separated list
10014 are evaluated from left to right, with the result of the entire
10015 expression being the last expression evaluated.
10018 Assignment. The value of an assignment expression is the value
10019 assigned. Defined on scalar types.
10022 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
10023 and translated to @w{@code{@var{a} = @var{a op b}}}.
10024 @w{@code{@var{op}=}} and @code{=} have the same precedence.
10025 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
10026 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
10029 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
10030 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
10034 Logical @sc{or}. Defined on integral types.
10037 Logical @sc{and}. Defined on integral types.
10040 Bitwise @sc{or}. Defined on integral types.
10043 Bitwise exclusive-@sc{or}. Defined on integral types.
10046 Bitwise @sc{and}. Defined on integral types.
10049 Equality and inequality. Defined on scalar types. The value of these
10050 expressions is 0 for false and non-zero for true.
10052 @item <@r{, }>@r{, }<=@r{, }>=
10053 Less than, greater than, less than or equal, greater than or equal.
10054 Defined on scalar types. The value of these expressions is 0 for false
10055 and non-zero for true.
10058 left shift, and right shift. Defined on integral types.
10061 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10064 Addition and subtraction. Defined on integral types, floating-point types and
10067 @item *@r{, }/@r{, }%
10068 Multiplication, division, and modulus. Multiplication and division are
10069 defined on integral and floating-point types. Modulus is defined on
10073 Increment and decrement. When appearing before a variable, the
10074 operation is performed before the variable is used in an expression;
10075 when appearing after it, the variable's value is used before the
10076 operation takes place.
10079 Pointer dereferencing. Defined on pointer types. Same precedence as
10083 Address operator. Defined on variables. Same precedence as @code{++}.
10085 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
10086 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
10087 to examine the address
10088 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
10092 Negative. Defined on integral and floating-point types. Same
10093 precedence as @code{++}.
10096 Logical negation. Defined on integral types. Same precedence as
10100 Bitwise complement operator. Defined on integral types. Same precedence as
10105 Structure member, and pointer-to-structure member. For convenience,
10106 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10107 pointer based on the stored type information.
10108 Defined on @code{struct} and @code{union} data.
10111 Dereferences of pointers to members.
10114 Array indexing. @code{@var{a}[@var{i}]} is defined as
10115 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10118 Function parameter list. Same precedence as @code{->}.
10121 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10122 and @code{class} types.
10125 Doubled colons also represent the @value{GDBN} scope operator
10126 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10130 If an operator is redefined in the user code, @value{GDBN} usually
10131 attempts to invoke the redefined version instead of using the operator's
10132 predefined meaning.
10135 @subsubsection C and C@t{++} Constants
10137 @cindex C and C@t{++} constants
10139 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10144 Integer constants are a sequence of digits. Octal constants are
10145 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10146 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10147 @samp{l}, specifying that the constant should be treated as a
10151 Floating point constants are a sequence of digits, followed by a decimal
10152 point, followed by a sequence of digits, and optionally followed by an
10153 exponent. An exponent is of the form:
10154 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10155 sequence of digits. The @samp{+} is optional for positive exponents.
10156 A floating-point constant may also end with a letter @samp{f} or
10157 @samp{F}, specifying that the constant should be treated as being of
10158 the @code{float} (as opposed to the default @code{double}) type; or with
10159 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10163 Enumerated constants consist of enumerated identifiers, or their
10164 integral equivalents.
10167 Character constants are a single character surrounded by single quotes
10168 (@code{'}), or a number---the ordinal value of the corresponding character
10169 (usually its @sc{ascii} value). Within quotes, the single character may
10170 be represented by a letter or by @dfn{escape sequences}, which are of
10171 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10172 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10173 @samp{@var{x}} is a predefined special character---for example,
10174 @samp{\n} for newline.
10177 String constants are a sequence of character constants surrounded by
10178 double quotes (@code{"}). Any valid character constant (as described
10179 above) may appear. Double quotes within the string must be preceded by
10180 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10184 Pointer constants are an integral value. You can also write pointers
10185 to constants using the C operator @samp{&}.
10188 Array constants are comma-separated lists surrounded by braces @samp{@{}
10189 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10190 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10191 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10194 @node C Plus Plus Expressions
10195 @subsubsection C@t{++} Expressions
10197 @cindex expressions in C@t{++}
10198 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10200 @cindex debugging C@t{++} programs
10201 @cindex C@t{++} compilers
10202 @cindex debug formats and C@t{++}
10203 @cindex @value{NGCC} and C@t{++}
10205 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10206 proper compiler and the proper debug format. Currently, @value{GDBN}
10207 works best when debugging C@t{++} code that is compiled with
10208 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10209 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10210 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10211 stabs+ as their default debug format, so you usually don't need to
10212 specify a debug format explicitly. Other compilers and/or debug formats
10213 are likely to work badly or not at all when using @value{GDBN} to debug
10219 @cindex member functions
10221 Member function calls are allowed; you can use expressions like
10224 count = aml->GetOriginal(x, y)
10227 @vindex this@r{, inside C@t{++} member functions}
10228 @cindex namespace in C@t{++}
10230 While a member function is active (in the selected stack frame), your
10231 expressions have the same namespace available as the member function;
10232 that is, @value{GDBN} allows implicit references to the class instance
10233 pointer @code{this} following the same rules as C@t{++}.
10235 @cindex call overloaded functions
10236 @cindex overloaded functions, calling
10237 @cindex type conversions in C@t{++}
10239 You can call overloaded functions; @value{GDBN} resolves the function
10240 call to the right definition, with some restrictions. @value{GDBN} does not
10241 perform overload resolution involving user-defined type conversions,
10242 calls to constructors, or instantiations of templates that do not exist
10243 in the program. It also cannot handle ellipsis argument lists or
10246 It does perform integral conversions and promotions, floating-point
10247 promotions, arithmetic conversions, pointer conversions, conversions of
10248 class objects to base classes, and standard conversions such as those of
10249 functions or arrays to pointers; it requires an exact match on the
10250 number of function arguments.
10252 Overload resolution is always performed, unless you have specified
10253 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10254 ,@value{GDBN} Features for C@t{++}}.
10256 You must specify @code{set overload-resolution off} in order to use an
10257 explicit function signature to call an overloaded function, as in
10259 p 'foo(char,int)'('x', 13)
10262 The @value{GDBN} command-completion facility can simplify this;
10263 see @ref{Completion, ,Command Completion}.
10265 @cindex reference declarations
10267 @value{GDBN} understands variables declared as C@t{++} references; you can use
10268 them in expressions just as you do in C@t{++} source---they are automatically
10271 In the parameter list shown when @value{GDBN} displays a frame, the values of
10272 reference variables are not displayed (unlike other variables); this
10273 avoids clutter, since references are often used for large structures.
10274 The @emph{address} of a reference variable is always shown, unless
10275 you have specified @samp{set print address off}.
10278 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10279 expressions can use it just as expressions in your program do. Since
10280 one scope may be defined in another, you can use @code{::} repeatedly if
10281 necessary, for example in an expression like
10282 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10283 resolving name scope by reference to source files, in both C and C@t{++}
10284 debugging (@pxref{Variables, ,Program Variables}).
10287 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10288 calling virtual functions correctly, printing out virtual bases of
10289 objects, calling functions in a base subobject, casting objects, and
10290 invoking user-defined operators.
10293 @subsubsection C and C@t{++} Defaults
10295 @cindex C and C@t{++} defaults
10297 If you allow @value{GDBN} to set type and range checking automatically, they
10298 both default to @code{off} whenever the working language changes to
10299 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10300 selects the working language.
10302 If you allow @value{GDBN} to set the language automatically, it
10303 recognizes source files whose names end with @file{.c}, @file{.C}, or
10304 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10305 these files, it sets the working language to C or C@t{++}.
10306 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10307 for further details.
10309 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10310 @c unimplemented. If (b) changes, it might make sense to let this node
10311 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10314 @subsubsection C and C@t{++} Type and Range Checks
10316 @cindex C and C@t{++} checks
10318 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10319 is not used. However, if you turn type checking on, @value{GDBN}
10320 considers two variables type equivalent if:
10324 The two variables are structured and have the same structure, union, or
10328 The two variables have the same type name, or types that have been
10329 declared equivalent through @code{typedef}.
10332 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10335 The two @code{struct}, @code{union}, or @code{enum} variables are
10336 declared in the same declaration. (Note: this may not be true for all C
10341 Range checking, if turned on, is done on mathematical operations. Array
10342 indices are not checked, since they are often used to index a pointer
10343 that is not itself an array.
10346 @subsubsection @value{GDBN} and C
10348 The @code{set print union} and @code{show print union} commands apply to
10349 the @code{union} type. When set to @samp{on}, any @code{union} that is
10350 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10351 appears as @samp{@{...@}}.
10353 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10354 with pointers and a memory allocation function. @xref{Expressions,
10357 @node Debugging C Plus Plus
10358 @subsubsection @value{GDBN} Features for C@t{++}
10360 @cindex commands for C@t{++}
10362 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10363 designed specifically for use with C@t{++}. Here is a summary:
10366 @cindex break in overloaded functions
10367 @item @r{breakpoint menus}
10368 When you want a breakpoint in a function whose name is overloaded,
10369 @value{GDBN} has the capability to display a menu of possible breakpoint
10370 locations to help you specify which function definition you want.
10371 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10373 @cindex overloading in C@t{++}
10374 @item rbreak @var{regex}
10375 Setting breakpoints using regular expressions is helpful for setting
10376 breakpoints on overloaded functions that are not members of any special
10378 @xref{Set Breaks, ,Setting Breakpoints}.
10380 @cindex C@t{++} exception handling
10383 Debug C@t{++} exception handling using these commands. @xref{Set
10384 Catchpoints, , Setting Catchpoints}.
10386 @cindex inheritance
10387 @item ptype @var{typename}
10388 Print inheritance relationships as well as other information for type
10390 @xref{Symbols, ,Examining the Symbol Table}.
10392 @cindex C@t{++} symbol display
10393 @item set print demangle
10394 @itemx show print demangle
10395 @itemx set print asm-demangle
10396 @itemx show print asm-demangle
10397 Control whether C@t{++} symbols display in their source form, both when
10398 displaying code as C@t{++} source and when displaying disassemblies.
10399 @xref{Print Settings, ,Print Settings}.
10401 @item set print object
10402 @itemx show print object
10403 Choose whether to print derived (actual) or declared types of objects.
10404 @xref{Print Settings, ,Print Settings}.
10406 @item set print vtbl
10407 @itemx show print vtbl
10408 Control the format for printing virtual function tables.
10409 @xref{Print Settings, ,Print Settings}.
10410 (The @code{vtbl} commands do not work on programs compiled with the HP
10411 ANSI C@t{++} compiler (@code{aCC}).)
10413 @kindex set overload-resolution
10414 @cindex overloaded functions, overload resolution
10415 @item set overload-resolution on
10416 Enable overload resolution for C@t{++} expression evaluation. The default
10417 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10418 and searches for a function whose signature matches the argument types,
10419 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10420 Expressions, ,C@t{++} Expressions}, for details).
10421 If it cannot find a match, it emits a message.
10423 @item set overload-resolution off
10424 Disable overload resolution for C@t{++} expression evaluation. For
10425 overloaded functions that are not class member functions, @value{GDBN}
10426 chooses the first function of the specified name that it finds in the
10427 symbol table, whether or not its arguments are of the correct type. For
10428 overloaded functions that are class member functions, @value{GDBN}
10429 searches for a function whose signature @emph{exactly} matches the
10432 @kindex show overload-resolution
10433 @item show overload-resolution
10434 Show the current setting of overload resolution.
10436 @item @r{Overloaded symbol names}
10437 You can specify a particular definition of an overloaded symbol, using
10438 the same notation that is used to declare such symbols in C@t{++}: type
10439 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10440 also use the @value{GDBN} command-line word completion facilities to list the
10441 available choices, or to finish the type list for you.
10442 @xref{Completion,, Command Completion}, for details on how to do this.
10445 @node Decimal Floating Point
10446 @subsubsection Decimal Floating Point format
10447 @cindex decimal floating point format
10449 @value{GDBN} can examine, set and perform computations with numbers in
10450 decimal floating point format, which in the C language correspond to the
10451 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
10452 specified by the extension to support decimal floating-point arithmetic.
10454 There are two encodings in use, depending on the architecture: BID (Binary
10455 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10456 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10459 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10460 to manipulate decimal floating point numbers, it is not possible to convert
10461 (using a cast, for example) integers wider than 32-bit to decimal float.
10463 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10464 point computations, error checking in decimal float operations ignores
10465 underflow, overflow and divide by zero exceptions.
10467 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10468 to inspect @code{_Decimal128} values stored in floating point registers. See
10469 @ref{PowerPC,,PowerPC} for more details.
10472 @subsection Objective-C
10474 @cindex Objective-C
10475 This section provides information about some commands and command
10476 options that are useful for debugging Objective-C code. See also
10477 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10478 few more commands specific to Objective-C support.
10481 * Method Names in Commands::
10482 * The Print Command with Objective-C::
10485 @node Method Names in Commands
10486 @subsubsection Method Names in Commands
10488 The following commands have been extended to accept Objective-C method
10489 names as line specifications:
10491 @kindex clear@r{, and Objective-C}
10492 @kindex break@r{, and Objective-C}
10493 @kindex info line@r{, and Objective-C}
10494 @kindex jump@r{, and Objective-C}
10495 @kindex list@r{, and Objective-C}
10499 @item @code{info line}
10504 A fully qualified Objective-C method name is specified as
10507 -[@var{Class} @var{methodName}]
10510 where the minus sign is used to indicate an instance method and a
10511 plus sign (not shown) is used to indicate a class method. The class
10512 name @var{Class} and method name @var{methodName} are enclosed in
10513 brackets, similar to the way messages are specified in Objective-C
10514 source code. For example, to set a breakpoint at the @code{create}
10515 instance method of class @code{Fruit} in the program currently being
10519 break -[Fruit create]
10522 To list ten program lines around the @code{initialize} class method,
10526 list +[NSText initialize]
10529 In the current version of @value{GDBN}, the plus or minus sign is
10530 required. In future versions of @value{GDBN}, the plus or minus
10531 sign will be optional, but you can use it to narrow the search. It
10532 is also possible to specify just a method name:
10538 You must specify the complete method name, including any colons. If
10539 your program's source files contain more than one @code{create} method,
10540 you'll be presented with a numbered list of classes that implement that
10541 method. Indicate your choice by number, or type @samp{0} to exit if
10544 As another example, to clear a breakpoint established at the
10545 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10548 clear -[NSWindow makeKeyAndOrderFront:]
10551 @node The Print Command with Objective-C
10552 @subsubsection The Print Command With Objective-C
10553 @cindex Objective-C, print objects
10554 @kindex print-object
10555 @kindex po @r{(@code{print-object})}
10557 The print command has also been extended to accept methods. For example:
10560 print -[@var{object} hash]
10563 @cindex print an Objective-C object description
10564 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10566 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10567 and print the result. Also, an additional command has been added,
10568 @code{print-object} or @code{po} for short, which is meant to print
10569 the description of an object. However, this command may only work
10570 with certain Objective-C libraries that have a particular hook
10571 function, @code{_NSPrintForDebugger}, defined.
10574 @subsection Fortran
10575 @cindex Fortran-specific support in @value{GDBN}
10577 @value{GDBN} can be used to debug programs written in Fortran, but it
10578 currently supports only the features of Fortran 77 language.
10580 @cindex trailing underscore, in Fortran symbols
10581 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10582 among them) append an underscore to the names of variables and
10583 functions. When you debug programs compiled by those compilers, you
10584 will need to refer to variables and functions with a trailing
10588 * Fortran Operators:: Fortran operators and expressions
10589 * Fortran Defaults:: Default settings for Fortran
10590 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10593 @node Fortran Operators
10594 @subsubsection Fortran Operators and Expressions
10596 @cindex Fortran operators and expressions
10598 Operators must be defined on values of specific types. For instance,
10599 @code{+} is defined on numbers, but not on characters or other non-
10600 arithmetic types. Operators are often defined on groups of types.
10604 The exponentiation operator. It raises the first operand to the power
10608 The range operator. Normally used in the form of array(low:high) to
10609 represent a section of array.
10612 The access component operator. Normally used to access elements in derived
10613 types. Also suitable for unions. As unions aren't part of regular Fortran,
10614 this can only happen when accessing a register that uses a gdbarch-defined
10618 @node Fortran Defaults
10619 @subsubsection Fortran Defaults
10621 @cindex Fortran Defaults
10623 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10624 default uses case-insensitive matches for Fortran symbols. You can
10625 change that with the @samp{set case-insensitive} command, see
10626 @ref{Symbols}, for the details.
10628 @node Special Fortran Commands
10629 @subsubsection Special Fortran Commands
10631 @cindex Special Fortran commands
10633 @value{GDBN} has some commands to support Fortran-specific features,
10634 such as displaying common blocks.
10637 @cindex @code{COMMON} blocks, Fortran
10638 @kindex info common
10639 @item info common @r{[}@var{common-name}@r{]}
10640 This command prints the values contained in the Fortran @code{COMMON}
10641 block whose name is @var{common-name}. With no argument, the names of
10642 all @code{COMMON} blocks visible at the current program location are
10649 @cindex Pascal support in @value{GDBN}, limitations
10650 Debugging Pascal programs which use sets, subranges, file variables, or
10651 nested functions does not currently work. @value{GDBN} does not support
10652 entering expressions, printing values, or similar features using Pascal
10655 The Pascal-specific command @code{set print pascal_static-members}
10656 controls whether static members of Pascal objects are displayed.
10657 @xref{Print Settings, pascal_static-members}.
10660 @subsection Modula-2
10662 @cindex Modula-2, @value{GDBN} support
10664 The extensions made to @value{GDBN} to support Modula-2 only support
10665 output from the @sc{gnu} Modula-2 compiler (which is currently being
10666 developed). Other Modula-2 compilers are not currently supported, and
10667 attempting to debug executables produced by them is most likely
10668 to give an error as @value{GDBN} reads in the executable's symbol
10671 @cindex expressions in Modula-2
10673 * M2 Operators:: Built-in operators
10674 * Built-In Func/Proc:: Built-in functions and procedures
10675 * M2 Constants:: Modula-2 constants
10676 * M2 Types:: Modula-2 types
10677 * M2 Defaults:: Default settings for Modula-2
10678 * Deviations:: Deviations from standard Modula-2
10679 * M2 Checks:: Modula-2 type and range checks
10680 * M2 Scope:: The scope operators @code{::} and @code{.}
10681 * GDB/M2:: @value{GDBN} and Modula-2
10685 @subsubsection Operators
10686 @cindex Modula-2 operators
10688 Operators must be defined on values of specific types. For instance,
10689 @code{+} is defined on numbers, but not on structures. Operators are
10690 often defined on groups of types. For the purposes of Modula-2, the
10691 following definitions hold:
10696 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10700 @emph{Character types} consist of @code{CHAR} and its subranges.
10703 @emph{Floating-point types} consist of @code{REAL}.
10706 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10710 @emph{Scalar types} consist of all of the above.
10713 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10716 @emph{Boolean types} consist of @code{BOOLEAN}.
10720 The following operators are supported, and appear in order of
10721 increasing precedence:
10725 Function argument or array index separator.
10728 Assignment. The value of @var{var} @code{:=} @var{value} is
10732 Less than, greater than on integral, floating-point, or enumerated
10736 Less than or equal to, greater than or equal to
10737 on integral, floating-point and enumerated types, or set inclusion on
10738 set types. Same precedence as @code{<}.
10740 @item =@r{, }<>@r{, }#
10741 Equality and two ways of expressing inequality, valid on scalar types.
10742 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10743 available for inequality, since @code{#} conflicts with the script
10747 Set membership. Defined on set types and the types of their members.
10748 Same precedence as @code{<}.
10751 Boolean disjunction. Defined on boolean types.
10754 Boolean conjunction. Defined on boolean types.
10757 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10760 Addition and subtraction on integral and floating-point types, or union
10761 and difference on set types.
10764 Multiplication on integral and floating-point types, or set intersection
10768 Division on floating-point types, or symmetric set difference on set
10769 types. Same precedence as @code{*}.
10772 Integer division and remainder. Defined on integral types. Same
10773 precedence as @code{*}.
10776 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10779 Pointer dereferencing. Defined on pointer types.
10782 Boolean negation. Defined on boolean types. Same precedence as
10786 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10787 precedence as @code{^}.
10790 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10793 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10797 @value{GDBN} and Modula-2 scope operators.
10801 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10802 treats the use of the operator @code{IN}, or the use of operators
10803 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10804 @code{<=}, and @code{>=} on sets as an error.
10808 @node Built-In Func/Proc
10809 @subsubsection Built-in Functions and Procedures
10810 @cindex Modula-2 built-ins
10812 Modula-2 also makes available several built-in procedures and functions.
10813 In describing these, the following metavariables are used:
10818 represents an @code{ARRAY} variable.
10821 represents a @code{CHAR} constant or variable.
10824 represents a variable or constant of integral type.
10827 represents an identifier that belongs to a set. Generally used in the
10828 same function with the metavariable @var{s}. The type of @var{s} should
10829 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10832 represents a variable or constant of integral or floating-point type.
10835 represents a variable or constant of floating-point type.
10841 represents a variable.
10844 represents a variable or constant of one of many types. See the
10845 explanation of the function for details.
10848 All Modula-2 built-in procedures also return a result, described below.
10852 Returns the absolute value of @var{n}.
10855 If @var{c} is a lower case letter, it returns its upper case
10856 equivalent, otherwise it returns its argument.
10859 Returns the character whose ordinal value is @var{i}.
10862 Decrements the value in the variable @var{v} by one. Returns the new value.
10864 @item DEC(@var{v},@var{i})
10865 Decrements the value in the variable @var{v} by @var{i}. Returns the
10868 @item EXCL(@var{m},@var{s})
10869 Removes the element @var{m} from the set @var{s}. Returns the new
10872 @item FLOAT(@var{i})
10873 Returns the floating point equivalent of the integer @var{i}.
10875 @item HIGH(@var{a})
10876 Returns the index of the last member of @var{a}.
10879 Increments the value in the variable @var{v} by one. Returns the new value.
10881 @item INC(@var{v},@var{i})
10882 Increments the value in the variable @var{v} by @var{i}. Returns the
10885 @item INCL(@var{m},@var{s})
10886 Adds the element @var{m} to the set @var{s} if it is not already
10887 there. Returns the new set.
10890 Returns the maximum value of the type @var{t}.
10893 Returns the minimum value of the type @var{t}.
10896 Returns boolean TRUE if @var{i} is an odd number.
10899 Returns the ordinal value of its argument. For example, the ordinal
10900 value of a character is its @sc{ascii} value (on machines supporting the
10901 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10902 integral, character and enumerated types.
10904 @item SIZE(@var{x})
10905 Returns the size of its argument. @var{x} can be a variable or a type.
10907 @item TRUNC(@var{r})
10908 Returns the integral part of @var{r}.
10910 @item TSIZE(@var{x})
10911 Returns the size of its argument. @var{x} can be a variable or a type.
10913 @item VAL(@var{t},@var{i})
10914 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10918 @emph{Warning:} Sets and their operations are not yet supported, so
10919 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10923 @cindex Modula-2 constants
10925 @subsubsection Constants
10927 @value{GDBN} allows you to express the constants of Modula-2 in the following
10933 Integer constants are simply a sequence of digits. When used in an
10934 expression, a constant is interpreted to be type-compatible with the
10935 rest of the expression. Hexadecimal integers are specified by a
10936 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10939 Floating point constants appear as a sequence of digits, followed by a
10940 decimal point and another sequence of digits. An optional exponent can
10941 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10942 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10943 digits of the floating point constant must be valid decimal (base 10)
10947 Character constants consist of a single character enclosed by a pair of
10948 like quotes, either single (@code{'}) or double (@code{"}). They may
10949 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10950 followed by a @samp{C}.
10953 String constants consist of a sequence of characters enclosed by a
10954 pair of like quotes, either single (@code{'}) or double (@code{"}).
10955 Escape sequences in the style of C are also allowed. @xref{C
10956 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10960 Enumerated constants consist of an enumerated identifier.
10963 Boolean constants consist of the identifiers @code{TRUE} and
10967 Pointer constants consist of integral values only.
10970 Set constants are not yet supported.
10974 @subsubsection Modula-2 Types
10975 @cindex Modula-2 types
10977 Currently @value{GDBN} can print the following data types in Modula-2
10978 syntax: array types, record types, set types, pointer types, procedure
10979 types, enumerated types, subrange types and base types. You can also
10980 print the contents of variables declared using these type.
10981 This section gives a number of simple source code examples together with
10982 sample @value{GDBN} sessions.
10984 The first example contains the following section of code:
10993 and you can request @value{GDBN} to interrogate the type and value of
10994 @code{r} and @code{s}.
10997 (@value{GDBP}) print s
10999 (@value{GDBP}) ptype s
11001 (@value{GDBP}) print r
11003 (@value{GDBP}) ptype r
11008 Likewise if your source code declares @code{s} as:
11012 s: SET ['A'..'Z'] ;
11016 then you may query the type of @code{s} by:
11019 (@value{GDBP}) ptype s
11020 type = SET ['A'..'Z']
11024 Note that at present you cannot interactively manipulate set
11025 expressions using the debugger.
11027 The following example shows how you might declare an array in Modula-2
11028 and how you can interact with @value{GDBN} to print its type and contents:
11032 s: ARRAY [-10..10] OF CHAR ;
11036 (@value{GDBP}) ptype s
11037 ARRAY [-10..10] OF CHAR
11040 Note that the array handling is not yet complete and although the type
11041 is printed correctly, expression handling still assumes that all
11042 arrays have a lower bound of zero and not @code{-10} as in the example
11045 Here are some more type related Modula-2 examples:
11049 colour = (blue, red, yellow, green) ;
11050 t = [blue..yellow] ;
11058 The @value{GDBN} interaction shows how you can query the data type
11059 and value of a variable.
11062 (@value{GDBP}) print s
11064 (@value{GDBP}) ptype t
11065 type = [blue..yellow]
11069 In this example a Modula-2 array is declared and its contents
11070 displayed. Observe that the contents are written in the same way as
11071 their @code{C} counterparts.
11075 s: ARRAY [1..5] OF CARDINAL ;
11081 (@value{GDBP}) print s
11082 $1 = @{1, 0, 0, 0, 0@}
11083 (@value{GDBP}) ptype s
11084 type = ARRAY [1..5] OF CARDINAL
11087 The Modula-2 language interface to @value{GDBN} also understands
11088 pointer types as shown in this example:
11092 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11099 and you can request that @value{GDBN} describes the type of @code{s}.
11102 (@value{GDBP}) ptype s
11103 type = POINTER TO ARRAY [1..5] OF CARDINAL
11106 @value{GDBN} handles compound types as we can see in this example.
11107 Here we combine array types, record types, pointer types and subrange
11118 myarray = ARRAY myrange OF CARDINAL ;
11119 myrange = [-2..2] ;
11121 s: POINTER TO ARRAY myrange OF foo ;
11125 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11129 (@value{GDBP}) ptype s
11130 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11133 f3 : ARRAY [-2..2] OF CARDINAL;
11138 @subsubsection Modula-2 Defaults
11139 @cindex Modula-2 defaults
11141 If type and range checking are set automatically by @value{GDBN}, they
11142 both default to @code{on} whenever the working language changes to
11143 Modula-2. This happens regardless of whether you or @value{GDBN}
11144 selected the working language.
11146 If you allow @value{GDBN} to set the language automatically, then entering
11147 code compiled from a file whose name ends with @file{.mod} sets the
11148 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11149 Infer the Source Language}, for further details.
11152 @subsubsection Deviations from Standard Modula-2
11153 @cindex Modula-2, deviations from
11155 A few changes have been made to make Modula-2 programs easier to debug.
11156 This is done primarily via loosening its type strictness:
11160 Unlike in standard Modula-2, pointer constants can be formed by
11161 integers. This allows you to modify pointer variables during
11162 debugging. (In standard Modula-2, the actual address contained in a
11163 pointer variable is hidden from you; it can only be modified
11164 through direct assignment to another pointer variable or expression that
11165 returned a pointer.)
11168 C escape sequences can be used in strings and characters to represent
11169 non-printable characters. @value{GDBN} prints out strings with these
11170 escape sequences embedded. Single non-printable characters are
11171 printed using the @samp{CHR(@var{nnn})} format.
11174 The assignment operator (@code{:=}) returns the value of its right-hand
11178 All built-in procedures both modify @emph{and} return their argument.
11182 @subsubsection Modula-2 Type and Range Checks
11183 @cindex Modula-2 checks
11186 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11189 @c FIXME remove warning when type/range checks added
11191 @value{GDBN} considers two Modula-2 variables type equivalent if:
11195 They are of types that have been declared equivalent via a @code{TYPE
11196 @var{t1} = @var{t2}} statement
11199 They have been declared on the same line. (Note: This is true of the
11200 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11203 As long as type checking is enabled, any attempt to combine variables
11204 whose types are not equivalent is an error.
11206 Range checking is done on all mathematical operations, assignment, array
11207 index bounds, and all built-in functions and procedures.
11210 @subsubsection The Scope Operators @code{::} and @code{.}
11212 @cindex @code{.}, Modula-2 scope operator
11213 @cindex colon, doubled as scope operator
11215 @vindex colon-colon@r{, in Modula-2}
11216 @c Info cannot handle :: but TeX can.
11219 @vindex ::@r{, in Modula-2}
11222 There are a few subtle differences between the Modula-2 scope operator
11223 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11228 @var{module} . @var{id}
11229 @var{scope} :: @var{id}
11233 where @var{scope} is the name of a module or a procedure,
11234 @var{module} the name of a module, and @var{id} is any declared
11235 identifier within your program, except another module.
11237 Using the @code{::} operator makes @value{GDBN} search the scope
11238 specified by @var{scope} for the identifier @var{id}. If it is not
11239 found in the specified scope, then @value{GDBN} searches all scopes
11240 enclosing the one specified by @var{scope}.
11242 Using the @code{.} operator makes @value{GDBN} search the current scope for
11243 the identifier specified by @var{id} that was imported from the
11244 definition module specified by @var{module}. With this operator, it is
11245 an error if the identifier @var{id} was not imported from definition
11246 module @var{module}, or if @var{id} is not an identifier in
11250 @subsubsection @value{GDBN} and Modula-2
11252 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11253 Five subcommands of @code{set print} and @code{show print} apply
11254 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11255 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11256 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11257 analogue in Modula-2.
11259 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11260 with any language, is not useful with Modula-2. Its
11261 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11262 created in Modula-2 as they can in C or C@t{++}. However, because an
11263 address can be specified by an integral constant, the construct
11264 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11266 @cindex @code{#} in Modula-2
11267 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11268 interpreted as the beginning of a comment. Use @code{<>} instead.
11274 The extensions made to @value{GDBN} for Ada only support
11275 output from the @sc{gnu} Ada (GNAT) compiler.
11276 Other Ada compilers are not currently supported, and
11277 attempting to debug executables produced by them is most likely
11281 @cindex expressions in Ada
11283 * Ada Mode Intro:: General remarks on the Ada syntax
11284 and semantics supported by Ada mode
11286 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11287 * Additions to Ada:: Extensions of the Ada expression syntax.
11288 * Stopping Before Main Program:: Debugging the program during elaboration.
11289 * Ada Tasks:: Listing and setting breakpoints in tasks.
11290 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
11291 * Ada Glitches:: Known peculiarities of Ada mode.
11294 @node Ada Mode Intro
11295 @subsubsection Introduction
11296 @cindex Ada mode, general
11298 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11299 syntax, with some extensions.
11300 The philosophy behind the design of this subset is
11304 That @value{GDBN} should provide basic literals and access to operations for
11305 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11306 leaving more sophisticated computations to subprograms written into the
11307 program (which therefore may be called from @value{GDBN}).
11310 That type safety and strict adherence to Ada language restrictions
11311 are not particularly important to the @value{GDBN} user.
11314 That brevity is important to the @value{GDBN} user.
11317 Thus, for brevity, the debugger acts as if all names declared in
11318 user-written packages are directly visible, even if they are not visible
11319 according to Ada rules, thus making it unnecessary to fully qualify most
11320 names with their packages, regardless of context. Where this causes
11321 ambiguity, @value{GDBN} asks the user's intent.
11323 The debugger will start in Ada mode if it detects an Ada main program.
11324 As for other languages, it will enter Ada mode when stopped in a program that
11325 was translated from an Ada source file.
11327 While in Ada mode, you may use `@t{--}' for comments. This is useful
11328 mostly for documenting command files. The standard @value{GDBN} comment
11329 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11330 middle (to allow based literals).
11332 The debugger supports limited overloading. Given a subprogram call in which
11333 the function symbol has multiple definitions, it will use the number of
11334 actual parameters and some information about their types to attempt to narrow
11335 the set of definitions. It also makes very limited use of context, preferring
11336 procedures to functions in the context of the @code{call} command, and
11337 functions to procedures elsewhere.
11339 @node Omissions from Ada
11340 @subsubsection Omissions from Ada
11341 @cindex Ada, omissions from
11343 Here are the notable omissions from the subset:
11347 Only a subset of the attributes are supported:
11351 @t{'First}, @t{'Last}, and @t{'Length}
11352 on array objects (not on types and subtypes).
11355 @t{'Min} and @t{'Max}.
11358 @t{'Pos} and @t{'Val}.
11364 @t{'Range} on array objects (not subtypes), but only as the right
11365 operand of the membership (@code{in}) operator.
11368 @t{'Access}, @t{'Unchecked_Access}, and
11369 @t{'Unrestricted_Access} (a GNAT extension).
11377 @code{Characters.Latin_1} are not available and
11378 concatenation is not implemented. Thus, escape characters in strings are
11379 not currently available.
11382 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11383 equality of representations. They will generally work correctly
11384 for strings and arrays whose elements have integer or enumeration types.
11385 They may not work correctly for arrays whose element
11386 types have user-defined equality, for arrays of real values
11387 (in particular, IEEE-conformant floating point, because of negative
11388 zeroes and NaNs), and for arrays whose elements contain unused bits with
11389 indeterminate values.
11392 The other component-by-component array operations (@code{and}, @code{or},
11393 @code{xor}, @code{not}, and relational tests other than equality)
11394 are not implemented.
11397 @cindex array aggregates (Ada)
11398 @cindex record aggregates (Ada)
11399 @cindex aggregates (Ada)
11400 There is limited support for array and record aggregates. They are
11401 permitted only on the right sides of assignments, as in these examples:
11404 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
11405 (@value{GDBP}) set An_Array := (1, others => 0)
11406 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11407 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11408 (@value{GDBP}) set A_Record := (1, "Peter", True);
11409 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
11413 discriminant's value by assigning an aggregate has an
11414 undefined effect if that discriminant is used within the record.
11415 However, you can first modify discriminants by directly assigning to
11416 them (which normally would not be allowed in Ada), and then performing an
11417 aggregate assignment. For example, given a variable @code{A_Rec}
11418 declared to have a type such as:
11421 type Rec (Len : Small_Integer := 0) is record
11423 Vals : IntArray (1 .. Len);
11427 you can assign a value with a different size of @code{Vals} with two
11431 (@value{GDBP}) set A_Rec.Len := 4
11432 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11435 As this example also illustrates, @value{GDBN} is very loose about the usual
11436 rules concerning aggregates. You may leave out some of the
11437 components of an array or record aggregate (such as the @code{Len}
11438 component in the assignment to @code{A_Rec} above); they will retain their
11439 original values upon assignment. You may freely use dynamic values as
11440 indices in component associations. You may even use overlapping or
11441 redundant component associations, although which component values are
11442 assigned in such cases is not defined.
11445 Calls to dispatching subprograms are not implemented.
11448 The overloading algorithm is much more limited (i.e., less selective)
11449 than that of real Ada. It makes only limited use of the context in
11450 which a subexpression appears to resolve its meaning, and it is much
11451 looser in its rules for allowing type matches. As a result, some
11452 function calls will be ambiguous, and the user will be asked to choose
11453 the proper resolution.
11456 The @code{new} operator is not implemented.
11459 Entry calls are not implemented.
11462 Aside from printing, arithmetic operations on the native VAX floating-point
11463 formats are not supported.
11466 It is not possible to slice a packed array.
11469 The names @code{True} and @code{False}, when not part of a qualified name,
11470 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
11472 Should your program
11473 redefine these names in a package or procedure (at best a dubious practice),
11474 you will have to use fully qualified names to access their new definitions.
11477 @node Additions to Ada
11478 @subsubsection Additions to Ada
11479 @cindex Ada, deviations from
11481 As it does for other languages, @value{GDBN} makes certain generic
11482 extensions to Ada (@pxref{Expressions}):
11486 If the expression @var{E} is a variable residing in memory (typically
11487 a local variable or array element) and @var{N} is a positive integer,
11488 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11489 @var{N}-1 adjacent variables following it in memory as an array. In
11490 Ada, this operator is generally not necessary, since its prime use is
11491 in displaying parts of an array, and slicing will usually do this in
11492 Ada. However, there are occasional uses when debugging programs in
11493 which certain debugging information has been optimized away.
11496 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11497 appears in function or file @var{B}.'' When @var{B} is a file name,
11498 you must typically surround it in single quotes.
11501 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11502 @var{type} that appears at address @var{addr}.''
11505 A name starting with @samp{$} is a convenience variable
11506 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11509 In addition, @value{GDBN} provides a few other shortcuts and outright
11510 additions specific to Ada:
11514 The assignment statement is allowed as an expression, returning
11515 its right-hand operand as its value. Thus, you may enter
11518 (@value{GDBP}) set x := y + 3
11519 (@value{GDBP}) print A(tmp := y + 1)
11523 The semicolon is allowed as an ``operator,'' returning as its value
11524 the value of its right-hand operand.
11525 This allows, for example,
11526 complex conditional breaks:
11529 (@value{GDBP}) break f
11530 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
11534 Rather than use catenation and symbolic character names to introduce special
11535 characters into strings, one may instead use a special bracket notation,
11536 which is also used to print strings. A sequence of characters of the form
11537 @samp{["@var{XX}"]} within a string or character literal denotes the
11538 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11539 sequence of characters @samp{["""]} also denotes a single quotation mark
11540 in strings. For example,
11542 "One line.["0a"]Next line.["0a"]"
11545 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11549 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11550 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11554 (@value{GDBP}) print 'max(x, y)
11558 When printing arrays, @value{GDBN} uses positional notation when the
11559 array has a lower bound of 1, and uses a modified named notation otherwise.
11560 For example, a one-dimensional array of three integers with a lower bound
11561 of 3 might print as
11568 That is, in contrast to valid Ada, only the first component has a @code{=>}
11572 You may abbreviate attributes in expressions with any unique,
11573 multi-character subsequence of
11574 their names (an exact match gets preference).
11575 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11576 in place of @t{a'length}.
11579 @cindex quoting Ada internal identifiers
11580 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11581 to lower case. The GNAT compiler uses upper-case characters for
11582 some of its internal identifiers, which are normally of no interest to users.
11583 For the rare occasions when you actually have to look at them,
11584 enclose them in angle brackets to avoid the lower-case mapping.
11587 (@value{GDBP}) print <JMPBUF_SAVE>[0]
11591 Printing an object of class-wide type or dereferencing an
11592 access-to-class-wide value will display all the components of the object's
11593 specific type (as indicated by its run-time tag). Likewise, component
11594 selection on such a value will operate on the specific type of the
11599 @node Stopping Before Main Program
11600 @subsubsection Stopping at the Very Beginning
11602 @cindex breakpointing Ada elaboration code
11603 It is sometimes necessary to debug the program during elaboration, and
11604 before reaching the main procedure.
11605 As defined in the Ada Reference
11606 Manual, the elaboration code is invoked from a procedure called
11607 @code{adainit}. To run your program up to the beginning of
11608 elaboration, simply use the following two commands:
11609 @code{tbreak adainit} and @code{run}.
11612 @subsubsection Extensions for Ada Tasks
11613 @cindex Ada, tasking
11615 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
11616 @value{GDBN} provides the following task-related commands:
11621 This command shows a list of current Ada tasks, as in the following example:
11628 (@value{GDBP}) info tasks
11629 ID TID P-ID Pri State Name
11630 1 8088000 0 15 Child Activation Wait main_task
11631 2 80a4000 1 15 Accept Statement b
11632 3 809a800 1 15 Child Activation Wait a
11633 * 4 80ae800 3 15 Runnable c
11638 In this listing, the asterisk before the last task indicates it to be the
11639 task currently being inspected.
11643 Represents @value{GDBN}'s internal task number.
11649 The parent's task ID (@value{GDBN}'s internal task number).
11652 The base priority of the task.
11655 Current state of the task.
11659 The task has been created but has not been activated. It cannot be
11663 The task is not blocked for any reason known to Ada. (It may be waiting
11664 for a mutex, though.) It is conceptually "executing" in normal mode.
11667 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
11668 that were waiting on terminate alternatives have been awakened and have
11669 terminated themselves.
11671 @item Child Activation Wait
11672 The task is waiting for created tasks to complete activation.
11674 @item Accept Statement
11675 The task is waiting on an accept or selective wait statement.
11677 @item Waiting on entry call
11678 The task is waiting on an entry call.
11680 @item Async Select Wait
11681 The task is waiting to start the abortable part of an asynchronous
11685 The task is waiting on a select statement with only a delay
11688 @item Child Termination Wait
11689 The task is sleeping having completed a master within itself, and is
11690 waiting for the tasks dependent on that master to become terminated or
11691 waiting on a terminate Phase.
11693 @item Wait Child in Term Alt
11694 The task is sleeping waiting for tasks on terminate alternatives to
11695 finish terminating.
11697 @item Accepting RV with @var{taskno}
11698 The task is accepting a rendez-vous with the task @var{taskno}.
11702 Name of the task in the program.
11706 @kindex info task @var{taskno}
11707 @item info task @var{taskno}
11708 This command shows detailled informations on the specified task, as in
11709 the following example:
11714 (@value{GDBP}) info tasks
11715 ID TID P-ID Pri State Name
11716 1 8077880 0 15 Child Activation Wait main_task
11717 * 2 807c468 1 15 Runnable task_1
11718 (@value{GDBP}) info task 2
11719 Ada Task: 0x807c468
11722 Parent: 1 (main_task)
11728 @kindex task@r{ (Ada)}
11729 @cindex current Ada task ID
11730 This command prints the ID of the current task.
11736 (@value{GDBP}) info tasks
11737 ID TID P-ID Pri State Name
11738 1 8077870 0 15 Child Activation Wait main_task
11739 * 2 807c458 1 15 Runnable t
11740 (@value{GDBP}) task
11741 [Current task is 2]
11744 @item task @var{taskno}
11745 @cindex Ada task switching
11746 This command is like the @code{thread @var{threadno}}
11747 command (@pxref{Threads}). It switches the context of debugging
11748 from the current task to the given task.
11754 (@value{GDBP}) info tasks
11755 ID TID P-ID Pri State Name
11756 1 8077870 0 15 Child Activation Wait main_task
11757 * 2 807c458 1 15 Runnable t
11758 (@value{GDBP}) task 1
11759 [Switching to task 1]
11760 #0 0x8067726 in pthread_cond_wait ()
11762 #0 0x8067726 in pthread_cond_wait ()
11763 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
11764 #2 0x805cb63 in system.task_primitives.operations.sleep ()
11765 #3 0x806153e in system.tasking.stages.activate_tasks ()
11766 #4 0x804aacc in un () at un.adb:5
11769 @item break @var{linespec} task @var{taskno}
11770 @itemx break @var{linespec} task @var{taskno} if @dots{}
11771 @cindex breakpoints and tasks, in Ada
11772 @cindex task breakpoints, in Ada
11773 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
11774 These commands are like the @code{break @dots{} thread @dots{}}
11775 command (@pxref{Thread Stops}).
11776 @var{linespec} specifies source lines, as described
11777 in @ref{Specify Location}.
11779 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
11780 to specify that you only want @value{GDBN} to stop the program when a
11781 particular Ada task reaches this breakpoint. @var{taskno} is one of the
11782 numeric task identifiers assigned by @value{GDBN}, shown in the first
11783 column of the @samp{info tasks} display.
11785 If you do not specify @samp{task @var{taskno}} when you set a
11786 breakpoint, the breakpoint applies to @emph{all} tasks of your
11789 You can use the @code{task} qualifier on conditional breakpoints as
11790 well; in this case, place @samp{task @var{taskno}} before the
11791 breakpoint condition (before the @code{if}).
11799 (@value{GDBP}) info tasks
11800 ID TID P-ID Pri State Name
11801 1 140022020 0 15 Child Activation Wait main_task
11802 2 140045060 1 15 Accept/Select Wait t2
11803 3 140044840 1 15 Runnable t1
11804 * 4 140056040 1 15 Runnable t3
11805 (@value{GDBP}) b 15 task 2
11806 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
11807 (@value{GDBP}) cont
11812 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
11814 (@value{GDBP}) info tasks
11815 ID TID P-ID Pri State Name
11816 1 140022020 0 15 Child Activation Wait main_task
11817 * 2 140045060 1 15 Runnable t2
11818 3 140044840 1 15 Runnable t1
11819 4 140056040 1 15 Delay Sleep t3
11823 @node Ada Tasks and Core Files
11824 @subsubsection Tasking Support when Debugging Core Files
11825 @cindex Ada tasking and core file debugging
11827 When inspecting a core file, as opposed to debugging a live program,
11828 tasking support may be limited or even unavailable, depending on
11829 the platform being used.
11830 For instance, on x86-linux, the list of tasks is available, but task
11831 switching is not supported. On Tru64, however, task switching will work
11834 On certain platforms, including Tru64, the debugger needs to perform some
11835 memory writes in order to provide Ada tasking support. When inspecting
11836 a core file, this means that the core file must be opened with read-write
11837 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
11838 Under these circumstances, you should make a backup copy of the core
11839 file before inspecting it with @value{GDBN}.
11842 @subsubsection Known Peculiarities of Ada Mode
11843 @cindex Ada, problems
11845 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11846 we know of several problems with and limitations of Ada mode in
11848 some of which will be fixed with planned future releases of the debugger
11849 and the GNU Ada compiler.
11853 Currently, the debugger
11854 has insufficient information to determine whether certain pointers represent
11855 pointers to objects or the objects themselves.
11856 Thus, the user may have to tack an extra @code{.all} after an expression
11857 to get it printed properly.
11860 Static constants that the compiler chooses not to materialize as objects in
11861 storage are invisible to the debugger.
11864 Named parameter associations in function argument lists are ignored (the
11865 argument lists are treated as positional).
11868 Many useful library packages are currently invisible to the debugger.
11871 Fixed-point arithmetic, conversions, input, and output is carried out using
11872 floating-point arithmetic, and may give results that only approximate those on
11876 The GNAT compiler never generates the prefix @code{Standard} for any of
11877 the standard symbols defined by the Ada language. @value{GDBN} knows about
11878 this: it will strip the prefix from names when you use it, and will never
11879 look for a name you have so qualified among local symbols, nor match against
11880 symbols in other packages or subprograms. If you have
11881 defined entities anywhere in your program other than parameters and
11882 local variables whose simple names match names in @code{Standard},
11883 GNAT's lack of qualification here can cause confusion. When this happens,
11884 you can usually resolve the confusion
11885 by qualifying the problematic names with package
11886 @code{Standard} explicitly.
11889 @node Unsupported Languages
11890 @section Unsupported Languages
11892 @cindex unsupported languages
11893 @cindex minimal language
11894 In addition to the other fully-supported programming languages,
11895 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11896 It does not represent a real programming language, but provides a set
11897 of capabilities close to what the C or assembly languages provide.
11898 This should allow most simple operations to be performed while debugging
11899 an application that uses a language currently not supported by @value{GDBN}.
11901 If the language is set to @code{auto}, @value{GDBN} will automatically
11902 select this language if the current frame corresponds to an unsupported
11906 @chapter Examining the Symbol Table
11908 The commands described in this chapter allow you to inquire about the
11909 symbols (names of variables, functions and types) defined in your
11910 program. This information is inherent in the text of your program and
11911 does not change as your program executes. @value{GDBN} finds it in your
11912 program's symbol table, in the file indicated when you started @value{GDBN}
11913 (@pxref{File Options, ,Choosing Files}), or by one of the
11914 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11916 @cindex symbol names
11917 @cindex names of symbols
11918 @cindex quoting names
11919 Occasionally, you may need to refer to symbols that contain unusual
11920 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11921 most frequent case is in referring to static variables in other
11922 source files (@pxref{Variables,,Program Variables}). File names
11923 are recorded in object files as debugging symbols, but @value{GDBN} would
11924 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11925 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11926 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11933 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11936 @cindex case-insensitive symbol names
11937 @cindex case sensitivity in symbol names
11938 @kindex set case-sensitive
11939 @item set case-sensitive on
11940 @itemx set case-sensitive off
11941 @itemx set case-sensitive auto
11942 Normally, when @value{GDBN} looks up symbols, it matches their names
11943 with case sensitivity determined by the current source language.
11944 Occasionally, you may wish to control that. The command @code{set
11945 case-sensitive} lets you do that by specifying @code{on} for
11946 case-sensitive matches or @code{off} for case-insensitive ones. If
11947 you specify @code{auto}, case sensitivity is reset to the default
11948 suitable for the source language. The default is case-sensitive
11949 matches for all languages except for Fortran, for which the default is
11950 case-insensitive matches.
11952 @kindex show case-sensitive
11953 @item show case-sensitive
11954 This command shows the current setting of case sensitivity for symbols
11957 @kindex info address
11958 @cindex address of a symbol
11959 @item info address @var{symbol}
11960 Describe where the data for @var{symbol} is stored. For a register
11961 variable, this says which register it is kept in. For a non-register
11962 local variable, this prints the stack-frame offset at which the variable
11965 Note the contrast with @samp{print &@var{symbol}}, which does not work
11966 at all for a register variable, and for a stack local variable prints
11967 the exact address of the current instantiation of the variable.
11969 @kindex info symbol
11970 @cindex symbol from address
11971 @cindex closest symbol and offset for an address
11972 @item info symbol @var{addr}
11973 Print the name of a symbol which is stored at the address @var{addr}.
11974 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11975 nearest symbol and an offset from it:
11978 (@value{GDBP}) info symbol 0x54320
11979 _initialize_vx + 396 in section .text
11983 This is the opposite of the @code{info address} command. You can use
11984 it to find out the name of a variable or a function given its address.
11986 For dynamically linked executables, the name of executable or shared
11987 library containing the symbol is also printed:
11990 (@value{GDBP}) info symbol 0x400225
11991 _start + 5 in section .text of /tmp/a.out
11992 (@value{GDBP}) info symbol 0x2aaaac2811cf
11993 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
11997 @item whatis [@var{arg}]
11998 Print the data type of @var{arg}, which can be either an expression or
11999 a data type. With no argument, print the data type of @code{$}, the
12000 last value in the value history. If @var{arg} is an expression, it is
12001 not actually evaluated, and any side-effecting operations (such as
12002 assignments or function calls) inside it do not take place. If
12003 @var{arg} is a type name, it may be the name of a type or typedef, or
12004 for C code it may have the form @samp{class @var{class-name}},
12005 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
12006 @samp{enum @var{enum-tag}}.
12007 @xref{Expressions, ,Expressions}.
12010 @item ptype [@var{arg}]
12011 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
12012 detailed description of the type, instead of just the name of the type.
12013 @xref{Expressions, ,Expressions}.
12015 For example, for this variable declaration:
12018 struct complex @{double real; double imag;@} v;
12022 the two commands give this output:
12026 (@value{GDBP}) whatis v
12027 type = struct complex
12028 (@value{GDBP}) ptype v
12029 type = struct complex @{
12037 As with @code{whatis}, using @code{ptype} without an argument refers to
12038 the type of @code{$}, the last value in the value history.
12040 @cindex incomplete type
12041 Sometimes, programs use opaque data types or incomplete specifications
12042 of complex data structure. If the debug information included in the
12043 program does not allow @value{GDBN} to display a full declaration of
12044 the data type, it will say @samp{<incomplete type>}. For example,
12045 given these declarations:
12049 struct foo *fooptr;
12053 but no definition for @code{struct foo} itself, @value{GDBN} will say:
12056 (@value{GDBP}) ptype foo
12057 $1 = <incomplete type>
12061 ``Incomplete type'' is C terminology for data types that are not
12062 completely specified.
12065 @item info types @var{regexp}
12067 Print a brief description of all types whose names match the regular
12068 expression @var{regexp} (or all types in your program, if you supply
12069 no argument). Each complete typename is matched as though it were a
12070 complete line; thus, @samp{i type value} gives information on all
12071 types in your program whose names include the string @code{value}, but
12072 @samp{i type ^value$} gives information only on types whose complete
12073 name is @code{value}.
12075 This command differs from @code{ptype} in two ways: first, like
12076 @code{whatis}, it does not print a detailed description; second, it
12077 lists all source files where a type is defined.
12080 @cindex local variables
12081 @item info scope @var{location}
12082 List all the variables local to a particular scope. This command
12083 accepts a @var{location} argument---a function name, a source line, or
12084 an address preceded by a @samp{*}, and prints all the variables local
12085 to the scope defined by that location. (@xref{Specify Location}, for
12086 details about supported forms of @var{location}.) For example:
12089 (@value{GDBP}) @b{info scope command_line_handler}
12090 Scope for command_line_handler:
12091 Symbol rl is an argument at stack/frame offset 8, length 4.
12092 Symbol linebuffer is in static storage at address 0x150a18, length 4.
12093 Symbol linelength is in static storage at address 0x150a1c, length 4.
12094 Symbol p is a local variable in register $esi, length 4.
12095 Symbol p1 is a local variable in register $ebx, length 4.
12096 Symbol nline is a local variable in register $edx, length 4.
12097 Symbol repeat is a local variable at frame offset -8, length 4.
12101 This command is especially useful for determining what data to collect
12102 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
12105 @kindex info source
12107 Show information about the current source file---that is, the source file for
12108 the function containing the current point of execution:
12111 the name of the source file, and the directory containing it,
12113 the directory it was compiled in,
12115 its length, in lines,
12117 which programming language it is written in,
12119 whether the executable includes debugging information for that file, and
12120 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
12122 whether the debugging information includes information about
12123 preprocessor macros.
12127 @kindex info sources
12129 Print the names of all source files in your program for which there is
12130 debugging information, organized into two lists: files whose symbols
12131 have already been read, and files whose symbols will be read when needed.
12133 @kindex info functions
12134 @item info functions
12135 Print the names and data types of all defined functions.
12137 @item info functions @var{regexp}
12138 Print the names and data types of all defined functions
12139 whose names contain a match for regular expression @var{regexp}.
12140 Thus, @samp{info fun step} finds all functions whose names
12141 include @code{step}; @samp{info fun ^step} finds those whose names
12142 start with @code{step}. If a function name contains characters
12143 that conflict with the regular expression language (e.g.@:
12144 @samp{operator*()}), they may be quoted with a backslash.
12146 @kindex info variables
12147 @item info variables
12148 Print the names and data types of all variables that are declared
12149 outside of functions (i.e.@: excluding local variables).
12151 @item info variables @var{regexp}
12152 Print the names and data types of all variables (except for local
12153 variables) whose names contain a match for regular expression
12156 @kindex info classes
12157 @cindex Objective-C, classes and selectors
12159 @itemx info classes @var{regexp}
12160 Display all Objective-C classes in your program, or
12161 (with the @var{regexp} argument) all those matching a particular regular
12164 @kindex info selectors
12165 @item info selectors
12166 @itemx info selectors @var{regexp}
12167 Display all Objective-C selectors in your program, or
12168 (with the @var{regexp} argument) all those matching a particular regular
12172 This was never implemented.
12173 @kindex info methods
12175 @itemx info methods @var{regexp}
12176 The @code{info methods} command permits the user to examine all defined
12177 methods within C@t{++} program, or (with the @var{regexp} argument) a
12178 specific set of methods found in the various C@t{++} classes. Many
12179 C@t{++} classes provide a large number of methods. Thus, the output
12180 from the @code{ptype} command can be overwhelming and hard to use. The
12181 @code{info-methods} command filters the methods, printing only those
12182 which match the regular-expression @var{regexp}.
12185 @cindex reloading symbols
12186 Some systems allow individual object files that make up your program to
12187 be replaced without stopping and restarting your program. For example,
12188 in VxWorks you can simply recompile a defective object file and keep on
12189 running. If you are running on one of these systems, you can allow
12190 @value{GDBN} to reload the symbols for automatically relinked modules:
12193 @kindex set symbol-reloading
12194 @item set symbol-reloading on
12195 Replace symbol definitions for the corresponding source file when an
12196 object file with a particular name is seen again.
12198 @item set symbol-reloading off
12199 Do not replace symbol definitions when encountering object files of the
12200 same name more than once. This is the default state; if you are not
12201 running on a system that permits automatic relinking of modules, you
12202 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12203 may discard symbols when linking large programs, that may contain
12204 several modules (from different directories or libraries) with the same
12207 @kindex show symbol-reloading
12208 @item show symbol-reloading
12209 Show the current @code{on} or @code{off} setting.
12212 @cindex opaque data types
12213 @kindex set opaque-type-resolution
12214 @item set opaque-type-resolution on
12215 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12216 declared as a pointer to a @code{struct}, @code{class}, or
12217 @code{union}---for example, @code{struct MyType *}---that is used in one
12218 source file although the full declaration of @code{struct MyType} is in
12219 another source file. The default is on.
12221 A change in the setting of this subcommand will not take effect until
12222 the next time symbols for a file are loaded.
12224 @item set opaque-type-resolution off
12225 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12226 is printed as follows:
12228 @{<no data fields>@}
12231 @kindex show opaque-type-resolution
12232 @item show opaque-type-resolution
12233 Show whether opaque types are resolved or not.
12235 @kindex set print symbol-loading
12236 @cindex print messages when symbols are loaded
12237 @item set print symbol-loading
12238 @itemx set print symbol-loading on
12239 @itemx set print symbol-loading off
12240 The @code{set print symbol-loading} command allows you to enable or
12241 disable printing of messages when @value{GDBN} loads symbols.
12242 By default, these messages will be printed, and normally this is what
12243 you want. Disabling these messages is useful when debugging applications
12244 with lots of shared libraries where the quantity of output can be more
12245 annoying than useful.
12247 @kindex show print symbol-loading
12248 @item show print symbol-loading
12249 Show whether messages will be printed when @value{GDBN} loads symbols.
12251 @kindex maint print symbols
12252 @cindex symbol dump
12253 @kindex maint print psymbols
12254 @cindex partial symbol dump
12255 @item maint print symbols @var{filename}
12256 @itemx maint print psymbols @var{filename}
12257 @itemx maint print msymbols @var{filename}
12258 Write a dump of debugging symbol data into the file @var{filename}.
12259 These commands are used to debug the @value{GDBN} symbol-reading code. Only
12260 symbols with debugging data are included. If you use @samp{maint print
12261 symbols}, @value{GDBN} includes all the symbols for which it has already
12262 collected full details: that is, @var{filename} reflects symbols for
12263 only those files whose symbols @value{GDBN} has read. You can use the
12264 command @code{info sources} to find out which files these are. If you
12265 use @samp{maint print psymbols} instead, the dump shows information about
12266 symbols that @value{GDBN} only knows partially---that is, symbols defined in
12267 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
12268 @samp{maint print msymbols} dumps just the minimal symbol information
12269 required for each object file from which @value{GDBN} has read some symbols.
12270 @xref{Files, ,Commands to Specify Files}, for a discussion of how
12271 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
12273 @kindex maint info symtabs
12274 @kindex maint info psymtabs
12275 @cindex listing @value{GDBN}'s internal symbol tables
12276 @cindex symbol tables, listing @value{GDBN}'s internal
12277 @cindex full symbol tables, listing @value{GDBN}'s internal
12278 @cindex partial symbol tables, listing @value{GDBN}'s internal
12279 @item maint info symtabs @r{[} @var{regexp} @r{]}
12280 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
12282 List the @code{struct symtab} or @code{struct partial_symtab}
12283 structures whose names match @var{regexp}. If @var{regexp} is not
12284 given, list them all. The output includes expressions which you can
12285 copy into a @value{GDBN} debugging this one to examine a particular
12286 structure in more detail. For example:
12289 (@value{GDBP}) maint info psymtabs dwarf2read
12290 @{ objfile /home/gnu/build/gdb/gdb
12291 ((struct objfile *) 0x82e69d0)
12292 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
12293 ((struct partial_symtab *) 0x8474b10)
12296 text addresses 0x814d3c8 -- 0x8158074
12297 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
12298 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
12299 dependencies (none)
12302 (@value{GDBP}) maint info symtabs
12306 We see that there is one partial symbol table whose filename contains
12307 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
12308 and we see that @value{GDBN} has not read in any symtabs yet at all.
12309 If we set a breakpoint on a function, that will cause @value{GDBN} to
12310 read the symtab for the compilation unit containing that function:
12313 (@value{GDBP}) break dwarf2_psymtab_to_symtab
12314 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
12316 (@value{GDBP}) maint info symtabs
12317 @{ objfile /home/gnu/build/gdb/gdb
12318 ((struct objfile *) 0x82e69d0)
12319 @{ symtab /home/gnu/src/gdb/dwarf2read.c
12320 ((struct symtab *) 0x86c1f38)
12323 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
12324 linetable ((struct linetable *) 0x8370fa0)
12325 debugformat DWARF 2
12334 @chapter Altering Execution
12336 Once you think you have found an error in your program, you might want to
12337 find out for certain whether correcting the apparent error would lead to
12338 correct results in the rest of the run. You can find the answer by
12339 experiment, using the @value{GDBN} features for altering execution of the
12342 For example, you can store new values into variables or memory
12343 locations, give your program a signal, restart it at a different
12344 address, or even return prematurely from a function.
12347 * Assignment:: Assignment to variables
12348 * Jumping:: Continuing at a different address
12349 * Signaling:: Giving your program a signal
12350 * Returning:: Returning from a function
12351 * Calling:: Calling your program's functions
12352 * Patching:: Patching your program
12356 @section Assignment to Variables
12359 @cindex setting variables
12360 To alter the value of a variable, evaluate an assignment expression.
12361 @xref{Expressions, ,Expressions}. For example,
12368 stores the value 4 into the variable @code{x}, and then prints the
12369 value of the assignment expression (which is 4).
12370 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
12371 information on operators in supported languages.
12373 @kindex set variable
12374 @cindex variables, setting
12375 If you are not interested in seeing the value of the assignment, use the
12376 @code{set} command instead of the @code{print} command. @code{set} is
12377 really the same as @code{print} except that the expression's value is
12378 not printed and is not put in the value history (@pxref{Value History,
12379 ,Value History}). The expression is evaluated only for its effects.
12381 If the beginning of the argument string of the @code{set} command
12382 appears identical to a @code{set} subcommand, use the @code{set
12383 variable} command instead of just @code{set}. This command is identical
12384 to @code{set} except for its lack of subcommands. For example, if your
12385 program has a variable @code{width}, you get an error if you try to set
12386 a new value with just @samp{set width=13}, because @value{GDBN} has the
12387 command @code{set width}:
12390 (@value{GDBP}) whatis width
12392 (@value{GDBP}) p width
12394 (@value{GDBP}) set width=47
12395 Invalid syntax in expression.
12399 The invalid expression, of course, is @samp{=47}. In
12400 order to actually set the program's variable @code{width}, use
12403 (@value{GDBP}) set var width=47
12406 Because the @code{set} command has many subcommands that can conflict
12407 with the names of program variables, it is a good idea to use the
12408 @code{set variable} command instead of just @code{set}. For example, if
12409 your program has a variable @code{g}, you run into problems if you try
12410 to set a new value with just @samp{set g=4}, because @value{GDBN} has
12411 the command @code{set gnutarget}, abbreviated @code{set g}:
12415 (@value{GDBP}) whatis g
12419 (@value{GDBP}) set g=4
12423 The program being debugged has been started already.
12424 Start it from the beginning? (y or n) y
12425 Starting program: /home/smith/cc_progs/a.out
12426 "/home/smith/cc_progs/a.out": can't open to read symbols:
12427 Invalid bfd target.
12428 (@value{GDBP}) show g
12429 The current BFD target is "=4".
12434 The program variable @code{g} did not change, and you silently set the
12435 @code{gnutarget} to an invalid value. In order to set the variable
12439 (@value{GDBP}) set var g=4
12442 @value{GDBN} allows more implicit conversions in assignments than C; you can
12443 freely store an integer value into a pointer variable or vice versa,
12444 and you can convert any structure to any other structure that is the
12445 same length or shorter.
12446 @comment FIXME: how do structs align/pad in these conversions?
12447 @comment /doc@cygnus.com 18dec1990
12449 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12450 construct to generate a value of specified type at a specified address
12451 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12452 to memory location @code{0x83040} as an integer (which implies a certain size
12453 and representation in memory), and
12456 set @{int@}0x83040 = 4
12460 stores the value 4 into that memory location.
12463 @section Continuing at a Different Address
12465 Ordinarily, when you continue your program, you do so at the place where
12466 it stopped, with the @code{continue} command. You can instead continue at
12467 an address of your own choosing, with the following commands:
12471 @item jump @var{linespec}
12472 @itemx jump @var{location}
12473 Resume execution at line @var{linespec} or at address given by
12474 @var{location}. Execution stops again immediately if there is a
12475 breakpoint there. @xref{Specify Location}, for a description of the
12476 different forms of @var{linespec} and @var{location}. It is common
12477 practice to use the @code{tbreak} command in conjunction with
12478 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
12480 The @code{jump} command does not change the current stack frame, or
12481 the stack pointer, or the contents of any memory location or any
12482 register other than the program counter. If line @var{linespec} is in
12483 a different function from the one currently executing, the results may
12484 be bizarre if the two functions expect different patterns of arguments or
12485 of local variables. For this reason, the @code{jump} command requests
12486 confirmation if the specified line is not in the function currently
12487 executing. However, even bizarre results are predictable if you are
12488 well acquainted with the machine-language code of your program.
12491 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
12492 On many systems, you can get much the same effect as the @code{jump}
12493 command by storing a new value into the register @code{$pc}. The
12494 difference is that this does not start your program running; it only
12495 changes the address of where it @emph{will} run when you continue. For
12503 makes the next @code{continue} command or stepping command execute at
12504 address @code{0x485}, rather than at the address where your program stopped.
12505 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12507 The most common occasion to use the @code{jump} command is to back
12508 up---perhaps with more breakpoints set---over a portion of a program
12509 that has already executed, in order to examine its execution in more
12514 @section Giving your Program a Signal
12515 @cindex deliver a signal to a program
12519 @item signal @var{signal}
12520 Resume execution where your program stopped, but immediately give it the
12521 signal @var{signal}. @var{signal} can be the name or the number of a
12522 signal. For example, on many systems @code{signal 2} and @code{signal
12523 SIGINT} are both ways of sending an interrupt signal.
12525 Alternatively, if @var{signal} is zero, continue execution without
12526 giving a signal. This is useful when your program stopped on account of
12527 a signal and would ordinary see the signal when resumed with the
12528 @code{continue} command; @samp{signal 0} causes it to resume without a
12531 @code{signal} does not repeat when you press @key{RET} a second time
12532 after executing the command.
12536 Invoking the @code{signal} command is not the same as invoking the
12537 @code{kill} utility from the shell. Sending a signal with @code{kill}
12538 causes @value{GDBN} to decide what to do with the signal depending on
12539 the signal handling tables (@pxref{Signals}). The @code{signal} command
12540 passes the signal directly to your program.
