1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
48 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
49 Free Software Foundation, Inc.
51 Permission is granted to copy, distribute and/or modify this document
52 under the terms of the GNU Free Documentation License, Version 1.1 or
53 any later version published by the Free Software Foundation; with the
54 Invariant Sections being ``Free Software'' and ``Free Software Needs
55 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
56 and with the Back-Cover Texts as in (a) below.
58 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
59 this GNU Manual. Buying copies from GNU Press supports the FSF in
60 developing GNU and promoting software freedom.''
64 This file documents the @sc{gnu} debugger @value{GDBN}.
66 This is the @value{EDITION} Edition, of @cite{Debugging with
67 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
68 @ifset VERSION_PACKAGE
69 @value{VERSION_PACKAGE}
71 Version @value{GDBVN}.
77 @title Debugging with @value{GDBN}
78 @subtitle The @sc{gnu} Source-Level Debugger
80 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
81 @ifset VERSION_PACKAGE
83 @subtitle @value{VERSION_PACKAGE}
85 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
89 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
90 \hfill {\it Debugging with @value{GDBN}}\par
91 \hfill \TeX{}info \texinfoversion\par
95 @vskip 0pt plus 1filll
96 Published by the Free Software Foundation @*
97 51 Franklin Street, Fifth Floor,
98 Boston, MA 02110-1301, USA@*
103 This edition of the GDB manual is dedicated to the memory of Fred
104 Fish. Fred was a long-standing contributor to GDB and to Free
105 software in general. We will miss him.
110 @node Top, Summary, (dir), (dir)
112 @top Debugging with @value{GDBN}
114 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
116 This is the @value{EDITION} Edition, for @value{GDBN}
117 @ifset VERSION_PACKAGE
118 @value{VERSION_PACKAGE}
120 Version @value{GDBVN}.
122 Copyright (C) 1988-2009 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Reverse Execution:: Running programs backward
137 * Stack:: Examining the stack
138 * Source:: Examining source files
139 * Data:: Examining data
140 * Macros:: Preprocessor Macros
141 * Tracepoints:: Debugging remote targets non-intrusively
142 * Overlays:: Debugging programs that use overlays
144 * Languages:: Using @value{GDBN} with different languages
146 * Symbols:: Examining the symbol table
147 * Altering:: Altering execution
148 * GDB Files:: @value{GDBN} files
149 * Targets:: Specifying a debugging target
150 * Remote Debugging:: Debugging remote programs
151 * Configurations:: Configuration-specific information
152 * Controlling GDB:: Controlling @value{GDBN}
153 * Extending GDB:: Extending @value{GDBN}
154 * Interpreters:: Command Interpreters
155 * TUI:: @value{GDBN} Text User Interface
156 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
157 * GDB/MI:: @value{GDBN}'s Machine Interface.
158 * Annotations:: @value{GDBN}'s annotation interface.
160 * GDB Bugs:: Reporting bugs in @value{GDBN}
162 * Command Line Editing:: Command Line Editing
163 * Using History Interactively:: Using History Interactively
164 * Formatting Documentation:: How to format and print @value{GDBN} documentation
165 * Installing GDB:: Installing GDB
166 * Maintenance Commands:: Maintenance Commands
167 * Remote Protocol:: GDB Remote Serial Protocol
168 * Agent Expressions:: The GDB Agent Expression Mechanism
169 * Target Descriptions:: How targets can describe themselves to
171 * Operating System Information:: Getting additional information from
173 * Copying:: GNU General Public License says
174 how you can copy and share GDB
175 * GNU Free Documentation License:: The license for this documentation
184 @unnumbered Summary of @value{GDBN}
186 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
187 going on ``inside'' another program while it executes---or what another
188 program was doing at the moment it crashed.
190 @value{GDBN} can do four main kinds of things (plus other things in support of
191 these) to help you catch bugs in the act:
195 Start your program, specifying anything that might affect its behavior.
198 Make your program stop on specified conditions.
201 Examine what has happened, when your program has stopped.
204 Change things in your program, so you can experiment with correcting the
205 effects of one bug and go on to learn about another.
208 You can use @value{GDBN} to debug programs written in C and C@t{++}.
209 For more information, see @ref{Supported Languages,,Supported Languages}.
210 For more information, see @ref{C,,C and C++}.
213 Support for Modula-2 is partial. For information on Modula-2, see
214 @ref{Modula-2,,Modula-2}.
217 Debugging Pascal programs which use sets, subranges, file variables, or
218 nested functions does not currently work. @value{GDBN} does not support
219 entering expressions, printing values, or similar features using Pascal
223 @value{GDBN} can be used to debug programs written in Fortran, although
224 it may be necessary to refer to some variables with a trailing
227 @value{GDBN} can be used to debug programs written in Objective-C,
228 using either the Apple/NeXT or the GNU Objective-C runtime.
231 * Free Software:: Freely redistributable software
232 * Contributors:: Contributors to GDB
236 @unnumberedsec Free Software
238 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
239 General Public License
240 (GPL). The GPL gives you the freedom to copy or adapt a licensed
241 program---but every person getting a copy also gets with it the
242 freedom to modify that copy (which means that they must get access to
243 the source code), and the freedom to distribute further copies.
244 Typical software companies use copyrights to limit your freedoms; the
245 Free Software Foundation uses the GPL to preserve these freedoms.
247 Fundamentally, the General Public License is a license which says that
248 you have these freedoms and that you cannot take these freedoms away
251 @unnumberedsec Free Software Needs Free Documentation
253 The biggest deficiency in the free software community today is not in
254 the software---it is the lack of good free documentation that we can
255 include with the free software. Many of our most important
256 programs do not come with free reference manuals and free introductory
257 texts. Documentation is an essential part of any software package;
258 when an important free software package does not come with a free
259 manual and a free tutorial, that is a major gap. We have many such
262 Consider Perl, for instance. The tutorial manuals that people
263 normally use are non-free. How did this come about? Because the
264 authors of those manuals published them with restrictive terms---no
265 copying, no modification, source files not available---which exclude
266 them from the free software world.
268 That wasn't the first time this sort of thing happened, and it was far
269 from the last. Many times we have heard a GNU user eagerly describe a
270 manual that he is writing, his intended contribution to the community,
271 only to learn that he had ruined everything by signing a publication
272 contract to make it non-free.
274 Free documentation, like free software, is a matter of freedom, not
275 price. The problem with the non-free manual is not that publishers
276 charge a price for printed copies---that in itself is fine. (The Free
277 Software Foundation sells printed copies of manuals, too.) The
278 problem is the restrictions on the use of the manual. Free manuals
279 are available in source code form, and give you permission to copy and
280 modify. Non-free manuals do not allow this.
282 The criteria of freedom for a free manual are roughly the same as for
283 free software. Redistribution (including the normal kinds of
284 commercial redistribution) must be permitted, so that the manual can
285 accompany every copy of the program, both on-line and on paper.
287 Permission for modification of the technical content is crucial too.
288 When people modify the software, adding or changing features, if they
289 are conscientious they will change the manual too---so they can
290 provide accurate and clear documentation for the modified program. A
291 manual that leaves you no choice but to write a new manual to document
292 a changed version of the program is not really available to our
295 Some kinds of limits on the way modification is handled are
296 acceptable. For example, requirements to preserve the original
297 author's copyright notice, the distribution terms, or the list of
298 authors, are ok. It is also no problem to require modified versions
299 to include notice that they were modified. Even entire sections that
300 may not be deleted or changed are acceptable, as long as they deal
301 with nontechnical topics (like this one). These kinds of restrictions
302 are acceptable because they don't obstruct the community's normal use
305 However, it must be possible to modify all the @emph{technical}
306 content of the manual, and then distribute the result in all the usual
307 media, through all the usual channels. Otherwise, the restrictions
308 obstruct the use of the manual, it is not free, and we need another
309 manual to replace it.
311 Please spread the word about this issue. Our community continues to
312 lose manuals to proprietary publishing. If we spread the word that
313 free software needs free reference manuals and free tutorials, perhaps
314 the next person who wants to contribute by writing documentation will
315 realize, before it is too late, that only free manuals contribute to
316 the free software community.
318 If you are writing documentation, please insist on publishing it under
319 the GNU Free Documentation License or another free documentation
320 license. Remember that this decision requires your approval---you
321 don't have to let the publisher decide. Some commercial publishers
322 will use a free license if you insist, but they will not propose the
323 option; it is up to you to raise the issue and say firmly that this is
324 what you want. If the publisher you are dealing with refuses, please
325 try other publishers. If you're not sure whether a proposed license
326 is free, write to @email{licensing@@gnu.org}.
328 You can encourage commercial publishers to sell more free, copylefted
329 manuals and tutorials by buying them, and particularly by buying
330 copies from the publishers that paid for their writing or for major
331 improvements. Meanwhile, try to avoid buying non-free documentation
332 at all. Check the distribution terms of a manual before you buy it,
333 and insist that whoever seeks your business must respect your freedom.
334 Check the history of the book, and try to reward the publishers that
335 have paid or pay the authors to work on it.
337 The Free Software Foundation maintains a list of free documentation
338 published by other publishers, at
339 @url{http://www.fsf.org/doc/other-free-books.html}.
342 @unnumberedsec Contributors to @value{GDBN}
344 Richard Stallman was the original author of @value{GDBN}, and of many
345 other @sc{gnu} programs. Many others have contributed to its
346 development. This section attempts to credit major contributors. One
347 of the virtues of free software is that everyone is free to contribute
348 to it; with regret, we cannot actually acknowledge everyone here. The
349 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
350 blow-by-blow account.
352 Changes much prior to version 2.0 are lost in the mists of time.
355 @emph{Plea:} Additions to this section are particularly welcome. If you
356 or your friends (or enemies, to be evenhanded) have been unfairly
357 omitted from this list, we would like to add your names!
360 So that they may not regard their many labors as thankless, we
361 particularly thank those who shepherded @value{GDBN} through major
363 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
364 Jim Blandy (release 4.18);
365 Jason Molenda (release 4.17);
366 Stan Shebs (release 4.14);
367 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
368 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
369 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
370 Jim Kingdon (releases 3.5, 3.4, and 3.3);
371 and Randy Smith (releases 3.2, 3.1, and 3.0).
373 Richard Stallman, assisted at various times by Peter TerMaat, Chris
374 Hanson, and Richard Mlynarik, handled releases through 2.8.
376 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
377 in @value{GDBN}, with significant additional contributions from Per
378 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
379 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
380 much general update work leading to release 3.0).
382 @value{GDBN} uses the BFD subroutine library to examine multiple
383 object-file formats; BFD was a joint project of David V.
384 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
386 David Johnson wrote the original COFF support; Pace Willison did
387 the original support for encapsulated COFF.
389 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
391 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
392 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
394 Jean-Daniel Fekete contributed Sun 386i support.
395 Chris Hanson improved the HP9000 support.
396 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
397 David Johnson contributed Encore Umax support.
398 Jyrki Kuoppala contributed Altos 3068 support.
399 Jeff Law contributed HP PA and SOM support.
400 Keith Packard contributed NS32K support.
401 Doug Rabson contributed Acorn Risc Machine support.
402 Bob Rusk contributed Harris Nighthawk CX-UX support.
403 Chris Smith contributed Convex support (and Fortran debugging).
404 Jonathan Stone contributed Pyramid support.
405 Michael Tiemann contributed SPARC support.
406 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
407 Pace Willison contributed Intel 386 support.
408 Jay Vosburgh contributed Symmetry support.
409 Marko Mlinar contributed OpenRISC 1000 support.
411 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
413 Rich Schaefer and Peter Schauer helped with support of SunOS shared
416 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
417 about several machine instruction sets.
419 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
420 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
421 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
422 and RDI targets, respectively.
424 Brian Fox is the author of the readline libraries providing
425 command-line editing and command history.
427 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
428 Modula-2 support, and contributed the Languages chapter of this manual.
430 Fred Fish wrote most of the support for Unix System Vr4.
431 He also enhanced the command-completion support to cover C@t{++} overloaded
434 Hitachi America (now Renesas America), Ltd. sponsored the support for
435 H8/300, H8/500, and Super-H processors.
437 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
439 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
442 Toshiba sponsored the support for the TX39 Mips processor.
444 Matsushita sponsored the support for the MN10200 and MN10300 processors.
446 Fujitsu sponsored the support for SPARClite and FR30 processors.
448 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
451 Michael Snyder added support for tracepoints.
453 Stu Grossman wrote gdbserver.
455 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
456 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
458 The following people at the Hewlett-Packard Company contributed
459 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
460 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
461 compiler, and the Text User Interface (nee Terminal User Interface):
462 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
463 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
464 provided HP-specific information in this manual.
466 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
467 Robert Hoehne made significant contributions to the DJGPP port.
469 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
470 development since 1991. Cygnus engineers who have worked on @value{GDBN}
471 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
472 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
473 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
474 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
475 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
476 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
477 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
478 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
479 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
480 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
481 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
482 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
483 Zuhn have made contributions both large and small.
485 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
486 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
488 Jim Blandy added support for preprocessor macros, while working for Red
491 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
492 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
493 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
494 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
495 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
496 with the migration of old architectures to this new framework.
498 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
499 unwinder framework, this consisting of a fresh new design featuring
500 frame IDs, independent frame sniffers, and the sentinel frame. Mark
501 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
502 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
503 trad unwinders. The architecture-specific changes, each involving a
504 complete rewrite of the architecture's frame code, were carried out by
505 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
506 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
507 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
508 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
511 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
512 Tensilica, Inc.@: contributed support for Xtensa processors. Others
513 who have worked on the Xtensa port of @value{GDBN} in the past include
514 Steve Tjiang, John Newlin, and Scott Foehner.
517 @chapter A Sample @value{GDBN} Session
519 You can use this manual at your leisure to read all about @value{GDBN}.
520 However, a handful of commands are enough to get started using the
521 debugger. This chapter illustrates those commands.
524 In this sample session, we emphasize user input like this: @b{input},
525 to make it easier to pick out from the surrounding output.
528 @c FIXME: this example may not be appropriate for some configs, where
529 @c FIXME...primary interest is in remote use.
531 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
532 processor) exhibits the following bug: sometimes, when we change its
533 quote strings from the default, the commands used to capture one macro
534 definition within another stop working. In the following short @code{m4}
535 session, we define a macro @code{foo} which expands to @code{0000}; we
536 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
537 same thing. However, when we change the open quote string to
538 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
539 procedure fails to define a new synonym @code{baz}:
548 @b{define(bar,defn(`foo'))}
552 @b{changequote(<QUOTE>,<UNQUOTE>)}
554 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
557 m4: End of input: 0: fatal error: EOF in string
561 Let us use @value{GDBN} to try to see what is going on.
564 $ @b{@value{GDBP} m4}
565 @c FIXME: this falsifies the exact text played out, to permit smallbook
566 @c FIXME... format to come out better.
567 @value{GDBN} is free software and you are welcome to distribute copies
568 of it under certain conditions; type "show copying" to see
570 There is absolutely no warranty for @value{GDBN}; type "show warranty"
573 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
578 @value{GDBN} reads only enough symbol data to know where to find the
579 rest when needed; as a result, the first prompt comes up very quickly.
580 We now tell @value{GDBN} to use a narrower display width than usual, so
581 that examples fit in this manual.
584 (@value{GDBP}) @b{set width 70}
588 We need to see how the @code{m4} built-in @code{changequote} works.
589 Having looked at the source, we know the relevant subroutine is
590 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
591 @code{break} command.
594 (@value{GDBP}) @b{break m4_changequote}
595 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
599 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
600 control; as long as control does not reach the @code{m4_changequote}
601 subroutine, the program runs as usual:
604 (@value{GDBP}) @b{run}
605 Starting program: /work/Editorial/gdb/gnu/m4/m4
613 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
614 suspends execution of @code{m4}, displaying information about the
615 context where it stops.
618 @b{changequote(<QUOTE>,<UNQUOTE>)}
620 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
622 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
626 Now we use the command @code{n} (@code{next}) to advance execution to
627 the next line of the current function.
631 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
636 @code{set_quotes} looks like a promising subroutine. We can go into it
637 by using the command @code{s} (@code{step}) instead of @code{next}.
638 @code{step} goes to the next line to be executed in @emph{any}
639 subroutine, so it steps into @code{set_quotes}.
643 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
645 530 if (lquote != def_lquote)
649 The display that shows the subroutine where @code{m4} is now
650 suspended (and its arguments) is called a stack frame display. It
651 shows a summary of the stack. We can use the @code{backtrace}
652 command (which can also be spelled @code{bt}), to see where we are
653 in the stack as a whole: the @code{backtrace} command displays a
654 stack frame for each active subroutine.
657 (@value{GDBP}) @b{bt}
658 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
660 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
662 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
663 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
665 #4 0x79dc in expand_input () at macro.c:40
666 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
670 We step through a few more lines to see what happens. The first two
671 times, we can use @samp{s}; the next two times we use @code{n} to avoid
672 falling into the @code{xstrdup} subroutine.
676 0x3b5c 532 if (rquote != def_rquote)
678 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
679 def_lquote : xstrdup(lq);
681 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
684 538 len_lquote = strlen(rquote);
688 The last line displayed looks a little odd; we can examine the variables
689 @code{lquote} and @code{rquote} to see if they are in fact the new left
690 and right quotes we specified. We use the command @code{p}
691 (@code{print}) to see their values.
694 (@value{GDBP}) @b{p lquote}
695 $1 = 0x35d40 "<QUOTE>"
696 (@value{GDBP}) @b{p rquote}
697 $2 = 0x35d50 "<UNQUOTE>"
701 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
702 To look at some context, we can display ten lines of source
703 surrounding the current line with the @code{l} (@code{list}) command.
709 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
711 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
714 538 len_lquote = strlen(rquote);
715 539 len_rquote = strlen(lquote);
722 Let us step past the two lines that set @code{len_lquote} and
723 @code{len_rquote}, and then examine the values of those variables.
727 539 len_rquote = strlen(lquote);
730 (@value{GDBP}) @b{p len_lquote}
732 (@value{GDBP}) @b{p len_rquote}
737 That certainly looks wrong, assuming @code{len_lquote} and
738 @code{len_rquote} are meant to be the lengths of @code{lquote} and
739 @code{rquote} respectively. We can set them to better values using
740 the @code{p} command, since it can print the value of
741 any expression---and that expression can include subroutine calls and
745 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
747 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
752 Is that enough to fix the problem of using the new quotes with the
753 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
754 executing with the @code{c} (@code{continue}) command, and then try the
755 example that caused trouble initially:
761 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
768 Success! The new quotes now work just as well as the default ones. The
769 problem seems to have been just the two typos defining the wrong
770 lengths. We allow @code{m4} exit by giving it an EOF as input:
774 Program exited normally.
778 The message @samp{Program exited normally.} is from @value{GDBN}; it
779 indicates @code{m4} has finished executing. We can end our @value{GDBN}
780 session with the @value{GDBN} @code{quit} command.
783 (@value{GDBP}) @b{quit}
787 @chapter Getting In and Out of @value{GDBN}
789 This chapter discusses how to start @value{GDBN}, and how to get out of it.
793 type @samp{@value{GDBP}} to start @value{GDBN}.
795 type @kbd{quit} or @kbd{Ctrl-d} to exit.
799 * Invoking GDB:: How to start @value{GDBN}
800 * Quitting GDB:: How to quit @value{GDBN}
801 * Shell Commands:: How to use shell commands inside @value{GDBN}
802 * Logging Output:: How to log @value{GDBN}'s output to a file
806 @section Invoking @value{GDBN}
808 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
809 @value{GDBN} reads commands from the terminal until you tell it to exit.
811 You can also run @code{@value{GDBP}} with a variety of arguments and options,
812 to specify more of your debugging environment at the outset.
814 The command-line options described here are designed
815 to cover a variety of situations; in some environments, some of these
816 options may effectively be unavailable.
818 The most usual way to start @value{GDBN} is with one argument,
819 specifying an executable program:
822 @value{GDBP} @var{program}
826 You can also start with both an executable program and a core file
830 @value{GDBP} @var{program} @var{core}
833 You can, instead, specify a process ID as a second argument, if you want
834 to debug a running process:
837 @value{GDBP} @var{program} 1234
841 would attach @value{GDBN} to process @code{1234} (unless you also have a file
842 named @file{1234}; @value{GDBN} does check for a core file first).
844 Taking advantage of the second command-line argument requires a fairly
845 complete operating system; when you use @value{GDBN} as a remote
846 debugger attached to a bare board, there may not be any notion of
847 ``process'', and there is often no way to get a core dump. @value{GDBN}
848 will warn you if it is unable to attach or to read core dumps.
850 You can optionally have @code{@value{GDBP}} pass any arguments after the
851 executable file to the inferior using @code{--args}. This option stops
854 @value{GDBP} --args gcc -O2 -c foo.c
856 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
857 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
859 You can run @code{@value{GDBP}} without printing the front material, which describes
860 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
867 You can further control how @value{GDBN} starts up by using command-line
868 options. @value{GDBN} itself can remind you of the options available.
878 to display all available options and briefly describe their use
879 (@samp{@value{GDBP} -h} is a shorter equivalent).
881 All options and command line arguments you give are processed
882 in sequential order. The order makes a difference when the
883 @samp{-x} option is used.
887 * File Options:: Choosing files
888 * Mode Options:: Choosing modes
889 * Startup:: What @value{GDBN} does during startup
893 @subsection Choosing Files
895 When @value{GDBN} starts, it reads any arguments other than options as
896 specifying an executable file and core file (or process ID). This is
897 the same as if the arguments were specified by the @samp{-se} and
898 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
899 first argument that does not have an associated option flag as
900 equivalent to the @samp{-se} option followed by that argument; and the
901 second argument that does not have an associated option flag, if any, as
902 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
903 If the second argument begins with a decimal digit, @value{GDBN} will
904 first attempt to attach to it as a process, and if that fails, attempt
905 to open it as a corefile. If you have a corefile whose name begins with
906 a digit, you can prevent @value{GDBN} from treating it as a pid by
907 prefixing it with @file{./}, e.g.@: @file{./12345}.
909 If @value{GDBN} has not been configured to included core file support,
910 such as for most embedded targets, then it will complain about a second
911 argument and ignore it.
913 Many options have both long and short forms; both are shown in the
914 following list. @value{GDBN} also recognizes the long forms if you truncate
915 them, so long as enough of the option is present to be unambiguous.
916 (If you prefer, you can flag option arguments with @samp{--} rather
917 than @samp{-}, though we illustrate the more usual convention.)
919 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
920 @c way, both those who look for -foo and --foo in the index, will find
924 @item -symbols @var{file}
926 @cindex @code{--symbols}
928 Read symbol table from file @var{file}.
930 @item -exec @var{file}
932 @cindex @code{--exec}
934 Use file @var{file} as the executable file to execute when appropriate,
935 and for examining pure data in conjunction with a core dump.
939 Read symbol table from file @var{file} and use it as the executable
942 @item -core @var{file}
944 @cindex @code{--core}
946 Use file @var{file} as a core dump to examine.
948 @item -pid @var{number}
949 @itemx -p @var{number}
952 Connect to process ID @var{number}, as with the @code{attach} command.
954 @item -command @var{file}
956 @cindex @code{--command}
958 Execute @value{GDBN} commands from file @var{file}. @xref{Command
959 Files,, Command files}.
961 @item -eval-command @var{command}
962 @itemx -ex @var{command}
963 @cindex @code{--eval-command}
965 Execute a single @value{GDBN} command.
967 This option may be used multiple times to call multiple commands. It may
968 also be interleaved with @samp{-command} as required.
971 @value{GDBP} -ex 'target sim' -ex 'load' \
972 -x setbreakpoints -ex 'run' a.out
975 @item -directory @var{directory}
976 @itemx -d @var{directory}
977 @cindex @code{--directory}
979 Add @var{directory} to the path to search for source and script files.
983 @cindex @code{--readnow}
985 Read each symbol file's entire symbol table immediately, rather than
986 the default, which is to read it incrementally as it is needed.
987 This makes startup slower, but makes future operations faster.
992 @subsection Choosing Modes
994 You can run @value{GDBN} in various alternative modes---for example, in
995 batch mode or quiet mode.
1002 Do not execute commands found in any initialization files. Normally,
1003 @value{GDBN} executes the commands in these files after all the command
1004 options and arguments have been processed. @xref{Command Files,,Command
1010 @cindex @code{--quiet}
1011 @cindex @code{--silent}
1013 ``Quiet''. Do not print the introductory and copyright messages. These
1014 messages are also suppressed in batch mode.
1017 @cindex @code{--batch}
1018 Run in batch mode. Exit with status @code{0} after processing all the
1019 command files specified with @samp{-x} (and all commands from
1020 initialization files, if not inhibited with @samp{-n}). Exit with
1021 nonzero status if an error occurs in executing the @value{GDBN} commands
1022 in the command files.
1024 Batch mode may be useful for running @value{GDBN} as a filter, for
1025 example to download and run a program on another computer; in order to
1026 make this more useful, the message
1029 Program exited normally.
1033 (which is ordinarily issued whenever a program running under
1034 @value{GDBN} control terminates) is not issued when running in batch
1038 @cindex @code{--batch-silent}
1039 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1040 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1041 unaffected). This is much quieter than @samp{-silent} and would be useless
1042 for an interactive session.
1044 This is particularly useful when using targets that give @samp{Loading section}
1045 messages, for example.
1047 Note that targets that give their output via @value{GDBN}, as opposed to
1048 writing directly to @code{stdout}, will also be made silent.
1050 @item -return-child-result
1051 @cindex @code{--return-child-result}
1052 The return code from @value{GDBN} will be the return code from the child
1053 process (the process being debugged), with the following exceptions:
1057 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1058 internal error. In this case the exit code is the same as it would have been
1059 without @samp{-return-child-result}.
1061 The user quits with an explicit value. E.g., @samp{quit 1}.
1063 The child process never runs, or is not allowed to terminate, in which case
1064 the exit code will be -1.
1067 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1068 when @value{GDBN} is being used as a remote program loader or simulator
1073 @cindex @code{--nowindows}
1075 ``No windows''. If @value{GDBN} comes with a graphical user interface
1076 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1077 interface. If no GUI is available, this option has no effect.
1081 @cindex @code{--windows}
1083 If @value{GDBN} includes a GUI, then this option requires it to be
1086 @item -cd @var{directory}
1088 Run @value{GDBN} using @var{directory} as its working directory,
1089 instead of the current directory.
1093 @cindex @code{--fullname}
1095 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1096 subprocess. It tells @value{GDBN} to output the full file name and line
1097 number in a standard, recognizable fashion each time a stack frame is
1098 displayed (which includes each time your program stops). This
1099 recognizable format looks like two @samp{\032} characters, followed by
1100 the file name, line number and character position separated by colons,
1101 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1102 @samp{\032} characters as a signal to display the source code for the
1106 @cindex @code{--epoch}
1107 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1108 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1109 routines so as to allow Epoch to display values of expressions in a
1112 @item -annotate @var{level}
1113 @cindex @code{--annotate}
1114 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1115 effect is identical to using @samp{set annotate @var{level}}
1116 (@pxref{Annotations}). The annotation @var{level} controls how much
1117 information @value{GDBN} prints together with its prompt, values of
1118 expressions, source lines, and other types of output. Level 0 is the
1119 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1120 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1121 that control @value{GDBN}, and level 2 has been deprecated.
1123 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1127 @cindex @code{--args}
1128 Change interpretation of command line so that arguments following the
1129 executable file are passed as command line arguments to the inferior.
1130 This option stops option processing.
1132 @item -baud @var{bps}
1134 @cindex @code{--baud}
1136 Set the line speed (baud rate or bits per second) of any serial
1137 interface used by @value{GDBN} for remote debugging.
1139 @item -l @var{timeout}
1141 Set the timeout (in seconds) of any communication used by @value{GDBN}
1142 for remote debugging.
1144 @item -tty @var{device}
1145 @itemx -t @var{device}
1146 @cindex @code{--tty}
1148 Run using @var{device} for your program's standard input and output.
1149 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1151 @c resolve the situation of these eventually
1153 @cindex @code{--tui}
1154 Activate the @dfn{Text User Interface} when starting. The Text User
1155 Interface manages several text windows on the terminal, showing
1156 source, assembly, registers and @value{GDBN} command outputs
1157 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1158 Text User Interface can be enabled by invoking the program
1159 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1160 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1163 @c @cindex @code{--xdb}
1164 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1165 @c For information, see the file @file{xdb_trans.html}, which is usually
1166 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1169 @item -interpreter @var{interp}
1170 @cindex @code{--interpreter}
1171 Use the interpreter @var{interp} for interface with the controlling
1172 program or device. This option is meant to be set by programs which
1173 communicate with @value{GDBN} using it as a back end.
1174 @xref{Interpreters, , Command Interpreters}.
1176 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1177 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1178 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1179 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1180 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1181 @sc{gdb/mi} interfaces are no longer supported.
1184 @cindex @code{--write}
1185 Open the executable and core files for both reading and writing. This
1186 is equivalent to the @samp{set write on} command inside @value{GDBN}
1190 @cindex @code{--statistics}
1191 This option causes @value{GDBN} to print statistics about time and
1192 memory usage after it completes each command and returns to the prompt.
1195 @cindex @code{--version}
1196 This option causes @value{GDBN} to print its version number and
1197 no-warranty blurb, and exit.
1202 @subsection What @value{GDBN} Does During Startup
1203 @cindex @value{GDBN} startup
1205 Here's the description of what @value{GDBN} does during session startup:
1209 Sets up the command interpreter as specified by the command line
1210 (@pxref{Mode Options, interpreter}).
1214 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1215 used when building @value{GDBN}; @pxref{System-wide configuration,
1216 ,System-wide configuration and settings}) and executes all the commands in
1220 Reads the init file (if any) in your home directory@footnote{On
1221 DOS/Windows systems, the home directory is the one pointed to by the
1222 @code{HOME} environment variable.} and executes all the commands in
1226 Processes command line options and operands.
1229 Reads and executes the commands from init file (if any) in the current
1230 working directory. This is only done if the current directory is
1231 different from your home directory. Thus, you can have more than one
1232 init file, one generic in your home directory, and another, specific
1233 to the program you are debugging, in the directory where you invoke
1237 Reads command files specified by the @samp{-x} option. @xref{Command
1238 Files}, for more details about @value{GDBN} command files.
1241 Reads the command history recorded in the @dfn{history file}.
1242 @xref{Command History}, for more details about the command history and the
1243 files where @value{GDBN} records it.
1246 Init files use the same syntax as @dfn{command files} (@pxref{Command
1247 Files}) and are processed by @value{GDBN} in the same way. The init
1248 file in your home directory can set options (such as @samp{set
1249 complaints}) that affect subsequent processing of command line options
1250 and operands. Init files are not executed if you use the @samp{-nx}
1251 option (@pxref{Mode Options, ,Choosing Modes}).
1253 To display the list of init files loaded by gdb at startup, you
1254 can use @kbd{gdb --help}.
1256 @cindex init file name
1257 @cindex @file{.gdbinit}
1258 @cindex @file{gdb.ini}
1259 The @value{GDBN} init files are normally called @file{.gdbinit}.
1260 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1261 the limitations of file names imposed by DOS filesystems. The Windows
1262 ports of @value{GDBN} use the standard name, but if they find a
1263 @file{gdb.ini} file, they warn you about that and suggest to rename
1264 the file to the standard name.
1268 @section Quitting @value{GDBN}
1269 @cindex exiting @value{GDBN}
1270 @cindex leaving @value{GDBN}
1273 @kindex quit @r{[}@var{expression}@r{]}
1274 @kindex q @r{(@code{quit})}
1275 @item quit @r{[}@var{expression}@r{]}
1277 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1278 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1279 do not supply @var{expression}, @value{GDBN} will terminate normally;
1280 otherwise it will terminate using the result of @var{expression} as the
1285 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1286 terminates the action of any @value{GDBN} command that is in progress and
1287 returns to @value{GDBN} command level. It is safe to type the interrupt
1288 character at any time because @value{GDBN} does not allow it to take effect
1289 until a time when it is safe.
1291 If you have been using @value{GDBN} to control an attached process or
1292 device, you can release it with the @code{detach} command
1293 (@pxref{Attach, ,Debugging an Already-running Process}).
1295 @node Shell Commands
1296 @section Shell Commands
1298 If you need to execute occasional shell commands during your
1299 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1300 just use the @code{shell} command.
1304 @cindex shell escape
1305 @item shell @var{command string}
1306 Invoke a standard shell to execute @var{command string}.
1307 If it exists, the environment variable @code{SHELL} determines which
1308 shell to run. Otherwise @value{GDBN} uses the default shell
1309 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1312 The utility @code{make} is often needed in development environments.
1313 You do not have to use the @code{shell} command for this purpose in
1318 @cindex calling make
1319 @item make @var{make-args}
1320 Execute the @code{make} program with the specified
1321 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1324 @node Logging Output
1325 @section Logging Output
1326 @cindex logging @value{GDBN} output
1327 @cindex save @value{GDBN} output to a file
1329 You may want to save the output of @value{GDBN} commands to a file.
1330 There are several commands to control @value{GDBN}'s logging.
1334 @item set logging on
1336 @item set logging off
1338 @cindex logging file name
1339 @item set logging file @var{file}
1340 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1341 @item set logging overwrite [on|off]
1342 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1343 you want @code{set logging on} to overwrite the logfile instead.
1344 @item set logging redirect [on|off]
1345 By default, @value{GDBN} output will go to both the terminal and the logfile.
1346 Set @code{redirect} if you want output to go only to the log file.
1347 @kindex show logging
1349 Show the current values of the logging settings.
1353 @chapter @value{GDBN} Commands
1355 You can abbreviate a @value{GDBN} command to the first few letters of the command
1356 name, if that abbreviation is unambiguous; and you can repeat certain
1357 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1358 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1359 show you the alternatives available, if there is more than one possibility).
1362 * Command Syntax:: How to give commands to @value{GDBN}
1363 * Completion:: Command completion
1364 * Help:: How to ask @value{GDBN} for help
1367 @node Command Syntax
1368 @section Command Syntax
1370 A @value{GDBN} command is a single line of input. There is no limit on
1371 how long it can be. It starts with a command name, which is followed by
1372 arguments whose meaning depends on the command name. For example, the
1373 command @code{step} accepts an argument which is the number of times to
1374 step, as in @samp{step 5}. You can also use the @code{step} command
1375 with no arguments. Some commands do not allow any arguments.
1377 @cindex abbreviation
1378 @value{GDBN} command names may always be truncated if that abbreviation is
1379 unambiguous. Other possible command abbreviations are listed in the
1380 documentation for individual commands. In some cases, even ambiguous
1381 abbreviations are allowed; for example, @code{s} is specially defined as
1382 equivalent to @code{step} even though there are other commands whose
1383 names start with @code{s}. You can test abbreviations by using them as
1384 arguments to the @code{help} command.
1386 @cindex repeating commands
1387 @kindex RET @r{(repeat last command)}
1388 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1389 repeat the previous command. Certain commands (for example, @code{run})
1390 will not repeat this way; these are commands whose unintentional
1391 repetition might cause trouble and which you are unlikely to want to
1392 repeat. User-defined commands can disable this feature; see
1393 @ref{Define, dont-repeat}.
1395 The @code{list} and @code{x} commands, when you repeat them with
1396 @key{RET}, construct new arguments rather than repeating
1397 exactly as typed. This permits easy scanning of source or memory.
1399 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1400 output, in a way similar to the common utility @code{more}
1401 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1402 @key{RET} too many in this situation, @value{GDBN} disables command
1403 repetition after any command that generates this sort of display.
1405 @kindex # @r{(a comment)}
1407 Any text from a @kbd{#} to the end of the line is a comment; it does
1408 nothing. This is useful mainly in command files (@pxref{Command
1409 Files,,Command Files}).
1411 @cindex repeating command sequences
1412 @kindex Ctrl-o @r{(operate-and-get-next)}
1413 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1414 commands. This command accepts the current line, like @key{RET}, and
1415 then fetches the next line relative to the current line from the history
1419 @section Command Completion
1422 @cindex word completion
1423 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1424 only one possibility; it can also show you what the valid possibilities
1425 are for the next word in a command, at any time. This works for @value{GDBN}
1426 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1428 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1429 of a word. If there is only one possibility, @value{GDBN} fills in the
1430 word, and waits for you to finish the command (or press @key{RET} to
1431 enter it). For example, if you type
1433 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1434 @c complete accuracy in these examples; space introduced for clarity.
1435 @c If texinfo enhancements make it unnecessary, it would be nice to
1436 @c replace " @key" by "@key" in the following...
1438 (@value{GDBP}) info bre @key{TAB}
1442 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1443 the only @code{info} subcommand beginning with @samp{bre}:
1446 (@value{GDBP}) info breakpoints
1450 You can either press @key{RET} at this point, to run the @code{info
1451 breakpoints} command, or backspace and enter something else, if
1452 @samp{breakpoints} does not look like the command you expected. (If you
1453 were sure you wanted @code{info breakpoints} in the first place, you
1454 might as well just type @key{RET} immediately after @samp{info bre},
1455 to exploit command abbreviations rather than command completion).
1457 If there is more than one possibility for the next word when you press
1458 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1459 characters and try again, or just press @key{TAB} a second time;
1460 @value{GDBN} displays all the possible completions for that word. For
1461 example, you might want to set a breakpoint on a subroutine whose name
1462 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1463 just sounds the bell. Typing @key{TAB} again displays all the
1464 function names in your program that begin with those characters, for
1468 (@value{GDBP}) b make_ @key{TAB}
1469 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1470 make_a_section_from_file make_environ
1471 make_abs_section make_function_type
1472 make_blockvector make_pointer_type
1473 make_cleanup make_reference_type
1474 make_command make_symbol_completion_list
1475 (@value{GDBP}) b make_
1479 After displaying the available possibilities, @value{GDBN} copies your
1480 partial input (@samp{b make_} in the example) so you can finish the
1483 If you just want to see the list of alternatives in the first place, you
1484 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1485 means @kbd{@key{META} ?}. You can type this either by holding down a
1486 key designated as the @key{META} shift on your keyboard (if there is
1487 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1489 @cindex quotes in commands
1490 @cindex completion of quoted strings
1491 Sometimes the string you need, while logically a ``word'', may contain
1492 parentheses or other characters that @value{GDBN} normally excludes from
1493 its notion of a word. To permit word completion to work in this
1494 situation, you may enclose words in @code{'} (single quote marks) in
1495 @value{GDBN} commands.
1497 The most likely situation where you might need this is in typing the
1498 name of a C@t{++} function. This is because C@t{++} allows function
1499 overloading (multiple definitions of the same function, distinguished
1500 by argument type). For example, when you want to set a breakpoint you
1501 may need to distinguish whether you mean the version of @code{name}
1502 that takes an @code{int} parameter, @code{name(int)}, or the version
1503 that takes a @code{float} parameter, @code{name(float)}. To use the
1504 word-completion facilities in this situation, type a single quote
1505 @code{'} at the beginning of the function name. This alerts
1506 @value{GDBN} that it may need to consider more information than usual
1507 when you press @key{TAB} or @kbd{M-?} to request word completion:
1510 (@value{GDBP}) b 'bubble( @kbd{M-?}
1511 bubble(double,double) bubble(int,int)
1512 (@value{GDBP}) b 'bubble(
1515 In some cases, @value{GDBN} can tell that completing a name requires using
1516 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1517 completing as much as it can) if you do not type the quote in the first
1521 (@value{GDBP}) b bub @key{TAB}
1522 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1523 (@value{GDBP}) b 'bubble(
1527 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1528 you have not yet started typing the argument list when you ask for
1529 completion on an overloaded symbol.
1531 For more information about overloaded functions, see @ref{C Plus Plus
1532 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1533 overload-resolution off} to disable overload resolution;
1534 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1536 @cindex completion of structure field names
1537 @cindex structure field name completion
1538 @cindex completion of union field names
1539 @cindex union field name completion
1540 When completing in an expression which looks up a field in a
1541 structure, @value{GDBN} also tries@footnote{The completer can be
1542 confused by certain kinds of invalid expressions. Also, it only
1543 examines the static type of the expression, not the dynamic type.} to
1544 limit completions to the field names available in the type of the
1548 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1549 magic to_delete to_fputs to_put to_rewind
1550 to_data to_flush to_isatty to_read to_write
1554 This is because the @code{gdb_stdout} is a variable of the type
1555 @code{struct ui_file} that is defined in @value{GDBN} sources as
1562 ui_file_flush_ftype *to_flush;
1563 ui_file_write_ftype *to_write;
1564 ui_file_fputs_ftype *to_fputs;
1565 ui_file_read_ftype *to_read;
1566 ui_file_delete_ftype *to_delete;
1567 ui_file_isatty_ftype *to_isatty;
1568 ui_file_rewind_ftype *to_rewind;
1569 ui_file_put_ftype *to_put;
1576 @section Getting Help
1577 @cindex online documentation
1580 You can always ask @value{GDBN} itself for information on its commands,
1581 using the command @code{help}.
1584 @kindex h @r{(@code{help})}
1587 You can use @code{help} (abbreviated @code{h}) with no arguments to
1588 display a short list of named classes of commands:
1592 List of classes of commands:
1594 aliases -- Aliases of other commands
1595 breakpoints -- Making program stop at certain points
1596 data -- Examining data
1597 files -- Specifying and examining files
1598 internals -- Maintenance commands
1599 obscure -- Obscure features
1600 running -- Running the program
1601 stack -- Examining the stack
1602 status -- Status inquiries
1603 support -- Support facilities
1604 tracepoints -- Tracing of program execution without
1605 stopping the program
1606 user-defined -- User-defined commands
1608 Type "help" followed by a class name for a list of
1609 commands in that class.
1610 Type "help" followed by command name for full
1612 Command name abbreviations are allowed if unambiguous.
1615 @c the above line break eliminates huge line overfull...
1617 @item help @var{class}
1618 Using one of the general help classes as an argument, you can get a
1619 list of the individual commands in that class. For example, here is the
1620 help display for the class @code{status}:
1623 (@value{GDBP}) help status
1628 @c Line break in "show" line falsifies real output, but needed
1629 @c to fit in smallbook page size.
1630 info -- Generic command for showing things
1631 about the program being debugged
1632 show -- Generic command for showing things
1635 Type "help" followed by command name for full
1637 Command name abbreviations are allowed if unambiguous.
1641 @item help @var{command}
1642 With a command name as @code{help} argument, @value{GDBN} displays a
1643 short paragraph on how to use that command.
1646 @item apropos @var{args}
1647 The @code{apropos} command searches through all of the @value{GDBN}
1648 commands, and their documentation, for the regular expression specified in
1649 @var{args}. It prints out all matches found. For example:
1660 set symbol-reloading -- Set dynamic symbol table reloading
1661 multiple times in one run
1662 show symbol-reloading -- Show dynamic symbol table reloading
1663 multiple times in one run
1668 @item complete @var{args}
1669 The @code{complete @var{args}} command lists all the possible completions
1670 for the beginning of a command. Use @var{args} to specify the beginning of the
1671 command you want completed. For example:
1677 @noindent results in:
1688 @noindent This is intended for use by @sc{gnu} Emacs.
1691 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1692 and @code{show} to inquire about the state of your program, or the state
1693 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1694 manual introduces each of them in the appropriate context. The listings
1695 under @code{info} and under @code{show} in the Index point to
1696 all the sub-commands. @xref{Index}.
1701 @kindex i @r{(@code{info})}
1703 This command (abbreviated @code{i}) is for describing the state of your
1704 program. For example, you can show the arguments passed to a function
1705 with @code{info args}, list the registers currently in use with @code{info
1706 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1707 You can get a complete list of the @code{info} sub-commands with
1708 @w{@code{help info}}.
1712 You can assign the result of an expression to an environment variable with
1713 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1714 @code{set prompt $}.
1718 In contrast to @code{info}, @code{show} is for describing the state of
1719 @value{GDBN} itself.
1720 You can change most of the things you can @code{show}, by using the
1721 related command @code{set}; for example, you can control what number
1722 system is used for displays with @code{set radix}, or simply inquire
1723 which is currently in use with @code{show radix}.
1726 To display all the settable parameters and their current
1727 values, you can use @code{show} with no arguments; you may also use
1728 @code{info set}. Both commands produce the same display.
1729 @c FIXME: "info set" violates the rule that "info" is for state of
1730 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1731 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1735 Here are three miscellaneous @code{show} subcommands, all of which are
1736 exceptional in lacking corresponding @code{set} commands:
1739 @kindex show version
1740 @cindex @value{GDBN} version number
1742 Show what version of @value{GDBN} is running. You should include this
1743 information in @value{GDBN} bug-reports. If multiple versions of
1744 @value{GDBN} are in use at your site, you may need to determine which
1745 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1746 commands are introduced, and old ones may wither away. Also, many
1747 system vendors ship variant versions of @value{GDBN}, and there are
1748 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1749 The version number is the same as the one announced when you start
1752 @kindex show copying
1753 @kindex info copying
1754 @cindex display @value{GDBN} copyright
1757 Display information about permission for copying @value{GDBN}.
1759 @kindex show warranty
1760 @kindex info warranty
1762 @itemx info warranty
1763 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1764 if your version of @value{GDBN} comes with one.
1769 @chapter Running Programs Under @value{GDBN}
1771 When you run a program under @value{GDBN}, you must first generate
1772 debugging information when you compile it.
1774 You may start @value{GDBN} with its arguments, if any, in an environment
1775 of your choice. If you are doing native debugging, you may redirect
1776 your program's input and output, debug an already running process, or
1777 kill a child process.
1780 * Compilation:: Compiling for debugging
1781 * Starting:: Starting your program
1782 * Arguments:: Your program's arguments
1783 * Environment:: Your program's environment
1785 * Working Directory:: Your program's working directory
1786 * Input/Output:: Your program's input and output
1787 * Attach:: Debugging an already-running process
1788 * Kill Process:: Killing the child process
1790 * Inferiors:: Debugging multiple inferiors
1791 * Threads:: Debugging programs with multiple threads
1792 * Processes:: Debugging programs with multiple processes
1793 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1797 @section Compiling for Debugging
1799 In order to debug a program effectively, you need to generate
1800 debugging information when you compile it. This debugging information
1801 is stored in the object file; it describes the data type of each
1802 variable or function and the correspondence between source line numbers
1803 and addresses in the executable code.
1805 To request debugging information, specify the @samp{-g} option when you run
1808 Programs that are to be shipped to your customers are compiled with
1809 optimizations, using the @samp{-O} compiler option. However, many
1810 compilers are unable to handle the @samp{-g} and @samp{-O} options
1811 together. Using those compilers, you cannot generate optimized
1812 executables containing debugging information.
1814 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1815 without @samp{-O}, making it possible to debug optimized code. We
1816 recommend that you @emph{always} use @samp{-g} whenever you compile a
1817 program. You may think your program is correct, but there is no sense
1818 in pushing your luck.
1820 @cindex optimized code, debugging
1821 @cindex debugging optimized code
1822 When you debug a program compiled with @samp{-g -O}, remember that the
1823 optimizer is rearranging your code; the debugger shows you what is
1824 really there. Do not be too surprised when the execution path does not
1825 exactly match your source file! An extreme example: if you define a
1826 variable, but never use it, @value{GDBN} never sees that
1827 variable---because the compiler optimizes it out of existence.
1829 Some things do not work as well with @samp{-g -O} as with just
1830 @samp{-g}, particularly on machines with instruction scheduling. If in
1831 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1832 please report it to us as a bug (including a test case!).
1833 @xref{Variables}, for more information about debugging optimized code.
1835 Older versions of the @sc{gnu} C compiler permitted a variant option
1836 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1837 format; if your @sc{gnu} C compiler has this option, do not use it.
1839 @value{GDBN} knows about preprocessor macros and can show you their
1840 expansion (@pxref{Macros}). Most compilers do not include information
1841 about preprocessor macros in the debugging information if you specify
1842 the @option{-g} flag alone, because this information is rather large.
1843 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1844 provides macro information if you specify the options
1845 @option{-gdwarf-2} and @option{-g3}; the former option requests
1846 debugging information in the Dwarf 2 format, and the latter requests
1847 ``extra information''. In the future, we hope to find more compact
1848 ways to represent macro information, so that it can be included with
1853 @section Starting your Program
1859 @kindex r @r{(@code{run})}
1862 Use the @code{run} command to start your program under @value{GDBN}.
1863 You must first specify the program name (except on VxWorks) with an
1864 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1865 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1866 (@pxref{Files, ,Commands to Specify Files}).
1870 If you are running your program in an execution environment that
1871 supports processes, @code{run} creates an inferior process and makes
1872 that process run your program. In some environments without processes,
1873 @code{run} jumps to the start of your program. Other targets,
1874 like @samp{remote}, are always running. If you get an error
1875 message like this one:
1878 The "remote" target does not support "run".
1879 Try "help target" or "continue".
1883 then use @code{continue} to run your program. You may need @code{load}
1884 first (@pxref{load}).
1886 The execution of a program is affected by certain information it
1887 receives from its superior. @value{GDBN} provides ways to specify this
1888 information, which you must do @emph{before} starting your program. (You
1889 can change it after starting your program, but such changes only affect
1890 your program the next time you start it.) This information may be
1891 divided into four categories:
1894 @item The @emph{arguments.}
1895 Specify the arguments to give your program as the arguments of the
1896 @code{run} command. If a shell is available on your target, the shell
1897 is used to pass the arguments, so that you may use normal conventions
1898 (such as wildcard expansion or variable substitution) in describing
1900 In Unix systems, you can control which shell is used with the
1901 @code{SHELL} environment variable.
1902 @xref{Arguments, ,Your Program's Arguments}.
1904 @item The @emph{environment.}
1905 Your program normally inherits its environment from @value{GDBN}, but you can
1906 use the @value{GDBN} commands @code{set environment} and @code{unset
1907 environment} to change parts of the environment that affect
1908 your program. @xref{Environment, ,Your Program's Environment}.
1910 @item The @emph{working directory.}
1911 Your program inherits its working directory from @value{GDBN}. You can set
1912 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1913 @xref{Working Directory, ,Your Program's Working Directory}.
1915 @item The @emph{standard input and output.}
1916 Your program normally uses the same device for standard input and
1917 standard output as @value{GDBN} is using. You can redirect input and output
1918 in the @code{run} command line, or you can use the @code{tty} command to
1919 set a different device for your program.
1920 @xref{Input/Output, ,Your Program's Input and Output}.
1923 @emph{Warning:} While input and output redirection work, you cannot use
1924 pipes to pass the output of the program you are debugging to another
1925 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1929 When you issue the @code{run} command, your program begins to execute
1930 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1931 of how to arrange for your program to stop. Once your program has
1932 stopped, you may call functions in your program, using the @code{print}
1933 or @code{call} commands. @xref{Data, ,Examining Data}.
1935 If the modification time of your symbol file has changed since the last
1936 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1937 table, and reads it again. When it does this, @value{GDBN} tries to retain
1938 your current breakpoints.
1943 @cindex run to main procedure
1944 The name of the main procedure can vary from language to language.
1945 With C or C@t{++}, the main procedure name is always @code{main}, but
1946 other languages such as Ada do not require a specific name for their
1947 main procedure. The debugger provides a convenient way to start the
1948 execution of the program and to stop at the beginning of the main
1949 procedure, depending on the language used.
1951 The @samp{start} command does the equivalent of setting a temporary
1952 breakpoint at the beginning of the main procedure and then invoking
1953 the @samp{run} command.
1955 @cindex elaboration phase
1956 Some programs contain an @dfn{elaboration} phase where some startup code is
1957 executed before the main procedure is called. This depends on the
1958 languages used to write your program. In C@t{++}, for instance,
1959 constructors for static and global objects are executed before
1960 @code{main} is called. It is therefore possible that the debugger stops
1961 before reaching the main procedure. However, the temporary breakpoint
1962 will remain to halt execution.
1964 Specify the arguments to give to your program as arguments to the
1965 @samp{start} command. These arguments will be given verbatim to the
1966 underlying @samp{run} command. Note that the same arguments will be
1967 reused if no argument is provided during subsequent calls to
1968 @samp{start} or @samp{run}.
1970 It is sometimes necessary to debug the program during elaboration. In
1971 these cases, using the @code{start} command would stop the execution of
1972 your program too late, as the program would have already completed the
1973 elaboration phase. Under these circumstances, insert breakpoints in your
1974 elaboration code before running your program.
1976 @kindex set exec-wrapper
1977 @item set exec-wrapper @var{wrapper}
1978 @itemx show exec-wrapper
1979 @itemx unset exec-wrapper
1980 When @samp{exec-wrapper} is set, the specified wrapper is used to
1981 launch programs for debugging. @value{GDBN} starts your program
1982 with a shell command of the form @kbd{exec @var{wrapper}
1983 @var{program}}. Quoting is added to @var{program} and its
1984 arguments, but not to @var{wrapper}, so you should add quotes if
1985 appropriate for your shell. The wrapper runs until it executes
1986 your program, and then @value{GDBN} takes control.
1988 You can use any program that eventually calls @code{execve} with
1989 its arguments as a wrapper. Several standard Unix utilities do
1990 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1991 with @code{exec "$@@"} will also work.
1993 For example, you can use @code{env} to pass an environment variable to
1994 the debugged program, without setting the variable in your shell's
1998 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2002 This command is available when debugging locally on most targets, excluding
2003 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2005 @kindex set disable-randomization
2006 @item set disable-randomization
2007 @itemx set disable-randomization on
2008 This option (enabled by default in @value{GDBN}) will turn off the native
2009 randomization of the virtual address space of the started program. This option
2010 is useful for multiple debugging sessions to make the execution better
2011 reproducible and memory addresses reusable across debugging sessions.
2013 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2017 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2020 @item set disable-randomization off
2021 Leave the behavior of the started executable unchanged. Some bugs rear their
2022 ugly heads only when the program is loaded at certain addresses. If your bug
2023 disappears when you run the program under @value{GDBN}, that might be because
2024 @value{GDBN} by default disables the address randomization on platforms, such
2025 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2026 disable-randomization off} to try to reproduce such elusive bugs.
2028 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2029 It protects the programs against some kinds of security attacks. In these
2030 cases the attacker needs to know the exact location of a concrete executable
2031 code. Randomizing its location makes it impossible to inject jumps misusing
2032 a code at its expected addresses.
2034 Prelinking shared libraries provides a startup performance advantage but it
2035 makes addresses in these libraries predictable for privileged processes by
2036 having just unprivileged access at the target system. Reading the shared
2037 library binary gives enough information for assembling the malicious code
2038 misusing it. Still even a prelinked shared library can get loaded at a new
2039 random address just requiring the regular relocation process during the
2040 startup. Shared libraries not already prelinked are always loaded at
2041 a randomly chosen address.
2043 Position independent executables (PIE) contain position independent code
2044 similar to the shared libraries and therefore such executables get loaded at
2045 a randomly chosen address upon startup. PIE executables always load even
2046 already prelinked shared libraries at a random address. You can build such
2047 executable using @command{gcc -fPIE -pie}.
2049 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2050 (as long as the randomization is enabled).
2052 @item show disable-randomization
2053 Show the current setting of the explicit disable of the native randomization of
2054 the virtual address space of the started program.
2059 @section Your Program's Arguments
2061 @cindex arguments (to your program)
2062 The arguments to your program can be specified by the arguments of the
2064 They are passed to a shell, which expands wildcard characters and
2065 performs redirection of I/O, and thence to your program. Your
2066 @code{SHELL} environment variable (if it exists) specifies what shell
2067 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2068 the default shell (@file{/bin/sh} on Unix).
2070 On non-Unix systems, the program is usually invoked directly by
2071 @value{GDBN}, which emulates I/O redirection via the appropriate system
2072 calls, and the wildcard characters are expanded by the startup code of
2073 the program, not by the shell.
2075 @code{run} with no arguments uses the same arguments used by the previous
2076 @code{run}, or those set by the @code{set args} command.
2081 Specify the arguments to be used the next time your program is run. If
2082 @code{set args} has no arguments, @code{run} executes your program
2083 with no arguments. Once you have run your program with arguments,
2084 using @code{set args} before the next @code{run} is the only way to run
2085 it again without arguments.
2089 Show the arguments to give your program when it is started.
2093 @section Your Program's Environment
2095 @cindex environment (of your program)
2096 The @dfn{environment} consists of a set of environment variables and
2097 their values. Environment variables conventionally record such things as
2098 your user name, your home directory, your terminal type, and your search
2099 path for programs to run. Usually you set up environment variables with
2100 the shell and they are inherited by all the other programs you run. When
2101 debugging, it can be useful to try running your program with a modified
2102 environment without having to start @value{GDBN} over again.
2106 @item path @var{directory}
2107 Add @var{directory} to the front of the @code{PATH} environment variable
2108 (the search path for executables) that will be passed to your program.
2109 The value of @code{PATH} used by @value{GDBN} does not change.
2110 You may specify several directory names, separated by whitespace or by a
2111 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2112 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2113 is moved to the front, so it is searched sooner.
2115 You can use the string @samp{$cwd} to refer to whatever is the current
2116 working directory at the time @value{GDBN} searches the path. If you
2117 use @samp{.} instead, it refers to the directory where you executed the
2118 @code{path} command. @value{GDBN} replaces @samp{.} in the
2119 @var{directory} argument (with the current path) before adding
2120 @var{directory} to the search path.
2121 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2122 @c document that, since repeating it would be a no-op.
2126 Display the list of search paths for executables (the @code{PATH}
2127 environment variable).
2129 @kindex show environment
2130 @item show environment @r{[}@var{varname}@r{]}
2131 Print the value of environment variable @var{varname} to be given to
2132 your program when it starts. If you do not supply @var{varname},
2133 print the names and values of all environment variables to be given to
2134 your program. You can abbreviate @code{environment} as @code{env}.
2136 @kindex set environment
2137 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2138 Set environment variable @var{varname} to @var{value}. The value
2139 changes for your program only, not for @value{GDBN} itself. @var{value} may
2140 be any string; the values of environment variables are just strings, and
2141 any interpretation is supplied by your program itself. The @var{value}
2142 parameter is optional; if it is eliminated, the variable is set to a
2144 @c "any string" here does not include leading, trailing
2145 @c blanks. Gnu asks: does anyone care?
2147 For example, this command:
2154 tells the debugged program, when subsequently run, that its user is named
2155 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2156 are not actually required.)
2158 @kindex unset environment
2159 @item unset environment @var{varname}
2160 Remove variable @var{varname} from the environment to be passed to your
2161 program. This is different from @samp{set env @var{varname} =};
2162 @code{unset environment} removes the variable from the environment,
2163 rather than assigning it an empty value.
2166 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2168 by your @code{SHELL} environment variable if it exists (or
2169 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2170 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2171 @file{.bashrc} for BASH---any variables you set in that file affect
2172 your program. You may wish to move setting of environment variables to
2173 files that are only run when you sign on, such as @file{.login} or
2176 @node Working Directory
2177 @section Your Program's Working Directory
2179 @cindex working directory (of your program)
2180 Each time you start your program with @code{run}, it inherits its
2181 working directory from the current working directory of @value{GDBN}.
2182 The @value{GDBN} working directory is initially whatever it inherited
2183 from its parent process (typically the shell), but you can specify a new
2184 working directory in @value{GDBN} with the @code{cd} command.
2186 The @value{GDBN} working directory also serves as a default for the commands
2187 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2192 @cindex change working directory
2193 @item cd @var{directory}
2194 Set the @value{GDBN} working directory to @var{directory}.
2198 Print the @value{GDBN} working directory.
2201 It is generally impossible to find the current working directory of
2202 the process being debugged (since a program can change its directory
2203 during its run). If you work on a system where @value{GDBN} is
2204 configured with the @file{/proc} support, you can use the @code{info
2205 proc} command (@pxref{SVR4 Process Information}) to find out the
2206 current working directory of the debuggee.
2209 @section Your Program's Input and Output
2214 By default, the program you run under @value{GDBN} does input and output to
2215 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2216 to its own terminal modes to interact with you, but it records the terminal
2217 modes your program was using and switches back to them when you continue
2218 running your program.
2221 @kindex info terminal
2223 Displays information recorded by @value{GDBN} about the terminal modes your
2227 You can redirect your program's input and/or output using shell
2228 redirection with the @code{run} command. For example,
2235 starts your program, diverting its output to the file @file{outfile}.
2238 @cindex controlling terminal
2239 Another way to specify where your program should do input and output is
2240 with the @code{tty} command. This command accepts a file name as
2241 argument, and causes this file to be the default for future @code{run}
2242 commands. It also resets the controlling terminal for the child
2243 process, for future @code{run} commands. For example,
2250 directs that processes started with subsequent @code{run} commands
2251 default to do input and output on the terminal @file{/dev/ttyb} and have
2252 that as their controlling terminal.
2254 An explicit redirection in @code{run} overrides the @code{tty} command's
2255 effect on the input/output device, but not its effect on the controlling
2258 When you use the @code{tty} command or redirect input in the @code{run}
2259 command, only the input @emph{for your program} is affected. The input
2260 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2261 for @code{set inferior-tty}.
2263 @cindex inferior tty
2264 @cindex set inferior controlling terminal
2265 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2266 display the name of the terminal that will be used for future runs of your
2270 @item set inferior-tty /dev/ttyb
2271 @kindex set inferior-tty
2272 Set the tty for the program being debugged to /dev/ttyb.
2274 @item show inferior-tty
2275 @kindex show inferior-tty
2276 Show the current tty for the program being debugged.
2280 @section Debugging an Already-running Process
2285 @item attach @var{process-id}
2286 This command attaches to a running process---one that was started
2287 outside @value{GDBN}. (@code{info files} shows your active
2288 targets.) The command takes as argument a process ID. The usual way to
2289 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2290 or with the @samp{jobs -l} shell command.
2292 @code{attach} does not repeat if you press @key{RET} a second time after
2293 executing the command.
2296 To use @code{attach}, your program must be running in an environment
2297 which supports processes; for example, @code{attach} does not work for
2298 programs on bare-board targets that lack an operating system. You must
2299 also have permission to send the process a signal.
2301 When you use @code{attach}, the debugger finds the program running in
2302 the process first by looking in the current working directory, then (if
2303 the program is not found) by using the source file search path
2304 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2305 the @code{file} command to load the program. @xref{Files, ,Commands to
2308 The first thing @value{GDBN} does after arranging to debug the specified
2309 process is to stop it. You can examine and modify an attached process
2310 with all the @value{GDBN} commands that are ordinarily available when
2311 you start processes with @code{run}. You can insert breakpoints; you
2312 can step and continue; you can modify storage. If you would rather the
2313 process continue running, you may use the @code{continue} command after
2314 attaching @value{GDBN} to the process.
2319 When you have finished debugging the attached process, you can use the
2320 @code{detach} command to release it from @value{GDBN} control. Detaching
2321 the process continues its execution. After the @code{detach} command,
2322 that process and @value{GDBN} become completely independent once more, and you
2323 are ready to @code{attach} another process or start one with @code{run}.
2324 @code{detach} does not repeat if you press @key{RET} again after
2325 executing the command.
2328 If you exit @value{GDBN} while you have an attached process, you detach
2329 that process. If you use the @code{run} command, you kill that process.
2330 By default, @value{GDBN} asks for confirmation if you try to do either of these
2331 things; you can control whether or not you need to confirm by using the
2332 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2336 @section Killing the Child Process
2341 Kill the child process in which your program is running under @value{GDBN}.
2344 This command is useful if you wish to debug a core dump instead of a
2345 running process. @value{GDBN} ignores any core dump file while your program
2348 On some operating systems, a program cannot be executed outside @value{GDBN}
2349 while you have breakpoints set on it inside @value{GDBN}. You can use the
2350 @code{kill} command in this situation to permit running your program
2351 outside the debugger.
2353 The @code{kill} command is also useful if you wish to recompile and
2354 relink your program, since on many systems it is impossible to modify an
2355 executable file while it is running in a process. In this case, when you
2356 next type @code{run}, @value{GDBN} notices that the file has changed, and
2357 reads the symbol table again (while trying to preserve your current
2358 breakpoint settings).
2361 @section Debugging Multiple Inferiors
2363 Some @value{GDBN} targets are able to run multiple processes created
2364 from a single executable. This can happen, for instance, with an
2365 embedded system reporting back several processes via the remote
2369 @value{GDBN} represents the state of each program execution with an
2370 object called an @dfn{inferior}. An inferior typically corresponds to
2371 a process, but is more general and applies also to targets that do not
2372 have processes. Inferiors may be created before a process runs, and
2373 may (in future) be retained after a process exits. Each run of an
2374 executable creates a new inferior, as does each attachment to an
2375 existing process. Inferiors have unique identifiers that are
2376 different from process ids, and may optionally be named as well.
2377 Usually each inferior will also have its own distinct address space,
2378 although some embedded targets may have several inferiors running in
2379 different parts of a single space.
2381 Each inferior may in turn have multiple threads running in it.
2383 To find out what inferiors exist at any moment, use @code{info inferiors}:
2386 @kindex info inferiors
2387 @item info inferiors
2388 Print a list of all inferiors currently being managed by @value{GDBN}.
2390 @kindex set print inferior-events
2391 @cindex print messages on inferior start and exit
2392 @item set print inferior-events
2393 @itemx set print inferior-events on
2394 @itemx set print inferior-events off
2395 The @code{set print inferior-events} command allows you to enable or
2396 disable printing of messages when @value{GDBN} notices that new
2397 inferiors have started or that inferiors have exited or have been
2398 detached. By default, these messages will not be printed.
2400 @kindex show print inferior-events
2401 @item show print inferior-events
2402 Show whether messages will be printed when @value{GDBN} detects that
2403 inferiors have started, exited or have been detached.
2407 @section Debugging Programs with Multiple Threads
2409 @cindex threads of execution
2410 @cindex multiple threads
2411 @cindex switching threads
2412 In some operating systems, such as HP-UX and Solaris, a single program
2413 may have more than one @dfn{thread} of execution. The precise semantics
2414 of threads differ from one operating system to another, but in general
2415 the threads of a single program are akin to multiple processes---except
2416 that they share one address space (that is, they can all examine and
2417 modify the same variables). On the other hand, each thread has its own
2418 registers and execution stack, and perhaps private memory.
2420 @value{GDBN} provides these facilities for debugging multi-thread
2424 @item automatic notification of new threads
2425 @item @samp{thread @var{threadno}}, a command to switch among threads
2426 @item @samp{info threads}, a command to inquire about existing threads
2427 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2428 a command to apply a command to a list of threads
2429 @item thread-specific breakpoints
2430 @item @samp{set print thread-events}, which controls printing of
2431 messages on thread start and exit.
2435 @emph{Warning:} These facilities are not yet available on every
2436 @value{GDBN} configuration where the operating system supports threads.
2437 If your @value{GDBN} does not support threads, these commands have no
2438 effect. For example, a system without thread support shows no output
2439 from @samp{info threads}, and always rejects the @code{thread} command,
2443 (@value{GDBP}) info threads
2444 (@value{GDBP}) thread 1
2445 Thread ID 1 not known. Use the "info threads" command to
2446 see the IDs of currently known threads.
2448 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2449 @c doesn't support threads"?
2452 @cindex focus of debugging
2453 @cindex current thread
2454 The @value{GDBN} thread debugging facility allows you to observe all
2455 threads while your program runs---but whenever @value{GDBN} takes
2456 control, one thread in particular is always the focus of debugging.
2457 This thread is called the @dfn{current thread}. Debugging commands show
2458 program information from the perspective of the current thread.
2460 @cindex @code{New} @var{systag} message
2461 @cindex thread identifier (system)
2462 @c FIXME-implementors!! It would be more helpful if the [New...] message
2463 @c included GDB's numeric thread handle, so you could just go to that
2464 @c thread without first checking `info threads'.
2465 Whenever @value{GDBN} detects a new thread in your program, it displays
2466 the target system's identification for the thread with a message in the
2467 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2468 whose form varies depending on the particular system. For example, on
2469 @sc{gnu}/Linux, you might see
2472 [New Thread 46912507313328 (LWP 25582)]
2476 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2477 the @var{systag} is simply something like @samp{process 368}, with no
2480 @c FIXME!! (1) Does the [New...] message appear even for the very first
2481 @c thread of a program, or does it only appear for the
2482 @c second---i.e.@: when it becomes obvious we have a multithread
2484 @c (2) *Is* there necessarily a first thread always? Or do some
2485 @c multithread systems permit starting a program with multiple
2486 @c threads ab initio?
2488 @cindex thread number
2489 @cindex thread identifier (GDB)
2490 For debugging purposes, @value{GDBN} associates its own thread
2491 number---always a single integer---with each thread in your program.
2494 @kindex info threads
2496 Display a summary of all threads currently in your
2497 program. @value{GDBN} displays for each thread (in this order):
2501 the thread number assigned by @value{GDBN}
2504 the target system's thread identifier (@var{systag})
2507 the current stack frame summary for that thread
2511 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2512 indicates the current thread.
2516 @c end table here to get a little more width for example
2519 (@value{GDBP}) info threads
2520 3 process 35 thread 27 0x34e5 in sigpause ()
2521 2 process 35 thread 23 0x34e5 in sigpause ()
2522 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2528 @cindex debugging multithreaded programs (on HP-UX)
2529 @cindex thread identifier (GDB), on HP-UX
2530 For debugging purposes, @value{GDBN} associates its own thread
2531 number---a small integer assigned in thread-creation order---with each
2532 thread in your program.
2534 @cindex @code{New} @var{systag} message, on HP-UX
2535 @cindex thread identifier (system), on HP-UX
2536 @c FIXME-implementors!! It would be more helpful if the [New...] message
2537 @c included GDB's numeric thread handle, so you could just go to that
2538 @c thread without first checking `info threads'.
2539 Whenever @value{GDBN} detects a new thread in your program, it displays
2540 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2541 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2542 whose form varies depending on the particular system. For example, on
2546 [New thread 2 (system thread 26594)]
2550 when @value{GDBN} notices a new thread.
2553 @kindex info threads (HP-UX)
2555 Display a summary of all threads currently in your
2556 program. @value{GDBN} displays for each thread (in this order):
2559 @item the thread number assigned by @value{GDBN}
2561 @item the target system's thread identifier (@var{systag})
2563 @item the current stack frame summary for that thread
2567 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2568 indicates the current thread.
2572 @c end table here to get a little more width for example
2575 (@value{GDBP}) info threads
2576 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2578 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2579 from /usr/lib/libc.2
2580 1 system thread 27905 0x7b003498 in _brk () \@*
2581 from /usr/lib/libc.2
2584 On Solaris, you can display more information about user threads with a
2585 Solaris-specific command:
2588 @item maint info sol-threads
2589 @kindex maint info sol-threads
2590 @cindex thread info (Solaris)
2591 Display info on Solaris user threads.
2595 @kindex thread @var{threadno}
2596 @item thread @var{threadno}
2597 Make thread number @var{threadno} the current thread. The command
2598 argument @var{threadno} is the internal @value{GDBN} thread number, as
2599 shown in the first field of the @samp{info threads} display.
2600 @value{GDBN} responds by displaying the system identifier of the thread
2601 you selected, and its current stack frame summary:
2604 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2605 (@value{GDBP}) thread 2
2606 [Switching to process 35 thread 23]
2607 0x34e5 in sigpause ()
2611 As with the @samp{[New @dots{}]} message, the form of the text after
2612 @samp{Switching to} depends on your system's conventions for identifying
2615 @kindex thread apply
2616 @cindex apply command to several threads
2617 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2618 The @code{thread apply} command allows you to apply the named
2619 @var{command} to one or more threads. Specify the numbers of the
2620 threads that you want affected with the command argument
2621 @var{threadno}. It can be a single thread number, one of the numbers
2622 shown in the first field of the @samp{info threads} display; or it
2623 could be a range of thread numbers, as in @code{2-4}. To apply a
2624 command to all threads, type @kbd{thread apply all @var{command}}.
2626 @kindex set print thread-events
2627 @cindex print messages on thread start and exit
2628 @item set print thread-events
2629 @itemx set print thread-events on
2630 @itemx set print thread-events off
2631 The @code{set print thread-events} command allows you to enable or
2632 disable printing of messages when @value{GDBN} notices that new threads have
2633 started or that threads have exited. By default, these messages will
2634 be printed if detection of these events is supported by the target.
2635 Note that these messages cannot be disabled on all targets.
2637 @kindex show print thread-events
2638 @item show print thread-events
2639 Show whether messages will be printed when @value{GDBN} detects that threads
2640 have started and exited.
2643 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2644 more information about how @value{GDBN} behaves when you stop and start
2645 programs with multiple threads.
2647 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2648 watchpoints in programs with multiple threads.
2651 @section Debugging Programs with Multiple Processes
2653 @cindex fork, debugging programs which call
2654 @cindex multiple processes
2655 @cindex processes, multiple
2656 On most systems, @value{GDBN} has no special support for debugging
2657 programs which create additional processes using the @code{fork}
2658 function. When a program forks, @value{GDBN} will continue to debug the
2659 parent process and the child process will run unimpeded. If you have
2660 set a breakpoint in any code which the child then executes, the child
2661 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2662 will cause it to terminate.
2664 However, if you want to debug the child process there is a workaround
2665 which isn't too painful. Put a call to @code{sleep} in the code which
2666 the child process executes after the fork. It may be useful to sleep
2667 only if a certain environment variable is set, or a certain file exists,
2668 so that the delay need not occur when you don't want to run @value{GDBN}
2669 on the child. While the child is sleeping, use the @code{ps} program to
2670 get its process ID. Then tell @value{GDBN} (a new invocation of
2671 @value{GDBN} if you are also debugging the parent process) to attach to
2672 the child process (@pxref{Attach}). From that point on you can debug
2673 the child process just like any other process which you attached to.
2675 On some systems, @value{GDBN} provides support for debugging programs that
2676 create additional processes using the @code{fork} or @code{vfork} functions.
2677 Currently, the only platforms with this feature are HP-UX (11.x and later
2678 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2680 By default, when a program forks, @value{GDBN} will continue to debug
2681 the parent process and the child process will run unimpeded.
2683 If you want to follow the child process instead of the parent process,
2684 use the command @w{@code{set follow-fork-mode}}.
2687 @kindex set follow-fork-mode
2688 @item set follow-fork-mode @var{mode}
2689 Set the debugger response to a program call of @code{fork} or
2690 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2691 process. The @var{mode} argument can be:
2695 The original process is debugged after a fork. The child process runs
2696 unimpeded. This is the default.
2699 The new process is debugged after a fork. The parent process runs
2704 @kindex show follow-fork-mode
2705 @item show follow-fork-mode
2706 Display the current debugger response to a @code{fork} or @code{vfork} call.
2709 @cindex debugging multiple processes
2710 On Linux, if you want to debug both the parent and child processes, use the
2711 command @w{@code{set detach-on-fork}}.
2714 @kindex set detach-on-fork
2715 @item set detach-on-fork @var{mode}
2716 Tells gdb whether to detach one of the processes after a fork, or
2717 retain debugger control over them both.
2721 The child process (or parent process, depending on the value of
2722 @code{follow-fork-mode}) will be detached and allowed to run
2723 independently. This is the default.
2726 Both processes will be held under the control of @value{GDBN}.
2727 One process (child or parent, depending on the value of
2728 @code{follow-fork-mode}) is debugged as usual, while the other
2733 @kindex show detach-on-fork
2734 @item show detach-on-fork
2735 Show whether detach-on-fork mode is on/off.
2738 If you choose to set @samp{detach-on-fork} mode off, then
2739 @value{GDBN} will retain control of all forked processes (including
2740 nested forks). You can list the forked processes under the control of
2741 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2742 from one fork to another by using the @w{@code{fork}} command.
2747 Print a list of all forked processes under the control of @value{GDBN}.
2748 The listing will include a fork id, a process id, and the current
2749 position (program counter) of the process.
2751 @kindex fork @var{fork-id}
2752 @item fork @var{fork-id}
2753 Make fork number @var{fork-id} the current process. The argument
2754 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2755 as shown in the first field of the @samp{info forks} display.
2757 @kindex process @var{process-id}
2758 @item process @var{process-id}
2759 Make process number @var{process-id} the current process. The
2760 argument @var{process-id} must be one that is listed in the output of
2765 To quit debugging one of the forked processes, you can either detach
2766 from it by using the @w{@code{detach fork}} command (allowing it to
2767 run independently), or delete (and kill) it using the
2768 @w{@code{delete fork}} command.
2771 @kindex detach fork @var{fork-id}
2772 @item detach fork @var{fork-id}
2773 Detach from the process identified by @value{GDBN} fork number
2774 @var{fork-id}, and remove it from the fork list. The process will be
2775 allowed to run independently.
2777 @kindex delete fork @var{fork-id}
2778 @item delete fork @var{fork-id}
2779 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2780 and remove it from the fork list.
2784 If you ask to debug a child process and a @code{vfork} is followed by an
2785 @code{exec}, @value{GDBN} executes the new target up to the first
2786 breakpoint in the new target. If you have a breakpoint set on
2787 @code{main} in your original program, the breakpoint will also be set on
2788 the child process's @code{main}.
2790 When a child process is spawned by @code{vfork}, you cannot debug the
2791 child or parent until an @code{exec} call completes.
2793 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2794 call executes, the new target restarts. To restart the parent process,
2795 use the @code{file} command with the parent executable name as its
2798 You can use the @code{catch} command to make @value{GDBN} stop whenever
2799 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2800 Catchpoints, ,Setting Catchpoints}.
2802 @node Checkpoint/Restart
2803 @section Setting a @emph{Bookmark} to Return to Later
2808 @cindex snapshot of a process
2809 @cindex rewind program state
2811 On certain operating systems@footnote{Currently, only
2812 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2813 program's state, called a @dfn{checkpoint}, and come back to it
2816 Returning to a checkpoint effectively undoes everything that has
2817 happened in the program since the @code{checkpoint} was saved. This
2818 includes changes in memory, registers, and even (within some limits)
2819 system state. Effectively, it is like going back in time to the
2820 moment when the checkpoint was saved.
2822 Thus, if you're stepping thru a program and you think you're
2823 getting close to the point where things go wrong, you can save
2824 a checkpoint. Then, if you accidentally go too far and miss
2825 the critical statement, instead of having to restart your program
2826 from the beginning, you can just go back to the checkpoint and
2827 start again from there.
2829 This can be especially useful if it takes a lot of time or
2830 steps to reach the point where you think the bug occurs.
2832 To use the @code{checkpoint}/@code{restart} method of debugging:
2837 Save a snapshot of the debugged program's current execution state.
2838 The @code{checkpoint} command takes no arguments, but each checkpoint
2839 is assigned a small integer id, similar to a breakpoint id.
2841 @kindex info checkpoints
2842 @item info checkpoints
2843 List the checkpoints that have been saved in the current debugging
2844 session. For each checkpoint, the following information will be
2851 @item Source line, or label
2854 @kindex restart @var{checkpoint-id}
2855 @item restart @var{checkpoint-id}
2856 Restore the program state that was saved as checkpoint number
2857 @var{checkpoint-id}. All program variables, registers, stack frames
2858 etc.@: will be returned to the values that they had when the checkpoint
2859 was saved. In essence, gdb will ``wind back the clock'' to the point
2860 in time when the checkpoint was saved.
2862 Note that breakpoints, @value{GDBN} variables, command history etc.
2863 are not affected by restoring a checkpoint. In general, a checkpoint
2864 only restores things that reside in the program being debugged, not in
2867 @kindex delete checkpoint @var{checkpoint-id}
2868 @item delete checkpoint @var{checkpoint-id}
2869 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2873 Returning to a previously saved checkpoint will restore the user state
2874 of the program being debugged, plus a significant subset of the system
2875 (OS) state, including file pointers. It won't ``un-write'' data from
2876 a file, but it will rewind the file pointer to the previous location,
2877 so that the previously written data can be overwritten. For files
2878 opened in read mode, the pointer will also be restored so that the
2879 previously read data can be read again.
2881 Of course, characters that have been sent to a printer (or other
2882 external device) cannot be ``snatched back'', and characters received
2883 from eg.@: a serial device can be removed from internal program buffers,
2884 but they cannot be ``pushed back'' into the serial pipeline, ready to
2885 be received again. Similarly, the actual contents of files that have
2886 been changed cannot be restored (at this time).
2888 However, within those constraints, you actually can ``rewind'' your
2889 program to a previously saved point in time, and begin debugging it
2890 again --- and you can change the course of events so as to debug a
2891 different execution path this time.
2893 @cindex checkpoints and process id
2894 Finally, there is one bit of internal program state that will be
2895 different when you return to a checkpoint --- the program's process
2896 id. Each checkpoint will have a unique process id (or @var{pid}),
2897 and each will be different from the program's original @var{pid}.
2898 If your program has saved a local copy of its process id, this could
2899 potentially pose a problem.
2901 @subsection A Non-obvious Benefit of Using Checkpoints
2903 On some systems such as @sc{gnu}/Linux, address space randomization
2904 is performed on new processes for security reasons. This makes it
2905 difficult or impossible to set a breakpoint, or watchpoint, on an
2906 absolute address if you have to restart the program, since the
2907 absolute location of a symbol will change from one execution to the
2910 A checkpoint, however, is an @emph{identical} copy of a process.
2911 Therefore if you create a checkpoint at (eg.@:) the start of main,
2912 and simply return to that checkpoint instead of restarting the
2913 process, you can avoid the effects of address randomization and
2914 your symbols will all stay in the same place.
2917 @chapter Stopping and Continuing
2919 The principal purposes of using a debugger are so that you can stop your
2920 program before it terminates; or so that, if your program runs into
2921 trouble, you can investigate and find out why.
2923 Inside @value{GDBN}, your program may stop for any of several reasons,
2924 such as a signal, a breakpoint, or reaching a new line after a
2925 @value{GDBN} command such as @code{step}. You may then examine and
2926 change variables, set new breakpoints or remove old ones, and then
2927 continue execution. Usually, the messages shown by @value{GDBN} provide
2928 ample explanation of the status of your program---but you can also
2929 explicitly request this information at any time.
2932 @kindex info program
2934 Display information about the status of your program: whether it is
2935 running or not, what process it is, and why it stopped.
2939 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2940 * Continuing and Stepping:: Resuming execution
2942 * Thread Stops:: Stopping and starting multi-thread programs
2946 @section Breakpoints, Watchpoints, and Catchpoints
2949 A @dfn{breakpoint} makes your program stop whenever a certain point in
2950 the program is reached. For each breakpoint, you can add conditions to
2951 control in finer detail whether your program stops. You can set
2952 breakpoints with the @code{break} command and its variants (@pxref{Set
2953 Breaks, ,Setting Breakpoints}), to specify the place where your program
2954 should stop by line number, function name or exact address in the
2957 On some systems, you can set breakpoints in shared libraries before
2958 the executable is run. There is a minor limitation on HP-UX systems:
2959 you must wait until the executable is run in order to set breakpoints
2960 in shared library routines that are not called directly by the program
2961 (for example, routines that are arguments in a @code{pthread_create}
2965 @cindex data breakpoints
2966 @cindex memory tracing
2967 @cindex breakpoint on memory address
2968 @cindex breakpoint on variable modification
2969 A @dfn{watchpoint} is a special breakpoint that stops your program
2970 when the value of an expression changes. The expression may be a value
2971 of a variable, or it could involve values of one or more variables
2972 combined by operators, such as @samp{a + b}. This is sometimes called
2973 @dfn{data breakpoints}. You must use a different command to set
2974 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2975 from that, you can manage a watchpoint like any other breakpoint: you
2976 enable, disable, and delete both breakpoints and watchpoints using the
2979 You can arrange to have values from your program displayed automatically
2980 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2984 @cindex breakpoint on events
2985 A @dfn{catchpoint} is another special breakpoint that stops your program
2986 when a certain kind of event occurs, such as the throwing of a C@t{++}
2987 exception or the loading of a library. As with watchpoints, you use a
2988 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2989 Catchpoints}), but aside from that, you can manage a catchpoint like any
2990 other breakpoint. (To stop when your program receives a signal, use the
2991 @code{handle} command; see @ref{Signals, ,Signals}.)
2993 @cindex breakpoint numbers
2994 @cindex numbers for breakpoints
2995 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2996 catchpoint when you create it; these numbers are successive integers
2997 starting with one. In many of the commands for controlling various
2998 features of breakpoints you use the breakpoint number to say which
2999 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3000 @dfn{disabled}; if disabled, it has no effect on your program until you
3003 @cindex breakpoint ranges
3004 @cindex ranges of breakpoints
3005 Some @value{GDBN} commands accept a range of breakpoints on which to
3006 operate. A breakpoint range is either a single breakpoint number, like
3007 @samp{5}, or two such numbers, in increasing order, separated by a
3008 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3009 all breakpoints in that range are operated on.
3012 * Set Breaks:: Setting breakpoints
3013 * Set Watchpoints:: Setting watchpoints
3014 * Set Catchpoints:: Setting catchpoints
3015 * Delete Breaks:: Deleting breakpoints
3016 * Disabling:: Disabling breakpoints
3017 * Conditions:: Break conditions
3018 * Break Commands:: Breakpoint command lists
3019 * Error in Breakpoints:: ``Cannot insert breakpoints''
3020 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3024 @subsection Setting Breakpoints
3026 @c FIXME LMB what does GDB do if no code on line of breakpt?
3027 @c consider in particular declaration with/without initialization.
3029 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3032 @kindex b @r{(@code{break})}
3033 @vindex $bpnum@r{, convenience variable}
3034 @cindex latest breakpoint
3035 Breakpoints are set with the @code{break} command (abbreviated
3036 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3037 number of the breakpoint you've set most recently; see @ref{Convenience
3038 Vars,, Convenience Variables}, for a discussion of what you can do with
3039 convenience variables.
3042 @item break @var{location}
3043 Set a breakpoint at the given @var{location}, which can specify a
3044 function name, a line number, or an address of an instruction.
3045 (@xref{Specify Location}, for a list of all the possible ways to
3046 specify a @var{location}.) The breakpoint will stop your program just
3047 before it executes any of the code in the specified @var{location}.
3049 When using source languages that permit overloading of symbols, such as
3050 C@t{++}, a function name may refer to more than one possible place to break.
3051 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3055 When called without any arguments, @code{break} sets a breakpoint at
3056 the next instruction to be executed in the selected stack frame
3057 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3058 innermost, this makes your program stop as soon as control
3059 returns to that frame. This is similar to the effect of a
3060 @code{finish} command in the frame inside the selected frame---except
3061 that @code{finish} does not leave an active breakpoint. If you use
3062 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3063 the next time it reaches the current location; this may be useful
3066 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3067 least one instruction has been executed. If it did not do this, you
3068 would be unable to proceed past a breakpoint without first disabling the
3069 breakpoint. This rule applies whether or not the breakpoint already
3070 existed when your program stopped.
3072 @item break @dots{} if @var{cond}
3073 Set a breakpoint with condition @var{cond}; evaluate the expression
3074 @var{cond} each time the breakpoint is reached, and stop only if the
3075 value is nonzero---that is, if @var{cond} evaluates as true.
3076 @samp{@dots{}} stands for one of the possible arguments described
3077 above (or no argument) specifying where to break. @xref{Conditions,
3078 ,Break Conditions}, for more information on breakpoint conditions.
3081 @item tbreak @var{args}
3082 Set a breakpoint enabled only for one stop. @var{args} are the
3083 same as for the @code{break} command, and the breakpoint is set in the same
3084 way, but the breakpoint is automatically deleted after the first time your
3085 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3088 @cindex hardware breakpoints
3089 @item hbreak @var{args}
3090 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3091 @code{break} command and the breakpoint is set in the same way, but the
3092 breakpoint requires hardware support and some target hardware may not
3093 have this support. The main purpose of this is EPROM/ROM code
3094 debugging, so you can set a breakpoint at an instruction without
3095 changing the instruction. This can be used with the new trap-generation
3096 provided by SPARClite DSU and most x86-based targets. These targets
3097 will generate traps when a program accesses some data or instruction
3098 address that is assigned to the debug registers. However the hardware
3099 breakpoint registers can take a limited number of breakpoints. For
3100 example, on the DSU, only two data breakpoints can be set at a time, and
3101 @value{GDBN} will reject this command if more than two are used. Delete
3102 or disable unused hardware breakpoints before setting new ones
3103 (@pxref{Disabling, ,Disabling Breakpoints}).
3104 @xref{Conditions, ,Break Conditions}.
3105 For remote targets, you can restrict the number of hardware
3106 breakpoints @value{GDBN} will use, see @ref{set remote
3107 hardware-breakpoint-limit}.
3110 @item thbreak @var{args}
3111 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3112 are the same as for the @code{hbreak} command and the breakpoint is set in
3113 the same way. However, like the @code{tbreak} command,
3114 the breakpoint is automatically deleted after the
3115 first time your program stops there. Also, like the @code{hbreak}
3116 command, the breakpoint requires hardware support and some target hardware
3117 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3118 See also @ref{Conditions, ,Break Conditions}.
3121 @cindex regular expression
3122 @cindex breakpoints in functions matching a regexp
3123 @cindex set breakpoints in many functions
3124 @item rbreak @var{regex}
3125 Set breakpoints on all functions matching the regular expression
3126 @var{regex}. This command sets an unconditional breakpoint on all
3127 matches, printing a list of all breakpoints it set. Once these
3128 breakpoints are set, they are treated just like the breakpoints set with
3129 the @code{break} command. You can delete them, disable them, or make
3130 them conditional the same way as any other breakpoint.
3132 The syntax of the regular expression is the standard one used with tools
3133 like @file{grep}. Note that this is different from the syntax used by
3134 shells, so for instance @code{foo*} matches all functions that include
3135 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3136 @code{.*} leading and trailing the regular expression you supply, so to
3137 match only functions that begin with @code{foo}, use @code{^foo}.
3139 @cindex non-member C@t{++} functions, set breakpoint in
3140 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3141 breakpoints on overloaded functions that are not members of any special
3144 @cindex set breakpoints on all functions
3145 The @code{rbreak} command can be used to set breakpoints in
3146 @strong{all} the functions in a program, like this:
3149 (@value{GDBP}) rbreak .
3152 @kindex info breakpoints
3153 @cindex @code{$_} and @code{info breakpoints}
3154 @item info breakpoints @r{[}@var{n}@r{]}
3155 @itemx info break @r{[}@var{n}@r{]}
3156 @itemx info watchpoints @r{[}@var{n}@r{]}
3157 Print a table of all breakpoints, watchpoints, and catchpoints set and
3158 not deleted. Optional argument @var{n} means print information only
3159 about the specified breakpoint (or watchpoint or catchpoint). For
3160 each breakpoint, following columns are printed:
3163 @item Breakpoint Numbers
3165 Breakpoint, watchpoint, or catchpoint.
3167 Whether the breakpoint is marked to be disabled or deleted when hit.
3168 @item Enabled or Disabled
3169 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3170 that are not enabled.
3172 Where the breakpoint is in your program, as a memory address. For a
3173 pending breakpoint whose address is not yet known, this field will
3174 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3175 library that has the symbol or line referred by breakpoint is loaded.
3176 See below for details. A breakpoint with several locations will
3177 have @samp{<MULTIPLE>} in this field---see below for details.
3179 Where the breakpoint is in the source for your program, as a file and
3180 line number. For a pending breakpoint, the original string passed to
3181 the breakpoint command will be listed as it cannot be resolved until
3182 the appropriate shared library is loaded in the future.
3186 If a breakpoint is conditional, @code{info break} shows the condition on
3187 the line following the affected breakpoint; breakpoint commands, if any,
3188 are listed after that. A pending breakpoint is allowed to have a condition
3189 specified for it. The condition is not parsed for validity until a shared
3190 library is loaded that allows the pending breakpoint to resolve to a
3194 @code{info break} with a breakpoint
3195 number @var{n} as argument lists only that breakpoint. The
3196 convenience variable @code{$_} and the default examining-address for
3197 the @code{x} command are set to the address of the last breakpoint
3198 listed (@pxref{Memory, ,Examining Memory}).
3201 @code{info break} displays a count of the number of times the breakpoint
3202 has been hit. This is especially useful in conjunction with the
3203 @code{ignore} command. You can ignore a large number of breakpoint
3204 hits, look at the breakpoint info to see how many times the breakpoint
3205 was hit, and then run again, ignoring one less than that number. This
3206 will get you quickly to the last hit of that breakpoint.
3209 @value{GDBN} allows you to set any number of breakpoints at the same place in
3210 your program. There is nothing silly or meaningless about this. When
3211 the breakpoints are conditional, this is even useful
3212 (@pxref{Conditions, ,Break Conditions}).
3214 @cindex multiple locations, breakpoints
3215 @cindex breakpoints, multiple locations
3216 It is possible that a breakpoint corresponds to several locations
3217 in your program. Examples of this situation are:
3221 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3222 instances of the function body, used in different cases.
3225 For a C@t{++} template function, a given line in the function can
3226 correspond to any number of instantiations.
3229 For an inlined function, a given source line can correspond to
3230 several places where that function is inlined.
3233 In all those cases, @value{GDBN} will insert a breakpoint at all
3234 the relevant locations@footnote{
3235 As of this writing, multiple-location breakpoints work only if there's
3236 line number information for all the locations. This means that they
3237 will generally not work in system libraries, unless you have debug
3238 info with line numbers for them.}.
3240 A breakpoint with multiple locations is displayed in the breakpoint
3241 table using several rows---one header row, followed by one row for
3242 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3243 address column. The rows for individual locations contain the actual
3244 addresses for locations, and show the functions to which those
3245 locations belong. The number column for a location is of the form
3246 @var{breakpoint-number}.@var{location-number}.
3251 Num Type Disp Enb Address What
3252 1 breakpoint keep y <MULTIPLE>
3254 breakpoint already hit 1 time
3255 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3256 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3259 Each location can be individually enabled or disabled by passing
3260 @var{breakpoint-number}.@var{location-number} as argument to the
3261 @code{enable} and @code{disable} commands. Note that you cannot
3262 delete the individual locations from the list, you can only delete the
3263 entire list of locations that belong to their parent breakpoint (with
3264 the @kbd{delete @var{num}} command, where @var{num} is the number of
3265 the parent breakpoint, 1 in the above example). Disabling or enabling
3266 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3267 that belong to that breakpoint.
3269 @cindex pending breakpoints
3270 It's quite common to have a breakpoint inside a shared library.
3271 Shared libraries can be loaded and unloaded explicitly,
3272 and possibly repeatedly, as the program is executed. To support
3273 this use case, @value{GDBN} updates breakpoint locations whenever
3274 any shared library is loaded or unloaded. Typically, you would
3275 set a breakpoint in a shared library at the beginning of your
3276 debugging session, when the library is not loaded, and when the
3277 symbols from the library are not available. When you try to set
3278 breakpoint, @value{GDBN} will ask you if you want to set
3279 a so called @dfn{pending breakpoint}---breakpoint whose address
3280 is not yet resolved.
3282 After the program is run, whenever a new shared library is loaded,
3283 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3284 shared library contains the symbol or line referred to by some
3285 pending breakpoint, that breakpoint is resolved and becomes an
3286 ordinary breakpoint. When a library is unloaded, all breakpoints
3287 that refer to its symbols or source lines become pending again.
3289 This logic works for breakpoints with multiple locations, too. For
3290 example, if you have a breakpoint in a C@t{++} template function, and
3291 a newly loaded shared library has an instantiation of that template,
3292 a new location is added to the list of locations for the breakpoint.
3294 Except for having unresolved address, pending breakpoints do not
3295 differ from regular breakpoints. You can set conditions or commands,
3296 enable and disable them and perform other breakpoint operations.
3298 @value{GDBN} provides some additional commands for controlling what
3299 happens when the @samp{break} command cannot resolve breakpoint
3300 address specification to an address:
3302 @kindex set breakpoint pending
3303 @kindex show breakpoint pending
3305 @item set breakpoint pending auto
3306 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3307 location, it queries you whether a pending breakpoint should be created.
3309 @item set breakpoint pending on
3310 This indicates that an unrecognized breakpoint location should automatically
3311 result in a pending breakpoint being created.
3313 @item set breakpoint pending off
3314 This indicates that pending breakpoints are not to be created. Any
3315 unrecognized breakpoint location results in an error. This setting does
3316 not affect any pending breakpoints previously created.
3318 @item show breakpoint pending
3319 Show the current behavior setting for creating pending breakpoints.
3322 The settings above only affect the @code{break} command and its
3323 variants. Once breakpoint is set, it will be automatically updated
3324 as shared libraries are loaded and unloaded.
3326 @cindex automatic hardware breakpoints
3327 For some targets, @value{GDBN} can automatically decide if hardware or
3328 software breakpoints should be used, depending on whether the
3329 breakpoint address is read-only or read-write. This applies to
3330 breakpoints set with the @code{break} command as well as to internal
3331 breakpoints set by commands like @code{next} and @code{finish}. For
3332 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3335 You can control this automatic behaviour with the following commands::
3337 @kindex set breakpoint auto-hw
3338 @kindex show breakpoint auto-hw
3340 @item set breakpoint auto-hw on
3341 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3342 will try to use the target memory map to decide if software or hardware
3343 breakpoint must be used.
3345 @item set breakpoint auto-hw off
3346 This indicates @value{GDBN} should not automatically select breakpoint
3347 type. If the target provides a memory map, @value{GDBN} will warn when
3348 trying to set software breakpoint at a read-only address.
3351 @value{GDBN} normally implements breakpoints by replacing the program code
3352 at the breakpoint address with a special instruction, which, when
3353 executed, given control to the debugger. By default, the program
3354 code is so modified only when the program is resumed. As soon as
3355 the program stops, @value{GDBN} restores the original instructions. This
3356 behaviour guards against leaving breakpoints inserted in the
3357 target should gdb abrubptly disconnect. However, with slow remote
3358 targets, inserting and removing breakpoint can reduce the performance.
3359 This behavior can be controlled with the following commands::
3361 @kindex set breakpoint always-inserted
3362 @kindex show breakpoint always-inserted
3364 @item set breakpoint always-inserted off
3365 All breakpoints, including newly added by the user, are inserted in
3366 the target only when the target is resumed. All breakpoints are
3367 removed from the target when it stops.
3369 @item set breakpoint always-inserted on
3370 Causes all breakpoints to be inserted in the target at all times. If
3371 the user adds a new breakpoint, or changes an existing breakpoint, the
3372 breakpoints in the target are updated immediately. A breakpoint is
3373 removed from the target only when breakpoint itself is removed.
3375 @cindex non-stop mode, and @code{breakpoint always-inserted}
3376 @item set breakpoint always-inserted auto
3377 This is the default mode. If @value{GDBN} is controlling the inferior
3378 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3379 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3380 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3381 @code{breakpoint always-inserted} mode is off.
3384 @cindex negative breakpoint numbers
3385 @cindex internal @value{GDBN} breakpoints
3386 @value{GDBN} itself sometimes sets breakpoints in your program for
3387 special purposes, such as proper handling of @code{longjmp} (in C
3388 programs). These internal breakpoints are assigned negative numbers,
3389 starting with @code{-1}; @samp{info breakpoints} does not display them.
3390 You can see these breakpoints with the @value{GDBN} maintenance command
3391 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3394 @node Set Watchpoints
3395 @subsection Setting Watchpoints
3397 @cindex setting watchpoints
3398 You can use a watchpoint to stop execution whenever the value of an
3399 expression changes, without having to predict a particular place where
3400 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3401 The expression may be as simple as the value of a single variable, or
3402 as complex as many variables combined by operators. Examples include:
3406 A reference to the value of a single variable.
3409 An address cast to an appropriate data type. For example,
3410 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3411 address (assuming an @code{int} occupies 4 bytes).
3414 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3415 expression can use any operators valid in the program's native
3416 language (@pxref{Languages}).
3419 You can set a watchpoint on an expression even if the expression can
3420 not be evaluated yet. For instance, you can set a watchpoint on
3421 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3422 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3423 the expression produces a valid value. If the expression becomes
3424 valid in some other way than changing a variable (e.g.@: if the memory
3425 pointed to by @samp{*global_ptr} becomes readable as the result of a
3426 @code{malloc} call), @value{GDBN} may not stop until the next time
3427 the expression changes.
3429 @cindex software watchpoints
3430 @cindex hardware watchpoints
3431 Depending on your system, watchpoints may be implemented in software or
3432 hardware. @value{GDBN} does software watchpointing by single-stepping your
3433 program and testing the variable's value each time, which is hundreds of
3434 times slower than normal execution. (But this may still be worth it, to
3435 catch errors where you have no clue what part of your program is the
3438 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3439 x86-based targets, @value{GDBN} includes support for hardware
3440 watchpoints, which do not slow down the running of your program.
3444 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3445 Set a watchpoint for an expression. @value{GDBN} will break when the
3446 expression @var{expr} is written into by the program and its value
3447 changes. The simplest (and the most popular) use of this command is
3448 to watch the value of a single variable:
3451 (@value{GDBP}) watch foo
3454 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3455 clause, @value{GDBN} breaks only when the thread identified by
3456 @var{threadnum} changes the value of @var{expr}. If any other threads
3457 change the value of @var{expr}, @value{GDBN} will not break. Note
3458 that watchpoints restricted to a single thread in this way only work
3459 with Hardware Watchpoints.
3462 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3463 Set a watchpoint that will break when the value of @var{expr} is read
3467 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3468 Set a watchpoint that will break when @var{expr} is either read from
3469 or written into by the program.
3471 @kindex info watchpoints @r{[}@var{n}@r{]}
3472 @item info watchpoints
3473 This command prints a list of watchpoints, breakpoints, and catchpoints;
3474 it is the same as @code{info break} (@pxref{Set Breaks}).
3477 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3478 watchpoints execute very quickly, and the debugger reports a change in
3479 value at the exact instruction where the change occurs. If @value{GDBN}
3480 cannot set a hardware watchpoint, it sets a software watchpoint, which
3481 executes more slowly and reports the change in value at the next
3482 @emph{statement}, not the instruction, after the change occurs.
3484 @cindex use only software watchpoints
3485 You can force @value{GDBN} to use only software watchpoints with the
3486 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3487 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3488 the underlying system supports them. (Note that hardware-assisted
3489 watchpoints that were set @emph{before} setting
3490 @code{can-use-hw-watchpoints} to zero will still use the hardware
3491 mechanism of watching expression values.)
3494 @item set can-use-hw-watchpoints
3495 @kindex set can-use-hw-watchpoints
3496 Set whether or not to use hardware watchpoints.
3498 @item show can-use-hw-watchpoints
3499 @kindex show can-use-hw-watchpoints
3500 Show the current mode of using hardware watchpoints.
3503 For remote targets, you can restrict the number of hardware
3504 watchpoints @value{GDBN} will use, see @ref{set remote
3505 hardware-breakpoint-limit}.
3507 When you issue the @code{watch} command, @value{GDBN} reports
3510 Hardware watchpoint @var{num}: @var{expr}
3514 if it was able to set a hardware watchpoint.
