1 \input texinfo @c -*-texinfo-*-
2 @c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003
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 Programming & development tools.
43 * Gdb: (gdb). The @sc{gnu} debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 Version @value{GDBVN}.
54 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
55 1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
57 Permission is granted to copy, distribute and/or modify this document
58 under the terms of the GNU Free Documentation License, Version 1.1 or
59 any later version published by the Free Software Foundation; with the
60 Invariant Sections being ``Free Software'' and ``Free Software Needs
61 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
62 and with the Back-Cover Texts as in (a) below.
64 (a) The Free Software Foundation's Back-Cover Text is: ``You have
65 freedom to copy and modify this GNU Manual, like GNU software. Copies
66 published by the Free Software Foundation raise funds for GNU
71 @title Debugging with @value{GDBN}
72 @subtitle The @sc{gnu} Source-Level Debugger
74 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
75 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
79 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
80 \hfill {\it Debugging with @value{GDBN}}\par
81 \hfill \TeX{}info \texinfoversion\par
85 @vskip 0pt plus 1filll
86 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
87 1996, 1998, 1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
89 Published by the Free Software Foundation @*
90 59 Temple Place - Suite 330, @*
91 Boston, MA 02111-1307 USA @*
94 Permission is granted to copy, distribute and/or modify this document
95 under the terms of the GNU Free Documentation License, Version 1.1 or
96 any later version published by the Free Software Foundation; with the
97 Invariant Sections being ``Free Software'' and ``Free Software Needs
98 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
99 and with the Back-Cover Texts as in (a) below.
101 (a) The Free Software Foundation's Back-Cover Text is: ``You have
102 freedom to copy and modify this GNU Manual, like GNU software. Copies
103 published by the Free Software Foundation raise funds for GNU
109 @node Top, Summary, (dir), (dir)
111 @top Debugging with @value{GDBN}
113 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
115 This is the @value{EDITION} Edition, for @value{GDBN} Version
118 Copyright (C) 1988-2003 Free Software Foundation, Inc.
121 * Summary:: Summary of @value{GDBN}
122 * Sample Session:: A sample @value{GDBN} session
124 * Invocation:: Getting in and out of @value{GDBN}
125 * Commands:: @value{GDBN} commands
126 * Running:: Running programs under @value{GDBN}
127 * Stopping:: Stopping and continuing
128 * Stack:: Examining the stack
129 * Source:: Examining source files
130 * Data:: Examining data
131 * Macros:: Preprocessor Macros
132 * Tracepoints:: Debugging remote targets non-intrusively
133 * Overlays:: Debugging programs that use overlays
135 * Languages:: Using @value{GDBN} with different languages
137 * Symbols:: Examining the symbol table
138 * Altering:: Altering execution
139 * GDB Files:: @value{GDBN} files
140 * Targets:: Specifying a debugging target
141 * Remote Debugging:: Debugging remote programs
142 * Configurations:: Configuration-specific information
143 * Controlling GDB:: Controlling @value{GDBN}
144 * Sequences:: Canned sequences of commands
145 * TUI:: @value{GDBN} Text User Interface
146 * Interpreters:: Command Interpreters
147 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
148 * Annotations:: @value{GDBN}'s annotation interface.
149 * GDB/MI:: @value{GDBN}'s Machine Interface.
151 * GDB Bugs:: Reporting bugs in @value{GDBN}
152 * Formatting Documentation:: How to format and print @value{GDBN} documentation
154 * Command Line Editing:: Command Line Editing
155 * Using History Interactively:: Using History Interactively
156 * Installing GDB:: Installing GDB
157 * Maintenance Commands:: Maintenance Commands
158 * Remote Protocol:: GDB Remote Serial Protocol
159 * Copying:: GNU General Public License says
160 how you can copy and share GDB
161 * GNU Free Documentation License:: The license for this documentation
170 @unnumbered Summary of @value{GDBN}
172 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
173 going on ``inside'' another program while it executes---or what another
174 program was doing at the moment it crashed.