12544 @section Returning from a Function
12547 @cindex returning from a function
12550 @itemx return @var{expression}
12551 You can cancel execution of a function call with the @code{return}
12552 command. If you give an
12553 @var{expression} argument, its value is used as the function's return
12557 When you use @code{return}, @value{GDBN} discards the selected stack frame
12558 (and all frames within it). You can think of this as making the
12559 discarded frame return prematurely. If you wish to specify a value to
12560 be returned, give that value as the argument to @code{return}.
12562 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12563 Frame}), and any other frames inside of it, leaving its caller as the
12564 innermost remaining frame. That frame becomes selected. The
12565 specified value is stored in the registers used for returning values
12568 The @code{return} command does not resume execution; it leaves the
12569 program stopped in the state that would exist if the function had just
12570 returned. In contrast, the @code{finish} command (@pxref{Continuing
12571 and Stepping, ,Continuing and Stepping}) resumes execution until the
12572 selected stack frame returns naturally.
12574 @value{GDBN} needs to know how the @var{expression} argument should be set for
12575 the inferior. The concrete registers assignment depends on the OS ABI and the
12576 type being returned by the selected stack frame. For example it is common for
12577 OS ABI to return floating point values in FPU registers while integer values in
12578 CPU registers. Still some ABIs return even floating point values in CPU
12579 registers. Larger integer widths (such as @code{long long int}) also have
12580 specific placement rules. @value{GDBN} already knows the OS ABI from its
12581 current target so it needs to find out also the type being returned to make the
12582 assignment into the right register(s).
12584 Normally, the selected stack frame has debug info. @value{GDBN} will always
12585 use the debug info instead of the implicit type of @var{expression} when the
12586 debug info is available. For example, if you type @kbd{return -1}, and the
12587 function in the current stack frame is declared to return a @code{long long
12588 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
12589 into a @code{long long int}:
12592 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
12594 (@value{GDBP}) return -1
12595 Make func return now? (y or n) y
12596 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
12597 43 printf ("result=%lld\n", func ());
12601 However, if the selected stack frame does not have a debug info, e.g., if the
12602 function was compiled without debug info, @value{GDBN} has to find out the type
12603 to return from user. Specifying a different type by mistake may set the value
12604 in different inferior registers than the caller code expects. For example,
12605 typing @kbd{return -1} with its implicit type @code{int} would set only a part
12606 of a @code{long long int} result for a debug info less function (on 32-bit
12607 architectures). Therefore the user is required to specify the return type by
12608 an appropriate cast explicitly:
12611 Breakpoint 2, 0x0040050b in func ()
12612 (@value{GDBP}) return -1
12613 Return value type not available for selected stack frame.
12614 Please use an explicit cast of the value to return.
12615 (@value{GDBP}) return (long long int) -1
12616 Make selected stack frame return now? (y or n) y
12617 #0 0x00400526 in main ()
12622 @section Calling Program Functions
12625 @cindex calling functions
12626 @cindex inferior functions, calling
12627 @item print @var{expr}
12628 Evaluate the expression @var{expr} and display the resulting value.
12629 @var{expr} may include calls to functions in the program being
12633 @item call @var{expr}
12634 Evaluate the expression @var{expr} without displaying @code{void}
12637 You can use this variant of the @code{print} command if you want to
12638 execute a function from your program that does not return anything
12639 (a.k.a.@: @dfn{a void function}), but without cluttering the output
12640 with @code{void} returned values that @value{GDBN} will otherwise
12641 print. If the result is not void, it is printed and saved in the
12645 It is possible for the function you call via the @code{print} or
12646 @code{call} command to generate a signal (e.g., if there's a bug in
12647 the function, or if you passed it incorrect arguments). What happens
12648 in that case is controlled by the @code{set unwindonsignal} command.
12651 @item set unwindonsignal
12652 @kindex set unwindonsignal
12653 @cindex unwind stack in called functions
12654 @cindex call dummy stack unwinding
12655 Set unwinding of the stack if a signal is received while in a function
12656 that @value{GDBN} called in the program being debugged. If set to on,
12657 @value{GDBN} unwinds the stack it created for the call and restores
12658 the context to what it was before the call. If set to off (the
12659 default), @value{GDBN} stops in the frame where the signal was
12662 @item show unwindonsignal
12663 @kindex show unwindonsignal
12664 Show the current setting of stack unwinding in the functions called by
12668 @cindex weak alias functions
12669 Sometimes, a function you wish to call is actually a @dfn{weak alias}
12670 for another function. In such case, @value{GDBN} might not pick up
12671 the type information, including the types of the function arguments,
12672 which causes @value{GDBN} to call the inferior function incorrectly.
12673 As a result, the called function will function erroneously and may
12674 even crash. A solution to that is to use the name of the aliased
12678 @section Patching Programs
12680 @cindex patching binaries
12681 @cindex writing into executables
12682 @cindex writing into corefiles
12684 By default, @value{GDBN} opens the file containing your program's
12685 executable code (or the corefile) read-only. This prevents accidental
12686 alterations to machine code; but it also prevents you from intentionally
12687 patching your program's binary.
12689 If you'd like to be able to patch the binary, you can specify that
12690 explicitly with the @code{set write} command. For example, you might
12691 want to turn on internal debugging flags, or even to make emergency
12697 @itemx set write off
12698 If you specify @samp{set write on}, @value{GDBN} opens executable and
12699 core files for both reading and writing; if you specify @kbd{set write
12700 off} (the default), @value{GDBN} opens them read-only.
12702 If you have already loaded a file, you must load it again (using the
12703 @code{exec-file} or @code{core-file} command) after changing @code{set
12704 write}, for your new setting to take effect.
12708 Display whether executable files and core files are opened for writing
12709 as well as reading.
12713 @chapter @value{GDBN} Files
12715 @value{GDBN} needs to know the file name of the program to be debugged,
12716 both in order to read its symbol table and in order to start your
12717 program. To debug a core dump of a previous run, you must also tell
12718 @value{GDBN} the name of the core dump file.
12721 * Files:: Commands to specify files
12722 * Separate Debug Files:: Debugging information in separate files
12723 * Symbol Errors:: Errors reading symbol files
12727 @section Commands to Specify Files
12729 @cindex symbol table
12730 @cindex core dump file
12732 You may want to specify executable and core dump file names. The usual
12733 way to do this is at start-up time, using the arguments to
12734 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
12735 Out of @value{GDBN}}).
12737 Occasionally it is necessary to change to a different file during a
12738 @value{GDBN} session. Or you may run @value{GDBN} and forget to
12739 specify a file you want to use. Or you are debugging a remote target
12740 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
12741 Program}). In these situations the @value{GDBN} commands to specify
12742 new files are useful.
12745 @cindex executable file
12747 @item file @var{filename}
12748 Use @var{filename} as the program to be debugged. It is read for its
12749 symbols and for the contents of pure memory. It is also the program
12750 executed when you use the @code{run} command. If you do not specify a
12751 directory and the file is not found in the @value{GDBN} working directory,
12752 @value{GDBN} uses the environment variable @code{PATH} as a list of
12753 directories to search, just as the shell does when looking for a program
12754 to run. You can change the value of this variable, for both @value{GDBN}
12755 and your program, using the @code{path} command.
12757 @cindex unlinked object files
12758 @cindex patching object files
12759 You can load unlinked object @file{.o} files into @value{GDBN} using
12760 the @code{file} command. You will not be able to ``run'' an object
12761 file, but you can disassemble functions and inspect variables. Also,
12762 if the underlying BFD functionality supports it, you could use
12763 @kbd{gdb -write} to patch object files using this technique. Note
12764 that @value{GDBN} can neither interpret nor modify relocations in this
12765 case, so branches and some initialized variables will appear to go to
12766 the wrong place. But this feature is still handy from time to time.
12769 @code{file} with no argument makes @value{GDBN} discard any information it
12770 has on both executable file and the symbol table.
12773 @item exec-file @r{[} @var{filename} @r{]}
12774 Specify that the program to be run (but not the symbol table) is found
12775 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12776 if necessary to locate your program. Omitting @var{filename} means to
12777 discard information on the executable file.
12779 @kindex symbol-file
12780 @item symbol-file @r{[} @var{filename} @r{]}
12781 Read symbol table information from file @var{filename}. @code{PATH} is
12782 searched when necessary. Use the @code{file} command to get both symbol
12783 table and program to run from the same file.
12785 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12786 program's symbol table.
12788 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12789 some breakpoints and auto-display expressions. This is because they may
12790 contain pointers to the internal data recording symbols and data types,
12791 which are part of the old symbol table data being discarded inside
12794 @code{symbol-file} does not repeat if you press @key{RET} again after
12797 When @value{GDBN} is configured for a particular environment, it
12798 understands debugging information in whatever format is the standard
12799 generated for that environment; you may use either a @sc{gnu} compiler, or
12800 other compilers that adhere to the local conventions.
12801 Best results are usually obtained from @sc{gnu} compilers; for example,
12802 using @code{@value{NGCC}} you can generate debugging information for
12805 For most kinds of object files, with the exception of old SVR3 systems
12806 using COFF, the @code{symbol-file} command does not normally read the
12807 symbol table in full right away. Instead, it scans the symbol table
12808 quickly to find which source files and which symbols are present. The
12809 details are read later, one source file at a time, as they are needed.
12811 The purpose of this two-stage reading strategy is to make @value{GDBN}
12812 start up faster. For the most part, it is invisible except for
12813 occasional pauses while the symbol table details for a particular source
12814 file are being read. (The @code{set verbose} command can turn these
12815 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12816 Warnings and Messages}.)
12818 We have not implemented the two-stage strategy for COFF yet. When the
12819 symbol table is stored in COFF format, @code{symbol-file} reads the
12820 symbol table data in full right away. Note that ``stabs-in-COFF''
12821 still does the two-stage strategy, since the debug info is actually
12825 @cindex reading symbols immediately
12826 @cindex symbols, reading immediately
12827 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12828 @itemx file @var{filename} @r{[} -readnow @r{]}
12829 You can override the @value{GDBN} two-stage strategy for reading symbol
12830 tables by using the @samp{-readnow} option with any of the commands that
12831 load symbol table information, if you want to be sure @value{GDBN} has the
12832 entire symbol table available.
12834 @c FIXME: for now no mention of directories, since this seems to be in
12835 @c flux. 13mar1992 status is that in theory GDB would look either in
12836 @c current dir or in same dir as myprog; but issues like competing
12837 @c GDB's, or clutter in system dirs, mean that in practice right now
12838 @c only current dir is used. FFish says maybe a special GDB hierarchy
12839 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
12843 @item core-file @r{[}@var{filename}@r{]}
12845 Specify the whereabouts of a core dump file to be used as the ``contents
12846 of memory''. Traditionally, core files contain only some parts of the
12847 address space of the process that generated them; @value{GDBN} can access the
12848 executable file itself for other parts.
12850 @code{core-file} with no argument specifies that no core file is
12853 Note that the core file is ignored when your program is actually running
12854 under @value{GDBN}. So, if you have been running your program and you
12855 wish to debug a core file instead, you must kill the subprocess in which
12856 the program is running. To do this, use the @code{kill} command
12857 (@pxref{Kill Process, ,Killing the Child Process}).
12859 @kindex add-symbol-file
12860 @cindex dynamic linking
12861 @item add-symbol-file @var{filename} @var{address}
12862 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12863 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12864 The @code{add-symbol-file} command reads additional symbol table
12865 information from the file @var{filename}. You would use this command
12866 when @var{filename} has been dynamically loaded (by some other means)
12867 into the program that is running. @var{address} should be the memory
12868 address at which the file has been loaded; @value{GDBN} cannot figure
12869 this out for itself. You can additionally specify an arbitrary number
12870 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12871 section name and base address for that section. You can specify any
12872 @var{address} as an expression.
12874 The symbol table of the file @var{filename} is added to the symbol table
12875 originally read with the @code{symbol-file} command. You can use the
12876 @code{add-symbol-file} command any number of times; the new symbol data
12877 thus read keeps adding to the old. To discard all old symbol data
12878 instead, use the @code{symbol-file} command without any arguments.
12880 @cindex relocatable object files, reading symbols from
12881 @cindex object files, relocatable, reading symbols from
12882 @cindex reading symbols from relocatable object files
12883 @cindex symbols, reading from relocatable object files
12884 @cindex @file{.o} files, reading symbols from
12885 Although @var{filename} is typically a shared library file, an
12886 executable file, or some other object file which has been fully
12887 relocated for loading into a process, you can also load symbolic
12888 information from relocatable @file{.o} files, as long as:
12892 the file's symbolic information refers only to linker symbols defined in
12893 that file, not to symbols defined by other object files,
12895 every section the file's symbolic information refers to has actually
12896 been loaded into the inferior, as it appears in the file, and
12898 you can determine the address at which every section was loaded, and
12899 provide these to the @code{add-symbol-file} command.
12903 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12904 relocatable files into an already running program; such systems
12905 typically make the requirements above easy to meet. However, it's
12906 important to recognize that many native systems use complex link
12907 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12908 assembly, for example) that make the requirements difficult to meet. In
12909 general, one cannot assume that using @code{add-symbol-file} to read a
12910 relocatable object file's symbolic information will have the same effect
12911 as linking the relocatable object file into the program in the normal
12914 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12916 @kindex add-symbol-file-from-memory
12917 @cindex @code{syscall DSO}
12918 @cindex load symbols from memory
12919 @item add-symbol-file-from-memory @var{address}
12920 Load symbols from the given @var{address} in a dynamically loaded
12921 object file whose image is mapped directly into the inferior's memory.
12922 For example, the Linux kernel maps a @code{syscall DSO} into each
12923 process's address space; this DSO provides kernel-specific code for
12924 some system calls. The argument can be any expression whose
12925 evaluation yields the address of the file's shared object file header.
12926 For this command to work, you must have used @code{symbol-file} or
12927 @code{exec-file} commands in advance.
12929 @kindex add-shared-symbol-files
12931 @item add-shared-symbol-files @var{library-file}
12932 @itemx assf @var{library-file}
12933 The @code{add-shared-symbol-files} command can currently be used only
12934 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12935 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12936 @value{GDBN} automatically looks for shared libraries, however if
12937 @value{GDBN} does not find yours, you can invoke
12938 @code{add-shared-symbol-files}. It takes one argument: the shared
12939 library's file name. @code{assf} is a shorthand alias for
12940 @code{add-shared-symbol-files}.
12943 @item section @var{section} @var{addr}
12944 The @code{section} command changes the base address of the named
12945 @var{section} of the exec file to @var{addr}. This can be used if the
12946 exec file does not contain section addresses, (such as in the
12947 @code{a.out} format), or when the addresses specified in the file
12948 itself are wrong. Each section must be changed separately. The
12949 @code{info files} command, described below, lists all the sections and
12953 @kindex info target
12956 @code{info files} and @code{info target} are synonymous; both print the
12957 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12958 including the names of the executable and core dump files currently in
12959 use by @value{GDBN}, and the files from which symbols were loaded. The
12960 command @code{help target} lists all possible targets rather than
12963 @kindex maint info sections
12964 @item maint info sections
12965 Another command that can give you extra information about program sections
12966 is @code{maint info sections}. In addition to the section information
12967 displayed by @code{info files}, this command displays the flags and file
12968 offset of each section in the executable and core dump files. In addition,
12969 @code{maint info sections} provides the following command options (which
12970 may be arbitrarily combined):
12974 Display sections for all loaded object files, including shared libraries.
12975 @item @var{sections}
12976 Display info only for named @var{sections}.
12977 @item @var{section-flags}
12978 Display info only for sections for which @var{section-flags} are true.
12979 The section flags that @value{GDBN} currently knows about are:
12982 Section will have space allocated in the process when loaded.
12983 Set for all sections except those containing debug information.
12985 Section will be loaded from the file into the child process memory.
12986 Set for pre-initialized code and data, clear for @code{.bss} sections.
12988 Section needs to be relocated before loading.
12990 Section cannot be modified by the child process.
12992 Section contains executable code only.
12994 Section contains data only (no executable code).
12996 Section will reside in ROM.
12998 Section contains data for constructor/destructor lists.
13000 Section is not empty.
13002 An instruction to the linker to not output the section.
13003 @item COFF_SHARED_LIBRARY
13004 A notification to the linker that the section contains
13005 COFF shared library information.
13007 Section contains common symbols.
13010 @kindex set trust-readonly-sections
13011 @cindex read-only sections
13012 @item set trust-readonly-sections on
13013 Tell @value{GDBN} that readonly sections in your object file
13014 really are read-only (i.e.@: that their contents will not change).
13015 In that case, @value{GDBN} can fetch values from these sections
13016 out of the object file, rather than from the target program.
13017 For some targets (notably embedded ones), this can be a significant
13018 enhancement to debugging performance.
13020 The default is off.
13022 @item set trust-readonly-sections off
13023 Tell @value{GDBN} not to trust readonly sections. This means that
13024 the contents of the section might change while the program is running,
13025 and must therefore be fetched from the target when needed.
13027 @item show trust-readonly-sections
13028 Show the current setting of trusting readonly sections.
13031 All file-specifying commands allow both absolute and relative file names
13032 as arguments. @value{GDBN} always converts the file name to an absolute file
13033 name and remembers it that way.
13035 @cindex shared libraries
13036 @anchor{Shared Libraries}
13037 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
13038 and IBM RS/6000 AIX shared libraries.
13040 On MS-Windows @value{GDBN} must be linked with the Expat library to support
13041 shared libraries. @xref{Expat}.
13043 @value{GDBN} automatically loads symbol definitions from shared libraries
13044 when you use the @code{run} command, or when you examine a core file.
13045 (Before you issue the @code{run} command, @value{GDBN} does not understand
13046 references to a function in a shared library, however---unless you are
13047 debugging a core file).
13049 On HP-UX, if the program loads a library explicitly, @value{GDBN}
13050 automatically loads the symbols at the time of the @code{shl_load} call.
13052 @c FIXME: some @value{GDBN} release may permit some refs to undef
13053 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
13054 @c FIXME...lib; check this from time to time when updating manual
13056 There are times, however, when you may wish to not automatically load
13057 symbol definitions from shared libraries, such as when they are
13058 particularly large or there are many of them.
13060 To control the automatic loading of shared library symbols, use the
13064 @kindex set auto-solib-add
13065 @item set auto-solib-add @var{mode}
13066 If @var{mode} is @code{on}, symbols from all shared object libraries
13067 will be loaded automatically when the inferior begins execution, you
13068 attach to an independently started inferior, or when the dynamic linker
13069 informs @value{GDBN} that a new library has been loaded. If @var{mode}
13070 is @code{off}, symbols must be loaded manually, using the
13071 @code{sharedlibrary} command. The default value is @code{on}.
13073 @cindex memory used for symbol tables
13074 If your program uses lots of shared libraries with debug info that
13075 takes large amounts of memory, you can decrease the @value{GDBN}
13076 memory footprint by preventing it from automatically loading the
13077 symbols from shared libraries. To that end, type @kbd{set
13078 auto-solib-add off} before running the inferior, then load each
13079 library whose debug symbols you do need with @kbd{sharedlibrary
13080 @var{regexp}}, where @var{regexp} is a regular expression that matches
13081 the libraries whose symbols you want to be loaded.
13083 @kindex show auto-solib-add
13084 @item show auto-solib-add
13085 Display the current autoloading mode.
13088 @cindex load shared library
13089 To explicitly load shared library symbols, use the @code{sharedlibrary}
13093 @kindex info sharedlibrary
13096 @itemx info sharedlibrary
13097 Print the names of the shared libraries which are currently loaded.
13099 @kindex sharedlibrary
13101 @item sharedlibrary @var{regex}
13102 @itemx share @var{regex}
13103 Load shared object library symbols for files matching a
13104 Unix regular expression.
13105 As with files loaded automatically, it only loads shared libraries
13106 required by your program for a core file or after typing @code{run}. If
13107 @var{regex} is omitted all shared libraries required by your program are
13110 @item nosharedlibrary
13111 @kindex nosharedlibrary
13112 @cindex unload symbols from shared libraries
13113 Unload all shared object library symbols. This discards all symbols
13114 that have been loaded from all shared libraries. Symbols from shared
13115 libraries that were loaded by explicit user requests are not
13119 Sometimes you may wish that @value{GDBN} stops and gives you control
13120 when any of shared library events happen. Use the @code{set
13121 stop-on-solib-events} command for this:
13124 @item set stop-on-solib-events
13125 @kindex set stop-on-solib-events
13126 This command controls whether @value{GDBN} should give you control
13127 when the dynamic linker notifies it about some shared library event.
13128 The most common event of interest is loading or unloading of a new
13131 @item show stop-on-solib-events
13132 @kindex show stop-on-solib-events
13133 Show whether @value{GDBN} stops and gives you control when shared
13134 library events happen.
13137 Shared libraries are also supported in many cross or remote debugging
13138 configurations. @value{GDBN} needs to have access to the target's libraries;
13139 this can be accomplished either by providing copies of the libraries
13140 on the host system, or by asking @value{GDBN} to automatically retrieve the
13141 libraries from the target. If copies of the target libraries are
13142 provided, they need to be the same as the target libraries, although the
13143 copies on the target can be stripped as long as the copies on the host are
13146 @cindex where to look for shared libraries
13147 For remote debugging, you need to tell @value{GDBN} where the target
13148 libraries are, so that it can load the correct copies---otherwise, it
13149 may try to load the host's libraries. @value{GDBN} has two variables
13150 to specify the search directories for target libraries.
13153 @cindex prefix for shared library file names
13154 @cindex system root, alternate
13155 @kindex set solib-absolute-prefix
13156 @kindex set sysroot
13157 @item set sysroot @var{path}
13158 Use @var{path} as the system root for the program being debugged. Any
13159 absolute shared library paths will be prefixed with @var{path}; many
13160 runtime loaders store the absolute paths to the shared library in the
13161 target program's memory. If you use @code{set sysroot} to find shared
13162 libraries, they need to be laid out in the same way that they are on
13163 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
13166 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
13167 retrieve the target libraries from the remote system. This is only
13168 supported when using a remote target that supports the @code{remote get}
13169 command (@pxref{File Transfer,,Sending files to a remote system}).
13170 The part of @var{path} following the initial @file{remote:}
13171 (if present) is used as system root prefix on the remote file system.
13172 @footnote{If you want to specify a local system root using a directory
13173 that happens to be named @file{remote:}, you need to use some equivalent
13174 variant of the name like @file{./remote:}.}
13176 The @code{set solib-absolute-prefix} command is an alias for @code{set
13179 @cindex default system root
13180 @cindex @samp{--with-sysroot}
13181 You can set the default system root by using the configure-time
13182 @samp{--with-sysroot} option. If the system root is inside
13183 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13184 @samp{--exec-prefix}), then the default system root will be updated
13185 automatically if the installed @value{GDBN} is moved to a new
13188 @kindex show sysroot
13190 Display the current shared library prefix.
13192 @kindex set solib-search-path
13193 @item set solib-search-path @var{path}
13194 If this variable is set, @var{path} is a colon-separated list of
13195 directories to search for shared libraries. @samp{solib-search-path}
13196 is used after @samp{sysroot} fails to locate the library, or if the
13197 path to the library is relative instead of absolute. If you want to
13198 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13199 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13200 finding your host's libraries. @samp{sysroot} is preferred; setting
13201 it to a nonexistent directory may interfere with automatic loading
13202 of shared library symbols.
13204 @kindex show solib-search-path
13205 @item show solib-search-path
13206 Display the current shared library search path.
13210 @node Separate Debug Files
13211 @section Debugging Information in Separate Files
13212 @cindex separate debugging information files
13213 @cindex debugging information in separate files
13214 @cindex @file{.debug} subdirectories
13215 @cindex debugging information directory, global
13216 @cindex global debugging information directory
13217 @cindex build ID, and separate debugging files
13218 @cindex @file{.build-id} directory
13220 @value{GDBN} allows you to put a program's debugging information in a
13221 file separate from the executable itself, in a way that allows
13222 @value{GDBN} to find and load the debugging information automatically.
13223 Since debugging information can be very large---sometimes larger
13224 than the executable code itself---some systems distribute debugging
13225 information for their executables in separate files, which users can
13226 install only when they need to debug a problem.
13228 @value{GDBN} supports two ways of specifying the separate debug info
13233 The executable contains a @dfn{debug link} that specifies the name of
13234 the separate debug info file. The separate debug file's name is
13235 usually @file{@var{executable}.debug}, where @var{executable} is the
13236 name of the corresponding executable file without leading directories
13237 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
13238 debug link specifies a CRC32 checksum for the debug file, which
13239 @value{GDBN} uses to validate that the executable and the debug file
13240 came from the same build.
13243 The executable contains a @dfn{build ID}, a unique bit string that is
13244 also present in the corresponding debug info file. (This is supported
13245 only on some operating systems, notably those which use the ELF format
13246 for binary files and the @sc{gnu} Binutils.) For more details about
13247 this feature, see the description of the @option{--build-id}
13248 command-line option in @ref{Options, , Command Line Options, ld.info,
13249 The GNU Linker}. The debug info file's name is not specified
13250 explicitly by the build ID, but can be computed from the build ID, see
13254 Depending on the way the debug info file is specified, @value{GDBN}
13255 uses two different methods of looking for the debug file:
13259 For the ``debug link'' method, @value{GDBN} looks up the named file in
13260 the directory of the executable file, then in a subdirectory of that
13261 directory named @file{.debug}, and finally under the global debug
13262 directory, in a subdirectory whose name is identical to the leading
13263 directories of the executable's absolute file name.
13266 For the ``build ID'' method, @value{GDBN} looks in the
13267 @file{.build-id} subdirectory of the global debug directory for a file
13268 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
13269 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
13270 are the rest of the bit string. (Real build ID strings are 32 or more
13271 hex characters, not 10.)
13274 So, for example, suppose you ask @value{GDBN} to debug
13275 @file{/usr/bin/ls}, which has a debug link that specifies the
13276 file @file{ls.debug}, and a build ID whose value in hex is
13277 @code{abcdef1234}. If the global debug directory is
13278 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
13279 debug information files, in the indicated order:
13283 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
13285 @file{/usr/bin/ls.debug}
13287 @file{/usr/bin/.debug/ls.debug}
13289 @file{/usr/lib/debug/usr/bin/ls.debug}.
13292 You can set the global debugging info directory's name, and view the
13293 name @value{GDBN} is currently using.
13297 @kindex set debug-file-directory
13298 @item set debug-file-directory @var{directory}
13299 Set the directory which @value{GDBN} searches for separate debugging
13300 information files to @var{directory}.
13302 @kindex show debug-file-directory
13303 @item show debug-file-directory
13304 Show the directory @value{GDBN} searches for separate debugging
13309 @cindex @code{.gnu_debuglink} sections
13310 @cindex debug link sections
13311 A debug link is a special section of the executable file named
13312 @code{.gnu_debuglink}. The section must contain:
13316 A filename, with any leading directory components removed, followed by
13319 zero to three bytes of padding, as needed to reach the next four-byte
13320 boundary within the section, and
13322 a four-byte CRC checksum, stored in the same endianness used for the
13323 executable file itself. The checksum is computed on the debugging
13324 information file's full contents by the function given below, passing
13325 zero as the @var{crc} argument.
13328 Any executable file format can carry a debug link, as long as it can
13329 contain a section named @code{.gnu_debuglink} with the contents
13332 @cindex @code{.note.gnu.build-id} sections
13333 @cindex build ID sections
13334 The build ID is a special section in the executable file (and in other
13335 ELF binary files that @value{GDBN} may consider). This section is
13336 often named @code{.note.gnu.build-id}, but that name is not mandatory.
13337 It contains unique identification for the built files---the ID remains
13338 the same across multiple builds of the same build tree. The default
13339 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
13340 content for the build ID string. The same section with an identical
13341 value is present in the original built binary with symbols, in its
13342 stripped variant, and in the separate debugging information file.
13344 The debugging information file itself should be an ordinary
13345 executable, containing a full set of linker symbols, sections, and
13346 debugging information. The sections of the debugging information file
13347 should have the same names, addresses, and sizes as the original file,
13348 but they need not contain any data---much like a @code{.bss} section
13349 in an ordinary executable.
13351 The @sc{gnu} binary utilities (Binutils) package includes the
13352 @samp{objcopy} utility that can produce
13353 the separated executable / debugging information file pairs using the
13354 following commands:
13357 @kbd{objcopy --only-keep-debug foo foo.debug}
13362 These commands remove the debugging
13363 information from the executable file @file{foo} and place it in the file
13364 @file{foo.debug}. You can use the first, second or both methods to link the
13369 The debug link method needs the following additional command to also leave
13370 behind a debug link in @file{foo}:
13373 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
13376 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
13377 a version of the @code{strip} command such that the command @kbd{strip foo -f
13378 foo.debug} has the same functionality as the two @code{objcopy} commands and
13379 the @code{ln -s} command above, together.
13382 Build ID gets embedded into the main executable using @code{ld --build-id} or
13383 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
13384 compatibility fixes for debug files separation are present in @sc{gnu} binary
13385 utilities (Binutils) package since version 2.18.
13390 Since there are many different ways to compute CRC's for the debug
13391 link (different polynomials, reversals, byte ordering, etc.), the
13392 simplest way to describe the CRC used in @code{.gnu_debuglink}
13393 sections is to give the complete code for a function that computes it:
13395 @kindex gnu_debuglink_crc32
13398 gnu_debuglink_crc32 (unsigned long crc,
13399 unsigned char *buf, size_t len)
13401 static const unsigned long crc32_table[256] =
13403 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
13404 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
13405 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
13406 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
13407 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
13408 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
13409 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
13410 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
13411 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
13412 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
13413 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
13414 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
13415 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
13416 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
13417 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
13418 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
13419 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
13420 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
13421 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
13422 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
13423 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
13424 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
13425 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
13426 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
13427 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
13428 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
13429 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
13430 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
13431 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
13432 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
13433 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
13434 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
13435 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
13436 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
13437 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
13438 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
13439 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
13440 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
13441 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
13442 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
13443 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
13444 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
13445 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
13446 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
13447 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
13448 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
13449 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
13450 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
13451 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
13452 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
13453 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
13456 unsigned char *end;
13458 crc = ~crc & 0xffffffff;
13459 for (end = buf + len; buf < end; ++buf)
13460 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
13461 return ~crc & 0xffffffff;
13466 This computation does not apply to the ``build ID'' method.
13469 @node Symbol Errors
13470 @section Errors Reading Symbol Files
13472 While reading a symbol file, @value{GDBN} occasionally encounters problems,
13473 such as symbol types it does not recognize, or known bugs in compiler
13474 output. By default, @value{GDBN} does not notify you of such problems, since
13475 they are relatively common and primarily of interest to people
13476 debugging compilers. If you are interested in seeing information
13477 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
13478 only one message about each such type of problem, no matter how many
13479 times the problem occurs; or you can ask @value{GDBN} to print more messages,
13480 to see how many times the problems occur, with the @code{set
13481 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
13484 The messages currently printed, and their meanings, include:
13487 @item inner block not inside outer block in @var{symbol}
13489 The symbol information shows where symbol scopes begin and end
13490 (such as at the start of a function or a block of statements). This
13491 error indicates that an inner scope block is not fully contained
13492 in its outer scope blocks.
13494 @value{GDBN} circumvents the problem by treating the inner block as if it had
13495 the same scope as the outer block. In the error message, @var{symbol}
13496 may be shown as ``@code{(don't know)}'' if the outer block is not a
13499 @item block at @var{address} out of order
13501 The symbol information for symbol scope blocks should occur in
13502 order of increasing addresses. This error indicates that it does not
13505 @value{GDBN} does not circumvent this problem, and has trouble
13506 locating symbols in the source file whose symbols it is reading. (You
13507 can often determine what source file is affected by specifying
13508 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
13511 @item bad block start address patched
13513 The symbol information for a symbol scope block has a start address
13514 smaller than the address of the preceding source line. This is known
13515 to occur in the SunOS 4.1.1 (and earlier) C compiler.
13517 @value{GDBN} circumvents the problem by treating the symbol scope block as
13518 starting on the previous source line.
13520 @item bad string table offset in symbol @var{n}
13523 Symbol number @var{n} contains a pointer into the string table which is
13524 larger than the size of the string table.
13526 @value{GDBN} circumvents the problem by considering the symbol to have the
13527 name @code{foo}, which may cause other problems if many symbols end up
13530 @item unknown symbol type @code{0x@var{nn}}
13532 The symbol information contains new data types that @value{GDBN} does
13533 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
13534 uncomprehended information, in hexadecimal.
13536 @value{GDBN} circumvents the error by ignoring this symbol information.
13537 This usually allows you to debug your program, though certain symbols
13538 are not accessible. If you encounter such a problem and feel like
13539 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
13540 on @code{complain}, then go up to the function @code{read_dbx_symtab}
13541 and examine @code{*bufp} to see the symbol.
13543 @item stub type has NULL name
13545 @value{GDBN} could not find the full definition for a struct or class.
13547 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
13548 The symbol information for a C@t{++} member function is missing some
13549 information that recent versions of the compiler should have output for
13552 @item info mismatch between compiler and debugger
13554 @value{GDBN} could not parse a type specification output by the compiler.
13559 @chapter Specifying a Debugging Target
13561 @cindex debugging target
13562 A @dfn{target} is the execution environment occupied by your program.
13564 Often, @value{GDBN} runs in the same host environment as your program;
13565 in that case, the debugging target is specified as a side effect when
13566 you use the @code{file} or @code{core} commands. When you need more
13567 flexibility---for example, running @value{GDBN} on a physically separate
13568 host, or controlling a standalone system over a serial port or a
13569 realtime system over a TCP/IP connection---you can use the @code{target}
13570 command to specify one of the target types configured for @value{GDBN}
13571 (@pxref{Target Commands, ,Commands for Managing Targets}).
13573 @cindex target architecture
13574 It is possible to build @value{GDBN} for several different @dfn{target
13575 architectures}. When @value{GDBN} is built like that, you can choose
13576 one of the available architectures with the @kbd{set architecture}
13580 @kindex set architecture
13581 @kindex show architecture
13582 @item set architecture @var{arch}
13583 This command sets the current target architecture to @var{arch}. The
13584 value of @var{arch} can be @code{"auto"}, in addition to one of the
13585 supported architectures.
13587 @item show architecture
13588 Show the current target architecture.
13590 @item set processor
13592 @kindex set processor
13593 @kindex show processor
13594 These are alias commands for, respectively, @code{set architecture}
13595 and @code{show architecture}.
13599 * Active Targets:: Active targets
13600 * Target Commands:: Commands for managing targets
13601 * Byte Order:: Choosing target byte order
13604 @node Active Targets
13605 @section Active Targets
13607 @cindex stacking targets
13608 @cindex active targets
13609 @cindex multiple targets
13611 There are three classes of targets: processes, core files, and
13612 executable files. @value{GDBN} can work concurrently on up to three
13613 active targets, one in each class. This allows you to (for example)
13614 start a process and inspect its activity without abandoning your work on
13617 For example, if you execute @samp{gdb a.out}, then the executable file
13618 @code{a.out} is the only active target. If you designate a core file as
13619 well---presumably from a prior run that crashed and coredumped---then
13620 @value{GDBN} has two active targets and uses them in tandem, looking
13621 first in the corefile target, then in the executable file, to satisfy
13622 requests for memory addresses. (Typically, these two classes of target
13623 are complementary, since core files contain only a program's
13624 read-write memory---variables and so on---plus machine status, while
13625 executable files contain only the program text and initialized data.)
13627 When you type @code{run}, your executable file becomes an active process
13628 target as well. When a process target is active, all @value{GDBN}
13629 commands requesting memory addresses refer to that target; addresses in
13630 an active core file or executable file target are obscured while the
13631 process target is active.
13633 Use the @code{core-file} and @code{exec-file} commands to select a new
13634 core file or executable target (@pxref{Files, ,Commands to Specify
13635 Files}). To specify as a target a process that is already running, use
13636 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
13639 @node Target Commands
13640 @section Commands for Managing Targets
13643 @item target @var{type} @var{parameters}
13644 Connects the @value{GDBN} host environment to a target machine or
13645 process. A target is typically a protocol for talking to debugging
13646 facilities. You use the argument @var{type} to specify the type or
13647 protocol of the target machine.
13649 Further @var{parameters} are interpreted by the target protocol, but
13650 typically include things like device names or host names to connect
13651 with, process numbers, and baud rates.
13653 The @code{target} command does not repeat if you press @key{RET} again
13654 after executing the command.
13656 @kindex help target
13658 Displays the names of all targets available. To display targets
13659 currently selected, use either @code{info target} or @code{info files}
13660 (@pxref{Files, ,Commands to Specify Files}).
13662 @item help target @var{name}
13663 Describe a particular target, including any parameters necessary to
13666 @kindex set gnutarget
13667 @item set gnutarget @var{args}
13668 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
13669 knows whether it is reading an @dfn{executable},
13670 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
13671 with the @code{set gnutarget} command. Unlike most @code{target} commands,
13672 with @code{gnutarget} the @code{target} refers to a program, not a machine.
13675 @emph{Warning:} To specify a file format with @code{set gnutarget},
13676 you must know the actual BFD name.
13680 @xref{Files, , Commands to Specify Files}.
13682 @kindex show gnutarget
13683 @item show gnutarget
13684 Use the @code{show gnutarget} command to display what file format
13685 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
13686 @value{GDBN} will determine the file format for each file automatically,
13687 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
13690 @cindex common targets
13691 Here are some common targets (available, or not, depending on the GDB
13696 @item target exec @var{program}
13697 @cindex executable file target
13698 An executable file. @samp{target exec @var{program}} is the same as
13699 @samp{exec-file @var{program}}.
13701 @item target core @var{filename}
13702 @cindex core dump file target
13703 A core dump file. @samp{target core @var{filename}} is the same as
13704 @samp{core-file @var{filename}}.
13706 @item target remote @var{medium}
13707 @cindex remote target
13708 A remote system connected to @value{GDBN} via a serial line or network
13709 connection. This command tells @value{GDBN} to use its own remote
13710 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
13712 For example, if you have a board connected to @file{/dev/ttya} on the
13713 machine running @value{GDBN}, you could say:
13716 target remote /dev/ttya
13719 @code{target remote} supports the @code{load} command. This is only
13720 useful if you have some other way of getting the stub to the target
13721 system, and you can put it somewhere in memory where it won't get
13722 clobbered by the download.
13725 @cindex built-in simulator target
13726 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
13734 works; however, you cannot assume that a specific memory map, device
13735 drivers, or even basic I/O is available, although some simulators do
13736 provide these. For info about any processor-specific simulator details,
13737 see the appropriate section in @ref{Embedded Processors, ,Embedded
13742 Some configurations may include these targets as well:
13746 @item target nrom @var{dev}
13747 @cindex NetROM ROM emulator target
13748 NetROM ROM emulator. This target only supports downloading.
13752 Different targets are available on different configurations of @value{GDBN};
13753 your configuration may have more or fewer targets.
13755 Many remote targets require you to download the executable's code once
13756 you've successfully established a connection. You may wish to control
13757 various aspects of this process.
13762 @kindex set hash@r{, for remote monitors}
13763 @cindex hash mark while downloading
13764 This command controls whether a hash mark @samp{#} is displayed while
13765 downloading a file to the remote monitor. If on, a hash mark is
13766 displayed after each S-record is successfully downloaded to the
13770 @kindex show hash@r{, for remote monitors}
13771 Show the current status of displaying the hash mark.
13773 @item set debug monitor
13774 @kindex set debug monitor
13775 @cindex display remote monitor communications
13776 Enable or disable display of communications messages between
13777 @value{GDBN} and the remote monitor.
13779 @item show debug monitor
13780 @kindex show debug monitor
13781 Show the current status of displaying communications between
13782 @value{GDBN} and the remote monitor.
13787 @kindex load @var{filename}
13788 @item load @var{filename}
13790 Depending on what remote debugging facilities are configured into
13791 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13792 is meant to make @var{filename} (an executable) available for debugging
13793 on the remote system---by downloading, or dynamic linking, for example.
13794 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
13795 the @code{add-symbol-file} command.
13797 If your @value{GDBN} does not have a @code{load} command, attempting to
13798 execute it gets the error message ``@code{You can't do that when your
13799 target is @dots{}}''
13801 The file is loaded at whatever address is specified in the executable.
13802 For some object file formats, you can specify the load address when you
13803 link the program; for other formats, like a.out, the object file format
13804 specifies a fixed address.
13805 @c FIXME! This would be a good place for an xref to the GNU linker doc.
13807 Depending on the remote side capabilities, @value{GDBN} may be able to
13808 load programs into flash memory.
13810 @code{load} does not repeat if you press @key{RET} again after using it.
13814 @section Choosing Target Byte Order
13816 @cindex choosing target byte order
13817 @cindex target byte order
13819 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
13820 offer the ability to run either big-endian or little-endian byte
13821 orders. Usually the executable or symbol will include a bit to
13822 designate the endian-ness, and you will not need to worry about
13823 which to use. However, you may still find it useful to adjust
13824 @value{GDBN}'s idea of processor endian-ness manually.
13828 @item set endian big
13829 Instruct @value{GDBN} to assume the target is big-endian.
13831 @item set endian little
13832 Instruct @value{GDBN} to assume the target is little-endian.
13834 @item set endian auto
13835 Instruct @value{GDBN} to use the byte order associated with the
13839 Display @value{GDBN}'s current idea of the target byte order.
13843 Note that these commands merely adjust interpretation of symbolic
13844 data on the host, and that they have absolutely no effect on the
13848 @node Remote Debugging
13849 @chapter Debugging Remote Programs
13850 @cindex remote debugging
13852 If you are trying to debug a program running on a machine that cannot run
13853 @value{GDBN} in the usual way, it is often useful to use remote debugging.
13854 For example, you might use remote debugging on an operating system kernel,
13855 or on a small system which does not have a general purpose operating system
13856 powerful enough to run a full-featured debugger.
13858 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
13859 to make this work with particular debugging targets. In addition,
13860 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
13861 but not specific to any particular target system) which you can use if you
13862 write the remote stubs---the code that runs on the remote system to
13863 communicate with @value{GDBN}.
13865 Other remote targets may be available in your
13866 configuration of @value{GDBN}; use @code{help target} to list them.
13869 * Connecting:: Connecting to a remote target
13870 * File Transfer:: Sending files to a remote system
13871 * Server:: Using the gdbserver program
13872 * Remote Configuration:: Remote configuration
13873 * Remote Stub:: Implementing a remote stub
13877 @section Connecting to a Remote Target
13879 On the @value{GDBN} host machine, you will need an unstripped copy of
13880 your program, since @value{GDBN} needs symbol and debugging information.
13881 Start up @value{GDBN} as usual, using the name of the local copy of your
13882 program as the first argument.
13884 @cindex @code{target remote}
13885 @value{GDBN} can communicate with the target over a serial line, or
13886 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13887 each case, @value{GDBN} uses the same protocol for debugging your
13888 program; only the medium carrying the debugging packets varies. The
13889 @code{target remote} command establishes a connection to the target.
13890 Its arguments indicate which medium to use:
13894 @item target remote @var{serial-device}
13895 @cindex serial line, @code{target remote}
13896 Use @var{serial-device} to communicate with the target. For example,
13897 to use a serial line connected to the device named @file{/dev/ttyb}:
13900 target remote /dev/ttyb
13903 If you're using a serial line, you may want to give @value{GDBN} the
13904 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13905 (@pxref{Remote Configuration, set remotebaud}) before the
13906 @code{target} command.
13908 @item target remote @code{@var{host}:@var{port}}
13909 @itemx target remote @code{tcp:@var{host}:@var{port}}
13910 @cindex @acronym{TCP} port, @code{target remote}
13911 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13912 The @var{host} may be either a host name or a numeric @acronym{IP}
13913 address; @var{port} must be a decimal number. The @var{host} could be
13914 the target machine itself, if it is directly connected to the net, or
13915 it might be a terminal server which in turn has a serial line to the
13918 For example, to connect to port 2828 on a terminal server named
13922 target remote manyfarms:2828
13925 If your remote target is actually running on the same machine as your
13926 debugger session (e.g.@: a simulator for your target running on the
13927 same host), you can omit the hostname. For example, to connect to
13928 port 1234 on your local machine:
13931 target remote :1234
13935 Note that the colon is still required here.
13937 @item target remote @code{udp:@var{host}:@var{port}}
13938 @cindex @acronym{UDP} port, @code{target remote}
13939 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13940 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13943 target remote udp:manyfarms:2828
13946 When using a @acronym{UDP} connection for remote debugging, you should
13947 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13948 can silently drop packets on busy or unreliable networks, which will
13949 cause havoc with your debugging session.
13951 @item target remote | @var{command}
13952 @cindex pipe, @code{target remote} to
13953 Run @var{command} in the background and communicate with it using a
13954 pipe. The @var{command} is a shell command, to be parsed and expanded
13955 by the system's command shell, @code{/bin/sh}; it should expect remote
13956 protocol packets on its standard input, and send replies on its
13957 standard output. You could use this to run a stand-alone simulator
13958 that speaks the remote debugging protocol, to make net connections
13959 using programs like @code{ssh}, or for other similar tricks.
13961 If @var{command} closes its standard output (perhaps by exiting),
13962 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13963 program has already exited, this will have no effect.)
13967 Once the connection has been established, you can use all the usual
13968 commands to examine and change data. The remote program is already
13969 running; you can use @kbd{step} and @kbd{continue}, and you do not
13970 need to use @kbd{run}.
13972 @cindex interrupting remote programs
13973 @cindex remote programs, interrupting
13974 Whenever @value{GDBN} is waiting for the remote program, if you type the
13975 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13976 program. This may or may not succeed, depending in part on the hardware
13977 and the serial drivers the remote system uses. If you type the
13978 interrupt character once again, @value{GDBN} displays this prompt:
13981 Interrupted while waiting for the program.
13982 Give up (and stop debugging it)? (y or n)
13985 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13986 (If you decide you want to try again later, you can use @samp{target
13987 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13988 goes back to waiting.
13991 @kindex detach (remote)
13993 When you have finished debugging the remote program, you can use the
13994 @code{detach} command to release it from @value{GDBN} control.
13995 Detaching from the target normally resumes its execution, but the results
13996 will depend on your particular remote stub. After the @code{detach}
13997 command, @value{GDBN} is free to connect to another target.
14001 The @code{disconnect} command behaves like @code{detach}, except that
14002 the target is generally not resumed. It will wait for @value{GDBN}
14003 (this instance or another one) to connect and continue debugging. After
14004 the @code{disconnect} command, @value{GDBN} is again free to connect to
14007 @cindex send command to remote monitor
14008 @cindex extend @value{GDBN} for remote targets
14009 @cindex add new commands for external monitor
14011 @item monitor @var{cmd}
14012 This command allows you to send arbitrary commands directly to the
14013 remote monitor. Since @value{GDBN} doesn't care about the commands it
14014 sends like this, this command is the way to extend @value{GDBN}---you
14015 can add new commands that only the external monitor will understand
14019 @node File Transfer
14020 @section Sending files to a remote system
14021 @cindex remote target, file transfer
14022 @cindex file transfer
14023 @cindex sending files to remote systems
14025 Some remote targets offer the ability to transfer files over the same
14026 connection used to communicate with @value{GDBN}. This is convenient
14027 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
14028 running @code{gdbserver} over a network interface. For other targets,
14029 e.g.@: embedded devices with only a single serial port, this may be
14030 the only way to upload or download files.
14032 Not all remote targets support these commands.
14036 @item remote put @var{hostfile} @var{targetfile}
14037 Copy file @var{hostfile} from the host system (the machine running
14038 @value{GDBN}) to @var{targetfile} on the target system.
14041 @item remote get @var{targetfile} @var{hostfile}
14042 Copy file @var{targetfile} from the target system to @var{hostfile}
14043 on the host system.
14045 @kindex remote delete
14046 @item remote delete @var{targetfile}
14047 Delete @var{targetfile} from the target system.
14052 @section Using the @code{gdbserver} Program
14055 @cindex remote connection without stubs
14056 @code{gdbserver} is a control program for Unix-like systems, which
14057 allows you to connect your program with a remote @value{GDBN} via
14058 @code{target remote}---but without linking in the usual debugging stub.
14060 @code{gdbserver} is not a complete replacement for the debugging stubs,
14061 because it requires essentially the same operating-system facilities
14062 that @value{GDBN} itself does. In fact, a system that can run
14063 @code{gdbserver} to connect to a remote @value{GDBN} could also run
14064 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
14065 because it is a much smaller program than @value{GDBN} itself. It is
14066 also easier to port than all of @value{GDBN}, so you may be able to get
14067 started more quickly on a new system by using @code{gdbserver}.
14068 Finally, if you develop code for real-time systems, you may find that
14069 the tradeoffs involved in real-time operation make it more convenient to
14070 do as much development work as possible on another system, for example
14071 by cross-compiling. You can use @code{gdbserver} to make a similar
14072 choice for debugging.
14074 @value{GDBN} and @code{gdbserver} communicate via either a serial line
14075 or a TCP connection, using the standard @value{GDBN} remote serial
14079 @emph{Warning:} @code{gdbserver} does not have any built-in security.
14080 Do not run @code{gdbserver} connected to any public network; a
14081 @value{GDBN} connection to @code{gdbserver} provides access to the
14082 target system with the same privileges as the user running
14086 @subsection Running @code{gdbserver}
14087 @cindex arguments, to @code{gdbserver}
14089 Run @code{gdbserver} on the target system. You need a copy of the
14090 program you want to debug, including any libraries it requires.
14091 @code{gdbserver} does not need your program's symbol table, so you can
14092 strip the program if necessary to save space. @value{GDBN} on the host
14093 system does all the symbol handling.
14095 To use the server, you must tell it how to communicate with @value{GDBN};
14096 the name of your program; and the arguments for your program. The usual
14100 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
14103 @var{comm} is either a device name (to use a serial line) or a TCP
14104 hostname and portnumber. For example, to debug Emacs with the argument
14105 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
14109 target> gdbserver /dev/com1 emacs foo.txt
14112 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
14115 To use a TCP connection instead of a serial line:
14118 target> gdbserver host:2345 emacs foo.txt
14121 The only difference from the previous example is the first argument,
14122 specifying that you are communicating with the host @value{GDBN} via
14123 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
14124 expect a TCP connection from machine @samp{host} to local TCP port 2345.
14125 (Currently, the @samp{host} part is ignored.) You can choose any number
14126 you want for the port number as long as it does not conflict with any
14127 TCP ports already in use on the target system (for example, @code{23} is
14128 reserved for @code{telnet}).@footnote{If you choose a port number that
14129 conflicts with another service, @code{gdbserver} prints an error message
14130 and exits.} You must use the same port number with the host @value{GDBN}
14131 @code{target remote} command.
14133 @subsubsection Attaching to a Running Program
14135 On some targets, @code{gdbserver} can also attach to running programs.
14136 This is accomplished via the @code{--attach} argument. The syntax is:
14139 target> gdbserver --attach @var{comm} @var{pid}
14142 @var{pid} is the process ID of a currently running process. It isn't necessary
14143 to point @code{gdbserver} at a binary for the running process.
14146 @cindex attach to a program by name
14147 You can debug processes by name instead of process ID if your target has the
14148 @code{pidof} utility:
14151 target> gdbserver --attach @var{comm} `pidof @var{program}`
14154 In case more than one copy of @var{program} is running, or @var{program}
14155 has multiple threads, most versions of @code{pidof} support the
14156 @code{-s} option to only return the first process ID.
14158 @subsubsection Multi-Process Mode for @code{gdbserver}
14159 @cindex gdbserver, multiple processes
14160 @cindex multiple processes with gdbserver
14162 When you connect to @code{gdbserver} using @code{target remote},
14163 @code{gdbserver} debugs the specified program only once. When the
14164 program exits, or you detach from it, @value{GDBN} closes the connection
14165 and @code{gdbserver} exits.
14167 If you connect using @kbd{target extended-remote}, @code{gdbserver}
14168 enters multi-process mode. When the debugged program exits, or you
14169 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
14170 though no program is running. The @code{run} and @code{attach}
14171 commands instruct @code{gdbserver} to run or attach to a new program.
14172 The @code{run} command uses @code{set remote exec-file} (@pxref{set
14173 remote exec-file}) to select the program to run. Command line
14174 arguments are supported, except for wildcard expansion and I/O
14175 redirection (@pxref{Arguments}).
14177 To start @code{gdbserver} without supplying an initial command to run
14178 or process ID to attach, use the @option{--multi} command line option.
14179 Then you can connect using @kbd{target extended-remote} and start
14180 the program you want to debug.
14182 @code{gdbserver} does not automatically exit in multi-process mode.
14183 You can terminate it by using @code{monitor exit}
14184 (@pxref{Monitor Commands for gdbserver}).
14186 @subsubsection Other Command-Line Arguments for @code{gdbserver}
14188 The @option{--debug} option tells @code{gdbserver} to display extra
14189 status information about the debugging process. The
14190 @option{--remote-debug} option tells @code{gdbserver} to display
14191 remote protocol debug output. These options are intended for
14192 @code{gdbserver} development and for bug reports to the developers.
14194 The @option{--wrapper} option specifies a wrapper to launch programs
14195 for debugging. The option should be followed by the name of the
14196 wrapper, then any command-line arguments to pass to the wrapper, then
14197 @kbd{--} indicating the end of the wrapper arguments.
14199 @code{gdbserver} runs the specified wrapper program with a combined
14200 command line including the wrapper arguments, then the name of the
14201 program to debug, then any arguments to the program. The wrapper
14202 runs until it executes your program, and then @value{GDBN} gains control.
14204 You can use any program that eventually calls @code{execve} with
14205 its arguments as a wrapper. Several standard Unix utilities do
14206 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
14207 with @code{exec "$@@"} will also work.
14209 For example, you can use @code{env} to pass an environment variable to
14210 the debugged program, without setting the variable in @code{gdbserver}'s
14214 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
14217 @subsection Connecting to @code{gdbserver}
14219 Run @value{GDBN} on the host system.
14221 First make sure you have the necessary symbol files. Load symbols for
14222 your application using the @code{file} command before you connect. Use
14223 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
14224 was compiled with the correct sysroot using @code{--with-sysroot}).
14226 The symbol file and target libraries must exactly match the executable
14227 and libraries on the target, with one exception: the files on the host
14228 system should not be stripped, even if the files on the target system
14229 are. Mismatched or missing files will lead to confusing results
14230 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
14231 files may also prevent @code{gdbserver} from debugging multi-threaded
14234 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
14235 For TCP connections, you must start up @code{gdbserver} prior to using
14236 the @code{target remote} command. Otherwise you may get an error whose
14237 text depends on the host system, but which usually looks something like
14238 @samp{Connection refused}. Don't use the @code{load}
14239 command in @value{GDBN} when using @code{gdbserver}, since the program is
14240 already on the target.
14242 @subsection Monitor Commands for @code{gdbserver}
14243 @cindex monitor commands, for @code{gdbserver}
14244 @anchor{Monitor Commands for gdbserver}
14246 During a @value{GDBN} session using @code{gdbserver}, you can use the
14247 @code{monitor} command to send special requests to @code{gdbserver}.
14248 Here are the available commands.
14252 List the available monitor commands.
14254 @item monitor set debug 0
14255 @itemx monitor set debug 1
14256 Disable or enable general debugging messages.
14258 @item monitor set remote-debug 0
14259 @itemx monitor set remote-debug 1
14260 Disable or enable specific debugging messages associated with the remote
14261 protocol (@pxref{Remote Protocol}).
14264 Tell gdbserver to exit immediately. This command should be followed by
14265 @code{disconnect} to close the debugging session. @code{gdbserver} will
14266 detach from any attached processes and kill any processes it created.
14267 Use @code{monitor exit} to terminate @code{gdbserver} at the end
14268 of a multi-process mode debug session.
14272 @node Remote Configuration
14273 @section Remote Configuration
14276 @kindex show remote
14277 This section documents the configuration options available when
14278 debugging remote programs. For the options related to the File I/O
14279 extensions of the remote protocol, see @ref{system,
14280 system-call-allowed}.
14283 @item set remoteaddresssize @var{bits}
14284 @cindex address size for remote targets
14285 @cindex bits in remote address
14286 Set the maximum size of address in a memory packet to the specified
14287 number of bits. @value{GDBN} will mask off the address bits above
14288 that number, when it passes addresses to the remote target. The
14289 default value is the number of bits in the target's address.
14291 @item show remoteaddresssize
14292 Show the current value of remote address size in bits.
14294 @item set remotebaud @var{n}
14295 @cindex baud rate for remote targets
14296 Set the baud rate for the remote serial I/O to @var{n} baud. The
14297 value is used to set the speed of the serial port used for debugging
14300 @item show remotebaud
14301 Show the current speed of the remote connection.
14303 @item set remotebreak
14304 @cindex interrupt remote programs
14305 @cindex BREAK signal instead of Ctrl-C
14306 @anchor{set remotebreak}
14307 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
14308 when you type @kbd{Ctrl-c} to interrupt the program running
14309 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
14310 character instead. The default is off, since most remote systems
14311 expect to see @samp{Ctrl-C} as the interrupt signal.
14313 @item show remotebreak
14314 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
14315 interrupt the remote program.
14317 @item set remoteflow on
14318 @itemx set remoteflow off
14319 @kindex set remoteflow
14320 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
14321 on the serial port used to communicate to the remote target.
14323 @item show remoteflow
14324 @kindex show remoteflow
14325 Show the current setting of hardware flow control.
14327 @item set remotelogbase @var{base}
14328 Set the base (a.k.a.@: radix) of logging serial protocol
14329 communications to @var{base}. Supported values of @var{base} are:
14330 @code{ascii}, @code{octal}, and @code{hex}. The default is
14333 @item show remotelogbase
14334 Show the current setting of the radix for logging remote serial
14337 @item set remotelogfile @var{file}
14338 @cindex record serial communications on file
14339 Record remote serial communications on the named @var{file}. The
14340 default is not to record at all.
14342 @item show remotelogfile.
14343 Show the current setting of the file name on which to record the
14344 serial communications.
14346 @item set remotetimeout @var{num}
14347 @cindex timeout for serial communications
14348 @cindex remote timeout
14349 Set the timeout limit to wait for the remote target to respond to
14350 @var{num} seconds. The default is 2 seconds.
14352 @item show remotetimeout
14353 Show the current number of seconds to wait for the remote target
14356 @cindex limit hardware breakpoints and watchpoints
14357 @cindex remote target, limit break- and watchpoints
14358 @anchor{set remote hardware-watchpoint-limit}
14359 @anchor{set remote hardware-breakpoint-limit}
14360 @item set remote hardware-watchpoint-limit @var{limit}
14361 @itemx set remote hardware-breakpoint-limit @var{limit}
14362 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
14363 watchpoints. A limit of -1, the default, is treated as unlimited.
14365 @item set remote exec-file @var{filename}
14366 @itemx show remote exec-file
14367 @anchor{set remote exec-file}
14368 @cindex executable file, for remote target
14369 Select the file used for @code{run} with @code{target
14370 extended-remote}. This should be set to a filename valid on the
14371 target system. If it is not set, the target will use a default
14372 filename (e.g.@: the last program run).
14376 @item set tcp auto-retry on
14377 @cindex auto-retry, for remote TCP target
14378 Enable auto-retry for remote TCP connections. This is useful if the remote
14379 debugging agent is launched in parallel with @value{GDBN}; there is a race
14380 condition because the agent may not become ready to accept the connection
14381 before @value{GDBN} attempts to connect. When auto-retry is
14382 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
14383 to establish the connection using the timeout specified by
14384 @code{set tcp connect-timeout}.
14386 @item set tcp auto-retry off
14387 Do not auto-retry failed TCP connections.
14389 @item show tcp auto-retry
14390 Show the current auto-retry setting.
14392 @item set tcp connect-timeout @var{seconds}
14393 @cindex connection timeout, for remote TCP target
14394 @cindex timeout, for remote target connection
14395 Set the timeout for establishing a TCP connection to the remote target to
14396 @var{seconds}. The timeout affects both polling to retry failed connections
14397 (enabled by @code{set tcp auto-retry on}) and waiting for connections
14398 that are merely slow to complete, and represents an approximate cumulative
14401 @item show tcp connect-timeout
14402 Show the current connection timeout setting.
14405 @cindex remote packets, enabling and disabling
14406 The @value{GDBN} remote protocol autodetects the packets supported by
14407 your debugging stub. If you need to override the autodetection, you
14408 can use these commands to enable or disable individual packets. Each
14409 packet can be set to @samp{on} (the remote target supports this
14410 packet), @samp{off} (the remote target does not support this packet),
14411 or @samp{auto} (detect remote target support for this packet). They
14412 all default to @samp{auto}. For more information about each packet,
14413 see @ref{Remote Protocol}.
14415 During normal use, you should not have to use any of these commands.
14416 If you do, that may be a bug in your remote debugging stub, or a bug
14417 in @value{GDBN}. You may want to report the problem to the
14418 @value{GDBN} developers.
14420 For each packet @var{name}, the command to enable or disable the
14421 packet is @code{set remote @var{name}-packet}. The available settings
14424 @multitable @columnfractions 0.28 0.32 0.25
14427 @tab Related Features
14429 @item @code{fetch-register}
14431 @tab @code{info registers}
14433 @item @code{set-register}
14437 @item @code{binary-download}
14439 @tab @code{load}, @code{set}
14441 @item @code{read-aux-vector}
14442 @tab @code{qXfer:auxv:read}
14443 @tab @code{info auxv}
14445 @item @code{symbol-lookup}
14446 @tab @code{qSymbol}
14447 @tab Detecting multiple threads
14449 @item @code{attach}
14450 @tab @code{vAttach}
14453 @item @code{verbose-resume}
14455 @tab Stepping or resuming multiple threads
14461 @item @code{software-breakpoint}
14465 @item @code{hardware-breakpoint}
14469 @item @code{write-watchpoint}
14473 @item @code{read-watchpoint}
14477 @item @code{access-watchpoint}
14481 @item @code{target-features}
14482 @tab @code{qXfer:features:read}
14483 @tab @code{set architecture}
14485 @item @code{library-info}
14486 @tab @code{qXfer:libraries:read}
14487 @tab @code{info sharedlibrary}
14489 @item @code{memory-map}
14490 @tab @code{qXfer:memory-map:read}
14491 @tab @code{info mem}
14493 @item @code{read-spu-object}
14494 @tab @code{qXfer:spu:read}
14495 @tab @code{info spu}
14497 @item @code{write-spu-object}
14498 @tab @code{qXfer:spu:write}
14499 @tab @code{info spu}
14501 @item @code{read-siginfo-object}
14502 @tab @code{qXfer:siginfo:read}
14503 @tab @code{print $_siginfo}
14505 @item @code{write-siginfo-object}
14506 @tab @code{qXfer:siginfo:write}
14507 @tab @code{set $_siginfo}
14509 @item @code{get-thread-local-@*storage-address}
14510 @tab @code{qGetTLSAddr}
14511 @tab Displaying @code{__thread} variables
14513 @item @code{search-memory}
14514 @tab @code{qSearch:memory}
14517 @item @code{supported-packets}
14518 @tab @code{qSupported}
14519 @tab Remote communications parameters
14521 @item @code{pass-signals}
14522 @tab @code{QPassSignals}
14523 @tab @code{handle @var{signal}}
14525 @item @code{hostio-close-packet}
14526 @tab @code{vFile:close}
14527 @tab @code{remote get}, @code{remote put}
14529 @item @code{hostio-open-packet}
14530 @tab @code{vFile:open}
14531 @tab @code{remote get}, @code{remote put}
14533 @item @code{hostio-pread-packet}
14534 @tab @code{vFile:pread}
14535 @tab @code{remote get}, @code{remote put}
14537 @item @code{hostio-pwrite-packet}
14538 @tab @code{vFile:pwrite}
14539 @tab @code{remote get}, @code{remote put}
14541 @item @code{hostio-unlink-packet}
14542 @tab @code{vFile:unlink}
14543 @tab @code{remote delete}
14545 @item @code{noack-packet}
14546 @tab @code{QStartNoAckMode}
14547 @tab Packet acknowledgment
14549 @item @code{osdata}
14550 @tab @code{qXfer:osdata:read}
14551 @tab @code{info os}
14553 @item @code{query-attached}
14554 @tab @code{qAttached}
14555 @tab Querying remote process attach state.
14559 @section Implementing a Remote Stub
14561 @cindex debugging stub, example
14562 @cindex remote stub, example
14563 @cindex stub example, remote debugging
14564 The stub files provided with @value{GDBN} implement the target side of the
14565 communication protocol, and the @value{GDBN} side is implemented in the
14566 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
14567 these subroutines to communicate, and ignore the details. (If you're
14568 implementing your own stub file, you can still ignore the details: start
14569 with one of the existing stub files. @file{sparc-stub.c} is the best
14570 organized, and therefore the easiest to read.)
14572 @cindex remote serial debugging, overview
14573 To debug a program running on another machine (the debugging
14574 @dfn{target} machine), you must first arrange for all the usual
14575 prerequisites for the program to run by itself. For example, for a C
14580 A startup routine to set up the C runtime environment; these usually
14581 have a name like @file{crt0}. The startup routine may be supplied by
14582 your hardware supplier, or you may have to write your own.
14585 A C subroutine library to support your program's
14586 subroutine calls, notably managing input and output.
14589 A way of getting your program to the other machine---for example, a
14590 download program. These are often supplied by the hardware
14591 manufacturer, but you may have to write your own from hardware
14595 The next step is to arrange for your program to use a serial port to
14596 communicate with the machine where @value{GDBN} is running (the @dfn{host}
14597 machine). In general terms, the scheme looks like this:
14601 @value{GDBN} already understands how to use this protocol; when everything
14602 else is set up, you can simply use the @samp{target remote} command
14603 (@pxref{Targets,,Specifying a Debugging Target}).
14605 @item On the target,
14606 you must link with your program a few special-purpose subroutines that
14607 implement the @value{GDBN} remote serial protocol. The file containing these
14608 subroutines is called a @dfn{debugging stub}.
14610 On certain remote targets, you can use an auxiliary program
14611 @code{gdbserver} instead of linking a stub into your program.
14612 @xref{Server,,Using the @code{gdbserver} Program}, for details.
14615 The debugging stub is specific to the architecture of the remote
14616 machine; for example, use @file{sparc-stub.c} to debug programs on
14619 @cindex remote serial stub list
14620 These working remote stubs are distributed with @value{GDBN}:
14625 @cindex @file{i386-stub.c}
14628 For Intel 386 and compatible architectures.
14631 @cindex @file{m68k-stub.c}
14632 @cindex Motorola 680x0
14634 For Motorola 680x0 architectures.
14637 @cindex @file{sh-stub.c}
14640 For Renesas SH architectures.
14643 @cindex @file{sparc-stub.c}
14645 For @sc{sparc} architectures.
14647 @item sparcl-stub.c
14648 @cindex @file{sparcl-stub.c}
14651 For Fujitsu @sc{sparclite} architectures.
14655 The @file{README} file in the @value{GDBN} distribution may list other
14656 recently added stubs.
14659 * Stub Contents:: What the stub can do for you
14660 * Bootstrapping:: What you must do for the stub
14661 * Debug Session:: Putting it all together
14664 @node Stub Contents
14665 @subsection What the Stub Can Do for You
14667 @cindex remote serial stub
14668 The debugging stub for your architecture supplies these three
14672 @item set_debug_traps
14673 @findex set_debug_traps
14674 @cindex remote serial stub, initialization
14675 This routine arranges for @code{handle_exception} to run when your
14676 program stops. You must call this subroutine explicitly near the
14677 beginning of your program.
14679 @item handle_exception
14680 @findex handle_exception
14681 @cindex remote serial stub, main routine
14682 This is the central workhorse, but your program never calls it
14683 explicitly---the setup code arranges for @code{handle_exception} to
14684 run when a trap is triggered.