3516 Currently, the @code{awatch} and @code{rwatch} commands can only set
3517 hardware watchpoints, because accesses to data that don't change the
3518 value of the watched expression cannot be detected without examining
3519 every instruction as it is being executed, and @value{GDBN} does not do
3520 that currently. If @value{GDBN} finds that it is unable to set a
3521 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3522 will print a message like this:
3525 Expression cannot be implemented with read/access watchpoint.
3528 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3529 data type of the watched expression is wider than what a hardware
3530 watchpoint on the target machine can handle. For example, some systems
3531 can only watch regions that are up to 4 bytes wide; on such systems you
3532 cannot set hardware watchpoints for an expression that yields a
3533 double-precision floating-point number (which is typically 8 bytes
3534 wide). As a work-around, it might be possible to break the large region
3535 into a series of smaller ones and watch them with separate watchpoints.
3537 If you set too many hardware watchpoints, @value{GDBN} might be unable
3538 to insert all of them when you resume the execution of your program.
3539 Since the precise number of active watchpoints is unknown until such
3540 time as the program is about to be resumed, @value{GDBN} might not be
3541 able to warn you about this when you set the watchpoints, and the
3542 warning will be printed only when the program is resumed:
3545 Hardware watchpoint @var{num}: Could not insert watchpoint
3549 If this happens, delete or disable some of the watchpoints.
3551 Watching complex expressions that reference many variables can also
3552 exhaust the resources available for hardware-assisted watchpoints.
3553 That's because @value{GDBN} needs to watch every variable in the
3554 expression with separately allocated resources.
3556 If you call a function interactively using @code{print} or @code{call},
3557 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3558 kind of breakpoint or the call completes.
3560 @value{GDBN} automatically deletes watchpoints that watch local
3561 (automatic) variables, or expressions that involve such variables, when
3562 they go out of scope, that is, when the execution leaves the block in
3563 which these variables were defined. In particular, when the program
3564 being debugged terminates, @emph{all} local variables go out of scope,
3565 and so only watchpoints that watch global variables remain set. If you
3566 rerun the program, you will need to set all such watchpoints again. One
3567 way of doing that would be to set a code breakpoint at the entry to the
3568 @code{main} function and when it breaks, set all the watchpoints.
3570 @cindex watchpoints and threads
3571 @cindex threads and watchpoints
3572 In multi-threaded programs, watchpoints will detect changes to the
3573 watched expression from every thread.
3576 @emph{Warning:} In multi-threaded programs, software watchpoints
3577 have only limited usefulness. If @value{GDBN} creates a software
3578 watchpoint, it can only watch the value of an expression @emph{in a
3579 single thread}. If you are confident that the expression can only
3580 change due to the current thread's activity (and if you are also
3581 confident that no other thread can become current), then you can use
3582 software watchpoints as usual. However, @value{GDBN} may not notice
3583 when a non-current thread's activity changes the expression. (Hardware
3584 watchpoints, in contrast, watch an expression in all threads.)
3587 @xref{set remote hardware-watchpoint-limit}.
3589 @node Set Catchpoints
3590 @subsection Setting Catchpoints
3591 @cindex catchpoints, setting
3592 @cindex exception handlers
3593 @cindex event handling
3595 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3596 kinds of program events, such as C@t{++} exceptions or the loading of a
3597 shared library. Use the @code{catch} command to set a catchpoint.
3601 @item catch @var{event}
3602 Stop when @var{event} occurs. @var{event} can be any of the following:
3605 @cindex stop on C@t{++} exceptions
3606 The throwing of a C@t{++} exception.
3609 The catching of a C@t{++} exception.
3612 @cindex Ada exception catching
3613 @cindex catch Ada exceptions
3614 An Ada exception being raised. If an exception name is specified
3615 at the end of the command (eg @code{catch exception Program_Error}),
3616 the debugger will stop only when this specific exception is raised.
3617 Otherwise, the debugger stops execution when any Ada exception is raised.
3619 When inserting an exception catchpoint on a user-defined exception whose
3620 name is identical to one of the exceptions defined by the language, the
3621 fully qualified name must be used as the exception name. Otherwise,
3622 @value{GDBN} will assume that it should stop on the pre-defined exception
3623 rather than the user-defined one. For instance, assuming an exception
3624 called @code{Constraint_Error} is defined in package @code{Pck}, then
3625 the command to use to catch such exceptions is @kbd{catch exception
3626 Pck.Constraint_Error}.
3628 @item exception unhandled
3629 An exception that was raised but is not handled by the program.
3632 A failed Ada assertion.
3635 @cindex break on fork/exec
3636 A call to @code{exec}. This is currently only available for HP-UX
3640 A call to @code{fork}. This is currently only available for HP-UX
3644 A call to @code{vfork}. This is currently only available for HP-UX
3649 @item tcatch @var{event}
3650 Set a catchpoint that is enabled only for one stop. The catchpoint is
3651 automatically deleted after the first time the event is caught.
3655 Use the @code{info break} command to list the current catchpoints.
3657 There are currently some limitations to C@t{++} exception handling
3658 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3662 If you call a function interactively, @value{GDBN} normally returns
3663 control to you when the function has finished executing. If the call
3664 raises an exception, however, the call may bypass the mechanism that
3665 returns control to you and cause your program either to abort or to
3666 simply continue running until it hits a breakpoint, catches a signal
3667 that @value{GDBN} is listening for, or exits. This is the case even if
3668 you set a catchpoint for the exception; catchpoints on exceptions are
3669 disabled within interactive calls.
3672 You cannot raise an exception interactively.
3675 You cannot install an exception handler interactively.
3678 @cindex raise exceptions
3679 Sometimes @code{catch} is not the best way to debug exception handling:
3680 if you need to know exactly where an exception is raised, it is better to
3681 stop @emph{before} the exception handler is called, since that way you
3682 can see the stack before any unwinding takes place. If you set a
3683 breakpoint in an exception handler instead, it may not be easy to find
3684 out where the exception was raised.
3686 To stop just before an exception handler is called, you need some
3687 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3688 raised by calling a library function named @code{__raise_exception}
3689 which has the following ANSI C interface:
3692 /* @var{addr} is where the exception identifier is stored.
3693 @var{id} is the exception identifier. */
3694 void __raise_exception (void **addr, void *id);
3698 To make the debugger catch all exceptions before any stack
3699 unwinding takes place, set a breakpoint on @code{__raise_exception}
3700 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3702 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3703 that depends on the value of @var{id}, you can stop your program when
3704 a specific exception is raised. You can use multiple conditional
3705 breakpoints to stop your program when any of a number of exceptions are
3710 @subsection Deleting Breakpoints
3712 @cindex clearing breakpoints, watchpoints, catchpoints
3713 @cindex deleting breakpoints, watchpoints, catchpoints
3714 It is often necessary to eliminate a breakpoint, watchpoint, or
3715 catchpoint once it has done its job and you no longer want your program
3716 to stop there. This is called @dfn{deleting} the breakpoint. A
3717 breakpoint that has been deleted no longer exists; it is forgotten.
3719 With the @code{clear} command you can delete breakpoints according to
3720 where they are in your program. With the @code{delete} command you can
3721 delete individual breakpoints, watchpoints, or catchpoints by specifying
3722 their breakpoint numbers.
3724 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3725 automatically ignores breakpoints on the first instruction to be executed
3726 when you continue execution without changing the execution address.
3731 Delete any breakpoints at the next instruction to be executed in the
3732 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3733 the innermost frame is selected, this is a good way to delete a
3734 breakpoint where your program just stopped.
3736 @item clear @var{location}
3737 Delete any breakpoints set at the specified @var{location}.
3738 @xref{Specify Location}, for the various forms of @var{location}; the
3739 most useful ones are listed below:
3742 @item clear @var{function}
3743 @itemx clear @var{filename}:@var{function}
3744 Delete any breakpoints set at entry to the named @var{function}.
3746 @item clear @var{linenum}
3747 @itemx clear @var{filename}:@var{linenum}
3748 Delete any breakpoints set at or within the code of the specified
3749 @var{linenum} of the specified @var{filename}.
3752 @cindex delete breakpoints
3754 @kindex d @r{(@code{delete})}
3755 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3756 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3757 ranges specified as arguments. If no argument is specified, delete all
3758 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3759 confirm off}). You can abbreviate this command as @code{d}.
3763 @subsection Disabling Breakpoints
3765 @cindex enable/disable a breakpoint
3766 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3767 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3768 it had been deleted, but remembers the information on the breakpoint so
3769 that you can @dfn{enable} it again later.
3771 You disable and enable breakpoints, watchpoints, and catchpoints with
3772 the @code{enable} and @code{disable} commands, optionally specifying one
3773 or more breakpoint numbers as arguments. Use @code{info break} or
3774 @code{info watch} to print a list of breakpoints, watchpoints, and
3775 catchpoints if you do not know which numbers to use.
3777 Disabling and enabling a breakpoint that has multiple locations
3778 affects all of its locations.
3780 A breakpoint, watchpoint, or catchpoint can have any of four different
3781 states of enablement:
3785 Enabled. The breakpoint stops your program. A breakpoint set
3786 with the @code{break} command starts out in this state.
3788 Disabled. The breakpoint has no effect on your program.
3790 Enabled once. The breakpoint stops your program, but then becomes
3793 Enabled for deletion. The breakpoint stops your program, but
3794 immediately after it does so it is deleted permanently. A breakpoint
3795 set with the @code{tbreak} command starts out in this state.
3798 You can use the following commands to enable or disable breakpoints,
3799 watchpoints, and catchpoints:
3803 @kindex dis @r{(@code{disable})}
3804 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3805 Disable the specified breakpoints---or all breakpoints, if none are
3806 listed. A disabled breakpoint has no effect but is not forgotten. All
3807 options such as ignore-counts, conditions and commands are remembered in
3808 case the breakpoint is enabled again later. You may abbreviate
3809 @code{disable} as @code{dis}.
3812 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3813 Enable the specified breakpoints (or all defined breakpoints). They
3814 become effective once again in stopping your program.
3816 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3817 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3818 of these breakpoints immediately after stopping your program.
3820 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3821 Enable the specified breakpoints to work once, then die. @value{GDBN}
3822 deletes any of these breakpoints as soon as your program stops there.
3823 Breakpoints set by the @code{tbreak} command start out in this state.
3826 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3827 @c confusing: tbreak is also initially enabled.
3828 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3829 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3830 subsequently, they become disabled or enabled only when you use one of
3831 the commands above. (The command @code{until} can set and delete a
3832 breakpoint of its own, but it does not change the state of your other
3833 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3837 @subsection Break Conditions
3838 @cindex conditional breakpoints
3839 @cindex breakpoint conditions
3841 @c FIXME what is scope of break condition expr? Context where wanted?
3842 @c in particular for a watchpoint?
3843 The simplest sort of breakpoint breaks every time your program reaches a
3844 specified place. You can also specify a @dfn{condition} for a
3845 breakpoint. A condition is just a Boolean expression in your
3846 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3847 a condition evaluates the expression each time your program reaches it,
3848 and your program stops only if the condition is @emph{true}.
3850 This is the converse of using assertions for program validation; in that
3851 situation, you want to stop when the assertion is violated---that is,
3852 when the condition is false. In C, if you want to test an assertion expressed
3853 by the condition @var{assert}, you should set the condition
3854 @samp{! @var{assert}} on the appropriate breakpoint.
3856 Conditions are also accepted for watchpoints; you may not need them,
3857 since a watchpoint is inspecting the value of an expression anyhow---but
3858 it might be simpler, say, to just set a watchpoint on a variable name,
3859 and specify a condition that tests whether the new value is an interesting
3862 Break conditions can have side effects, and may even call functions in
3863 your program. This can be useful, for example, to activate functions
3864 that log program progress, or to use your own print functions to
3865 format special data structures. The effects are completely predictable
3866 unless there is another enabled breakpoint at the same address. (In
3867 that case, @value{GDBN} might see the other breakpoint first and stop your
3868 program without checking the condition of this one.) Note that
3869 breakpoint commands are usually more convenient and flexible than break
3871 purpose of performing side effects when a breakpoint is reached
3872 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3874 Break conditions can be specified when a breakpoint is set, by using
3875 @samp{if} in the arguments to the @code{break} command. @xref{Set
3876 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3877 with the @code{condition} command.
3879 You can also use the @code{if} keyword with the @code{watch} command.
3880 The @code{catch} command does not recognize the @code{if} keyword;
3881 @code{condition} is the only way to impose a further condition on a
3886 @item condition @var{bnum} @var{expression}
3887 Specify @var{expression} as the break condition for breakpoint,
3888 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3889 breakpoint @var{bnum} stops your program only if the value of
3890 @var{expression} is true (nonzero, in C). When you use
3891 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3892 syntactic correctness, and to determine whether symbols in it have
3893 referents in the context of your breakpoint. If @var{expression} uses
3894 symbols not referenced in the context of the breakpoint, @value{GDBN}
3895 prints an error message:
3898 No symbol "foo" in current context.
3903 not actually evaluate @var{expression} at the time the @code{condition}
3904 command (or a command that sets a breakpoint with a condition, like
3905 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3907 @item condition @var{bnum}
3908 Remove the condition from breakpoint number @var{bnum}. It becomes
3909 an ordinary unconditional breakpoint.
3912 @cindex ignore count (of breakpoint)
3913 A special case of a breakpoint condition is to stop only when the
3914 breakpoint has been reached a certain number of times. This is so
3915 useful that there is a special way to do it, using the @dfn{ignore
3916 count} of the breakpoint. Every breakpoint has an ignore count, which
3917 is an integer. Most of the time, the ignore count is zero, and
3918 therefore has no effect. But if your program reaches a breakpoint whose
3919 ignore count is positive, then instead of stopping, it just decrements
3920 the ignore count by one and continues. As a result, if the ignore count
3921 value is @var{n}, the breakpoint does not stop the next @var{n} times
3922 your program reaches it.
3926 @item ignore @var{bnum} @var{count}
3927 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3928 The next @var{count} times the breakpoint is reached, your program's
3929 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3932 To make the breakpoint stop the next time it is reached, specify
3935 When you use @code{continue} to resume execution of your program from a
3936 breakpoint, you can specify an ignore count directly as an argument to
3937 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3938 Stepping,,Continuing and Stepping}.
3940 If a breakpoint has a positive ignore count and a condition, the
3941 condition is not checked. Once the ignore count reaches zero,
3942 @value{GDBN} resumes checking the condition.
3944 You could achieve the effect of the ignore count with a condition such
3945 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3946 is decremented each time. @xref{Convenience Vars, ,Convenience
3950 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3953 @node Break Commands
3954 @subsection Breakpoint Command Lists
3956 @cindex breakpoint commands
3957 You can give any breakpoint (or watchpoint or catchpoint) a series of
3958 commands to execute when your program stops due to that breakpoint. For
3959 example, you might want to print the values of certain expressions, or
3960 enable other breakpoints.
3964 @kindex end@r{ (breakpoint commands)}
3965 @item commands @r{[}@var{bnum}@r{]}
3966 @itemx @dots{} @var{command-list} @dots{}
3968 Specify a list of commands for breakpoint number @var{bnum}. The commands
3969 themselves appear on the following lines. Type a line containing just
3970 @code{end} to terminate the commands.
3972 To remove all commands from a breakpoint, type @code{commands} and
3973 follow it immediately with @code{end}; that is, give no commands.
3975 With no @var{bnum} argument, @code{commands} refers to the last
3976 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3977 recently encountered).
3980 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3981 disabled within a @var{command-list}.
3983 You can use breakpoint commands to start your program up again. Simply
3984 use the @code{continue} command, or @code{step}, or any other command
3985 that resumes execution.
3987 Any other commands in the command list, after a command that resumes
3988 execution, are ignored. This is because any time you resume execution
3989 (even with a simple @code{next} or @code{step}), you may encounter
3990 another breakpoint---which could have its own command list, leading to
3991 ambiguities about which list to execute.
3994 If the first command you specify in a command list is @code{silent}, the
3995 usual message about stopping at a breakpoint is not printed. This may
3996 be desirable for breakpoints that are to print a specific message and
3997 then continue. If none of the remaining commands print anything, you
3998 see no sign that the breakpoint was reached. @code{silent} is
3999 meaningful only at the beginning of a breakpoint command list.
4001 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4002 print precisely controlled output, and are often useful in silent
4003 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4005 For example, here is how you could use breakpoint commands to print the
4006 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4012 printf "x is %d\n",x
4017 One application for breakpoint commands is to compensate for one bug so
4018 you can test for another. Put a breakpoint just after the erroneous line
4019 of code, give it a condition to detect the case in which something
4020 erroneous has been done, and give it commands to assign correct values
4021 to any variables that need them. End with the @code{continue} command
4022 so that your program does not stop, and start with the @code{silent}
4023 command so that no output is produced. Here is an example:
4034 @c @ifclear BARETARGET
4035 @node Error in Breakpoints
4036 @subsection ``Cannot insert breakpoints''
4038 If you request too many active hardware-assisted breakpoints and
4039 watchpoints, you will see this error message:
4041 @c FIXME: the precise wording of this message may change; the relevant
4042 @c source change is not committed yet (Sep 3, 1999).
4044 Stopped; cannot insert breakpoints.
4045 You may have requested too many hardware breakpoints and watchpoints.
4049 This message is printed when you attempt to resume the program, since
4050 only then @value{GDBN} knows exactly how many hardware breakpoints and
4051 watchpoints it needs to insert.
4053 When this message is printed, you need to disable or remove some of the
4054 hardware-assisted breakpoints and watchpoints, and then continue.
4056 @node Breakpoint-related Warnings
4057 @subsection ``Breakpoint address adjusted...''
4058 @cindex breakpoint address adjusted
4060 Some processor architectures place constraints on the addresses at
4061 which breakpoints may be placed. For architectures thus constrained,
4062 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4063 with the constraints dictated by the architecture.
4065 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4066 a VLIW architecture in which a number of RISC-like instructions may be
4067 bundled together for parallel execution. The FR-V architecture
4068 constrains the location of a breakpoint instruction within such a
4069 bundle to the instruction with the lowest address. @value{GDBN}
4070 honors this constraint by adjusting a breakpoint's address to the
4071 first in the bundle.
4073 It is not uncommon for optimized code to have bundles which contain
4074 instructions from different source statements, thus it may happen that
4075 a breakpoint's address will be adjusted from one source statement to
4076 another. Since this adjustment may significantly alter @value{GDBN}'s
4077 breakpoint related behavior from what the user expects, a warning is
4078 printed when the breakpoint is first set and also when the breakpoint
4081 A warning like the one below is printed when setting a breakpoint
4082 that's been subject to address adjustment:
4085 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4088 Such warnings are printed both for user settable and @value{GDBN}'s
4089 internal breakpoints. If you see one of these warnings, you should
4090 verify that a breakpoint set at the adjusted address will have the
4091 desired affect. If not, the breakpoint in question may be removed and
4092 other breakpoints may be set which will have the desired behavior.
4093 E.g., it may be sufficient to place the breakpoint at a later
4094 instruction. A conditional breakpoint may also be useful in some
4095 cases to prevent the breakpoint from triggering too often.
4097 @value{GDBN} will also issue a warning when stopping at one of these
4098 adjusted breakpoints:
4101 warning: Breakpoint 1 address previously adjusted from 0x00010414
4105 When this warning is encountered, it may be too late to take remedial
4106 action except in cases where the breakpoint is hit earlier or more
4107 frequently than expected.
4109 @node Continuing and Stepping
4110 @section Continuing and Stepping
4114 @cindex resuming execution
4115 @dfn{Continuing} means resuming program execution until your program
4116 completes normally. In contrast, @dfn{stepping} means executing just
4117 one more ``step'' of your program, where ``step'' may mean either one
4118 line of source code, or one machine instruction (depending on what
4119 particular command you use). Either when continuing or when stepping,
4120 your program may stop even sooner, due to a breakpoint or a signal. (If
4121 it stops due to a signal, you may want to use @code{handle}, or use
4122 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4126 @kindex c @r{(@code{continue})}
4127 @kindex fg @r{(resume foreground execution)}
4128 @item continue @r{[}@var{ignore-count}@r{]}
4129 @itemx c @r{[}@var{ignore-count}@r{]}
4130 @itemx fg @r{[}@var{ignore-count}@r{]}
4131 Resume program execution, at the address where your program last stopped;
4132 any breakpoints set at that address are bypassed. The optional argument
4133 @var{ignore-count} allows you to specify a further number of times to
4134 ignore a breakpoint at this location; its effect is like that of
4135 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4137 The argument @var{ignore-count} is meaningful only when your program
4138 stopped due to a breakpoint. At other times, the argument to
4139 @code{continue} is ignored.
4141 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4142 debugged program is deemed to be the foreground program) are provided
4143 purely for convenience, and have exactly the same behavior as
4147 To resume execution at a different place, you can use @code{return}
4148 (@pxref{Returning, ,Returning from a Function}) to go back to the
4149 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4150 Different Address}) to go to an arbitrary location in your program.
4152 A typical technique for using stepping is to set a breakpoint
4153 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4154 beginning of the function or the section of your program where a problem
4155 is believed to lie, run your program until it stops at that breakpoint,
4156 and then step through the suspect area, examining the variables that are
4157 interesting, until you see the problem happen.
4161 @kindex s @r{(@code{step})}
4163 Continue running your program until control reaches a different source
4164 line, then stop it and return control to @value{GDBN}. This command is
4165 abbreviated @code{s}.
4168 @c "without debugging information" is imprecise; actually "without line
4169 @c numbers in the debugging information". (gcc -g1 has debugging info but
4170 @c not line numbers). But it seems complex to try to make that
4171 @c distinction here.
4172 @emph{Warning:} If you use the @code{step} command while control is
4173 within a function that was compiled without debugging information,
4174 execution proceeds until control reaches a function that does have
4175 debugging information. Likewise, it will not step into a function which
4176 is compiled without debugging information. To step through functions
4177 without debugging information, use the @code{stepi} command, described
4181 The @code{step} command only stops at the first instruction of a source
4182 line. This prevents the multiple stops that could otherwise occur in
4183 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4184 to stop if a function that has debugging information is called within
4185 the line. In other words, @code{step} @emph{steps inside} any functions
4186 called within the line.
4188 Also, the @code{step} command only enters a function if there is line
4189 number information for the function. Otherwise it acts like the
4190 @code{next} command. This avoids problems when using @code{cc -gl}
4191 on MIPS machines. Previously, @code{step} entered subroutines if there
4192 was any debugging information about the routine.
4194 @item step @var{count}
4195 Continue running as in @code{step}, but do so @var{count} times. If a
4196 breakpoint is reached, or a signal not related to stepping occurs before
4197 @var{count} steps, stepping stops right away.
4200 @kindex n @r{(@code{next})}
4201 @item next @r{[}@var{count}@r{]}
4202 Continue to the next source line in the current (innermost) stack frame.
4203 This is similar to @code{step}, but function calls that appear within
4204 the line of code are executed without stopping. Execution stops when
4205 control reaches a different line of code at the original stack level
4206 that was executing when you gave the @code{next} command. This command
4207 is abbreviated @code{n}.
4209 An argument @var{count} is a repeat count, as for @code{step}.
4212 @c FIX ME!! Do we delete this, or is there a way it fits in with
4213 @c the following paragraph? --- Vctoria
4215 @c @code{next} within a function that lacks debugging information acts like
4216 @c @code{step}, but any function calls appearing within the code of the
4217 @c function are executed without stopping.
4219 The @code{next} command only stops at the first instruction of a
4220 source line. This prevents multiple stops that could otherwise occur in
4221 @code{switch} statements, @code{for} loops, etc.
4223 @kindex set step-mode
4225 @cindex functions without line info, and stepping
4226 @cindex stepping into functions with no line info
4227 @itemx set step-mode on
4228 The @code{set step-mode on} command causes the @code{step} command to
4229 stop at the first instruction of a function which contains no debug line
4230 information rather than stepping over it.
4232 This is useful in cases where you may be interested in inspecting the
4233 machine instructions of a function which has no symbolic info and do not
4234 want @value{GDBN} to automatically skip over this function.
4236 @item set step-mode off
4237 Causes the @code{step} command to step over any functions which contains no
4238 debug information. This is the default.
4240 @item show step-mode
4241 Show whether @value{GDBN} will stop in or step over functions without
4242 source line debug information.
4245 @kindex fin @r{(@code{finish})}
4247 Continue running until just after function in the selected stack frame
4248 returns. Print the returned value (if any). This command can be
4249 abbreviated as @code{fin}.
4251 Contrast this with the @code{return} command (@pxref{Returning,
4252 ,Returning from a Function}).
4255 @kindex u @r{(@code{until})}
4256 @cindex run until specified location
4259 Continue running until a source line past the current line, in the
4260 current stack frame, is reached. This command is used to avoid single
4261 stepping through a loop more than once. It is like the @code{next}
4262 command, except that when @code{until} encounters a jump, it
4263 automatically continues execution until the program counter is greater
4264 than the address of the jump.
4266 This means that when you reach the end of a loop after single stepping
4267 though it, @code{until} makes your program continue execution until it
4268 exits the loop. In contrast, a @code{next} command at the end of a loop
4269 simply steps back to the beginning of the loop, which forces you to step
4270 through the next iteration.
4272 @code{until} always stops your program if it attempts to exit the current
4275 @code{until} may produce somewhat counterintuitive results if the order
4276 of machine code does not match the order of the source lines. For
4277 example, in the following excerpt from a debugging session, the @code{f}
4278 (@code{frame}) command shows that execution is stopped at line
4279 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4283 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4285 (@value{GDBP}) until
4286 195 for ( ; argc > 0; NEXTARG) @{
4289 This happened because, for execution efficiency, the compiler had
4290 generated code for the loop closure test at the end, rather than the
4291 start, of the loop---even though the test in a C @code{for}-loop is
4292 written before the body of the loop. The @code{until} command appeared
4293 to step back to the beginning of the loop when it advanced to this
4294 expression; however, it has not really gone to an earlier
4295 statement---not in terms of the actual machine code.
4297 @code{until} with no argument works by means of single
4298 instruction stepping, and hence is slower than @code{until} with an
4301 @item until @var{location}
4302 @itemx u @var{location}
4303 Continue running your program until either the specified location is
4304 reached, or the current stack frame returns. @var{location} is any of
4305 the forms described in @ref{Specify Location}.
4306 This form of the command uses temporary breakpoints, and
4307 hence is quicker than @code{until} without an argument. The specified
4308 location is actually reached only if it is in the current frame. This
4309 implies that @code{until} can be used to skip over recursive function
4310 invocations. For instance in the code below, if the current location is
4311 line @code{96}, issuing @code{until 99} will execute the program up to
4312 line @code{99} in the same invocation of factorial, i.e., after the inner
4313 invocations have returned.
4316 94 int factorial (int value)
4318 96 if (value > 1) @{
4319 97 value *= factorial (value - 1);
4326 @kindex advance @var{location}
4327 @itemx advance @var{location}
4328 Continue running the program up to the given @var{location}. An argument is
4329 required, which should be of one of the forms described in
4330 @ref{Specify Location}.
4331 Execution will also stop upon exit from the current stack
4332 frame. This command is similar to @code{until}, but @code{advance} will
4333 not skip over recursive function calls, and the target location doesn't
4334 have to be in the same frame as the current one.
4338 @kindex si @r{(@code{stepi})}
4340 @itemx stepi @var{arg}
4342 Execute one machine instruction, then stop and return to the debugger.
4344 It is often useful to do @samp{display/i $pc} when stepping by machine
4345 instructions. This makes @value{GDBN} automatically display the next
4346 instruction to be executed, each time your program stops. @xref{Auto
4347 Display,, Automatic Display}.
4349 An argument is a repeat count, as in @code{step}.
4353 @kindex ni @r{(@code{nexti})}
4355 @itemx nexti @var{arg}
4357 Execute one machine instruction, but if it is a function call,
4358 proceed until the function returns.
4360 An argument is a repeat count, as in @code{next}.
4367 A signal is an asynchronous event that can happen in a program. The
4368 operating system defines the possible kinds of signals, and gives each
4369 kind a name and a number. For example, in Unix @code{SIGINT} is the
4370 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4371 @code{SIGSEGV} is the signal a program gets from referencing a place in
4372 memory far away from all the areas in use; @code{SIGALRM} occurs when
4373 the alarm clock timer goes off (which happens only if your program has
4374 requested an alarm).
4376 @cindex fatal signals
4377 Some signals, including @code{SIGALRM}, are a normal part of the
4378 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4379 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4380 program has not specified in advance some other way to handle the signal.
4381 @code{SIGINT} does not indicate an error in your program, but it is normally
4382 fatal so it can carry out the purpose of the interrupt: to kill the program.
4384 @value{GDBN} has the ability to detect any occurrence of a signal in your
4385 program. You can tell @value{GDBN} in advance what to do for each kind of
4388 @cindex handling signals
4389 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4390 @code{SIGALRM} be silently passed to your program
4391 (so as not to interfere with their role in the program's functioning)
4392 but to stop your program immediately whenever an error signal happens.
4393 You can change these settings with the @code{handle} command.
4396 @kindex info signals
4400 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4401 handle each one. You can use this to see the signal numbers of all
4402 the defined types of signals.
4404 @item info signals @var{sig}
4405 Similar, but print information only about the specified signal number.
4407 @code{info handle} is an alias for @code{info signals}.
4410 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4411 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4412 can be the number of a signal or its name (with or without the
4413 @samp{SIG} at the beginning); a list of signal numbers of the form
4414 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4415 known signals. Optional arguments @var{keywords}, described below,
4416 say what change to make.
4420 The keywords allowed by the @code{handle} command can be abbreviated.
4421 Their full names are:
4425 @value{GDBN} should not stop your program when this signal happens. It may
4426 still print a message telling you that the signal has come in.
4429 @value{GDBN} should stop your program when this signal happens. This implies
4430 the @code{print} keyword as well.
4433 @value{GDBN} should print a message when this signal happens.
4436 @value{GDBN} should not mention the occurrence of the signal at all. This
4437 implies the @code{nostop} keyword as well.
4441 @value{GDBN} should allow your program to see this signal; your program
4442 can handle the signal, or else it may terminate if the signal is fatal
4443 and not handled. @code{pass} and @code{noignore} are synonyms.
4447 @value{GDBN} should not allow your program to see this signal.
4448 @code{nopass} and @code{ignore} are synonyms.
4452 When a signal stops your program, the signal is not visible to the
4454 continue. Your program sees the signal then, if @code{pass} is in
4455 effect for the signal in question @emph{at that time}. In other words,
4456 after @value{GDBN} reports a signal, you can use the @code{handle}
4457 command with @code{pass} or @code{nopass} to control whether your
4458 program sees that signal when you continue.
4460 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4461 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4462 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4465 You can also use the @code{signal} command to prevent your program from
4466 seeing a signal, or cause it to see a signal it normally would not see,
4467 or to give it any signal at any time. For example, if your program stopped
4468 due to some sort of memory reference error, you might store correct
4469 values into the erroneous variables and continue, hoping to see more
4470 execution; but your program would probably terminate immediately as
4471 a result of the fatal signal once it saw the signal. To prevent this,
4472 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4476 @section Stopping and Starting Multi-thread Programs
4478 @cindex stopped threads
4479 @cindex threads, stopped
4481 @cindex continuing threads
4482 @cindex threads, continuing
4484 @value{GDBN} supports debugging programs with multiple threads
4485 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4486 are two modes of controlling execution of your program within the
4487 debugger. In the default mode, referred to as @dfn{all-stop mode},
4488 when any thread in your program stops (for example, at a breakpoint
4489 or while being stepped), all other threads in the program are also stopped by
4490 @value{GDBN}. On some targets, @value{GDBN} also supports
4491 @dfn{non-stop mode}, in which other threads can continue to run freely while
4492 you examine the stopped thread in the debugger.
4495 * All-Stop Mode:: All threads stop when GDB takes control
4496 * Non-Stop Mode:: Other threads continue to execute
4497 * Background Execution:: Running your program asynchronously
4498 * Thread-Specific Breakpoints:: Controlling breakpoints
4499 * Interrupted System Calls:: GDB may interfere with system calls
4503 @subsection All-Stop Mode
4505 @cindex all-stop mode
4507 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4508 @emph{all} threads of execution stop, not just the current thread. This
4509 allows you to examine the overall state of the program, including
4510 switching between threads, without worrying that things may change
4513 Conversely, whenever you restart the program, @emph{all} threads start
4514 executing. @emph{This is true even when single-stepping} with commands
4515 like @code{step} or @code{next}.
4517 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4518 Since thread scheduling is up to your debugging target's operating
4519 system (not controlled by @value{GDBN}), other threads may
4520 execute more than one statement while the current thread completes a
4521 single step. Moreover, in general other threads stop in the middle of a
4522 statement, rather than at a clean statement boundary, when the program
4525 You might even find your program stopped in another thread after
4526 continuing or even single-stepping. This happens whenever some other
4527 thread runs into a breakpoint, a signal, or an exception before the
4528 first thread completes whatever you requested.
4530 @cindex automatic thread selection
4531 @cindex switching threads automatically
4532 @cindex threads, automatic switching
4533 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4534 signal, it automatically selects the thread where that breakpoint or
4535 signal happened. @value{GDBN} alerts you to the context switch with a
4536 message such as @samp{[Switching to Thread @var{n}]} to identify the
4539 On some OSes, you can modify @value{GDBN}'s default behavior by
4540 locking the OS scheduler to allow only a single thread to run.
4543 @item set scheduler-locking @var{mode}
4544 @cindex scheduler locking mode
4545 @cindex lock scheduler
4546 Set the scheduler locking mode. If it is @code{off}, then there is no
4547 locking and any thread may run at any time. If @code{on}, then only the
4548 current thread may run when the inferior is resumed. The @code{step}
4549 mode optimizes for single-stepping; it prevents other threads
4550 from preempting the current thread while you are stepping, so that
4551 the focus of debugging does not change unexpectedly.
4552 Other threads only rarely (or never) get a chance to run
4553 when you step. They are more likely to run when you @samp{next} over a
4554 function call, and they are completely free to run when you use commands
4555 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4556 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4557 the current thread away from the thread that you are debugging.
4559 @item show scheduler-locking
4560 Display the current scheduler locking mode.
4564 @subsection Non-Stop Mode
4566 @cindex non-stop mode
4568 @c This section is really only a place-holder, and needs to be expanded
4569 @c with more details.
4571 For some multi-threaded targets, @value{GDBN} supports an optional
4572 mode of operation in which you can examine stopped program threads in
4573 the debugger while other threads continue to execute freely. This
4574 minimizes intrusion when debugging live systems, such as programs
4575 where some threads have real-time constraints or must continue to
4576 respond to external events. This is referred to as @dfn{non-stop} mode.
4578 In non-stop mode, when a thread stops to report a debugging event,
4579 @emph{only} that thread is stopped; @value{GDBN} does not stop other
4580 threads as well, in contrast to the all-stop mode behavior. Additionally,
4581 execution commands such as @code{continue} and @code{step} apply by default
4582 only to the current thread in non-stop mode, rather than all threads as
4583 in all-stop mode. This allows you to control threads explicitly in
4584 ways that are not possible in all-stop mode --- for example, stepping
4585 one thread while allowing others to run freely, stepping
4586 one thread while holding all others stopped, or stepping several threads
4587 independently and simultaneously.
4589 To enter non-stop mode, use this sequence of commands before you run
4590 or attach to your program:
4593 # Enable the async interface.
4596 # If using the CLI, pagination breaks non-stop.
4599 # Finally, turn it on!
4603 You can use these commands to manipulate the non-stop mode setting:
4606 @kindex set non-stop
4607 @item set non-stop on
4608 Enable selection of non-stop mode.
4609 @item set non-stop off
4610 Disable selection of non-stop mode.
4611 @kindex show non-stop
4613 Show the current non-stop enablement setting.
4616 Note these commands only reflect whether non-stop mode is enabled,
4617 not whether the currently-executing program is being run in non-stop mode.
4618 In particular, the @code{set non-stop} preference is only consulted when
4619 @value{GDBN} starts or connects to the target program, and it is generally
4620 not possible to switch modes once debugging has started. Furthermore,
4621 since not all targets support non-stop mode, even when you have enabled
4622 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
4625 In non-stop mode, all execution commands apply only to the current thread
4626 by default. That is, @code{continue} only continues one thread.
4627 To continue all threads, issue @code{continue -a} or @code{c -a}.
4629 You can use @value{GDBN}'s background execution commands
4630 (@pxref{Background Execution}) to run some threads in the background
4631 while you continue to examine or step others from @value{GDBN}.
4632 The MI execution commands (@pxref{GDB/MI Program Execution}) are
4633 always executed asynchronously in non-stop mode.
4635 Suspending execution is done with the @code{interrupt} command when
4636 running in the background, or @kbd{Ctrl-c} during foreground execution.
4637 In all-stop mode, this stops the whole process;
4638 but in non-stop mode the interrupt applies only to the current thread.
4639 To stop the whole program, use @code{interrupt -a}.
4641 Other execution commands do not currently support the @code{-a} option.
4643 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
4644 that thread current, as it does in all-stop mode. This is because the
4645 thread stop notifications are asynchronous with respect to @value{GDBN}'s
4646 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
4647 changed to a different thread just as you entered a command to operate on the
4648 previously current thread.
4650 @node Background Execution
4651 @subsection Background Execution
4653 @cindex foreground execution
4654 @cindex background execution
4655 @cindex asynchronous execution
4656 @cindex execution, foreground, background and asynchronous
4658 @value{GDBN}'s execution commands have two variants: the normal
4659 foreground (synchronous) behavior, and a background
4660 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
4661 the program to report that some thread has stopped before prompting for
4662 another command. In background execution, @value{GDBN} immediately gives
4663 a command prompt so that you can issue other commands while your program runs.
4665 To specify background execution, add a @code{&} to the command. For example,
4666 the background form of the @code{continue} command is @code{continue&}, or
4667 just @code{c&}. The execution commands that accept background execution
4673 @xref{Starting, , Starting your Program}.
4677 @xref{Attach, , Debugging an Already-running Process}.
4681 @xref{Continuing and Stepping, step}.
4685 @xref{Continuing and Stepping, stepi}.
4689 @xref{Continuing and Stepping, next}.
4693 @xref{Continuing and Stepping, nexti}.
4697 @xref{Continuing and Stepping, continue}.
4701 @xref{Continuing and Stepping, finish}.
4705 @xref{Continuing and Stepping, until}.
4709 Background execution is especially useful in conjunction with non-stop
4710 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
4711 However, you can also use these commands in the normal all-stop mode with
4712 the restriction that you cannot issue another execution command until the
4713 previous one finishes. Examples of commands that are valid in all-stop
4714 mode while the program is running include @code{help} and @code{info break}.
4716 You can interrupt your program while it is running in the background by
4717 using the @code{interrupt} command.
4724 Suspend execution of the running program. In all-stop mode,
4725 @code{interrupt} stops the whole process, but in non-stop mode, it stops
4726 only the current thread. To stop the whole program in non-stop mode,
4727 use @code{interrupt -a}.
4730 You may need to explicitly enable async mode before you can use background
4731 execution commands, with the @code{set target-async 1} command. If the
4732 target doesn't support async mode, @value{GDBN} issues an error message
4733 if you attempt to use the background execution commands.
4735 @node Thread-Specific Breakpoints
4736 @subsection Thread-Specific Breakpoints
4738 When your program has multiple threads (@pxref{Threads,, Debugging
4739 Programs with Multiple Threads}), you can choose whether to set
4740 breakpoints on all threads, or on a particular thread.
4743 @cindex breakpoints and threads
4744 @cindex thread breakpoints
4745 @kindex break @dots{} thread @var{threadno}
4746 @item break @var{linespec} thread @var{threadno}
4747 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4748 @var{linespec} specifies source lines; there are several ways of
4749 writing them (@pxref{Specify Location}), but the effect is always to
4750 specify some source line.
4752 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4753 to specify that you only want @value{GDBN} to stop the program when a
4754 particular thread reaches this breakpoint. @var{threadno} is one of the
4755 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4756 column of the @samp{info threads} display.
4758 If you do not specify @samp{thread @var{threadno}} when you set a
4759 breakpoint, the breakpoint applies to @emph{all} threads of your
4762 You can use the @code{thread} qualifier on conditional breakpoints as
4763 well; in this case, place @samp{thread @var{threadno}} before the
4764 breakpoint condition, like this:
4767 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4772 @node Interrupted System Calls
4773 @subsection Interrupted System Calls
4775 @cindex thread breakpoints and system calls
4776 @cindex system calls and thread breakpoints
4777 @cindex premature return from system calls
4778 There is an unfortunate side effect when using @value{GDBN} to debug
4779 multi-threaded programs. If one thread stops for a
4780 breakpoint, or for some other reason, and another thread is blocked in a
4781 system call, then the system call may return prematurely. This is a
4782 consequence of the interaction between multiple threads and the signals
4783 that @value{GDBN} uses to implement breakpoints and other events that
4786 To handle this problem, your program should check the return value of
4787 each system call and react appropriately. This is good programming
4790 For example, do not write code like this:
4796 The call to @code{sleep} will return early if a different thread stops
4797 at a breakpoint or for some other reason.
4799 Instead, write this:
4804 unslept = sleep (unslept);
4807 A system call is allowed to return early, so the system is still
4808 conforming to its specification. But @value{GDBN} does cause your
4809 multi-threaded program to behave differently than it would without
4812 Also, @value{GDBN} uses internal breakpoints in the thread library to
4813 monitor certain events such as thread creation and thread destruction.
4814 When such an event happens, a system call in another thread may return
4815 prematurely, even though your program does not appear to stop.
4818 @node Reverse Execution
4819 @chapter Running programs backward
4820 @cindex reverse execution
4821 @cindex running programs backward
4823 When you are debugging a program, it is not unusual to realize that
4824 you have gone too far, and some event of interest has already happened.
4825 If the target environment supports it, @value{GDBN} can allow you to
4826 ``rewind'' the program by running it backward.
4828 A target environment that supports reverse execution should be able
4829 to ``undo'' the changes in machine state that have taken place as the
4830 program was executing normally. Variables, registers etc.@: should
4831 revert to their previous values. Obviously this requires a great
4832 deal of sophistication on the part of the target environment; not
4833 all target environments can support reverse execution.
4835 When a program is executed in reverse, the instructions that
4836 have most recently been executed are ``un-executed'', in reverse
4837 order. The program counter runs backward, following the previous
4838 thread of execution in reverse. As each instruction is ``un-executed'',
4839 the values of memory and/or registers that were changed by that
4840 instruction are reverted to their previous states. After executing
4841 a piece of source code in reverse, all side effects of that code
4842 should be ``undone'', and all variables should be returned to their
4843 prior values@footnote{
4844 Note that some side effects are easier to undo than others. For instance,
4845 memory and registers are relatively easy, but device I/O is hard. Some
4846 targets may be able undo things like device I/O, and some may not.
4848 The contract between @value{GDBN} and the reverse executing target
4849 requires only that the target do something reasonable when
4850 @value{GDBN} tells it to execute backwards, and then report the
4851 results back to @value{GDBN}. Whatever the target reports back to
4852 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
4853 assumes that the memory and registers that the target reports are in a
4854 consistant state, but @value{GDBN} accepts whatever it is given.
4857 If you are debugging in a target environment that supports
4858 reverse execution, @value{GDBN} provides the following commands.
4861 @kindex reverse-continue
4862 @kindex rc @r{(@code{reverse-continue})}
4863 @item reverse-continue @r{[}@var{ignore-count}@r{]}
4864 @itemx rc @r{[}@var{ignore-count}@r{]}
4865 Beginning at the point where your program last stopped, start executing
4866 in reverse. Reverse execution will stop for breakpoints and synchronous
4867 exceptions (signals), just like normal execution. Behavior of
4868 asynchronous signals depends on the target environment.
4870 @kindex reverse-step
4871 @kindex rs @r{(@code{step})}
4872 @item reverse-step @r{[}@var{count}@r{]}
4873 Run the program backward until control reaches the start of a
4874 different source line; then stop it, and return control to @value{GDBN}.
4876 Like the @code{step} command, @code{reverse-step} will only stop
4877 at the beginning of a source line. It ``un-executes'' the previously
4878 executed source line. If the previous source line included calls to
4879 debuggable functions, @code{reverse-step} will step (backward) into
4880 the called function, stopping at the beginning of the @emph{last}
4881 statement in the called function (typically a return statement).
4883 Also, as with the @code{step} command, if non-debuggable functions are
4884 called, @code{reverse-step} will run thru them backward without stopping.
4886 @kindex reverse-stepi
4887 @kindex rsi @r{(@code{reverse-stepi})}
4888 @item reverse-stepi @r{[}@var{count}@r{]}
4889 Reverse-execute one machine instruction. Note that the instruction
4890 to be reverse-executed is @emph{not} the one pointed to by the program
4891 counter, but the instruction executed prior to that one. For instance,
4892 if the last instruction was a jump, @code{reverse-stepi} will take you
4893 back from the destination of the jump to the jump instruction itself.
4895 @kindex reverse-next
4896 @kindex rn @r{(@code{reverse-next})}
4897 @item reverse-next @r{[}@var{count}@r{]}
4898 Run backward to the beginning of the previous line executed in
4899 the current (innermost) stack frame. If the line contains function
4900 calls, they will be ``un-executed'' without stopping. Starting from
4901 the first line of a function, @code{reverse-next} will take you back
4902 to the caller of that function, @emph{before} the function was called,
4903 just as the normal @code{next} command would take you from the last
4904 line of a function back to its return to its caller
4905 @footnote{Unles the code is too heavily optimized.}.
4907 @kindex reverse-nexti
4908 @kindex rni @r{(@code{reverse-nexti})}
4909 @item reverse-nexti @r{[}@var{count}@r{]}
4910 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
4911 in reverse, except that called functions are ``un-executed'' atomically.
4912 That is, if the previously executed instruction was a return from
4913 another instruction, @code{reverse-nexti} will continue to execute
4914 in reverse until the call to that function (from the current stack
4917 @kindex reverse-finish
4918 @item reverse-finish
4919 Just as the @code{finish} command takes you to the point where the
4920 current function returns, @code{reverse-finish} takes you to the point
4921 where it was called. Instead of ending up at the end of the current
4922 function invocation, you end up at the beginning.
4924 @kindex set exec-direction
4925 @item set exec-direction
4926 Set the direction of target execution.
4927 @itemx set exec-direction reverse
4928 @cindex execute forward or backward in time
4929 @value{GDBN} will perform all execution commands in reverse, until the
4930 exec-direction mode is changed to ``forward''. Affected commands include
4931 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
4932 command cannot be used in reverse mode.
4933 @item set exec-direction forward
4934 @value{GDBN} will perform all execution commands in the normal fashion.
4935 This is the default.
4940 @chapter Examining the Stack
4942 When your program has stopped, the first thing you need to know is where it
4943 stopped and how it got there.
4946 Each time your program performs a function call, information about the call
4948 That information includes the location of the call in your program,
4949 the arguments of the call,
4950 and the local variables of the function being called.
4951 The information is saved in a block of data called a @dfn{stack frame}.
4952 The stack frames are allocated in a region of memory called the @dfn{call
4955 When your program stops, the @value{GDBN} commands for examining the
4956 stack allow you to see all of this information.
4958 @cindex selected frame
4959 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4960 @value{GDBN} commands refer implicitly to the selected frame. In
4961 particular, whenever you ask @value{GDBN} for the value of a variable in
4962 your program, the value is found in the selected frame. There are
4963 special @value{GDBN} commands to select whichever frame you are
4964 interested in. @xref{Selection, ,Selecting a Frame}.
4966 When your program stops, @value{GDBN} automatically selects the
4967 currently executing frame and describes it briefly, similar to the
4968 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4971 * Frames:: Stack frames
4972 * Backtrace:: Backtraces
4973 * Selection:: Selecting a frame
4974 * Frame Info:: Information on a frame
4979 @section Stack Frames
4981 @cindex frame, definition
4983 The call stack is divided up into contiguous pieces called @dfn{stack
4984 frames}, or @dfn{frames} for short; each frame is the data associated
4985 with one call to one function. The frame contains the arguments given
4986 to the function, the function's local variables, and the address at
4987 which the function is executing.
4989 @cindex initial frame
4990 @cindex outermost frame
4991 @cindex innermost frame
4992 When your program is started, the stack has only one frame, that of the
4993 function @code{main}. This is called the @dfn{initial} frame or the
4994 @dfn{outermost} frame. Each time a function is called, a new frame is
4995 made. Each time a function returns, the frame for that function invocation
4996 is eliminated. If a function is recursive, there can be many frames for
4997 the same function. The frame for the function in which execution is
4998 actually occurring is called the @dfn{innermost} frame. This is the most
4999 recently created of all the stack frames that still exist.
5001 @cindex frame pointer
5002 Inside your program, stack frames are identified by their addresses. A
5003 stack frame consists of many bytes, each of which has its own address; each
5004 kind of computer has a convention for choosing one byte whose
5005 address serves as the address of the frame. Usually this address is kept
5006 in a register called the @dfn{frame pointer register}
5007 (@pxref{Registers, $fp}) while execution is going on in that frame.
5009 @cindex frame number
5010 @value{GDBN} assigns numbers to all existing stack frames, starting with
5011 zero for the innermost frame, one for the frame that called it,
5012 and so on upward. These numbers do not really exist in your program;
5013 they are assigned by @value{GDBN} to give you a way of designating stack
5014 frames in @value{GDBN} commands.
5016 @c The -fomit-frame-pointer below perennially causes hbox overflow
5017 @c underflow problems.
5018 @cindex frameless execution
5019 Some compilers provide a way to compile functions so that they operate
5020 without stack frames. (For example, the @value{NGCC} option
5022 @samp{-fomit-frame-pointer}
5024 generates functions without a frame.)
5025 This is occasionally done with heavily used library functions to save
5026 the frame setup time. @value{GDBN} has limited facilities for dealing
5027 with these function invocations. If the innermost function invocation
5028 has no stack frame, @value{GDBN} nevertheless regards it as though
5029 it had a separate frame, which is numbered zero as usual, allowing
5030 correct tracing of the function call chain. However, @value{GDBN} has
5031 no provision for frameless functions elsewhere in the stack.
5034 @kindex frame@r{, command}
5035 @cindex current stack frame
5036 @item frame @var{args}
5037 The @code{frame} command allows you to move from one stack frame to another,
5038 and to print the stack frame you select. @var{args} may be either the
5039 address of the frame or the stack frame number. Without an argument,
5040 @code{frame} prints the current stack frame.
5042 @kindex select-frame
5043 @cindex selecting frame silently
5045 The @code{select-frame} command allows you to move from one stack frame
5046 to another without printing the frame. This is the silent version of
5054 @cindex call stack traces
5055 A backtrace is a summary of how your program got where it is. It shows one
5056 line per frame, for many frames, starting with the currently executing
5057 frame (frame zero), followed by its caller (frame one), and on up the
5062 @kindex bt @r{(@code{backtrace})}
5065 Print a backtrace of the entire stack: one line per frame for all
5066 frames in the stack.
5068 You can stop the backtrace at any time by typing the system interrupt
5069 character, normally @kbd{Ctrl-c}.
5071 @item backtrace @var{n}
5073 Similar, but print only the innermost @var{n} frames.
5075 @item backtrace -@var{n}
5077 Similar, but print only the outermost @var{n} frames.
5079 @item backtrace full
5081 @itemx bt full @var{n}
5082 @itemx bt full -@var{n}
5083 Print the values of the local variables also. @var{n} specifies the
5084 number of frames to print, as described above.
5089 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5090 are additional aliases for @code{backtrace}.
5092 @cindex multiple threads, backtrace
5093 In a multi-threaded program, @value{GDBN} by default shows the
5094 backtrace only for the current thread. To display the backtrace for
5095 several or all of the threads, use the command @code{thread apply}
5096 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5097 apply all backtrace}, @value{GDBN} will display the backtrace for all
5098 the threads; this is handy when you debug a core dump of a
5099 multi-threaded program.
5101 Each line in the backtrace shows the frame number and the function name.
5102 The program counter value is also shown---unless you use @code{set
5103 print address off}. The backtrace also shows the source file name and
5104 line number, as well as the arguments to the function. The program
5105 counter value is omitted if it is at the beginning of the code for that
5108 Here is an example of a backtrace. It was made with the command
5109 @samp{bt 3}, so it shows the innermost three frames.
5113 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5115 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
5116 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5118 (More stack frames follow...)
5123 The display for frame zero does not begin with a program counter
5124 value, indicating that your program has stopped at the beginning of the
5125 code for line @code{993} of @code{builtin.c}.
5127 @cindex value optimized out, in backtrace
5128 @cindex function call arguments, optimized out
5129 If your program was compiled with optimizations, some compilers will
5130 optimize away arguments passed to functions if those arguments are
5131 never used after the call. Such optimizations generate code that
5132 passes arguments through registers, but doesn't store those arguments
5133 in the stack frame. @value{GDBN} has no way of displaying such
5134 arguments in stack frames other than the innermost one. Here's what
5135 such a backtrace might look like:
5139 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5141 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5142 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5144 (More stack frames follow...)
5149 The values of arguments that were not saved in their stack frames are
5150 shown as @samp{<value optimized out>}.
5152 If you need to display the values of such optimized-out arguments,
5153 either deduce that from other variables whose values depend on the one
5154 you are interested in, or recompile without optimizations.
5156 @cindex backtrace beyond @code{main} function
5157 @cindex program entry point
5158 @cindex startup code, and backtrace
5159 Most programs have a standard user entry point---a place where system
5160 libraries and startup code transition into user code. For C this is
5161 @code{main}@footnote{
5162 Note that embedded programs (the so-called ``free-standing''
5163 environment) are not required to have a @code{main} function as the
5164 entry point. They could even have multiple entry points.}.
5165 When @value{GDBN} finds the entry function in a backtrace
5166 it will terminate the backtrace, to avoid tracing into highly
5167 system-specific (and generally uninteresting) code.
5169 If you need to examine the startup code, or limit the number of levels
5170 in a backtrace, you can change this behavior:
5173 @item set backtrace past-main
5174 @itemx set backtrace past-main on
5175 @kindex set backtrace
5176 Backtraces will continue past the user entry point.
5178 @item set backtrace past-main off
5179 Backtraces will stop when they encounter the user entry point. This is the
5182 @item show backtrace past-main
5183 @kindex show backtrace
5184 Display the current user entry point backtrace policy.
5186 @item set backtrace past-entry
5187 @itemx set backtrace past-entry on
5188 Backtraces will continue past the internal entry point of an application.
5189 This entry point is encoded by the linker when the application is built,
5190 and is likely before the user entry point @code{main} (or equivalent) is called.
5192 @item set backtrace past-entry off
5193 Backtraces will stop when they encounter the internal entry point of an
5194 application. This is the default.
5196 @item show backtrace past-entry
5197 Display the current internal entry point backtrace policy.
5199 @item set backtrace limit @var{n}
5200 @itemx set backtrace limit 0
5201 @cindex backtrace limit
5202 Limit the backtrace to @var{n} levels. A value of zero means
5205 @item show backtrace limit
5206 Display the current limit on backtrace levels.
5210 @section Selecting a Frame
5212 Most commands for examining the stack and other data in your program work on
5213 whichever stack frame is selected at the moment. Here are the commands for
5214 selecting a stack frame; all of them finish by printing a brief description
5215 of the stack frame just selected.
5218 @kindex frame@r{, selecting}
5219 @kindex f @r{(@code{frame})}
5222 Select frame number @var{n}. Recall that frame zero is the innermost
5223 (currently executing) frame, frame one is the frame that called the
5224 innermost one, and so on. The highest-numbered frame is the one for
5227 @item frame @var{addr}
5229 Select the frame at address @var{addr}. This is useful mainly if the
5230 chaining of stack frames has been damaged by a bug, making it
5231 impossible for @value{GDBN} to assign numbers properly to all frames. In
5232 addition, this can be useful when your program has multiple stacks and
5233 switches between them.
5235 On the SPARC architecture, @code{frame} needs two addresses to
5236 select an arbitrary frame: a frame pointer and a stack pointer.
5238 On the MIPS and Alpha architecture, it needs two addresses: a stack
5239 pointer and a program counter.
5241 On the 29k architecture, it needs three addresses: a register stack
5242 pointer, a program counter, and a memory stack pointer.
5246 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5247 advances toward the outermost frame, to higher frame numbers, to frames
5248 that have existed longer. @var{n} defaults to one.
5251 @kindex do @r{(@code{down})}
5253 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5254 advances toward the innermost frame, to lower frame numbers, to frames
5255 that were created more recently. @var{n} defaults to one. You may
5256 abbreviate @code{down} as @code{do}.
5259 All of these commands end by printing two lines of output describing the
5260 frame. The first line shows the frame number, the function name, the
5261 arguments, and the source file and line number of execution in that
5262 frame. The second line shows the text of that source line.
5270 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5272 10 read_input_file (argv[i]);
5276 After such a printout, the @code{list} command with no arguments
5277 prints ten lines centered on the point of execution in the frame.
5278 You can also edit the program at the point of execution with your favorite
5279 editing program by typing @code{edit}.
5280 @xref{List, ,Printing Source Lines},
5284 @kindex down-silently
5286 @item up-silently @var{n}
5287 @itemx down-silently @var{n}
5288 These two commands are variants of @code{up} and @code{down},
5289 respectively; they differ in that they do their work silently, without
5290 causing display of the new frame. They are intended primarily for use
5291 in @value{GDBN} command scripts, where the output might be unnecessary and
5296 @section Information About a Frame
5298 There are several other commands to print information about the selected
5304 When used without any argument, this command does not change which
5305 frame is selected, but prints a brief description of the currently
5306 selected stack frame. It can be abbreviated @code{f}. With an
5307 argument, this command is used to select a stack frame.
5308 @xref{Selection, ,Selecting a Frame}.
5311 @kindex info f @r{(@code{info frame})}
5314 This command prints a verbose description of the selected stack frame,
5319 the address of the frame
5321 the address of the next frame down (called by this frame)
5323 the address of the next frame up (caller of this frame)
5325 the language in which the source code corresponding to this frame is written
5327 the address of the frame's arguments
5329 the address of the frame's local variables
5331 the program counter saved in it (the address of execution in the caller frame)
5333 which registers were saved in the frame
5336 @noindent The verbose description is useful when
5337 something has gone wrong that has made the stack format fail to fit
5338 the usual conventions.
5340 @item info frame @var{addr}
5341 @itemx info f @var{addr}
5342 Print a verbose description of the frame at address @var{addr}, without
5343 selecting that frame. The selected frame remains unchanged by this
5344 command. This requires the same kind of address (more than one for some
5345 architectures) that you specify in the @code{frame} command.
5346 @xref{Selection, ,Selecting a Frame}.
5350 Print the arguments of the selected frame, each on a separate line.
5354 Print the local variables of the selected frame, each on a separate
5355 line. These are all variables (declared either static or automatic)
5356 accessible at the point of execution of the selected frame.
5359 @cindex catch exceptions, list active handlers
5360 @cindex exception handlers, how to list
5362 Print a list of all the exception handlers that are active in the
5363 current stack frame at the current point of execution. To see other
5364 exception handlers, visit the associated frame (using the @code{up},
5365 @code{down}, or @code{frame} commands); then type @code{info catch}.
5366 @xref{Set Catchpoints, , Setting Catchpoints}.
5372 @chapter Examining Source Files
5374 @value{GDBN} can print parts of your program's source, since the debugging
5375 information recorded in the program tells @value{GDBN} what source files were
5376 used to build it. When your program stops, @value{GDBN} spontaneously prints
5377 the line where it stopped. Likewise, when you select a stack frame
5378 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5379 execution in that frame has stopped. You can print other portions of
5380 source files by explicit command.
5382 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5383 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5384 @value{GDBN} under @sc{gnu} Emacs}.
5387 * List:: Printing source lines
5388 * Specify Location:: How to specify code locations
5389 * Edit:: Editing source files
5390 * Search:: Searching source files
5391 * Source Path:: Specifying source directories
5392 * Machine Code:: Source and machine code
5396 @section Printing Source Lines
5399 @kindex l @r{(@code{list})}
5400 To print lines from a source file, use the @code{list} command
5401 (abbreviated @code{l}). By default, ten lines are printed.
5402 There are several ways to specify what part of the file you want to
5403 print; see @ref{Specify Location}, for the full list.
5405 Here are the forms of the @code{list} command most commonly used:
5408 @item list @var{linenum}
5409 Print lines centered around line number @var{linenum} in the
5410 current source file.
5412 @item list @var{function}
5413 Print lines centered around the beginning of function
5417 Print more lines. If the last lines printed were printed with a
5418 @code{list} command, this prints lines following the last lines
5419 printed; however, if the last line printed was a solitary line printed
5420 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5421 Stack}), this prints lines centered around that line.
5424 Print lines just before the lines last printed.
5427 @cindex @code{list}, how many lines to display
5428 By default, @value{GDBN} prints ten source lines with any of these forms of
5429 the @code{list} command. You can change this using @code{set listsize}:
5432 @kindex set listsize
5433 @item set listsize @var{count}
5434 Make the @code{list} command display @var{count} source lines (unless
5435 the @code{list} argument explicitly specifies some other number).
5437 @kindex show listsize
5439 Display the number of lines that @code{list} prints.
5442 Repeating a @code{list} command with @key{RET} discards the argument,
5443 so it is equivalent to typing just @code{list}. This is more useful
5444 than listing the same lines again. An exception is made for an
5445 argument of @samp{-}; that argument is preserved in repetition so that
5446 each repetition moves up in the source file.
5448 In general, the @code{list} command expects you to supply zero, one or two
5449 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5450 of writing them (@pxref{Specify Location}), but the effect is always
5451 to specify some source line.
5453 Here is a complete description of the possible arguments for @code{list}:
5456 @item list @var{linespec}
5457 Print lines centered around the line specified by @var{linespec}.
5459 @item list @var{first},@var{last}
5460 Print lines from @var{first} to @var{last}. Both arguments are
5461 linespecs. When a @code{list} command has two linespecs, and the
5462 source file of the second linespec is omitted, this refers to
5463 the same source file as the first linespec.
5465 @item list ,@var{last}
5466 Print lines ending with @var{last}.
5468 @item list @var{first},
5469 Print lines starting with @var{first}.
5472 Print lines just after the lines last printed.
5475 Print lines just before the lines last printed.
5478 As described in the preceding table.
5481 @node Specify Location
5482 @section Specifying a Location
5483 @cindex specifying location
5486 Several @value{GDBN} commands accept arguments that specify a location
5487 of your program's code. Since @value{GDBN} is a source-level
5488 debugger, a location usually specifies some line in the source code;
5489 for that reason, locations are also known as @dfn{linespecs}.
5491 Here are all the different ways of specifying a code location that
5492 @value{GDBN} understands:
5496 Specifies the line number @var{linenum} of the current source file.
5499 @itemx +@var{offset}
5500 Specifies the line @var{offset} lines before or after the @dfn{current
5501 line}. For the @code{list} command, the current line is the last one
5502 printed; for the breakpoint commands, this is the line at which
5503 execution stopped in the currently selected @dfn{stack frame}
5504 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5505 used as the second of the two linespecs in a @code{list} command,
5506 this specifies the line @var{offset} lines up or down from the first
5509 @item @var{filename}:@var{linenum}
5510 Specifies the line @var{linenum} in the source file @var{filename}.
5512 @item @var{function}
5513 Specifies the line that begins the body of the function @var{function}.
5514 For example, in C, this is the line with the open brace.
5516 @item @var{filename}:@var{function}
5517 Specifies the line that begins the body of the function @var{function}
5518 in the file @var{filename}. You only need the file name with a
5519 function name to avoid ambiguity when there are identically named
5520 functions in different source files.
5522 @item *@var{address}
5523 Specifies the program address @var{address}. For line-oriented
5524 commands, such as @code{list} and @code{edit}, this specifies a source
5525 line that contains @var{address}. For @code{break} and other
5526 breakpoint oriented commands, this can be used to set breakpoints in
5527 parts of your program which do not have debugging information or
5530 Here @var{address} may be any expression valid in the current working
5531 language (@pxref{Languages, working language}) that specifies a code
5532 address. In addition, as a convenience, @value{GDBN} extends the
5533 semantics of expressions used in locations to cover the situations
5534 that frequently happen during debugging. Here are the various forms
5538 @item @var{expression}
5539 Any expression valid in the current working language.
5541 @item @var{funcaddr}
5542 An address of a function or procedure derived from its name. In C,
5543 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5544 simply the function's name @var{function} (and actually a special case
5545 of a valid expression). In Pascal and Modula-2, this is
5546 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5547 (although the Pascal form also works).
5549 This form specifies the address of the function's first instruction,
5550 before the stack frame and arguments have been set up.
5552 @item '@var{filename}'::@var{funcaddr}
5553 Like @var{funcaddr} above, but also specifies the name of the source
5554 file explicitly. This is useful if the name of the function does not
5555 specify the function unambiguously, e.g., if there are several
5556 functions with identical names in different source files.
5563 @section Editing Source Files
5564 @cindex editing source files
5567 @kindex e @r{(@code{edit})}
5568 To edit the lines in a source file, use the @code{edit} command.
5569 The editing program of your choice
5570 is invoked with the current line set to
5571 the active line in the program.
5572 Alternatively, there are several ways to specify what part of the file you
5573 want to print if you want to see other parts of the program:
5576 @item edit @var{location}
5577 Edit the source file specified by @code{location}. Editing starts at
5578 that @var{location}, e.g., at the specified source line of the
5579 specified file. @xref{Specify Location}, for all the possible forms
5580 of the @var{location} argument; here are the forms of the @code{edit}
5581 command most commonly used:
5584 @item edit @var{number}
5585 Edit the current source file with @var{number} as the active line number.
5587 @item edit @var{function}
5588 Edit the file containing @var{function} at the beginning of its definition.
5593 @subsection Choosing your Editor
5594 You can customize @value{GDBN} to use any editor you want
5596 The only restriction is that your editor (say @code{ex}), recognizes the
5597 following command-line syntax:
5599 ex +@var{number} file
5601 The optional numeric value +@var{number} specifies the number of the line in
5602 the file where to start editing.}.
5603 By default, it is @file{@value{EDITOR}}, but you can change this
5604 by setting the environment variable @code{EDITOR} before using
5605 @value{GDBN}. For example, to configure @value{GDBN} to use the
5606 @code{vi} editor, you could use these commands with the @code{sh} shell:
5612 or in the @code{csh} shell,
5614 setenv EDITOR /usr/bin/vi
5619 @section Searching Source Files
5620 @cindex searching source files
5622 There are two commands for searching through the current source file for a
5627 @kindex forward-search
5628 @item forward-search @var{regexp}
5629 @itemx search @var{regexp}
5630 The command @samp{forward-search @var{regexp}} checks each line,
5631 starting with the one following the last line listed, for a match for
5632 @var{regexp}. It lists the line that is found. You can use the
5633 synonym @samp{search @var{regexp}} or abbreviate the command name as
5636 @kindex reverse-search
5637 @item reverse-search @var{regexp}
5638 The command @samp{reverse-search @var{regexp}} checks each line, starting
5639 with the one before the last line listed and going backward, for a match
5640 for @var{regexp}. It lists the line that is found. You can abbreviate
5641 this command as @code{rev}.
5645 @section Specifying Source Directories
5648 @cindex directories for source files
5649 Executable programs sometimes do not record the directories of the source
5650 files from which they were compiled, just the names. Even when they do,
5651 the directories could be moved between the compilation and your debugging
5652 session. @value{GDBN} has a list of directories to search for source files;
5653 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5654 it tries all the directories in the list, in the order they are present
5655 in the list, until it finds a file with the desired name.
5657 For example, suppose an executable references the file
5658 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5659 @file{/mnt/cross}. The file is first looked up literally; if this
5660 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5661 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5662 message is printed. @value{GDBN} does not look up the parts of the
5663 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5664 Likewise, the subdirectories of the source path are not searched: if
5665 the source path is @file{/mnt/cross}, and the binary refers to
5666 @file{foo.c}, @value{GDBN} would not find it under
5667 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5669 Plain file names, relative file names with leading directories, file
5670 names containing dots, etc.@: are all treated as described above; for
5671 instance, if the source path is @file{/mnt/cross}, and the source file
5672 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5673 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5674 that---@file{/mnt/cross/foo.c}.
5676 Note that the executable search path is @emph{not} used to locate the
5679 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5680 any information it has cached about where source files are found and where
5681 each line is in the file.
5685 When you start @value{GDBN}, its source path includes only @samp{cdir}
5686 and @samp{cwd}, in that order.
5687 To add other directories, use the @code{directory} command.
5689 The search path is used to find both program source files and @value{GDBN}
5690 script files (read using the @samp{-command} option and @samp{source} command).
5692 In addition to the source path, @value{GDBN} provides a set of commands
5693 that manage a list of source path substitution rules. A @dfn{substitution
5694 rule} specifies how to rewrite source directories stored in the program's
5695 debug information in case the sources were moved to a different
5696 directory between compilation and debugging. A rule is made of
5697 two strings, the first specifying what needs to be rewritten in
5698 the path, and the second specifying how it should be rewritten.
5699 In @ref{set substitute-path}, we name these two parts @var{from} and
5700 @var{to} respectively. @value{GDBN} does a simple string replacement
5701 of @var{from} with @var{to} at the start of the directory part of the
5702 source file name, and uses that result instead of the original file
5703 name to look up the sources.
5705 Using the previous example, suppose the @file{foo-1.0} tree has been
5706 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5707 @value{GDBN} to replace @file{/usr/src} in all source path names with
5708 @file{/mnt/cross}. The first lookup will then be
5709 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5710 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5711 substitution rule, use the @code{set substitute-path} command
5712 (@pxref{set substitute-path}).
5714 To avoid unexpected substitution results, a rule is applied only if the
5715 @var{from} part of the directory name ends at a directory separator.
5716 For instance, a rule substituting @file{/usr/source} into
5717 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5718 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5719 is applied only at the beginning of the directory name, this rule will
5720 not be applied to @file{/root/usr/source/baz.c} either.
5722 In many cases, you can achieve the same result using the @code{directory}
5723 command. However, @code{set substitute-path} can be more efficient in
5724 the case where the sources are organized in a complex tree with multiple
5725 subdirectories. With the @code{directory} command, you need to add each
5726 subdirectory of your project. If you moved the entire tree while
5727 preserving its internal organization, then @code{set substitute-path}
5728 allows you to direct the debugger to all the sources with one single
5731 @code{set substitute-path} is also more than just a shortcut command.
5732 The source path is only used if the file at the original location no
5733 longer exists. On the other hand, @code{set substitute-path} modifies
5734 the debugger behavior to look at the rewritten location instead. So, if
5735 for any reason a source file that is not relevant to your executable is
5736 located at the original location, a substitution rule is the only
5737 method available to point @value{GDBN} at the new location.
5740 @item directory @var{dirname} @dots{}
5741 @item dir @var{dirname} @dots{}
5742 Add directory @var{dirname} to the front of the source path. Several
5743 directory names may be given to this command, separated by @samp{:}
5744 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5745 part of absolute file names) or
5746 whitespace. You may specify a directory that is already in the source
5747 path; this moves it forward, so @value{GDBN} searches it sooner.
5751 @vindex $cdir@r{, convenience variable}
5752 @vindex $cwd@r{, convenience variable}
5753 @cindex compilation directory
5754 @cindex current directory
5755 @cindex working directory
5756 @cindex directory, current
5757 @cindex directory, compilation
5758 You can use the string @samp{$cdir} to refer to the compilation
5759 directory (if one is recorded), and @samp{$cwd} to refer to the current
5760 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5761 tracks the current working directory as it changes during your @value{GDBN}
5762 session, while the latter is immediately expanded to the current
5763 directory at the time you add an entry to the source path.
5766 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5768 @c RET-repeat for @code{directory} is explicitly disabled, but since
5769 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5771 @item show directories
5772 @kindex show directories
5773 Print the source path: show which directories it contains.
5775 @anchor{set substitute-path}
5776 @item set substitute-path @var{from} @var{to}
5777 @kindex set substitute-path
5778 Define a source path substitution rule, and add it at the end of the
5779 current list of existing substitution rules. If a rule with the same
5780 @var{from} was already defined, then the old rule is also deleted.
5782 For example, if the file @file{/foo/bar/baz.c} was moved to
5783 @file{/mnt/cross/baz.c}, then the command
5786 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5790 will tell @value{GDBN} to replace @samp{/usr/src} with
5791 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5792 @file{baz.c} even though it was moved.
5794 In the case when more than one substitution rule have been defined,
5795 the rules are evaluated one by one in the order where they have been
5796 defined. The first one matching, if any, is selected to perform
5799 For instance, if we had entered the following commands:
5802 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5803 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5807 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5808 @file{/mnt/include/defs.h} by using the first rule. However, it would
5809 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5810 @file{/mnt/src/lib/foo.c}.
5813 @item unset substitute-path [path]
5814 @kindex unset substitute-path
5815 If a path is specified, search the current list of substitution rules
5816 for a rule that would rewrite that path. Delete that rule if found.
5817 A warning is emitted by the debugger if no rule could be found.
5819 If no path is specified, then all substitution rules are deleted.
5821 @item show substitute-path [path]
5822 @kindex show substitute-path
5823 If a path is specified, then print the source path substitution rule
5824 which would rewrite that path, if any.
5826 If no path is specified, then print all existing source path substitution
5831 If your source path is cluttered with directories that are no longer of
5832 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5833 versions of source. You can correct the situation as follows:
5837 Use @code{directory} with no argument to reset the source path to its default value.
5840 Use @code{directory} with suitable arguments to reinstall the
5841 directories you want in the source path. You can add all the
5842 directories in one command.
5846 @section Source and Machine Code
5847 @cindex source line and its code address
5849 You can use the command @code{info line} to map source lines to program
5850 addresses (and vice versa), and the command @code{disassemble} to display
5851 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5852 mode, the @code{info line} command causes the arrow to point to the
5853 line specified. Also, @code{info line} prints addresses in symbolic form as
5858 @item info line @var{linespec}
5859 Print the starting and ending addresses of the compiled code for
5860 source line @var{linespec}. You can specify source lines in any of
5861 the ways documented in @ref{Specify Location}.
5864 For example, we can use @code{info line} to discover the location of
5865 the object code for the first line of function
5866 @code{m4_changequote}:
5868 @c FIXME: I think this example should also show the addresses in
5869 @c symbolic form, as they usually would be displayed.
5871 (@value{GDBP}) info line m4_changequote
5872 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5876 @cindex code address and its source line
5877 We can also inquire (using @code{*@var{addr}} as the form for
5878 @var{linespec}) what source line covers a particular address:
5880 (@value{GDBP}) info line *0x63ff
5881 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5884 @cindex @code{$_} and @code{info line}
5885 @cindex @code{x} command, default address
5886 @kindex x@r{(examine), and} info line
5887 After @code{info line}, the default address for the @code{x} command
5888 is changed to the starting address of the line, so that @samp{x/i} is
5889 sufficient to begin examining the machine code (@pxref{Memory,
5890 ,Examining Memory}). Also, this address is saved as the value of the
5891 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5896 @cindex assembly instructions
5897 @cindex instructions, assembly
5898 @cindex machine instructions
5899 @cindex listing machine instructions
5901 @itemx disassemble /m
5902 This specialized command dumps a range of memory as machine
5903 instructions. It can also print mixed source+disassembly by specifying
5904 the @code{/m} modifier.
5905 The default memory range is the function surrounding the
5906 program counter of the selected frame. A single argument to this
5907 command is a program counter value; @value{GDBN} dumps the function
5908 surrounding this value. Two arguments specify a range of addresses
5909 (first inclusive, second exclusive) to dump.
5912 The following example shows the disassembly of a range of addresses of
5913 HP PA-RISC 2.0 code:
5916 (@value{GDBP}) disas 0x32c4 0x32e4
5917 Dump of assembler code from 0x32c4 to 0x32e4:
5918 0x32c4 <main+204>: addil 0,dp
5919 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5920 0x32cc <main+212>: ldil 0x3000,r31
5921 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5922 0x32d4 <main+220>: ldo 0(r31),rp
5923 0x32d8 <main+224>: addil -0x800,dp
5924 0x32dc <main+228>: ldo 0x588(r1),r26
5925 0x32e0 <main+232>: ldil 0x3000,r31
5926 End of assembler dump.
5929 Here is an example showing mixed source+assembly for Intel x86:
5932 (@value{GDBP}) disas /m main
5933 Dump of assembler code for function main:
5935 0x08048330 <main+0>: push %ebp
5936 0x08048331 <main+1>: mov %esp,%ebp
5937 0x08048333 <main+3>: sub $0x8,%esp
5938 0x08048336 <main+6>: and $0xfffffff0,%esp
5939 0x08048339 <main+9>: sub $0x10,%esp
5941 6 printf ("Hello.\n");
5942 0x0804833c <main+12>: movl $0x8048440,(%esp)
5943 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
5947 0x08048348 <main+24>: mov $0x0,%eax
5948 0x0804834d <main+29>: leave
5949 0x0804834e <main+30>: ret
5951 End of assembler dump.
5954 Some architectures have more than one commonly-used set of instruction
5955 mnemonics or other syntax.
5957 For programs that were dynamically linked and use shared libraries,
5958 instructions that call functions or branch to locations in the shared
5959 libraries might show a seemingly bogus location---it's actually a
5960 location of the relocation table. On some architectures, @value{GDBN}
5961 might be able to resolve these to actual function names.
5964 @kindex set disassembly-flavor
5965 @cindex Intel disassembly flavor
5966 @cindex AT&T disassembly flavor
5967 @item set disassembly-flavor @var{instruction-set}
5968 Select the instruction set to use when disassembling the
5969 program via the @code{disassemble} or @code{x/i} commands.
5971 Currently this command is only defined for the Intel x86 family. You
5972 can set @var{instruction-set} to either @code{intel} or @code{att}.
5973 The default is @code{att}, the AT&T flavor used by default by Unix
5974 assemblers for x86-based targets.
5976 @kindex show disassembly-flavor
5977 @item show disassembly-flavor
5978 Show the current setting of the disassembly flavor.
5983 @chapter Examining Data
5985 @cindex printing data
5986 @cindex examining data
5989 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5990 @c document because it is nonstandard... Under Epoch it displays in a
5991 @c different window or something like that.
5992 The usual way to examine data in your program is with the @code{print}
5993 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5994 evaluates and prints the value of an expression of the language your
5995 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5996 Different Languages}).
5999 @item print @var{expr}
6000 @itemx print /@var{f} @var{expr}
6001 @var{expr} is an expression (in the source language). By default the
6002 value of @var{expr} is printed in a format appropriate to its data type;
6003 you can choose a different format by specifying @samp{/@var{f}}, where
6004 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6008 @itemx print /@var{f}
6009 @cindex reprint the last value
6010 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6011 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6012 conveniently inspect the same value in an alternative format.
6015 A more low-level way of examining data is with the @code{x} command.
6016 It examines data in memory at a specified address and prints it in a
6017 specified format. @xref{Memory, ,Examining Memory}.
6019 If you are interested in information about types, or about how the
6020 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6021 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6025 * Expressions:: Expressions
6026 * Ambiguous Expressions:: Ambiguous Expressions
6027 * Variables:: Program variables
6028 * Arrays:: Artificial arrays
6029 * Output Formats:: Output formats
6030 * Memory:: Examining memory
6031 * Auto Display:: Automatic display
6032 * Print Settings:: Print settings
6033 * Value History:: Value history
6034 * Convenience Vars:: Convenience variables
6035 * Registers:: Registers
6036 * Floating Point Hardware:: Floating point hardware
6037 * Vector Unit:: Vector Unit
6038 * OS Information:: Auxiliary data provided by operating system
6039 * Memory Region Attributes:: Memory region attributes
6040 * Dump/Restore Files:: Copy between memory and a file
6041 * Core File Generation:: Cause a program dump its core
6042 * Character Sets:: Debugging programs that use a different
6043 character set than GDB does
6044 * Caching Remote Data:: Data caching for remote targets
6045 * Searching Memory:: Searching memory for a sequence of bytes
6049 @section Expressions
6052 @code{print} and many other @value{GDBN} commands accept an expression and
6053 compute its value. Any kind of constant, variable or operator defined
6054 by the programming language you are using is valid in an expression in
6055 @value{GDBN}. This includes conditional expressions, function calls,
6056 casts, and string constants. It also includes preprocessor macros, if
6057 you compiled your program to include this information; see
6060 @cindex arrays in expressions
6061 @value{GDBN} supports array constants in expressions input by
6062 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6063 you can use the command @code{print @{1, 2, 3@}} to create an array
6064 of three integers. If you pass an array to a function or assign it
6065 to a program variable, @value{GDBN} copies the array to memory that
6066 is @code{malloc}ed in the target program.
6068 Because C is so widespread, most of the expressions shown in examples in
6069 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6070 Languages}, for information on how to use expressions in other
6073 In this section, we discuss operators that you can use in @value{GDBN}
6074 expressions regardless of your programming language.
6076 @cindex casts, in expressions
6077 Casts are supported in all languages, not just in C, because it is so
6078 useful to cast a number into a pointer in order to examine a structure
6079 at that address in memory.
6080 @c FIXME: casts supported---Mod2 true?
6082 @value{GDBN} supports these operators, in addition to those common
6083 to programming languages:
6087 @samp{@@} is a binary operator for treating parts of memory as arrays.
6088 @xref{Arrays, ,Artificial Arrays}, for more information.
6091 @samp{::} allows you to specify a variable in terms of the file or
6092 function where it is defined. @xref{Variables, ,Program Variables}.
6094 @cindex @{@var{type}@}
6095 @cindex type casting memory
6096 @cindex memory, viewing as typed object
6097 @cindex casts, to view memory
6098 @item @{@var{type}@} @var{addr}
6099 Refers to an object of type @var{type} stored at address @var{addr} in
6100 memory. @var{addr} may be any expression whose value is an integer or
6101 pointer (but parentheses are required around binary operators, just as in
6102 a cast). This construct is allowed regardless of what kind of data is
6103 normally supposed to reside at @var{addr}.
6106 @node Ambiguous Expressions
6107 @section Ambiguous Expressions
6108 @cindex ambiguous expressions
6110 Expressions can sometimes contain some ambiguous elements. For instance,
6111 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6112 a single function name to be defined several times, for application in
6113 different contexts. This is called @dfn{overloading}. Another example
6114 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6115 templates and is typically instantiated several times, resulting in
6116 the same function name being defined in different contexts.
6118 In some cases and depending on the language, it is possible to adjust
6119 the expression to remove the ambiguity. For instance in C@t{++}, you
6120 can specify the signature of the function you want to break on, as in
6121 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6122 qualified name of your function often makes the expression unambiguous
6125 When an ambiguity that needs to be resolved is detected, the debugger
6126 has the capability to display a menu of numbered choices for each
6127 possibility, and then waits for the selection with the prompt @samp{>}.
6128 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6129 aborts the current command. If the command in which the expression was
6130 used allows more than one choice to be selected, the next option in the
6131 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6134 For example, the following session excerpt shows an attempt to set a
6135 breakpoint at the overloaded symbol @code{String::after}.
6136 We choose three particular definitions of that function name:
6138 @c FIXME! This is likely to change to show arg type lists, at least
6141 (@value{GDBP}) b String::after
6144 [2] file:String.cc; line number:867
6145 [3] file:String.cc; line number:860
6146 [4] file:String.cc; line number:875
6147 [5] file:String.cc; line number:853
6148 [6] file:String.cc; line number:846
6149 [7] file:String.cc; line number:735
6151 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6152 Breakpoint 2 at 0xb344: file String.cc, line 875.
6153 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6154 Multiple breakpoints were set.
6155 Use the "delete" command to delete unwanted
6162 @kindex set multiple-symbols
6163 @item set multiple-symbols @var{mode}
6164 @cindex multiple-symbols menu
6166 This option allows you to adjust the debugger behavior when an expression
6169 By default, @var{mode} is set to @code{all}. If the command with which
6170 the expression is used allows more than one choice, then @value{GDBN}
6171 automatically selects all possible choices. For instance, inserting
6172 a breakpoint on a function using an ambiguous name results in a breakpoint
6173 inserted on each possible match. However, if a unique choice must be made,
6174 then @value{GDBN} uses the menu to help you disambiguate the expression.
6175 For instance, printing the address of an overloaded function will result
6176 in the use of the menu.
6178 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6179 when an ambiguity is detected.
6181 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6182 an error due to the ambiguity and the command is aborted.
6184 @kindex show multiple-symbols
6185 @item show multiple-symbols
6186 Show the current value of the @code{multiple-symbols} setting.
6190 @section Program Variables
6192 The most common kind of expression to use is the name of a variable
6195 Variables in expressions are understood in the selected stack frame
6196 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6200 global (or file-static)
6207 visible according to the scope rules of the
6208 programming language from the point of execution in that frame
6211 @noindent This means that in the function
6226 you can examine and use the variable @code{a} whenever your program is
6227 executing within the function @code{foo}, but you can only use or
6228 examine the variable @code{b} while your program is executing inside
6229 the block where @code{b} is declared.
6231 @cindex variable name conflict
6232 There is an exception: you can refer to a variable or function whose
6233 scope is a single source file even if the current execution point is not
6234 in this file. But it is possible to have more than one such variable or
6235 function with the same name (in different source files). If that
6236 happens, referring to that name has unpredictable effects. If you wish,
6237 you can specify a static variable in a particular function or file,
6238 using the colon-colon (@code{::}) notation:
6240 @cindex colon-colon, context for variables/functions
6242 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6243 @cindex @code{::}, context for variables/functions
6246 @var{file}::@var{variable}
6247 @var{function}::@var{variable}
6251 Here @var{file} or @var{function} is the name of the context for the
6252 static @var{variable}. In the case of file names, you can use quotes to
6253 make sure @value{GDBN} parses the file name as a single word---for example,
6254 to print a global value of @code{x} defined in @file{f2.c}:
6257 (@value{GDBP}) p 'f2.c'::x
6260 @cindex C@t{++} scope resolution
6261 This use of @samp{::} is very rarely in conflict with the very similar
6262 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6263 scope resolution operator in @value{GDBN} expressions.
6264 @c FIXME: Um, so what happens in one of those rare cases where it's in
6267 @cindex wrong values
6268 @cindex variable values, wrong
6269 @cindex function entry/exit, wrong values of variables
6270 @cindex optimized code, wrong values of variables
6272 @emph{Warning:} Occasionally, a local variable may appear to have the
6273 wrong value at certain points in a function---just after entry to a new
6274 scope, and just before exit.
6276 You may see this problem when you are stepping by machine instructions.
6277 This is because, on most machines, it takes more than one instruction to
6278 set up a stack frame (including local variable definitions); if you are
6279 stepping by machine instructions, variables may appear to have the wrong
6280 values until the stack frame is completely built. On exit, it usually
6281 also takes more than one machine instruction to destroy a stack frame;
6282 after you begin stepping through that group of instructions, local
6283 variable definitions may be gone.
6285 This may also happen when the compiler does significant optimizations.
6286 To be sure of always seeing accurate values, turn off all optimization
6289 @cindex ``No symbol "foo" in current context''
6290 Another possible effect of compiler optimizations is to optimize
6291 unused variables out of existence, or assign variables to registers (as
6292 opposed to memory addresses). Depending on the support for such cases
6293 offered by the debug info format used by the compiler, @value{GDBN}
6294 might not be able to display values for such local variables. If that
6295 happens, @value{GDBN} will print a message like this:
6298 No symbol "foo" in current context.
6301 To solve such problems, either recompile without optimizations, or use a
6302 different debug info format, if the compiler supports several such
6303 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6304 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6305 produces debug info in a format that is superior to formats such as
6306 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6307 an effective form for debug info. @xref{Debugging Options,,Options
6308 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6309 Compiler Collection (GCC)}.
6310 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6311 that are best suited to C@t{++} programs.
6313 If you ask to print an object whose contents are unknown to
6314 @value{GDBN}, e.g., because its data type is not completely specified
6315 by the debug information, @value{GDBN} will say @samp{<incomplete
6316 type>}. @xref{Symbols, incomplete type}, for more about this.
6318 Strings are identified as arrays of @code{char} values without specified
6319 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6320 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6321 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6322 defines literal string type @code{"char"} as @code{char} without a sign.
6327 signed char var1[] = "A";
6330 You get during debugging
6335 $2 = @{65 'A', 0 '\0'@}
6339 @section Artificial Arrays
6341 @cindex artificial array
6343 @kindex @@@r{, referencing memory as an array}
6344 It is often useful to print out several successive objects of the
6345 same type in memory; a section of an array, or an array of
6346 dynamically determined size for which only a pointer exists in the
6349 You can do this by referring to a contiguous span of memory as an
6350 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6351 operand of @samp{@@} should be the first element of the desired array
6352 and be an individual object. The right operand should be the desired length
6353 of the array. The result is an array value whose elements are all of
6354 the type of the left argument. The first element is actually the left
6355 argument; the second element comes from bytes of memory immediately
6356 following those that hold the first element, and so on. Here is an
6357 example. If a program says
6360 int *array = (int *) malloc (len * sizeof (int));
6364 you can print the contents of @code{array} with
6370 The left operand of @samp{@@} must reside in memory. Array values made
6371 with @samp{@@} in this way behave just like other arrays in terms of
6372 subscripting, and are coerced to pointers when used in expressions.
6373 Artificial arrays most often appear in expressions via the value history
6374 (@pxref{Value History, ,Value History}), after printing one out.
6376 Another way to create an artificial array is to use a cast.
6377 This re-interprets a value as if it were an array.
6378 The value need not be in memory:
6380 (@value{GDBP}) p/x (short[2])0x12345678
6381 $1 = @{0x1234, 0x5678@}
6384 As a convenience, if you leave the array length out (as in
6385 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6386 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6388 (@value{GDBP}) p/x (short[])0x12345678
6389 $2 = @{0x1234, 0x5678@}
6392 Sometimes the artificial array mechanism is not quite enough; in
6393 moderately complex data structures, the elements of interest may not
6394 actually be adjacent---for example, if you are interested in the values
6395 of pointers in an array. One useful work-around in this situation is
6396 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6397 Variables}) as a counter in an expression that prints the first
6398 interesting value, and then repeat that expression via @key{RET}. For
6399 instance, suppose you have an array @code{dtab} of pointers to
6400 structures, and you are interested in the values of a field @code{fv}
6401 in each structure. Here is an example of what you might type:
6411 @node Output Formats
6412 @section Output Formats
6414 @cindex formatted output
6415 @cindex output formats
6416 By default, @value{GDBN} prints a value according to its data type. Sometimes
6417 this is not what you want. For example, you might want to print a number
6418 in hex, or a pointer in decimal. Or you might want to view data in memory
6419 at a certain address as a character string or as an instruction. To do
6420 these things, specify an @dfn{output format} when you print a value.
6422 The simplest use of output formats is to say how to print a value
6423 already computed. This is done by starting the arguments of the
6424 @code{print} command with a slash and a format letter. The format
6425 letters supported are:
6429 Regard the bits of the value as an integer, and print the integer in
6433 Print as integer in signed decimal.
6436 Print as integer in unsigned decimal.
6439 Print as integer in octal.
6442 Print as integer in binary. The letter @samp{t} stands for ``two''.
6443 @footnote{@samp{b} cannot be used because these format letters are also
6444 used with the @code{x} command, where @samp{b} stands for ``byte'';
6445 see @ref{Memory,,Examining Memory}.}
6448 @cindex unknown address, locating
6449 @cindex locate address
6450 Print as an address, both absolute in hexadecimal and as an offset from
6451 the nearest preceding symbol. You can use this format used to discover
6452 where (in what function) an unknown address is located:
6455 (@value{GDBP}) p/a 0x54320
6456 $3 = 0x54320 <_initialize_vx+396>
6460 The command @code{info symbol 0x54320} yields similar results.
6461 @xref{Symbols, info symbol}.
6464 Regard as an integer and print it as a character constant. This
6465 prints both the numerical value and its character representation. The
6466 character representation is replaced with the octal escape @samp{\nnn}
6467 for characters outside the 7-bit @sc{ascii} range.
6469 Without this format, @value{GDBN} displays @code{char},
6470 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6471 constants. Single-byte members of vectors are displayed as integer
6475 Regard the bits of the value as a floating point number and print
6476 using typical floating point syntax.
6479 @cindex printing strings
6480 @cindex printing byte arrays
6481 Regard as a string, if possible. With this format, pointers to single-byte
6482 data are displayed as null-terminated strings and arrays of single-byte data
6483 are displayed as fixed-length strings. Other values are displayed in their
6486 Without this format, @value{GDBN} displays pointers to and arrays of
6487 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6488 strings. Single-byte members of a vector are displayed as an integer
6492 For example, to print the program counter in hex (@pxref{Registers}), type
6499 Note that no space is required before the slash; this is because command
6500 names in @value{GDBN} cannot contain a slash.
6502 To reprint the last value in the value history with a different format,
6503 you can use the @code{print} command with just a format and no
6504 expression. For example, @samp{p/x} reprints the last value in hex.
6507 @section Examining Memory
6509 You can use the command @code{x} (for ``examine'') to examine memory in
6510 any of several formats, independently of your program's data types.
6512 @cindex examining memory
6514 @kindex x @r{(examine memory)}
6515 @item x/@var{nfu} @var{addr}
6518 Use the @code{x} command to examine memory.
6521 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6522 much memory to display and how to format it; @var{addr} is an
6523 expression giving the address where you want to start displaying memory.
6524 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6525 Several commands set convenient defaults for @var{addr}.
6528 @item @var{n}, the repeat count
6529 The repeat count is a decimal integer; the default is 1. It specifies
6530 how much memory (counting by units @var{u}) to display.
6531 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6534 @item @var{f}, the display format
6535 The display format is one of the formats used by @code{print}
6536 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6537 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6538 The default is @samp{x} (hexadecimal) initially. The default changes
6539 each time you use either @code{x} or @code{print}.
6541 @item @var{u}, the unit size
6542 The unit size is any of
6548 Halfwords (two bytes).
6550 Words (four bytes). This is the initial default.
6552 Giant words (eight bytes).
6555 Each time you specify a unit size with @code{x}, that size becomes the
6556 default unit the next time you use @code{x}. (For the @samp{s} and
6557 @samp{i} formats, the unit size is ignored and is normally not written.)
6559 @item @var{addr}, starting display address
6560 @var{addr} is the address where you want @value{GDBN} to begin displaying
6561 memory. The expression need not have a pointer value (though it may);
6562 it is always interpreted as an integer address of a byte of memory.
6563 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6564 @var{addr} is usually just after the last address examined---but several
6565 other commands also set the default address: @code{info breakpoints} (to
6566 the address of the last breakpoint listed), @code{info line} (to the
6567 starting address of a line), and @code{print} (if you use it to display
6568 a value from memory).
6571 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6572 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6573 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6574 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6575 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6577 Since the letters indicating unit sizes are all distinct from the
6578 letters specifying output formats, you do not have to remember whether
6579 unit size or format comes first; either order works. The output
6580 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6581 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6583 Even though the unit size @var{u} is ignored for the formats @samp{s}
6584 and @samp{i}, you might still want to use a count @var{n}; for example,
6585 @samp{3i} specifies that you want to see three machine instructions,
6586 including any operands. For convenience, especially when used with
6587 the @code{display} command, the @samp{i} format also prints branch delay
6588 slot instructions, if any, beyond the count specified, which immediately
6589 follow the last instruction that is within the count. The command
6590 @code{disassemble} gives an alternative way of inspecting machine
6591 instructions; see @ref{Machine Code,,Source and Machine Code}.
6593 All the defaults for the arguments to @code{x} are designed to make it
6594 easy to continue scanning memory with minimal specifications each time
6595 you use @code{x}. For example, after you have inspected three machine
6596 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6597 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6598 the repeat count @var{n} is used again; the other arguments default as
6599 for successive uses of @code{x}.
6601 @cindex @code{$_}, @code{$__}, and value history
6602 The addresses and contents printed by the @code{x} command are not saved
6603 in the value history because there is often too much of them and they
6604 would get in the way. Instead, @value{GDBN} makes these values available for
6605 subsequent use in expressions as values of the convenience variables
6606 @code{$_} and @code{$__}. After an @code{x} command, the last address
6607 examined is available for use in expressions in the convenience variable
6608 @code{$_}. The contents of that address, as examined, are available in
6609 the convenience variable @code{$__}.
6611 If the @code{x} command has a repeat count, the address and contents saved
6612 are from the last memory unit printed; this is not the same as the last
6613 address printed if several units were printed on the last line of output.
6615 @cindex remote memory comparison
6616 @cindex verify remote memory image
6617 When you are debugging a program running on a remote target machine
6618 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6619 remote machine's memory against the executable file you downloaded to
6620 the target. The @code{compare-sections} command is provided for such
6624 @kindex compare-sections
6625 @item compare-sections @r{[}@var{section-name}@r{]}
6626 Compare the data of a loadable section @var{section-name} in the
6627 executable file of the program being debugged with the same section in
6628 the remote machine's memory, and report any mismatches. With no
6629 arguments, compares all loadable sections. This command's
6630 availability depends on the target's support for the @code{"qCRC"}
6635 @section Automatic Display
6636 @cindex automatic display
6637 @cindex display of expressions
6639 If you find that you want to print the value of an expression frequently
6640 (to see how it changes), you might want to add it to the @dfn{automatic
6641 display list} so that @value{GDBN} prints its value each time your program stops.
6642 Each expression added to the list is given a number to identify it;
6643 to remove an expression from the list, you specify that number.
6644 The automatic display looks like this:
6648 3: bar[5] = (struct hack *) 0x3804
6652 This display shows item numbers, expressions and their current values. As with
6653 displays you request manually using @code{x} or @code{print}, you can
6654 specify the output format you prefer; in fact, @code{display} decides
6655 whether to use @code{print} or @code{x} depending your format
6656 specification---it uses @code{x} if you specify either the @samp{i}
6657 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6661 @item display @var{expr}
6662 Add the expression @var{expr} to the list of expressions to display
6663 each time your program stops. @xref{Expressions, ,Expressions}.
6665 @code{display} does not repeat if you press @key{RET} again after using it.
6667 @item display/@var{fmt} @var{expr}
6668 For @var{fmt} specifying only a display format and not a size or
6669 count, add the expression @var{expr} to the auto-display list but
6670 arrange to display it each time in the specified format @var{fmt}.
6671 @xref{Output Formats,,Output Formats}.
6673 @item display/@var{fmt} @var{addr}
6674 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6675 number of units, add the expression @var{addr} as a memory address to
6676 be examined each time your program stops. Examining means in effect
6677 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6680 For example, @samp{display/i $pc} can be helpful, to see the machine
6681 instruction about to be executed each time execution stops (@samp{$pc}
6682 is a common name for the program counter; @pxref{Registers, ,Registers}).
6685 @kindex delete display
6687 @item undisplay @var{dnums}@dots{}
6688 @itemx delete display @var{dnums}@dots{}
6689 Remove item numbers @var{dnums} from the list of expressions to display.
6691 @code{undisplay} does not repeat if you press @key{RET} after using it.
6692 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6694 @kindex disable display
6695 @item disable display @var{dnums}@dots{}
6696 Disable the display of item numbers @var{dnums}. A disabled display
6697 item is not printed automatically, but is not forgotten. It may be
6698 enabled again later.
6700 @kindex enable display
6701 @item enable display @var{dnums}@dots{}
6702 Enable display of item numbers @var{dnums}. It becomes effective once
6703 again in auto display of its expression, until you specify otherwise.
6706 Display the current values of the expressions on the list, just as is
6707 done when your program stops.
6709 @kindex info display
6711 Print the list of expressions previously set up to display
6712 automatically, each one with its item number, but without showing the
6713 values. This includes disabled expressions, which are marked as such.
6714 It also includes expressions which would not be displayed right now
6715 because they refer to automatic variables not currently available.
6718 @cindex display disabled out of scope
6719 If a display expression refers to local variables, then it does not make
6720 sense outside the lexical context for which it was set up. Such an
6721 expression is disabled when execution enters a context where one of its
6722 variables is not defined. For example, if you give the command
6723 @code{display last_char} while inside a function with an argument
6724 @code{last_char}, @value{GDBN} displays this argument while your program
6725 continues to stop inside that function. When it stops elsewhere---where
6726 there is no variable @code{last_char}---the display is disabled
6727 automatically. The next time your program stops where @code{last_char}
6728 is meaningful, you can enable the display expression once again.
6730 @node Print Settings
6731 @section Print Settings
6733 @cindex format options
6734 @cindex print settings
6735 @value{GDBN} provides the following ways to control how arrays, structures,
6736 and symbols are printed.
6739 These settings are useful for debugging programs in any language:
6743 @item set print address
6744 @itemx set print address on
6745 @cindex print/don't print memory addresses
6746 @value{GDBN} prints memory addresses showing the location of stack
6747 traces, structure values, pointer values, breakpoints, and so forth,
6748 even when it also displays the contents of those addresses. The default
6749 is @code{on}. For example, this is what a stack frame display looks like with
6750 @code{set print address on}:
6755 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6757 530 if (lquote != def_lquote)
6761 @item set print address off
6762 Do not print addresses when displaying their contents. For example,
6763 this is the same stack frame displayed with @code{set print address off}:
6767 (@value{GDBP}) set print addr off
6769 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6770 530 if (lquote != def_lquote)
6774 You can use @samp{set print address off} to eliminate all machine
6775 dependent displays from the @value{GDBN} interface. For example, with
6776 @code{print address off}, you should get the same text for backtraces on
6777 all machines---whether or not they involve pointer arguments.
6780 @item show print address
6781 Show whether or not addresses are to be printed.
6784 When @value{GDBN} prints a symbolic address, it normally prints the
6785 closest earlier symbol plus an offset. If that symbol does not uniquely
6786 identify the address (for example, it is a name whose scope is a single
6787 source file), you may need to clarify. One way to do this is with
6788 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6789 you can set @value{GDBN} to print the source file and line number when
6790 it prints a symbolic address:
6793 @item set print symbol-filename on
6794 @cindex source file and line of a symbol
6795 @cindex symbol, source file and line
6796 Tell @value{GDBN} to print the source file name and line number of a
6797 symbol in the symbolic form of an address.
6799 @item set print symbol-filename off
6800 Do not print source file name and line number of a symbol. This is the
6803 @item show print symbol-filename
6804 Show whether or not @value{GDBN} will print the source file name and
6805 line number of a symbol in the symbolic form of an address.
6808 Another situation where it is helpful to show symbol filenames and line
6809 numbers is when disassembling code; @value{GDBN} shows you the line
6810 number and source file that corresponds to each instruction.