176 @value{GDBN} can do four main kinds of things (plus other things in support of
177 these) to help you catch bugs in the act:
181 Start your program, specifying anything that might affect its behavior.
184 Make your program stop on specified conditions.
187 Examine what has happened, when your program has stopped.
190 Change things in your program, so you can experiment with correcting the
191 effects of one bug and go on to learn about another.
194 You can use @value{GDBN} to debug programs written in C and C++.
195 For more information, see @ref{Support,,Supported languages}.
196 For more information, see @ref{C,,C and C++}.
199 Support for Modula-2 is partial. For information on Modula-2, see
200 @ref{Modula-2,,Modula-2}.
203 Debugging Pascal programs which use sets, subranges, file variables, or
204 nested functions does not currently work. @value{GDBN} does not support
205 entering expressions, printing values, or similar features using Pascal
209 @value{GDBN} can be used to debug programs written in Fortran, although
210 it may be necessary to refer to some variables with a trailing
214 * Free Software:: Freely redistributable software
215 * Contributors:: Contributors to GDB
219 @unnumberedsec Free software
221 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
222 General Public License
223 (GPL). The GPL gives you the freedom to copy or adapt a licensed
224 program---but every person getting a copy also gets with it the
225 freedom to modify that copy (which means that they must get access to
226 the source code), and the freedom to distribute further copies.
227 Typical software companies use copyrights to limit your freedoms; the
228 Free Software Foundation uses the GPL to preserve these freedoms.
230 Fundamentally, the General Public License is a license which says that
231 you have these freedoms and that you cannot take these freedoms away
234 @unnumberedsec Free Software Needs Free Documentation
236 The biggest deficiency in the free software community today is not in
237 the software---it is the lack of good free documentation that we can
238 include with the free software. Many of our most important
239 programs do not come with free reference manuals and free introductory
240 texts. Documentation is an essential part of any software package;
241 when an important free software package does not come with a free
242 manual and a free tutorial, that is a major gap. We have many such
245 Consider Perl, for instance. The tutorial manuals that people
246 normally use are non-free. How did this come about? Because the
247 authors of those manuals published them with restrictive terms---no
248 copying, no modification, source files not available---which exclude
249 them from the free software world.
251 That wasn't the first time this sort of thing happened, and it was far
252 from the last. Many times we have heard a GNU user eagerly describe a
253 manual that he is writing, his intended contribution to the community,
254 only to learn that he had ruined everything by signing a publication
255 contract to make it non-free.
257 Free documentation, like free software, is a matter of freedom, not
258 price. The problem with the non-free manual is not that publishers
259 charge a price for printed copies---that in itself is fine. (The Free
260 Software Foundation sells printed copies of manuals, too.) The
261 problem is the restrictions on the use of the manual. Free manuals
262 are available in source code form, and give you permission to copy and
263 modify. Non-free manuals do not allow this.
265 The criteria of freedom for a free manual are roughly the same as for
266 free software. Redistribution (including the normal kinds of
267 commercial redistribution) must be permitted, so that the manual can
268 accompany every copy of the program, both on-line and on paper.
270 Permission for modification of the technical content is crucial too.
271 When people modify the software, adding or changing features, if they
272 are conscientious they will change the manual too---so they can
273 provide accurate and clear documentation for the modified program. A
274 manual that leaves you no choice but to write a new manual to document
275 a changed version of the program is not really available to our
278 Some kinds of limits on the way modification is handled are
279 acceptable. For example, requirements to preserve the original
280 author's copyright notice, the distribution terms, or the list of
281 authors, are ok. It is also no problem to require modified versions
282 to include notice that they were modified. Even entire sections that
283 may not be deleted or changed are acceptable, as long as they deal
284 with nontechnical topics (like this one). These kinds of restrictions
285 are acceptable because they don't obstruct the community's normal use
288 However, it must be possible to modify all the @emph{technical}
289 content of the manual, and then distribute the result in all the usual
290 media, through all the usual channels. Otherwise, the restrictions
291 obstruct the use of the manual, it is not free, and we need another
292 manual to replace it.
294 Please spread the word about this issue. Our community continues to
295 lose manuals to proprietary publishing. If we spread the word that
296 free software needs free reference manuals and free tutorials, perhaps
297 the next person who wants to contribute by writing documentation will
298 realize, before it is too late, that only free manuals contribute to
299 the free software community.