14686 @code{handle_exception} takes control when your program stops during
14687 execution (for example, on a breakpoint), and mediates communications
14688 with @value{GDBN} on the host machine. This is where the communications
14689 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
14690 representative on the target machine. It begins by sending summary
14691 information on the state of your program, then continues to execute,
14692 retrieving and transmitting any information @value{GDBN} needs, until you
14693 execute a @value{GDBN} command that makes your program resume; at that point,
14694 @code{handle_exception} returns control to your own code on the target
14698 @cindex @code{breakpoint} subroutine, remote
14699 Use this auxiliary subroutine to make your program contain a
14700 breakpoint. Depending on the particular situation, this may be the only
14701 way for @value{GDBN} to get control. For instance, if your target
14702 machine has some sort of interrupt button, you won't need to call this;
14703 pressing the interrupt button transfers control to
14704 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
14705 simply receiving characters on the serial port may also trigger a trap;
14706 again, in that situation, you don't need to call @code{breakpoint} from
14707 your own program---simply running @samp{target remote} from the host
14708 @value{GDBN} session gets control.
14710 Call @code{breakpoint} if none of these is true, or if you simply want
14711 to make certain your program stops at a predetermined point for the
14712 start of your debugging session.
14715 @node Bootstrapping
14716 @subsection What You Must Do for the Stub
14718 @cindex remote stub, support routines
14719 The debugging stubs that come with @value{GDBN} are set up for a particular
14720 chip architecture, but they have no information about the rest of your
14721 debugging target machine.
14723 First of all you need to tell the stub how to communicate with the
14727 @item int getDebugChar()
14728 @findex getDebugChar
14729 Write this subroutine to read a single character from the serial port.
14730 It may be identical to @code{getchar} for your target system; a
14731 different name is used to allow you to distinguish the two if you wish.
14733 @item void putDebugChar(int)
14734 @findex putDebugChar
14735 Write this subroutine to write a single character to the serial port.
14736 It may be identical to @code{putchar} for your target system; a
14737 different name is used to allow you to distinguish the two if you wish.
14740 @cindex control C, and remote debugging
14741 @cindex interrupting remote targets
14742 If you want @value{GDBN} to be able to stop your program while it is
14743 running, you need to use an interrupt-driven serial driver, and arrange
14744 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
14745 character). That is the character which @value{GDBN} uses to tell the
14746 remote system to stop.
14748 Getting the debugging target to return the proper status to @value{GDBN}
14749 probably requires changes to the standard stub; one quick and dirty way
14750 is to just execute a breakpoint instruction (the ``dirty'' part is that
14751 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
14753 Other routines you need to supply are:
14756 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
14757 @findex exceptionHandler
14758 Write this function to install @var{exception_address} in the exception
14759 handling tables. You need to do this because the stub does not have any
14760 way of knowing what the exception handling tables on your target system
14761 are like (for example, the processor's table might be in @sc{rom},
14762 containing entries which point to a table in @sc{ram}).
14763 @var{exception_number} is the exception number which should be changed;
14764 its meaning is architecture-dependent (for example, different numbers
14765 might represent divide by zero, misaligned access, etc). When this
14766 exception occurs, control should be transferred directly to
14767 @var{exception_address}, and the processor state (stack, registers,
14768 and so on) should be just as it is when a processor exception occurs. So if
14769 you want to use a jump instruction to reach @var{exception_address}, it
14770 should be a simple jump, not a jump to subroutine.
14772 For the 386, @var{exception_address} should be installed as an interrupt
14773 gate so that interrupts are masked while the handler runs. The gate
14774 should be at privilege level 0 (the most privileged level). The
14775 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
14776 help from @code{exceptionHandler}.
14778 @item void flush_i_cache()
14779 @findex flush_i_cache
14780 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
14781 instruction cache, if any, on your target machine. If there is no
14782 instruction cache, this subroutine may be a no-op.
14784 On target machines that have instruction caches, @value{GDBN} requires this
14785 function to make certain that the state of your program is stable.
14789 You must also make sure this library routine is available:
14792 @item void *memset(void *, int, int)
14794 This is the standard library function @code{memset} that sets an area of
14795 memory to a known value. If you have one of the free versions of
14796 @code{libc.a}, @code{memset} can be found there; otherwise, you must
14797 either obtain it from your hardware manufacturer, or write your own.
14800 If you do not use the GNU C compiler, you may need other standard
14801 library subroutines as well; this varies from one stub to another,
14802 but in general the stubs are likely to use any of the common library
14803 subroutines which @code{@value{NGCC}} generates as inline code.
14806 @node Debug Session
14807 @subsection Putting it All Together
14809 @cindex remote serial debugging summary
14810 In summary, when your program is ready to debug, you must follow these
14815 Make sure you have defined the supporting low-level routines
14816 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
14818 @code{getDebugChar}, @code{putDebugChar},
14819 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
14823 Insert these lines near the top of your program:
14831 For the 680x0 stub only, you need to provide a variable called
14832 @code{exceptionHook}. Normally you just use:
14835 void (*exceptionHook)() = 0;
14839 but if before calling @code{set_debug_traps}, you set it to point to a
14840 function in your program, that function is called when
14841 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
14842 error). The function indicated by @code{exceptionHook} is called with
14843 one parameter: an @code{int} which is the exception number.
14846 Compile and link together: your program, the @value{GDBN} debugging stub for
14847 your target architecture, and the supporting subroutines.
14850 Make sure you have a serial connection between your target machine and
14851 the @value{GDBN} host, and identify the serial port on the host.
14854 @c The "remote" target now provides a `load' command, so we should
14855 @c document that. FIXME.
14856 Download your program to your target machine (or get it there by
14857 whatever means the manufacturer provides), and start it.
14860 Start @value{GDBN} on the host, and connect to the target
14861 (@pxref{Connecting,,Connecting to a Remote Target}).
14865 @node Configurations
14866 @chapter Configuration-Specific Information
14868 While nearly all @value{GDBN} commands are available for all native and
14869 cross versions of the debugger, there are some exceptions. This chapter
14870 describes things that are only available in certain configurations.
14872 There are three major categories of configurations: native
14873 configurations, where the host and target are the same, embedded
14874 operating system configurations, which are usually the same for several
14875 different processor architectures, and bare embedded processors, which
14876 are quite different from each other.
14881 * Embedded Processors::
14888 This section describes details specific to particular native
14893 * BSD libkvm Interface:: Debugging BSD kernel memory images
14894 * SVR4 Process Information:: SVR4 process information
14895 * DJGPP Native:: Features specific to the DJGPP port
14896 * Cygwin Native:: Features specific to the Cygwin port
14897 * Hurd Native:: Features specific to @sc{gnu} Hurd
14898 * Neutrino:: Features specific to QNX Neutrino
14899 * Darwin:: Features specific to Darwin
14905 On HP-UX systems, if you refer to a function or variable name that
14906 begins with a dollar sign, @value{GDBN} searches for a user or system
14907 name first, before it searches for a convenience variable.
14910 @node BSD libkvm Interface
14911 @subsection BSD libkvm Interface
14914 @cindex kernel memory image
14915 @cindex kernel crash dump
14917 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14918 interface that provides a uniform interface for accessing kernel virtual
14919 memory images, including live systems and crash dumps. @value{GDBN}
14920 uses this interface to allow you to debug live kernels and kernel crash
14921 dumps on many native BSD configurations. This is implemented as a
14922 special @code{kvm} debugging target. For debugging a live system, load
14923 the currently running kernel into @value{GDBN} and connect to the
14927 (@value{GDBP}) @b{target kvm}
14930 For debugging crash dumps, provide the file name of the crash dump as an
14934 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14937 Once connected to the @code{kvm} target, the following commands are
14943 Set current context from the @dfn{Process Control Block} (PCB) address.
14946 Set current context from proc address. This command isn't available on
14947 modern FreeBSD systems.
14950 @node SVR4 Process Information
14951 @subsection SVR4 Process Information
14953 @cindex examine process image
14954 @cindex process info via @file{/proc}
14956 Many versions of SVR4 and compatible systems provide a facility called
14957 @samp{/proc} that can be used to examine the image of a running
14958 process using file-system subroutines. If @value{GDBN} is configured
14959 for an operating system with this facility, the command @code{info
14960 proc} is available to report information about the process running
14961 your program, or about any process running on your system. @code{info
14962 proc} works only on SVR4 systems that include the @code{procfs} code.
14963 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14964 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14970 @itemx info proc @var{process-id}
14971 Summarize available information about any running process. If a
14972 process ID is specified by @var{process-id}, display information about
14973 that process; otherwise display information about the program being
14974 debugged. The summary includes the debugged process ID, the command
14975 line used to invoke it, its current working directory, and its
14976 executable file's absolute file name.
14978 On some systems, @var{process-id} can be of the form
14979 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14980 within a process. If the optional @var{pid} part is missing, it means
14981 a thread from the process being debugged (the leading @samp{/} still
14982 needs to be present, or else @value{GDBN} will interpret the number as
14983 a process ID rather than a thread ID).
14985 @item info proc mappings
14986 @cindex memory address space mappings
14987 Report the memory address space ranges accessible in the program, with
14988 information on whether the process has read, write, or execute access
14989 rights to each range. On @sc{gnu}/Linux systems, each memory range
14990 includes the object file which is mapped to that range, instead of the
14991 memory access rights to that range.
14993 @item info proc stat
14994 @itemx info proc status
14995 @cindex process detailed status information
14996 These subcommands are specific to @sc{gnu}/Linux systems. They show
14997 the process-related information, including the user ID and group ID;
14998 how many threads are there in the process; its virtual memory usage;
14999 the signals that are pending, blocked, and ignored; its TTY; its
15000 consumption of system and user time; its stack size; its @samp{nice}
15001 value; etc. For more information, see the @samp{proc} man page
15002 (type @kbd{man 5 proc} from your shell prompt).
15004 @item info proc all
15005 Show all the information about the process described under all of the
15006 above @code{info proc} subcommands.
15009 @comment These sub-options of 'info proc' were not included when
15010 @comment procfs.c was re-written. Keep their descriptions around
15011 @comment against the day when someone finds the time to put them back in.
15012 @kindex info proc times
15013 @item info proc times
15014 Starting time, user CPU time, and system CPU time for your program and
15017 @kindex info proc id
15019 Report on the process IDs related to your program: its own process ID,
15020 the ID of its parent, the process group ID, and the session ID.
15023 @item set procfs-trace
15024 @kindex set procfs-trace
15025 @cindex @code{procfs} API calls
15026 This command enables and disables tracing of @code{procfs} API calls.
15028 @item show procfs-trace
15029 @kindex show procfs-trace
15030 Show the current state of @code{procfs} API call tracing.
15032 @item set procfs-file @var{file}
15033 @kindex set procfs-file
15034 Tell @value{GDBN} to write @code{procfs} API trace to the named
15035 @var{file}. @value{GDBN} appends the trace info to the previous
15036 contents of the file. The default is to display the trace on the
15039 @item show procfs-file
15040 @kindex show procfs-file
15041 Show the file to which @code{procfs} API trace is written.
15043 @item proc-trace-entry
15044 @itemx proc-trace-exit
15045 @itemx proc-untrace-entry
15046 @itemx proc-untrace-exit
15047 @kindex proc-trace-entry
15048 @kindex proc-trace-exit
15049 @kindex proc-untrace-entry
15050 @kindex proc-untrace-exit
15051 These commands enable and disable tracing of entries into and exits
15052 from the @code{syscall} interface.
15055 @kindex info pidlist
15056 @cindex process list, QNX Neutrino
15057 For QNX Neutrino only, this command displays the list of all the
15058 processes and all the threads within each process.
15061 @kindex info meminfo
15062 @cindex mapinfo list, QNX Neutrino
15063 For QNX Neutrino only, this command displays the list of all mapinfos.
15067 @subsection Features for Debugging @sc{djgpp} Programs
15068 @cindex @sc{djgpp} debugging
15069 @cindex native @sc{djgpp} debugging
15070 @cindex MS-DOS-specific commands
15073 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
15074 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
15075 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
15076 top of real-mode DOS systems and their emulations.
15078 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
15079 defines a few commands specific to the @sc{djgpp} port. This
15080 subsection describes those commands.
15085 This is a prefix of @sc{djgpp}-specific commands which print
15086 information about the target system and important OS structures.
15089 @cindex MS-DOS system info
15090 @cindex free memory information (MS-DOS)
15091 @item info dos sysinfo
15092 This command displays assorted information about the underlying
15093 platform: the CPU type and features, the OS version and flavor, the
15094 DPMI version, and the available conventional and DPMI memory.
15099 @cindex segment descriptor tables
15100 @cindex descriptor tables display
15102 @itemx info dos ldt
15103 @itemx info dos idt
15104 These 3 commands display entries from, respectively, Global, Local,
15105 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
15106 tables are data structures which store a descriptor for each segment
15107 that is currently in use. The segment's selector is an index into a
15108 descriptor table; the table entry for that index holds the
15109 descriptor's base address and limit, and its attributes and access
15112 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
15113 segment (used for both data and the stack), and a DOS segment (which
15114 allows access to DOS/BIOS data structures and absolute addresses in
15115 conventional memory). However, the DPMI host will usually define
15116 additional segments in order to support the DPMI environment.
15118 @cindex garbled pointers
15119 These commands allow to display entries from the descriptor tables.
15120 Without an argument, all entries from the specified table are
15121 displayed. An argument, which should be an integer expression, means
15122 display a single entry whose index is given by the argument. For
15123 example, here's a convenient way to display information about the
15124 debugged program's data segment:
15127 @exdent @code{(@value{GDBP}) info dos ldt $ds}
15128 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
15132 This comes in handy when you want to see whether a pointer is outside
15133 the data segment's limit (i.e.@: @dfn{garbled}).
15135 @cindex page tables display (MS-DOS)
15137 @itemx info dos pte
15138 These two commands display entries from, respectively, the Page
15139 Directory and the Page Tables. Page Directories and Page Tables are
15140 data structures which control how virtual memory addresses are mapped
15141 into physical addresses. A Page Table includes an entry for every
15142 page of memory that is mapped into the program's address space; there
15143 may be several Page Tables, each one holding up to 4096 entries. A
15144 Page Directory has up to 4096 entries, one each for every Page Table
15145 that is currently in use.
15147 Without an argument, @kbd{info dos pde} displays the entire Page
15148 Directory, and @kbd{info dos pte} displays all the entries in all of
15149 the Page Tables. An argument, an integer expression, given to the
15150 @kbd{info dos pde} command means display only that entry from the Page
15151 Directory table. An argument given to the @kbd{info dos pte} command
15152 means display entries from a single Page Table, the one pointed to by
15153 the specified entry in the Page Directory.
15155 @cindex direct memory access (DMA) on MS-DOS
15156 These commands are useful when your program uses @dfn{DMA} (Direct
15157 Memory Access), which needs physical addresses to program the DMA
15160 These commands are supported only with some DPMI servers.
15162 @cindex physical address from linear address
15163 @item info dos address-pte @var{addr}
15164 This command displays the Page Table entry for a specified linear
15165 address. The argument @var{addr} is a linear address which should
15166 already have the appropriate segment's base address added to it,
15167 because this command accepts addresses which may belong to @emph{any}
15168 segment. For example, here's how to display the Page Table entry for
15169 the page where a variable @code{i} is stored:
15172 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
15173 @exdent @code{Page Table entry for address 0x11a00d30:}
15174 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
15178 This says that @code{i} is stored at offset @code{0xd30} from the page
15179 whose physical base address is @code{0x02698000}, and shows all the
15180 attributes of that page.
15182 Note that you must cast the addresses of variables to a @code{char *},
15183 since otherwise the value of @code{__djgpp_base_address}, the base
15184 address of all variables and functions in a @sc{djgpp} program, will
15185 be added using the rules of C pointer arithmetics: if @code{i} is
15186 declared an @code{int}, @value{GDBN} will add 4 times the value of
15187 @code{__djgpp_base_address} to the address of @code{i}.
15189 Here's another example, it displays the Page Table entry for the
15193 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
15194 @exdent @code{Page Table entry for address 0x29110:}
15195 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
15199 (The @code{+ 3} offset is because the transfer buffer's address is the
15200 3rd member of the @code{_go32_info_block} structure.) The output
15201 clearly shows that this DPMI server maps the addresses in conventional
15202 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
15203 linear (@code{0x29110}) addresses are identical.
15205 This command is supported only with some DPMI servers.
15208 @cindex DOS serial data link, remote debugging
15209 In addition to native debugging, the DJGPP port supports remote
15210 debugging via a serial data link. The following commands are specific
15211 to remote serial debugging in the DJGPP port of @value{GDBN}.
15214 @kindex set com1base
15215 @kindex set com1irq
15216 @kindex set com2base
15217 @kindex set com2irq
15218 @kindex set com3base
15219 @kindex set com3irq
15220 @kindex set com4base
15221 @kindex set com4irq
15222 @item set com1base @var{addr}
15223 This command sets the base I/O port address of the @file{COM1} serial
15226 @item set com1irq @var{irq}
15227 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
15228 for the @file{COM1} serial port.
15230 There are similar commands @samp{set com2base}, @samp{set com3irq},
15231 etc.@: for setting the port address and the @code{IRQ} lines for the
15234 @kindex show com1base
15235 @kindex show com1irq
15236 @kindex show com2base
15237 @kindex show com2irq
15238 @kindex show com3base
15239 @kindex show com3irq
15240 @kindex show com4base
15241 @kindex show com4irq
15242 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
15243 display the current settings of the base address and the @code{IRQ}
15244 lines used by the COM ports.
15247 @kindex info serial
15248 @cindex DOS serial port status
15249 This command prints the status of the 4 DOS serial ports. For each
15250 port, it prints whether it's active or not, its I/O base address and
15251 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
15252 counts of various errors encountered so far.
15256 @node Cygwin Native
15257 @subsection Features for Debugging MS Windows PE Executables
15258 @cindex MS Windows debugging
15259 @cindex native Cygwin debugging
15260 @cindex Cygwin-specific commands
15262 @value{GDBN} supports native debugging of MS Windows programs, including
15263 DLLs with and without symbolic debugging information. There are various
15264 additional Cygwin-specific commands, described in this section.
15265 Working with DLLs that have no debugging symbols is described in
15266 @ref{Non-debug DLL Symbols}.
15271 This is a prefix of MS Windows-specific commands which print
15272 information about the target system and important OS structures.
15274 @item info w32 selector
15275 This command displays information returned by
15276 the Win32 API @code{GetThreadSelectorEntry} function.
15277 It takes an optional argument that is evaluated to
15278 a long value to give the information about this given selector.
15279 Without argument, this command displays information
15280 about the six segment registers.
15284 This is a Cygwin-specific alias of @code{info shared}.
15286 @kindex dll-symbols
15288 This command loads symbols from a dll similarly to
15289 add-sym command but without the need to specify a base address.
15291 @kindex set cygwin-exceptions
15292 @cindex debugging the Cygwin DLL
15293 @cindex Cygwin DLL, debugging
15294 @item set cygwin-exceptions @var{mode}
15295 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
15296 happen inside the Cygwin DLL. If @var{mode} is @code{off},
15297 @value{GDBN} will delay recognition of exceptions, and may ignore some
15298 exceptions which seem to be caused by internal Cygwin DLL
15299 ``bookkeeping''. This option is meant primarily for debugging the
15300 Cygwin DLL itself; the default value is @code{off} to avoid annoying
15301 @value{GDBN} users with false @code{SIGSEGV} signals.
15303 @kindex show cygwin-exceptions
15304 @item show cygwin-exceptions
15305 Displays whether @value{GDBN} will break on exceptions that happen
15306 inside the Cygwin DLL itself.
15308 @kindex set new-console
15309 @item set new-console @var{mode}
15310 If @var{mode} is @code{on} the debuggee will
15311 be started in a new console on next start.
15312 If @var{mode} is @code{off}i, the debuggee will
15313 be started in the same console as the debugger.
15315 @kindex show new-console
15316 @item show new-console
15317 Displays whether a new console is used
15318 when the debuggee is started.
15320 @kindex set new-group
15321 @item set new-group @var{mode}
15322 This boolean value controls whether the debuggee should
15323 start a new group or stay in the same group as the debugger.
15324 This affects the way the Windows OS handles
15327 @kindex show new-group
15328 @item show new-group
15329 Displays current value of new-group boolean.
15331 @kindex set debugevents
15332 @item set debugevents
15333 This boolean value adds debug output concerning kernel events related
15334 to the debuggee seen by the debugger. This includes events that
15335 signal thread and process creation and exit, DLL loading and
15336 unloading, console interrupts, and debugging messages produced by the
15337 Windows @code{OutputDebugString} API call.
15339 @kindex set debugexec
15340 @item set debugexec
15341 This boolean value adds debug output concerning execute events
15342 (such as resume thread) seen by the debugger.
15344 @kindex set debugexceptions
15345 @item set debugexceptions
15346 This boolean value adds debug output concerning exceptions in the
15347 debuggee seen by the debugger.
15349 @kindex set debugmemory
15350 @item set debugmemory
15351 This boolean value adds debug output concerning debuggee memory reads
15352 and writes by the debugger.
15356 This boolean values specifies whether the debuggee is called
15357 via a shell or directly (default value is on).
15361 Displays if the debuggee will be started with a shell.
15366 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
15369 @node Non-debug DLL Symbols
15370 @subsubsection Support for DLLs without Debugging Symbols
15371 @cindex DLLs with no debugging symbols
15372 @cindex Minimal symbols and DLLs
15374 Very often on windows, some of the DLLs that your program relies on do
15375 not include symbolic debugging information (for example,
15376 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
15377 symbols in a DLL, it relies on the minimal amount of symbolic
15378 information contained in the DLL's export table. This section
15379 describes working with such symbols, known internally to @value{GDBN} as
15380 ``minimal symbols''.
15382 Note that before the debugged program has started execution, no DLLs
15383 will have been loaded. The easiest way around this problem is simply to
15384 start the program --- either by setting a breakpoint or letting the
15385 program run once to completion. It is also possible to force
15386 @value{GDBN} to load a particular DLL before starting the executable ---
15387 see the shared library information in @ref{Files}, or the
15388 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
15389 explicitly loading symbols from a DLL with no debugging information will
15390 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
15391 which may adversely affect symbol lookup performance.
15393 @subsubsection DLL Name Prefixes
15395 In keeping with the naming conventions used by the Microsoft debugging
15396 tools, DLL export symbols are made available with a prefix based on the
15397 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
15398 also entered into the symbol table, so @code{CreateFileA} is often
15399 sufficient. In some cases there will be name clashes within a program
15400 (particularly if the executable itself includes full debugging symbols)
15401 necessitating the use of the fully qualified name when referring to the
15402 contents of the DLL. Use single-quotes around the name to avoid the
15403 exclamation mark (``!'') being interpreted as a language operator.
15405 Note that the internal name of the DLL may be all upper-case, even
15406 though the file name of the DLL is lower-case, or vice-versa. Since
15407 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
15408 some confusion. If in doubt, try the @code{info functions} and
15409 @code{info variables} commands or even @code{maint print msymbols}
15410 (@pxref{Symbols}). Here's an example:
15413 (@value{GDBP}) info function CreateFileA
15414 All functions matching regular expression "CreateFileA":
15416 Non-debugging symbols:
15417 0x77e885f4 CreateFileA
15418 0x77e885f4 KERNEL32!CreateFileA
15422 (@value{GDBP}) info function !
15423 All functions matching regular expression "!":
15425 Non-debugging symbols:
15426 0x6100114c cygwin1!__assert
15427 0x61004034 cygwin1!_dll_crt0@@0
15428 0x61004240 cygwin1!dll_crt0(per_process *)
15432 @subsubsection Working with Minimal Symbols
15434 Symbols extracted from a DLL's export table do not contain very much
15435 type information. All that @value{GDBN} can do is guess whether a symbol
15436 refers to a function or variable depending on the linker section that
15437 contains the symbol. Also note that the actual contents of the memory
15438 contained in a DLL are not available unless the program is running. This
15439 means that you cannot examine the contents of a variable or disassemble
15440 a function within a DLL without a running program.
15442 Variables are generally treated as pointers and dereferenced
15443 automatically. For this reason, it is often necessary to prefix a
15444 variable name with the address-of operator (``&'') and provide explicit
15445 type information in the command. Here's an example of the type of
15449 (@value{GDBP}) print 'cygwin1!__argv'
15454 (@value{GDBP}) x 'cygwin1!__argv'
15455 0x10021610: "\230y\""
15458 And two possible solutions:
15461 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
15462 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
15466 (@value{GDBP}) x/2x &'cygwin1!__argv'
15467 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
15468 (@value{GDBP}) x/x 0x10021608
15469 0x10021608: 0x0022fd98
15470 (@value{GDBP}) x/s 0x0022fd98
15471 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
15474 Setting a break point within a DLL is possible even before the program
15475 starts execution. However, under these circumstances, @value{GDBN} can't
15476 examine the initial instructions of the function in order to skip the
15477 function's frame set-up code. You can work around this by using ``*&''
15478 to set the breakpoint at a raw memory address:
15481 (@value{GDBP}) break *&'python22!PyOS_Readline'
15482 Breakpoint 1 at 0x1e04eff0
15485 The author of these extensions is not entirely convinced that setting a
15486 break point within a shared DLL like @file{kernel32.dll} is completely
15490 @subsection Commands Specific to @sc{gnu} Hurd Systems
15491 @cindex @sc{gnu} Hurd debugging
15493 This subsection describes @value{GDBN} commands specific to the
15494 @sc{gnu} Hurd native debugging.
15499 @kindex set signals@r{, Hurd command}
15500 @kindex set sigs@r{, Hurd command}
15501 This command toggles the state of inferior signal interception by
15502 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
15503 affected by this command. @code{sigs} is a shorthand alias for
15508 @kindex show signals@r{, Hurd command}
15509 @kindex show sigs@r{, Hurd command}
15510 Show the current state of intercepting inferior's signals.
15512 @item set signal-thread
15513 @itemx set sigthread
15514 @kindex set signal-thread
15515 @kindex set sigthread
15516 This command tells @value{GDBN} which thread is the @code{libc} signal
15517 thread. That thread is run when a signal is delivered to a running
15518 process. @code{set sigthread} is the shorthand alias of @code{set
15521 @item show signal-thread
15522 @itemx show sigthread
15523 @kindex show signal-thread
15524 @kindex show sigthread
15525 These two commands show which thread will run when the inferior is
15526 delivered a signal.
15529 @kindex set stopped@r{, Hurd command}
15530 This commands tells @value{GDBN} that the inferior process is stopped,
15531 as with the @code{SIGSTOP} signal. The stopped process can be
15532 continued by delivering a signal to it.
15535 @kindex show stopped@r{, Hurd command}
15536 This command shows whether @value{GDBN} thinks the debuggee is
15539 @item set exceptions
15540 @kindex set exceptions@r{, Hurd command}
15541 Use this command to turn off trapping of exceptions in the inferior.
15542 When exception trapping is off, neither breakpoints nor
15543 single-stepping will work. To restore the default, set exception
15546 @item show exceptions
15547 @kindex show exceptions@r{, Hurd command}
15548 Show the current state of trapping exceptions in the inferior.
15550 @item set task pause
15551 @kindex set task@r{, Hurd commands}
15552 @cindex task attributes (@sc{gnu} Hurd)
15553 @cindex pause current task (@sc{gnu} Hurd)
15554 This command toggles task suspension when @value{GDBN} has control.
15555 Setting it to on takes effect immediately, and the task is suspended
15556 whenever @value{GDBN} gets control. Setting it to off will take
15557 effect the next time the inferior is continued. If this option is set
15558 to off, you can use @code{set thread default pause on} or @code{set
15559 thread pause on} (see below) to pause individual threads.
15561 @item show task pause
15562 @kindex show task@r{, Hurd commands}
15563 Show the current state of task suspension.
15565 @item set task detach-suspend-count
15566 @cindex task suspend count
15567 @cindex detach from task, @sc{gnu} Hurd
15568 This command sets the suspend count the task will be left with when
15569 @value{GDBN} detaches from it.
15571 @item show task detach-suspend-count
15572 Show the suspend count the task will be left with when detaching.
15574 @item set task exception-port
15575 @itemx set task excp
15576 @cindex task exception port, @sc{gnu} Hurd
15577 This command sets the task exception port to which @value{GDBN} will
15578 forward exceptions. The argument should be the value of the @dfn{send
15579 rights} of the task. @code{set task excp} is a shorthand alias.
15581 @item set noninvasive
15582 @cindex noninvasive task options
15583 This command switches @value{GDBN} to a mode that is the least
15584 invasive as far as interfering with the inferior is concerned. This
15585 is the same as using @code{set task pause}, @code{set exceptions}, and
15586 @code{set signals} to values opposite to the defaults.
15588 @item info send-rights
15589 @itemx info receive-rights
15590 @itemx info port-rights
15591 @itemx info port-sets
15592 @itemx info dead-names
15595 @cindex send rights, @sc{gnu} Hurd
15596 @cindex receive rights, @sc{gnu} Hurd
15597 @cindex port rights, @sc{gnu} Hurd
15598 @cindex port sets, @sc{gnu} Hurd
15599 @cindex dead names, @sc{gnu} Hurd
15600 These commands display information about, respectively, send rights,
15601 receive rights, port rights, port sets, and dead names of a task.
15602 There are also shorthand aliases: @code{info ports} for @code{info
15603 port-rights} and @code{info psets} for @code{info port-sets}.
15605 @item set thread pause
15606 @kindex set thread@r{, Hurd command}
15607 @cindex thread properties, @sc{gnu} Hurd
15608 @cindex pause current thread (@sc{gnu} Hurd)
15609 This command toggles current thread suspension when @value{GDBN} has
15610 control. Setting it to on takes effect immediately, and the current
15611 thread is suspended whenever @value{GDBN} gets control. Setting it to
15612 off will take effect the next time the inferior is continued.
15613 Normally, this command has no effect, since when @value{GDBN} has
15614 control, the whole task is suspended. However, if you used @code{set
15615 task pause off} (see above), this command comes in handy to suspend
15616 only the current thread.
15618 @item show thread pause
15619 @kindex show thread@r{, Hurd command}
15620 This command shows the state of current thread suspension.
15622 @item set thread run
15623 This command sets whether the current thread is allowed to run.
15625 @item show thread run
15626 Show whether the current thread is allowed to run.
15628 @item set thread detach-suspend-count
15629 @cindex thread suspend count, @sc{gnu} Hurd
15630 @cindex detach from thread, @sc{gnu} Hurd
15631 This command sets the suspend count @value{GDBN} will leave on a
15632 thread when detaching. This number is relative to the suspend count
15633 found by @value{GDBN} when it notices the thread; use @code{set thread
15634 takeover-suspend-count} to force it to an absolute value.
15636 @item show thread detach-suspend-count
15637 Show the suspend count @value{GDBN} will leave on the thread when
15640 @item set thread exception-port
15641 @itemx set thread excp
15642 Set the thread exception port to which to forward exceptions. This
15643 overrides the port set by @code{set task exception-port} (see above).
15644 @code{set thread excp} is the shorthand alias.
15646 @item set thread takeover-suspend-count
15647 Normally, @value{GDBN}'s thread suspend counts are relative to the
15648 value @value{GDBN} finds when it notices each thread. This command
15649 changes the suspend counts to be absolute instead.
15651 @item set thread default
15652 @itemx show thread default
15653 @cindex thread default settings, @sc{gnu} Hurd
15654 Each of the above @code{set thread} commands has a @code{set thread
15655 default} counterpart (e.g., @code{set thread default pause}, @code{set
15656 thread default exception-port}, etc.). The @code{thread default}
15657 variety of commands sets the default thread properties for all
15658 threads; you can then change the properties of individual threads with
15659 the non-default commands.
15664 @subsection QNX Neutrino
15665 @cindex QNX Neutrino
15667 @value{GDBN} provides the following commands specific to the QNX
15671 @item set debug nto-debug
15672 @kindex set debug nto-debug
15673 When set to on, enables debugging messages specific to the QNX
15676 @item show debug nto-debug
15677 @kindex show debug nto-debug
15678 Show the current state of QNX Neutrino messages.
15685 @value{GDBN} provides the following commands specific to the Darwin target:
15688 @item set debug darwin @var{num}
15689 @kindex set debug darwin
15690 When set to a non zero value, enables debugging messages specific to
15691 the Darwin support. Higher values produce more verbose output.
15693 @item show debug darwin
15694 @kindex show debug darwin
15695 Show the current state of Darwin messages.
15697 @item set debug mach-o @var{num}
15698 @kindex set debug mach-o
15699 When set to a non zero value, enables debugging messages while
15700 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
15701 file format used on Darwin for object and executable files.) Higher
15702 values produce more verbose output. This is a command to diagnose
15703 problems internal to @value{GDBN} and should not be needed in normal
15706 @item show debug mach-o
15707 @kindex show debug mach-o
15708 Show the current state of Mach-O file messages.
15710 @item set mach-exceptions on
15711 @itemx set mach-exceptions off
15712 @kindex set mach-exceptions
15713 On Darwin, faults are first reported as a Mach exception and are then
15714 mapped to a Posix signal. Use this command to turn on trapping of
15715 Mach exceptions in the inferior. This might be sometimes useful to
15716 better understand the cause of a fault. The default is off.
15718 @item show mach-exceptions
15719 @kindex show mach-exceptions
15720 Show the current state of exceptions trapping.
15725 @section Embedded Operating Systems
15727 This section describes configurations involving the debugging of
15728 embedded operating systems that are available for several different
15732 * VxWorks:: Using @value{GDBN} with VxWorks
15735 @value{GDBN} includes the ability to debug programs running on
15736 various real-time operating systems.
15739 @subsection Using @value{GDBN} with VxWorks
15745 @kindex target vxworks
15746 @item target vxworks @var{machinename}
15747 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
15748 is the target system's machine name or IP address.
15752 On VxWorks, @code{load} links @var{filename} dynamically on the
15753 current target system as well as adding its symbols in @value{GDBN}.
15755 @value{GDBN} enables developers to spawn and debug tasks running on networked
15756 VxWorks targets from a Unix host. Already-running tasks spawned from
15757 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
15758 both the Unix host and on the VxWorks target. The program
15759 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
15760 installed with the name @code{vxgdb}, to distinguish it from a
15761 @value{GDBN} for debugging programs on the host itself.)
15764 @item VxWorks-timeout @var{args}
15765 @kindex vxworks-timeout
15766 All VxWorks-based targets now support the option @code{vxworks-timeout}.
15767 This option is set by the user, and @var{args} represents the number of
15768 seconds @value{GDBN} waits for responses to rpc's. You might use this if
15769 your VxWorks target is a slow software simulator or is on the far side
15770 of a thin network line.
15773 The following information on connecting to VxWorks was current when
15774 this manual was produced; newer releases of VxWorks may use revised
15777 @findex INCLUDE_RDB
15778 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
15779 to include the remote debugging interface routines in the VxWorks
15780 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
15781 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
15782 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
15783 source debugging task @code{tRdbTask} when VxWorks is booted. For more
15784 information on configuring and remaking VxWorks, see the manufacturer's
15786 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
15788 Once you have included @file{rdb.a} in your VxWorks system image and set
15789 your Unix execution search path to find @value{GDBN}, you are ready to
15790 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
15791 @code{vxgdb}, depending on your installation).
15793 @value{GDBN} comes up showing the prompt:
15800 * VxWorks Connection:: Connecting to VxWorks
15801 * VxWorks Download:: VxWorks download
15802 * VxWorks Attach:: Running tasks
15805 @node VxWorks Connection
15806 @subsubsection Connecting to VxWorks
15808 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
15809 network. To connect to a target whose host name is ``@code{tt}'', type:
15812 (vxgdb) target vxworks tt
15816 @value{GDBN} displays messages like these:
15819 Attaching remote machine across net...
15824 @value{GDBN} then attempts to read the symbol tables of any object modules
15825 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
15826 these files by searching the directories listed in the command search
15827 path (@pxref{Environment, ,Your Program's Environment}); if it fails
15828 to find an object file, it displays a message such as:
15831 prog.o: No such file or directory.
15834 When this happens, add the appropriate directory to the search path with
15835 the @value{GDBN} command @code{path}, and execute the @code{target}
15838 @node VxWorks Download
15839 @subsubsection VxWorks Download
15841 @cindex download to VxWorks
15842 If you have connected to the VxWorks target and you want to debug an
15843 object that has not yet been loaded, you can use the @value{GDBN}
15844 @code{load} command to download a file from Unix to VxWorks
15845 incrementally. The object file given as an argument to the @code{load}
15846 command is actually opened twice: first by the VxWorks target in order
15847 to download the code, then by @value{GDBN} in order to read the symbol
15848 table. This can lead to problems if the current working directories on
15849 the two systems differ. If both systems have NFS mounted the same
15850 filesystems, you can avoid these problems by using absolute paths.
15851 Otherwise, it is simplest to set the working directory on both systems
15852 to the directory in which the object file resides, and then to reference
15853 the file by its name, without any path. For instance, a program
15854 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
15855 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
15856 program, type this on VxWorks:
15859 -> cd "@var{vxpath}/vw/demo/rdb"
15863 Then, in @value{GDBN}, type:
15866 (vxgdb) cd @var{hostpath}/vw/demo/rdb
15867 (vxgdb) load prog.o
15870 @value{GDBN} displays a response similar to this:
15873 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
15876 You can also use the @code{load} command to reload an object module
15877 after editing and recompiling the corresponding source file. Note that
15878 this makes @value{GDBN} delete all currently-defined breakpoints,
15879 auto-displays, and convenience variables, and to clear the value
15880 history. (This is necessary in order to preserve the integrity of
15881 debugger's data structures that reference the target system's symbol
15884 @node VxWorks Attach
15885 @subsubsection Running Tasks
15887 @cindex running VxWorks tasks
15888 You can also attach to an existing task using the @code{attach} command as
15892 (vxgdb) attach @var{task}
15896 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
15897 or suspended when you attach to it. Running tasks are suspended at
15898 the time of attachment.
15900 @node Embedded Processors
15901 @section Embedded Processors
15903 This section goes into details specific to particular embedded
15906 @cindex send command to simulator
15907 Whenever a specific embedded processor has a simulator, @value{GDBN}
15908 allows to send an arbitrary command to the simulator.
15911 @item sim @var{command}
15912 @kindex sim@r{, a command}
15913 Send an arbitrary @var{command} string to the simulator. Consult the
15914 documentation for the specific simulator in use for information about
15915 acceptable commands.
15921 * M32R/D:: Renesas M32R/D
15922 * M68K:: Motorola M68K
15923 * MIPS Embedded:: MIPS Embedded
15924 * OpenRISC 1000:: OpenRisc 1000
15925 * PA:: HP PA Embedded
15926 * PowerPC Embedded:: PowerPC Embedded
15927 * Sparclet:: Tsqware Sparclet
15928 * Sparclite:: Fujitsu Sparclite
15929 * Z8000:: Zilog Z8000
15932 * Super-H:: Renesas Super-H
15941 @item target rdi @var{dev}
15942 ARM Angel monitor, via RDI library interface to ADP protocol. You may
15943 use this target to communicate with both boards running the Angel
15944 monitor, or with the EmbeddedICE JTAG debug device.
15947 @item target rdp @var{dev}
15952 @value{GDBN} provides the following ARM-specific commands:
15955 @item set arm disassembler
15957 This commands selects from a list of disassembly styles. The
15958 @code{"std"} style is the standard style.
15960 @item show arm disassembler
15962 Show the current disassembly style.
15964 @item set arm apcs32
15965 @cindex ARM 32-bit mode
15966 This command toggles ARM operation mode between 32-bit and 26-bit.
15968 @item show arm apcs32
15969 Display the current usage of the ARM 32-bit mode.
15971 @item set arm fpu @var{fputype}
15972 This command sets the ARM floating-point unit (FPU) type. The
15973 argument @var{fputype} can be one of these:
15977 Determine the FPU type by querying the OS ABI.
15979 Software FPU, with mixed-endian doubles on little-endian ARM
15982 GCC-compiled FPA co-processor.
15984 Software FPU with pure-endian doubles.
15990 Show the current type of the FPU.
15993 This command forces @value{GDBN} to use the specified ABI.
15996 Show the currently used ABI.
15998 @item set arm fallback-mode (arm|thumb|auto)
15999 @value{GDBN} uses the symbol table, when available, to determine
16000 whether instructions are ARM or Thumb. This command controls
16001 @value{GDBN}'s default behavior when the symbol table is not
16002 available. The default is @samp{auto}, which causes @value{GDBN} to
16003 use the current execution mode (from the @code{T} bit in the @code{CPSR}
16006 @item show arm fallback-mode
16007 Show the current fallback instruction mode.
16009 @item set arm force-mode (arm|thumb|auto)
16010 This command overrides use of the symbol table to determine whether
16011 instructions are ARM or Thumb. The default is @samp{auto}, which
16012 causes @value{GDBN} to use the symbol table and then the setting
16013 of @samp{set arm fallback-mode}.
16015 @item show arm force-mode
16016 Show the current forced instruction mode.
16018 @item set debug arm
16019 Toggle whether to display ARM-specific debugging messages from the ARM
16020 target support subsystem.
16022 @item show debug arm
16023 Show whether ARM-specific debugging messages are enabled.
16026 The following commands are available when an ARM target is debugged
16027 using the RDI interface:
16030 @item rdilogfile @r{[}@var{file}@r{]}
16032 @cindex ADP (Angel Debugger Protocol) logging
16033 Set the filename for the ADP (Angel Debugger Protocol) packet log.
16034 With an argument, sets the log file to the specified @var{file}. With
16035 no argument, show the current log file name. The default log file is
16038 @item rdilogenable @r{[}@var{arg}@r{]}
16039 @kindex rdilogenable
16040 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
16041 enables logging, with an argument 0 or @code{"no"} disables it. With
16042 no arguments displays the current setting. When logging is enabled,
16043 ADP packets exchanged between @value{GDBN} and the RDI target device
16044 are logged to a file.
16046 @item set rdiromatzero
16047 @kindex set rdiromatzero
16048 @cindex ROM at zero address, RDI
16049 Tell @value{GDBN} whether the target has ROM at address 0. If on,
16050 vector catching is disabled, so that zero address can be used. If off
16051 (the default), vector catching is enabled. For this command to take
16052 effect, it needs to be invoked prior to the @code{target rdi} command.
16054 @item show rdiromatzero
16055 @kindex show rdiromatzero
16056 Show the current setting of ROM at zero address.
16058 @item set rdiheartbeat
16059 @kindex set rdiheartbeat
16060 @cindex RDI heartbeat
16061 Enable or disable RDI heartbeat packets. It is not recommended to
16062 turn on this option, since it confuses ARM and EPI JTAG interface, as
16063 well as the Angel monitor.
16065 @item show rdiheartbeat
16066 @kindex show rdiheartbeat
16067 Show the setting of RDI heartbeat packets.
16072 @subsection Renesas M32R/D and M32R/SDI
16075 @kindex target m32r
16076 @item target m32r @var{dev}
16077 Renesas M32R/D ROM monitor.
16079 @kindex target m32rsdi
16080 @item target m32rsdi @var{dev}
16081 Renesas M32R SDI server, connected via parallel port to the board.
16084 The following @value{GDBN} commands are specific to the M32R monitor:
16087 @item set download-path @var{path}
16088 @kindex set download-path
16089 @cindex find downloadable @sc{srec} files (M32R)
16090 Set the default path for finding downloadable @sc{srec} files.
16092 @item show download-path
16093 @kindex show download-path
16094 Show the default path for downloadable @sc{srec} files.
16096 @item set board-address @var{addr}
16097 @kindex set board-address
16098 @cindex M32-EVA target board address
16099 Set the IP address for the M32R-EVA target board.
16101 @item show board-address
16102 @kindex show board-address
16103 Show the current IP address of the target board.
16105 @item set server-address @var{addr}
16106 @kindex set server-address
16107 @cindex download server address (M32R)
16108 Set the IP address for the download server, which is the @value{GDBN}'s
16111 @item show server-address
16112 @kindex show server-address
16113 Display the IP address of the download server.
16115 @item upload @r{[}@var{file}@r{]}
16116 @kindex upload@r{, M32R}
16117 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
16118 upload capability. If no @var{file} argument is given, the current
16119 executable file is uploaded.
16121 @item tload @r{[}@var{file}@r{]}
16122 @kindex tload@r{, M32R}
16123 Test the @code{upload} command.
16126 The following commands are available for M32R/SDI:
16131 @cindex reset SDI connection, M32R
16132 This command resets the SDI connection.
16136 This command shows the SDI connection status.
16139 @kindex debug_chaos
16140 @cindex M32R/Chaos debugging
16141 Instructs the remote that M32R/Chaos debugging is to be used.
16143 @item use_debug_dma
16144 @kindex use_debug_dma
16145 Instructs the remote to use the DEBUG_DMA method of accessing memory.
16148 @kindex use_mon_code
16149 Instructs the remote to use the MON_CODE method of accessing memory.
16152 @kindex use_ib_break
16153 Instructs the remote to set breakpoints by IB break.
16155 @item use_dbt_break
16156 @kindex use_dbt_break
16157 Instructs the remote to set breakpoints by DBT.
16163 The Motorola m68k configuration includes ColdFire support, and a
16164 target command for the following ROM monitor.
16168 @kindex target dbug
16169 @item target dbug @var{dev}
16170 dBUG ROM monitor for Motorola ColdFire.
16174 @node MIPS Embedded
16175 @subsection MIPS Embedded
16177 @cindex MIPS boards
16178 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
16179 MIPS board attached to a serial line. This is available when
16180 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
16183 Use these @value{GDBN} commands to specify the connection to your target board:
16186 @item target mips @var{port}
16187 @kindex target mips @var{port}
16188 To run a program on the board, start up @code{@value{GDBP}} with the
16189 name of your program as the argument. To connect to the board, use the
16190 command @samp{target mips @var{port}}, where @var{port} is the name of
16191 the serial port connected to the board. If the program has not already
16192 been downloaded to the board, you may use the @code{load} command to
16193 download it. You can then use all the usual @value{GDBN} commands.
16195 For example, this sequence connects to the target board through a serial
16196 port, and loads and runs a program called @var{prog} through the
16200 host$ @value{GDBP} @var{prog}
16201 @value{GDBN} is free software and @dots{}
16202 (@value{GDBP}) target mips /dev/ttyb
16203 (@value{GDBP}) load @var{prog}
16207 @item target mips @var{hostname}:@var{portnumber}
16208 On some @value{GDBN} host configurations, you can specify a TCP
16209 connection (for instance, to a serial line managed by a terminal
16210 concentrator) instead of a serial port, using the syntax
16211 @samp{@var{hostname}:@var{portnumber}}.
16213 @item target pmon @var{port}
16214 @kindex target pmon @var{port}
16217 @item target ddb @var{port}
16218 @kindex target ddb @var{port}
16219 NEC's DDB variant of PMON for Vr4300.
16221 @item target lsi @var{port}
16222 @kindex target lsi @var{port}
16223 LSI variant of PMON.
16225 @kindex target r3900
16226 @item target r3900 @var{dev}
16227 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
16229 @kindex target array
16230 @item target array @var{dev}
16231 Array Tech LSI33K RAID controller board.
16237 @value{GDBN} also supports these special commands for MIPS targets:
16240 @item set mipsfpu double
16241 @itemx set mipsfpu single
16242 @itemx set mipsfpu none
16243 @itemx set mipsfpu auto
16244 @itemx show mipsfpu
16245 @kindex set mipsfpu
16246 @kindex show mipsfpu
16247 @cindex MIPS remote floating point
16248 @cindex floating point, MIPS remote
16249 If your target board does not support the MIPS floating point
16250 coprocessor, you should use the command @samp{set mipsfpu none} (if you
16251 need this, you may wish to put the command in your @value{GDBN} init
16252 file). This tells @value{GDBN} how to find the return value of
16253 functions which return floating point values. It also allows
16254 @value{GDBN} to avoid saving the floating point registers when calling
16255 functions on the board. If you are using a floating point coprocessor
16256 with only single precision floating point support, as on the @sc{r4650}
16257 processor, use the command @samp{set mipsfpu single}. The default
16258 double precision floating point coprocessor may be selected using
16259 @samp{set mipsfpu double}.
16261 In previous versions the only choices were double precision or no
16262 floating point, so @samp{set mipsfpu on} will select double precision
16263 and @samp{set mipsfpu off} will select no floating point.
16265 As usual, you can inquire about the @code{mipsfpu} variable with
16266 @samp{show mipsfpu}.
16268 @item set timeout @var{seconds}
16269 @itemx set retransmit-timeout @var{seconds}
16270 @itemx show timeout
16271 @itemx show retransmit-timeout
16272 @cindex @code{timeout}, MIPS protocol
16273 @cindex @code{retransmit-timeout}, MIPS protocol
16274 @kindex set timeout
16275 @kindex show timeout
16276 @kindex set retransmit-timeout
16277 @kindex show retransmit-timeout
16278 You can control the timeout used while waiting for a packet, in the MIPS
16279 remote protocol, with the @code{set timeout @var{seconds}} command. The
16280 default is 5 seconds. Similarly, you can control the timeout used while
16281 waiting for an acknowledgment of a packet with the @code{set
16282 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
16283 You can inspect both values with @code{show timeout} and @code{show
16284 retransmit-timeout}. (These commands are @emph{only} available when
16285 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
16287 The timeout set by @code{set timeout} does not apply when @value{GDBN}
16288 is waiting for your program to stop. In that case, @value{GDBN} waits
16289 forever because it has no way of knowing how long the program is going
16290 to run before stopping.
16292 @item set syn-garbage-limit @var{num}
16293 @kindex set syn-garbage-limit@r{, MIPS remote}
16294 @cindex synchronize with remote MIPS target
16295 Limit the maximum number of characters @value{GDBN} should ignore when
16296 it tries to synchronize with the remote target. The default is 10
16297 characters. Setting the limit to -1 means there's no limit.
16299 @item show syn-garbage-limit
16300 @kindex show syn-garbage-limit@r{, MIPS remote}
16301 Show the current limit on the number of characters to ignore when
16302 trying to synchronize with the remote system.
16304 @item set monitor-prompt @var{prompt}
16305 @kindex set monitor-prompt@r{, MIPS remote}
16306 @cindex remote monitor prompt
16307 Tell @value{GDBN} to expect the specified @var{prompt} string from the
16308 remote monitor. The default depends on the target:
16318 @item show monitor-prompt
16319 @kindex show monitor-prompt@r{, MIPS remote}
16320 Show the current strings @value{GDBN} expects as the prompt from the
16323 @item set monitor-warnings
16324 @kindex set monitor-warnings@r{, MIPS remote}
16325 Enable or disable monitor warnings about hardware breakpoints. This
16326 has effect only for the @code{lsi} target. When on, @value{GDBN} will
16327 display warning messages whose codes are returned by the @code{lsi}
16328 PMON monitor for breakpoint commands.
16330 @item show monitor-warnings
16331 @kindex show monitor-warnings@r{, MIPS remote}
16332 Show the current setting of printing monitor warnings.
16334 @item pmon @var{command}
16335 @kindex pmon@r{, MIPS remote}
16336 @cindex send PMON command
16337 This command allows sending an arbitrary @var{command} string to the
16338 monitor. The monitor must be in debug mode for this to work.
16341 @node OpenRISC 1000
16342 @subsection OpenRISC 1000
16343 @cindex OpenRISC 1000
16345 @cindex or1k boards
16346 See OR1k Architecture document (@uref{www.opencores.org}) for more information
16347 about platform and commands.
16351 @kindex target jtag
16352 @item target jtag jtag://@var{host}:@var{port}
16354 Connects to remote JTAG server.
16355 JTAG remote server can be either an or1ksim or JTAG server,
16356 connected via parallel port to the board.
16358 Example: @code{target jtag jtag://localhost:9999}
16361 @item or1ksim @var{command}
16362 If connected to @code{or1ksim} OpenRISC 1000 Architectural
16363 Simulator, proprietary commands can be executed.
16365 @kindex info or1k spr
16366 @item info or1k spr
16367 Displays spr groups.
16369 @item info or1k spr @var{group}
16370 @itemx info or1k spr @var{groupno}
16371 Displays register names in selected group.
16373 @item info or1k spr @var{group} @var{register}
16374 @itemx info or1k spr @var{register}
16375 @itemx info or1k spr @var{groupno} @var{registerno}
16376 @itemx info or1k spr @var{registerno}
16377 Shows information about specified spr register.
16380 @item spr @var{group} @var{register} @var{value}
16381 @itemx spr @var{register @var{value}}
16382 @itemx spr @var{groupno} @var{registerno @var{value}}
16383 @itemx spr @var{registerno @var{value}}
16384 Writes @var{value} to specified spr register.
16387 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
16388 It is very similar to @value{GDBN} trace, except it does not interfere with normal
16389 program execution and is thus much faster. Hardware breakpoints/watchpoint
16390 triggers can be set using:
16393 Load effective address/data
16395 Store effective address/data
16397 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
16402 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
16403 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
16405 @code{htrace} commands:
16406 @cindex OpenRISC 1000 htrace
16409 @item hwatch @var{conditional}
16410 Set hardware watchpoint on combination of Load/Store Effective Address(es)
16411 or Data. For example:
16413 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16415 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16419 Display information about current HW trace configuration.
16421 @item htrace trigger @var{conditional}
16422 Set starting criteria for HW trace.
16424 @item htrace qualifier @var{conditional}
16425 Set acquisition qualifier for HW trace.
16427 @item htrace stop @var{conditional}
16428 Set HW trace stopping criteria.
16430 @item htrace record [@var{data}]*
16431 Selects the data to be recorded, when qualifier is met and HW trace was
16434 @item htrace enable
16435 @itemx htrace disable
16436 Enables/disables the HW trace.
16438 @item htrace rewind [@var{filename}]
16439 Clears currently recorded trace data.
16441 If filename is specified, new trace file is made and any newly collected data
16442 will be written there.
16444 @item htrace print [@var{start} [@var{len}]]
16445 Prints trace buffer, using current record configuration.
16447 @item htrace mode continuous
16448 Set continuous trace mode.
16450 @item htrace mode suspend
16451 Set suspend trace mode.
16455 @node PowerPC Embedded
16456 @subsection PowerPC Embedded
16458 @value{GDBN} provides the following PowerPC-specific commands:
16461 @kindex set powerpc
16462 @item set powerpc soft-float
16463 @itemx show powerpc soft-float
16464 Force @value{GDBN} to use (or not use) a software floating point calling
16465 convention. By default, @value{GDBN} selects the calling convention based
16466 on the selected architecture and the provided executable file.
16468 @item set powerpc vector-abi
16469 @itemx show powerpc vector-abi
16470 Force @value{GDBN} to use the specified calling convention for vector
16471 arguments and return values. The valid options are @samp{auto};
16472 @samp{generic}, to avoid vector registers even if they are present;
16473 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
16474 registers. By default, @value{GDBN} selects the calling convention
16475 based on the selected architecture and the provided executable file.
16477 @kindex target dink32
16478 @item target dink32 @var{dev}
16479 DINK32 ROM monitor.
16481 @kindex target ppcbug
16482 @item target ppcbug @var{dev}
16483 @kindex target ppcbug1
16484 @item target ppcbug1 @var{dev}
16485 PPCBUG ROM monitor for PowerPC.
16488 @item target sds @var{dev}
16489 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
16492 @cindex SDS protocol
16493 The following commands specific to the SDS protocol are supported
16497 @item set sdstimeout @var{nsec}
16498 @kindex set sdstimeout
16499 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
16500 default is 2 seconds.
16502 @item show sdstimeout
16503 @kindex show sdstimeout
16504 Show the current value of the SDS timeout.
16506 @item sds @var{command}
16507 @kindex sds@r{, a command}
16508 Send the specified @var{command} string to the SDS monitor.
16513 @subsection HP PA Embedded
16517 @kindex target op50n
16518 @item target op50n @var{dev}
16519 OP50N monitor, running on an OKI HPPA board.
16521 @kindex target w89k
16522 @item target w89k @var{dev}
16523 W89K monitor, running on a Winbond HPPA board.
16528 @subsection Tsqware Sparclet
16532 @value{GDBN} enables developers to debug tasks running on
16533 Sparclet targets from a Unix host.
16534 @value{GDBN} uses code that runs on
16535 both the Unix host and on the Sparclet target. The program
16536 @code{@value{GDBP}} is installed and executed on the Unix host.
16539 @item remotetimeout @var{args}
16540 @kindex remotetimeout
16541 @value{GDBN} supports the option @code{remotetimeout}.
16542 This option is set by the user, and @var{args} represents the number of
16543 seconds @value{GDBN} waits for responses.
16546 @cindex compiling, on Sparclet
16547 When compiling for debugging, include the options @samp{-g} to get debug
16548 information and @samp{-Ttext} to relocate the program to where you wish to
16549 load it on the target. You may also want to add the options @samp{-n} or
16550 @samp{-N} in order to reduce the size of the sections. Example:
16553 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
16556 You can use @code{objdump} to verify that the addresses are what you intended:
16559 sparclet-aout-objdump --headers --syms prog
16562 @cindex running, on Sparclet
16564 your Unix execution search path to find @value{GDBN}, you are ready to
16565 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
16566 (or @code{sparclet-aout-gdb}, depending on your installation).
16568 @value{GDBN} comes up showing the prompt:
16575 * Sparclet File:: Setting the file to debug
16576 * Sparclet Connection:: Connecting to Sparclet
16577 * Sparclet Download:: Sparclet download
16578 * Sparclet Execution:: Running and debugging
16581 @node Sparclet File
16582 @subsubsection Setting File to Debug
16584 The @value{GDBN} command @code{file} lets you choose with program to debug.
16587 (gdbslet) file prog
16591 @value{GDBN} then attempts to read the symbol table of @file{prog}.
16592 @value{GDBN} locates
16593 the file by searching the directories listed in the command search
16595 If the file was compiled with debug information (option @samp{-g}), source
16596 files will be searched as well.
16597 @value{GDBN} locates
16598 the source files by searching the directories listed in the directory search
16599 path (@pxref{Environment, ,Your Program's Environment}).
16601 to find a file, it displays a message such as:
16604 prog: No such file or directory.
16607 When this happens, add the appropriate directories to the search paths with
16608 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
16609 @code{target} command again.
16611 @node Sparclet Connection
16612 @subsubsection Connecting to Sparclet
16614 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
16615 To connect to a target on serial port ``@code{ttya}'', type:
16618 (gdbslet) target sparclet /dev/ttya
16619 Remote target sparclet connected to /dev/ttya
16620 main () at ../prog.c:3
16624 @value{GDBN} displays messages like these:
16630 @node Sparclet Download
16631 @subsubsection Sparclet Download
16633 @cindex download to Sparclet
16634 Once connected to the Sparclet target,
16635 you can use the @value{GDBN}
16636 @code{load} command to download the file from the host to the target.
16637 The file name and load offset should be given as arguments to the @code{load}
16639 Since the file format is aout, the program must be loaded to the starting
16640 address. You can use @code{objdump} to find out what this value is. The load
16641 offset is an offset which is added to the VMA (virtual memory address)
16642 of each of the file's sections.
16643 For instance, if the program
16644 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
16645 and bss at 0x12010170, in @value{GDBN}, type:
16648 (gdbslet) load prog 0x12010000
16649 Loading section .text, size 0xdb0 vma 0x12010000
16652 If the code is loaded at a different address then what the program was linked
16653 to, you may need to use the @code{section} and @code{add-symbol-file} commands
16654 to tell @value{GDBN} where to map the symbol table.
16656 @node Sparclet Execution
16657 @subsubsection Running and Debugging
16659 @cindex running and debugging Sparclet programs
16660 You can now begin debugging the task using @value{GDBN}'s execution control
16661 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
16662 manual for the list of commands.
16666 Breakpoint 1 at 0x12010000: file prog.c, line 3.
16668 Starting program: prog
16669 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
16670 3 char *symarg = 0;
16672 4 char *execarg = "hello!";
16677 @subsection Fujitsu Sparclite
16681 @kindex target sparclite
16682 @item target sparclite @var{dev}
16683 Fujitsu sparclite boards, used only for the purpose of loading.
16684 You must use an additional command to debug the program.
16685 For example: target remote @var{dev} using @value{GDBN} standard
16691 @subsection Zilog Z8000
16694 @cindex simulator, Z8000
16695 @cindex Zilog Z8000 simulator
16697 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
16700 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
16701 unsegmented variant of the Z8000 architecture) or the Z8001 (the
16702 segmented variant). The simulator recognizes which architecture is
16703 appropriate by inspecting the object code.
16706 @item target sim @var{args}
16708 @kindex target sim@r{, with Z8000}
16709 Debug programs on a simulated CPU. If the simulator supports setup
16710 options, specify them via @var{args}.
16714 After specifying this target, you can debug programs for the simulated
16715 CPU in the same style as programs for your host computer; use the
16716 @code{file} command to load a new program image, the @code{run} command
16717 to run your program, and so on.
16719 As well as making available all the usual machine registers
16720 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
16721 additional items of information as specially named registers:
16726 Counts clock-ticks in the simulator.
16729 Counts instructions run in the simulator.
16732 Execution time in 60ths of a second.
16736 You can refer to these values in @value{GDBN} expressions with the usual
16737 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
16738 conditional breakpoint that suspends only after at least 5000
16739 simulated clock ticks.
16742 @subsection Atmel AVR
16745 When configured for debugging the Atmel AVR, @value{GDBN} supports the
16746 following AVR-specific commands:
16749 @item info io_registers
16750 @kindex info io_registers@r{, AVR}
16751 @cindex I/O registers (Atmel AVR)
16752 This command displays information about the AVR I/O registers. For
16753 each register, @value{GDBN} prints its number and value.
16760 When configured for debugging CRIS, @value{GDBN} provides the
16761 following CRIS-specific commands:
16764 @item set cris-version @var{ver}
16765 @cindex CRIS version
16766 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
16767 The CRIS version affects register names and sizes. This command is useful in
16768 case autodetection of the CRIS version fails.
16770 @item show cris-version
16771 Show the current CRIS version.
16773 @item set cris-dwarf2-cfi
16774 @cindex DWARF-2 CFI and CRIS
16775 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
16776 Change to @samp{off} when using @code{gcc-cris} whose version is below
16779 @item show cris-dwarf2-cfi
16780 Show the current state of using DWARF-2 CFI.
16782 @item set cris-mode @var{mode}
16784 Set the current CRIS mode to @var{mode}. It should only be changed when
16785 debugging in guru mode, in which case it should be set to
16786 @samp{guru} (the default is @samp{normal}).
16788 @item show cris-mode
16789 Show the current CRIS mode.
16793 @subsection Renesas Super-H
16796 For the Renesas Super-H processor, @value{GDBN} provides these
16801 @kindex regs@r{, Super-H}
16802 Show the values of all Super-H registers.
16804 @item set sh calling-convention @var{convention}
16805 @kindex set sh calling-convention
16806 Set the calling-convention used when calling functions from @value{GDBN}.
16807 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
16808 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
16809 convention. If the DWARF-2 information of the called function specifies
16810 that the function follows the Renesas calling convention, the function
16811 is called using the Renesas calling convention. If the calling convention
16812 is set to @samp{renesas}, the Renesas calling convention is always used,
16813 regardless of the DWARF-2 information. This can be used to override the
16814 default of @samp{gcc} if debug information is missing, or the compiler
16815 does not emit the DWARF-2 calling convention entry for a function.
16817 @item show sh calling-convention
16818 @kindex show sh calling-convention
16819 Show the current calling convention setting.
16824 @node Architectures
16825 @section Architectures
16827 This section describes characteristics of architectures that affect
16828 all uses of @value{GDBN} with the architecture, both native and cross.
16835 * HPPA:: HP PA architecture
16836 * SPU:: Cell Broadband Engine SPU architecture
16841 @subsection x86 Architecture-specific Issues
16844 @item set struct-convention @var{mode}
16845 @kindex set struct-convention
16846 @cindex struct return convention
16847 @cindex struct/union returned in registers
16848 Set the convention used by the inferior to return @code{struct}s and
16849 @code{union}s from functions to @var{mode}. Possible values of
16850 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
16851 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
16852 are returned on the stack, while @code{"reg"} means that a
16853 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
16854 be returned in a register.
16856 @item show struct-convention
16857 @kindex show struct-convention
16858 Show the current setting of the convention to return @code{struct}s
16867 @kindex set rstack_high_address
16868 @cindex AMD 29K register stack
16869 @cindex register stack, AMD29K
16870 @item set rstack_high_address @var{address}
16871 On AMD 29000 family processors, registers are saved in a separate
16872 @dfn{register stack}. There is no way for @value{GDBN} to determine the
16873 extent of this stack. Normally, @value{GDBN} just assumes that the
16874 stack is ``large enough''. This may result in @value{GDBN} referencing
16875 memory locations that do not exist. If necessary, you can get around
16876 this problem by specifying the ending address of the register stack with
16877 the @code{set rstack_high_address} command. The argument should be an
16878 address, which you probably want to precede with @samp{0x} to specify in
16881 @kindex show rstack_high_address
16882 @item show rstack_high_address
16883 Display the current limit of the register stack, on AMD 29000 family
16891 See the following section.
16896 @cindex stack on Alpha
16897 @cindex stack on MIPS
16898 @cindex Alpha stack
16900 Alpha- and MIPS-based computers use an unusual stack frame, which
16901 sometimes requires @value{GDBN} to search backward in the object code to
16902 find the beginning of a function.
16904 @cindex response time, MIPS debugging
16905 To improve response time (especially for embedded applications, where
16906 @value{GDBN} may be restricted to a slow serial line for this search)
16907 you may want to limit the size of this search, using one of these
16911 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
16912 @item set heuristic-fence-post @var{limit}
16913 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
16914 search for the beginning of a function. A value of @var{0} (the
16915 default) means there is no limit. However, except for @var{0}, the
16916 larger the limit the more bytes @code{heuristic-fence-post} must search
16917 and therefore the longer it takes to run. You should only need to use
16918 this command when debugging a stripped executable.
16920 @item show heuristic-fence-post
16921 Display the current limit.
16925 These commands are available @emph{only} when @value{GDBN} is configured
16926 for debugging programs on Alpha or MIPS processors.
16928 Several MIPS-specific commands are available when debugging MIPS
16932 @item set mips abi @var{arg}
16933 @kindex set mips abi
16934 @cindex set ABI for MIPS
16935 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
16936 values of @var{arg} are:
16940 The default ABI associated with the current binary (this is the
16951 @item show mips abi
16952 @kindex show mips abi
16953 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
16956 @itemx show mipsfpu
16957 @xref{MIPS Embedded, set mipsfpu}.
16959 @item set mips mask-address @var{arg}
16960 @kindex set mips mask-address
16961 @cindex MIPS addresses, masking
16962 This command determines whether the most-significant 32 bits of 64-bit
16963 MIPS addresses are masked off. The argument @var{arg} can be
16964 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
16965 setting, which lets @value{GDBN} determine the correct value.
16967 @item show mips mask-address
16968 @kindex show mips mask-address
16969 Show whether the upper 32 bits of MIPS addresses are masked off or
16972 @item set remote-mips64-transfers-32bit-regs
16973 @kindex set remote-mips64-transfers-32bit-regs
16974 This command controls compatibility with 64-bit MIPS targets that
16975 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16976 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16977 and 64 bits for other registers, set this option to @samp{on}.
16979 @item show remote-mips64-transfers-32bit-regs
16980 @kindex show remote-mips64-transfers-32bit-regs
16981 Show the current setting of compatibility with older MIPS 64 targets.
16983 @item set debug mips
16984 @kindex set debug mips
16985 This command turns on and off debugging messages for the MIPS-specific
16986 target code in @value{GDBN}.