6812 Also, you may wish to see the symbolic form only if the address being
6813 printed is reasonably close to the closest earlier symbol:
6816 @item set print max-symbolic-offset @var{max-offset}
6817 @cindex maximum value for offset of closest symbol
6818 Tell @value{GDBN} to only display the symbolic form of an address if the
6819 offset between the closest earlier symbol and the address is less than
6820 @var{max-offset}. The default is 0, which tells @value{GDBN}
6821 to always print the symbolic form of an address if any symbol precedes it.
6823 @item show print max-symbolic-offset
6824 Ask how large the maximum offset is that @value{GDBN} prints in a
6828 @cindex wild pointer, interpreting
6829 @cindex pointer, finding referent
6830 If you have a pointer and you are not sure where it points, try
6831 @samp{set print symbol-filename on}. Then you can determine the name
6832 and source file location of the variable where it points, using
6833 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6834 For example, here @value{GDBN} shows that a variable @code{ptt} points
6835 at another variable @code{t}, defined in @file{hi2.c}:
6838 (@value{GDBP}) set print symbol-filename on
6839 (@value{GDBP}) p/a ptt
6840 $4 = 0xe008 <t in hi2.c>
6844 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6845 does not show the symbol name and filename of the referent, even with
6846 the appropriate @code{set print} options turned on.
6849 Other settings control how different kinds of objects are printed:
6852 @item set print array
6853 @itemx set print array on
6854 @cindex pretty print arrays
6855 Pretty print arrays. This format is more convenient to read,
6856 but uses more space. The default is off.
6858 @item set print array off
6859 Return to compressed format for arrays.
6861 @item show print array
6862 Show whether compressed or pretty format is selected for displaying
6865 @cindex print array indexes
6866 @item set print array-indexes
6867 @itemx set print array-indexes on
6868 Print the index of each element when displaying arrays. May be more
6869 convenient to locate a given element in the array or quickly find the
6870 index of a given element in that printed array. The default is off.
6872 @item set print array-indexes off
6873 Stop printing element indexes when displaying arrays.
6875 @item show print array-indexes
6876 Show whether the index of each element is printed when displaying
6879 @item set print elements @var{number-of-elements}
6880 @cindex number of array elements to print
6881 @cindex limit on number of printed array elements
6882 Set a limit on how many elements of an array @value{GDBN} will print.
6883 If @value{GDBN} is printing a large array, it stops printing after it has
6884 printed the number of elements set by the @code{set print elements} command.
6885 This limit also applies to the display of strings.
6886 When @value{GDBN} starts, this limit is set to 200.
6887 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6889 @item show print elements
6890 Display the number of elements of a large array that @value{GDBN} will print.
6891 If the number is 0, then the printing is unlimited.
6893 @item set print frame-arguments @var{value}
6894 @cindex printing frame argument values
6895 @cindex print all frame argument values
6896 @cindex print frame argument values for scalars only
6897 @cindex do not print frame argument values
6898 This command allows to control how the values of arguments are printed
6899 when the debugger prints a frame (@pxref{Frames}). The possible
6904 The values of all arguments are printed. This is the default.
6907 Print the value of an argument only if it is a scalar. The value of more
6908 complex arguments such as arrays, structures, unions, etc, is replaced
6909 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6912 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6917 None of the argument values are printed. Instead, the value of each argument
6918 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6921 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6926 By default, all argument values are always printed. But this command
6927 can be useful in several cases. For instance, it can be used to reduce
6928 the amount of information printed in each frame, making the backtrace
6929 more readable. Also, this command can be used to improve performance
6930 when displaying Ada frames, because the computation of large arguments
6931 can sometimes be CPU-intensive, especiallly in large applications.
6932 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6933 avoids this computation, thus speeding up the display of each Ada frame.
6935 @item show print frame-arguments
6936 Show how the value of arguments should be displayed when printing a frame.
6938 @item set print repeats
6939 @cindex repeated array elements
6940 Set the threshold for suppressing display of repeated array
6941 elements. When the number of consecutive identical elements of an
6942 array exceeds the threshold, @value{GDBN} prints the string
6943 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6944 identical repetitions, instead of displaying the identical elements
6945 themselves. Setting the threshold to zero will cause all elements to
6946 be individually printed. The default threshold is 10.
6948 @item show print repeats
6949 Display the current threshold for printing repeated identical
6952 @item set print null-stop
6953 @cindex @sc{null} elements in arrays
6954 Cause @value{GDBN} to stop printing the characters of an array when the first
6955 @sc{null} is encountered. This is useful when large arrays actually
6956 contain only short strings.
6959 @item show print null-stop
6960 Show whether @value{GDBN} stops printing an array on the first
6961 @sc{null} character.
6963 @item set print pretty on
6964 @cindex print structures in indented form
6965 @cindex indentation in structure display
6966 Cause @value{GDBN} to print structures in an indented format with one member
6967 per line, like this:
6982 @item set print pretty off
6983 Cause @value{GDBN} to print structures in a compact format, like this:
6987 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6988 meat = 0x54 "Pork"@}
6993 This is the default format.
6995 @item show print pretty
6996 Show which format @value{GDBN} is using to print structures.
6998 @item set print sevenbit-strings on
6999 @cindex eight-bit characters in strings
7000 @cindex octal escapes in strings
7001 Print using only seven-bit characters; if this option is set,
7002 @value{GDBN} displays any eight-bit characters (in strings or
7003 character values) using the notation @code{\}@var{nnn}. This setting is
7004 best if you are working in English (@sc{ascii}) and you use the
7005 high-order bit of characters as a marker or ``meta'' bit.
7007 @item set print sevenbit-strings off
7008 Print full eight-bit characters. This allows the use of more
7009 international character sets, and is the default.
7011 @item show print sevenbit-strings
7012 Show whether or not @value{GDBN} is printing only seven-bit characters.
7014 @item set print union on
7015 @cindex unions in structures, printing
7016 Tell @value{GDBN} to print unions which are contained in structures
7017 and other unions. This is the default setting.
7019 @item set print union off
7020 Tell @value{GDBN} not to print unions which are contained in
7021 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7024 @item show print union
7025 Ask @value{GDBN} whether or not it will print unions which are contained in
7026 structures and other unions.
7028 For example, given the declarations
7031 typedef enum @{Tree, Bug@} Species;
7032 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7033 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7044 struct thing foo = @{Tree, @{Acorn@}@};
7048 with @code{set print union on} in effect @samp{p foo} would print
7051 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7055 and with @code{set print union off} in effect it would print
7058 $1 = @{it = Tree, form = @{...@}@}
7062 @code{set print union} affects programs written in C-like languages
7068 These settings are of interest when debugging C@t{++} programs:
7071 @cindex demangling C@t{++} names
7072 @item set print demangle
7073 @itemx set print demangle on
7074 Print C@t{++} names in their source form rather than in the encoded
7075 (``mangled'') form passed to the assembler and linker for type-safe
7076 linkage. The default is on.
7078 @item show print demangle
7079 Show whether C@t{++} names are printed in mangled or demangled form.
7081 @item set print asm-demangle
7082 @itemx set print asm-demangle on
7083 Print C@t{++} names in their source form rather than their mangled form, even
7084 in assembler code printouts such as instruction disassemblies.
7087 @item show print asm-demangle
7088 Show whether C@t{++} names in assembly listings are printed in mangled
7091 @cindex C@t{++} symbol decoding style
7092 @cindex symbol decoding style, C@t{++}
7093 @kindex set demangle-style
7094 @item set demangle-style @var{style}
7095 Choose among several encoding schemes used by different compilers to
7096 represent C@t{++} names. The choices for @var{style} are currently:
7100 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7103 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7104 This is the default.
7107 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7110 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7113 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7114 @strong{Warning:} this setting alone is not sufficient to allow
7115 debugging @code{cfront}-generated executables. @value{GDBN} would
7116 require further enhancement to permit that.
7119 If you omit @var{style}, you will see a list of possible formats.
7121 @item show demangle-style
7122 Display the encoding style currently in use for decoding C@t{++} symbols.
7124 @item set print object
7125 @itemx set print object on
7126 @cindex derived type of an object, printing
7127 @cindex display derived types
7128 When displaying a pointer to an object, identify the @emph{actual}
7129 (derived) type of the object rather than the @emph{declared} type, using
7130 the virtual function table.
7132 @item set print object off
7133 Display only the declared type of objects, without reference to the
7134 virtual function table. This is the default setting.
7136 @item show print object
7137 Show whether actual, or declared, object types are displayed.
7139 @item set print static-members
7140 @itemx set print static-members on
7141 @cindex static members of C@t{++} objects
7142 Print static members when displaying a C@t{++} object. The default is on.
7144 @item set print static-members off
7145 Do not print static members when displaying a C@t{++} object.
7147 @item show print static-members
7148 Show whether C@t{++} static members are printed or not.
7150 @item set print pascal_static-members
7151 @itemx set print pascal_static-members on
7152 @cindex static members of Pascal objects
7153 @cindex Pascal objects, static members display
7154 Print static members when displaying a Pascal object. The default is on.
7156 @item set print pascal_static-members off
7157 Do not print static members when displaying a Pascal object.
7159 @item show print pascal_static-members
7160 Show whether Pascal static members are printed or not.
7162 @c These don't work with HP ANSI C++ yet.
7163 @item set print vtbl
7164 @itemx set print vtbl on
7165 @cindex pretty print C@t{++} virtual function tables
7166 @cindex virtual functions (C@t{++}) display
7167 @cindex VTBL display
7168 Pretty print C@t{++} virtual function tables. The default is off.
7169 (The @code{vtbl} commands do not work on programs compiled with the HP
7170 ANSI C@t{++} compiler (@code{aCC}).)
7172 @item set print vtbl off
7173 Do not pretty print C@t{++} virtual function tables.
7175 @item show print vtbl
7176 Show whether C@t{++} virtual function tables are pretty printed, or not.
7180 @section Value History
7182 @cindex value history
7183 @cindex history of values printed by @value{GDBN}
7184 Values printed by the @code{print} command are saved in the @value{GDBN}
7185 @dfn{value history}. This allows you to refer to them in other expressions.
7186 Values are kept until the symbol table is re-read or discarded
7187 (for example with the @code{file} or @code{symbol-file} commands).
7188 When the symbol table changes, the value history is discarded,
7189 since the values may contain pointers back to the types defined in the
7194 @cindex history number
7195 The values printed are given @dfn{history numbers} by which you can
7196 refer to them. These are successive integers starting with one.
7197 @code{print} shows you the history number assigned to a value by
7198 printing @samp{$@var{num} = } before the value; here @var{num} is the
7201 To refer to any previous value, use @samp{$} followed by the value's
7202 history number. The way @code{print} labels its output is designed to
7203 remind you of this. Just @code{$} refers to the most recent value in
7204 the history, and @code{$$} refers to the value before that.
7205 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7206 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7207 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7209 For example, suppose you have just printed a pointer to a structure and
7210 want to see the contents of the structure. It suffices to type
7216 If you have a chain of structures where the component @code{next} points
7217 to the next one, you can print the contents of the next one with this:
7224 You can print successive links in the chain by repeating this
7225 command---which you can do by just typing @key{RET}.
7227 Note that the history records values, not expressions. If the value of
7228 @code{x} is 4 and you type these commands:
7236 then the value recorded in the value history by the @code{print} command
7237 remains 4 even though the value of @code{x} has changed.
7242 Print the last ten values in the value history, with their item numbers.
7243 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7244 values} does not change the history.
7246 @item show values @var{n}
7247 Print ten history values centered on history item number @var{n}.
7250 Print ten history values just after the values last printed. If no more
7251 values are available, @code{show values +} produces no display.
7254 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7255 same effect as @samp{show values +}.
7257 @node Convenience Vars
7258 @section Convenience Variables
7260 @cindex convenience variables
7261 @cindex user-defined variables
7262 @value{GDBN} provides @dfn{convenience variables} that you can use within
7263 @value{GDBN} to hold on to a value and refer to it later. These variables
7264 exist entirely within @value{GDBN}; they are not part of your program, and
7265 setting a convenience variable has no direct effect on further execution
7266 of your program. That is why you can use them freely.
7268 Convenience variables are prefixed with @samp{$}. Any name preceded by
7269 @samp{$} can be used for a convenience variable, unless it is one of
7270 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7271 (Value history references, in contrast, are @emph{numbers} preceded
7272 by @samp{$}. @xref{Value History, ,Value History}.)
7274 You can save a value in a convenience variable with an assignment
7275 expression, just as you would set a variable in your program.
7279 set $foo = *object_ptr
7283 would save in @code{$foo} the value contained in the object pointed to by
7286 Using a convenience variable for the first time creates it, but its
7287 value is @code{void} until you assign a new value. You can alter the
7288 value with another assignment at any time.
7290 Convenience variables have no fixed types. You can assign a convenience
7291 variable any type of value, including structures and arrays, even if
7292 that variable already has a value of a different type. The convenience
7293 variable, when used as an expression, has the type of its current value.
7296 @kindex show convenience
7297 @cindex show all user variables
7298 @item show convenience
7299 Print a list of convenience variables used so far, and their values.
7300 Abbreviated @code{show conv}.
7302 @kindex init-if-undefined
7303 @cindex convenience variables, initializing
7304 @item init-if-undefined $@var{variable} = @var{expression}
7305 Set a convenience variable if it has not already been set. This is useful
7306 for user-defined commands that keep some state. It is similar, in concept,
7307 to using local static variables with initializers in C (except that
7308 convenience variables are global). It can also be used to allow users to
7309 override default values used in a command script.
7311 If the variable is already defined then the expression is not evaluated so
7312 any side-effects do not occur.
7315 One of the ways to use a convenience variable is as a counter to be
7316 incremented or a pointer to be advanced. For example, to print
7317 a field from successive elements of an array of structures:
7321 print bar[$i++]->contents
7325 Repeat that command by typing @key{RET}.
7327 Some convenience variables are created automatically by @value{GDBN} and given
7328 values likely to be useful.
7331 @vindex $_@r{, convenience variable}
7333 The variable @code{$_} is automatically set by the @code{x} command to
7334 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7335 commands which provide a default address for @code{x} to examine also
7336 set @code{$_} to that address; these commands include @code{info line}
7337 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7338 except when set by the @code{x} command, in which case it is a pointer
7339 to the type of @code{$__}.
7341 @vindex $__@r{, convenience variable}
7343 The variable @code{$__} is automatically set by the @code{x} command
7344 to the value found in the last address examined. Its type is chosen
7345 to match the format in which the data was printed.
7348 @vindex $_exitcode@r{, convenience variable}
7349 The variable @code{$_exitcode} is automatically set to the exit code when
7350 the program being debugged terminates.
7353 On HP-UX systems, if you refer to a function or variable name that
7354 begins with a dollar sign, @value{GDBN} searches for a user or system
7355 name first, before it searches for a convenience variable.
7361 You can refer to machine register contents, in expressions, as variables
7362 with names starting with @samp{$}. The names of registers are different
7363 for each machine; use @code{info registers} to see the names used on
7367 @kindex info registers
7368 @item info registers
7369 Print the names and values of all registers except floating-point
7370 and vector registers (in the selected stack frame).
7372 @kindex info all-registers
7373 @cindex floating point registers
7374 @item info all-registers
7375 Print the names and values of all registers, including floating-point
7376 and vector registers (in the selected stack frame).
7378 @item info registers @var{regname} @dots{}
7379 Print the @dfn{relativized} value of each specified register @var{regname}.
7380 As discussed in detail below, register values are normally relative to
7381 the selected stack frame. @var{regname} may be any register name valid on
7382 the machine you are using, with or without the initial @samp{$}.
7385 @cindex stack pointer register
7386 @cindex program counter register
7387 @cindex process status register
7388 @cindex frame pointer register
7389 @cindex standard registers
7390 @value{GDBN} has four ``standard'' register names that are available (in
7391 expressions) on most machines---whenever they do not conflict with an
7392 architecture's canonical mnemonics for registers. The register names
7393 @code{$pc} and @code{$sp} are used for the program counter register and
7394 the stack pointer. @code{$fp} is used for a register that contains a
7395 pointer to the current stack frame, and @code{$ps} is used for a
7396 register that contains the processor status. For example,
7397 you could print the program counter in hex with
7404 or print the instruction to be executed next with
7411 or add four to the stack pointer@footnote{This is a way of removing
7412 one word from the stack, on machines where stacks grow downward in
7413 memory (most machines, nowadays). This assumes that the innermost
7414 stack frame is selected; setting @code{$sp} is not allowed when other
7415 stack frames are selected. To pop entire frames off the stack,
7416 regardless of machine architecture, use @code{return};
7417 see @ref{Returning, ,Returning from a Function}.} with
7423 Whenever possible, these four standard register names are available on
7424 your machine even though the machine has different canonical mnemonics,
7425 so long as there is no conflict. The @code{info registers} command
7426 shows the canonical names. For example, on the SPARC, @code{info
7427 registers} displays the processor status register as @code{$psr} but you
7428 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7429 is an alias for the @sc{eflags} register.
7431 @value{GDBN} always considers the contents of an ordinary register as an
7432 integer when the register is examined in this way. Some machines have
7433 special registers which can hold nothing but floating point; these
7434 registers are considered to have floating point values. There is no way
7435 to refer to the contents of an ordinary register as floating point value
7436 (although you can @emph{print} it as a floating point value with
7437 @samp{print/f $@var{regname}}).
7439 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7440 means that the data format in which the register contents are saved by
7441 the operating system is not the same one that your program normally
7442 sees. For example, the registers of the 68881 floating point
7443 coprocessor are always saved in ``extended'' (raw) format, but all C
7444 programs expect to work with ``double'' (virtual) format. In such
7445 cases, @value{GDBN} normally works with the virtual format only (the format
7446 that makes sense for your program), but the @code{info registers} command
7447 prints the data in both formats.
7449 @cindex SSE registers (x86)
7450 @cindex MMX registers (x86)
7451 Some machines have special registers whose contents can be interpreted
7452 in several different ways. For example, modern x86-based machines
7453 have SSE and MMX registers that can hold several values packed
7454 together in several different formats. @value{GDBN} refers to such
7455 registers in @code{struct} notation:
7458 (@value{GDBP}) print $xmm1
7460 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7461 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7462 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7463 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7464 v4_int32 = @{0, 20657912, 11, 13@},
7465 v2_int64 = @{88725056443645952, 55834574859@},
7466 uint128 = 0x0000000d0000000b013b36f800000000
7471 To set values of such registers, you need to tell @value{GDBN} which
7472 view of the register you wish to change, as if you were assigning
7473 value to a @code{struct} member:
7476 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7479 Normally, register values are relative to the selected stack frame
7480 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7481 value that the register would contain if all stack frames farther in
7482 were exited and their saved registers restored. In order to see the
7483 true contents of hardware registers, you must select the innermost
7484 frame (with @samp{frame 0}).
7486 However, @value{GDBN} must deduce where registers are saved, from the machine
7487 code generated by your compiler. If some registers are not saved, or if
7488 @value{GDBN} is unable to locate the saved registers, the selected stack
7489 frame makes no difference.
7491 @node Floating Point Hardware
7492 @section Floating Point Hardware
7493 @cindex floating point
7495 Depending on the configuration, @value{GDBN} may be able to give
7496 you more information about the status of the floating point hardware.
7501 Display hardware-dependent information about the floating
7502 point unit. The exact contents and layout vary depending on the
7503 floating point chip. Currently, @samp{info float} is supported on
7504 the ARM and x86 machines.
7508 @section Vector Unit
7511 Depending on the configuration, @value{GDBN} may be able to give you
7512 more information about the status of the vector unit.
7517 Display information about the vector unit. The exact contents and
7518 layout vary depending on the hardware.
7521 @node OS Information
7522 @section Operating System Auxiliary Information
7523 @cindex OS information
7525 @value{GDBN} provides interfaces to useful OS facilities that can help
7526 you debug your program.
7528 @cindex @code{ptrace} system call
7529 @cindex @code{struct user} contents
7530 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7531 machines), it interfaces with the inferior via the @code{ptrace}
7532 system call. The operating system creates a special sata structure,
7533 called @code{struct user}, for this interface. You can use the
7534 command @code{info udot} to display the contents of this data
7540 Display the contents of the @code{struct user} maintained by the OS
7541 kernel for the program being debugged. @value{GDBN} displays the
7542 contents of @code{struct user} as a list of hex numbers, similar to
7543 the @code{examine} command.
7546 @cindex auxiliary vector
7547 @cindex vector, auxiliary
7548 Some operating systems supply an @dfn{auxiliary vector} to programs at
7549 startup. This is akin to the arguments and environment that you
7550 specify for a program, but contains a system-dependent variety of
7551 binary values that tell system libraries important details about the
7552 hardware, operating system, and process. Each value's purpose is
7553 identified by an integer tag; the meanings are well-known but system-specific.
7554 Depending on the configuration and operating system facilities,
7555 @value{GDBN} may be able to show you this information. For remote
7556 targets, this functionality may further depend on the remote stub's
7557 support of the @samp{qXfer:auxv:read} packet, see
7558 @ref{qXfer auxiliary vector read}.
7563 Display the auxiliary vector of the inferior, which can be either a
7564 live process or a core dump file. @value{GDBN} prints each tag value
7565 numerically, and also shows names and text descriptions for recognized
7566 tags. Some values in the vector are numbers, some bit masks, and some
7567 pointers to strings or other data. @value{GDBN} displays each value in the
7568 most appropriate form for a recognized tag, and in hexadecimal for
7569 an unrecognized tag.
7572 On some targets, @value{GDBN} can access operating-system-specific information
7573 and display it to user, without interpretation. For remote targets,
7574 this functionality depends on the remote stub's support of the
7575 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
7578 @kindex info os processes
7579 @item info os processes
7580 Display the list of processes on the target. For each process,
7581 @value{GDBN} prints the process identifier, the name of the user, and
7582 the command corresponding to the process.
7585 @node Memory Region Attributes
7586 @section Memory Region Attributes
7587 @cindex memory region attributes
7589 @dfn{Memory region attributes} allow you to describe special handling
7590 required by regions of your target's memory. @value{GDBN} uses
7591 attributes to determine whether to allow certain types of memory
7592 accesses; whether to use specific width accesses; and whether to cache
7593 target memory. By default the description of memory regions is
7594 fetched from the target (if the current target supports this), but the
7595 user can override the fetched regions.
7597 Defined memory regions can be individually enabled and disabled. When a
7598 memory region is disabled, @value{GDBN} uses the default attributes when
7599 accessing memory in that region. Similarly, if no memory regions have
7600 been defined, @value{GDBN} uses the default attributes when accessing
7603 When a memory region is defined, it is given a number to identify it;
7604 to enable, disable, or remove a memory region, you specify that number.
7608 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7609 Define a memory region bounded by @var{lower} and @var{upper} with
7610 attributes @var{attributes}@dots{}, and add it to the list of regions
7611 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7612 case: it is treated as the target's maximum memory address.
7613 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7616 Discard any user changes to the memory regions and use target-supplied
7617 regions, if available, or no regions if the target does not support.
7620 @item delete mem @var{nums}@dots{}
7621 Remove memory regions @var{nums}@dots{} from the list of regions
7622 monitored by @value{GDBN}.
7625 @item disable mem @var{nums}@dots{}
7626 Disable monitoring of memory regions @var{nums}@dots{}.
7627 A disabled memory region is not forgotten.
7628 It may be enabled again later.
7631 @item enable mem @var{nums}@dots{}
7632 Enable monitoring of memory regions @var{nums}@dots{}.
7636 Print a table of all defined memory regions, with the following columns
7640 @item Memory Region Number
7641 @item Enabled or Disabled.
7642 Enabled memory regions are marked with @samp{y}.
7643 Disabled memory regions are marked with @samp{n}.
7646 The address defining the inclusive lower bound of the memory region.
7649 The address defining the exclusive upper bound of the memory region.
7652 The list of attributes set for this memory region.
7657 @subsection Attributes
7659 @subsubsection Memory Access Mode
7660 The access mode attributes set whether @value{GDBN} may make read or
7661 write accesses to a memory region.
7663 While these attributes prevent @value{GDBN} from performing invalid
7664 memory accesses, they do nothing to prevent the target system, I/O DMA,
7665 etc.@: from accessing memory.
7669 Memory is read only.
7671 Memory is write only.
7673 Memory is read/write. This is the default.
7676 @subsubsection Memory Access Size
7677 The access size attribute tells @value{GDBN} to use specific sized
7678 accesses in the memory region. Often memory mapped device registers
7679 require specific sized accesses. If no access size attribute is
7680 specified, @value{GDBN} may use accesses of any size.
7684 Use 8 bit memory accesses.
7686 Use 16 bit memory accesses.
7688 Use 32 bit memory accesses.
7690 Use 64 bit memory accesses.
7693 @c @subsubsection Hardware/Software Breakpoints
7694 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7695 @c will use hardware or software breakpoints for the internal breakpoints
7696 @c used by the step, next, finish, until, etc. commands.
7700 @c Always use hardware breakpoints
7701 @c @item swbreak (default)
7704 @subsubsection Data Cache
7705 The data cache attributes set whether @value{GDBN} will cache target
7706 memory. While this generally improves performance by reducing debug
7707 protocol overhead, it can lead to incorrect results because @value{GDBN}
7708 does not know about volatile variables or memory mapped device
7713 Enable @value{GDBN} to cache target memory.
7715 Disable @value{GDBN} from caching target memory. This is the default.
7718 @subsection Memory Access Checking
7719 @value{GDBN} can be instructed to refuse accesses to memory that is
7720 not explicitly described. This can be useful if accessing such
7721 regions has undesired effects for a specific target, or to provide
7722 better error checking. The following commands control this behaviour.
7725 @kindex set mem inaccessible-by-default
7726 @item set mem inaccessible-by-default [on|off]
7727 If @code{on} is specified, make @value{GDBN} treat memory not
7728 explicitly described by the memory ranges as non-existent and refuse accesses
7729 to such memory. The checks are only performed if there's at least one
7730 memory range defined. If @code{off} is specified, make @value{GDBN}
7731 treat the memory not explicitly described by the memory ranges as RAM.
7732 The default value is @code{on}.
7733 @kindex show mem inaccessible-by-default
7734 @item show mem inaccessible-by-default
7735 Show the current handling of accesses to unknown memory.
7739 @c @subsubsection Memory Write Verification
7740 @c The memory write verification attributes set whether @value{GDBN}
7741 @c will re-reads data after each write to verify the write was successful.
7745 @c @item noverify (default)
7748 @node Dump/Restore Files
7749 @section Copy Between Memory and a File
7750 @cindex dump/restore files
7751 @cindex append data to a file
7752 @cindex dump data to a file
7753 @cindex restore data from a file
7755 You can use the commands @code{dump}, @code{append}, and
7756 @code{restore} to copy data between target memory and a file. The
7757 @code{dump} and @code{append} commands write data to a file, and the
7758 @code{restore} command reads data from a file back into the inferior's
7759 memory. Files may be in binary, Motorola S-record, Intel hex, or
7760 Tektronix Hex format; however, @value{GDBN} can only append to binary
7766 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7767 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7768 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7769 or the value of @var{expr}, to @var{filename} in the given format.
7771 The @var{format} parameter may be any one of:
7778 Motorola S-record format.
7780 Tektronix Hex format.
7783 @value{GDBN} uses the same definitions of these formats as the
7784 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7785 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7789 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7790 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7791 Append the contents of memory from @var{start_addr} to @var{end_addr},
7792 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7793 (@value{GDBN} can only append data to files in raw binary form.)
7796 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7797 Restore the contents of file @var{filename} into memory. The
7798 @code{restore} command can automatically recognize any known @sc{bfd}
7799 file format, except for raw binary. To restore a raw binary file you
7800 must specify the optional keyword @code{binary} after the filename.
7802 If @var{bias} is non-zero, its value will be added to the addresses
7803 contained in the file. Binary files always start at address zero, so
7804 they will be restored at address @var{bias}. Other bfd files have
7805 a built-in location; they will be restored at offset @var{bias}
7808 If @var{start} and/or @var{end} are non-zero, then only data between
7809 file offset @var{start} and file offset @var{end} will be restored.
7810 These offsets are relative to the addresses in the file, before
7811 the @var{bias} argument is applied.
7815 @node Core File Generation
7816 @section How to Produce a Core File from Your Program
7817 @cindex dump core from inferior
7819 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7820 image of a running process and its process status (register values
7821 etc.). Its primary use is post-mortem debugging of a program that
7822 crashed while it ran outside a debugger. A program that crashes
7823 automatically produces a core file, unless this feature is disabled by
7824 the user. @xref{Files}, for information on invoking @value{GDBN} in
7825 the post-mortem debugging mode.
7827 Occasionally, you may wish to produce a core file of the program you
7828 are debugging in order to preserve a snapshot of its state.
7829 @value{GDBN} has a special command for that.
7833 @kindex generate-core-file
7834 @item generate-core-file [@var{file}]
7835 @itemx gcore [@var{file}]
7836 Produce a core dump of the inferior process. The optional argument
7837 @var{file} specifies the file name where to put the core dump. If not
7838 specified, the file name defaults to @file{core.@var{pid}}, where
7839 @var{pid} is the inferior process ID.
7841 Note that this command is implemented only for some systems (as of
7842 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7845 @node Character Sets
7846 @section Character Sets
7847 @cindex character sets
7849 @cindex translating between character sets
7850 @cindex host character set
7851 @cindex target character set
7853 If the program you are debugging uses a different character set to
7854 represent characters and strings than the one @value{GDBN} uses itself,
7855 @value{GDBN} can automatically translate between the character sets for
7856 you. The character set @value{GDBN} uses we call the @dfn{host
7857 character set}; the one the inferior program uses we call the
7858 @dfn{target character set}.
7860 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7861 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7862 remote protocol (@pxref{Remote Debugging}) to debug a program
7863 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7864 then the host character set is Latin-1, and the target character set is
7865 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7866 target-charset EBCDIC-US}, then @value{GDBN} translates between
7867 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7868 character and string literals in expressions.
7870 @value{GDBN} has no way to automatically recognize which character set
7871 the inferior program uses; you must tell it, using the @code{set
7872 target-charset} command, described below.
7874 Here are the commands for controlling @value{GDBN}'s character set
7878 @item set target-charset @var{charset}
7879 @kindex set target-charset
7880 Set the current target character set to @var{charset}. We list the
7881 character set names @value{GDBN} recognizes below, but if you type
7882 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7883 list the target character sets it supports.
7887 @item set host-charset @var{charset}
7888 @kindex set host-charset
7889 Set the current host character set to @var{charset}.
7891 By default, @value{GDBN} uses a host character set appropriate to the
7892 system it is running on; you can override that default using the
7893 @code{set host-charset} command.
7895 @value{GDBN} can only use certain character sets as its host character
7896 set. We list the character set names @value{GDBN} recognizes below, and
7897 indicate which can be host character sets, but if you type
7898 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7899 list the host character sets it supports.
7901 @item set charset @var{charset}
7903 Set the current host and target character sets to @var{charset}. As
7904 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7905 @value{GDBN} will list the name of the character sets that can be used
7906 for both host and target.
7910 @kindex show charset
7911 Show the names of the current host and target charsets.
7913 @itemx show host-charset
7914 @kindex show host-charset
7915 Show the name of the current host charset.
7917 @itemx show target-charset
7918 @kindex show target-charset
7919 Show the name of the current target charset.
7923 @value{GDBN} currently includes support for the following character
7929 @cindex ASCII character set
7930 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7934 @cindex ISO 8859-1 character set
7935 @cindex ISO Latin 1 character set
7936 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7937 characters needed for French, German, and Spanish. @value{GDBN} can use
7938 this as its host character set.
7942 @cindex EBCDIC character set
7943 @cindex IBM1047 character set
7944 Variants of the @sc{ebcdic} character set, used on some of IBM's
7945 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7946 @value{GDBN} cannot use these as its host character set.
7950 Note that these are all single-byte character sets. More work inside
7951 @value{GDBN} is needed to support multi-byte or variable-width character
7952 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7954 Here is an example of @value{GDBN}'s character set support in action.
7955 Assume that the following source code has been placed in the file
7956 @file{charset-test.c}:
7962 = @{72, 101, 108, 108, 111, 44, 32, 119,
7963 111, 114, 108, 100, 33, 10, 0@};
7964 char ibm1047_hello[]
7965 = @{200, 133, 147, 147, 150, 107, 64, 166,
7966 150, 153, 147, 132, 90, 37, 0@};
7970 printf ("Hello, world!\n");
7974 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7975 containing the string @samp{Hello, world!} followed by a newline,
7976 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7978 We compile the program, and invoke the debugger on it:
7981 $ gcc -g charset-test.c -o charset-test
7982 $ gdb -nw charset-test
7983 GNU gdb 2001-12-19-cvs
7984 Copyright 2001 Free Software Foundation, Inc.
7989 We can use the @code{show charset} command to see what character sets
7990 @value{GDBN} is currently using to interpret and display characters and
7994 (@value{GDBP}) show charset
7995 The current host and target character set is `ISO-8859-1'.
7999 For the sake of printing this manual, let's use @sc{ascii} as our
8000 initial character set:
8002 (@value{GDBP}) set charset ASCII
8003 (@value{GDBP}) show charset
8004 The current host and target character set is `ASCII'.
8008 Let's assume that @sc{ascii} is indeed the correct character set for our
8009 host system --- in other words, let's assume that if @value{GDBN} prints
8010 characters using the @sc{ascii} character set, our terminal will display
8011 them properly. Since our current target character set is also
8012 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8015 (@value{GDBP}) print ascii_hello
8016 $1 = 0x401698 "Hello, world!\n"
8017 (@value{GDBP}) print ascii_hello[0]
8022 @value{GDBN} uses the target character set for character and string
8023 literals you use in expressions:
8026 (@value{GDBP}) print '+'
8031 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8034 @value{GDBN} relies on the user to tell it which character set the
8035 target program uses. If we print @code{ibm1047_hello} while our target
8036 character set is still @sc{ascii}, we get jibberish:
8039 (@value{GDBP}) print ibm1047_hello
8040 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8041 (@value{GDBP}) print ibm1047_hello[0]
8046 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8047 @value{GDBN} tells us the character sets it supports:
8050 (@value{GDBP}) set target-charset
8051 ASCII EBCDIC-US IBM1047 ISO-8859-1
8052 (@value{GDBP}) set target-charset
8055 We can select @sc{ibm1047} as our target character set, and examine the
8056 program's strings again. Now the @sc{ascii} string is wrong, but
8057 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8058 target character set, @sc{ibm1047}, to the host character set,
8059 @sc{ascii}, and they display correctly:
8062 (@value{GDBP}) set target-charset IBM1047
8063 (@value{GDBP}) show charset
8064 The current host character set is `ASCII'.
8065 The current target character set is `IBM1047'.
8066 (@value{GDBP}) print ascii_hello
8067 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8068 (@value{GDBP}) print ascii_hello[0]
8070 (@value{GDBP}) print ibm1047_hello
8071 $8 = 0x4016a8 "Hello, world!\n"
8072 (@value{GDBP}) print ibm1047_hello[0]
8077 As above, @value{GDBN} uses the target character set for character and
8078 string literals you use in expressions:
8081 (@value{GDBP}) print '+'
8086 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8089 @node Caching Remote Data
8090 @section Caching Data of Remote Targets
8091 @cindex caching data of remote targets
8093 @value{GDBN} can cache data exchanged between the debugger and a
8094 remote target (@pxref{Remote Debugging}). Such caching generally improves
8095 performance, because it reduces the overhead of the remote protocol by
8096 bundling memory reads and writes into large chunks. Unfortunately,
8097 @value{GDBN} does not currently know anything about volatile
8098 registers, and thus data caching will produce incorrect results when
8099 volatile registers are in use.
8102 @kindex set remotecache
8103 @item set remotecache on
8104 @itemx set remotecache off
8105 Set caching state for remote targets. When @code{ON}, use data
8106 caching. By default, this option is @code{OFF}.
8108 @kindex show remotecache
8109 @item show remotecache
8110 Show the current state of data caching for remote targets.
8114 Print the information about the data cache performance. The
8115 information displayed includes: the dcache width and depth; and for
8116 each cache line, how many times it was referenced, and its data and
8117 state (invalid, dirty, valid). This command is useful for debugging
8118 the data cache operation.
8121 @node Searching Memory
8122 @section Search Memory
8123 @cindex searching memory
8125 Memory can be searched for a particular sequence of bytes with the
8126 @code{find} command.
8130 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8131 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8132 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8133 etc. The search begins at address @var{start_addr} and continues for either
8134 @var{len} bytes or through to @var{end_addr} inclusive.
8137 @var{s} and @var{n} are optional parameters.
8138 They may be specified in either order, apart or together.
8141 @item @var{s}, search query size
8142 The size of each search query value.
8148 halfwords (two bytes)
8152 giant words (eight bytes)
8155 All values are interpreted in the current language.
8156 This means, for example, that if the current source language is C/C@t{++}
8157 then searching for the string ``hello'' includes the trailing '\0'.
8159 If the value size is not specified, it is taken from the
8160 value's type in the current language.
8161 This is useful when one wants to specify the search
8162 pattern as a mixture of types.
8163 Note that this means, for example, that in the case of C-like languages
8164 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8165 which is typically four bytes.
8167 @item @var{n}, maximum number of finds
8168 The maximum number of matches to print. The default is to print all finds.
8171 You can use strings as search values. Quote them with double-quotes
8173 The string value is copied into the search pattern byte by byte,
8174 regardless of the endianness of the target and the size specification.
8176 The address of each match found is printed as well as a count of the
8177 number of matches found.
8179 The address of the last value found is stored in convenience variable
8181 A count of the number of matches is stored in @samp{$numfound}.
8183 For example, if stopped at the @code{printf} in this function:
8189 static char hello[] = "hello-hello";
8190 static struct @{ char c; short s; int i; @}
8191 __attribute__ ((packed)) mixed
8192 = @{ 'c', 0x1234, 0x87654321 @};
8193 printf ("%s\n", hello);
8198 you get during debugging:
8201 (gdb) find &hello[0], +sizeof(hello), "hello"
8202 0x804956d <hello.1620+6>
8204 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8205 0x8049567 <hello.1620>
8206 0x804956d <hello.1620+6>
8208 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8209 0x8049567 <hello.1620>
8211 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8212 0x8049560 <mixed.1625>
8214 (gdb) print $numfound
8217 $2 = (void *) 0x8049560
8221 @chapter C Preprocessor Macros
8223 Some languages, such as C and C@t{++}, provide a way to define and invoke
8224 ``preprocessor macros'' which expand into strings of tokens.
8225 @value{GDBN} can evaluate expressions containing macro invocations, show
8226 the result of macro expansion, and show a macro's definition, including
8227 where it was defined.
8229 You may need to compile your program specially to provide @value{GDBN}
8230 with information about preprocessor macros. Most compilers do not
8231 include macros in their debugging information, even when you compile
8232 with the @option{-g} flag. @xref{Compilation}.
8234 A program may define a macro at one point, remove that definition later,
8235 and then provide a different definition after that. Thus, at different
8236 points in the program, a macro may have different definitions, or have
8237 no definition at all. If there is a current stack frame, @value{GDBN}
8238 uses the macros in scope at that frame's source code line. Otherwise,
8239 @value{GDBN} uses the macros in scope at the current listing location;
8242 Whenever @value{GDBN} evaluates an expression, it always expands any
8243 macro invocations present in the expression. @value{GDBN} also provides
8244 the following commands for working with macros explicitly.
8248 @kindex macro expand
8249 @cindex macro expansion, showing the results of preprocessor
8250 @cindex preprocessor macro expansion, showing the results of
8251 @cindex expanding preprocessor macros
8252 @item macro expand @var{expression}
8253 @itemx macro exp @var{expression}
8254 Show the results of expanding all preprocessor macro invocations in
8255 @var{expression}. Since @value{GDBN} simply expands macros, but does
8256 not parse the result, @var{expression} need not be a valid expression;
8257 it can be any string of tokens.
8260 @item macro expand-once @var{expression}
8261 @itemx macro exp1 @var{expression}
8262 @cindex expand macro once
8263 @i{(This command is not yet implemented.)} Show the results of
8264 expanding those preprocessor macro invocations that appear explicitly in
8265 @var{expression}. Macro invocations appearing in that expansion are
8266 left unchanged. This command allows you to see the effect of a
8267 particular macro more clearly, without being confused by further
8268 expansions. Since @value{GDBN} simply expands macros, but does not
8269 parse the result, @var{expression} need not be a valid expression; it
8270 can be any string of tokens.
8273 @cindex macro definition, showing
8274 @cindex definition, showing a macro's
8275 @item info macro @var{macro}
8276 Show the definition of the macro named @var{macro}, and describe the
8277 source location where that definition was established.
8279 @kindex macro define
8280 @cindex user-defined macros
8281 @cindex defining macros interactively
8282 @cindex macros, user-defined
8283 @item macro define @var{macro} @var{replacement-list}
8284 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8285 Introduce a definition for a preprocessor macro named @var{macro},
8286 invocations of which are replaced by the tokens given in
8287 @var{replacement-list}. The first form of this command defines an
8288 ``object-like'' macro, which takes no arguments; the second form
8289 defines a ``function-like'' macro, which takes the arguments given in
8292 A definition introduced by this command is in scope in every
8293 expression evaluated in @value{GDBN}, until it is removed with the
8294 @code{macro undef} command, described below. The definition overrides
8295 all definitions for @var{macro} present in the program being debugged,
8296 as well as any previous user-supplied definition.
8299 @item macro undef @var{macro}
8300 Remove any user-supplied definition for the macro named @var{macro}.
8301 This command only affects definitions provided with the @code{macro
8302 define} command, described above; it cannot remove definitions present
8303 in the program being debugged.
8307 List all the macros defined using the @code{macro define} command.
8310 @cindex macros, example of debugging with
8311 Here is a transcript showing the above commands in action. First, we
8312 show our source files:
8320 #define ADD(x) (M + x)
8325 printf ("Hello, world!\n");
8327 printf ("We're so creative.\n");
8329 printf ("Goodbye, world!\n");
8336 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8337 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8338 compiler includes information about preprocessor macros in the debugging
8342 $ gcc -gdwarf-2 -g3 sample.c -o sample
8346 Now, we start @value{GDBN} on our sample program:
8350 GNU gdb 2002-05-06-cvs
8351 Copyright 2002 Free Software Foundation, Inc.
8352 GDB is free software, @dots{}
8356 We can expand macros and examine their definitions, even when the
8357 program is not running. @value{GDBN} uses the current listing position
8358 to decide which macro definitions are in scope:
8361 (@value{GDBP}) list main
8364 5 #define ADD(x) (M + x)
8369 10 printf ("Hello, world!\n");
8371 12 printf ("We're so creative.\n");
8372 (@value{GDBP}) info macro ADD
8373 Defined at /home/jimb/gdb/macros/play/sample.c:5
8374 #define ADD(x) (M + x)
8375 (@value{GDBP}) info macro Q
8376 Defined at /home/jimb/gdb/macros/play/sample.h:1
8377 included at /home/jimb/gdb/macros/play/sample.c:2
8379 (@value{GDBP}) macro expand ADD(1)
8380 expands to: (42 + 1)
8381 (@value{GDBP}) macro expand-once ADD(1)
8382 expands to: once (M + 1)
8386 In the example above, note that @code{macro expand-once} expands only
8387 the macro invocation explicit in the original text --- the invocation of
8388 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8389 which was introduced by @code{ADD}.
8391 Once the program is running, @value{GDBN} uses the macro definitions in
8392 force at the source line of the current stack frame:
8395 (@value{GDBP}) break main
8396 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8398 Starting program: /home/jimb/gdb/macros/play/sample
8400 Breakpoint 1, main () at sample.c:10
8401 10 printf ("Hello, world!\n");
8405 At line 10, the definition of the macro @code{N} at line 9 is in force:
8408 (@value{GDBP}) info macro N
8409 Defined at /home/jimb/gdb/macros/play/sample.c:9
8411 (@value{GDBP}) macro expand N Q M
8413 (@value{GDBP}) print N Q M
8418 As we step over directives that remove @code{N}'s definition, and then
8419 give it a new definition, @value{GDBN} finds the definition (or lack
8420 thereof) in force at each point:
8425 12 printf ("We're so creative.\n");
8426 (@value{GDBP}) info macro N
8427 The symbol `N' has no definition as a C/C++ preprocessor macro
8428 at /home/jimb/gdb/macros/play/sample.c:12
8431 14 printf ("Goodbye, world!\n");
8432 (@value{GDBP}) info macro N
8433 Defined at /home/jimb/gdb/macros/play/sample.c:13
8435 (@value{GDBP}) macro expand N Q M
8436 expands to: 1729 < 42
8437 (@value{GDBP}) print N Q M
8444 @chapter Tracepoints
8445 @c This chapter is based on the documentation written by Michael
8446 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8449 In some applications, it is not feasible for the debugger to interrupt
8450 the program's execution long enough for the developer to learn
8451 anything helpful about its behavior. If the program's correctness
8452 depends on its real-time behavior, delays introduced by a debugger
8453 might cause the program to change its behavior drastically, or perhaps
8454 fail, even when the code itself is correct. It is useful to be able
8455 to observe the program's behavior without interrupting it.
8457 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8458 specify locations in the program, called @dfn{tracepoints}, and
8459 arbitrary expressions to evaluate when those tracepoints are reached.
8460 Later, using the @code{tfind} command, you can examine the values
8461 those expressions had when the program hit the tracepoints. The
8462 expressions may also denote objects in memory---structures or arrays,
8463 for example---whose values @value{GDBN} should record; while visiting
8464 a particular tracepoint, you may inspect those objects as if they were
8465 in memory at that moment. However, because @value{GDBN} records these
8466 values without interacting with you, it can do so quickly and
8467 unobtrusively, hopefully not disturbing the program's behavior.
8469 The tracepoint facility is currently available only for remote
8470 targets. @xref{Targets}. In addition, your remote target must know
8471 how to collect trace data. This functionality is implemented in the
8472 remote stub; however, none of the stubs distributed with @value{GDBN}
8473 support tracepoints as of this writing. The format of the remote
8474 packets used to implement tracepoints are described in @ref{Tracepoint
8477 This chapter describes the tracepoint commands and features.
8481 * Analyze Collected Data::
8482 * Tracepoint Variables::
8485 @node Set Tracepoints
8486 @section Commands to Set Tracepoints
8488 Before running such a @dfn{trace experiment}, an arbitrary number of
8489 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
8490 tracepoint has a number assigned to it by @value{GDBN}. Like with
8491 breakpoints, tracepoint numbers are successive integers starting from
8492 one. Many of the commands associated with tracepoints take the
8493 tracepoint number as their argument, to identify which tracepoint to
8496 For each tracepoint, you can specify, in advance, some arbitrary set
8497 of data that you want the target to collect in the trace buffer when
8498 it hits that tracepoint. The collected data can include registers,
8499 local variables, or global data. Later, you can use @value{GDBN}
8500 commands to examine the values these data had at the time the
8503 This section describes commands to set tracepoints and associated
8504 conditions and actions.
8507 * Create and Delete Tracepoints::
8508 * Enable and Disable Tracepoints::
8509 * Tracepoint Passcounts::
8510 * Tracepoint Actions::
8511 * Listing Tracepoints::
8512 * Starting and Stopping Trace Experiments::
8515 @node Create and Delete Tracepoints
8516 @subsection Create and Delete Tracepoints
8519 @cindex set tracepoint
8522 The @code{trace} command is very similar to the @code{break} command.
8523 Its argument can be a source line, a function name, or an address in
8524 the target program. @xref{Set Breaks}. The @code{trace} command
8525 defines a tracepoint, which is a point in the target program where the
8526 debugger will briefly stop, collect some data, and then allow the
8527 program to continue. Setting a tracepoint or changing its commands
8528 doesn't take effect until the next @code{tstart} command; thus, you
8529 cannot change the tracepoint attributes once a trace experiment is
8532 Here are some examples of using the @code{trace} command:
8535 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8537 (@value{GDBP}) @b{trace +2} // 2 lines forward
8539 (@value{GDBP}) @b{trace my_function} // first source line of function
8541 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8543 (@value{GDBP}) @b{trace *0x2117c4} // an address
8547 You can abbreviate @code{trace} as @code{tr}.
8550 @cindex last tracepoint number
8551 @cindex recent tracepoint number
8552 @cindex tracepoint number
8553 The convenience variable @code{$tpnum} records the tracepoint number
8554 of the most recently set tracepoint.
8556 @kindex delete tracepoint
8557 @cindex tracepoint deletion
8558 @item delete tracepoint @r{[}@var{num}@r{]}
8559 Permanently delete one or more tracepoints. With no argument, the
8560 default is to delete all tracepoints.
8565 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8567 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8571 You can abbreviate this command as @code{del tr}.
8574 @node Enable and Disable Tracepoints
8575 @subsection Enable and Disable Tracepoints
8578 @kindex disable tracepoint
8579 @item disable tracepoint @r{[}@var{num}@r{]}
8580 Disable tracepoint @var{num}, or all tracepoints if no argument
8581 @var{num} is given. A disabled tracepoint will have no effect during
8582 the next trace experiment, but it is not forgotten. You can re-enable
8583 a disabled tracepoint using the @code{enable tracepoint} command.
8585 @kindex enable tracepoint
8586 @item enable tracepoint @r{[}@var{num}@r{]}
8587 Enable tracepoint @var{num}, or all tracepoints. The enabled
8588 tracepoints will become effective the next time a trace experiment is
8592 @node Tracepoint Passcounts
8593 @subsection Tracepoint Passcounts
8597 @cindex tracepoint pass count
8598 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8599 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8600 automatically stop a trace experiment. If a tracepoint's passcount is
8601 @var{n}, then the trace experiment will be automatically stopped on
8602 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8603 @var{num} is not specified, the @code{passcount} command sets the
8604 passcount of the most recently defined tracepoint. If no passcount is
8605 given, the trace experiment will run until stopped explicitly by the
8611 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8612 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8614 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8615 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8616 (@value{GDBP}) @b{trace foo}
8617 (@value{GDBP}) @b{pass 3}
8618 (@value{GDBP}) @b{trace bar}
8619 (@value{GDBP}) @b{pass 2}
8620 (@value{GDBP}) @b{trace baz}
8621 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8622 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8623 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8624 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8628 @node Tracepoint Actions
8629 @subsection Tracepoint Action Lists
8633 @cindex tracepoint actions
8634 @item actions @r{[}@var{num}@r{]}
8635 This command will prompt for a list of actions to be taken when the
8636 tracepoint is hit. If the tracepoint number @var{num} is not
8637 specified, this command sets the actions for the one that was most
8638 recently defined (so that you can define a tracepoint and then say
8639 @code{actions} without bothering about its number). You specify the
8640 actions themselves on the following lines, one action at a time, and
8641 terminate the actions list with a line containing just @code{end}. So
8642 far, the only defined actions are @code{collect} and
8643 @code{while-stepping}.
8645 @cindex remove actions from a tracepoint
8646 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8647 and follow it immediately with @samp{end}.
8650 (@value{GDBP}) @b{collect @var{data}} // collect some data
8652 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8654 (@value{GDBP}) @b{end} // signals the end of actions.
8657 In the following example, the action list begins with @code{collect}
8658 commands indicating the things to be collected when the tracepoint is
8659 hit. Then, in order to single-step and collect additional data
8660 following the tracepoint, a @code{while-stepping} command is used,
8661 followed by the list of things to be collected while stepping. The
8662 @code{while-stepping} command is terminated by its own separate
8663 @code{end} command. Lastly, the action list is terminated by an
8667 (@value{GDBP}) @b{trace foo}
8668 (@value{GDBP}) @b{actions}
8669 Enter actions for tracepoint 1, one per line:
8678 @kindex collect @r{(tracepoints)}
8679 @item collect @var{expr1}, @var{expr2}, @dots{}
8680 Collect values of the given expressions when the tracepoint is hit.
8681 This command accepts a comma-separated list of any valid expressions.
8682 In addition to global, static, or local variables, the following
8683 special arguments are supported:
8687 collect all registers
8690 collect all function arguments
8693 collect all local variables.
8696 You can give several consecutive @code{collect} commands, each one
8697 with a single argument, or one @code{collect} command with several
8698 arguments separated by commas: the effect is the same.
8700 The command @code{info scope} (@pxref{Symbols, info scope}) is
8701 particularly useful for figuring out what data to collect.
8703 @kindex while-stepping @r{(tracepoints)}
8704 @item while-stepping @var{n}
8705 Perform @var{n} single-step traces after the tracepoint, collecting
8706 new data at each step. The @code{while-stepping} command is
8707 followed by the list of what to collect while stepping (followed by
8708 its own @code{end} command):
8712 > collect $regs, myglobal
8718 You may abbreviate @code{while-stepping} as @code{ws} or
8722 @node Listing Tracepoints
8723 @subsection Listing Tracepoints
8726 @kindex info tracepoints
8728 @cindex information about tracepoints
8729 @item info tracepoints @r{[}@var{num}@r{]}
8730 Display information about the tracepoint @var{num}. If you don't specify
8731 a tracepoint number, displays information about all the tracepoints
8732 defined so far. For each tracepoint, the following information is
8739 whether it is enabled or disabled
8743 its passcount as given by the @code{passcount @var{n}} command
8745 its step count as given by the @code{while-stepping @var{n}} command
8747 where in the source files is the tracepoint set
8749 its action list as given by the @code{actions} command
8753 (@value{GDBP}) @b{info trace}
8754 Num Enb Address PassC StepC What
8755 1 y 0x002117c4 0 0 <gdb_asm>
8756 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8757 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8762 This command can be abbreviated @code{info tp}.
8765 @node Starting and Stopping Trace Experiments
8766 @subsection Starting and Stopping Trace Experiments
8770 @cindex start a new trace experiment
8771 @cindex collected data discarded
8773 This command takes no arguments. It starts the trace experiment, and
8774 begins collecting data. This has the side effect of discarding all
8775 the data collected in the trace buffer during the previous trace
8779 @cindex stop a running trace experiment
8781 This command takes no arguments. It ends the trace experiment, and
8782 stops collecting data.
8784 @strong{Note}: a trace experiment and data collection may stop
8785 automatically if any tracepoint's passcount is reached
8786 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8789 @cindex status of trace data collection
8790 @cindex trace experiment, status of
8792 This command displays the status of the current trace data
8796 Here is an example of the commands we described so far:
8799 (@value{GDBP}) @b{trace gdb_c_test}
8800 (@value{GDBP}) @b{actions}
8801 Enter actions for tracepoint #1, one per line.
8802 > collect $regs,$locals,$args
8807 (@value{GDBP}) @b{tstart}
8808 [time passes @dots{}]
8809 (@value{GDBP}) @b{tstop}
8813 @node Analyze Collected Data
8814 @section Using the Collected Data
8816 After the tracepoint experiment ends, you use @value{GDBN} commands
8817 for examining the trace data. The basic idea is that each tracepoint
8818 collects a trace @dfn{snapshot} every time it is hit and another
8819 snapshot every time it single-steps. All these snapshots are
8820 consecutively numbered from zero and go into a buffer, and you can
8821 examine them later. The way you examine them is to @dfn{focus} on a
8822 specific trace snapshot. When the remote stub is focused on a trace
8823 snapshot, it will respond to all @value{GDBN} requests for memory and
8824 registers by reading from the buffer which belongs to that snapshot,
8825 rather than from @emph{real} memory or registers of the program being
8826 debugged. This means that @strong{all} @value{GDBN} commands
8827 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8828 behave as if we were currently debugging the program state as it was
8829 when the tracepoint occurred. Any requests for data that are not in
8830 the buffer will fail.
8833 * tfind:: How to select a trace snapshot
8834 * tdump:: How to display all data for a snapshot
8835 * save-tracepoints:: How to save tracepoints for a future run
8839 @subsection @code{tfind @var{n}}
8842 @cindex select trace snapshot
8843 @cindex find trace snapshot
8844 The basic command for selecting a trace snapshot from the buffer is
8845 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8846 counting from zero. If no argument @var{n} is given, the next
8847 snapshot is selected.
8849 Here are the various forms of using the @code{tfind} command.
8853 Find the first snapshot in the buffer. This is a synonym for
8854 @code{tfind 0} (since 0 is the number of the first snapshot).
8857 Stop debugging trace snapshots, resume @emph{live} debugging.
8860 Same as @samp{tfind none}.
8863 No argument means find the next trace snapshot.
8866 Find the previous trace snapshot before the current one. This permits
8867 retracing earlier steps.
8869 @item tfind tracepoint @var{num}
8870 Find the next snapshot associated with tracepoint @var{num}. Search
8871 proceeds forward from the last examined trace snapshot. If no
8872 argument @var{num} is given, it means find the next snapshot collected
8873 for the same tracepoint as the current snapshot.
8875 @item tfind pc @var{addr}
8876 Find the next snapshot associated with the value @var{addr} of the
8877 program counter. Search proceeds forward from the last examined trace
8878 snapshot. If no argument @var{addr} is given, it means find the next
8879 snapshot with the same value of PC as the current snapshot.
8881 @item tfind outside @var{addr1}, @var{addr2}
8882 Find the next snapshot whose PC is outside the given range of
8885 @item tfind range @var{addr1}, @var{addr2}
8886 Find the next snapshot whose PC is between @var{addr1} and
8887 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8889 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8890 Find the next snapshot associated with the source line @var{n}. If
8891 the optional argument @var{file} is given, refer to line @var{n} in
8892 that source file. Search proceeds forward from the last examined
8893 trace snapshot. If no argument @var{n} is given, it means find the
8894 next line other than the one currently being examined; thus saying
8895 @code{tfind line} repeatedly can appear to have the same effect as
8896 stepping from line to line in a @emph{live} debugging session.
8899 The default arguments for the @code{tfind} commands are specifically
8900 designed to make it easy to scan through the trace buffer. For
8901 instance, @code{tfind} with no argument selects the next trace
8902 snapshot, and @code{tfind -} with no argument selects the previous
8903 trace snapshot. So, by giving one @code{tfind} command, and then
8904 simply hitting @key{RET} repeatedly you can examine all the trace
8905 snapshots in order. Or, by saying @code{tfind -} and then hitting
8906 @key{RET} repeatedly you can examine the snapshots in reverse order.
8907 The @code{tfind line} command with no argument selects the snapshot
8908 for the next source line executed. The @code{tfind pc} command with
8909 no argument selects the next snapshot with the same program counter
8910 (PC) as the current frame. The @code{tfind tracepoint} command with
8911 no argument selects the next trace snapshot collected by the same
8912 tracepoint as the current one.
8914 In addition to letting you scan through the trace buffer manually,
8915 these commands make it easy to construct @value{GDBN} scripts that
8916 scan through the trace buffer and print out whatever collected data
8917 you are interested in. Thus, if we want to examine the PC, FP, and SP
8918 registers from each trace frame in the buffer, we can say this:
8921 (@value{GDBP}) @b{tfind start}
8922 (@value{GDBP}) @b{while ($trace_frame != -1)}
8923 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8924 $trace_frame, $pc, $sp, $fp
8928 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8929 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8930 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8931 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8932 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8933 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8934 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8935 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8936 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8937 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8938 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8941 Or, if we want to examine the variable @code{X} at each source line in
8945 (@value{GDBP}) @b{tfind start}
8946 (@value{GDBP}) @b{while ($trace_frame != -1)}
8947 > printf "Frame %d, X == %d\n", $trace_frame, X
8957 @subsection @code{tdump}
8959 @cindex dump all data collected at tracepoint
8960 @cindex tracepoint data, display
8962 This command takes no arguments. It prints all the data collected at
8963 the current trace snapshot.
8966 (@value{GDBP}) @b{trace 444}
8967 (@value{GDBP}) @b{actions}
8968 Enter actions for tracepoint #2, one per line:
8969 > collect $regs, $locals, $args, gdb_long_test
8972 (@value{GDBP}) @b{tstart}
8974 (@value{GDBP}) @b{tfind line 444}
8975 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8977 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8979 (@value{GDBP}) @b{tdump}
8980 Data collected at tracepoint 2, trace frame 1:
8981 d0 0xc4aa0085 -995491707
8985 d4 0x71aea3d 119204413
8990 a1 0x3000668 50333288
8993 a4 0x3000698 50333336
8995 fp 0x30bf3c 0x30bf3c
8996 sp 0x30bf34 0x30bf34
8998 pc 0x20b2c8 0x20b2c8
9002 p = 0x20e5b4 "gdb-test"
9009 gdb_long_test = 17 '\021'
9014 @node save-tracepoints
9015 @subsection @code{save-tracepoints @var{filename}}
9016 @kindex save-tracepoints
9017 @cindex save tracepoints for future sessions
9019 This command saves all current tracepoint definitions together with
9020 their actions and passcounts, into a file @file{@var{filename}}
9021 suitable for use in a later debugging session. To read the saved
9022 tracepoint definitions, use the @code{source} command (@pxref{Command
9025 @node Tracepoint Variables
9026 @section Convenience Variables for Tracepoints
9027 @cindex tracepoint variables
9028 @cindex convenience variables for tracepoints
9031 @vindex $trace_frame
9032 @item (int) $trace_frame
9033 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9034 snapshot is selected.
9037 @item (int) $tracepoint
9038 The tracepoint for the current trace snapshot.
9041 @item (int) $trace_line
9042 The line number for the current trace snapshot.
9045 @item (char []) $trace_file
9046 The source file for the current trace snapshot.
9049 @item (char []) $trace_func
9050 The name of the function containing @code{$tracepoint}.
9053 Note: @code{$trace_file} is not suitable for use in @code{printf},
9054 use @code{output} instead.
9056 Here's a simple example of using these convenience variables for
9057 stepping through all the trace snapshots and printing some of their
9061 (@value{GDBP}) @b{tfind start}
9063 (@value{GDBP}) @b{while $trace_frame != -1}
9064 > output $trace_file
9065 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9071 @chapter Debugging Programs That Use Overlays
9074 If your program is too large to fit completely in your target system's
9075 memory, you can sometimes use @dfn{overlays} to work around this
9076 problem. @value{GDBN} provides some support for debugging programs that
9080 * How Overlays Work:: A general explanation of overlays.
9081 * Overlay Commands:: Managing overlays in @value{GDBN}.
9082 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9083 mapped by asking the inferior.
9084 * Overlay Sample Program:: A sample program using overlays.
9087 @node How Overlays Work
9088 @section How Overlays Work
9089 @cindex mapped overlays
9090 @cindex unmapped overlays
9091 @cindex load address, overlay's
9092 @cindex mapped address
9093 @cindex overlay area
9095 Suppose you have a computer whose instruction address space is only 64
9096 kilobytes long, but which has much more memory which can be accessed by
9097 other means: special instructions, segment registers, or memory
9098 management hardware, for example. Suppose further that you want to
9099 adapt a program which is larger than 64 kilobytes to run on this system.
9101 One solution is to identify modules of your program which are relatively
9102 independent, and need not call each other directly; call these modules
9103 @dfn{overlays}. Separate the overlays from the main program, and place
9104 their machine code in the larger memory. Place your main program in
9105 instruction memory, but leave at least enough space there to hold the
9106 largest overlay as well.
9108 Now, to call a function located in an overlay, you must first copy that
9109 overlay's machine code from the large memory into the space set aside
9110 for it in the instruction memory, and then jump to its entry point
9113 @c NB: In the below the mapped area's size is greater or equal to the
9114 @c size of all overlays. This is intentional to remind the developer
9115 @c that overlays don't necessarily need to be the same size.
9119 Data Instruction Larger
9120 Address Space Address Space Address Space
9121 +-----------+ +-----------+ +-----------+
9123 +-----------+ +-----------+ +-----------+<-- overlay 1
9124 | program | | main | .----| overlay 1 | load address
9125 | variables | | program | | +-----------+
9126 | and heap | | | | | |
9127 +-----------+ | | | +-----------+<-- overlay 2
9128 | | +-----------+ | | | load address
9129 +-----------+ | | | .-| overlay 2 |
9131 mapped --->+-----------+ | | +-----------+
9133 | overlay | <-' | | |
9134 | area | <---' +-----------+<-- overlay 3
9135 | | <---. | | load address
9136 +-----------+ `--| overlay 3 |
9143 @anchor{A code overlay}A code overlay
9147 The diagram (@pxref{A code overlay}) shows a system with separate data
9148 and instruction address spaces. To map an overlay, the program copies
9149 its code from the larger address space to the instruction address space.
9150 Since the overlays shown here all use the same mapped address, only one
9151 may be mapped at a time. For a system with a single address space for
9152 data and instructions, the diagram would be similar, except that the
9153 program variables and heap would share an address space with the main
9154 program and the overlay area.
9156 An overlay loaded into instruction memory and ready for use is called a
9157 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9158 instruction memory. An overlay not present (or only partially present)
9159 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9160 is its address in the larger memory. The mapped address is also called
9161 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9162 called the @dfn{load memory address}, or @dfn{LMA}.
9164 Unfortunately, overlays are not a completely transparent way to adapt a
9165 program to limited instruction memory. They introduce a new set of
9166 global constraints you must keep in mind as you design your program:
9171 Before calling or returning to a function in an overlay, your program
9172 must make sure that overlay is actually mapped. Otherwise, the call or
9173 return will transfer control to the right address, but in the wrong
9174 overlay, and your program will probably crash.
9177 If the process of mapping an overlay is expensive on your system, you
9178 will need to choose your overlays carefully to minimize their effect on
9179 your program's performance.
9182 The executable file you load onto your system must contain each
9183 overlay's instructions, appearing at the overlay's load address, not its
9184 mapped address. However, each overlay's instructions must be relocated
9185 and its symbols defined as if the overlay were at its mapped address.
9186 You can use GNU linker scripts to specify different load and relocation
9187 addresses for pieces of your program; see @ref{Overlay Description,,,
9188 ld.info, Using ld: the GNU linker}.
9191 The procedure for loading executable files onto your system must be able
9192 to load their contents into the larger address space as well as the
9193 instruction and data spaces.
9197 The overlay system described above is rather simple, and could be
9198 improved in many ways:
9203 If your system has suitable bank switch registers or memory management
9204 hardware, you could use those facilities to make an overlay's load area
9205 contents simply appear at their mapped address in instruction space.
9206 This would probably be faster than copying the overlay to its mapped
9207 area in the usual way.
9210 If your overlays are small enough, you could set aside more than one
9211 overlay area, and have more than one overlay mapped at a time.
9214 You can use overlays to manage data, as well as instructions. In
9215 general, data overlays are even less transparent to your design than
9216 code overlays: whereas code overlays only require care when you call or
9217 return to functions, data overlays require care every time you access
9218 the data. Also, if you change the contents of a data overlay, you
9219 must copy its contents back out to its load address before you can copy a
9220 different data overlay into the same mapped area.
9225 @node Overlay Commands
9226 @section Overlay Commands
9228 To use @value{GDBN}'s overlay support, each overlay in your program must
9229 correspond to a separate section of the executable file. The section's
9230 virtual memory address and load memory address must be the overlay's
9231 mapped and load addresses. Identifying overlays with sections allows
9232 @value{GDBN} to determine the appropriate address of a function or
9233 variable, depending on whether the overlay is mapped or not.
9235 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9236 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9241 Disable @value{GDBN}'s overlay support. When overlay support is
9242 disabled, @value{GDBN} assumes that all functions and variables are
9243 always present at their mapped addresses. By default, @value{GDBN}'s
9244 overlay support is disabled.
9246 @item overlay manual
9247 @cindex manual overlay debugging
9248 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9249 relies on you to tell it which overlays are mapped, and which are not,
9250 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9251 commands described below.
9253 @item overlay map-overlay @var{overlay}
9254 @itemx overlay map @var{overlay}
9255 @cindex map an overlay
9256 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9257 be the name of the object file section containing the overlay. When an
9258 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9259 functions and variables at their mapped addresses. @value{GDBN} assumes
9260 that any other overlays whose mapped ranges overlap that of
9261 @var{overlay} are now unmapped.
9263 @item overlay unmap-overlay @var{overlay}
9264 @itemx overlay unmap @var{overlay}
9265 @cindex unmap an overlay
9266 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9267 must be the name of the object file section containing the overlay.
9268 When an overlay is unmapped, @value{GDBN} assumes it can find the
9269 overlay's functions and variables at their load addresses.
9272 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9273 consults a data structure the overlay manager maintains in the inferior
9274 to see which overlays are mapped. For details, see @ref{Automatic
9277 @item overlay load-target
9279 @cindex reloading the overlay table
9280 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9281 re-reads the table @value{GDBN} automatically each time the inferior
9282 stops, so this command should only be necessary if you have changed the
9283 overlay mapping yourself using @value{GDBN}. This command is only
9284 useful when using automatic overlay debugging.
9286 @item overlay list-overlays
9288 @cindex listing mapped overlays
9289 Display a list of the overlays currently mapped, along with their mapped
9290 addresses, load addresses, and sizes.
9294 Normally, when @value{GDBN} prints a code address, it includes the name
9295 of the function the address falls in:
9298 (@value{GDBP}) print main
9299 $3 = @{int ()@} 0x11a0 <main>
9302 When overlay debugging is enabled, @value{GDBN} recognizes code in
9303 unmapped overlays, and prints the names of unmapped functions with
9304 asterisks around them. For example, if @code{foo} is a function in an
9305 unmapped overlay, @value{GDBN} prints it this way:
9308 (@value{GDBP}) overlay list
9309 No sections are mapped.
9310 (@value{GDBP}) print foo
9311 $5 = @{int (int)@} 0x100000 <*foo*>
9314 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9318 (@value{GDBP}) overlay list
9319 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9320 mapped at 0x1016 - 0x104a
9321 (@value{GDBP}) print foo
9322 $6 = @{int (int)@} 0x1016 <foo>
9325 When overlay debugging is enabled, @value{GDBN} can find the correct
9326 address for functions and variables in an overlay, whether or not the
9327 overlay is mapped. This allows most @value{GDBN} commands, like
9328 @code{break} and @code{disassemble}, to work normally, even on unmapped
9329 code. However, @value{GDBN}'s breakpoint support has some limitations:
9333 @cindex breakpoints in overlays
9334 @cindex overlays, setting breakpoints in
9335 You can set breakpoints in functions in unmapped overlays, as long as
9336 @value{GDBN} can write to the overlay at its load address.
9338 @value{GDBN} can not set hardware or simulator-based breakpoints in
9339 unmapped overlays. However, if you set a breakpoint at the end of your
9340 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9341 you are using manual overlay management), @value{GDBN} will re-set its
9342 breakpoints properly.
9346 @node Automatic Overlay Debugging
9347 @section Automatic Overlay Debugging
9348 @cindex automatic overlay debugging
9350 @value{GDBN} can automatically track which overlays are mapped and which
9351 are not, given some simple co-operation from the overlay manager in the
9352 inferior. If you enable automatic overlay debugging with the
9353 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
9354 looks in the inferior's memory for certain variables describing the
9355 current state of the overlays.
9357 Here are the variables your overlay manager must define to support
9358 @value{GDBN}'s automatic overlay debugging:
9362 @item @code{_ovly_table}:
9363 This variable must be an array of the following structures:
9368 /* The overlay's mapped address. */
9371 /* The size of the overlay, in bytes. */
9374 /* The overlay's load address. */
9377 /* Non-zero if the overlay is currently mapped;
9379 unsigned long mapped;
9383 @item @code{_novlys}:
9384 This variable must be a four-byte signed integer, holding the total
9385 number of elements in @code{_ovly_table}.
9389 To decide whether a particular overlay is mapped or not, @value{GDBN}
9390 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9391 @code{lma} members equal the VMA and LMA of the overlay's section in the
9392 executable file. When @value{GDBN} finds a matching entry, it consults
9393 the entry's @code{mapped} member to determine whether the overlay is
9396 In addition, your overlay manager may define a function called
9397 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9398 will silently set a breakpoint there. If the overlay manager then
9399 calls this function whenever it has changed the overlay table, this
9400 will enable @value{GDBN} to accurately keep track of which overlays
9401 are in program memory, and update any breakpoints that may be set
9402 in overlays. This will allow breakpoints to work even if the
9403 overlays are kept in ROM or other non-writable memory while they
9404 are not being executed.
9406 @node Overlay Sample Program
9407 @section Overlay Sample Program
9408 @cindex overlay example program
9410 When linking a program which uses overlays, you must place the overlays
9411 at their load addresses, while relocating them to run at their mapped
9412 addresses. To do this, you must write a linker script (@pxref{Overlay
9413 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9414 since linker scripts are specific to a particular host system, target
9415 architecture, and target memory layout, this manual cannot provide
9416 portable sample code demonstrating @value{GDBN}'s overlay support.
9418 However, the @value{GDBN} source distribution does contain an overlaid
9419 program, with linker scripts for a few systems, as part of its test
9420 suite. The program consists of the following files from
9421 @file{gdb/testsuite/gdb.base}:
9425 The main program file.
9427 A simple overlay manager, used by @file{overlays.c}.
9432 Overlay modules, loaded and used by @file{overlays.c}.
9435 Linker scripts for linking the test program on the @code{d10v-elf}
9436 and @code{m32r-elf} targets.
9439 You can build the test program using the @code{d10v-elf} GCC
9440 cross-compiler like this:
9443 $ d10v-elf-gcc -g -c overlays.c
9444 $ d10v-elf-gcc -g -c ovlymgr.c
9445 $ d10v-elf-gcc -g -c foo.c
9446 $ d10v-elf-gcc -g -c bar.c
9447 $ d10v-elf-gcc -g -c baz.c
9448 $ d10v-elf-gcc -g -c grbx.c
9449 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9450 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9453 The build process is identical for any other architecture, except that
9454 you must substitute the appropriate compiler and linker script for the
9455 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9459 @chapter Using @value{GDBN} with Different Languages
9462 Although programming languages generally have common aspects, they are
9463 rarely expressed in the same manner. For instance, in ANSI C,
9464 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9465 Modula-2, it is accomplished by @code{p^}. Values can also be
9466 represented (and displayed) differently. Hex numbers in C appear as
9467 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9469 @cindex working language
9470 Language-specific information is built into @value{GDBN} for some languages,
9471 allowing you to express operations like the above in your program's
9472 native language, and allowing @value{GDBN} to output values in a manner
9473 consistent with the syntax of your program's native language. The
9474 language you use to build expressions is called the @dfn{working
9478 * Setting:: Switching between source languages
9479 * Show:: Displaying the language
9480 * Checks:: Type and range checks
9481 * Supported Languages:: Supported languages
9482 * Unsupported Languages:: Unsupported languages
9486 @section Switching Between Source Languages
9488 There are two ways to control the working language---either have @value{GDBN}
9489 set it automatically, or select it manually yourself. You can use the
9490 @code{set language} command for either purpose. On startup, @value{GDBN}
9491 defaults to setting the language automatically. The working language is
9492 used to determine how expressions you type are interpreted, how values
9495 In addition to the working language, every source file that
9496 @value{GDBN} knows about has its own working language. For some object
9497 file formats, the compiler might indicate which language a particular
9498 source file is in. However, most of the time @value{GDBN} infers the
9499 language from the name of the file. The language of a source file
9500 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9501 show each frame appropriately for its own language. There is no way to
9502 set the language of a source file from within @value{GDBN}, but you can
9503 set the language associated with a filename extension. @xref{Show, ,
9504 Displaying the Language}.
9506 This is most commonly a problem when you use a program, such
9507 as @code{cfront} or @code{f2c}, that generates C but is written in
9508 another language. In that case, make the
9509 program use @code{#line} directives in its C output; that way
9510 @value{GDBN} will know the correct language of the source code of the original
9511 program, and will display that source code, not the generated C code.
9514 * Filenames:: Filename extensions and languages.
9515 * Manually:: Setting the working language manually
9516 * Automatically:: Having @value{GDBN} infer the source language
9520 @subsection List of Filename Extensions and Languages
9522 If a source file name ends in one of the following extensions, then
9523 @value{GDBN} infers that its language is the one indicated.
9544 Objective-C source file
9551 Modula-2 source file
9555 Assembler source file. This actually behaves almost like C, but
9556 @value{GDBN} does not skip over function prologues when stepping.
9559 In addition, you may set the language associated with a filename
9560 extension. @xref{Show, , Displaying the Language}.
9563 @subsection Setting the Working Language
9565 If you allow @value{GDBN} to set the language automatically,
9566 expressions are interpreted the same way in your debugging session and
9569 @kindex set language
9570 If you wish, you may set the language manually. To do this, issue the
9571 command @samp{set language @var{lang}}, where @var{lang} is the name of
9573 @code{c} or @code{modula-2}.
9574 For a list of the supported languages, type @samp{set language}.
9576 Setting the language manually prevents @value{GDBN} from updating the working
9577 language automatically. This can lead to confusion if you try
9578 to debug a program when the working language is not the same as the
9579 source language, when an expression is acceptable to both
9580 languages---but means different things. For instance, if the current
9581 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9589 might not have the effect you intended. In C, this means to add
9590 @code{b} and @code{c} and place the result in @code{a}. The result
9591 printed would be the value of @code{a}. In Modula-2, this means to compare
9592 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9595 @subsection Having @value{GDBN} Infer the Source Language
9597 To have @value{GDBN} set the working language automatically, use
9598 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9599 then infers the working language. That is, when your program stops in a
9600 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9601 working language to the language recorded for the function in that
9602 frame. If the language for a frame is unknown (that is, if the function
9603 or block corresponding to the frame was defined in a source file that
9604 does not have a recognized extension), the current working language is
9605 not changed, and @value{GDBN} issues a warning.
9607 This may not seem necessary for most programs, which are written
9608 entirely in one source language. However, program modules and libraries
9609 written in one source language can be used by a main program written in
9610 a different source language. Using @samp{set language auto} in this
9611 case frees you from having to set the working language manually.
9614 @section Displaying the Language
9616 The following commands help you find out which language is the
9617 working language, and also what language source files were written in.
9621 @kindex show language
9622 Display the current working language. This is the
9623 language you can use with commands such as @code{print} to
9624 build and compute expressions that may involve variables in your program.
9627 @kindex info frame@r{, show the source language}
9628 Display the source language for this frame. This language becomes the
9629 working language if you use an identifier from this frame.
9630 @xref{Frame Info, ,Information about a Frame}, to identify the other
9631 information listed here.
9634 @kindex info source@r{, show the source language}
9635 Display the source language of this source file.
9636 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9637 information listed here.
9640 In unusual circumstances, you may have source files with extensions
9641 not in the standard list. You can then set the extension associated
9642 with a language explicitly:
9645 @item set extension-language @var{ext} @var{language}
9646 @kindex set extension-language
9647 Tell @value{GDBN} that source files with extension @var{ext} are to be
9648 assumed as written in the source language @var{language}.
9650 @item info extensions
9651 @kindex info extensions
9652 List all the filename extensions and the associated languages.
9656 @section Type and Range Checking
9659 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9660 checking are included, but they do not yet have any effect. This
9661 section documents the intended facilities.
9663 @c FIXME remove warning when type/range code added
9665 Some languages are designed to guard you against making seemingly common
9666 errors through a series of compile- and run-time checks. These include
9667 checking the type of arguments to functions and operators, and making
9668 sure mathematical overflows are caught at run time. Checks such as
9669 these help to ensure a program's correctness once it has been compiled
9670 by eliminating type mismatches, and providing active checks for range
9671 errors when your program is running.
9673 @value{GDBN} can check for conditions like the above if you wish.
9674 Although @value{GDBN} does not check the statements in your program,
9675 it can check expressions entered directly into @value{GDBN} for
9676 evaluation via the @code{print} command, for example. As with the
9677 working language, @value{GDBN} can also decide whether or not to check
9678 automatically based on your program's source language.
9679 @xref{Supported Languages, ,Supported Languages}, for the default
9680 settings of supported languages.
9683 * Type Checking:: An overview of type checking
9684 * Range Checking:: An overview of range checking
9687 @cindex type checking
9688 @cindex checks, type
9690 @subsection An Overview of Type Checking
9692 Some languages, such as Modula-2, are strongly typed, meaning that the
9693 arguments to operators and functions have to be of the correct type,
9694 otherwise an error occurs. These checks prevent type mismatch
9695 errors from ever causing any run-time problems. For example,
9703 The second example fails because the @code{CARDINAL} 1 is not
9704 type-compatible with the @code{REAL} 2.3.
9706 For the expressions you use in @value{GDBN} commands, you can tell the
9707 @value{GDBN} type checker to skip checking;
9708 to treat any mismatches as errors and abandon the expression;
9709 or to only issue warnings when type mismatches occur,
9710 but evaluate the expression anyway. When you choose the last of
9711 these, @value{GDBN} evaluates expressions like the second example above, but
9712 also issues a warning.
9714 Even if you turn type checking off, there may be other reasons
9715 related to type that prevent @value{GDBN} from evaluating an expression.
9716 For instance, @value{GDBN} does not know how to add an @code{int} and
9717 a @code{struct foo}. These particular type errors have nothing to do
9718 with the language in use, and usually arise from expressions, such as
9719 the one described above, which make little sense to evaluate anyway.
9721 Each language defines to what degree it is strict about type. For
9722 instance, both Modula-2 and C require the arguments to arithmetical
9723 operators to be numbers. In C, enumerated types and pointers can be
9724 represented as numbers, so that they are valid arguments to mathematical
9725 operators. @xref{Supported Languages, ,Supported Languages}, for further
9726 details on specific languages.
9728 @value{GDBN} provides some additional commands for controlling the type checker:
9730 @kindex set check type
9731 @kindex show check type
9733 @item set check type auto
9734 Set type checking on or off based on the current working language.
9735 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9738 @item set check type on
9739 @itemx set check type off
9740 Set type checking on or off, overriding the default setting for the
9741 current working language. Issue a warning if the setting does not
9742 match the language default. If any type mismatches occur in
9743 evaluating an expression while type checking is on, @value{GDBN} prints a
9744 message and aborts evaluation of the expression.
9746 @item set check type warn
9747 Cause the type checker to issue warnings, but to always attempt to
9748 evaluate the expression. Evaluating the expression may still
9749 be impossible for other reasons. For example, @value{GDBN} cannot add
9750 numbers and structures.
9753 Show the current setting of the type checker, and whether or not @value{GDBN}
9754 is setting it automatically.
9757 @cindex range checking
9758 @cindex checks, range
9759 @node Range Checking
9760 @subsection An Overview of Range Checking
9762 In some languages (such as Modula-2), it is an error to exceed the
9763 bounds of a type; this is enforced with run-time checks. Such range
9764 checking is meant to ensure program correctness by making sure
9765 computations do not overflow, or indices on an array element access do
9766 not exceed the bounds of the array.
9768 For expressions you use in @value{GDBN} commands, you can tell
9769 @value{GDBN} to treat range errors in one of three ways: ignore them,
9770 always treat them as errors and abandon the expression, or issue
9771 warnings but evaluate the expression anyway.
9773 A range error can result from numerical overflow, from exceeding an
9774 array index bound, or when you type a constant that is not a member
9775 of any type. Some languages, however, do not treat overflows as an
9776 error. In many implementations of C, mathematical overflow causes the
9777 result to ``wrap around'' to lower values---for example, if @var{m} is
9778 the largest integer value, and @var{s} is the smallest, then
9781 @var{m} + 1 @result{} @var{s}
9784 This, too, is specific to individual languages, and in some cases
9785 specific to individual compilers or machines. @xref{Supported Languages, ,
9786 Supported Languages}, for further details on specific languages.
9788 @value{GDBN} provides some additional commands for controlling the range checker:
9790 @kindex set check range
9791 @kindex show check range
9793 @item set check range auto
9794 Set range checking on or off based on the current working language.
9795 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9798 @item set check range on
9799 @itemx set check range off
9800 Set range checking on or off, overriding the default setting for the
9801 current working language. A warning is issued if the setting does not
9802 match the language default. If a range error occurs and range checking is on,
9803 then a message is printed and evaluation of the expression is aborted.
9805 @item set check range warn
9806 Output messages when the @value{GDBN} range checker detects a range error,
9807 but attempt to evaluate the expression anyway. Evaluating the
9808 expression may still be impossible for other reasons, such as accessing
9809 memory that the process does not own (a typical example from many Unix
9813 Show the current setting of the range checker, and whether or not it is
9814 being set automatically by @value{GDBN}.
9817 @node Supported Languages
9818 @section Supported Languages
9820 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9821 assembly, Modula-2, and Ada.
9822 @c This is false ...
9823 Some @value{GDBN} features may be used in expressions regardless of the
9824 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9825 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9826 ,Expressions}) can be used with the constructs of any supported
9829 The following sections detail to what degree each source language is
9830 supported by @value{GDBN}. These sections are not meant to be language
9831 tutorials or references, but serve only as a reference guide to what the
9832 @value{GDBN} expression parser accepts, and what input and output
9833 formats should look like for different languages. There are many good
9834 books written on each of these languages; please look to these for a
9835 language reference or tutorial.
9839 * Objective-C:: Objective-C
9842 * Modula-2:: Modula-2
9847 @subsection C and C@t{++}
9849 @cindex C and C@t{++}
9850 @cindex expressions in C or C@t{++}
9852 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9853 to both languages. Whenever this is the case, we discuss those languages
9857 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9858 @cindex @sc{gnu} C@t{++}
9859 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9860 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9861 effectively, you must compile your C@t{++} programs with a supported
9862 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9863 compiler (@code{aCC}).
9865 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9866 format; if it doesn't work on your system, try the stabs+ debugging
9867 format. You can select those formats explicitly with the @code{g++}
9868 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9869 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9870 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9873 * C Operators:: C and C@t{++} operators
9874 * C Constants:: C and C@t{++} constants
9875 * C Plus Plus Expressions:: C@t{++} expressions
9876 * C Defaults:: Default settings for C and C@t{++}
9877 * C Checks:: C and C@t{++} type and range checks
9878 * Debugging C:: @value{GDBN} and C
9879 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9880 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9884 @subsubsection C and C@t{++} Operators
9886 @cindex C and C@t{++} operators
9888 Operators must be defined on values of specific types. For instance,
9889 @code{+} is defined on numbers, but not on structures. Operators are
9890 often defined on groups of types.
9892 For the purposes of C and C@t{++}, the following definitions hold:
9897 @emph{Integral types} include @code{int} with any of its storage-class
9898 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9901 @emph{Floating-point types} include @code{float}, @code{double}, and
9902 @code{long double} (if supported by the target platform).
9905 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9908 @emph{Scalar types} include all of the above.
9913 The following operators are supported. They are listed here
9914 in order of increasing precedence:
9918 The comma or sequencing operator. Expressions in a comma-separated list
9919 are evaluated from left to right, with the result of the entire
9920 expression being the last expression evaluated.
9923 Assignment. The value of an assignment expression is the value
9924 assigned. Defined on scalar types.
9927 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9928 and translated to @w{@code{@var{a} = @var{a op b}}}.
9929 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9930 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9931 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9934 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9935 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9939 Logical @sc{or}. Defined on integral types.
9942 Logical @sc{and}. Defined on integral types.
9945 Bitwise @sc{or}. Defined on integral types.
9948 Bitwise exclusive-@sc{or}. Defined on integral types.
9951 Bitwise @sc{and}. Defined on integral types.
9954 Equality and inequality. Defined on scalar types. The value of these
9955 expressions is 0 for false and non-zero for true.
9957 @item <@r{, }>@r{, }<=@r{, }>=
9958 Less than, greater than, less than or equal, greater than or equal.
9959 Defined on scalar types. The value of these expressions is 0 for false
9960 and non-zero for true.
9963 left shift, and right shift. Defined on integral types.
9966 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9969 Addition and subtraction. Defined on integral types, floating-point types and
9972 @item *@r{, }/@r{, }%
9973 Multiplication, division, and modulus. Multiplication and division are
9974 defined on integral and floating-point types. Modulus is defined on
9978 Increment and decrement. When appearing before a variable, the
9979 operation is performed before the variable is used in an expression;
9980 when appearing after it, the variable's value is used before the
9981 operation takes place.
9984 Pointer dereferencing. Defined on pointer types. Same precedence as
9988 Address operator. Defined on variables. Same precedence as @code{++}.
9990 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9991 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9992 to examine the address
9993 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9997 Negative. Defined on integral and floating-point types. Same
9998 precedence as @code{++}.
10001 Logical negation. Defined on integral types. Same precedence as
10005 Bitwise complement operator. Defined on integral types. Same precedence as
10010 Structure member, and pointer-to-structure member. For convenience,
10011 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10012 pointer based on the stored type information.
10013 Defined on @code{struct} and @code{union} data.
10016 Dereferences of pointers to members.
10019 Array indexing. @code{@var{a}[@var{i}]} is defined as
10020 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10023 Function parameter list. Same precedence as @code{->}.
10026 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10027 and @code{class} types.
10030 Doubled colons also represent the @value{GDBN} scope operator
10031 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10035 If an operator is redefined in the user code, @value{GDBN} usually
10036 attempts to invoke the redefined version instead of using the operator's
10037 predefined meaning.
10040 @subsubsection C and C@t{++} Constants
10042 @cindex C and C@t{++} constants
10044 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10049 Integer constants are a sequence of digits. Octal constants are
10050 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10051 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10052 @samp{l}, specifying that the constant should be treated as a
10056 Floating point constants are a sequence of digits, followed by a decimal
10057 point, followed by a sequence of digits, and optionally followed by an
10058 exponent. An exponent is of the form:
10059 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10060 sequence of digits. The @samp{+} is optional for positive exponents.
10061 A floating-point constant may also end with a letter @samp{f} or
10062 @samp{F}, specifying that the constant should be treated as being of
10063 the @code{float} (as opposed to the default @code{double}) type; or with
10064 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10068 Enumerated constants consist of enumerated identifiers, or their
10069 integral equivalents.
10072 Character constants are a single character surrounded by single quotes
10073 (@code{'}), or a number---the ordinal value of the corresponding character
10074 (usually its @sc{ascii} value). Within quotes, the single character may
10075 be represented by a letter or by @dfn{escape sequences}, which are of
10076 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10077 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10078 @samp{@var{x}} is a predefined special character---for example,
10079 @samp{\n} for newline.
10082 String constants are a sequence of character constants surrounded by
10083 double quotes (@code{"}). Any valid character constant (as described
10084 above) may appear. Double quotes within the string must be preceded by
10085 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10089 Pointer constants are an integral value. You can also write pointers
10090 to constants using the C operator @samp{&}.
10093 Array constants are comma-separated lists surrounded by braces @samp{@{}
10094 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10095 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10096 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10099 @node C Plus Plus Expressions
10100 @subsubsection C@t{++} Expressions
10102 @cindex expressions in C@t{++}
10103 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10105 @cindex debugging C@t{++} programs
10106 @cindex C@t{++} compilers
10107 @cindex debug formats and C@t{++}
10108 @cindex @value{NGCC} and C@t{++}
10110 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10111 proper compiler and the proper debug format. Currently, @value{GDBN}
10112 works best when debugging C@t{++} code that is compiled with
10113 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10114 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10115 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10116 stabs+ as their default debug format, so you usually don't need to
10117 specify a debug format explicitly. Other compilers and/or debug formats
10118 are likely to work badly or not at all when using @value{GDBN} to debug
10124 @cindex member functions
10126 Member function calls are allowed; you can use expressions like
10129 count = aml->GetOriginal(x, y)
10132 @vindex this@r{, inside C@t{++} member functions}
10133 @cindex namespace in C@t{++}
10135 While a member function is active (in the selected stack frame), your
10136 expressions have the same namespace available as the member function;
10137 that is, @value{GDBN} allows implicit references to the class instance
10138 pointer @code{this} following the same rules as C@t{++}.
10140 @cindex call overloaded functions
10141 @cindex overloaded functions, calling
10142 @cindex type conversions in C@t{++}
10144 You can call overloaded functions; @value{GDBN} resolves the function
10145 call to the right definition, with some restrictions. @value{GDBN} does not
10146 perform overload resolution involving user-defined type conversions,
10147 calls to constructors, or instantiations of templates that do not exist
10148 in the program. It also cannot handle ellipsis argument lists or
10151 It does perform integral conversions and promotions, floating-point
10152 promotions, arithmetic conversions, pointer conversions, conversions of
10153 class objects to base classes, and standard conversions such as those of
10154 functions or arrays to pointers; it requires an exact match on the
10155 number of function arguments.
10157 Overload resolution is always performed, unless you have specified
10158 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10159 ,@value{GDBN} Features for C@t{++}}.
10161 You must specify @code{set overload-resolution off} in order to use an
10162 explicit function signature to call an overloaded function, as in
10164 p 'foo(char,int)'('x', 13)
10167 The @value{GDBN} command-completion facility can simplify this;
10168 see @ref{Completion, ,Command Completion}.
10170 @cindex reference declarations
10172 @value{GDBN} understands variables declared as C@t{++} references; you can use
10173 them in expressions just as you do in C@t{++} source---they are automatically
10176 In the parameter list shown when @value{GDBN} displays a frame, the values of
10177 reference variables are not displayed (unlike other variables); this
10178 avoids clutter, since references are often used for large structures.
10179 The @emph{address} of a reference variable is always shown, unless
10180 you have specified @samp{set print address off}.
10183 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10184 expressions can use it just as expressions in your program do. Since
10185 one scope may be defined in another, you can use @code{::} repeatedly if
10186 necessary, for example in an expression like
10187 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10188 resolving name scope by reference to source files, in both C and C@t{++}
10189 debugging (@pxref{Variables, ,Program Variables}).
10192 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10193 calling virtual functions correctly, printing out virtual bases of
10194 objects, calling functions in a base subobject, casting objects, and
10195 invoking user-defined operators.
10198 @subsubsection C and C@t{++} Defaults
10200 @cindex C and C@t{++} defaults
10202 If you allow @value{GDBN} to set type and range checking automatically, they
10203 both default to @code{off} whenever the working language changes to
10204 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10205 selects the working language.
10207 If you allow @value{GDBN} to set the language automatically, it
10208 recognizes source files whose names end with @file{.c}, @file{.C}, or
10209 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10210 these files, it sets the working language to C or C@t{++}.
10211 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10212 for further details.
10214 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10215 @c unimplemented. If (b) changes, it might make sense to let this node
10216 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10219 @subsubsection C and C@t{++} Type and Range Checks
10221 @cindex C and C@t{++} checks
10223 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10224 is not used. However, if you turn type checking on, @value{GDBN}
10225 considers two variables type equivalent if:
10229 The two variables are structured and have the same structure, union, or
10233 The two variables have the same type name, or types that have been
10234 declared equivalent through @code{typedef}.
10237 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10240 The two @code{struct}, @code{union}, or @code{enum} variables are
10241 declared in the same declaration. (Note: this may not be true for all C
10246 Range checking, if turned on, is done on mathematical operations. Array
10247 indices are not checked, since they are often used to index a pointer
10248 that is not itself an array.
10251 @subsubsection @value{GDBN} and C
10253 The @code{set print union} and @code{show print union} commands apply to
10254 the @code{union} type. When set to @samp{on}, any @code{union} that is
10255 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10256 appears as @samp{@{...@}}.
10258 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10259 with pointers and a memory allocation function. @xref{Expressions,
10262 @node Debugging C Plus Plus
10263 @subsubsection @value{GDBN} Features for C@t{++}
10265 @cindex commands for C@t{++}
10267 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10268 designed specifically for use with C@t{++}. Here is a summary:
10271 @cindex break in overloaded functions
10272 @item @r{breakpoint menus}
10273 When you want a breakpoint in a function whose name is overloaded,
10274 @value{GDBN} has the capability to display a menu of possible breakpoint
10275 locations to help you specify which function definition you want.
10276 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10278 @cindex overloading in C@t{++}
10279 @item rbreak @var{regex}
10280 Setting breakpoints using regular expressions is helpful for setting
10281 breakpoints on overloaded functions that are not members of any special
10283 @xref{Set Breaks, ,Setting Breakpoints}.
10285 @cindex C@t{++} exception handling
10288 Debug C@t{++} exception handling using these commands. @xref{Set
10289 Catchpoints, , Setting Catchpoints}.
10291 @cindex inheritance
10292 @item ptype @var{typename}
10293 Print inheritance relationships as well as other information for type
10295 @xref{Symbols, ,Examining the Symbol Table}.
10297 @cindex C@t{++} symbol display
10298 @item set print demangle
10299 @itemx show print demangle
10300 @itemx set print asm-demangle
10301 @itemx show print asm-demangle
10302 Control whether C@t{++} symbols display in their source form, both when
10303 displaying code as C@t{++} source and when displaying disassemblies.
10304 @xref{Print Settings, ,Print Settings}.
10306 @item set print object
10307 @itemx show print object
10308 Choose whether to print derived (actual) or declared types of objects.
10309 @xref{Print Settings, ,Print Settings}.
10311 @item set print vtbl
10312 @itemx show print vtbl
10313 Control the format for printing virtual function tables.
10314 @xref{Print Settings, ,Print Settings}.
10315 (The @code{vtbl} commands do not work on programs compiled with the HP
10316 ANSI C@t{++} compiler (@code{aCC}).)
10318 @kindex set overload-resolution
10319 @cindex overloaded functions, overload resolution
10320 @item set overload-resolution on
10321 Enable overload resolution for C@t{++} expression evaluation. The default
10322 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10323 and searches for a function whose signature matches the argument types,
10324 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10325 Expressions, ,C@t{++} Expressions}, for details).
10326 If it cannot find a match, it emits a message.
10328 @item set overload-resolution off
10329 Disable overload resolution for C@t{++} expression evaluation. For
10330 overloaded functions that are not class member functions, @value{GDBN}
10331 chooses the first function of the specified name that it finds in the
10332 symbol table, whether or not its arguments are of the correct type. For
10333 overloaded functions that are class member functions, @value{GDBN}
10334 searches for a function whose signature @emph{exactly} matches the
10337 @kindex show overload-resolution
10338 @item show overload-resolution
10339 Show the current setting of overload resolution.
10341 @item @r{Overloaded symbol names}
10342 You can specify a particular definition of an overloaded symbol, using
10343 the same notation that is used to declare such symbols in C@t{++}: type
10344 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10345 also use the @value{GDBN} command-line word completion facilities to list the
10346 available choices, or to finish the type list for you.
10347 @xref{Completion,, Command Completion}, for details on how to do this.
10350 @node Decimal Floating Point
10351 @subsubsection Decimal Floating Point format
10352 @cindex decimal floating point format
10354 @value{GDBN} can examine, set and perform computations with numbers in
10355 decimal floating point format, which in the C language correspond to the
10356 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
10357 specified by the extension to support decimal floating-point arithmetic.
10359 There are two encodings in use, depending on the architecture: BID (Binary
10360 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10361 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10364 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10365 to manipulate decimal floating point numbers, it is not possible to convert
10366 (using a cast, for example) integers wider than 32-bit to decimal float.
10368 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10369 point computations, error checking in decimal float operations ignores
10370 underflow, overflow and divide by zero exceptions.
10372 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10373 to inspect @code{_Decimal128} values stored in floating point registers. See
10374 @ref{PowerPC,,PowerPC} for more details.
10377 @subsection Objective-C
10379 @cindex Objective-C
10380 This section provides information about some commands and command
10381 options that are useful for debugging Objective-C code. See also
10382 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10383 few more commands specific to Objective-C support.
10386 * Method Names in Commands::
10387 * The Print Command with Objective-C::
10390 @node Method Names in Commands
10391 @subsubsection Method Names in Commands
10393 The following commands have been extended to accept Objective-C method
10394 names as line specifications:
10396 @kindex clear@r{, and Objective-C}
10397 @kindex break@r{, and Objective-C}
10398 @kindex info line@r{, and Objective-C}
10399 @kindex jump@r{, and Objective-C}
10400 @kindex list@r{, and Objective-C}
10404 @item @code{info line}
10409 A fully qualified Objective-C method name is specified as
10412 -[@var{Class} @var{methodName}]
10415 where the minus sign is used to indicate an instance method and a
10416 plus sign (not shown) is used to indicate a class method. The class
10417 name @var{Class} and method name @var{methodName} are enclosed in
10418 brackets, similar to the way messages are specified in Objective-C
10419 source code. For example, to set a breakpoint at the @code{create}
10420 instance method of class @code{Fruit} in the program currently being
10424 break -[Fruit create]
10427 To list ten program lines around the @code{initialize} class method,
10431 list +[NSText initialize]
10434 In the current version of @value{GDBN}, the plus or minus sign is
10435 required. In future versions of @value{GDBN}, the plus or minus
10436 sign will be optional, but you can use it to narrow the search. It
10437 is also possible to specify just a method name:
10443 You must specify the complete method name, including any colons. If
10444 your program's source files contain more than one @code{create} method,
10445 you'll be presented with a numbered list of classes that implement that
10446 method. Indicate your choice by number, or type @samp{0} to exit if
10449 As another example, to clear a breakpoint established at the
10450 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10453 clear -[NSWindow makeKeyAndOrderFront:]
10456 @node The Print Command with Objective-C
10457 @subsubsection The Print Command With Objective-C
10458 @cindex Objective-C, print objects
10459 @kindex print-object
10460 @kindex po @r{(@code{print-object})}
10462 The print command has also been extended to accept methods. For example:
10465 print -[@var{object} hash]
10468 @cindex print an Objective-C object description
10469 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10471 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10472 and print the result. Also, an additional command has been added,
10473 @code{print-object} or @code{po} for short, which is meant to print
10474 the description of an object. However, this command may only work
10475 with certain Objective-C libraries that have a particular hook
10476 function, @code{_NSPrintForDebugger}, defined.
10479 @subsection Fortran
10480 @cindex Fortran-specific support in @value{GDBN}
10482 @value{GDBN} can be used to debug programs written in Fortran, but it
10483 currently supports only the features of Fortran 77 language.
10485 @cindex trailing underscore, in Fortran symbols
10486 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10487 among them) append an underscore to the names of variables and
10488 functions. When you debug programs compiled by those compilers, you
10489 will need to refer to variables and functions with a trailing
10493 * Fortran Operators:: Fortran operators and expressions
10494 * Fortran Defaults:: Default settings for Fortran
10495 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10498 @node Fortran Operators
10499 @subsubsection Fortran Operators and Expressions
10501 @cindex Fortran operators and expressions
10503 Operators must be defined on values of specific types. For instance,
10504 @code{+} is defined on numbers, but not on characters or other non-
10505 arithmetic types. Operators are often defined on groups of types.
10509 The exponentiation operator. It raises the first operand to the power
10513 The range operator. Normally used in the form of array(low:high) to
10514 represent a section of array.
10517 The access component operator. Normally used to access elements in derived
10518 types. Also suitable for unions. As unions aren't part of regular Fortran,
10519 this can only happen when accessing a register that uses a gdbarch-defined
10523 @node Fortran Defaults
10524 @subsubsection Fortran Defaults
10526 @cindex Fortran Defaults
10528 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10529 default uses case-insensitive matches for Fortran symbols. You can
10530 change that with the @samp{set case-insensitive} command, see
10531 @ref{Symbols}, for the details.