301 If you are writing documentation, please insist on publishing it under
302 the GNU Free Documentation License or another free documentation
303 license. Remember that this decision requires your approval---you
304 don't have to let the publisher decide. Some commercial publishers
305 will use a free license if you insist, but they will not propose the
306 option; it is up to you to raise the issue and say firmly that this is
307 what you want. If the publisher you are dealing with refuses, please
308 try other publishers. If you're not sure whether a proposed license
309 is free, write to @email{licensing@@gnu.org}.
311 You can encourage commercial publishers to sell more free, copylefted
312 manuals and tutorials by buying them, and particularly by buying
313 copies from the publishers that paid for their writing or for major
314 improvements. Meanwhile, try to avoid buying non-free documentation
315 at all. Check the distribution terms of a manual before you buy it,
316 and insist that whoever seeks your business must respect your freedom.
317 Check the history of the book, and try to reward the publishers that
318 have paid or pay the authors to work on it.
320 The Free Software Foundation maintains a list of free documentation
321 published by other publishers, at
322 @url{http://www.fsf.org/doc/other-free-books.html}.
325 @unnumberedsec Contributors to @value{GDBN}
327 Richard Stallman was the original author of @value{GDBN}, and of many
328 other @sc{gnu} programs. Many others have contributed to its
329 development. This section attempts to credit major contributors. One
330 of the virtues of free software is that everyone is free to contribute
331 to it; with regret, we cannot actually acknowledge everyone here. The
332 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
333 blow-by-blow account.
335 Changes much prior to version 2.0 are lost in the mists of time.
338 @emph{Plea:} Additions to this section are particularly welcome. If you
339 or your friends (or enemies, to be evenhanded) have been unfairly
340 omitted from this list, we would like to add your names!
343 So that they may not regard their many labors as thankless, we
344 particularly thank those who shepherded @value{GDBN} through major
346 Andrew Cagney (releases 5.3, 5.2, 5.1 and 5.0);
347 Jim Blandy (release 4.18);
348 Jason Molenda (release 4.17);
349 Stan Shebs (release 4.14);
350 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
351 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
352 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
353 Jim Kingdon (releases 3.5, 3.4, and 3.3);
354 and Randy Smith (releases 3.2, 3.1, and 3.0).
356 Richard Stallman, assisted at various times by Peter TerMaat, Chris
357 Hanson, and Richard Mlynarik, handled releases through 2.8.
359 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
360 in @value{GDBN}, with significant additional contributions from Per
361 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
362 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
363 much general update work leading to release 3.0).
365 @value{GDBN} uses the BFD subroutine library to examine multiple
366 object-file formats; BFD was a joint project of David V.
367 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
369 David Johnson wrote the original COFF support; Pace Willison did
370 the original support for encapsulated COFF.
372 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
374 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
375 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
377 Jean-Daniel Fekete contributed Sun 386i support.
378 Chris Hanson improved the HP9000 support.
379 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
380 David Johnson contributed Encore Umax support.
381 Jyrki Kuoppala contributed Altos 3068 support.
382 Jeff Law contributed HP PA and SOM support.
383 Keith Packard contributed NS32K support.
384 Doug Rabson contributed Acorn Risc Machine support.
385 Bob Rusk contributed Harris Nighthawk CX-UX support.
386 Chris Smith contributed Convex support (and Fortran debugging).
387 Jonathan Stone contributed Pyramid support.
388 Michael Tiemann contributed SPARC support.
389 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
390 Pace Willison contributed Intel 386 support.
391 Jay Vosburgh contributed Symmetry support.
392 Marko Mlinar contributed OpenRISC 1000 support.
394 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
396 Rich Schaefer and Peter Schauer helped with support of SunOS shared
399 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
400 about several machine instruction sets.
402 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
403 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
404 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
405 and RDI targets, respectively.
407 Brian Fox is the author of the readline libraries providing
408 command-line editing and command history.