16988 @item show debug mips
16989 @kindex show debug mips
16990 Show the current setting of MIPS debugging messages.
16996 @cindex HPPA support
16998 When @value{GDBN} is debugging the HP PA architecture, it provides the
16999 following special commands:
17002 @item set debug hppa
17003 @kindex set debug hppa
17004 This command determines whether HPPA architecture-specific debugging
17005 messages are to be displayed.
17007 @item show debug hppa
17008 Show whether HPPA debugging messages are displayed.
17010 @item maint print unwind @var{address}
17011 @kindex maint print unwind@r{, HPPA}
17012 This command displays the contents of the unwind table entry at the
17013 given @var{address}.
17019 @subsection Cell Broadband Engine SPU architecture
17020 @cindex Cell Broadband Engine
17023 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
17024 it provides the following special commands:
17027 @item info spu event
17029 Display SPU event facility status. Shows current event mask
17030 and pending event status.
17032 @item info spu signal
17033 Display SPU signal notification facility status. Shows pending
17034 signal-control word and signal notification mode of both signal
17035 notification channels.
17037 @item info spu mailbox
17038 Display SPU mailbox facility status. Shows all pending entries,
17039 in order of processing, in each of the SPU Write Outbound,
17040 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
17043 Display MFC DMA status. Shows all pending commands in the MFC
17044 DMA queue. For each entry, opcode, tag, class IDs, effective
17045 and local store addresses and transfer size are shown.
17047 @item info spu proxydma
17048 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
17049 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
17050 and local store addresses and transfer size are shown.
17055 @subsection PowerPC
17056 @cindex PowerPC architecture
17058 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
17059 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
17060 numbers stored in the floating point registers. These values must be stored
17061 in two consecutive registers, always starting at an even register like
17062 @code{f0} or @code{f2}.
17064 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
17065 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
17066 @code{f2} and @code{f3} for @code{$dl1} and so on.
17068 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
17069 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
17072 @node Controlling GDB
17073 @chapter Controlling @value{GDBN}
17075 You can alter the way @value{GDBN} interacts with you by using the
17076 @code{set} command. For commands controlling how @value{GDBN} displays
17077 data, see @ref{Print Settings, ,Print Settings}. Other settings are
17082 * Editing:: Command editing
17083 * Command History:: Command history
17084 * Screen Size:: Screen size
17085 * Numbers:: Numbers
17086 * ABI:: Configuring the current ABI
17087 * Messages/Warnings:: Optional warnings and messages
17088 * Debugging Output:: Optional messages about internal happenings
17096 @value{GDBN} indicates its readiness to read a command by printing a string
17097 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
17098 can change the prompt string with the @code{set prompt} command. For
17099 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
17100 the prompt in one of the @value{GDBN} sessions so that you can always tell
17101 which one you are talking to.
17103 @emph{Note:} @code{set prompt} does not add a space for you after the
17104 prompt you set. This allows you to set a prompt which ends in a space
17105 or a prompt that does not.
17109 @item set prompt @var{newprompt}
17110 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
17112 @kindex show prompt
17114 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
17118 @section Command Editing
17120 @cindex command line editing
17122 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
17123 @sc{gnu} library provides consistent behavior for programs which provide a
17124 command line interface to the user. Advantages are @sc{gnu} Emacs-style
17125 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
17126 substitution, and a storage and recall of command history across
17127 debugging sessions.
17129 You may control the behavior of command line editing in @value{GDBN} with the
17130 command @code{set}.
17133 @kindex set editing
17136 @itemx set editing on
17137 Enable command line editing (enabled by default).
17139 @item set editing off
17140 Disable command line editing.
17142 @kindex show editing
17144 Show whether command line editing is enabled.
17147 @xref{Command Line Editing}, for more details about the Readline
17148 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
17149 encouraged to read that chapter.
17151 @node Command History
17152 @section Command History
17153 @cindex command history
17155 @value{GDBN} can keep track of the commands you type during your
17156 debugging sessions, so that you can be certain of precisely what
17157 happened. Use these commands to manage the @value{GDBN} command
17160 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
17161 package, to provide the history facility. @xref{Using History
17162 Interactively}, for the detailed description of the History library.
17164 To issue a command to @value{GDBN} without affecting certain aspects of
17165 the state which is seen by users, prefix it with @samp{server }
17166 (@pxref{Server Prefix}). This
17167 means that this command will not affect the command history, nor will it
17168 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
17169 pressed on a line by itself.
17171 @cindex @code{server}, command prefix
17172 The server prefix does not affect the recording of values into the value
17173 history; to print a value without recording it into the value history,
17174 use the @code{output} command instead of the @code{print} command.
17176 Here is the description of @value{GDBN} commands related to command
17180 @cindex history substitution
17181 @cindex history file
17182 @kindex set history filename
17183 @cindex @env{GDBHISTFILE}, environment variable
17184 @item set history filename @var{fname}
17185 Set the name of the @value{GDBN} command history file to @var{fname}.
17186 This is the file where @value{GDBN} reads an initial command history
17187 list, and where it writes the command history from this session when it
17188 exits. You can access this list through history expansion or through
17189 the history command editing characters listed below. This file defaults
17190 to the value of the environment variable @code{GDBHISTFILE}, or to
17191 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
17194 @cindex save command history
17195 @kindex set history save
17196 @item set history save
17197 @itemx set history save on
17198 Record command history in a file, whose name may be specified with the
17199 @code{set history filename} command. By default, this option is disabled.
17201 @item set history save off
17202 Stop recording command history in a file.
17204 @cindex history size
17205 @kindex set history size
17206 @cindex @env{HISTSIZE}, environment variable
17207 @item set history size @var{size}
17208 Set the number of commands which @value{GDBN} keeps in its history list.
17209 This defaults to the value of the environment variable
17210 @code{HISTSIZE}, or to 256 if this variable is not set.
17213 History expansion assigns special meaning to the character @kbd{!}.
17214 @xref{Event Designators}, for more details.
17216 @cindex history expansion, turn on/off
17217 Since @kbd{!} is also the logical not operator in C, history expansion
17218 is off by default. If you decide to enable history expansion with the
17219 @code{set history expansion on} command, you may sometimes need to
17220 follow @kbd{!} (when it is used as logical not, in an expression) with
17221 a space or a tab to prevent it from being expanded. The readline
17222 history facilities do not attempt substitution on the strings
17223 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
17225 The commands to control history expansion are:
17228 @item set history expansion on
17229 @itemx set history expansion
17230 @kindex set history expansion
17231 Enable history expansion. History expansion is off by default.
17233 @item set history expansion off
17234 Disable history expansion.
17237 @kindex show history
17239 @itemx show history filename
17240 @itemx show history save
17241 @itemx show history size
17242 @itemx show history expansion
17243 These commands display the state of the @value{GDBN} history parameters.
17244 @code{show history} by itself displays all four states.
17249 @kindex show commands
17250 @cindex show last commands
17251 @cindex display command history
17252 @item show commands
17253 Display the last ten commands in the command history.
17255 @item show commands @var{n}
17256 Print ten commands centered on command number @var{n}.
17258 @item show commands +
17259 Print ten commands just after the commands last printed.
17263 @section Screen Size
17264 @cindex size of screen
17265 @cindex pauses in output
17267 Certain commands to @value{GDBN} may produce large amounts of
17268 information output to the screen. To help you read all of it,
17269 @value{GDBN} pauses and asks you for input at the end of each page of
17270 output. Type @key{RET} when you want to continue the output, or @kbd{q}
17271 to discard the remaining output. Also, the screen width setting
17272 determines when to wrap lines of output. Depending on what is being
17273 printed, @value{GDBN} tries to break the line at a readable place,
17274 rather than simply letting it overflow onto the following line.
17276 Normally @value{GDBN} knows the size of the screen from the terminal
17277 driver software. For example, on Unix @value{GDBN} uses the termcap data base
17278 together with the value of the @code{TERM} environment variable and the
17279 @code{stty rows} and @code{stty cols} settings. If this is not correct,
17280 you can override it with the @code{set height} and @code{set
17287 @kindex show height
17288 @item set height @var{lpp}
17290 @itemx set width @var{cpl}
17292 These @code{set} commands specify a screen height of @var{lpp} lines and
17293 a screen width of @var{cpl} characters. The associated @code{show}
17294 commands display the current settings.
17296 If you specify a height of zero lines, @value{GDBN} does not pause during
17297 output no matter how long the output is. This is useful if output is to a
17298 file or to an editor buffer.
17300 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
17301 from wrapping its output.
17303 @item set pagination on
17304 @itemx set pagination off
17305 @kindex set pagination
17306 Turn the output pagination on or off; the default is on. Turning
17307 pagination off is the alternative to @code{set height 0}.
17309 @item show pagination
17310 @kindex show pagination
17311 Show the current pagination mode.
17316 @cindex number representation
17317 @cindex entering numbers
17319 You can always enter numbers in octal, decimal, or hexadecimal in
17320 @value{GDBN} by the usual conventions: octal numbers begin with
17321 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
17322 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
17323 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
17324 10; likewise, the default display for numbers---when no particular
17325 format is specified---is base 10. You can change the default base for
17326 both input and output with the commands described below.
17329 @kindex set input-radix
17330 @item set input-radix @var{base}
17331 Set the default base for numeric input. Supported choices
17332 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17333 specified either unambiguously or using the current input radix; for
17337 set input-radix 012
17338 set input-radix 10.
17339 set input-radix 0xa
17343 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
17344 leaves the input radix unchanged, no matter what it was, since
17345 @samp{10}, being without any leading or trailing signs of its base, is
17346 interpreted in the current radix. Thus, if the current radix is 16,
17347 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
17350 @kindex set output-radix
17351 @item set output-radix @var{base}
17352 Set the default base for numeric display. Supported choices
17353 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17354 specified either unambiguously or using the current input radix.
17356 @kindex show input-radix
17357 @item show input-radix
17358 Display the current default base for numeric input.
17360 @kindex show output-radix
17361 @item show output-radix
17362 Display the current default base for numeric display.
17364 @item set radix @r{[}@var{base}@r{]}
17368 These commands set and show the default base for both input and output
17369 of numbers. @code{set radix} sets the radix of input and output to
17370 the same base; without an argument, it resets the radix back to its
17371 default value of 10.
17376 @section Configuring the Current ABI
17378 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
17379 application automatically. However, sometimes you need to override its
17380 conclusions. Use these commands to manage @value{GDBN}'s view of the
17387 One @value{GDBN} configuration can debug binaries for multiple operating
17388 system targets, either via remote debugging or native emulation.
17389 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
17390 but you can override its conclusion using the @code{set osabi} command.
17391 One example where this is useful is in debugging of binaries which use
17392 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
17393 not have the same identifying marks that the standard C library for your
17398 Show the OS ABI currently in use.
17401 With no argument, show the list of registered available OS ABI's.
17403 @item set osabi @var{abi}
17404 Set the current OS ABI to @var{abi}.
17407 @cindex float promotion
17409 Generally, the way that an argument of type @code{float} is passed to a
17410 function depends on whether the function is prototyped. For a prototyped
17411 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
17412 according to the architecture's convention for @code{float}. For unprototyped
17413 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
17414 @code{double} and then passed.
17416 Unfortunately, some forms of debug information do not reliably indicate whether
17417 a function is prototyped. If @value{GDBN} calls a function that is not marked
17418 as prototyped, it consults @kbd{set coerce-float-to-double}.
17421 @kindex set coerce-float-to-double
17422 @item set coerce-float-to-double
17423 @itemx set coerce-float-to-double on
17424 Arguments of type @code{float} will be promoted to @code{double} when passed
17425 to an unprototyped function. This is the default setting.
17427 @item set coerce-float-to-double off
17428 Arguments of type @code{float} will be passed directly to unprototyped
17431 @kindex show coerce-float-to-double
17432 @item show coerce-float-to-double
17433 Show the current setting of promoting @code{float} to @code{double}.
17437 @kindex show cp-abi
17438 @value{GDBN} needs to know the ABI used for your program's C@t{++}
17439 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
17440 used to build your application. @value{GDBN} only fully supports
17441 programs with a single C@t{++} ABI; if your program contains code using
17442 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
17443 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
17444 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
17445 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
17446 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
17447 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
17452 Show the C@t{++} ABI currently in use.
17455 With no argument, show the list of supported C@t{++} ABI's.
17457 @item set cp-abi @var{abi}
17458 @itemx set cp-abi auto
17459 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
17462 @node Messages/Warnings
17463 @section Optional Warnings and Messages
17465 @cindex verbose operation
17466 @cindex optional warnings
17467 By default, @value{GDBN} is silent about its inner workings. If you are
17468 running on a slow machine, you may want to use the @code{set verbose}
17469 command. This makes @value{GDBN} tell you when it does a lengthy
17470 internal operation, so you will not think it has crashed.
17472 Currently, the messages controlled by @code{set verbose} are those
17473 which announce that the symbol table for a source file is being read;
17474 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
17477 @kindex set verbose
17478 @item set verbose on
17479 Enables @value{GDBN} output of certain informational messages.
17481 @item set verbose off
17482 Disables @value{GDBN} output of certain informational messages.
17484 @kindex show verbose
17486 Displays whether @code{set verbose} is on or off.
17489 By default, if @value{GDBN} encounters bugs in the symbol table of an
17490 object file, it is silent; but if you are debugging a compiler, you may
17491 find this information useful (@pxref{Symbol Errors, ,Errors Reading
17496 @kindex set complaints
17497 @item set complaints @var{limit}
17498 Permits @value{GDBN} to output @var{limit} complaints about each type of
17499 unusual symbols before becoming silent about the problem. Set
17500 @var{limit} to zero to suppress all complaints; set it to a large number
17501 to prevent complaints from being suppressed.
17503 @kindex show complaints
17504 @item show complaints
17505 Displays how many symbol complaints @value{GDBN} is permitted to produce.
17509 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
17510 lot of stupid questions to confirm certain commands. For example, if
17511 you try to run a program which is already running:
17515 The program being debugged has been started already.
17516 Start it from the beginning? (y or n)
17519 If you are willing to unflinchingly face the consequences of your own
17520 commands, you can disable this ``feature'':
17524 @kindex set confirm
17526 @cindex confirmation
17527 @cindex stupid questions
17528 @item set confirm off
17529 Disables confirmation requests.
17531 @item set confirm on
17532 Enables confirmation requests (the default).
17534 @kindex show confirm
17536 Displays state of confirmation requests.
17540 @cindex command tracing
17541 If you need to debug user-defined commands or sourced files you may find it
17542 useful to enable @dfn{command tracing}. In this mode each command will be
17543 printed as it is executed, prefixed with one or more @samp{+} symbols, the
17544 quantity denoting the call depth of each command.
17547 @kindex set trace-commands
17548 @cindex command scripts, debugging
17549 @item set trace-commands on
17550 Enable command tracing.
17551 @item set trace-commands off
17552 Disable command tracing.
17553 @item show trace-commands
17554 Display the current state of command tracing.
17557 @node Debugging Output
17558 @section Optional Messages about Internal Happenings
17559 @cindex optional debugging messages
17561 @value{GDBN} has commands that enable optional debugging messages from
17562 various @value{GDBN} subsystems; normally these commands are of
17563 interest to @value{GDBN} maintainers, or when reporting a bug. This
17564 section documents those commands.
17567 @kindex set exec-done-display
17568 @item set exec-done-display
17569 Turns on or off the notification of asynchronous commands'
17570 completion. When on, @value{GDBN} will print a message when an
17571 asynchronous command finishes its execution. The default is off.
17572 @kindex show exec-done-display
17573 @item show exec-done-display
17574 Displays the current setting of asynchronous command completion
17577 @cindex gdbarch debugging info
17578 @cindex architecture debugging info
17579 @item set debug arch
17580 Turns on or off display of gdbarch debugging info. The default is off
17582 @item show debug arch
17583 Displays the current state of displaying gdbarch debugging info.
17584 @item set debug aix-thread
17585 @cindex AIX threads
17586 Display debugging messages about inner workings of the AIX thread
17588 @item show debug aix-thread
17589 Show the current state of AIX thread debugging info display.
17590 @item set debug dwarf2-die
17591 @cindex DWARF2 DIEs
17592 Dump DWARF2 DIEs after they are read in.
17593 The value is the number of nesting levels to print.
17594 A value of zero turns off the display.
17595 @item show debug dwarf2-die
17596 Show the current state of DWARF2 DIE debugging.
17597 @item set debug displaced
17598 @cindex displaced stepping debugging info
17599 Turns on or off display of @value{GDBN} debugging info for the
17600 displaced stepping support. The default is off.
17601 @item show debug displaced
17602 Displays the current state of displaying @value{GDBN} debugging info
17603 related to displaced stepping.
17604 @item set debug event
17605 @cindex event debugging info
17606 Turns on or off display of @value{GDBN} event debugging info. The
17608 @item show debug event
17609 Displays the current state of displaying @value{GDBN} event debugging
17611 @item set debug expression
17612 @cindex expression debugging info
17613 Turns on or off display of debugging info about @value{GDBN}
17614 expression parsing. The default is off.
17615 @item show debug expression
17616 Displays the current state of displaying debugging info about
17617 @value{GDBN} expression parsing.
17618 @item set debug frame
17619 @cindex frame debugging info
17620 Turns on or off display of @value{GDBN} frame debugging info. The
17622 @item show debug frame
17623 Displays the current state of displaying @value{GDBN} frame debugging
17625 @item set debug infrun
17626 @cindex inferior debugging info
17627 Turns on or off display of @value{GDBN} debugging info for running the inferior.
17628 The default is off. @file{infrun.c} contains GDB's runtime state machine used
17629 for implementing operations such as single-stepping the inferior.
17630 @item show debug infrun
17631 Displays the current state of @value{GDBN} inferior debugging.
17632 @item set debug lin-lwp
17633 @cindex @sc{gnu}/Linux LWP debug messages
17634 @cindex Linux lightweight processes
17635 Turns on or off debugging messages from the Linux LWP debug support.
17636 @item show debug lin-lwp
17637 Show the current state of Linux LWP debugging messages.
17638 @item set debug lin-lwp-async
17639 @cindex @sc{gnu}/Linux LWP async debug messages
17640 @cindex Linux lightweight processes
17641 Turns on or off debugging messages from the Linux LWP async debug support.
17642 @item show debug lin-lwp-async
17643 Show the current state of Linux LWP async debugging messages.
17644 @item set debug observer
17645 @cindex observer debugging info
17646 Turns on or off display of @value{GDBN} observer debugging. This
17647 includes info such as the notification of observable events.
17648 @item show debug observer
17649 Displays the current state of observer debugging.
17650 @item set debug overload
17651 @cindex C@t{++} overload debugging info
17652 Turns on or off display of @value{GDBN} C@t{++} overload debugging
17653 info. This includes info such as ranking of functions, etc. The default
17655 @item show debug overload
17656 Displays the current state of displaying @value{GDBN} C@t{++} overload
17658 @cindex packets, reporting on stdout
17659 @cindex serial connections, debugging
17660 @cindex debug remote protocol
17661 @cindex remote protocol debugging
17662 @cindex display remote packets
17663 @item set debug remote
17664 Turns on or off display of reports on all packets sent back and forth across
17665 the serial line to the remote machine. The info is printed on the
17666 @value{GDBN} standard output stream. The default is off.
17667 @item show debug remote
17668 Displays the state of display of remote packets.
17669 @item set debug serial
17670 Turns on or off display of @value{GDBN} serial debugging info. The
17672 @item show debug serial
17673 Displays the current state of displaying @value{GDBN} serial debugging
17675 @item set debug solib-frv
17676 @cindex FR-V shared-library debugging
17677 Turns on or off debugging messages for FR-V shared-library code.
17678 @item show debug solib-frv
17679 Display the current state of FR-V shared-library code debugging
17681 @item set debug target
17682 @cindex target debugging info
17683 Turns on or off display of @value{GDBN} target debugging info. This info
17684 includes what is going on at the target level of GDB, as it happens. The
17685 default is 0. Set it to 1 to track events, and to 2 to also track the
17686 value of large memory transfers. Changes to this flag do not take effect
17687 until the next time you connect to a target or use the @code{run} command.
17688 @item show debug target
17689 Displays the current state of displaying @value{GDBN} target debugging
17691 @item set debug timestamp
17692 @cindex timestampping debugging info
17693 Turns on or off display of timestamps with @value{GDBN} debugging info.
17694 When enabled, seconds and microseconds are displayed before each debugging
17696 @item show debug timestamp
17697 Displays the current state of displaying timestamps with @value{GDBN}
17699 @item set debugvarobj
17700 @cindex variable object debugging info
17701 Turns on or off display of @value{GDBN} variable object debugging
17702 info. The default is off.
17703 @item show debugvarobj
17704 Displays the current state of displaying @value{GDBN} variable object
17706 @item set debug xml
17707 @cindex XML parser debugging
17708 Turns on or off debugging messages for built-in XML parsers.
17709 @item show debug xml
17710 Displays the current state of XML debugging messages.
17713 @node Extending GDB
17714 @chapter Extending @value{GDBN}
17715 @cindex extending GDB
17717 @value{GDBN} provides two mechanisms for extension. The first is based
17718 on composition of @value{GDBN} commands, and the second is based on the
17719 Python scripting language.
17722 * Sequences:: Canned Sequences of Commands
17723 * Python:: Scripting @value{GDBN} using Python
17727 @section Canned Sequences of Commands
17729 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
17730 Command Lists}), @value{GDBN} provides two ways to store sequences of
17731 commands for execution as a unit: user-defined commands and command
17735 * Define:: How to define your own commands
17736 * Hooks:: Hooks for user-defined commands
17737 * Command Files:: How to write scripts of commands to be stored in a file
17738 * Output:: Commands for controlled output
17742 @subsection User-defined Commands
17744 @cindex user-defined command
17745 @cindex arguments, to user-defined commands
17746 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
17747 which you assign a new name as a command. This is done with the
17748 @code{define} command. User commands may accept up to 10 arguments
17749 separated by whitespace. Arguments are accessed within the user command
17750 via @code{$arg0@dots{}$arg9}. A trivial example:
17754 print $arg0 + $arg1 + $arg2
17759 To execute the command use:
17766 This defines the command @code{adder}, which prints the sum of
17767 its three arguments. Note the arguments are text substitutions, so they may
17768 reference variables, use complex expressions, or even perform inferior
17771 @cindex argument count in user-defined commands
17772 @cindex how many arguments (user-defined commands)
17773 In addition, @code{$argc} may be used to find out how many arguments have
17774 been passed. This expands to a number in the range 0@dots{}10.
17779 print $arg0 + $arg1
17782 print $arg0 + $arg1 + $arg2
17790 @item define @var{commandname}
17791 Define a command named @var{commandname}. If there is already a command
17792 by that name, you are asked to confirm that you want to redefine it.
17793 @var{commandname} may be a bare command name consisting of letters,
17794 numbers, dashes, and underscores. It may also start with any predefined
17795 prefix command. For example, @samp{define target my-target} creates
17796 a user-defined @samp{target my-target} command.
17798 The definition of the command is made up of other @value{GDBN} command lines,
17799 which are given following the @code{define} command. The end of these
17800 commands is marked by a line containing @code{end}.
17803 @kindex end@r{ (user-defined commands)}
17804 @item document @var{commandname}
17805 Document the user-defined command @var{commandname}, so that it can be
17806 accessed by @code{help}. The command @var{commandname} must already be
17807 defined. This command reads lines of documentation just as @code{define}
17808 reads the lines of the command definition, ending with @code{end}.
17809 After the @code{document} command is finished, @code{help} on command
17810 @var{commandname} displays the documentation you have written.
17812 You may use the @code{document} command again to change the
17813 documentation of a command. Redefining the command with @code{define}
17814 does not change the documentation.
17816 @kindex dont-repeat
17817 @cindex don't repeat command
17819 Used inside a user-defined command, this tells @value{GDBN} that this
17820 command should not be repeated when the user hits @key{RET}
17821 (@pxref{Command Syntax, repeat last command}).
17823 @kindex help user-defined
17824 @item help user-defined
17825 List all user-defined commands, with the first line of the documentation
17830 @itemx show user @var{commandname}
17831 Display the @value{GDBN} commands used to define @var{commandname} (but
17832 not its documentation). If no @var{commandname} is given, display the
17833 definitions for all user-defined commands.
17835 @cindex infinite recursion in user-defined commands
17836 @kindex show max-user-call-depth
17837 @kindex set max-user-call-depth
17838 @item show max-user-call-depth
17839 @itemx set max-user-call-depth
17840 The value of @code{max-user-call-depth} controls how many recursion
17841 levels are allowed in user-defined commands before @value{GDBN} suspects an
17842 infinite recursion and aborts the command.
17845 In addition to the above commands, user-defined commands frequently
17846 use control flow commands, described in @ref{Command Files}.
17848 When user-defined commands are executed, the
17849 commands of the definition are not printed. An error in any command
17850 stops execution of the user-defined command.
17852 If used interactively, commands that would ask for confirmation proceed
17853 without asking when used inside a user-defined command. Many @value{GDBN}
17854 commands that normally print messages to say what they are doing omit the
17855 messages when used in a user-defined command.
17858 @subsection User-defined Command Hooks
17859 @cindex command hooks
17860 @cindex hooks, for commands
17861 @cindex hooks, pre-command
17864 You may define @dfn{hooks}, which are a special kind of user-defined
17865 command. Whenever you run the command @samp{foo}, if the user-defined
17866 command @samp{hook-foo} exists, it is executed (with no arguments)
17867 before that command.
17869 @cindex hooks, post-command
17871 A hook may also be defined which is run after the command you executed.
17872 Whenever you run the command @samp{foo}, if the user-defined command
17873 @samp{hookpost-foo} exists, it is executed (with no arguments) after
17874 that command. Post-execution hooks may exist simultaneously with
17875 pre-execution hooks, for the same command.
17877 It is valid for a hook to call the command which it hooks. If this
17878 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
17880 @c It would be nice if hookpost could be passed a parameter indicating
17881 @c if the command it hooks executed properly or not. FIXME!
17883 @kindex stop@r{, a pseudo-command}
17884 In addition, a pseudo-command, @samp{stop} exists. Defining
17885 (@samp{hook-stop}) makes the associated commands execute every time
17886 execution stops in your program: before breakpoint commands are run,
17887 displays are printed, or the stack frame is printed.
17889 For example, to ignore @code{SIGALRM} signals while
17890 single-stepping, but treat them normally during normal execution,
17895 handle SIGALRM nopass
17899 handle SIGALRM pass
17902 define hook-continue
17903 handle SIGALRM pass
17907 As a further example, to hook at the beginning and end of the @code{echo}
17908 command, and to add extra text to the beginning and end of the message,
17916 define hookpost-echo
17920 (@value{GDBP}) echo Hello World
17921 <<<---Hello World--->>>
17926 You can define a hook for any single-word command in @value{GDBN}, but
17927 not for command aliases; you should define a hook for the basic command
17928 name, e.g.@: @code{backtrace} rather than @code{bt}.
17929 @c FIXME! So how does Joe User discover whether a command is an alias
17931 You can hook a multi-word command by adding @code{hook-} or
17932 @code{hookpost-} to the last word of the command, e.g.@:
17933 @samp{define target hook-remote} to add a hook to @samp{target remote}.
17935 If an error occurs during the execution of your hook, execution of
17936 @value{GDBN} commands stops and @value{GDBN} issues a prompt
17937 (before the command that you actually typed had a chance to run).
17939 If you try to define a hook which does not match any known command, you
17940 get a warning from the @code{define} command.
17942 @node Command Files
17943 @subsection Command Files
17945 @cindex command files
17946 @cindex scripting commands
17947 A command file for @value{GDBN} is a text file made of lines that are
17948 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
17949 also be included. An empty line in a command file does nothing; it
17950 does not mean to repeat the last command, as it would from the
17953 You can request the execution of a command file with the @code{source}
17958 @cindex execute commands from a file
17959 @item source [@code{-v}] @var{filename}
17960 Execute the command file @var{filename}.
17963 The lines in a command file are generally executed sequentially,
17964 unless the order of execution is changed by one of the
17965 @emph{flow-control commands} described below. The commands are not
17966 printed as they are executed. An error in any command terminates
17967 execution of the command file and control is returned to the console.
17969 @value{GDBN} searches for @var{filename} in the current directory and then
17970 on the search path (specified with the @samp{directory} command).
17972 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
17973 each command as it is executed. The option must be given before
17974 @var{filename}, and is interpreted as part of the filename anywhere else.
17976 Commands that would ask for confirmation if used interactively proceed
17977 without asking when used in a command file. Many @value{GDBN} commands that
17978 normally print messages to say what they are doing omit the messages
17979 when called from command files.
17981 @value{GDBN} also accepts command input from standard input. In this
17982 mode, normal output goes to standard output and error output goes to
17983 standard error. Errors in a command file supplied on standard input do
17984 not terminate execution of the command file---execution continues with
17988 gdb < cmds > log 2>&1
17991 (The syntax above will vary depending on the shell used.) This example
17992 will execute commands from the file @file{cmds}. All output and errors
17993 would be directed to @file{log}.
17995 Since commands stored on command files tend to be more general than
17996 commands typed interactively, they frequently need to deal with
17997 complicated situations, such as different or unexpected values of
17998 variables and symbols, changes in how the program being debugged is
17999 built, etc. @value{GDBN} provides a set of flow-control commands to
18000 deal with these complexities. Using these commands, you can write
18001 complex scripts that loop over data structures, execute commands
18002 conditionally, etc.
18009 This command allows to include in your script conditionally executed
18010 commands. The @code{if} command takes a single argument, which is an
18011 expression to evaluate. It is followed by a series of commands that
18012 are executed only if the expression is true (its value is nonzero).
18013 There can then optionally be an @code{else} line, followed by a series
18014 of commands that are only executed if the expression was false. The
18015 end of the list is marked by a line containing @code{end}.
18019 This command allows to write loops. Its syntax is similar to
18020 @code{if}: the command takes a single argument, which is an expression
18021 to evaluate, and must be followed by the commands to execute, one per
18022 line, terminated by an @code{end}. These commands are called the
18023 @dfn{body} of the loop. The commands in the body of @code{while} are
18024 executed repeatedly as long as the expression evaluates to true.
18028 This command exits the @code{while} loop in whose body it is included.
18029 Execution of the script continues after that @code{while}s @code{end}
18032 @kindex loop_continue
18033 @item loop_continue
18034 This command skips the execution of the rest of the body of commands
18035 in the @code{while} loop in whose body it is included. Execution
18036 branches to the beginning of the @code{while} loop, where it evaluates
18037 the controlling expression.
18039 @kindex end@r{ (if/else/while commands)}
18041 Terminate the block of commands that are the body of @code{if},
18042 @code{else}, or @code{while} flow-control commands.
18047 @subsection Commands for Controlled Output
18049 During the execution of a command file or a user-defined command, normal
18050 @value{GDBN} output is suppressed; the only output that appears is what is
18051 explicitly printed by the commands in the definition. This section
18052 describes three commands useful for generating exactly the output you
18057 @item echo @var{text}
18058 @c I do not consider backslash-space a standard C escape sequence
18059 @c because it is not in ANSI.
18060 Print @var{text}. Nonprinting characters can be included in
18061 @var{text} using C escape sequences, such as @samp{\n} to print a
18062 newline. @strong{No newline is printed unless you specify one.}
18063 In addition to the standard C escape sequences, a backslash followed
18064 by a space stands for a space. This is useful for displaying a
18065 string with spaces at the beginning or the end, since leading and
18066 trailing spaces are otherwise trimmed from all arguments.
18067 To print @samp{@w{ }and foo =@w{ }}, use the command
18068 @samp{echo \@w{ }and foo = \@w{ }}.
18070 A backslash at the end of @var{text} can be used, as in C, to continue
18071 the command onto subsequent lines. For example,
18074 echo This is some text\n\
18075 which is continued\n\
18076 onto several lines.\n
18079 produces the same output as
18082 echo This is some text\n
18083 echo which is continued\n
18084 echo onto several lines.\n
18088 @item output @var{expression}
18089 Print the value of @var{expression} and nothing but that value: no
18090 newlines, no @samp{$@var{nn} = }. The value is not entered in the
18091 value history either. @xref{Expressions, ,Expressions}, for more information
18094 @item output/@var{fmt} @var{expression}
18095 Print the value of @var{expression} in format @var{fmt}. You can use
18096 the same formats as for @code{print}. @xref{Output Formats,,Output
18097 Formats}, for more information.
18100 @item printf @var{template}, @var{expressions}@dots{}
18101 Print the values of one or more @var{expressions} under the control of
18102 the string @var{template}. To print several values, make
18103 @var{expressions} be a comma-separated list of individual expressions,
18104 which may be either numbers or pointers. Their values are printed as
18105 specified by @var{template}, exactly as a C program would do by
18106 executing the code below:
18109 printf (@var{template}, @var{expressions}@dots{});
18112 As in @code{C} @code{printf}, ordinary characters in @var{template}
18113 are printed verbatim, while @dfn{conversion specification} introduced
18114 by the @samp{%} character cause subsequent @var{expressions} to be
18115 evaluated, their values converted and formatted according to type and
18116 style information encoded in the conversion specifications, and then
18119 For example, you can print two values in hex like this:
18122 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
18125 @code{printf} supports all the standard @code{C} conversion
18126 specifications, including the flags and modifiers between the @samp{%}
18127 character and the conversion letter, with the following exceptions:
18131 The argument-ordering modifiers, such as @samp{2$}, are not supported.
18134 The modifier @samp{*} is not supported for specifying precision or
18138 The @samp{'} flag (for separation of digits into groups according to
18139 @code{LC_NUMERIC'}) is not supported.
18142 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
18146 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
18149 The conversion letters @samp{a} and @samp{A} are not supported.
18153 Note that the @samp{ll} type modifier is supported only if the
18154 underlying @code{C} implementation used to build @value{GDBN} supports
18155 the @code{long long int} type, and the @samp{L} type modifier is
18156 supported only if @code{long double} type is available.
18158 As in @code{C}, @code{printf} supports simple backslash-escape
18159 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
18160 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
18161 single character. Octal and hexadecimal escape sequences are not
18164 Additionally, @code{printf} supports conversion specifications for DFP
18165 (@dfn{Decimal Floating Point}) types using the following length modifiers
18166 together with a floating point specifier.
18171 @samp{H} for printing @code{Decimal32} types.
18174 @samp{D} for printing @code{Decimal64} types.
18177 @samp{DD} for printing @code{Decimal128} types.
18180 If the underlying @code{C} implementation used to build @value{GDBN} has
18181 support for the three length modifiers for DFP types, other modifiers
18182 such as width and precision will also be available for @value{GDBN} to use.
18184 In case there is no such @code{C} support, no additional modifiers will be
18185 available and the value will be printed in the standard way.
18187 Here's an example of printing DFP types using the above conversion letters:
18189 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
18195 @section Scripting @value{GDBN} using Python
18196 @cindex python scripting
18197 @cindex scripting with python
18199 You can script @value{GDBN} using the @uref{http://www.python.org/,
18200 Python programming language}. This feature is available only if
18201 @value{GDBN} was configured using @option{--with-python}.
18204 * Python Commands:: Accessing Python from @value{GDBN}.
18205 * Python API:: Accessing @value{GDBN} from Python.
18208 @node Python Commands
18209 @subsection Python Commands
18210 @cindex python commands
18211 @cindex commands to access python
18213 @value{GDBN} provides one command for accessing the Python interpreter,
18214 and one related setting:
18218 @item python @r{[}@var{code}@r{]}
18219 The @code{python} command can be used to evaluate Python code.
18221 If given an argument, the @code{python} command will evaluate the
18222 argument as a Python command. For example:
18225 (@value{GDBP}) python print 23
18229 If you do not provide an argument to @code{python}, it will act as a
18230 multi-line command, like @code{define}. In this case, the Python
18231 script is made up of subsequent command lines, given after the
18232 @code{python} command. This command list is terminated using a line
18233 containing @code{end}. For example:
18236 (@value{GDBP}) python
18238 End with a line saying just "end".
18244 @kindex maint set python print-stack
18245 @item maint set python print-stack
18246 By default, @value{GDBN} will print a stack trace when an error occurs
18247 in a Python script. This can be controlled using @code{maint set
18248 python print-stack}: if @code{on}, the default, then Python stack
18249 printing is enabled; if @code{off}, then Python stack printing is
18254 @subsection Python API
18256 @cindex programming in python
18258 @cindex python stdout
18259 @cindex python pagination
18260 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
18261 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
18262 A Python program which outputs to one of these streams may have its
18263 output interrupted by the user (@pxref{Screen Size}). In this
18264 situation, a Python @code{KeyboardInterrupt} exception is thrown.
18267 * Basic Python:: Basic Python Functions.
18268 * Exception Handling::
18269 * Values From Inferior::
18270 * Commands In Python:: Implementing new commands in Python.
18271 * Functions In Python:: Writing new convenience functions.
18272 * Frames In Python:: Acessing inferior stack frames from Python.
18276 @subsubsection Basic Python
18278 @cindex python functions
18279 @cindex python module
18281 @value{GDBN} introduces a new Python module, named @code{gdb}. All
18282 methods and classes added by @value{GDBN} are placed in this module.
18283 @value{GDBN} automatically @code{import}s the @code{gdb} module for
18284 use in all scripts evaluated by the @code{python} command.
18286 @findex gdb.execute
18287 @defun execute command [from_tty]
18288 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
18289 If a GDB exception happens while @var{command} runs, it is
18290 translated as described in @ref{Exception Handling,,Exception Handling}.
18291 If no exceptions occur, this function returns @code{None}.
18293 @var{from_tty} specifies whether @value{GDBN} ought to consider this
18294 command as having originated from the user invoking it interactively.
18295 It must be a boolean value. If omitted, it defaults to @code{False}.
18298 @findex gdb.get_parameter
18299 @defun get_parameter parameter
18300 Return the value of a @value{GDBN} parameter. @var{parameter} is a
18301 string naming the parameter to look up; @var{parameter} may contain
18302 spaces if the parameter has a multi-part name. For example,
18303 @samp{print object} is a valid parameter name.
18305 If the named parameter does not exist, this function throws a
18306 @code{RuntimeError}. Otherwise, the parameter's value is converted to
18307 a Python value of the appropriate type, and returned.
18310 @findex gdb.history
18311 @defun history number
18312 Return a value from @value{GDBN}'s value history (@pxref{Value
18313 History}). @var{number} indicates which history element to return.
18314 If @var{number} is negative, then @value{GDBN} will take its absolute value
18315 and count backward from the last element (i.e., the most recent element) to
18316 find the value to return. If @var{number} is zero, then @value{GDBN} will
18317 return the most recent element. If the element specified by @var{number}
18318 doesn't exist in the value history, a @code{RuntimeError} exception will be
18321 If no exception is raised, the return value is always an instance of
18322 @code{gdb.Value} (@pxref{Values From Inferior}).
18326 @defun write string
18327 Print a string to @value{GDBN}'s paginated standard output stream.
18328 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
18329 call this function.
18334 Flush @value{GDBN}'s paginated standard output stream. Flushing
18335 @code{sys.stdout} or @code{sys.stderr} will automatically call this
18339 @node Exception Handling
18340 @subsubsection Exception Handling
18341 @cindex python exceptions
18342 @cindex exceptions, python
18344 When executing the @code{python} command, Python exceptions
18345 uncaught within the Python code are translated to calls to
18346 @value{GDBN} error-reporting mechanism. If the command that called
18347 @code{python} does not handle the error, @value{GDBN} will
18348 terminate it and print an error message containing the Python
18349 exception name, the associated value, and the Python call stack
18350 backtrace at the point where the exception was raised. Example:
18353 (@value{GDBP}) python print foo
18354 Traceback (most recent call last):
18355 File "<string>", line 1, in <module>
18356 NameError: name 'foo' is not defined
18359 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
18360 code are converted to Python @code{RuntimeError} exceptions. User
18361 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
18362 prompt) is translated to a Python @code{KeyboardInterrupt}
18363 exception. If you catch these exceptions in your Python code, your
18364 exception handler will see @code{RuntimeError} or
18365 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
18366 message as its value, and the Python call stack backtrace at the
18367 Python statement closest to where the @value{GDBN} error occured as the
18370 @node Values From Inferior
18371 @subsubsection Values From Inferior
18372 @cindex values from inferior, with Python
18373 @cindex python, working with values from inferior
18375 @cindex @code{gdb.Value}
18376 @value{GDBN} provides values it obtains from the inferior program in
18377 an object of type @code{gdb.Value}. @value{GDBN} uses this object
18378 for its internal bookkeeping of the inferior's values, and for
18379 fetching values when necessary.
18381 Inferior values that are simple scalars can be used directly in
18382 Python expressions that are valid for the value's data type. Here's
18383 an example for an integer or floating-point value @code{some_val}:
18390 As result of this, @code{bar} will also be a @code{gdb.Value} object
18391 whose values are of the same type as those of @code{some_val}.
18393 Inferior values that are structures or instances of some class can
18394 be accessed using the Python @dfn{dictionary syntax}. For example, if
18395 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
18396 can access its @code{foo} element with:
18399 bar = some_val['foo']
18402 Again, @code{bar} will also be a @code{gdb.Value} object.
18404 The following attributes are provided:
18407 @defmethod Value address
18408 If this object is addressable, this read-only attribute holds a
18409 @code{gdb.Value} object representing the address. Otherwise,
18410 this attribute holds @code{None}.
18413 @cindex optimized out value in Python
18414 @defmethod Value is_optimized_out
18415 This read-only boolean attribute is true if the compiler optimized out
18416 this value, thus it is not available for fetching from the inferior.
18420 The following methods are provided:
18423 @defmethod Value dereference
18424 For pointer data types, this method returns a new @code{gdb.Value} object
18425 whose contents is the object pointed to by the pointer. For example, if
18426 @code{foo} is a C pointer to an @code{int}, declared in your C program as
18433 then you can use the corresponding @code{gdb.Value} to access what
18434 @code{foo} points to like this:
18437 bar = foo.dereference ()
18440 The result @code{bar} will be a @code{gdb.Value} object holding the
18441 value pointed to by @code{foo}.
18444 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]}
18445 If this @code{gdb.Value} represents a string, then this method
18446 converts the contents to a Python string. Otherwise, this method will
18447 throw an exception.
18449 Strings are recognized in a language-specific way; whether a given
18450 @code{gdb.Value} represents a string is determined by the current
18453 For C-like languages, a value is a string if it is a pointer to or an
18454 array of characters or ints. The string is assumed to be terminated
18455 by a zero of the appropriate width.
18457 If the optional @var{encoding} argument is given, it must be a string
18458 naming the encoding of the string in the @code{gdb.Value}, such as
18459 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
18460 the same encodings as the corresponding argument to Python's
18461 @code{string.decode} method, and the Python codec machinery will be used
18462 to convert the string. If @var{encoding} is not given, or if
18463 @var{encoding} is the empty string, then either the @code{target-charset}
18464 (@pxref{Character Sets}) will be used, or a language-specific encoding
18465 will be used, if the current language is able to supply one.
18467 The optional @var{errors} argument is the same as the corresponding
18468 argument to Python's @code{string.decode} method.
18472 @node Commands In Python
18473 @subsubsection Commands In Python
18475 @cindex commands in python
18476 @cindex python commands
18477 You can implement new @value{GDBN} CLI commands in Python. A CLI
18478 command is implemented using an instance of the @code{gdb.Command}
18479 class, most commonly using a subclass.
18481 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
18482 The object initializer for @code{Command} registers the new command
18483 with @value{GDBN}. This initializer is normally invoked from the
18484 subclass' own @code{__init__} method.
18486 @var{name} is the name of the command. If @var{name} consists of
18487 multiple words, then the initial words are looked for as prefix
18488 commands. In this case, if one of the prefix commands does not exist,
18489 an exception is raised.
18491 There is no support for multi-line commands.
18493 @var{command_class} should be one of the @samp{COMMAND_} constants
18494 defined below. This argument tells @value{GDBN} how to categorize the
18495 new command in the help system.
18497 @var{completer_class} is an optional argument. If given, it should be
18498 one of the @samp{COMPLETE_} constants defined below. This argument
18499 tells @value{GDBN} how to perform completion for this command. If not
18500 given, @value{GDBN} will attempt to complete using the object's
18501 @code{complete} method (see below); if no such method is found, an
18502 error will occur when completion is attempted.
18504 @var{prefix} is an optional argument. If @code{True}, then the new
18505 command is a prefix command; sub-commands of this command may be
18508 The help text for the new command is taken from the Python
18509 documentation string for the command's class, if there is one. If no
18510 documentation string is provided, the default value ``This command is
18511 not documented.'' is used.
18514 @cindex don't repeat Python command
18515 @defmethod Command dont_repeat
18516 By default, a @value{GDBN} command is repeated when the user enters a
18517 blank line at the command prompt. A command can suppress this
18518 behavior by invoking the @code{dont_repeat} method. This is similar
18519 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
18522 @defmethod Command invoke argument from_tty
18523 This method is called by @value{GDBN} when this command is invoked.
18525 @var{argument} is a string. It is the argument to the command, after
18526 leading and trailing whitespace has been stripped.
18528 @var{from_tty} is a boolean argument. When true, this means that the
18529 command was entered by the user at the terminal; when false it means
18530 that the command came from elsewhere.
18532 If this method throws an exception, it is turned into a @value{GDBN}
18533 @code{error} call. Otherwise, the return value is ignored.
18536 @cindex completion of Python commands
18537 @defmethod Command complete text word
18538 This method is called by @value{GDBN} when the user attempts
18539 completion on this command. All forms of completion are handled by
18540 this method, that is, the @key{TAB} and @key{M-?} key bindings
18541 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
18544 The arguments @var{text} and @var{word} are both strings. @var{text}
18545 holds the complete command line up to the cursor's location.
18546 @var{word} holds the last word of the command line; this is computed
18547 using a word-breaking heuristic.
18549 The @code{complete} method can return several values:
18552 If the return value is a sequence, the contents of the sequence are
18553 used as the completions. It is up to @code{complete} to ensure that the
18554 contents actually do complete the word. A zero-length sequence is
18555 allowed, it means that there were no completions available. Only
18556 string elements of the sequence are used; other elements in the
18557 sequence are ignored.
18560 If the return value is one of the @samp{COMPLETE_} constants defined
18561 below, then the corresponding @value{GDBN}-internal completion
18562 function is invoked, and its result is used.
18565 All other results are treated as though there were no available
18570 When a new command is registered, it must be declared as a member of
18571 some general class of commands. This is used to classify top-level
18572 commands in the on-line help system; note that prefix commands are not
18573 listed under their own category but rather that of their top-level
18574 command. The available classifications are represented by constants
18575 defined in the @code{gdb} module:
18578 @findex COMMAND_NONE
18579 @findex gdb.COMMAND_NONE
18581 The command does not belong to any particular class. A command in
18582 this category will not be displayed in any of the help categories.
18584 @findex COMMAND_RUNNING
18585 @findex gdb.COMMAND_RUNNING
18586 @item COMMAND_RUNNING
18587 The command is related to running the inferior. For example,
18588 @code{start}, @code{step}, and @code{continue} are in this category.
18589 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
18590 commands in this category.
18592 @findex COMMAND_DATA
18593 @findex gdb.COMMAND_DATA
18595 The command is related to data or variables. For example,
18596 @code{call}, @code{find}, and @code{print} are in this category. Type
18597 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
18600 @findex COMMAND_STACK
18601 @findex gdb.COMMAND_STACK
18602 @item COMMAND_STACK
18603 The command has to do with manipulation of the stack. For example,
18604 @code{backtrace}, @code{frame}, and @code{return} are in this
18605 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
18606 list of commands in this category.
18608 @findex COMMAND_FILES
18609 @findex gdb.COMMAND_FILES
18610 @item COMMAND_FILES
18611 This class is used for file-related commands. For example,
18612 @code{file}, @code{list} and @code{section} are in this category.
18613 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
18614 commands in this category.
18616 @findex COMMAND_SUPPORT
18617 @findex gdb.COMMAND_SUPPORT
18618 @item COMMAND_SUPPORT
18619 This should be used for ``support facilities'', generally meaning
18620 things that are useful to the user when interacting with @value{GDBN},
18621 but not related to the state of the inferior. For example,
18622 @code{help}, @code{make}, and @code{shell} are in this category. Type
18623 @kbd{help support} at the @value{GDBN} prompt to see a list of
18624 commands in this category.
18626 @findex COMMAND_STATUS
18627 @findex gdb.COMMAND_STATUS
18628 @item COMMAND_STATUS
18629 The command is an @samp{info}-related command, that is, related to the
18630 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
18631 and @code{show} are in this category. Type @kbd{help status} at the
18632 @value{GDBN} prompt to see a list of commands in this category.
18634 @findex COMMAND_BREAKPOINTS
18635 @findex gdb.COMMAND_BREAKPOINTS
18636 @item COMMAND_BREAKPOINTS
18637 The command has to do with breakpoints. For example, @code{break},
18638 @code{clear}, and @code{delete} are in this category. Type @kbd{help
18639 breakpoints} at the @value{GDBN} prompt to see a list of commands in
18642 @findex COMMAND_TRACEPOINTS
18643 @findex gdb.COMMAND_TRACEPOINTS
18644 @item COMMAND_TRACEPOINTS
18645 The command has to do with tracepoints. For example, @code{trace},
18646 @code{actions}, and @code{tfind} are in this category. Type
18647 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
18648 commands in this category.
18650 @findex COMMAND_OBSCURE
18651 @findex gdb.COMMAND_OBSCURE
18652 @item COMMAND_OBSCURE
18653 The command is only used in unusual circumstances, or is not of
18654 general interest to users. For example, @code{checkpoint},
18655 @code{fork}, and @code{stop} are in this category. Type @kbd{help
18656 obscure} at the @value{GDBN} prompt to see a list of commands in this
18659 @findex COMMAND_MAINTENANCE
18660 @findex gdb.COMMAND_MAINTENANCE
18661 @item COMMAND_MAINTENANCE
18662 The command is only useful to @value{GDBN} maintainers. The
18663 @code{maintenance} and @code{flushregs} commands are in this category.
18664 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
18665 commands in this category.
18668 A new command can use a predefined completion function, either by
18669 specifying it via an argument at initialization, or by returning it
18670 from the @code{complete} method. These predefined completion
18671 constants are all defined in the @code{gdb} module:
18674 @findex COMPLETE_NONE
18675 @findex gdb.COMPLETE_NONE
18676 @item COMPLETE_NONE
18677 This constant means that no completion should be done.
18679 @findex COMPLETE_FILENAME
18680 @findex gdb.COMPLETE_FILENAME
18681 @item COMPLETE_FILENAME
18682 This constant means that filename completion should be performed.
18684 @findex COMPLETE_LOCATION
18685 @findex gdb.COMPLETE_LOCATION
18686 @item COMPLETE_LOCATION
18687 This constant means that location completion should be done.
18688 @xref{Specify Location}.
18690 @findex COMPLETE_COMMAND
18691 @findex gdb.COMPLETE_COMMAND
18692 @item COMPLETE_COMMAND
18693 This constant means that completion should examine @value{GDBN}
18696 @findex COMPLETE_SYMBOL
18697 @findex gdb.COMPLETE_SYMBOL
18698 @item COMPLETE_SYMBOL
18699 This constant means that completion should be done using symbol names
18703 The following code snippet shows how a trivial CLI command can be
18704 implemented in Python:
18707 class HelloWorld (gdb.Command):
18708 """Greet the whole world."""
18710 def __init__ (self):
18711 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
18713 def invoke (self, arg, from_tty):
18714 print "Hello, World!"
18719 The last line instantiates the class, and is necessary to trigger the
18720 registration of the command with @value{GDBN}. Depending on how the
18721 Python code is read into @value{GDBN}, you may need to import the
18722 @code{gdb} module explicitly.
18724 @node Functions In Python
18725 @subsubsection Writing new convenience functions
18727 @cindex writing convenience functions
18728 @cindex convenience functions in python
18729 @cindex python convenience functions
18730 @tindex gdb.Function
18732 You can implement new convenience functions (@pxref{Convenience Vars})
18733 in Python. A convenience function is an instance of a subclass of the
18734 class @code{gdb.Function}.
18736 @defmethod Function __init__ name
18737 The initializer for @code{Function} registers the new function with
18738 @value{GDBN}. The argument @var{name} is the name of the function,
18739 a string. The function will be visible to the user as a convenience
18740 variable of type @code{internal function}, whose name is the same as
18741 the given @var{name}.
18743 The documentation for the new function is taken from the documentation
18744 string for the new class.
18747 @defmethod Function invoke @var{*args}
18748 When a convenience function is evaluated, its arguments are converted
18749 to instances of @code{gdb.Value}, and then the function's
18750 @code{invoke} method is called. Note that @value{GDBN} does not
18751 predetermine the arity of convenience functions. Instead, all
18752 available arguments are passed to @code{invoke}, following the
18753 standard Python calling convention. In particular, a convenience
18754 function can have default values for parameters without ill effect.
18756 The return value of this method is used as its value in the enclosing
18757 expression. If an ordinary Python value is returned, it is converted
18758 to a @code{gdb.Value} following the usual rules.
18761 The following code snippet shows how a trivial convenience function can
18762 be implemented in Python:
18765 class Greet (gdb.Function):
18766 """Return string to greet someone.
18767 Takes a name as argument."""
18769 def __init__ (self):
18770 super (Greet, self).__init__ ("greet")
18772 def invoke (self, name):
18773 return "Hello, %s!" % name.string ()
18778 The last line instantiates the class, and is necessary to trigger the
18779 registration of the function with @value{GDBN}. Depending on how the
18780 Python code is read into @value{GDBN}, you may need to import the
18781 @code{gdb} module explicitly.
18783 @node Frames In Python
18784 @subsubsection Acessing inferior stack frames from Python.
18786 @cindex frames in python
18787 When the debugged program stops, @value{GDBN} is able to analyze its call
18788 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
18789 represents a frame in the stack. A @code{gdb.Frame} object is only valid
18790 while its corresponding frame exists in the inferior's stack. If you try
18791 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
18794 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
18798 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
18802 The following frame-related functions are available in the @code{gdb} module:
18804 @findex gdb.selected_frame
18805 @defun selected_frame
18806 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
18809 @defun frame_stop_reason_string reason
18810 Return a string explaining the reason why @value{GDBN} stopped unwinding
18811 frames, as expressed by the given @var{reason} code (an integer, see the
18812 @code{unwind_stop_reason} method further down in this section).
18815 A @code{gdb.Frame} object has the following methods:
18818 @defmethod Frame is_valid
18819 Returns true if the @code{gdb.Frame} object is valid, false if not.
18820 A frame object can become invalid if the frame it refers to doesn't
18821 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
18822 an exception if it is invalid at the time the method is called.
18825 @defmethod Frame name
18826 Returns the function name of the frame, or @code{None} if it can't be
18830 @defmethod Frame type
18831 Returns the type of the frame. The value can be one of
18832 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
18833 or @code{gdb.SENTINEL_FRAME}.
18836 @defmethod Frame unwind_stop_reason
18837 Return an integer representing the reason why it's not possible to find
18838 more frames toward the outermost frame. Use
18839 @code{gdb.frame_stop_reason_string} to convert the value returned by this
18840 function to a string.
18843 @defmethod Frame pc
18844 Returns the frame's resume address.
18847 @defmethod Frame older
18848 Return the frame that called this frame.
18851 @defmethod Frame newer
18852 Return the frame called by this frame.
18855 @defmethod Frame read_var variable
18856 Return the value of the given variable in this frame. @var{variable} must
18862 @chapter Command Interpreters
18863 @cindex command interpreters
18865 @value{GDBN} supports multiple command interpreters, and some command
18866 infrastructure to allow users or user interface writers to switch
18867 between interpreters or run commands in other interpreters.
18869 @value{GDBN} currently supports two command interpreters, the console
18870 interpreter (sometimes called the command-line interpreter or @sc{cli})
18871 and the machine interface interpreter (or @sc{gdb/mi}). This manual
18872 describes both of these interfaces in great detail.
18874 By default, @value{GDBN} will start with the console interpreter.
18875 However, the user may choose to start @value{GDBN} with another
18876 interpreter by specifying the @option{-i} or @option{--interpreter}
18877 startup options. Defined interpreters include:
18881 @cindex console interpreter
18882 The traditional console or command-line interpreter. This is the most often
18883 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
18884 @value{GDBN} will use this interpreter.
18887 @cindex mi interpreter
18888 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
18889 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
18890 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
18894 @cindex mi2 interpreter
18895 The current @sc{gdb/mi} interface.
18898 @cindex mi1 interpreter
18899 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
18903 @cindex invoke another interpreter
18904 The interpreter being used by @value{GDBN} may not be dynamically
18905 switched at runtime. Although possible, this could lead to a very
18906 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
18907 enters the command "interpreter-set console" in a console view,
18908 @value{GDBN} would switch to using the console interpreter, rendering
18909 the IDE inoperable!
18911 @kindex interpreter-exec
18912 Although you may only choose a single interpreter at startup, you may execute
18913 commands in any interpreter from the current interpreter using the appropriate
18914 command. If you are running the console interpreter, simply use the
18915 @code{interpreter-exec} command:
18918 interpreter-exec mi "-data-list-register-names"
18921 @sc{gdb/mi} has a similar command, although it is only available in versions of
18922 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
18925 @chapter @value{GDBN} Text User Interface
18927 @cindex Text User Interface
18930 * TUI Overview:: TUI overview
18931 * TUI Keys:: TUI key bindings
18932 * TUI Single Key Mode:: TUI single key mode
18933 * TUI Commands:: TUI-specific commands
18934 * TUI Configuration:: TUI configuration variables
18937 The @value{GDBN} Text User Interface (TUI) is a terminal
18938 interface which uses the @code{curses} library to show the source
18939 file, the assembly output, the program registers and @value{GDBN}
18940 commands in separate text windows. The TUI mode is supported only
18941 on platforms where a suitable version of the @code{curses} library
18944 @pindex @value{GDBTUI}
18945 The TUI mode is enabled by default when you invoke @value{GDBN} as
18946 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
18947 You can also switch in and out of TUI mode while @value{GDBN} runs by
18948 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
18949 @xref{TUI Keys, ,TUI Key Bindings}.
18952 @section TUI Overview
18954 In TUI mode, @value{GDBN} can display several text windows:
18958 This window is the @value{GDBN} command window with the @value{GDBN}
18959 prompt and the @value{GDBN} output. The @value{GDBN} input is still
18960 managed using readline.
18963 The source window shows the source file of the program. The current
18964 line and active breakpoints are displayed in this window.
18967 The assembly window shows the disassembly output of the program.
18970 This window shows the processor registers. Registers are highlighted
18971 when their values change.
18974 The source and assembly windows show the current program position
18975 by highlighting the current line and marking it with a @samp{>} marker.
18976 Breakpoints are indicated with two markers. The first marker
18977 indicates the breakpoint type:
18981 Breakpoint which was hit at least once.
18984 Breakpoint which was never hit.
18987 Hardware breakpoint which was hit at least once.
18990 Hardware breakpoint which was never hit.
18993 The second marker indicates whether the breakpoint is enabled or not:
18997 Breakpoint is enabled.
19000 Breakpoint is disabled.
19003 The source, assembly and register windows are updated when the current
19004 thread changes, when the frame changes, or when the program counter
19007 These windows are not all visible at the same time. The command
19008 window is always visible. The others can be arranged in several
19019 source and assembly,
19022 source and registers, or
19025 assembly and registers.
19028 A status line above the command window shows the following information:
19032 Indicates the current @value{GDBN} target.
19033 (@pxref{Targets, ,Specifying a Debugging Target}).
19036 Gives the current process or thread number.
19037 When no process is being debugged, this field is set to @code{No process}.
19040 Gives the current function name for the selected frame.
19041 The name is demangled if demangling is turned on (@pxref{Print Settings}).
19042 When there is no symbol corresponding to the current program counter,
19043 the string @code{??} is displayed.
19046 Indicates the current line number for the selected frame.
19047 When the current line number is not known, the string @code{??} is displayed.
19050 Indicates the current program counter address.
19054 @section TUI Key Bindings
19055 @cindex TUI key bindings
19057 The TUI installs several key bindings in the readline keymaps
19058 (@pxref{Command Line Editing}). The following key bindings
19059 are installed for both TUI mode and the @value{GDBN} standard mode.
19068 Enter or leave the TUI mode. When leaving the TUI mode,
19069 the curses window management stops and @value{GDBN} operates using
19070 its standard mode, writing on the terminal directly. When reentering
19071 the TUI mode, control is given back to the curses windows.
19072 The screen is then refreshed.
19076 Use a TUI layout with only one window. The layout will
19077 either be @samp{source} or @samp{assembly}. When the TUI mode
19078 is not active, it will switch to the TUI mode.
19080 Think of this key binding as the Emacs @kbd{C-x 1} binding.
19084 Use a TUI layout with at least two windows. When the current
19085 layout already has two windows, the next layout with two windows is used.
19086 When a new layout is chosen, one window will always be common to the
19087 previous layout and the new one.
19089 Think of it as the Emacs @kbd{C-x 2} binding.
19093 Change the active window. The TUI associates several key bindings
19094 (like scrolling and arrow keys) with the active window. This command
19095 gives the focus to the next TUI window.
19097 Think of it as the Emacs @kbd{C-x o} binding.
19101 Switch in and out of the TUI SingleKey mode that binds single
19102 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
19105 The following key bindings only work in the TUI mode:
19110 Scroll the active window one page up.
19114 Scroll the active window one page down.
19118 Scroll the active window one line up.
19122 Scroll the active window one line down.
19126 Scroll the active window one column left.
19130 Scroll the active window one column right.
19134 Refresh the screen.
19137 Because the arrow keys scroll the active window in the TUI mode, they
19138 are not available for their normal use by readline unless the command
19139 window has the focus. When another window is active, you must use
19140 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
19141 and @kbd{C-f} to control the command window.
19143 @node TUI Single Key Mode
19144 @section TUI Single Key Mode
19145 @cindex TUI single key mode
19147 The TUI also provides a @dfn{SingleKey} mode, which binds several
19148 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
19149 switch into this mode, where the following key bindings are used:
19152 @kindex c @r{(SingleKey TUI key)}
19156 @kindex d @r{(SingleKey TUI key)}
19160 @kindex f @r{(SingleKey TUI key)}
19164 @kindex n @r{(SingleKey TUI key)}
19168 @kindex q @r{(SingleKey TUI key)}
19170 exit the SingleKey mode.
19172 @kindex r @r{(SingleKey TUI key)}
19176 @kindex s @r{(SingleKey TUI key)}
19180 @kindex u @r{(SingleKey TUI key)}
19184 @kindex v @r{(SingleKey TUI key)}
19188 @kindex w @r{(SingleKey TUI key)}
19193 Other keys temporarily switch to the @value{GDBN} command prompt.
19194 The key that was pressed is inserted in the editing buffer so that
19195 it is possible to type most @value{GDBN} commands without interaction
19196 with the TUI SingleKey mode. Once the command is entered the TUI
19197 SingleKey mode is restored. The only way to permanently leave
19198 this mode is by typing @kbd{q} or @kbd{C-x s}.
19202 @section TUI-specific Commands
19203 @cindex TUI commands
19205 The TUI has specific commands to control the text windows.
19206 These commands are always available, even when @value{GDBN} is not in
19207 the TUI mode. When @value{GDBN} is in the standard mode, most
19208 of these commands will automatically switch to the TUI mode.
19213 List and give the size of all displayed windows.
19217 Display the next layout.
19220 Display the previous layout.
19223 Display the source window only.
19226 Display the assembly window only.
19229 Display the source and assembly window.
19232 Display the register window together with the source or assembly window.
19236 Make the next window active for scrolling.
19239 Make the previous window active for scrolling.
19242 Make the source window active for scrolling.
19245 Make the assembly window active for scrolling.
19248 Make the register window active for scrolling.
19251 Make the command window active for scrolling.
19255 Refresh the screen. This is similar to typing @kbd{C-L}.
19257 @item tui reg float
19259 Show the floating point registers in the register window.
19261 @item tui reg general
19262 Show the general registers in the register window.
19265 Show the next register group. The list of register groups as well as
19266 their order is target specific. The predefined register groups are the
19267 following: @code{general}, @code{float}, @code{system}, @code{vector},
19268 @code{all}, @code{save}, @code{restore}.
19270 @item tui reg system
19271 Show the system registers in the register window.
19275 Update the source window and the current execution point.
19277 @item winheight @var{name} +@var{count}
19278 @itemx winheight @var{name} -@var{count}
19280 Change the height of the window @var{name} by @var{count}
19281 lines. Positive counts increase the height, while negative counts
19284 @item tabset @var{nchars}
19286 Set the width of tab stops to be @var{nchars} characters.
19289 @node TUI Configuration
19290 @section TUI Configuration Variables
19291 @cindex TUI configuration variables
19293 Several configuration variables control the appearance of TUI windows.
19296 @item set tui border-kind @var{kind}
19297 @kindex set tui border-kind
19298 Select the border appearance for the source, assembly and register windows.
19299 The possible values are the following:
19302 Use a space character to draw the border.
19305 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
19308 Use the Alternate Character Set to draw the border. The border is
19309 drawn using character line graphics if the terminal supports them.
19312 @item set tui border-mode @var{mode}
19313 @kindex set tui border-mode
19314 @itemx set tui active-border-mode @var{mode}
19315 @kindex set tui active-border-mode
19316 Select the display attributes for the borders of the inactive windows
19317 or the active window. The @var{mode} can be one of the following:
19320 Use normal attributes to display the border.
19326 Use reverse video mode.
19329 Use half bright mode.
19331 @item half-standout
19332 Use half bright and standout mode.
19335 Use extra bright or bold mode.
19337 @item bold-standout
19338 Use extra bright or bold and standout mode.
19343 @chapter Using @value{GDBN} under @sc{gnu} Emacs
19346 @cindex @sc{gnu} Emacs
19347 A special interface allows you to use @sc{gnu} Emacs to view (and
19348 edit) the source files for the program you are debugging with
19351 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
19352 executable file you want to debug as an argument. This command starts
19353 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
19354 created Emacs buffer.
19355 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
19357 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
19362 All ``terminal'' input and output goes through an Emacs buffer, called
19365 This applies both to @value{GDBN} commands and their output, and to the input
19366 and output done by the program you are debugging.
19368 This is useful because it means that you can copy the text of previous
19369 commands and input them again; you can even use parts of the output
19372 All the facilities of Emacs' Shell mode are available for interacting
19373 with your program. In particular, you can send signals the usual
19374 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
19378 @value{GDBN} displays source code through Emacs.
19380 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
19381 source file for that frame and puts an arrow (@samp{=>}) at the
19382 left margin of the current line. Emacs uses a separate buffer for
19383 source display, and splits the screen to show both your @value{GDBN} session
19386 Explicit @value{GDBN} @code{list} or search commands still produce output as
19387 usual, but you probably have no reason to use them from Emacs.
19390 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
19391 a graphical mode, enabled by default, which provides further buffers
19392 that can control the execution and describe the state of your program.
19393 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
19395 If you specify an absolute file name when prompted for the @kbd{M-x
19396 gdb} argument, then Emacs sets your current working directory to where
19397 your program resides. If you only specify the file name, then Emacs
19398 sets your current working directory to to the directory associated
19399 with the previous buffer. In this case, @value{GDBN} may find your
19400 program by searching your environment's @code{PATH} variable, but on
19401 some operating systems it might not find the source. So, although the
19402 @value{GDBN} input and output session proceeds normally, the auxiliary
19403 buffer does not display the current source and line of execution.