10533 @node Special Fortran Commands
10534 @subsubsection Special Fortran Commands
10536 @cindex Special Fortran commands
10538 @value{GDBN} has some commands to support Fortran-specific features,
10539 such as displaying common blocks.
10542 @cindex @code{COMMON} blocks, Fortran
10543 @kindex info common
10544 @item info common @r{[}@var{common-name}@r{]}
10545 This command prints the values contained in the Fortran @code{COMMON}
10546 block whose name is @var{common-name}. With no argument, the names of
10547 all @code{COMMON} blocks visible at the current program location are
10554 @cindex Pascal support in @value{GDBN}, limitations
10555 Debugging Pascal programs which use sets, subranges, file variables, or
10556 nested functions does not currently work. @value{GDBN} does not support
10557 entering expressions, printing values, or similar features using Pascal
10560 The Pascal-specific command @code{set print pascal_static-members}
10561 controls whether static members of Pascal objects are displayed.
10562 @xref{Print Settings, pascal_static-members}.
10565 @subsection Modula-2
10567 @cindex Modula-2, @value{GDBN} support
10569 The extensions made to @value{GDBN} to support Modula-2 only support
10570 output from the @sc{gnu} Modula-2 compiler (which is currently being
10571 developed). Other Modula-2 compilers are not currently supported, and
10572 attempting to debug executables produced by them is most likely
10573 to give an error as @value{GDBN} reads in the executable's symbol
10576 @cindex expressions in Modula-2
10578 * M2 Operators:: Built-in operators
10579 * Built-In Func/Proc:: Built-in functions and procedures
10580 * M2 Constants:: Modula-2 constants
10581 * M2 Types:: Modula-2 types
10582 * M2 Defaults:: Default settings for Modula-2
10583 * Deviations:: Deviations from standard Modula-2
10584 * M2 Checks:: Modula-2 type and range checks
10585 * M2 Scope:: The scope operators @code{::} and @code{.}
10586 * GDB/M2:: @value{GDBN} and Modula-2
10590 @subsubsection Operators
10591 @cindex Modula-2 operators
10593 Operators must be defined on values of specific types. For instance,
10594 @code{+} is defined on numbers, but not on structures. Operators are
10595 often defined on groups of types. For the purposes of Modula-2, the
10596 following definitions hold:
10601 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10605 @emph{Character types} consist of @code{CHAR} and its subranges.
10608 @emph{Floating-point types} consist of @code{REAL}.
10611 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10615 @emph{Scalar types} consist of all of the above.
10618 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10621 @emph{Boolean types} consist of @code{BOOLEAN}.
10625 The following operators are supported, and appear in order of
10626 increasing precedence:
10630 Function argument or array index separator.
10633 Assignment. The value of @var{var} @code{:=} @var{value} is
10637 Less than, greater than on integral, floating-point, or enumerated
10641 Less than or equal to, greater than or equal to
10642 on integral, floating-point and enumerated types, or set inclusion on
10643 set types. Same precedence as @code{<}.
10645 @item =@r{, }<>@r{, }#
10646 Equality and two ways of expressing inequality, valid on scalar types.
10647 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10648 available for inequality, since @code{#} conflicts with the script
10652 Set membership. Defined on set types and the types of their members.
10653 Same precedence as @code{<}.
10656 Boolean disjunction. Defined on boolean types.
10659 Boolean conjunction. Defined on boolean types.
10662 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10665 Addition and subtraction on integral and floating-point types, or union
10666 and difference on set types.
10669 Multiplication on integral and floating-point types, or set intersection
10673 Division on floating-point types, or symmetric set difference on set
10674 types. Same precedence as @code{*}.
10677 Integer division and remainder. Defined on integral types. Same
10678 precedence as @code{*}.
10681 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10684 Pointer dereferencing. Defined on pointer types.
10687 Boolean negation. Defined on boolean types. Same precedence as
10691 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10692 precedence as @code{^}.
10695 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10698 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10702 @value{GDBN} and Modula-2 scope operators.
10706 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10707 treats the use of the operator @code{IN}, or the use of operators
10708 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10709 @code{<=}, and @code{>=} on sets as an error.
10713 @node Built-In Func/Proc
10714 @subsubsection Built-in Functions and Procedures
10715 @cindex Modula-2 built-ins
10717 Modula-2 also makes available several built-in procedures and functions.
10718 In describing these, the following metavariables are used:
10723 represents an @code{ARRAY} variable.
10726 represents a @code{CHAR} constant or variable.
10729 represents a variable or constant of integral type.
10732 represents an identifier that belongs to a set. Generally used in the
10733 same function with the metavariable @var{s}. The type of @var{s} should
10734 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10737 represents a variable or constant of integral or floating-point type.
10740 represents a variable or constant of floating-point type.
10746 represents a variable.
10749 represents a variable or constant of one of many types. See the
10750 explanation of the function for details.
10753 All Modula-2 built-in procedures also return a result, described below.
10757 Returns the absolute value of @var{n}.
10760 If @var{c} is a lower case letter, it returns its upper case
10761 equivalent, otherwise it returns its argument.
10764 Returns the character whose ordinal value is @var{i}.
10767 Decrements the value in the variable @var{v} by one. Returns the new value.
10769 @item DEC(@var{v},@var{i})
10770 Decrements the value in the variable @var{v} by @var{i}. Returns the
10773 @item EXCL(@var{m},@var{s})
10774 Removes the element @var{m} from the set @var{s}. Returns the new
10777 @item FLOAT(@var{i})
10778 Returns the floating point equivalent of the integer @var{i}.
10780 @item HIGH(@var{a})
10781 Returns the index of the last member of @var{a}.
10784 Increments the value in the variable @var{v} by one. Returns the new value.
10786 @item INC(@var{v},@var{i})
10787 Increments the value in the variable @var{v} by @var{i}. Returns the
10790 @item INCL(@var{m},@var{s})
10791 Adds the element @var{m} to the set @var{s} if it is not already
10792 there. Returns the new set.
10795 Returns the maximum value of the type @var{t}.
10798 Returns the minimum value of the type @var{t}.
10801 Returns boolean TRUE if @var{i} is an odd number.
10804 Returns the ordinal value of its argument. For example, the ordinal
10805 value of a character is its @sc{ascii} value (on machines supporting the
10806 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10807 integral, character and enumerated types.
10809 @item SIZE(@var{x})
10810 Returns the size of its argument. @var{x} can be a variable or a type.
10812 @item TRUNC(@var{r})
10813 Returns the integral part of @var{r}.
10815 @item TSIZE(@var{x})
10816 Returns the size of its argument. @var{x} can be a variable or a type.
10818 @item VAL(@var{t},@var{i})
10819 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10823 @emph{Warning:} Sets and their operations are not yet supported, so
10824 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10828 @cindex Modula-2 constants
10830 @subsubsection Constants
10832 @value{GDBN} allows you to express the constants of Modula-2 in the following
10838 Integer constants are simply a sequence of digits. When used in an
10839 expression, a constant is interpreted to be type-compatible with the
10840 rest of the expression. Hexadecimal integers are specified by a
10841 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10844 Floating point constants appear as a sequence of digits, followed by a
10845 decimal point and another sequence of digits. An optional exponent can
10846 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10847 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10848 digits of the floating point constant must be valid decimal (base 10)
10852 Character constants consist of a single character enclosed by a pair of
10853 like quotes, either single (@code{'}) or double (@code{"}). They may
10854 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10855 followed by a @samp{C}.
10858 String constants consist of a sequence of characters enclosed by a
10859 pair of like quotes, either single (@code{'}) or double (@code{"}).
10860 Escape sequences in the style of C are also allowed. @xref{C
10861 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10865 Enumerated constants consist of an enumerated identifier.
10868 Boolean constants consist of the identifiers @code{TRUE} and
10872 Pointer constants consist of integral values only.
10875 Set constants are not yet supported.
10879 @subsubsection Modula-2 Types
10880 @cindex Modula-2 types
10882 Currently @value{GDBN} can print the following data types in Modula-2
10883 syntax: array types, record types, set types, pointer types, procedure
10884 types, enumerated types, subrange types and base types. You can also
10885 print the contents of variables declared using these type.
10886 This section gives a number of simple source code examples together with
10887 sample @value{GDBN} sessions.
10889 The first example contains the following section of code:
10898 and you can request @value{GDBN} to interrogate the type and value of
10899 @code{r} and @code{s}.
10902 (@value{GDBP}) print s
10904 (@value{GDBP}) ptype s
10906 (@value{GDBP}) print r
10908 (@value{GDBP}) ptype r
10913 Likewise if your source code declares @code{s} as:
10917 s: SET ['A'..'Z'] ;
10921 then you may query the type of @code{s} by:
10924 (@value{GDBP}) ptype s
10925 type = SET ['A'..'Z']
10929 Note that at present you cannot interactively manipulate set
10930 expressions using the debugger.
10932 The following example shows how you might declare an array in Modula-2
10933 and how you can interact with @value{GDBN} to print its type and contents:
10937 s: ARRAY [-10..10] OF CHAR ;
10941 (@value{GDBP}) ptype s
10942 ARRAY [-10..10] OF CHAR
10945 Note that the array handling is not yet complete and although the type
10946 is printed correctly, expression handling still assumes that all
10947 arrays have a lower bound of zero and not @code{-10} as in the example
10950 Here are some more type related Modula-2 examples:
10954 colour = (blue, red, yellow, green) ;
10955 t = [blue..yellow] ;
10963 The @value{GDBN} interaction shows how you can query the data type
10964 and value of a variable.
10967 (@value{GDBP}) print s
10969 (@value{GDBP}) ptype t
10970 type = [blue..yellow]
10974 In this example a Modula-2 array is declared and its contents
10975 displayed. Observe that the contents are written in the same way as
10976 their @code{C} counterparts.
10980 s: ARRAY [1..5] OF CARDINAL ;
10986 (@value{GDBP}) print s
10987 $1 = @{1, 0, 0, 0, 0@}
10988 (@value{GDBP}) ptype s
10989 type = ARRAY [1..5] OF CARDINAL
10992 The Modula-2 language interface to @value{GDBN} also understands
10993 pointer types as shown in this example:
10997 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11004 and you can request that @value{GDBN} describes the type of @code{s}.
11007 (@value{GDBP}) ptype s
11008 type = POINTER TO ARRAY [1..5] OF CARDINAL
11011 @value{GDBN} handles compound types as we can see in this example.
11012 Here we combine array types, record types, pointer types and subrange
11023 myarray = ARRAY myrange OF CARDINAL ;
11024 myrange = [-2..2] ;
11026 s: POINTER TO ARRAY myrange OF foo ;
11030 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11034 (@value{GDBP}) ptype s
11035 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11038 f3 : ARRAY [-2..2] OF CARDINAL;
11043 @subsubsection Modula-2 Defaults
11044 @cindex Modula-2 defaults
11046 If type and range checking are set automatically by @value{GDBN}, they
11047 both default to @code{on} whenever the working language changes to
11048 Modula-2. This happens regardless of whether you or @value{GDBN}
11049 selected the working language.
11051 If you allow @value{GDBN} to set the language automatically, then entering
11052 code compiled from a file whose name ends with @file{.mod} sets the
11053 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11054 Infer the Source Language}, for further details.
11057 @subsubsection Deviations from Standard Modula-2
11058 @cindex Modula-2, deviations from
11060 A few changes have been made to make Modula-2 programs easier to debug.
11061 This is done primarily via loosening its type strictness:
11065 Unlike in standard Modula-2, pointer constants can be formed by
11066 integers. This allows you to modify pointer variables during
11067 debugging. (In standard Modula-2, the actual address contained in a
11068 pointer variable is hidden from you; it can only be modified
11069 through direct assignment to another pointer variable or expression that
11070 returned a pointer.)
11073 C escape sequences can be used in strings and characters to represent
11074 non-printable characters. @value{GDBN} prints out strings with these
11075 escape sequences embedded. Single non-printable characters are
11076 printed using the @samp{CHR(@var{nnn})} format.
11079 The assignment operator (@code{:=}) returns the value of its right-hand
11083 All built-in procedures both modify @emph{and} return their argument.
11087 @subsubsection Modula-2 Type and Range Checks
11088 @cindex Modula-2 checks
11091 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11094 @c FIXME remove warning when type/range checks added
11096 @value{GDBN} considers two Modula-2 variables type equivalent if:
11100 They are of types that have been declared equivalent via a @code{TYPE
11101 @var{t1} = @var{t2}} statement
11104 They have been declared on the same line. (Note: This is true of the
11105 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11108 As long as type checking is enabled, any attempt to combine variables
11109 whose types are not equivalent is an error.
11111 Range checking is done on all mathematical operations, assignment, array
11112 index bounds, and all built-in functions and procedures.
11115 @subsubsection The Scope Operators @code{::} and @code{.}
11117 @cindex @code{.}, Modula-2 scope operator
11118 @cindex colon, doubled as scope operator
11120 @vindex colon-colon@r{, in Modula-2}
11121 @c Info cannot handle :: but TeX can.
11124 @vindex ::@r{, in Modula-2}
11127 There are a few subtle differences between the Modula-2 scope operator
11128 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11133 @var{module} . @var{id}
11134 @var{scope} :: @var{id}
11138 where @var{scope} is the name of a module or a procedure,
11139 @var{module} the name of a module, and @var{id} is any declared
11140 identifier within your program, except another module.
11142 Using the @code{::} operator makes @value{GDBN} search the scope
11143 specified by @var{scope} for the identifier @var{id}. If it is not
11144 found in the specified scope, then @value{GDBN} searches all scopes
11145 enclosing the one specified by @var{scope}.
11147 Using the @code{.} operator makes @value{GDBN} search the current scope for
11148 the identifier specified by @var{id} that was imported from the
11149 definition module specified by @var{module}. With this operator, it is
11150 an error if the identifier @var{id} was not imported from definition
11151 module @var{module}, or if @var{id} is not an identifier in
11155 @subsubsection @value{GDBN} and Modula-2
11157 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11158 Five subcommands of @code{set print} and @code{show print} apply
11159 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11160 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11161 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11162 analogue in Modula-2.
11164 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11165 with any language, is not useful with Modula-2. Its
11166 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11167 created in Modula-2 as they can in C or C@t{++}. However, because an
11168 address can be specified by an integral constant, the construct
11169 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11171 @cindex @code{#} in Modula-2
11172 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11173 interpreted as the beginning of a comment. Use @code{<>} instead.
11179 The extensions made to @value{GDBN} for Ada only support
11180 output from the @sc{gnu} Ada (GNAT) compiler.
11181 Other Ada compilers are not currently supported, and
11182 attempting to debug executables produced by them is most likely
11186 @cindex expressions in Ada
11188 * Ada Mode Intro:: General remarks on the Ada syntax
11189 and semantics supported by Ada mode
11191 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11192 * Additions to Ada:: Extensions of the Ada expression syntax.
11193 * Stopping Before Main Program:: Debugging the program during elaboration.
11194 * Ada Tasks:: Listing and setting breakpoints in tasks.
11195 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
11196 * Ada Glitches:: Known peculiarities of Ada mode.
11199 @node Ada Mode Intro
11200 @subsubsection Introduction
11201 @cindex Ada mode, general
11203 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11204 syntax, with some extensions.
11205 The philosophy behind the design of this subset is
11209 That @value{GDBN} should provide basic literals and access to operations for
11210 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11211 leaving more sophisticated computations to subprograms written into the
11212 program (which therefore may be called from @value{GDBN}).
11215 That type safety and strict adherence to Ada language restrictions
11216 are not particularly important to the @value{GDBN} user.
11219 That brevity is important to the @value{GDBN} user.
11222 Thus, for brevity, the debugger acts as if all names declared in
11223 user-written packages are directly visible, even if they are not visible
11224 according to Ada rules, thus making it unnecessary to fully qualify most
11225 names with their packages, regardless of context. Where this causes
11226 ambiguity, @value{GDBN} asks the user's intent.
11228 The debugger will start in Ada mode if it detects an Ada main program.
11229 As for other languages, it will enter Ada mode when stopped in a program that
11230 was translated from an Ada source file.
11232 While in Ada mode, you may use `@t{--}' for comments. This is useful
11233 mostly for documenting command files. The standard @value{GDBN} comment
11234 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11235 middle (to allow based literals).
11237 The debugger supports limited overloading. Given a subprogram call in which
11238 the function symbol has multiple definitions, it will use the number of
11239 actual parameters and some information about their types to attempt to narrow
11240 the set of definitions. It also makes very limited use of context, preferring
11241 procedures to functions in the context of the @code{call} command, and
11242 functions to procedures elsewhere.
11244 @node Omissions from Ada
11245 @subsubsection Omissions from Ada
11246 @cindex Ada, omissions from
11248 Here are the notable omissions from the subset:
11252 Only a subset of the attributes are supported:
11256 @t{'First}, @t{'Last}, and @t{'Length}
11257 on array objects (not on types and subtypes).
11260 @t{'Min} and @t{'Max}.
11263 @t{'Pos} and @t{'Val}.
11269 @t{'Range} on array objects (not subtypes), but only as the right
11270 operand of the membership (@code{in}) operator.
11273 @t{'Access}, @t{'Unchecked_Access}, and
11274 @t{'Unrestricted_Access} (a GNAT extension).
11282 @code{Characters.Latin_1} are not available and
11283 concatenation is not implemented. Thus, escape characters in strings are
11284 not currently available.
11287 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11288 equality of representations. They will generally work correctly
11289 for strings and arrays whose elements have integer or enumeration types.
11290 They may not work correctly for arrays whose element
11291 types have user-defined equality, for arrays of real values
11292 (in particular, IEEE-conformant floating point, because of negative
11293 zeroes and NaNs), and for arrays whose elements contain unused bits with
11294 indeterminate values.
11297 The other component-by-component array operations (@code{and}, @code{or},
11298 @code{xor}, @code{not}, and relational tests other than equality)
11299 are not implemented.
11302 @cindex array aggregates (Ada)
11303 @cindex record aggregates (Ada)
11304 @cindex aggregates (Ada)
11305 There is limited support for array and record aggregates. They are
11306 permitted only on the right sides of assignments, as in these examples:
11309 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
11310 (@value{GDBP}) set An_Array := (1, others => 0)
11311 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11312 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11313 (@value{GDBP}) set A_Record := (1, "Peter", True);
11314 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
11318 discriminant's value by assigning an aggregate has an
11319 undefined effect if that discriminant is used within the record.
11320 However, you can first modify discriminants by directly assigning to
11321 them (which normally would not be allowed in Ada), and then performing an
11322 aggregate assignment. For example, given a variable @code{A_Rec}
11323 declared to have a type such as:
11326 type Rec (Len : Small_Integer := 0) is record
11328 Vals : IntArray (1 .. Len);
11332 you can assign a value with a different size of @code{Vals} with two
11336 (@value{GDBP}) set A_Rec.Len := 4
11337 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11340 As this example also illustrates, @value{GDBN} is very loose about the usual
11341 rules concerning aggregates. You may leave out some of the
11342 components of an array or record aggregate (such as the @code{Len}
11343 component in the assignment to @code{A_Rec} above); they will retain their
11344 original values upon assignment. You may freely use dynamic values as
11345 indices in component associations. You may even use overlapping or
11346 redundant component associations, although which component values are
11347 assigned in such cases is not defined.
11350 Calls to dispatching subprograms are not implemented.
11353 The overloading algorithm is much more limited (i.e., less selective)
11354 than that of real Ada. It makes only limited use of the context in
11355 which a subexpression appears to resolve its meaning, and it is much
11356 looser in its rules for allowing type matches. As a result, some
11357 function calls will be ambiguous, and the user will be asked to choose
11358 the proper resolution.
11361 The @code{new} operator is not implemented.
11364 Entry calls are not implemented.
11367 Aside from printing, arithmetic operations on the native VAX floating-point
11368 formats are not supported.
11371 It is not possible to slice a packed array.
11374 The names @code{True} and @code{False}, when not part of a qualified name,
11375 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
11377 Should your program
11378 redefine these names in a package or procedure (at best a dubious practice),
11379 you will have to use fully qualified names to access their new definitions.
11382 @node Additions to Ada
11383 @subsubsection Additions to Ada
11384 @cindex Ada, deviations from
11386 As it does for other languages, @value{GDBN} makes certain generic
11387 extensions to Ada (@pxref{Expressions}):
11391 If the expression @var{E} is a variable residing in memory (typically
11392 a local variable or array element) and @var{N} is a positive integer,
11393 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11394 @var{N}-1 adjacent variables following it in memory as an array. In
11395 Ada, this operator is generally not necessary, since its prime use is
11396 in displaying parts of an array, and slicing will usually do this in
11397 Ada. However, there are occasional uses when debugging programs in
11398 which certain debugging information has been optimized away.
11401 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11402 appears in function or file @var{B}.'' When @var{B} is a file name,
11403 you must typically surround it in single quotes.
11406 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11407 @var{type} that appears at address @var{addr}.''
11410 A name starting with @samp{$} is a convenience variable
11411 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11414 In addition, @value{GDBN} provides a few other shortcuts and outright
11415 additions specific to Ada:
11419 The assignment statement is allowed as an expression, returning
11420 its right-hand operand as its value. Thus, you may enter
11423 (@value{GDBP}) set x := y + 3
11424 (@value{GDBP}) print A(tmp := y + 1)
11428 The semicolon is allowed as an ``operator,'' returning as its value
11429 the value of its right-hand operand.
11430 This allows, for example,
11431 complex conditional breaks:
11434 (@value{GDBP}) break f
11435 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
11439 Rather than use catenation and symbolic character names to introduce special
11440 characters into strings, one may instead use a special bracket notation,
11441 which is also used to print strings. A sequence of characters of the form
11442 @samp{["@var{XX}"]} within a string or character literal denotes the
11443 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11444 sequence of characters @samp{["""]} also denotes a single quotation mark
11445 in strings. For example,
11447 "One line.["0a"]Next line.["0a"]"
11450 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11454 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11455 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11459 (@value{GDBP}) print 'max(x, y)
11463 When printing arrays, @value{GDBN} uses positional notation when the
11464 array has a lower bound of 1, and uses a modified named notation otherwise.
11465 For example, a one-dimensional array of three integers with a lower bound
11466 of 3 might print as
11473 That is, in contrast to valid Ada, only the first component has a @code{=>}
11477 You may abbreviate attributes in expressions with any unique,
11478 multi-character subsequence of
11479 their names (an exact match gets preference).
11480 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11481 in place of @t{a'length}.
11484 @cindex quoting Ada internal identifiers
11485 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11486 to lower case. The GNAT compiler uses upper-case characters for
11487 some of its internal identifiers, which are normally of no interest to users.
11488 For the rare occasions when you actually have to look at them,
11489 enclose them in angle brackets to avoid the lower-case mapping.
11492 (@value{GDBP}) print <JMPBUF_SAVE>[0]
11496 Printing an object of class-wide type or dereferencing an
11497 access-to-class-wide value will display all the components of the object's
11498 specific type (as indicated by its run-time tag). Likewise, component
11499 selection on such a value will operate on the specific type of the
11504 @node Stopping Before Main Program
11505 @subsubsection Stopping at the Very Beginning
11507 @cindex breakpointing Ada elaboration code
11508 It is sometimes necessary to debug the program during elaboration, and
11509 before reaching the main procedure.
11510 As defined in the Ada Reference
11511 Manual, the elaboration code is invoked from a procedure called
11512 @code{adainit}. To run your program up to the beginning of
11513 elaboration, simply use the following two commands:
11514 @code{tbreak adainit} and @code{run}.
11517 @subsubsection Extensions for Ada Tasks
11518 @cindex Ada, tasking
11520 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
11521 @value{GDBN} provides the following task-related commands:
11526 This command shows a list of current Ada tasks, as in the following example:
11533 (@value{GDBP}) info tasks
11534 ID TID P-ID Pri State Name
11535 1 8088000 0 15 Child Activation Wait main_task
11536 2 80a4000 1 15 Accept Statement b
11537 3 809a800 1 15 Child Activation Wait a
11538 * 4 80ae800 3 15 Running c
11543 In this listing, the asterisk before the last task indicates it to be the
11544 task currently being inspected.
11548 Represents @value{GDBN}'s internal task number.
11554 The parent's task ID (@value{GDBN}'s internal task number).
11557 The base priority of the task.
11560 Current state of the task.
11564 The task has been created but has not been activated. It cannot be
11568 The task currently running.
11571 The task is not blocked for any reason known to Ada. (It may be waiting
11572 for a mutex, though.) It is conceptually "executing" in normal mode.
11575 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
11576 that were waiting on terminate alternatives have been awakened and have
11577 terminated themselves.
11579 @item Child Activation Wait
11580 The task is waiting for created tasks to complete activation.
11582 @item Accept Statement
11583 The task is waiting on an accept or selective wait statement.
11585 @item Waiting on entry call
11586 The task is waiting on an entry call.
11588 @item Async Select Wait
11589 The task is waiting to start the abortable part of an asynchronous
11593 The task is waiting on a select statement with only a delay
11596 @item Child Termination Wait
11597 The task is sleeping having completed a master within itself, and is
11598 waiting for the tasks dependent on that master to become terminated or
11599 waiting on a terminate Phase.
11601 @item Wait Child in Term Alt
11602 The task is sleeping waiting for tasks on terminate alternatives to
11603 finish terminating.
11605 @item Accepting RV with @var{taskno}
11606 The task is accepting a rendez-vous with the task @var{taskno}.
11610 Name of the task in the program.
11614 @kindex info task @var{taskno}
11615 @item info task @var{taskno}
11616 This command shows detailled informations on the specified task, as in
11617 the following example:
11622 (@value{GDBP}) info tasks
11623 ID TID P-ID Pri State Name
11624 1 8077880 0 15 Child Activation Wait main_task
11625 * 2 807c468 1 15 Running task_1
11626 (@value{GDBP}) info task 2
11627 Ada Task: 0x807c468
11630 Parent: 1 (main_task)
11636 @kindex task@r{ (Ada)}
11637 @cindex current Ada task ID
11638 This command prints the ID of the current task.
11644 (@value{GDBP}) info tasks
11645 ID TID P-ID Pri State Name
11646 1 8077870 0 15 Child Activation Wait main_task
11647 * 2 807c458 1 15 Running t
11648 (@value{GDBP}) task
11649 [Current task is 2]
11652 @item task @var{taskno}
11653 @cindex Ada task switching
11654 This command is like the @code{thread @var{threadno}}
11655 command (@pxref{Threads}). It switches the context of debugging
11656 from the current task to the given task.
11662 (@value{GDBP}) info tasks
11663 ID TID P-ID Pri State Name
11664 1 8077870 0 15 Child Activation Wait main_task
11665 * 2 807c458 1 15 Running t
11666 (@value{GDBP}) task 1
11667 [Switching to task 1]
11668 #0 0x8067726 in pthread_cond_wait ()
11670 #0 0x8067726 in pthread_cond_wait ()
11671 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
11672 #2 0x805cb63 in system.task_primitives.operations.sleep ()
11673 #3 0x806153e in system.tasking.stages.activate_tasks ()
11674 #4 0x804aacc in un () at un.adb:5
11679 @node Ada Tasks and Core Files
11680 @subsubsection Tasking Support when Debugging Core Files
11681 @cindex Ada tasking and core file debugging
11683 When inspecting a core file, as opposed to debugging a live program,
11684 tasking support may be limited or even unavailable, depending on
11685 the platform being used.
11686 For instance, on x86-linux, the list of tasks is available, but task
11687 switching is not supported. On Tru64, however, task switching will work
11690 On certain platforms, including Tru64, the debugger needs to perform some
11691 memory writes in order to provide Ada tasking support. When inspecting
11692 a core file, this means that the core file must be opened with read-write
11693 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
11694 Under these circumstances, you should make a backup copy of the core
11695 file before inspecting it with @value{GDBN}.
11698 @subsubsection Known Peculiarities of Ada Mode
11699 @cindex Ada, problems
11701 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11702 we know of several problems with and limitations of Ada mode in
11704 some of which will be fixed with planned future releases of the debugger
11705 and the GNU Ada compiler.
11709 Currently, the debugger
11710 has insufficient information to determine whether certain pointers represent
11711 pointers to objects or the objects themselves.
11712 Thus, the user may have to tack an extra @code{.all} after an expression
11713 to get it printed properly.
11716 Static constants that the compiler chooses not to materialize as objects in
11717 storage are invisible to the debugger.
11720 Named parameter associations in function argument lists are ignored (the
11721 argument lists are treated as positional).
11724 Many useful library packages are currently invisible to the debugger.
11727 Fixed-point arithmetic, conversions, input, and output is carried out using
11728 floating-point arithmetic, and may give results that only approximate those on
11732 The GNAT compiler never generates the prefix @code{Standard} for any of
11733 the standard symbols defined by the Ada language. @value{GDBN} knows about
11734 this: it will strip the prefix from names when you use it, and will never
11735 look for a name you have so qualified among local symbols, nor match against
11736 symbols in other packages or subprograms. If you have
11737 defined entities anywhere in your program other than parameters and
11738 local variables whose simple names match names in @code{Standard},
11739 GNAT's lack of qualification here can cause confusion. When this happens,
11740 you can usually resolve the confusion
11741 by qualifying the problematic names with package
11742 @code{Standard} explicitly.
11745 @node Unsupported Languages
11746 @section Unsupported Languages
11748 @cindex unsupported languages
11749 @cindex minimal language
11750 In addition to the other fully-supported programming languages,
11751 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11752 It does not represent a real programming language, but provides a set
11753 of capabilities close to what the C or assembly languages provide.
11754 This should allow most simple operations to be performed while debugging
11755 an application that uses a language currently not supported by @value{GDBN}.
11757 If the language is set to @code{auto}, @value{GDBN} will automatically
11758 select this language if the current frame corresponds to an unsupported
11762 @chapter Examining the Symbol Table
11764 The commands described in this chapter allow you to inquire about the
11765 symbols (names of variables, functions and types) defined in your
11766 program. This information is inherent in the text of your program and
11767 does not change as your program executes. @value{GDBN} finds it in your
11768 program's symbol table, in the file indicated when you started @value{GDBN}
11769 (@pxref{File Options, ,Choosing Files}), or by one of the
11770 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11772 @cindex symbol names
11773 @cindex names of symbols
11774 @cindex quoting names
11775 Occasionally, you may need to refer to symbols that contain unusual
11776 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11777 most frequent case is in referring to static variables in other
11778 source files (@pxref{Variables,,Program Variables}). File names
11779 are recorded in object files as debugging symbols, but @value{GDBN} would
11780 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11781 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11782 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11789 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11792 @cindex case-insensitive symbol names
11793 @cindex case sensitivity in symbol names
11794 @kindex set case-sensitive
11795 @item set case-sensitive on
11796 @itemx set case-sensitive off
11797 @itemx set case-sensitive auto
11798 Normally, when @value{GDBN} looks up symbols, it matches their names
11799 with case sensitivity determined by the current source language.
11800 Occasionally, you may wish to control that. The command @code{set
11801 case-sensitive} lets you do that by specifying @code{on} for
11802 case-sensitive matches or @code{off} for case-insensitive ones. If
11803 you specify @code{auto}, case sensitivity is reset to the default
11804 suitable for the source language. The default is case-sensitive
11805 matches for all languages except for Fortran, for which the default is
11806 case-insensitive matches.
11808 @kindex show case-sensitive
11809 @item show case-sensitive
11810 This command shows the current setting of case sensitivity for symbols
11813 @kindex info address
11814 @cindex address of a symbol
11815 @item info address @var{symbol}
11816 Describe where the data for @var{symbol} is stored. For a register
11817 variable, this says which register it is kept in. For a non-register
11818 local variable, this prints the stack-frame offset at which the variable
11821 Note the contrast with @samp{print &@var{symbol}}, which does not work
11822 at all for a register variable, and for a stack local variable prints
11823 the exact address of the current instantiation of the variable.
11825 @kindex info symbol
11826 @cindex symbol from address
11827 @cindex closest symbol and offset for an address
11828 @item info symbol @var{addr}
11829 Print the name of a symbol which is stored at the address @var{addr}.
11830 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11831 nearest symbol and an offset from it:
11834 (@value{GDBP}) info symbol 0x54320
11835 _initialize_vx + 396 in section .text
11839 This is the opposite of the @code{info address} command. You can use
11840 it to find out the name of a variable or a function given its address.
11842 For dynamically linked executables, the name of executable or shared
11843 library containing the symbol is also printed:
11846 (@value{GDBP}) info symbol 0x400225
11847 _start + 5 in section .text of /tmp/a.out
11848 (@value{GDBP}) info symbol 0x2aaaac2811cf
11849 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
11853 @item whatis [@var{arg}]
11854 Print the data type of @var{arg}, which can be either an expression or
11855 a data type. With no argument, print the data type of @code{$}, the
11856 last value in the value history. If @var{arg} is an expression, it is
11857 not actually evaluated, and any side-effecting operations (such as
11858 assignments or function calls) inside it do not take place. If
11859 @var{arg} is a type name, it may be the name of a type or typedef, or
11860 for C code it may have the form @samp{class @var{class-name}},
11861 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11862 @samp{enum @var{enum-tag}}.
11863 @xref{Expressions, ,Expressions}.
11866 @item ptype [@var{arg}]
11867 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11868 detailed description of the type, instead of just the name of the type.
11869 @xref{Expressions, ,Expressions}.
11871 For example, for this variable declaration:
11874 struct complex @{double real; double imag;@} v;
11878 the two commands give this output:
11882 (@value{GDBP}) whatis v
11883 type = struct complex
11884 (@value{GDBP}) ptype v
11885 type = struct complex @{
11893 As with @code{whatis}, using @code{ptype} without an argument refers to
11894 the type of @code{$}, the last value in the value history.
11896 @cindex incomplete type
11897 Sometimes, programs use opaque data types or incomplete specifications
11898 of complex data structure. If the debug information included in the
11899 program does not allow @value{GDBN} to display a full declaration of
11900 the data type, it will say @samp{<incomplete type>}. For example,
11901 given these declarations:
11905 struct foo *fooptr;
11909 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11912 (@value{GDBP}) ptype foo
11913 $1 = <incomplete type>
11917 ``Incomplete type'' is C terminology for data types that are not
11918 completely specified.
11921 @item info types @var{regexp}
11923 Print a brief description of all types whose names match the regular
11924 expression @var{regexp} (or all types in your program, if you supply
11925 no argument). Each complete typename is matched as though it were a
11926 complete line; thus, @samp{i type value} gives information on all
11927 types in your program whose names include the string @code{value}, but
11928 @samp{i type ^value$} gives information only on types whose complete
11929 name is @code{value}.
11931 This command differs from @code{ptype} in two ways: first, like
11932 @code{whatis}, it does not print a detailed description; second, it
11933 lists all source files where a type is defined.
11936 @cindex local variables
11937 @item info scope @var{location}
11938 List all the variables local to a particular scope. This command
11939 accepts a @var{location} argument---a function name, a source line, or
11940 an address preceded by a @samp{*}, and prints all the variables local
11941 to the scope defined by that location. (@xref{Specify Location}, for
11942 details about supported forms of @var{location}.) For example:
11945 (@value{GDBP}) @b{info scope command_line_handler}
11946 Scope for command_line_handler:
11947 Symbol rl is an argument at stack/frame offset 8, length 4.
11948 Symbol linebuffer is in static storage at address 0x150a18, length 4.
11949 Symbol linelength is in static storage at address 0x150a1c, length 4.
11950 Symbol p is a local variable in register $esi, length 4.
11951 Symbol p1 is a local variable in register $ebx, length 4.
11952 Symbol nline is a local variable in register $edx, length 4.
11953 Symbol repeat is a local variable at frame offset -8, length 4.
11957 This command is especially useful for determining what data to collect
11958 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11961 @kindex info source
11963 Show information about the current source file---that is, the source file for
11964 the function containing the current point of execution:
11967 the name of the source file, and the directory containing it,
11969 the directory it was compiled in,
11971 its length, in lines,
11973 which programming language it is written in,
11975 whether the executable includes debugging information for that file, and
11976 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11978 whether the debugging information includes information about
11979 preprocessor macros.
11983 @kindex info sources
11985 Print the names of all source files in your program for which there is
11986 debugging information, organized into two lists: files whose symbols
11987 have already been read, and files whose symbols will be read when needed.
11989 @kindex info functions
11990 @item info functions
11991 Print the names and data types of all defined functions.
11993 @item info functions @var{regexp}
11994 Print the names and data types of all defined functions
11995 whose names contain a match for regular expression @var{regexp}.
11996 Thus, @samp{info fun step} finds all functions whose names
11997 include @code{step}; @samp{info fun ^step} finds those whose names
11998 start with @code{step}. If a function name contains characters
11999 that conflict with the regular expression language (e.g.@:
12000 @samp{operator*()}), they may be quoted with a backslash.
12002 @kindex info variables
12003 @item info variables
12004 Print the names and data types of all variables that are declared
12005 outside of functions (i.e.@: excluding local variables).
12007 @item info variables @var{regexp}
12008 Print the names and data types of all variables (except for local
12009 variables) whose names contain a match for regular expression
12012 @kindex info classes
12013 @cindex Objective-C, classes and selectors
12015 @itemx info classes @var{regexp}
12016 Display all Objective-C classes in your program, or
12017 (with the @var{regexp} argument) all those matching a particular regular
12020 @kindex info selectors
12021 @item info selectors
12022 @itemx info selectors @var{regexp}
12023 Display all Objective-C selectors in your program, or
12024 (with the @var{regexp} argument) all those matching a particular regular
12028 This was never implemented.
12029 @kindex info methods
12031 @itemx info methods @var{regexp}
12032 The @code{info methods} command permits the user to examine all defined
12033 methods within C@t{++} program, or (with the @var{regexp} argument) a
12034 specific set of methods found in the various C@t{++} classes. Many
12035 C@t{++} classes provide a large number of methods. Thus, the output
12036 from the @code{ptype} command can be overwhelming and hard to use. The
12037 @code{info-methods} command filters the methods, printing only those
12038 which match the regular-expression @var{regexp}.
12041 @cindex reloading symbols
12042 Some systems allow individual object files that make up your program to
12043 be replaced without stopping and restarting your program. For example,
12044 in VxWorks you can simply recompile a defective object file and keep on
12045 running. If you are running on one of these systems, you can allow
12046 @value{GDBN} to reload the symbols for automatically relinked modules:
12049 @kindex set symbol-reloading
12050 @item set symbol-reloading on
12051 Replace symbol definitions for the corresponding source file when an
12052 object file with a particular name is seen again.
12054 @item set symbol-reloading off
12055 Do not replace symbol definitions when encountering object files of the
12056 same name more than once. This is the default state; if you are not
12057 running on a system that permits automatic relinking of modules, you
12058 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12059 may discard symbols when linking large programs, that may contain
12060 several modules (from different directories or libraries) with the same
12063 @kindex show symbol-reloading
12064 @item show symbol-reloading
12065 Show the current @code{on} or @code{off} setting.
12068 @cindex opaque data types
12069 @kindex set opaque-type-resolution
12070 @item set opaque-type-resolution on
12071 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12072 declared as a pointer to a @code{struct}, @code{class}, or
12073 @code{union}---for example, @code{struct MyType *}---that is used in one
12074 source file although the full declaration of @code{struct MyType} is in
12075 another source file. The default is on.
12077 A change in the setting of this subcommand will not take effect until
12078 the next time symbols for a file are loaded.
12080 @item set opaque-type-resolution off
12081 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12082 is printed as follows:
12084 @{<no data fields>@}
12087 @kindex show opaque-type-resolution
12088 @item show opaque-type-resolution
12089 Show whether opaque types are resolved or not.
12091 @kindex set print symbol-loading
12092 @cindex print messages when symbols are loaded
12093 @item set print symbol-loading
12094 @itemx set print symbol-loading on
12095 @itemx set print symbol-loading off
12096 The @code{set print symbol-loading} command allows you to enable or
12097 disable printing of messages when @value{GDBN} loads symbols.
12098 By default, these messages will be printed, and normally this is what
12099 you want. Disabling these messages is useful when debugging applications
12100 with lots of shared libraries where the quantity of output can be more
12101 annoying than useful.
12103 @kindex show print symbol-loading
12104 @item show print symbol-loading
12105 Show whether messages will be printed when @value{GDBN} loads symbols.
12107 @kindex maint print symbols
12108 @cindex symbol dump
12109 @kindex maint print psymbols
12110 @cindex partial symbol dump
12111 @item maint print symbols @var{filename}
12112 @itemx maint print psymbols @var{filename}
12113 @itemx maint print msymbols @var{filename}
12114 Write a dump of debugging symbol data into the file @var{filename}.
12115 These commands are used to debug the @value{GDBN} symbol-reading code. Only
12116 symbols with debugging data are included. If you use @samp{maint print
12117 symbols}, @value{GDBN} includes all the symbols for which it has already
12118 collected full details: that is, @var{filename} reflects symbols for
12119 only those files whose symbols @value{GDBN} has read. You can use the
12120 command @code{info sources} to find out which files these are. If you
12121 use @samp{maint print psymbols} instead, the dump shows information about
12122 symbols that @value{GDBN} only knows partially---that is, symbols defined in
12123 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
12124 @samp{maint print msymbols} dumps just the minimal symbol information
12125 required for each object file from which @value{GDBN} has read some symbols.
12126 @xref{Files, ,Commands to Specify Files}, for a discussion of how
12127 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
12129 @kindex maint info symtabs
12130 @kindex maint info psymtabs
12131 @cindex listing @value{GDBN}'s internal symbol tables
12132 @cindex symbol tables, listing @value{GDBN}'s internal
12133 @cindex full symbol tables, listing @value{GDBN}'s internal
12134 @cindex partial symbol tables, listing @value{GDBN}'s internal
12135 @item maint info symtabs @r{[} @var{regexp} @r{]}
12136 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
12138 List the @code{struct symtab} or @code{struct partial_symtab}
12139 structures whose names match @var{regexp}. If @var{regexp} is not
12140 given, list them all. The output includes expressions which you can
12141 copy into a @value{GDBN} debugging this one to examine a particular
12142 structure in more detail. For example:
12145 (@value{GDBP}) maint info psymtabs dwarf2read
12146 @{ objfile /home/gnu/build/gdb/gdb
12147 ((struct objfile *) 0x82e69d0)
12148 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
12149 ((struct partial_symtab *) 0x8474b10)
12152 text addresses 0x814d3c8 -- 0x8158074
12153 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
12154 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
12155 dependencies (none)
12158 (@value{GDBP}) maint info symtabs
12162 We see that there is one partial symbol table whose filename contains
12163 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
12164 and we see that @value{GDBN} has not read in any symtabs yet at all.
12165 If we set a breakpoint on a function, that will cause @value{GDBN} to
12166 read the symtab for the compilation unit containing that function:
12169 (@value{GDBP}) break dwarf2_psymtab_to_symtab
12170 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
12172 (@value{GDBP}) maint info symtabs
12173 @{ objfile /home/gnu/build/gdb/gdb
12174 ((struct objfile *) 0x82e69d0)
12175 @{ symtab /home/gnu/src/gdb/dwarf2read.c
12176 ((struct symtab *) 0x86c1f38)
12179 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
12180 linetable ((struct linetable *) 0x8370fa0)
12181 debugformat DWARF 2
12190 @chapter Altering Execution
12192 Once you think you have found an error in your program, you might want to
12193 find out for certain whether correcting the apparent error would lead to
12194 correct results in the rest of the run. You can find the answer by
12195 experiment, using the @value{GDBN} features for altering execution of the
12198 For example, you can store new values into variables or memory
12199 locations, give your program a signal, restart it at a different
12200 address, or even return prematurely from a function.
12203 * Assignment:: Assignment to variables
12204 * Jumping:: Continuing at a different address
12205 * Signaling:: Giving your program a signal
12206 * Returning:: Returning from a function
12207 * Calling:: Calling your program's functions
12208 * Patching:: Patching your program
12212 @section Assignment to Variables
12215 @cindex setting variables
12216 To alter the value of a variable, evaluate an assignment expression.
12217 @xref{Expressions, ,Expressions}. For example,
12224 stores the value 4 into the variable @code{x}, and then prints the
12225 value of the assignment expression (which is 4).
12226 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
12227 information on operators in supported languages.
12229 @kindex set variable
12230 @cindex variables, setting
12231 If you are not interested in seeing the value of the assignment, use the
12232 @code{set} command instead of the @code{print} command. @code{set} is
12233 really the same as @code{print} except that the expression's value is
12234 not printed and is not put in the value history (@pxref{Value History,
12235 ,Value History}). The expression is evaluated only for its effects.
12237 If the beginning of the argument string of the @code{set} command
12238 appears identical to a @code{set} subcommand, use the @code{set
12239 variable} command instead of just @code{set}. This command is identical
12240 to @code{set} except for its lack of subcommands. For example, if your
12241 program has a variable @code{width}, you get an error if you try to set
12242 a new value with just @samp{set width=13}, because @value{GDBN} has the
12243 command @code{set width}:
12246 (@value{GDBP}) whatis width
12248 (@value{GDBP}) p width
12250 (@value{GDBP}) set width=47
12251 Invalid syntax in expression.
12255 The invalid expression, of course, is @samp{=47}. In
12256 order to actually set the program's variable @code{width}, use
12259 (@value{GDBP}) set var width=47
12262 Because the @code{set} command has many subcommands that can conflict
12263 with the names of program variables, it is a good idea to use the
12264 @code{set variable} command instead of just @code{set}. For example, if
12265 your program has a variable @code{g}, you run into problems if you try
12266 to set a new value with just @samp{set g=4}, because @value{GDBN} has
12267 the command @code{set gnutarget}, abbreviated @code{set g}:
12271 (@value{GDBP}) whatis g
12275 (@value{GDBP}) set g=4
12279 The program being debugged has been started already.
12280 Start it from the beginning? (y or n) y
12281 Starting program: /home/smith/cc_progs/a.out
12282 "/home/smith/cc_progs/a.out": can't open to read symbols:
12283 Invalid bfd target.
12284 (@value{GDBP}) show g
12285 The current BFD target is "=4".
12290 The program variable @code{g} did not change, and you silently set the
12291 @code{gnutarget} to an invalid value. In order to set the variable
12295 (@value{GDBP}) set var g=4
12298 @value{GDBN} allows more implicit conversions in assignments than C; you can
12299 freely store an integer value into a pointer variable or vice versa,
12300 and you can convert any structure to any other structure that is the
12301 same length or shorter.
12302 @comment FIXME: how do structs align/pad in these conversions?
12303 @comment /doc@cygnus.com 18dec1990
12305 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12306 construct to generate a value of specified type at a specified address
12307 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12308 to memory location @code{0x83040} as an integer (which implies a certain size
12309 and representation in memory), and
12312 set @{int@}0x83040 = 4
12316 stores the value 4 into that memory location.
12319 @section Continuing at a Different Address
12321 Ordinarily, when you continue your program, you do so at the place where
12322 it stopped, with the @code{continue} command. You can instead continue at
12323 an address of your own choosing, with the following commands:
12327 @item jump @var{linespec}
12328 @itemx jump @var{location}
12329 Resume execution at line @var{linespec} or at address given by
12330 @var{location}. Execution stops again immediately if there is a
12331 breakpoint there. @xref{Specify Location}, for a description of the
12332 different forms of @var{linespec} and @var{location}. It is common
12333 practice to use the @code{tbreak} command in conjunction with
12334 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
12336 The @code{jump} command does not change the current stack frame, or
12337 the stack pointer, or the contents of any memory location or any
12338 register other than the program counter. If line @var{linespec} is in
12339 a different function from the one currently executing, the results may
12340 be bizarre if the two functions expect different patterns of arguments or
12341 of local variables. For this reason, the @code{jump} command requests
12342 confirmation if the specified line is not in the function currently
12343 executing. However, even bizarre results are predictable if you are
12344 well acquainted with the machine-language code of your program.
12347 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
12348 On many systems, you can get much the same effect as the @code{jump}
12349 command by storing a new value into the register @code{$pc}. The
12350 difference is that this does not start your program running; it only
12351 changes the address of where it @emph{will} run when you continue. For
12359 makes the next @code{continue} command or stepping command execute at
12360 address @code{0x485}, rather than at the address where your program stopped.
12361 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12363 The most common occasion to use the @code{jump} command is to back
12364 up---perhaps with more breakpoints set---over a portion of a program
12365 that has already executed, in order to examine its execution in more
12370 @section Giving your Program a Signal
12371 @cindex deliver a signal to a program
12375 @item signal @var{signal}
12376 Resume execution where your program stopped, but immediately give it the
12377 signal @var{signal}. @var{signal} can be the name or the number of a
12378 signal. For example, on many systems @code{signal 2} and @code{signal
12379 SIGINT} are both ways of sending an interrupt signal.
12381 Alternatively, if @var{signal} is zero, continue execution without
12382 giving a signal. This is useful when your program stopped on account of
12383 a signal and would ordinary see the signal when resumed with the
12384 @code{continue} command; @samp{signal 0} causes it to resume without a
12387 @code{signal} does not repeat when you press @key{RET} a second time
12388 after executing the command.
12392 Invoking the @code{signal} command is not the same as invoking the
12393 @code{kill} utility from the shell. Sending a signal with @code{kill}
12394 causes @value{GDBN} to decide what to do with the signal depending on
12395 the signal handling tables (@pxref{Signals}). The @code{signal} command
12396 passes the signal directly to your program.
12400 @section Returning from a Function
12403 @cindex returning from a function
12406 @itemx return @var{expression}
12407 You can cancel execution of a function call with the @code{return}
12408 command. If you give an
12409 @var{expression} argument, its value is used as the function's return
12413 When you use @code{return}, @value{GDBN} discards the selected stack frame
12414 (and all frames within it). You can think of this as making the
12415 discarded frame return prematurely. If you wish to specify a value to
12416 be returned, give that value as the argument to @code{return}.
12418 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12419 Frame}), and any other frames inside of it, leaving its caller as the
12420 innermost remaining frame. That frame becomes selected. The
12421 specified value is stored in the registers used for returning values
12424 The @code{return} command does not resume execution; it leaves the
12425 program stopped in the state that would exist if the function had just
12426 returned. In contrast, the @code{finish} command (@pxref{Continuing
12427 and Stepping, ,Continuing and Stepping}) resumes execution until the
12428 selected stack frame returns naturally.
12431 @section Calling Program Functions
12434 @cindex calling functions
12435 @cindex inferior functions, calling
12436 @item print @var{expr}
12437 Evaluate the expression @var{expr} and display the resulting value.
12438 @var{expr} may include calls to functions in the program being
12442 @item call @var{expr}
12443 Evaluate the expression @var{expr} without displaying @code{void}
12446 You can use this variant of the @code{print} command if you want to
12447 execute a function from your program that does not return anything
12448 (a.k.a.@: @dfn{a void function}), but without cluttering the output
12449 with @code{void} returned values that @value{GDBN} will otherwise
12450 print. If the result is not void, it is printed and saved in the
12454 It is possible for the function you call via the @code{print} or
12455 @code{call} command to generate a signal (e.g., if there's a bug in
12456 the function, or if you passed it incorrect arguments). What happens
12457 in that case is controlled by the @code{set unwindonsignal} command.
12460 @item set unwindonsignal
12461 @kindex set unwindonsignal
12462 @cindex unwind stack in called functions
12463 @cindex call dummy stack unwinding
12464 Set unwinding of the stack if a signal is received while in a function
12465 that @value{GDBN} called in the program being debugged. If set to on,
12466 @value{GDBN} unwinds the stack it created for the call and restores
12467 the context to what it was before the call. If set to off (the
12468 default), @value{GDBN} stops in the frame where the signal was
12471 @item show unwindonsignal
12472 @kindex show unwindonsignal
12473 Show the current setting of stack unwinding in the functions called by
12477 @cindex weak alias functions
12478 Sometimes, a function you wish to call is actually a @dfn{weak alias}
12479 for another function. In such case, @value{GDBN} might not pick up
12480 the type information, including the types of the function arguments,
12481 which causes @value{GDBN} to call the inferior function incorrectly.
12482 As a result, the called function will function erroneously and may
12483 even crash. A solution to that is to use the name of the aliased
12487 @section Patching Programs
12489 @cindex patching binaries
12490 @cindex writing into executables
12491 @cindex writing into corefiles
12493 By default, @value{GDBN} opens the file containing your program's
12494 executable code (or the corefile) read-only. This prevents accidental
12495 alterations to machine code; but it also prevents you from intentionally
12496 patching your program's binary.
12498 If you'd like to be able to patch the binary, you can specify that
12499 explicitly with the @code{set write} command. For example, you might
12500 want to turn on internal debugging flags, or even to make emergency
12506 @itemx set write off
12507 If you specify @samp{set write on}, @value{GDBN} opens executable and
12508 core files for both reading and writing; if you specify @kbd{set write
12509 off} (the default), @value{GDBN} opens them read-only.
12511 If you have already loaded a file, you must load it again (using the
12512 @code{exec-file} or @code{core-file} command) after changing @code{set
12513 write}, for your new setting to take effect.
12517 Display whether executable files and core files are opened for writing
12518 as well as reading.
12522 @chapter @value{GDBN} Files
12524 @value{GDBN} needs to know the file name of the program to be debugged,
12525 both in order to read its symbol table and in order to start your
12526 program. To debug a core dump of a previous run, you must also tell
12527 @value{GDBN} the name of the core dump file.
12530 * Files:: Commands to specify files
12531 * Separate Debug Files:: Debugging information in separate files
12532 * Symbol Errors:: Errors reading symbol files
12536 @section Commands to Specify Files
12538 @cindex symbol table
12539 @cindex core dump file
12541 You may want to specify executable and core dump file names. The usual
12542 way to do this is at start-up time, using the arguments to
12543 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
12544 Out of @value{GDBN}}).
12546 Occasionally it is necessary to change to a different file during a
12547 @value{GDBN} session. Or you may run @value{GDBN} and forget to
12548 specify a file you want to use. Or you are debugging a remote target
12549 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
12550 Program}). In these situations the @value{GDBN} commands to specify
12551 new files are useful.
12554 @cindex executable file
12556 @item file @var{filename}
12557 Use @var{filename} as the program to be debugged. It is read for its
12558 symbols and for the contents of pure memory. It is also the program
12559 executed when you use the @code{run} command. If you do not specify a
12560 directory and the file is not found in the @value{GDBN} working directory,
12561 @value{GDBN} uses the environment variable @code{PATH} as a list of
12562 directories to search, just as the shell does when looking for a program
12563 to run. You can change the value of this variable, for both @value{GDBN}
12564 and your program, using the @code{path} command.
12566 @cindex unlinked object files
12567 @cindex patching object files
12568 You can load unlinked object @file{.o} files into @value{GDBN} using
12569 the @code{file} command. You will not be able to ``run'' an object
12570 file, but you can disassemble functions and inspect variables. Also,
12571 if the underlying BFD functionality supports it, you could use
12572 @kbd{gdb -write} to patch object files using this technique. Note
12573 that @value{GDBN} can neither interpret nor modify relocations in this
12574 case, so branches and some initialized variables will appear to go to
12575 the wrong place. But this feature is still handy from time to time.
12578 @code{file} with no argument makes @value{GDBN} discard any information it
12579 has on both executable file and the symbol table.
12582 @item exec-file @r{[} @var{filename} @r{]}
12583 Specify that the program to be run (but not the symbol table) is found
12584 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12585 if necessary to locate your program. Omitting @var{filename} means to
12586 discard information on the executable file.
12588 @kindex symbol-file
12589 @item symbol-file @r{[} @var{filename} @r{]}
12590 Read symbol table information from file @var{filename}. @code{PATH} is
12591 searched when necessary. Use the @code{file} command to get both symbol
12592 table and program to run from the same file.
12594 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12595 program's symbol table.
12597 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12598 some breakpoints and auto-display expressions. This is because they may
12599 contain pointers to the internal data recording symbols and data types,
12600 which are part of the old symbol table data being discarded inside
12603 @code{symbol-file} does not repeat if you press @key{RET} again after
12606 When @value{GDBN} is configured for a particular environment, it
12607 understands debugging information in whatever format is the standard
12608 generated for that environment; you may use either a @sc{gnu} compiler, or
12609 other compilers that adhere to the local conventions.
12610 Best results are usually obtained from @sc{gnu} compilers; for example,
12611 using @code{@value{NGCC}} you can generate debugging information for
12614 For most kinds of object files, with the exception of old SVR3 systems
12615 using COFF, the @code{symbol-file} command does not normally read the
12616 symbol table in full right away. Instead, it scans the symbol table
12617 quickly to find which source files and which symbols are present. The
12618 details are read later, one source file at a time, as they are needed.
12620 The purpose of this two-stage reading strategy is to make @value{GDBN}
12621 start up faster. For the most part, it is invisible except for
12622 occasional pauses while the symbol table details for a particular source
12623 file are being read. (The @code{set verbose} command can turn these
12624 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12625 Warnings and Messages}.)
12627 We have not implemented the two-stage strategy for COFF yet. When the
12628 symbol table is stored in COFF format, @code{symbol-file} reads the
12629 symbol table data in full right away. Note that ``stabs-in-COFF''
12630 still does the two-stage strategy, since the debug info is actually
12634 @cindex reading symbols immediately
12635 @cindex symbols, reading immediately
12636 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12637 @itemx file @var{filename} @r{[} -readnow @r{]}
12638 You can override the @value{GDBN} two-stage strategy for reading symbol
12639 tables by using the @samp{-readnow} option with any of the commands that
12640 load symbol table information, if you want to be sure @value{GDBN} has the
12641 entire symbol table available.
12643 @c FIXME: for now no mention of directories, since this seems to be in
12644 @c flux. 13mar1992 status is that in theory GDB would look either in
12645 @c current dir or in same dir as myprog; but issues like competing
12646 @c GDB's, or clutter in system dirs, mean that in practice right now
12647 @c only current dir is used. FFish says maybe a special GDB hierarchy
12648 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
12652 @item core-file @r{[}@var{filename}@r{]}
12654 Specify the whereabouts of a core dump file to be used as the ``contents
12655 of memory''. Traditionally, core files contain only some parts of the
12656 address space of the process that generated them; @value{GDBN} can access the
12657 executable file itself for other parts.
12659 @code{core-file} with no argument specifies that no core file is
12662 Note that the core file is ignored when your program is actually running
12663 under @value{GDBN}. So, if you have been running your program and you
12664 wish to debug a core file instead, you must kill the subprocess in which
12665 the program is running. To do this, use the @code{kill} command
12666 (@pxref{Kill Process, ,Killing the Child Process}).
12668 @kindex add-symbol-file
12669 @cindex dynamic linking
12670 @item add-symbol-file @var{filename} @var{address}
12671 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12672 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12673 The @code{add-symbol-file} command reads additional symbol table
12674 information from the file @var{filename}. You would use this command
12675 when @var{filename} has been dynamically loaded (by some other means)
12676 into the program that is running. @var{address} should be the memory
12677 address at which the file has been loaded; @value{GDBN} cannot figure
12678 this out for itself. You can additionally specify an arbitrary number
12679 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12680 section name and base address for that section. You can specify any
12681 @var{address} as an expression.
12683 The symbol table of the file @var{filename} is added to the symbol table
12684 originally read with the @code{symbol-file} command. You can use the
12685 @code{add-symbol-file} command any number of times; the new symbol data
12686 thus read keeps adding to the old. To discard all old symbol data
12687 instead, use the @code{symbol-file} command without any arguments.
12689 @cindex relocatable object files, reading symbols from
12690 @cindex object files, relocatable, reading symbols from
12691 @cindex reading symbols from relocatable object files
12692 @cindex symbols, reading from relocatable object files
12693 @cindex @file{.o} files, reading symbols from
12694 Although @var{filename} is typically a shared library file, an
12695 executable file, or some other object file which has been fully
12696 relocated for loading into a process, you can also load symbolic
12697 information from relocatable @file{.o} files, as long as:
12701 the file's symbolic information refers only to linker symbols defined in
12702 that file, not to symbols defined by other object files,
12704 every section the file's symbolic information refers to has actually
12705 been loaded into the inferior, as it appears in the file, and
12707 you can determine the address at which every section was loaded, and
12708 provide these to the @code{add-symbol-file} command.
12712 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12713 relocatable files into an already running program; such systems
12714 typically make the requirements above easy to meet. However, it's
12715 important to recognize that many native systems use complex link
12716 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12717 assembly, for example) that make the requirements difficult to meet. In
12718 general, one cannot assume that using @code{add-symbol-file} to read a
12719 relocatable object file's symbolic information will have the same effect
12720 as linking the relocatable object file into the program in the normal
12723 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12725 @kindex add-symbol-file-from-memory
12726 @cindex @code{syscall DSO}
12727 @cindex load symbols from memory
12728 @item add-symbol-file-from-memory @var{address}
12729 Load symbols from the given @var{address} in a dynamically loaded
12730 object file whose image is mapped directly into the inferior's memory.
12731 For example, the Linux kernel maps a @code{syscall DSO} into each
12732 process's address space; this DSO provides kernel-specific code for
12733 some system calls. The argument can be any expression whose
12734 evaluation yields the address of the file's shared object file header.
12735 For this command to work, you must have used @code{symbol-file} or
12736 @code{exec-file} commands in advance.
12738 @kindex add-shared-symbol-files
12740 @item add-shared-symbol-files @var{library-file}
12741 @itemx assf @var{library-file}
12742 The @code{add-shared-symbol-files} command can currently be used only
12743 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12744 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12745 @value{GDBN} automatically looks for shared libraries, however if
12746 @value{GDBN} does not find yours, you can invoke
12747 @code{add-shared-symbol-files}. It takes one argument: the shared
12748 library's file name. @code{assf} is a shorthand alias for
12749 @code{add-shared-symbol-files}.
12752 @item section @var{section} @var{addr}
12753 The @code{section} command changes the base address of the named
12754 @var{section} of the exec file to @var{addr}. This can be used if the
12755 exec file does not contain section addresses, (such as in the
12756 @code{a.out} format), or when the addresses specified in the file
12757 itself are wrong. Each section must be changed separately. The
12758 @code{info files} command, described below, lists all the sections and
12762 @kindex info target
12765 @code{info files} and @code{info target} are synonymous; both print the
12766 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12767 including the names of the executable and core dump files currently in
12768 use by @value{GDBN}, and the files from which symbols were loaded. The
12769 command @code{help target} lists all possible targets rather than
12772 @kindex maint info sections
12773 @item maint info sections
12774 Another command that can give you extra information about program sections
12775 is @code{maint info sections}. In addition to the section information
12776 displayed by @code{info files}, this command displays the flags and file
12777 offset of each section in the executable and core dump files. In addition,
12778 @code{maint info sections} provides the following command options (which
12779 may be arbitrarily combined):
12783 Display sections for all loaded object files, including shared libraries.
12784 @item @var{sections}
12785 Display info only for named @var{sections}.
12786 @item @var{section-flags}
12787 Display info only for sections for which @var{section-flags} are true.
12788 The section flags that @value{GDBN} currently knows about are:
12791 Section will have space allocated in the process when loaded.
12792 Set for all sections except those containing debug information.
12794 Section will be loaded from the file into the child process memory.
12795 Set for pre-initialized code and data, clear for @code{.bss} sections.
12797 Section needs to be relocated before loading.
12799 Section cannot be modified by the child process.
12801 Section contains executable code only.
12803 Section contains data only (no executable code).
12805 Section will reside in ROM.
12807 Section contains data for constructor/destructor lists.
12809 Section is not empty.
12811 An instruction to the linker to not output the section.
12812 @item COFF_SHARED_LIBRARY
12813 A notification to the linker that the section contains
12814 COFF shared library information.
12816 Section contains common symbols.
12819 @kindex set trust-readonly-sections
12820 @cindex read-only sections
12821 @item set trust-readonly-sections on
12822 Tell @value{GDBN} that readonly sections in your object file
12823 really are read-only (i.e.@: that their contents will not change).
12824 In that case, @value{GDBN} can fetch values from these sections
12825 out of the object file, rather than from the target program.
12826 For some targets (notably embedded ones), this can be a significant
12827 enhancement to debugging performance.
12829 The default is off.
12831 @item set trust-readonly-sections off
12832 Tell @value{GDBN} not to trust readonly sections. This means that
12833 the contents of the section might change while the program is running,
12834 and must therefore be fetched from the target when needed.
12836 @item show trust-readonly-sections
12837 Show the current setting of trusting readonly sections.
12840 All file-specifying commands allow both absolute and relative file names
12841 as arguments. @value{GDBN} always converts the file name to an absolute file
12842 name and remembers it that way.
12844 @cindex shared libraries
12845 @anchor{Shared Libraries}
12846 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
12847 and IBM RS/6000 AIX shared libraries.
12849 On MS-Windows @value{GDBN} must be linked with the Expat library to support
12850 shared libraries. @xref{Expat}.
12852 @value{GDBN} automatically loads symbol definitions from shared libraries
12853 when you use the @code{run} command, or when you examine a core file.
12854 (Before you issue the @code{run} command, @value{GDBN} does not understand
12855 references to a function in a shared library, however---unless you are
12856 debugging a core file).
12858 On HP-UX, if the program loads a library explicitly, @value{GDBN}
12859 automatically loads the symbols at the time of the @code{shl_load} call.
12861 @c FIXME: some @value{GDBN} release may permit some refs to undef
12862 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
12863 @c FIXME...lib; check this from time to time when updating manual
12865 There are times, however, when you may wish to not automatically load
12866 symbol definitions from shared libraries, such as when they are
12867 particularly large or there are many of them.
12869 To control the automatic loading of shared library symbols, use the
12873 @kindex set auto-solib-add
12874 @item set auto-solib-add @var{mode}
12875 If @var{mode} is @code{on}, symbols from all shared object libraries
12876 will be loaded automatically when the inferior begins execution, you
12877 attach to an independently started inferior, or when the dynamic linker
12878 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12879 is @code{off}, symbols must be loaded manually, using the
12880 @code{sharedlibrary} command. The default value is @code{on}.
12882 @cindex memory used for symbol tables
12883 If your program uses lots of shared libraries with debug info that
12884 takes large amounts of memory, you can decrease the @value{GDBN}
12885 memory footprint by preventing it from automatically loading the
12886 symbols from shared libraries. To that end, type @kbd{set
12887 auto-solib-add off} before running the inferior, then load each
12888 library whose debug symbols you do need with @kbd{sharedlibrary
12889 @var{regexp}}, where @var{regexp} is a regular expression that matches
12890 the libraries whose symbols you want to be loaded.
12892 @kindex show auto-solib-add
12893 @item show auto-solib-add
12894 Display the current autoloading mode.
12897 @cindex load shared library
12898 To explicitly load shared library symbols, use the @code{sharedlibrary}
12902 @kindex info sharedlibrary
12905 @itemx info sharedlibrary
12906 Print the names of the shared libraries which are currently loaded.
12908 @kindex sharedlibrary
12910 @item sharedlibrary @var{regex}
12911 @itemx share @var{regex}
12912 Load shared object library symbols for files matching a
12913 Unix regular expression.
12914 As with files loaded automatically, it only loads shared libraries
12915 required by your program for a core file or after typing @code{run}. If
12916 @var{regex} is omitted all shared libraries required by your program are
12919 @item nosharedlibrary
12920 @kindex nosharedlibrary
12921 @cindex unload symbols from shared libraries
12922 Unload all shared object library symbols. This discards all symbols
12923 that have been loaded from all shared libraries. Symbols from shared
12924 libraries that were loaded by explicit user requests are not
12928 Sometimes you may wish that @value{GDBN} stops and gives you control
12929 when any of shared library events happen. Use the @code{set
12930 stop-on-solib-events} command for this:
12933 @item set stop-on-solib-events
12934 @kindex set stop-on-solib-events
12935 This command controls whether @value{GDBN} should give you control
12936 when the dynamic linker notifies it about some shared library event.
12937 The most common event of interest is loading or unloading of a new
12940 @item show stop-on-solib-events
12941 @kindex show stop-on-solib-events
12942 Show whether @value{GDBN} stops and gives you control when shared
12943 library events happen.
12946 Shared libraries are also supported in many cross or remote debugging
12947 configurations. @value{GDBN} needs to have access to the target's libraries;
12948 this can be accomplished either by providing copies of the libraries
12949 on the host system, or by asking @value{GDBN} to automatically retrieve the
12950 libraries from the target. If copies of the target libraries are
12951 provided, they need to be the same as the target libraries, although the
12952 copies on the target can be stripped as long as the copies on the host are
12955 @cindex where to look for shared libraries
12956 For remote debugging, you need to tell @value{GDBN} where the target
12957 libraries are, so that it can load the correct copies---otherwise, it
12958 may try to load the host's libraries. @value{GDBN} has two variables
12959 to specify the search directories for target libraries.
12962 @cindex prefix for shared library file names
12963 @cindex system root, alternate
12964 @kindex set solib-absolute-prefix
12965 @kindex set sysroot
12966 @item set sysroot @var{path}
12967 Use @var{path} as the system root for the program being debugged. Any
12968 absolute shared library paths will be prefixed with @var{path}; many
12969 runtime loaders store the absolute paths to the shared library in the
12970 target program's memory. If you use @code{set sysroot} to find shared
12971 libraries, they need to be laid out in the same way that they are on
12972 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
12975 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
12976 retrieve the target libraries from the remote system. This is only
12977 supported when using a remote target that supports the @code{remote get}
12978 command (@pxref{File Transfer,,Sending files to a remote system}).
12979 The part of @var{path} following the initial @file{remote:}
12980 (if present) is used as system root prefix on the remote file system.
12981 @footnote{If you want to specify a local system root using a directory
12982 that happens to be named @file{remote:}, you need to use some equivalent
12983 variant of the name like @file{./remote:}.}
12985 The @code{set solib-absolute-prefix} command is an alias for @code{set
12988 @cindex default system root
12989 @cindex @samp{--with-sysroot}
12990 You can set the default system root by using the configure-time
12991 @samp{--with-sysroot} option. If the system root is inside
12992 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
12993 @samp{--exec-prefix}), then the default system root will be updated
12994 automatically if the installed @value{GDBN} is moved to a new
12997 @kindex show sysroot
12999 Display the current shared library prefix.
13001 @kindex set solib-search-path
13002 @item set solib-search-path @var{path}
13003 If this variable is set, @var{path} is a colon-separated list of
13004 directories to search for shared libraries. @samp{solib-search-path}
13005 is used after @samp{sysroot} fails to locate the library, or if the
13006 path to the library is relative instead of absolute. If you want to
13007 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13008 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13009 finding your host's libraries. @samp{sysroot} is preferred; setting
13010 it to a nonexistent directory may interfere with automatic loading
13011 of shared library symbols.
13013 @kindex show solib-search-path
13014 @item show solib-search-path
13015 Display the current shared library search path.
13019 @node Separate Debug Files
13020 @section Debugging Information in Separate Files
13021 @cindex separate debugging information files
13022 @cindex debugging information in separate files
13023 @cindex @file{.debug} subdirectories
13024 @cindex debugging information directory, global
13025 @cindex global debugging information directory
13026 @cindex build ID, and separate debugging files
13027 @cindex @file{.build-id} directory
13029 @value{GDBN} allows you to put a program's debugging information in a
13030 file separate from the executable itself, in a way that allows
13031 @value{GDBN} to find and load the debugging information automatically.
13032 Since debugging information can be very large---sometimes larger
13033 than the executable code itself---some systems distribute debugging
13034 information for their executables in separate files, which users can
13035 install only when they need to debug a problem.
13037 @value{GDBN} supports two ways of specifying the separate debug info
13042 The executable contains a @dfn{debug link} that specifies the name of
13043 the separate debug info file. The separate debug file's name is
13044 usually @file{@var{executable}.debug}, where @var{executable} is the
13045 name of the corresponding executable file without leading directories
13046 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
13047 debug link specifies a CRC32 checksum for the debug file, which
13048 @value{GDBN} uses to validate that the executable and the debug file
13049 came from the same build.
13052 The executable contains a @dfn{build ID}, a unique bit string that is
13053 also present in the corresponding debug info file. (This is supported
13054 only on some operating systems, notably those which use the ELF format
13055 for binary files and the @sc{gnu} Binutils.) For more details about
13056 this feature, see the description of the @option{--build-id}
13057 command-line option in @ref{Options, , Command Line Options, ld.info,
13058 The GNU Linker}. The debug info file's name is not specified
13059 explicitly by the build ID, but can be computed from the build ID, see
13063 Depending on the way the debug info file is specified, @value{GDBN}
13064 uses two different methods of looking for the debug file:
13068 For the ``debug link'' method, @value{GDBN} looks up the named file in
13069 the directory of the executable file, then in a subdirectory of that
13070 directory named @file{.debug}, and finally under the global debug
13071 directory, in a subdirectory whose name is identical to the leading
13072 directories of the executable's absolute file name.
13075 For the ``build ID'' method, @value{GDBN} looks in the
13076 @file{.build-id} subdirectory of the global debug directory for a file
13077 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
13078 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
13079 are the rest of the bit string. (Real build ID strings are 32 or more
13080 hex characters, not 10.)
13083 So, for example, suppose you ask @value{GDBN} to debug
13084 @file{/usr/bin/ls}, which has a debug link that specifies the
13085 file @file{ls.debug}, and a build ID whose value in hex is
13086 @code{abcdef1234}. If the global debug directory is
13087 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
13088 debug information files, in the indicated order:
13092 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
13094 @file{/usr/bin/ls.debug}
13096 @file{/usr/bin/.debug/ls.debug}
13098 @file{/usr/lib/debug/usr/bin/ls.debug}.
13101 You can set the global debugging info directory's name, and view the
13102 name @value{GDBN} is currently using.
13106 @kindex set debug-file-directory
13107 @item set debug-file-directory @var{directory}
13108 Set the directory which @value{GDBN} searches for separate debugging
13109 information files to @var{directory}.
13111 @kindex show debug-file-directory
13112 @item show debug-file-directory
13113 Show the directory @value{GDBN} searches for separate debugging
13118 @cindex @code{.gnu_debuglink} sections
13119 @cindex debug link sections
13120 A debug link is a special section of the executable file named
13121 @code{.gnu_debuglink}. The section must contain:
13125 A filename, with any leading directory components removed, followed by
13128 zero to three bytes of padding, as needed to reach the next four-byte
13129 boundary within the section, and
13131 a four-byte CRC checksum, stored in the same endianness used for the
13132 executable file itself. The checksum is computed on the debugging
13133 information file's full contents by the function given below, passing
13134 zero as the @var{crc} argument.
13137 Any executable file format can carry a debug link, as long as it can
13138 contain a section named @code{.gnu_debuglink} with the contents
13141 @cindex @code{.note.gnu.build-id} sections
13142 @cindex build ID sections
13143 The build ID is a special section in the executable file (and in other
13144 ELF binary files that @value{GDBN} may consider). This section is
13145 often named @code{.note.gnu.build-id}, but that name is not mandatory.
13146 It contains unique identification for the built files---the ID remains
13147 the same across multiple builds of the same build tree. The default
13148 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
13149 content for the build ID string. The same section with an identical
13150 value is present in the original built binary with symbols, in its
13151 stripped variant, and in the separate debugging information file.
13153 The debugging information file itself should be an ordinary
13154 executable, containing a full set of linker symbols, sections, and
13155 debugging information. The sections of the debugging information file
13156 should have the same names, addresses, and sizes as the original file,
13157 but they need not contain any data---much like a @code{.bss} section
13158 in an ordinary executable.
13160 The @sc{gnu} binary utilities (Binutils) package includes the
13161 @samp{objcopy} utility that can produce
13162 the separated executable / debugging information file pairs using the
13163 following commands:
13166 @kbd{objcopy --only-keep-debug foo foo.debug}
13171 These commands remove the debugging
13172 information from the executable file @file{foo} and place it in the file
13173 @file{foo.debug}. You can use the first, second or both methods to link the
13178 The debug link method needs the following additional command to also leave
13179 behind a debug link in @file{foo}:
13182 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
13185 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
13186 a version of the @code{strip} command such that the command @kbd{strip foo -f
13187 foo.debug} has the same functionality as the two @code{objcopy} commands and
13188 the @code{ln -s} command above, together.
13191 Build ID gets embedded into the main executable using @code{ld --build-id} or
13192 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
13193 compatibility fixes for debug files separation are present in @sc{gnu} binary
13194 utilities (Binutils) package since version 2.18.
13199 Since there are many different ways to compute CRC's for the debug
13200 link (different polynomials, reversals, byte ordering, etc.), the
13201 simplest way to describe the CRC used in @code{.gnu_debuglink}
13202 sections is to give the complete code for a function that computes it:
13204 @kindex gnu_debuglink_crc32
13207 gnu_debuglink_crc32 (unsigned long crc,
13208 unsigned char *buf, size_t len)
13210 static const unsigned long crc32_table[256] =
13212 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
13213 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
13214 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
13215 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
13216 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
13217 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
13218 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
13219 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
13220 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
13221 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
13222 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
13223 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
13224 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
13225 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
13226 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
13227 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
13228 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
13229 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
13230 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
13231 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
13232 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
13233 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
13234 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
13235 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
13236 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
13237 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
13238 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
13239 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
13240 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
13241 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
13242 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
13243 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
13244 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
13245 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
13246 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
13247 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
13248 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
13249 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
13250 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
13251 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
13252 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
13253 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
13254 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
13255 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
13256 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
13257 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
13258 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
13259 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
13260 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
13261 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
13262 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
13265 unsigned char *end;
13267 crc = ~crc & 0xffffffff;
13268 for (end = buf + len; buf < end; ++buf)
13269 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
13270 return ~crc & 0xffffffff;
13275 This computation does not apply to the ``build ID'' method.
13278 @node Symbol Errors
13279 @section Errors Reading Symbol Files
13281 While reading a symbol file, @value{GDBN} occasionally encounters problems,
13282 such as symbol types it does not recognize, or known bugs in compiler
13283 output. By default, @value{GDBN} does not notify you of such problems, since
13284 they are relatively common and primarily of interest to people
13285 debugging compilers. If you are interested in seeing information
13286 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
13287 only one message about each such type of problem, no matter how many
13288 times the problem occurs; or you can ask @value{GDBN} to print more messages,
13289 to see how many times the problems occur, with the @code{set
13290 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
13293 The messages currently printed, and their meanings, include:
13296 @item inner block not inside outer block in @var{symbol}
13298 The symbol information shows where symbol scopes begin and end
13299 (such as at the start of a function or a block of statements). This
13300 error indicates that an inner scope block is not fully contained
13301 in its outer scope blocks.
13303 @value{GDBN} circumvents the problem by treating the inner block as if it had
13304 the same scope as the outer block. In the error message, @var{symbol}
13305 may be shown as ``@code{(don't know)}'' if the outer block is not a
13308 @item block at @var{address} out of order
13310 The symbol information for symbol scope blocks should occur in
13311 order of increasing addresses. This error indicates that it does not
13314 @value{GDBN} does not circumvent this problem, and has trouble
13315 locating symbols in the source file whose symbols it is reading. (You
13316 can often determine what source file is affected by specifying
13317 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
13320 @item bad block start address patched
13322 The symbol information for a symbol scope block has a start address
13323 smaller than the address of the preceding source line. This is known
13324 to occur in the SunOS 4.1.1 (and earlier) C compiler.
13326 @value{GDBN} circumvents the problem by treating the symbol scope block as
13327 starting on the previous source line.
13329 @item bad string table offset in symbol @var{n}
13332 Symbol number @var{n} contains a pointer into the string table which is
13333 larger than the size of the string table.
13335 @value{GDBN} circumvents the problem by considering the symbol to have the
13336 name @code{foo}, which may cause other problems if many symbols end up
13339 @item unknown symbol type @code{0x@var{nn}}
13341 The symbol information contains new data types that @value{GDBN} does
13342 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
13343 uncomprehended information, in hexadecimal.
13345 @value{GDBN} circumvents the error by ignoring this symbol information.
13346 This usually allows you to debug your program, though certain symbols
13347 are not accessible. If you encounter such a problem and feel like
13348 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
13349 on @code{complain}, then go up to the function @code{read_dbx_symtab}
13350 and examine @code{*bufp} to see the symbol.
13352 @item stub type has NULL name
13354 @value{GDBN} could not find the full definition for a struct or class.
13356 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
13357 The symbol information for a C@t{++} member function is missing some
13358 information that recent versions of the compiler should have output for
13361 @item info mismatch between compiler and debugger
13363 @value{GDBN} could not parse a type specification output by the compiler.
13368 @chapter Specifying a Debugging Target
13370 @cindex debugging target
13371 A @dfn{target} is the execution environment occupied by your program.
13373 Often, @value{GDBN} runs in the same host environment as your program;
13374 in that case, the debugging target is specified as a side effect when
13375 you use the @code{file} or @code{core} commands. When you need more
13376 flexibility---for example, running @value{GDBN} on a physically separate
13377 host, or controlling a standalone system over a serial port or a
13378 realtime system over a TCP/IP connection---you can use the @code{target}
13379 command to specify one of the target types configured for @value{GDBN}
13380 (@pxref{Target Commands, ,Commands for Managing Targets}).
13382 @cindex target architecture
13383 It is possible to build @value{GDBN} for several different @dfn{target
13384 architectures}. When @value{GDBN} is built like that, you can choose
13385 one of the available architectures with the @kbd{set architecture}
13389 @kindex set architecture
13390 @kindex show architecture
13391 @item set architecture @var{arch}
13392 This command sets the current target architecture to @var{arch}. The
13393 value of @var{arch} can be @code{"auto"}, in addition to one of the
13394 supported architectures.
13396 @item show architecture
13397 Show the current target architecture.
13399 @item set processor
13401 @kindex set processor
13402 @kindex show processor
13403 These are alias commands for, respectively, @code{set architecture}
13404 and @code{show architecture}.
13408 * Active Targets:: Active targets
13409 * Target Commands:: Commands for managing targets
13410 * Byte Order:: Choosing target byte order
13413 @node Active Targets
13414 @section Active Targets
13416 @cindex stacking targets
13417 @cindex active targets
13418 @cindex multiple targets
13420 There are three classes of targets: processes, core files, and
13421 executable files. @value{GDBN} can work concurrently on up to three
13422 active targets, one in each class. This allows you to (for example)
13423 start a process and inspect its activity without abandoning your work on
13426 For example, if you execute @samp{gdb a.out}, then the executable file
13427 @code{a.out} is the only active target. If you designate a core file as
13428 well---presumably from a prior run that crashed and coredumped---then
13429 @value{GDBN} has two active targets and uses them in tandem, looking
13430 first in the corefile target, then in the executable file, to satisfy
13431 requests for memory addresses. (Typically, these two classes of target
13432 are complementary, since core files contain only a program's
13433 read-write memory---variables and so on---plus machine status, while
13434 executable files contain only the program text and initialized data.)
13436 When you type @code{run}, your executable file becomes an active process
13437 target as well. When a process target is active, all @value{GDBN}
13438 commands requesting memory addresses refer to that target; addresses in
13439 an active core file or executable file target are obscured while the
13440 process target is active.
13442 Use the @code{core-file} and @code{exec-file} commands to select a new
13443 core file or executable target (@pxref{Files, ,Commands to Specify
13444 Files}). To specify as a target a process that is already running, use
13445 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
13448 @node Target Commands
13449 @section Commands for Managing Targets
13452 @item target @var{type} @var{parameters}
13453 Connects the @value{GDBN} host environment to a target machine or
13454 process. A target is typically a protocol for talking to debugging
13455 facilities. You use the argument @var{type} to specify the type or
13456 protocol of the target machine.
13458 Further @var{parameters} are interpreted by the target protocol, but
13459 typically include things like device names or host names to connect
13460 with, process numbers, and baud rates.
13462 The @code{target} command does not repeat if you press @key{RET} again
13463 after executing the command.
13465 @kindex help target
13467 Displays the names of all targets available. To display targets
13468 currently selected, use either @code{info target} or @code{info files}
13469 (@pxref{Files, ,Commands to Specify Files}).
13471 @item help target @var{name}
13472 Describe a particular target, including any parameters necessary to
13475 @kindex set gnutarget
13476 @item set gnutarget @var{args}
13477 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
13478 knows whether it is reading an @dfn{executable},
13479 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
13480 with the @code{set gnutarget} command. Unlike most @code{target} commands,
13481 with @code{gnutarget} the @code{target} refers to a program, not a machine.
13484 @emph{Warning:} To specify a file format with @code{set gnutarget},
13485 you must know the actual BFD name.
13489 @xref{Files, , Commands to Specify Files}.
13491 @kindex show gnutarget
13492 @item show gnutarget
13493 Use the @code{show gnutarget} command to display what file format
13494 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
13495 @value{GDBN} will determine the file format for each file automatically,
13496 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
13499 @cindex common targets
13500 Here are some common targets (available, or not, depending on the GDB
13505 @item target exec @var{program}
13506 @cindex executable file target
13507 An executable file. @samp{target exec @var{program}} is the same as
13508 @samp{exec-file @var{program}}.
13510 @item target core @var{filename}
13511 @cindex core dump file target
13512 A core dump file. @samp{target core @var{filename}} is the same as
13513 @samp{core-file @var{filename}}.
13515 @item target remote @var{medium}
13516 @cindex remote target
13517 A remote system connected to @value{GDBN} via a serial line or network
13518 connection. This command tells @value{GDBN} to use its own remote
13519 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
13521 For example, if you have a board connected to @file{/dev/ttya} on the
13522 machine running @value{GDBN}, you could say:
13525 target remote /dev/ttya
13528 @code{target remote} supports the @code{load} command. This is only
13529 useful if you have some other way of getting the stub to the target
13530 system, and you can put it somewhere in memory where it won't get
13531 clobbered by the download.
13534 @cindex built-in simulator target
13535 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
13543 works; however, you cannot assume that a specific memory map, device
13544 drivers, or even basic I/O is available, although some simulators do
13545 provide these. For info about any processor-specific simulator details,
13546 see the appropriate section in @ref{Embedded Processors, ,Embedded
13551 Some configurations may include these targets as well:
13555 @item target nrom @var{dev}
13556 @cindex NetROM ROM emulator target
13557 NetROM ROM emulator. This target only supports downloading.
13561 Different targets are available on different configurations of @value{GDBN};
13562 your configuration may have more or fewer targets.
13564 Many remote targets require you to download the executable's code once
13565 you've successfully established a connection. You may wish to control
13566 various aspects of this process.
13571 @kindex set hash@r{, for remote monitors}
13572 @cindex hash mark while downloading
13573 This command controls whether a hash mark @samp{#} is displayed while
13574 downloading a file to the remote monitor. If on, a hash mark is
13575 displayed after each S-record is successfully downloaded to the
13579 @kindex show hash@r{, for remote monitors}
13580 Show the current status of displaying the hash mark.
13582 @item set debug monitor
13583 @kindex set debug monitor
13584 @cindex display remote monitor communications
13585 Enable or disable display of communications messages between
13586 @value{GDBN} and the remote monitor.
13588 @item show debug monitor
13589 @kindex show debug monitor
13590 Show the current status of displaying communications between
13591 @value{GDBN} and the remote monitor.
13596 @kindex load @var{filename}
13597 @item load @var{filename}
13599 Depending on what remote debugging facilities are configured into
13600 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13601 is meant to make @var{filename} (an executable) available for debugging
13602 on the remote system---by downloading, or dynamic linking, for example.
13603 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
13604 the @code{add-symbol-file} command.
13606 If your @value{GDBN} does not have a @code{load} command, attempting to
13607 execute it gets the error message ``@code{You can't do that when your
13608 target is @dots{}}''
13610 The file is loaded at whatever address is specified in the executable.
13611 For some object file formats, you can specify the load address when you
13612 link the program; for other formats, like a.out, the object file format
13613 specifies a fixed address.
13614 @c FIXME! This would be a good place for an xref to the GNU linker doc.
13616 Depending on the remote side capabilities, @value{GDBN} may be able to
13617 load programs into flash memory.
13619 @code{load} does not repeat if you press @key{RET} again after using it.
13623 @section Choosing Target Byte Order
13625 @cindex choosing target byte order
13626 @cindex target byte order
13628 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
13629 offer the ability to run either big-endian or little-endian byte
13630 orders. Usually the executable or symbol will include a bit to
13631 designate the endian-ness, and you will not need to worry about
13632 which to use. However, you may still find it useful to adjust
13633 @value{GDBN}'s idea of processor endian-ness manually.
13637 @item set endian big
13638 Instruct @value{GDBN} to assume the target is big-endian.
13640 @item set endian little
13641 Instruct @value{GDBN} to assume the target is little-endian.
13643 @item set endian auto
13644 Instruct @value{GDBN} to use the byte order associated with the
13648 Display @value{GDBN}'s current idea of the target byte order.
13652 Note that these commands merely adjust interpretation of symbolic
13653 data on the host, and that they have absolutely no effect on the
13657 @node Remote Debugging
13658 @chapter Debugging Remote Programs
13659 @cindex remote debugging
13661 If you are trying to debug a program running on a machine that cannot run
13662 @value{GDBN} in the usual way, it is often useful to use remote debugging.
13663 For example, you might use remote debugging on an operating system kernel,
13664 or on a small system which does not have a general purpose operating system
13665 powerful enough to run a full-featured debugger.
13667 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
13668 to make this work with particular debugging targets. In addition,
13669 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
13670 but not specific to any particular target system) which you can use if you
13671 write the remote stubs---the code that runs on the remote system to
13672 communicate with @value{GDBN}.
13674 Other remote targets may be available in your
13675 configuration of @value{GDBN}; use @code{help target} to list them.
13678 * Connecting:: Connecting to a remote target
13679 * File Transfer:: Sending files to a remote system
13680 * Server:: Using the gdbserver program
13681 * Remote Configuration:: Remote configuration
13682 * Remote Stub:: Implementing a remote stub
13686 @section Connecting to a Remote Target
13688 On the @value{GDBN} host machine, you will need an unstripped copy of
13689 your program, since @value{GDBN} needs symbol and debugging information.
13690 Start up @value{GDBN} as usual, using the name of the local copy of your
13691 program as the first argument.
13693 @cindex @code{target remote}
13694 @value{GDBN} can communicate with the target over a serial line, or
13695 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13696 each case, @value{GDBN} uses the same protocol for debugging your
13697 program; only the medium carrying the debugging packets varies. The
13698 @code{target remote} command establishes a connection to the target.
13699 Its arguments indicate which medium to use:
13703 @item target remote @var{serial-device}
13704 @cindex serial line, @code{target remote}
13705 Use @var{serial-device} to communicate with the target. For example,
13706 to use a serial line connected to the device named @file{/dev/ttyb}:
13709 target remote /dev/ttyb
13712 If you're using a serial line, you may want to give @value{GDBN} the
13713 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13714 (@pxref{Remote Configuration, set remotebaud}) before the
13715 @code{target} command.
13717 @item target remote @code{@var{host}:@var{port}}
13718 @itemx target remote @code{tcp:@var{host}:@var{port}}
13719 @cindex @acronym{TCP} port, @code{target remote}
13720 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13721 The @var{host} may be either a host name or a numeric @acronym{IP}
13722 address; @var{port} must be a decimal number. The @var{host} could be
13723 the target machine itself, if it is directly connected to the net, or
13724 it might be a terminal server which in turn has a serial line to the
13727 For example, to connect to port 2828 on a terminal server named
13731 target remote manyfarms:2828
13734 If your remote target is actually running on the same machine as your
13735 debugger session (e.g.@: a simulator for your target running on the
13736 same host), you can omit the hostname. For example, to connect to
13737 port 1234 on your local machine:
13740 target remote :1234
13744 Note that the colon is still required here.
13746 @item target remote @code{udp:@var{host}:@var{port}}
13747 @cindex @acronym{UDP} port, @code{target remote}
13748 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13749 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13752 target remote udp:manyfarms:2828
13755 When using a @acronym{UDP} connection for remote debugging, you should
13756 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13757 can silently drop packets on busy or unreliable networks, which will
13758 cause havoc with your debugging session.
13760 @item target remote | @var{command}
13761 @cindex pipe, @code{target remote} to
13762 Run @var{command} in the background and communicate with it using a
13763 pipe. The @var{command} is a shell command, to be parsed and expanded
13764 by the system's command shell, @code{/bin/sh}; it should expect remote
13765 protocol packets on its standard input, and send replies on its
13766 standard output. You could use this to run a stand-alone simulator
13767 that speaks the remote debugging protocol, to make net connections
13768 using programs like @code{ssh}, or for other similar tricks.
13770 If @var{command} closes its standard output (perhaps by exiting),
13771 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13772 program has already exited, this will have no effect.)
13776 Once the connection has been established, you can use all the usual
13777 commands to examine and change data. The remote program is already
13778 running; you can use @kbd{step} and @kbd{continue}, and you do not
13779 need to use @kbd{run}.
13781 @cindex interrupting remote programs
13782 @cindex remote programs, interrupting
13783 Whenever @value{GDBN} is waiting for the remote program, if you type the
13784 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13785 program. This may or may not succeed, depending in part on the hardware
13786 and the serial drivers the remote system uses. If you type the
13787 interrupt character once again, @value{GDBN} displays this prompt:
13790 Interrupted while waiting for the program.
13791 Give up (and stop debugging it)? (y or n)
13794 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13795 (If you decide you want to try again later, you can use @samp{target
13796 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13797 goes back to waiting.
13800 @kindex detach (remote)
13802 When you have finished debugging the remote program, you can use the
13803 @code{detach} command to release it from @value{GDBN} control.
13804 Detaching from the target normally resumes its execution, but the results
13805 will depend on your particular remote stub. After the @code{detach}
13806 command, @value{GDBN} is free to connect to another target.
13810 The @code{disconnect} command behaves like @code{detach}, except that
13811 the target is generally not resumed. It will wait for @value{GDBN}
13812 (this instance or another one) to connect and continue debugging. After
13813 the @code{disconnect} command, @value{GDBN} is again free to connect to
13816 @cindex send command to remote monitor
13817 @cindex extend @value{GDBN} for remote targets
13818 @cindex add new commands for external monitor
13820 @item monitor @var{cmd}
13821 This command allows you to send arbitrary commands directly to the
13822 remote monitor. Since @value{GDBN} doesn't care about the commands it
13823 sends like this, this command is the way to extend @value{GDBN}---you
13824 can add new commands that only the external monitor will understand
13828 @node File Transfer
13829 @section Sending files to a remote system
13830 @cindex remote target, file transfer
13831 @cindex file transfer
13832 @cindex sending files to remote systems
13834 Some remote targets offer the ability to transfer files over the same
13835 connection used to communicate with @value{GDBN}. This is convenient
13836 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
13837 running @code{gdbserver} over a network interface. For other targets,
13838 e.g.@: embedded devices with only a single serial port, this may be
13839 the only way to upload or download files.
13841 Not all remote targets support these commands.
13845 @item remote put @var{hostfile} @var{targetfile}
13846 Copy file @var{hostfile} from the host system (the machine running
13847 @value{GDBN}) to @var{targetfile} on the target system.
13850 @item remote get @var{targetfile} @var{hostfile}
13851 Copy file @var{targetfile} from the target system to @var{hostfile}
13852 on the host system.
13854 @kindex remote delete
13855 @item remote delete @var{targetfile}
13856 Delete @var{targetfile} from the target system.
13861 @section Using the @code{gdbserver} Program
13864 @cindex remote connection without stubs
13865 @code{gdbserver} is a control program for Unix-like systems, which
13866 allows you to connect your program with a remote @value{GDBN} via
13867 @code{target remote}---but without linking in the usual debugging stub.
13869 @code{gdbserver} is not a complete replacement for the debugging stubs,
13870 because it requires essentially the same operating-system facilities
13871 that @value{GDBN} itself does. In fact, a system that can run
13872 @code{gdbserver} to connect to a remote @value{GDBN} could also run
13873 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
13874 because it is a much smaller program than @value{GDBN} itself. It is
13875 also easier to port than all of @value{GDBN}, so you may be able to get
13876 started more quickly on a new system by using @code{gdbserver}.
13877 Finally, if you develop code for real-time systems, you may find that
13878 the tradeoffs involved in real-time operation make it more convenient to
13879 do as much development work as possible on another system, for example
13880 by cross-compiling. You can use @code{gdbserver} to make a similar
13881 choice for debugging.
13883 @value{GDBN} and @code{gdbserver} communicate via either a serial line
13884 or a TCP connection, using the standard @value{GDBN} remote serial
13888 @emph{Warning:} @code{gdbserver} does not have any built-in security.
13889 Do not run @code{gdbserver} connected to any public network; a
13890 @value{GDBN} connection to @code{gdbserver} provides access to the
13891 target system with the same privileges as the user running
13895 @subsection Running @code{gdbserver}
13896 @cindex arguments, to @code{gdbserver}
13898 Run @code{gdbserver} on the target system. You need a copy of the
13899 program you want to debug, including any libraries it requires.
13900 @code{gdbserver} does not need your program's symbol table, so you can
13901 strip the program if necessary to save space. @value{GDBN} on the host
13902 system does all the symbol handling.
13904 To use the server, you must tell it how to communicate with @value{GDBN};
13905 the name of your program; and the arguments for your program. The usual
13909 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
13912 @var{comm} is either a device name (to use a serial line) or a TCP
13913 hostname and portnumber. For example, to debug Emacs with the argument
13914 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
13918 target> gdbserver /dev/com1 emacs foo.txt
13921 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
13924 To use a TCP connection instead of a serial line:
13927 target> gdbserver host:2345 emacs foo.txt
13930 The only difference from the previous example is the first argument,
13931 specifying that you are communicating with the host @value{GDBN} via
13932 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
13933 expect a TCP connection from machine @samp{host} to local TCP port 2345.
13934 (Currently, the @samp{host} part is ignored.) You can choose any number
13935 you want for the port number as long as it does not conflict with any
13936 TCP ports already in use on the target system (for example, @code{23} is
13937 reserved for @code{telnet}).@footnote{If you choose a port number that
13938 conflicts with another service, @code{gdbserver} prints an error message
13939 and exits.} You must use the same port number with the host @value{GDBN}
13940 @code{target remote} command.
13942 @subsubsection Attaching to a Running Program
13944 On some targets, @code{gdbserver} can also attach to running programs.
13945 This is accomplished via the @code{--attach} argument. The syntax is:
13948 target> gdbserver --attach @var{comm} @var{pid}
13951 @var{pid} is the process ID of a currently running process. It isn't necessary
13952 to point @code{gdbserver} at a binary for the running process.
13955 @cindex attach to a program by name
13956 You can debug processes by name instead of process ID if your target has the
13957 @code{pidof} utility:
13960 target> gdbserver --attach @var{comm} `pidof @var{program}`
13963 In case more than one copy of @var{program} is running, or @var{program}
13964 has multiple threads, most versions of @code{pidof} support the
13965 @code{-s} option to only return the first process ID.
13967 @subsubsection Multi-Process Mode for @code{gdbserver}
13968 @cindex gdbserver, multiple processes
13969 @cindex multiple processes with gdbserver
13971 When you connect to @code{gdbserver} using @code{target remote},
13972 @code{gdbserver} debugs the specified program only once. When the
13973 program exits, or you detach from it, @value{GDBN} closes the connection
13974 and @code{gdbserver} exits.
13976 If you connect using @kbd{target extended-remote}, @code{gdbserver}
13977 enters multi-process mode. When the debugged program exits, or you
13978 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
13979 though no program is running. The @code{run} and @code{attach}
13980 commands instruct @code{gdbserver} to run or attach to a new program.
13981 The @code{run} command uses @code{set remote exec-file} (@pxref{set
13982 remote exec-file}) to select the program to run. Command line
13983 arguments are supported, except for wildcard expansion and I/O
13984 redirection (@pxref{Arguments}).
13986 To start @code{gdbserver} without supplying an initial command to run
13987 or process ID to attach, use the @option{--multi} command line option.
13988 Then you can connect using @kbd{target extended-remote} and start
13989 the program you want to debug.
13991 @code{gdbserver} does not automatically exit in multi-process mode.
13992 You can terminate it by using @code{monitor exit}
13993 (@pxref{Monitor Commands for gdbserver}).
13995 @subsubsection Other Command-Line Arguments for @code{gdbserver}
13997 The @option{--debug} option tells @code{gdbserver} to display extra
13998 status information about the debugging process. The
13999 @option{--remote-debug} option tells @code{gdbserver} to display
14000 remote protocol debug output. These options are intended for
14001 @code{gdbserver} development and for bug reports to the developers.
14003 The @option{--wrapper} option specifies a wrapper to launch programs
14004 for debugging. The option should be followed by the name of the
14005 wrapper, then any command-line arguments to pass to the wrapper, then
14006 @kbd{--} indicating the end of the wrapper arguments.
14008 @code{gdbserver} runs the specified wrapper program with a combined
14009 command line including the wrapper arguments, then the name of the
14010 program to debug, then any arguments to the program. The wrapper
14011 runs until it executes your program, and then @value{GDBN} gains control.
14013 You can use any program that eventually calls @code{execve} with
14014 its arguments as a wrapper. Several standard Unix utilities do
14015 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
14016 with @code{exec "$@@"} will also work.
14018 For example, you can use @code{env} to pass an environment variable to
14019 the debugged program, without setting the variable in @code{gdbserver}'s
14023 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
14026 @subsection Connecting to @code{gdbserver}
14028 Run @value{GDBN} on the host system.
14030 First make sure you have the necessary symbol files. Load symbols for
14031 your application using the @code{file} command before you connect. Use
14032 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
14033 was compiled with the correct sysroot using @code{--with-sysroot}).
14035 The symbol file and target libraries must exactly match the executable
14036 and libraries on the target, with one exception: the files on the host
14037 system should not be stripped, even if the files on the target system
14038 are. Mismatched or missing files will lead to confusing results
14039 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
14040 files may also prevent @code{gdbserver} from debugging multi-threaded
14043 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
14044 For TCP connections, you must start up @code{gdbserver} prior to using
14045 the @code{target remote} command. Otherwise you may get an error whose
14046 text depends on the host system, but which usually looks something like
14047 @samp{Connection refused}. Don't use the @code{load}
14048 command in @value{GDBN} when using @code{gdbserver}, since the program is
14049 already on the target.
14051 @subsection Monitor Commands for @code{gdbserver}
14052 @cindex monitor commands, for @code{gdbserver}
14053 @anchor{Monitor Commands for gdbserver}
14055 During a @value{GDBN} session using @code{gdbserver}, you can use the
14056 @code{monitor} command to send special requests to @code{gdbserver}.
14057 Here are the available commands.
14061 List the available monitor commands.
14063 @item monitor set debug 0
14064 @itemx monitor set debug 1
14065 Disable or enable general debugging messages.
14067 @item monitor set remote-debug 0
14068 @itemx monitor set remote-debug 1
14069 Disable or enable specific debugging messages associated with the remote
14070 protocol (@pxref{Remote Protocol}).