410 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
411 Modula-2 support, and contributed the Languages chapter of this manual.
413 Fred Fish wrote most of the support for Unix System Vr4.
414 He also enhanced the command-completion support to cover C@t{++} overloaded
417 Hitachi America, Ltd. sponsored the support for H8/300, H8/500, and
420 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
422 Mitsubishi sponsored the support for D10V, D30V, and M32R/D processors.
424 Toshiba sponsored the support for the TX39 Mips processor.
426 Matsushita sponsored the support for the MN10200 and MN10300 processors.
428 Fujitsu sponsored the support for SPARClite and FR30 processors.
430 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
433 Michael Snyder added support for tracepoints.
435 Stu Grossman wrote gdbserver.
437 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
438 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
440 The following people at the Hewlett-Packard Company contributed
441 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
442 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
443 compiler, and the terminal user interface: Ben Krepp, Richard Title,
444 John Bishop, Susan Macchia, Kathy Mann, Satish Pai, India Paul, Steve
445 Rehrauer, and Elena Zannoni. Kim Haase provided HP-specific
446 information in this manual.
448 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
449 Robert Hoehne made significant contributions to the DJGPP port.
451 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
452 development since 1991. Cygnus engineers who have worked on @value{GDBN}
453 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
454 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
455 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
456 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
457 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
458 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
459 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
460 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
461 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
462 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
463 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
464 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
465 Zuhn have made contributions both large and small.
467 Jim Blandy added support for preprocessor macros, while working for Red
471 @chapter A Sample @value{GDBN} Session
473 You can use this manual at your leisure to read all about @value{GDBN}.
474 However, a handful of commands are enough to get started using the
475 debugger. This chapter illustrates those commands.
478 In this sample session, we emphasize user input like this: @b{input},
479 to make it easier to pick out from the surrounding output.
482 @c FIXME: this example may not be appropriate for some configs, where
483 @c FIXME...primary interest is in remote use.
485 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
486 processor) exhibits the following bug: sometimes, when we change its
487 quote strings from the default, the commands used to capture one macro
488 definition within another stop working. In the following short @code{m4}
489 session, we define a macro @code{foo} which expands to @code{0000}; we
490 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
491 same thing. However, when we change the open quote string to
492 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
493 procedure fails to define a new synonym @code{baz}:
502 @b{define(bar,defn(`foo'))}
506 @b{changequote(<QUOTE>,<UNQUOTE>)}
508 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
511 m4: End of input: 0: fatal error: EOF in string
515 Let us use @value{GDBN} to try to see what is going on.
518 $ @b{@value{GDBP} m4}
519 @c FIXME: this falsifies the exact text played out, to permit smallbook
520 @c FIXME... format to come out better.
521 @value{GDBN} is free software and you are welcome to distribute copies
522 of it under certain conditions; type "show copying" to see
524 There is absolutely no warranty for @value{GDBN}; type "show warranty"
527 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
532 @value{GDBN} reads only enough symbol data to know where to find the
533 rest when needed; as a result, the first prompt comes up very quickly.
534 We now tell @value{GDBN} to use a narrower display width than usual, so
535 that examples fit in this manual.
538 (@value{GDBP}) @b{set width 70}
542 We need to see how the @code{m4} built-in @code{changequote} works.
543 Having looked at the source, we know the relevant subroutine is
544 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
545 @code{break} command.
548 (@value{GDBP}) @b{break m4_changequote}
549 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
553 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
554 control; as long as control does not reach the @code{m4_changequote}
555 subroutine, the program runs as usual:
558 (@value{GDBP}) @b{run}
559 Starting program: /work/Editorial/gdb/gnu/m4/m4
567 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
568 suspends execution of @code{m4}, displaying information about the
569 context where it stops.
572 @b{changequote(<QUOTE>,<UNQUOTE>)}
574 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
576 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
580 Now we use the command @code{n} (@code{next}) to advance execution to
581 the next line of the current function.
585 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
590 @code{set_quotes} looks like a promising subroutine. We can go into it
591 by using the command @code{s} (@code{step}) instead of @code{next}.
592 @code{step} goes to the next line to be executed in @emph{any}
593 subroutine, so it steps into @code{set_quotes}.