19405 The initial working directory of @value{GDBN} is printed on the top
19406 line of the GUD buffer and this serves as a default for the commands
19407 that specify files for @value{GDBN} to operate on. @xref{Files,
19408 ,Commands to Specify Files}.
19410 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
19411 need to call @value{GDBN} by a different name (for example, if you
19412 keep several configurations around, with different names) you can
19413 customize the Emacs variable @code{gud-gdb-command-name} to run the
19416 In the GUD buffer, you can use these special Emacs commands in
19417 addition to the standard Shell mode commands:
19421 Describe the features of Emacs' GUD Mode.
19424 Execute to another source line, like the @value{GDBN} @code{step} command; also
19425 update the display window to show the current file and location.
19428 Execute to next source line in this function, skipping all function
19429 calls, like the @value{GDBN} @code{next} command. Then update the display window
19430 to show the current file and location.
19433 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
19434 display window accordingly.
19437 Execute until exit from the selected stack frame, like the @value{GDBN}
19438 @code{finish} command.
19441 Continue execution of your program, like the @value{GDBN} @code{continue}
19445 Go up the number of frames indicated by the numeric argument
19446 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
19447 like the @value{GDBN} @code{up} command.
19450 Go down the number of frames indicated by the numeric argument, like the
19451 @value{GDBN} @code{down} command.
19454 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
19455 tells @value{GDBN} to set a breakpoint on the source line point is on.
19457 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
19458 separate frame which shows a backtrace when the GUD buffer is current.
19459 Move point to any frame in the stack and type @key{RET} to make it
19460 become the current frame and display the associated source in the
19461 source buffer. Alternatively, click @kbd{Mouse-2} to make the
19462 selected frame become the current one. In graphical mode, the
19463 speedbar displays watch expressions.
19465 If you accidentally delete the source-display buffer, an easy way to get
19466 it back is to type the command @code{f} in the @value{GDBN} buffer, to
19467 request a frame display; when you run under Emacs, this recreates
19468 the source buffer if necessary to show you the context of the current
19471 The source files displayed in Emacs are in ordinary Emacs buffers
19472 which are visiting the source files in the usual way. You can edit
19473 the files with these buffers if you wish; but keep in mind that @value{GDBN}
19474 communicates with Emacs in terms of line numbers. If you add or
19475 delete lines from the text, the line numbers that @value{GDBN} knows cease
19476 to correspond properly with the code.
19478 A more detailed description of Emacs' interaction with @value{GDBN} is
19479 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
19482 @c The following dropped because Epoch is nonstandard. Reactivate
19483 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
19485 @kindex Emacs Epoch environment
19489 Version 18 of @sc{gnu} Emacs has a built-in window system
19490 called the @code{epoch}
19491 environment. Users of this environment can use a new command,
19492 @code{inspect} which performs identically to @code{print} except that
19493 each value is printed in its own window.
19498 @chapter The @sc{gdb/mi} Interface
19500 @unnumberedsec Function and Purpose
19502 @cindex @sc{gdb/mi}, its purpose
19503 @sc{gdb/mi} is a line based machine oriented text interface to
19504 @value{GDBN} and is activated by specifying using the
19505 @option{--interpreter} command line option (@pxref{Mode Options}). It
19506 is specifically intended to support the development of systems which
19507 use the debugger as just one small component of a larger system.
19509 This chapter is a specification of the @sc{gdb/mi} interface. It is written
19510 in the form of a reference manual.
19512 Note that @sc{gdb/mi} is still under construction, so some of the
19513 features described below are incomplete and subject to change
19514 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
19516 @unnumberedsec Notation and Terminology
19518 @cindex notational conventions, for @sc{gdb/mi}
19519 This chapter uses the following notation:
19523 @code{|} separates two alternatives.
19526 @code{[ @var{something} ]} indicates that @var{something} is optional:
19527 it may or may not be given.
19530 @code{( @var{group} )*} means that @var{group} inside the parentheses
19531 may repeat zero or more times.
19534 @code{( @var{group} )+} means that @var{group} inside the parentheses
19535 may repeat one or more times.
19538 @code{"@var{string}"} means a literal @var{string}.
19542 @heading Dependencies
19546 * GDB/MI General Design::
19547 * GDB/MI Command Syntax::
19548 * GDB/MI Compatibility with CLI::
19549 * GDB/MI Development and Front Ends::
19550 * GDB/MI Output Records::
19551 * GDB/MI Simple Examples::
19552 * GDB/MI Command Description Format::
19553 * GDB/MI Breakpoint Commands::
19554 * GDB/MI Program Context::
19555 * GDB/MI Thread Commands::
19556 * GDB/MI Program Execution::
19557 * GDB/MI Stack Manipulation::
19558 * GDB/MI Variable Objects::
19559 * GDB/MI Data Manipulation::
19560 * GDB/MI Tracepoint Commands::
19561 * GDB/MI Symbol Query::
19562 * GDB/MI File Commands::
19564 * GDB/MI Kod Commands::
19565 * GDB/MI Memory Overlay Commands::
19566 * GDB/MI Signal Handling Commands::
19568 * GDB/MI Target Manipulation::
19569 * GDB/MI File Transfer Commands::
19570 * GDB/MI Miscellaneous Commands::
19573 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19574 @node GDB/MI General Design
19575 @section @sc{gdb/mi} General Design
19576 @cindex GDB/MI General Design
19578 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
19579 parts---commands sent to @value{GDBN}, responses to those commands
19580 and notifications. Each command results in exactly one response,
19581 indicating either successful completion of the command, or an error.
19582 For the commands that do not resume the target, the response contains the
19583 requested information. For the commands that resume the target, the
19584 response only indicates whether the target was successfully resumed.
19585 Notifications is the mechanism for reporting changes in the state of the
19586 target, or in @value{GDBN} state, that cannot conveniently be associated with
19587 a command and reported as part of that command response.
19589 The important examples of notifications are:
19593 Exec notifications. These are used to report changes in
19594 target state---when a target is resumed, or stopped. It would not
19595 be feasible to include this information in response of resuming
19596 commands, because one resume commands can result in multiple events in
19597 different threads. Also, quite some time may pass before any event
19598 happens in the target, while a frontend needs to know whether the resuming
19599 command itself was successfully executed.
19602 Console output, and status notifications. Console output
19603 notifications are used to report output of CLI commands, as well as
19604 diagnostics for other commands. Status notifications are used to
19605 report the progress of a long-running operation. Naturally, including
19606 this information in command response would mean no output is produced
19607 until the command is finished, which is undesirable.
19610 General notifications. Commands may have various side effects on
19611 the @value{GDBN} or target state beyond their official purpose. For example,
19612 a command may change the selected thread. Although such changes can
19613 be included in command response, using notification allows for more
19614 orthogonal frontend design.
19618 There's no guarantee that whenever an MI command reports an error,
19619 @value{GDBN} or the target are in any specific state, and especially,
19620 the state is not reverted to the state before the MI command was
19621 processed. Therefore, whenever an MI command results in an error,
19622 we recommend that the frontend refreshes all the information shown in
19623 the user interface.
19625 @subsection Context management
19627 In most cases when @value{GDBN} accesses the target, this access is
19628 done in context of a specific thread and frame (@pxref{Frames}).
19629 Often, even when accessing global data, the target requires that a thread
19630 be specified. The CLI interface maintains the selected thread and frame,
19631 and supplies them to target on each command. This is convenient,
19632 because a command line user would not want to specify that information
19633 explicitly on each command, and because user interacts with
19634 @value{GDBN} via a single terminal, so no confusion is possible as
19635 to what thread and frame are the current ones.
19637 In the case of MI, the concept of selected thread and frame is less
19638 useful. First, a frontend can easily remember this information
19639 itself. Second, a graphical frontend can have more than one window,
19640 each one used for debugging a different thread, and the frontend might
19641 want to access additional threads for internal purposes. This
19642 increases the risk that by relying on implicitly selected thread, the
19643 frontend may be operating on a wrong one. Therefore, each MI command
19644 should explicitly specify which thread and frame to operate on. To
19645 make it possible, each MI command accepts the @samp{--thread} and
19646 @samp{--frame} options, the value to each is @value{GDBN} identifier
19647 for thread and frame to operate on.
19649 Usually, each top-level window in a frontend allows the user to select
19650 a thread and a frame, and remembers the user selection for further
19651 operations. However, in some cases @value{GDBN} may suggest that the
19652 current thread be changed. For example, when stopping on a breakpoint
19653 it is reasonable to switch to the thread where breakpoint is hit. For
19654 another example, if the user issues the CLI @samp{thread} command via
19655 the frontend, it is desirable to change the frontend's selected thread to the
19656 one specified by user. @value{GDBN} communicates the suggestion to
19657 change current thread using the @samp{=thread-selected} notification.
19658 No such notification is available for the selected frame at the moment.
19660 Note that historically, MI shares the selected thread with CLI, so
19661 frontends used the @code{-thread-select} to execute commands in the
19662 right context. However, getting this to work right is cumbersome. The
19663 simplest way is for frontend to emit @code{-thread-select} command
19664 before every command. This doubles the number of commands that need
19665 to be sent. The alternative approach is to suppress @code{-thread-select}
19666 if the selected thread in @value{GDBN} is supposed to be identical to the
19667 thread the frontend wants to operate on. However, getting this
19668 optimization right can be tricky. In particular, if the frontend
19669 sends several commands to @value{GDBN}, and one of the commands changes the
19670 selected thread, then the behaviour of subsequent commands will
19671 change. So, a frontend should either wait for response from such
19672 problematic commands, or explicitly add @code{-thread-select} for
19673 all subsequent commands. No frontend is known to do this exactly
19674 right, so it is suggested to just always pass the @samp{--thread} and
19675 @samp{--frame} options.
19677 @subsection Asynchronous command execution and non-stop mode
19679 On some targets, @value{GDBN} is capable of processing MI commands
19680 even while the target is running. This is called @dfn{asynchronous
19681 command execution} (@pxref{Background Execution}). The frontend may
19682 specify a preferrence for asynchronous execution using the
19683 @code{-gdb-set target-async 1} command, which should be emitted before
19684 either running the executable or attaching to the target. After the
19685 frontend has started the executable or attached to the target, it can
19686 find if asynchronous execution is enabled using the
19687 @code{-list-target-features} command.
19689 Even if @value{GDBN} can accept a command while target is running,
19690 many commands that access the target do not work when the target is
19691 running. Therefore, asynchronous command execution is most useful
19692 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
19693 it is possible to examine the state of one thread, while other threads
19696 When a given thread is running, MI commands that try to access the
19697 target in the context of that thread may not work, or may work only on
19698 some targets. In particular, commands that try to operate on thread's
19699 stack will not work, on any target. Commands that read memory, or
19700 modify breakpoints, may work or not work, depending on the target. Note
19701 that even commands that operate on global state, such as @code{print},
19702 @code{set}, and breakpoint commands, still access the target in the
19703 context of a specific thread, so frontend should try to find a
19704 stopped thread and perform the operation on that thread (using the
19705 @samp{--thread} option).
19707 Which commands will work in the context of a running thread is
19708 highly target dependent. However, the two commands
19709 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
19710 to find the state of a thread, will always work.
19712 @subsection Thread groups
19713 @value{GDBN} may be used to debug several processes at the same time.
19714 On some platfroms, @value{GDBN} may support debugging of several
19715 hardware systems, each one having several cores with several different
19716 processes running on each core. This section describes the MI
19717 mechanism to support such debugging scenarios.
19719 The key observation is that regardless of the structure of the
19720 target, MI can have a global list of threads, because most commands that
19721 accept the @samp{--thread} option do not need to know what process that
19722 thread belongs to. Therefore, it is not necessary to introduce
19723 neither additional @samp{--process} option, nor an notion of the
19724 current process in the MI interface. The only strictly new feature
19725 that is required is the ability to find how the threads are grouped
19728 To allow the user to discover such grouping, and to support arbitrary
19729 hierarchy of machines/cores/processes, MI introduces the concept of a
19730 @dfn{thread group}. Thread group is a collection of threads and other
19731 thread groups. A thread group always has a string identifier, a type,
19732 and may have additional attributes specific to the type. A new
19733 command, @code{-list-thread-groups}, returns the list of top-level
19734 thread groups, which correspond to processes that @value{GDBN} is
19735 debugging at the moment. By passing an identifier of a thread group
19736 to the @code{-list-thread-groups} command, it is possible to obtain
19737 the members of specific thread group.
19739 To allow the user to easily discover processes, and other objects, he
19740 wishes to debug, a concept of @dfn{available thread group} is
19741 introduced. Available thread group is an thread group that
19742 @value{GDBN} is not debugging, but that can be attached to, using the
19743 @code{-target-attach} command. The list of available top-level thread
19744 groups can be obtained using @samp{-list-thread-groups --available}.
19745 In general, the content of a thread group may be only retrieved only
19746 after attaching to that thread group.
19748 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19749 @node GDB/MI Command Syntax
19750 @section @sc{gdb/mi} Command Syntax
19753 * GDB/MI Input Syntax::
19754 * GDB/MI Output Syntax::
19757 @node GDB/MI Input Syntax
19758 @subsection @sc{gdb/mi} Input Syntax
19760 @cindex input syntax for @sc{gdb/mi}
19761 @cindex @sc{gdb/mi}, input syntax
19763 @item @var{command} @expansion{}
19764 @code{@var{cli-command} | @var{mi-command}}
19766 @item @var{cli-command} @expansion{}
19767 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
19768 @var{cli-command} is any existing @value{GDBN} CLI command.
19770 @item @var{mi-command} @expansion{}
19771 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
19772 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
19774 @item @var{token} @expansion{}
19775 "any sequence of digits"
19777 @item @var{option} @expansion{}
19778 @code{"-" @var{parameter} [ " " @var{parameter} ]}
19780 @item @var{parameter} @expansion{}
19781 @code{@var{non-blank-sequence} | @var{c-string}}
19783 @item @var{operation} @expansion{}
19784 @emph{any of the operations described in this chapter}
19786 @item @var{non-blank-sequence} @expansion{}
19787 @emph{anything, provided it doesn't contain special characters such as
19788 "-", @var{nl}, """ and of course " "}
19790 @item @var{c-string} @expansion{}
19791 @code{""" @var{seven-bit-iso-c-string-content} """}
19793 @item @var{nl} @expansion{}
19802 The CLI commands are still handled by the @sc{mi} interpreter; their
19803 output is described below.
19806 The @code{@var{token}}, when present, is passed back when the command
19810 Some @sc{mi} commands accept optional arguments as part of the parameter
19811 list. Each option is identified by a leading @samp{-} (dash) and may be
19812 followed by an optional argument parameter. Options occur first in the
19813 parameter list and can be delimited from normal parameters using
19814 @samp{--} (this is useful when some parameters begin with a dash).
19821 We want easy access to the existing CLI syntax (for debugging).
19824 We want it to be easy to spot a @sc{mi} operation.
19827 @node GDB/MI Output Syntax
19828 @subsection @sc{gdb/mi} Output Syntax
19830 @cindex output syntax of @sc{gdb/mi}
19831 @cindex @sc{gdb/mi}, output syntax
19832 The output from @sc{gdb/mi} consists of zero or more out-of-band records
19833 followed, optionally, by a single result record. This result record
19834 is for the most recent command. The sequence of output records is
19835 terminated by @samp{(gdb)}.
19837 If an input command was prefixed with a @code{@var{token}} then the
19838 corresponding output for that command will also be prefixed by that same
19842 @item @var{output} @expansion{}
19843 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
19845 @item @var{result-record} @expansion{}
19846 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
19848 @item @var{out-of-band-record} @expansion{}
19849 @code{@var{async-record} | @var{stream-record}}
19851 @item @var{async-record} @expansion{}
19852 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
19854 @item @var{exec-async-output} @expansion{}
19855 @code{[ @var{token} ] "*" @var{async-output}}
19857 @item @var{status-async-output} @expansion{}
19858 @code{[ @var{token} ] "+" @var{async-output}}
19860 @item @var{notify-async-output} @expansion{}
19861 @code{[ @var{token} ] "=" @var{async-output}}
19863 @item @var{async-output} @expansion{}
19864 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
19866 @item @var{result-class} @expansion{}
19867 @code{"done" | "running" | "connected" | "error" | "exit"}
19869 @item @var{async-class} @expansion{}
19870 @code{"stopped" | @var{others}} (where @var{others} will be added
19871 depending on the needs---this is still in development).
19873 @item @var{result} @expansion{}
19874 @code{ @var{variable} "=" @var{value}}
19876 @item @var{variable} @expansion{}
19877 @code{ @var{string} }
19879 @item @var{value} @expansion{}
19880 @code{ @var{const} | @var{tuple} | @var{list} }
19882 @item @var{const} @expansion{}
19883 @code{@var{c-string}}
19885 @item @var{tuple} @expansion{}
19886 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
19888 @item @var{list} @expansion{}
19889 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
19890 @var{result} ( "," @var{result} )* "]" }
19892 @item @var{stream-record} @expansion{}
19893 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
19895 @item @var{console-stream-output} @expansion{}
19896 @code{"~" @var{c-string}}
19898 @item @var{target-stream-output} @expansion{}
19899 @code{"@@" @var{c-string}}
19901 @item @var{log-stream-output} @expansion{}
19902 @code{"&" @var{c-string}}
19904 @item @var{nl} @expansion{}
19907 @item @var{token} @expansion{}
19908 @emph{any sequence of digits}.
19916 All output sequences end in a single line containing a period.
19919 The @code{@var{token}} is from the corresponding request. Note that
19920 for all async output, while the token is allowed by the grammar and
19921 may be output by future versions of @value{GDBN} for select async
19922 output messages, it is generally omitted. Frontends should treat
19923 all async output as reporting general changes in the state of the
19924 target and there should be no need to associate async output to any
19928 @cindex status output in @sc{gdb/mi}
19929 @var{status-async-output} contains on-going status information about the
19930 progress of a slow operation. It can be discarded. All status output is
19931 prefixed by @samp{+}.
19934 @cindex async output in @sc{gdb/mi}
19935 @var{exec-async-output} contains asynchronous state change on the target
19936 (stopped, started, disappeared). All async output is prefixed by
19940 @cindex notify output in @sc{gdb/mi}
19941 @var{notify-async-output} contains supplementary information that the
19942 client should handle (e.g., a new breakpoint information). All notify
19943 output is prefixed by @samp{=}.
19946 @cindex console output in @sc{gdb/mi}
19947 @var{console-stream-output} is output that should be displayed as is in the
19948 console. It is the textual response to a CLI command. All the console
19949 output is prefixed by @samp{~}.
19952 @cindex target output in @sc{gdb/mi}
19953 @var{target-stream-output} is the output produced by the target program.
19954 All the target output is prefixed by @samp{@@}.
19957 @cindex log output in @sc{gdb/mi}
19958 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
19959 instance messages that should be displayed as part of an error log. All
19960 the log output is prefixed by @samp{&}.
19963 @cindex list output in @sc{gdb/mi}
19964 New @sc{gdb/mi} commands should only output @var{lists} containing
19970 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
19971 details about the various output records.
19973 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19974 @node GDB/MI Compatibility with CLI
19975 @section @sc{gdb/mi} Compatibility with CLI
19977 @cindex compatibility, @sc{gdb/mi} and CLI
19978 @cindex @sc{gdb/mi}, compatibility with CLI
19980 For the developers convenience CLI commands can be entered directly,
19981 but there may be some unexpected behaviour. For example, commands
19982 that query the user will behave as if the user replied yes, breakpoint
19983 command lists are not executed and some CLI commands, such as
19984 @code{if}, @code{when} and @code{define}, prompt for further input with
19985 @samp{>}, which is not valid MI output.
19987 This feature may be removed at some stage in the future and it is
19988 recommended that front ends use the @code{-interpreter-exec} command
19989 (@pxref{-interpreter-exec}).
19991 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19992 @node GDB/MI Development and Front Ends
19993 @section @sc{gdb/mi} Development and Front Ends
19994 @cindex @sc{gdb/mi} development
19996 The application which takes the MI output and presents the state of the
19997 program being debugged to the user is called a @dfn{front end}.
19999 Although @sc{gdb/mi} is still incomplete, it is currently being used
20000 by a variety of front ends to @value{GDBN}. This makes it difficult
20001 to introduce new functionality without breaking existing usage. This
20002 section tries to minimize the problems by describing how the protocol
20005 Some changes in MI need not break a carefully designed front end, and
20006 for these the MI version will remain unchanged. The following is a
20007 list of changes that may occur within one level, so front ends should
20008 parse MI output in a way that can handle them:
20012 New MI commands may be added.
20015 New fields may be added to the output of any MI command.
20018 The range of values for fields with specified values, e.g.,
20019 @code{in_scope} (@pxref{-var-update}) may be extended.
20021 @c The format of field's content e.g type prefix, may change so parse it
20022 @c at your own risk. Yes, in general?
20024 @c The order of fields may change? Shouldn't really matter but it might
20025 @c resolve inconsistencies.
20028 If the changes are likely to break front ends, the MI version level
20029 will be increased by one. This will allow the front end to parse the
20030 output according to the MI version. Apart from mi0, new versions of
20031 @value{GDBN} will not support old versions of MI and it will be the
20032 responsibility of the front end to work with the new one.
20034 @c Starting with mi3, add a new command -mi-version that prints the MI
20037 The best way to avoid unexpected changes in MI that might break your front
20038 end is to make your project known to @value{GDBN} developers and
20039 follow development on @email{gdb@@sourceware.org} and
20040 @email{gdb-patches@@sourceware.org}.
20041 @cindex mailing lists
20043 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20044 @node GDB/MI Output Records
20045 @section @sc{gdb/mi} Output Records
20048 * GDB/MI Result Records::
20049 * GDB/MI Stream Records::
20050 * GDB/MI Async Records::
20051 * GDB/MI Frame Information::
20054 @node GDB/MI Result Records
20055 @subsection @sc{gdb/mi} Result Records
20057 @cindex result records in @sc{gdb/mi}
20058 @cindex @sc{gdb/mi}, result records
20059 In addition to a number of out-of-band notifications, the response to a
20060 @sc{gdb/mi} command includes one of the following result indications:
20064 @item "^done" [ "," @var{results} ]
20065 The synchronous operation was successful, @code{@var{results}} are the return
20070 @c Is this one correct? Should it be an out-of-band notification?
20071 The asynchronous operation was successfully started. The target is
20076 @value{GDBN} has connected to a remote target.
20078 @item "^error" "," @var{c-string}
20080 The operation failed. The @code{@var{c-string}} contains the corresponding
20085 @value{GDBN} has terminated.
20089 @node GDB/MI Stream Records
20090 @subsection @sc{gdb/mi} Stream Records
20092 @cindex @sc{gdb/mi}, stream records
20093 @cindex stream records in @sc{gdb/mi}
20094 @value{GDBN} internally maintains a number of output streams: the console, the
20095 target, and the log. The output intended for each of these streams is
20096 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
20098 Each stream record begins with a unique @dfn{prefix character} which
20099 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
20100 Syntax}). In addition to the prefix, each stream record contains a
20101 @code{@var{string-output}}. This is either raw text (with an implicit new
20102 line) or a quoted C string (which does not contain an implicit newline).
20105 @item "~" @var{string-output}
20106 The console output stream contains text that should be displayed in the
20107 CLI console window. It contains the textual responses to CLI commands.
20109 @item "@@" @var{string-output}
20110 The target output stream contains any textual output from the running
20111 target. This is only present when GDB's event loop is truly
20112 asynchronous, which is currently only the case for remote targets.
20114 @item "&" @var{string-output}
20115 The log stream contains debugging messages being produced by @value{GDBN}'s
20119 @node GDB/MI Async Records
20120 @subsection @sc{gdb/mi} Async Records
20122 @cindex async records in @sc{gdb/mi}
20123 @cindex @sc{gdb/mi}, async records
20124 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
20125 additional changes that have occurred. Those changes can either be a
20126 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
20127 target activity (e.g., target stopped).
20129 The following is the list of possible async records:
20133 @item *running,thread-id="@var{thread}"
20134 The target is now running. The @var{thread} field tells which
20135 specific thread is now running, and can be @samp{all} if all threads
20136 are running. The frontend should assume that no interaction with a
20137 running thread is possible after this notification is produced.
20138 The frontend should not assume that this notification is output
20139 only once for any command. @value{GDBN} may emit this notification
20140 several times, either for different threads, because it cannot resume
20141 all threads together, or even for a single thread, if the thread must
20142 be stepped though some code before letting it run freely.
20144 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}"
20145 The target has stopped. The @var{reason} field can have one of the
20149 @item breakpoint-hit
20150 A breakpoint was reached.
20151 @item watchpoint-trigger
20152 A watchpoint was triggered.
20153 @item read-watchpoint-trigger
20154 A read watchpoint was triggered.
20155 @item access-watchpoint-trigger
20156 An access watchpoint was triggered.
20157 @item function-finished
20158 An -exec-finish or similar CLI command was accomplished.
20159 @item location-reached
20160 An -exec-until or similar CLI command was accomplished.
20161 @item watchpoint-scope
20162 A watchpoint has gone out of scope.
20163 @item end-stepping-range
20164 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
20165 similar CLI command was accomplished.
20166 @item exited-signalled
20167 The inferior exited because of a signal.
20169 The inferior exited.
20170 @item exited-normally
20171 The inferior exited normally.
20172 @item signal-received
20173 A signal was received by the inferior.
20176 The @var{id} field identifies the thread that directly caused the stop
20177 -- for example by hitting a breakpoint. Depending on whether all-stop
20178 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
20179 stop all threads, or only the thread that directly triggered the stop.
20180 If all threads are stopped, the @var{stopped} field will have the
20181 value of @code{"all"}. Otherwise, the value of the @var{stopped}
20182 field will be a list of thread identifiers. Presently, this list will
20183 always include a single thread, but frontend should be prepared to see
20184 several threads in the list.
20186 @item =thread-group-created,id="@var{id}"
20187 @itemx =thread-group-exited,id="@var{id}"
20188 A thread thread group either was attached to, or has exited/detached
20189 from. The @var{id} field contains the @value{GDBN} identifier of the
20192 @item =thread-created,id="@var{id}",group-id="@var{gid}"
20193 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
20194 A thread either was created, or has exited. The @var{id} field
20195 contains the @value{GDBN} identifier of the thread. The @var{gid}
20196 field identifies the thread group this thread belongs to.
20198 @item =thread-selected,id="@var{id}"
20199 Informs that the selected thread was changed as result of the last
20200 command. This notification is not emitted as result of @code{-thread-select}
20201 command but is emitted whenever an MI command that is not documented
20202 to change the selected thread actually changes it. In particular,
20203 invoking, directly or indirectly (via user-defined command), the CLI
20204 @code{thread} command, will generate this notification.
20206 We suggest that in response to this notification, front ends
20207 highlight the selected thread and cause subsequent commands to apply to
20210 @item =library-loaded,...
20211 Reports that a new library file was loaded by the program. This
20212 notification has 4 fields---@var{id}, @var{target-name},
20213 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
20214 opaque identifier of the library. For remote debugging case,
20215 @var{target-name} and @var{host-name} fields give the name of the
20216 library file on the target, and on the host respectively. For native
20217 debugging, both those fields have the same value. The
20218 @var{symbols-loaded} field reports if the debug symbols for this
20219 library are loaded.
20221 @item =library-unloaded,...
20222 Reports that a library was unloaded by the program. This notification
20223 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
20224 the same meaning as for the @code{=library-loaded} notification
20228 @node GDB/MI Frame Information
20229 @subsection @sc{gdb/mi} Frame Information
20231 Response from many MI commands includes an information about stack
20232 frame. This information is a tuple that may have the following
20237 The level of the stack frame. The innermost frame has the level of
20238 zero. This field is always present.
20241 The name of the function corresponding to the frame. This field may
20242 be absent if @value{GDBN} is unable to determine the function name.
20245 The code address for the frame. This field is always present.
20248 The name of the source files that correspond to the frame's code
20249 address. This field may be absent.
20252 The source line corresponding to the frames' code address. This field
20256 The name of the binary file (either executable or shared library) the
20257 corresponds to the frame's code address. This field may be absent.
20262 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20263 @node GDB/MI Simple Examples
20264 @section Simple Examples of @sc{gdb/mi} Interaction
20265 @cindex @sc{gdb/mi}, simple examples
20267 This subsection presents several simple examples of interaction using
20268 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
20269 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
20270 the output received from @sc{gdb/mi}.
20272 Note the line breaks shown in the examples are here only for
20273 readability, they don't appear in the real output.
20275 @subheading Setting a Breakpoint
20277 Setting a breakpoint generates synchronous output which contains detailed
20278 information of the breakpoint.
20281 -> -break-insert main
20282 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20283 enabled="y",addr="0x08048564",func="main",file="myprog.c",
20284 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
20288 @subheading Program Execution
20290 Program execution generates asynchronous records and MI gives the
20291 reason that execution stopped.
20297 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
20298 frame=@{addr="0x08048564",func="main",
20299 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
20300 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
20305 <- *stopped,reason="exited-normally"
20309 @subheading Quitting @value{GDBN}
20311 Quitting @value{GDBN} just prints the result class @samp{^exit}.
20319 @subheading A Bad Command
20321 Here's what happens if you pass a non-existent command:
20325 <- ^error,msg="Undefined MI command: rubbish"
20330 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20331 @node GDB/MI Command Description Format
20332 @section @sc{gdb/mi} Command Description Format
20334 The remaining sections describe blocks of commands. Each block of
20335 commands is laid out in a fashion similar to this section.
20337 @subheading Motivation
20339 The motivation for this collection of commands.
20341 @subheading Introduction
20343 A brief introduction to this collection of commands as a whole.
20345 @subheading Commands
20347 For each command in the block, the following is described:
20349 @subsubheading Synopsis
20352 -command @var{args}@dots{}
20355 @subsubheading Result
20357 @subsubheading @value{GDBN} Command
20359 The corresponding @value{GDBN} CLI command(s), if any.
20361 @subsubheading Example
20363 Example(s) formatted for readability. Some of the described commands have
20364 not been implemented yet and these are labeled N.A.@: (not available).
20367 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20368 @node GDB/MI Breakpoint Commands
20369 @section @sc{gdb/mi} Breakpoint Commands
20371 @cindex breakpoint commands for @sc{gdb/mi}
20372 @cindex @sc{gdb/mi}, breakpoint commands
20373 This section documents @sc{gdb/mi} commands for manipulating
20376 @subheading The @code{-break-after} Command
20377 @findex -break-after
20379 @subsubheading Synopsis
20382 -break-after @var{number} @var{count}
20385 The breakpoint number @var{number} is not in effect until it has been
20386 hit @var{count} times. To see how this is reflected in the output of
20387 the @samp{-break-list} command, see the description of the
20388 @samp{-break-list} command below.
20390 @subsubheading @value{GDBN} Command
20392 The corresponding @value{GDBN} command is @samp{ignore}.
20394 @subsubheading Example
20399 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20400 enabled="y",addr="0x000100d0",func="main",file="hello.c",
20401 fullname="/home/foo/hello.c",line="5",times="0"@}
20408 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20409 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20410 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20411 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20412 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20413 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20414 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20415 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20416 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20417 line="5",times="0",ignore="3"@}]@}
20422 @subheading The @code{-break-catch} Command
20423 @findex -break-catch
20425 @subheading The @code{-break-commands} Command
20426 @findex -break-commands
20430 @subheading The @code{-break-condition} Command
20431 @findex -break-condition
20433 @subsubheading Synopsis
20436 -break-condition @var{number} @var{expr}
20439 Breakpoint @var{number} will stop the program only if the condition in
20440 @var{expr} is true. The condition becomes part of the
20441 @samp{-break-list} output (see the description of the @samp{-break-list}
20444 @subsubheading @value{GDBN} Command
20446 The corresponding @value{GDBN} command is @samp{condition}.
20448 @subsubheading Example
20452 -break-condition 1 1
20456 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20457 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20458 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20459 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20460 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20461 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20462 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20463 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20464 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20465 line="5",cond="1",times="0",ignore="3"@}]@}
20469 @subheading The @code{-break-delete} Command
20470 @findex -break-delete
20472 @subsubheading Synopsis
20475 -break-delete ( @var{breakpoint} )+
20478 Delete the breakpoint(s) whose number(s) are specified in the argument
20479 list. This is obviously reflected in the breakpoint list.
20481 @subsubheading @value{GDBN} Command
20483 The corresponding @value{GDBN} command is @samp{delete}.
20485 @subsubheading Example
20493 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20494 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20495 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20496 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20497 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20498 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20499 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20504 @subheading The @code{-break-disable} Command
20505 @findex -break-disable
20507 @subsubheading Synopsis
20510 -break-disable ( @var{breakpoint} )+
20513 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
20514 break list is now set to @samp{n} for the named @var{breakpoint}(s).
20516 @subsubheading @value{GDBN} Command
20518 The corresponding @value{GDBN} command is @samp{disable}.
20520 @subsubheading Example
20528 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20529 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20530 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20531 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20532 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20533 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20534 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20535 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
20536 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20537 line="5",times="0"@}]@}
20541 @subheading The @code{-break-enable} Command
20542 @findex -break-enable
20544 @subsubheading Synopsis
20547 -break-enable ( @var{breakpoint} )+
20550 Enable (previously disabled) @var{breakpoint}(s).
20552 @subsubheading @value{GDBN} Command
20554 The corresponding @value{GDBN} command is @samp{enable}.
20556 @subsubheading Example
20564 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20565 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20566 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20567 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20568 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20569 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20570 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20571 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20572 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20573 line="5",times="0"@}]@}
20577 @subheading The @code{-break-info} Command
20578 @findex -break-info
20580 @subsubheading Synopsis
20583 -break-info @var{breakpoint}
20587 Get information about a single breakpoint.
20589 @subsubheading @value{GDBN} Command
20591 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
20593 @subsubheading Example
20596 @subheading The @code{-break-insert} Command
20597 @findex -break-insert
20599 @subsubheading Synopsis
20602 -break-insert [ -t ] [ -h ] [ -f ] [ -d ]
20603 [ -c @var{condition} ] [ -i @var{ignore-count} ]
20604 [ -p @var{thread} ] [ @var{location} ]
20608 If specified, @var{location}, can be one of:
20615 @item filename:linenum
20616 @item filename:function
20620 The possible optional parameters of this command are:
20624 Insert a temporary breakpoint.
20626 Insert a hardware breakpoint.
20627 @item -c @var{condition}
20628 Make the breakpoint conditional on @var{condition}.
20629 @item -i @var{ignore-count}
20630 Initialize the @var{ignore-count}.
20632 If @var{location} cannot be parsed (for example if it
20633 refers to unknown files or functions), create a pending
20634 breakpoint. Without this flag, @value{GDBN} will report
20635 an error, and won't create a breakpoint, if @var{location}
20638 Create a disabled breakpoint.
20641 @subsubheading Result
20643 The result is in the form:
20646 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
20647 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
20648 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
20649 times="@var{times}"@}
20653 where @var{number} is the @value{GDBN} number for this breakpoint,
20654 @var{funcname} is the name of the function where the breakpoint was
20655 inserted, @var{filename} is the name of the source file which contains
20656 this function, @var{lineno} is the source line number within that file
20657 and @var{times} the number of times that the breakpoint has been hit
20658 (always 0 for -break-insert but may be greater for -break-info or -break-list
20659 which use the same output).
20661 Note: this format is open to change.
20662 @c An out-of-band breakpoint instead of part of the result?
20664 @subsubheading @value{GDBN} Command
20666 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
20667 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
20669 @subsubheading Example
20674 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
20675 fullname="/home/foo/recursive2.c,line="4",times="0"@}
20677 -break-insert -t foo
20678 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
20679 fullname="/home/foo/recursive2.c,line="11",times="0"@}
20682 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20683 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20684 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20685 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20686 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20687 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20688 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20689 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20690 addr="0x0001072c", func="main",file="recursive2.c",
20691 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
20692 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
20693 addr="0x00010774",func="foo",file="recursive2.c",
20694 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
20696 -break-insert -r foo.*
20697 ~int foo(int, int);
20698 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
20699 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
20703 @subheading The @code{-break-list} Command
20704 @findex -break-list
20706 @subsubheading Synopsis
20712 Displays the list of inserted breakpoints, showing the following fields:
20716 number of the breakpoint
20718 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
20720 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
20723 is the breakpoint enabled or no: @samp{y} or @samp{n}
20725 memory location at which the breakpoint is set
20727 logical location of the breakpoint, expressed by function name, file
20730 number of times the breakpoint has been hit
20733 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
20734 @code{body} field is an empty list.
20736 @subsubheading @value{GDBN} Command
20738 The corresponding @value{GDBN} command is @samp{info break}.
20740 @subsubheading Example
20745 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20746 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20747 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20748 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20749 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20750 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20751 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20752 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20753 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
20754 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20755 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
20756 line="13",times="0"@}]@}
20760 Here's an example of the result when there are no breakpoints:
20765 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20766 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20767 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20768 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20769 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20770 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20771 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20776 @subheading The @code{-break-watch} Command
20777 @findex -break-watch
20779 @subsubheading Synopsis
20782 -break-watch [ -a | -r ]
20785 Create a watchpoint. With the @samp{-a} option it will create an
20786 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
20787 read from or on a write to the memory location. With the @samp{-r}
20788 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
20789 trigger only when the memory location is accessed for reading. Without
20790 either of the options, the watchpoint created is a regular watchpoint,
20791 i.e., it will trigger when the memory location is accessed for writing.
20792 @xref{Set Watchpoints, , Setting Watchpoints}.
20794 Note that @samp{-break-list} will report a single list of watchpoints and
20795 breakpoints inserted.
20797 @subsubheading @value{GDBN} Command
20799 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
20802 @subsubheading Example
20804 Setting a watchpoint on a variable in the @code{main} function:
20809 ^done,wpt=@{number="2",exp="x"@}
20814 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
20815 value=@{old="-268439212",new="55"@},
20816 frame=@{func="main",args=[],file="recursive2.c",
20817 fullname="/home/foo/bar/recursive2.c",line="5"@}
20821 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
20822 the program execution twice: first for the variable changing value, then
20823 for the watchpoint going out of scope.
20828 ^done,wpt=@{number="5",exp="C"@}
20833 *stopped,reason="watchpoint-trigger",
20834 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
20835 frame=@{func="callee4",args=[],
20836 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20837 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20842 *stopped,reason="watchpoint-scope",wpnum="5",
20843 frame=@{func="callee3",args=[@{name="strarg",
20844 value="0x11940 \"A string argument.\""@}],
20845 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20846 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20850 Listing breakpoints and watchpoints, at different points in the program
20851 execution. Note that once the watchpoint goes out of scope, it is
20857 ^done,wpt=@{number="2",exp="C"@}
20860 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20861 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20862 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20863 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20864 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20865 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20866 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20867 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20868 addr="0x00010734",func="callee4",
20869 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20870 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
20871 bkpt=@{number="2",type="watchpoint",disp="keep",
20872 enabled="y",addr="",what="C",times="0"@}]@}
20877 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
20878 value=@{old="-276895068",new="3"@},
20879 frame=@{func="callee4",args=[],
20880 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20881 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20884 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20885 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20886 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20887 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20888 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20889 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20890 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20891 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20892 addr="0x00010734",func="callee4",
20893 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20894 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
20895 bkpt=@{number="2",type="watchpoint",disp="keep",
20896 enabled="y",addr="",what="C",times="-5"@}]@}
20900 ^done,reason="watchpoint-scope",wpnum="2",
20901 frame=@{func="callee3",args=[@{name="strarg",
20902 value="0x11940 \"A string argument.\""@}],
20903 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20904 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20907 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20908 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20909 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20910 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20911 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20912 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20913 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20914 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20915 addr="0x00010734",func="callee4",
20916 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20917 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
20922 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20923 @node GDB/MI Program Context
20924 @section @sc{gdb/mi} Program Context
20926 @subheading The @code{-exec-arguments} Command
20927 @findex -exec-arguments
20930 @subsubheading Synopsis
20933 -exec-arguments @var{args}
20936 Set the inferior program arguments, to be used in the next
20939 @subsubheading @value{GDBN} Command
20941 The corresponding @value{GDBN} command is @samp{set args}.
20943 @subsubheading Example
20947 -exec-arguments -v word
20953 @subheading The @code{-exec-show-arguments} Command
20954 @findex -exec-show-arguments
20956 @subsubheading Synopsis
20959 -exec-show-arguments
20962 Print the arguments of the program.
20964 @subsubheading @value{GDBN} Command
20966 The corresponding @value{GDBN} command is @samp{show args}.
20968 @subsubheading Example
20972 @subheading The @code{-environment-cd} Command
20973 @findex -environment-cd
20975 @subsubheading Synopsis
20978 -environment-cd @var{pathdir}
20981 Set @value{GDBN}'s working directory.
20983 @subsubheading @value{GDBN} Command
20985 The corresponding @value{GDBN} command is @samp{cd}.
20987 @subsubheading Example
20991 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20997 @subheading The @code{-environment-directory} Command
20998 @findex -environment-directory
21000 @subsubheading Synopsis
21003 -environment-directory [ -r ] [ @var{pathdir} ]+
21006 Add directories @var{pathdir} to beginning of search path for source files.
21007 If the @samp{-r} option is used, the search path is reset to the default
21008 search path. If directories @var{pathdir} are supplied in addition to the
21009 @samp{-r} option, the search path is first reset and then addition
21011 Multiple directories may be specified, separated by blanks. Specifying
21012 multiple directories in a single command
21013 results in the directories added to the beginning of the
21014 search path in the same order they were presented in the command.
21015 If blanks are needed as
21016 part of a directory name, double-quotes should be used around
21017 the name. In the command output, the path will show up separated
21018 by the system directory-separator character. The directory-separator
21019 character must not be used
21020 in any directory name.
21021 If no directories are specified, the current search path is displayed.
21023 @subsubheading @value{GDBN} Command
21025 The corresponding @value{GDBN} command is @samp{dir}.
21027 @subsubheading Example
21031 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
21032 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
21034 -environment-directory ""
21035 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
21037 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
21038 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
21040 -environment-directory -r
21041 ^done,source-path="$cdir:$cwd"
21046 @subheading The @code{-environment-path} Command
21047 @findex -environment-path
21049 @subsubheading Synopsis
21052 -environment-path [ -r ] [ @var{pathdir} ]+
21055 Add directories @var{pathdir} to beginning of search path for object files.
21056 If the @samp{-r} option is used, the search path is reset to the original
21057 search path that existed at gdb start-up. If directories @var{pathdir} are
21058 supplied in addition to the
21059 @samp{-r} option, the search path is first reset and then addition
21061 Multiple directories may be specified, separated by blanks. Specifying
21062 multiple directories in a single command
21063 results in the directories added to the beginning of the
21064 search path in the same order they were presented in the command.
21065 If blanks are needed as
21066 part of a directory name, double-quotes should be used around
21067 the name. In the command output, the path will show up separated
21068 by the system directory-separator character. The directory-separator
21069 character must not be used
21070 in any directory name.
21071 If no directories are specified, the current path is displayed.
21074 @subsubheading @value{GDBN} Command
21076 The corresponding @value{GDBN} command is @samp{path}.
21078 @subsubheading Example
21083 ^done,path="/usr/bin"
21085 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
21086 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
21088 -environment-path -r /usr/local/bin
21089 ^done,path="/usr/local/bin:/usr/bin"
21094 @subheading The @code{-environment-pwd} Command
21095 @findex -environment-pwd
21097 @subsubheading Synopsis
21103 Show the current working directory.
21105 @subsubheading @value{GDBN} Command
21107 The corresponding @value{GDBN} command is @samp{pwd}.
21109 @subsubheading Example
21114 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
21118 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21119 @node GDB/MI Thread Commands
21120 @section @sc{gdb/mi} Thread Commands
21123 @subheading The @code{-thread-info} Command
21124 @findex -thread-info
21126 @subsubheading Synopsis
21129 -thread-info [ @var{thread-id} ]
21132 Reports information about either a specific thread, if
21133 the @var{thread-id} parameter is present, or about all
21134 threads. When printing information about all threads,
21135 also reports the current thread.
21137 @subsubheading @value{GDBN} Command
21139 The @samp{info thread} command prints the same information
21142 @subsubheading Example
21147 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
21148 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
21149 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
21150 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
21151 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
21152 current-thread-id="1"
21156 The @samp{state} field may have the following values:
21160 The thread is stopped. Frame information is available for stopped
21164 The thread is running. There's no frame information for running
21169 @subheading The @code{-thread-list-ids} Command
21170 @findex -thread-list-ids
21172 @subsubheading Synopsis
21178 Produces a list of the currently known @value{GDBN} thread ids. At the
21179 end of the list it also prints the total number of such threads.
21181 This command is retained for historical reasons, the
21182 @code{-thread-info} command should be used instead.
21184 @subsubheading @value{GDBN} Command
21186 Part of @samp{info threads} supplies the same information.
21188 @subsubheading Example
21193 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
21194 current-thread-id="1",number-of-threads="3"
21199 @subheading The @code{-thread-select} Command
21200 @findex -thread-select
21202 @subsubheading Synopsis
21205 -thread-select @var{threadnum}
21208 Make @var{threadnum} the current thread. It prints the number of the new
21209 current thread, and the topmost frame for that thread.
21211 This command is deprecated in favor of explicitly using the
21212 @samp{--thread} option to each command.
21214 @subsubheading @value{GDBN} Command
21216 The corresponding @value{GDBN} command is @samp{thread}.
21218 @subsubheading Example
21225 *stopped,reason="end-stepping-range",thread-id="2",line="187",
21226 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
21230 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
21231 number-of-threads="3"
21234 ^done,new-thread-id="3",
21235 frame=@{level="0",func="vprintf",
21236 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
21237 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
21241 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21242 @node GDB/MI Program Execution
21243 @section @sc{gdb/mi} Program Execution
21245 These are the asynchronous commands which generate the out-of-band
21246 record @samp{*stopped}. Currently @value{GDBN} only really executes
21247 asynchronously with remote targets and this interaction is mimicked in
21250 @subheading The @code{-exec-continue} Command
21251 @findex -exec-continue
21253 @subsubheading Synopsis
21256 -exec-continue [--all|--thread-group N]
21259 Resumes the execution of the inferior program until a breakpoint is
21260 encountered, or until the inferior exits. In all-stop mode
21261 (@pxref{All-Stop Mode}), may resume only one thread, or all threads,
21262 depending on the value of the @samp{scheduler-locking} variable. In
21263 non-stop mode (@pxref{Non-Stop Mode}), if the @samp{--all} is not
21264 specified, only the thread specified with the @samp{--thread} option
21265 (or current thread, if no @samp{--thread} is provided) is resumed. If
21266 @samp{--all} is specified, all threads will be resumed. The
21267 @samp{--all} option is ignored in all-stop mode. If the
21268 @samp{--thread-group} options is specified, then all threads in that
21269 thread group are resumed.
21271 @subsubheading @value{GDBN} Command
21273 The corresponding @value{GDBN} corresponding is @samp{continue}.
21275 @subsubheading Example
21282 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
21283 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
21289 @subheading The @code{-exec-finish} Command
21290 @findex -exec-finish
21292 @subsubheading Synopsis
21298 Resumes the execution of the inferior program until the current
21299 function is exited. Displays the results returned by the function.
21301 @subsubheading @value{GDBN} Command
21303 The corresponding @value{GDBN} command is @samp{finish}.
21305 @subsubheading Example
21307 Function returning @code{void}.
21314 *stopped,reason="function-finished",frame=@{func="main",args=[],
21315 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
21319 Function returning other than @code{void}. The name of the internal
21320 @value{GDBN} variable storing the result is printed, together with the
21327 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
21328 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
21329 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21330 gdb-result-var="$1",return-value="0"
21335 @subheading The @code{-exec-interrupt} Command
21336 @findex -exec-interrupt
21338 @subsubheading Synopsis
21341 -exec-interrupt [--all|--thread-group N]
21344 Interrupts the background execution of the target. Note how the token
21345 associated with the stop message is the one for the execution command
21346 that has been interrupted. The token for the interrupt itself only
21347 appears in the @samp{^done} output. If the user is trying to
21348 interrupt a non-running program, an error message will be printed.
21350 Note that when asynchronous execution is enabled, this command is
21351 asynchronous just like other execution commands. That is, first the
21352 @samp{^done} response will be printed, and the target stop will be
21353 reported after that using the @samp{*stopped} notification.
21355 In non-stop mode, only the context thread is interrupted by default.
21356 All threads will be interrupted if the @samp{--all} option is
21357 specified. If the @samp{--thread-group} option is specified, all
21358 threads in that group will be interrupted.
21360 @subsubheading @value{GDBN} Command
21362 The corresponding @value{GDBN} command is @samp{interrupt}.
21364 @subsubheading Example
21375 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
21376 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
21377 fullname="/home/foo/bar/try.c",line="13"@}
21382 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
21387 @subheading The @code{-exec-next} Command
21390 @subsubheading Synopsis
21396 Resumes execution of the inferior program, stopping when the beginning
21397 of the next source line is reached.
21399 @subsubheading @value{GDBN} Command
21401 The corresponding @value{GDBN} command is @samp{next}.
21403 @subsubheading Example
21409 *stopped,reason="end-stepping-range",line="8",file="hello.c"
21414 @subheading The @code{-exec-next-instruction} Command
21415 @findex -exec-next-instruction
21417 @subsubheading Synopsis
21420 -exec-next-instruction
21423 Executes one machine instruction. If the instruction is a function
21424 call, continues until the function returns. If the program stops at an
21425 instruction in the middle of a source line, the address will be
21428 @subsubheading @value{GDBN} Command
21430 The corresponding @value{GDBN} command is @samp{nexti}.
21432 @subsubheading Example
21436 -exec-next-instruction
21440 *stopped,reason="end-stepping-range",
21441 addr="0x000100d4",line="5",file="hello.c"
21446 @subheading The @code{-exec-return} Command
21447 @findex -exec-return
21449 @subsubheading Synopsis
21455 Makes current function return immediately. Doesn't execute the inferior.
21456 Displays the new current frame.
21458 @subsubheading @value{GDBN} Command
21460 The corresponding @value{GDBN} command is @samp{return}.
21462 @subsubheading Example
21466 200-break-insert callee4
21467 200^done,bkpt=@{number="1",addr="0x00010734",
21468 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21473 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21474 frame=@{func="callee4",args=[],
21475 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21476 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21482 111^done,frame=@{level="0",func="callee3",
21483 args=[@{name="strarg",
21484 value="0x11940 \"A string argument.\""@}],
21485 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21486 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
21491 @subheading The @code{-exec-run} Command
21494 @subsubheading Synopsis
21500 Starts execution of the inferior from the beginning. The inferior
21501 executes until either a breakpoint is encountered or the program
21502 exits. In the latter case the output will include an exit code, if
21503 the program has exited exceptionally.
21505 @subsubheading @value{GDBN} Command
21507 The corresponding @value{GDBN} command is @samp{run}.
21509 @subsubheading Examples
21514 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
21519 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21520 frame=@{func="main",args=[],file="recursive2.c",
21521 fullname="/home/foo/bar/recursive2.c",line="4"@}
21526 Program exited normally:
21534 *stopped,reason="exited-normally"
21539 Program exited exceptionally:
21547 *stopped,reason="exited",exit-code="01"
21551 Another way the program can terminate is if it receives a signal such as
21552 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
21556 *stopped,reason="exited-signalled",signal-name="SIGINT",
21557 signal-meaning="Interrupt"
21561 @c @subheading -exec-signal
21564 @subheading The @code{-exec-step} Command
21567 @subsubheading Synopsis
21573 Resumes execution of the inferior program, stopping when the beginning
21574 of the next source line is reached, if the next source line is not a
21575 function call. If it is, stop at the first instruction of the called
21578 @subsubheading @value{GDBN} Command
21580 The corresponding @value{GDBN} command is @samp{step}.
21582 @subsubheading Example
21584 Stepping into a function:
21590 *stopped,reason="end-stepping-range",
21591 frame=@{func="foo",args=[@{name="a",value="10"@},
21592 @{name="b",value="0"@}],file="recursive2.c",
21593 fullname="/home/foo/bar/recursive2.c",line="11"@}
21603 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
21608 @subheading The @code{-exec-step-instruction} Command
21609 @findex -exec-step-instruction
21611 @subsubheading Synopsis
21614 -exec-step-instruction
21617 Resumes the inferior which executes one machine instruction. The
21618 output, once @value{GDBN} has stopped, will vary depending on whether
21619 we have stopped in the middle of a source line or not. In the former
21620 case, the address at which the program stopped will be printed as
21623 @subsubheading @value{GDBN} Command
21625 The corresponding @value{GDBN} command is @samp{stepi}.
21627 @subsubheading Example
21631 -exec-step-instruction
21635 *stopped,reason="end-stepping-range",
21636 frame=@{func="foo",args=[],file="try.c",
21637 fullname="/home/foo/bar/try.c",line="10"@}
21639 -exec-step-instruction
21643 *stopped,reason="end-stepping-range",
21644 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
21645 fullname="/home/foo/bar/try.c",line="10"@}
21650 @subheading The @code{-exec-until} Command
21651 @findex -exec-until
21653 @subsubheading Synopsis
21656 -exec-until [ @var{location} ]
21659 Executes the inferior until the @var{location} specified in the
21660 argument is reached. If there is no argument, the inferior executes
21661 until a source line greater than the current one is reached. The
21662 reason for stopping in this case will be @samp{location-reached}.
21664 @subsubheading @value{GDBN} Command
21666 The corresponding @value{GDBN} command is @samp{until}.
21668 @subsubheading Example
21672 -exec-until recursive2.c:6
21676 *stopped,reason="location-reached",frame=@{func="main",args=[],
21677 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
21682 @subheading -file-clear
21683 Is this going away????
21686 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21687 @node GDB/MI Stack Manipulation
21688 @section @sc{gdb/mi} Stack Manipulation Commands
21691 @subheading The @code{-stack-info-frame} Command
21692 @findex -stack-info-frame
21694 @subsubheading Synopsis
21700 Get info on the selected frame.
21702 @subsubheading @value{GDBN} Command
21704 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
21705 (without arguments).
21707 @subsubheading Example
21712 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
21713 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21714 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
21718 @subheading The @code{-stack-info-depth} Command
21719 @findex -stack-info-depth
21721 @subsubheading Synopsis
21724 -stack-info-depth [ @var{max-depth} ]
21727 Return the depth of the stack. If the integer argument @var{max-depth}
21728 is specified, do not count beyond @var{max-depth} frames.
21730 @subsubheading @value{GDBN} Command
21732 There's no equivalent @value{GDBN} command.
21734 @subsubheading Example
21736 For a stack with frame levels 0 through 11:
21743 -stack-info-depth 4
21746 -stack-info-depth 12
21749 -stack-info-depth 11
21752 -stack-info-depth 13
21757 @subheading The @code{-stack-list-arguments} Command
21758 @findex -stack-list-arguments
21760 @subsubheading Synopsis
21763 -stack-list-arguments @var{show-values}
21764 [ @var{low-frame} @var{high-frame} ]
21767 Display a list of the arguments for the frames between @var{low-frame}
21768 and @var{high-frame} (inclusive). If @var{low-frame} and
21769 @var{high-frame} are not provided, list the arguments for the whole
21770 call stack. If the two arguments are equal, show the single frame
21771 at the corresponding level. It is an error if @var{low-frame} is
21772 larger than the actual number of frames. On the other hand,
21773 @var{high-frame} may be larger than the actual number of frames, in
21774 which case only existing frames will be returned.
21776 The @var{show-values} argument must have a value of 0 or 1. A value of
21777 0 means that only the names of the arguments are listed, a value of 1
21778 means that both names and values of the arguments are printed.
21780 @subsubheading @value{GDBN} Command
21782 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
21783 @samp{gdb_get_args} command which partially overlaps with the
21784 functionality of @samp{-stack-list-arguments}.
21786 @subsubheading Example
21793 frame=@{level="0",addr="0x00010734",func="callee4",
21794 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21795 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
21796 frame=@{level="1",addr="0x0001076c",func="callee3",
21797 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21798 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
21799 frame=@{level="2",addr="0x0001078c",func="callee2",
21800 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21801 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
21802 frame=@{level="3",addr="0x000107b4",func="callee1",
21803 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21804 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
21805 frame=@{level="4",addr="0x000107e0",func="main",
21806 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21807 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
21809 -stack-list-arguments 0
21812 frame=@{level="0",args=[]@},
21813 frame=@{level="1",args=[name="strarg"]@},
21814 frame=@{level="2",args=[name="intarg",name="strarg"]@},
21815 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
21816 frame=@{level="4",args=[]@}]
21818 -stack-list-arguments 1
21821 frame=@{level="0",args=[]@},
21823 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21824 frame=@{level="2",args=[
21825 @{name="intarg",value="2"@},
21826 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21827 @{frame=@{level="3",args=[
21828 @{name="intarg",value="2"@},
21829 @{name="strarg",value="0x11940 \"A string argument.\""@},
21830 @{name="fltarg",value="3.5"@}]@},
21831 frame=@{level="4",args=[]@}]
21833 -stack-list-arguments 0 2 2
21834 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
21836 -stack-list-arguments 1 2 2
21837 ^done,stack-args=[frame=@{level="2",
21838 args=[@{name="intarg",value="2"@},
21839 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
21843 @c @subheading -stack-list-exception-handlers
21846 @subheading The @code{-stack-list-frames} Command
21847 @findex -stack-list-frames
21849 @subsubheading Synopsis
21852 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
21855 List the frames currently on the stack. For each frame it displays the
21860 The frame number, 0 being the topmost frame, i.e., the innermost function.
21862 The @code{$pc} value for that frame.
21866 File name of the source file where the function lives.
21868 Line number corresponding to the @code{$pc}.
21871 If invoked without arguments, this command prints a backtrace for the
21872 whole stack. If given two integer arguments, it shows the frames whose
21873 levels are between the two arguments (inclusive). If the two arguments
21874 are equal, it shows the single frame at the corresponding level. It is
21875 an error if @var{low-frame} is larger than the actual number of
21876 frames. On the other hand, @var{high-frame} may be larger than the
21877 actual number of frames, in which case only existing frames will be returned.
21879 @subsubheading @value{GDBN} Command
21881 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
21883 @subsubheading Example
21885 Full stack backtrace:
21891 [frame=@{level="0",addr="0x0001076c",func="foo",
21892 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
21893 frame=@{level="1",addr="0x000107a4",func="foo",
21894 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21895 frame=@{level="2",addr="0x000107a4",func="foo",
21896 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21897 frame=@{level="3",addr="0x000107a4",func="foo",
21898 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21899 frame=@{level="4",addr="0x000107a4",func="foo",
21900 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21901 frame=@{level="5",addr="0x000107a4",func="foo",
21902 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21903 frame=@{level="6",addr="0x000107a4",func="foo",
21904 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21905 frame=@{level="7",addr="0x000107a4",func="foo",
21906 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21907 frame=@{level="8",addr="0x000107a4",func="foo",
21908 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21909 frame=@{level="9",addr="0x000107a4",func="foo",
21910 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21911 frame=@{level="10",addr="0x000107a4",func="foo",
21912 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21913 frame=@{level="11",addr="0x00010738",func="main",
21914 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
21918 Show frames between @var{low_frame} and @var{high_frame}:
21922 -stack-list-frames 3 5
21924 [frame=@{level="3",addr="0x000107a4",func="foo",
21925 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21926 frame=@{level="4",addr="0x000107a4",func="foo",
21927 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21928 frame=@{level="5",addr="0x000107a4",func="foo",
21929 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21933 Show a single frame:
21937 -stack-list-frames 3 3
21939 [frame=@{level="3",addr="0x000107a4",func="foo",
21940 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21945 @subheading The @code{-stack-list-locals} Command
21946 @findex -stack-list-locals
21948 @subsubheading Synopsis
21951 -stack-list-locals @var{print-values}
21954 Display the local variable names for the selected frame. If
21955 @var{print-values} is 0 or @code{--no-values}, print only the names of
21956 the variables; if it is 1 or @code{--all-values}, print also their
21957 values; and if it is 2 or @code{--simple-values}, print the name,
21958 type and value for simple data types and the name and type for arrays,
21959 structures and unions. In this last case, a frontend can immediately
21960 display the value of simple data types and create variable objects for
21961 other data types when the user wishes to explore their values in
21964 @subsubheading @value{GDBN} Command
21966 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
21968 @subsubheading Example
21972 -stack-list-locals 0
21973 ^done,locals=[name="A",name="B",name="C"]
21975 -stack-list-locals --all-values
21976 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
21977 @{name="C",value="@{1, 2, 3@}"@}]
21978 -stack-list-locals --simple-values
21979 ^done,locals=[@{name="A",type="int",value="1"@},
21980 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
21985 @subheading The @code{-stack-select-frame} Command
21986 @findex -stack-select-frame
21988 @subsubheading Synopsis
21991 -stack-select-frame @var{framenum}
21994 Change the selected frame. Select a different frame @var{framenum} on
21997 This command in deprecated in favor of passing the @samp{--frame}
21998 option to every command.
22000 @subsubheading @value{GDBN} Command
22002 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
22003 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
22005 @subsubheading Example
22009 -stack-select-frame 2
22014 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22015 @node GDB/MI Variable Objects
22016 @section @sc{gdb/mi} Variable Objects
22020 @subheading Motivation for Variable Objects in @sc{gdb/mi}
22022 For the implementation of a variable debugger window (locals, watched
22023 expressions, etc.), we are proposing the adaptation of the existing code
22024 used by @code{Insight}.
22026 The two main reasons for that are:
22030 It has been proven in practice (it is already on its second generation).
22033 It will shorten development time (needless to say how important it is
22037 The original interface was designed to be used by Tcl code, so it was
22038 slightly changed so it could be used through @sc{gdb/mi}. This section
22039 describes the @sc{gdb/mi} operations that will be available and gives some
22040 hints about their use.
22042 @emph{Note}: In addition to the set of operations described here, we
22043 expect the @sc{gui} implementation of a variable window to require, at
22044 least, the following operations:
22047 @item @code{-gdb-show} @code{output-radix}
22048 @item @code{-stack-list-arguments}
22049 @item @code{-stack-list-locals}
22050 @item @code{-stack-select-frame}
22055 @subheading Introduction to Variable Objects
22057 @cindex variable objects in @sc{gdb/mi}
22059 Variable objects are "object-oriented" MI interface for examining and
22060 changing values of expressions. Unlike some other MI interfaces that
22061 work with expressions, variable objects are specifically designed for
22062 simple and efficient presentation in the frontend. A variable object
22063 is identified by string name. When a variable object is created, the
22064 frontend specifies the expression for that variable object. The
22065 expression can be a simple variable, or it can be an arbitrary complex
22066 expression, and can even involve CPU registers. After creating a
22067 variable object, the frontend can invoke other variable object
22068 operations---for example to obtain or change the value of a variable
22069 object, or to change display format.
22071 Variable objects have hierarchical tree structure. Any variable object
22072 that corresponds to a composite type, such as structure in C, has
22073 a number of child variable objects, for example corresponding to each
22074 element of a structure. A child variable object can itself have
22075 children, recursively. Recursion ends when we reach
22076 leaf variable objects, which always have built-in types. Child variable
22077 objects are created only by explicit request, so if a frontend
22078 is not interested in the children of a particular variable object, no
22079 child will be created.
22081 For a leaf variable object it is possible to obtain its value as a
22082 string, or set the value from a string. String value can be also
22083 obtained for a non-leaf variable object, but it's generally a string
22084 that only indicates the type of the object, and does not list its
22085 contents. Assignment to a non-leaf variable object is not allowed.
22087 A frontend does not need to read the values of all variable objects each time
22088 the program stops. Instead, MI provides an update command that lists all
22089 variable objects whose values has changed since the last update
22090 operation. This considerably reduces the amount of data that must
22091 be transferred to the frontend. As noted above, children variable
22092 objects are created on demand, and only leaf variable objects have a
22093 real value. As result, gdb will read target memory only for leaf
22094 variables that frontend has created.
22096 The automatic update is not always desirable. For example, a frontend
22097 might want to keep a value of some expression for future reference,
22098 and never update it. For another example, fetching memory is
22099 relatively slow for embedded targets, so a frontend might want
22100 to disable automatic update for the variables that are either not
22101 visible on the screen, or ``closed''. This is possible using so
22102 called ``frozen variable objects''. Such variable objects are never
22103 implicitly updated.
22105 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
22106 fixed variable object, the expression is parsed when the variable
22107 object is created, including associating identifiers to specific
22108 variables. The meaning of expression never changes. For a floating
22109 variable object the values of variables whose names appear in the
22110 expressions are re-evaluated every time in the context of the current
22111 frame. Consider this example:
22116 struct work_state state;
22123 If a fixed variable object for the @code{state} variable is created in
22124 this function, and we enter the recursive call, the the variable
22125 object will report the value of @code{state} in the top-level
22126 @code{do_work} invocation. On the other hand, a floating variable
22127 object will report the value of @code{state} in the current frame.
22129 If an expression specified when creating a fixed variable object
22130 refers to a local variable, the variable object becomes bound to the
22131 thread and frame in which the variable object is created. When such
22132 variable object is updated, @value{GDBN} makes sure that the
22133 thread/frame combination the variable object is bound to still exists,
22134 and re-evaluates the variable object in context of that thread/frame.
22136 The following is the complete set of @sc{gdb/mi} operations defined to
22137 access this functionality:
22139 @multitable @columnfractions .4 .6
22140 @item @strong{Operation}
22141 @tab @strong{Description}
22143 @item @code{-var-create}
22144 @tab create a variable object
22145 @item @code{-var-delete}
22146 @tab delete the variable object and/or its children
22147 @item @code{-var-set-format}
22148 @tab set the display format of this variable
22149 @item @code{-var-show-format}
22150 @tab show the display format of this variable
22151 @item @code{-var-info-num-children}
22152 @tab tells how many children this object has
22153 @item @code{-var-list-children}
22154 @tab return a list of the object's children
22155 @item @code{-var-info-type}
22156 @tab show the type of this variable object
22157 @item @code{-var-info-expression}
22158 @tab print parent-relative expression that this variable object represents
22159 @item @code{-var-info-path-expression}
22160 @tab print full expression that this variable object represents
22161 @item @code{-var-show-attributes}
22162 @tab is this variable editable? does it exist here?
22163 @item @code{-var-evaluate-expression}
22164 @tab get the value of this variable
22165 @item @code{-var-assign}
22166 @tab set the value of this variable
22167 @item @code{-var-update}
22168 @tab update the variable and its children
22169 @item @code{-var-set-frozen}
22170 @tab set frozeness attribute
22173 In the next subsection we describe each operation in detail and suggest
22174 how it can be used.
22176 @subheading Description And Use of Operations on Variable Objects
22178 @subheading The @code{-var-create} Command
22179 @findex -var-create
22181 @subsubheading Synopsis
22184 -var-create @{@var{name} | "-"@}
22185 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
22188 This operation creates a variable object, which allows the monitoring of
22189 a variable, the result of an expression, a memory cell or a CPU
22192 The @var{name} parameter is the string by which the object can be
22193 referenced. It must be unique. If @samp{-} is specified, the varobj
22194 system will generate a string ``varNNNNNN'' automatically. It will be
22195 unique provided that one does not specify @var{name} of that format.
22196 The command fails if a duplicate name is found.
22198 The frame under which the expression should be evaluated can be
22199 specified by @var{frame-addr}. A @samp{*} indicates that the current
22200 frame should be used. A @samp{@@} indicates that a floating variable
22201 object must be created.