14073 Tell gdbserver to exit immediately. This command should be followed by
14074 @code{disconnect} to close the debugging session. @code{gdbserver} will
14075 detach from any attached processes and kill any processes it created.
14076 Use @code{monitor exit} to terminate @code{gdbserver} at the end
14077 of a multi-process mode debug session.
14081 @node Remote Configuration
14082 @section Remote Configuration
14085 @kindex show remote
14086 This section documents the configuration options available when
14087 debugging remote programs. For the options related to the File I/O
14088 extensions of the remote protocol, see @ref{system,
14089 system-call-allowed}.
14092 @item set remoteaddresssize @var{bits}
14093 @cindex address size for remote targets
14094 @cindex bits in remote address
14095 Set the maximum size of address in a memory packet to the specified
14096 number of bits. @value{GDBN} will mask off the address bits above
14097 that number, when it passes addresses to the remote target. The
14098 default value is the number of bits in the target's address.
14100 @item show remoteaddresssize
14101 Show the current value of remote address size in bits.
14103 @item set remotebaud @var{n}
14104 @cindex baud rate for remote targets
14105 Set the baud rate for the remote serial I/O to @var{n} baud. The
14106 value is used to set the speed of the serial port used for debugging
14109 @item show remotebaud
14110 Show the current speed of the remote connection.
14112 @item set remotebreak
14113 @cindex interrupt remote programs
14114 @cindex BREAK signal instead of Ctrl-C
14115 @anchor{set remotebreak}
14116 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
14117 when you type @kbd{Ctrl-c} to interrupt the program running
14118 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
14119 character instead. The default is off, since most remote systems
14120 expect to see @samp{Ctrl-C} as the interrupt signal.
14122 @item show remotebreak
14123 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
14124 interrupt the remote program.
14126 @item set remoteflow on
14127 @itemx set remoteflow off
14128 @kindex set remoteflow
14129 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
14130 on the serial port used to communicate to the remote target.
14132 @item show remoteflow
14133 @kindex show remoteflow
14134 Show the current setting of hardware flow control.
14136 @item set remotelogbase @var{base}
14137 Set the base (a.k.a.@: radix) of logging serial protocol
14138 communications to @var{base}. Supported values of @var{base} are:
14139 @code{ascii}, @code{octal}, and @code{hex}. The default is
14142 @item show remotelogbase
14143 Show the current setting of the radix for logging remote serial
14146 @item set remotelogfile @var{file}
14147 @cindex record serial communications on file
14148 Record remote serial communications on the named @var{file}. The
14149 default is not to record at all.
14151 @item show remotelogfile.
14152 Show the current setting of the file name on which to record the
14153 serial communications.
14155 @item set remotetimeout @var{num}
14156 @cindex timeout for serial communications
14157 @cindex remote timeout
14158 Set the timeout limit to wait for the remote target to respond to
14159 @var{num} seconds. The default is 2 seconds.
14161 @item show remotetimeout
14162 Show the current number of seconds to wait for the remote target
14165 @cindex limit hardware breakpoints and watchpoints
14166 @cindex remote target, limit break- and watchpoints
14167 @anchor{set remote hardware-watchpoint-limit}
14168 @anchor{set remote hardware-breakpoint-limit}
14169 @item set remote hardware-watchpoint-limit @var{limit}
14170 @itemx set remote hardware-breakpoint-limit @var{limit}
14171 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
14172 watchpoints. A limit of -1, the default, is treated as unlimited.
14174 @item set remote exec-file @var{filename}
14175 @itemx show remote exec-file
14176 @anchor{set remote exec-file}
14177 @cindex executable file, for remote target
14178 Select the file used for @code{run} with @code{target
14179 extended-remote}. This should be set to a filename valid on the
14180 target system. If it is not set, the target will use a default
14181 filename (e.g.@: the last program run).
14185 @item set tcp auto-retry on
14186 @cindex auto-retry, for remote TCP target
14187 Enable auto-retry for remote TCP connections. This is useful if the remote
14188 debugging agent is launched in parallel with @value{GDBN}; there is a race
14189 condition because the agent may not become ready to accept the connection
14190 before @value{GDBN} attempts to connect. When auto-retry is
14191 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
14192 to establish the connection using the timeout specified by
14193 @code{set tcp connect-timeout}.
14195 @item set tcp auto-retry off
14196 Do not auto-retry failed TCP connections.
14198 @item show tcp auto-retry
14199 Show the current auto-retry setting.
14201 @item set tcp connect-timeout @var{seconds}
14202 @cindex connection timeout, for remote TCP target
14203 @cindex timeout, for remote target connection
14204 Set the timeout for establishing a TCP connection to the remote target to
14205 @var{seconds}. The timeout affects both polling to retry failed connections
14206 (enabled by @code{set tcp auto-retry on}) and waiting for connections
14207 that are merely slow to complete, and represents an approximate cumulative
14210 @item show tcp connect-timeout
14211 Show the current connection timeout setting.
14214 @cindex remote packets, enabling and disabling
14215 The @value{GDBN} remote protocol autodetects the packets supported by
14216 your debugging stub. If you need to override the autodetection, you
14217 can use these commands to enable or disable individual packets. Each
14218 packet can be set to @samp{on} (the remote target supports this
14219 packet), @samp{off} (the remote target does not support this packet),
14220 or @samp{auto} (detect remote target support for this packet). They
14221 all default to @samp{auto}. For more information about each packet,
14222 see @ref{Remote Protocol}.
14224 During normal use, you should not have to use any of these commands.
14225 If you do, that may be a bug in your remote debugging stub, or a bug
14226 in @value{GDBN}. You may want to report the problem to the
14227 @value{GDBN} developers.
14229 For each packet @var{name}, the command to enable or disable the
14230 packet is @code{set remote @var{name}-packet}. The available settings
14233 @multitable @columnfractions 0.28 0.32 0.25
14236 @tab Related Features
14238 @item @code{fetch-register}
14240 @tab @code{info registers}
14242 @item @code{set-register}
14246 @item @code{binary-download}
14248 @tab @code{load}, @code{set}
14250 @item @code{read-aux-vector}
14251 @tab @code{qXfer:auxv:read}
14252 @tab @code{info auxv}
14254 @item @code{symbol-lookup}
14255 @tab @code{qSymbol}
14256 @tab Detecting multiple threads
14258 @item @code{attach}
14259 @tab @code{vAttach}
14262 @item @code{verbose-resume}
14264 @tab Stepping or resuming multiple threads
14270 @item @code{software-breakpoint}
14274 @item @code{hardware-breakpoint}
14278 @item @code{write-watchpoint}
14282 @item @code{read-watchpoint}
14286 @item @code{access-watchpoint}
14290 @item @code{target-features}
14291 @tab @code{qXfer:features:read}
14292 @tab @code{set architecture}
14294 @item @code{library-info}
14295 @tab @code{qXfer:libraries:read}
14296 @tab @code{info sharedlibrary}
14298 @item @code{memory-map}
14299 @tab @code{qXfer:memory-map:read}
14300 @tab @code{info mem}
14302 @item @code{read-spu-object}
14303 @tab @code{qXfer:spu:read}
14304 @tab @code{info spu}
14306 @item @code{write-spu-object}
14307 @tab @code{qXfer:spu:write}
14308 @tab @code{info spu}
14310 @item @code{get-thread-local-@*storage-address}
14311 @tab @code{qGetTLSAddr}
14312 @tab Displaying @code{__thread} variables
14314 @item @code{search-memory}
14315 @tab @code{qSearch:memory}
14318 @item @code{supported-packets}
14319 @tab @code{qSupported}
14320 @tab Remote communications parameters
14322 @item @code{pass-signals}
14323 @tab @code{QPassSignals}
14324 @tab @code{handle @var{signal}}
14326 @item @code{hostio-close-packet}
14327 @tab @code{vFile:close}
14328 @tab @code{remote get}, @code{remote put}
14330 @item @code{hostio-open-packet}
14331 @tab @code{vFile:open}
14332 @tab @code{remote get}, @code{remote put}
14334 @item @code{hostio-pread-packet}
14335 @tab @code{vFile:pread}
14336 @tab @code{remote get}, @code{remote put}
14338 @item @code{hostio-pwrite-packet}
14339 @tab @code{vFile:pwrite}
14340 @tab @code{remote get}, @code{remote put}
14342 @item @code{hostio-unlink-packet}
14343 @tab @code{vFile:unlink}
14344 @tab @code{remote delete}
14346 @item @code{noack-packet}
14347 @tab @code{QStartNoAckMode}
14348 @tab Packet acknowledgment
14350 @item @code{osdata}
14351 @tab @code{qXfer:osdata:read}
14352 @tab @code{info os}
14356 @section Implementing a Remote Stub
14358 @cindex debugging stub, example
14359 @cindex remote stub, example
14360 @cindex stub example, remote debugging
14361 The stub files provided with @value{GDBN} implement the target side of the
14362 communication protocol, and the @value{GDBN} side is implemented in the
14363 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
14364 these subroutines to communicate, and ignore the details. (If you're
14365 implementing your own stub file, you can still ignore the details: start
14366 with one of the existing stub files. @file{sparc-stub.c} is the best
14367 organized, and therefore the easiest to read.)
14369 @cindex remote serial debugging, overview
14370 To debug a program running on another machine (the debugging
14371 @dfn{target} machine), you must first arrange for all the usual
14372 prerequisites for the program to run by itself. For example, for a C
14377 A startup routine to set up the C runtime environment; these usually
14378 have a name like @file{crt0}. The startup routine may be supplied by
14379 your hardware supplier, or you may have to write your own.
14382 A C subroutine library to support your program's
14383 subroutine calls, notably managing input and output.
14386 A way of getting your program to the other machine---for example, a
14387 download program. These are often supplied by the hardware
14388 manufacturer, but you may have to write your own from hardware
14392 The next step is to arrange for your program to use a serial port to
14393 communicate with the machine where @value{GDBN} is running (the @dfn{host}
14394 machine). In general terms, the scheme looks like this:
14398 @value{GDBN} already understands how to use this protocol; when everything
14399 else is set up, you can simply use the @samp{target remote} command
14400 (@pxref{Targets,,Specifying a Debugging Target}).
14402 @item On the target,
14403 you must link with your program a few special-purpose subroutines that
14404 implement the @value{GDBN} remote serial protocol. The file containing these
14405 subroutines is called a @dfn{debugging stub}.
14407 On certain remote targets, you can use an auxiliary program
14408 @code{gdbserver} instead of linking a stub into your program.
14409 @xref{Server,,Using the @code{gdbserver} Program}, for details.
14412 The debugging stub is specific to the architecture of the remote
14413 machine; for example, use @file{sparc-stub.c} to debug programs on
14416 @cindex remote serial stub list
14417 These working remote stubs are distributed with @value{GDBN}:
14422 @cindex @file{i386-stub.c}
14425 For Intel 386 and compatible architectures.
14428 @cindex @file{m68k-stub.c}
14429 @cindex Motorola 680x0
14431 For Motorola 680x0 architectures.
14434 @cindex @file{sh-stub.c}
14437 For Renesas SH architectures.
14440 @cindex @file{sparc-stub.c}
14442 For @sc{sparc} architectures.
14444 @item sparcl-stub.c
14445 @cindex @file{sparcl-stub.c}
14448 For Fujitsu @sc{sparclite} architectures.
14452 The @file{README} file in the @value{GDBN} distribution may list other
14453 recently added stubs.
14456 * Stub Contents:: What the stub can do for you
14457 * Bootstrapping:: What you must do for the stub
14458 * Debug Session:: Putting it all together
14461 @node Stub Contents
14462 @subsection What the Stub Can Do for You
14464 @cindex remote serial stub
14465 The debugging stub for your architecture supplies these three
14469 @item set_debug_traps
14470 @findex set_debug_traps
14471 @cindex remote serial stub, initialization
14472 This routine arranges for @code{handle_exception} to run when your
14473 program stops. You must call this subroutine explicitly near the
14474 beginning of your program.
14476 @item handle_exception
14477 @findex handle_exception
14478 @cindex remote serial stub, main routine
14479 This is the central workhorse, but your program never calls it
14480 explicitly---the setup code arranges for @code{handle_exception} to
14481 run when a trap is triggered.
14483 @code{handle_exception} takes control when your program stops during
14484 execution (for example, on a breakpoint), and mediates communications
14485 with @value{GDBN} on the host machine. This is where the communications
14486 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
14487 representative on the target machine. It begins by sending summary
14488 information on the state of your program, then continues to execute,
14489 retrieving and transmitting any information @value{GDBN} needs, until you
14490 execute a @value{GDBN} command that makes your program resume; at that point,
14491 @code{handle_exception} returns control to your own code on the target
14495 @cindex @code{breakpoint} subroutine, remote
14496 Use this auxiliary subroutine to make your program contain a
14497 breakpoint. Depending on the particular situation, this may be the only
14498 way for @value{GDBN} to get control. For instance, if your target
14499 machine has some sort of interrupt button, you won't need to call this;
14500 pressing the interrupt button transfers control to
14501 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
14502 simply receiving characters on the serial port may also trigger a trap;
14503 again, in that situation, you don't need to call @code{breakpoint} from
14504 your own program---simply running @samp{target remote} from the host
14505 @value{GDBN} session gets control.
14507 Call @code{breakpoint} if none of these is true, or if you simply want
14508 to make certain your program stops at a predetermined point for the
14509 start of your debugging session.
14512 @node Bootstrapping
14513 @subsection What You Must Do for the Stub
14515 @cindex remote stub, support routines
14516 The debugging stubs that come with @value{GDBN} are set up for a particular
14517 chip architecture, but they have no information about the rest of your
14518 debugging target machine.
14520 First of all you need to tell the stub how to communicate with the
14524 @item int getDebugChar()
14525 @findex getDebugChar
14526 Write this subroutine to read a single character from the serial port.
14527 It may be identical to @code{getchar} for your target system; a
14528 different name is used to allow you to distinguish the two if you wish.
14530 @item void putDebugChar(int)
14531 @findex putDebugChar
14532 Write this subroutine to write a single character to the serial port.
14533 It may be identical to @code{putchar} for your target system; a
14534 different name is used to allow you to distinguish the two if you wish.
14537 @cindex control C, and remote debugging
14538 @cindex interrupting remote targets
14539 If you want @value{GDBN} to be able to stop your program while it is
14540 running, you need to use an interrupt-driven serial driver, and arrange
14541 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
14542 character). That is the character which @value{GDBN} uses to tell the
14543 remote system to stop.
14545 Getting the debugging target to return the proper status to @value{GDBN}
14546 probably requires changes to the standard stub; one quick and dirty way
14547 is to just execute a breakpoint instruction (the ``dirty'' part is that
14548 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
14550 Other routines you need to supply are:
14553 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
14554 @findex exceptionHandler
14555 Write this function to install @var{exception_address} in the exception
14556 handling tables. You need to do this because the stub does not have any
14557 way of knowing what the exception handling tables on your target system
14558 are like (for example, the processor's table might be in @sc{rom},
14559 containing entries which point to a table in @sc{ram}).
14560 @var{exception_number} is the exception number which should be changed;
14561 its meaning is architecture-dependent (for example, different numbers
14562 might represent divide by zero, misaligned access, etc). When this
14563 exception occurs, control should be transferred directly to
14564 @var{exception_address}, and the processor state (stack, registers,
14565 and so on) should be just as it is when a processor exception occurs. So if
14566 you want to use a jump instruction to reach @var{exception_address}, it
14567 should be a simple jump, not a jump to subroutine.
14569 For the 386, @var{exception_address} should be installed as an interrupt
14570 gate so that interrupts are masked while the handler runs. The gate
14571 should be at privilege level 0 (the most privileged level). The
14572 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
14573 help from @code{exceptionHandler}.
14575 @item void flush_i_cache()
14576 @findex flush_i_cache
14577 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
14578 instruction cache, if any, on your target machine. If there is no
14579 instruction cache, this subroutine may be a no-op.
14581 On target machines that have instruction caches, @value{GDBN} requires this
14582 function to make certain that the state of your program is stable.
14586 You must also make sure this library routine is available:
14589 @item void *memset(void *, int, int)
14591 This is the standard library function @code{memset} that sets an area of
14592 memory to a known value. If you have one of the free versions of
14593 @code{libc.a}, @code{memset} can be found there; otherwise, you must
14594 either obtain it from your hardware manufacturer, or write your own.
14597 If you do not use the GNU C compiler, you may need other standard
14598 library subroutines as well; this varies from one stub to another,
14599 but in general the stubs are likely to use any of the common library
14600 subroutines which @code{@value{NGCC}} generates as inline code.
14603 @node Debug Session
14604 @subsection Putting it All Together
14606 @cindex remote serial debugging summary
14607 In summary, when your program is ready to debug, you must follow these
14612 Make sure you have defined the supporting low-level routines
14613 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
14615 @code{getDebugChar}, @code{putDebugChar},
14616 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
14620 Insert these lines near the top of your program:
14628 For the 680x0 stub only, you need to provide a variable called
14629 @code{exceptionHook}. Normally you just use:
14632 void (*exceptionHook)() = 0;
14636 but if before calling @code{set_debug_traps}, you set it to point to a
14637 function in your program, that function is called when
14638 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
14639 error). The function indicated by @code{exceptionHook} is called with
14640 one parameter: an @code{int} which is the exception number.
14643 Compile and link together: your program, the @value{GDBN} debugging stub for
14644 your target architecture, and the supporting subroutines.
14647 Make sure you have a serial connection between your target machine and
14648 the @value{GDBN} host, and identify the serial port on the host.
14651 @c The "remote" target now provides a `load' command, so we should
14652 @c document that. FIXME.
14653 Download your program to your target machine (or get it there by
14654 whatever means the manufacturer provides), and start it.
14657 Start @value{GDBN} on the host, and connect to the target
14658 (@pxref{Connecting,,Connecting to a Remote Target}).
14662 @node Configurations
14663 @chapter Configuration-Specific Information
14665 While nearly all @value{GDBN} commands are available for all native and
14666 cross versions of the debugger, there are some exceptions. This chapter
14667 describes things that are only available in certain configurations.
14669 There are three major categories of configurations: native
14670 configurations, where the host and target are the same, embedded
14671 operating system configurations, which are usually the same for several
14672 different processor architectures, and bare embedded processors, which
14673 are quite different from each other.
14678 * Embedded Processors::
14685 This section describes details specific to particular native
14690 * BSD libkvm Interface:: Debugging BSD kernel memory images
14691 * SVR4 Process Information:: SVR4 process information
14692 * DJGPP Native:: Features specific to the DJGPP port
14693 * Cygwin Native:: Features specific to the Cygwin port
14694 * Hurd Native:: Features specific to @sc{gnu} Hurd
14695 * Neutrino:: Features specific to QNX Neutrino
14696 * Darwin:: Features specific to Darwin
14702 On HP-UX systems, if you refer to a function or variable name that
14703 begins with a dollar sign, @value{GDBN} searches for a user or system
14704 name first, before it searches for a convenience variable.
14707 @node BSD libkvm Interface
14708 @subsection BSD libkvm Interface
14711 @cindex kernel memory image
14712 @cindex kernel crash dump
14714 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14715 interface that provides a uniform interface for accessing kernel virtual
14716 memory images, including live systems and crash dumps. @value{GDBN}
14717 uses this interface to allow you to debug live kernels and kernel crash
14718 dumps on many native BSD configurations. This is implemented as a
14719 special @code{kvm} debugging target. For debugging a live system, load
14720 the currently running kernel into @value{GDBN} and connect to the
14724 (@value{GDBP}) @b{target kvm}
14727 For debugging crash dumps, provide the file name of the crash dump as an
14731 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14734 Once connected to the @code{kvm} target, the following commands are
14740 Set current context from the @dfn{Process Control Block} (PCB) address.
14743 Set current context from proc address. This command isn't available on
14744 modern FreeBSD systems.
14747 @node SVR4 Process Information
14748 @subsection SVR4 Process Information
14750 @cindex examine process image
14751 @cindex process info via @file{/proc}
14753 Many versions of SVR4 and compatible systems provide a facility called
14754 @samp{/proc} that can be used to examine the image of a running
14755 process using file-system subroutines. If @value{GDBN} is configured
14756 for an operating system with this facility, the command @code{info
14757 proc} is available to report information about the process running
14758 your program, or about any process running on your system. @code{info
14759 proc} works only on SVR4 systems that include the @code{procfs} code.
14760 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14761 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14767 @itemx info proc @var{process-id}
14768 Summarize available information about any running process. If a
14769 process ID is specified by @var{process-id}, display information about
14770 that process; otherwise display information about the program being
14771 debugged. The summary includes the debugged process ID, the command
14772 line used to invoke it, its current working directory, and its
14773 executable file's absolute file name.
14775 On some systems, @var{process-id} can be of the form
14776 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14777 within a process. If the optional @var{pid} part is missing, it means
14778 a thread from the process being debugged (the leading @samp{/} still
14779 needs to be present, or else @value{GDBN} will interpret the number as
14780 a process ID rather than a thread ID).
14782 @item info proc mappings
14783 @cindex memory address space mappings
14784 Report the memory address space ranges accessible in the program, with
14785 information on whether the process has read, write, or execute access
14786 rights to each range. On @sc{gnu}/Linux systems, each memory range
14787 includes the object file which is mapped to that range, instead of the
14788 memory access rights to that range.
14790 @item info proc stat
14791 @itemx info proc status
14792 @cindex process detailed status information
14793 These subcommands are specific to @sc{gnu}/Linux systems. They show
14794 the process-related information, including the user ID and group ID;
14795 how many threads are there in the process; its virtual memory usage;
14796 the signals that are pending, blocked, and ignored; its TTY; its
14797 consumption of system and user time; its stack size; its @samp{nice}
14798 value; etc. For more information, see the @samp{proc} man page
14799 (type @kbd{man 5 proc} from your shell prompt).
14801 @item info proc all
14802 Show all the information about the process described under all of the
14803 above @code{info proc} subcommands.
14806 @comment These sub-options of 'info proc' were not included when
14807 @comment procfs.c was re-written. Keep their descriptions around
14808 @comment against the day when someone finds the time to put them back in.
14809 @kindex info proc times
14810 @item info proc times
14811 Starting time, user CPU time, and system CPU time for your program and
14814 @kindex info proc id
14816 Report on the process IDs related to your program: its own process ID,
14817 the ID of its parent, the process group ID, and the session ID.
14820 @item set procfs-trace
14821 @kindex set procfs-trace
14822 @cindex @code{procfs} API calls
14823 This command enables and disables tracing of @code{procfs} API calls.
14825 @item show procfs-trace
14826 @kindex show procfs-trace
14827 Show the current state of @code{procfs} API call tracing.
14829 @item set procfs-file @var{file}
14830 @kindex set procfs-file
14831 Tell @value{GDBN} to write @code{procfs} API trace to the named
14832 @var{file}. @value{GDBN} appends the trace info to the previous
14833 contents of the file. The default is to display the trace on the
14836 @item show procfs-file
14837 @kindex show procfs-file
14838 Show the file to which @code{procfs} API trace is written.
14840 @item proc-trace-entry
14841 @itemx proc-trace-exit
14842 @itemx proc-untrace-entry
14843 @itemx proc-untrace-exit
14844 @kindex proc-trace-entry
14845 @kindex proc-trace-exit
14846 @kindex proc-untrace-entry
14847 @kindex proc-untrace-exit
14848 These commands enable and disable tracing of entries into and exits
14849 from the @code{syscall} interface.
14852 @kindex info pidlist
14853 @cindex process list, QNX Neutrino
14854 For QNX Neutrino only, this command displays the list of all the
14855 processes and all the threads within each process.
14858 @kindex info meminfo
14859 @cindex mapinfo list, QNX Neutrino
14860 For QNX Neutrino only, this command displays the list of all mapinfos.
14864 @subsection Features for Debugging @sc{djgpp} Programs
14865 @cindex @sc{djgpp} debugging
14866 @cindex native @sc{djgpp} debugging
14867 @cindex MS-DOS-specific commands
14870 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
14871 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
14872 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
14873 top of real-mode DOS systems and their emulations.
14875 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
14876 defines a few commands specific to the @sc{djgpp} port. This
14877 subsection describes those commands.
14882 This is a prefix of @sc{djgpp}-specific commands which print
14883 information about the target system and important OS structures.
14886 @cindex MS-DOS system info
14887 @cindex free memory information (MS-DOS)
14888 @item info dos sysinfo
14889 This command displays assorted information about the underlying
14890 platform: the CPU type and features, the OS version and flavor, the
14891 DPMI version, and the available conventional and DPMI memory.
14896 @cindex segment descriptor tables
14897 @cindex descriptor tables display
14899 @itemx info dos ldt
14900 @itemx info dos idt
14901 These 3 commands display entries from, respectively, Global, Local,
14902 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
14903 tables are data structures which store a descriptor for each segment
14904 that is currently in use. The segment's selector is an index into a
14905 descriptor table; the table entry for that index holds the
14906 descriptor's base address and limit, and its attributes and access
14909 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
14910 segment (used for both data and the stack), and a DOS segment (which
14911 allows access to DOS/BIOS data structures and absolute addresses in
14912 conventional memory). However, the DPMI host will usually define
14913 additional segments in order to support the DPMI environment.
14915 @cindex garbled pointers
14916 These commands allow to display entries from the descriptor tables.
14917 Without an argument, all entries from the specified table are
14918 displayed. An argument, which should be an integer expression, means
14919 display a single entry whose index is given by the argument. For
14920 example, here's a convenient way to display information about the
14921 debugged program's data segment:
14924 @exdent @code{(@value{GDBP}) info dos ldt $ds}
14925 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
14929 This comes in handy when you want to see whether a pointer is outside
14930 the data segment's limit (i.e.@: @dfn{garbled}).
14932 @cindex page tables display (MS-DOS)
14934 @itemx info dos pte
14935 These two commands display entries from, respectively, the Page
14936 Directory and the Page Tables. Page Directories and Page Tables are
14937 data structures which control how virtual memory addresses are mapped
14938 into physical addresses. A Page Table includes an entry for every
14939 page of memory that is mapped into the program's address space; there
14940 may be several Page Tables, each one holding up to 4096 entries. A
14941 Page Directory has up to 4096 entries, one each for every Page Table
14942 that is currently in use.
14944 Without an argument, @kbd{info dos pde} displays the entire Page
14945 Directory, and @kbd{info dos pte} displays all the entries in all of
14946 the Page Tables. An argument, an integer expression, given to the
14947 @kbd{info dos pde} command means display only that entry from the Page
14948 Directory table. An argument given to the @kbd{info dos pte} command
14949 means display entries from a single Page Table, the one pointed to by
14950 the specified entry in the Page Directory.
14952 @cindex direct memory access (DMA) on MS-DOS
14953 These commands are useful when your program uses @dfn{DMA} (Direct
14954 Memory Access), which needs physical addresses to program the DMA
14957 These commands are supported only with some DPMI servers.
14959 @cindex physical address from linear address
14960 @item info dos address-pte @var{addr}
14961 This command displays the Page Table entry for a specified linear
14962 address. The argument @var{addr} is a linear address which should
14963 already have the appropriate segment's base address added to it,
14964 because this command accepts addresses which may belong to @emph{any}
14965 segment. For example, here's how to display the Page Table entry for
14966 the page where a variable @code{i} is stored:
14969 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
14970 @exdent @code{Page Table entry for address 0x11a00d30:}
14971 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
14975 This says that @code{i} is stored at offset @code{0xd30} from the page
14976 whose physical base address is @code{0x02698000}, and shows all the
14977 attributes of that page.
14979 Note that you must cast the addresses of variables to a @code{char *},
14980 since otherwise the value of @code{__djgpp_base_address}, the base
14981 address of all variables and functions in a @sc{djgpp} program, will
14982 be added using the rules of C pointer arithmetics: if @code{i} is
14983 declared an @code{int}, @value{GDBN} will add 4 times the value of
14984 @code{__djgpp_base_address} to the address of @code{i}.
14986 Here's another example, it displays the Page Table entry for the
14990 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
14991 @exdent @code{Page Table entry for address 0x29110:}
14992 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
14996 (The @code{+ 3} offset is because the transfer buffer's address is the
14997 3rd member of the @code{_go32_info_block} structure.) The output
14998 clearly shows that this DPMI server maps the addresses in conventional
14999 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
15000 linear (@code{0x29110}) addresses are identical.
15002 This command is supported only with some DPMI servers.
15005 @cindex DOS serial data link, remote debugging
15006 In addition to native debugging, the DJGPP port supports remote
15007 debugging via a serial data link. The following commands are specific
15008 to remote serial debugging in the DJGPP port of @value{GDBN}.
15011 @kindex set com1base
15012 @kindex set com1irq
15013 @kindex set com2base
15014 @kindex set com2irq
15015 @kindex set com3base
15016 @kindex set com3irq
15017 @kindex set com4base
15018 @kindex set com4irq
15019 @item set com1base @var{addr}
15020 This command sets the base I/O port address of the @file{COM1} serial
15023 @item set com1irq @var{irq}
15024 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
15025 for the @file{COM1} serial port.
15027 There are similar commands @samp{set com2base}, @samp{set com3irq},
15028 etc.@: for setting the port address and the @code{IRQ} lines for the
15031 @kindex show com1base
15032 @kindex show com1irq
15033 @kindex show com2base
15034 @kindex show com2irq
15035 @kindex show com3base
15036 @kindex show com3irq
15037 @kindex show com4base
15038 @kindex show com4irq
15039 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
15040 display the current settings of the base address and the @code{IRQ}
15041 lines used by the COM ports.
15044 @kindex info serial
15045 @cindex DOS serial port status
15046 This command prints the status of the 4 DOS serial ports. For each
15047 port, it prints whether it's active or not, its I/O base address and
15048 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
15049 counts of various errors encountered so far.
15053 @node Cygwin Native
15054 @subsection Features for Debugging MS Windows PE Executables
15055 @cindex MS Windows debugging
15056 @cindex native Cygwin debugging
15057 @cindex Cygwin-specific commands
15059 @value{GDBN} supports native debugging of MS Windows programs, including
15060 DLLs with and without symbolic debugging information. There are various
15061 additional Cygwin-specific commands, described in this section.
15062 Working with DLLs that have no debugging symbols is described in
15063 @ref{Non-debug DLL Symbols}.
15068 This is a prefix of MS Windows-specific commands which print
15069 information about the target system and important OS structures.
15071 @item info w32 selector
15072 This command displays information returned by
15073 the Win32 API @code{GetThreadSelectorEntry} function.
15074 It takes an optional argument that is evaluated to
15075 a long value to give the information about this given selector.
15076 Without argument, this command displays information
15077 about the six segment registers.
15081 This is a Cygwin-specific alias of @code{info shared}.
15083 @kindex dll-symbols
15085 This command loads symbols from a dll similarly to
15086 add-sym command but without the need to specify a base address.
15088 @kindex set cygwin-exceptions
15089 @cindex debugging the Cygwin DLL
15090 @cindex Cygwin DLL, debugging
15091 @item set cygwin-exceptions @var{mode}
15092 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
15093 happen inside the Cygwin DLL. If @var{mode} is @code{off},
15094 @value{GDBN} will delay recognition of exceptions, and may ignore some
15095 exceptions which seem to be caused by internal Cygwin DLL
15096 ``bookkeeping''. This option is meant primarily for debugging the
15097 Cygwin DLL itself; the default value is @code{off} to avoid annoying
15098 @value{GDBN} users with false @code{SIGSEGV} signals.
15100 @kindex show cygwin-exceptions
15101 @item show cygwin-exceptions
15102 Displays whether @value{GDBN} will break on exceptions that happen
15103 inside the Cygwin DLL itself.
15105 @kindex set new-console
15106 @item set new-console @var{mode}
15107 If @var{mode} is @code{on} the debuggee will
15108 be started in a new console on next start.
15109 If @var{mode} is @code{off}i, the debuggee will
15110 be started in the same console as the debugger.
15112 @kindex show new-console
15113 @item show new-console
15114 Displays whether a new console is used
15115 when the debuggee is started.
15117 @kindex set new-group
15118 @item set new-group @var{mode}
15119 This boolean value controls whether the debuggee should
15120 start a new group or stay in the same group as the debugger.
15121 This affects the way the Windows OS handles
15124 @kindex show new-group
15125 @item show new-group
15126 Displays current value of new-group boolean.
15128 @kindex set debugevents
15129 @item set debugevents
15130 This boolean value adds debug output concerning kernel events related
15131 to the debuggee seen by the debugger. This includes events that
15132 signal thread and process creation and exit, DLL loading and
15133 unloading, console interrupts, and debugging messages produced by the
15134 Windows @code{OutputDebugString} API call.
15136 @kindex set debugexec
15137 @item set debugexec
15138 This boolean value adds debug output concerning execute events
15139 (such as resume thread) seen by the debugger.
15141 @kindex set debugexceptions
15142 @item set debugexceptions
15143 This boolean value adds debug output concerning exceptions in the
15144 debuggee seen by the debugger.
15146 @kindex set debugmemory
15147 @item set debugmemory
15148 This boolean value adds debug output concerning debuggee memory reads
15149 and writes by the debugger.
15153 This boolean values specifies whether the debuggee is called
15154 via a shell or directly (default value is on).
15158 Displays if the debuggee will be started with a shell.
15163 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
15166 @node Non-debug DLL Symbols
15167 @subsubsection Support for DLLs without Debugging Symbols
15168 @cindex DLLs with no debugging symbols
15169 @cindex Minimal symbols and DLLs
15171 Very often on windows, some of the DLLs that your program relies on do
15172 not include symbolic debugging information (for example,
15173 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
15174 symbols in a DLL, it relies on the minimal amount of symbolic
15175 information contained in the DLL's export table. This section
15176 describes working with such symbols, known internally to @value{GDBN} as
15177 ``minimal symbols''.
15179 Note that before the debugged program has started execution, no DLLs
15180 will have been loaded. The easiest way around this problem is simply to
15181 start the program --- either by setting a breakpoint or letting the
15182 program run once to completion. It is also possible to force
15183 @value{GDBN} to load a particular DLL before starting the executable ---
15184 see the shared library information in @ref{Files}, or the
15185 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
15186 explicitly loading symbols from a DLL with no debugging information will
15187 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
15188 which may adversely affect symbol lookup performance.
15190 @subsubsection DLL Name Prefixes
15192 In keeping with the naming conventions used by the Microsoft debugging
15193 tools, DLL export symbols are made available with a prefix based on the
15194 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
15195 also entered into the symbol table, so @code{CreateFileA} is often
15196 sufficient. In some cases there will be name clashes within a program
15197 (particularly if the executable itself includes full debugging symbols)
15198 necessitating the use of the fully qualified name when referring to the
15199 contents of the DLL. Use single-quotes around the name to avoid the
15200 exclamation mark (``!'') being interpreted as a language operator.
15202 Note that the internal name of the DLL may be all upper-case, even
15203 though the file name of the DLL is lower-case, or vice-versa. Since
15204 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
15205 some confusion. If in doubt, try the @code{info functions} and
15206 @code{info variables} commands or even @code{maint print msymbols}
15207 (@pxref{Symbols}). Here's an example:
15210 (@value{GDBP}) info function CreateFileA
15211 All functions matching regular expression "CreateFileA":
15213 Non-debugging symbols:
15214 0x77e885f4 CreateFileA
15215 0x77e885f4 KERNEL32!CreateFileA
15219 (@value{GDBP}) info function !
15220 All functions matching regular expression "!":
15222 Non-debugging symbols:
15223 0x6100114c cygwin1!__assert
15224 0x61004034 cygwin1!_dll_crt0@@0
15225 0x61004240 cygwin1!dll_crt0(per_process *)
15229 @subsubsection Working with Minimal Symbols
15231 Symbols extracted from a DLL's export table do not contain very much
15232 type information. All that @value{GDBN} can do is guess whether a symbol
15233 refers to a function or variable depending on the linker section that
15234 contains the symbol. Also note that the actual contents of the memory
15235 contained in a DLL are not available unless the program is running. This
15236 means that you cannot examine the contents of a variable or disassemble
15237 a function within a DLL without a running program.
15239 Variables are generally treated as pointers and dereferenced
15240 automatically. For this reason, it is often necessary to prefix a
15241 variable name with the address-of operator (``&'') and provide explicit
15242 type information in the command. Here's an example of the type of
15246 (@value{GDBP}) print 'cygwin1!__argv'
15251 (@value{GDBP}) x 'cygwin1!__argv'
15252 0x10021610: "\230y\""
15255 And two possible solutions:
15258 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
15259 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
15263 (@value{GDBP}) x/2x &'cygwin1!__argv'
15264 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
15265 (@value{GDBP}) x/x 0x10021608
15266 0x10021608: 0x0022fd98
15267 (@value{GDBP}) x/s 0x0022fd98
15268 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
15271 Setting a break point within a DLL is possible even before the program
15272 starts execution. However, under these circumstances, @value{GDBN} can't
15273 examine the initial instructions of the function in order to skip the
15274 function's frame set-up code. You can work around this by using ``*&''
15275 to set the breakpoint at a raw memory address:
15278 (@value{GDBP}) break *&'python22!PyOS_Readline'
15279 Breakpoint 1 at 0x1e04eff0
15282 The author of these extensions is not entirely convinced that setting a
15283 break point within a shared DLL like @file{kernel32.dll} is completely
15287 @subsection Commands Specific to @sc{gnu} Hurd Systems
15288 @cindex @sc{gnu} Hurd debugging
15290 This subsection describes @value{GDBN} commands specific to the
15291 @sc{gnu} Hurd native debugging.
15296 @kindex set signals@r{, Hurd command}
15297 @kindex set sigs@r{, Hurd command}
15298 This command toggles the state of inferior signal interception by
15299 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
15300 affected by this command. @code{sigs} is a shorthand alias for
15305 @kindex show signals@r{, Hurd command}
15306 @kindex show sigs@r{, Hurd command}
15307 Show the current state of intercepting inferior's signals.
15309 @item set signal-thread
15310 @itemx set sigthread
15311 @kindex set signal-thread
15312 @kindex set sigthread
15313 This command tells @value{GDBN} which thread is the @code{libc} signal
15314 thread. That thread is run when a signal is delivered to a running
15315 process. @code{set sigthread} is the shorthand alias of @code{set
15318 @item show signal-thread
15319 @itemx show sigthread
15320 @kindex show signal-thread
15321 @kindex show sigthread
15322 These two commands show which thread will run when the inferior is
15323 delivered a signal.
15326 @kindex set stopped@r{, Hurd command}
15327 This commands tells @value{GDBN} that the inferior process is stopped,
15328 as with the @code{SIGSTOP} signal. The stopped process can be
15329 continued by delivering a signal to it.
15332 @kindex show stopped@r{, Hurd command}
15333 This command shows whether @value{GDBN} thinks the debuggee is
15336 @item set exceptions
15337 @kindex set exceptions@r{, Hurd command}
15338 Use this command to turn off trapping of exceptions in the inferior.
15339 When exception trapping is off, neither breakpoints nor
15340 single-stepping will work. To restore the default, set exception
15343 @item show exceptions
15344 @kindex show exceptions@r{, Hurd command}
15345 Show the current state of trapping exceptions in the inferior.
15347 @item set task pause
15348 @kindex set task@r{, Hurd commands}
15349 @cindex task attributes (@sc{gnu} Hurd)
15350 @cindex pause current task (@sc{gnu} Hurd)
15351 This command toggles task suspension when @value{GDBN} has control.
15352 Setting it to on takes effect immediately, and the task is suspended
15353 whenever @value{GDBN} gets control. Setting it to off will take
15354 effect the next time the inferior is continued. If this option is set
15355 to off, you can use @code{set thread default pause on} or @code{set
15356 thread pause on} (see below) to pause individual threads.
15358 @item show task pause
15359 @kindex show task@r{, Hurd commands}
15360 Show the current state of task suspension.
15362 @item set task detach-suspend-count
15363 @cindex task suspend count
15364 @cindex detach from task, @sc{gnu} Hurd
15365 This command sets the suspend count the task will be left with when
15366 @value{GDBN} detaches from it.
15368 @item show task detach-suspend-count
15369 Show the suspend count the task will be left with when detaching.
15371 @item set task exception-port
15372 @itemx set task excp
15373 @cindex task exception port, @sc{gnu} Hurd
15374 This command sets the task exception port to which @value{GDBN} will
15375 forward exceptions. The argument should be the value of the @dfn{send
15376 rights} of the task. @code{set task excp} is a shorthand alias.
15378 @item set noninvasive
15379 @cindex noninvasive task options
15380 This command switches @value{GDBN} to a mode that is the least
15381 invasive as far as interfering with the inferior is concerned. This
15382 is the same as using @code{set task pause}, @code{set exceptions}, and
15383 @code{set signals} to values opposite to the defaults.
15385 @item info send-rights
15386 @itemx info receive-rights
15387 @itemx info port-rights
15388 @itemx info port-sets
15389 @itemx info dead-names
15392 @cindex send rights, @sc{gnu} Hurd
15393 @cindex receive rights, @sc{gnu} Hurd
15394 @cindex port rights, @sc{gnu} Hurd
15395 @cindex port sets, @sc{gnu} Hurd
15396 @cindex dead names, @sc{gnu} Hurd
15397 These commands display information about, respectively, send rights,
15398 receive rights, port rights, port sets, and dead names of a task.
15399 There are also shorthand aliases: @code{info ports} for @code{info
15400 port-rights} and @code{info psets} for @code{info port-sets}.
15402 @item set thread pause
15403 @kindex set thread@r{, Hurd command}
15404 @cindex thread properties, @sc{gnu} Hurd
15405 @cindex pause current thread (@sc{gnu} Hurd)
15406 This command toggles current thread suspension when @value{GDBN} has
15407 control. Setting it to on takes effect immediately, and the current
15408 thread is suspended whenever @value{GDBN} gets control. Setting it to
15409 off will take effect the next time the inferior is continued.
15410 Normally, this command has no effect, since when @value{GDBN} has
15411 control, the whole task is suspended. However, if you used @code{set
15412 task pause off} (see above), this command comes in handy to suspend
15413 only the current thread.
15415 @item show thread pause
15416 @kindex show thread@r{, Hurd command}
15417 This command shows the state of current thread suspension.
15419 @item set thread run
15420 This command sets whether the current thread is allowed to run.
15422 @item show thread run
15423 Show whether the current thread is allowed to run.
15425 @item set thread detach-suspend-count
15426 @cindex thread suspend count, @sc{gnu} Hurd
15427 @cindex detach from thread, @sc{gnu} Hurd
15428 This command sets the suspend count @value{GDBN} will leave on a
15429 thread when detaching. This number is relative to the suspend count
15430 found by @value{GDBN} when it notices the thread; use @code{set thread
15431 takeover-suspend-count} to force it to an absolute value.
15433 @item show thread detach-suspend-count
15434 Show the suspend count @value{GDBN} will leave on the thread when
15437 @item set thread exception-port
15438 @itemx set thread excp
15439 Set the thread exception port to which to forward exceptions. This
15440 overrides the port set by @code{set task exception-port} (see above).
15441 @code{set thread excp} is the shorthand alias.
15443 @item set thread takeover-suspend-count
15444 Normally, @value{GDBN}'s thread suspend counts are relative to the
15445 value @value{GDBN} finds when it notices each thread. This command
15446 changes the suspend counts to be absolute instead.
15448 @item set thread default
15449 @itemx show thread default
15450 @cindex thread default settings, @sc{gnu} Hurd
15451 Each of the above @code{set thread} commands has a @code{set thread
15452 default} counterpart (e.g., @code{set thread default pause}, @code{set
15453 thread default exception-port}, etc.). The @code{thread default}
15454 variety of commands sets the default thread properties for all
15455 threads; you can then change the properties of individual threads with
15456 the non-default commands.
15461 @subsection QNX Neutrino
15462 @cindex QNX Neutrino
15464 @value{GDBN} provides the following commands specific to the QNX
15468 @item set debug nto-debug
15469 @kindex set debug nto-debug
15470 When set to on, enables debugging messages specific to the QNX
15473 @item show debug nto-debug
15474 @kindex show debug nto-debug
15475 Show the current state of QNX Neutrino messages.
15482 @value{GDBN} provides the following commands specific to the Darwin target:
15485 @item set debug darwin @var{num}
15486 @kindex set debug darwin
15487 When set to a non zero value, enables debugging messages specific to
15488 the Darwin support. Higher values produce more verbose output.
15490 @item show debug darwin
15491 @kindex show debug darwin
15492 Show the current state of Darwin messages.
15494 @item set debug mach-o @var{num}
15495 @kindex set debug mach-o
15496 When set to a non zero value, enables debugging messages while
15497 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
15498 file format used on Darwin for object and executable files.) Higher
15499 values produce more verbose output. This is a command to diagnose
15500 problems internal to @value{GDBN} and should not be needed in normal
15503 @item show debug mach-o
15504 @kindex show debug mach-o
15505 Show the current state of Mach-O file messages.
15507 @item set mach-exceptions on
15508 @itemx set mach-exceptions off
15509 @kindex set mach-exceptions
15510 On Darwin, faults are first reported as a Mach exception and are then
15511 mapped to a Posix signal. Use this command to turn on trapping of
15512 Mach exceptions in the inferior. This might be sometimes useful to
15513 better understand the cause of a fault. The default is off.
15515 @item show mach-exceptions
15516 @kindex show mach-exceptions
15517 Show the current state of exceptions trapping.
15522 @section Embedded Operating Systems
15524 This section describes configurations involving the debugging of
15525 embedded operating systems that are available for several different
15529 * VxWorks:: Using @value{GDBN} with VxWorks
15532 @value{GDBN} includes the ability to debug programs running on
15533 various real-time operating systems.
15536 @subsection Using @value{GDBN} with VxWorks
15542 @kindex target vxworks
15543 @item target vxworks @var{machinename}
15544 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
15545 is the target system's machine name or IP address.
15549 On VxWorks, @code{load} links @var{filename} dynamically on the
15550 current target system as well as adding its symbols in @value{GDBN}.
15552 @value{GDBN} enables developers to spawn and debug tasks running on networked
15553 VxWorks targets from a Unix host. Already-running tasks spawned from
15554 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
15555 both the Unix host and on the VxWorks target. The program
15556 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
15557 installed with the name @code{vxgdb}, to distinguish it from a
15558 @value{GDBN} for debugging programs on the host itself.)
15561 @item VxWorks-timeout @var{args}
15562 @kindex vxworks-timeout
15563 All VxWorks-based targets now support the option @code{vxworks-timeout}.
15564 This option is set by the user, and @var{args} represents the number of
15565 seconds @value{GDBN} waits for responses to rpc's. You might use this if
15566 your VxWorks target is a slow software simulator or is on the far side
15567 of a thin network line.
15570 The following information on connecting to VxWorks was current when
15571 this manual was produced; newer releases of VxWorks may use revised
15574 @findex INCLUDE_RDB
15575 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
15576 to include the remote debugging interface routines in the VxWorks
15577 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
15578 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
15579 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
15580 source debugging task @code{tRdbTask} when VxWorks is booted. For more
15581 information on configuring and remaking VxWorks, see the manufacturer's
15583 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
15585 Once you have included @file{rdb.a} in your VxWorks system image and set
15586 your Unix execution search path to find @value{GDBN}, you are ready to
15587 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
15588 @code{vxgdb}, depending on your installation).
15590 @value{GDBN} comes up showing the prompt:
15597 * VxWorks Connection:: Connecting to VxWorks
15598 * VxWorks Download:: VxWorks download
15599 * VxWorks Attach:: Running tasks
15602 @node VxWorks Connection
15603 @subsubsection Connecting to VxWorks
15605 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
15606 network. To connect to a target whose host name is ``@code{tt}'', type:
15609 (vxgdb) target vxworks tt
15613 @value{GDBN} displays messages like these:
15616 Attaching remote machine across net...
15621 @value{GDBN} then attempts to read the symbol tables of any object modules
15622 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
15623 these files by searching the directories listed in the command search
15624 path (@pxref{Environment, ,Your Program's Environment}); if it fails
15625 to find an object file, it displays a message such as:
15628 prog.o: No such file or directory.
15631 When this happens, add the appropriate directory to the search path with
15632 the @value{GDBN} command @code{path}, and execute the @code{target}
15635 @node VxWorks Download
15636 @subsubsection VxWorks Download
15638 @cindex download to VxWorks
15639 If you have connected to the VxWorks target and you want to debug an
15640 object that has not yet been loaded, you can use the @value{GDBN}
15641 @code{load} command to download a file from Unix to VxWorks
15642 incrementally. The object file given as an argument to the @code{load}
15643 command is actually opened twice: first by the VxWorks target in order
15644 to download the code, then by @value{GDBN} in order to read the symbol
15645 table. This can lead to problems if the current working directories on
15646 the two systems differ. If both systems have NFS mounted the same
15647 filesystems, you can avoid these problems by using absolute paths.
15648 Otherwise, it is simplest to set the working directory on both systems
15649 to the directory in which the object file resides, and then to reference
15650 the file by its name, without any path. For instance, a program
15651 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
15652 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
15653 program, type this on VxWorks:
15656 -> cd "@var{vxpath}/vw/demo/rdb"
15660 Then, in @value{GDBN}, type:
15663 (vxgdb) cd @var{hostpath}/vw/demo/rdb
15664 (vxgdb) load prog.o
15667 @value{GDBN} displays a response similar to this:
15670 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
15673 You can also use the @code{load} command to reload an object module
15674 after editing and recompiling the corresponding source file. Note that
15675 this makes @value{GDBN} delete all currently-defined breakpoints,
15676 auto-displays, and convenience variables, and to clear the value
15677 history. (This is necessary in order to preserve the integrity of
15678 debugger's data structures that reference the target system's symbol
15681 @node VxWorks Attach
15682 @subsubsection Running Tasks
15684 @cindex running VxWorks tasks
15685 You can also attach to an existing task using the @code{attach} command as
15689 (vxgdb) attach @var{task}
15693 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
15694 or suspended when you attach to it. Running tasks are suspended at
15695 the time of attachment.
15697 @node Embedded Processors
15698 @section Embedded Processors
15700 This section goes into details specific to particular embedded
15703 @cindex send command to simulator
15704 Whenever a specific embedded processor has a simulator, @value{GDBN}
15705 allows to send an arbitrary command to the simulator.
15708 @item sim @var{command}
15709 @kindex sim@r{, a command}
15710 Send an arbitrary @var{command} string to the simulator. Consult the
15711 documentation for the specific simulator in use for information about
15712 acceptable commands.
15718 * M32R/D:: Renesas M32R/D
15719 * M68K:: Motorola M68K
15720 * MIPS Embedded:: MIPS Embedded
15721 * OpenRISC 1000:: OpenRisc 1000
15722 * PA:: HP PA Embedded
15723 * PowerPC Embedded:: PowerPC Embedded
15724 * Sparclet:: Tsqware Sparclet
15725 * Sparclite:: Fujitsu Sparclite
15726 * Z8000:: Zilog Z8000
15729 * Super-H:: Renesas Super-H
15738 @item target rdi @var{dev}
15739 ARM Angel monitor, via RDI library interface to ADP protocol. You may
15740 use this target to communicate with both boards running the Angel
15741 monitor, or with the EmbeddedICE JTAG debug device.
15744 @item target rdp @var{dev}
15749 @value{GDBN} provides the following ARM-specific commands:
15752 @item set arm disassembler
15754 This commands selects from a list of disassembly styles. The
15755 @code{"std"} style is the standard style.
15757 @item show arm disassembler
15759 Show the current disassembly style.
15761 @item set arm apcs32
15762 @cindex ARM 32-bit mode
15763 This command toggles ARM operation mode between 32-bit and 26-bit.
15765 @item show arm apcs32
15766 Display the current usage of the ARM 32-bit mode.
15768 @item set arm fpu @var{fputype}
15769 This command sets the ARM floating-point unit (FPU) type. The
15770 argument @var{fputype} can be one of these:
15774 Determine the FPU type by querying the OS ABI.
15776 Software FPU, with mixed-endian doubles on little-endian ARM
15779 GCC-compiled FPA co-processor.
15781 Software FPU with pure-endian doubles.
15787 Show the current type of the FPU.
15790 This command forces @value{GDBN} to use the specified ABI.
15793 Show the currently used ABI.
15795 @item set arm fallback-mode (arm|thumb|auto)
15796 @value{GDBN} uses the symbol table, when available, to determine
15797 whether instructions are ARM or Thumb. This command controls
15798 @value{GDBN}'s default behavior when the symbol table is not
15799 available. The default is @samp{auto}, which causes @value{GDBN} to
15800 use the current execution mode (from the @code{T} bit in the @code{CPSR}
15803 @item show arm fallback-mode
15804 Show the current fallback instruction mode.
15806 @item set arm force-mode (arm|thumb|auto)
15807 This command overrides use of the symbol table to determine whether
15808 instructions are ARM or Thumb. The default is @samp{auto}, which
15809 causes @value{GDBN} to use the symbol table and then the setting
15810 of @samp{set arm fallback-mode}.
15812 @item show arm force-mode
15813 Show the current forced instruction mode.
15815 @item set debug arm
15816 Toggle whether to display ARM-specific debugging messages from the ARM
15817 target support subsystem.
15819 @item show debug arm
15820 Show whether ARM-specific debugging messages are enabled.
15823 The following commands are available when an ARM target is debugged
15824 using the RDI interface:
15827 @item rdilogfile @r{[}@var{file}@r{]}
15829 @cindex ADP (Angel Debugger Protocol) logging
15830 Set the filename for the ADP (Angel Debugger Protocol) packet log.
15831 With an argument, sets the log file to the specified @var{file}. With
15832 no argument, show the current log file name. The default log file is
15835 @item rdilogenable @r{[}@var{arg}@r{]}
15836 @kindex rdilogenable
15837 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
15838 enables logging, with an argument 0 or @code{"no"} disables it. With
15839 no arguments displays the current setting. When logging is enabled,
15840 ADP packets exchanged between @value{GDBN} and the RDI target device
15841 are logged to a file.
15843 @item set rdiromatzero
15844 @kindex set rdiromatzero
15845 @cindex ROM at zero address, RDI
15846 Tell @value{GDBN} whether the target has ROM at address 0. If on,
15847 vector catching is disabled, so that zero address can be used. If off
15848 (the default), vector catching is enabled. For this command to take
15849 effect, it needs to be invoked prior to the @code{target rdi} command.
15851 @item show rdiromatzero
15852 @kindex show rdiromatzero
15853 Show the current setting of ROM at zero address.
15855 @item set rdiheartbeat
15856 @kindex set rdiheartbeat
15857 @cindex RDI heartbeat
15858 Enable or disable RDI heartbeat packets. It is not recommended to
15859 turn on this option, since it confuses ARM and EPI JTAG interface, as
15860 well as the Angel monitor.
15862 @item show rdiheartbeat
15863 @kindex show rdiheartbeat
15864 Show the setting of RDI heartbeat packets.
15869 @subsection Renesas M32R/D and M32R/SDI
15872 @kindex target m32r
15873 @item target m32r @var{dev}
15874 Renesas M32R/D ROM monitor.
15876 @kindex target m32rsdi
15877 @item target m32rsdi @var{dev}
15878 Renesas M32R SDI server, connected via parallel port to the board.
15881 The following @value{GDBN} commands are specific to the M32R monitor:
15884 @item set download-path @var{path}
15885 @kindex set download-path
15886 @cindex find downloadable @sc{srec} files (M32R)
15887 Set the default path for finding downloadable @sc{srec} files.
15889 @item show download-path
15890 @kindex show download-path
15891 Show the default path for downloadable @sc{srec} files.
15893 @item set board-address @var{addr}
15894 @kindex set board-address
15895 @cindex M32-EVA target board address
15896 Set the IP address for the M32R-EVA target board.
15898 @item show board-address
15899 @kindex show board-address
15900 Show the current IP address of the target board.
15902 @item set server-address @var{addr}
15903 @kindex set server-address
15904 @cindex download server address (M32R)
15905 Set the IP address for the download server, which is the @value{GDBN}'s
15908 @item show server-address
15909 @kindex show server-address
15910 Display the IP address of the download server.
15912 @item upload @r{[}@var{file}@r{]}
15913 @kindex upload@r{, M32R}
15914 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
15915 upload capability. If no @var{file} argument is given, the current
15916 executable file is uploaded.
15918 @item tload @r{[}@var{file}@r{]}
15919 @kindex tload@r{, M32R}
15920 Test the @code{upload} command.
15923 The following commands are available for M32R/SDI:
15928 @cindex reset SDI connection, M32R
15929 This command resets the SDI connection.
15933 This command shows the SDI connection status.
15936 @kindex debug_chaos
15937 @cindex M32R/Chaos debugging
15938 Instructs the remote that M32R/Chaos debugging is to be used.
15940 @item use_debug_dma
15941 @kindex use_debug_dma
15942 Instructs the remote to use the DEBUG_DMA method of accessing memory.
15945 @kindex use_mon_code
15946 Instructs the remote to use the MON_CODE method of accessing memory.
15949 @kindex use_ib_break
15950 Instructs the remote to set breakpoints by IB break.
15952 @item use_dbt_break
15953 @kindex use_dbt_break
15954 Instructs the remote to set breakpoints by DBT.
15960 The Motorola m68k configuration includes ColdFire support, and a
15961 target command for the following ROM monitor.
15965 @kindex target dbug
15966 @item target dbug @var{dev}
15967 dBUG ROM monitor for Motorola ColdFire.
15971 @node MIPS Embedded
15972 @subsection MIPS Embedded
15974 @cindex MIPS boards
15975 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
15976 MIPS board attached to a serial line. This is available when
15977 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
15980 Use these @value{GDBN} commands to specify the connection to your target board:
15983 @item target mips @var{port}
15984 @kindex target mips @var{port}
15985 To run a program on the board, start up @code{@value{GDBP}} with the
15986 name of your program as the argument. To connect to the board, use the
15987 command @samp{target mips @var{port}}, where @var{port} is the name of
15988 the serial port connected to the board. If the program has not already
15989 been downloaded to the board, you may use the @code{load} command to
15990 download it. You can then use all the usual @value{GDBN} commands.
15992 For example, this sequence connects to the target board through a serial
15993 port, and loads and runs a program called @var{prog} through the
15997 host$ @value{GDBP} @var{prog}
15998 @value{GDBN} is free software and @dots{}
15999 (@value{GDBP}) target mips /dev/ttyb
16000 (@value{GDBP}) load @var{prog}
16004 @item target mips @var{hostname}:@var{portnumber}
16005 On some @value{GDBN} host configurations, you can specify a TCP
16006 connection (for instance, to a serial line managed by a terminal
16007 concentrator) instead of a serial port, using the syntax
16008 @samp{@var{hostname}:@var{portnumber}}.
16010 @item target pmon @var{port}
16011 @kindex target pmon @var{port}
16014 @item target ddb @var{port}
16015 @kindex target ddb @var{port}
16016 NEC's DDB variant of PMON for Vr4300.
16018 @item target lsi @var{port}
16019 @kindex target lsi @var{port}
16020 LSI variant of PMON.
16022 @kindex target r3900
16023 @item target r3900 @var{dev}
16024 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
16026 @kindex target array
16027 @item target array @var{dev}
16028 Array Tech LSI33K RAID controller board.
16034 @value{GDBN} also supports these special commands for MIPS targets:
16037 @item set mipsfpu double
16038 @itemx set mipsfpu single
16039 @itemx set mipsfpu none
16040 @itemx set mipsfpu auto
16041 @itemx show mipsfpu
16042 @kindex set mipsfpu
16043 @kindex show mipsfpu
16044 @cindex MIPS remote floating point
16045 @cindex floating point, MIPS remote
16046 If your target board does not support the MIPS floating point
16047 coprocessor, you should use the command @samp{set mipsfpu none} (if you
16048 need this, you may wish to put the command in your @value{GDBN} init
16049 file). This tells @value{GDBN} how to find the return value of
16050 functions which return floating point values. It also allows
16051 @value{GDBN} to avoid saving the floating point registers when calling
16052 functions on the board. If you are using a floating point coprocessor
16053 with only single precision floating point support, as on the @sc{r4650}
16054 processor, use the command @samp{set mipsfpu single}. The default
16055 double precision floating point coprocessor may be selected using
16056 @samp{set mipsfpu double}.
16058 In previous versions the only choices were double precision or no
16059 floating point, so @samp{set mipsfpu on} will select double precision
16060 and @samp{set mipsfpu off} will select no floating point.
16062 As usual, you can inquire about the @code{mipsfpu} variable with
16063 @samp{show mipsfpu}.
16065 @item set timeout @var{seconds}
16066 @itemx set retransmit-timeout @var{seconds}
16067 @itemx show timeout
16068 @itemx show retransmit-timeout
16069 @cindex @code{timeout}, MIPS protocol
16070 @cindex @code{retransmit-timeout}, MIPS protocol
16071 @kindex set timeout
16072 @kindex show timeout
16073 @kindex set retransmit-timeout
16074 @kindex show retransmit-timeout
16075 You can control the timeout used while waiting for a packet, in the MIPS
16076 remote protocol, with the @code{set timeout @var{seconds}} command. The
16077 default is 5 seconds. Similarly, you can control the timeout used while
16078 waiting for an acknowledgment of a packet with the @code{set
16079 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
16080 You can inspect both values with @code{show timeout} and @code{show
16081 retransmit-timeout}. (These commands are @emph{only} available when
16082 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
16084 The timeout set by @code{set timeout} does not apply when @value{GDBN}
16085 is waiting for your program to stop. In that case, @value{GDBN} waits
16086 forever because it has no way of knowing how long the program is going
16087 to run before stopping.
16089 @item set syn-garbage-limit @var{num}
16090 @kindex set syn-garbage-limit@r{, MIPS remote}
16091 @cindex synchronize with remote MIPS target
16092 Limit the maximum number of characters @value{GDBN} should ignore when
16093 it tries to synchronize with the remote target. The default is 10
16094 characters. Setting the limit to -1 means there's no limit.
16096 @item show syn-garbage-limit
16097 @kindex show syn-garbage-limit@r{, MIPS remote}
16098 Show the current limit on the number of characters to ignore when
16099 trying to synchronize with the remote system.
16101 @item set monitor-prompt @var{prompt}
16102 @kindex set monitor-prompt@r{, MIPS remote}
16103 @cindex remote monitor prompt
16104 Tell @value{GDBN} to expect the specified @var{prompt} string from the
16105 remote monitor. The default depends on the target:
16115 @item show monitor-prompt
16116 @kindex show monitor-prompt@r{, MIPS remote}
16117 Show the current strings @value{GDBN} expects as the prompt from the
16120 @item set monitor-warnings
16121 @kindex set monitor-warnings@r{, MIPS remote}
16122 Enable or disable monitor warnings about hardware breakpoints. This
16123 has effect only for the @code{lsi} target. When on, @value{GDBN} will
16124 display warning messages whose codes are returned by the @code{lsi}
16125 PMON monitor for breakpoint commands.
16127 @item show monitor-warnings
16128 @kindex show monitor-warnings@r{, MIPS remote}
16129 Show the current setting of printing monitor warnings.
16131 @item pmon @var{command}
16132 @kindex pmon@r{, MIPS remote}
16133 @cindex send PMON command
16134 This command allows sending an arbitrary @var{command} string to the
16135 monitor. The monitor must be in debug mode for this to work.
16138 @node OpenRISC 1000
16139 @subsection OpenRISC 1000
16140 @cindex OpenRISC 1000
16142 @cindex or1k boards
16143 See OR1k Architecture document (@uref{www.opencores.org}) for more information
16144 about platform and commands.
16148 @kindex target jtag
16149 @item target jtag jtag://@var{host}:@var{port}
16151 Connects to remote JTAG server.
16152 JTAG remote server can be either an or1ksim or JTAG server,
16153 connected via parallel port to the board.
16155 Example: @code{target jtag jtag://localhost:9999}
16158 @item or1ksim @var{command}
16159 If connected to @code{or1ksim} OpenRISC 1000 Architectural
16160 Simulator, proprietary commands can be executed.
16162 @kindex info or1k spr
16163 @item info or1k spr
16164 Displays spr groups.
16166 @item info or1k spr @var{group}
16167 @itemx info or1k spr @var{groupno}
16168 Displays register names in selected group.
16170 @item info or1k spr @var{group} @var{register}
16171 @itemx info or1k spr @var{register}
16172 @itemx info or1k spr @var{groupno} @var{registerno}
16173 @itemx info or1k spr @var{registerno}
16174 Shows information about specified spr register.
16177 @item spr @var{group} @var{register} @var{value}
16178 @itemx spr @var{register @var{value}}
16179 @itemx spr @var{groupno} @var{registerno @var{value}}
16180 @itemx spr @var{registerno @var{value}}
16181 Writes @var{value} to specified spr register.
16184 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
16185 It is very similar to @value{GDBN} trace, except it does not interfere with normal
16186 program execution and is thus much faster. Hardware breakpoints/watchpoint
16187 triggers can be set using:
16190 Load effective address/data
16192 Store effective address/data
16194 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
16199 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
16200 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
16202 @code{htrace} commands:
16203 @cindex OpenRISC 1000 htrace
16206 @item hwatch @var{conditional}
16207 Set hardware watchpoint on combination of Load/Store Effective Address(es)
16208 or Data. For example:
16210 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16212 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16216 Display information about current HW trace configuration.
16218 @item htrace trigger @var{conditional}
16219 Set starting criteria for HW trace.
16221 @item htrace qualifier @var{conditional}
16222 Set acquisition qualifier for HW trace.
16224 @item htrace stop @var{conditional}
16225 Set HW trace stopping criteria.
16227 @item htrace record [@var{data}]*
16228 Selects the data to be recorded, when qualifier is met and HW trace was
16231 @item htrace enable
16232 @itemx htrace disable
16233 Enables/disables the HW trace.
16235 @item htrace rewind [@var{filename}]
16236 Clears currently recorded trace data.
16238 If filename is specified, new trace file is made and any newly collected data
16239 will be written there.
16241 @item htrace print [@var{start} [@var{len}]]
16242 Prints trace buffer, using current record configuration.
16244 @item htrace mode continuous
16245 Set continuous trace mode.
16247 @item htrace mode suspend
16248 Set suspend trace mode.
16252 @node PowerPC Embedded
16253 @subsection PowerPC Embedded
16255 @value{GDBN} provides the following PowerPC-specific commands:
16258 @kindex set powerpc
16259 @item set powerpc soft-float
16260 @itemx show powerpc soft-float
16261 Force @value{GDBN} to use (or not use) a software floating point calling
16262 convention. By default, @value{GDBN} selects the calling convention based
16263 on the selected architecture and the provided executable file.
16265 @item set powerpc vector-abi
16266 @itemx show powerpc vector-abi
16267 Force @value{GDBN} to use the specified calling convention for vector
16268 arguments and return values. The valid options are @samp{auto};
16269 @samp{generic}, to avoid vector registers even if they are present;
16270 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
16271 registers. By default, @value{GDBN} selects the calling convention
16272 based on the selected architecture and the provided executable file.
16274 @kindex target dink32
16275 @item target dink32 @var{dev}
16276 DINK32 ROM monitor.
16278 @kindex target ppcbug
16279 @item target ppcbug @var{dev}
16280 @kindex target ppcbug1
16281 @item target ppcbug1 @var{dev}
16282 PPCBUG ROM monitor for PowerPC.
16285 @item target sds @var{dev}
16286 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
16289 @cindex SDS protocol
16290 The following commands specific to the SDS protocol are supported
16294 @item set sdstimeout @var{nsec}
16295 @kindex set sdstimeout
16296 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
16297 default is 2 seconds.
16299 @item show sdstimeout
16300 @kindex show sdstimeout
16301 Show the current value of the SDS timeout.
16303 @item sds @var{command}
16304 @kindex sds@r{, a command}
16305 Send the specified @var{command} string to the SDS monitor.
16310 @subsection HP PA Embedded
16314 @kindex target op50n
16315 @item target op50n @var{dev}
16316 OP50N monitor, running on an OKI HPPA board.
16318 @kindex target w89k
16319 @item target w89k @var{dev}
16320 W89K monitor, running on a Winbond HPPA board.
16325 @subsection Tsqware Sparclet
16329 @value{GDBN} enables developers to debug tasks running on
16330 Sparclet targets from a Unix host.
16331 @value{GDBN} uses code that runs on
16332 both the Unix host and on the Sparclet target. The program
16333 @code{@value{GDBP}} is installed and executed on the Unix host.
16336 @item remotetimeout @var{args}
16337 @kindex remotetimeout
16338 @value{GDBN} supports the option @code{remotetimeout}.
16339 This option is set by the user, and @var{args} represents the number of
16340 seconds @value{GDBN} waits for responses.
16343 @cindex compiling, on Sparclet
16344 When compiling for debugging, include the options @samp{-g} to get debug
16345 information and @samp{-Ttext} to relocate the program to where you wish to
16346 load it on the target. You may also want to add the options @samp{-n} or
16347 @samp{-N} in order to reduce the size of the sections. Example:
16350 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
16353 You can use @code{objdump} to verify that the addresses are what you intended:
16356 sparclet-aout-objdump --headers --syms prog
16359 @cindex running, on Sparclet
16361 your Unix execution search path to find @value{GDBN}, you are ready to
16362 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
16363 (or @code{sparclet-aout-gdb}, depending on your installation).
16365 @value{GDBN} comes up showing the prompt:
16372 * Sparclet File:: Setting the file to debug
16373 * Sparclet Connection:: Connecting to Sparclet
16374 * Sparclet Download:: Sparclet download
16375 * Sparclet Execution:: Running and debugging
16378 @node Sparclet File
16379 @subsubsection Setting File to Debug
16381 The @value{GDBN} command @code{file} lets you choose with program to debug.
16384 (gdbslet) file prog
16388 @value{GDBN} then attempts to read the symbol table of @file{prog}.
16389 @value{GDBN} locates
16390 the file by searching the directories listed in the command search
16392 If the file was compiled with debug information (option @samp{-g}), source
16393 files will be searched as well.
16394 @value{GDBN} locates
16395 the source files by searching the directories listed in the directory search
16396 path (@pxref{Environment, ,Your Program's Environment}).
16398 to find a file, it displays a message such as:
16401 prog: No such file or directory.
16404 When this happens, add the appropriate directories to the search paths with
16405 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
16406 @code{target} command again.
16408 @node Sparclet Connection
16409 @subsubsection Connecting to Sparclet
16411 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
16412 To connect to a target on serial port ``@code{ttya}'', type:
16415 (gdbslet) target sparclet /dev/ttya
16416 Remote target sparclet connected to /dev/ttya
16417 main () at ../prog.c:3
16421 @value{GDBN} displays messages like these:
16427 @node Sparclet Download
16428 @subsubsection Sparclet Download
16430 @cindex download to Sparclet
16431 Once connected to the Sparclet target,
16432 you can use the @value{GDBN}
16433 @code{load} command to download the file from the host to the target.
16434 The file name and load offset should be given as arguments to the @code{load}
16436 Since the file format is aout, the program must be loaded to the starting
16437 address. You can use @code{objdump} to find out what this value is. The load
16438 offset is an offset which is added to the VMA (virtual memory address)
16439 of each of the file's sections.
16440 For instance, if the program
16441 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
16442 and bss at 0x12010170, in @value{GDBN}, type:
16445 (gdbslet) load prog 0x12010000
16446 Loading section .text, size 0xdb0 vma 0x12010000
16449 If the code is loaded at a different address then what the program was linked
16450 to, you may need to use the @code{section} and @code{add-symbol-file} commands
16451 to tell @value{GDBN} where to map the symbol table.
16453 @node Sparclet Execution
16454 @subsubsection Running and Debugging
16456 @cindex running and debugging Sparclet programs
16457 You can now begin debugging the task using @value{GDBN}'s execution control
16458 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
16459 manual for the list of commands.
16463 Breakpoint 1 at 0x12010000: file prog.c, line 3.
16465 Starting program: prog
16466 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
16467 3 char *symarg = 0;
16469 4 char *execarg = "hello!";
16474 @subsection Fujitsu Sparclite
16478 @kindex target sparclite
16479 @item target sparclite @var{dev}
16480 Fujitsu sparclite boards, used only for the purpose of loading.
16481 You must use an additional command to debug the program.
16482 For example: target remote @var{dev} using @value{GDBN} standard
16488 @subsection Zilog Z8000
16491 @cindex simulator, Z8000
16492 @cindex Zilog Z8000 simulator
16494 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
16497 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
16498 unsegmented variant of the Z8000 architecture) or the Z8001 (the
16499 segmented variant). The simulator recognizes which architecture is
16500 appropriate by inspecting the object code.
16503 @item target sim @var{args}
16505 @kindex target sim@r{, with Z8000}
16506 Debug programs on a simulated CPU. If the simulator supports setup
16507 options, specify them via @var{args}.
16511 After specifying this target, you can debug programs for the simulated
16512 CPU in the same style as programs for your host computer; use the
16513 @code{file} command to load a new program image, the @code{run} command
16514 to run your program, and so on.
16516 As well as making available all the usual machine registers
16517 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
16518 additional items of information as specially named registers:
16523 Counts clock-ticks in the simulator.
16526 Counts instructions run in the simulator.
16529 Execution time in 60ths of a second.
16533 You can refer to these values in @value{GDBN} expressions with the usual
16534 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
16535 conditional breakpoint that suspends only after at least 5000
16536 simulated clock ticks.
16539 @subsection Atmel AVR
16542 When configured for debugging the Atmel AVR, @value{GDBN} supports the
16543 following AVR-specific commands:
16546 @item info io_registers
16547 @kindex info io_registers@r{, AVR}
16548 @cindex I/O registers (Atmel AVR)
16549 This command displays information about the AVR I/O registers. For
16550 each register, @value{GDBN} prints its number and value.
16557 When configured for debugging CRIS, @value{GDBN} provides the
16558 following CRIS-specific commands:
16561 @item set cris-version @var{ver}
16562 @cindex CRIS version
16563 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
16564 The CRIS version affects register names and sizes. This command is useful in
16565 case autodetection of the CRIS version fails.
16567 @item show cris-version
16568 Show the current CRIS version.
16570 @item set cris-dwarf2-cfi
16571 @cindex DWARF-2 CFI and CRIS
16572 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
16573 Change to @samp{off} when using @code{gcc-cris} whose version is below
16576 @item show cris-dwarf2-cfi
16577 Show the current state of using DWARF-2 CFI.
16579 @item set cris-mode @var{mode}
16581 Set the current CRIS mode to @var{mode}. It should only be changed when
16582 debugging in guru mode, in which case it should be set to
16583 @samp{guru} (the default is @samp{normal}).
16585 @item show cris-mode
16586 Show the current CRIS mode.
16590 @subsection Renesas Super-H
16593 For the Renesas Super-H processor, @value{GDBN} provides these
16598 @kindex regs@r{, Super-H}
16599 Show the values of all Super-H registers.
16601 @item set sh calling-convention @var{convention}
16602 @kindex set sh calling-convention
16603 Set the calling-convention used when calling functions from @value{GDBN}.
16604 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
16605 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
16606 convention. If the DWARF-2 information of the called function specifies
16607 that the function follows the Renesas calling convention, the function
16608 is called using the Renesas calling convention. If the calling convention
16609 is set to @samp{renesas}, the Renesas calling convention is always used,
16610 regardless of the DWARF-2 information. This can be used to override the
16611 default of @samp{gcc} if debug information is missing, or the compiler
16612 does not emit the DWARF-2 calling convention entry for a function.
16614 @item show sh calling-convention
16615 @kindex show sh calling-convention
16616 Show the current calling convention setting.
16621 @node Architectures
16622 @section Architectures
16624 This section describes characteristics of architectures that affect
16625 all uses of @value{GDBN} with the architecture, both native and cross.
16632 * HPPA:: HP PA architecture
16633 * SPU:: Cell Broadband Engine SPU architecture
16638 @subsection x86 Architecture-specific Issues
16641 @item set struct-convention @var{mode}
16642 @kindex set struct-convention
16643 @cindex struct return convention
16644 @cindex struct/union returned in registers
16645 Set the convention used by the inferior to return @code{struct}s and
16646 @code{union}s from functions to @var{mode}. Possible values of
16647 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
16648 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
16649 are returned on the stack, while @code{"reg"} means that a
16650 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
16651 be returned in a register.
16653 @item show struct-convention
16654 @kindex show struct-convention
16655 Show the current setting of the convention to return @code{struct}s
16664 @kindex set rstack_high_address
16665 @cindex AMD 29K register stack
16666 @cindex register stack, AMD29K
16667 @item set rstack_high_address @var{address}
16668 On AMD 29000 family processors, registers are saved in a separate
16669 @dfn{register stack}. There is no way for @value{GDBN} to determine the
16670 extent of this stack. Normally, @value{GDBN} just assumes that the
16671 stack is ``large enough''. This may result in @value{GDBN} referencing
16672 memory locations that do not exist. If necessary, you can get around
16673 this problem by specifying the ending address of the register stack with
16674 the @code{set rstack_high_address} command. The argument should be an
16675 address, which you probably want to precede with @samp{0x} to specify in
16678 @kindex show rstack_high_address
16679 @item show rstack_high_address
16680 Display the current limit of the register stack, on AMD 29000 family
16688 See the following section.
16693 @cindex stack on Alpha
16694 @cindex stack on MIPS
16695 @cindex Alpha stack
16697 Alpha- and MIPS-based computers use an unusual stack frame, which
16698 sometimes requires @value{GDBN} to search backward in the object code to
16699 find the beginning of a function.
16701 @cindex response time, MIPS debugging
16702 To improve response time (especially for embedded applications, where
16703 @value{GDBN} may be restricted to a slow serial line for this search)
16704 you may want to limit the size of this search, using one of these
16708 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
16709 @item set heuristic-fence-post @var{limit}
16710 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
16711 search for the beginning of a function. A value of @var{0} (the
16712 default) means there is no limit. However, except for @var{0}, the
16713 larger the limit the more bytes @code{heuristic-fence-post} must search
16714 and therefore the longer it takes to run. You should only need to use
16715 this command when debugging a stripped executable.
16717 @item show heuristic-fence-post
16718 Display the current limit.
16722 These commands are available @emph{only} when @value{GDBN} is configured
16723 for debugging programs on Alpha or MIPS processors.
16725 Several MIPS-specific commands are available when debugging MIPS
16729 @item set mips abi @var{arg}
16730 @kindex set mips abi
16731 @cindex set ABI for MIPS
16732 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
16733 values of @var{arg} are:
16737 The default ABI associated with the current binary (this is the
16748 @item show mips abi
16749 @kindex show mips abi
16750 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
16753 @itemx show mipsfpu
16754 @xref{MIPS Embedded, set mipsfpu}.
16756 @item set mips mask-address @var{arg}
16757 @kindex set mips mask-address
16758 @cindex MIPS addresses, masking
16759 This command determines whether the most-significant 32 bits of 64-bit
16760 MIPS addresses are masked off. The argument @var{arg} can be
16761 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
16762 setting, which lets @value{GDBN} determine the correct value.
16764 @item show mips mask-address
16765 @kindex show mips mask-address
16766 Show whether the upper 32 bits of MIPS addresses are masked off or
16769 @item set remote-mips64-transfers-32bit-regs
16770 @kindex set remote-mips64-transfers-32bit-regs
16771 This command controls compatibility with 64-bit MIPS targets that
16772 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16773 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16774 and 64 bits for other registers, set this option to @samp{on}.
16776 @item show remote-mips64-transfers-32bit-regs
16777 @kindex show remote-mips64-transfers-32bit-regs
16778 Show the current setting of compatibility with older MIPS 64 targets.
16780 @item set debug mips
16781 @kindex set debug mips
16782 This command turns on and off debugging messages for the MIPS-specific
16783 target code in @value{GDBN}.
16785 @item show debug mips
16786 @kindex show debug mips
16787 Show the current setting of MIPS debugging messages.
16793 @cindex HPPA support
16795 When @value{GDBN} is debugging the HP PA architecture, it provides the
16796 following special commands:
16799 @item set debug hppa
16800 @kindex set debug hppa
16801 This command determines whether HPPA architecture-specific debugging
16802 messages are to be displayed.
16804 @item show debug hppa
16805 Show whether HPPA debugging messages are displayed.
16807 @item maint print unwind @var{address}
16808 @kindex maint print unwind@r{, HPPA}
16809 This command displays the contents of the unwind table entry at the
16810 given @var{address}.
16816 @subsection Cell Broadband Engine SPU architecture
16817 @cindex Cell Broadband Engine
16820 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
16821 it provides the following special commands:
16824 @item info spu event
16826 Display SPU event facility status. Shows current event mask
16827 and pending event status.
16829 @item info spu signal
16830 Display SPU signal notification facility status. Shows pending
16831 signal-control word and signal notification mode of both signal
16832 notification channels.
16834 @item info spu mailbox
16835 Display SPU mailbox facility status. Shows all pending entries,
16836 in order of processing, in each of the SPU Write Outbound,
16837 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
16840 Display MFC DMA status. Shows all pending commands in the MFC
16841 DMA queue. For each entry, opcode, tag, class IDs, effective
16842 and local store addresses and transfer size are shown.
16844 @item info spu proxydma
16845 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
16846 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
16847 and local store addresses and transfer size are shown.
16852 @subsection PowerPC
16853 @cindex PowerPC architecture
16855 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
16856 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
16857 numbers stored in the floating point registers. These values must be stored
16858 in two consecutive registers, always starting at an even register like
16859 @code{f0} or @code{f2}.
16861 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
16862 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
16863 @code{f2} and @code{f3} for @code{$dl1} and so on.
16865 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
16866 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
16869 @node Controlling GDB
16870 @chapter Controlling @value{GDBN}
16872 You can alter the way @value{GDBN} interacts with you by using the
16873 @code{set} command. For commands controlling how @value{GDBN} displays
16874 data, see @ref{Print Settings, ,Print Settings}. Other settings are
16879 * Editing:: Command editing
16880 * Command History:: Command history
16881 * Screen Size:: Screen size
16882 * Numbers:: Numbers
16883 * ABI:: Configuring the current ABI
16884 * Messages/Warnings:: Optional warnings and messages
16885 * Debugging Output:: Optional messages about internal happenings
16893 @value{GDBN} indicates its readiness to read a command by printing a string
16894 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
16895 can change the prompt string with the @code{set prompt} command. For
16896 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
16897 the prompt in one of the @value{GDBN} sessions so that you can always tell
16898 which one you are talking to.
16900 @emph{Note:} @code{set prompt} does not add a space for you after the
16901 prompt you set. This allows you to set a prompt which ends in a space
16902 or a prompt that does not.
16906 @item set prompt @var{newprompt}
16907 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
16909 @kindex show prompt
16911 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
16915 @section Command Editing
16917 @cindex command line editing
16919 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
16920 @sc{gnu} library provides consistent behavior for programs which provide a
16921 command line interface to the user. Advantages are @sc{gnu} Emacs-style
16922 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
16923 substitution, and a storage and recall of command history across
16924 debugging sessions.
16926 You may control the behavior of command line editing in @value{GDBN} with the
16927 command @code{set}.
16930 @kindex set editing
16933 @itemx set editing on
16934 Enable command line editing (enabled by default).
16936 @item set editing off
16937 Disable command line editing.
16939 @kindex show editing
16941 Show whether command line editing is enabled.
16944 @xref{Command Line Editing}, for more details about the Readline
16945 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
16946 encouraged to read that chapter.
16948 @node Command History
16949 @section Command History
16950 @cindex command history
16952 @value{GDBN} can keep track of the commands you type during your
16953 debugging sessions, so that you can be certain of precisely what
16954 happened. Use these commands to manage the @value{GDBN} command
16957 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
16958 package, to provide the history facility. @xref{Using History
16959 Interactively}, for the detailed description of the History library.
16961 To issue a command to @value{GDBN} without affecting certain aspects of
16962 the state which is seen by users, prefix it with @samp{server }
16963 (@pxref{Server Prefix}). This
16964 means that this command will not affect the command history, nor will it
16965 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
16966 pressed on a line by itself.
16968 @cindex @code{server}, command prefix
16969 The server prefix does not affect the recording of values into the value
16970 history; to print a value without recording it into the value history,
16971 use the @code{output} command instead of the @code{print} command.
16973 Here is the description of @value{GDBN} commands related to command
16977 @cindex history substitution
16978 @cindex history file
16979 @kindex set history filename
16980 @cindex @env{GDBHISTFILE}, environment variable
16981 @item set history filename @var{fname}
16982 Set the name of the @value{GDBN} command history file to @var{fname}.
16983 This is the file where @value{GDBN} reads an initial command history
16984 list, and where it writes the command history from this session when it
16985 exits. You can access this list through history expansion or through
16986 the history command editing characters listed below. This file defaults
16987 to the value of the environment variable @code{GDBHISTFILE}, or to
16988 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
16991 @cindex save command history
16992 @kindex set history save
16993 @item set history save
16994 @itemx set history save on
16995 Record command history in a file, whose name may be specified with the
16996 @code{set history filename} command. By default, this option is disabled.
16998 @item set history save off
16999 Stop recording command history in a file.
17001 @cindex history size
17002 @kindex set history size
17003 @cindex @env{HISTSIZE}, environment variable
17004 @item set history size @var{size}
17005 Set the number of commands which @value{GDBN} keeps in its history list.
17006 This defaults to the value of the environment variable
17007 @code{HISTSIZE}, or to 256 if this variable is not set.
17010 History expansion assigns special meaning to the character @kbd{!}.
17011 @xref{Event Designators}, for more details.
17013 @cindex history expansion, turn on/off
17014 Since @kbd{!} is also the logical not operator in C, history expansion
17015 is off by default. If you decide to enable history expansion with the
17016 @code{set history expansion on} command, you may sometimes need to
17017 follow @kbd{!} (when it is used as logical not, in an expression) with
17018 a space or a tab to prevent it from being expanded. The readline
17019 history facilities do not attempt substitution on the strings
17020 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
17022 The commands to control history expansion are:
17025 @item set history expansion on
17026 @itemx set history expansion
17027 @kindex set history expansion
17028 Enable history expansion. History expansion is off by default.
17030 @item set history expansion off
17031 Disable history expansion.
17034 @kindex show history
17036 @itemx show history filename
17037 @itemx show history save
17038 @itemx show history size
17039 @itemx show history expansion
17040 These commands display the state of the @value{GDBN} history parameters.
17041 @code{show history} by itself displays all four states.
17046 @kindex show commands
17047 @cindex show last commands
17048 @cindex display command history
17049 @item show commands
17050 Display the last ten commands in the command history.
17052 @item show commands @var{n}
17053 Print ten commands centered on command number @var{n}.
17055 @item show commands +
17056 Print ten commands just after the commands last printed.
17060 @section Screen Size
17061 @cindex size of screen
17062 @cindex pauses in output
17064 Certain commands to @value{GDBN} may produce large amounts of
17065 information output to the screen. To help you read all of it,
17066 @value{GDBN} pauses and asks you for input at the end of each page of
17067 output. Type @key{RET} when you want to continue the output, or @kbd{q}
17068 to discard the remaining output. Also, the screen width setting
17069 determines when to wrap lines of output. Depending on what is being
17070 printed, @value{GDBN} tries to break the line at a readable place,
17071 rather than simply letting it overflow onto the following line.
17073 Normally @value{GDBN} knows the size of the screen from the terminal
17074 driver software. For example, on Unix @value{GDBN} uses the termcap data base
17075 together with the value of the @code{TERM} environment variable and the
17076 @code{stty rows} and @code{stty cols} settings. If this is not correct,
17077 you can override it with the @code{set height} and @code{set
17084 @kindex show height
17085 @item set height @var{lpp}
17087 @itemx set width @var{cpl}
17089 These @code{set} commands specify a screen height of @var{lpp} lines and
17090 a screen width of @var{cpl} characters. The associated @code{show}
17091 commands display the current settings.
17093 If you specify a height of zero lines, @value{GDBN} does not pause during
17094 output no matter how long the output is. This is useful if output is to a
17095 file or to an editor buffer.
17097 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
17098 from wrapping its output.
17100 @item set pagination on
17101 @itemx set pagination off
17102 @kindex set pagination
17103 Turn the output pagination on or off; the default is on. Turning
17104 pagination off is the alternative to @code{set height 0}.
17106 @item show pagination
17107 @kindex show pagination
17108 Show the current pagination mode.
17113 @cindex number representation
17114 @cindex entering numbers
17116 You can always enter numbers in octal, decimal, or hexadecimal in
17117 @value{GDBN} by the usual conventions: octal numbers begin with
17118 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
17119 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
17120 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
17121 10; likewise, the default display for numbers---when no particular
17122 format is specified---is base 10. You can change the default base for
17123 both input and output with the commands described below.
17126 @kindex set input-radix
17127 @item set input-radix @var{base}
17128 Set the default base for numeric input. Supported choices
17129 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17130 specified either unambiguously or using the current input radix; for
17134 set input-radix 012
17135 set input-radix 10.
17136 set input-radix 0xa
17140 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
17141 leaves the input radix unchanged, no matter what it was, since
17142 @samp{10}, being without any leading or trailing signs of its base, is
17143 interpreted in the current radix. Thus, if the current radix is 16,
17144 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
17147 @kindex set output-radix
17148 @item set output-radix @var{base}
17149 Set the default base for numeric display. Supported choices
17150 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17151 specified either unambiguously or using the current input radix.
17153 @kindex show input-radix
17154 @item show input-radix
17155 Display the current default base for numeric input.
17157 @kindex show output-radix
17158 @item show output-radix
17159 Display the current default base for numeric display.
17161 @item set radix @r{[}@var{base}@r{]}
17165 These commands set and show the default base for both input and output
17166 of numbers. @code{set radix} sets the radix of input and output to
17167 the same base; without an argument, it resets the radix back to its
17168 default value of 10.
17173 @section Configuring the Current ABI
17175 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
17176 application automatically. However, sometimes you need to override its
17177 conclusions. Use these commands to manage @value{GDBN}'s view of the
17184 One @value{GDBN} configuration can debug binaries for multiple operating
17185 system targets, either via remote debugging or native emulation.
17186 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
17187 but you can override its conclusion using the @code{set osabi} command.
17188 One example where this is useful is in debugging of binaries which use
17189 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
17190 not have the same identifying marks that the standard C library for your
17195 Show the OS ABI currently in use.
17198 With no argument, show the list of registered available OS ABI's.
17200 @item set osabi @var{abi}
17201 Set the current OS ABI to @var{abi}.
17204 @cindex float promotion
17206 Generally, the way that an argument of type @code{float} is passed to a
17207 function depends on whether the function is prototyped. For a prototyped
17208 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
17209 according to the architecture's convention for @code{float}. For unprototyped
17210 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
17211 @code{double} and then passed.
17213 Unfortunately, some forms of debug information do not reliably indicate whether
17214 a function is prototyped. If @value{GDBN} calls a function that is not marked
17215 as prototyped, it consults @kbd{set coerce-float-to-double}.
17218 @kindex set coerce-float-to-double
17219 @item set coerce-float-to-double
17220 @itemx set coerce-float-to-double on
17221 Arguments of type @code{float} will be promoted to @code{double} when passed
17222 to an unprototyped function. This is the default setting.
17224 @item set coerce-float-to-double off
17225 Arguments of type @code{float} will be passed directly to unprototyped
17228 @kindex show coerce-float-to-double
17229 @item show coerce-float-to-double
17230 Show the current setting of promoting @code{float} to @code{double}.
17234 @kindex show cp-abi
17235 @value{GDBN} needs to know the ABI used for your program's C@t{++}
17236 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
17237 used to build your application. @value{GDBN} only fully supports
17238 programs with a single C@t{++} ABI; if your program contains code using
17239 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
17240 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
17241 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
17242 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
17243 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
17244 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
17249 Show the C@t{++} ABI currently in use.
17252 With no argument, show the list of supported C@t{++} ABI's.
17254 @item set cp-abi @var{abi}
17255 @itemx set cp-abi auto
17256 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
17259 @node Messages/Warnings
17260 @section Optional Warnings and Messages
17262 @cindex verbose operation
17263 @cindex optional warnings
17264 By default, @value{GDBN} is silent about its inner workings. If you are
17265 running on a slow machine, you may want to use the @code{set verbose}
17266 command. This makes @value{GDBN} tell you when it does a lengthy
17267 internal operation, so you will not think it has crashed.
17269 Currently, the messages controlled by @code{set verbose} are those
17270 which announce that the symbol table for a source file is being read;
17271 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
17274 @kindex set verbose
17275 @item set verbose on
17276 Enables @value{GDBN} output of certain informational messages.
17278 @item set verbose off
17279 Disables @value{GDBN} output of certain informational messages.
17281 @kindex show verbose
17283 Displays whether @code{set verbose} is on or off.
17286 By default, if @value{GDBN} encounters bugs in the symbol table of an
17287 object file, it is silent; but if you are debugging a compiler, you may
17288 find this information useful (@pxref{Symbol Errors, ,Errors Reading
17293 @kindex set complaints
17294 @item set complaints @var{limit}
17295 Permits @value{GDBN} to output @var{limit} complaints about each type of
17296 unusual symbols before becoming silent about the problem. Set
17297 @var{limit} to zero to suppress all complaints; set it to a large number
17298 to prevent complaints from being suppressed.
17300 @kindex show complaints
17301 @item show complaints
17302 Displays how many symbol complaints @value{GDBN} is permitted to produce.
17306 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
17307 lot of stupid questions to confirm certain commands. For example, if
17308 you try to run a program which is already running:
17312 The program being debugged has been started already.
17313 Start it from the beginning? (y or n)
17316 If you are willing to unflinchingly face the consequences of your own
17317 commands, you can disable this ``feature'':
17321 @kindex set confirm
17323 @cindex confirmation
17324 @cindex stupid questions
17325 @item set confirm off
17326 Disables confirmation requests.
17328 @item set confirm on
17329 Enables confirmation requests (the default).
17331 @kindex show confirm
17333 Displays state of confirmation requests.
17337 @cindex command tracing
17338 If you need to debug user-defined commands or sourced files you may find it
17339 useful to enable @dfn{command tracing}. In this mode each command will be
17340 printed as it is executed, prefixed with one or more @samp{+} symbols, the
17341 quantity denoting the call depth of each command.
17344 @kindex set trace-commands
17345 @cindex command scripts, debugging
17346 @item set trace-commands on
17347 Enable command tracing.
17348 @item set trace-commands off
17349 Disable command tracing.
17350 @item show trace-commands
17351 Display the current state of command tracing.
17354 @node Debugging Output
17355 @section Optional Messages about Internal Happenings
17356 @cindex optional debugging messages
17358 @value{GDBN} has commands that enable optional debugging messages from
17359 various @value{GDBN} subsystems; normally these commands are of
17360 interest to @value{GDBN} maintainers, or when reporting a bug. This
17361 section documents those commands.
17364 @kindex set exec-done-display
17365 @item set exec-done-display
17366 Turns on or off the notification of asynchronous commands'
17367 completion. When on, @value{GDBN} will print a message when an
17368 asynchronous command finishes its execution. The default is off.
17369 @kindex show exec-done-display
17370 @item show exec-done-display
17371 Displays the current setting of asynchronous command completion
17374 @cindex gdbarch debugging info
17375 @cindex architecture debugging info
17376 @item set debug arch
17377 Turns on or off display of gdbarch debugging info. The default is off
17379 @item show debug arch
17380 Displays the current state of displaying gdbarch debugging info.
17381 @item set debug aix-thread
17382 @cindex AIX threads
17383 Display debugging messages about inner workings of the AIX thread
17385 @item show debug aix-thread
17386 Show the current state of AIX thread debugging info display.
17387 @item set debug dwarf2-die
17388 @cindex DWARF2 DIEs
17389 Dump DWARF2 DIEs after they are read in.
17390 The value is the number of nesting levels to print.
17391 A value of zero turns off the display.
17392 @item show debug dwarf2-die
17393 Show the current state of DWARF2 DIE debugging.
17394 @item set debug displaced
17395 @cindex displaced stepping debugging info
17396 Turns on or off display of @value{GDBN} debugging info for the
17397 displaced stepping support. The default is off.
17398 @item show debug displaced
17399 Displays the current state of displaying @value{GDBN} debugging info
17400 related to displaced stepping.
17401 @item set debug event
17402 @cindex event debugging info
17403 Turns on or off display of @value{GDBN} event debugging info. The
17405 @item show debug event
17406 Displays the current state of displaying @value{GDBN} event debugging
17408 @item set debug expression
17409 @cindex expression debugging info
17410 Turns on or off display of debugging info about @value{GDBN}
17411 expression parsing. The default is off.
17412 @item show debug expression
17413 Displays the current state of displaying debugging info about
17414 @value{GDBN} expression parsing.
17415 @item set debug frame
17416 @cindex frame debugging info
17417 Turns on or off display of @value{GDBN} frame debugging info. The
17419 @item show debug frame
17420 Displays the current state of displaying @value{GDBN} frame debugging
17422 @item set debug infrun
17423 @cindex inferior debugging info
17424 Turns on or off display of @value{GDBN} debugging info for running the inferior.
17425 The default is off. @file{infrun.c} contains GDB's runtime state machine used
17426 for implementing operations such as single-stepping the inferior.
17427 @item show debug infrun
17428 Displays the current state of @value{GDBN} inferior debugging.
17429 @item set debug lin-lwp
17430 @cindex @sc{gnu}/Linux LWP debug messages
17431 @cindex Linux lightweight processes
17432 Turns on or off debugging messages from the Linux LWP debug support.
17433 @item show debug lin-lwp
17434 Show the current state of Linux LWP debugging messages.
17435 @item set debug lin-lwp-async
17436 @cindex @sc{gnu}/Linux LWP async debug messages
17437 @cindex Linux lightweight processes
17438 Turns on or off debugging messages from the Linux LWP async debug support.
17439 @item show debug lin-lwp-async
17440 Show the current state of Linux LWP async debugging messages.
17441 @item set debug observer
17442 @cindex observer debugging info
17443 Turns on or off display of @value{GDBN} observer debugging. This
17444 includes info such as the notification of observable events.
17445 @item show debug observer
17446 Displays the current state of observer debugging.
17447 @item set debug overload
17448 @cindex C@t{++} overload debugging info
17449 Turns on or off display of @value{GDBN} C@t{++} overload debugging
17450 info. This includes info such as ranking of functions, etc. The default
17452 @item show debug overload
17453 Displays the current state of displaying @value{GDBN} C@t{++} overload
17455 @cindex packets, reporting on stdout
17456 @cindex serial connections, debugging
17457 @cindex debug remote protocol
17458 @cindex remote protocol debugging
17459 @cindex display remote packets
17460 @item set debug remote
17461 Turns on or off display of reports on all packets sent back and forth across
17462 the serial line to the remote machine. The info is printed on the
17463 @value{GDBN} standard output stream. The default is off.
17464 @item show debug remote
17465 Displays the state of display of remote packets.
17466 @item set debug serial
17467 Turns on or off display of @value{GDBN} serial debugging info. The
17469 @item show debug serial
17470 Displays the current state of displaying @value{GDBN} serial debugging
17472 @item set debug solib-frv
17473 @cindex FR-V shared-library debugging
17474 Turns on or off debugging messages for FR-V shared-library code.
17475 @item show debug solib-frv
17476 Display the current state of FR-V shared-library code debugging
17478 @item set debug target
17479 @cindex target debugging info
17480 Turns on or off display of @value{GDBN} target debugging info. This info
17481 includes what is going on at the target level of GDB, as it happens. The
17482 default is 0. Set it to 1 to track events, and to 2 to also track the
17483 value of large memory transfers. Changes to this flag do not take effect
17484 until the next time you connect to a target or use the @code{run} command.
17485 @item show debug target
17486 Displays the current state of displaying @value{GDBN} target debugging
17488 @item set debug timestamp
17489 @cindex timestampping debugging info
17490 Turns on or off display of timestamps with @value{GDBN} debugging info.
17491 When enabled, seconds and microseconds are displayed before each debugging
17493 @item show debug timestamp
17494 Displays the current state of displaying timestamps with @value{GDBN}
17496 @item set debugvarobj
17497 @cindex variable object debugging info
17498 Turns on or off display of @value{GDBN} variable object debugging
17499 info. The default is off.
17500 @item show debugvarobj
17501 Displays the current state of displaying @value{GDBN} variable object
17503 @item set debug xml
17504 @cindex XML parser debugging
17505 Turns on or off debugging messages for built-in XML parsers.
17506 @item show debug xml
17507 Displays the current state of XML debugging messages.
17510 @node Extending GDB
17511 @chapter Extending @value{GDBN}
17512 @cindex extending GDB
17514 @value{GDBN} provides two mechanisms for extension. The first is based
17515 on composition of @value{GDBN} commands, and the second is based on the
17516 Python scripting language.
17519 * Sequences:: Canned Sequences of Commands
17520 * Python:: Scripting @value{GDBN} using Python
17524 @section Canned Sequences of Commands
17526 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
17527 Command Lists}), @value{GDBN} provides two ways to store sequences of
17528 commands for execution as a unit: user-defined commands and command
17532 * Define:: How to define your own commands
17533 * Hooks:: Hooks for user-defined commands
17534 * Command Files:: How to write scripts of commands to be stored in a file
17535 * Output:: Commands for controlled output
17539 @subsection User-defined Commands
17541 @cindex user-defined command
17542 @cindex arguments, to user-defined commands
17543 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
17544 which you assign a new name as a command. This is done with the
17545 @code{define} command. User commands may accept up to 10 arguments
17546 separated by whitespace. Arguments are accessed within the user command
17547 via @code{$arg0@dots{}$arg9}. A trivial example:
17551 print $arg0 + $arg1 + $arg2
17556 To execute the command use:
17563 This defines the command @code{adder}, which prints the sum of
17564 its three arguments. Note the arguments are text substitutions, so they may
17565 reference variables, use complex expressions, or even perform inferior
17568 @cindex argument count in user-defined commands
17569 @cindex how many arguments (user-defined commands)
17570 In addition, @code{$argc} may be used to find out how many arguments have
17571 been passed. This expands to a number in the range 0@dots{}10.
17576 print $arg0 + $arg1
17579 print $arg0 + $arg1 + $arg2
17587 @item define @var{commandname}
17588 Define a command named @var{commandname}. If there is already a command
17589 by that name, you are asked to confirm that you want to redefine it.
17590 @var{commandname} may be a bare command name consisting of letters,
17591 numbers, dashes, and underscores. It may also start with any predefined
17592 prefix command. For example, @samp{define target my-target} creates
17593 a user-defined @samp{target my-target} command.
17595 The definition of the command is made up of other @value{GDBN} command lines,
17596 which are given following the @code{define} command. The end of these
17597 commands is marked by a line containing @code{end}.
17600 @kindex end@r{ (user-defined commands)}
17601 @item document @var{commandname}
17602 Document the user-defined command @var{commandname}, so that it can be
17603 accessed by @code{help}. The command @var{commandname} must already be
17604 defined. This command reads lines of documentation just as @code{define}
17605 reads the lines of the command definition, ending with @code{end}.