597 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
599 530 if (lquote != def_lquote)
603 The display that shows the subroutine where @code{m4} is now
604 suspended (and its arguments) is called a stack frame display. It
605 shows a summary of the stack. We can use the @code{backtrace}
606 command (which can also be spelled @code{bt}), to see where we are
607 in the stack as a whole: the @code{backtrace} command displays a
608 stack frame for each active subroutine.
611 (@value{GDBP}) @b{bt}
612 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
614 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
616 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
617 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
619 #4 0x79dc in expand_input () at macro.c:40
620 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
624 We step through a few more lines to see what happens. The first two
625 times, we can use @samp{s}; the next two times we use @code{n} to avoid
626 falling into the @code{xstrdup} subroutine.
630 0x3b5c 532 if (rquote != def_rquote)
632 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
633 def_lquote : xstrdup(lq);
635 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
638 538 len_lquote = strlen(rquote);
642 The last line displayed looks a little odd; we can examine the variables
643 @code{lquote} and @code{rquote} to see if they are in fact the new left
644 and right quotes we specified. We use the command @code{p}
645 (@code{print}) to see their values.
648 (@value{GDBP}) @b{p lquote}
649 $1 = 0x35d40 "<QUOTE>"
650 (@value{GDBP}) @b{p rquote}
651 $2 = 0x35d50 "<UNQUOTE>"
655 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
656 To look at some context, we can display ten lines of source
657 surrounding the current line with the @code{l} (@code{list}) command.
663 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
665 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
668 538 len_lquote = strlen(rquote);
669 539 len_rquote = strlen(lquote);
676 Let us step past the two lines that set @code{len_lquote} and
677 @code{len_rquote}, and then examine the values of those variables.
681 539 len_rquote = strlen(lquote);
684 (@value{GDBP}) @b{p len_lquote}
686 (@value{GDBP}) @b{p len_rquote}
691 That certainly looks wrong, assuming @code{len_lquote} and
692 @code{len_rquote} are meant to be the lengths of @code{lquote} and
693 @code{rquote} respectively. We can set them to better values using
694 the @code{p} command, since it can print the value of
695 any expression---and that expression can include subroutine calls and
699 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
701 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
706 Is that enough to fix the problem of using the new quotes with the
707 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
708 executing with the @code{c} (@code{continue}) command, and then try the
709 example that caused trouble initially:
715 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
722 Success! The new quotes now work just as well as the default ones. The
723 problem seems to have been just the two typos defining the wrong
724 lengths. We allow @code{m4} exit by giving it an EOF as input:
728 Program exited normally.
732 The message @samp{Program exited normally.} is from @value{GDBN}; it
733 indicates @code{m4} has finished executing. We can end our @value{GDBN}
734 session with the @value{GDBN} @code{quit} command.
737 (@value{GDBP}) @b{quit}
741 @chapter Getting In and Out of @value{GDBN}
743 This chapter discusses how to start @value{GDBN}, and how to get out of it.
747 type @samp{@value{GDBP}} to start @value{GDBN}.
749 type @kbd{quit} or @kbd{C-d} to exit.
753 * Invoking GDB:: How to start @value{GDBN}
754 * Quitting GDB:: How to quit @value{GDBN}
755 * Shell Commands:: How to use shell commands inside @value{GDBN}
759 @section Invoking @value{GDBN}
761 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
762 @value{GDBN} reads commands from the terminal until you tell it to exit.
764 You can also run @code{@value{GDBP}} with a variety of arguments and options,
765 to specify more of your debugging environment at the outset.
767 The command-line options described here are designed
768 to cover a variety of situations; in some environments, some of these
769 options may effectively be unavailable.
771 The most usual way to start @value{GDBN} is with one argument,
772 specifying an executable program:
775 @value{GDBP} @var{program}
779 You can also start with both an executable program and a core file
783 @value{GDBP} @var{program} @var{core}
786 You can, instead, specify a process ID as a second argument, if you want
787 to debug a running process:
790 @value{GDBP} @var{program} 1234
794 would attach @value{GDBN} to process @code{1234} (unless you also have a file
795 named @file{1234}; @value{GDBN} does check for a core file first).