22203 @var{expression} is any expression valid on the current language set (must not
22204 begin with a @samp{*}), or one of the following:
22208 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
22211 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
22214 @samp{$@var{regname}} --- a CPU register name
22217 @subsubheading Result
22219 This operation returns the name, number of children and the type of the
22220 object created. Type is returned as a string as the ones generated by
22221 the @value{GDBN} CLI. If a fixed variable object is bound to a
22222 specific thread, the thread is is also printed:
22225 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}"
22229 @subheading The @code{-var-delete} Command
22230 @findex -var-delete
22232 @subsubheading Synopsis
22235 -var-delete [ -c ] @var{name}
22238 Deletes a previously created variable object and all of its children.
22239 With the @samp{-c} option, just deletes the children.
22241 Returns an error if the object @var{name} is not found.
22244 @subheading The @code{-var-set-format} Command
22245 @findex -var-set-format
22247 @subsubheading Synopsis
22250 -var-set-format @var{name} @var{format-spec}
22253 Sets the output format for the value of the object @var{name} to be
22256 @anchor{-var-set-format}
22257 The syntax for the @var{format-spec} is as follows:
22260 @var{format-spec} @expansion{}
22261 @{binary | decimal | hexadecimal | octal | natural@}
22264 The natural format is the default format choosen automatically
22265 based on the variable type (like decimal for an @code{int}, hex
22266 for pointers, etc.).
22268 For a variable with children, the format is set only on the
22269 variable itself, and the children are not affected.
22271 @subheading The @code{-var-show-format} Command
22272 @findex -var-show-format
22274 @subsubheading Synopsis
22277 -var-show-format @var{name}
22280 Returns the format used to display the value of the object @var{name}.
22283 @var{format} @expansion{}
22288 @subheading The @code{-var-info-num-children} Command
22289 @findex -var-info-num-children
22291 @subsubheading Synopsis
22294 -var-info-num-children @var{name}
22297 Returns the number of children of a variable object @var{name}:
22304 @subheading The @code{-var-list-children} Command
22305 @findex -var-list-children
22307 @subsubheading Synopsis
22310 -var-list-children [@var{print-values}] @var{name}
22312 @anchor{-var-list-children}
22314 Return a list of the children of the specified variable object and
22315 create variable objects for them, if they do not already exist. With
22316 a single argument or if @var{print-values} has a value for of 0 or
22317 @code{--no-values}, print only the names of the variables; if
22318 @var{print-values} is 1 or @code{--all-values}, also print their
22319 values; and if it is 2 or @code{--simple-values} print the name and
22320 value for simple data types and just the name for arrays, structures
22323 @subsubheading Example
22327 -var-list-children n
22328 ^done,numchild=@var{n},children=[@{name=@var{name},
22329 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
22331 -var-list-children --all-values n
22332 ^done,numchild=@var{n},children=[@{name=@var{name},
22333 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
22337 @subheading The @code{-var-info-type} Command
22338 @findex -var-info-type
22340 @subsubheading Synopsis
22343 -var-info-type @var{name}
22346 Returns the type of the specified variable @var{name}. The type is
22347 returned as a string in the same format as it is output by the
22351 type=@var{typename}
22355 @subheading The @code{-var-info-expression} Command
22356 @findex -var-info-expression
22358 @subsubheading Synopsis
22361 -var-info-expression @var{name}
22364 Returns a string that is suitable for presenting this
22365 variable object in user interface. The string is generally
22366 not valid expression in the current language, and cannot be evaluated.
22368 For example, if @code{a} is an array, and variable object
22369 @code{A} was created for @code{a}, then we'll get this output:
22372 (gdb) -var-info-expression A.1
22373 ^done,lang="C",exp="1"
22377 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
22379 Note that the output of the @code{-var-list-children} command also
22380 includes those expressions, so the @code{-var-info-expression} command
22383 @subheading The @code{-var-info-path-expression} Command
22384 @findex -var-info-path-expression
22386 @subsubheading Synopsis
22389 -var-info-path-expression @var{name}
22392 Returns an expression that can be evaluated in the current
22393 context and will yield the same value that a variable object has.
22394 Compare this with the @code{-var-info-expression} command, which
22395 result can be used only for UI presentation. Typical use of
22396 the @code{-var-info-path-expression} command is creating a
22397 watchpoint from a variable object.
22399 For example, suppose @code{C} is a C@t{++} class, derived from class
22400 @code{Base}, and that the @code{Base} class has a member called
22401 @code{m_size}. Assume a variable @code{c} is has the type of
22402 @code{C} and a variable object @code{C} was created for variable
22403 @code{c}. Then, we'll get this output:
22405 (gdb) -var-info-path-expression C.Base.public.m_size
22406 ^done,path_expr=((Base)c).m_size)
22409 @subheading The @code{-var-show-attributes} Command
22410 @findex -var-show-attributes
22412 @subsubheading Synopsis
22415 -var-show-attributes @var{name}
22418 List attributes of the specified variable object @var{name}:
22421 status=@var{attr} [ ( ,@var{attr} )* ]
22425 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
22427 @subheading The @code{-var-evaluate-expression} Command
22428 @findex -var-evaluate-expression
22430 @subsubheading Synopsis
22433 -var-evaluate-expression [-f @var{format-spec}] @var{name}
22436 Evaluates the expression that is represented by the specified variable
22437 object and returns its value as a string. The format of the string
22438 can be specified with the @samp{-f} option. The possible values of
22439 this option are the same as for @code{-var-set-format}
22440 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
22441 the current display format will be used. The current display format
22442 can be changed using the @code{-var-set-format} command.
22448 Note that one must invoke @code{-var-list-children} for a variable
22449 before the value of a child variable can be evaluated.
22451 @subheading The @code{-var-assign} Command
22452 @findex -var-assign
22454 @subsubheading Synopsis
22457 -var-assign @var{name} @var{expression}
22460 Assigns the value of @var{expression} to the variable object specified
22461 by @var{name}. The object must be @samp{editable}. If the variable's
22462 value is altered by the assign, the variable will show up in any
22463 subsequent @code{-var-update} list.
22465 @subsubheading Example
22473 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
22477 @subheading The @code{-var-update} Command
22478 @findex -var-update
22480 @subsubheading Synopsis
22483 -var-update [@var{print-values}] @{@var{name} | "*"@}
22486 Reevaluate the expressions corresponding to the variable object
22487 @var{name} and all its direct and indirect children, and return the
22488 list of variable objects whose values have changed; @var{name} must
22489 be a root variable object. Here, ``changed'' means that the result of
22490 @code{-var-evaluate-expression} before and after the
22491 @code{-var-update} is different. If @samp{*} is used as the variable
22492 object names, all existing variable objects are updated, except
22493 for frozen ones (@pxref{-var-set-frozen}). The option
22494 @var{print-values} determines whether both names and values, or just
22495 names are printed. The possible values of this option are the same
22496 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
22497 recommended to use the @samp{--all-values} option, to reduce the
22498 number of MI commands needed on each program stop.
22500 With the @samp{*} parameter, if a variable object is bound to a
22501 currently running thread, it will not be updated, without any
22504 @subsubheading Example
22511 -var-update --all-values var1
22512 ^done,changelist=[@{name="var1",value="3",in_scope="true",
22513 type_changed="false"@}]
22517 @anchor{-var-update}
22518 The field in_scope may take three values:
22522 The variable object's current value is valid.
22525 The variable object does not currently hold a valid value but it may
22526 hold one in the future if its associated expression comes back into
22530 The variable object no longer holds a valid value.
22531 This can occur when the executable file being debugged has changed,
22532 either through recompilation or by using the @value{GDBN} @code{file}
22533 command. The front end should normally choose to delete these variable
22537 In the future new values may be added to this list so the front should
22538 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
22540 @subheading The @code{-var-set-frozen} Command
22541 @findex -var-set-frozen
22542 @anchor{-var-set-frozen}
22544 @subsubheading Synopsis
22547 -var-set-frozen @var{name} @var{flag}
22550 Set the frozenness flag on the variable object @var{name}. The
22551 @var{flag} parameter should be either @samp{1} to make the variable
22552 frozen or @samp{0} to make it unfrozen. If a variable object is
22553 frozen, then neither itself, nor any of its children, are
22554 implicitly updated by @code{-var-update} of
22555 a parent variable or by @code{-var-update *}. Only
22556 @code{-var-update} of the variable itself will update its value and
22557 values of its children. After a variable object is unfrozen, it is
22558 implicitly updated by all subsequent @code{-var-update} operations.
22559 Unfreezing a variable does not update it, only subsequent
22560 @code{-var-update} does.
22562 @subsubheading Example
22566 -var-set-frozen V 1
22572 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22573 @node GDB/MI Data Manipulation
22574 @section @sc{gdb/mi} Data Manipulation
22576 @cindex data manipulation, in @sc{gdb/mi}
22577 @cindex @sc{gdb/mi}, data manipulation
22578 This section describes the @sc{gdb/mi} commands that manipulate data:
22579 examine memory and registers, evaluate expressions, etc.
22581 @c REMOVED FROM THE INTERFACE.
22582 @c @subheading -data-assign
22583 @c Change the value of a program variable. Plenty of side effects.
22584 @c @subsubheading GDB Command
22586 @c @subsubheading Example
22589 @subheading The @code{-data-disassemble} Command
22590 @findex -data-disassemble
22592 @subsubheading Synopsis
22596 [ -s @var{start-addr} -e @var{end-addr} ]
22597 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
22605 @item @var{start-addr}
22606 is the beginning address (or @code{$pc})
22607 @item @var{end-addr}
22609 @item @var{filename}
22610 is the name of the file to disassemble
22611 @item @var{linenum}
22612 is the line number to disassemble around
22614 is the number of disassembly lines to be produced. If it is -1,
22615 the whole function will be disassembled, in case no @var{end-addr} is
22616 specified. If @var{end-addr} is specified as a non-zero value, and
22617 @var{lines} is lower than the number of disassembly lines between
22618 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
22619 displayed; if @var{lines} is higher than the number of lines between
22620 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
22623 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
22627 @subsubheading Result
22629 The output for each instruction is composed of four fields:
22638 Note that whatever included in the instruction field, is not manipulated
22639 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
22641 @subsubheading @value{GDBN} Command
22643 There's no direct mapping from this command to the CLI.
22645 @subsubheading Example
22647 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
22651 -data-disassemble -s $pc -e "$pc + 20" -- 0
22654 @{address="0x000107c0",func-name="main",offset="4",
22655 inst="mov 2, %o0"@},
22656 @{address="0x000107c4",func-name="main",offset="8",
22657 inst="sethi %hi(0x11800), %o2"@},
22658 @{address="0x000107c8",func-name="main",offset="12",
22659 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
22660 @{address="0x000107cc",func-name="main",offset="16",
22661 inst="sethi %hi(0x11800), %o2"@},
22662 @{address="0x000107d0",func-name="main",offset="20",
22663 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
22667 Disassemble the whole @code{main} function. Line 32 is part of
22671 -data-disassemble -f basics.c -l 32 -- 0
22673 @{address="0x000107bc",func-name="main",offset="0",
22674 inst="save %sp, -112, %sp"@},
22675 @{address="0x000107c0",func-name="main",offset="4",
22676 inst="mov 2, %o0"@},
22677 @{address="0x000107c4",func-name="main",offset="8",
22678 inst="sethi %hi(0x11800), %o2"@},
22680 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
22681 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
22685 Disassemble 3 instructions from the start of @code{main}:
22689 -data-disassemble -f basics.c -l 32 -n 3 -- 0
22691 @{address="0x000107bc",func-name="main",offset="0",
22692 inst="save %sp, -112, %sp"@},
22693 @{address="0x000107c0",func-name="main",offset="4",
22694 inst="mov 2, %o0"@},
22695 @{address="0x000107c4",func-name="main",offset="8",
22696 inst="sethi %hi(0x11800), %o2"@}]
22700 Disassemble 3 instructions from the start of @code{main} in mixed mode:
22704 -data-disassemble -f basics.c -l 32 -n 3 -- 1
22706 src_and_asm_line=@{line="31",
22707 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22708 testsuite/gdb.mi/basics.c",line_asm_insn=[
22709 @{address="0x000107bc",func-name="main",offset="0",
22710 inst="save %sp, -112, %sp"@}]@},
22711 src_and_asm_line=@{line="32",
22712 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22713 testsuite/gdb.mi/basics.c",line_asm_insn=[
22714 @{address="0x000107c0",func-name="main",offset="4",
22715 inst="mov 2, %o0"@},
22716 @{address="0x000107c4",func-name="main",offset="8",
22717 inst="sethi %hi(0x11800), %o2"@}]@}]
22722 @subheading The @code{-data-evaluate-expression} Command
22723 @findex -data-evaluate-expression
22725 @subsubheading Synopsis
22728 -data-evaluate-expression @var{expr}
22731 Evaluate @var{expr} as an expression. The expression could contain an
22732 inferior function call. The function call will execute synchronously.
22733 If the expression contains spaces, it must be enclosed in double quotes.
22735 @subsubheading @value{GDBN} Command
22737 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
22738 @samp{call}. In @code{gdbtk} only, there's a corresponding
22739 @samp{gdb_eval} command.
22741 @subsubheading Example
22743 In the following example, the numbers that precede the commands are the
22744 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
22745 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
22749 211-data-evaluate-expression A
22752 311-data-evaluate-expression &A
22753 311^done,value="0xefffeb7c"
22755 411-data-evaluate-expression A+3
22758 511-data-evaluate-expression "A + 3"
22764 @subheading The @code{-data-list-changed-registers} Command
22765 @findex -data-list-changed-registers
22767 @subsubheading Synopsis
22770 -data-list-changed-registers
22773 Display a list of the registers that have changed.
22775 @subsubheading @value{GDBN} Command
22777 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
22778 has the corresponding command @samp{gdb_changed_register_list}.
22780 @subsubheading Example
22782 On a PPC MBX board:
22790 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
22791 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
22794 -data-list-changed-registers
22795 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
22796 "10","11","13","14","15","16","17","18","19","20","21","22","23",
22797 "24","25","26","27","28","30","31","64","65","66","67","69"]
22802 @subheading The @code{-data-list-register-names} Command
22803 @findex -data-list-register-names
22805 @subsubheading Synopsis
22808 -data-list-register-names [ ( @var{regno} )+ ]
22811 Show a list of register names for the current target. If no arguments
22812 are given, it shows a list of the names of all the registers. If
22813 integer numbers are given as arguments, it will print a list of the
22814 names of the registers corresponding to the arguments. To ensure
22815 consistency between a register name and its number, the output list may
22816 include empty register names.
22818 @subsubheading @value{GDBN} Command
22820 @value{GDBN} does not have a command which corresponds to
22821 @samp{-data-list-register-names}. In @code{gdbtk} there is a
22822 corresponding command @samp{gdb_regnames}.
22824 @subsubheading Example
22826 For the PPC MBX board:
22829 -data-list-register-names
22830 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
22831 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
22832 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
22833 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
22834 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
22835 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
22836 "", "pc","ps","cr","lr","ctr","xer"]
22838 -data-list-register-names 1 2 3
22839 ^done,register-names=["r1","r2","r3"]
22843 @subheading The @code{-data-list-register-values} Command
22844 @findex -data-list-register-values
22846 @subsubheading Synopsis
22849 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
22852 Display the registers' contents. @var{fmt} is the format according to
22853 which the registers' contents are to be returned, followed by an optional
22854 list of numbers specifying the registers to display. A missing list of
22855 numbers indicates that the contents of all the registers must be returned.
22857 Allowed formats for @var{fmt} are:
22874 @subsubheading @value{GDBN} Command
22876 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
22877 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
22879 @subsubheading Example
22881 For a PPC MBX board (note: line breaks are for readability only, they
22882 don't appear in the actual output):
22886 -data-list-register-values r 64 65
22887 ^done,register-values=[@{number="64",value="0xfe00a300"@},
22888 @{number="65",value="0x00029002"@}]
22890 -data-list-register-values x
22891 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
22892 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
22893 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
22894 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
22895 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
22896 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
22897 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
22898 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
22899 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
22900 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
22901 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
22902 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
22903 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
22904 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
22905 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
22906 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
22907 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
22908 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
22909 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
22910 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
22911 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
22912 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
22913 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
22914 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
22915 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
22916 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
22917 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
22918 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
22919 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
22920 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
22921 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
22922 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
22923 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
22924 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
22925 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
22926 @{number="69",value="0x20002b03"@}]
22931 @subheading The @code{-data-read-memory} Command
22932 @findex -data-read-memory
22934 @subsubheading Synopsis
22937 -data-read-memory [ -o @var{byte-offset} ]
22938 @var{address} @var{word-format} @var{word-size}
22939 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
22946 @item @var{address}
22947 An expression specifying the address of the first memory word to be
22948 read. Complex expressions containing embedded white space should be
22949 quoted using the C convention.
22951 @item @var{word-format}
22952 The format to be used to print the memory words. The notation is the
22953 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
22956 @item @var{word-size}
22957 The size of each memory word in bytes.
22959 @item @var{nr-rows}
22960 The number of rows in the output table.
22962 @item @var{nr-cols}
22963 The number of columns in the output table.
22966 If present, indicates that each row should include an @sc{ascii} dump. The
22967 value of @var{aschar} is used as a padding character when a byte is not a
22968 member of the printable @sc{ascii} character set (printable @sc{ascii}
22969 characters are those whose code is between 32 and 126, inclusively).
22971 @item @var{byte-offset}
22972 An offset to add to the @var{address} before fetching memory.
22975 This command displays memory contents as a table of @var{nr-rows} by
22976 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
22977 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
22978 (returned as @samp{total-bytes}). Should less than the requested number
22979 of bytes be returned by the target, the missing words are identified
22980 using @samp{N/A}. The number of bytes read from the target is returned
22981 in @samp{nr-bytes} and the starting address used to read memory in
22984 The address of the next/previous row or page is available in
22985 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
22988 @subsubheading @value{GDBN} Command
22990 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
22991 @samp{gdb_get_mem} memory read command.
22993 @subsubheading Example
22995 Read six bytes of memory starting at @code{bytes+6} but then offset by
22996 @code{-6} bytes. Format as three rows of two columns. One byte per
22997 word. Display each word in hex.
23001 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
23002 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
23003 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
23004 prev-page="0x0000138a",memory=[
23005 @{addr="0x00001390",data=["0x00","0x01"]@},
23006 @{addr="0x00001392",data=["0x02","0x03"]@},
23007 @{addr="0x00001394",data=["0x04","0x05"]@}]
23011 Read two bytes of memory starting at address @code{shorts + 64} and
23012 display as a single word formatted in decimal.
23016 5-data-read-memory shorts+64 d 2 1 1
23017 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
23018 next-row="0x00001512",prev-row="0x0000150e",
23019 next-page="0x00001512",prev-page="0x0000150e",memory=[
23020 @{addr="0x00001510",data=["128"]@}]
23024 Read thirty two bytes of memory starting at @code{bytes+16} and format
23025 as eight rows of four columns. Include a string encoding with @samp{x}
23026 used as the non-printable character.
23030 4-data-read-memory bytes+16 x 1 8 4 x
23031 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
23032 next-row="0x000013c0",prev-row="0x0000139c",
23033 next-page="0x000013c0",prev-page="0x00001380",memory=[
23034 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
23035 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
23036 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
23037 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
23038 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
23039 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
23040 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
23041 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
23045 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23046 @node GDB/MI Tracepoint Commands
23047 @section @sc{gdb/mi} Tracepoint Commands
23049 The tracepoint commands are not yet implemented.
23051 @c @subheading -trace-actions
23053 @c @subheading -trace-delete
23055 @c @subheading -trace-disable
23057 @c @subheading -trace-dump
23059 @c @subheading -trace-enable
23061 @c @subheading -trace-exists
23063 @c @subheading -trace-find
23065 @c @subheading -trace-frame-number
23067 @c @subheading -trace-info
23069 @c @subheading -trace-insert
23071 @c @subheading -trace-list
23073 @c @subheading -trace-pass-count
23075 @c @subheading -trace-save
23077 @c @subheading -trace-start
23079 @c @subheading -trace-stop
23082 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23083 @node GDB/MI Symbol Query
23084 @section @sc{gdb/mi} Symbol Query Commands
23087 @subheading The @code{-symbol-info-address} Command
23088 @findex -symbol-info-address
23090 @subsubheading Synopsis
23093 -symbol-info-address @var{symbol}
23096 Describe where @var{symbol} is stored.
23098 @subsubheading @value{GDBN} Command
23100 The corresponding @value{GDBN} command is @samp{info address}.
23102 @subsubheading Example
23106 @subheading The @code{-symbol-info-file} Command
23107 @findex -symbol-info-file
23109 @subsubheading Synopsis
23115 Show the file for the symbol.
23117 @subsubheading @value{GDBN} Command
23119 There's no equivalent @value{GDBN} command. @code{gdbtk} has
23120 @samp{gdb_find_file}.
23122 @subsubheading Example
23126 @subheading The @code{-symbol-info-function} Command
23127 @findex -symbol-info-function
23129 @subsubheading Synopsis
23132 -symbol-info-function
23135 Show which function the symbol lives in.
23137 @subsubheading @value{GDBN} Command
23139 @samp{gdb_get_function} in @code{gdbtk}.
23141 @subsubheading Example
23145 @subheading The @code{-symbol-info-line} Command
23146 @findex -symbol-info-line
23148 @subsubheading Synopsis
23154 Show the core addresses of the code for a source line.
23156 @subsubheading @value{GDBN} Command
23158 The corresponding @value{GDBN} command is @samp{info line}.
23159 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
23161 @subsubheading Example
23165 @subheading The @code{-symbol-info-symbol} Command
23166 @findex -symbol-info-symbol
23168 @subsubheading Synopsis
23171 -symbol-info-symbol @var{addr}
23174 Describe what symbol is at location @var{addr}.
23176 @subsubheading @value{GDBN} Command
23178 The corresponding @value{GDBN} command is @samp{info symbol}.
23180 @subsubheading Example
23184 @subheading The @code{-symbol-list-functions} Command
23185 @findex -symbol-list-functions
23187 @subsubheading Synopsis
23190 -symbol-list-functions
23193 List the functions in the executable.
23195 @subsubheading @value{GDBN} Command
23197 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
23198 @samp{gdb_search} in @code{gdbtk}.
23200 @subsubheading Example
23204 @subheading The @code{-symbol-list-lines} Command
23205 @findex -symbol-list-lines
23207 @subsubheading Synopsis
23210 -symbol-list-lines @var{filename}
23213 Print the list of lines that contain code and their associated program
23214 addresses for the given source filename. The entries are sorted in
23215 ascending PC order.
23217 @subsubheading @value{GDBN} Command
23219 There is no corresponding @value{GDBN} command.
23221 @subsubheading Example
23224 -symbol-list-lines basics.c
23225 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
23230 @subheading The @code{-symbol-list-types} Command
23231 @findex -symbol-list-types
23233 @subsubheading Synopsis
23239 List all the type names.
23241 @subsubheading @value{GDBN} Command
23243 The corresponding commands are @samp{info types} in @value{GDBN},
23244 @samp{gdb_search} in @code{gdbtk}.
23246 @subsubheading Example
23250 @subheading The @code{-symbol-list-variables} Command
23251 @findex -symbol-list-variables
23253 @subsubheading Synopsis
23256 -symbol-list-variables
23259 List all the global and static variable names.
23261 @subsubheading @value{GDBN} Command
23263 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
23265 @subsubheading Example
23269 @subheading The @code{-symbol-locate} Command
23270 @findex -symbol-locate
23272 @subsubheading Synopsis
23278 @subsubheading @value{GDBN} Command
23280 @samp{gdb_loc} in @code{gdbtk}.
23282 @subsubheading Example
23286 @subheading The @code{-symbol-type} Command
23287 @findex -symbol-type
23289 @subsubheading Synopsis
23292 -symbol-type @var{variable}
23295 Show type of @var{variable}.
23297 @subsubheading @value{GDBN} Command
23299 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
23300 @samp{gdb_obj_variable}.
23302 @subsubheading Example
23306 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23307 @node GDB/MI File Commands
23308 @section @sc{gdb/mi} File Commands
23310 This section describes the GDB/MI commands to specify executable file names
23311 and to read in and obtain symbol table information.
23313 @subheading The @code{-file-exec-and-symbols} Command
23314 @findex -file-exec-and-symbols
23316 @subsubheading Synopsis
23319 -file-exec-and-symbols @var{file}
23322 Specify the executable file to be debugged. This file is the one from
23323 which the symbol table is also read. If no file is specified, the
23324 command clears the executable and symbol information. If breakpoints
23325 are set when using this command with no arguments, @value{GDBN} will produce
23326 error messages. Otherwise, no output is produced, except a completion
23329 @subsubheading @value{GDBN} Command
23331 The corresponding @value{GDBN} command is @samp{file}.
23333 @subsubheading Example
23337 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23343 @subheading The @code{-file-exec-file} Command
23344 @findex -file-exec-file
23346 @subsubheading Synopsis
23349 -file-exec-file @var{file}
23352 Specify the executable file to be debugged. Unlike
23353 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
23354 from this file. If used without argument, @value{GDBN} clears the information
23355 about the executable file. No output is produced, except a completion
23358 @subsubheading @value{GDBN} Command
23360 The corresponding @value{GDBN} command is @samp{exec-file}.
23362 @subsubheading Example
23366 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23372 @subheading The @code{-file-list-exec-sections} Command
23373 @findex -file-list-exec-sections
23375 @subsubheading Synopsis
23378 -file-list-exec-sections
23381 List the sections of the current executable file.
23383 @subsubheading @value{GDBN} Command
23385 The @value{GDBN} command @samp{info file} shows, among the rest, the same
23386 information as this command. @code{gdbtk} has a corresponding command
23387 @samp{gdb_load_info}.
23389 @subsubheading Example
23393 @subheading The @code{-file-list-exec-source-file} Command
23394 @findex -file-list-exec-source-file
23396 @subsubheading Synopsis
23399 -file-list-exec-source-file
23402 List the line number, the current source file, and the absolute path
23403 to the current source file for the current executable. The macro
23404 information field has a value of @samp{1} or @samp{0} depending on
23405 whether or not the file includes preprocessor macro information.
23407 @subsubheading @value{GDBN} Command
23409 The @value{GDBN} equivalent is @samp{info source}
23411 @subsubheading Example
23415 123-file-list-exec-source-file
23416 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
23421 @subheading The @code{-file-list-exec-source-files} Command
23422 @findex -file-list-exec-source-files
23424 @subsubheading Synopsis
23427 -file-list-exec-source-files
23430 List the source files for the current executable.
23432 It will always output the filename, but only when @value{GDBN} can find
23433 the absolute file name of a source file, will it output the fullname.
23435 @subsubheading @value{GDBN} Command
23437 The @value{GDBN} equivalent is @samp{info sources}.
23438 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
23440 @subsubheading Example
23443 -file-list-exec-source-files
23445 @{file=foo.c,fullname=/home/foo.c@},
23446 @{file=/home/bar.c,fullname=/home/bar.c@},
23447 @{file=gdb_could_not_find_fullpath.c@}]
23451 @subheading The @code{-file-list-shared-libraries} Command
23452 @findex -file-list-shared-libraries
23454 @subsubheading Synopsis
23457 -file-list-shared-libraries
23460 List the shared libraries in the program.
23462 @subsubheading @value{GDBN} Command
23464 The corresponding @value{GDBN} command is @samp{info shared}.
23466 @subsubheading Example
23470 @subheading The @code{-file-list-symbol-files} Command
23471 @findex -file-list-symbol-files
23473 @subsubheading Synopsis
23476 -file-list-symbol-files
23481 @subsubheading @value{GDBN} Command
23483 The corresponding @value{GDBN} command is @samp{info file} (part of it).
23485 @subsubheading Example
23489 @subheading The @code{-file-symbol-file} Command
23490 @findex -file-symbol-file
23492 @subsubheading Synopsis
23495 -file-symbol-file @var{file}
23498 Read symbol table info from the specified @var{file} argument. When
23499 used without arguments, clears @value{GDBN}'s symbol table info. No output is
23500 produced, except for a completion notification.
23502 @subsubheading @value{GDBN} Command
23504 The corresponding @value{GDBN} command is @samp{symbol-file}.
23506 @subsubheading Example
23510 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23516 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23517 @node GDB/MI Memory Overlay Commands
23518 @section @sc{gdb/mi} Memory Overlay Commands
23520 The memory overlay commands are not implemented.
23522 @c @subheading -overlay-auto
23524 @c @subheading -overlay-list-mapping-state
23526 @c @subheading -overlay-list-overlays
23528 @c @subheading -overlay-map
23530 @c @subheading -overlay-off
23532 @c @subheading -overlay-on
23534 @c @subheading -overlay-unmap
23536 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23537 @node GDB/MI Signal Handling Commands
23538 @section @sc{gdb/mi} Signal Handling Commands
23540 Signal handling commands are not implemented.
23542 @c @subheading -signal-handle
23544 @c @subheading -signal-list-handle-actions
23546 @c @subheading -signal-list-signal-types
23550 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23551 @node GDB/MI Target Manipulation
23552 @section @sc{gdb/mi} Target Manipulation Commands
23555 @subheading The @code{-target-attach} Command
23556 @findex -target-attach
23558 @subsubheading Synopsis
23561 -target-attach @var{pid} | @var{gid} | @var{file}
23564 Attach to a process @var{pid} or a file @var{file} outside of
23565 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
23566 group, the id previously returned by
23567 @samp{-list-thread-groups --available} must be used.
23569 @subsubheading @value{GDBN} Command
23571 The corresponding @value{GDBN} command is @samp{attach}.
23573 @subsubheading Example
23577 =thread-created,id="1"
23578 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
23583 @subheading The @code{-target-compare-sections} Command
23584 @findex -target-compare-sections
23586 @subsubheading Synopsis
23589 -target-compare-sections [ @var{section} ]
23592 Compare data of section @var{section} on target to the exec file.
23593 Without the argument, all sections are compared.
23595 @subsubheading @value{GDBN} Command
23597 The @value{GDBN} equivalent is @samp{compare-sections}.
23599 @subsubheading Example
23603 @subheading The @code{-target-detach} Command
23604 @findex -target-detach
23606 @subsubheading Synopsis
23609 -target-detach [ @var{pid} | @var{gid} ]
23612 Detach from the remote target which normally resumes its execution.
23613 If either @var{pid} or @var{gid} is specified, detaches from either
23614 the specified process, or specified thread group. There's no output.
23616 @subsubheading @value{GDBN} Command
23618 The corresponding @value{GDBN} command is @samp{detach}.
23620 @subsubheading Example
23630 @subheading The @code{-target-disconnect} Command
23631 @findex -target-disconnect
23633 @subsubheading Synopsis
23639 Disconnect from the remote target. There's no output and the target is
23640 generally not resumed.
23642 @subsubheading @value{GDBN} Command
23644 The corresponding @value{GDBN} command is @samp{disconnect}.
23646 @subsubheading Example
23656 @subheading The @code{-target-download} Command
23657 @findex -target-download
23659 @subsubheading Synopsis
23665 Loads the executable onto the remote target.
23666 It prints out an update message every half second, which includes the fields:
23670 The name of the section.
23672 The size of what has been sent so far for that section.
23674 The size of the section.
23676 The total size of what was sent so far (the current and the previous sections).
23678 The size of the overall executable to download.
23682 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
23683 @sc{gdb/mi} Output Syntax}).
23685 In addition, it prints the name and size of the sections, as they are
23686 downloaded. These messages include the following fields:
23690 The name of the section.
23692 The size of the section.
23694 The size of the overall executable to download.
23698 At the end, a summary is printed.
23700 @subsubheading @value{GDBN} Command
23702 The corresponding @value{GDBN} command is @samp{load}.
23704 @subsubheading Example
23706 Note: each status message appears on a single line. Here the messages
23707 have been broken down so that they can fit onto a page.
23712 +download,@{section=".text",section-size="6668",total-size="9880"@}
23713 +download,@{section=".text",section-sent="512",section-size="6668",
23714 total-sent="512",total-size="9880"@}
23715 +download,@{section=".text",section-sent="1024",section-size="6668",
23716 total-sent="1024",total-size="9880"@}
23717 +download,@{section=".text",section-sent="1536",section-size="6668",
23718 total-sent="1536",total-size="9880"@}
23719 +download,@{section=".text",section-sent="2048",section-size="6668",
23720 total-sent="2048",total-size="9880"@}
23721 +download,@{section=".text",section-sent="2560",section-size="6668",
23722 total-sent="2560",total-size="9880"@}
23723 +download,@{section=".text",section-sent="3072",section-size="6668",
23724 total-sent="3072",total-size="9880"@}
23725 +download,@{section=".text",section-sent="3584",section-size="6668",
23726 total-sent="3584",total-size="9880"@}
23727 +download,@{section=".text",section-sent="4096",section-size="6668",
23728 total-sent="4096",total-size="9880"@}
23729 +download,@{section=".text",section-sent="4608",section-size="6668",
23730 total-sent="4608",total-size="9880"@}
23731 +download,@{section=".text",section-sent="5120",section-size="6668",
23732 total-sent="5120",total-size="9880"@}
23733 +download,@{section=".text",section-sent="5632",section-size="6668",
23734 total-sent="5632",total-size="9880"@}
23735 +download,@{section=".text",section-sent="6144",section-size="6668",
23736 total-sent="6144",total-size="9880"@}
23737 +download,@{section=".text",section-sent="6656",section-size="6668",
23738 total-sent="6656",total-size="9880"@}
23739 +download,@{section=".init",section-size="28",total-size="9880"@}
23740 +download,@{section=".fini",section-size="28",total-size="9880"@}
23741 +download,@{section=".data",section-size="3156",total-size="9880"@}
23742 +download,@{section=".data",section-sent="512",section-size="3156",
23743 total-sent="7236",total-size="9880"@}
23744 +download,@{section=".data",section-sent="1024",section-size="3156",
23745 total-sent="7748",total-size="9880"@}
23746 +download,@{section=".data",section-sent="1536",section-size="3156",
23747 total-sent="8260",total-size="9880"@}
23748 +download,@{section=".data",section-sent="2048",section-size="3156",
23749 total-sent="8772",total-size="9880"@}
23750 +download,@{section=".data",section-sent="2560",section-size="3156",
23751 total-sent="9284",total-size="9880"@}
23752 +download,@{section=".data",section-sent="3072",section-size="3156",
23753 total-sent="9796",total-size="9880"@}
23754 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
23760 @subheading The @code{-target-exec-status} Command
23761 @findex -target-exec-status
23763 @subsubheading Synopsis
23766 -target-exec-status
23769 Provide information on the state of the target (whether it is running or
23770 not, for instance).
23772 @subsubheading @value{GDBN} Command
23774 There's no equivalent @value{GDBN} command.
23776 @subsubheading Example
23780 @subheading The @code{-target-list-available-targets} Command
23781 @findex -target-list-available-targets
23783 @subsubheading Synopsis
23786 -target-list-available-targets
23789 List the possible targets to connect to.
23791 @subsubheading @value{GDBN} Command
23793 The corresponding @value{GDBN} command is @samp{help target}.
23795 @subsubheading Example
23799 @subheading The @code{-target-list-current-targets} Command
23800 @findex -target-list-current-targets
23802 @subsubheading Synopsis
23805 -target-list-current-targets
23808 Describe the current target.
23810 @subsubheading @value{GDBN} Command
23812 The corresponding information is printed by @samp{info file} (among
23815 @subsubheading Example
23819 @subheading The @code{-target-list-parameters} Command
23820 @findex -target-list-parameters
23822 @subsubheading Synopsis
23825 -target-list-parameters
23830 @subsubheading @value{GDBN} Command
23834 @subsubheading Example
23838 @subheading The @code{-target-select} Command
23839 @findex -target-select
23841 @subsubheading Synopsis
23844 -target-select @var{type} @var{parameters @dots{}}
23847 Connect @value{GDBN} to the remote target. This command takes two args:
23851 The type of target, for instance @samp{remote}, etc.
23852 @item @var{parameters}
23853 Device names, host names and the like. @xref{Target Commands, ,
23854 Commands for Managing Targets}, for more details.
23857 The output is a connection notification, followed by the address at
23858 which the target program is, in the following form:
23861 ^connected,addr="@var{address}",func="@var{function name}",
23862 args=[@var{arg list}]
23865 @subsubheading @value{GDBN} Command
23867 The corresponding @value{GDBN} command is @samp{target}.
23869 @subsubheading Example
23873 -target-select remote /dev/ttya
23874 ^connected,addr="0xfe00a300",func="??",args=[]
23878 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23879 @node GDB/MI File Transfer Commands
23880 @section @sc{gdb/mi} File Transfer Commands
23883 @subheading The @code{-target-file-put} Command
23884 @findex -target-file-put
23886 @subsubheading Synopsis
23889 -target-file-put @var{hostfile} @var{targetfile}
23892 Copy file @var{hostfile} from the host system (the machine running
23893 @value{GDBN}) to @var{targetfile} on the target system.
23895 @subsubheading @value{GDBN} Command
23897 The corresponding @value{GDBN} command is @samp{remote put}.
23899 @subsubheading Example
23903 -target-file-put localfile remotefile
23909 @subheading The @code{-target-file-get} Command
23910 @findex -target-file-get
23912 @subsubheading Synopsis
23915 -target-file-get @var{targetfile} @var{hostfile}
23918 Copy file @var{targetfile} from the target system to @var{hostfile}
23919 on the host system.
23921 @subsubheading @value{GDBN} Command
23923 The corresponding @value{GDBN} command is @samp{remote get}.
23925 @subsubheading Example
23929 -target-file-get remotefile localfile
23935 @subheading The @code{-target-file-delete} Command
23936 @findex -target-file-delete
23938 @subsubheading Synopsis
23941 -target-file-delete @var{targetfile}
23944 Delete @var{targetfile} from the target system.
23946 @subsubheading @value{GDBN} Command
23948 The corresponding @value{GDBN} command is @samp{remote delete}.
23950 @subsubheading Example
23954 -target-file-delete remotefile
23960 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23961 @node GDB/MI Miscellaneous Commands
23962 @section Miscellaneous @sc{gdb/mi} Commands
23964 @c @subheading -gdb-complete
23966 @subheading The @code{-gdb-exit} Command
23969 @subsubheading Synopsis
23975 Exit @value{GDBN} immediately.
23977 @subsubheading @value{GDBN} Command
23979 Approximately corresponds to @samp{quit}.
23981 @subsubheading Example
23990 @subheading The @code{-exec-abort} Command
23991 @findex -exec-abort
23993 @subsubheading Synopsis
23999 Kill the inferior running program.
24001 @subsubheading @value{GDBN} Command
24003 The corresponding @value{GDBN} command is @samp{kill}.
24005 @subsubheading Example
24009 @subheading The @code{-gdb-set} Command
24012 @subsubheading Synopsis
24018 Set an internal @value{GDBN} variable.
24019 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
24021 @subsubheading @value{GDBN} Command
24023 The corresponding @value{GDBN} command is @samp{set}.
24025 @subsubheading Example
24035 @subheading The @code{-gdb-show} Command
24038 @subsubheading Synopsis
24044 Show the current value of a @value{GDBN} variable.
24046 @subsubheading @value{GDBN} Command
24048 The corresponding @value{GDBN} command is @samp{show}.
24050 @subsubheading Example
24059 @c @subheading -gdb-source
24062 @subheading The @code{-gdb-version} Command
24063 @findex -gdb-version
24065 @subsubheading Synopsis
24071 Show version information for @value{GDBN}. Used mostly in testing.
24073 @subsubheading @value{GDBN} Command
24075 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
24076 default shows this information when you start an interactive session.
24078 @subsubheading Example
24080 @c This example modifies the actual output from GDB to avoid overfull
24086 ~Copyright 2000 Free Software Foundation, Inc.
24087 ~GDB is free software, covered by the GNU General Public License, and
24088 ~you are welcome to change it and/or distribute copies of it under
24089 ~ certain conditions.
24090 ~Type "show copying" to see the conditions.
24091 ~There is absolutely no warranty for GDB. Type "show warranty" for
24093 ~This GDB was configured as
24094 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
24099 @subheading The @code{-list-features} Command
24100 @findex -list-features
24102 Returns a list of particular features of the MI protocol that
24103 this version of gdb implements. A feature can be a command,
24104 or a new field in an output of some command, or even an
24105 important bugfix. While a frontend can sometimes detect presence
24106 of a feature at runtime, it is easier to perform detection at debugger
24109 The command returns a list of strings, with each string naming an
24110 available feature. Each returned string is just a name, it does not
24111 have any internal structure. The list of possible feature names
24117 (gdb) -list-features
24118 ^done,result=["feature1","feature2"]
24121 The current list of features is:
24124 @item frozen-varobjs
24125 Indicates presence of the @code{-var-set-frozen} command, as well
24126 as possible presense of the @code{frozen} field in the output
24127 of @code{-varobj-create}.
24128 @item pending-breakpoints
24129 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
24131 Indicates presence of the @code{-thread-info} command.
24135 @subheading The @code{-list-target-features} Command
24136 @findex -list-target-features
24138 Returns a list of particular features that are supported by the
24139 target. Those features affect the permitted MI commands, but
24140 unlike the features reported by the @code{-list-features} command, the
24141 features depend on which target GDB is using at the moment. Whenever
24142 a target can change, due to commands such as @code{-target-select},
24143 @code{-target-attach} or @code{-exec-run}, the list of target features
24144 may change, and the frontend should obtain it again.
24148 (gdb) -list-features
24149 ^done,result=["async"]
24152 The current list of features is:
24156 Indicates that the target is capable of asynchronous command
24157 execution, which means that @value{GDBN} will accept further commands
24158 while the target is running.
24162 @subheading The @code{-list-thread-groups} Command
24163 @findex -list-thread-groups
24165 @subheading Synopsis
24168 -list-thread-groups [ --available ] [ @var{group} ]
24171 When used without the @var{group} parameter, lists top-level thread
24172 groups that are being debugged. When used with the @var{group}
24173 parameter, the children of the specified group are listed. The
24174 children can be either threads, or other groups. At present,
24175 @value{GDBN} will not report both threads and groups as children at
24176 the same time, but it may change in future.
24178 With the @samp{--available} option, instead of reporting groups that
24179 are been debugged, GDB will report all thread groups available on the
24180 target. Using the @samp{--available} option together with @var{group}
24183 @subheading Example
24187 -list-thread-groups
24188 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
24189 -list-thread-groups 17
24190 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
24191 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
24192 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
24193 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
24194 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
24197 @subheading The @code{-interpreter-exec} Command
24198 @findex -interpreter-exec
24200 @subheading Synopsis
24203 -interpreter-exec @var{interpreter} @var{command}
24205 @anchor{-interpreter-exec}
24207 Execute the specified @var{command} in the given @var{interpreter}.
24209 @subheading @value{GDBN} Command
24211 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
24213 @subheading Example
24217 -interpreter-exec console "break main"
24218 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
24219 &"During symbol reading, bad structure-type format.\n"
24220 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
24225 @subheading The @code{-inferior-tty-set} Command
24226 @findex -inferior-tty-set
24228 @subheading Synopsis
24231 -inferior-tty-set /dev/pts/1
24234 Set terminal for future runs of the program being debugged.
24236 @subheading @value{GDBN} Command
24238 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
24240 @subheading Example
24244 -inferior-tty-set /dev/pts/1
24249 @subheading The @code{-inferior-tty-show} Command
24250 @findex -inferior-tty-show
24252 @subheading Synopsis
24258 Show terminal for future runs of program being debugged.
24260 @subheading @value{GDBN} Command
24262 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
24264 @subheading Example
24268 -inferior-tty-set /dev/pts/1
24272 ^done,inferior_tty_terminal="/dev/pts/1"
24276 @subheading The @code{-enable-timings} Command
24277 @findex -enable-timings
24279 @subheading Synopsis
24282 -enable-timings [yes | no]
24285 Toggle the printing of the wallclock, user and system times for an MI
24286 command as a field in its output. This command is to help frontend
24287 developers optimize the performance of their code. No argument is
24288 equivalent to @samp{yes}.
24290 @subheading @value{GDBN} Command
24294 @subheading Example
24302 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24303 addr="0x080484ed",func="main",file="myprog.c",
24304 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
24305 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
24313 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24314 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
24315 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
24316 fullname="/home/nickrob/myprog.c",line="73"@}
24321 @chapter @value{GDBN} Annotations
24323 This chapter describes annotations in @value{GDBN}. Annotations were
24324 designed to interface @value{GDBN} to graphical user interfaces or other
24325 similar programs which want to interact with @value{GDBN} at a
24326 relatively high level.
24328 The annotation mechanism has largely been superseded by @sc{gdb/mi}
24332 This is Edition @value{EDITION}, @value{DATE}.
24336 * Annotations Overview:: What annotations are; the general syntax.
24337 * Server Prefix:: Issuing a command without affecting user state.
24338 * Prompting:: Annotations marking @value{GDBN}'s need for input.
24339 * Errors:: Annotations for error messages.
24340 * Invalidation:: Some annotations describe things now invalid.
24341 * Annotations for Running::
24342 Whether the program is running, how it stopped, etc.
24343 * Source Annotations:: Annotations describing source code.
24346 @node Annotations Overview
24347 @section What is an Annotation?
24348 @cindex annotations
24350 Annotations start with a newline character, two @samp{control-z}
24351 characters, and the name of the annotation. If there is no additional
24352 information associated with this annotation, the name of the annotation
24353 is followed immediately by a newline. If there is additional
24354 information, the name of the annotation is followed by a space, the
24355 additional information, and a newline. The additional information
24356 cannot contain newline characters.
24358 Any output not beginning with a newline and two @samp{control-z}
24359 characters denotes literal output from @value{GDBN}. Currently there is
24360 no need for @value{GDBN} to output a newline followed by two
24361 @samp{control-z} characters, but if there was such a need, the
24362 annotations could be extended with an @samp{escape} annotation which
24363 means those three characters as output.
24365 The annotation @var{level}, which is specified using the
24366 @option{--annotate} command line option (@pxref{Mode Options}), controls
24367 how much information @value{GDBN} prints together with its prompt,
24368 values of expressions, source lines, and other types of output. Level 0
24369 is for no annotations, level 1 is for use when @value{GDBN} is run as a
24370 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
24371 for programs that control @value{GDBN}, and level 2 annotations have
24372 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
24373 Interface, annotate, GDB's Obsolete Annotations}).
24376 @kindex set annotate
24377 @item set annotate @var{level}
24378 The @value{GDBN} command @code{set annotate} sets the level of
24379 annotations to the specified @var{level}.
24381 @item show annotate
24382 @kindex show annotate
24383 Show the current annotation level.
24386 This chapter describes level 3 annotations.
24388 A simple example of starting up @value{GDBN} with annotations is:
24391 $ @kbd{gdb --annotate=3}
24393 Copyright 2003 Free Software Foundation, Inc.
24394 GDB is free software, covered by the GNU General Public License,
24395 and you are welcome to change it and/or distribute copies of it
24396 under certain conditions.
24397 Type "show copying" to see the conditions.
24398 There is absolutely no warranty for GDB. Type "show warranty"
24400 This GDB was configured as "i386-pc-linux-gnu"
24411 Here @samp{quit} is input to @value{GDBN}; the rest is output from
24412 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
24413 denotes a @samp{control-z} character) are annotations; the rest is
24414 output from @value{GDBN}.
24416 @node Server Prefix
24417 @section The Server Prefix
24418 @cindex server prefix
24420 If you prefix a command with @samp{server } then it will not affect
24421 the command history, nor will it affect @value{GDBN}'s notion of which
24422 command to repeat if @key{RET} is pressed on a line by itself. This
24423 means that commands can be run behind a user's back by a front-end in
24424 a transparent manner.
24426 The server prefix does not affect the recording of values into the value
24427 history; to print a value without recording it into the value history,
24428 use the @code{output} command instead of the @code{print} command.
24431 @section Annotation for @value{GDBN} Input
24433 @cindex annotations for prompts
24434 When @value{GDBN} prompts for input, it annotates this fact so it is possible
24435 to know when to send output, when the output from a given command is
24438 Different kinds of input each have a different @dfn{input type}. Each
24439 input type has three annotations: a @code{pre-} annotation, which
24440 denotes the beginning of any prompt which is being output, a plain
24441 annotation, which denotes the end of the prompt, and then a @code{post-}
24442 annotation which denotes the end of any echo which may (or may not) be
24443 associated with the input. For example, the @code{prompt} input type
24444 features the following annotations:
24452 The input types are
24455 @findex pre-prompt annotation
24456 @findex prompt annotation
24457 @findex post-prompt annotation
24459 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
24461 @findex pre-commands annotation
24462 @findex commands annotation
24463 @findex post-commands annotation
24465 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
24466 command. The annotations are repeated for each command which is input.
24468 @findex pre-overload-choice annotation
24469 @findex overload-choice annotation
24470 @findex post-overload-choice annotation
24471 @item overload-choice
24472 When @value{GDBN} wants the user to select between various overloaded functions.
24474 @findex pre-query annotation
24475 @findex query annotation
24476 @findex post-query annotation
24478 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
24480 @findex pre-prompt-for-continue annotation
24481 @findex prompt-for-continue annotation
24482 @findex post-prompt-for-continue annotation
24483 @item prompt-for-continue
24484 When @value{GDBN} is asking the user to press return to continue. Note: Don't
24485 expect this to work well; instead use @code{set height 0} to disable
24486 prompting. This is because the counting of lines is buggy in the
24487 presence of annotations.
24492 @cindex annotations for errors, warnings and interrupts
24494 @findex quit annotation
24499 This annotation occurs right before @value{GDBN} responds to an interrupt.
24501 @findex error annotation
24506 This annotation occurs right before @value{GDBN} responds to an error.
24508 Quit and error annotations indicate that any annotations which @value{GDBN} was
24509 in the middle of may end abruptly. For example, if a
24510 @code{value-history-begin} annotation is followed by a @code{error}, one
24511 cannot expect to receive the matching @code{value-history-end}. One
24512 cannot expect not to receive it either, however; an error annotation
24513 does not necessarily mean that @value{GDBN} is immediately returning all the way
24516 @findex error-begin annotation
24517 A quit or error annotation may be preceded by
24523 Any output between that and the quit or error annotation is the error
24526 Warning messages are not yet annotated.
24527 @c If we want to change that, need to fix warning(), type_error(),
24528 @c range_error(), and possibly other places.
24531 @section Invalidation Notices
24533 @cindex annotations for invalidation messages
24534 The following annotations say that certain pieces of state may have
24538 @findex frames-invalid annotation
24539 @item ^Z^Zframes-invalid
24541 The frames (for example, output from the @code{backtrace} command) may
24544 @findex breakpoints-invalid annotation
24545 @item ^Z^Zbreakpoints-invalid
24547 The breakpoints may have changed. For example, the user just added or
24548 deleted a breakpoint.
24551 @node Annotations for Running
24552 @section Running the Program
24553 @cindex annotations for running programs
24555 @findex starting annotation
24556 @findex stopping annotation
24557 When the program starts executing due to a @value{GDBN} command such as
24558 @code{step} or @code{continue},
24564 is output. When the program stops,
24570 is output. Before the @code{stopped} annotation, a variety of
24571 annotations describe how the program stopped.
24574 @findex exited annotation
24575 @item ^Z^Zexited @var{exit-status}
24576 The program exited, and @var{exit-status} is the exit status (zero for
24577 successful exit, otherwise nonzero).
24579 @findex signalled annotation
24580 @findex signal-name annotation
24581 @findex signal-name-end annotation
24582 @findex signal-string annotation
24583 @findex signal-string-end annotation
24584 @item ^Z^Zsignalled
24585 The program exited with a signal. After the @code{^Z^Zsignalled}, the
24586 annotation continues:
24592 ^Z^Zsignal-name-end
24596 ^Z^Zsignal-string-end
24601 where @var{name} is the name of the signal, such as @code{SIGILL} or
24602 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
24603 as @code{Illegal Instruction} or @code{Segmentation fault}.
24604 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
24605 user's benefit and have no particular format.
24607 @findex signal annotation
24609 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
24610 just saying that the program received the signal, not that it was
24611 terminated with it.
24613 @findex breakpoint annotation
24614 @item ^Z^Zbreakpoint @var{number}
24615 The program hit breakpoint number @var{number}.
24617 @findex watchpoint annotation
24618 @item ^Z^Zwatchpoint @var{number}
24619 The program hit watchpoint number @var{number}.
24622 @node Source Annotations
24623 @section Displaying Source
24624 @cindex annotations for source display
24626 @findex source annotation
24627 The following annotation is used instead of displaying source code:
24630 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
24633 where @var{filename} is an absolute file name indicating which source
24634 file, @var{line} is the line number within that file (where 1 is the
24635 first line in the file), @var{character} is the character position
24636 within the file (where 0 is the first character in the file) (for most
24637 debug formats this will necessarily point to the beginning of a line),
24638 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
24639 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
24640 @var{addr} is the address in the target program associated with the
24641 source which is being displayed. @var{addr} is in the form @samp{0x}
24642 followed by one or more lowercase hex digits (note that this does not
24643 depend on the language).
24646 @chapter Reporting Bugs in @value{GDBN}
24647 @cindex bugs in @value{GDBN}
24648 @cindex reporting bugs in @value{GDBN}
24650 Your bug reports play an essential role in making @value{GDBN} reliable.
24652 Reporting a bug may help you by bringing a solution to your problem, or it
24653 may not. But in any case the principal function of a bug report is to help
24654 the entire community by making the next version of @value{GDBN} work better. Bug
24655 reports are your contribution to the maintenance of @value{GDBN}.
24657 In order for a bug report to serve its purpose, you must include the
24658 information that enables us to fix the bug.
24661 * Bug Criteria:: Have you found a bug?
24662 * Bug Reporting:: How to report bugs
24666 @section Have You Found a Bug?
24667 @cindex bug criteria
24669 If you are not sure whether you have found a bug, here are some guidelines:
24672 @cindex fatal signal
24673 @cindex debugger crash
24674 @cindex crash of debugger
24676 If the debugger gets a fatal signal, for any input whatever, that is a
24677 @value{GDBN} bug. Reliable debuggers never crash.
24679 @cindex error on valid input
24681 If @value{GDBN} produces an error message for valid input, that is a
24682 bug. (Note that if you're cross debugging, the problem may also be
24683 somewhere in the connection to the target.)
24685 @cindex invalid input
24687 If @value{GDBN} does not produce an error message for invalid input,
24688 that is a bug. However, you should note that your idea of
24689 ``invalid input'' might be our idea of ``an extension'' or ``support
24690 for traditional practice''.
24693 If you are an experienced user of debugging tools, your suggestions
24694 for improvement of @value{GDBN} are welcome in any case.
24697 @node Bug Reporting
24698 @section How to Report Bugs
24699 @cindex bug reports
24700 @cindex @value{GDBN} bugs, reporting
24702 A number of companies and individuals offer support for @sc{gnu} products.
24703 If you obtained @value{GDBN} from a support organization, we recommend you
24704 contact that organization first.
24706 You can find contact information for many support companies and
24707 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
24709 @c should add a web page ref...
24712 @ifset BUGURL_DEFAULT
24713 In any event, we also recommend that you submit bug reports for
24714 @value{GDBN}. The preferred method is to submit them directly using
24715 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
24716 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
24719 @strong{Do not send bug reports to @samp{info-gdb}, or to
24720 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
24721 not want to receive bug reports. Those that do have arranged to receive
24724 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
24725 serves as a repeater. The mailing list and the newsgroup carry exactly
24726 the same messages. Often people think of posting bug reports to the
24727 newsgroup instead of mailing them. This appears to work, but it has one
24728 problem which can be crucial: a newsgroup posting often lacks a mail
24729 path back to the sender. Thus, if we need to ask for more information,
24730 we may be unable to reach you. For this reason, it is better to send
24731 bug reports to the mailing list.
24733 @ifclear BUGURL_DEFAULT
24734 In any event, we also recommend that you submit bug reports for
24735 @value{GDBN} to @value{BUGURL}.
24739 The fundamental principle of reporting bugs usefully is this:
24740 @strong{report all the facts}. If you are not sure whether to state a
24741 fact or leave it out, state it!
24743 Often people omit facts because they think they know what causes the
24744 problem and assume that some details do not matter. Thus, you might
24745 assume that the name of the variable you use in an example does not matter.
24746 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
24747 stray memory reference which happens to fetch from the location where that
24748 name is stored in memory; perhaps, if the name were different, the contents
24749 of that location would fool the debugger into doing the right thing despite
24750 the bug. Play it safe and give a specific, complete example. That is the
24751 easiest thing for you to do, and the most helpful.
24753 Keep in mind that the purpose of a bug report is to enable us to fix the
24754 bug. It may be that the bug has been reported previously, but neither
24755 you nor we can know that unless your bug report is complete and
24758 Sometimes people give a few sketchy facts and ask, ``Does this ring a
24759 bell?'' Those bug reports are useless, and we urge everyone to
24760 @emph{refuse to respond to them} except to chide the sender to report
24763 To enable us to fix the bug, you should include all these things:
24767 The version of @value{GDBN}. @value{GDBN} announces it if you start
24768 with no arguments; you can also print it at any time using @code{show
24771 Without this, we will not know whether there is any point in looking for
24772 the bug in the current version of @value{GDBN}.
24775 The type of machine you are using, and the operating system name and
24779 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
24780 ``@value{GCC}--2.8.1''.
24783 What compiler (and its version) was used to compile the program you are
24784 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
24785 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
24786 to get this information; for other compilers, see the documentation for
24790 The command arguments you gave the compiler to compile your example and
24791 observe the bug. For example, did you use @samp{-O}? To guarantee
24792 you will not omit something important, list them all. A copy of the
24793 Makefile (or the output from make) is sufficient.
24795 If we were to try to guess the arguments, we would probably guess wrong
24796 and then we might not encounter the bug.
24799 A complete input script, and all necessary source files, that will
24803 A description of what behavior you observe that you believe is
24804 incorrect. For example, ``It gets a fatal signal.''
24806 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
24807 will certainly notice it. But if the bug is incorrect output, we might
24808 not notice unless it is glaringly wrong. You might as well not give us
24809 a chance to make a mistake.
24811 Even if the problem you experience is a fatal signal, you should still
24812 say so explicitly. Suppose something strange is going on, such as, your
24813 copy of @value{GDBN} is out of synch, or you have encountered a bug in
24814 the C library on your system. (This has happened!) Your copy might
24815 crash and ours would not. If you told us to expect a crash, then when
24816 ours fails to crash, we would know that the bug was not happening for
24817 us. If you had not told us to expect a crash, then we would not be able
24818 to draw any conclusion from our observations.
24821 @cindex recording a session script
24822 To collect all this information, you can use a session recording program
24823 such as @command{script}, which is available on many Unix systems.
24824 Just run your @value{GDBN} session inside @command{script} and then
24825 include the @file{typescript} file with your bug report.
24827 Another way to record a @value{GDBN} session is to run @value{GDBN}
24828 inside Emacs and then save the entire buffer to a file.
24831 If you wish to suggest changes to the @value{GDBN} source, send us context
24832 diffs. If you even discuss something in the @value{GDBN} source, refer to
24833 it by context, not by line number.
24835 The line numbers in our development sources will not match those in your
24836 sources. Your line numbers would convey no useful information to us.
24840 Here are some things that are not necessary:
24844 A description of the envelope of the bug.
24846 Often people who encounter a bug spend a lot of time investigating
24847 which changes to the input file will make the bug go away and which
24848 changes will not affect it.
24850 This is often time consuming and not very useful, because the way we
24851 will find the bug is by running a single example under the debugger
24852 with breakpoints, not by pure deduction from a series of examples.
24853 We recommend that you save your time for something else.
24855 Of course, if you can find a simpler example to report @emph{instead}
24856 of the original one, that is a convenience for us. Errors in the
24857 output will be easier to spot, running under the debugger will take
24858 less time, and so on.
24860 However, simplification is not vital; if you do not want to do this,
24861 report the bug anyway and send us the entire test case you used.
24864 A patch for the bug.
24866 A patch for the bug does help us if it is a good one. But do not omit
24867 the necessary information, such as the test case, on the assumption that
24868 a patch is all we need. We might see problems with your patch and decide
24869 to fix the problem another way, or we might not understand it at all.
24871 Sometimes with a program as complicated as @value{GDBN} it is very hard to
24872 construct an example that will make the program follow a certain path
24873 through the code. If you do not send us the example, we will not be able
24874 to construct one, so we will not be able to verify that the bug is fixed.
24876 And if we cannot understand what bug you are trying to fix, or why your
24877 patch should be an improvement, we will not install it. A test case will
24878 help us to understand.
24881 A guess about what the bug is or what it depends on.
24883 Such guesses are usually wrong. Even we cannot guess right about such
24884 things without first using the debugger to find the facts.
24887 @c The readline documentation is distributed with the readline code
24888 @c and consists of the two following files:
24890 @c inc-hist.texinfo
24891 @c Use -I with makeinfo to point to the appropriate directory,
24892 @c environment var TEXINPUTS with TeX.
24893 @include rluser.texi
24894 @include inc-hist.texinfo
24897 @node Formatting Documentation
24898 @appendix Formatting Documentation
24900 @cindex @value{GDBN} reference card
24901 @cindex reference card
24902 The @value{GDBN} 4 release includes an already-formatted reference card, ready
24903 for printing with PostScript or Ghostscript, in the @file{gdb}
24904 subdirectory of the main source directory@footnote{In
24905 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
24906 release.}. If you can use PostScript or Ghostscript with your printer,
24907 you can print the reference card immediately with @file{refcard.ps}.
24909 The release also includes the source for the reference card. You
24910 can format it, using @TeX{}, by typing:
24916 The @value{GDBN} reference card is designed to print in @dfn{landscape}
24917 mode on US ``letter'' size paper;
24918 that is, on a sheet 11 inches wide by 8.5 inches
24919 high. You will need to specify this form of printing as an option to
24920 your @sc{dvi} output program.
24922 @cindex documentation
24924 All the documentation for @value{GDBN} comes as part of the machine-readable
24925 distribution. The documentation is written in Texinfo format, which is
24926 a documentation system that uses a single source file to produce both
24927 on-line information and a printed manual. You can use one of the Info
24928 formatting commands to create the on-line version of the documentation
24929 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
24931 @value{GDBN} includes an already formatted copy of the on-line Info
24932 version of this manual in the @file{gdb} subdirectory. The main Info
24933 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
24934 subordinate files matching @samp{gdb.info*} in the same directory. If
24935 necessary, you can print out these files, or read them with any editor;
24936 but they are easier to read using the @code{info} subsystem in @sc{gnu}
24937 Emacs or the standalone @code{info} program, available as part of the
24938 @sc{gnu} Texinfo distribution.
24940 If you want to format these Info files yourself, you need one of the
24941 Info formatting programs, such as @code{texinfo-format-buffer} or
24944 If you have @code{makeinfo} installed, and are in the top level
24945 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
24946 version @value{GDBVN}), you can make the Info file by typing:
24953 If you want to typeset and print copies of this manual, you need @TeX{},
24954 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
24955 Texinfo definitions file.
24957 @TeX{} is a typesetting program; it does not print files directly, but
24958 produces output files called @sc{dvi} files. To print a typeset
24959 document, you need a program to print @sc{dvi} files. If your system
24960 has @TeX{} installed, chances are it has such a program. The precise
24961 command to use depends on your system; @kbd{lpr -d} is common; another
24962 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
24963 require a file name without any extension or a @samp{.dvi} extension.
24965 @TeX{} also requires a macro definitions file called
24966 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
24967 written in Texinfo format. On its own, @TeX{} cannot either read or
24968 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
24969 and is located in the @file{gdb-@var{version-number}/texinfo}
24972 If you have @TeX{} and a @sc{dvi} printer program installed, you can
24973 typeset and print this manual. First switch to the @file{gdb}
24974 subdirectory of the main source directory (for example, to
24975 @file{gdb-@value{GDBVN}/gdb}) and type:
24981 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
24983 @node Installing GDB
24984 @appendix Installing @value{GDBN}
24985 @cindex installation
24988 * Requirements:: Requirements for building @value{GDBN}
24989 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
24990 * Separate Objdir:: Compiling @value{GDBN} in another directory
24991 * Config Names:: Specifying names for hosts and targets
24992 * Configure Options:: Summary of options for configure
24993 * System-wide configuration:: Having a system-wide init file
24997 @section Requirements for Building @value{GDBN}
24998 @cindex building @value{GDBN}, requirements for
25000 Building @value{GDBN} requires various tools and packages to be available.
25001 Other packages will be used only if they are found.
25003 @heading Tools/Packages Necessary for Building @value{GDBN}
25005 @item ISO C90 compiler
25006 @value{GDBN} is written in ISO C90. It should be buildable with any
25007 working C90 compiler, e.g.@: GCC.
25011 @heading Tools/Packages Optional for Building @value{GDBN}
25015 @value{GDBN} can use the Expat XML parsing library. This library may be
25016 included with your operating system distribution; if it is not, you
25017 can get the latest version from @url{http://expat.sourceforge.net}.
25018 The @file{configure} script will search for this library in several
25019 standard locations; if it is installed in an unusual path, you can
25020 use the @option{--with-libexpat-prefix} option to specify its location.
25026 Remote protocol memory maps (@pxref{Memory Map Format})
25028 Target descriptions (@pxref{Target Descriptions})
25030 Remote shared library lists (@pxref{Library List Format})
25032 MS-Windows shared libraries (@pxref{Shared Libraries})
25036 @cindex compressed debug sections
25037 @value{GDBN} will use the @samp{zlib} library, if available, to read
25038 compressed debug sections. Some linkers, such as GNU gold, are capable
25039 of producing binaries with compressed debug sections. If @value{GDBN}
25040 is compiled with @samp{zlib}, it will be able to read the debug
25041 information in such binaries.
25043 The @samp{zlib} library is likely included with your operating system
25044 distribution; if it is not, you can get the latest version from
25045 @url{http://zlib.net}.
25048 @value{GDBN}'s features related to character sets (@pxref{Character
25049 Sets}) require a functioning @code{iconv} implementation. If you are
25050 on a GNU system, then this is provided by the GNU C Library. Some
25051 other systems also provide a working @code{iconv}.
25053 On systems with @code{iconv}, you can install GNU Libiconv. If you
25054 have previously installed Libiconv, you can use the
25055 @option{--with-libiconv-prefix} option to configure.
25057 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
25058 arrange to build Libiconv if a directory named @file{libiconv} appears
25059 in the top-most source directory. If Libiconv is built this way, and
25060 if the operating system does not provide a suitable @code{iconv}
25061 implementation, then the just-built library will automatically be used
25062 by @value{GDBN}. One easy way to set this up is to download GNU
25063 Libiconv, unpack it, and then rename the directory holding the
25064 Libiconv source code to @samp{libiconv}.
25067 @node Running Configure
25068 @section Invoking the @value{GDBN} @file{configure} Script
25069 @cindex configuring @value{GDBN}
25070 @value{GDBN} comes with a @file{configure} script that automates the process
25071 of preparing @value{GDBN} for installation; you can then use @code{make} to
25072 build the @code{gdb} program.
25074 @c irrelevant in info file; it's as current as the code it lives with.
25075 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
25076 look at the @file{README} file in the sources; we may have improved the
25077 installation procedures since publishing this manual.}
25080 The @value{GDBN} distribution includes all the source code you need for
25081 @value{GDBN} in a single directory, whose name is usually composed by
25082 appending the version number to @samp{gdb}.