17606 After the @code{document} command is finished, @code{help} on command
17607 @var{commandname} displays the documentation you have written.
17609 You may use the @code{document} command again to change the
17610 documentation of a command. Redefining the command with @code{define}
17611 does not change the documentation.
17613 @kindex dont-repeat
17614 @cindex don't repeat command
17616 Used inside a user-defined command, this tells @value{GDBN} that this
17617 command should not be repeated when the user hits @key{RET}
17618 (@pxref{Command Syntax, repeat last command}).
17620 @kindex help user-defined
17621 @item help user-defined
17622 List all user-defined commands, with the first line of the documentation
17627 @itemx show user @var{commandname}
17628 Display the @value{GDBN} commands used to define @var{commandname} (but
17629 not its documentation). If no @var{commandname} is given, display the
17630 definitions for all user-defined commands.
17632 @cindex infinite recursion in user-defined commands
17633 @kindex show max-user-call-depth
17634 @kindex set max-user-call-depth
17635 @item show max-user-call-depth
17636 @itemx set max-user-call-depth
17637 The value of @code{max-user-call-depth} controls how many recursion
17638 levels are allowed in user-defined commands before @value{GDBN} suspects an
17639 infinite recursion and aborts the command.
17642 In addition to the above commands, user-defined commands frequently
17643 use control flow commands, described in @ref{Command Files}.
17645 When user-defined commands are executed, the
17646 commands of the definition are not printed. An error in any command
17647 stops execution of the user-defined command.
17649 If used interactively, commands that would ask for confirmation proceed
17650 without asking when used inside a user-defined command. Many @value{GDBN}
17651 commands that normally print messages to say what they are doing omit the
17652 messages when used in a user-defined command.
17655 @subsection User-defined Command Hooks
17656 @cindex command hooks
17657 @cindex hooks, for commands
17658 @cindex hooks, pre-command
17661 You may define @dfn{hooks}, which are a special kind of user-defined
17662 command. Whenever you run the command @samp{foo}, if the user-defined
17663 command @samp{hook-foo} exists, it is executed (with no arguments)
17664 before that command.
17666 @cindex hooks, post-command
17668 A hook may also be defined which is run after the command you executed.
17669 Whenever you run the command @samp{foo}, if the user-defined command
17670 @samp{hookpost-foo} exists, it is executed (with no arguments) after
17671 that command. Post-execution hooks may exist simultaneously with
17672 pre-execution hooks, for the same command.
17674 It is valid for a hook to call the command which it hooks. If this
17675 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
17677 @c It would be nice if hookpost could be passed a parameter indicating
17678 @c if the command it hooks executed properly or not. FIXME!
17680 @kindex stop@r{, a pseudo-command}
17681 In addition, a pseudo-command, @samp{stop} exists. Defining
17682 (@samp{hook-stop}) makes the associated commands execute every time
17683 execution stops in your program: before breakpoint commands are run,
17684 displays are printed, or the stack frame is printed.
17686 For example, to ignore @code{SIGALRM} signals while
17687 single-stepping, but treat them normally during normal execution,
17692 handle SIGALRM nopass
17696 handle SIGALRM pass
17699 define hook-continue
17700 handle SIGALRM pass
17704 As a further example, to hook at the beginning and end of the @code{echo}
17705 command, and to add extra text to the beginning and end of the message,
17713 define hookpost-echo
17717 (@value{GDBP}) echo Hello World
17718 <<<---Hello World--->>>
17723 You can define a hook for any single-word command in @value{GDBN}, but
17724 not for command aliases; you should define a hook for the basic command
17725 name, e.g.@: @code{backtrace} rather than @code{bt}.
17726 @c FIXME! So how does Joe User discover whether a command is an alias
17728 You can hook a multi-word command by adding @code{hook-} or
17729 @code{hookpost-} to the last word of the command, e.g.@:
17730 @samp{define target hook-remote} to add a hook to @samp{target remote}.
17732 If an error occurs during the execution of your hook, execution of
17733 @value{GDBN} commands stops and @value{GDBN} issues a prompt
17734 (before the command that you actually typed had a chance to run).
17736 If you try to define a hook which does not match any known command, you
17737 get a warning from the @code{define} command.
17739 @node Command Files
17740 @subsection Command Files
17742 @cindex command files
17743 @cindex scripting commands
17744 A command file for @value{GDBN} is a text file made of lines that are
17745 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
17746 also be included. An empty line in a command file does nothing; it
17747 does not mean to repeat the last command, as it would from the
17750 You can request the execution of a command file with the @code{source}
17755 @cindex execute commands from a file
17756 @item source [@code{-v}] @var{filename}
17757 Execute the command file @var{filename}.
17760 The lines in a command file are generally executed sequentially,
17761 unless the order of execution is changed by one of the
17762 @emph{flow-control commands} described below. The commands are not
17763 printed as they are executed. An error in any command terminates
17764 execution of the command file and control is returned to the console.
17766 @value{GDBN} searches for @var{filename} in the current directory and then
17767 on the search path (specified with the @samp{directory} command).
17769 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
17770 each command as it is executed. The option must be given before
17771 @var{filename}, and is interpreted as part of the filename anywhere else.
17773 Commands that would ask for confirmation if used interactively proceed
17774 without asking when used in a command file. Many @value{GDBN} commands that
17775 normally print messages to say what they are doing omit the messages
17776 when called from command files.
17778 @value{GDBN} also accepts command input from standard input. In this
17779 mode, normal output goes to standard output and error output goes to
17780 standard error. Errors in a command file supplied on standard input do
17781 not terminate execution of the command file---execution continues with
17785 gdb < cmds > log 2>&1
17788 (The syntax above will vary depending on the shell used.) This example
17789 will execute commands from the file @file{cmds}. All output and errors
17790 would be directed to @file{log}.
17792 Since commands stored on command files tend to be more general than
17793 commands typed interactively, they frequently need to deal with
17794 complicated situations, such as different or unexpected values of
17795 variables and symbols, changes in how the program being debugged is
17796 built, etc. @value{GDBN} provides a set of flow-control commands to
17797 deal with these complexities. Using these commands, you can write
17798 complex scripts that loop over data structures, execute commands
17799 conditionally, etc.
17806 This command allows to include in your script conditionally executed
17807 commands. The @code{if} command takes a single argument, which is an
17808 expression to evaluate. It is followed by a series of commands that
17809 are executed only if the expression is true (its value is nonzero).
17810 There can then optionally be an @code{else} line, followed by a series
17811 of commands that are only executed if the expression was false. The
17812 end of the list is marked by a line containing @code{end}.
17816 This command allows to write loops. Its syntax is similar to
17817 @code{if}: the command takes a single argument, which is an expression
17818 to evaluate, and must be followed by the commands to execute, one per
17819 line, terminated by an @code{end}. These commands are called the
17820 @dfn{body} of the loop. The commands in the body of @code{while} are
17821 executed repeatedly as long as the expression evaluates to true.
17825 This command exits the @code{while} loop in whose body it is included.
17826 Execution of the script continues after that @code{while}s @code{end}
17829 @kindex loop_continue
17830 @item loop_continue
17831 This command skips the execution of the rest of the body of commands
17832 in the @code{while} loop in whose body it is included. Execution
17833 branches to the beginning of the @code{while} loop, where it evaluates
17834 the controlling expression.
17836 @kindex end@r{ (if/else/while commands)}
17838 Terminate the block of commands that are the body of @code{if},
17839 @code{else}, or @code{while} flow-control commands.
17844 @subsection Commands for Controlled Output
17846 During the execution of a command file or a user-defined command, normal
17847 @value{GDBN} output is suppressed; the only output that appears is what is
17848 explicitly printed by the commands in the definition. This section
17849 describes three commands useful for generating exactly the output you
17854 @item echo @var{text}
17855 @c I do not consider backslash-space a standard C escape sequence
17856 @c because it is not in ANSI.
17857 Print @var{text}. Nonprinting characters can be included in
17858 @var{text} using C escape sequences, such as @samp{\n} to print a
17859 newline. @strong{No newline is printed unless you specify one.}
17860 In addition to the standard C escape sequences, a backslash followed
17861 by a space stands for a space. This is useful for displaying a
17862 string with spaces at the beginning or the end, since leading and
17863 trailing spaces are otherwise trimmed from all arguments.
17864 To print @samp{@w{ }and foo =@w{ }}, use the command
17865 @samp{echo \@w{ }and foo = \@w{ }}.
17867 A backslash at the end of @var{text} can be used, as in C, to continue
17868 the command onto subsequent lines. For example,
17871 echo This is some text\n\
17872 which is continued\n\
17873 onto several lines.\n
17876 produces the same output as
17879 echo This is some text\n
17880 echo which is continued\n
17881 echo onto several lines.\n
17885 @item output @var{expression}
17886 Print the value of @var{expression} and nothing but that value: no
17887 newlines, no @samp{$@var{nn} = }. The value is not entered in the
17888 value history either. @xref{Expressions, ,Expressions}, for more information
17891 @item output/@var{fmt} @var{expression}
17892 Print the value of @var{expression} in format @var{fmt}. You can use
17893 the same formats as for @code{print}. @xref{Output Formats,,Output
17894 Formats}, for more information.
17897 @item printf @var{template}, @var{expressions}@dots{}
17898 Print the values of one or more @var{expressions} under the control of
17899 the string @var{template}. To print several values, make
17900 @var{expressions} be a comma-separated list of individual expressions,
17901 which may be either numbers or pointers. Their values are printed as
17902 specified by @var{template}, exactly as a C program would do by
17903 executing the code below:
17906 printf (@var{template}, @var{expressions}@dots{});
17909 As in @code{C} @code{printf}, ordinary characters in @var{template}
17910 are printed verbatim, while @dfn{conversion specification} introduced
17911 by the @samp{%} character cause subsequent @var{expressions} to be
17912 evaluated, their values converted and formatted according to type and
17913 style information encoded in the conversion specifications, and then
17916 For example, you can print two values in hex like this:
17919 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
17922 @code{printf} supports all the standard @code{C} conversion
17923 specifications, including the flags and modifiers between the @samp{%}
17924 character and the conversion letter, with the following exceptions:
17928 The argument-ordering modifiers, such as @samp{2$}, are not supported.
17931 The modifier @samp{*} is not supported for specifying precision or
17935 The @samp{'} flag (for separation of digits into groups according to
17936 @code{LC_NUMERIC'}) is not supported.
17939 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
17943 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
17946 The conversion letters @samp{a} and @samp{A} are not supported.
17950 Note that the @samp{ll} type modifier is supported only if the
17951 underlying @code{C} implementation used to build @value{GDBN} supports
17952 the @code{long long int} type, and the @samp{L} type modifier is
17953 supported only if @code{long double} type is available.
17955 As in @code{C}, @code{printf} supports simple backslash-escape
17956 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
17957 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
17958 single character. Octal and hexadecimal escape sequences are not
17961 Additionally, @code{printf} supports conversion specifications for DFP
17962 (@dfn{Decimal Floating Point}) types using the following length modifiers
17963 together with a floating point specifier.
17968 @samp{H} for printing @code{Decimal32} types.
17971 @samp{D} for printing @code{Decimal64} types.
17974 @samp{DD} for printing @code{Decimal128} types.
17977 If the underlying @code{C} implementation used to build @value{GDBN} has
17978 support for the three length modifiers for DFP types, other modifiers
17979 such as width and precision will also be available for @value{GDBN} to use.
17981 In case there is no such @code{C} support, no additional modifiers will be
17982 available and the value will be printed in the standard way.
17984 Here's an example of printing DFP types using the above conversion letters:
17986 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
17992 @section Scripting @value{GDBN} using Python
17993 @cindex python scripting
17994 @cindex scripting with python
17996 You can script @value{GDBN} using the @uref{http://www.python.org/,
17997 Python programming language}. This feature is available only if
17998 @value{GDBN} was configured using @option{--with-python}.
18001 * Python Commands:: Accessing Python from @value{GDBN}.
18002 * Python API:: Accessing @value{GDBN} from Python.
18005 @node Python Commands
18006 @subsection Python Commands
18007 @cindex python commands
18008 @cindex commands to access python
18010 @value{GDBN} provides one command for accessing the Python interpreter,
18011 and one related setting:
18015 @item python @r{[}@var{code}@r{]}
18016 The @code{python} command can be used to evaluate Python code.
18018 If given an argument, the @code{python} command will evaluate the
18019 argument as a Python command. For example:
18022 (@value{GDBP}) python print 23
18026 If you do not provide an argument to @code{python}, it will act as a
18027 multi-line command, like @code{define}. In this case, the Python
18028 script is made up of subsequent command lines, given after the
18029 @code{python} command. This command list is terminated using a line
18030 containing @code{end}. For example:
18033 (@value{GDBP}) python
18035 End with a line saying just "end".
18041 @kindex maint set python print-stack
18042 @item maint set python print-stack
18043 By default, @value{GDBN} will print a stack trace when an error occurs
18044 in a Python script. This can be controlled using @code{maint set
18045 python print-stack}: if @code{on}, the default, then Python stack
18046 printing is enabled; if @code{off}, then Python stack printing is
18051 @subsection Python API
18053 @cindex programming in python
18055 @cindex python stdout
18056 @cindex python pagination
18057 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
18058 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
18059 A Python program which outputs to one of these streams may have its
18060 output interrupted by the user (@pxref{Screen Size}). In this
18061 situation, a Python @code{KeyboardInterrupt} exception is thrown.
18064 * Basic Python:: Basic Python Functions.
18065 * Exception Handling::
18066 * Values From Inferior::
18067 * Commands In Python:: Implementing new commands in Python.
18071 @subsubsection Basic Python
18073 @cindex python functions
18074 @cindex python module
18076 @value{GDBN} introduces a new Python module, named @code{gdb}. All
18077 methods and classes added by @value{GDBN} are placed in this module.
18078 @value{GDBN} automatically @code{import}s the @code{gdb} module for
18079 use in all scripts evaluated by the @code{python} command.
18081 @findex gdb.execute
18082 @defun execute command [from_tty]
18083 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
18084 If a GDB exception happens while @var{command} runs, it is
18085 translated as described in @ref{Exception Handling,,Exception Handling}.
18086 If no exceptions occur, this function returns @code{None}.
18088 @var{from_tty} specifies whether @value{GDBN} ought to consider this
18089 command as having originated from the user invoking it interactively.
18090 It must be a boolean value. If omitted, it defaults to @code{False}.
18093 @findex gdb.get_parameter
18094 @defun get_parameter parameter
18095 Return the value of a @value{GDBN} parameter. @var{parameter} is a
18096 string naming the parameter to look up; @var{parameter} may contain
18097 spaces if the parameter has a multi-part name. For example,
18098 @samp{print object} is a valid parameter name.
18100 If the named parameter does not exist, this function throws a
18101 @code{RuntimeError}. Otherwise, the parameter's value is converted to
18102 a Python value of the appropriate type, and returned.
18105 @findex gdb.history
18106 @defun history number
18107 Return a value from @value{GDBN}'s value history (@pxref{Value
18108 History}). @var{number} indicates which history element to return.
18109 If @var{number} is negative, then @value{GDBN} will take its absolute value
18110 and count backward from the last element (i.e., the most recent element) to
18111 find the value to return. If @var{number} is zero, then @value{GDBN} will
18112 return the most recent element. If the element specified by @value{number}
18113 doesn't exist in the value history, a @code{RuntimeError} exception will be
18116 If no exception is raised, the return value is always an instance of
18117 @code{gdb.Value} (@pxref{Values From Inferior}).
18121 @defun write string
18122 Print a string to @value{GDBN}'s paginated standard output stream.
18123 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
18124 call this function.
18129 Flush @value{GDBN}'s paginated standard output stream. Flushing
18130 @code{sys.stdout} or @code{sys.stderr} will automatically call this
18134 @node Exception Handling
18135 @subsubsection Exception Handling
18136 @cindex python exceptions
18137 @cindex exceptions, python
18139 When executing the @code{python} command, Python exceptions
18140 uncaught within the Python code are translated to calls to
18141 @value{GDBN} error-reporting mechanism. If the command that called
18142 @code{python} does not handle the error, @value{GDBN} will
18143 terminate it and print an error message containing the Python
18144 exception name, the associated value, and the Python call stack
18145 backtrace at the point where the exception was raised. Example:
18148 (@value{GDBP}) python print foo
18149 Traceback (most recent call last):
18150 File "<string>", line 1, in <module>
18151 NameError: name 'foo' is not defined
18154 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
18155 code are converted to Python @code{RuntimeError} exceptions. User
18156 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
18157 prompt) is translated to a Python @code{KeyboardInterrupt}
18158 exception. If you catch these exceptions in your Python code, your
18159 exception handler will see @code{RuntimeError} or
18160 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
18161 message as its value, and the Python call stack backtrace at the
18162 Python statement closest to where the @value{GDBN} error occured as the
18165 @node Values From Inferior
18166 @subsubsection Values From Inferior
18167 @cindex values from inferior, with Python
18168 @cindex python, working with values from inferior
18170 @cindex @code{gdb.Value}
18171 @value{GDBN} provides values it obtains from the inferior program in
18172 an object of type @code{gdb.Value}. @value{GDBN} uses this object
18173 for its internal bookkeeping of the inferior's values, and for
18174 fetching values when necessary.
18176 Inferior values that are simple scalars can be used directly in
18177 Python expressions that are valid for the value's data type. Here's
18178 an example for an integer or floating-point value @code{some_val}:
18185 As result of this, @code{bar} will also be a @code{gdb.Value} object
18186 whose values are of the same type as those of @code{some_val}.
18188 Inferior values that are structures or instances of some class can
18189 be accessed using the Python @dfn{dictionary syntax}. For example, if
18190 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
18191 can access its @code{foo} element with:
18194 bar = some_val['foo']
18197 Again, @code{bar} will also be a @code{gdb.Value} object.
18199 For pointer data types, @code{gdb.Value} provides a method for
18200 dereferencing the pointer to obtain the object it points to.
18202 @defmethod Value dereference
18203 This method returns a new @code{gdb.Value} object whose contents is
18204 the object pointed to by the pointer. For example, if @code{foo} is
18205 a C pointer to an @code{int}, declared in your C program as
18212 then you can use the corresponding @code{gdb.Value} to access what
18213 @code{foo} points to like this:
18216 bar = foo.dereference ()
18219 The result @code{bar} will be a @code{gdb.Value} object holding the
18220 value pointed to by @code{foo}.
18223 @defmethod Value string @r{[}encoding @r{[}errors@r{]}@r{]}
18224 If this @code{gdb.Value} represents a string, then this method
18225 converts the contents to a Python string. Otherwise, this method will
18226 throw an exception.
18228 Strings are recognized in a language-specific way; whether a given
18229 @code{gdb.Value} represents a string is determined by the current
18232 For C-like languages, a value is a string if it is a pointer to or an
18233 array of characters or ints. The string is assumed to be terminated
18234 by a zero of the appropriate width.
18236 If the optional @var{encoding} argument is given, it must be a string
18237 naming the encoding of the string in the @code{gdb.Value}, such as
18238 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
18239 the same encodings as the corresponding argument to Python's
18240 @code{string.decode} method, and the Python codec machinery will be used
18241 to convert the string. If @var{encoding} is not given, or if
18242 @var{encoding} is the empty string, then either the @code{target-charset}
18243 (@pxref{Character Sets}) will be used, or a language-specific encoding
18244 will be used, if the current language is able to supply one.
18246 The optional @var{errors} argument is the same as the corresponding
18247 argument to Python's @code{string.decode} method.
18250 @node Commands In Python
18251 @subsubsection Commands In Python
18253 @cindex commands in python
18254 @cindex python commands
18256 @tindex gdb.Command
18257 You can implement new @value{GDBN} CLI commands in Python. A CLI
18258 command is implemented using an instance of the @code{gdb.Command}
18259 class, most commonly using a subclass.
18261 @defmethod Command __init__ name @var{command-class} @r{[}@var{completer-class} @var{prefix}@r{]}
18262 The object initializer for @code{Command} registers the new command
18263 with @value{GDBN}. This initializer is normally invoked from the
18264 subclass' own @code{__init__} method.
18266 @var{name} is the name of the command. If @var{name} consists of
18267 multiple words, then the initial words are looked for as prefix
18268 commands. In this case, if one of the prefix commands does not exist,
18269 an exception is raised.
18271 There is no support for multi-line commands.
18273 @var{command-class} should be one of the @samp{COMMAND_} constants
18274 defined below. This argument tells @value{GDBN} how to categorize the
18275 new command in the help system.
18277 @var{completer-class} is an optional argument. If given, it should be
18278 one of the @samp{COMPLETE_} constants defined below. This argument
18279 tells @value{GDBN} how to perform completion for this command. If not
18280 given, @value{GDBN} will attempt to complete using the object's
18281 @code{complete} method (see below); if no such method is found, an
18282 error will occur when completion is attempted.
18284 @var{prefix} is an optional argument. If @code{True}, then the new
18285 command is a prefix command; sub-commands of this command may be
18288 The help text for the new command is taken from the Python
18289 documentation string for the command's class, if there is one. If no
18290 documentation string is provided, the default value ``This command is
18291 not documented.'' is used.
18294 @defmethod Command dont_repeat
18295 By default, a @value{GDBN} command is repeated when the user enters a
18296 blank line at the command prompt. A command can suppress this
18297 behavior by invoking the @code{dont_repeat} method. This is similar
18298 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
18301 @defmethod Command invoke argument from_tty
18302 This method is called by @value{GDBN} when this command is invoked.
18304 @var{argument} is a string. It is the argument to the command, after
18305 leading and trailing whitespace has been stripped.
18307 @var{from_tty} is a boolean argument. When true, this means that the
18308 command was entered by the user at the terminal; when false it means
18309 that the command came from elsewhere.
18311 If this method throws an exception, it is turned into a @value{GDBN}
18312 @code{error} call. Otherwise, the return value is ignored.
18315 @defmethod Command complete text word
18316 This method is called by @value{GDBN} when the user attempts
18317 completion on this command. All forms of completion are handled by
18318 this method, that is, the @key{TAB} and @key{M-?} key bindings, and
18319 the @code{complete} command.
18321 The arguments @var{text} and @var{word} are both strings. @var{text}
18322 holds the complete command line up to the cursor's location.
18323 @var{word} holds the last word of the command line; this is computed
18324 using a word-breaking heuristic.
18326 The @code{complete} method can return several values:
18329 If the return value is a sequence, the contents of the sequence are
18330 used as the completions. It is up to @code{complete} to ensure that the
18331 contents actually do complete the word. A zero-length sequence is
18332 allowed, it means that there were no completions available. Only
18333 string elements of the sequence are used; other elements in the
18334 sequence are ignored.
18337 If the return value is one of the @samp{COMPLETE_} constants defined
18338 below, then the corresponding @value{GDBN}-internal completion
18339 function is invoked, and its result is used.
18342 All other results are treated as though there were no available
18348 When a new command is registered, it must be declared as a member of
18349 some general class of commands. This is used to classify top-level
18350 commands in the on-line help system; note that prefix commands are not
18351 listed under their own category but rather that of their top-level
18352 command. The available classifications are represented by constants
18353 defined in the @code{gdb} module:
18356 @findex COMMAND_NONE
18357 @findex gdb.COMMAND_NONE
18359 The command does not belong to any particular class. A command in
18360 this category will not be displayed in any of the help categories.
18362 @findex COMMAND_RUNNING
18363 @findex gdb.COMMAND_RUNNING
18365 The command is related to running the inferior. For example,
18366 @code{start}, @code{step}, and @code{continue} are in this category.
18367 Type @code{help running} at the @value{GDBN} prompt to see a list of
18368 commands in this category.
18370 @findex COMMAND_DATA
18371 @findex gdb.COMMAND_DATA
18373 The command is related to data or variables. For example,
18374 @code{call}, @code{find}, and @code{print} are in this category. Type
18375 @code{help data} at the @value{GDBN} prompt to see a list of commands
18378 @findex COMMAND_STACK
18379 @findex gdb.COMMAND_STACK
18380 @item COMMAND_STACK
18381 The command has to do with manipulation of the stack. For example,
18382 @code{backtrace}, @code{frame}, and @code{return} are in this
18383 category. Type @code{help stack} at the @value{GDBN} prompt to see a
18384 list of commands in this category.
18386 @findex COMMAND_FILES
18387 @findex gdb.COMMAND_FILES
18388 @item COMMAND_FILES
18389 This class is used for file-related commands. For example,
18390 @code{file}, @code{list} and @code{section} are in this category.
18391 Type @code{help files} at the @value{GDBN} prompt to see a list of
18392 commands in this category.
18394 @findex COMMAND_SUPPORT
18395 @findex gdb.COMMAND_SUPPORT
18396 @item COMMAND_SUPPORT
18397 This should be used for ``support facilities'', generally meaning
18398 things that are useful to the user when interacting with @value{GDBN},
18399 but not related to the state of the inferior. For example,
18400 @code{help}, @code{make}, and @code{shell} are in this category. Type
18401 @code{help support} at the @value{GDBN} prompt to see a list of
18402 commands in this category.
18404 @findex COMMAND_STATUS
18405 @findex gdb.COMMAND_STATUS
18407 The command is an @samp{info}-related command, that is, related to the
18408 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
18409 and @code{show} are in this category. Type @code{help status} at the
18410 @value{GDBN} prompt to see a list of commands in this category.
18412 @findex COMMAND_BREAKPOINTS
18413 @findex gdb.COMMAND_BREAKPOINTS
18414 @item COMMAND_BREAKPOINT
18415 The command has to do with breakpoints. For example, @code{break},
18416 @code{clear}, and @code{delete} are in this category. Type @code{help
18417 breakpoints} at the @value{GDBN} prompt to see a list of commands in
18420 @findex COMMAND_TRACEPOINTS
18421 @findex gdb.COMMAND_TRACEPOINTS
18422 @item COMMAND_TRACE
18423 The command has to do with tracepoints. For example, @code{trace},
18424 @code{actions}, and @code{tfind} are in this category. Type
18425 @code{help tracepoints} at the @value{GDBN} prompt to see a list of
18426 commands in this category.
18428 @findex COMMAND_OBSCURE
18429 @findex gdb.COMMAND_OBSCURE
18430 @item COMMAND_OBSCURE
18431 The command is only used in unusual circumstances, or is not of
18432 general interest to users. For example, @code{checkpoint},
18433 @code{fork}, and @code{stop} are in this category. Type @code{help
18434 obscure} at the @value{GDBN} prompt to see a list of commands in this
18437 @findex COMMAND_MAINTENANCE
18438 @findex gdb.COMMAND_MAINTENANCE
18439 @item COMMAND_MAINTENANCE
18440 The command is only useful to @value{GDBN} maintainers. The
18441 @code{maintenance} and @code{flushregs} commands are in this category.
18442 Type @code{help internals} at the @value{GDBN} prompt to see a list of
18443 commands in this category.
18447 A new command can use a predefined completion function, either by
18448 specifying it via an argument at initialization, or by returning it
18449 from the @code{complete} method. These predefined completion
18450 constants are all defined in the @code{gdb} module:
18453 @findex COMPLETE_NONE
18454 @findex gdb.COMPLETE_NONE
18455 @item COMPLETE_NONE
18456 This constant means that no completion should be done.
18458 @findex COMPLETE_FILENAME
18459 @findex gdb.COMPLETE_FILENAME
18460 @item COMPLETE_FILENAME
18461 This constant means that filename completion should be performed.
18463 @findex COMPLETE_LOCATION
18464 @findex gdb.COMPLETE_LOCATION
18465 @item COMPLETE_LOCATION
18466 This constant means that location completion should be done.
18467 @xref{Specify Location}.
18469 @findex COMPLETE_COMMAND
18470 @findex gdb.COMPLETE_COMMAND
18471 @item COMPLETE_COMMAND
18472 This constant means that completion should examine @value{GDBN}
18475 @findex COMPLETE_SYMBOL
18476 @findex gdb.COMPLETE_SYMBOL
18477 @item COMPLETE_SYMBOL
18478 This constant means that completion should be done using symbol names
18482 The following code snippet shows how a trivial CLI command can be
18483 implemented in Python:
18486 class HelloWorld (gdb.Command):
18487 """Greet the whole world."""
18489 def __init__ (self):
18490 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
18492 def invoke (self, arg, from_tty):
18493 print "Hello, World!"
18498 The last line instantiates the class, and is necessary to trigger the
18499 registration of the command with @value{GDBN}. Depending on how the
18500 Python code is read into @value{GDBN}, you may need to import the
18501 @code{gdb} module explicitly.
18504 @chapter Command Interpreters
18505 @cindex command interpreters
18507 @value{GDBN} supports multiple command interpreters, and some command
18508 infrastructure to allow users or user interface writers to switch
18509 between interpreters or run commands in other interpreters.
18511 @value{GDBN} currently supports two command interpreters, the console
18512 interpreter (sometimes called the command-line interpreter or @sc{cli})
18513 and the machine interface interpreter (or @sc{gdb/mi}). This manual
18514 describes both of these interfaces in great detail.
18516 By default, @value{GDBN} will start with the console interpreter.
18517 However, the user may choose to start @value{GDBN} with another
18518 interpreter by specifying the @option{-i} or @option{--interpreter}
18519 startup options. Defined interpreters include:
18523 @cindex console interpreter
18524 The traditional console or command-line interpreter. This is the most often
18525 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
18526 @value{GDBN} will use this interpreter.
18529 @cindex mi interpreter
18530 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
18531 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
18532 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
18536 @cindex mi2 interpreter
18537 The current @sc{gdb/mi} interface.
18540 @cindex mi1 interpreter
18541 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
18545 @cindex invoke another interpreter
18546 The interpreter being used by @value{GDBN} may not be dynamically
18547 switched at runtime. Although possible, this could lead to a very
18548 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
18549 enters the command "interpreter-set console" in a console view,
18550 @value{GDBN} would switch to using the console interpreter, rendering
18551 the IDE inoperable!
18553 @kindex interpreter-exec
18554 Although you may only choose a single interpreter at startup, you may execute
18555 commands in any interpreter from the current interpreter using the appropriate
18556 command. If you are running the console interpreter, simply use the
18557 @code{interpreter-exec} command:
18560 interpreter-exec mi "-data-list-register-names"
18563 @sc{gdb/mi} has a similar command, although it is only available in versions of
18564 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
18567 @chapter @value{GDBN} Text User Interface
18569 @cindex Text User Interface
18572 * TUI Overview:: TUI overview
18573 * TUI Keys:: TUI key bindings
18574 * TUI Single Key Mode:: TUI single key mode
18575 * TUI Commands:: TUI-specific commands
18576 * TUI Configuration:: TUI configuration variables
18579 The @value{GDBN} Text User Interface (TUI) is a terminal
18580 interface which uses the @code{curses} library to show the source
18581 file, the assembly output, the program registers and @value{GDBN}
18582 commands in separate text windows. The TUI mode is supported only
18583 on platforms where a suitable version of the @code{curses} library
18586 @pindex @value{GDBTUI}
18587 The TUI mode is enabled by default when you invoke @value{GDBN} as
18588 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
18589 You can also switch in and out of TUI mode while @value{GDBN} runs by
18590 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
18591 @xref{TUI Keys, ,TUI Key Bindings}.
18594 @section TUI Overview
18596 In TUI mode, @value{GDBN} can display several text windows:
18600 This window is the @value{GDBN} command window with the @value{GDBN}
18601 prompt and the @value{GDBN} output. The @value{GDBN} input is still
18602 managed using readline.
18605 The source window shows the source file of the program. The current
18606 line and active breakpoints are displayed in this window.
18609 The assembly window shows the disassembly output of the program.
18612 This window shows the processor registers. Registers are highlighted
18613 when their values change.
18616 The source and assembly windows show the current program position
18617 by highlighting the current line and marking it with a @samp{>} marker.
18618 Breakpoints are indicated with two markers. The first marker
18619 indicates the breakpoint type:
18623 Breakpoint which was hit at least once.
18626 Breakpoint which was never hit.
18629 Hardware breakpoint which was hit at least once.
18632 Hardware breakpoint which was never hit.
18635 The second marker indicates whether the breakpoint is enabled or not:
18639 Breakpoint is enabled.
18642 Breakpoint is disabled.
18645 The source, assembly and register windows are updated when the current
18646 thread changes, when the frame changes, or when the program counter
18649 These windows are not all visible at the same time. The command
18650 window is always visible. The others can be arranged in several
18661 source and assembly,
18664 source and registers, or
18667 assembly and registers.
18670 A status line above the command window shows the following information:
18674 Indicates the current @value{GDBN} target.
18675 (@pxref{Targets, ,Specifying a Debugging Target}).
18678 Gives the current process or thread number.
18679 When no process is being debugged, this field is set to @code{No process}.
18682 Gives the current function name for the selected frame.
18683 The name is demangled if demangling is turned on (@pxref{Print Settings}).
18684 When there is no symbol corresponding to the current program counter,
18685 the string @code{??} is displayed.
18688 Indicates the current line number for the selected frame.
18689 When the current line number is not known, the string @code{??} is displayed.
18692 Indicates the current program counter address.
18696 @section TUI Key Bindings
18697 @cindex TUI key bindings
18699 The TUI installs several key bindings in the readline keymaps
18700 (@pxref{Command Line Editing}). The following key bindings
18701 are installed for both TUI mode and the @value{GDBN} standard mode.
18710 Enter or leave the TUI mode. When leaving the TUI mode,
18711 the curses window management stops and @value{GDBN} operates using
18712 its standard mode, writing on the terminal directly. When reentering
18713 the TUI mode, control is given back to the curses windows.
18714 The screen is then refreshed.
18718 Use a TUI layout with only one window. The layout will
18719 either be @samp{source} or @samp{assembly}. When the TUI mode
18720 is not active, it will switch to the TUI mode.
18722 Think of this key binding as the Emacs @kbd{C-x 1} binding.
18726 Use a TUI layout with at least two windows. When the current
18727 layout already has two windows, the next layout with two windows is used.
18728 When a new layout is chosen, one window will always be common to the
18729 previous layout and the new one.
18731 Think of it as the Emacs @kbd{C-x 2} binding.
18735 Change the active window. The TUI associates several key bindings
18736 (like scrolling and arrow keys) with the active window. This command
18737 gives the focus to the next TUI window.
18739 Think of it as the Emacs @kbd{C-x o} binding.
18743 Switch in and out of the TUI SingleKey mode that binds single
18744 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
18747 The following key bindings only work in the TUI mode:
18752 Scroll the active window one page up.
18756 Scroll the active window one page down.
18760 Scroll the active window one line up.
18764 Scroll the active window one line down.
18768 Scroll the active window one column left.
18772 Scroll the active window one column right.
18776 Refresh the screen.
18779 Because the arrow keys scroll the active window in the TUI mode, they
18780 are not available for their normal use by readline unless the command
18781 window has the focus. When another window is active, you must use
18782 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
18783 and @kbd{C-f} to control the command window.
18785 @node TUI Single Key Mode
18786 @section TUI Single Key Mode
18787 @cindex TUI single key mode
18789 The TUI also provides a @dfn{SingleKey} mode, which binds several
18790 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
18791 switch into this mode, where the following key bindings are used:
18794 @kindex c @r{(SingleKey TUI key)}
18798 @kindex d @r{(SingleKey TUI key)}
18802 @kindex f @r{(SingleKey TUI key)}
18806 @kindex n @r{(SingleKey TUI key)}
18810 @kindex q @r{(SingleKey TUI key)}
18812 exit the SingleKey mode.
18814 @kindex r @r{(SingleKey TUI key)}
18818 @kindex s @r{(SingleKey TUI key)}
18822 @kindex u @r{(SingleKey TUI key)}
18826 @kindex v @r{(SingleKey TUI key)}
18830 @kindex w @r{(SingleKey TUI key)}
18835 Other keys temporarily switch to the @value{GDBN} command prompt.
18836 The key that was pressed is inserted in the editing buffer so that
18837 it is possible to type most @value{GDBN} commands without interaction
18838 with the TUI SingleKey mode. Once the command is entered the TUI
18839 SingleKey mode is restored. The only way to permanently leave
18840 this mode is by typing @kbd{q} or @kbd{C-x s}.
18844 @section TUI-specific Commands
18845 @cindex TUI commands
18847 The TUI has specific commands to control the text windows.
18848 These commands are always available, even when @value{GDBN} is not in
18849 the TUI mode. When @value{GDBN} is in the standard mode, most
18850 of these commands will automatically switch to the TUI mode.
18855 List and give the size of all displayed windows.
18859 Display the next layout.
18862 Display the previous layout.
18865 Display the source window only.
18868 Display the assembly window only.
18871 Display the source and assembly window.
18874 Display the register window together with the source or assembly window.
18878 Make the next window active for scrolling.
18881 Make the previous window active for scrolling.
18884 Make the source window active for scrolling.
18887 Make the assembly window active for scrolling.
18890 Make the register window active for scrolling.
18893 Make the command window active for scrolling.
18897 Refresh the screen. This is similar to typing @kbd{C-L}.
18899 @item tui reg float
18901 Show the floating point registers in the register window.
18903 @item tui reg general
18904 Show the general registers in the register window.
18907 Show the next register group. The list of register groups as well as
18908 their order is target specific. The predefined register groups are the
18909 following: @code{general}, @code{float}, @code{system}, @code{vector},
18910 @code{all}, @code{save}, @code{restore}.
18912 @item tui reg system
18913 Show the system registers in the register window.
18917 Update the source window and the current execution point.
18919 @item winheight @var{name} +@var{count}
18920 @itemx winheight @var{name} -@var{count}
18922 Change the height of the window @var{name} by @var{count}
18923 lines. Positive counts increase the height, while negative counts
18926 @item tabset @var{nchars}
18928 Set the width of tab stops to be @var{nchars} characters.
18931 @node TUI Configuration
18932 @section TUI Configuration Variables
18933 @cindex TUI configuration variables
18935 Several configuration variables control the appearance of TUI windows.
18938 @item set tui border-kind @var{kind}
18939 @kindex set tui border-kind
18940 Select the border appearance for the source, assembly and register windows.
18941 The possible values are the following:
18944 Use a space character to draw the border.
18947 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
18950 Use the Alternate Character Set to draw the border. The border is
18951 drawn using character line graphics if the terminal supports them.
18954 @item set tui border-mode @var{mode}
18955 @kindex set tui border-mode
18956 @itemx set tui active-border-mode @var{mode}
18957 @kindex set tui active-border-mode
18958 Select the display attributes for the borders of the inactive windows
18959 or the active window. The @var{mode} can be one of the following:
18962 Use normal attributes to display the border.
18968 Use reverse video mode.
18971 Use half bright mode.
18973 @item half-standout
18974 Use half bright and standout mode.
18977 Use extra bright or bold mode.
18979 @item bold-standout
18980 Use extra bright or bold and standout mode.
18985 @chapter Using @value{GDBN} under @sc{gnu} Emacs
18988 @cindex @sc{gnu} Emacs
18989 A special interface allows you to use @sc{gnu} Emacs to view (and
18990 edit) the source files for the program you are debugging with
18993 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
18994 executable file you want to debug as an argument. This command starts
18995 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
18996 created Emacs buffer.
18997 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
18999 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
19004 All ``terminal'' input and output goes through an Emacs buffer, called
19007 This applies both to @value{GDBN} commands and their output, and to the input
19008 and output done by the program you are debugging.
19010 This is useful because it means that you can copy the text of previous
19011 commands and input them again; you can even use parts of the output
19014 All the facilities of Emacs' Shell mode are available for interacting
19015 with your program. In particular, you can send signals the usual
19016 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
19020 @value{GDBN} displays source code through Emacs.
19022 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
19023 source file for that frame and puts an arrow (@samp{=>}) at the
19024 left margin of the current line. Emacs uses a separate buffer for
19025 source display, and splits the screen to show both your @value{GDBN} session
19028 Explicit @value{GDBN} @code{list} or search commands still produce output as
19029 usual, but you probably have no reason to use them from Emacs.
19032 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
19033 a graphical mode, enabled by default, which provides further buffers
19034 that can control the execution and describe the state of your program.
19035 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
19037 If you specify an absolute file name when prompted for the @kbd{M-x
19038 gdb} argument, then Emacs sets your current working directory to where
19039 your program resides. If you only specify the file name, then Emacs
19040 sets your current working directory to to the directory associated
19041 with the previous buffer. In this case, @value{GDBN} may find your
19042 program by searching your environment's @code{PATH} variable, but on
19043 some operating systems it might not find the source. So, although the
19044 @value{GDBN} input and output session proceeds normally, the auxiliary
19045 buffer does not display the current source and line of execution.
19047 The initial working directory of @value{GDBN} is printed on the top
19048 line of the GUD buffer and this serves as a default for the commands
19049 that specify files for @value{GDBN} to operate on. @xref{Files,
19050 ,Commands to Specify Files}.
19052 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
19053 need to call @value{GDBN} by a different name (for example, if you
19054 keep several configurations around, with different names) you can
19055 customize the Emacs variable @code{gud-gdb-command-name} to run the
19058 In the GUD buffer, you can use these special Emacs commands in
19059 addition to the standard Shell mode commands:
19063 Describe the features of Emacs' GUD Mode.
19066 Execute to another source line, like the @value{GDBN} @code{step} command; also
19067 update the display window to show the current file and location.
19070 Execute to next source line in this function, skipping all function
19071 calls, like the @value{GDBN} @code{next} command. Then update the display window
19072 to show the current file and location.
19075 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
19076 display window accordingly.
19079 Execute until exit from the selected stack frame, like the @value{GDBN}
19080 @code{finish} command.
19083 Continue execution of your program, like the @value{GDBN} @code{continue}
19087 Go up the number of frames indicated by the numeric argument
19088 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
19089 like the @value{GDBN} @code{up} command.
19092 Go down the number of frames indicated by the numeric argument, like the
19093 @value{GDBN} @code{down} command.
19096 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
19097 tells @value{GDBN} to set a breakpoint on the source line point is on.
19099 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
19100 separate frame which shows a backtrace when the GUD buffer is current.
19101 Move point to any frame in the stack and type @key{RET} to make it
19102 become the current frame and display the associated source in the
19103 source buffer. Alternatively, click @kbd{Mouse-2} to make the
19104 selected frame become the current one. In graphical mode, the
19105 speedbar displays watch expressions.
19107 If you accidentally delete the source-display buffer, an easy way to get
19108 it back is to type the command @code{f} in the @value{GDBN} buffer, to
19109 request a frame display; when you run under Emacs, this recreates
19110 the source buffer if necessary to show you the context of the current
19113 The source files displayed in Emacs are in ordinary Emacs buffers
19114 which are visiting the source files in the usual way. You can edit
19115 the files with these buffers if you wish; but keep in mind that @value{GDBN}
19116 communicates with Emacs in terms of line numbers. If you add or
19117 delete lines from the text, the line numbers that @value{GDBN} knows cease
19118 to correspond properly with the code.
19120 A more detailed description of Emacs' interaction with @value{GDBN} is
19121 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
19124 @c The following dropped because Epoch is nonstandard. Reactivate
19125 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
19127 @kindex Emacs Epoch environment
19131 Version 18 of @sc{gnu} Emacs has a built-in window system
19132 called the @code{epoch}
19133 environment. Users of this environment can use a new command,
19134 @code{inspect} which performs identically to @code{print} except that
19135 each value is printed in its own window.
19140 @chapter The @sc{gdb/mi} Interface
19142 @unnumberedsec Function and Purpose
19144 @cindex @sc{gdb/mi}, its purpose
19145 @sc{gdb/mi} is a line based machine oriented text interface to
19146 @value{GDBN} and is activated by specifying using the
19147 @option{--interpreter} command line option (@pxref{Mode Options}). It
19148 is specifically intended to support the development of systems which
19149 use the debugger as just one small component of a larger system.
19151 This chapter is a specification of the @sc{gdb/mi} interface. It is written
19152 in the form of a reference manual.
19154 Note that @sc{gdb/mi} is still under construction, so some of the
19155 features described below are incomplete and subject to change
19156 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
19158 @unnumberedsec Notation and Terminology
19160 @cindex notational conventions, for @sc{gdb/mi}
19161 This chapter uses the following notation:
19165 @code{|} separates two alternatives.
19168 @code{[ @var{something} ]} indicates that @var{something} is optional:
19169 it may or may not be given.
19172 @code{( @var{group} )*} means that @var{group} inside the parentheses
19173 may repeat zero or more times.
19176 @code{( @var{group} )+} means that @var{group} inside the parentheses
19177 may repeat one or more times.
19180 @code{"@var{string}"} means a literal @var{string}.
19184 @heading Dependencies
19188 * GDB/MI General Design::
19189 * GDB/MI Command Syntax::
19190 * GDB/MI Compatibility with CLI::
19191 * GDB/MI Development and Front Ends::
19192 * GDB/MI Output Records::
19193 * GDB/MI Simple Examples::
19194 * GDB/MI Command Description Format::
19195 * GDB/MI Breakpoint Commands::
19196 * GDB/MI Program Context::
19197 * GDB/MI Thread Commands::
19198 * GDB/MI Program Execution::
19199 * GDB/MI Stack Manipulation::
19200 * GDB/MI Variable Objects::
19201 * GDB/MI Data Manipulation::
19202 * GDB/MI Tracepoint Commands::
19203 * GDB/MI Symbol Query::
19204 * GDB/MI File Commands::
19206 * GDB/MI Kod Commands::
19207 * GDB/MI Memory Overlay Commands::
19208 * GDB/MI Signal Handling Commands::
19210 * GDB/MI Target Manipulation::
19211 * GDB/MI File Transfer Commands::
19212 * GDB/MI Miscellaneous Commands::
19215 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19216 @node GDB/MI General Design
19217 @section @sc{gdb/mi} General Design
19218 @cindex GDB/MI General Design
19220 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
19221 parts---commands sent to @value{GDBN}, responses to those commands
19222 and notifications. Each command results in exactly one response,
19223 indicating either successful completion of the command, or an error.
19224 For the commands that do not resume the target, the response contains the
19225 requested information. For the commands that resume the target, the
19226 response only indicates whether the target was successfully resumed.
19227 Notifications is the mechanism for reporting changes in the state of the
19228 target, or in @value{GDBN} state, that cannot conveniently be associated with
19229 a command and reported as part of that command response.
19231 The important examples of notifications are:
19235 Exec notifications. These are used to report changes in
19236 target state---when a target is resumed, or stopped. It would not
19237 be feasible to include this information in response of resuming
19238 commands, because one resume commands can result in multiple events in
19239 different threads. Also, quite some time may pass before any event
19240 happens in the target, while a frontend needs to know whether the resuming
19241 command itself was successfully executed.
19244 Console output, and status notifications. Console output
19245 notifications are used to report output of CLI commands, as well as
19246 diagnostics for other commands. Status notifications are used to
19247 report the progress of a long-running operation. Naturally, including
19248 this information in command response would mean no output is produced
19249 until the command is finished, which is undesirable.
19252 General notifications. Commands may have various side effects on
19253 the @value{GDBN} or target state beyond their official purpose. For example,
19254 a command may change the selected thread. Although such changes can
19255 be included in command response, using notification allows for more
19256 orthogonal frontend design.
19260 There's no guarantee that whenever an MI command reports an error,
19261 @value{GDBN} or the target are in any specific state, and especially,
19262 the state is not reverted to the state before the MI command was
19263 processed. Therefore, whenever an MI command results in an error,
19264 we recommend that the frontend refreshes all the information shown in
19265 the user interface.
19267 @subsection Context management
19269 In most cases when @value{GDBN} accesses the target, this access is
19270 done in context of a specific thread and frame (@pxref{Frames}).
19271 Often, even when accessing global data, the target requires that a thread
19272 be specified. The CLI interface maintains the selected thread and frame,
19273 and supplies them to target on each command. This is convenient,
19274 because a command line user would not want to specify that information
19275 explicitly on each command, and because user interacts with
19276 @value{GDBN} via a single terminal, so no confusion is possible as
19277 to what thread and frame are the current ones.
19279 In the case of MI, the concept of selected thread and frame is less
19280 useful. First, a frontend can easily remember this information
19281 itself. Second, a graphical frontend can have more than one window,
19282 each one used for debugging a different thread, and the frontend might
19283 want to access additional threads for internal purposes. This
19284 increases the risk that by relying on implicitly selected thread, the
19285 frontend may be operating on a wrong one. Therefore, each MI command
19286 should explicitly specify which thread and frame to operate on. To
19287 make it possible, each MI command accepts the @samp{--thread} and
19288 @samp{--frame} options, the value to each is @value{GDBN} identifier
19289 for thread and frame to operate on.
19291 Usually, each top-level window in a frontend allows the user to select
19292 a thread and a frame, and remembers the user selection for further
19293 operations. However, in some cases @value{GDBN} may suggest that the
19294 current thread be changed. For example, when stopping on a breakpoint
19295 it is reasonable to switch to the thread where breakpoint is hit. For
19296 another example, if the user issues the CLI @samp{thread} command via
19297 the frontend, it is desirable to change the frontend's selected thread to the
19298 one specified by user. @value{GDBN} communicates the suggestion to
19299 change current thread using the @samp{=thread-selected} notification.
19300 No such notification is available for the selected frame at the moment.
19302 Note that historically, MI shares the selected thread with CLI, so
19303 frontends used the @code{-thread-select} to execute commands in the
19304 right context. However, getting this to work right is cumbersome. The
19305 simplest way is for frontend to emit @code{-thread-select} command
19306 before every command. This doubles the number of commands that need
19307 to be sent. The alternative approach is to suppress @code{-thread-select}
19308 if the selected thread in @value{GDBN} is supposed to be identical to the
19309 thread the frontend wants to operate on. However, getting this
19310 optimization right can be tricky. In particular, if the frontend
19311 sends several commands to @value{GDBN}, and one of the commands changes the
19312 selected thread, then the behaviour of subsequent commands will
19313 change. So, a frontend should either wait for response from such
19314 problematic commands, or explicitly add @code{-thread-select} for
19315 all subsequent commands. No frontend is known to do this exactly
19316 right, so it is suggested to just always pass the @samp{--thread} and
19317 @samp{--frame} options.
19319 @subsection Asynchronous command execution and non-stop mode
19321 On some targets, @value{GDBN} is capable of processing MI commands
19322 even while the target is running. This is called @dfn{asynchronous
19323 command execution} (@pxref{Background Execution}). The frontend may
19324 specify a preferrence for asynchronous execution using the
19325 @code{-gdb-set target-async 1} command, which should be emitted before
19326 either running the executable or attaching to the target. After the
19327 frontend has started the executable or attached to the target, it can
19328 find if asynchronous execution is enabled using the
19329 @code{-list-target-features} command.
19331 Even if @value{GDBN} can accept a command while target is running,
19332 many commands that access the target do not work when the target is
19333 running. Therefore, asynchronous command execution is most useful
19334 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
19335 it is possible to examine the state of one thread, while other threads
19338 When a given thread is running, MI commands that try to access the
19339 target in the context of that thread may not work, or may work only on
19340 some targets. In particular, commands that try to operate on thread's
19341 stack will not work, on any target. Commands that read memory, or
19342 modify breakpoints, may work or not work, depending on the target. Note
19343 that even commands that operate on global state, such as @code{print},
19344 @code{set}, and breakpoint commands, still access the target in the
19345 context of a specific thread, so frontend should try to find a
19346 stopped thread and perform the operation on that thread (using the
19347 @samp{--thread} option).
19349 Which commands will work in the context of a running thread is
19350 highly target dependent. However, the two commands
19351 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
19352 to find the state of a thread, will always work.
19354 @subsection Thread groups
19355 @value{GDBN} may be used to debug several processes at the same time.
19356 On some platfroms, @value{GDBN} may support debugging of several
19357 hardware systems, each one having several cores with several different
19358 processes running on each core. This section describes the MI
19359 mechanism to support such debugging scenarios.
19361 The key observation is that regardless of the structure of the
19362 target, MI can have a global list of threads, because most commands that
19363 accept the @samp{--thread} option do not need to know what process that
19364 thread belongs to. Therefore, it is not necessary to introduce
19365 neither additional @samp{--process} option, nor an notion of the
19366 current process in the MI interface. The only strictly new feature
19367 that is required is the ability to find how the threads are grouped
19370 To allow the user to discover such grouping, and to support arbitrary
19371 hierarchy of machines/cores/processes, MI introduces the concept of a
19372 @dfn{thread group}. Thread group is a collection of threads and other
19373 thread groups. A thread group always has a string identifier, a type,
19374 and may have additional attributes specific to the type. A new
19375 command, @code{-list-thread-groups}, returns the list of top-level
19376 thread groups, which correspond to processes that @value{GDBN} is
19377 debugging at the moment. By passing an identifier of a thread group
19378 to the @code{-list-thread-groups} command, it is possible to obtain
19379 the members of specific thread group.
19381 To allow the user to easily discover processes, and other objects, he
19382 wishes to debug, a concept of @dfn{available thread group} is
19383 introduced. Available thread group is an thread group that
19384 @value{GDBN} is not debugging, but that can be attached to, using the
19385 @code{-target-attach} command. The list of available top-level thread
19386 groups can be obtained using @samp{-list-thread-groups --available}.
19387 In general, the content of a thread group may be only retrieved only
19388 after attaching to that thread group.
19390 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19391 @node GDB/MI Command Syntax
19392 @section @sc{gdb/mi} Command Syntax
19395 * GDB/MI Input Syntax::
19396 * GDB/MI Output Syntax::
19399 @node GDB/MI Input Syntax
19400 @subsection @sc{gdb/mi} Input Syntax
19402 @cindex input syntax for @sc{gdb/mi}
19403 @cindex @sc{gdb/mi}, input syntax
19405 @item @var{command} @expansion{}
19406 @code{@var{cli-command} | @var{mi-command}}
19408 @item @var{cli-command} @expansion{}
19409 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
19410 @var{cli-command} is any existing @value{GDBN} CLI command.
19412 @item @var{mi-command} @expansion{}
19413 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
19414 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
19416 @item @var{token} @expansion{}
19417 "any sequence of digits"
19419 @item @var{option} @expansion{}
19420 @code{"-" @var{parameter} [ " " @var{parameter} ]}
19422 @item @var{parameter} @expansion{}
19423 @code{@var{non-blank-sequence} | @var{c-string}}
19425 @item @var{operation} @expansion{}
19426 @emph{any of the operations described in this chapter}
19428 @item @var{non-blank-sequence} @expansion{}
19429 @emph{anything, provided it doesn't contain special characters such as
19430 "-", @var{nl}, """ and of course " "}
19432 @item @var{c-string} @expansion{}
19433 @code{""" @var{seven-bit-iso-c-string-content} """}
19435 @item @var{nl} @expansion{}
19444 The CLI commands are still handled by the @sc{mi} interpreter; their
19445 output is described below.
19448 The @code{@var{token}}, when present, is passed back when the command
19452 Some @sc{mi} commands accept optional arguments as part of the parameter
19453 list. Each option is identified by a leading @samp{-} (dash) and may be
19454 followed by an optional argument parameter. Options occur first in the
19455 parameter list and can be delimited from normal parameters using
19456 @samp{--} (this is useful when some parameters begin with a dash).
19463 We want easy access to the existing CLI syntax (for debugging).
19466 We want it to be easy to spot a @sc{mi} operation.
19469 @node GDB/MI Output Syntax
19470 @subsection @sc{gdb/mi} Output Syntax
19472 @cindex output syntax of @sc{gdb/mi}
19473 @cindex @sc{gdb/mi}, output syntax
19474 The output from @sc{gdb/mi} consists of zero or more out-of-band records
19475 followed, optionally, by a single result record. This result record
19476 is for the most recent command. The sequence of output records is
19477 terminated by @samp{(gdb)}.
19479 If an input command was prefixed with a @code{@var{token}} then the
19480 corresponding output for that command will also be prefixed by that same
19484 @item @var{output} @expansion{}
19485 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
19487 @item @var{result-record} @expansion{}
19488 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
19490 @item @var{out-of-band-record} @expansion{}
19491 @code{@var{async-record} | @var{stream-record}}
19493 @item @var{async-record} @expansion{}
19494 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
19496 @item @var{exec-async-output} @expansion{}
19497 @code{[ @var{token} ] "*" @var{async-output}}
19499 @item @var{status-async-output} @expansion{}
19500 @code{[ @var{token} ] "+" @var{async-output}}
19502 @item @var{notify-async-output} @expansion{}
19503 @code{[ @var{token} ] "=" @var{async-output}}
19505 @item @var{async-output} @expansion{}
19506 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
19508 @item @var{result-class} @expansion{}
19509 @code{"done" | "running" | "connected" | "error" | "exit"}
19511 @item @var{async-class} @expansion{}
19512 @code{"stopped" | @var{others}} (where @var{others} will be added
19513 depending on the needs---this is still in development).
19515 @item @var{result} @expansion{}
19516 @code{ @var{variable} "=" @var{value}}
19518 @item @var{variable} @expansion{}
19519 @code{ @var{string} }
19521 @item @var{value} @expansion{}
19522 @code{ @var{const} | @var{tuple} | @var{list} }
19524 @item @var{const} @expansion{}
19525 @code{@var{c-string}}
19527 @item @var{tuple} @expansion{}
19528 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
19530 @item @var{list} @expansion{}
19531 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
19532 @var{result} ( "," @var{result} )* "]" }
19534 @item @var{stream-record} @expansion{}
19535 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
19537 @item @var{console-stream-output} @expansion{}
19538 @code{"~" @var{c-string}}
19540 @item @var{target-stream-output} @expansion{}
19541 @code{"@@" @var{c-string}}
19543 @item @var{log-stream-output} @expansion{}
19544 @code{"&" @var{c-string}}
19546 @item @var{nl} @expansion{}
19549 @item @var{token} @expansion{}
19550 @emph{any sequence of digits}.
19558 All output sequences end in a single line containing a period.
19561 The @code{@var{token}} is from the corresponding request. Note that
19562 for all async output, while the token is allowed by the grammar and
19563 may be output by future versions of @value{GDBN} for select async
19564 output messages, it is generally omitted. Frontends should treat
19565 all async output as reporting general changes in the state of the
19566 target and there should be no need to associate async output to any
19570 @cindex status output in @sc{gdb/mi}
19571 @var{status-async-output} contains on-going status information about the
19572 progress of a slow operation. It can be discarded. All status output is
19573 prefixed by @samp{+}.
19576 @cindex async output in @sc{gdb/mi}
19577 @var{exec-async-output} contains asynchronous state change on the target
19578 (stopped, started, disappeared). All async output is prefixed by
19582 @cindex notify output in @sc{gdb/mi}
19583 @var{notify-async-output} contains supplementary information that the
19584 client should handle (e.g., a new breakpoint information). All notify
19585 output is prefixed by @samp{=}.
19588 @cindex console output in @sc{gdb/mi}
19589 @var{console-stream-output} is output that should be displayed as is in the
19590 console. It is the textual response to a CLI command. All the console
19591 output is prefixed by @samp{~}.
19594 @cindex target output in @sc{gdb/mi}
19595 @var{target-stream-output} is the output produced by the target program.
19596 All the target output is prefixed by @samp{@@}.
19599 @cindex log output in @sc{gdb/mi}
19600 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
19601 instance messages that should be displayed as part of an error log. All
19602 the log output is prefixed by @samp{&}.
19605 @cindex list output in @sc{gdb/mi}
19606 New @sc{gdb/mi} commands should only output @var{lists} containing
19612 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
19613 details about the various output records.
19615 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19616 @node GDB/MI Compatibility with CLI
19617 @section @sc{gdb/mi} Compatibility with CLI
19619 @cindex compatibility, @sc{gdb/mi} and CLI
19620 @cindex @sc{gdb/mi}, compatibility with CLI
19622 For the developers convenience CLI commands can be entered directly,
19623 but there may be some unexpected behaviour. For example, commands
19624 that query the user will behave as if the user replied yes, breakpoint
19625 command lists are not executed and some CLI commands, such as
19626 @code{if}, @code{when} and @code{define}, prompt for further input with
19627 @samp{>}, which is not valid MI output.
19629 This feature may be removed at some stage in the future and it is
19630 recommended that front ends use the @code{-interpreter-exec} command
19631 (@pxref{-interpreter-exec}).
19633 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19634 @node GDB/MI Development and Front Ends
19635 @section @sc{gdb/mi} Development and Front Ends
19636 @cindex @sc{gdb/mi} development
19638 The application which takes the MI output and presents the state of the
19639 program being debugged to the user is called a @dfn{front end}.
19641 Although @sc{gdb/mi} is still incomplete, it is currently being used
19642 by a variety of front ends to @value{GDBN}. This makes it difficult
19643 to introduce new functionality without breaking existing usage. This
19644 section tries to minimize the problems by describing how the protocol
19647 Some changes in MI need not break a carefully designed front end, and
19648 for these the MI version will remain unchanged. The following is a
19649 list of changes that may occur within one level, so front ends should
19650 parse MI output in a way that can handle them:
19654 New MI commands may be added.
19657 New fields may be added to the output of any MI command.
19660 The range of values for fields with specified values, e.g.,
19661 @code{in_scope} (@pxref{-var-update}) may be extended.
19663 @c The format of field's content e.g type prefix, may change so parse it
19664 @c at your own risk. Yes, in general?
19666 @c The order of fields may change? Shouldn't really matter but it might
19667 @c resolve inconsistencies.
19670 If the changes are likely to break front ends, the MI version level
19671 will be increased by one. This will allow the front end to parse the
19672 output according to the MI version. Apart from mi0, new versions of
19673 @value{GDBN} will not support old versions of MI and it will be the
19674 responsibility of the front end to work with the new one.
19676 @c Starting with mi3, add a new command -mi-version that prints the MI
19679 The best way to avoid unexpected changes in MI that might break your front
19680 end is to make your project known to @value{GDBN} developers and
19681 follow development on @email{gdb@@sourceware.org} and
19682 @email{gdb-patches@@sourceware.org}.
19683 @cindex mailing lists
19685 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19686 @node GDB/MI Output Records
19687 @section @sc{gdb/mi} Output Records
19690 * GDB/MI Result Records::
19691 * GDB/MI Stream Records::
19692 * GDB/MI Async Records::
19693 * GDB/MI Frame Information::
19696 @node GDB/MI Result Records
19697 @subsection @sc{gdb/mi} Result Records
19699 @cindex result records in @sc{gdb/mi}
19700 @cindex @sc{gdb/mi}, result records
19701 In addition to a number of out-of-band notifications, the response to a
19702 @sc{gdb/mi} command includes one of the following result indications:
19706 @item "^done" [ "," @var{results} ]
19707 The synchronous operation was successful, @code{@var{results}} are the return
19712 @c Is this one correct? Should it be an out-of-band notification?
19713 The asynchronous operation was successfully started. The target is
19718 @value{GDBN} has connected to a remote target.
19720 @item "^error" "," @var{c-string}
19722 The operation failed. The @code{@var{c-string}} contains the corresponding
19727 @value{GDBN} has terminated.
19731 @node GDB/MI Stream Records
19732 @subsection @sc{gdb/mi} Stream Records
19734 @cindex @sc{gdb/mi}, stream records
19735 @cindex stream records in @sc{gdb/mi}
19736 @value{GDBN} internally maintains a number of output streams: the console, the
19737 target, and the log. The output intended for each of these streams is
19738 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
19740 Each stream record begins with a unique @dfn{prefix character} which
19741 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
19742 Syntax}). In addition to the prefix, each stream record contains a
19743 @code{@var{string-output}}. This is either raw text (with an implicit new
19744 line) or a quoted C string (which does not contain an implicit newline).
19747 @item "~" @var{string-output}
19748 The console output stream contains text that should be displayed in the
19749 CLI console window. It contains the textual responses to CLI commands.
19751 @item "@@" @var{string-output}
19752 The target output stream contains any textual output from the running
19753 target. This is only present when GDB's event loop is truly
19754 asynchronous, which is currently only the case for remote targets.
19756 @item "&" @var{string-output}
19757 The log stream contains debugging messages being produced by @value{GDBN}'s
19761 @node GDB/MI Async Records
19762 @subsection @sc{gdb/mi} Async Records
19764 @cindex async records in @sc{gdb/mi}
19765 @cindex @sc{gdb/mi}, async records
19766 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
19767 additional changes that have occurred. Those changes can either be a
19768 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
19769 target activity (e.g., target stopped).
19771 The following is the list of possible async records:
19775 @item *running,thread-id="@var{thread}"
19776 The target is now running. The @var{thread} field tells which
19777 specific thread is now running, and can be @samp{all} if all threads
19778 are running. The frontend should assume that no interaction with a
19779 running thread is possible after this notification is produced.
19780 The frontend should not assume that this notification is output
19781 only once for any command. @value{GDBN} may emit this notification
19782 several times, either for different threads, because it cannot resume
19783 all threads together, or even for a single thread, if the thread must
19784 be stepped though some code before letting it run freely.
19786 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}"
19787 The target has stopped. The @var{reason} field can have one of the
19791 @item breakpoint-hit
19792 A breakpoint was reached.
19793 @item watchpoint-trigger
19794 A watchpoint was triggered.
19795 @item read-watchpoint-trigger
19796 A read watchpoint was triggered.
19797 @item access-watchpoint-trigger
19798 An access watchpoint was triggered.
19799 @item function-finished
19800 An -exec-finish or similar CLI command was accomplished.
19801 @item location-reached
19802 An -exec-until or similar CLI command was accomplished.
19803 @item watchpoint-scope
19804 A watchpoint has gone out of scope.
19805 @item end-stepping-range
19806 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
19807 similar CLI command was accomplished.
19808 @item exited-signalled
19809 The inferior exited because of a signal.
19811 The inferior exited.
19812 @item exited-normally
19813 The inferior exited normally.
19814 @item signal-received
19815 A signal was received by the inferior.
19818 The @var{id} field identifies the thread that directly caused the stop
19819 -- for example by hitting a breakpoint. Depending on whether all-stop
19820 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
19821 stop all threads, or only the thread that directly triggered the stop.
19822 If all threads are stopped, the @var{stopped} field will have the
19823 value of @code{"all"}. Otherwise, the value of the @var{stopped}
19824 field will be a list of thread identifiers. Presently, this list will
19825 always include a single thread, but frontend should be prepared to see
19826 several threads in the list.
19828 @item =thread-group-created,id="@var{id}"
19829 @itemx =thread-group-exited,id="@var{id}"
19830 A thread thread group either was attached to, or has exited/detached
19831 from. The @var{id} field contains the @value{GDBN} identifier of the
19834 @item =thread-created,id="@var{id}",group-id="@var{gid}"
19835 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
19836 A thread either was created, or has exited. The @var{id} field
19837 contains the @value{GDBN} identifier of the thread. The @var{gid}
19838 field identifies the thread group this thread belongs to.
19840 @item =thread-selected,id="@var{id}"
19841 Informs that the selected thread was changed as result of the last
19842 command. This notification is not emitted as result of @code{-thread-select}
19843 command but is emitted whenever an MI command that is not documented
19844 to change the selected thread actually changes it. In particular,
19845 invoking, directly or indirectly (via user-defined command), the CLI
19846 @code{thread} command, will generate this notification.
19848 We suggest that in response to this notification, front ends
19849 highlight the selected thread and cause subsequent commands to apply to
19854 @node GDB/MI Frame Information
19855 @subsection @sc{gdb/mi} Frame Information
19857 Response from many MI commands includes an information about stack
19858 frame. This information is a tuple that may have the following
19863 The level of the stack frame. The innermost frame has the level of
19864 zero. This field is always present.
19867 The name of the function corresponding to the frame. This field may
19868 be absent if @value{GDBN} is unable to determine the function name.
19871 The code address for the frame. This field is always present.
19874 The name of the source files that correspond to the frame's code
19875 address. This field may be absent.
19878 The source line corresponding to the frames' code address. This field
19882 The name of the binary file (either executable or shared library) the
19883 corresponds to the frame's code address. This field may be absent.
19888 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19889 @node GDB/MI Simple Examples
19890 @section Simple Examples of @sc{gdb/mi} Interaction
19891 @cindex @sc{gdb/mi}, simple examples
19893 This subsection presents several simple examples of interaction using
19894 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
19895 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
19896 the output received from @sc{gdb/mi}.
19898 Note the line breaks shown in the examples are here only for
19899 readability, they don't appear in the real output.
19901 @subheading Setting a Breakpoint
19903 Setting a breakpoint generates synchronous output which contains detailed
19904 information of the breakpoint.
19907 -> -break-insert main
19908 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
19909 enabled="y",addr="0x08048564",func="main",file="myprog.c",
19910 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
19914 @subheading Program Execution
19916 Program execution generates asynchronous records and MI gives the
19917 reason that execution stopped.
19923 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
19924 frame=@{addr="0x08048564",func="main",
19925 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
19926 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
19931 <- *stopped,reason="exited-normally"
19935 @subheading Quitting @value{GDBN}
19937 Quitting @value{GDBN} just prints the result class @samp{^exit}.
19945 @subheading A Bad Command
19947 Here's what happens if you pass a non-existent command:
19951 <- ^error,msg="Undefined MI command: rubbish"
19956 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19957 @node GDB/MI Command Description Format
19958 @section @sc{gdb/mi} Command Description Format
19960 The remaining sections describe blocks of commands. Each block of
19961 commands is laid out in a fashion similar to this section.
19963 @subheading Motivation
19965 The motivation for this collection of commands.
19967 @subheading Introduction
19969 A brief introduction to this collection of commands as a whole.
19971 @subheading Commands
19973 For each command in the block, the following is described:
19975 @subsubheading Synopsis
19978 -command @var{args}@dots{}
19981 @subsubheading Result
19983 @subsubheading @value{GDBN} Command
19985 The corresponding @value{GDBN} CLI command(s), if any.
19987 @subsubheading Example
19989 Example(s) formatted for readability. Some of the described commands have
19990 not been implemented yet and these are labeled N.A.@: (not available).
19993 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19994 @node GDB/MI Breakpoint Commands
19995 @section @sc{gdb/mi} Breakpoint Commands
19997 @cindex breakpoint commands for @sc{gdb/mi}
19998 @cindex @sc{gdb/mi}, breakpoint commands
19999 This section documents @sc{gdb/mi} commands for manipulating
20002 @subheading The @code{-break-after} Command
20003 @findex -break-after
20005 @subsubheading Synopsis
20008 -break-after @var{number} @var{count}
20011 The breakpoint number @var{number} is not in effect until it has been
20012 hit @var{count} times. To see how this is reflected in the output of
20013 the @samp{-break-list} command, see the description of the
20014 @samp{-break-list} command below.
20016 @subsubheading @value{GDBN} Command
20018 The corresponding @value{GDBN} command is @samp{ignore}.
20020 @subsubheading Example
20025 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20026 enabled="y",addr="0x000100d0",func="main",file="hello.c",
20027 fullname="/home/foo/hello.c",line="5",times="0"@}
20034 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20035 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20036 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20037 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20038 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20039 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20040 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20041 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20042 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20043 line="5",times="0",ignore="3"@}]@}
20048 @subheading The @code{-break-catch} Command
20049 @findex -break-catch
20051 @subheading The @code{-break-commands} Command
20052 @findex -break-commands
20056 @subheading The @code{-break-condition} Command
20057 @findex -break-condition
20059 @subsubheading Synopsis
20062 -break-condition @var{number} @var{expr}
20065 Breakpoint @var{number} will stop the program only if the condition in
20066 @var{expr} is true. The condition becomes part of the
20067 @samp{-break-list} output (see the description of the @samp{-break-list}
20070 @subsubheading @value{GDBN} Command
20072 The corresponding @value{GDBN} command is @samp{condition}.
20074 @subsubheading Example
20078 -break-condition 1 1
20082 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20083 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20084 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20085 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20086 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20087 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20088 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20089 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20090 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20091 line="5",cond="1",times="0",ignore="3"@}]@}
20095 @subheading The @code{-break-delete} Command
20096 @findex -break-delete
20098 @subsubheading Synopsis
20101 -break-delete ( @var{breakpoint} )+
20104 Delete the breakpoint(s) whose number(s) are specified in the argument
20105 list. This is obviously reflected in the breakpoint list.
20107 @subsubheading @value{GDBN} Command
20109 The corresponding @value{GDBN} command is @samp{delete}.
20111 @subsubheading Example
20119 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20120 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20121 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20122 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20123 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20124 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20125 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20130 @subheading The @code{-break-disable} Command
20131 @findex -break-disable
20133 @subsubheading Synopsis
20136 -break-disable ( @var{breakpoint} )+
20139 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
20140 break list is now set to @samp{n} for the named @var{breakpoint}(s).
20142 @subsubheading @value{GDBN} Command
20144 The corresponding @value{GDBN} command is @samp{disable}.
20146 @subsubheading Example
20154 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20155 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20156 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20157 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20158 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20159 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20160 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20161 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
20162 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20163 line="5",times="0"@}]@}
20167 @subheading The @code{-break-enable} Command
20168 @findex -break-enable
20170 @subsubheading Synopsis
20173 -break-enable ( @var{breakpoint} )+
20176 Enable (previously disabled) @var{breakpoint}(s).
20178 @subsubheading @value{GDBN} Command
20180 The corresponding @value{GDBN} command is @samp{enable}.
20182 @subsubheading Example
20190 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20191 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20192 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20193 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20194 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20195 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20196 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20197 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20198 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20199 line="5",times="0"@}]@}
20203 @subheading The @code{-break-info} Command
20204 @findex -break-info
20206 @subsubheading Synopsis
20209 -break-info @var{breakpoint}
20213 Get information about a single breakpoint.
20215 @subsubheading @value{GDBN} Command
20217 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
20219 @subsubheading Example
20222 @subheading The @code{-break-insert} Command
20223 @findex -break-insert
20225 @subsubheading Synopsis
20228 -break-insert [ -t ] [ -h ] [ -f ] [ -d ]
20229 [ -c @var{condition} ] [ -i @var{ignore-count} ]
20230 [ -p @var{thread} ] [ @var{location} ]
20234 If specified, @var{location}, can be one of:
20241 @item filename:linenum
20242 @item filename:function
20246 The possible optional parameters of this command are:
20250 Insert a temporary breakpoint.
20252 Insert a hardware breakpoint.
20253 @item -c @var{condition}
20254 Make the breakpoint conditional on @var{condition}.
20255 @item -i @var{ignore-count}
20256 Initialize the @var{ignore-count}.
20258 If @var{location} cannot be parsed (for example if it
20259 refers to unknown files or functions), create a pending
20260 breakpoint. Without this flag, @value{GDBN} will report
20261 an error, and won't create a breakpoint, if @var{location}
20264 Create a disabled breakpoint.
20267 @subsubheading Result
20269 The result is in the form:
20272 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
20273 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
20274 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
20275 times="@var{times}"@}
20279 where @var{number} is the @value{GDBN} number for this breakpoint,
20280 @var{funcname} is the name of the function where the breakpoint was
20281 inserted, @var{filename} is the name of the source file which contains
20282 this function, @var{lineno} is the source line number within that file
20283 and @var{times} the number of times that the breakpoint has been hit
20284 (always 0 for -break-insert but may be greater for -break-info or -break-list
20285 which use the same output).
20287 Note: this format is open to change.
20288 @c An out-of-band breakpoint instead of part of the result?
20290 @subsubheading @value{GDBN} Command
20292 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
20293 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
20295 @subsubheading Example
20300 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
20301 fullname="/home/foo/recursive2.c,line="4",times="0"@}
20303 -break-insert -t foo
20304 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
20305 fullname="/home/foo/recursive2.c,line="11",times="0"@}
20308 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20309 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20310 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20311 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20312 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20313 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20314 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20315 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20316 addr="0x0001072c", func="main",file="recursive2.c",
20317 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
20318 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
20319 addr="0x00010774",func="foo",file="recursive2.c",
20320 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
20322 -break-insert -r foo.*
20323 ~int foo(int, int);
20324 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
20325 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
20329 @subheading The @code{-break-list} Command
20330 @findex -break-list
20332 @subsubheading Synopsis
20338 Displays the list of inserted breakpoints, showing the following fields:
20342 number of the breakpoint
20344 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
20346 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
20349 is the breakpoint enabled or no: @samp{y} or @samp{n}
20351 memory location at which the breakpoint is set
20353 logical location of the breakpoint, expressed by function name, file
20356 number of times the breakpoint has been hit
20359 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
20360 @code{body} field is an empty list.
20362 @subsubheading @value{GDBN} Command
20364 The corresponding @value{GDBN} command is @samp{info break}.
20366 @subsubheading Example
20371 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20372 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20373 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20374 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20375 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20376 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20377 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20378 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20379 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
20380 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20381 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
20382 line="13",times="0"@}]@}
20386 Here's an example of the result when there are no breakpoints:
20391 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20392 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20393 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20394 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20395 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20396 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20397 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20402 @subheading The @code{-break-watch} Command
20403 @findex -break-watch
20405 @subsubheading Synopsis
20408 -break-watch [ -a | -r ]
20411 Create a watchpoint. With the @samp{-a} option it will create an
20412 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
20413 read from or on a write to the memory location. With the @samp{-r}
20414 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
20415 trigger only when the memory location is accessed for reading. Without
20416 either of the options, the watchpoint created is a regular watchpoint,
20417 i.e., it will trigger when the memory location is accessed for writing.
20418 @xref{Set Watchpoints, , Setting Watchpoints}.
20420 Note that @samp{-break-list} will report a single list of watchpoints and
20421 breakpoints inserted.
20423 @subsubheading @value{GDBN} Command
20425 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
20428 @subsubheading Example
20430 Setting a watchpoint on a variable in the @code{main} function:
20435 ^done,wpt=@{number="2",exp="x"@}
20440 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
20441 value=@{old="-268439212",new="55"@},
20442 frame=@{func="main",args=[],file="recursive2.c",
20443 fullname="/home/foo/bar/recursive2.c",line="5"@}
20447 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
20448 the program execution twice: first for the variable changing value, then
20449 for the watchpoint going out of scope.
20454 ^done,wpt=@{number="5",exp="C"@}
20459 *stopped,reason="watchpoint-trigger",
20460 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
20461 frame=@{func="callee4",args=[],
20462 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20463 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20468 *stopped,reason="watchpoint-scope",wpnum="5",
20469 frame=@{func="callee3",args=[@{name="strarg",
20470 value="0x11940 \"A string argument.\""@}],
20471 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20472 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20476 Listing breakpoints and watchpoints, at different points in the program
20477 execution. Note that once the watchpoint goes out of scope, it is
20483 ^done,wpt=@{number="2",exp="C"@}
20486 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20487 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20488 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20489 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20490 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20491 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20492 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20493 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20494 addr="0x00010734",func="callee4",
20495 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20496 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
20497 bkpt=@{number="2",type="watchpoint",disp="keep",
20498 enabled="y",addr="",what="C",times="0"@}]@}
20503 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
20504 value=@{old="-276895068",new="3"@},
20505 frame=@{func="callee4",args=[],
20506 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20507 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20510 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20511 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20512 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20513 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20514 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20515 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20516 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20517 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20518 addr="0x00010734",func="callee4",
20519 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20520 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
20521 bkpt=@{number="2",type="watchpoint",disp="keep",
20522 enabled="y",addr="",what="C",times="-5"@}]@}
20526 ^done,reason="watchpoint-scope",wpnum="2",
20527 frame=@{func="callee3",args=[@{name="strarg",
20528 value="0x11940 \"A string argument.\""@}],
20529 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20530 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20533 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20534 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20535 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20536 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20537 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20538 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20539 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20540 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20541 addr="0x00010734",func="callee4",
20542 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20543 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
20548 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20549 @node GDB/MI Program Context
20550 @section @sc{gdb/mi} Program Context
20552 @subheading The @code{-exec-arguments} Command
20553 @findex -exec-arguments
20556 @subsubheading Synopsis
20559 -exec-arguments @var{args}
20562 Set the inferior program arguments, to be used in the next
20565 @subsubheading @value{GDBN} Command
20567 The corresponding @value{GDBN} command is @samp{set args}.
20569 @subsubheading Example
20573 -exec-arguments -v word
20579 @subheading The @code{-exec-show-arguments} Command
20580 @findex -exec-show-arguments
20582 @subsubheading Synopsis
20585 -exec-show-arguments
20588 Print the arguments of the program.
20590 @subsubheading @value{GDBN} Command
20592 The corresponding @value{GDBN} command is @samp{show args}.
20594 @subsubheading Example
20598 @subheading The @code{-environment-cd} Command
20599 @findex -environment-cd
20601 @subsubheading Synopsis
20604 -environment-cd @var{pathdir}
20607 Set @value{GDBN}'s working directory.
20609 @subsubheading @value{GDBN} Command
20611 The corresponding @value{GDBN} command is @samp{cd}.
20613 @subsubheading Example
20617 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20623 @subheading The @code{-environment-directory} Command
20624 @findex -environment-directory
20626 @subsubheading Synopsis
20629 -environment-directory [ -r ] [ @var{pathdir} ]+
20632 Add directories @var{pathdir} to beginning of search path for source files.
20633 If the @samp{-r} option is used, the search path is reset to the default
20634 search path. If directories @var{pathdir} are supplied in addition to the
20635 @samp{-r} option, the search path is first reset and then addition
20637 Multiple directories may be specified, separated by blanks. Specifying
20638 multiple directories in a single command
20639 results in the directories added to the beginning of the
20640 search path in the same order they were presented in the command.
20641 If blanks are needed as
20642 part of a directory name, double-quotes should be used around
20643 the name. In the command output, the path will show up separated
20644 by the system directory-separator character. The directory-separator
20645 character must not be used
20646 in any directory name.
20647 If no directories are specified, the current search path is displayed.
20649 @subsubheading @value{GDBN} Command
20651 The corresponding @value{GDBN} command is @samp{dir}.
20653 @subsubheading Example
20657 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20658 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
20660 -environment-directory ""
20661 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
20663 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
20664 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
20666 -environment-directory -r
20667 ^done,source-path="$cdir:$cwd"
20672 @subheading The @code{-environment-path} Command
20673 @findex -environment-path
20675 @subsubheading Synopsis
20678 -environment-path [ -r ] [ @var{pathdir} ]+
20681 Add directories @var{pathdir} to beginning of search path for object files.
20682 If the @samp{-r} option is used, the search path is reset to the original
20683 search path that existed at gdb start-up. If directories @var{pathdir} are
20684 supplied in addition to the
20685 @samp{-r} option, the search path is first reset and then addition
20687 Multiple directories may be specified, separated by blanks. Specifying
20688 multiple directories in a single command
20689 results in the directories added to the beginning of the
20690 search path in the same order they were presented in the command.
20691 If blanks are needed as
20692 part of a directory name, double-quotes should be used around
20693 the name. In the command output, the path will show up separated
20694 by the system directory-separator character. The directory-separator
20695 character must not be used
20696 in any directory name.
20697 If no directories are specified, the current path is displayed.
20700 @subsubheading @value{GDBN} Command
20702 The corresponding @value{GDBN} command is @samp{path}.
20704 @subsubheading Example
20709 ^done,path="/usr/bin"
20711 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
20712 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
20714 -environment-path -r /usr/local/bin
20715 ^done,path="/usr/local/bin:/usr/bin"
20720 @subheading The @code{-environment-pwd} Command
20721 @findex -environment-pwd
20723 @subsubheading Synopsis
20729 Show the current working directory.
20731 @subsubheading @value{GDBN} Command
20733 The corresponding @value{GDBN} command is @samp{pwd}.
20735 @subsubheading Example
20740 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
20744 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20745 @node GDB/MI Thread Commands
20746 @section @sc{gdb/mi} Thread Commands
20749 @subheading The @code{-thread-info} Command
20750 @findex -thread-info
20752 @subsubheading Synopsis
20755 -thread-info [ @var{thread-id} ]
20758 Reports information about either a specific thread, if
20759 the @var{thread-id} parameter is present, or about all
20760 threads. When printing information about all threads,
20761 also reports the current thread.
20763 @subsubheading @value{GDBN} Command
20765 The @samp{info thread} command prints the same information
20768 @subsubheading Example
20773 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
20774 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
20775 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
20776 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
20777 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
20778 current-thread-id="1"
20782 The @samp{state} field may have the following values:
20786 The thread is stopped. Frame information is available for stopped
20790 The thread is running. There's no frame information for running
20795 @subheading The @code{-thread-list-ids} Command
20796 @findex -thread-list-ids
20798 @subsubheading Synopsis
20804 Produces a list of the currently known @value{GDBN} thread ids. At the
20805 end of the list it also prints the total number of such threads.
20807 This command is retained for historical reasons, the
20808 @code{-thread-info} command should be used instead.
20810 @subsubheading @value{GDBN} Command
20812 Part of @samp{info threads} supplies the same information.
20814 @subsubheading Example
20819 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20820 current-thread-id="1",number-of-threads="3"
20825 @subheading The @code{-thread-select} Command
20826 @findex -thread-select
20828 @subsubheading Synopsis
20831 -thread-select @var{threadnum}
20834 Make @var{threadnum} the current thread. It prints the number of the new
20835 current thread, and the topmost frame for that thread.
20837 This command is deprecated in favor of explicitly using the
20838 @samp{--thread} option to each command.
20840 @subsubheading @value{GDBN} Command
20842 The corresponding @value{GDBN} command is @samp{thread}.
20844 @subsubheading Example
20851 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20852 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20856 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20857 number-of-threads="3"
20860 ^done,new-thread-id="3",
20861 frame=@{level="0",func="vprintf",
20862 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20863 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20867 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20868 @node GDB/MI Program Execution
20869 @section @sc{gdb/mi} Program Execution
20871 These are the asynchronous commands which generate the out-of-band
20872 record @samp{*stopped}. Currently @value{GDBN} only really executes
20873 asynchronously with remote targets and this interaction is mimicked in
20876 @subheading The @code{-exec-continue} Command
20877 @findex -exec-continue
20879 @subsubheading Synopsis
20882 -exec-continue [--all|--thread-group N]
20885 Resumes the execution of the inferior program until a breakpoint is
20886 encountered, or until the inferior exits. In all-stop mode
20887 (@pxref{All-Stop Mode}), may resume only one thread, or all threads,
20888 depending on the value of the @samp{scheduler-locking} variable. In
20889 non-stop mode (@pxref{Non-Stop Mode}), if the @samp{--all} is not
20890 specified, only the thread specified with the @samp{--thread} option
20891 (or current thread, if no @samp{--thread} is provided) is resumed. If
20892 @samp{--all} is specified, all threads will be resumed. The
20893 @samp{--all} option is ignored in all-stop mode. If the
20894 @samp{--thread-group} options is specified, then all threads in that
20895 thread group are resumed.
20897 @subsubheading @value{GDBN} Command
20899 The corresponding @value{GDBN} corresponding is @samp{continue}.
20901 @subsubheading Example
20908 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
20909 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
20915 @subheading The @code{-exec-finish} Command
20916 @findex -exec-finish
20918 @subsubheading Synopsis
20924 Resumes the execution of the inferior program until the current
20925 function is exited. Displays the results returned by the function.
20927 @subsubheading @value{GDBN} Command
20929 The corresponding @value{GDBN} command is @samp{finish}.
20931 @subsubheading Example
20933 Function returning @code{void}.
20940 *stopped,reason="function-finished",frame=@{func="main",args=[],
20941 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
20945 Function returning other than @code{void}. The name of the internal
20946 @value{GDBN} variable storing the result is printed, together with the
20953 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
20954 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
20955 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20956 gdb-result-var="$1",return-value="0"
20961 @subheading The @code{-exec-interrupt} Command
20962 @findex -exec-interrupt
20964 @subsubheading Synopsis
20967 -exec-interrupt [--all|--thread-group N]
20970 Interrupts the background execution of the target. Note how the token
20971 associated with the stop message is the one for the execution command
20972 that has been interrupted. The token for the interrupt itself only
20973 appears in the @samp{^done} output. If the user is trying to
20974 interrupt a non-running program, an error message will be printed.
20976 Note that when asynchronous execution is enabled, this command is
20977 asynchronous just like other execution commands. That is, first the
20978 @samp{^done} response will be printed, and the target stop will be
20979 reported after that using the @samp{*stopped} notification.
20981 In non-stop mode, only the context thread is interrupted by default.
20982 All threads will be interrupted if the @samp{--all} option is
20983 specified. If the @samp{--thread-group} option is specified, all
20984 threads in that group will be interrupted.
20986 @subsubheading @value{GDBN} Command
20988 The corresponding @value{GDBN} command is @samp{interrupt}.
20990 @subsubheading Example
21001 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
21002 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
21003 fullname="/home/foo/bar/try.c",line="13"@}
21008 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
21013 @subheading The @code{-exec-next} Command
21016 @subsubheading Synopsis
21022 Resumes execution of the inferior program, stopping when the beginning
21023 of the next source line is reached.
21025 @subsubheading @value{GDBN} Command
21027 The corresponding @value{GDBN} command is @samp{next}.
21029 @subsubheading Example
21035 *stopped,reason="end-stepping-range",line="8",file="hello.c"
21040 @subheading The @code{-exec-next-instruction} Command
21041 @findex -exec-next-instruction
21043 @subsubheading Synopsis
21046 -exec-next-instruction
21049 Executes one machine instruction. If the instruction is a function
21050 call, continues until the function returns. If the program stops at an
21051 instruction in the middle of a source line, the address will be
21054 @subsubheading @value{GDBN} Command
21056 The corresponding @value{GDBN} command is @samp{nexti}.
21058 @subsubheading Example
21062 -exec-next-instruction
21066 *stopped,reason="end-stepping-range",
21067 addr="0x000100d4",line="5",file="hello.c"
21072 @subheading The @code{-exec-return} Command
21073 @findex -exec-return
21075 @subsubheading Synopsis
21081 Makes current function return immediately. Doesn't execute the inferior.
21082 Displays the new current frame.
21084 @subsubheading @value{GDBN} Command
21086 The corresponding @value{GDBN} command is @samp{return}.
21088 @subsubheading Example
21092 200-break-insert callee4
21093 200^done,bkpt=@{number="1",addr="0x00010734",
21094 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21099 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21100 frame=@{func="callee4",args=[],
21101 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21102 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21108 111^done,frame=@{level="0",func="callee3",
21109 args=[@{name="strarg",
21110 value="0x11940 \"A string argument.\""@}],
21111 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21112 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
21117 @subheading The @code{-exec-run} Command
21120 @subsubheading Synopsis
21126 Starts execution of the inferior from the beginning. The inferior
21127 executes until either a breakpoint is encountered or the program
21128 exits. In the latter case the output will include an exit code, if
21129 the program has exited exceptionally.
21131 @subsubheading @value{GDBN} Command
21133 The corresponding @value{GDBN} command is @samp{run}.
21135 @subsubheading Examples
21140 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
21145 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21146 frame=@{func="main",args=[],file="recursive2.c",
21147 fullname="/home/foo/bar/recursive2.c",line="4"@}
21152 Program exited normally:
21160 *stopped,reason="exited-normally"
21165 Program exited exceptionally:
21173 *stopped,reason="exited",exit-code="01"
21177 Another way the program can terminate is if it receives a signal such as
21178 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
21182 *stopped,reason="exited-signalled",signal-name="SIGINT",
21183 signal-meaning="Interrupt"
21187 @c @subheading -exec-signal
21190 @subheading The @code{-exec-step} Command
21193 @subsubheading Synopsis
21199 Resumes execution of the inferior program, stopping when the beginning
21200 of the next source line is reached, if the next source line is not a
21201 function call. If it is, stop at the first instruction of the called
21204 @subsubheading @value{GDBN} Command
21206 The corresponding @value{GDBN} command is @samp{step}.
21208 @subsubheading Example
21210 Stepping into a function:
21216 *stopped,reason="end-stepping-range",
21217 frame=@{func="foo",args=[@{name="a",value="10"@},
21218 @{name="b",value="0"@}],file="recursive2.c",
21219 fullname="/home/foo/bar/recursive2.c",line="11"@}
21229 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
21234 @subheading The @code{-exec-step-instruction} Command
21235 @findex -exec-step-instruction
21237 @subsubheading Synopsis
21240 -exec-step-instruction
21243 Resumes the inferior which executes one machine instruction. The
21244 output, once @value{GDBN} has stopped, will vary depending on whether
21245 we have stopped in the middle of a source line or not. In the former
21246 case, the address at which the program stopped will be printed as
21249 @subsubheading @value{GDBN} Command
21251 The corresponding @value{GDBN} command is @samp{stepi}.
21253 @subsubheading Example
21257 -exec-step-instruction
21261 *stopped,reason="end-stepping-range",
21262 frame=@{func="foo",args=[],file="try.c",
21263 fullname="/home/foo/bar/try.c",line="10"@}
21265 -exec-step-instruction
21269 *stopped,reason="end-stepping-range",
21270 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
21271 fullname="/home/foo/bar/try.c",line="10"@}
21276 @subheading The @code{-exec-until} Command
21277 @findex -exec-until
21279 @subsubheading Synopsis
21282 -exec-until [ @var{location} ]
21285 Executes the inferior until the @var{location} specified in the
21286 argument is reached. If there is no argument, the inferior executes
21287 until a source line greater than the current one is reached. The
21288 reason for stopping in this case will be @samp{location-reached}.
21290 @subsubheading @value{GDBN} Command
21292 The corresponding @value{GDBN} command is @samp{until}.
21294 @subsubheading Example
21298 -exec-until recursive2.c:6
21302 *stopped,reason="location-reached",frame=@{func="main",args=[],
21303 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
21308 @subheading -file-clear
21309 Is this going away????
21312 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21313 @node GDB/MI Stack Manipulation
21314 @section @sc{gdb/mi} Stack Manipulation Commands
21317 @subheading The @code{-stack-info-frame} Command
21318 @findex -stack-info-frame
21320 @subsubheading Synopsis
21326 Get info on the selected frame.
21328 @subsubheading @value{GDBN} Command
21330 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
21331 (without arguments).
21333 @subsubheading Example
21338 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
21339 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21340 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
21344 @subheading The @code{-stack-info-depth} Command
21345 @findex -stack-info-depth
21347 @subsubheading Synopsis
21350 -stack-info-depth [ @var{max-depth} ]
21353 Return the depth of the stack. If the integer argument @var{max-depth}
21354 is specified, do not count beyond @var{max-depth} frames.
21356 @subsubheading @value{GDBN} Command
21358 There's no equivalent @value{GDBN} command.
21360 @subsubheading Example
21362 For a stack with frame levels 0 through 11:
21369 -stack-info-depth 4
21372 -stack-info-depth 12
21375 -stack-info-depth 11
21378 -stack-info-depth 13
21383 @subheading The @code{-stack-list-arguments} Command
21384 @findex -stack-list-arguments
21386 @subsubheading Synopsis
21389 -stack-list-arguments @var{show-values}
21390 [ @var{low-frame} @var{high-frame} ]
21393 Display a list of the arguments for the frames between @var{low-frame}
21394 and @var{high-frame} (inclusive). If @var{low-frame} and
21395 @var{high-frame} are not provided, list the arguments for the whole
21396 call stack. If the two arguments are equal, show the single frame
21397 at the corresponding level. It is an error if @var{low-frame} is
21398 larger than the actual number of frames. On the other hand,
21399 @var{high-frame} may be larger than the actual number of frames, in
21400 which case only existing frames will be returned.
21402 The @var{show-values} argument must have a value of 0 or 1. A value of
21403 0 means that only the names of the arguments are listed, a value of 1
21404 means that both names and values of the arguments are printed.
21406 @subsubheading @value{GDBN} Command
21408 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
21409 @samp{gdb_get_args} command which partially overlaps with the
21410 functionality of @samp{-stack-list-arguments}.
21412 @subsubheading Example
21419 frame=@{level="0",addr="0x00010734",func="callee4",
21420 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21421 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
21422 frame=@{level="1",addr="0x0001076c",func="callee3",
21423 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21424 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
21425 frame=@{level="2",addr="0x0001078c",func="callee2",
21426 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21427 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
21428 frame=@{level="3",addr="0x000107b4",func="callee1",
21429 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21430 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
21431 frame=@{level="4",addr="0x000107e0",func="main",
21432 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21433 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
21435 -stack-list-arguments 0
21438 frame=@{level="0",args=[]@},
21439 frame=@{level="1",args=[name="strarg"]@},
21440 frame=@{level="2",args=[name="intarg",name="strarg"]@},
21441 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
21442 frame=@{level="4",args=[]@}]
21444 -stack-list-arguments 1
21447 frame=@{level="0",args=[]@},
21449 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21450 frame=@{level="2",args=[
21451 @{name="intarg",value="2"@},
21452 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21453 @{frame=@{level="3",args=[
21454 @{name="intarg",value="2"@},
21455 @{name="strarg",value="0x11940 \"A string argument.\""@},
21456 @{name="fltarg",value="3.5"@}]@},
21457 frame=@{level="4",args=[]@}]
21459 -stack-list-arguments 0 2 2
21460 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
21462 -stack-list-arguments 1 2 2
21463 ^done,stack-args=[frame=@{level="2",
21464 args=[@{name="intarg",value="2"@},
21465 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
21469 @c @subheading -stack-list-exception-handlers
21472 @subheading The @code{-stack-list-frames} Command
21473 @findex -stack-list-frames
21475 @subsubheading Synopsis
21478 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
21481 List the frames currently on the stack. For each frame it displays the
21486 The frame number, 0 being the topmost frame, i.e., the innermost function.
21488 The @code{$pc} value for that frame.
21492 File name of the source file where the function lives.
21494 Line number corresponding to the @code{$pc}.
21497 If invoked without arguments, this command prints a backtrace for the
21498 whole stack. If given two integer arguments, it shows the frames whose
21499 levels are between the two arguments (inclusive). If the two arguments
21500 are equal, it shows the single frame at the corresponding level. It is
21501 an error if @var{low-frame} is larger than the actual number of
21502 frames. On the other hand, @var{high-frame} may be larger than the
21503 actual number of frames, in which case only existing frames will be returned.
21505 @subsubheading @value{GDBN} Command
21507 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
21509 @subsubheading Example
21511 Full stack backtrace:
21517 [frame=@{level="0",addr="0x0001076c",func="foo",
21518 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
21519 frame=@{level="1",addr="0x000107a4",func="foo",
21520 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21521 frame=@{level="2",addr="0x000107a4",func="foo",
21522 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21523 frame=@{level="3",addr="0x000107a4",func="foo",
21524 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21525 frame=@{level="4",addr="0x000107a4",func="foo",
21526 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21527 frame=@{level="5",addr="0x000107a4",func="foo",
21528 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21529 frame=@{level="6",addr="0x000107a4",func="foo",
21530 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21531 frame=@{level="7",addr="0x000107a4",func="foo",
21532 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21533 frame=@{level="8",addr="0x000107a4",func="foo",
21534 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21535 frame=@{level="9",addr="0x000107a4",func="foo",
21536 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21537 frame=@{level="10",addr="0x000107a4",func="foo",
21538 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21539 frame=@{level="11",addr="0x00010738",func="main",
21540 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
21544 Show frames between @var{low_frame} and @var{high_frame}:
21548 -stack-list-frames 3 5
21550 [frame=@{level="3",addr="0x000107a4",func="foo",
21551 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21552 frame=@{level="4",addr="0x000107a4",func="foo",
21553 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21554 frame=@{level="5",addr="0x000107a4",func="foo",
21555 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21559 Show a single frame:
21563 -stack-list-frames 3 3
21565 [frame=@{level="3",addr="0x000107a4",func="foo",
21566 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21571 @subheading The @code{-stack-list-locals} Command
21572 @findex -stack-list-locals
21574 @subsubheading Synopsis
21577 -stack-list-locals @var{print-values}
21580 Display the local variable names for the selected frame. If
21581 @var{print-values} is 0 or @code{--no-values}, print only the names of
21582 the variables; if it is 1 or @code{--all-values}, print also their
21583 values; and if it is 2 or @code{--simple-values}, print the name,
21584 type and value for simple data types and the name and type for arrays,
21585 structures and unions. In this last case, a frontend can immediately
21586 display the value of simple data types and create variable objects for
21587 other data types when the user wishes to explore their values in
21590 @subsubheading @value{GDBN} Command
21592 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
21594 @subsubheading Example
21598 -stack-list-locals 0
21599 ^done,locals=[name="A",name="B",name="C"]
21601 -stack-list-locals --all-values
21602 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
21603 @{name="C",value="@{1, 2, 3@}"@}]
21604 -stack-list-locals --simple-values
21605 ^done,locals=[@{name="A",type="int",value="1"@},
21606 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
21611 @subheading The @code{-stack-select-frame} Command
21612 @findex -stack-select-frame
21614 @subsubheading Synopsis
21617 -stack-select-frame @var{framenum}
21620 Change the selected frame. Select a different frame @var{framenum} on
21623 This command in deprecated in favor of passing the @samp{--frame}
21624 option to every command.
21626 @subsubheading @value{GDBN} Command
21628 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
21629 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
21631 @subsubheading Example
21635 -stack-select-frame 2
21640 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21641 @node GDB/MI Variable Objects
21642 @section @sc{gdb/mi} Variable Objects
21646 @subheading Motivation for Variable Objects in @sc{gdb/mi}
21648 For the implementation of a variable debugger window (locals, watched
21649 expressions, etc.), we are proposing the adaptation of the existing code
21650 used by @code{Insight}.
21652 The two main reasons for that are:
21656 It has been proven in practice (it is already on its second generation).
21659 It will shorten development time (needless to say how important it is
21663 The original interface was designed to be used by Tcl code, so it was
21664 slightly changed so it could be used through @sc{gdb/mi}. This section
21665 describes the @sc{gdb/mi} operations that will be available and gives some
21666 hints about their use.
21668 @emph{Note}: In addition to the set of operations described here, we
21669 expect the @sc{gui} implementation of a variable window to require, at
21670 least, the following operations:
21673 @item @code{-gdb-show} @code{output-radix}
21674 @item @code{-stack-list-arguments}
21675 @item @code{-stack-list-locals}
21676 @item @code{-stack-select-frame}
21681 @subheading Introduction to Variable Objects
21683 @cindex variable objects in @sc{gdb/mi}
21685 Variable objects are "object-oriented" MI interface for examining and
21686 changing values of expressions. Unlike some other MI interfaces that
21687 work with expressions, variable objects are specifically designed for
21688 simple and efficient presentation in the frontend. A variable object
21689 is identified by string name. When a variable object is created, the
21690 frontend specifies the expression for that variable object. The
21691 expression can be a simple variable, or it can be an arbitrary complex
21692 expression, and can even involve CPU registers. After creating a
21693 variable object, the frontend can invoke other variable object
21694 operations---for example to obtain or change the value of a variable
21695 object, or to change display format.