797 Taking advantage of the second command-line argument requires a fairly
798 complete operating system; when you use @value{GDBN} as a remote
799 debugger attached to a bare board, there may not be any notion of
800 ``process'', and there is often no way to get a core dump. @value{GDBN}
801 will warn you if it is unable to attach or to read core dumps.
803 You can optionally have @code{@value{GDBP}} pass any arguments after the
804 executable file to the inferior using @code{--args}. This option stops
807 gdb --args gcc -O2 -c foo.c
809 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
810 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
812 You can run @code{@value{GDBP}} without printing the front material, which describes
813 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
820 You can further control how @value{GDBN} starts up by using command-line
821 options. @value{GDBN} itself can remind you of the options available.
831 to display all available options and briefly describe their use
832 (@samp{@value{GDBP} -h} is a shorter equivalent).
834 All options and command line arguments you give are processed
835 in sequential order. The order makes a difference when the
836 @samp{-x} option is used.
840 * File Options:: Choosing files
841 * Mode Options:: Choosing modes
845 @subsection Choosing files
847 When @value{GDBN} starts, it reads any arguments other than options as
848 specifying an executable file and core file (or process ID). This is
849 the same as if the arguments were specified by the @samp{-se} and
850 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
851 first argument that does not have an associated option flag as
852 equivalent to the @samp{-se} option followed by that argument; and the
853 second argument that does not have an associated option flag, if any, as
854 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
855 If the second argument begins with a decimal digit, @value{GDBN} will
856 first attempt to attach to it as a process, and if that fails, attempt
857 to open it as a corefile. If you have a corefile whose name begins with
858 a digit, you can prevent @value{GDBN} from treating it as a pid by
859 prefixing it with @file{./}, eg. @file{./12345}.
861 If @value{GDBN} has not been configured to included core file support,
862 such as for most embedded targets, then it will complain about a second
863 argument and ignore it.
865 Many options have both long and short forms; both are shown in the
866 following list. @value{GDBN} also recognizes the long forms if you truncate
867 them, so long as enough of the option is present to be unambiguous.
868 (If you prefer, you can flag option arguments with @samp{--} rather
869 than @samp{-}, though we illustrate the more usual convention.)
871 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
872 @c way, both those who look for -foo and --foo in the index, will find
876 @item -symbols @var{file}
878 @cindex @code{--symbols}
880 Read symbol table from file @var{file}.
882 @item -exec @var{file}
884 @cindex @code{--exec}
886 Use file @var{file} as the executable file to execute when appropriate,
887 and for examining pure data in conjunction with a core dump.
891 Read symbol table from file @var{file} and use it as the executable
894 @item -core @var{file}
896 @cindex @code{--core}
898 Use file @var{file} as a core dump to examine.
900 @item -c @var{number}
901 @item -pid @var{number}
902 @itemx -p @var{number}
905 Connect to process ID @var{number}, as with the @code{attach} command.
906 If there is no such process, @value{GDBN} will attempt to open a core
907 file named @var{number}.
909 @item -command @var{file}
911 @cindex @code{--command}
913 Execute @value{GDBN} commands from file @var{file}. @xref{Command
914 Files,, Command files}.
916 @item -directory @var{directory}
917 @itemx -d @var{directory}
918 @cindex @code{--directory}
920 Add @var{directory} to the path to search for source files.
924 @cindex @code{--mapped}
926 @emph{Warning: this option depends on operating system facilities that are not
927 supported on all systems.}@*
928 If memory-mapped files are available on your system through the @code{mmap}
929 system call, you can use this option
930 to have @value{GDBN} write the symbols from your
931 program into a reusable file in the current directory. If the program you are debugging is
932 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
933 Future @value{GDBN} debugging sessions notice the presence of this file,
934 and can quickly map in symbol information from it, rather than reading
935 the symbol table from the executable program.
937 The @file{.syms} file is specific to the host machine where @value{GDBN}
938 is run. It holds an exact image of the internal @value{GDBN} symbol
939 table. It cannot be shared across multiple host platforms.