25084 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
25085 @file{gdb-@value{GDBVN}} directory. That directory contains:
25088 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
25089 script for configuring @value{GDBN} and all its supporting libraries
25091 @item gdb-@value{GDBVN}/gdb
25092 the source specific to @value{GDBN} itself
25094 @item gdb-@value{GDBVN}/bfd
25095 source for the Binary File Descriptor library
25097 @item gdb-@value{GDBVN}/include
25098 @sc{gnu} include files
25100 @item gdb-@value{GDBVN}/libiberty
25101 source for the @samp{-liberty} free software library
25103 @item gdb-@value{GDBVN}/opcodes
25104 source for the library of opcode tables and disassemblers
25106 @item gdb-@value{GDBVN}/readline
25107 source for the @sc{gnu} command-line interface
25109 @item gdb-@value{GDBVN}/glob
25110 source for the @sc{gnu} filename pattern-matching subroutine
25112 @item gdb-@value{GDBVN}/mmalloc
25113 source for the @sc{gnu} memory-mapped malloc package
25116 The simplest way to configure and build @value{GDBN} is to run @file{configure}
25117 from the @file{gdb-@var{version-number}} source directory, which in
25118 this example is the @file{gdb-@value{GDBVN}} directory.
25120 First switch to the @file{gdb-@var{version-number}} source directory
25121 if you are not already in it; then run @file{configure}. Pass the
25122 identifier for the platform on which @value{GDBN} will run as an
25128 cd gdb-@value{GDBVN}
25129 ./configure @var{host}
25134 where @var{host} is an identifier such as @samp{sun4} or
25135 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
25136 (You can often leave off @var{host}; @file{configure} tries to guess the
25137 correct value by examining your system.)
25139 Running @samp{configure @var{host}} and then running @code{make} builds the
25140 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
25141 libraries, then @code{gdb} itself. The configured source files, and the
25142 binaries, are left in the corresponding source directories.
25145 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
25146 system does not recognize this automatically when you run a different
25147 shell, you may need to run @code{sh} on it explicitly:
25150 sh configure @var{host}
25153 If you run @file{configure} from a directory that contains source
25154 directories for multiple libraries or programs, such as the
25155 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
25157 creates configuration files for every directory level underneath (unless
25158 you tell it not to, with the @samp{--norecursion} option).
25160 You should run the @file{configure} script from the top directory in the
25161 source tree, the @file{gdb-@var{version-number}} directory. If you run
25162 @file{configure} from one of the subdirectories, you will configure only
25163 that subdirectory. That is usually not what you want. In particular,
25164 if you run the first @file{configure} from the @file{gdb} subdirectory
25165 of the @file{gdb-@var{version-number}} directory, you will omit the
25166 configuration of @file{bfd}, @file{readline}, and other sibling
25167 directories of the @file{gdb} subdirectory. This leads to build errors
25168 about missing include files such as @file{bfd/bfd.h}.
25170 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
25171 However, you should make sure that the shell on your path (named by
25172 the @samp{SHELL} environment variable) is publicly readable. Remember
25173 that @value{GDBN} uses the shell to start your program---some systems refuse to
25174 let @value{GDBN} debug child processes whose programs are not readable.
25176 @node Separate Objdir
25177 @section Compiling @value{GDBN} in Another Directory
25179 If you want to run @value{GDBN} versions for several host or target machines,
25180 you need a different @code{gdb} compiled for each combination of
25181 host and target. @file{configure} is designed to make this easy by
25182 allowing you to generate each configuration in a separate subdirectory,
25183 rather than in the source directory. If your @code{make} program
25184 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
25185 @code{make} in each of these directories builds the @code{gdb}
25186 program specified there.
25188 To build @code{gdb} in a separate directory, run @file{configure}
25189 with the @samp{--srcdir} option to specify where to find the source.
25190 (You also need to specify a path to find @file{configure}
25191 itself from your working directory. If the path to @file{configure}
25192 would be the same as the argument to @samp{--srcdir}, you can leave out
25193 the @samp{--srcdir} option; it is assumed.)
25195 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
25196 separate directory for a Sun 4 like this:
25200 cd gdb-@value{GDBVN}
25203 ../gdb-@value{GDBVN}/configure sun4
25208 When @file{configure} builds a configuration using a remote source
25209 directory, it creates a tree for the binaries with the same structure
25210 (and using the same names) as the tree under the source directory. In
25211 the example, you'd find the Sun 4 library @file{libiberty.a} in the
25212 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
25213 @file{gdb-sun4/gdb}.
25215 Make sure that your path to the @file{configure} script has just one
25216 instance of @file{gdb} in it. If your path to @file{configure} looks
25217 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
25218 one subdirectory of @value{GDBN}, not the whole package. This leads to
25219 build errors about missing include files such as @file{bfd/bfd.h}.
25221 One popular reason to build several @value{GDBN} configurations in separate
25222 directories is to configure @value{GDBN} for cross-compiling (where
25223 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
25224 programs that run on another machine---the @dfn{target}).
25225 You specify a cross-debugging target by
25226 giving the @samp{--target=@var{target}} option to @file{configure}.
25228 When you run @code{make} to build a program or library, you must run
25229 it in a configured directory---whatever directory you were in when you
25230 called @file{configure} (or one of its subdirectories).
25232 The @code{Makefile} that @file{configure} generates in each source
25233 directory also runs recursively. If you type @code{make} in a source
25234 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
25235 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
25236 will build all the required libraries, and then build GDB.
25238 When you have multiple hosts or targets configured in separate
25239 directories, you can run @code{make} on them in parallel (for example,
25240 if they are NFS-mounted on each of the hosts); they will not interfere
25244 @section Specifying Names for Hosts and Targets
25246 The specifications used for hosts and targets in the @file{configure}
25247 script are based on a three-part naming scheme, but some short predefined
25248 aliases are also supported. The full naming scheme encodes three pieces
25249 of information in the following pattern:
25252 @var{architecture}-@var{vendor}-@var{os}
25255 For example, you can use the alias @code{sun4} as a @var{host} argument,
25256 or as the value for @var{target} in a @code{--target=@var{target}}
25257 option. The equivalent full name is @samp{sparc-sun-sunos4}.
25259 The @file{configure} script accompanying @value{GDBN} does not provide
25260 any query facility to list all supported host and target names or
25261 aliases. @file{configure} calls the Bourne shell script
25262 @code{config.sub} to map abbreviations to full names; you can read the
25263 script, if you wish, or you can use it to test your guesses on
25264 abbreviations---for example:
25267 % sh config.sub i386-linux
25269 % sh config.sub alpha-linux
25270 alpha-unknown-linux-gnu
25271 % sh config.sub hp9k700
25273 % sh config.sub sun4
25274 sparc-sun-sunos4.1.1
25275 % sh config.sub sun3
25276 m68k-sun-sunos4.1.1
25277 % sh config.sub i986v
25278 Invalid configuration `i986v': machine `i986v' not recognized
25282 @code{config.sub} is also distributed in the @value{GDBN} source
25283 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
25285 @node Configure Options
25286 @section @file{configure} Options
25288 Here is a summary of the @file{configure} options and arguments that
25289 are most often useful for building @value{GDBN}. @file{configure} also has
25290 several other options not listed here. @inforef{What Configure
25291 Does,,configure.info}, for a full explanation of @file{configure}.
25294 configure @r{[}--help@r{]}
25295 @r{[}--prefix=@var{dir}@r{]}
25296 @r{[}--exec-prefix=@var{dir}@r{]}
25297 @r{[}--srcdir=@var{dirname}@r{]}
25298 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
25299 @r{[}--target=@var{target}@r{]}
25304 You may introduce options with a single @samp{-} rather than
25305 @samp{--} if you prefer; but you may abbreviate option names if you use
25310 Display a quick summary of how to invoke @file{configure}.
25312 @item --prefix=@var{dir}
25313 Configure the source to install programs and files under directory
25316 @item --exec-prefix=@var{dir}
25317 Configure the source to install programs under directory
25320 @c avoid splitting the warning from the explanation:
25322 @item --srcdir=@var{dirname}
25323 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
25324 @code{make} that implements the @code{VPATH} feature.}@*
25325 Use this option to make configurations in directories separate from the
25326 @value{GDBN} source directories. Among other things, you can use this to
25327 build (or maintain) several configurations simultaneously, in separate
25328 directories. @file{configure} writes configuration-specific files in
25329 the current directory, but arranges for them to use the source in the
25330 directory @var{dirname}. @file{configure} creates directories under
25331 the working directory in parallel to the source directories below
25334 @item --norecursion
25335 Configure only the directory level where @file{configure} is executed; do not
25336 propagate configuration to subdirectories.
25338 @item --target=@var{target}
25339 Configure @value{GDBN} for cross-debugging programs running on the specified
25340 @var{target}. Without this option, @value{GDBN} is configured to debug
25341 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
25343 There is no convenient way to generate a list of all available targets.
25345 @item @var{host} @dots{}
25346 Configure @value{GDBN} to run on the specified @var{host}.
25348 There is no convenient way to generate a list of all available hosts.
25351 There are many other options available as well, but they are generally
25352 needed for special purposes only.
25354 @node System-wide configuration
25355 @section System-wide configuration and settings
25356 @cindex system-wide init file
25358 @value{GDBN} can be configured to have a system-wide init file;
25359 this file will be read and executed at startup (@pxref{Startup, , What
25360 @value{GDBN} does during startup}).
25362 Here is the corresponding configure option:
25365 @item --with-system-gdbinit=@var{file}
25366 Specify that the default location of the system-wide init file is
25370 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
25371 it may be subject to relocation. Two possible cases:
25375 If the default location of this init file contains @file{$prefix},
25376 it will be subject to relocation. Suppose that the configure options
25377 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
25378 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
25379 init file is looked for as @file{$install/etc/gdbinit} instead of
25380 @file{$prefix/etc/gdbinit}.
25383 By contrast, if the default location does not contain the prefix,
25384 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
25385 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
25386 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
25387 wherever @value{GDBN} is installed.
25390 @node Maintenance Commands
25391 @appendix Maintenance Commands
25392 @cindex maintenance commands
25393 @cindex internal commands
25395 In addition to commands intended for @value{GDBN} users, @value{GDBN}
25396 includes a number of commands intended for @value{GDBN} developers,
25397 that are not documented elsewhere in this manual. These commands are
25398 provided here for reference. (For commands that turn on debugging
25399 messages, see @ref{Debugging Output}.)
25402 @kindex maint agent
25403 @item maint agent @var{expression}
25404 Translate the given @var{expression} into remote agent bytecodes.
25405 This command is useful for debugging the Agent Expression mechanism
25406 (@pxref{Agent Expressions}).
25408 @kindex maint info breakpoints
25409 @item @anchor{maint info breakpoints}maint info breakpoints
25410 Using the same format as @samp{info breakpoints}, display both the
25411 breakpoints you've set explicitly, and those @value{GDBN} is using for
25412 internal purposes. Internal breakpoints are shown with negative
25413 breakpoint numbers. The type column identifies what kind of breakpoint
25418 Normal, explicitly set breakpoint.
25421 Normal, explicitly set watchpoint.
25424 Internal breakpoint, used to handle correctly stepping through
25425 @code{longjmp} calls.
25427 @item longjmp resume
25428 Internal breakpoint at the target of a @code{longjmp}.
25431 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
25434 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
25437 Shared library events.
25441 @kindex set displaced-stepping
25442 @kindex show displaced-stepping
25443 @cindex displaced stepping support
25444 @cindex out-of-line single-stepping
25445 @item set displaced-stepping
25446 @itemx show displaced-stepping
25447 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
25448 if the target supports it. Displaced stepping is a way to single-step
25449 over breakpoints without removing them from the inferior, by executing
25450 an out-of-line copy of the instruction that was originally at the
25451 breakpoint location. It is also known as out-of-line single-stepping.
25454 @item set displaced-stepping on
25455 If the target architecture supports it, @value{GDBN} will use
25456 displaced stepping to step over breakpoints.
25458 @item set displaced-stepping off
25459 @value{GDBN} will not use displaced stepping to step over breakpoints,
25460 even if such is supported by the target architecture.
25462 @cindex non-stop mode, and @samp{set displaced-stepping}
25463 @item set displaced-stepping auto
25464 This is the default mode. @value{GDBN} will use displaced stepping
25465 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
25466 architecture supports displaced stepping.
25469 @kindex maint check-symtabs
25470 @item maint check-symtabs
25471 Check the consistency of psymtabs and symtabs.
25473 @kindex maint cplus first_component
25474 @item maint cplus first_component @var{name}
25475 Print the first C@t{++} class/namespace component of @var{name}.
25477 @kindex maint cplus namespace
25478 @item maint cplus namespace
25479 Print the list of possible C@t{++} namespaces.
25481 @kindex maint demangle
25482 @item maint demangle @var{name}
25483 Demangle a C@t{++} or Objective-C mangled @var{name}.
25485 @kindex maint deprecate
25486 @kindex maint undeprecate
25487 @cindex deprecated commands
25488 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
25489 @itemx maint undeprecate @var{command}
25490 Deprecate or undeprecate the named @var{command}. Deprecated commands
25491 cause @value{GDBN} to issue a warning when you use them. The optional
25492 argument @var{replacement} says which newer command should be used in
25493 favor of the deprecated one; if it is given, @value{GDBN} will mention
25494 the replacement as part of the warning.
25496 @kindex maint dump-me
25497 @item maint dump-me
25498 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
25499 Cause a fatal signal in the debugger and force it to dump its core.
25500 This is supported only on systems which support aborting a program
25501 with the @code{SIGQUIT} signal.
25503 @kindex maint internal-error
25504 @kindex maint internal-warning
25505 @item maint internal-error @r{[}@var{message-text}@r{]}
25506 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
25507 Cause @value{GDBN} to call the internal function @code{internal_error}
25508 or @code{internal_warning} and hence behave as though an internal error
25509 or internal warning has been detected. In addition to reporting the
25510 internal problem, these functions give the user the opportunity to
25511 either quit @value{GDBN} or create a core file of the current
25512 @value{GDBN} session.
25514 These commands take an optional parameter @var{message-text} that is
25515 used as the text of the error or warning message.
25517 Here's an example of using @code{internal-error}:
25520 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
25521 @dots{}/maint.c:121: internal-error: testing, 1, 2
25522 A problem internal to GDB has been detected. Further
25523 debugging may prove unreliable.
25524 Quit this debugging session? (y or n) @kbd{n}
25525 Create a core file? (y or n) @kbd{n}
25529 @cindex @value{GDBN} internal error
25530 @cindex internal errors, control of @value{GDBN} behavior
25532 @kindex maint set internal-error
25533 @kindex maint show internal-error
25534 @kindex maint set internal-warning
25535 @kindex maint show internal-warning
25536 @item maint set internal-error @var{action} [ask|yes|no]
25537 @itemx maint show internal-error @var{action}
25538 @itemx maint set internal-warning @var{action} [ask|yes|no]
25539 @itemx maint show internal-warning @var{action}
25540 When @value{GDBN} reports an internal problem (error or warning) it
25541 gives the user the opportunity to both quit @value{GDBN} and create a
25542 core file of the current @value{GDBN} session. These commands let you
25543 override the default behaviour for each particular @var{action},
25544 described in the table below.
25548 You can specify that @value{GDBN} should always (yes) or never (no)
25549 quit. The default is to ask the user what to do.
25552 You can specify that @value{GDBN} should always (yes) or never (no)
25553 create a core file. The default is to ask the user what to do.
25556 @kindex maint packet
25557 @item maint packet @var{text}
25558 If @value{GDBN} is talking to an inferior via the serial protocol,
25559 then this command sends the string @var{text} to the inferior, and
25560 displays the response packet. @value{GDBN} supplies the initial
25561 @samp{$} character, the terminating @samp{#} character, and the
25564 @kindex maint print architecture
25565 @item maint print architecture @r{[}@var{file}@r{]}
25566 Print the entire architecture configuration. The optional argument
25567 @var{file} names the file where the output goes.
25569 @kindex maint print c-tdesc
25570 @item maint print c-tdesc
25571 Print the current target description (@pxref{Target Descriptions}) as
25572 a C source file. The created source file can be used in @value{GDBN}
25573 when an XML parser is not available to parse the description.
25575 @kindex maint print dummy-frames
25576 @item maint print dummy-frames
25577 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
25580 (@value{GDBP}) @kbd{b add}
25582 (@value{GDBP}) @kbd{print add(2,3)}
25583 Breakpoint 2, add (a=2, b=3) at @dots{}
25585 The program being debugged stopped while in a function called from GDB.
25587 (@value{GDBP}) @kbd{maint print dummy-frames}
25588 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
25589 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
25590 call_lo=0x01014000 call_hi=0x01014001
25594 Takes an optional file parameter.
25596 @kindex maint print registers
25597 @kindex maint print raw-registers
25598 @kindex maint print cooked-registers
25599 @kindex maint print register-groups
25600 @item maint print registers @r{[}@var{file}@r{]}
25601 @itemx maint print raw-registers @r{[}@var{file}@r{]}
25602 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
25603 @itemx maint print register-groups @r{[}@var{file}@r{]}
25604 Print @value{GDBN}'s internal register data structures.
25606 The command @code{maint print raw-registers} includes the contents of
25607 the raw register cache; the command @code{maint print cooked-registers}
25608 includes the (cooked) value of all registers; and the command
25609 @code{maint print register-groups} includes the groups that each
25610 register is a member of. @xref{Registers,, Registers, gdbint,
25611 @value{GDBN} Internals}.
25613 These commands take an optional parameter, a file name to which to
25614 write the information.
25616 @kindex maint print reggroups
25617 @item maint print reggroups @r{[}@var{file}@r{]}
25618 Print @value{GDBN}'s internal register group data structures. The
25619 optional argument @var{file} tells to what file to write the
25622 The register groups info looks like this:
25625 (@value{GDBP}) @kbd{maint print reggroups}
25638 This command forces @value{GDBN} to flush its internal register cache.
25640 @kindex maint print objfiles
25641 @cindex info for known object files
25642 @item maint print objfiles
25643 Print a dump of all known object files. For each object file, this
25644 command prints its name, address in memory, and all of its psymtabs
25647 @kindex maint print statistics
25648 @cindex bcache statistics
25649 @item maint print statistics
25650 This command prints, for each object file in the program, various data
25651 about that object file followed by the byte cache (@dfn{bcache})
25652 statistics for the object file. The objfile data includes the number
25653 of minimal, partial, full, and stabs symbols, the number of types
25654 defined by the objfile, the number of as yet unexpanded psym tables,
25655 the number of line tables and string tables, and the amount of memory
25656 used by the various tables. The bcache statistics include the counts,
25657 sizes, and counts of duplicates of all and unique objects, max,
25658 average, and median entry size, total memory used and its overhead and
25659 savings, and various measures of the hash table size and chain
25662 @kindex maint print target-stack
25663 @cindex target stack description
25664 @item maint print target-stack
25665 A @dfn{target} is an interface between the debugger and a particular
25666 kind of file or process. Targets can be stacked in @dfn{strata},
25667 so that more than one target can potentially respond to a request.
25668 In particular, memory accesses will walk down the stack of targets
25669 until they find a target that is interested in handling that particular
25672 This command prints a short description of each layer that was pushed on
25673 the @dfn{target stack}, starting from the top layer down to the bottom one.
25675 @kindex maint print type
25676 @cindex type chain of a data type
25677 @item maint print type @var{expr}
25678 Print the type chain for a type specified by @var{expr}. The argument
25679 can be either a type name or a symbol. If it is a symbol, the type of
25680 that symbol is described. The type chain produced by this command is
25681 a recursive definition of the data type as stored in @value{GDBN}'s
25682 data structures, including its flags and contained types.
25684 @kindex maint set dwarf2 max-cache-age
25685 @kindex maint show dwarf2 max-cache-age
25686 @item maint set dwarf2 max-cache-age
25687 @itemx maint show dwarf2 max-cache-age
25688 Control the DWARF 2 compilation unit cache.
25690 @cindex DWARF 2 compilation units cache
25691 In object files with inter-compilation-unit references, such as those
25692 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
25693 reader needs to frequently refer to previously read compilation units.
25694 This setting controls how long a compilation unit will remain in the
25695 cache if it is not referenced. A higher limit means that cached
25696 compilation units will be stored in memory longer, and more total
25697 memory will be used. Setting it to zero disables caching, which will
25698 slow down @value{GDBN} startup, but reduce memory consumption.
25700 @kindex maint set profile
25701 @kindex maint show profile
25702 @cindex profiling GDB
25703 @item maint set profile
25704 @itemx maint show profile
25705 Control profiling of @value{GDBN}.
25707 Profiling will be disabled until you use the @samp{maint set profile}
25708 command to enable it. When you enable profiling, the system will begin
25709 collecting timing and execution count data; when you disable profiling or
25710 exit @value{GDBN}, the results will be written to a log file. Remember that
25711 if you use profiling, @value{GDBN} will overwrite the profiling log file
25712 (often called @file{gmon.out}). If you have a record of important profiling
25713 data in a @file{gmon.out} file, be sure to move it to a safe location.
25715 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
25716 compiled with the @samp{-pg} compiler option.
25718 @kindex maint show-debug-regs
25719 @cindex x86 hardware debug registers
25720 @item maint show-debug-regs
25721 Control whether to show variables that mirror the x86 hardware debug
25722 registers. Use @code{ON} to enable, @code{OFF} to disable. If
25723 enabled, the debug registers values are shown when @value{GDBN} inserts or
25724 removes a hardware breakpoint or watchpoint, and when the inferior
25725 triggers a hardware-assisted breakpoint or watchpoint.
25727 @kindex maint space
25728 @cindex memory used by commands
25730 Control whether to display memory usage for each command. If set to a
25731 nonzero value, @value{GDBN} will display how much memory each command
25732 took, following the command's own output. This can also be requested
25733 by invoking @value{GDBN} with the @option{--statistics} command-line
25734 switch (@pxref{Mode Options}).
25737 @cindex time of command execution
25739 Control whether to display the execution time for each command. If
25740 set to a nonzero value, @value{GDBN} will display how much time it
25741 took to execute each command, following the command's own output.
25742 The time is not printed for the commands that run the target, since
25743 there's no mechanism currently to compute how much time was spend
25744 by @value{GDBN} and how much time was spend by the program been debugged.
25745 it's not possibly currently
25746 This can also be requested by invoking @value{GDBN} with the
25747 @option{--statistics} command-line switch (@pxref{Mode Options}).
25749 @kindex maint translate-address
25750 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
25751 Find the symbol stored at the location specified by the address
25752 @var{addr} and an optional section name @var{section}. If found,
25753 @value{GDBN} prints the name of the closest symbol and an offset from
25754 the symbol's location to the specified address. This is similar to
25755 the @code{info address} command (@pxref{Symbols}), except that this
25756 command also allows to find symbols in other sections.
25758 If section was not specified, the section in which the symbol was found
25759 is also printed. For dynamically linked executables, the name of
25760 executable or shared library containing the symbol is printed as well.
25764 The following command is useful for non-interactive invocations of
25765 @value{GDBN}, such as in the test suite.
25768 @item set watchdog @var{nsec}
25769 @kindex set watchdog
25770 @cindex watchdog timer
25771 @cindex timeout for commands
25772 Set the maximum number of seconds @value{GDBN} will wait for the
25773 target operation to finish. If this time expires, @value{GDBN}
25774 reports and error and the command is aborted.
25776 @item show watchdog
25777 Show the current setting of the target wait timeout.
25780 @node Remote Protocol
25781 @appendix @value{GDBN} Remote Serial Protocol
25786 * Stop Reply Packets::
25787 * General Query Packets::
25788 * Register Packet Format::
25789 * Tracepoint Packets::
25790 * Host I/O Packets::
25792 * Notification Packets::
25793 * Remote Non-Stop::
25794 * Packet Acknowledgment::
25796 * File-I/O Remote Protocol Extension::
25797 * Library List Format::
25798 * Memory Map Format::
25804 There may be occasions when you need to know something about the
25805 protocol---for example, if there is only one serial port to your target
25806 machine, you might want your program to do something special if it
25807 recognizes a packet meant for @value{GDBN}.
25809 In the examples below, @samp{->} and @samp{<-} are used to indicate
25810 transmitted and received data, respectively.
25812 @cindex protocol, @value{GDBN} remote serial
25813 @cindex serial protocol, @value{GDBN} remote
25814 @cindex remote serial protocol
25815 All @value{GDBN} commands and responses (other than acknowledgments
25816 and notifications, see @ref{Notification Packets}) are sent as a
25817 @var{packet}. A @var{packet} is introduced with the character
25818 @samp{$}, the actual @var{packet-data}, and the terminating character
25819 @samp{#} followed by a two-digit @var{checksum}:
25822 @code{$}@var{packet-data}@code{#}@var{checksum}
25826 @cindex checksum, for @value{GDBN} remote
25828 The two-digit @var{checksum} is computed as the modulo 256 sum of all
25829 characters between the leading @samp{$} and the trailing @samp{#} (an
25830 eight bit unsigned checksum).
25832 Implementors should note that prior to @value{GDBN} 5.0 the protocol
25833 specification also included an optional two-digit @var{sequence-id}:
25836 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
25839 @cindex sequence-id, for @value{GDBN} remote
25841 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
25842 has never output @var{sequence-id}s. Stubs that handle packets added
25843 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
25845 When either the host or the target machine receives a packet, the first
25846 response expected is an acknowledgment: either @samp{+} (to indicate
25847 the package was received correctly) or @samp{-} (to request
25851 -> @code{$}@var{packet-data}@code{#}@var{checksum}
25856 The @samp{+}/@samp{-} acknowledgments can be disabled
25857 once a connection is established.
25858 @xref{Packet Acknowledgment}, for details.
25860 The host (@value{GDBN}) sends @var{command}s, and the target (the
25861 debugging stub incorporated in your program) sends a @var{response}. In
25862 the case of step and continue @var{command}s, the response is only sent
25863 when the operation has completed, and the target has again stopped all
25864 threads in all attached processes. This is the default all-stop mode
25865 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
25866 execution mode; see @ref{Remote Non-Stop}, for details.
25868 @var{packet-data} consists of a sequence of characters with the
25869 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
25872 @cindex remote protocol, field separator
25873 Fields within the packet should be separated using @samp{,} @samp{;} or
25874 @samp{:}. Except where otherwise noted all numbers are represented in
25875 @sc{hex} with leading zeros suppressed.
25877 Implementors should note that prior to @value{GDBN} 5.0, the character
25878 @samp{:} could not appear as the third character in a packet (as it
25879 would potentially conflict with the @var{sequence-id}).
25881 @cindex remote protocol, binary data
25882 @anchor{Binary Data}
25883 Binary data in most packets is encoded either as two hexadecimal
25884 digits per byte of binary data. This allowed the traditional remote
25885 protocol to work over connections which were only seven-bit clean.
25886 Some packets designed more recently assume an eight-bit clean
25887 connection, and use a more efficient encoding to send and receive
25890 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
25891 as an escape character. Any escaped byte is transmitted as the escape
25892 character followed by the original character XORed with @code{0x20}.
25893 For example, the byte @code{0x7d} would be transmitted as the two
25894 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
25895 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
25896 @samp{@}}) must always be escaped. Responses sent by the stub
25897 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
25898 is not interpreted as the start of a run-length encoded sequence
25901 Response @var{data} can be run-length encoded to save space.
25902 Run-length encoding replaces runs of identical characters with one
25903 instance of the repeated character, followed by a @samp{*} and a
25904 repeat count. The repeat count is itself sent encoded, to avoid
25905 binary characters in @var{data}: a value of @var{n} is sent as
25906 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
25907 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
25908 code 32) for a repeat count of 3. (This is because run-length
25909 encoding starts to win for counts 3 or more.) Thus, for example,
25910 @samp{0* } is a run-length encoding of ``0000'': the space character
25911 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
25914 The printable characters @samp{#} and @samp{$} or with a numeric value
25915 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
25916 seven repeats (@samp{$}) can be expanded using a repeat count of only
25917 five (@samp{"}). For example, @samp{00000000} can be encoded as
25920 The error response returned for some packets includes a two character
25921 error number. That number is not well defined.
25923 @cindex empty response, for unsupported packets
25924 For any @var{command} not supported by the stub, an empty response
25925 (@samp{$#00}) should be returned. That way it is possible to extend the
25926 protocol. A newer @value{GDBN} can tell if a packet is supported based
25929 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
25930 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
25936 The following table provides a complete list of all currently defined
25937 @var{command}s and their corresponding response @var{data}.
25938 @xref{File-I/O Remote Protocol Extension}, for details about the File
25939 I/O extension of the remote protocol.
25941 Each packet's description has a template showing the packet's overall
25942 syntax, followed by an explanation of the packet's meaning. We
25943 include spaces in some of the templates for clarity; these are not
25944 part of the packet's syntax. No @value{GDBN} packet uses spaces to
25945 separate its components. For example, a template like @samp{foo
25946 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
25947 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
25948 @var{baz}. @value{GDBN} does not transmit a space character between the
25949 @samp{foo} and the @var{bar}, or between the @var{bar} and the
25952 @cindex @var{thread-id}, in remote protocol
25953 @anchor{thread-id syntax}
25954 Several packets and replies include a @var{thread-id} field to identify
25955 a thread. Normally these are positive numbers with a target-specific
25956 interpretation, formatted as big-endian hex strings. A @var{thread-id}
25957 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
25960 In addition, the remote protocol supports a multiprocess feature in
25961 which the @var{thread-id} syntax is extended to optionally include both
25962 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
25963 The @var{pid} (process) and @var{tid} (thread) components each have the
25964 format described above: a positive number with target-specific
25965 interpretation formatted as a big-endian hex string, literal @samp{-1}
25966 to indicate all processes or threads (respectively), or @samp{0} to
25967 indicate an arbitrary process or thread. Specifying just a process, as
25968 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
25969 error to specify all processes but a specific thread, such as
25970 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
25971 for those packets and replies explicitly documented to include a process
25972 ID, rather than a @var{thread-id}.
25974 The multiprocess @var{thread-id} syntax extensions are only used if both
25975 @value{GDBN} and the stub report support for the @samp{multiprocess}
25976 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
25979 Note that all packet forms beginning with an upper- or lower-case
25980 letter, other than those described here, are reserved for future use.
25982 Here are the packet descriptions.
25987 @cindex @samp{!} packet
25988 @anchor{extended mode}
25989 Enable extended mode. In extended mode, the remote server is made
25990 persistent. The @samp{R} packet is used to restart the program being
25996 The remote target both supports and has enabled extended mode.
26000 @cindex @samp{?} packet
26001 Indicate the reason the target halted. The reply is the same as for
26002 step and continue. This packet has a special interpretation when the
26003 target is in non-stop mode; see @ref{Remote Non-Stop}.
26006 @xref{Stop Reply Packets}, for the reply specifications.
26008 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
26009 @cindex @samp{A} packet
26010 Initialized @code{argv[]} array passed into program. @var{arglen}
26011 specifies the number of bytes in the hex encoded byte stream
26012 @var{arg}. See @code{gdbserver} for more details.
26017 The arguments were set.
26023 @cindex @samp{b} packet
26024 (Don't use this packet; its behavior is not well-defined.)
26025 Change the serial line speed to @var{baud}.
26027 JTC: @emph{When does the transport layer state change? When it's
26028 received, or after the ACK is transmitted. In either case, there are
26029 problems if the command or the acknowledgment packet is dropped.}
26031 Stan: @emph{If people really wanted to add something like this, and get
26032 it working for the first time, they ought to modify ser-unix.c to send
26033 some kind of out-of-band message to a specially-setup stub and have the
26034 switch happen "in between" packets, so that from remote protocol's point
26035 of view, nothing actually happened.}
26037 @item B @var{addr},@var{mode}
26038 @cindex @samp{B} packet
26039 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
26040 breakpoint at @var{addr}.
26042 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
26043 (@pxref{insert breakpoint or watchpoint packet}).
26046 @cindex @samp{bc} packet
26047 Backward continue. Execute the target system in reverse. No parameter.
26048 @xref{Reverse Execution}, for more information.
26051 @xref{Stop Reply Packets}, for the reply specifications.
26054 @cindex @samp{bs} packet
26055 Backward single step. Execute one instruction in reverse. No parameter.
26056 @xref{Reverse Execution}, for more information.
26059 @xref{Stop Reply Packets}, for the reply specifications.
26061 @item c @r{[}@var{addr}@r{]}
26062 @cindex @samp{c} packet
26063 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
26064 resume at current address.
26067 @xref{Stop Reply Packets}, for the reply specifications.
26069 @item C @var{sig}@r{[};@var{addr}@r{]}
26070 @cindex @samp{C} packet
26071 Continue with signal @var{sig} (hex signal number). If
26072 @samp{;@var{addr}} is omitted, resume at same address.
26075 @xref{Stop Reply Packets}, for the reply specifications.
26078 @cindex @samp{d} packet
26081 Don't use this packet; instead, define a general set packet
26082 (@pxref{General Query Packets}).
26086 @cindex @samp{D} packet
26087 The first form of the packet is used to detach @value{GDBN} from the
26088 remote system. It is sent to the remote target
26089 before @value{GDBN} disconnects via the @code{detach} command.
26091 The second form, including a process ID, is used when multiprocess
26092 protocol extensions are enabled (@pxref{multiprocess extensions}), to
26093 detach only a specific process. The @var{pid} is specified as a
26094 big-endian hex string.
26104 @item F @var{RC},@var{EE},@var{CF};@var{XX}
26105 @cindex @samp{F} packet
26106 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
26107 This is part of the File-I/O protocol extension. @xref{File-I/O
26108 Remote Protocol Extension}, for the specification.
26111 @anchor{read registers packet}
26112 @cindex @samp{g} packet
26113 Read general registers.
26117 @item @var{XX@dots{}}
26118 Each byte of register data is described by two hex digits. The bytes
26119 with the register are transmitted in target byte order. The size of
26120 each register and their position within the @samp{g} packet are
26121 determined by the @value{GDBN} internal gdbarch functions
26122 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
26123 specification of several standard @samp{g} packets is specified below.
26128 @item G @var{XX@dots{}}
26129 @cindex @samp{G} packet
26130 Write general registers. @xref{read registers packet}, for a
26131 description of the @var{XX@dots{}} data.
26141 @item H @var{c} @var{thread-id}
26142 @cindex @samp{H} packet
26143 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
26144 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
26145 should be @samp{c} for step and continue operations, @samp{g} for other
26146 operations. The thread designator @var{thread-id} has the format and
26147 interpretation described in @ref{thread-id syntax}.
26158 @c 'H': How restrictive (or permissive) is the thread model. If a
26159 @c thread is selected and stopped, are other threads allowed
26160 @c to continue to execute? As I mentioned above, I think the
26161 @c semantics of each command when a thread is selected must be
26162 @c described. For example:
26164 @c 'g': If the stub supports threads and a specific thread is
26165 @c selected, returns the register block from that thread;
26166 @c otherwise returns current registers.
26168 @c 'G' If the stub supports threads and a specific thread is
26169 @c selected, sets the registers of the register block of
26170 @c that thread; otherwise sets current registers.
26172 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
26173 @anchor{cycle step packet}
26174 @cindex @samp{i} packet
26175 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
26176 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
26177 step starting at that address.
26180 @cindex @samp{I} packet
26181 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
26185 @cindex @samp{k} packet
26188 FIXME: @emph{There is no description of how to operate when a specific
26189 thread context has been selected (i.e.@: does 'k' kill only that
26192 @item m @var{addr},@var{length}
26193 @cindex @samp{m} packet
26194 Read @var{length} bytes of memory starting at address @var{addr}.
26195 Note that @var{addr} may not be aligned to any particular boundary.
26197 The stub need not use any particular size or alignment when gathering
26198 data from memory for the response; even if @var{addr} is word-aligned
26199 and @var{length} is a multiple of the word size, the stub is free to
26200 use byte accesses, or not. For this reason, this packet may not be
26201 suitable for accessing memory-mapped I/O devices.
26202 @cindex alignment of remote memory accesses
26203 @cindex size of remote memory accesses
26204 @cindex memory, alignment and size of remote accesses
26208 @item @var{XX@dots{}}
26209 Memory contents; each byte is transmitted as a two-digit hexadecimal
26210 number. The reply may contain fewer bytes than requested if the
26211 server was able to read only part of the region of memory.
26216 @item M @var{addr},@var{length}:@var{XX@dots{}}
26217 @cindex @samp{M} packet
26218 Write @var{length} bytes of memory starting at address @var{addr}.
26219 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
26220 hexadecimal number.
26227 for an error (this includes the case where only part of the data was
26232 @cindex @samp{p} packet
26233 Read the value of register @var{n}; @var{n} is in hex.
26234 @xref{read registers packet}, for a description of how the returned
26235 register value is encoded.
26239 @item @var{XX@dots{}}
26240 the register's value
26244 Indicating an unrecognized @var{query}.
26247 @item P @var{n@dots{}}=@var{r@dots{}}
26248 @anchor{write register packet}
26249 @cindex @samp{P} packet
26250 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
26251 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
26252 digits for each byte in the register (target byte order).
26262 @item q @var{name} @var{params}@dots{}
26263 @itemx Q @var{name} @var{params}@dots{}
26264 @cindex @samp{q} packet
26265 @cindex @samp{Q} packet
26266 General query (@samp{q}) and set (@samp{Q}). These packets are
26267 described fully in @ref{General Query Packets}.
26270 @cindex @samp{r} packet
26271 Reset the entire system.
26273 Don't use this packet; use the @samp{R} packet instead.
26276 @cindex @samp{R} packet
26277 Restart the program being debugged. @var{XX}, while needed, is ignored.
26278 This packet is only available in extended mode (@pxref{extended mode}).
26280 The @samp{R} packet has no reply.
26282 @item s @r{[}@var{addr}@r{]}
26283 @cindex @samp{s} packet
26284 Single step. @var{addr} is the address at which to resume. If
26285 @var{addr} is omitted, resume at same address.
26288 @xref{Stop Reply Packets}, for the reply specifications.
26290 @item S @var{sig}@r{[};@var{addr}@r{]}
26291 @anchor{step with signal packet}
26292 @cindex @samp{S} packet
26293 Step with signal. This is analogous to the @samp{C} packet, but
26294 requests a single-step, rather than a normal resumption of execution.
26297 @xref{Stop Reply Packets}, for the reply specifications.
26299 @item t @var{addr}:@var{PP},@var{MM}
26300 @cindex @samp{t} packet
26301 Search backwards starting at address @var{addr} for a match with pattern
26302 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
26303 @var{addr} must be at least 3 digits.
26305 @item T @var{thread-id}
26306 @cindex @samp{T} packet
26307 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
26312 thread is still alive
26318 Packets starting with @samp{v} are identified by a multi-letter name,
26319 up to the first @samp{;} or @samp{?} (or the end of the packet).
26321 @item vAttach;@var{pid}
26322 @cindex @samp{vAttach} packet
26323 Attach to a new process with the specified process ID @var{pid}.
26324 The process ID is a
26325 hexadecimal integer identifying the process. In all-stop mode, all
26326 threads in the attached process are stopped; in non-stop mode, it may be
26327 attached without being stopped if that is supported by the target.
26329 @c In non-stop mode, on a successful vAttach, the stub should set the
26330 @c current thread to a thread of the newly-attached process. After
26331 @c attaching, GDB queries for the attached process's thread ID with qC.
26332 @c Also note that, from a user perspective, whether or not the
26333 @c target is stopped on attach in non-stop mode depends on whether you
26334 @c use the foreground or background version of the attach command, not
26335 @c on what vAttach does; GDB does the right thing with respect to either
26336 @c stopping or restarting threads.
26338 This packet is only available in extended mode (@pxref{extended mode}).
26344 @item @r{Any stop packet}
26345 for success in all-stop mode (@pxref{Stop Reply Packets})
26347 for success in non-stop mode (@pxref{Remote Non-Stop})
26350 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
26351 @cindex @samp{vCont} packet
26352 Resume the inferior, specifying different actions for each thread.
26353 If an action is specified with no @var{thread-id}, then it is applied to any
26354 threads that don't have a specific action specified; if no default action is
26355 specified then other threads should remain stopped in all-stop mode and
26356 in their current state in non-stop mode.
26357 Specifying multiple
26358 default actions is an error; specifying no actions is also an error.
26359 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
26361 Currently supported actions are:
26367 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
26371 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
26375 Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
26378 The optional argument @var{addr} normally associated with the
26379 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
26380 not supported in @samp{vCont}.
26382 The @samp{t} and @samp{T} actions are only relevant in non-stop mode
26383 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
26384 A stop reply should be generated for any affected thread not already stopped.
26385 When a thread is stopped by means of a @samp{t} action,
26386 the corresponding stop reply should indicate that the thread has stopped with
26387 signal @samp{0}, regardless of whether the target uses some other signal
26388 as an implementation detail.
26391 @xref{Stop Reply Packets}, for the reply specifications.
26394 @cindex @samp{vCont?} packet
26395 Request a list of actions supported by the @samp{vCont} packet.
26399 @item vCont@r{[};@var{action}@dots{}@r{]}
26400 The @samp{vCont} packet is supported. Each @var{action} is a supported
26401 command in the @samp{vCont} packet.
26403 The @samp{vCont} packet is not supported.
26406 @item vFile:@var{operation}:@var{parameter}@dots{}
26407 @cindex @samp{vFile} packet
26408 Perform a file operation on the target system. For details,
26409 see @ref{Host I/O Packets}.
26411 @item vFlashErase:@var{addr},@var{length}
26412 @cindex @samp{vFlashErase} packet
26413 Direct the stub to erase @var{length} bytes of flash starting at
26414 @var{addr}. The region may enclose any number of flash blocks, but
26415 its start and end must fall on block boundaries, as indicated by the
26416 flash block size appearing in the memory map (@pxref{Memory Map
26417 Format}). @value{GDBN} groups flash memory programming operations
26418 together, and sends a @samp{vFlashDone} request after each group; the
26419 stub is allowed to delay erase operation until the @samp{vFlashDone}
26420 packet is received.
26422 The stub must support @samp{vCont} if it reports support for
26423 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
26424 this case @samp{vCont} actions can be specified to apply to all threads
26425 in a process by using the @samp{p@var{pid}.-1} form of the
26436 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
26437 @cindex @samp{vFlashWrite} packet
26438 Direct the stub to write data to flash address @var{addr}. The data
26439 is passed in binary form using the same encoding as for the @samp{X}
26440 packet (@pxref{Binary Data}). The memory ranges specified by
26441 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
26442 not overlap, and must appear in order of increasing addresses
26443 (although @samp{vFlashErase} packets for higher addresses may already
26444 have been received; the ordering is guaranteed only between
26445 @samp{vFlashWrite} packets). If a packet writes to an address that was
26446 neither erased by a preceding @samp{vFlashErase} packet nor by some other
26447 target-specific method, the results are unpredictable.
26455 for vFlashWrite addressing non-flash memory
26461 @cindex @samp{vFlashDone} packet
26462 Indicate to the stub that flash programming operation is finished.
26463 The stub is permitted to delay or batch the effects of a group of
26464 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
26465 @samp{vFlashDone} packet is received. The contents of the affected
26466 regions of flash memory are unpredictable until the @samp{vFlashDone}
26467 request is completed.
26469 @item vKill;@var{pid}
26470 @cindex @samp{vKill} packet
26471 Kill the process with the specified process ID. @var{pid} is a
26472 hexadecimal integer identifying the process. This packet is used in
26473 preference to @samp{k} when multiprocess protocol extensions are
26474 supported; see @ref{multiprocess extensions}.
26484 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
26485 @cindex @samp{vRun} packet
26486 Run the program @var{filename}, passing it each @var{argument} on its
26487 command line. The file and arguments are hex-encoded strings. If
26488 @var{filename} is an empty string, the stub may use a default program
26489 (e.g.@: the last program run). The program is created in the stopped
26492 @c FIXME: What about non-stop mode?
26494 This packet is only available in extended mode (@pxref{extended mode}).
26500 @item @r{Any stop packet}
26501 for success (@pxref{Stop Reply Packets})
26505 @anchor{vStopped packet}
26506 @cindex @samp{vStopped} packet
26508 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
26509 reply and prompt for the stub to report another one.
26513 @item @r{Any stop packet}
26514 if there is another unreported stop event (@pxref{Stop Reply Packets})
26516 if there are no unreported stop events
26519 @item X @var{addr},@var{length}:@var{XX@dots{}}
26521 @cindex @samp{X} packet
26522 Write data to memory, where the data is transmitted in binary.
26523 @var{addr} is address, @var{length} is number of bytes,
26524 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
26534 @item z @var{type},@var{addr},@var{length}
26535 @itemx Z @var{type},@var{addr},@var{length}
26536 @anchor{insert breakpoint or watchpoint packet}
26537 @cindex @samp{z} packet
26538 @cindex @samp{Z} packets
26539 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
26540 watchpoint starting at address @var{address} and covering the next
26541 @var{length} bytes.
26543 Each breakpoint and watchpoint packet @var{type} is documented
26546 @emph{Implementation notes: A remote target shall return an empty string
26547 for an unrecognized breakpoint or watchpoint packet @var{type}. A
26548 remote target shall support either both or neither of a given
26549 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
26550 avoid potential problems with duplicate packets, the operations should
26551 be implemented in an idempotent way.}
26553 @item z0,@var{addr},@var{length}
26554 @itemx Z0,@var{addr},@var{length}
26555 @cindex @samp{z0} packet
26556 @cindex @samp{Z0} packet
26557 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
26558 @var{addr} of size @var{length}.
26560 A memory breakpoint is implemented by replacing the instruction at
26561 @var{addr} with a software breakpoint or trap instruction. The
26562 @var{length} is used by targets that indicates the size of the
26563 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
26564 @sc{mips} can insert either a 2 or 4 byte breakpoint).
26566 @emph{Implementation note: It is possible for a target to copy or move
26567 code that contains memory breakpoints (e.g., when implementing
26568 overlays). The behavior of this packet, in the presence of such a
26569 target, is not defined.}
26581 @item z1,@var{addr},@var{length}
26582 @itemx Z1,@var{addr},@var{length}
26583 @cindex @samp{z1} packet
26584 @cindex @samp{Z1} packet
26585 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
26586 address @var{addr} of size @var{length}.
26588 A hardware breakpoint is implemented using a mechanism that is not
26589 dependant on being able to modify the target's memory.
26591 @emph{Implementation note: A hardware breakpoint is not affected by code
26604 @item z2,@var{addr},@var{length}
26605 @itemx Z2,@var{addr},@var{length}
26606 @cindex @samp{z2} packet
26607 @cindex @samp{Z2} packet
26608 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
26620 @item z3,@var{addr},@var{length}
26621 @itemx Z3,@var{addr},@var{length}
26622 @cindex @samp{z3} packet
26623 @cindex @samp{Z3} packet
26624 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
26636 @item z4,@var{addr},@var{length}
26637 @itemx Z4,@var{addr},@var{length}
26638 @cindex @samp{z4} packet
26639 @cindex @samp{Z4} packet
26640 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
26654 @node Stop Reply Packets
26655 @section Stop Reply Packets
26656 @cindex stop reply packets
26658 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
26659 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
26660 receive any of the below as a reply. Except for @samp{?}
26661 and @samp{vStopped}, that reply is only returned
26662 when the target halts. In the below the exact meaning of @dfn{signal
26663 number} is defined by the header @file{include/gdb/signals.h} in the
26664 @value{GDBN} source code.
26666 As in the description of request packets, we include spaces in the
26667 reply templates for clarity; these are not part of the reply packet's
26668 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
26674 The program received signal number @var{AA} (a two-digit hexadecimal
26675 number). This is equivalent to a @samp{T} response with no
26676 @var{n}:@var{r} pairs.
26678 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
26679 @cindex @samp{T} packet reply
26680 The program received signal number @var{AA} (a two-digit hexadecimal
26681 number). This is equivalent to an @samp{S} response, except that the
26682 @samp{@var{n}:@var{r}} pairs can carry values of important registers
26683 and other information directly in the stop reply packet, reducing
26684 round-trip latency. Single-step and breakpoint traps are reported
26685 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
26689 If @var{n} is a hexadecimal number, it is a register number, and the
26690 corresponding @var{r} gives that register's value. @var{r} is a
26691 series of bytes in target byte order, with each byte given by a
26692 two-digit hex number.
26695 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
26696 the stopped thread, as specified in @ref{thread-id syntax}.
26699 If @var{n} is a recognized @dfn{stop reason}, it describes a more
26700 specific event that stopped the target. The currently defined stop
26701 reasons are listed below. @var{aa} should be @samp{05}, the trap
26702 signal. At most one stop reason should be present.
26705 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
26706 and go on to the next; this allows us to extend the protocol in the
26710 The currently defined stop reasons are:
26716 The packet indicates a watchpoint hit, and @var{r} is the data address, in
26719 @cindex shared library events, remote reply
26721 The packet indicates that the loaded libraries have changed.
26722 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
26723 list of loaded libraries. @var{r} is ignored.
26725 @cindex replay log events, remote reply
26727 The packet indicates that the target cannot continue replaying
26728 logged execution events, because it has reached the end (or the
26729 beginning when executing backward) of the log. The value of @var{r}
26730 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
26731 for more information.
26737 @itemx W @var{AA} ; process:@var{pid}
26738 The process exited, and @var{AA} is the exit status. This is only
26739 applicable to certain targets.
26741 The second form of the response, including the process ID of the exited
26742 process, can be used only when @value{GDBN} has reported support for
26743 multiprocess protocol extensions; see @ref{multiprocess extensions}.
26744 The @var{pid} is formatted as a big-endian hex string.
26747 @itemx X @var{AA} ; process:@var{pid}
26748 The process terminated with signal @var{AA}.
26750 The second form of the response, including the process ID of the
26751 terminated process, can be used only when @value{GDBN} has reported
26752 support for multiprocess protocol extensions; see @ref{multiprocess
26753 extensions}. The @var{pid} is formatted as a big-endian hex string.
26755 @item O @var{XX}@dots{}
26756 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
26757 written as the program's console output. This can happen at any time
26758 while the program is running and the debugger should continue to wait
26759 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
26761 @item F @var{call-id},@var{parameter}@dots{}
26762 @var{call-id} is the identifier which says which host system call should
26763 be called. This is just the name of the function. Translation into the
26764 correct system call is only applicable as it's defined in @value{GDBN}.
26765 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
26768 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
26769 this very system call.
26771 The target replies with this packet when it expects @value{GDBN} to
26772 call a host system call on behalf of the target. @value{GDBN} replies
26773 with an appropriate @samp{F} packet and keeps up waiting for the next
26774 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
26775 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
26776 Protocol Extension}, for more details.
26780 @node General Query Packets
26781 @section General Query Packets
26782 @cindex remote query requests
26784 Packets starting with @samp{q} are @dfn{general query packets};
26785 packets starting with @samp{Q} are @dfn{general set packets}. General
26786 query and set packets are a semi-unified form for retrieving and
26787 sending information to and from the stub.
26789 The initial letter of a query or set packet is followed by a name
26790 indicating what sort of thing the packet applies to. For example,
26791 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
26792 definitions with the stub. These packet names follow some
26797 The name must not contain commas, colons or semicolons.
26799 Most @value{GDBN} query and set packets have a leading upper case
26802 The names of custom vendor packets should use a company prefix, in
26803 lower case, followed by a period. For example, packets designed at
26804 the Acme Corporation might begin with @samp{qacme.foo} (for querying
26805 foos) or @samp{Qacme.bar} (for setting bars).
26808 The name of a query or set packet should be separated from any
26809 parameters by a @samp{:}; the parameters themselves should be
26810 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
26811 full packet name, and check for a separator or the end of the packet,
26812 in case two packet names share a common prefix. New packets should not begin
26813 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
26814 packets predate these conventions, and have arguments without any terminator
26815 for the packet name; we suspect they are in widespread use in places that
26816 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
26817 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
26820 Like the descriptions of the other packets, each description here
26821 has a template showing the packet's overall syntax, followed by an
26822 explanation of the packet's meaning. We include spaces in some of the
26823 templates for clarity; these are not part of the packet's syntax. No
26824 @value{GDBN} packet uses spaces to separate its components.
26826 Here are the currently defined query and set packets:
26831 @cindex current thread, remote request
26832 @cindex @samp{qC} packet
26833 Return the current thread ID.
26837 @item QC @var{thread-id}
26838 Where @var{thread-id} is a thread ID as documented in
26839 @ref{thread-id syntax}.
26840 @item @r{(anything else)}
26841 Any other reply implies the old thread ID.
26844 @item qCRC:@var{addr},@var{length}
26845 @cindex CRC of memory block, remote request
26846 @cindex @samp{qCRC} packet
26847 Compute the CRC checksum of a block of memory.
26851 An error (such as memory fault)
26852 @item C @var{crc32}
26853 The specified memory region's checksum is @var{crc32}.
26857 @itemx qsThreadInfo
26858 @cindex list active threads, remote request
26859 @cindex @samp{qfThreadInfo} packet
26860 @cindex @samp{qsThreadInfo} packet
26861 Obtain a list of all active thread IDs from the target (OS). Since there
26862 may be too many active threads to fit into one reply packet, this query
26863 works iteratively: it may require more than one query/reply sequence to
26864 obtain the entire list of threads. The first query of the sequence will
26865 be the @samp{qfThreadInfo} query; subsequent queries in the
26866 sequence will be the @samp{qsThreadInfo} query.
26868 NOTE: This packet replaces the @samp{qL} query (see below).
26872 @item m @var{thread-id}
26874 @item m @var{thread-id},@var{thread-id}@dots{}
26875 a comma-separated list of thread IDs
26877 (lower case letter @samp{L}) denotes end of list.
26880 In response to each query, the target will reply with a list of one or
26881 more thread IDs, separated by commas.
26882 @value{GDBN} will respond to each reply with a request for more thread
26883 ids (using the @samp{qs} form of the query), until the target responds
26884 with @samp{l} (lower-case el, for @dfn{last}).
26885 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
26888 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
26889 @cindex get thread-local storage address, remote request
26890 @cindex @samp{qGetTLSAddr} packet
26891 Fetch the address associated with thread local storage specified
26892 by @var{thread-id}, @var{offset}, and @var{lm}.
26894 @var{thread-id} is the thread ID associated with the
26895 thread for which to fetch the TLS address. @xref{thread-id syntax}.
26897 @var{offset} is the (big endian, hex encoded) offset associated with the
26898 thread local variable. (This offset is obtained from the debug
26899 information associated with the variable.)
26901 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
26902 the load module associated with the thread local storage. For example,
26903 a @sc{gnu}/Linux system will pass the link map address of the shared
26904 object associated with the thread local storage under consideration.
26905 Other operating environments may choose to represent the load module
26906 differently, so the precise meaning of this parameter will vary.
26910 @item @var{XX}@dots{}
26911 Hex encoded (big endian) bytes representing the address of the thread
26912 local storage requested.
26915 An error occurred. @var{nn} are hex digits.
26918 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
26921 @item qL @var{startflag} @var{threadcount} @var{nextthread}
26922 Obtain thread information from RTOS. Where: @var{startflag} (one hex
26923 digit) is one to indicate the first query and zero to indicate a
26924 subsequent query; @var{threadcount} (two hex digits) is the maximum
26925 number of threads the response packet can contain; and @var{nextthread}
26926 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
26927 returned in the response as @var{argthread}.
26929 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
26933 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
26934 Where: @var{count} (two hex digits) is the number of threads being
26935 returned; @var{done} (one hex digit) is zero to indicate more threads
26936 and one indicates no further threads; @var{argthreadid} (eight hex
26937 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
26938 is a sequence of thread IDs from the target. @var{threadid} (eight hex
26939 digits). See @code{remote.c:parse_threadlist_response()}.
26943 @cindex section offsets, remote request
26944 @cindex @samp{qOffsets} packet
26945 Get section offsets that the target used when relocating the downloaded
26950 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
26951 Relocate the @code{Text} section by @var{xxx} from its original address.
26952 Relocate the @code{Data} section by @var{yyy} from its original address.
26953 If the object file format provides segment information (e.g.@: @sc{elf}
26954 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
26955 segments by the supplied offsets.
26957 @emph{Note: while a @code{Bss} offset may be included in the response,
26958 @value{GDBN} ignores this and instead applies the @code{Data} offset
26959 to the @code{Bss} section.}
26961 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
26962 Relocate the first segment of the object file, which conventionally
26963 contains program code, to a starting address of @var{xxx}. If
26964 @samp{DataSeg} is specified, relocate the second segment, which
26965 conventionally contains modifiable data, to a starting address of
26966 @var{yyy}. @value{GDBN} will report an error if the object file
26967 does not contain segment information, or does not contain at least
26968 as many segments as mentioned in the reply. Extra segments are
26969 kept at fixed offsets relative to the last relocated segment.
26972 @item qP @var{mode} @var{thread-id}
26973 @cindex thread information, remote request
26974 @cindex @samp{qP} packet
26975 Returns information on @var{thread-id}. Where: @var{mode} is a hex
26976 encoded 32 bit mode; @var{thread-id} is a thread ID
26977 (@pxref{thread-id syntax}).
26979 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
26982 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
26986 @cindex non-stop mode, remote request
26987 @cindex @samp{QNonStop} packet
26989 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
26990 @xref{Remote Non-Stop}, for more information.
26995 The request succeeded.
26998 An error occurred. @var{nn} are hex digits.
27001 An empty reply indicates that @samp{QNonStop} is not supported by
27005 This packet is not probed by default; the remote stub must request it,
27006 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27007 Use of this packet is controlled by the @code{set non-stop} command;
27008 @pxref{Non-Stop Mode}.
27010 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
27011 @cindex pass signals to inferior, remote request
27012 @cindex @samp{QPassSignals} packet
27013 @anchor{QPassSignals}
27014 Each listed @var{signal} should be passed directly to the inferior process.
27015 Signals are numbered identically to continue packets and stop replies
27016 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
27017 strictly greater than the previous item. These signals do not need to stop
27018 the inferior, or be reported to @value{GDBN}. All other signals should be
27019 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
27020 combine; any earlier @samp{QPassSignals} list is completely replaced by the
27021 new list. This packet improves performance when using @samp{handle
27022 @var{signal} nostop noprint pass}.
27027 The request succeeded.
27030 An error occurred. @var{nn} are hex digits.
27033 An empty reply indicates that @samp{QPassSignals} is not supported by
27037 Use of this packet is controlled by the @code{set remote pass-signals}
27038 command (@pxref{Remote Configuration, set remote pass-signals}).
27039 This packet is not probed by default; the remote stub must request it,
27040 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27042 @item qRcmd,@var{command}
27043 @cindex execute remote command, remote request
27044 @cindex @samp{qRcmd} packet
27045 @var{command} (hex encoded) is passed to the local interpreter for
27046 execution. Invalid commands should be reported using the output
27047 string. Before the final result packet, the target may also respond
27048 with a number of intermediate @samp{O@var{output}} console output
27049 packets. @emph{Implementors should note that providing access to a
27050 stubs's interpreter may have security implications}.
27055 A command response with no output.
27057 A command response with the hex encoded output string @var{OUTPUT}.
27059 Indicate a badly formed request.
27061 An empty reply indicates that @samp{qRcmd} is not recognized.
27064 (Note that the @code{qRcmd} packet's name is separated from the
27065 command by a @samp{,}, not a @samp{:}, contrary to the naming
27066 conventions above. Please don't use this packet as a model for new
27069 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
27070 @cindex searching memory, in remote debugging
27071 @cindex @samp{qSearch:memory} packet
27072 @anchor{qSearch memory}
27073 Search @var{length} bytes at @var{address} for @var{search-pattern}.
27074 @var{address} and @var{length} are encoded in hex.
27075 @var{search-pattern} is a sequence of bytes, hex encoded.
27080 The pattern was not found.
27082 The pattern was found at @var{address}.
27084 A badly formed request or an error was encountered while searching memory.
27086 An empty reply indicates that @samp{qSearch:memory} is not recognized.
27089 @item QStartNoAckMode
27090 @cindex @samp{QStartNoAckMode} packet
27091 @anchor{QStartNoAckMode}
27092 Request that the remote stub disable the normal @samp{+}/@samp{-}
27093 protocol acknowledgments (@pxref{Packet Acknowledgment}).
27098 The stub has switched to no-acknowledgment mode.
27099 @value{GDBN} acknowledges this reponse,
27100 but neither the stub nor @value{GDBN} shall send or expect further
27101 @samp{+}/@samp{-} acknowledgments in the current connection.
27103 An empty reply indicates that the stub does not support no-acknowledgment mode.
27106 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
27107 @cindex supported packets, remote query
27108 @cindex features of the remote protocol
27109 @cindex @samp{qSupported} packet
27110 @anchor{qSupported}
27111 Tell the remote stub about features supported by @value{GDBN}, and
27112 query the stub for features it supports. This packet allows
27113 @value{GDBN} and the remote stub to take advantage of each others'
27114 features. @samp{qSupported} also consolidates multiple feature probes
27115 at startup, to improve @value{GDBN} performance---a single larger
27116 packet performs better than multiple smaller probe packets on
27117 high-latency links. Some features may enable behavior which must not
27118 be on by default, e.g.@: because it would confuse older clients or
27119 stubs. Other features may describe packets which could be
27120 automatically probed for, but are not. These features must be
27121 reported before @value{GDBN} will use them. This ``default
27122 unsupported'' behavior is not appropriate for all packets, but it
27123 helps to keep the initial connection time under control with new
27124 versions of @value{GDBN} which support increasing numbers of packets.
27128 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
27129 The stub supports or does not support each returned @var{stubfeature},
27130 depending on the form of each @var{stubfeature} (see below for the
27133 An empty reply indicates that @samp{qSupported} is not recognized,
27134 or that no features needed to be reported to @value{GDBN}.
27137 The allowed forms for each feature (either a @var{gdbfeature} in the
27138 @samp{qSupported} packet, or a @var{stubfeature} in the response)
27142 @item @var{name}=@var{value}
27143 The remote protocol feature @var{name} is supported, and associated
27144 with the specified @var{value}. The format of @var{value} depends
27145 on the feature, but it must not include a semicolon.
27147 The remote protocol feature @var{name} is supported, and does not
27148 need an associated value.
27150 The remote protocol feature @var{name} is not supported.
27152 The remote protocol feature @var{name} may be supported, and
27153 @value{GDBN} should auto-detect support in some other way when it is
27154 needed. This form will not be used for @var{gdbfeature} notifications,
27155 but may be used for @var{stubfeature} responses.
27158 Whenever the stub receives a @samp{qSupported} request, the
27159 supplied set of @value{GDBN} features should override any previous
27160 request. This allows @value{GDBN} to put the stub in a known
27161 state, even if the stub had previously been communicating with
27162 a different version of @value{GDBN}.
27164 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
27169 This feature indicates whether @value{GDBN} supports multiprocess
27170 extensions to the remote protocol. @value{GDBN} does not use such
27171 extensions unless the stub also reports that it supports them by
27172 including @samp{multiprocess+} in its @samp{qSupported} reply.
27173 @xref{multiprocess extensions}, for details.
27176 Stubs should ignore any unknown values for
27177 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
27178 packet supports receiving packets of unlimited length (earlier
27179 versions of @value{GDBN} may reject overly long responses). Additional values
27180 for @var{gdbfeature} may be defined in the future to let the stub take
27181 advantage of new features in @value{GDBN}, e.g.@: incompatible
27182 improvements in the remote protocol---the @samp{multiprocess} feature is
27183 an example of such a feature. The stub's reply should be independent
27184 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
27185 describes all the features it supports, and then the stub replies with
27186 all the features it supports.
27188 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
27189 responses, as long as each response uses one of the standard forms.
27191 Some features are flags. A stub which supports a flag feature
27192 should respond with a @samp{+} form response. Other features
27193 require values, and the stub should respond with an @samp{=}
27196 Each feature has a default value, which @value{GDBN} will use if
27197 @samp{qSupported} is not available or if the feature is not mentioned
27198 in the @samp{qSupported} response. The default values are fixed; a
27199 stub is free to omit any feature responses that match the defaults.
27201 Not all features can be probed, but for those which can, the probing
27202 mechanism is useful: in some cases, a stub's internal
27203 architecture may not allow the protocol layer to know some information
27204 about the underlying target in advance. This is especially common in
27205 stubs which may be configured for multiple targets.
27207 These are the currently defined stub features and their properties:
27209 @multitable @columnfractions 0.35 0.2 0.12 0.2
27210 @c NOTE: The first row should be @headitem, but we do not yet require
27211 @c a new enough version of Texinfo (4.7) to use @headitem.
27213 @tab Value Required
27217 @item @samp{PacketSize}
27222 @item @samp{qXfer:auxv:read}
27227 @item @samp{qXfer:features:read}
27232 @item @samp{qXfer:libraries:read}
27237 @item @samp{qXfer:memory-map:read}
27242 @item @samp{qXfer:spu:read}
27247 @item @samp{qXfer:spu:write}
27252 @item @samp{qXfer:siginfo:read}
27257 @item @samp{qXfer:siginfo:write}
27262 @item @samp{QNonStop}
27267 @item @samp{QPassSignals}
27272 @item @samp{QStartNoAckMode}
27277 @item @samp{multiprocess}
27284 These are the currently defined stub features, in more detail:
27287 @cindex packet size, remote protocol
27288 @item PacketSize=@var{bytes}
27289 The remote stub can accept packets up to at least @var{bytes} in
27290 length. @value{GDBN} will send packets up to this size for bulk
27291 transfers, and will never send larger packets. This is a limit on the
27292 data characters in the packet, including the frame and checksum.
27293 There is no trailing NUL byte in a remote protocol packet; if the stub
27294 stores packets in a NUL-terminated format, it should allow an extra
27295 byte in its buffer for the NUL. If this stub feature is not supported,
27296 @value{GDBN} guesses based on the size of the @samp{g} packet response.
27298 @item qXfer:auxv:read
27299 The remote stub understands the @samp{qXfer:auxv:read} packet
27300 (@pxref{qXfer auxiliary vector read}).
27302 @item qXfer:features:read
27303 The remote stub understands the @samp{qXfer:features:read} packet
27304 (@pxref{qXfer target description read}).
27306 @item qXfer:libraries:read
27307 The remote stub understands the @samp{qXfer:libraries:read} packet
27308 (@pxref{qXfer library list read}).
27310 @item qXfer:memory-map:read
27311 The remote stub understands the @samp{qXfer:memory-map:read} packet
27312 (@pxref{qXfer memory map read}).
27314 @item qXfer:spu:read
27315 The remote stub understands the @samp{qXfer:spu:read} packet
27316 (@pxref{qXfer spu read}).
27318 @item qXfer:spu:write
27319 The remote stub understands the @samp{qXfer:spu:write} packet
27320 (@pxref{qXfer spu write}).
27322 @item qXfer:siginfo:read
27323 The remote stub understands the @samp{qXfer:siginfo:read} packet
27324 (@pxref{qXfer siginfo read}).
27326 @item qXfer:siginfo:write
27327 The remote stub understands the @samp{qXfer:siginfo:write} packet
27328 (@pxref{qXfer siginfo write}).
27331 The remote stub understands the @samp{QNonStop} packet
27332 (@pxref{QNonStop}).
27335 The remote stub understands the @samp{QPassSignals} packet
27336 (@pxref{QPassSignals}).
27338 @item QStartNoAckMode
27339 The remote stub understands the @samp{QStartNoAckMode} packet and
27340 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
27343 @anchor{multiprocess extensions}
27344 @cindex multiprocess extensions, in remote protocol
27345 The remote stub understands the multiprocess extensions to the remote
27346 protocol syntax. The multiprocess extensions affect the syntax of
27347 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
27348 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
27349 replies. Note that reporting this feature indicates support for the
27350 syntactic extensions only, not that the stub necessarily supports
27351 debugging of more than one process at a time. The stub must not use
27352 multiprocess extensions in packet replies unless @value{GDBN} has also
27353 indicated it supports them in its @samp{qSupported} request.
27355 @item qXfer:osdata:read
27356 The remote stub understands the @samp{qXfer:osdata:read} packet
27357 ((@pxref{qXfer osdata read}).