21697 Variable objects have hierarchical tree structure. Any variable object
21698 that corresponds to a composite type, such as structure in C, has
21699 a number of child variable objects, for example corresponding to each
21700 element of a structure. A child variable object can itself have
21701 children, recursively. Recursion ends when we reach
21702 leaf variable objects, which always have built-in types. Child variable
21703 objects are created only by explicit request, so if a frontend
21704 is not interested in the children of a particular variable object, no
21705 child will be created.
21707 For a leaf variable object it is possible to obtain its value as a
21708 string, or set the value from a string. String value can be also
21709 obtained for a non-leaf variable object, but it's generally a string
21710 that only indicates the type of the object, and does not list its
21711 contents. Assignment to a non-leaf variable object is not allowed.
21713 A frontend does not need to read the values of all variable objects each time
21714 the program stops. Instead, MI provides an update command that lists all
21715 variable objects whose values has changed since the last update
21716 operation. This considerably reduces the amount of data that must
21717 be transferred to the frontend. As noted above, children variable
21718 objects are created on demand, and only leaf variable objects have a
21719 real value. As result, gdb will read target memory only for leaf
21720 variables that frontend has created.
21722 The automatic update is not always desirable. For example, a frontend
21723 might want to keep a value of some expression for future reference,
21724 and never update it. For another example, fetching memory is
21725 relatively slow for embedded targets, so a frontend might want
21726 to disable automatic update for the variables that are either not
21727 visible on the screen, or ``closed''. This is possible using so
21728 called ``frozen variable objects''. Such variable objects are never
21729 implicitly updated.
21731 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
21732 fixed variable object, the expression is parsed when the variable
21733 object is created, including associating identifiers to specific
21734 variables. The meaning of expression never changes. For a floating
21735 variable object the values of variables whose names appear in the
21736 expressions are re-evaluated every time in the context of the current
21737 frame. Consider this example:
21742 struct work_state state;
21749 If a fixed variable object for the @code{state} variable is created in
21750 this function, and we enter the recursive call, the the variable
21751 object will report the value of @code{state} in the top-level
21752 @code{do_work} invocation. On the other hand, a floating variable
21753 object will report the value of @code{state} in the current frame.
21755 If an expression specified when creating a fixed variable object
21756 refers to a local variable, the variable object becomes bound to the
21757 thread and frame in which the variable object is created. When such
21758 variable object is updated, @value{GDBN} makes sure that the
21759 thread/frame combination the variable object is bound to still exists,
21760 and re-evaluates the variable object in context of that thread/frame.
21762 The following is the complete set of @sc{gdb/mi} operations defined to
21763 access this functionality:
21765 @multitable @columnfractions .4 .6
21766 @item @strong{Operation}
21767 @tab @strong{Description}
21769 @item @code{-var-create}
21770 @tab create a variable object
21771 @item @code{-var-delete}
21772 @tab delete the variable object and/or its children
21773 @item @code{-var-set-format}
21774 @tab set the display format of this variable
21775 @item @code{-var-show-format}
21776 @tab show the display format of this variable
21777 @item @code{-var-info-num-children}
21778 @tab tells how many children this object has
21779 @item @code{-var-list-children}
21780 @tab return a list of the object's children
21781 @item @code{-var-info-type}
21782 @tab show the type of this variable object
21783 @item @code{-var-info-expression}
21784 @tab print parent-relative expression that this variable object represents
21785 @item @code{-var-info-path-expression}
21786 @tab print full expression that this variable object represents
21787 @item @code{-var-show-attributes}
21788 @tab is this variable editable? does it exist here?
21789 @item @code{-var-evaluate-expression}
21790 @tab get the value of this variable
21791 @item @code{-var-assign}
21792 @tab set the value of this variable
21793 @item @code{-var-update}
21794 @tab update the variable and its children
21795 @item @code{-var-set-frozen}
21796 @tab set frozeness attribute
21799 In the next subsection we describe each operation in detail and suggest
21800 how it can be used.
21802 @subheading Description And Use of Operations on Variable Objects
21804 @subheading The @code{-var-create} Command
21805 @findex -var-create
21807 @subsubheading Synopsis
21810 -var-create @{@var{name} | "-"@}
21811 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
21814 This operation creates a variable object, which allows the monitoring of
21815 a variable, the result of an expression, a memory cell or a CPU
21818 The @var{name} parameter is the string by which the object can be
21819 referenced. It must be unique. If @samp{-} is specified, the varobj
21820 system will generate a string ``varNNNNNN'' automatically. It will be
21821 unique provided that one does not specify @var{name} of that format.
21822 The command fails if a duplicate name is found.
21824 The frame under which the expression should be evaluated can be
21825 specified by @var{frame-addr}. A @samp{*} indicates that the current
21826 frame should be used. A @samp{@@} indicates that a floating variable
21827 object must be created.
21829 @var{expression} is any expression valid on the current language set (must not
21830 begin with a @samp{*}), or one of the following:
21834 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
21837 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
21840 @samp{$@var{regname}} --- a CPU register name
21843 @subsubheading Result
21845 This operation returns the name, number of children and the type of the
21846 object created. Type is returned as a string as the ones generated by
21847 the @value{GDBN} CLI. If a fixed variable object is bound to a
21848 specific thread, the thread is is also printed:
21851 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}"
21855 @subheading The @code{-var-delete} Command
21856 @findex -var-delete
21858 @subsubheading Synopsis
21861 -var-delete [ -c ] @var{name}
21864 Deletes a previously created variable object and all of its children.
21865 With the @samp{-c} option, just deletes the children.
21867 Returns an error if the object @var{name} is not found.
21870 @subheading The @code{-var-set-format} Command
21871 @findex -var-set-format
21873 @subsubheading Synopsis
21876 -var-set-format @var{name} @var{format-spec}
21879 Sets the output format for the value of the object @var{name} to be
21882 @anchor{-var-set-format}
21883 The syntax for the @var{format-spec} is as follows:
21886 @var{format-spec} @expansion{}
21887 @{binary | decimal | hexadecimal | octal | natural@}
21890 The natural format is the default format choosen automatically
21891 based on the variable type (like decimal for an @code{int}, hex
21892 for pointers, etc.).
21894 For a variable with children, the format is set only on the
21895 variable itself, and the children are not affected.
21897 @subheading The @code{-var-show-format} Command
21898 @findex -var-show-format
21900 @subsubheading Synopsis
21903 -var-show-format @var{name}
21906 Returns the format used to display the value of the object @var{name}.
21909 @var{format} @expansion{}
21914 @subheading The @code{-var-info-num-children} Command
21915 @findex -var-info-num-children
21917 @subsubheading Synopsis
21920 -var-info-num-children @var{name}
21923 Returns the number of children of a variable object @var{name}:
21930 @subheading The @code{-var-list-children} Command
21931 @findex -var-list-children
21933 @subsubheading Synopsis
21936 -var-list-children [@var{print-values}] @var{name}
21938 @anchor{-var-list-children}
21940 Return a list of the children of the specified variable object and
21941 create variable objects for them, if they do not already exist. With
21942 a single argument or if @var{print-values} has a value for of 0 or
21943 @code{--no-values}, print only the names of the variables; if
21944 @var{print-values} is 1 or @code{--all-values}, also print their
21945 values; and if it is 2 or @code{--simple-values} print the name and
21946 value for simple data types and just the name for arrays, structures
21949 @subsubheading Example
21953 -var-list-children n
21954 ^done,numchild=@var{n},children=[@{name=@var{name},
21955 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
21957 -var-list-children --all-values n
21958 ^done,numchild=@var{n},children=[@{name=@var{name},
21959 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
21963 @subheading The @code{-var-info-type} Command
21964 @findex -var-info-type
21966 @subsubheading Synopsis
21969 -var-info-type @var{name}
21972 Returns the type of the specified variable @var{name}. The type is
21973 returned as a string in the same format as it is output by the
21977 type=@var{typename}
21981 @subheading The @code{-var-info-expression} Command
21982 @findex -var-info-expression
21984 @subsubheading Synopsis
21987 -var-info-expression @var{name}
21990 Returns a string that is suitable for presenting this
21991 variable object in user interface. The string is generally
21992 not valid expression in the current language, and cannot be evaluated.
21994 For example, if @code{a} is an array, and variable object
21995 @code{A} was created for @code{a}, then we'll get this output:
21998 (gdb) -var-info-expression A.1
21999 ^done,lang="C",exp="1"
22003 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
22005 Note that the output of the @code{-var-list-children} command also
22006 includes those expressions, so the @code{-var-info-expression} command
22009 @subheading The @code{-var-info-path-expression} Command
22010 @findex -var-info-path-expression
22012 @subsubheading Synopsis
22015 -var-info-path-expression @var{name}
22018 Returns an expression that can be evaluated in the current
22019 context and will yield the same value that a variable object has.
22020 Compare this with the @code{-var-info-expression} command, which
22021 result can be used only for UI presentation. Typical use of
22022 the @code{-var-info-path-expression} command is creating a
22023 watchpoint from a variable object.
22025 For example, suppose @code{C} is a C@t{++} class, derived from class
22026 @code{Base}, and that the @code{Base} class has a member called
22027 @code{m_size}. Assume a variable @code{c} is has the type of
22028 @code{C} and a variable object @code{C} was created for variable
22029 @code{c}. Then, we'll get this output:
22031 (gdb) -var-info-path-expression C.Base.public.m_size
22032 ^done,path_expr=((Base)c).m_size)
22035 @subheading The @code{-var-show-attributes} Command
22036 @findex -var-show-attributes
22038 @subsubheading Synopsis
22041 -var-show-attributes @var{name}
22044 List attributes of the specified variable object @var{name}:
22047 status=@var{attr} [ ( ,@var{attr} )* ]
22051 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
22053 @subheading The @code{-var-evaluate-expression} Command
22054 @findex -var-evaluate-expression
22056 @subsubheading Synopsis
22059 -var-evaluate-expression [-f @var{format-spec}] @var{name}
22062 Evaluates the expression that is represented by the specified variable
22063 object and returns its value as a string. The format of the string
22064 can be specified with the @samp{-f} option. The possible values of
22065 this option are the same as for @code{-var-set-format}
22066 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
22067 the current display format will be used. The current display format
22068 can be changed using the @code{-var-set-format} command.
22074 Note that one must invoke @code{-var-list-children} for a variable
22075 before the value of a child variable can be evaluated.
22077 @subheading The @code{-var-assign} Command
22078 @findex -var-assign
22080 @subsubheading Synopsis
22083 -var-assign @var{name} @var{expression}
22086 Assigns the value of @var{expression} to the variable object specified
22087 by @var{name}. The object must be @samp{editable}. If the variable's
22088 value is altered by the assign, the variable will show up in any
22089 subsequent @code{-var-update} list.
22091 @subsubheading Example
22099 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
22103 @subheading The @code{-var-update} Command
22104 @findex -var-update
22106 @subsubheading Synopsis
22109 -var-update [@var{print-values}] @{@var{name} | "*"@}
22112 Reevaluate the expressions corresponding to the variable object
22113 @var{name} and all its direct and indirect children, and return the
22114 list of variable objects whose values have changed; @var{name} must
22115 be a root variable object. Here, ``changed'' means that the result of
22116 @code{-var-evaluate-expression} before and after the
22117 @code{-var-update} is different. If @samp{*} is used as the variable
22118 object names, all existing variable objects are updated, except
22119 for frozen ones (@pxref{-var-set-frozen}). The option
22120 @var{print-values} determines whether both names and values, or just
22121 names are printed. The possible values of this option are the same
22122 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
22123 recommended to use the @samp{--all-values} option, to reduce the
22124 number of MI commands needed on each program stop.
22126 With the @samp{*} parameter, if a variable object is bound to a
22127 currently running thread, it will not be updated, without any
22130 @subsubheading Example
22137 -var-update --all-values var1
22138 ^done,changelist=[@{name="var1",value="3",in_scope="true",
22139 type_changed="false"@}]
22143 @anchor{-var-update}
22144 The field in_scope may take three values:
22148 The variable object's current value is valid.
22151 The variable object does not currently hold a valid value but it may
22152 hold one in the future if its associated expression comes back into
22156 The variable object no longer holds a valid value.
22157 This can occur when the executable file being debugged has changed,
22158 either through recompilation or by using the @value{GDBN} @code{file}
22159 command. The front end should normally choose to delete these variable
22163 In the future new values may be added to this list so the front should
22164 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
22166 @subheading The @code{-var-set-frozen} Command
22167 @findex -var-set-frozen
22168 @anchor{-var-set-frozen}
22170 @subsubheading Synopsis
22173 -var-set-frozen @var{name} @var{flag}
22176 Set the frozenness flag on the variable object @var{name}. The
22177 @var{flag} parameter should be either @samp{1} to make the variable
22178 frozen or @samp{0} to make it unfrozen. If a variable object is
22179 frozen, then neither itself, nor any of its children, are
22180 implicitly updated by @code{-var-update} of
22181 a parent variable or by @code{-var-update *}. Only
22182 @code{-var-update} of the variable itself will update its value and
22183 values of its children. After a variable object is unfrozen, it is
22184 implicitly updated by all subsequent @code{-var-update} operations.
22185 Unfreezing a variable does not update it, only subsequent
22186 @code{-var-update} does.
22188 @subsubheading Example
22192 -var-set-frozen V 1
22198 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22199 @node GDB/MI Data Manipulation
22200 @section @sc{gdb/mi} Data Manipulation
22202 @cindex data manipulation, in @sc{gdb/mi}
22203 @cindex @sc{gdb/mi}, data manipulation
22204 This section describes the @sc{gdb/mi} commands that manipulate data:
22205 examine memory and registers, evaluate expressions, etc.
22207 @c REMOVED FROM THE INTERFACE.
22208 @c @subheading -data-assign
22209 @c Change the value of a program variable. Plenty of side effects.
22210 @c @subsubheading GDB Command
22212 @c @subsubheading Example
22215 @subheading The @code{-data-disassemble} Command
22216 @findex -data-disassemble
22218 @subsubheading Synopsis
22222 [ -s @var{start-addr} -e @var{end-addr} ]
22223 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
22231 @item @var{start-addr}
22232 is the beginning address (or @code{$pc})
22233 @item @var{end-addr}
22235 @item @var{filename}
22236 is the name of the file to disassemble
22237 @item @var{linenum}
22238 is the line number to disassemble around
22240 is the number of disassembly lines to be produced. If it is -1,
22241 the whole function will be disassembled, in case no @var{end-addr} is
22242 specified. If @var{end-addr} is specified as a non-zero value, and
22243 @var{lines} is lower than the number of disassembly lines between
22244 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
22245 displayed; if @var{lines} is higher than the number of lines between
22246 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
22249 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
22253 @subsubheading Result
22255 The output for each instruction is composed of four fields:
22264 Note that whatever included in the instruction field, is not manipulated
22265 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
22267 @subsubheading @value{GDBN} Command
22269 There's no direct mapping from this command to the CLI.
22271 @subsubheading Example
22273 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
22277 -data-disassemble -s $pc -e "$pc + 20" -- 0
22280 @{address="0x000107c0",func-name="main",offset="4",
22281 inst="mov 2, %o0"@},
22282 @{address="0x000107c4",func-name="main",offset="8",
22283 inst="sethi %hi(0x11800), %o2"@},
22284 @{address="0x000107c8",func-name="main",offset="12",
22285 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
22286 @{address="0x000107cc",func-name="main",offset="16",
22287 inst="sethi %hi(0x11800), %o2"@},
22288 @{address="0x000107d0",func-name="main",offset="20",
22289 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
22293 Disassemble the whole @code{main} function. Line 32 is part of
22297 -data-disassemble -f basics.c -l 32 -- 0
22299 @{address="0x000107bc",func-name="main",offset="0",
22300 inst="save %sp, -112, %sp"@},
22301 @{address="0x000107c0",func-name="main",offset="4",
22302 inst="mov 2, %o0"@},
22303 @{address="0x000107c4",func-name="main",offset="8",
22304 inst="sethi %hi(0x11800), %o2"@},
22306 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
22307 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
22311 Disassemble 3 instructions from the start of @code{main}:
22315 -data-disassemble -f basics.c -l 32 -n 3 -- 0
22317 @{address="0x000107bc",func-name="main",offset="0",
22318 inst="save %sp, -112, %sp"@},
22319 @{address="0x000107c0",func-name="main",offset="4",
22320 inst="mov 2, %o0"@},
22321 @{address="0x000107c4",func-name="main",offset="8",
22322 inst="sethi %hi(0x11800), %o2"@}]
22326 Disassemble 3 instructions from the start of @code{main} in mixed mode:
22330 -data-disassemble -f basics.c -l 32 -n 3 -- 1
22332 src_and_asm_line=@{line="31",
22333 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22334 testsuite/gdb.mi/basics.c",line_asm_insn=[
22335 @{address="0x000107bc",func-name="main",offset="0",
22336 inst="save %sp, -112, %sp"@}]@},
22337 src_and_asm_line=@{line="32",
22338 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22339 testsuite/gdb.mi/basics.c",line_asm_insn=[
22340 @{address="0x000107c0",func-name="main",offset="4",
22341 inst="mov 2, %o0"@},
22342 @{address="0x000107c4",func-name="main",offset="8",
22343 inst="sethi %hi(0x11800), %o2"@}]@}]
22348 @subheading The @code{-data-evaluate-expression} Command
22349 @findex -data-evaluate-expression
22351 @subsubheading Synopsis
22354 -data-evaluate-expression @var{expr}
22357 Evaluate @var{expr} as an expression. The expression could contain an
22358 inferior function call. The function call will execute synchronously.
22359 If the expression contains spaces, it must be enclosed in double quotes.
22361 @subsubheading @value{GDBN} Command
22363 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
22364 @samp{call}. In @code{gdbtk} only, there's a corresponding
22365 @samp{gdb_eval} command.
22367 @subsubheading Example
22369 In the following example, the numbers that precede the commands are the
22370 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
22371 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
22375 211-data-evaluate-expression A
22378 311-data-evaluate-expression &A
22379 311^done,value="0xefffeb7c"
22381 411-data-evaluate-expression A+3
22384 511-data-evaluate-expression "A + 3"
22390 @subheading The @code{-data-list-changed-registers} Command
22391 @findex -data-list-changed-registers
22393 @subsubheading Synopsis
22396 -data-list-changed-registers
22399 Display a list of the registers that have changed.
22401 @subsubheading @value{GDBN} Command
22403 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
22404 has the corresponding command @samp{gdb_changed_register_list}.
22406 @subsubheading Example
22408 On a PPC MBX board:
22416 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
22417 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
22420 -data-list-changed-registers
22421 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
22422 "10","11","13","14","15","16","17","18","19","20","21","22","23",
22423 "24","25","26","27","28","30","31","64","65","66","67","69"]
22428 @subheading The @code{-data-list-register-names} Command
22429 @findex -data-list-register-names
22431 @subsubheading Synopsis
22434 -data-list-register-names [ ( @var{regno} )+ ]
22437 Show a list of register names for the current target. If no arguments
22438 are given, it shows a list of the names of all the registers. If
22439 integer numbers are given as arguments, it will print a list of the
22440 names of the registers corresponding to the arguments. To ensure
22441 consistency between a register name and its number, the output list may
22442 include empty register names.
22444 @subsubheading @value{GDBN} Command
22446 @value{GDBN} does not have a command which corresponds to
22447 @samp{-data-list-register-names}. In @code{gdbtk} there is a
22448 corresponding command @samp{gdb_regnames}.
22450 @subsubheading Example
22452 For the PPC MBX board:
22455 -data-list-register-names
22456 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
22457 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
22458 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
22459 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
22460 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
22461 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
22462 "", "pc","ps","cr","lr","ctr","xer"]
22464 -data-list-register-names 1 2 3
22465 ^done,register-names=["r1","r2","r3"]
22469 @subheading The @code{-data-list-register-values} Command
22470 @findex -data-list-register-values
22472 @subsubheading Synopsis
22475 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
22478 Display the registers' contents. @var{fmt} is the format according to
22479 which the registers' contents are to be returned, followed by an optional
22480 list of numbers specifying the registers to display. A missing list of
22481 numbers indicates that the contents of all the registers must be returned.
22483 Allowed formats for @var{fmt} are:
22500 @subsubheading @value{GDBN} Command
22502 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
22503 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
22505 @subsubheading Example
22507 For a PPC MBX board (note: line breaks are for readability only, they
22508 don't appear in the actual output):
22512 -data-list-register-values r 64 65
22513 ^done,register-values=[@{number="64",value="0xfe00a300"@},
22514 @{number="65",value="0x00029002"@}]
22516 -data-list-register-values x
22517 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
22518 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
22519 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
22520 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
22521 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
22522 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
22523 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
22524 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
22525 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
22526 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
22527 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
22528 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
22529 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
22530 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
22531 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
22532 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
22533 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
22534 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
22535 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
22536 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
22537 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
22538 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
22539 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
22540 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
22541 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
22542 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
22543 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
22544 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
22545 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
22546 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
22547 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
22548 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
22549 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
22550 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
22551 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
22552 @{number="69",value="0x20002b03"@}]
22557 @subheading The @code{-data-read-memory} Command
22558 @findex -data-read-memory
22560 @subsubheading Synopsis
22563 -data-read-memory [ -o @var{byte-offset} ]
22564 @var{address} @var{word-format} @var{word-size}
22565 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
22572 @item @var{address}
22573 An expression specifying the address of the first memory word to be
22574 read. Complex expressions containing embedded white space should be
22575 quoted using the C convention.
22577 @item @var{word-format}
22578 The format to be used to print the memory words. The notation is the
22579 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
22582 @item @var{word-size}
22583 The size of each memory word in bytes.
22585 @item @var{nr-rows}
22586 The number of rows in the output table.
22588 @item @var{nr-cols}
22589 The number of columns in the output table.
22592 If present, indicates that each row should include an @sc{ascii} dump. The
22593 value of @var{aschar} is used as a padding character when a byte is not a
22594 member of the printable @sc{ascii} character set (printable @sc{ascii}
22595 characters are those whose code is between 32 and 126, inclusively).
22597 @item @var{byte-offset}
22598 An offset to add to the @var{address} before fetching memory.
22601 This command displays memory contents as a table of @var{nr-rows} by
22602 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
22603 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
22604 (returned as @samp{total-bytes}). Should less than the requested number
22605 of bytes be returned by the target, the missing words are identified
22606 using @samp{N/A}. The number of bytes read from the target is returned
22607 in @samp{nr-bytes} and the starting address used to read memory in
22610 The address of the next/previous row or page is available in
22611 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
22614 @subsubheading @value{GDBN} Command
22616 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
22617 @samp{gdb_get_mem} memory read command.
22619 @subsubheading Example
22621 Read six bytes of memory starting at @code{bytes+6} but then offset by
22622 @code{-6} bytes. Format as three rows of two columns. One byte per
22623 word. Display each word in hex.
22627 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
22628 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
22629 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
22630 prev-page="0x0000138a",memory=[
22631 @{addr="0x00001390",data=["0x00","0x01"]@},
22632 @{addr="0x00001392",data=["0x02","0x03"]@},
22633 @{addr="0x00001394",data=["0x04","0x05"]@}]
22637 Read two bytes of memory starting at address @code{shorts + 64} and
22638 display as a single word formatted in decimal.
22642 5-data-read-memory shorts+64 d 2 1 1
22643 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
22644 next-row="0x00001512",prev-row="0x0000150e",
22645 next-page="0x00001512",prev-page="0x0000150e",memory=[
22646 @{addr="0x00001510",data=["128"]@}]
22650 Read thirty two bytes of memory starting at @code{bytes+16} and format
22651 as eight rows of four columns. Include a string encoding with @samp{x}
22652 used as the non-printable character.
22656 4-data-read-memory bytes+16 x 1 8 4 x
22657 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
22658 next-row="0x000013c0",prev-row="0x0000139c",
22659 next-page="0x000013c0",prev-page="0x00001380",memory=[
22660 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
22661 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
22662 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
22663 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
22664 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
22665 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
22666 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
22667 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
22671 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22672 @node GDB/MI Tracepoint Commands
22673 @section @sc{gdb/mi} Tracepoint Commands
22675 The tracepoint commands are not yet implemented.
22677 @c @subheading -trace-actions
22679 @c @subheading -trace-delete
22681 @c @subheading -trace-disable
22683 @c @subheading -trace-dump
22685 @c @subheading -trace-enable
22687 @c @subheading -trace-exists
22689 @c @subheading -trace-find
22691 @c @subheading -trace-frame-number
22693 @c @subheading -trace-info
22695 @c @subheading -trace-insert
22697 @c @subheading -trace-list
22699 @c @subheading -trace-pass-count
22701 @c @subheading -trace-save
22703 @c @subheading -trace-start
22705 @c @subheading -trace-stop
22708 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22709 @node GDB/MI Symbol Query
22710 @section @sc{gdb/mi} Symbol Query Commands
22713 @subheading The @code{-symbol-info-address} Command
22714 @findex -symbol-info-address
22716 @subsubheading Synopsis
22719 -symbol-info-address @var{symbol}
22722 Describe where @var{symbol} is stored.
22724 @subsubheading @value{GDBN} Command
22726 The corresponding @value{GDBN} command is @samp{info address}.
22728 @subsubheading Example
22732 @subheading The @code{-symbol-info-file} Command
22733 @findex -symbol-info-file
22735 @subsubheading Synopsis
22741 Show the file for the symbol.
22743 @subsubheading @value{GDBN} Command
22745 There's no equivalent @value{GDBN} command. @code{gdbtk} has
22746 @samp{gdb_find_file}.
22748 @subsubheading Example
22752 @subheading The @code{-symbol-info-function} Command
22753 @findex -symbol-info-function
22755 @subsubheading Synopsis
22758 -symbol-info-function
22761 Show which function the symbol lives in.
22763 @subsubheading @value{GDBN} Command
22765 @samp{gdb_get_function} in @code{gdbtk}.
22767 @subsubheading Example
22771 @subheading The @code{-symbol-info-line} Command
22772 @findex -symbol-info-line
22774 @subsubheading Synopsis
22780 Show the core addresses of the code for a source line.
22782 @subsubheading @value{GDBN} Command
22784 The corresponding @value{GDBN} command is @samp{info line}.
22785 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
22787 @subsubheading Example
22791 @subheading The @code{-symbol-info-symbol} Command
22792 @findex -symbol-info-symbol
22794 @subsubheading Synopsis
22797 -symbol-info-symbol @var{addr}
22800 Describe what symbol is at location @var{addr}.
22802 @subsubheading @value{GDBN} Command
22804 The corresponding @value{GDBN} command is @samp{info symbol}.
22806 @subsubheading Example
22810 @subheading The @code{-symbol-list-functions} Command
22811 @findex -symbol-list-functions
22813 @subsubheading Synopsis
22816 -symbol-list-functions
22819 List the functions in the executable.
22821 @subsubheading @value{GDBN} Command
22823 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
22824 @samp{gdb_search} in @code{gdbtk}.
22826 @subsubheading Example
22830 @subheading The @code{-symbol-list-lines} Command
22831 @findex -symbol-list-lines
22833 @subsubheading Synopsis
22836 -symbol-list-lines @var{filename}
22839 Print the list of lines that contain code and their associated program
22840 addresses for the given source filename. The entries are sorted in
22841 ascending PC order.
22843 @subsubheading @value{GDBN} Command
22845 There is no corresponding @value{GDBN} command.
22847 @subsubheading Example
22850 -symbol-list-lines basics.c
22851 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
22856 @subheading The @code{-symbol-list-types} Command
22857 @findex -symbol-list-types
22859 @subsubheading Synopsis
22865 List all the type names.
22867 @subsubheading @value{GDBN} Command
22869 The corresponding commands are @samp{info types} in @value{GDBN},
22870 @samp{gdb_search} in @code{gdbtk}.
22872 @subsubheading Example
22876 @subheading The @code{-symbol-list-variables} Command
22877 @findex -symbol-list-variables
22879 @subsubheading Synopsis
22882 -symbol-list-variables
22885 List all the global and static variable names.
22887 @subsubheading @value{GDBN} Command
22889 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
22891 @subsubheading Example
22895 @subheading The @code{-symbol-locate} Command
22896 @findex -symbol-locate
22898 @subsubheading Synopsis
22904 @subsubheading @value{GDBN} Command
22906 @samp{gdb_loc} in @code{gdbtk}.
22908 @subsubheading Example
22912 @subheading The @code{-symbol-type} Command
22913 @findex -symbol-type
22915 @subsubheading Synopsis
22918 -symbol-type @var{variable}
22921 Show type of @var{variable}.
22923 @subsubheading @value{GDBN} Command
22925 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
22926 @samp{gdb_obj_variable}.
22928 @subsubheading Example
22932 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22933 @node GDB/MI File Commands
22934 @section @sc{gdb/mi} File Commands
22936 This section describes the GDB/MI commands to specify executable file names
22937 and to read in and obtain symbol table information.
22939 @subheading The @code{-file-exec-and-symbols} Command
22940 @findex -file-exec-and-symbols
22942 @subsubheading Synopsis
22945 -file-exec-and-symbols @var{file}
22948 Specify the executable file to be debugged. This file is the one from
22949 which the symbol table is also read. If no file is specified, the
22950 command clears the executable and symbol information. If breakpoints
22951 are set when using this command with no arguments, @value{GDBN} will produce
22952 error messages. Otherwise, no output is produced, except a completion
22955 @subsubheading @value{GDBN} Command
22957 The corresponding @value{GDBN} command is @samp{file}.
22959 @subsubheading Example
22963 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
22969 @subheading The @code{-file-exec-file} Command
22970 @findex -file-exec-file
22972 @subsubheading Synopsis
22975 -file-exec-file @var{file}
22978 Specify the executable file to be debugged. Unlike
22979 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
22980 from this file. If used without argument, @value{GDBN} clears the information
22981 about the executable file. No output is produced, except a completion
22984 @subsubheading @value{GDBN} Command
22986 The corresponding @value{GDBN} command is @samp{exec-file}.
22988 @subsubheading Example
22992 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
22998 @subheading The @code{-file-list-exec-sections} Command
22999 @findex -file-list-exec-sections
23001 @subsubheading Synopsis
23004 -file-list-exec-sections
23007 List the sections of the current executable file.
23009 @subsubheading @value{GDBN} Command
23011 The @value{GDBN} command @samp{info file} shows, among the rest, the same
23012 information as this command. @code{gdbtk} has a corresponding command
23013 @samp{gdb_load_info}.
23015 @subsubheading Example
23019 @subheading The @code{-file-list-exec-source-file} Command
23020 @findex -file-list-exec-source-file
23022 @subsubheading Synopsis
23025 -file-list-exec-source-file
23028 List the line number, the current source file, and the absolute path
23029 to the current source file for the current executable. The macro
23030 information field has a value of @samp{1} or @samp{0} depending on
23031 whether or not the file includes preprocessor macro information.
23033 @subsubheading @value{GDBN} Command
23035 The @value{GDBN} equivalent is @samp{info source}
23037 @subsubheading Example
23041 123-file-list-exec-source-file
23042 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
23047 @subheading The @code{-file-list-exec-source-files} Command
23048 @findex -file-list-exec-source-files
23050 @subsubheading Synopsis
23053 -file-list-exec-source-files
23056 List the source files for the current executable.
23058 It will always output the filename, but only when @value{GDBN} can find
23059 the absolute file name of a source file, will it output the fullname.
23061 @subsubheading @value{GDBN} Command
23063 The @value{GDBN} equivalent is @samp{info sources}.
23064 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
23066 @subsubheading Example
23069 -file-list-exec-source-files
23071 @{file=foo.c,fullname=/home/foo.c@},
23072 @{file=/home/bar.c,fullname=/home/bar.c@},
23073 @{file=gdb_could_not_find_fullpath.c@}]
23077 @subheading The @code{-file-list-shared-libraries} Command
23078 @findex -file-list-shared-libraries
23080 @subsubheading Synopsis
23083 -file-list-shared-libraries
23086 List the shared libraries in the program.
23088 @subsubheading @value{GDBN} Command
23090 The corresponding @value{GDBN} command is @samp{info shared}.
23092 @subsubheading Example
23096 @subheading The @code{-file-list-symbol-files} Command
23097 @findex -file-list-symbol-files
23099 @subsubheading Synopsis
23102 -file-list-symbol-files
23107 @subsubheading @value{GDBN} Command
23109 The corresponding @value{GDBN} command is @samp{info file} (part of it).
23111 @subsubheading Example
23115 @subheading The @code{-file-symbol-file} Command
23116 @findex -file-symbol-file
23118 @subsubheading Synopsis
23121 -file-symbol-file @var{file}
23124 Read symbol table info from the specified @var{file} argument. When
23125 used without arguments, clears @value{GDBN}'s symbol table info. No output is
23126 produced, except for a completion notification.
23128 @subsubheading @value{GDBN} Command
23130 The corresponding @value{GDBN} command is @samp{symbol-file}.
23132 @subsubheading Example
23136 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23142 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23143 @node GDB/MI Memory Overlay Commands
23144 @section @sc{gdb/mi} Memory Overlay Commands
23146 The memory overlay commands are not implemented.
23148 @c @subheading -overlay-auto
23150 @c @subheading -overlay-list-mapping-state
23152 @c @subheading -overlay-list-overlays
23154 @c @subheading -overlay-map
23156 @c @subheading -overlay-off
23158 @c @subheading -overlay-on
23160 @c @subheading -overlay-unmap
23162 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23163 @node GDB/MI Signal Handling Commands
23164 @section @sc{gdb/mi} Signal Handling Commands
23166 Signal handling commands are not implemented.
23168 @c @subheading -signal-handle
23170 @c @subheading -signal-list-handle-actions
23172 @c @subheading -signal-list-signal-types
23176 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23177 @node GDB/MI Target Manipulation
23178 @section @sc{gdb/mi} Target Manipulation Commands
23181 @subheading The @code{-target-attach} Command
23182 @findex -target-attach
23184 @subsubheading Synopsis
23187 -target-attach @var{pid} | @var{gid} | @var{file}
23190 Attach to a process @var{pid} or a file @var{file} outside of
23191 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
23192 group, the id previously returned by
23193 @samp{-list-thread-groups --available} must be used.
23195 @subsubheading @value{GDBN} Command
23197 The corresponding @value{GDBN} command is @samp{attach}.
23199 @subsubheading Example
23203 =thread-created,id="1"
23204 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
23209 @subheading The @code{-target-compare-sections} Command
23210 @findex -target-compare-sections
23212 @subsubheading Synopsis
23215 -target-compare-sections [ @var{section} ]
23218 Compare data of section @var{section} on target to the exec file.
23219 Without the argument, all sections are compared.
23221 @subsubheading @value{GDBN} Command
23223 The @value{GDBN} equivalent is @samp{compare-sections}.
23225 @subsubheading Example
23229 @subheading The @code{-target-detach} Command
23230 @findex -target-detach
23232 @subsubheading Synopsis
23235 -target-detach [ @var{pid} | @var{gid} ]
23238 Detach from the remote target which normally resumes its execution.
23239 If either @var{pid} or @var{gid} is specified, detaches from either
23240 the specified process, or specified thread group. There's no output.
23242 @subsubheading @value{GDBN} Command
23244 The corresponding @value{GDBN} command is @samp{detach}.
23246 @subsubheading Example
23256 @subheading The @code{-target-disconnect} Command
23257 @findex -target-disconnect
23259 @subsubheading Synopsis
23265 Disconnect from the remote target. There's no output and the target is
23266 generally not resumed.
23268 @subsubheading @value{GDBN} Command
23270 The corresponding @value{GDBN} command is @samp{disconnect}.
23272 @subsubheading Example
23282 @subheading The @code{-target-download} Command
23283 @findex -target-download
23285 @subsubheading Synopsis
23291 Loads the executable onto the remote target.
23292 It prints out an update message every half second, which includes the fields:
23296 The name of the section.
23298 The size of what has been sent so far for that section.
23300 The size of the section.
23302 The total size of what was sent so far (the current and the previous sections).
23304 The size of the overall executable to download.
23308 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
23309 @sc{gdb/mi} Output Syntax}).
23311 In addition, it prints the name and size of the sections, as they are
23312 downloaded. These messages include the following fields:
23316 The name of the section.
23318 The size of the section.
23320 The size of the overall executable to download.
23324 At the end, a summary is printed.
23326 @subsubheading @value{GDBN} Command
23328 The corresponding @value{GDBN} command is @samp{load}.
23330 @subsubheading Example
23332 Note: each status message appears on a single line. Here the messages
23333 have been broken down so that they can fit onto a page.
23338 +download,@{section=".text",section-size="6668",total-size="9880"@}
23339 +download,@{section=".text",section-sent="512",section-size="6668",
23340 total-sent="512",total-size="9880"@}
23341 +download,@{section=".text",section-sent="1024",section-size="6668",
23342 total-sent="1024",total-size="9880"@}
23343 +download,@{section=".text",section-sent="1536",section-size="6668",
23344 total-sent="1536",total-size="9880"@}
23345 +download,@{section=".text",section-sent="2048",section-size="6668",
23346 total-sent="2048",total-size="9880"@}
23347 +download,@{section=".text",section-sent="2560",section-size="6668",
23348 total-sent="2560",total-size="9880"@}
23349 +download,@{section=".text",section-sent="3072",section-size="6668",
23350 total-sent="3072",total-size="9880"@}
23351 +download,@{section=".text",section-sent="3584",section-size="6668",
23352 total-sent="3584",total-size="9880"@}
23353 +download,@{section=".text",section-sent="4096",section-size="6668",
23354 total-sent="4096",total-size="9880"@}
23355 +download,@{section=".text",section-sent="4608",section-size="6668",
23356 total-sent="4608",total-size="9880"@}
23357 +download,@{section=".text",section-sent="5120",section-size="6668",
23358 total-sent="5120",total-size="9880"@}
23359 +download,@{section=".text",section-sent="5632",section-size="6668",
23360 total-sent="5632",total-size="9880"@}
23361 +download,@{section=".text",section-sent="6144",section-size="6668",
23362 total-sent="6144",total-size="9880"@}
23363 +download,@{section=".text",section-sent="6656",section-size="6668",
23364 total-sent="6656",total-size="9880"@}
23365 +download,@{section=".init",section-size="28",total-size="9880"@}
23366 +download,@{section=".fini",section-size="28",total-size="9880"@}
23367 +download,@{section=".data",section-size="3156",total-size="9880"@}
23368 +download,@{section=".data",section-sent="512",section-size="3156",
23369 total-sent="7236",total-size="9880"@}
23370 +download,@{section=".data",section-sent="1024",section-size="3156",
23371 total-sent="7748",total-size="9880"@}
23372 +download,@{section=".data",section-sent="1536",section-size="3156",
23373 total-sent="8260",total-size="9880"@}
23374 +download,@{section=".data",section-sent="2048",section-size="3156",
23375 total-sent="8772",total-size="9880"@}
23376 +download,@{section=".data",section-sent="2560",section-size="3156",
23377 total-sent="9284",total-size="9880"@}
23378 +download,@{section=".data",section-sent="3072",section-size="3156",
23379 total-sent="9796",total-size="9880"@}
23380 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
23386 @subheading The @code{-target-exec-status} Command
23387 @findex -target-exec-status
23389 @subsubheading Synopsis
23392 -target-exec-status
23395 Provide information on the state of the target (whether it is running or
23396 not, for instance).
23398 @subsubheading @value{GDBN} Command
23400 There's no equivalent @value{GDBN} command.
23402 @subsubheading Example
23406 @subheading The @code{-target-list-available-targets} Command
23407 @findex -target-list-available-targets
23409 @subsubheading Synopsis
23412 -target-list-available-targets
23415 List the possible targets to connect to.
23417 @subsubheading @value{GDBN} Command
23419 The corresponding @value{GDBN} command is @samp{help target}.
23421 @subsubheading Example
23425 @subheading The @code{-target-list-current-targets} Command
23426 @findex -target-list-current-targets
23428 @subsubheading Synopsis
23431 -target-list-current-targets
23434 Describe the current target.
23436 @subsubheading @value{GDBN} Command
23438 The corresponding information is printed by @samp{info file} (among
23441 @subsubheading Example
23445 @subheading The @code{-target-list-parameters} Command
23446 @findex -target-list-parameters
23448 @subsubheading Synopsis
23451 -target-list-parameters
23456 @subsubheading @value{GDBN} Command
23460 @subsubheading Example
23464 @subheading The @code{-target-select} Command
23465 @findex -target-select
23467 @subsubheading Synopsis
23470 -target-select @var{type} @var{parameters @dots{}}
23473 Connect @value{GDBN} to the remote target. This command takes two args:
23477 The type of target, for instance @samp{remote}, etc.
23478 @item @var{parameters}
23479 Device names, host names and the like. @xref{Target Commands, ,
23480 Commands for Managing Targets}, for more details.
23483 The output is a connection notification, followed by the address at
23484 which the target program is, in the following form:
23487 ^connected,addr="@var{address}",func="@var{function name}",
23488 args=[@var{arg list}]
23491 @subsubheading @value{GDBN} Command
23493 The corresponding @value{GDBN} command is @samp{target}.
23495 @subsubheading Example
23499 -target-select remote /dev/ttya
23500 ^connected,addr="0xfe00a300",func="??",args=[]
23504 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23505 @node GDB/MI File Transfer Commands
23506 @section @sc{gdb/mi} File Transfer Commands
23509 @subheading The @code{-target-file-put} Command
23510 @findex -target-file-put
23512 @subsubheading Synopsis
23515 -target-file-put @var{hostfile} @var{targetfile}
23518 Copy file @var{hostfile} from the host system (the machine running
23519 @value{GDBN}) to @var{targetfile} on the target system.
23521 @subsubheading @value{GDBN} Command
23523 The corresponding @value{GDBN} command is @samp{remote put}.
23525 @subsubheading Example
23529 -target-file-put localfile remotefile
23535 @subheading The @code{-target-file-get} Command
23536 @findex -target-file-get
23538 @subsubheading Synopsis
23541 -target-file-get @var{targetfile} @var{hostfile}
23544 Copy file @var{targetfile} from the target system to @var{hostfile}
23545 on the host system.
23547 @subsubheading @value{GDBN} Command
23549 The corresponding @value{GDBN} command is @samp{remote get}.
23551 @subsubheading Example
23555 -target-file-get remotefile localfile
23561 @subheading The @code{-target-file-delete} Command
23562 @findex -target-file-delete
23564 @subsubheading Synopsis
23567 -target-file-delete @var{targetfile}
23570 Delete @var{targetfile} from the target system.
23572 @subsubheading @value{GDBN} Command
23574 The corresponding @value{GDBN} command is @samp{remote delete}.
23576 @subsubheading Example
23580 -target-file-delete remotefile
23586 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23587 @node GDB/MI Miscellaneous Commands
23588 @section Miscellaneous @sc{gdb/mi} Commands
23590 @c @subheading -gdb-complete
23592 @subheading The @code{-gdb-exit} Command
23595 @subsubheading Synopsis
23601 Exit @value{GDBN} immediately.
23603 @subsubheading @value{GDBN} Command
23605 Approximately corresponds to @samp{quit}.
23607 @subsubheading Example
23616 @subheading The @code{-exec-abort} Command
23617 @findex -exec-abort
23619 @subsubheading Synopsis
23625 Kill the inferior running program.
23627 @subsubheading @value{GDBN} Command
23629 The corresponding @value{GDBN} command is @samp{kill}.
23631 @subsubheading Example
23635 @subheading The @code{-gdb-set} Command
23638 @subsubheading Synopsis
23644 Set an internal @value{GDBN} variable.
23645 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
23647 @subsubheading @value{GDBN} Command
23649 The corresponding @value{GDBN} command is @samp{set}.
23651 @subsubheading Example
23661 @subheading The @code{-gdb-show} Command
23664 @subsubheading Synopsis
23670 Show the current value of a @value{GDBN} variable.
23672 @subsubheading @value{GDBN} Command
23674 The corresponding @value{GDBN} command is @samp{show}.
23676 @subsubheading Example
23685 @c @subheading -gdb-source
23688 @subheading The @code{-gdb-version} Command
23689 @findex -gdb-version
23691 @subsubheading Synopsis
23697 Show version information for @value{GDBN}. Used mostly in testing.
23699 @subsubheading @value{GDBN} Command
23701 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
23702 default shows this information when you start an interactive session.
23704 @subsubheading Example
23706 @c This example modifies the actual output from GDB to avoid overfull
23712 ~Copyright 2000 Free Software Foundation, Inc.
23713 ~GDB is free software, covered by the GNU General Public License, and
23714 ~you are welcome to change it and/or distribute copies of it under
23715 ~ certain conditions.
23716 ~Type "show copying" to see the conditions.
23717 ~There is absolutely no warranty for GDB. Type "show warranty" for
23719 ~This GDB was configured as
23720 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
23725 @subheading The @code{-list-features} Command
23726 @findex -list-features
23728 Returns a list of particular features of the MI protocol that
23729 this version of gdb implements. A feature can be a command,
23730 or a new field in an output of some command, or even an
23731 important bugfix. While a frontend can sometimes detect presence
23732 of a feature at runtime, it is easier to perform detection at debugger
23735 The command returns a list of strings, with each string naming an
23736 available feature. Each returned string is just a name, it does not
23737 have any internal structure. The list of possible feature names
23743 (gdb) -list-features
23744 ^done,result=["feature1","feature2"]
23747 The current list of features is:
23750 @item frozen-varobjs
23751 Indicates presence of the @code{-var-set-frozen} command, as well
23752 as possible presense of the @code{frozen} field in the output
23753 of @code{-varobj-create}.
23754 @item pending-breakpoints
23755 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
23757 Indicates presence of the @code{-thread-info} command.
23761 @subheading The @code{-list-target-features} Command
23762 @findex -list-target-features
23764 Returns a list of particular features that are supported by the
23765 target. Those features affect the permitted MI commands, but
23766 unlike the features reported by the @code{-list-features} command, the
23767 features depend on which target GDB is using at the moment. Whenever
23768 a target can change, due to commands such as @code{-target-select},
23769 @code{-target-attach} or @code{-exec-run}, the list of target features
23770 may change, and the frontend should obtain it again.
23774 (gdb) -list-features
23775 ^done,result=["async"]
23778 The current list of features is:
23782 Indicates that the target is capable of asynchronous command
23783 execution, which means that @value{GDBN} will accept further commands
23784 while the target is running.
23788 @subheading The @code{-list-thread-groups} Command
23789 @findex -list-thread-groups
23791 @subheading Synopsis
23794 -list-thread-groups [ --available ] [ @var{group} ]
23797 When used without the @var{group} parameter, lists top-level thread
23798 groups that are being debugged. When used with the @var{group}
23799 parameter, the children of the specified group are listed. The
23800 children can be either threads, or other groups. At present,
23801 @value{GDBN} will not report both threads and groups as children at
23802 the same time, but it may change in future.
23804 With the @samp{--available} option, instead of reporting groups that
23805 are been debugged, GDB will report all thread groups available on the
23806 target. Using the @samp{--available} option together with @var{group}
23809 @subheading Example
23813 -list-thread-groups
23814 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
23815 -list-thread-groups 17
23816 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
23817 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
23818 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
23819 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
23820 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
23823 @subheading The @code{-interpreter-exec} Command
23824 @findex -interpreter-exec
23826 @subheading Synopsis
23829 -interpreter-exec @var{interpreter} @var{command}
23831 @anchor{-interpreter-exec}
23833 Execute the specified @var{command} in the given @var{interpreter}.
23835 @subheading @value{GDBN} Command
23837 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
23839 @subheading Example
23843 -interpreter-exec console "break main"
23844 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
23845 &"During symbol reading, bad structure-type format.\n"
23846 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
23851 @subheading The @code{-inferior-tty-set} Command
23852 @findex -inferior-tty-set
23854 @subheading Synopsis
23857 -inferior-tty-set /dev/pts/1
23860 Set terminal for future runs of the program being debugged.
23862 @subheading @value{GDBN} Command
23864 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
23866 @subheading Example
23870 -inferior-tty-set /dev/pts/1
23875 @subheading The @code{-inferior-tty-show} Command
23876 @findex -inferior-tty-show
23878 @subheading Synopsis
23884 Show terminal for future runs of program being debugged.
23886 @subheading @value{GDBN} Command
23888 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
23890 @subheading Example
23894 -inferior-tty-set /dev/pts/1
23898 ^done,inferior_tty_terminal="/dev/pts/1"
23902 @subheading The @code{-enable-timings} Command
23903 @findex -enable-timings
23905 @subheading Synopsis
23908 -enable-timings [yes | no]
23911 Toggle the printing of the wallclock, user and system times for an MI
23912 command as a field in its output. This command is to help frontend
23913 developers optimize the performance of their code. No argument is
23914 equivalent to @samp{yes}.
23916 @subheading @value{GDBN} Command
23920 @subheading Example
23928 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23929 addr="0x080484ed",func="main",file="myprog.c",
23930 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
23931 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
23939 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
23940 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
23941 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
23942 fullname="/home/nickrob/myprog.c",line="73"@}
23947 @chapter @value{GDBN} Annotations
23949 This chapter describes annotations in @value{GDBN}. Annotations were
23950 designed to interface @value{GDBN} to graphical user interfaces or other
23951 similar programs which want to interact with @value{GDBN} at a
23952 relatively high level.
23954 The annotation mechanism has largely been superseded by @sc{gdb/mi}
23958 This is Edition @value{EDITION}, @value{DATE}.
23962 * Annotations Overview:: What annotations are; the general syntax.
23963 * Server Prefix:: Issuing a command without affecting user state.
23964 * Prompting:: Annotations marking @value{GDBN}'s need for input.
23965 * Errors:: Annotations for error messages.
23966 * Invalidation:: Some annotations describe things now invalid.
23967 * Annotations for Running::
23968 Whether the program is running, how it stopped, etc.
23969 * Source Annotations:: Annotations describing source code.
23972 @node Annotations Overview
23973 @section What is an Annotation?
23974 @cindex annotations
23976 Annotations start with a newline character, two @samp{control-z}
23977 characters, and the name of the annotation. If there is no additional
23978 information associated with this annotation, the name of the annotation
23979 is followed immediately by a newline. If there is additional
23980 information, the name of the annotation is followed by a space, the
23981 additional information, and a newline. The additional information
23982 cannot contain newline characters.
23984 Any output not beginning with a newline and two @samp{control-z}
23985 characters denotes literal output from @value{GDBN}. Currently there is
23986 no need for @value{GDBN} to output a newline followed by two
23987 @samp{control-z} characters, but if there was such a need, the
23988 annotations could be extended with an @samp{escape} annotation which
23989 means those three characters as output.
23991 The annotation @var{level}, which is specified using the
23992 @option{--annotate} command line option (@pxref{Mode Options}), controls
23993 how much information @value{GDBN} prints together with its prompt,
23994 values of expressions, source lines, and other types of output. Level 0
23995 is for no annotations, level 1 is for use when @value{GDBN} is run as a
23996 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
23997 for programs that control @value{GDBN}, and level 2 annotations have
23998 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
23999 Interface, annotate, GDB's Obsolete Annotations}).
24002 @kindex set annotate
24003 @item set annotate @var{level}
24004 The @value{GDBN} command @code{set annotate} sets the level of
24005 annotations to the specified @var{level}.
24007 @item show annotate
24008 @kindex show annotate
24009 Show the current annotation level.
24012 This chapter describes level 3 annotations.
24014 A simple example of starting up @value{GDBN} with annotations is:
24017 $ @kbd{gdb --annotate=3}
24019 Copyright 2003 Free Software Foundation, Inc.
24020 GDB is free software, covered by the GNU General Public License,
24021 and you are welcome to change it and/or distribute copies of it
24022 under certain conditions.
24023 Type "show copying" to see the conditions.
24024 There is absolutely no warranty for GDB. Type "show warranty"
24026 This GDB was configured as "i386-pc-linux-gnu"
24037 Here @samp{quit} is input to @value{GDBN}; the rest is output from
24038 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
24039 denotes a @samp{control-z} character) are annotations; the rest is
24040 output from @value{GDBN}.
24042 @node Server Prefix
24043 @section The Server Prefix
24044 @cindex server prefix
24046 If you prefix a command with @samp{server } then it will not affect
24047 the command history, nor will it affect @value{GDBN}'s notion of which
24048 command to repeat if @key{RET} is pressed on a line by itself. This
24049 means that commands can be run behind a user's back by a front-end in
24050 a transparent manner.
24052 The server prefix does not affect the recording of values into the value
24053 history; to print a value without recording it into the value history,
24054 use the @code{output} command instead of the @code{print} command.
24057 @section Annotation for @value{GDBN} Input
24059 @cindex annotations for prompts
24060 When @value{GDBN} prompts for input, it annotates this fact so it is possible
24061 to know when to send output, when the output from a given command is
24064 Different kinds of input each have a different @dfn{input type}. Each
24065 input type has three annotations: a @code{pre-} annotation, which
24066 denotes the beginning of any prompt which is being output, a plain
24067 annotation, which denotes the end of the prompt, and then a @code{post-}
24068 annotation which denotes the end of any echo which may (or may not) be
24069 associated with the input. For example, the @code{prompt} input type
24070 features the following annotations:
24078 The input types are
24081 @findex pre-prompt annotation
24082 @findex prompt annotation
24083 @findex post-prompt annotation
24085 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
24087 @findex pre-commands annotation
24088 @findex commands annotation
24089 @findex post-commands annotation
24091 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
24092 command. The annotations are repeated for each command which is input.
24094 @findex pre-overload-choice annotation
24095 @findex overload-choice annotation
24096 @findex post-overload-choice annotation
24097 @item overload-choice
24098 When @value{GDBN} wants the user to select between various overloaded functions.
24100 @findex pre-query annotation
24101 @findex query annotation
24102 @findex post-query annotation
24104 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
24106 @findex pre-prompt-for-continue annotation
24107 @findex prompt-for-continue annotation
24108 @findex post-prompt-for-continue annotation
24109 @item prompt-for-continue
24110 When @value{GDBN} is asking the user to press return to continue. Note: Don't
24111 expect this to work well; instead use @code{set height 0} to disable
24112 prompting. This is because the counting of lines is buggy in the
24113 presence of annotations.
24118 @cindex annotations for errors, warnings and interrupts
24120 @findex quit annotation
24125 This annotation occurs right before @value{GDBN} responds to an interrupt.
24127 @findex error annotation
24132 This annotation occurs right before @value{GDBN} responds to an error.
24134 Quit and error annotations indicate that any annotations which @value{GDBN} was
24135 in the middle of may end abruptly. For example, if a
24136 @code{value-history-begin} annotation is followed by a @code{error}, one
24137 cannot expect to receive the matching @code{value-history-end}. One
24138 cannot expect not to receive it either, however; an error annotation
24139 does not necessarily mean that @value{GDBN} is immediately returning all the way
24142 @findex error-begin annotation
24143 A quit or error annotation may be preceded by
24149 Any output between that and the quit or error annotation is the error
24152 Warning messages are not yet annotated.
24153 @c If we want to change that, need to fix warning(), type_error(),
24154 @c range_error(), and possibly other places.
24157 @section Invalidation Notices
24159 @cindex annotations for invalidation messages
24160 The following annotations say that certain pieces of state may have
24164 @findex frames-invalid annotation
24165 @item ^Z^Zframes-invalid
24167 The frames (for example, output from the @code{backtrace} command) may
24170 @findex breakpoints-invalid annotation
24171 @item ^Z^Zbreakpoints-invalid
24173 The breakpoints may have changed. For example, the user just added or
24174 deleted a breakpoint.
24177 @node Annotations for Running
24178 @section Running the Program
24179 @cindex annotations for running programs
24181 @findex starting annotation
24182 @findex stopping annotation
24183 When the program starts executing due to a @value{GDBN} command such as
24184 @code{step} or @code{continue},
24190 is output. When the program stops,
24196 is output. Before the @code{stopped} annotation, a variety of
24197 annotations describe how the program stopped.
24200 @findex exited annotation
24201 @item ^Z^Zexited @var{exit-status}
24202 The program exited, and @var{exit-status} is the exit status (zero for
24203 successful exit, otherwise nonzero).
24205 @findex signalled annotation
24206 @findex signal-name annotation
24207 @findex signal-name-end annotation
24208 @findex signal-string annotation
24209 @findex signal-string-end annotation
24210 @item ^Z^Zsignalled
24211 The program exited with a signal. After the @code{^Z^Zsignalled}, the
24212 annotation continues:
24218 ^Z^Zsignal-name-end
24222 ^Z^Zsignal-string-end
24227 where @var{name} is the name of the signal, such as @code{SIGILL} or
24228 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
24229 as @code{Illegal Instruction} or @code{Segmentation fault}.
24230 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
24231 user's benefit and have no particular format.
24233 @findex signal annotation
24235 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
24236 just saying that the program received the signal, not that it was
24237 terminated with it.
24239 @findex breakpoint annotation
24240 @item ^Z^Zbreakpoint @var{number}
24241 The program hit breakpoint number @var{number}.
24243 @findex watchpoint annotation
24244 @item ^Z^Zwatchpoint @var{number}
24245 The program hit watchpoint number @var{number}.
24248 @node Source Annotations
24249 @section Displaying Source
24250 @cindex annotations for source display
24252 @findex source annotation
24253 The following annotation is used instead of displaying source code:
24256 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
24259 where @var{filename} is an absolute file name indicating which source
24260 file, @var{line} is the line number within that file (where 1 is the
24261 first line in the file), @var{character} is the character position
24262 within the file (where 0 is the first character in the file) (for most
24263 debug formats this will necessarily point to the beginning of a line),
24264 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
24265 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
24266 @var{addr} is the address in the target program associated with the
24267 source which is being displayed. @var{addr} is in the form @samp{0x}
24268 followed by one or more lowercase hex digits (note that this does not
24269 depend on the language).
24272 @chapter Reporting Bugs in @value{GDBN}
24273 @cindex bugs in @value{GDBN}
24274 @cindex reporting bugs in @value{GDBN}
24276 Your bug reports play an essential role in making @value{GDBN} reliable.
24278 Reporting a bug may help you by bringing a solution to your problem, or it
24279 may not. But in any case the principal function of a bug report is to help
24280 the entire community by making the next version of @value{GDBN} work better. Bug
24281 reports are your contribution to the maintenance of @value{GDBN}.
24283 In order for a bug report to serve its purpose, you must include the
24284 information that enables us to fix the bug.
24287 * Bug Criteria:: Have you found a bug?
24288 * Bug Reporting:: How to report bugs
24292 @section Have You Found a Bug?
24293 @cindex bug criteria
24295 If you are not sure whether you have found a bug, here are some guidelines:
24298 @cindex fatal signal
24299 @cindex debugger crash
24300 @cindex crash of debugger
24302 If the debugger gets a fatal signal, for any input whatever, that is a
24303 @value{GDBN} bug. Reliable debuggers never crash.
24305 @cindex error on valid input
24307 If @value{GDBN} produces an error message for valid input, that is a
24308 bug. (Note that if you're cross debugging, the problem may also be
24309 somewhere in the connection to the target.)
24311 @cindex invalid input
24313 If @value{GDBN} does not produce an error message for invalid input,
24314 that is a bug. However, you should note that your idea of
24315 ``invalid input'' might be our idea of ``an extension'' or ``support
24316 for traditional practice''.
24319 If you are an experienced user of debugging tools, your suggestions
24320 for improvement of @value{GDBN} are welcome in any case.
24323 @node Bug Reporting
24324 @section How to Report Bugs
24325 @cindex bug reports
24326 @cindex @value{GDBN} bugs, reporting
24328 A number of companies and individuals offer support for @sc{gnu} products.
24329 If you obtained @value{GDBN} from a support organization, we recommend you
24330 contact that organization first.
24332 You can find contact information for many support companies and
24333 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
24335 @c should add a web page ref...
24338 @ifset BUGURL_DEFAULT
24339 In any event, we also recommend that you submit bug reports for
24340 @value{GDBN}. The preferred method is to submit them directly using
24341 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
24342 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
24345 @strong{Do not send bug reports to @samp{info-gdb}, or to
24346 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
24347 not want to receive bug reports. Those that do have arranged to receive
24350 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
24351 serves as a repeater. The mailing list and the newsgroup carry exactly
24352 the same messages. Often people think of posting bug reports to the
24353 newsgroup instead of mailing them. This appears to work, but it has one
24354 problem which can be crucial: a newsgroup posting often lacks a mail
24355 path back to the sender. Thus, if we need to ask for more information,
24356 we may be unable to reach you. For this reason, it is better to send
24357 bug reports to the mailing list.
24359 @ifclear BUGURL_DEFAULT
24360 In any event, we also recommend that you submit bug reports for
24361 @value{GDBN} to @value{BUGURL}.
24365 The fundamental principle of reporting bugs usefully is this:
24366 @strong{report all the facts}. If you are not sure whether to state a
24367 fact or leave it out, state it!
24369 Often people omit facts because they think they know what causes the
24370 problem and assume that some details do not matter. Thus, you might
24371 assume that the name of the variable you use in an example does not matter.
24372 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
24373 stray memory reference which happens to fetch from the location where that
24374 name is stored in memory; perhaps, if the name were different, the contents
24375 of that location would fool the debugger into doing the right thing despite
24376 the bug. Play it safe and give a specific, complete example. That is the
24377 easiest thing for you to do, and the most helpful.
24379 Keep in mind that the purpose of a bug report is to enable us to fix the
24380 bug. It may be that the bug has been reported previously, but neither
24381 you nor we can know that unless your bug report is complete and
24384 Sometimes people give a few sketchy facts and ask, ``Does this ring a
24385 bell?'' Those bug reports are useless, and we urge everyone to
24386 @emph{refuse to respond to them} except to chide the sender to report
24389 To enable us to fix the bug, you should include all these things:
24393 The version of @value{GDBN}. @value{GDBN} announces it if you start
24394 with no arguments; you can also print it at any time using @code{show
24397 Without this, we will not know whether there is any point in looking for
24398 the bug in the current version of @value{GDBN}.
24401 The type of machine you are using, and the operating system name and
24405 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
24406 ``@value{GCC}--2.8.1''.
24409 What compiler (and its version) was used to compile the program you are
24410 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
24411 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
24412 to get this information; for other compilers, see the documentation for
24416 The command arguments you gave the compiler to compile your example and
24417 observe the bug. For example, did you use @samp{-O}? To guarantee
24418 you will not omit something important, list them all. A copy of the
24419 Makefile (or the output from make) is sufficient.
24421 If we were to try to guess the arguments, we would probably guess wrong
24422 and then we might not encounter the bug.
24425 A complete input script, and all necessary source files, that will
24429 A description of what behavior you observe that you believe is
24430 incorrect. For example, ``It gets a fatal signal.''
24432 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
24433 will certainly notice it. But if the bug is incorrect output, we might
24434 not notice unless it is glaringly wrong. You might as well not give us
24435 a chance to make a mistake.
24437 Even if the problem you experience is a fatal signal, you should still
24438 say so explicitly. Suppose something strange is going on, such as, your
24439 copy of @value{GDBN} is out of synch, or you have encountered a bug in
24440 the C library on your system. (This has happened!) Your copy might
24441 crash and ours would not. If you told us to expect a crash, then when
24442 ours fails to crash, we would know that the bug was not happening for
24443 us. If you had not told us to expect a crash, then we would not be able
24444 to draw any conclusion from our observations.
24447 @cindex recording a session script
24448 To collect all this information, you can use a session recording program
24449 such as @command{script}, which is available on many Unix systems.
24450 Just run your @value{GDBN} session inside @command{script} and then
24451 include the @file{typescript} file with your bug report.
24453 Another way to record a @value{GDBN} session is to run @value{GDBN}
24454 inside Emacs and then save the entire buffer to a file.
24457 If you wish to suggest changes to the @value{GDBN} source, send us context
24458 diffs. If you even discuss something in the @value{GDBN} source, refer to
24459 it by context, not by line number.
24461 The line numbers in our development sources will not match those in your
24462 sources. Your line numbers would convey no useful information to us.
24466 Here are some things that are not necessary:
24470 A description of the envelope of the bug.
24472 Often people who encounter a bug spend a lot of time investigating
24473 which changes to the input file will make the bug go away and which
24474 changes will not affect it.
24476 This is often time consuming and not very useful, because the way we
24477 will find the bug is by running a single example under the debugger
24478 with breakpoints, not by pure deduction from a series of examples.
24479 We recommend that you save your time for something else.
24481 Of course, if you can find a simpler example to report @emph{instead}
24482 of the original one, that is a convenience for us. Errors in the
24483 output will be easier to spot, running under the debugger will take
24484 less time, and so on.
24486 However, simplification is not vital; if you do not want to do this,
24487 report the bug anyway and send us the entire test case you used.
24490 A patch for the bug.
24492 A patch for the bug does help us if it is a good one. But do not omit
24493 the necessary information, such as the test case, on the assumption that
24494 a patch is all we need. We might see problems with your patch and decide
24495 to fix the problem another way, or we might not understand it at all.
24497 Sometimes with a program as complicated as @value{GDBN} it is very hard to
24498 construct an example that will make the program follow a certain path
24499 through the code. If you do not send us the example, we will not be able
24500 to construct one, so we will not be able to verify that the bug is fixed.
24502 And if we cannot understand what bug you are trying to fix, or why your
24503 patch should be an improvement, we will not install it. A test case will
24504 help us to understand.
24507 A guess about what the bug is or what it depends on.
24509 Such guesses are usually wrong. Even we cannot guess right about such
24510 things without first using the debugger to find the facts.
24513 @c The readline documentation is distributed with the readline code
24514 @c and consists of the two following files:
24516 @c inc-hist.texinfo
24517 @c Use -I with makeinfo to point to the appropriate directory,
24518 @c environment var TEXINPUTS with TeX.
24519 @include rluser.texi
24520 @include inc-hist.texinfo
24523 @node Formatting Documentation
24524 @appendix Formatting Documentation
24526 @cindex @value{GDBN} reference card
24527 @cindex reference card
24528 The @value{GDBN} 4 release includes an already-formatted reference card, ready
24529 for printing with PostScript or Ghostscript, in the @file{gdb}
24530 subdirectory of the main source directory@footnote{In
24531 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
24532 release.}. If you can use PostScript or Ghostscript with your printer,
24533 you can print the reference card immediately with @file{refcard.ps}.
24535 The release also includes the source for the reference card. You
24536 can format it, using @TeX{}, by typing:
24542 The @value{GDBN} reference card is designed to print in @dfn{landscape}
24543 mode on US ``letter'' size paper;
24544 that is, on a sheet 11 inches wide by 8.5 inches
24545 high. You will need to specify this form of printing as an option to
24546 your @sc{dvi} output program.
24548 @cindex documentation
24550 All the documentation for @value{GDBN} comes as part of the machine-readable
24551 distribution. The documentation is written in Texinfo format, which is
24552 a documentation system that uses a single source file to produce both
24553 on-line information and a printed manual. You can use one of the Info
24554 formatting commands to create the on-line version of the documentation
24555 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
24557 @value{GDBN} includes an already formatted copy of the on-line Info
24558 version of this manual in the @file{gdb} subdirectory. The main Info
24559 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
24560 subordinate files matching @samp{gdb.info*} in the same directory. If
24561 necessary, you can print out these files, or read them with any editor;
24562 but they are easier to read using the @code{info} subsystem in @sc{gnu}
24563 Emacs or the standalone @code{info} program, available as part of the
24564 @sc{gnu} Texinfo distribution.
24566 If you want to format these Info files yourself, you need one of the
24567 Info formatting programs, such as @code{texinfo-format-buffer} or
24570 If you have @code{makeinfo} installed, and are in the top level
24571 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
24572 version @value{GDBVN}), you can make the Info file by typing:
24579 If you want to typeset and print copies of this manual, you need @TeX{},
24580 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
24581 Texinfo definitions file.
24583 @TeX{} is a typesetting program; it does not print files directly, but
24584 produces output files called @sc{dvi} files. To print a typeset
24585 document, you need a program to print @sc{dvi} files. If your system
24586 has @TeX{} installed, chances are it has such a program. The precise
24587 command to use depends on your system; @kbd{lpr -d} is common; another
24588 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
24589 require a file name without any extension or a @samp{.dvi} extension.
24591 @TeX{} also requires a macro definitions file called
24592 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
24593 written in Texinfo format. On its own, @TeX{} cannot either read or
24594 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
24595 and is located in the @file{gdb-@var{version-number}/texinfo}
24598 If you have @TeX{} and a @sc{dvi} printer program installed, you can
24599 typeset and print this manual. First switch to the @file{gdb}
24600 subdirectory of the main source directory (for example, to
24601 @file{gdb-@value{GDBVN}/gdb}) and type:
24607 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
24609 @node Installing GDB
24610 @appendix Installing @value{GDBN}
24611 @cindex installation
24614 * Requirements:: Requirements for building @value{GDBN}
24615 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
24616 * Separate Objdir:: Compiling @value{GDBN} in another directory
24617 * Config Names:: Specifying names for hosts and targets
24618 * Configure Options:: Summary of options for configure
24619 * System-wide configuration:: Having a system-wide init file
24623 @section Requirements for Building @value{GDBN}
24624 @cindex building @value{GDBN}, requirements for
24626 Building @value{GDBN} requires various tools and packages to be available.
24627 Other packages will be used only if they are found.
24629 @heading Tools/Packages Necessary for Building @value{GDBN}
24631 @item ISO C90 compiler
24632 @value{GDBN} is written in ISO C90. It should be buildable with any
24633 working C90 compiler, e.g.@: GCC.
24637 @heading Tools/Packages Optional for Building @value{GDBN}
24641 @value{GDBN} can use the Expat XML parsing library. This library may be
24642 included with your operating system distribution; if it is not, you
24643 can get the latest version from @url{http://expat.sourceforge.net}.
24644 The @file{configure} script will search for this library in several
24645 standard locations; if it is installed in an unusual path, you can
24646 use the @option{--with-libexpat-prefix} option to specify its location.
24652 Remote protocol memory maps (@pxref{Memory Map Format})
24654 Target descriptions (@pxref{Target Descriptions})
24656 Remote shared library lists (@pxref{Library List Format})
24658 MS-Windows shared libraries (@pxref{Shared Libraries})
24662 @cindex compressed debug sections
24663 @value{GDBN} will use the @samp{zlib} library, if available, to read
24664 compressed debug sections. Some linkers, such as GNU gold, are capable
24665 of producing binaries with compressed debug sections. If @value{GDBN}
24666 is compiled with @samp{zlib}, it will be able to read the debug
24667 information in such binaries.
24669 The @samp{zlib} library is likely included with your operating system
24670 distribution; if it is not, you can get the latest version from
24671 @url{http://zlib.net}.
24675 @node Running Configure
24676 @section Invoking the @value{GDBN} @file{configure} Script
24677 @cindex configuring @value{GDBN}
24678 @value{GDBN} comes with a @file{configure} script that automates the process
24679 of preparing @value{GDBN} for installation; you can then use @code{make} to
24680 build the @code{gdb} program.
24682 @c irrelevant in info file; it's as current as the code it lives with.
24683 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
24684 look at the @file{README} file in the sources; we may have improved the
24685 installation procedures since publishing this manual.}
24688 The @value{GDBN} distribution includes all the source code you need for
24689 @value{GDBN} in a single directory, whose name is usually composed by
24690 appending the version number to @samp{gdb}.
24692 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
24693 @file{gdb-@value{GDBVN}} directory. That directory contains:
24696 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
24697 script for configuring @value{GDBN} and all its supporting libraries
24699 @item gdb-@value{GDBVN}/gdb
24700 the source specific to @value{GDBN} itself
24702 @item gdb-@value{GDBVN}/bfd
24703 source for the Binary File Descriptor library
24705 @item gdb-@value{GDBVN}/include
24706 @sc{gnu} include files
24708 @item gdb-@value{GDBVN}/libiberty
24709 source for the @samp{-liberty} free software library
24711 @item gdb-@value{GDBVN}/opcodes
24712 source for the library of opcode tables and disassemblers
24714 @item gdb-@value{GDBVN}/readline
24715 source for the @sc{gnu} command-line interface
24717 @item gdb-@value{GDBVN}/glob
24718 source for the @sc{gnu} filename pattern-matching subroutine
24720 @item gdb-@value{GDBVN}/mmalloc
24721 source for the @sc{gnu} memory-mapped malloc package
24724 The simplest way to configure and build @value{GDBN} is to run @file{configure}
24725 from the @file{gdb-@var{version-number}} source directory, which in
24726 this example is the @file{gdb-@value{GDBVN}} directory.
24728 First switch to the @file{gdb-@var{version-number}} source directory
24729 if you are not already in it; then run @file{configure}. Pass the
24730 identifier for the platform on which @value{GDBN} will run as an
24736 cd gdb-@value{GDBVN}
24737 ./configure @var{host}
24742 where @var{host} is an identifier such as @samp{sun4} or
24743 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
24744 (You can often leave off @var{host}; @file{configure} tries to guess the
24745 correct value by examining your system.)
24747 Running @samp{configure @var{host}} and then running @code{make} builds the
24748 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
24749 libraries, then @code{gdb} itself. The configured source files, and the
24750 binaries, are left in the corresponding source directories.
24753 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
24754 system does not recognize this automatically when you run a different
24755 shell, you may need to run @code{sh} on it explicitly:
24758 sh configure @var{host}
24761 If you run @file{configure} from a directory that contains source
24762 directories for multiple libraries or programs, such as the
24763 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
24765 creates configuration files for every directory level underneath (unless
24766 you tell it not to, with the @samp{--norecursion} option).
24768 You should run the @file{configure} script from the top directory in the
24769 source tree, the @file{gdb-@var{version-number}} directory. If you run
24770 @file{configure} from one of the subdirectories, you will configure only
24771 that subdirectory. That is usually not what you want. In particular,
24772 if you run the first @file{configure} from the @file{gdb} subdirectory
24773 of the @file{gdb-@var{version-number}} directory, you will omit the
24774 configuration of @file{bfd}, @file{readline}, and other sibling
24775 directories of the @file{gdb} subdirectory. This leads to build errors
24776 about missing include files such as @file{bfd/bfd.h}.
24778 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
24779 However, you should make sure that the shell on your path (named by
24780 the @samp{SHELL} environment variable) is publicly readable. Remember
24781 that @value{GDBN} uses the shell to start your program---some systems refuse to
24782 let @value{GDBN} debug child processes whose programs are not readable.
24784 @node Separate Objdir
24785 @section Compiling @value{GDBN} in Another Directory
24787 If you want to run @value{GDBN} versions for several host or target machines,
24788 you need a different @code{gdb} compiled for each combination of
24789 host and target. @file{configure} is designed to make this easy by
24790 allowing you to generate each configuration in a separate subdirectory,
24791 rather than in the source directory. If your @code{make} program
24792 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
24793 @code{make} in each of these directories builds the @code{gdb}
24794 program specified there.
24796 To build @code{gdb} in a separate directory, run @file{configure}
24797 with the @samp{--srcdir} option to specify where to find the source.
24798 (You also need to specify a path to find @file{configure}
24799 itself from your working directory. If the path to @file{configure}
24800 would be the same as the argument to @samp{--srcdir}, you can leave out
24801 the @samp{--srcdir} option; it is assumed.)
24803 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
24804 separate directory for a Sun 4 like this:
24808 cd gdb-@value{GDBVN}
24811 ../gdb-@value{GDBVN}/configure sun4
24816 When @file{configure} builds a configuration using a remote source
24817 directory, it creates a tree for the binaries with the same structure
24818 (and using the same names) as the tree under the source directory. In
24819 the example, you'd find the Sun 4 library @file{libiberty.a} in the
24820 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
24821 @file{gdb-sun4/gdb}.
24823 Make sure that your path to the @file{configure} script has just one
24824 instance of @file{gdb} in it. If your path to @file{configure} looks
24825 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
24826 one subdirectory of @value{GDBN}, not the whole package. This leads to
24827 build errors about missing include files such as @file{bfd/bfd.h}.
24829 One popular reason to build several @value{GDBN} configurations in separate
24830 directories is to configure @value{GDBN} for cross-compiling (where
24831 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
24832 programs that run on another machine---the @dfn{target}).
24833 You specify a cross-debugging target by
24834 giving the @samp{--target=@var{target}} option to @file{configure}.
24836 When you run @code{make} to build a program or library, you must run
24837 it in a configured directory---whatever directory you were in when you
24838 called @file{configure} (or one of its subdirectories).
24840 The @code{Makefile} that @file{configure} generates in each source
24841 directory also runs recursively. If you type @code{make} in a source
24842 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
24843 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
24844 will build all the required libraries, and then build GDB.
24846 When you have multiple hosts or targets configured in separate
24847 directories, you can run @code{make} on them in parallel (for example,
24848 if they are NFS-mounted on each of the hosts); they will not interfere
24852 @section Specifying Names for Hosts and Targets
24854 The specifications used for hosts and targets in the @file{configure}
24855 script are based on a three-part naming scheme, but some short predefined
24856 aliases are also supported. The full naming scheme encodes three pieces
24857 of information in the following pattern:
24860 @var{architecture}-@var{vendor}-@var{os}
24863 For example, you can use the alias @code{sun4} as a @var{host} argument,
24864 or as the value for @var{target} in a @code{--target=@var{target}}
24865 option. The equivalent full name is @samp{sparc-sun-sunos4}.
24867 The @file{configure} script accompanying @value{GDBN} does not provide
24868 any query facility to list all supported host and target names or
24869 aliases. @file{configure} calls the Bourne shell script
24870 @code{config.sub} to map abbreviations to full names; you can read the
24871 script, if you wish, or you can use it to test your guesses on
24872 abbreviations---for example:
24875 % sh config.sub i386-linux
24877 % sh config.sub alpha-linux
24878 alpha-unknown-linux-gnu
24879 % sh config.sub hp9k700
24881 % sh config.sub sun4
24882 sparc-sun-sunos4.1.1
24883 % sh config.sub sun3
24884 m68k-sun-sunos4.1.1
24885 % sh config.sub i986v
24886 Invalid configuration `i986v': machine `i986v' not recognized
24890 @code{config.sub} is also distributed in the @value{GDBN} source
24891 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
24893 @node Configure Options
24894 @section @file{configure} Options
24896 Here is a summary of the @file{configure} options and arguments that
24897 are most often useful for building @value{GDBN}. @file{configure} also has
24898 several other options not listed here. @inforef{What Configure
24899 Does,,configure.info}, for a full explanation of @file{configure}.
24902 configure @r{[}--help@r{]}
24903 @r{[}--prefix=@var{dir}@r{]}
24904 @r{[}--exec-prefix=@var{dir}@r{]}
24905 @r{[}--srcdir=@var{dirname}@r{]}
24906 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
24907 @r{[}--target=@var{target}@r{]}
24912 You may introduce options with a single @samp{-} rather than
24913 @samp{--} if you prefer; but you may abbreviate option names if you use
24918 Display a quick summary of how to invoke @file{configure}.
24920 @item --prefix=@var{dir}
24921 Configure the source to install programs and files under directory
24924 @item --exec-prefix=@var{dir}
24925 Configure the source to install programs under directory
24928 @c avoid splitting the warning from the explanation:
24930 @item --srcdir=@var{dirname}
24931 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
24932 @code{make} that implements the @code{VPATH} feature.}@*
24933 Use this option to make configurations in directories separate from the
24934 @value{GDBN} source directories. Among other things, you can use this to
24935 build (or maintain) several configurations simultaneously, in separate
24936 directories. @file{configure} writes configuration-specific files in
24937 the current directory, but arranges for them to use the source in the
24938 directory @var{dirname}. @file{configure} creates directories under
24939 the working directory in parallel to the source directories below
24942 @item --norecursion
24943 Configure only the directory level where @file{configure} is executed; do not
24944 propagate configuration to subdirectories.
24946 @item --target=@var{target}
24947 Configure @value{GDBN} for cross-debugging programs running on the specified
24948 @var{target}. Without this option, @value{GDBN} is configured to debug
24949 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
24951 There is no convenient way to generate a list of all available targets.
24953 @item @var{host} @dots{}
24954 Configure @value{GDBN} to run on the specified @var{host}.
24956 There is no convenient way to generate a list of all available hosts.
24959 There are many other options available as well, but they are generally
24960 needed for special purposes only.
24962 @node System-wide configuration
24963 @section System-wide configuration and settings
24964 @cindex system-wide init file
24966 @value{GDBN} can be configured to have a system-wide init file;
24967 this file will be read and executed at startup (@pxref{Startup, , What
24968 @value{GDBN} does during startup}).
24970 Here is the corresponding configure option:
24973 @item --with-system-gdbinit=@var{file}
24974 Specify that the default location of the system-wide init file is
24978 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
24979 it may be subject to relocation. Two possible cases:
24983 If the default location of this init file contains @file{$prefix},
24984 it will be subject to relocation. Suppose that the configure options
24985 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
24986 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
24987 init file is looked for as @file{$install/etc/gdbinit} instead of
24988 @file{$prefix/etc/gdbinit}.
24991 By contrast, if the default location does not contain the prefix,
24992 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
24993 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
24994 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
24995 wherever @value{GDBN} is installed.
24998 @node Maintenance Commands
24999 @appendix Maintenance Commands
25000 @cindex maintenance commands
25001 @cindex internal commands
25003 In addition to commands intended for @value{GDBN} users, @value{GDBN}
25004 includes a number of commands intended for @value{GDBN} developers,
25005 that are not documented elsewhere in this manual. These commands are
25006 provided here for reference. (For commands that turn on debugging
25007 messages, see @ref{Debugging Output}.)
25010 @kindex maint agent
25011 @item maint agent @var{expression}
25012 Translate the given @var{expression} into remote agent bytecodes.
25013 This command is useful for debugging the Agent Expression mechanism
25014 (@pxref{Agent Expressions}).
25016 @kindex maint info breakpoints
25017 @item @anchor{maint info breakpoints}maint info breakpoints
25018 Using the same format as @samp{info breakpoints}, display both the
25019 breakpoints you've set explicitly, and those @value{GDBN} is using for
25020 internal purposes. Internal breakpoints are shown with negative
25021 breakpoint numbers. The type column identifies what kind of breakpoint
25026 Normal, explicitly set breakpoint.
25029 Normal, explicitly set watchpoint.
25032 Internal breakpoint, used to handle correctly stepping through
25033 @code{longjmp} calls.
25035 @item longjmp resume
25036 Internal breakpoint at the target of a @code{longjmp}.
25039 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
25042 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
25045 Shared library events.
25049 @kindex set displaced-stepping
25050 @kindex show displaced-stepping
25051 @cindex displaced stepping support
25052 @cindex out-of-line single-stepping
25053 @item set displaced-stepping
25054 @itemx show displaced-stepping
25055 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
25056 if the target supports it. Displaced stepping is a way to single-step
25057 over breakpoints without removing them from the inferior, by executing
25058 an out-of-line copy of the instruction that was originally at the
25059 breakpoint location. It is also known as out-of-line single-stepping.
25062 @item set displaced-stepping on
25063 If the target architecture supports it, @value{GDBN} will use
25064 displaced stepping to step over breakpoints.
25066 @item set displaced-stepping off
25067 @value{GDBN} will not use displaced stepping to step over breakpoints,
25068 even if such is supported by the target architecture.
25070 @cindex non-stop mode, and @samp{set displaced-stepping}
25071 @item set displaced-stepping auto
25072 This is the default mode. @value{GDBN} will use displaced stepping
25073 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
25074 architecture supports displaced stepping.
25077 @kindex maint check-symtabs
25078 @item maint check-symtabs
25079 Check the consistency of psymtabs and symtabs.
25081 @kindex maint cplus first_component
25082 @item maint cplus first_component @var{name}
25083 Print the first C@t{++} class/namespace component of @var{name}.
25085 @kindex maint cplus namespace
25086 @item maint cplus namespace
25087 Print the list of possible C@t{++} namespaces.
25089 @kindex maint demangle
25090 @item maint demangle @var{name}
25091 Demangle a C@t{++} or Objective-C mangled @var{name}.
25093 @kindex maint deprecate
25094 @kindex maint undeprecate
25095 @cindex deprecated commands
25096 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
25097 @itemx maint undeprecate @var{command}
25098 Deprecate or undeprecate the named @var{command}. Deprecated commands
25099 cause @value{GDBN} to issue a warning when you use them. The optional
25100 argument @var{replacement} says which newer command should be used in
25101 favor of the deprecated one; if it is given, @value{GDBN} will mention
25102 the replacement as part of the warning.
25104 @kindex maint dump-me
25105 @item maint dump-me
25106 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
25107 Cause a fatal signal in the debugger and force it to dump its core.
25108 This is supported only on systems which support aborting a program
25109 with the @code{SIGQUIT} signal.
25111 @kindex maint internal-error
25112 @kindex maint internal-warning
25113 @item maint internal-error @r{[}@var{message-text}@r{]}
25114 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
25115 Cause @value{GDBN} to call the internal function @code{internal_error}
25116 or @code{internal_warning} and hence behave as though an internal error
25117 or internal warning has been detected. In addition to reporting the
25118 internal problem, these functions give the user the opportunity to
25119 either quit @value{GDBN} or create a core file of the current
25120 @value{GDBN} session.
25122 These commands take an optional parameter @var{message-text} that is
25123 used as the text of the error or warning message.
25125 Here's an example of using @code{internal-error}:
25128 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
25129 @dots{}/maint.c:121: internal-error: testing, 1, 2
25130 A problem internal to GDB has been detected. Further
25131 debugging may prove unreliable.
25132 Quit this debugging session? (y or n) @kbd{n}
25133 Create a core file? (y or n) @kbd{n}
25137 @cindex @value{GDBN} internal error
25138 @cindex internal errors, control of @value{GDBN} behavior
25140 @kindex maint set internal-error
25141 @kindex maint show internal-error
25142 @kindex maint set internal-warning
25143 @kindex maint show internal-warning
25144 @item maint set internal-error @var{action} [ask|yes|no]
25145 @itemx maint show internal-error @var{action}
25146 @itemx maint set internal-warning @var{action} [ask|yes|no]
25147 @itemx maint show internal-warning @var{action}
25148 When @value{GDBN} reports an internal problem (error or warning) it
25149 gives the user the opportunity to both quit @value{GDBN} and create a
25150 core file of the current @value{GDBN} session. These commands let you
25151 override the default behaviour for each particular @var{action},
25152 described in the table below.
25156 You can specify that @value{GDBN} should always (yes) or never (no)
25157 quit. The default is to ask the user what to do.
25160 You can specify that @value{GDBN} should always (yes) or never (no)
25161 create a core file. The default is to ask the user what to do.
25164 @kindex maint packet
25165 @item maint packet @var{text}
25166 If @value{GDBN} is talking to an inferior via the serial protocol,
25167 then this command sends the string @var{text} to the inferior, and
25168 displays the response packet. @value{GDBN} supplies the initial
25169 @samp{$} character, the terminating @samp{#} character, and the
25172 @kindex maint print architecture
25173 @item maint print architecture @r{[}@var{file}@r{]}
25174 Print the entire architecture configuration. The optional argument
25175 @var{file} names the file where the output goes.
25177 @kindex maint print c-tdesc
25178 @item maint print c-tdesc
25179 Print the current target description (@pxref{Target Descriptions}) as
25180 a C source file. The created source file can be used in @value{GDBN}
25181 when an XML parser is not available to parse the description.
25183 @kindex maint print dummy-frames
25184 @item maint print dummy-frames
25185 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
25188 (@value{GDBP}) @kbd{b add}
25190 (@value{GDBP}) @kbd{print add(2,3)}
25191 Breakpoint 2, add (a=2, b=3) at @dots{}
25193 The program being debugged stopped while in a function called from GDB.
25195 (@value{GDBP}) @kbd{maint print dummy-frames}
25196 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
25197 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
25198 call_lo=0x01014000 call_hi=0x01014001
25202 Takes an optional file parameter.
25204 @kindex maint print registers
25205 @kindex maint print raw-registers
25206 @kindex maint print cooked-registers
25207 @kindex maint print register-groups
25208 @item maint print registers @r{[}@var{file}@r{]}
25209 @itemx maint print raw-registers @r{[}@var{file}@r{]}
25210 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
25211 @itemx maint print register-groups @r{[}@var{file}@r{]}
25212 Print @value{GDBN}'s internal register data structures.
25214 The command @code{maint print raw-registers} includes the contents of
25215 the raw register cache; the command @code{maint print cooked-registers}
25216 includes the (cooked) value of all registers; and the command
25217 @code{maint print register-groups} includes the groups that each
25218 register is a member of. @xref{Registers,, Registers, gdbint,
25219 @value{GDBN} Internals}.
25221 These commands take an optional parameter, a file name to which to
25222 write the information.
25224 @kindex maint print reggroups
25225 @item maint print reggroups @r{[}@var{file}@r{]}
25226 Print @value{GDBN}'s internal register group data structures. The
25227 optional argument @var{file} tells to what file to write the
25230 The register groups info looks like this:
25233 (@value{GDBP}) @kbd{maint print reggroups}
25246 This command forces @value{GDBN} to flush its internal register cache.
25248 @kindex maint print objfiles
25249 @cindex info for known object files
25250 @item maint print objfiles
25251 Print a dump of all known object files. For each object file, this
25252 command prints its name, address in memory, and all of its psymtabs
25255 @kindex maint print statistics
25256 @cindex bcache statistics
25257 @item maint print statistics
25258 This command prints, for each object file in the program, various data
25259 about that object file followed by the byte cache (@dfn{bcache})
25260 statistics for the object file. The objfile data includes the number
25261 of minimal, partial, full, and stabs symbols, the number of types
25262 defined by the objfile, the number of as yet unexpanded psym tables,
25263 the number of line tables and string tables, and the amount of memory
25264 used by the various tables. The bcache statistics include the counts,
25265 sizes, and counts of duplicates of all and unique objects, max,
25266 average, and median entry size, total memory used and its overhead and
25267 savings, and various measures of the hash table size and chain
25270 @kindex maint print target-stack
25271 @cindex target stack description
25272 @item maint print target-stack
25273 A @dfn{target} is an interface between the debugger and a particular
25274 kind of file or process. Targets can be stacked in @dfn{strata},
25275 so that more than one target can potentially respond to a request.
25276 In particular, memory accesses will walk down the stack of targets
25277 until they find a target that is interested in handling that particular
25280 This command prints a short description of each layer that was pushed on
25281 the @dfn{target stack}, starting from the top layer down to the bottom one.
25283 @kindex maint print type
25284 @cindex type chain of a data type
25285 @item maint print type @var{expr}
25286 Print the type chain for a type specified by @var{expr}. The argument
25287 can be either a type name or a symbol. If it is a symbol, the type of
25288 that symbol is described. The type chain produced by this command is
25289 a recursive definition of the data type as stored in @value{GDBN}'s
25290 data structures, including its flags and contained types.
25292 @kindex maint set dwarf2 max-cache-age
25293 @kindex maint show dwarf2 max-cache-age
25294 @item maint set dwarf2 max-cache-age
25295 @itemx maint show dwarf2 max-cache-age
25296 Control the DWARF 2 compilation unit cache.
25298 @cindex DWARF 2 compilation units cache
25299 In object files with inter-compilation-unit references, such as those
25300 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
25301 reader needs to frequently refer to previously read compilation units.
25302 This setting controls how long a compilation unit will remain in the
25303 cache if it is not referenced. A higher limit means that cached
25304 compilation units will be stored in memory longer, and more total
25305 memory will be used. Setting it to zero disables caching, which will
25306 slow down @value{GDBN} startup, but reduce memory consumption.
25308 @kindex maint set profile
25309 @kindex maint show profile
25310 @cindex profiling GDB
25311 @item maint set profile
25312 @itemx maint show profile
25313 Control profiling of @value{GDBN}.
25315 Profiling will be disabled until you use the @samp{maint set profile}
25316 command to enable it. When you enable profiling, the system will begin
25317 collecting timing and execution count data; when you disable profiling or
25318 exit @value{GDBN}, the results will be written to a log file. Remember that
25319 if you use profiling, @value{GDBN} will overwrite the profiling log file
25320 (often called @file{gmon.out}). If you have a record of important profiling
25321 data in a @file{gmon.out} file, be sure to move it to a safe location.
25323 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
25324 compiled with the @samp{-pg} compiler option.
25326 @kindex maint set linux-async
25327 @kindex maint show linux-async
25328 @cindex asynchronous support
25329 @item maint set linux-async
25330 @itemx maint show linux-async
25331 Control the GNU/Linux native asynchronous support
25332 (@pxref{Background Execution}) of @value{GDBN}.
25334 GNU/Linux native asynchronous support will be disabled until you use
25335 the @samp{maint set linux-async} command to enable it.
25337 @kindex maint set remote-async
25338 @kindex maint show remote-async
25339 @cindex asynchronous support
25340 @item maint set remote-async
25341 @itemx maint show remote-async
25342 Control the remote asynchronous support
25343 (@pxref{Background Execution}) of @value{GDBN}.
25345 Remote asynchronous support will be disabled until you use
25346 the @samp{maint set remote-async} command to enable it.
25348 @kindex maint show-debug-regs
25349 @cindex x86 hardware debug registers
25350 @item maint show-debug-regs
25351 Control whether to show variables that mirror the x86 hardware debug
25352 registers. Use @code{ON} to enable, @code{OFF} to disable. If
25353 enabled, the debug registers values are shown when @value{GDBN} inserts or
25354 removes a hardware breakpoint or watchpoint, and when the inferior
25355 triggers a hardware-assisted breakpoint or watchpoint.
25357 @kindex maint space
25358 @cindex memory used by commands
25360 Control whether to display memory usage for each command. If set to a
25361 nonzero value, @value{GDBN} will display how much memory each command
25362 took, following the command's own output. This can also be requested
25363 by invoking @value{GDBN} with the @option{--statistics} command-line
25364 switch (@pxref{Mode Options}).
25367 @cindex time of command execution
25369 Control whether to display the execution time for each command. If
25370 set to a nonzero value, @value{GDBN} will display how much time it
25371 took to execute each command, following the command's own output.
25372 The time is not printed for the commands that run the target, since
25373 there's no mechanism currently to compute how much time was spend
25374 by @value{GDBN} and how much time was spend by the program been debugged.
25375 it's not possibly currently
25376 This can also be requested by invoking @value{GDBN} with the
25377 @option{--statistics} command-line switch (@pxref{Mode Options}).
25379 @kindex maint translate-address
25380 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
25381 Find the symbol stored at the location specified by the address
25382 @var{addr} and an optional section name @var{section}. If found,
25383 @value{GDBN} prints the name of the closest symbol and an offset from
25384 the symbol's location to the specified address. This is similar to
25385 the @code{info address} command (@pxref{Symbols}), except that this
25386 command also allows to find symbols in other sections.
25388 If section was not specified, the section in which the symbol was found
25389 is also printed. For dynamically linked executables, the name of
25390 executable or shared library containing the symbol is printed as well.
25394 The following command is useful for non-interactive invocations of
25395 @value{GDBN}, such as in the test suite.
25398 @item set watchdog @var{nsec}
25399 @kindex set watchdog
25400 @cindex watchdog timer
25401 @cindex timeout for commands
25402 Set the maximum number of seconds @value{GDBN} will wait for the
25403 target operation to finish. If this time expires, @value{GDBN}
25404 reports and error and the command is aborted.
25406 @item show watchdog
25407 Show the current setting of the target wait timeout.
25410 @node Remote Protocol
25411 @appendix @value{GDBN} Remote Serial Protocol
25416 * Stop Reply Packets::
25417 * General Query Packets::
25418 * Register Packet Format::
25419 * Tracepoint Packets::
25420 * Host I/O Packets::
25422 * Notification Packets::
25423 * Remote Non-Stop::
25424 * Packet Acknowledgment::
25426 * File-I/O Remote Protocol Extension::
25427 * Library List Format::
25428 * Memory Map Format::
25434 There may be occasions when you need to know something about the
25435 protocol---for example, if there is only one serial port to your target
25436 machine, you might want your program to do something special if it
25437 recognizes a packet meant for @value{GDBN}.
25439 In the examples below, @samp{->} and @samp{<-} are used to indicate
25440 transmitted and received data, respectively.
25442 @cindex protocol, @value{GDBN} remote serial
25443 @cindex serial protocol, @value{GDBN} remote
25444 @cindex remote serial protocol
25445 All @value{GDBN} commands and responses (other than acknowledgments
25446 and notifications, see @ref{Notification Packets}) are sent as a
25447 @var{packet}. A @var{packet} is introduced with the character
25448 @samp{$}, the actual @var{packet-data}, and the terminating character
25449 @samp{#} followed by a two-digit @var{checksum}:
25452 @code{$}@var{packet-data}@code{#}@var{checksum}
25456 @cindex checksum, for @value{GDBN} remote
25458 The two-digit @var{checksum} is computed as the modulo 256 sum of all
25459 characters between the leading @samp{$} and the trailing @samp{#} (an
25460 eight bit unsigned checksum).
25462 Implementors should note that prior to @value{GDBN} 5.0 the protocol
25463 specification also included an optional two-digit @var{sequence-id}:
25466 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
25469 @cindex sequence-id, for @value{GDBN} remote
25471 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
25472 has never output @var{sequence-id}s. Stubs that handle packets added
25473 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
25475 When either the host or the target machine receives a packet, the first
25476 response expected is an acknowledgment: either @samp{+} (to indicate
25477 the package was received correctly) or @samp{-} (to request
25481 -> @code{$}@var{packet-data}@code{#}@var{checksum}
25486 The @samp{+}/@samp{-} acknowledgments can be disabled
25487 once a connection is established.
25488 @xref{Packet Acknowledgment}, for details.
25490 The host (@value{GDBN}) sends @var{command}s, and the target (the
25491 debugging stub incorporated in your program) sends a @var{response}. In
25492 the case of step and continue @var{command}s, the response is only sent
25493 when the operation has completed, and the target has again stopped all
25494 threads in all attached processes. This is the default all-stop mode
25495 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
25496 execution mode; see @ref{Remote Non-Stop}, for details.
25498 @var{packet-data} consists of a sequence of characters with the
25499 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
25502 @cindex remote protocol, field separator
25503 Fields within the packet should be separated using @samp{,} @samp{;} or
25504 @samp{:}. Except where otherwise noted all numbers are represented in
25505 @sc{hex} with leading zeros suppressed.
25507 Implementors should note that prior to @value{GDBN} 5.0, the character
25508 @samp{:} could not appear as the third character in a packet (as it
25509 would potentially conflict with the @var{sequence-id}).
25511 @cindex remote protocol, binary data
25512 @anchor{Binary Data}
25513 Binary data in most packets is encoded either as two hexadecimal
25514 digits per byte of binary data. This allowed the traditional remote
25515 protocol to work over connections which were only seven-bit clean.
25516 Some packets designed more recently assume an eight-bit clean
25517 connection, and use a more efficient encoding to send and receive
25520 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
25521 as an escape character. Any escaped byte is transmitted as the escape
25522 character followed by the original character XORed with @code{0x20}.
25523 For example, the byte @code{0x7d} would be transmitted as the two
25524 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
25525 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
25526 @samp{@}}) must always be escaped. Responses sent by the stub
25527 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
25528 is not interpreted as the start of a run-length encoded sequence
25531 Response @var{data} can be run-length encoded to save space.
25532 Run-length encoding replaces runs of identical characters with one
25533 instance of the repeated character, followed by a @samp{*} and a
25534 repeat count. The repeat count is itself sent encoded, to avoid
25535 binary characters in @var{data}: a value of @var{n} is sent as
25536 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
25537 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
25538 code 32) for a repeat count of 3. (This is because run-length
25539 encoding starts to win for counts 3 or more.) Thus, for example,
25540 @samp{0* } is a run-length encoding of ``0000'': the space character
25541 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
25544 The printable characters @samp{#} and @samp{$} or with a numeric value
25545 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
25546 seven repeats (@samp{$}) can be expanded using a repeat count of only
25547 five (@samp{"}). For example, @samp{00000000} can be encoded as
25550 The error response returned for some packets includes a two character
25551 error number. That number is not well defined.
25553 @cindex empty response, for unsupported packets
25554 For any @var{command} not supported by the stub, an empty response
25555 (@samp{$#00}) should be returned. That way it is possible to extend the
25556 protocol. A newer @value{GDBN} can tell if a packet is supported based
25559 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
25560 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
25566 The following table provides a complete list of all currently defined
25567 @var{command}s and their corresponding response @var{data}.
25568 @xref{File-I/O Remote Protocol Extension}, for details about the File
25569 I/O extension of the remote protocol.
25571 Each packet's description has a template showing the packet's overall
25572 syntax, followed by an explanation of the packet's meaning. We
25573 include spaces in some of the templates for clarity; these are not
25574 part of the packet's syntax. No @value{GDBN} packet uses spaces to
25575 separate its components. For example, a template like @samp{foo
25576 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
25577 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
25578 @var{baz}. @value{GDBN} does not transmit a space character between the
25579 @samp{foo} and the @var{bar}, or between the @var{bar} and the
25582 @cindex @var{thread-id}, in remote protocol
25583 @anchor{thread-id syntax}
25584 Several packets and replies include a @var{thread-id} field to identify
25585 a thread. Normally these are positive numbers with a target-specific
25586 interpretation, formatted as big-endian hex strings. A @var{thread-id}
25587 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
25590 In addition, the remote protocol supports a multiprocess feature in
25591 which the @var{thread-id} syntax is extended to optionally include both
25592 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
25593 The @var{pid} (process) and @var{tid} (thread) components each have the
25594 format described above: a positive number with target-specific
25595 interpretation formatted as a big-endian hex string, literal @samp{-1}
25596 to indicate all processes or threads (respectively), or @samp{0} to
25597 indicate an arbitrary process or thread. Specifying just a process, as
25598 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
25599 error to specify all processes but a specific thread, such as
25600 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
25601 for those packets and replies explicitly documented to include a process
25602 ID, rather than a @var{thread-id}.
25604 The multiprocess @var{thread-id} syntax extensions are only used if both
25605 @value{GDBN} and the stub report support for the @samp{multiprocess}
25606 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
25609 Note that all packet forms beginning with an upper- or lower-case
25610 letter, other than those described here, are reserved for future use.
25612 Here are the packet descriptions.
25617 @cindex @samp{!} packet
25618 @anchor{extended mode}
25619 Enable extended mode. In extended mode, the remote server is made
25620 persistent. The @samp{R} packet is used to restart the program being
25626 The remote target both supports and has enabled extended mode.
25630 @cindex @samp{?} packet
25631 Indicate the reason the target halted. The reply is the same as for
25632 step and continue. This packet has a special interpretation when the
25633 target is in non-stop mode; see @ref{Remote Non-Stop}.
25636 @xref{Stop Reply Packets}, for the reply specifications.
25638 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
25639 @cindex @samp{A} packet
25640 Initialized @code{argv[]} array passed into program. @var{arglen}
25641 specifies the number of bytes in the hex encoded byte stream
25642 @var{arg}. See @code{gdbserver} for more details.
25647 The arguments were set.
25653 @cindex @samp{b} packet
25654 (Don't use this packet; its behavior is not well-defined.)