27362 @cindex symbol lookup, remote request
27363 @cindex @samp{qSymbol} packet
27364 Notify the target that @value{GDBN} is prepared to serve symbol lookup
27365 requests. Accept requests from the target for the values of symbols.
27370 The target does not need to look up any (more) symbols.
27371 @item qSymbol:@var{sym_name}
27372 The target requests the value of symbol @var{sym_name} (hex encoded).
27373 @value{GDBN} may provide the value by using the
27374 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
27378 @item qSymbol:@var{sym_value}:@var{sym_name}
27379 Set the value of @var{sym_name} to @var{sym_value}.
27381 @var{sym_name} (hex encoded) is the name of a symbol whose value the
27382 target has previously requested.
27384 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
27385 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
27391 The target does not need to look up any (more) symbols.
27392 @item qSymbol:@var{sym_name}
27393 The target requests the value of a new symbol @var{sym_name} (hex
27394 encoded). @value{GDBN} will continue to supply the values of symbols
27395 (if available), until the target ceases to request them.
27400 @xref{Tracepoint Packets}.
27402 @item qThreadExtraInfo,@var{thread-id}
27403 @cindex thread attributes info, remote request
27404 @cindex @samp{qThreadExtraInfo} packet
27405 Obtain a printable string description of a thread's attributes from
27406 the target OS. @var{thread-id} is a thread ID;
27407 see @ref{thread-id syntax}. This
27408 string may contain anything that the target OS thinks is interesting
27409 for @value{GDBN} to tell the user about the thread. The string is
27410 displayed in @value{GDBN}'s @code{info threads} display. Some
27411 examples of possible thread extra info strings are @samp{Runnable}, or
27412 @samp{Blocked on Mutex}.
27416 @item @var{XX}@dots{}
27417 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
27418 comprising the printable string containing the extra information about
27419 the thread's attributes.
27422 (Note that the @code{qThreadExtraInfo} packet's name is separated from
27423 the command by a @samp{,}, not a @samp{:}, contrary to the naming
27424 conventions above. Please don't use this packet as a model for new
27432 @xref{Tracepoint Packets}.
27434 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
27435 @cindex read special object, remote request
27436 @cindex @samp{qXfer} packet
27437 @anchor{qXfer read}
27438 Read uninterpreted bytes from the target's special data area
27439 identified by the keyword @var{object}. Request @var{length} bytes
27440 starting at @var{offset} bytes into the data. The content and
27441 encoding of @var{annex} is specific to @var{object}; it can supply
27442 additional details about what data to access.
27444 Here are the specific requests of this form defined so far. All
27445 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
27446 formats, listed below.
27449 @item qXfer:auxv:read::@var{offset},@var{length}
27450 @anchor{qXfer auxiliary vector read}
27451 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
27452 auxiliary vector}. Note @var{annex} must be empty.
27454 This packet is not probed by default; the remote stub must request it,
27455 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27457 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
27458 @anchor{qXfer target description read}
27459 Access the @dfn{target description}. @xref{Target Descriptions}. The
27460 annex specifies which XML document to access. The main description is
27461 always loaded from the @samp{target.xml} annex.
27463 This packet is not probed by default; the remote stub must request it,
27464 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27466 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
27467 @anchor{qXfer library list read}
27468 Access the target's list of loaded libraries. @xref{Library List Format}.
27469 The annex part of the generic @samp{qXfer} packet must be empty
27470 (@pxref{qXfer read}).
27472 Targets which maintain a list of libraries in the program's memory do
27473 not need to implement this packet; it is designed for platforms where
27474 the operating system manages the list of loaded libraries.
27476 This packet is not probed by default; the remote stub must request it,
27477 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27479 @item qXfer:memory-map:read::@var{offset},@var{length}
27480 @anchor{qXfer memory map read}
27481 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
27482 annex part of the generic @samp{qXfer} packet must be empty
27483 (@pxref{qXfer read}).
27485 This packet is not probed by default; the remote stub must request it,
27486 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27488 @item qXfer:siginfo:read::@var{offset},@var{length}
27489 @anchor{qXfer siginfo read}
27490 Read contents of the extra signal information on the target
27491 system. The annex part of the generic @samp{qXfer} packet must be
27492 empty (@pxref{qXfer read}).
27494 This packet is not probed by default; the remote stub must request it,
27495 by supplying an appropriate @samp{qSupported} response
27496 (@pxref{qSupported}).
27498 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
27499 @anchor{qXfer spu read}
27500 Read contents of an @code{spufs} file on the target system. The
27501 annex specifies which file to read; it must be of the form
27502 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27503 in the target process, and @var{name} identifes the @code{spufs} file
27504 in that context to be accessed.
27506 This packet is not probed by default; the remote stub must request it,
27507 by supplying an appropriate @samp{qSupported} response
27508 (@pxref{qSupported}).
27510 @item qXfer:osdata:read::@var{offset},@var{length}
27511 @anchor{qXfer osdata read}
27512 Access the target's @dfn{operating system information}.
27513 @xref{Operating System Information}.
27520 Data @var{data} (@pxref{Binary Data}) has been read from the
27521 target. There may be more data at a higher address (although
27522 it is permitted to return @samp{m} even for the last valid
27523 block of data, as long as at least one byte of data was read).
27524 @var{data} may have fewer bytes than the @var{length} in the
27528 Data @var{data} (@pxref{Binary Data}) has been read from the target.
27529 There is no more data to be read. @var{data} may have fewer bytes
27530 than the @var{length} in the request.
27533 The @var{offset} in the request is at the end of the data.
27534 There is no more data to be read.
27537 The request was malformed, or @var{annex} was invalid.
27540 The offset was invalid, or there was an error encountered reading the data.
27541 @var{nn} is a hex-encoded @code{errno} value.
27544 An empty reply indicates the @var{object} string was not recognized by
27545 the stub, or that the object does not support reading.
27548 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
27549 @cindex write data into object, remote request
27550 @anchor{qXfer write}
27551 Write uninterpreted bytes into the target's special data area
27552 identified by the keyword @var{object}, starting at @var{offset} bytes
27553 into the data. @var{data}@dots{} is the binary-encoded data
27554 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
27555 is specific to @var{object}; it can supply additional details about what data
27558 Here are the specific requests of this form defined so far. All
27559 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
27560 formats, listed below.
27563 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
27564 @anchor{qXfer siginfo write}
27565 Write @var{data} to the extra signal information on the target system.
27566 The annex part of the generic @samp{qXfer} packet must be
27567 empty (@pxref{qXfer write}).
27569 This packet is not probed by default; the remote stub must request it,
27570 by supplying an appropriate @samp{qSupported} response
27571 (@pxref{qSupported}).
27573 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
27574 @anchor{qXfer spu write}
27575 Write @var{data} to an @code{spufs} file on the target system. The
27576 annex specifies which file to write; it must be of the form
27577 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27578 in the target process, and @var{name} identifes the @code{spufs} file
27579 in that context to be accessed.
27581 This packet is not probed by default; the remote stub must request it,
27582 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27588 @var{nn} (hex encoded) is the number of bytes written.
27589 This may be fewer bytes than supplied in the request.
27592 The request was malformed, or @var{annex} was invalid.
27595 The offset was invalid, or there was an error encountered writing the data.
27596 @var{nn} is a hex-encoded @code{errno} value.
27599 An empty reply indicates the @var{object} string was not
27600 recognized by the stub, or that the object does not support writing.
27603 @item qXfer:@var{object}:@var{operation}:@dots{}
27604 Requests of this form may be added in the future. When a stub does
27605 not recognize the @var{object} keyword, or its support for
27606 @var{object} does not recognize the @var{operation} keyword, the stub
27607 must respond with an empty packet.
27609 @item qAttached:@var{pid}
27610 @cindex query attached, remote request
27611 @cindex @samp{qAttached} packet
27612 Return an indication of whether the remote server attached to an
27613 existing process or created a new process. When the multiprocess
27614 protocol extensions are supported (@pxref{multiprocess extensions}),
27615 @var{pid} is an integer in hexadecimal format identifying the target
27616 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
27617 the query packet will be simplified as @samp{qAttached}.
27619 This query is used, for example, to know whether the remote process
27620 should be detached or killed when a @value{GDBN} session is ended with
27621 the @code{quit} command.
27626 The remote server attached to an existing process.
27628 The remote server created a new process.
27630 A badly formed request or an error was encountered.
27635 @node Register Packet Format
27636 @section Register Packet Format
27638 The following @code{g}/@code{G} packets have previously been defined.
27639 In the below, some thirty-two bit registers are transferred as
27640 sixty-four bits. Those registers should be zero/sign extended (which?)
27641 to fill the space allocated. Register bytes are transferred in target
27642 byte order. The two nibbles within a register byte are transferred
27643 most-significant - least-significant.
27649 All registers are transferred as thirty-two bit quantities in the order:
27650 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
27651 registers; fsr; fir; fp.
27655 All registers are transferred as sixty-four bit quantities (including
27656 thirty-two bit registers such as @code{sr}). The ordering is the same
27661 @node Tracepoint Packets
27662 @section Tracepoint Packets
27663 @cindex tracepoint packets
27664 @cindex packets, tracepoint
27666 Here we describe the packets @value{GDBN} uses to implement
27667 tracepoints (@pxref{Tracepoints}).
27671 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
27672 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
27673 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
27674 the tracepoint is disabled. @var{step} is the tracepoint's step
27675 count, and @var{pass} is its pass count. If the trailing @samp{-} is
27676 present, further @samp{QTDP} packets will follow to specify this
27677 tracepoint's actions.
27682 The packet was understood and carried out.
27684 The packet was not recognized.
27687 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
27688 Define actions to be taken when a tracepoint is hit. @var{n} and
27689 @var{addr} must be the same as in the initial @samp{QTDP} packet for
27690 this tracepoint. This packet may only be sent immediately after
27691 another @samp{QTDP} packet that ended with a @samp{-}. If the
27692 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
27693 specifying more actions for this tracepoint.
27695 In the series of action packets for a given tracepoint, at most one
27696 can have an @samp{S} before its first @var{action}. If such a packet
27697 is sent, it and the following packets define ``while-stepping''
27698 actions. Any prior packets define ordinary actions --- that is, those
27699 taken when the tracepoint is first hit. If no action packet has an
27700 @samp{S}, then all the packets in the series specify ordinary
27701 tracepoint actions.
27703 The @samp{@var{action}@dots{}} portion of the packet is a series of
27704 actions, concatenated without separators. Each action has one of the
27710 Collect the registers whose bits are set in @var{mask}. @var{mask} is
27711 a hexadecimal number whose @var{i}'th bit is set if register number
27712 @var{i} should be collected. (The least significant bit is numbered
27713 zero.) Note that @var{mask} may be any number of digits long; it may
27714 not fit in a 32-bit word.
27716 @item M @var{basereg},@var{offset},@var{len}
27717 Collect @var{len} bytes of memory starting at the address in register
27718 number @var{basereg}, plus @var{offset}. If @var{basereg} is
27719 @samp{-1}, then the range has a fixed address: @var{offset} is the
27720 address of the lowest byte to collect. The @var{basereg},
27721 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
27722 values (the @samp{-1} value for @var{basereg} is a special case).
27724 @item X @var{len},@var{expr}
27725 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
27726 it directs. @var{expr} is an agent expression, as described in
27727 @ref{Agent Expressions}. Each byte of the expression is encoded as a
27728 two-digit hex number in the packet; @var{len} is the number of bytes
27729 in the expression (and thus one-half the number of hex digits in the
27734 Any number of actions may be packed together in a single @samp{QTDP}
27735 packet, as long as the packet does not exceed the maximum packet
27736 length (400 bytes, for many stubs). There may be only one @samp{R}
27737 action per tracepoint, and it must precede any @samp{M} or @samp{X}
27738 actions. Any registers referred to by @samp{M} and @samp{X} actions
27739 must be collected by a preceding @samp{R} action. (The
27740 ``while-stepping'' actions are treated as if they were attached to a
27741 separate tracepoint, as far as these restrictions are concerned.)
27746 The packet was understood and carried out.
27748 The packet was not recognized.
27751 @item QTFrame:@var{n}
27752 Select the @var{n}'th tracepoint frame from the buffer, and use the
27753 register and memory contents recorded there to answer subsequent
27754 request packets from @value{GDBN}.
27756 A successful reply from the stub indicates that the stub has found the
27757 requested frame. The response is a series of parts, concatenated
27758 without separators, describing the frame we selected. Each part has
27759 one of the following forms:
27763 The selected frame is number @var{n} in the trace frame buffer;
27764 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
27765 was no frame matching the criteria in the request packet.
27768 The selected trace frame records a hit of tracepoint number @var{t};
27769 @var{t} is a hexadecimal number.
27773 @item QTFrame:pc:@var{addr}
27774 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27775 currently selected frame whose PC is @var{addr};
27776 @var{addr} is a hexadecimal number.
27778 @item QTFrame:tdp:@var{t}
27779 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27780 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
27781 is a hexadecimal number.
27783 @item QTFrame:range:@var{start}:@var{end}
27784 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27785 currently selected frame whose PC is between @var{start} (inclusive)
27786 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
27789 @item QTFrame:outside:@var{start}:@var{end}
27790 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
27791 frame @emph{outside} the given range of addresses.
27794 Begin the tracepoint experiment. Begin collecting data from tracepoint
27795 hits in the trace frame buffer.
27798 End the tracepoint experiment. Stop collecting trace frames.
27801 Clear the table of tracepoints, and empty the trace frame buffer.
27803 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
27804 Establish the given ranges of memory as ``transparent''. The stub
27805 will answer requests for these ranges from memory's current contents,
27806 if they were not collected as part of the tracepoint hit.
27808 @value{GDBN} uses this to mark read-only regions of memory, like those
27809 containing program code. Since these areas never change, they should
27810 still have the same contents they did when the tracepoint was hit, so
27811 there's no reason for the stub to refuse to provide their contents.
27814 Ask the stub if there is a trace experiment running right now.
27819 There is no trace experiment running.
27821 There is a trace experiment running.
27827 @node Host I/O Packets
27828 @section Host I/O Packets
27829 @cindex Host I/O, remote protocol
27830 @cindex file transfer, remote protocol
27832 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
27833 operations on the far side of a remote link. For example, Host I/O is
27834 used to upload and download files to a remote target with its own
27835 filesystem. Host I/O uses the same constant values and data structure
27836 layout as the target-initiated File-I/O protocol. However, the
27837 Host I/O packets are structured differently. The target-initiated
27838 protocol relies on target memory to store parameters and buffers.
27839 Host I/O requests are initiated by @value{GDBN}, and the
27840 target's memory is not involved. @xref{File-I/O Remote Protocol
27841 Extension}, for more details on the target-initiated protocol.
27843 The Host I/O request packets all encode a single operation along with
27844 its arguments. They have this format:
27848 @item vFile:@var{operation}: @var{parameter}@dots{}
27849 @var{operation} is the name of the particular request; the target
27850 should compare the entire packet name up to the second colon when checking
27851 for a supported operation. The format of @var{parameter} depends on
27852 the operation. Numbers are always passed in hexadecimal. Negative
27853 numbers have an explicit minus sign (i.e.@: two's complement is not
27854 used). Strings (e.g.@: filenames) are encoded as a series of
27855 hexadecimal bytes. The last argument to a system call may be a
27856 buffer of escaped binary data (@pxref{Binary Data}).
27860 The valid responses to Host I/O packets are:
27864 @item F @var{result} [, @var{errno}] [; @var{attachment}]
27865 @var{result} is the integer value returned by this operation, usually
27866 non-negative for success and -1 for errors. If an error has occured,
27867 @var{errno} will be included in the result. @var{errno} will have a
27868 value defined by the File-I/O protocol (@pxref{Errno Values}). For
27869 operations which return data, @var{attachment} supplies the data as a
27870 binary buffer. Binary buffers in response packets are escaped in the
27871 normal way (@pxref{Binary Data}). See the individual packet
27872 documentation for the interpretation of @var{result} and
27876 An empty response indicates that this operation is not recognized.
27880 These are the supported Host I/O operations:
27883 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
27884 Open a file at @var{pathname} and return a file descriptor for it, or
27885 return -1 if an error occurs. @var{pathname} is a string,
27886 @var{flags} is an integer indicating a mask of open flags
27887 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
27888 of mode bits to use if the file is created (@pxref{mode_t Values}).
27889 @xref{open}, for details of the open flags and mode values.
27891 @item vFile:close: @var{fd}
27892 Close the open file corresponding to @var{fd} and return 0, or
27893 -1 if an error occurs.
27895 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
27896 Read data from the open file corresponding to @var{fd}. Up to
27897 @var{count} bytes will be read from the file, starting at @var{offset}
27898 relative to the start of the file. The target may read fewer bytes;
27899 common reasons include packet size limits and an end-of-file
27900 condition. The number of bytes read is returned. Zero should only be
27901 returned for a successful read at the end of the file, or if
27902 @var{count} was zero.
27904 The data read should be returned as a binary attachment on success.
27905 If zero bytes were read, the response should include an empty binary
27906 attachment (i.e.@: a trailing semicolon). The return value is the
27907 number of target bytes read; the binary attachment may be longer if
27908 some characters were escaped.
27910 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
27911 Write @var{data} (a binary buffer) to the open file corresponding
27912 to @var{fd}. Start the write at @var{offset} from the start of the
27913 file. Unlike many @code{write} system calls, there is no
27914 separate @var{count} argument; the length of @var{data} in the
27915 packet is used. @samp{vFile:write} returns the number of bytes written,
27916 which may be shorter than the length of @var{data}, or -1 if an
27919 @item vFile:unlink: @var{pathname}
27920 Delete the file at @var{pathname} on the target. Return 0,
27921 or -1 if an error occurs. @var{pathname} is a string.
27926 @section Interrupts
27927 @cindex interrupts (remote protocol)
27929 When a program on the remote target is running, @value{GDBN} may
27930 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
27931 control of which is specified via @value{GDBN}'s @samp{remotebreak}
27932 setting (@pxref{set remotebreak}).
27934 The precise meaning of @code{BREAK} is defined by the transport
27935 mechanism and may, in fact, be undefined. @value{GDBN} does not
27936 currently define a @code{BREAK} mechanism for any of the network
27937 interfaces except for TCP, in which case @value{GDBN} sends the
27938 @code{telnet} BREAK sequence.
27940 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
27941 transport mechanisms. It is represented by sending the single byte
27942 @code{0x03} without any of the usual packet overhead described in
27943 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
27944 transmitted as part of a packet, it is considered to be packet data
27945 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
27946 (@pxref{X packet}), used for binary downloads, may include an unescaped
27947 @code{0x03} as part of its packet.
27949 Stubs are not required to recognize these interrupt mechanisms and the
27950 precise meaning associated with receipt of the interrupt is
27951 implementation defined. If the target supports debugging of multiple
27952 threads and/or processes, it should attempt to interrupt all
27953 currently-executing threads and processes.
27954 If the stub is successful at interrupting the
27955 running program, it should send one of the stop
27956 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
27957 of successfully stopping the program in all-stop mode, and a stop reply
27958 for each stopped thread in non-stop mode.
27959 Interrupts received while the
27960 program is stopped are discarded.
27962 @node Notification Packets
27963 @section Notification Packets
27964 @cindex notification packets
27965 @cindex packets, notification
27967 The @value{GDBN} remote serial protocol includes @dfn{notifications},
27968 packets that require no acknowledgment. Both the GDB and the stub
27969 may send notifications (although the only notifications defined at
27970 present are sent by the stub). Notifications carry information
27971 without incurring the round-trip latency of an acknowledgment, and so
27972 are useful for low-impact communications where occasional packet loss
27975 A notification packet has the form @samp{% @var{data} #
27976 @var{checksum}}, where @var{data} is the content of the notification,
27977 and @var{checksum} is a checksum of @var{data}, computed and formatted
27978 as for ordinary @value{GDBN} packets. A notification's @var{data}
27979 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
27980 receiving a notification, the recipient sends no @samp{+} or @samp{-}
27981 to acknowledge the notification's receipt or to report its corruption.
27983 Every notification's @var{data} begins with a name, which contains no
27984 colon characters, followed by a colon character.
27986 Recipients should silently ignore corrupted notifications and
27987 notifications they do not understand. Recipients should restart
27988 timeout periods on receipt of a well-formed notification, whether or
27989 not they understand it.
27991 Senders should only send the notifications described here when this
27992 protocol description specifies that they are permitted. In the
27993 future, we may extend the protocol to permit existing notifications in
27994 new contexts; this rule helps older senders avoid confusing newer
27997 (Older versions of @value{GDBN} ignore bytes received until they see
27998 the @samp{$} byte that begins an ordinary packet, so new stubs may
27999 transmit notifications without fear of confusing older clients. There
28000 are no notifications defined for @value{GDBN} to send at the moment, but we
28001 assume that most older stubs would ignore them, as well.)
28003 The following notification packets from the stub to @value{GDBN} are
28007 @item Stop: @var{reply}
28008 Report an asynchronous stop event in non-stop mode.
28009 The @var{reply} has the form of a stop reply, as
28010 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
28011 for information on how these notifications are acknowledged by
28015 @node Remote Non-Stop
28016 @section Remote Protocol Support for Non-Stop Mode
28018 @value{GDBN}'s remote protocol supports non-stop debugging of
28019 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
28020 supports non-stop mode, it should report that to @value{GDBN} by including
28021 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
28023 @value{GDBN} typically sends a @samp{QNonStop} packet only when
28024 establishing a new connection with the stub. Entering non-stop mode
28025 does not alter the state of any currently-running threads, but targets
28026 must stop all threads in any already-attached processes when entering
28027 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
28028 probe the target state after a mode change.
28030 In non-stop mode, when an attached process encounters an event that
28031 would otherwise be reported with a stop reply, it uses the
28032 asynchronous notification mechanism (@pxref{Notification Packets}) to
28033 inform @value{GDBN}. In contrast to all-stop mode, where all threads
28034 in all processes are stopped when a stop reply is sent, in non-stop
28035 mode only the thread reporting the stop event is stopped. That is,
28036 when reporting a @samp{S} or @samp{T} response to indicate completion
28037 of a step operation, hitting a breakpoint, or a fault, only the
28038 affected thread is stopped; any other still-running threads continue
28039 to run. When reporting a @samp{W} or @samp{X} response, all running
28040 threads belonging to other attached processes continue to run.
28042 Only one stop reply notification at a time may be pending; if
28043 additional stop events occur before @value{GDBN} has acknowledged the
28044 previous notification, they must be queued by the stub for later
28045 synchronous transmission in response to @samp{vStopped} packets from
28046 @value{GDBN}. Because the notification mechanism is unreliable,
28047 the stub is permitted to resend a stop reply notification
28048 if it believes @value{GDBN} may not have received it. @value{GDBN}
28049 ignores additional stop reply notifications received before it has
28050 finished processing a previous notification and the stub has completed
28051 sending any queued stop events.
28053 Otherwise, @value{GDBN} must be prepared to receive a stop reply
28054 notification at any time. Specifically, they may appear when
28055 @value{GDBN} is not otherwise reading input from the stub, or when
28056 @value{GDBN} is expecting to read a normal synchronous response or a
28057 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
28058 Notification packets are distinct from any other communication from
28059 the stub so there is no ambiguity.
28061 After receiving a stop reply notification, @value{GDBN} shall
28062 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
28063 as a regular, synchronous request to the stub. Such acknowledgment
28064 is not required to happen immediately, as @value{GDBN} is permitted to
28065 send other, unrelated packets to the stub first, which the stub should
28068 Upon receiving a @samp{vStopped} packet, if the stub has other queued
28069 stop events to report to @value{GDBN}, it shall respond by sending a
28070 normal stop reply response. @value{GDBN} shall then send another
28071 @samp{vStopped} packet to solicit further responses; again, it is
28072 permitted to send other, unrelated packets as well which the stub
28073 should process normally.
28075 If the stub receives a @samp{vStopped} packet and there are no
28076 additional stop events to report, the stub shall return an @samp{OK}
28077 response. At this point, if further stop events occur, the stub shall
28078 send a new stop reply notification, @value{GDBN} shall accept the
28079 notification, and the process shall be repeated.
28081 In non-stop mode, the target shall respond to the @samp{?} packet as
28082 follows. First, any incomplete stop reply notification/@samp{vStopped}
28083 sequence in progress is abandoned. The target must begin a new
28084 sequence reporting stop events for all stopped threads, whether or not
28085 it has previously reported those events to @value{GDBN}. The first
28086 stop reply is sent as a synchronous reply to the @samp{?} packet, and
28087 subsequent stop replies are sent as responses to @samp{vStopped} packets
28088 using the mechanism described above. The target must not send
28089 asynchronous stop reply notifications until the sequence is complete.
28090 If all threads are running when the target receives the @samp{?} packet,
28091 or if the target is not attached to any process, it shall respond
28094 @node Packet Acknowledgment
28095 @section Packet Acknowledgment
28097 @cindex acknowledgment, for @value{GDBN} remote
28098 @cindex packet acknowledgment, for @value{GDBN} remote
28099 By default, when either the host or the target machine receives a packet,
28100 the first response expected is an acknowledgment: either @samp{+} (to indicate
28101 the package was received correctly) or @samp{-} (to request retransmission).
28102 This mechanism allows the @value{GDBN} remote protocol to operate over
28103 unreliable transport mechanisms, such as a serial line.
28105 In cases where the transport mechanism is itself reliable (such as a pipe or
28106 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
28107 It may be desirable to disable them in that case to reduce communication
28108 overhead, or for other reasons. This can be accomplished by means of the
28109 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
28111 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
28112 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
28113 and response format still includes the normal checksum, as described in
28114 @ref{Overview}, but the checksum may be ignored by the receiver.
28116 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
28117 no-acknowledgment mode, it should report that to @value{GDBN}
28118 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
28119 @pxref{qSupported}.
28120 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
28121 disabled via the @code{set remote noack-packet off} command
28122 (@pxref{Remote Configuration}),
28123 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
28124 Only then may the stub actually turn off packet acknowledgments.
28125 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
28126 response, which can be safely ignored by the stub.
28128 Note that @code{set remote noack-packet} command only affects negotiation
28129 between @value{GDBN} and the stub when subsequent connections are made;
28130 it does not affect the protocol acknowledgment state for any current
28132 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
28133 new connection is established,
28134 there is also no protocol request to re-enable the acknowledgments
28135 for the current connection, once disabled.
28140 Example sequence of a target being re-started. Notice how the restart
28141 does not get any direct output:
28146 @emph{target restarts}
28149 <- @code{T001:1234123412341234}
28153 Example sequence of a target being stepped by a single instruction:
28156 -> @code{G1445@dots{}}
28161 <- @code{T001:1234123412341234}
28165 <- @code{1455@dots{}}
28169 @node File-I/O Remote Protocol Extension
28170 @section File-I/O Remote Protocol Extension
28171 @cindex File-I/O remote protocol extension
28174 * File-I/O Overview::
28175 * Protocol Basics::
28176 * The F Request Packet::
28177 * The F Reply Packet::
28178 * The Ctrl-C Message::
28180 * List of Supported Calls::
28181 * Protocol-specific Representation of Datatypes::
28183 * File-I/O Examples::
28186 @node File-I/O Overview
28187 @subsection File-I/O Overview
28188 @cindex file-i/o overview
28190 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
28191 target to use the host's file system and console I/O to perform various
28192 system calls. System calls on the target system are translated into a
28193 remote protocol packet to the host system, which then performs the needed
28194 actions and returns a response packet to the target system.
28195 This simulates file system operations even on targets that lack file systems.
28197 The protocol is defined to be independent of both the host and target systems.
28198 It uses its own internal representation of datatypes and values. Both
28199 @value{GDBN} and the target's @value{GDBN} stub are responsible for
28200 translating the system-dependent value representations into the internal
28201 protocol representations when data is transmitted.
28203 The communication is synchronous. A system call is possible only when
28204 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
28205 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
28206 the target is stopped to allow deterministic access to the target's
28207 memory. Therefore File-I/O is not interruptible by target signals. On
28208 the other hand, it is possible to interrupt File-I/O by a user interrupt
28209 (@samp{Ctrl-C}) within @value{GDBN}.
28211 The target's request to perform a host system call does not finish
28212 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
28213 after finishing the system call, the target returns to continuing the
28214 previous activity (continue, step). No additional continue or step
28215 request from @value{GDBN} is required.
28218 (@value{GDBP}) continue
28219 <- target requests 'system call X'
28220 target is stopped, @value{GDBN} executes system call
28221 -> @value{GDBN} returns result
28222 ... target continues, @value{GDBN} returns to wait for the target
28223 <- target hits breakpoint and sends a Txx packet
28226 The protocol only supports I/O on the console and to regular files on
28227 the host file system. Character or block special devices, pipes,
28228 named pipes, sockets or any other communication method on the host
28229 system are not supported by this protocol.
28231 File I/O is not supported in non-stop mode.
28233 @node Protocol Basics
28234 @subsection Protocol Basics
28235 @cindex protocol basics, file-i/o
28237 The File-I/O protocol uses the @code{F} packet as the request as well
28238 as reply packet. Since a File-I/O system call can only occur when
28239 @value{GDBN} is waiting for a response from the continuing or stepping target,
28240 the File-I/O request is a reply that @value{GDBN} has to expect as a result
28241 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
28242 This @code{F} packet contains all information needed to allow @value{GDBN}
28243 to call the appropriate host system call:
28247 A unique identifier for the requested system call.
28250 All parameters to the system call. Pointers are given as addresses
28251 in the target memory address space. Pointers to strings are given as
28252 pointer/length pair. Numerical values are given as they are.
28253 Numerical control flags are given in a protocol-specific representation.
28257 At this point, @value{GDBN} has to perform the following actions.
28261 If the parameters include pointer values to data needed as input to a
28262 system call, @value{GDBN} requests this data from the target with a
28263 standard @code{m} packet request. This additional communication has to be
28264 expected by the target implementation and is handled as any other @code{m}
28268 @value{GDBN} translates all value from protocol representation to host
28269 representation as needed. Datatypes are coerced into the host types.
28272 @value{GDBN} calls the system call.
28275 It then coerces datatypes back to protocol representation.
28278 If the system call is expected to return data in buffer space specified
28279 by pointer parameters to the call, the data is transmitted to the
28280 target using a @code{M} or @code{X} packet. This packet has to be expected
28281 by the target implementation and is handled as any other @code{M} or @code{X}
28286 Eventually @value{GDBN} replies with another @code{F} packet which contains all
28287 necessary information for the target to continue. This at least contains
28294 @code{errno}, if has been changed by the system call.
28301 After having done the needed type and value coercion, the target continues
28302 the latest continue or step action.
28304 @node The F Request Packet
28305 @subsection The @code{F} Request Packet
28306 @cindex file-i/o request packet
28307 @cindex @code{F} request packet
28309 The @code{F} request packet has the following format:
28312 @item F@var{call-id},@var{parameter@dots{}}
28314 @var{call-id} is the identifier to indicate the host system call to be called.
28315 This is just the name of the function.
28317 @var{parameter@dots{}} are the parameters to the system call.
28318 Parameters are hexadecimal integer values, either the actual values in case
28319 of scalar datatypes, pointers to target buffer space in case of compound
28320 datatypes and unspecified memory areas, or pointer/length pairs in case
28321 of string parameters. These are appended to the @var{call-id} as a
28322 comma-delimited list. All values are transmitted in ASCII
28323 string representation, pointer/length pairs separated by a slash.
28329 @node The F Reply Packet
28330 @subsection The @code{F} Reply Packet
28331 @cindex file-i/o reply packet
28332 @cindex @code{F} reply packet
28334 The @code{F} reply packet has the following format:
28338 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
28340 @var{retcode} is the return code of the system call as hexadecimal value.
28342 @var{errno} is the @code{errno} set by the call, in protocol-specific
28344 This parameter can be omitted if the call was successful.
28346 @var{Ctrl-C flag} is only sent if the user requested a break. In this
28347 case, @var{errno} must be sent as well, even if the call was successful.
28348 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
28355 or, if the call was interrupted before the host call has been performed:
28362 assuming 4 is the protocol-specific representation of @code{EINTR}.
28367 @node The Ctrl-C Message
28368 @subsection The @samp{Ctrl-C} Message
28369 @cindex ctrl-c message, in file-i/o protocol
28371 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
28372 reply packet (@pxref{The F Reply Packet}),
28373 the target should behave as if it had
28374 gotten a break message. The meaning for the target is ``system call
28375 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
28376 (as with a break message) and return to @value{GDBN} with a @code{T02}
28379 It's important for the target to know in which
28380 state the system call was interrupted. There are two possible cases:
28384 The system call hasn't been performed on the host yet.
28387 The system call on the host has been finished.
28391 These two states can be distinguished by the target by the value of the
28392 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
28393 call hasn't been performed. This is equivalent to the @code{EINTR} handling
28394 on POSIX systems. In any other case, the target may presume that the
28395 system call has been finished --- successfully or not --- and should behave
28396 as if the break message arrived right after the system call.
28398 @value{GDBN} must behave reliably. If the system call has not been called
28399 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
28400 @code{errno} in the packet. If the system call on the host has been finished
28401 before the user requests a break, the full action must be finished by
28402 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
28403 The @code{F} packet may only be sent when either nothing has happened
28404 or the full action has been completed.
28407 @subsection Console I/O
28408 @cindex console i/o as part of file-i/o
28410 By default and if not explicitly closed by the target system, the file
28411 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
28412 on the @value{GDBN} console is handled as any other file output operation
28413 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
28414 by @value{GDBN} so that after the target read request from file descriptor
28415 0 all following typing is buffered until either one of the following
28420 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
28422 system call is treated as finished.
28425 The user presses @key{RET}. This is treated as end of input with a trailing
28429 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
28430 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
28434 If the user has typed more characters than fit in the buffer given to
28435 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
28436 either another @code{read(0, @dots{})} is requested by the target, or debugging
28437 is stopped at the user's request.
28440 @node List of Supported Calls
28441 @subsection List of Supported Calls
28442 @cindex list of supported file-i/o calls
28459 @unnumberedsubsubsec open
28460 @cindex open, file-i/o system call
28465 int open(const char *pathname, int flags);
28466 int open(const char *pathname, int flags, mode_t mode);
28470 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
28473 @var{flags} is the bitwise @code{OR} of the following values:
28477 If the file does not exist it will be created. The host
28478 rules apply as far as file ownership and time stamps
28482 When used with @code{O_CREAT}, if the file already exists it is
28483 an error and open() fails.
28486 If the file already exists and the open mode allows
28487 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
28488 truncated to zero length.
28491 The file is opened in append mode.
28494 The file is opened for reading only.
28497 The file is opened for writing only.
28500 The file is opened for reading and writing.
28504 Other bits are silently ignored.
28508 @var{mode} is the bitwise @code{OR} of the following values:
28512 User has read permission.
28515 User has write permission.
28518 Group has read permission.
28521 Group has write permission.
28524 Others have read permission.
28527 Others have write permission.
28531 Other bits are silently ignored.
28534 @item Return value:
28535 @code{open} returns the new file descriptor or -1 if an error
28542 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
28545 @var{pathname} refers to a directory.
28548 The requested access is not allowed.
28551 @var{pathname} was too long.
28554 A directory component in @var{pathname} does not exist.
28557 @var{pathname} refers to a device, pipe, named pipe or socket.
28560 @var{pathname} refers to a file on a read-only filesystem and
28561 write access was requested.
28564 @var{pathname} is an invalid pointer value.
28567 No space on device to create the file.
28570 The process already has the maximum number of files open.
28573 The limit on the total number of files open on the system
28577 The call was interrupted by the user.
28583 @unnumberedsubsubsec close
28584 @cindex close, file-i/o system call
28593 @samp{Fclose,@var{fd}}
28595 @item Return value:
28596 @code{close} returns zero on success, or -1 if an error occurred.
28602 @var{fd} isn't a valid open file descriptor.
28605 The call was interrupted by the user.
28611 @unnumberedsubsubsec read
28612 @cindex read, file-i/o system call
28617 int read(int fd, void *buf, unsigned int count);
28621 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
28623 @item Return value:
28624 On success, the number of bytes read is returned.
28625 Zero indicates end of file. If count is zero, read
28626 returns zero as well. On error, -1 is returned.
28632 @var{fd} is not a valid file descriptor or is not open for
28636 @var{bufptr} is an invalid pointer value.
28639 The call was interrupted by the user.
28645 @unnumberedsubsubsec write
28646 @cindex write, file-i/o system call
28651 int write(int fd, const void *buf, unsigned int count);
28655 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
28657 @item Return value:
28658 On success, the number of bytes written are returned.
28659 Zero indicates nothing was written. On error, -1
28666 @var{fd} is not a valid file descriptor or is not open for
28670 @var{bufptr} is an invalid pointer value.
28673 An attempt was made to write a file that exceeds the
28674 host-specific maximum file size allowed.
28677 No space on device to write the data.
28680 The call was interrupted by the user.
28686 @unnumberedsubsubsec lseek
28687 @cindex lseek, file-i/o system call
28692 long lseek (int fd, long offset, int flag);
28696 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
28698 @var{flag} is one of:
28702 The offset is set to @var{offset} bytes.
28705 The offset is set to its current location plus @var{offset}
28709 The offset is set to the size of the file plus @var{offset}
28713 @item Return value:
28714 On success, the resulting unsigned offset in bytes from
28715 the beginning of the file is returned. Otherwise, a
28716 value of -1 is returned.
28722 @var{fd} is not a valid open file descriptor.
28725 @var{fd} is associated with the @value{GDBN} console.
28728 @var{flag} is not a proper value.
28731 The call was interrupted by the user.
28737 @unnumberedsubsubsec rename
28738 @cindex rename, file-i/o system call
28743 int rename(const char *oldpath, const char *newpath);
28747 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
28749 @item Return value:
28750 On success, zero is returned. On error, -1 is returned.
28756 @var{newpath} is an existing directory, but @var{oldpath} is not a
28760 @var{newpath} is a non-empty directory.
28763 @var{oldpath} or @var{newpath} is a directory that is in use by some
28767 An attempt was made to make a directory a subdirectory
28771 A component used as a directory in @var{oldpath} or new
28772 path is not a directory. Or @var{oldpath} is a directory
28773 and @var{newpath} exists but is not a directory.
28776 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
28779 No access to the file or the path of the file.
28783 @var{oldpath} or @var{newpath} was too long.
28786 A directory component in @var{oldpath} or @var{newpath} does not exist.
28789 The file is on a read-only filesystem.
28792 The device containing the file has no room for the new
28796 The call was interrupted by the user.
28802 @unnumberedsubsubsec unlink
28803 @cindex unlink, file-i/o system call
28808 int unlink(const char *pathname);
28812 @samp{Funlink,@var{pathnameptr}/@var{len}}
28814 @item Return value:
28815 On success, zero is returned. On error, -1 is returned.
28821 No access to the file or the path of the file.
28824 The system does not allow unlinking of directories.
28827 The file @var{pathname} cannot be unlinked because it's
28828 being used by another process.
28831 @var{pathnameptr} is an invalid pointer value.
28834 @var{pathname} was too long.
28837 A directory component in @var{pathname} does not exist.
28840 A component of the path is not a directory.
28843 The file is on a read-only filesystem.
28846 The call was interrupted by the user.
28852 @unnumberedsubsubsec stat/fstat
28853 @cindex fstat, file-i/o system call
28854 @cindex stat, file-i/o system call
28859 int stat(const char *pathname, struct stat *buf);
28860 int fstat(int fd, struct stat *buf);
28864 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
28865 @samp{Ffstat,@var{fd},@var{bufptr}}
28867 @item Return value:
28868 On success, zero is returned. On error, -1 is returned.
28874 @var{fd} is not a valid open file.
28877 A directory component in @var{pathname} does not exist or the
28878 path is an empty string.
28881 A component of the path is not a directory.
28884 @var{pathnameptr} is an invalid pointer value.
28887 No access to the file or the path of the file.
28890 @var{pathname} was too long.
28893 The call was interrupted by the user.
28899 @unnumberedsubsubsec gettimeofday
28900 @cindex gettimeofday, file-i/o system call
28905 int gettimeofday(struct timeval *tv, void *tz);
28909 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
28911 @item Return value:
28912 On success, 0 is returned, -1 otherwise.
28918 @var{tz} is a non-NULL pointer.
28921 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
28927 @unnumberedsubsubsec isatty
28928 @cindex isatty, file-i/o system call
28933 int isatty(int fd);
28937 @samp{Fisatty,@var{fd}}
28939 @item Return value:
28940 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
28946 The call was interrupted by the user.
28951 Note that the @code{isatty} call is treated as a special case: it returns
28952 1 to the target if the file descriptor is attached
28953 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
28954 would require implementing @code{ioctl} and would be more complex than
28959 @unnumberedsubsubsec system
28960 @cindex system, file-i/o system call
28965 int system(const char *command);
28969 @samp{Fsystem,@var{commandptr}/@var{len}}
28971 @item Return value:
28972 If @var{len} is zero, the return value indicates whether a shell is
28973 available. A zero return value indicates a shell is not available.
28974 For non-zero @var{len}, the value returned is -1 on error and the
28975 return status of the command otherwise. Only the exit status of the
28976 command is returned, which is extracted from the host's @code{system}
28977 return value by calling @code{WEXITSTATUS(retval)}. In case
28978 @file{/bin/sh} could not be executed, 127 is returned.
28984 The call was interrupted by the user.
28989 @value{GDBN} takes over the full task of calling the necessary host calls
28990 to perform the @code{system} call. The return value of @code{system} on
28991 the host is simplified before it's returned
28992 to the target. Any termination signal information from the child process
28993 is discarded, and the return value consists
28994 entirely of the exit status of the called command.
28996 Due to security concerns, the @code{system} call is by default refused
28997 by @value{GDBN}. The user has to allow this call explicitly with the
28998 @code{set remote system-call-allowed 1} command.
29001 @item set remote system-call-allowed
29002 @kindex set remote system-call-allowed
29003 Control whether to allow the @code{system} calls in the File I/O
29004 protocol for the remote target. The default is zero (disabled).
29006 @item show remote system-call-allowed
29007 @kindex show remote system-call-allowed
29008 Show whether the @code{system} calls are allowed in the File I/O
29012 @node Protocol-specific Representation of Datatypes
29013 @subsection Protocol-specific Representation of Datatypes
29014 @cindex protocol-specific representation of datatypes, in file-i/o protocol
29017 * Integral Datatypes::
29019 * Memory Transfer::
29024 @node Integral Datatypes
29025 @unnumberedsubsubsec Integral Datatypes
29026 @cindex integral datatypes, in file-i/o protocol
29028 The integral datatypes used in the system calls are @code{int},
29029 @code{unsigned int}, @code{long}, @code{unsigned long},
29030 @code{mode_t}, and @code{time_t}.
29032 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
29033 implemented as 32 bit values in this protocol.
29035 @code{long} and @code{unsigned long} are implemented as 64 bit types.
29037 @xref{Limits}, for corresponding MIN and MAX values (similar to those
29038 in @file{limits.h}) to allow range checking on host and target.
29040 @code{time_t} datatypes are defined as seconds since the Epoch.
29042 All integral datatypes transferred as part of a memory read or write of a
29043 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
29046 @node Pointer Values
29047 @unnumberedsubsubsec Pointer Values
29048 @cindex pointer values, in file-i/o protocol
29050 Pointers to target data are transmitted as they are. An exception
29051 is made for pointers to buffers for which the length isn't
29052 transmitted as part of the function call, namely strings. Strings
29053 are transmitted as a pointer/length pair, both as hex values, e.g.@:
29060 which is a pointer to data of length 18 bytes at position 0x1aaf.
29061 The length is defined as the full string length in bytes, including
29062 the trailing null byte. For example, the string @code{"hello world"}
29063 at address 0x123456 is transmitted as
29069 @node Memory Transfer
29070 @unnumberedsubsubsec Memory Transfer
29071 @cindex memory transfer, in file-i/o protocol
29073 Structured data which is transferred using a memory read or write (for
29074 example, a @code{struct stat}) is expected to be in a protocol-specific format
29075 with all scalar multibyte datatypes being big endian. Translation to
29076 this representation needs to be done both by the target before the @code{F}
29077 packet is sent, and by @value{GDBN} before
29078 it transfers memory to the target. Transferred pointers to structured
29079 data should point to the already-coerced data at any time.
29083 @unnumberedsubsubsec struct stat
29084 @cindex struct stat, in file-i/o protocol
29086 The buffer of type @code{struct stat} used by the target and @value{GDBN}
29087 is defined as follows:
29091 unsigned int st_dev; /* device */
29092 unsigned int st_ino; /* inode */
29093 mode_t st_mode; /* protection */
29094 unsigned int st_nlink; /* number of hard links */
29095 unsigned int st_uid; /* user ID of owner */
29096 unsigned int st_gid; /* group ID of owner */
29097 unsigned int st_rdev; /* device type (if inode device) */
29098 unsigned long st_size; /* total size, in bytes */
29099 unsigned long st_blksize; /* blocksize for filesystem I/O */
29100 unsigned long st_blocks; /* number of blocks allocated */
29101 time_t st_atime; /* time of last access */
29102 time_t st_mtime; /* time of last modification */
29103 time_t st_ctime; /* time of last change */
29107 The integral datatypes conform to the definitions given in the
29108 appropriate section (see @ref{Integral Datatypes}, for details) so this
29109 structure is of size 64 bytes.
29111 The values of several fields have a restricted meaning and/or
29117 A value of 0 represents a file, 1 the console.
29120 No valid meaning for the target. Transmitted unchanged.
29123 Valid mode bits are described in @ref{Constants}. Any other
29124 bits have currently no meaning for the target.
29129 No valid meaning for the target. Transmitted unchanged.
29134 These values have a host and file system dependent
29135 accuracy. Especially on Windows hosts, the file system may not
29136 support exact timing values.
29139 The target gets a @code{struct stat} of the above representation and is
29140 responsible for coercing it to the target representation before
29143 Note that due to size differences between the host, target, and protocol
29144 representations of @code{struct stat} members, these members could eventually
29145 get truncated on the target.
29147 @node struct timeval
29148 @unnumberedsubsubsec struct timeval
29149 @cindex struct timeval, in file-i/o protocol
29151 The buffer of type @code{struct timeval} used by the File-I/O protocol
29152 is defined as follows:
29156 time_t tv_sec; /* second */
29157 long tv_usec; /* microsecond */
29161 The integral datatypes conform to the definitions given in the
29162 appropriate section (see @ref{Integral Datatypes}, for details) so this
29163 structure is of size 8 bytes.
29166 @subsection Constants
29167 @cindex constants, in file-i/o protocol
29169 The following values are used for the constants inside of the
29170 protocol. @value{GDBN} and target are responsible for translating these
29171 values before and after the call as needed.
29182 @unnumberedsubsubsec Open Flags
29183 @cindex open flags, in file-i/o protocol
29185 All values are given in hexadecimal representation.
29197 @node mode_t Values
29198 @unnumberedsubsubsec mode_t Values
29199 @cindex mode_t values, in file-i/o protocol
29201 All values are given in octal representation.
29218 @unnumberedsubsubsec Errno Values
29219 @cindex errno values, in file-i/o protocol
29221 All values are given in decimal representation.
29246 @code{EUNKNOWN} is used as a fallback error value if a host system returns
29247 any error value not in the list of supported error numbers.
29250 @unnumberedsubsubsec Lseek Flags
29251 @cindex lseek flags, in file-i/o protocol
29260 @unnumberedsubsubsec Limits
29261 @cindex limits, in file-i/o protocol
29263 All values are given in decimal representation.
29266 INT_MIN -2147483648
29268 UINT_MAX 4294967295
29269 LONG_MIN -9223372036854775808
29270 LONG_MAX 9223372036854775807
29271 ULONG_MAX 18446744073709551615
29274 @node File-I/O Examples
29275 @subsection File-I/O Examples
29276 @cindex file-i/o examples
29278 Example sequence of a write call, file descriptor 3, buffer is at target
29279 address 0x1234, 6 bytes should be written:
29282 <- @code{Fwrite,3,1234,6}
29283 @emph{request memory read from target}
29286 @emph{return "6 bytes written"}
29290 Example sequence of a read call, file descriptor 3, buffer is at target
29291 address 0x1234, 6 bytes should be read:
29294 <- @code{Fread,3,1234,6}
29295 @emph{request memory write to target}
29296 -> @code{X1234,6:XXXXXX}
29297 @emph{return "6 bytes read"}
29301 Example sequence of a read call, call fails on the host due to invalid
29302 file descriptor (@code{EBADF}):
29305 <- @code{Fread,3,1234,6}
29309 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
29313 <- @code{Fread,3,1234,6}
29318 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
29322 <- @code{Fread,3,1234,6}
29323 -> @code{X1234,6:XXXXXX}
29327 @node Library List Format
29328 @section Library List Format
29329 @cindex library list format, remote protocol
29331 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
29332 same process as your application to manage libraries. In this case,
29333 @value{GDBN} can use the loader's symbol table and normal memory
29334 operations to maintain a list of shared libraries. On other
29335 platforms, the operating system manages loaded libraries.
29336 @value{GDBN} can not retrieve the list of currently loaded libraries
29337 through memory operations, so it uses the @samp{qXfer:libraries:read}
29338 packet (@pxref{qXfer library list read}) instead. The remote stub
29339 queries the target's operating system and reports which libraries
29342 The @samp{qXfer:libraries:read} packet returns an XML document which
29343 lists loaded libraries and their offsets. Each library has an
29344 associated name and one or more segment or section base addresses,
29345 which report where the library was loaded in memory.
29347 For the common case of libraries that are fully linked binaries, the
29348 library should have a list of segments. If the target supports
29349 dynamic linking of a relocatable object file, its library XML element
29350 should instead include a list of allocated sections. The segment or
29351 section bases are start addresses, not relocation offsets; they do not
29352 depend on the library's link-time base addresses.
29354 @value{GDBN} must be linked with the Expat library to support XML
29355 library lists. @xref{Expat}.
29357 A simple memory map, with one loaded library relocated by a single
29358 offset, looks like this:
29362 <library name="/lib/libc.so.6">
29363 <segment address="0x10000000"/>
29368 Another simple memory map, with one loaded library with three
29369 allocated sections (.text, .data, .bss), looks like this:
29373 <library name="sharedlib.o">
29374 <section address="0x10000000"/>
29375 <section address="0x20000000"/>
29376 <section address="0x30000000"/>
29381 The format of a library list is described by this DTD:
29384 <!-- library-list: Root element with versioning -->
29385 <!ELEMENT library-list (library)*>
29386 <!ATTLIST library-list version CDATA #FIXED "1.0">
29387 <!ELEMENT library (segment*, section*)>
29388 <!ATTLIST library name CDATA #REQUIRED>
29389 <!ELEMENT segment EMPTY>
29390 <!ATTLIST segment address CDATA #REQUIRED>
29391 <!ELEMENT section EMPTY>
29392 <!ATTLIST section address CDATA #REQUIRED>
29395 In addition, segments and section descriptors cannot be mixed within a
29396 single library element, and you must supply at least one segment or
29397 section for each library.
29399 @node Memory Map Format
29400 @section Memory Map Format
29401 @cindex memory map format
29403 To be able to write into flash memory, @value{GDBN} needs to obtain a
29404 memory map from the target. This section describes the format of the
29407 The memory map is obtained using the @samp{qXfer:memory-map:read}
29408 (@pxref{qXfer memory map read}) packet and is an XML document that
29409 lists memory regions.
29411 @value{GDBN} must be linked with the Expat library to support XML
29412 memory maps. @xref{Expat}.
29414 The top-level structure of the document is shown below:
29417 <?xml version="1.0"?>
29418 <!DOCTYPE memory-map
29419 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
29420 "http://sourceware.org/gdb/gdb-memory-map.dtd">
29426 Each region can be either:
29431 A region of RAM starting at @var{addr} and extending for @var{length}
29435 <memory type="ram" start="@var{addr}" length="@var{length}"/>
29440 A region of read-only memory:
29443 <memory type="rom" start="@var{addr}" length="@var{length}"/>
29448 A region of flash memory, with erasure blocks @var{blocksize}
29452 <memory type="flash" start="@var{addr}" length="@var{length}">
29453 <property name="blocksize">@var{blocksize}</property>
29459 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
29460 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
29461 packets to write to addresses in such ranges.
29463 The formal DTD for memory map format is given below:
29466 <!-- ................................................... -->
29467 <!-- Memory Map XML DTD ................................ -->
29468 <!-- File: memory-map.dtd .............................. -->
29469 <!-- .................................... .............. -->
29470 <!-- memory-map.dtd -->
29471 <!-- memory-map: Root element with versioning -->
29472 <!ELEMENT memory-map (memory | property)>
29473 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
29474 <!ELEMENT memory (property)>
29475 <!-- memory: Specifies a memory region,
29476 and its type, or device. -->
29477 <!ATTLIST memory type CDATA #REQUIRED
29478 start CDATA #REQUIRED
29479 length CDATA #REQUIRED
29480 device CDATA #IMPLIED>
29481 <!-- property: Generic attribute tag -->
29482 <!ELEMENT property (#PCDATA | property)*>
29483 <!ATTLIST property name CDATA #REQUIRED>
29486 @include agentexpr.texi
29488 @node Target Descriptions
29489 @appendix Target Descriptions
29490 @cindex target descriptions
29492 @strong{Warning:} target descriptions are still under active development,
29493 and the contents and format may change between @value{GDBN} releases.
29494 The format is expected to stabilize in the future.
29496 One of the challenges of using @value{GDBN} to debug embedded systems
29497 is that there are so many minor variants of each processor
29498 architecture in use. It is common practice for vendors to start with
29499 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
29500 and then make changes to adapt it to a particular market niche. Some
29501 architectures have hundreds of variants, available from dozens of
29502 vendors. This leads to a number of problems:
29506 With so many different customized processors, it is difficult for
29507 the @value{GDBN} maintainers to keep up with the changes.
29509 Since individual variants may have short lifetimes or limited
29510 audiences, it may not be worthwhile to carry information about every
29511 variant in the @value{GDBN} source tree.
29513 When @value{GDBN} does support the architecture of the embedded system
29514 at hand, the task of finding the correct architecture name to give the
29515 @command{set architecture} command can be error-prone.
29518 To address these problems, the @value{GDBN} remote protocol allows a
29519 target system to not only identify itself to @value{GDBN}, but to
29520 actually describe its own features. This lets @value{GDBN} support
29521 processor variants it has never seen before --- to the extent that the
29522 descriptions are accurate, and that @value{GDBN} understands them.
29524 @value{GDBN} must be linked with the Expat library to support XML
29525 target descriptions. @xref{Expat}.
29528 * Retrieving Descriptions:: How descriptions are fetched from a target.
29529 * Target Description Format:: The contents of a target description.
29530 * Predefined Target Types:: Standard types available for target
29532 * Standard Target Features:: Features @value{GDBN} knows about.
29535 @node Retrieving Descriptions
29536 @section Retrieving Descriptions
29538 Target descriptions can be read from the target automatically, or
29539 specified by the user manually. The default behavior is to read the
29540 description from the target. @value{GDBN} retrieves it via the remote
29541 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
29542 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
29543 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
29544 XML document, of the form described in @ref{Target Description
29547 Alternatively, you can specify a file to read for the target description.
29548 If a file is set, the target will not be queried. The commands to
29549 specify a file are:
29552 @cindex set tdesc filename
29553 @item set tdesc filename @var{path}
29554 Read the target description from @var{path}.
29556 @cindex unset tdesc filename
29557 @item unset tdesc filename
29558 Do not read the XML target description from a file. @value{GDBN}
29559 will use the description supplied by the current target.
29561 @cindex show tdesc filename
29562 @item show tdesc filename
29563 Show the filename to read for a target description, if any.
29567 @node Target Description Format
29568 @section Target Description Format
29569 @cindex target descriptions, XML format
29571 A target description annex is an @uref{http://www.w3.org/XML/, XML}
29572 document which complies with the Document Type Definition provided in
29573 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
29574 means you can use generally available tools like @command{xmllint} to
29575 check that your feature descriptions are well-formed and valid.
29576 However, to help people unfamiliar with XML write descriptions for
29577 their targets, we also describe the grammar here.
29579 Target descriptions can identify the architecture of the remote target
29580 and (for some architectures) provide information about custom register
29581 sets. @value{GDBN} can use this information to autoconfigure for your
29582 target, or to warn you if you connect to an unsupported target.
29584 Here is a simple target description:
29587 <target version="1.0">
29588 <architecture>i386:x86-64</architecture>
29593 This minimal description only says that the target uses
29594 the x86-64 architecture.
29596 A target description has the following overall form, with [ ] marking
29597 optional elements and @dots{} marking repeatable elements. The elements
29598 are explained further below.
29601 <?xml version="1.0"?>
29602 <!DOCTYPE target SYSTEM "gdb-target.dtd">
29603 <target version="1.0">
29604 @r{[}@var{architecture}@r{]}
29605 @r{[}@var{feature}@dots{}@r{]}
29610 The description is generally insensitive to whitespace and line
29611 breaks, under the usual common-sense rules. The XML version
29612 declaration and document type declaration can generally be omitted
29613 (@value{GDBN} does not require them), but specifying them may be
29614 useful for XML validation tools. The @samp{version} attribute for
29615 @samp{<target>} may also be omitted, but we recommend
29616 including it; if future versions of @value{GDBN} use an incompatible
29617 revision of @file{gdb-target.dtd}, they will detect and report
29618 the version mismatch.
29620 @subsection Inclusion
29621 @cindex target descriptions, inclusion
29624 @cindex <xi:include>
29627 It can sometimes be valuable to split a target description up into
29628 several different annexes, either for organizational purposes, or to
29629 share files between different possible target descriptions. You can
29630 divide a description into multiple files by replacing any element of
29631 the target description with an inclusion directive of the form:
29634 <xi:include href="@var{document}"/>
29638 When @value{GDBN} encounters an element of this form, it will retrieve
29639 the named XML @var{document}, and replace the inclusion directive with
29640 the contents of that document. If the current description was read
29641 using @samp{qXfer}, then so will be the included document;
29642 @var{document} will be interpreted as the name of an annex. If the
29643 current description was read from a file, @value{GDBN} will look for
29644 @var{document} as a file in the same directory where it found the
29645 original description.
29647 @subsection Architecture
29648 @cindex <architecture>
29650 An @samp{<architecture>} element has this form:
29653 <architecture>@var{arch}</architecture>
29656 @var{arch} is an architecture name from the same selection
29657 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
29658 Debugging Target}).
29660 @subsection Features
29663 Each @samp{<feature>} describes some logical portion of the target
29664 system. Features are currently used to describe available CPU
29665 registers and the types of their contents. A @samp{<feature>} element
29669 <feature name="@var{name}">
29670 @r{[}@var{type}@dots{}@r{]}
29676 Each feature's name should be unique within the description. The name
29677 of a feature does not matter unless @value{GDBN} has some special
29678 knowledge of the contents of that feature; if it does, the feature
29679 should have its standard name. @xref{Standard Target Features}.
29683 Any register's value is a collection of bits which @value{GDBN} must
29684 interpret. The default interpretation is a two's complement integer,
29685 but other types can be requested by name in the register description.
29686 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
29687 Target Types}), and the description can define additional composite types.
29689 Each type element must have an @samp{id} attribute, which gives
29690 a unique (within the containing @samp{<feature>}) name to the type.
29691 Types must be defined before they are used.
29694 Some targets offer vector registers, which can be treated as arrays
29695 of scalar elements. These types are written as @samp{<vector>} elements,
29696 specifying the array element type, @var{type}, and the number of elements,
29700 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
29704 If a register's value is usefully viewed in multiple ways, define it
29705 with a union type containing the useful representations. The
29706 @samp{<union>} element contains one or more @samp{<field>} elements,
29707 each of which has a @var{name} and a @var{type}:
29710 <union id="@var{id}">
29711 <field name="@var{name}" type="@var{type}"/>
29716 @subsection Registers
29719 Each register is represented as an element with this form:
29722 <reg name="@var{name}"
29723 bitsize="@var{size}"
29724 @r{[}regnum="@var{num}"@r{]}
29725 @r{[}save-restore="@var{save-restore}"@r{]}
29726 @r{[}type="@var{type}"@r{]}
29727 @r{[}group="@var{group}"@r{]}/>
29731 The components are as follows:
29736 The register's name; it must be unique within the target description.
29739 The register's size, in bits.
29742 The register's number. If omitted, a register's number is one greater
29743 than that of the previous register (either in the current feature or in
29744 a preceeding feature); the first register in the target description
29745 defaults to zero. This register number is used to read or write
29746 the register; e.g.@: it is used in the remote @code{p} and @code{P}
29747 packets, and registers appear in the @code{g} and @code{G} packets
29748 in order of increasing register number.
29751 Whether the register should be preserved across inferior function
29752 calls; this must be either @code{yes} or @code{no}. The default is
29753 @code{yes}, which is appropriate for most registers except for
29754 some system control registers; this is not related to the target's
29758 The type of the register. @var{type} may be a predefined type, a type
29759 defined in the current feature, or one of the special types @code{int}
29760 and @code{float}. @code{int} is an integer type of the correct size
29761 for @var{bitsize}, and @code{float} is a floating point type (in the
29762 architecture's normal floating point format) of the correct size for
29763 @var{bitsize}. The default is @code{int}.
29766 The register group to which this register belongs. @var{group} must
29767 be either @code{general}, @code{float}, or @code{vector}. If no
29768 @var{group} is specified, @value{GDBN} will not display the register
29769 in @code{info registers}.
29773 @node Predefined Target Types
29774 @section Predefined Target Types
29775 @cindex target descriptions, predefined types
29777 Type definitions in the self-description can build up composite types
29778 from basic building blocks, but can not define fundamental types. Instead,
29779 standard identifiers are provided by @value{GDBN} for the fundamental
29780 types. The currently supported types are:
29789 Signed integer types holding the specified number of bits.
29796 Unsigned integer types holding the specified number of bits.
29800 Pointers to unspecified code and data. The program counter and
29801 any dedicated return address register may be marked as code
29802 pointers; printing a code pointer converts it into a symbolic
29803 address. The stack pointer and any dedicated address registers
29804 may be marked as data pointers.
29807 Single precision IEEE floating point.
29810 Double precision IEEE floating point.
29813 The 12-byte extended precision format used by ARM FPA registers.
29817 @node Standard Target Features
29818 @section Standard Target Features
29819 @cindex target descriptions, standard features
29821 A target description must contain either no registers or all the
29822 target's registers. If the description contains no registers, then
29823 @value{GDBN} will assume a default register layout, selected based on
29824 the architecture. If the description contains any registers, the
29825 default layout will not be used; the standard registers must be
29826 described in the target description, in such a way that @value{GDBN}
29827 can recognize them.
29829 This is accomplished by giving specific names to feature elements
29830 which contain standard registers. @value{GDBN} will look for features
29831 with those names and verify that they contain the expected registers;
29832 if any known feature is missing required registers, or if any required
29833 feature is missing, @value{GDBN} will reject the target
29834 description. You can add additional registers to any of the
29835 standard features --- @value{GDBN} will display them just as if
29836 they were added to an unrecognized feature.
29838 This section lists the known features and their expected contents.
29839 Sample XML documents for these features are included in the
29840 @value{GDBN} source tree, in the directory @file{gdb/features}.
29842 Names recognized by @value{GDBN} should include the name of the
29843 company or organization which selected the name, and the overall
29844 architecture to which the feature applies; so e.g.@: the feature
29845 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
29847 The names of registers are not case sensitive for the purpose
29848 of recognizing standard features, but @value{GDBN} will only display
29849 registers using the capitalization used in the description.
29855 * PowerPC Features::
29860 @subsection ARM Features
29861 @cindex target descriptions, ARM features
29863 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
29864 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
29865 @samp{lr}, @samp{pc}, and @samp{cpsr}.
29867 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
29868 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
29870 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
29871 it should contain at least registers @samp{wR0} through @samp{wR15} and
29872 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
29873 @samp{wCSSF}, and @samp{wCASF} registers are optional.
29875 @node MIPS Features
29876 @subsection MIPS Features
29877 @cindex target descriptions, MIPS features
29879 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
29880 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
29881 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
29884 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
29885 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
29886 registers. They may be 32-bit or 64-bit depending on the target.
29888 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
29889 it may be optional in a future version of @value{GDBN}. It should
29890 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
29891 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
29893 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
29894 contain a single register, @samp{restart}, which is used by the
29895 Linux kernel to control restartable syscalls.
29897 @node M68K Features
29898 @subsection M68K Features
29899 @cindex target descriptions, M68K features
29902 @item @samp{org.gnu.gdb.m68k.core}
29903 @itemx @samp{org.gnu.gdb.coldfire.core}
29904 @itemx @samp{org.gnu.gdb.fido.core}
29905 One of those features must be always present.
29906 The feature that is present determines which flavor of m68k is
29907 used. The feature that is present should contain registers
29908 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
29909 @samp{sp}, @samp{ps} and @samp{pc}.
29911 @item @samp{org.gnu.gdb.coldfire.fp}
29912 This feature is optional. If present, it should contain registers
29913 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
29917 @node PowerPC Features
29918 @subsection PowerPC Features
29919 @cindex target descriptions, PowerPC features
29921 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
29922 targets. It should contain registers @samp{r0} through @samp{r31},
29923 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
29924 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
29926 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
29927 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
29929 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
29930 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
29933 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
29934 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
29935 will combine these registers with the floating point registers
29936 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
29937 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
29938 through @samp{vs63}, the set of vector registers for POWER7.
29940 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
29941 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
29942 @samp{spefscr}. SPE targets should provide 32-bit registers in
29943 @samp{org.gnu.gdb.power.core} and provide the upper halves in
29944 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
29945 these to present registers @samp{ev0} through @samp{ev31} to the
29948 @node Operating System Information
29949 @appendix Operating System Information
29950 @cindex operating system information
29956 Users of @value{GDBN} often wish to obtain information about the state of
29957 the operating system running on the target---for example the list of
29958 processes, or the list of open files. This section describes the
29959 mechanism that makes it possible. This mechanism is similar to the
29960 target features mechanism (@pxref{Target Descriptions}), but focuses
29961 on a different aspect of target.
29963 Operating system information is retrived from the target via the
29964 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
29965 read}). The object name in the request should be @samp{osdata}, and
29966 the @var{annex} identifies the data to be fetched.
29969 @appendixsection Process list
29970 @cindex operating system information, process list
29972 When requesting the process list, the @var{annex} field in the
29973 @samp{qXfer} request should be @samp{processes}. The returned data is
29974 an XML document. The formal syntax of this document is defined in
29975 @file{gdb/features/osdata.dtd}.
29977 An example document is:
29980 <?xml version="1.0"?>
29981 <!DOCTYPE target SYSTEM "osdata.dtd">
29982 <osdata type="processes">
29984 <column name="pid">1</column>
29985 <column name="user">root</column>
29986 <column name="command">/sbin/init</column>
29991 Each item should include a column whose name is @samp{pid}. The value
29992 of that column should identify the process on the target. The
29993 @samp{user} and @samp{command} columns are optional, and will be
29994 displayed by @value{GDBN}. Target may provide additional columns,
29995 which @value{GDBN} currently ignores.
30009 % I think something like @colophon should be in texinfo. In the
30011 \long\def\colophon{\hbox to0pt{}\vfill
30012 \centerline{The body of this manual is set in}
30013 \centerline{\fontname\tenrm,}
30014 \centerline{with headings in {\bf\fontname\tenbf}}
30015 \centerline{and examples in {\tt\fontname\tentt}.}
30016 \centerline{{\it\fontname\tenit\/},}
30017 \centerline{{\bf\fontname\tenbf}, and}
30018 \centerline{{\sl\fontname\tensl\/}}
30019 \centerline{are used for emphasis.}\vfill}
30021 % Blame: doc@cygnus.com, 1991.