25655 Change the serial line speed to @var{baud}.
25657 JTC: @emph{When does the transport layer state change? When it's
25658 received, or after the ACK is transmitted. In either case, there are
25659 problems if the command or the acknowledgment packet is dropped.}
25661 Stan: @emph{If people really wanted to add something like this, and get
25662 it working for the first time, they ought to modify ser-unix.c to send
25663 some kind of out-of-band message to a specially-setup stub and have the
25664 switch happen "in between" packets, so that from remote protocol's point
25665 of view, nothing actually happened.}
25667 @item B @var{addr},@var{mode}
25668 @cindex @samp{B} packet
25669 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
25670 breakpoint at @var{addr}.
25672 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
25673 (@pxref{insert breakpoint or watchpoint packet}).
25676 @cindex @samp{bc} packet
25677 Backward continue. Execute the target system in reverse. No parameter.
25678 @xref{Reverse Execution}, for more information.
25681 @xref{Stop Reply Packets}, for the reply specifications.
25684 @cindex @samp{bs} packet
25685 Backward single step. Execute one instruction in reverse. No parameter.
25686 @xref{Reverse Execution}, for more information.
25689 @xref{Stop Reply Packets}, for the reply specifications.
25691 @item c @r{[}@var{addr}@r{]}
25692 @cindex @samp{c} packet
25693 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
25694 resume at current address.
25697 @xref{Stop Reply Packets}, for the reply specifications.
25699 @item C @var{sig}@r{[};@var{addr}@r{]}
25700 @cindex @samp{C} packet
25701 Continue with signal @var{sig} (hex signal number). If
25702 @samp{;@var{addr}} is omitted, resume at same address.
25705 @xref{Stop Reply Packets}, for the reply specifications.
25708 @cindex @samp{d} packet
25711 Don't use this packet; instead, define a general set packet
25712 (@pxref{General Query Packets}).
25716 @cindex @samp{D} packet
25717 The first form of the packet is used to detach @value{GDBN} from the
25718 remote system. It is sent to the remote target
25719 before @value{GDBN} disconnects via the @code{detach} command.
25721 The second form, including a process ID, is used when multiprocess
25722 protocol extensions are enabled (@pxref{multiprocess extensions}), to
25723 detach only a specific process. The @var{pid} is specified as a
25724 big-endian hex string.
25734 @item F @var{RC},@var{EE},@var{CF};@var{XX}
25735 @cindex @samp{F} packet
25736 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
25737 This is part of the File-I/O protocol extension. @xref{File-I/O
25738 Remote Protocol Extension}, for the specification.
25741 @anchor{read registers packet}
25742 @cindex @samp{g} packet
25743 Read general registers.
25747 @item @var{XX@dots{}}
25748 Each byte of register data is described by two hex digits. The bytes
25749 with the register are transmitted in target byte order. The size of
25750 each register and their position within the @samp{g} packet are
25751 determined by the @value{GDBN} internal gdbarch functions
25752 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
25753 specification of several standard @samp{g} packets is specified below.
25758 @item G @var{XX@dots{}}
25759 @cindex @samp{G} packet
25760 Write general registers. @xref{read registers packet}, for a
25761 description of the @var{XX@dots{}} data.
25771 @item H @var{c} @var{thread-id}
25772 @cindex @samp{H} packet
25773 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
25774 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
25775 should be @samp{c} for step and continue operations, @samp{g} for other
25776 operations. The thread designator @var{thread-id} has the format and
25777 interpretation described in @ref{thread-id syntax}.
25788 @c 'H': How restrictive (or permissive) is the thread model. If a
25789 @c thread is selected and stopped, are other threads allowed
25790 @c to continue to execute? As I mentioned above, I think the
25791 @c semantics of each command when a thread is selected must be
25792 @c described. For example:
25794 @c 'g': If the stub supports threads and a specific thread is
25795 @c selected, returns the register block from that thread;
25796 @c otherwise returns current registers.
25798 @c 'G' If the stub supports threads and a specific thread is
25799 @c selected, sets the registers of the register block of
25800 @c that thread; otherwise sets current registers.
25802 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
25803 @anchor{cycle step packet}
25804 @cindex @samp{i} packet
25805 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
25806 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
25807 step starting at that address.
25810 @cindex @samp{I} packet
25811 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
25815 @cindex @samp{k} packet
25818 FIXME: @emph{There is no description of how to operate when a specific
25819 thread context has been selected (i.e.@: does 'k' kill only that
25822 @item m @var{addr},@var{length}
25823 @cindex @samp{m} packet
25824 Read @var{length} bytes of memory starting at address @var{addr}.
25825 Note that @var{addr} may not be aligned to any particular boundary.
25827 The stub need not use any particular size or alignment when gathering
25828 data from memory for the response; even if @var{addr} is word-aligned
25829 and @var{length} is a multiple of the word size, the stub is free to
25830 use byte accesses, or not. For this reason, this packet may not be
25831 suitable for accessing memory-mapped I/O devices.
25832 @cindex alignment of remote memory accesses
25833 @cindex size of remote memory accesses
25834 @cindex memory, alignment and size of remote accesses
25838 @item @var{XX@dots{}}
25839 Memory contents; each byte is transmitted as a two-digit hexadecimal
25840 number. The reply may contain fewer bytes than requested if the
25841 server was able to read only part of the region of memory.
25846 @item M @var{addr},@var{length}:@var{XX@dots{}}
25847 @cindex @samp{M} packet
25848 Write @var{length} bytes of memory starting at address @var{addr}.
25849 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
25850 hexadecimal number.
25857 for an error (this includes the case where only part of the data was
25862 @cindex @samp{p} packet
25863 Read the value of register @var{n}; @var{n} is in hex.
25864 @xref{read registers packet}, for a description of how the returned
25865 register value is encoded.
25869 @item @var{XX@dots{}}
25870 the register's value
25874 Indicating an unrecognized @var{query}.
25877 @item P @var{n@dots{}}=@var{r@dots{}}
25878 @anchor{write register packet}
25879 @cindex @samp{P} packet
25880 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
25881 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
25882 digits for each byte in the register (target byte order).
25892 @item q @var{name} @var{params}@dots{}
25893 @itemx Q @var{name} @var{params}@dots{}
25894 @cindex @samp{q} packet
25895 @cindex @samp{Q} packet
25896 General query (@samp{q}) and set (@samp{Q}). These packets are
25897 described fully in @ref{General Query Packets}.
25900 @cindex @samp{r} packet
25901 Reset the entire system.
25903 Don't use this packet; use the @samp{R} packet instead.
25906 @cindex @samp{R} packet
25907 Restart the program being debugged. @var{XX}, while needed, is ignored.
25908 This packet is only available in extended mode (@pxref{extended mode}).
25910 The @samp{R} packet has no reply.
25912 @item s @r{[}@var{addr}@r{]}
25913 @cindex @samp{s} packet
25914 Single step. @var{addr} is the address at which to resume. If
25915 @var{addr} is omitted, resume at same address.
25918 @xref{Stop Reply Packets}, for the reply specifications.
25920 @item S @var{sig}@r{[};@var{addr}@r{]}
25921 @anchor{step with signal packet}
25922 @cindex @samp{S} packet
25923 Step with signal. This is analogous to the @samp{C} packet, but
25924 requests a single-step, rather than a normal resumption of execution.
25927 @xref{Stop Reply Packets}, for the reply specifications.
25929 @item t @var{addr}:@var{PP},@var{MM}
25930 @cindex @samp{t} packet
25931 Search backwards starting at address @var{addr} for a match with pattern
25932 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
25933 @var{addr} must be at least 3 digits.
25935 @item T @var{thread-id}
25936 @cindex @samp{T} packet
25937 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
25942 thread is still alive
25948 Packets starting with @samp{v} are identified by a multi-letter name,
25949 up to the first @samp{;} or @samp{?} (or the end of the packet).
25951 @item vAttach;@var{pid}
25952 @cindex @samp{vAttach} packet
25953 Attach to a new process with the specified process ID @var{pid}.
25954 The process ID is a
25955 hexadecimal integer identifying the process. In all-stop mode, all
25956 threads in the attached process are stopped; in non-stop mode, it may be
25957 attached without being stopped if that is supported by the target.
25959 @c In non-stop mode, on a successful vAttach, the stub should set the
25960 @c current thread to a thread of the newly-attached process. After
25961 @c attaching, GDB queries for the attached process's thread ID with qC.
25962 @c Also note that, from a user perspective, whether or not the
25963 @c target is stopped on attach in non-stop mode depends on whether you
25964 @c use the foreground or background version of the attach command, not
25965 @c on what vAttach does; GDB does the right thing with respect to either
25966 @c stopping or restarting threads.
25968 This packet is only available in extended mode (@pxref{extended mode}).
25974 @item @r{Any stop packet}
25975 for success in all-stop mode (@pxref{Stop Reply Packets})
25977 for success in non-stop mode (@pxref{Remote Non-Stop})
25980 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
25981 @cindex @samp{vCont} packet
25982 Resume the inferior, specifying different actions for each thread.
25983 If an action is specified with no @var{thread-id}, then it is applied to any
25984 threads that don't have a specific action specified; if no default action is
25985 specified then other threads should remain stopped in all-stop mode and
25986 in their current state in non-stop mode.
25987 Specifying multiple
25988 default actions is an error; specifying no actions is also an error.
25989 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
25991 Currently supported actions are:
25997 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
26001 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
26005 Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
26008 The optional argument @var{addr} normally associated with the
26009 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
26010 not supported in @samp{vCont}.
26012 The @samp{t} and @samp{T} actions are only relevant in non-stop mode
26013 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
26014 A stop reply should be generated for any affected thread not already stopped.
26015 When a thread is stopped by means of a @samp{t} action,
26016 the corresponding stop reply should indicate that the thread has stopped with
26017 signal @samp{0}, regardless of whether the target uses some other signal
26018 as an implementation detail.
26021 @xref{Stop Reply Packets}, for the reply specifications.
26024 @cindex @samp{vCont?} packet
26025 Request a list of actions supported by the @samp{vCont} packet.
26029 @item vCont@r{[};@var{action}@dots{}@r{]}
26030 The @samp{vCont} packet is supported. Each @var{action} is a supported
26031 command in the @samp{vCont} packet.
26033 The @samp{vCont} packet is not supported.
26036 @item vFile:@var{operation}:@var{parameter}@dots{}
26037 @cindex @samp{vFile} packet
26038 Perform a file operation on the target system. For details,
26039 see @ref{Host I/O Packets}.
26041 @item vFlashErase:@var{addr},@var{length}
26042 @cindex @samp{vFlashErase} packet
26043 Direct the stub to erase @var{length} bytes of flash starting at
26044 @var{addr}. The region may enclose any number of flash blocks, but
26045 its start and end must fall on block boundaries, as indicated by the
26046 flash block size appearing in the memory map (@pxref{Memory Map
26047 Format}). @value{GDBN} groups flash memory programming operations
26048 together, and sends a @samp{vFlashDone} request after each group; the
26049 stub is allowed to delay erase operation until the @samp{vFlashDone}
26050 packet is received.
26052 The stub must support @samp{vCont} if it reports support for
26053 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
26054 this case @samp{vCont} actions can be specified to apply to all threads
26055 in a process by using the @samp{p@var{pid}.-1} form of the
26066 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
26067 @cindex @samp{vFlashWrite} packet
26068 Direct the stub to write data to flash address @var{addr}. The data
26069 is passed in binary form using the same encoding as for the @samp{X}
26070 packet (@pxref{Binary Data}). The memory ranges specified by
26071 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
26072 not overlap, and must appear in order of increasing addresses
26073 (although @samp{vFlashErase} packets for higher addresses may already
26074 have been received; the ordering is guaranteed only between
26075 @samp{vFlashWrite} packets). If a packet writes to an address that was
26076 neither erased by a preceding @samp{vFlashErase} packet nor by some other
26077 target-specific method, the results are unpredictable.
26085 for vFlashWrite addressing non-flash memory
26091 @cindex @samp{vFlashDone} packet
26092 Indicate to the stub that flash programming operation is finished.
26093 The stub is permitted to delay or batch the effects of a group of
26094 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
26095 @samp{vFlashDone} packet is received. The contents of the affected
26096 regions of flash memory are unpredictable until the @samp{vFlashDone}
26097 request is completed.
26099 @item vKill;@var{pid}
26100 @cindex @samp{vKill} packet
26101 Kill the process with the specified process ID. @var{pid} is a
26102 hexadecimal integer identifying the process. This packet is used in
26103 preference to @samp{k} when multiprocess protocol extensions are
26104 supported; see @ref{multiprocess extensions}.
26114 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
26115 @cindex @samp{vRun} packet
26116 Run the program @var{filename}, passing it each @var{argument} on its
26117 command line. The file and arguments are hex-encoded strings. If
26118 @var{filename} is an empty string, the stub may use a default program
26119 (e.g.@: the last program run). The program is created in the stopped
26122 @c FIXME: What about non-stop mode?
26124 This packet is only available in extended mode (@pxref{extended mode}).
26130 @item @r{Any stop packet}
26131 for success (@pxref{Stop Reply Packets})
26135 @anchor{vStopped packet}
26136 @cindex @samp{vStopped} packet
26138 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
26139 reply and prompt for the stub to report another one.
26143 @item @r{Any stop packet}
26144 if there is another unreported stop event (@pxref{Stop Reply Packets})
26146 if there are no unreported stop events
26149 @item X @var{addr},@var{length}:@var{XX@dots{}}
26151 @cindex @samp{X} packet
26152 Write data to memory, where the data is transmitted in binary.
26153 @var{addr} is address, @var{length} is number of bytes,
26154 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
26164 @item z @var{type},@var{addr},@var{length}
26165 @itemx Z @var{type},@var{addr},@var{length}
26166 @anchor{insert breakpoint or watchpoint packet}
26167 @cindex @samp{z} packet
26168 @cindex @samp{Z} packets
26169 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
26170 watchpoint starting at address @var{address} and covering the next
26171 @var{length} bytes.
26173 Each breakpoint and watchpoint packet @var{type} is documented
26176 @emph{Implementation notes: A remote target shall return an empty string
26177 for an unrecognized breakpoint or watchpoint packet @var{type}. A
26178 remote target shall support either both or neither of a given
26179 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
26180 avoid potential problems with duplicate packets, the operations should
26181 be implemented in an idempotent way.}
26183 @item z0,@var{addr},@var{length}
26184 @itemx Z0,@var{addr},@var{length}
26185 @cindex @samp{z0} packet
26186 @cindex @samp{Z0} packet
26187 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
26188 @var{addr} of size @var{length}.
26190 A memory breakpoint is implemented by replacing the instruction at
26191 @var{addr} with a software breakpoint or trap instruction. The
26192 @var{length} is used by targets that indicates the size of the
26193 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
26194 @sc{mips} can insert either a 2 or 4 byte breakpoint).
26196 @emph{Implementation note: It is possible for a target to copy or move
26197 code that contains memory breakpoints (e.g., when implementing
26198 overlays). The behavior of this packet, in the presence of such a
26199 target, is not defined.}
26211 @item z1,@var{addr},@var{length}
26212 @itemx Z1,@var{addr},@var{length}
26213 @cindex @samp{z1} packet
26214 @cindex @samp{Z1} packet
26215 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
26216 address @var{addr} of size @var{length}.
26218 A hardware breakpoint is implemented using a mechanism that is not
26219 dependant on being able to modify the target's memory.
26221 @emph{Implementation note: A hardware breakpoint is not affected by code
26234 @item z2,@var{addr},@var{length}
26235 @itemx Z2,@var{addr},@var{length}
26236 @cindex @samp{z2} packet
26237 @cindex @samp{Z2} packet
26238 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
26250 @item z3,@var{addr},@var{length}
26251 @itemx Z3,@var{addr},@var{length}
26252 @cindex @samp{z3} packet
26253 @cindex @samp{Z3} packet
26254 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
26266 @item z4,@var{addr},@var{length}
26267 @itemx Z4,@var{addr},@var{length}
26268 @cindex @samp{z4} packet
26269 @cindex @samp{Z4} packet
26270 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
26284 @node Stop Reply Packets
26285 @section Stop Reply Packets
26286 @cindex stop reply packets
26288 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
26289 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
26290 receive any of the below as a reply. Except for @samp{?}
26291 and @samp{vStopped}, that reply is only returned
26292 when the target halts. In the below the exact meaning of @dfn{signal
26293 number} is defined by the header @file{include/gdb/signals.h} in the
26294 @value{GDBN} source code.
26296 As in the description of request packets, we include spaces in the
26297 reply templates for clarity; these are not part of the reply packet's
26298 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
26304 The program received signal number @var{AA} (a two-digit hexadecimal
26305 number). This is equivalent to a @samp{T} response with no
26306 @var{n}:@var{r} pairs.
26308 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
26309 @cindex @samp{T} packet reply
26310 The program received signal number @var{AA} (a two-digit hexadecimal
26311 number). This is equivalent to an @samp{S} response, except that the
26312 @samp{@var{n}:@var{r}} pairs can carry values of important registers
26313 and other information directly in the stop reply packet, reducing
26314 round-trip latency. Single-step and breakpoint traps are reported
26315 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
26319 If @var{n} is a hexadecimal number, it is a register number, and the
26320 corresponding @var{r} gives that register's value. @var{r} is a
26321 series of bytes in target byte order, with each byte given by a
26322 two-digit hex number.
26325 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
26326 the stopped thread, as specified in @ref{thread-id syntax}.
26329 If @var{n} is a recognized @dfn{stop reason}, it describes a more
26330 specific event that stopped the target. The currently defined stop
26331 reasons are listed below. @var{aa} should be @samp{05}, the trap
26332 signal. At most one stop reason should be present.
26335 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
26336 and go on to the next; this allows us to extend the protocol in the
26340 The currently defined stop reasons are:
26346 The packet indicates a watchpoint hit, and @var{r} is the data address, in
26349 @cindex shared library events, remote reply
26351 The packet indicates that the loaded libraries have changed.
26352 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
26353 list of loaded libraries. @var{r} is ignored.
26355 @cindex replay log events, remote reply
26357 The packet indicates that the target cannot continue replaying
26358 logged execution events, because it has reached the end (or the
26359 beginning when executing backward) of the log. The value of @var{r}
26360 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
26361 for more information.
26367 @itemx W @var{AA} ; process:@var{pid}
26368 The process exited, and @var{AA} is the exit status. This is only
26369 applicable to certain targets.
26371 The second form of the response, including the process ID of the exited
26372 process, can be used only when @value{GDBN} has reported support for
26373 multiprocess protocol extensions; see @ref{multiprocess extensions}.
26374 The @var{pid} is formatted as a big-endian hex string.
26377 @itemx X @var{AA} ; process:@var{pid}
26378 The process terminated with signal @var{AA}.
26380 The second form of the response, including the process ID of the
26381 terminated process, can be used only when @value{GDBN} has reported
26382 support for multiprocess protocol extensions; see @ref{multiprocess
26383 extensions}. The @var{pid} is formatted as a big-endian hex string.
26385 @item O @var{XX}@dots{}
26386 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
26387 written as the program's console output. This can happen at any time
26388 while the program is running and the debugger should continue to wait
26389 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
26391 @item F @var{call-id},@var{parameter}@dots{}
26392 @var{call-id} is the identifier which says which host system call should
26393 be called. This is just the name of the function. Translation into the
26394 correct system call is only applicable as it's defined in @value{GDBN}.
26395 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
26398 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
26399 this very system call.
26401 The target replies with this packet when it expects @value{GDBN} to
26402 call a host system call on behalf of the target. @value{GDBN} replies
26403 with an appropriate @samp{F} packet and keeps up waiting for the next
26404 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
26405 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
26406 Protocol Extension}, for more details.
26410 @node General Query Packets
26411 @section General Query Packets
26412 @cindex remote query requests
26414 Packets starting with @samp{q} are @dfn{general query packets};
26415 packets starting with @samp{Q} are @dfn{general set packets}. General
26416 query and set packets are a semi-unified form for retrieving and
26417 sending information to and from the stub.
26419 The initial letter of a query or set packet is followed by a name
26420 indicating what sort of thing the packet applies to. For example,
26421 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
26422 definitions with the stub. These packet names follow some
26427 The name must not contain commas, colons or semicolons.
26429 Most @value{GDBN} query and set packets have a leading upper case
26432 The names of custom vendor packets should use a company prefix, in
26433 lower case, followed by a period. For example, packets designed at
26434 the Acme Corporation might begin with @samp{qacme.foo} (for querying
26435 foos) or @samp{Qacme.bar} (for setting bars).
26438 The name of a query or set packet should be separated from any
26439 parameters by a @samp{:}; the parameters themselves should be
26440 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
26441 full packet name, and check for a separator or the end of the packet,
26442 in case two packet names share a common prefix. New packets should not begin
26443 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
26444 packets predate these conventions, and have arguments without any terminator
26445 for the packet name; we suspect they are in widespread use in places that
26446 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
26447 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
26450 Like the descriptions of the other packets, each description here
26451 has a template showing the packet's overall syntax, followed by an
26452 explanation of the packet's meaning. We include spaces in some of the
26453 templates for clarity; these are not part of the packet's syntax. No
26454 @value{GDBN} packet uses spaces to separate its components.
26456 Here are the currently defined query and set packets:
26461 @cindex current thread, remote request
26462 @cindex @samp{qC} packet
26463 Return the current thread ID.
26467 @item QC @var{thread-id}
26468 Where @var{thread-id} is a thread ID as documented in
26469 @ref{thread-id syntax}.
26470 @item @r{(anything else)}
26471 Any other reply implies the old thread ID.
26474 @item qCRC:@var{addr},@var{length}
26475 @cindex CRC of memory block, remote request
26476 @cindex @samp{qCRC} packet
26477 Compute the CRC checksum of a block of memory.
26481 An error (such as memory fault)
26482 @item C @var{crc32}
26483 The specified memory region's checksum is @var{crc32}.
26487 @itemx qsThreadInfo
26488 @cindex list active threads, remote request
26489 @cindex @samp{qfThreadInfo} packet
26490 @cindex @samp{qsThreadInfo} packet
26491 Obtain a list of all active thread IDs from the target (OS). Since there
26492 may be too many active threads to fit into one reply packet, this query
26493 works iteratively: it may require more than one query/reply sequence to
26494 obtain the entire list of threads. The first query of the sequence will
26495 be the @samp{qfThreadInfo} query; subsequent queries in the
26496 sequence will be the @samp{qsThreadInfo} query.
26498 NOTE: This packet replaces the @samp{qL} query (see below).
26502 @item m @var{thread-id}
26504 @item m @var{thread-id},@var{thread-id}@dots{}
26505 a comma-separated list of thread IDs
26507 (lower case letter @samp{L}) denotes end of list.
26510 In response to each query, the target will reply with a list of one or
26511 more thread IDs, separated by commas.
26512 @value{GDBN} will respond to each reply with a request for more thread
26513 ids (using the @samp{qs} form of the query), until the target responds
26514 with @samp{l} (lower-case el, for @dfn{last}).
26515 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
26518 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
26519 @cindex get thread-local storage address, remote request
26520 @cindex @samp{qGetTLSAddr} packet
26521 Fetch the address associated with thread local storage specified
26522 by @var{thread-id}, @var{offset}, and @var{lm}.
26524 @var{thread-id} is the thread ID associated with the
26525 thread for which to fetch the TLS address. @xref{thread-id syntax}.
26527 @var{offset} is the (big endian, hex encoded) offset associated with the
26528 thread local variable. (This offset is obtained from the debug
26529 information associated with the variable.)
26531 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
26532 the load module associated with the thread local storage. For example,
26533 a @sc{gnu}/Linux system will pass the link map address of the shared
26534 object associated with the thread local storage under consideration.
26535 Other operating environments may choose to represent the load module
26536 differently, so the precise meaning of this parameter will vary.
26540 @item @var{XX}@dots{}
26541 Hex encoded (big endian) bytes representing the address of the thread
26542 local storage requested.
26545 An error occurred. @var{nn} are hex digits.
26548 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
26551 @item qL @var{startflag} @var{threadcount} @var{nextthread}
26552 Obtain thread information from RTOS. Where: @var{startflag} (one hex
26553 digit) is one to indicate the first query and zero to indicate a
26554 subsequent query; @var{threadcount} (two hex digits) is the maximum
26555 number of threads the response packet can contain; and @var{nextthread}
26556 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
26557 returned in the response as @var{argthread}.
26559 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
26563 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
26564 Where: @var{count} (two hex digits) is the number of threads being
26565 returned; @var{done} (one hex digit) is zero to indicate more threads
26566 and one indicates no further threads; @var{argthreadid} (eight hex
26567 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
26568 is a sequence of thread IDs from the target. @var{threadid} (eight hex
26569 digits). See @code{remote.c:parse_threadlist_response()}.
26573 @cindex section offsets, remote request
26574 @cindex @samp{qOffsets} packet
26575 Get section offsets that the target used when relocating the downloaded
26580 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
26581 Relocate the @code{Text} section by @var{xxx} from its original address.
26582 Relocate the @code{Data} section by @var{yyy} from its original address.
26583 If the object file format provides segment information (e.g.@: @sc{elf}
26584 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
26585 segments by the supplied offsets.
26587 @emph{Note: while a @code{Bss} offset may be included in the response,
26588 @value{GDBN} ignores this and instead applies the @code{Data} offset
26589 to the @code{Bss} section.}
26591 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
26592 Relocate the first segment of the object file, which conventionally
26593 contains program code, to a starting address of @var{xxx}. If
26594 @samp{DataSeg} is specified, relocate the second segment, which
26595 conventionally contains modifiable data, to a starting address of
26596 @var{yyy}. @value{GDBN} will report an error if the object file
26597 does not contain segment information, or does not contain at least
26598 as many segments as mentioned in the reply. Extra segments are
26599 kept at fixed offsets relative to the last relocated segment.
26602 @item qP @var{mode} @var{thread-id}
26603 @cindex thread information, remote request
26604 @cindex @samp{qP} packet
26605 Returns information on @var{thread-id}. Where: @var{mode} is a hex
26606 encoded 32 bit mode; @var{thread-id} is a thread ID
26607 (@pxref{thread-id syntax}).
26609 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
26612 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
26616 @cindex non-stop mode, remote request
26617 @cindex @samp{QNonStop} packet
26619 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
26620 @xref{Remote Non-Stop}, for more information.
26625 The request succeeded.
26628 An error occurred. @var{nn} are hex digits.
26631 An empty reply indicates that @samp{QNonStop} is not supported by
26635 This packet is not probed by default; the remote stub must request it,
26636 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26637 Use of this packet is controlled by the @code{set non-stop} command;
26638 @pxref{Non-Stop Mode}.
26640 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
26641 @cindex pass signals to inferior, remote request
26642 @cindex @samp{QPassSignals} packet
26643 @anchor{QPassSignals}
26644 Each listed @var{signal} should be passed directly to the inferior process.
26645 Signals are numbered identically to continue packets and stop replies
26646 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
26647 strictly greater than the previous item. These signals do not need to stop
26648 the inferior, or be reported to @value{GDBN}. All other signals should be
26649 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
26650 combine; any earlier @samp{QPassSignals} list is completely replaced by the
26651 new list. This packet improves performance when using @samp{handle
26652 @var{signal} nostop noprint pass}.
26657 The request succeeded.
26660 An error occurred. @var{nn} are hex digits.
26663 An empty reply indicates that @samp{QPassSignals} is not supported by
26667 Use of this packet is controlled by the @code{set remote pass-signals}
26668 command (@pxref{Remote Configuration, set remote pass-signals}).
26669 This packet is not probed by default; the remote stub must request it,
26670 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26672 @item qRcmd,@var{command}
26673 @cindex execute remote command, remote request
26674 @cindex @samp{qRcmd} packet
26675 @var{command} (hex encoded) is passed to the local interpreter for
26676 execution. Invalid commands should be reported using the output
26677 string. Before the final result packet, the target may also respond
26678 with a number of intermediate @samp{O@var{output}} console output
26679 packets. @emph{Implementors should note that providing access to a
26680 stubs's interpreter may have security implications}.
26685 A command response with no output.
26687 A command response with the hex encoded output string @var{OUTPUT}.
26689 Indicate a badly formed request.
26691 An empty reply indicates that @samp{qRcmd} is not recognized.
26694 (Note that the @code{qRcmd} packet's name is separated from the
26695 command by a @samp{,}, not a @samp{:}, contrary to the naming
26696 conventions above. Please don't use this packet as a model for new
26699 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
26700 @cindex searching memory, in remote debugging
26701 @cindex @samp{qSearch:memory} packet
26702 @anchor{qSearch memory}
26703 Search @var{length} bytes at @var{address} for @var{search-pattern}.
26704 @var{address} and @var{length} are encoded in hex.
26705 @var{search-pattern} is a sequence of bytes, hex encoded.
26710 The pattern was not found.
26712 The pattern was found at @var{address}.
26714 A badly formed request or an error was encountered while searching memory.
26716 An empty reply indicates that @samp{qSearch:memory} is not recognized.
26719 @item QStartNoAckMode
26720 @cindex @samp{QStartNoAckMode} packet
26721 @anchor{QStartNoAckMode}
26722 Request that the remote stub disable the normal @samp{+}/@samp{-}
26723 protocol acknowledgments (@pxref{Packet Acknowledgment}).
26728 The stub has switched to no-acknowledgment mode.
26729 @value{GDBN} acknowledges this reponse,
26730 but neither the stub nor @value{GDBN} shall send or expect further
26731 @samp{+}/@samp{-} acknowledgments in the current connection.
26733 An empty reply indicates that the stub does not support no-acknowledgment mode.
26736 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
26737 @cindex supported packets, remote query
26738 @cindex features of the remote protocol
26739 @cindex @samp{qSupported} packet
26740 @anchor{qSupported}
26741 Tell the remote stub about features supported by @value{GDBN}, and
26742 query the stub for features it supports. This packet allows
26743 @value{GDBN} and the remote stub to take advantage of each others'
26744 features. @samp{qSupported} also consolidates multiple feature probes
26745 at startup, to improve @value{GDBN} performance---a single larger
26746 packet performs better than multiple smaller probe packets on
26747 high-latency links. Some features may enable behavior which must not
26748 be on by default, e.g.@: because it would confuse older clients or
26749 stubs. Other features may describe packets which could be
26750 automatically probed for, but are not. These features must be
26751 reported before @value{GDBN} will use them. This ``default
26752 unsupported'' behavior is not appropriate for all packets, but it
26753 helps to keep the initial connection time under control with new
26754 versions of @value{GDBN} which support increasing numbers of packets.
26758 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
26759 The stub supports or does not support each returned @var{stubfeature},
26760 depending on the form of each @var{stubfeature} (see below for the
26763 An empty reply indicates that @samp{qSupported} is not recognized,
26764 or that no features needed to be reported to @value{GDBN}.
26767 The allowed forms for each feature (either a @var{gdbfeature} in the
26768 @samp{qSupported} packet, or a @var{stubfeature} in the response)
26772 @item @var{name}=@var{value}
26773 The remote protocol feature @var{name} is supported, and associated
26774 with the specified @var{value}. The format of @var{value} depends
26775 on the feature, but it must not include a semicolon.
26777 The remote protocol feature @var{name} is supported, and does not
26778 need an associated value.
26780 The remote protocol feature @var{name} is not supported.
26782 The remote protocol feature @var{name} may be supported, and
26783 @value{GDBN} should auto-detect support in some other way when it is
26784 needed. This form will not be used for @var{gdbfeature} notifications,
26785 but may be used for @var{stubfeature} responses.
26788 Whenever the stub receives a @samp{qSupported} request, the
26789 supplied set of @value{GDBN} features should override any previous
26790 request. This allows @value{GDBN} to put the stub in a known
26791 state, even if the stub had previously been communicating with
26792 a different version of @value{GDBN}.
26794 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
26799 This feature indicates whether @value{GDBN} supports multiprocess
26800 extensions to the remote protocol. @value{GDBN} does not use such
26801 extensions unless the stub also reports that it supports them by
26802 including @samp{multiprocess+} in its @samp{qSupported} reply.
26803 @xref{multiprocess extensions}, for details.
26806 Stubs should ignore any unknown values for
26807 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
26808 packet supports receiving packets of unlimited length (earlier
26809 versions of @value{GDBN} may reject overly long responses). Additional values
26810 for @var{gdbfeature} may be defined in the future to let the stub take
26811 advantage of new features in @value{GDBN}, e.g.@: incompatible
26812 improvements in the remote protocol---the @samp{multiprocess} feature is
26813 an example of such a feature. The stub's reply should be independent
26814 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
26815 describes all the features it supports, and then the stub replies with
26816 all the features it supports.
26818 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
26819 responses, as long as each response uses one of the standard forms.
26821 Some features are flags. A stub which supports a flag feature
26822 should respond with a @samp{+} form response. Other features
26823 require values, and the stub should respond with an @samp{=}
26826 Each feature has a default value, which @value{GDBN} will use if
26827 @samp{qSupported} is not available or if the feature is not mentioned
26828 in the @samp{qSupported} response. The default values are fixed; a
26829 stub is free to omit any feature responses that match the defaults.
26831 Not all features can be probed, but for those which can, the probing
26832 mechanism is useful: in some cases, a stub's internal
26833 architecture may not allow the protocol layer to know some information
26834 about the underlying target in advance. This is especially common in
26835 stubs which may be configured for multiple targets.
26837 These are the currently defined stub features and their properties:
26839 @multitable @columnfractions 0.35 0.2 0.12 0.2
26840 @c NOTE: The first row should be @headitem, but we do not yet require
26841 @c a new enough version of Texinfo (4.7) to use @headitem.
26843 @tab Value Required
26847 @item @samp{PacketSize}
26852 @item @samp{qXfer:auxv:read}
26857 @item @samp{qXfer:features:read}
26862 @item @samp{qXfer:libraries:read}
26867 @item @samp{qXfer:memory-map:read}
26872 @item @samp{qXfer:spu:read}
26877 @item @samp{qXfer:spu:write}
26882 @item @samp{QNonStop}
26887 @item @samp{QPassSignals}
26892 @item @samp{QStartNoAckMode}
26897 @item @samp{multiprocess}
26904 These are the currently defined stub features, in more detail:
26907 @cindex packet size, remote protocol
26908 @item PacketSize=@var{bytes}
26909 The remote stub can accept packets up to at least @var{bytes} in
26910 length. @value{GDBN} will send packets up to this size for bulk
26911 transfers, and will never send larger packets. This is a limit on the
26912 data characters in the packet, including the frame and checksum.
26913 There is no trailing NUL byte in a remote protocol packet; if the stub
26914 stores packets in a NUL-terminated format, it should allow an extra
26915 byte in its buffer for the NUL. If this stub feature is not supported,
26916 @value{GDBN} guesses based on the size of the @samp{g} packet response.
26918 @item qXfer:auxv:read
26919 The remote stub understands the @samp{qXfer:auxv:read} packet
26920 (@pxref{qXfer auxiliary vector read}).
26922 @item qXfer:features:read
26923 The remote stub understands the @samp{qXfer:features:read} packet
26924 (@pxref{qXfer target description read}).
26926 @item qXfer:libraries:read
26927 The remote stub understands the @samp{qXfer:libraries:read} packet
26928 (@pxref{qXfer library list read}).
26930 @item qXfer:memory-map:read
26931 The remote stub understands the @samp{qXfer:memory-map:read} packet
26932 (@pxref{qXfer memory map read}).
26934 @item qXfer:spu:read
26935 The remote stub understands the @samp{qXfer:spu:read} packet
26936 (@pxref{qXfer spu read}).
26938 @item qXfer:spu:write
26939 The remote stub understands the @samp{qXfer:spu:write} packet
26940 (@pxref{qXfer spu write}).
26943 The remote stub understands the @samp{QNonStop} packet
26944 (@pxref{QNonStop}).
26947 The remote stub understands the @samp{QPassSignals} packet
26948 (@pxref{QPassSignals}).
26950 @item QStartNoAckMode
26951 The remote stub understands the @samp{QStartNoAckMode} packet and
26952 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
26955 @anchor{multiprocess extensions}
26956 @cindex multiprocess extensions, in remote protocol
26957 The remote stub understands the multiprocess extensions to the remote
26958 protocol syntax. The multiprocess extensions affect the syntax of
26959 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
26960 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
26961 replies. Note that reporting this feature indicates support for the
26962 syntactic extensions only, not that the stub necessarily supports
26963 debugging of more than one process at a time. The stub must not use
26964 multiprocess extensions in packet replies unless @value{GDBN} has also
26965 indicated it supports them in its @samp{qSupported} request.
26967 @item qXfer:osdata:read
26968 The remote stub understands the @samp{qXfer:osdata:read} packet
26969 ((@pxref{qXfer osdata read}).
26974 @cindex symbol lookup, remote request
26975 @cindex @samp{qSymbol} packet
26976 Notify the target that @value{GDBN} is prepared to serve symbol lookup
26977 requests. Accept requests from the target for the values of symbols.
26982 The target does not need to look up any (more) symbols.
26983 @item qSymbol:@var{sym_name}
26984 The target requests the value of symbol @var{sym_name} (hex encoded).
26985 @value{GDBN} may provide the value by using the
26986 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
26990 @item qSymbol:@var{sym_value}:@var{sym_name}
26991 Set the value of @var{sym_name} to @var{sym_value}.
26993 @var{sym_name} (hex encoded) is the name of a symbol whose value the
26994 target has previously requested.
26996 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
26997 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
27003 The target does not need to look up any (more) symbols.
27004 @item qSymbol:@var{sym_name}
27005 The target requests the value of a new symbol @var{sym_name} (hex
27006 encoded). @value{GDBN} will continue to supply the values of symbols
27007 (if available), until the target ceases to request them.
27012 @xref{Tracepoint Packets}.
27014 @item qThreadExtraInfo,@var{thread-id}
27015 @cindex thread attributes info, remote request
27016 @cindex @samp{qThreadExtraInfo} packet
27017 Obtain a printable string description of a thread's attributes from
27018 the target OS. @var{thread-id} is a thread ID;
27019 see @ref{thread-id syntax}. This
27020 string may contain anything that the target OS thinks is interesting
27021 for @value{GDBN} to tell the user about the thread. The string is
27022 displayed in @value{GDBN}'s @code{info threads} display. Some
27023 examples of possible thread extra info strings are @samp{Runnable}, or
27024 @samp{Blocked on Mutex}.
27028 @item @var{XX}@dots{}
27029 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
27030 comprising the printable string containing the extra information about
27031 the thread's attributes.
27034 (Note that the @code{qThreadExtraInfo} packet's name is separated from
27035 the command by a @samp{,}, not a @samp{:}, contrary to the naming
27036 conventions above. Please don't use this packet as a model for new
27044 @xref{Tracepoint Packets}.
27046 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
27047 @cindex read special object, remote request
27048 @cindex @samp{qXfer} packet
27049 @anchor{qXfer read}
27050 Read uninterpreted bytes from the target's special data area
27051 identified by the keyword @var{object}. Request @var{length} bytes
27052 starting at @var{offset} bytes into the data. The content and
27053 encoding of @var{annex} is specific to @var{object}; it can supply
27054 additional details about what data to access.
27056 Here are the specific requests of this form defined so far. All
27057 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
27058 formats, listed below.
27061 @item qXfer:auxv:read::@var{offset},@var{length}
27062 @anchor{qXfer auxiliary vector read}
27063 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
27064 auxiliary vector}. Note @var{annex} must be empty.
27066 This packet is not probed by default; the remote stub must request it,
27067 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27069 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
27070 @anchor{qXfer target description read}
27071 Access the @dfn{target description}. @xref{Target Descriptions}. The
27072 annex specifies which XML document to access. The main description is
27073 always loaded from the @samp{target.xml} annex.
27075 This packet is not probed by default; the remote stub must request it,
27076 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27078 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
27079 @anchor{qXfer library list read}
27080 Access the target's list of loaded libraries. @xref{Library List Format}.
27081 The annex part of the generic @samp{qXfer} packet must be empty
27082 (@pxref{qXfer read}).
27084 Targets which maintain a list of libraries in the program's memory do
27085 not need to implement this packet; it is designed for platforms where
27086 the operating system manages the list of loaded libraries.
27088 This packet is not probed by default; the remote stub must request it,
27089 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27091 @item qXfer:memory-map:read::@var{offset},@var{length}
27092 @anchor{qXfer memory map read}
27093 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
27094 annex part of the generic @samp{qXfer} packet must be empty
27095 (@pxref{qXfer read}).
27097 This packet is not probed by default; the remote stub must request it,
27098 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27100 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
27101 @anchor{qXfer spu read}
27102 Read contents of an @code{spufs} file on the target system. The
27103 annex specifies which file to read; it must be of the form
27104 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27105 in the target process, and @var{name} identifes the @code{spufs} file
27106 in that context to be accessed.
27108 This packet is not probed by default; the remote stub must request it,
27109 by supplying an appropriate @samp{qSupported} response
27110 (@pxref{qSupported}).
27112 @item qXfer:osdata:read::@var{offset},@var{length}
27113 @anchor{qXfer osdata read}
27114 Access the target's @dfn{operating system information}.
27115 @xref{Operating System Information}.
27122 Data @var{data} (@pxref{Binary Data}) has been read from the
27123 target. There may be more data at a higher address (although
27124 it is permitted to return @samp{m} even for the last valid
27125 block of data, as long as at least one byte of data was read).
27126 @var{data} may have fewer bytes than the @var{length} in the
27130 Data @var{data} (@pxref{Binary Data}) has been read from the target.
27131 There is no more data to be read. @var{data} may have fewer bytes
27132 than the @var{length} in the request.
27135 The @var{offset} in the request is at the end of the data.
27136 There is no more data to be read.
27139 The request was malformed, or @var{annex} was invalid.
27142 The offset was invalid, or there was an error encountered reading the data.
27143 @var{nn} is a hex-encoded @code{errno} value.
27146 An empty reply indicates the @var{object} string was not recognized by
27147 the stub, or that the object does not support reading.
27150 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
27151 @cindex write data into object, remote request
27152 Write uninterpreted bytes into the target's special data area
27153 identified by the keyword @var{object}, starting at @var{offset} bytes
27154 into the data. @var{data}@dots{} is the binary-encoded data
27155 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
27156 is specific to @var{object}; it can supply additional details about what data
27159 Here are the specific requests of this form defined so far. All
27160 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
27161 formats, listed below.
27164 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
27165 @anchor{qXfer spu write}
27166 Write @var{data} to an @code{spufs} file on the target system. The
27167 annex specifies which file to write; it must be of the form
27168 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27169 in the target process, and @var{name} identifes the @code{spufs} file
27170 in that context to be accessed.
27172 This packet is not probed by default; the remote stub must request it,
27173 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27179 @var{nn} (hex encoded) is the number of bytes written.
27180 This may be fewer bytes than supplied in the request.
27183 The request was malformed, or @var{annex} was invalid.
27186 The offset was invalid, or there was an error encountered writing the data.
27187 @var{nn} is a hex-encoded @code{errno} value.
27190 An empty reply indicates the @var{object} string was not
27191 recognized by the stub, or that the object does not support writing.
27194 @item qXfer:@var{object}:@var{operation}:@dots{}
27195 Requests of this form may be added in the future. When a stub does
27196 not recognize the @var{object} keyword, or its support for
27197 @var{object} does not recognize the @var{operation} keyword, the stub
27198 must respond with an empty packet.
27202 @node Register Packet Format
27203 @section Register Packet Format
27205 The following @code{g}/@code{G} packets have previously been defined.
27206 In the below, some thirty-two bit registers are transferred as
27207 sixty-four bits. Those registers should be zero/sign extended (which?)
27208 to fill the space allocated. Register bytes are transferred in target
27209 byte order. The two nibbles within a register byte are transferred
27210 most-significant - least-significant.
27216 All registers are transferred as thirty-two bit quantities in the order:
27217 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
27218 registers; fsr; fir; fp.
27222 All registers are transferred as sixty-four bit quantities (including
27223 thirty-two bit registers such as @code{sr}). The ordering is the same
27228 @node Tracepoint Packets
27229 @section Tracepoint Packets
27230 @cindex tracepoint packets
27231 @cindex packets, tracepoint
27233 Here we describe the packets @value{GDBN} uses to implement
27234 tracepoints (@pxref{Tracepoints}).
27238 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
27239 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
27240 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
27241 the tracepoint is disabled. @var{step} is the tracepoint's step
27242 count, and @var{pass} is its pass count. If the trailing @samp{-} is
27243 present, further @samp{QTDP} packets will follow to specify this
27244 tracepoint's actions.
27249 The packet was understood and carried out.
27251 The packet was not recognized.
27254 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
27255 Define actions to be taken when a tracepoint is hit. @var{n} and
27256 @var{addr} must be the same as in the initial @samp{QTDP} packet for
27257 this tracepoint. This packet may only be sent immediately after
27258 another @samp{QTDP} packet that ended with a @samp{-}. If the
27259 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
27260 specifying more actions for this tracepoint.
27262 In the series of action packets for a given tracepoint, at most one
27263 can have an @samp{S} before its first @var{action}. If such a packet
27264 is sent, it and the following packets define ``while-stepping''
27265 actions. Any prior packets define ordinary actions --- that is, those
27266 taken when the tracepoint is first hit. If no action packet has an
27267 @samp{S}, then all the packets in the series specify ordinary
27268 tracepoint actions.
27270 The @samp{@var{action}@dots{}} portion of the packet is a series of
27271 actions, concatenated without separators. Each action has one of the
27277 Collect the registers whose bits are set in @var{mask}. @var{mask} is
27278 a hexadecimal number whose @var{i}'th bit is set if register number
27279 @var{i} should be collected. (The least significant bit is numbered
27280 zero.) Note that @var{mask} may be any number of digits long; it may
27281 not fit in a 32-bit word.
27283 @item M @var{basereg},@var{offset},@var{len}
27284 Collect @var{len} bytes of memory starting at the address in register
27285 number @var{basereg}, plus @var{offset}. If @var{basereg} is
27286 @samp{-1}, then the range has a fixed address: @var{offset} is the
27287 address of the lowest byte to collect. The @var{basereg},
27288 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
27289 values (the @samp{-1} value for @var{basereg} is a special case).
27291 @item X @var{len},@var{expr}
27292 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
27293 it directs. @var{expr} is an agent expression, as described in
27294 @ref{Agent Expressions}. Each byte of the expression is encoded as a
27295 two-digit hex number in the packet; @var{len} is the number of bytes
27296 in the expression (and thus one-half the number of hex digits in the
27301 Any number of actions may be packed together in a single @samp{QTDP}
27302 packet, as long as the packet does not exceed the maximum packet
27303 length (400 bytes, for many stubs). There may be only one @samp{R}
27304 action per tracepoint, and it must precede any @samp{M} or @samp{X}
27305 actions. Any registers referred to by @samp{M} and @samp{X} actions
27306 must be collected by a preceding @samp{R} action. (The
27307 ``while-stepping'' actions are treated as if they were attached to a
27308 separate tracepoint, as far as these restrictions are concerned.)
27313 The packet was understood and carried out.
27315 The packet was not recognized.
27318 @item QTFrame:@var{n}
27319 Select the @var{n}'th tracepoint frame from the buffer, and use the
27320 register and memory contents recorded there to answer subsequent
27321 request packets from @value{GDBN}.
27323 A successful reply from the stub indicates that the stub has found the
27324 requested frame. The response is a series of parts, concatenated
27325 without separators, describing the frame we selected. Each part has
27326 one of the following forms:
27330 The selected frame is number @var{n} in the trace frame buffer;
27331 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
27332 was no frame matching the criteria in the request packet.
27335 The selected trace frame records a hit of tracepoint number @var{t};
27336 @var{t} is a hexadecimal number.
27340 @item QTFrame:pc:@var{addr}
27341 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27342 currently selected frame whose PC is @var{addr};
27343 @var{addr} is a hexadecimal number.
27345 @item QTFrame:tdp:@var{t}
27346 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27347 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
27348 is a hexadecimal number.
27350 @item QTFrame:range:@var{start}:@var{end}
27351 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27352 currently selected frame whose PC is between @var{start} (inclusive)
27353 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
27356 @item QTFrame:outside:@var{start}:@var{end}
27357 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
27358 frame @emph{outside} the given range of addresses.
27361 Begin the tracepoint experiment. Begin collecting data from tracepoint
27362 hits in the trace frame buffer.
27365 End the tracepoint experiment. Stop collecting trace frames.
27368 Clear the table of tracepoints, and empty the trace frame buffer.
27370 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
27371 Establish the given ranges of memory as ``transparent''. The stub
27372 will answer requests for these ranges from memory's current contents,
27373 if they were not collected as part of the tracepoint hit.
27375 @value{GDBN} uses this to mark read-only regions of memory, like those
27376 containing program code. Since these areas never change, they should
27377 still have the same contents they did when the tracepoint was hit, so
27378 there's no reason for the stub to refuse to provide their contents.
27381 Ask the stub if there is a trace experiment running right now.
27386 There is no trace experiment running.
27388 There is a trace experiment running.
27394 @node Host I/O Packets
27395 @section Host I/O Packets
27396 @cindex Host I/O, remote protocol
27397 @cindex file transfer, remote protocol
27399 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
27400 operations on the far side of a remote link. For example, Host I/O is
27401 used to upload and download files to a remote target with its own
27402 filesystem. Host I/O uses the same constant values and data structure
27403 layout as the target-initiated File-I/O protocol. However, the
27404 Host I/O packets are structured differently. The target-initiated
27405 protocol relies on target memory to store parameters and buffers.
27406 Host I/O requests are initiated by @value{GDBN}, and the
27407 target's memory is not involved. @xref{File-I/O Remote Protocol
27408 Extension}, for more details on the target-initiated protocol.
27410 The Host I/O request packets all encode a single operation along with
27411 its arguments. They have this format:
27415 @item vFile:@var{operation}: @var{parameter}@dots{}
27416 @var{operation} is the name of the particular request; the target
27417 should compare the entire packet name up to the second colon when checking
27418 for a supported operation. The format of @var{parameter} depends on
27419 the operation. Numbers are always passed in hexadecimal. Negative
27420 numbers have an explicit minus sign (i.e.@: two's complement is not
27421 used). Strings (e.g.@: filenames) are encoded as a series of
27422 hexadecimal bytes. The last argument to a system call may be a
27423 buffer of escaped binary data (@pxref{Binary Data}).
27427 The valid responses to Host I/O packets are:
27431 @item F @var{result} [, @var{errno}] [; @var{attachment}]
27432 @var{result} is the integer value returned by this operation, usually
27433 non-negative for success and -1 for errors. If an error has occured,
27434 @var{errno} will be included in the result. @var{errno} will have a
27435 value defined by the File-I/O protocol (@pxref{Errno Values}). For
27436 operations which return data, @var{attachment} supplies the data as a
27437 binary buffer. Binary buffers in response packets are escaped in the
27438 normal way (@pxref{Binary Data}). See the individual packet
27439 documentation for the interpretation of @var{result} and
27443 An empty response indicates that this operation is not recognized.
27447 These are the supported Host I/O operations:
27450 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
27451 Open a file at @var{pathname} and return a file descriptor for it, or
27452 return -1 if an error occurs. @var{pathname} is a string,
27453 @var{flags} is an integer indicating a mask of open flags
27454 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
27455 of mode bits to use if the file is created (@pxref{mode_t Values}).
27456 @xref{open}, for details of the open flags and mode values.
27458 @item vFile:close: @var{fd}
27459 Close the open file corresponding to @var{fd} and return 0, or
27460 -1 if an error occurs.
27462 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
27463 Read data from the open file corresponding to @var{fd}. Up to
27464 @var{count} bytes will be read from the file, starting at @var{offset}
27465 relative to the start of the file. The target may read fewer bytes;
27466 common reasons include packet size limits and an end-of-file
27467 condition. The number of bytes read is returned. Zero should only be
27468 returned for a successful read at the end of the file, or if
27469 @var{count} was zero.
27471 The data read should be returned as a binary attachment on success.
27472 If zero bytes were read, the response should include an empty binary
27473 attachment (i.e.@: a trailing semicolon). The return value is the
27474 number of target bytes read; the binary attachment may be longer if
27475 some characters were escaped.
27477 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
27478 Write @var{data} (a binary buffer) to the open file corresponding
27479 to @var{fd}. Start the write at @var{offset} from the start of the
27480 file. Unlike many @code{write} system calls, there is no
27481 separate @var{count} argument; the length of @var{data} in the
27482 packet is used. @samp{vFile:write} returns the number of bytes written,
27483 which may be shorter than the length of @var{data}, or -1 if an
27486 @item vFile:unlink: @var{pathname}
27487 Delete the file at @var{pathname} on the target. Return 0,
27488 or -1 if an error occurs. @var{pathname} is a string.
27493 @section Interrupts
27494 @cindex interrupts (remote protocol)
27496 When a program on the remote target is running, @value{GDBN} may
27497 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
27498 control of which is specified via @value{GDBN}'s @samp{remotebreak}
27499 setting (@pxref{set remotebreak}).
27501 The precise meaning of @code{BREAK} is defined by the transport
27502 mechanism and may, in fact, be undefined. @value{GDBN} does not
27503 currently define a @code{BREAK} mechanism for any of the network
27504 interfaces except for TCP, in which case @value{GDBN} sends the
27505 @code{telnet} BREAK sequence.
27507 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
27508 transport mechanisms. It is represented by sending the single byte
27509 @code{0x03} without any of the usual packet overhead described in
27510 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
27511 transmitted as part of a packet, it is considered to be packet data
27512 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
27513 (@pxref{X packet}), used for binary downloads, may include an unescaped
27514 @code{0x03} as part of its packet.
27516 Stubs are not required to recognize these interrupt mechanisms and the
27517 precise meaning associated with receipt of the interrupt is
27518 implementation defined. If the target supports debugging of multiple
27519 threads and/or processes, it should attempt to interrupt all
27520 currently-executing threads and processes.
27521 If the stub is successful at interrupting the
27522 running program, it should send one of the stop
27523 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
27524 of successfully stopping the program in all-stop mode, and a stop reply
27525 for each stopped thread in non-stop mode.
27526 Interrupts received while the
27527 program is stopped are discarded.
27529 @node Notification Packets
27530 @section Notification Packets
27531 @cindex notification packets
27532 @cindex packets, notification
27534 The @value{GDBN} remote serial protocol includes @dfn{notifications},
27535 packets that require no acknowledgment. Both the GDB and the stub
27536 may send notifications (although the only notifications defined at
27537 present are sent by the stub). Notifications carry information
27538 without incurring the round-trip latency of an acknowledgment, and so
27539 are useful for low-impact communications where occasional packet loss
27542 A notification packet has the form @samp{% @var{data} #
27543 @var{checksum}}, where @var{data} is the content of the notification,
27544 and @var{checksum} is a checksum of @var{data}, computed and formatted
27545 as for ordinary @value{GDBN} packets. A notification's @var{data}
27546 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
27547 receiving a notification, the recipient sends no @samp{+} or @samp{-}
27548 to acknowledge the notification's receipt or to report its corruption.
27550 Every notification's @var{data} begins with a name, which contains no
27551 colon characters, followed by a colon character.
27553 Recipients should silently ignore corrupted notifications and
27554 notifications they do not understand. Recipients should restart
27555 timeout periods on receipt of a well-formed notification, whether or
27556 not they understand it.
27558 Senders should only send the notifications described here when this
27559 protocol description specifies that they are permitted. In the
27560 future, we may extend the protocol to permit existing notifications in
27561 new contexts; this rule helps older senders avoid confusing newer
27564 (Older versions of @value{GDBN} ignore bytes received until they see
27565 the @samp{$} byte that begins an ordinary packet, so new stubs may
27566 transmit notifications without fear of confusing older clients. There
27567 are no notifications defined for @value{GDBN} to send at the moment, but we
27568 assume that most older stubs would ignore them, as well.)
27570 The following notification packets from the stub to @value{GDBN} are
27574 @item Stop: @var{reply}
27575 Report an asynchronous stop event in non-stop mode.
27576 The @var{reply} has the form of a stop reply, as
27577 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
27578 for information on how these notifications are acknowledged by
27582 @node Remote Non-Stop
27583 @section Remote Protocol Support for Non-Stop Mode
27585 @value{GDBN}'s remote protocol supports non-stop debugging of
27586 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
27587 supports non-stop mode, it should report that to @value{GDBN} by including
27588 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
27590 @value{GDBN} typically sends a @samp{QNonStop} packet only when
27591 establishing a new connection with the stub. Entering non-stop mode
27592 does not alter the state of any currently-running threads, but targets
27593 must stop all threads in any already-attached processes when entering
27594 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
27595 probe the target state after a mode change.
27597 In non-stop mode, when an attached process encounters an event that
27598 would otherwise be reported with a stop reply, it uses the
27599 asynchronous notification mechanism (@pxref{Notification Packets}) to
27600 inform @value{GDBN}. In contrast to all-stop mode, where all threads
27601 in all processes are stopped when a stop reply is sent, in non-stop
27602 mode only the thread reporting the stop event is stopped. That is,
27603 when reporting a @samp{S} or @samp{T} response to indicate completion
27604 of a step operation, hitting a breakpoint, or a fault, only the
27605 affected thread is stopped; any other still-running threads continue
27606 to run. When reporting a @samp{W} or @samp{X} response, all running
27607 threads belonging to other attached processes continue to run.
27609 Only one stop reply notification at a time may be pending; if
27610 additional stop events occur before @value{GDBN} has acknowledged the
27611 previous notification, they must be queued by the stub for later
27612 synchronous transmission in response to @samp{vStopped} packets from
27613 @value{GDBN}. Because the notification mechanism is unreliable,
27614 the stub is permitted to resend a stop reply notification
27615 if it believes @value{GDBN} may not have received it. @value{GDBN}
27616 ignores additional stop reply notifications received before it has
27617 finished processing a previous notification and the stub has completed
27618 sending any queued stop events.
27620 Otherwise, @value{GDBN} must be prepared to receive a stop reply
27621 notification at any time. Specifically, they may appear when
27622 @value{GDBN} is not otherwise reading input from the stub, or when
27623 @value{GDBN} is expecting to read a normal synchronous response or a
27624 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
27625 Notification packets are distinct from any other communication from
27626 the stub so there is no ambiguity.
27628 After receiving a stop reply notification, @value{GDBN} shall
27629 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
27630 as a regular, synchronous request to the stub. Such acknowledgment
27631 is not required to happen immediately, as @value{GDBN} is permitted to
27632 send other, unrelated packets to the stub first, which the stub should
27635 Upon receiving a @samp{vStopped} packet, if the stub has other queued
27636 stop events to report to @value{GDBN}, it shall respond by sending a
27637 normal stop reply response. @value{GDBN} shall then send another
27638 @samp{vStopped} packet to solicit further responses; again, it is
27639 permitted to send other, unrelated packets as well which the stub
27640 should process normally.
27642 If the stub receives a @samp{vStopped} packet and there are no
27643 additional stop events to report, the stub shall return an @samp{OK}
27644 response. At this point, if further stop events occur, the stub shall
27645 send a new stop reply notification, @value{GDBN} shall accept the
27646 notification, and the process shall be repeated.
27648 In non-stop mode, the target shall respond to the @samp{?} packet as
27649 follows. First, any incomplete stop reply notification/@samp{vStopped}
27650 sequence in progress is abandoned. The target must begin a new
27651 sequence reporting stop events for all stopped threads, whether or not
27652 it has previously reported those events to @value{GDBN}. The first
27653 stop reply is sent as a synchronous reply to the @samp{?} packet, and
27654 subsequent stop replies are sent as responses to @samp{vStopped} packets
27655 using the mechanism described above. The target must not send
27656 asynchronous stop reply notifications until the sequence is complete.
27657 If all threads are running when the target receives the @samp{?} packet,
27658 or if the target is not attached to any process, it shall respond
27661 @node Packet Acknowledgment
27662 @section Packet Acknowledgment
27664 @cindex acknowledgment, for @value{GDBN} remote
27665 @cindex packet acknowledgment, for @value{GDBN} remote
27666 By default, when either the host or the target machine receives a packet,
27667 the first response expected is an acknowledgment: either @samp{+} (to indicate
27668 the package was received correctly) or @samp{-} (to request retransmission).
27669 This mechanism allows the @value{GDBN} remote protocol to operate over
27670 unreliable transport mechanisms, such as a serial line.
27672 In cases where the transport mechanism is itself reliable (such as a pipe or
27673 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
27674 It may be desirable to disable them in that case to reduce communication
27675 overhead, or for other reasons. This can be accomplished by means of the
27676 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
27678 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
27679 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
27680 and response format still includes the normal checksum, as described in
27681 @ref{Overview}, but the checksum may be ignored by the receiver.
27683 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
27684 no-acknowledgment mode, it should report that to @value{GDBN}
27685 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
27686 @pxref{qSupported}.
27687 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
27688 disabled via the @code{set remote noack-packet off} command
27689 (@pxref{Remote Configuration}),
27690 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
27691 Only then may the stub actually turn off packet acknowledgments.
27692 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
27693 response, which can be safely ignored by the stub.
27695 Note that @code{set remote noack-packet} command only affects negotiation
27696 between @value{GDBN} and the stub when subsequent connections are made;
27697 it does not affect the protocol acknowledgment state for any current
27699 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
27700 new connection is established,
27701 there is also no protocol request to re-enable the acknowledgments
27702 for the current connection, once disabled.
27707 Example sequence of a target being re-started. Notice how the restart
27708 does not get any direct output:
27713 @emph{target restarts}
27716 <- @code{T001:1234123412341234}
27720 Example sequence of a target being stepped by a single instruction:
27723 -> @code{G1445@dots{}}
27728 <- @code{T001:1234123412341234}
27732 <- @code{1455@dots{}}
27736 @node File-I/O Remote Protocol Extension
27737 @section File-I/O Remote Protocol Extension
27738 @cindex File-I/O remote protocol extension
27741 * File-I/O Overview::
27742 * Protocol Basics::
27743 * The F Request Packet::
27744 * The F Reply Packet::
27745 * The Ctrl-C Message::
27747 * List of Supported Calls::
27748 * Protocol-specific Representation of Datatypes::
27750 * File-I/O Examples::
27753 @node File-I/O Overview
27754 @subsection File-I/O Overview
27755 @cindex file-i/o overview
27757 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
27758 target to use the host's file system and console I/O to perform various
27759 system calls. System calls on the target system are translated into a
27760 remote protocol packet to the host system, which then performs the needed
27761 actions and returns a response packet to the target system.
27762 This simulates file system operations even on targets that lack file systems.
27764 The protocol is defined to be independent of both the host and target systems.
27765 It uses its own internal representation of datatypes and values. Both
27766 @value{GDBN} and the target's @value{GDBN} stub are responsible for
27767 translating the system-dependent value representations into the internal
27768 protocol representations when data is transmitted.
27770 The communication is synchronous. A system call is possible only when
27771 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
27772 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
27773 the target is stopped to allow deterministic access to the target's
27774 memory. Therefore File-I/O is not interruptible by target signals. On
27775 the other hand, it is possible to interrupt File-I/O by a user interrupt
27776 (@samp{Ctrl-C}) within @value{GDBN}.
27778 The target's request to perform a host system call does not finish
27779 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
27780 after finishing the system call, the target returns to continuing the
27781 previous activity (continue, step). No additional continue or step
27782 request from @value{GDBN} is required.
27785 (@value{GDBP}) continue
27786 <- target requests 'system call X'
27787 target is stopped, @value{GDBN} executes system call
27788 -> @value{GDBN} returns result
27789 ... target continues, @value{GDBN} returns to wait for the target
27790 <- target hits breakpoint and sends a Txx packet
27793 The protocol only supports I/O on the console and to regular files on
27794 the host file system. Character or block special devices, pipes,
27795 named pipes, sockets or any other communication method on the host
27796 system are not supported by this protocol.
27798 File I/O is not supported in non-stop mode.
27800 @node Protocol Basics
27801 @subsection Protocol Basics
27802 @cindex protocol basics, file-i/o
27804 The File-I/O protocol uses the @code{F} packet as the request as well
27805 as reply packet. Since a File-I/O system call can only occur when
27806 @value{GDBN} is waiting for a response from the continuing or stepping target,
27807 the File-I/O request is a reply that @value{GDBN} has to expect as a result
27808 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
27809 This @code{F} packet contains all information needed to allow @value{GDBN}
27810 to call the appropriate host system call:
27814 A unique identifier for the requested system call.
27817 All parameters to the system call. Pointers are given as addresses
27818 in the target memory address space. Pointers to strings are given as
27819 pointer/length pair. Numerical values are given as they are.
27820 Numerical control flags are given in a protocol-specific representation.
27824 At this point, @value{GDBN} has to perform the following actions.
27828 If the parameters include pointer values to data needed as input to a
27829 system call, @value{GDBN} requests this data from the target with a
27830 standard @code{m} packet request. This additional communication has to be
27831 expected by the target implementation and is handled as any other @code{m}
27835 @value{GDBN} translates all value from protocol representation to host
27836 representation as needed. Datatypes are coerced into the host types.
27839 @value{GDBN} calls the system call.
27842 It then coerces datatypes back to protocol representation.
27845 If the system call is expected to return data in buffer space specified
27846 by pointer parameters to the call, the data is transmitted to the
27847 target using a @code{M} or @code{X} packet. This packet has to be expected
27848 by the target implementation and is handled as any other @code{M} or @code{X}
27853 Eventually @value{GDBN} replies with another @code{F} packet which contains all
27854 necessary information for the target to continue. This at least contains
27861 @code{errno}, if has been changed by the system call.
27868 After having done the needed type and value coercion, the target continues
27869 the latest continue or step action.
27871 @node The F Request Packet
27872 @subsection The @code{F} Request Packet
27873 @cindex file-i/o request packet
27874 @cindex @code{F} request packet
27876 The @code{F} request packet has the following format:
27879 @item F@var{call-id},@var{parameter@dots{}}
27881 @var{call-id} is the identifier to indicate the host system call to be called.
27882 This is just the name of the function.
27884 @var{parameter@dots{}} are the parameters to the system call.
27885 Parameters are hexadecimal integer values, either the actual values in case
27886 of scalar datatypes, pointers to target buffer space in case of compound
27887 datatypes and unspecified memory areas, or pointer/length pairs in case
27888 of string parameters. These are appended to the @var{call-id} as a
27889 comma-delimited list. All values are transmitted in ASCII
27890 string representation, pointer/length pairs separated by a slash.
27896 @node The F Reply Packet
27897 @subsection The @code{F} Reply Packet
27898 @cindex file-i/o reply packet
27899 @cindex @code{F} reply packet
27901 The @code{F} reply packet has the following format:
27905 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
27907 @var{retcode} is the return code of the system call as hexadecimal value.
27909 @var{errno} is the @code{errno} set by the call, in protocol-specific
27911 This parameter can be omitted if the call was successful.
27913 @var{Ctrl-C flag} is only sent if the user requested a break. In this
27914 case, @var{errno} must be sent as well, even if the call was successful.
27915 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
27922 or, if the call was interrupted before the host call has been performed:
27929 assuming 4 is the protocol-specific representation of @code{EINTR}.
27934 @node The Ctrl-C Message
27935 @subsection The @samp{Ctrl-C} Message
27936 @cindex ctrl-c message, in file-i/o protocol
27938 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
27939 reply packet (@pxref{The F Reply Packet}),
27940 the target should behave as if it had
27941 gotten a break message. The meaning for the target is ``system call
27942 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
27943 (as with a break message) and return to @value{GDBN} with a @code{T02}
27946 It's important for the target to know in which
27947 state the system call was interrupted. There are two possible cases:
27951 The system call hasn't been performed on the host yet.
27954 The system call on the host has been finished.
27958 These two states can be distinguished by the target by the value of the
27959 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
27960 call hasn't been performed. This is equivalent to the @code{EINTR} handling
27961 on POSIX systems. In any other case, the target may presume that the
27962 system call has been finished --- successfully or not --- and should behave
27963 as if the break message arrived right after the system call.
27965 @value{GDBN} must behave reliably. If the system call has not been called
27966 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
27967 @code{errno} in the packet. If the system call on the host has been finished
27968 before the user requests a break, the full action must be finished by
27969 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
27970 The @code{F} packet may only be sent when either nothing has happened
27971 or the full action has been completed.
27974 @subsection Console I/O
27975 @cindex console i/o as part of file-i/o
27977 By default and if not explicitly closed by the target system, the file
27978 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
27979 on the @value{GDBN} console is handled as any other file output operation
27980 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
27981 by @value{GDBN} so that after the target read request from file descriptor
27982 0 all following typing is buffered until either one of the following
27987 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
27989 system call is treated as finished.
27992 The user presses @key{RET}. This is treated as end of input with a trailing
27996 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
27997 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
28001 If the user has typed more characters than fit in the buffer given to
28002 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
28003 either another @code{read(0, @dots{})} is requested by the target, or debugging
28004 is stopped at the user's request.
28007 @node List of Supported Calls
28008 @subsection List of Supported Calls
28009 @cindex list of supported file-i/o calls
28026 @unnumberedsubsubsec open
28027 @cindex open, file-i/o system call
28032 int open(const char *pathname, int flags);
28033 int open(const char *pathname, int flags, mode_t mode);
28037 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
28040 @var{flags} is the bitwise @code{OR} of the following values:
28044 If the file does not exist it will be created. The host
28045 rules apply as far as file ownership and time stamps
28049 When used with @code{O_CREAT}, if the file already exists it is
28050 an error and open() fails.
28053 If the file already exists and the open mode allows
28054 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
28055 truncated to zero length.
28058 The file is opened in append mode.
28061 The file is opened for reading only.
28064 The file is opened for writing only.
28067 The file is opened for reading and writing.
28071 Other bits are silently ignored.
28075 @var{mode} is the bitwise @code{OR} of the following values:
28079 User has read permission.
28082 User has write permission.
28085 Group has read permission.
28088 Group has write permission.
28091 Others have read permission.
28094 Others have write permission.
28098 Other bits are silently ignored.
28101 @item Return value:
28102 @code{open} returns the new file descriptor or -1 if an error
28109 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
28112 @var{pathname} refers to a directory.
28115 The requested access is not allowed.
28118 @var{pathname} was too long.
28121 A directory component in @var{pathname} does not exist.
28124 @var{pathname} refers to a device, pipe, named pipe or socket.
28127 @var{pathname} refers to a file on a read-only filesystem and
28128 write access was requested.
28131 @var{pathname} is an invalid pointer value.
28134 No space on device to create the file.
28137 The process already has the maximum number of files open.
28140 The limit on the total number of files open on the system
28144 The call was interrupted by the user.
28150 @unnumberedsubsubsec close
28151 @cindex close, file-i/o system call
28160 @samp{Fclose,@var{fd}}
28162 @item Return value:
28163 @code{close} returns zero on success, or -1 if an error occurred.
28169 @var{fd} isn't a valid open file descriptor.
28172 The call was interrupted by the user.
28178 @unnumberedsubsubsec read
28179 @cindex read, file-i/o system call
28184 int read(int fd, void *buf, unsigned int count);
28188 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
28190 @item Return value:
28191 On success, the number of bytes read is returned.
28192 Zero indicates end of file. If count is zero, read
28193 returns zero as well. On error, -1 is returned.
28199 @var{fd} is not a valid file descriptor or is not open for
28203 @var{bufptr} is an invalid pointer value.
28206 The call was interrupted by the user.
28212 @unnumberedsubsubsec write
28213 @cindex write, file-i/o system call
28218 int write(int fd, const void *buf, unsigned int count);
28222 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
28224 @item Return value:
28225 On success, the number of bytes written are returned.
28226 Zero indicates nothing was written. On error, -1
28233 @var{fd} is not a valid file descriptor or is not open for
28237 @var{bufptr} is an invalid pointer value.
28240 An attempt was made to write a file that exceeds the
28241 host-specific maximum file size allowed.
28244 No space on device to write the data.
28247 The call was interrupted by the user.
28253 @unnumberedsubsubsec lseek
28254 @cindex lseek, file-i/o system call
28259 long lseek (int fd, long offset, int flag);
28263 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
28265 @var{flag} is one of:
28269 The offset is set to @var{offset} bytes.
28272 The offset is set to its current location plus @var{offset}
28276 The offset is set to the size of the file plus @var{offset}
28280 @item Return value:
28281 On success, the resulting unsigned offset in bytes from
28282 the beginning of the file is returned. Otherwise, a
28283 value of -1 is returned.
28289 @var{fd} is not a valid open file descriptor.
28292 @var{fd} is associated with the @value{GDBN} console.
28295 @var{flag} is not a proper value.
28298 The call was interrupted by the user.
28304 @unnumberedsubsubsec rename
28305 @cindex rename, file-i/o system call
28310 int rename(const char *oldpath, const char *newpath);
28314 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
28316 @item Return value:
28317 On success, zero is returned. On error, -1 is returned.
28323 @var{newpath} is an existing directory, but @var{oldpath} is not a
28327 @var{newpath} is a non-empty directory.
28330 @var{oldpath} or @var{newpath} is a directory that is in use by some
28334 An attempt was made to make a directory a subdirectory
28338 A component used as a directory in @var{oldpath} or new
28339 path is not a directory. Or @var{oldpath} is a directory
28340 and @var{newpath} exists but is not a directory.
28343 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
28346 No access to the file or the path of the file.
28350 @var{oldpath} or @var{newpath} was too long.
28353 A directory component in @var{oldpath} or @var{newpath} does not exist.
28356 The file is on a read-only filesystem.
28359 The device containing the file has no room for the new
28363 The call was interrupted by the user.
28369 @unnumberedsubsubsec unlink
28370 @cindex unlink, file-i/o system call
28375 int unlink(const char *pathname);
28379 @samp{Funlink,@var{pathnameptr}/@var{len}}
28381 @item Return value:
28382 On success, zero is returned. On error, -1 is returned.
28388 No access to the file or the path of the file.
28391 The system does not allow unlinking of directories.
28394 The file @var{pathname} cannot be unlinked because it's
28395 being used by another process.
28398 @var{pathnameptr} is an invalid pointer value.
28401 @var{pathname} was too long.
28404 A directory component in @var{pathname} does not exist.
28407 A component of the path is not a directory.
28410 The file is on a read-only filesystem.
28413 The call was interrupted by the user.
28419 @unnumberedsubsubsec stat/fstat
28420 @cindex fstat, file-i/o system call
28421 @cindex stat, file-i/o system call
28426 int stat(const char *pathname, struct stat *buf);
28427 int fstat(int fd, struct stat *buf);
28431 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
28432 @samp{Ffstat,@var{fd},@var{bufptr}}
28434 @item Return value:
28435 On success, zero is returned. On error, -1 is returned.
28441 @var{fd} is not a valid open file.
28444 A directory component in @var{pathname} does not exist or the
28445 path is an empty string.
28448 A component of the path is not a directory.
28451 @var{pathnameptr} is an invalid pointer value.
28454 No access to the file or the path of the file.
28457 @var{pathname} was too long.
28460 The call was interrupted by the user.
28466 @unnumberedsubsubsec gettimeofday
28467 @cindex gettimeofday, file-i/o system call
28472 int gettimeofday(struct timeval *tv, void *tz);
28476 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
28478 @item Return value:
28479 On success, 0 is returned, -1 otherwise.
28485 @var{tz} is a non-NULL pointer.
28488 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
28494 @unnumberedsubsubsec isatty
28495 @cindex isatty, file-i/o system call
28500 int isatty(int fd);
28504 @samp{Fisatty,@var{fd}}
28506 @item Return value:
28507 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
28513 The call was interrupted by the user.
28518 Note that the @code{isatty} call is treated as a special case: it returns
28519 1 to the target if the file descriptor is attached
28520 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
28521 would require implementing @code{ioctl} and would be more complex than
28526 @unnumberedsubsubsec system
28527 @cindex system, file-i/o system call
28532 int system(const char *command);
28536 @samp{Fsystem,@var{commandptr}/@var{len}}
28538 @item Return value:
28539 If @var{len} is zero, the return value indicates whether a shell is
28540 available. A zero return value indicates a shell is not available.
28541 For non-zero @var{len}, the value returned is -1 on error and the
28542 return status of the command otherwise. Only the exit status of the
28543 command is returned, which is extracted from the host's @code{system}
28544 return value by calling @code{WEXITSTATUS(retval)}. In case
28545 @file{/bin/sh} could not be executed, 127 is returned.
28551 The call was interrupted by the user.
28556 @value{GDBN} takes over the full task of calling the necessary host calls
28557 to perform the @code{system} call. The return value of @code{system} on
28558 the host is simplified before it's returned
28559 to the target. Any termination signal information from the child process
28560 is discarded, and the return value consists
28561 entirely of the exit status of the called command.
28563 Due to security concerns, the @code{system} call is by default refused
28564 by @value{GDBN}. The user has to allow this call explicitly with the
28565 @code{set remote system-call-allowed 1} command.
28568 @item set remote system-call-allowed
28569 @kindex set remote system-call-allowed
28570 Control whether to allow the @code{system} calls in the File I/O
28571 protocol for the remote target. The default is zero (disabled).
28573 @item show remote system-call-allowed
28574 @kindex show remote system-call-allowed
28575 Show whether the @code{system} calls are allowed in the File I/O
28579 @node Protocol-specific Representation of Datatypes
28580 @subsection Protocol-specific Representation of Datatypes
28581 @cindex protocol-specific representation of datatypes, in file-i/o protocol
28584 * Integral Datatypes::
28586 * Memory Transfer::
28591 @node Integral Datatypes
28592 @unnumberedsubsubsec Integral Datatypes
28593 @cindex integral datatypes, in file-i/o protocol
28595 The integral datatypes used in the system calls are @code{int},
28596 @code{unsigned int}, @code{long}, @code{unsigned long},
28597 @code{mode_t}, and @code{time_t}.
28599 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
28600 implemented as 32 bit values in this protocol.
28602 @code{long} and @code{unsigned long} are implemented as 64 bit types.
28604 @xref{Limits}, for corresponding MIN and MAX values (similar to those
28605 in @file{limits.h}) to allow range checking on host and target.
28607 @code{time_t} datatypes are defined as seconds since the Epoch.
28609 All integral datatypes transferred as part of a memory read or write of a
28610 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
28613 @node Pointer Values
28614 @unnumberedsubsubsec Pointer Values
28615 @cindex pointer values, in file-i/o protocol
28617 Pointers to target data are transmitted as they are. An exception
28618 is made for pointers to buffers for which the length isn't
28619 transmitted as part of the function call, namely strings. Strings
28620 are transmitted as a pointer/length pair, both as hex values, e.g.@:
28627 which is a pointer to data of length 18 bytes at position 0x1aaf.
28628 The length is defined as the full string length in bytes, including
28629 the trailing null byte. For example, the string @code{"hello world"}
28630 at address 0x123456 is transmitted as
28636 @node Memory Transfer
28637 @unnumberedsubsubsec Memory Transfer
28638 @cindex memory transfer, in file-i/o protocol
28640 Structured data which is transferred using a memory read or write (for
28641 example, a @code{struct stat}) is expected to be in a protocol-specific format
28642 with all scalar multibyte datatypes being big endian. Translation to
28643 this representation needs to be done both by the target before the @code{F}
28644 packet is sent, and by @value{GDBN} before
28645 it transfers memory to the target. Transferred pointers to structured
28646 data should point to the already-coerced data at any time.
28650 @unnumberedsubsubsec struct stat
28651 @cindex struct stat, in file-i/o protocol
28653 The buffer of type @code{struct stat} used by the target and @value{GDBN}
28654 is defined as follows:
28658 unsigned int st_dev; /* device */
28659 unsigned int st_ino; /* inode */
28660 mode_t st_mode; /* protection */
28661 unsigned int st_nlink; /* number of hard links */
28662 unsigned int st_uid; /* user ID of owner */
28663 unsigned int st_gid; /* group ID of owner */
28664 unsigned int st_rdev; /* device type (if inode device) */
28665 unsigned long st_size; /* total size, in bytes */
28666 unsigned long st_blksize; /* blocksize for filesystem I/O */
28667 unsigned long st_blocks; /* number of blocks allocated */
28668 time_t st_atime; /* time of last access */
28669 time_t st_mtime; /* time of last modification */
28670 time_t st_ctime; /* time of last change */
28674 The integral datatypes conform to the definitions given in the
28675 appropriate section (see @ref{Integral Datatypes}, for details) so this
28676 structure is of size 64 bytes.
28678 The values of several fields have a restricted meaning and/or
28684 A value of 0 represents a file, 1 the console.
28687 No valid meaning for the target. Transmitted unchanged.
28690 Valid mode bits are described in @ref{Constants}. Any other
28691 bits have currently no meaning for the target.
28696 No valid meaning for the target. Transmitted unchanged.
28701 These values have a host and file system dependent
28702 accuracy. Especially on Windows hosts, the file system may not
28703 support exact timing values.
28706 The target gets a @code{struct stat} of the above representation and is
28707 responsible for coercing it to the target representation before
28710 Note that due to size differences between the host, target, and protocol
28711 representations of @code{struct stat} members, these members could eventually
28712 get truncated on the target.
28714 @node struct timeval
28715 @unnumberedsubsubsec struct timeval
28716 @cindex struct timeval, in file-i/o protocol
28718 The buffer of type @code{struct timeval} used by the File-I/O protocol
28719 is defined as follows:
28723 time_t tv_sec; /* second */
28724 long tv_usec; /* microsecond */
28728 The integral datatypes conform to the definitions given in the
28729 appropriate section (see @ref{Integral Datatypes}, for details) so this
28730 structure is of size 8 bytes.
28733 @subsection Constants
28734 @cindex constants, in file-i/o protocol
28736 The following values are used for the constants inside of the
28737 protocol. @value{GDBN} and target are responsible for translating these
28738 values before and after the call as needed.
28749 @unnumberedsubsubsec Open Flags
28750 @cindex open flags, in file-i/o protocol
28752 All values are given in hexadecimal representation.
28764 @node mode_t Values
28765 @unnumberedsubsubsec mode_t Values
28766 @cindex mode_t values, in file-i/o protocol
28768 All values are given in octal representation.
28785 @unnumberedsubsubsec Errno Values
28786 @cindex errno values, in file-i/o protocol
28788 All values are given in decimal representation.
28813 @code{EUNKNOWN} is used as a fallback error value if a host system returns
28814 any error value not in the list of supported error numbers.
28817 @unnumberedsubsubsec Lseek Flags
28818 @cindex lseek flags, in file-i/o protocol
28827 @unnumberedsubsubsec Limits
28828 @cindex limits, in file-i/o protocol
28830 All values are given in decimal representation.
28833 INT_MIN -2147483648
28835 UINT_MAX 4294967295
28836 LONG_MIN -9223372036854775808
28837 LONG_MAX 9223372036854775807
28838 ULONG_MAX 18446744073709551615
28841 @node File-I/O Examples
28842 @subsection File-I/O Examples
28843 @cindex file-i/o examples
28845 Example sequence of a write call, file descriptor 3, buffer is at target
28846 address 0x1234, 6 bytes should be written:
28849 <- @code{Fwrite,3,1234,6}
28850 @emph{request memory read from target}
28853 @emph{return "6 bytes written"}
28857 Example sequence of a read call, file descriptor 3, buffer is at target
28858 address 0x1234, 6 bytes should be read:
28861 <- @code{Fread,3,1234,6}
28862 @emph{request memory write to target}
28863 -> @code{X1234,6:XXXXXX}
28864 @emph{return "6 bytes read"}
28868 Example sequence of a read call, call fails on the host due to invalid
28869 file descriptor (@code{EBADF}):
28872 <- @code{Fread,3,1234,6}
28876 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
28880 <- @code{Fread,3,1234,6}
28885 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
28889 <- @code{Fread,3,1234,6}
28890 -> @code{X1234,6:XXXXXX}
28894 @node Library List Format
28895 @section Library List Format
28896 @cindex library list format, remote protocol
28898 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
28899 same process as your application to manage libraries. In this case,
28900 @value{GDBN} can use the loader's symbol table and normal memory
28901 operations to maintain a list of shared libraries. On other
28902 platforms, the operating system manages loaded libraries.
28903 @value{GDBN} can not retrieve the list of currently loaded libraries
28904 through memory operations, so it uses the @samp{qXfer:libraries:read}
28905 packet (@pxref{qXfer library list read}) instead. The remote stub
28906 queries the target's operating system and reports which libraries
28909 The @samp{qXfer:libraries:read} packet returns an XML document which
28910 lists loaded libraries and their offsets. Each library has an
28911 associated name and one or more segment or section base addresses,
28912 which report where the library was loaded in memory.
28914 For the common case of libraries that are fully linked binaries, the
28915 library should have a list of segments. If the target supports
28916 dynamic linking of a relocatable object file, its library XML element
28917 should instead include a list of allocated sections. The segment or
28918 section bases are start addresses, not relocation offsets; they do not
28919 depend on the library's link-time base addresses.
28921 @value{GDBN} must be linked with the Expat library to support XML
28922 library lists. @xref{Expat}.
28924 A simple memory map, with one loaded library relocated by a single
28925 offset, looks like this:
28929 <library name="/lib/libc.so.6">
28930 <segment address="0x10000000"/>
28935 Another simple memory map, with one loaded library with three
28936 allocated sections (.text, .data, .bss), looks like this:
28940 <library name="sharedlib.o">
28941 <section address="0x10000000"/>
28942 <section address="0x20000000"/>
28943 <section address="0x30000000"/>
28948 The format of a library list is described by this DTD:
28951 <!-- library-list: Root element with versioning -->
28952 <!ELEMENT library-list (library)*>
28953 <!ATTLIST library-list version CDATA #FIXED "1.0">
28954 <!ELEMENT library (segment*, section*)>
28955 <!ATTLIST library name CDATA #REQUIRED>
28956 <!ELEMENT segment EMPTY>
28957 <!ATTLIST segment address CDATA #REQUIRED>
28958 <!ELEMENT section EMPTY>
28959 <!ATTLIST section address CDATA #REQUIRED>
28962 In addition, segments and section descriptors cannot be mixed within a
28963 single library element, and you must supply at least one segment or
28964 section for each library.
28966 @node Memory Map Format
28967 @section Memory Map Format
28968 @cindex memory map format
28970 To be able to write into flash memory, @value{GDBN} needs to obtain a
28971 memory map from the target. This section describes the format of the
28974 The memory map is obtained using the @samp{qXfer:memory-map:read}
28975 (@pxref{qXfer memory map read}) packet and is an XML document that
28976 lists memory regions.
28978 @value{GDBN} must be linked with the Expat library to support XML
28979 memory maps. @xref{Expat}.
28981 The top-level structure of the document is shown below:
28984 <?xml version="1.0"?>
28985 <!DOCTYPE memory-map
28986 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
28987 "http://sourceware.org/gdb/gdb-memory-map.dtd">
28993 Each region can be either:
28998 A region of RAM starting at @var{addr} and extending for @var{length}
29002 <memory type="ram" start="@var{addr}" length="@var{length}"/>
29007 A region of read-only memory:
29010 <memory type="rom" start="@var{addr}" length="@var{length}"/>
29015 A region of flash memory, with erasure blocks @var{blocksize}
29019 <memory type="flash" start="@var{addr}" length="@var{length}">
29020 <property name="blocksize">@var{blocksize}</property>
29026 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
29027 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
29028 packets to write to addresses in such ranges.
29030 The formal DTD for memory map format is given below:
29033 <!-- ................................................... -->
29034 <!-- Memory Map XML DTD ................................ -->
29035 <!-- File: memory-map.dtd .............................. -->
29036 <!-- .................................... .............. -->
29037 <!-- memory-map.dtd -->
29038 <!-- memory-map: Root element with versioning -->
29039 <!ELEMENT memory-map (memory | property)>
29040 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
29041 <!ELEMENT memory (property)>
29042 <!-- memory: Specifies a memory region,
29043 and its type, or device. -->
29044 <!ATTLIST memory type CDATA #REQUIRED
29045 start CDATA #REQUIRED
29046 length CDATA #REQUIRED
29047 device CDATA #IMPLIED>
29048 <!-- property: Generic attribute tag -->
29049 <!ELEMENT property (#PCDATA | property)*>
29050 <!ATTLIST property name CDATA #REQUIRED>
29053 @include agentexpr.texi
29055 @node Target Descriptions
29056 @appendix Target Descriptions
29057 @cindex target descriptions
29059 @strong{Warning:} target descriptions are still under active development,
29060 and the contents and format may change between @value{GDBN} releases.
29061 The format is expected to stabilize in the future.
29063 One of the challenges of using @value{GDBN} to debug embedded systems
29064 is that there are so many minor variants of each processor
29065 architecture in use. It is common practice for vendors to start with
29066 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
29067 and then make changes to adapt it to a particular market niche. Some
29068 architectures have hundreds of variants, available from dozens of
29069 vendors. This leads to a number of problems:
29073 With so many different customized processors, it is difficult for
29074 the @value{GDBN} maintainers to keep up with the changes.
29076 Since individual variants may have short lifetimes or limited
29077 audiences, it may not be worthwhile to carry information about every
29078 variant in the @value{GDBN} source tree.
29080 When @value{GDBN} does support the architecture of the embedded system
29081 at hand, the task of finding the correct architecture name to give the
29082 @command{set architecture} command can be error-prone.
29085 To address these problems, the @value{GDBN} remote protocol allows a
29086 target system to not only identify itself to @value{GDBN}, but to
29087 actually describe its own features. This lets @value{GDBN} support
29088 processor variants it has never seen before --- to the extent that the
29089 descriptions are accurate, and that @value{GDBN} understands them.
29091 @value{GDBN} must be linked with the Expat library to support XML
29092 target descriptions. @xref{Expat}.
29095 * Retrieving Descriptions:: How descriptions are fetched from a target.
29096 * Target Description Format:: The contents of a target description.
29097 * Predefined Target Types:: Standard types available for target
29099 * Standard Target Features:: Features @value{GDBN} knows about.
29102 @node Retrieving Descriptions
29103 @section Retrieving Descriptions
29105 Target descriptions can be read from the target automatically, or
29106 specified by the user manually. The default behavior is to read the
29107 description from the target. @value{GDBN} retrieves it via the remote
29108 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
29109 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
29110 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
29111 XML document, of the form described in @ref{Target Description
29114 Alternatively, you can specify a file to read for the target description.
29115 If a file is set, the target will not be queried. The commands to
29116 specify a file are:
29119 @cindex set tdesc filename
29120 @item set tdesc filename @var{path}
29121 Read the target description from @var{path}.
29123 @cindex unset tdesc filename
29124 @item unset tdesc filename
29125 Do not read the XML target description from a file. @value{GDBN}
29126 will use the description supplied by the current target.
29128 @cindex show tdesc filename
29129 @item show tdesc filename
29130 Show the filename to read for a target description, if any.
29134 @node Target Description Format
29135 @section Target Description Format
29136 @cindex target descriptions, XML format
29138 A target description annex is an @uref{http://www.w3.org/XML/, XML}
29139 document which complies with the Document Type Definition provided in
29140 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
29141 means you can use generally available tools like @command{xmllint} to
29142 check that your feature descriptions are well-formed and valid.
29143 However, to help people unfamiliar with XML write descriptions for
29144 their targets, we also describe the grammar here.
29146 Target descriptions can identify the architecture of the remote target
29147 and (for some architectures) provide information about custom register
29148 sets. @value{GDBN} can use this information to autoconfigure for your
29149 target, or to warn you if you connect to an unsupported target.
29151 Here is a simple target description:
29154 <target version="1.0">
29155 <architecture>i386:x86-64</architecture>
29160 This minimal description only says that the target uses
29161 the x86-64 architecture.
29163 A target description has the following overall form, with [ ] marking
29164 optional elements and @dots{} marking repeatable elements. The elements
29165 are explained further below.
29168 <?xml version="1.0"?>
29169 <!DOCTYPE target SYSTEM "gdb-target.dtd">
29170 <target version="1.0">
29171 @r{[}@var{architecture}@r{]}
29172 @r{[}@var{feature}@dots{}@r{]}
29177 The description is generally insensitive to whitespace and line
29178 breaks, under the usual common-sense rules. The XML version
29179 declaration and document type declaration can generally be omitted
29180 (@value{GDBN} does not require them), but specifying them may be
29181 useful for XML validation tools. The @samp{version} attribute for
29182 @samp{<target>} may also be omitted, but we recommend
29183 including it; if future versions of @value{GDBN} use an incompatible
29184 revision of @file{gdb-target.dtd}, they will detect and report
29185 the version mismatch.
29187 @subsection Inclusion
29188 @cindex target descriptions, inclusion
29191 @cindex <xi:include>
29194 It can sometimes be valuable to split a target description up into
29195 several different annexes, either for organizational purposes, or to
29196 share files between different possible target descriptions. You can
29197 divide a description into multiple files by replacing any element of
29198 the target description with an inclusion directive of the form:
29201 <xi:include href="@var{document}"/>
29205 When @value{GDBN} encounters an element of this form, it will retrieve
29206 the named XML @var{document}, and replace the inclusion directive with
29207 the contents of that document. If the current description was read
29208 using @samp{qXfer}, then so will be the included document;
29209 @var{document} will be interpreted as the name of an annex. If the
29210 current description was read from a file, @value{GDBN} will look for
29211 @var{document} as a file in the same directory where it found the
29212 original description.
29214 @subsection Architecture
29215 @cindex <architecture>
29217 An @samp{<architecture>} element has this form:
29220 <architecture>@var{arch}</architecture>
29223 @var{arch} is an architecture name from the same selection
29224 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
29225 Debugging Target}).
29227 @subsection Features
29230 Each @samp{<feature>} describes some logical portion of the target
29231 system. Features are currently used to describe available CPU
29232 registers and the types of their contents. A @samp{<feature>} element
29236 <feature name="@var{name}">
29237 @r{[}@var{type}@dots{}@r{]}
29243 Each feature's name should be unique within the description. The name
29244 of a feature does not matter unless @value{GDBN} has some special
29245 knowledge of the contents of that feature; if it does, the feature
29246 should have its standard name. @xref{Standard Target Features}.
29250 Any register's value is a collection of bits which @value{GDBN} must
29251 interpret. The default interpretation is a two's complement integer,
29252 but other types can be requested by name in the register description.
29253 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
29254 Target Types}), and the description can define additional composite types.
29256 Each type element must have an @samp{id} attribute, which gives
29257 a unique (within the containing @samp{<feature>}) name to the type.
29258 Types must be defined before they are used.
29261 Some targets offer vector registers, which can be treated as arrays
29262 of scalar elements. These types are written as @samp{<vector>} elements,
29263 specifying the array element type, @var{type}, and the number of elements,
29267 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
29271 If a register's value is usefully viewed in multiple ways, define it
29272 with a union type containing the useful representations. The
29273 @samp{<union>} element contains one or more @samp{<field>} elements,
29274 each of which has a @var{name} and a @var{type}:
29277 <union id="@var{id}">
29278 <field name="@var{name}" type="@var{type}"/>
29283 @subsection Registers
29286 Each register is represented as an element with this form:
29289 <reg name="@var{name}"
29290 bitsize="@var{size}"
29291 @r{[}regnum="@var{num}"@r{]}
29292 @r{[}save-restore="@var{save-restore}"@r{]}
29293 @r{[}type="@var{type}"@r{]}
29294 @r{[}group="@var{group}"@r{]}/>
29298 The components are as follows:
29303 The register's name; it must be unique within the target description.
29306 The register's size, in bits.
29309 The register's number. If omitted, a register's number is one greater
29310 than that of the previous register (either in the current feature or in
29311 a preceeding feature); the first register in the target description
29312 defaults to zero. This register number is used to read or write
29313 the register; e.g.@: it is used in the remote @code{p} and @code{P}
29314 packets, and registers appear in the @code{g} and @code{G} packets
29315 in order of increasing register number.
29318 Whether the register should be preserved across inferior function
29319 calls; this must be either @code{yes} or @code{no}. The default is
29320 @code{yes}, which is appropriate for most registers except for
29321 some system control registers; this is not related to the target's
29325 The type of the register. @var{type} may be a predefined type, a type
29326 defined in the current feature, or one of the special types @code{int}
29327 and @code{float}. @code{int} is an integer type of the correct size
29328 for @var{bitsize}, and @code{float} is a floating point type (in the
29329 architecture's normal floating point format) of the correct size for
29330 @var{bitsize}. The default is @code{int}.
29333 The register group to which this register belongs. @var{group} must
29334 be either @code{general}, @code{float}, or @code{vector}. If no
29335 @var{group} is specified, @value{GDBN} will not display the register
29336 in @code{info registers}.
29340 @node Predefined Target Types
29341 @section Predefined Target Types
29342 @cindex target descriptions, predefined types
29344 Type definitions in the self-description can build up composite types
29345 from basic building blocks, but can not define fundamental types. Instead,
29346 standard identifiers are provided by @value{GDBN} for the fundamental
29347 types. The currently supported types are:
29356 Signed integer types holding the specified number of bits.
29363 Unsigned integer types holding the specified number of bits.
29367 Pointers to unspecified code and data. The program counter and
29368 any dedicated return address register may be marked as code
29369 pointers; printing a code pointer converts it into a symbolic
29370 address. The stack pointer and any dedicated address registers
29371 may be marked as data pointers.
29374 Single precision IEEE floating point.
29377 Double precision IEEE floating point.
29380 The 12-byte extended precision format used by ARM FPA registers.
29384 @node Standard Target Features
29385 @section Standard Target Features
29386 @cindex target descriptions, standard features
29388 A target description must contain either no registers or all the
29389 target's registers. If the description contains no registers, then
29390 @value{GDBN} will assume a default register layout, selected based on
29391 the architecture. If the description contains any registers, the
29392 default layout will not be used; the standard registers must be
29393 described in the target description, in such a way that @value{GDBN}
29394 can recognize them.
29396 This is accomplished by giving specific names to feature elements
29397 which contain standard registers. @value{GDBN} will look for features
29398 with those names and verify that they contain the expected registers;
29399 if any known feature is missing required registers, or if any required
29400 feature is missing, @value{GDBN} will reject the target
29401 description. You can add additional registers to any of the
29402 standard features --- @value{GDBN} will display them just as if
29403 they were added to an unrecognized feature.
29405 This section lists the known features and their expected contents.
29406 Sample XML documents for these features are included in the
29407 @value{GDBN} source tree, in the directory @file{gdb/features}.
29409 Names recognized by @value{GDBN} should include the name of the
29410 company or organization which selected the name, and the overall
29411 architecture to which the feature applies; so e.g.@: the feature
29412 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
29414 The names of registers are not case sensitive for the purpose
29415 of recognizing standard features, but @value{GDBN} will only display
29416 registers using the capitalization used in the description.
29422 * PowerPC Features::
29427 @subsection ARM Features
29428 @cindex target descriptions, ARM features
29430 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
29431 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
29432 @samp{lr}, @samp{pc}, and @samp{cpsr}.
29434 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
29435 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
29437 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
29438 it should contain at least registers @samp{wR0} through @samp{wR15} and
29439 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
29440 @samp{wCSSF}, and @samp{wCASF} registers are optional.
29442 @node MIPS Features
29443 @subsection MIPS Features
29444 @cindex target descriptions, MIPS features
29446 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
29447 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
29448 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
29451 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
29452 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
29453 registers. They may be 32-bit or 64-bit depending on the target.
29455 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
29456 it may be optional in a future version of @value{GDBN}. It should
29457 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
29458 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
29460 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
29461 contain a single register, @samp{restart}, which is used by the
29462 Linux kernel to control restartable syscalls.
29464 @node M68K Features
29465 @subsection M68K Features
29466 @cindex target descriptions, M68K features
29469 @item @samp{org.gnu.gdb.m68k.core}
29470 @itemx @samp{org.gnu.gdb.coldfire.core}
29471 @itemx @samp{org.gnu.gdb.fido.core}
29472 One of those features must be always present.
29473 The feature that is present determines which flavor of m68k is
29474 used. The feature that is present should contain registers
29475 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
29476 @samp{sp}, @samp{ps} and @samp{pc}.
29478 @item @samp{org.gnu.gdb.coldfire.fp}
29479 This feature is optional. If present, it should contain registers
29480 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
29484 @node PowerPC Features
29485 @subsection PowerPC Features
29486 @cindex target descriptions, PowerPC features
29488 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
29489 targets. It should contain registers @samp{r0} through @samp{r31},
29490 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
29491 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
29493 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
29494 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
29496 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
29497 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
29500 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
29501 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
29502 will combine these registers with the floating point registers
29503 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
29504 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
29505 through @samp{vs63}, the set of vector registers for POWER7.
29507 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
29508 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
29509 @samp{spefscr}. SPE targets should provide 32-bit registers in
29510 @samp{org.gnu.gdb.power.core} and provide the upper halves in
29511 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
29512 these to present registers @samp{ev0} through @samp{ev31} to the
29515 @node Operating System Information
29516 @appendix Operating System Information
29517 @cindex operating system information
29523 Users of @value{GDBN} often wish to obtain information about the state of
29524 the operating system running on the target---for example the list of
29525 processes, or the list of open files. This section describes the
29526 mechanism that makes it possible. This mechanism is similar to the
29527 target features mechanism (@pxref{Target Descriptions}), but focuses
29528 on a different aspect of target.
29530 Operating system information is retrived from the target via the
29531 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
29532 read}). The object name in the request should be @samp{osdata}, and
29533 the @var{annex} identifies the data to be fetched.
29536 @appendixsection Process list
29537 @cindex operating system information, process list
29539 When requesting the process list, the @var{annex} field in the
29540 @samp{qXfer} request should be @samp{processes}. The returned data is
29541 an XML document. The formal syntax of this document is defined in
29542 @file{gdb/features/osdata.dtd}.
29544 An example document is:
29547 <?xml version="1.0"?>
29548 <!DOCTYPE target SYSTEM "osdata.dtd">
29549 <osdata type="processes">
29551 <column name="pid">1</column>
29552 <column name="user">root</column>
29553 <column name="command">/sbin/init</column>
29558 Each item should include a column whose name is @samp{pid}. The value
29559 of that column should identify the process on the target. The
29560 @samp{user} and @samp{command} columns are optional, and will be
29561 displayed by @value{GDBN}. Target may provide additional columns,
29562 which @value{GDBN} currently ignores.
29576 % I think something like @colophon should be in texinfo. In the
29578 \long\def\colophon{\hbox to0pt{}\vfill
29579 \centerline{The body of this manual is set in}
29580 \centerline{\fontname\tenrm,}
29581 \centerline{with headings in {\bf\fontname\tenbf}}
29582 \centerline{and examples in {\tt\fontname\tentt}.}
29583 \centerline{{\it\fontname\tenit\/},}
29584 \centerline{{\bf\fontname\tenbf}, and}
29585 \centerline{{\sl\fontname\tensl\/}}
29586 \centerline{are used for emphasis.}\vfill}
29588 % Blame: doc@cygnus.com, 1991.