943 @cindex @code{--readnow}
945 Read each symbol file's entire symbol table immediately, rather than
946 the default, which is to read it incrementally as it is needed.
947 This makes startup slower, but makes future operations faster.
951 You typically combine the @code{-mapped} and @code{-readnow} options in
952 order to build a @file{.syms} file that contains complete symbol
953 information. (@xref{Files,,Commands to specify files}, for information
954 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
955 but build a @file{.syms} file for future use is:
958 gdb -batch -nx -mapped -readnow programname
962 @subsection Choosing modes
964 You can run @value{GDBN} in various alternative modes---for example, in
965 batch mode or quiet mode.
972 Do not execute commands found in any initialization files. Normally,
973 @value{GDBN} executes the commands in these files after all the command
974 options and arguments have been processed. @xref{Command Files,,Command
980 @cindex @code{--quiet}
981 @cindex @code{--silent}
983 ``Quiet''. Do not print the introductory and copyright messages. These
984 messages are also suppressed in batch mode.
987 @cindex @code{--batch}
988 Run in batch mode. Exit with status @code{0} after processing all the
989 command files specified with @samp{-x} (and all commands from
990 initialization files, if not inhibited with @samp{-n}). Exit with
991 nonzero status if an error occurs in executing the @value{GDBN} commands
992 in the command files.
994 Batch mode may be useful for running @value{GDBN} as a filter, for
995 example to download and run a program on another computer; in order to
996 make this more useful, the message
999 Program exited normally.
1003 (which is ordinarily issued whenever a program running under
1004 @value{GDBN} control terminates) is not issued when running in batch
1009 @cindex @code{--nowindows}
1011 ``No windows''. If @value{GDBN} comes with a graphical user interface
1012 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1013 interface. If no GUI is available, this option has no effect.
1017 @cindex @code{--windows}
1019 If @value{GDBN} includes a GUI, then this option requires it to be
1022 @item -cd @var{directory}
1024 Run @value{GDBN} using @var{directory} as its working directory,
1025 instead of the current directory.
1029 @cindex @code{--fullname}
1031 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1032 subprocess. It tells @value{GDBN} to output the full file name and line
1033 number in a standard, recognizable fashion each time a stack frame is
1034 displayed (which includes each time your program stops). This
1035 recognizable format looks like two @samp{\032} characters, followed by
1036 the file name, line number and character position separated by colons,
1037 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1038 @samp{\032} characters as a signal to display the source code for the
1042 @cindex @code{--epoch}
1043 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1044 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1045 routines so as to allow Epoch to display values of expressions in a
1048 @item -annotate @var{level}
1049 @cindex @code{--annotate}
1050 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1051 effect is identical to using @samp{set annotate @var{level}}
1052 (@pxref{Annotations}).
1053 Annotation level controls how much information does @value{GDBN} print
1054 together with its prompt, values of expressions, source lines, and other
1055 types of output. Level 0 is the normal, level 1 is for use when
1056 @value{GDBN} is run as a subprocess of @sc{gnu} Emacs, level 2 is the
1057 maximum annotation suitable for programs that control @value{GDBN}.
1060 @cindex @code{--async}
1061 Use the asynchronous event loop for the command-line interface.
1062 @value{GDBN} processes all events, such as user keyboard input, via a
1063 special event loop. This allows @value{GDBN} to accept and process user
1064 commands in parallel with the debugged process being
1065 run@footnote{@value{GDBN} built with @sc{djgpp} tools for
1066 MS-DOS/MS-Windows supports this mode of operation, but the event loop is
1067 suspended when the debuggee runs.}, so you don't need to wait for
1068 control to return to @value{GDBN} before you type the next command.
1069 (@emph{Note:} as of version 5.1, the target side of the asynchronous
1070 operation is not yet in place, so @samp{-async} does not work fully
1072 @c FIXME: when the target side of the event loop is done, the above NOTE
1073 @c should be removed.
1075 When the standard input is connected to a terminal device, @value{GDBN}
1076 uses the asynchronous event loop by default, unless disabled by the
1077 @samp{-noasync} option.
1080 @cindex @code{--noasync}
1081 Disable the asynchronous event loop for the command-line interface.
1084 @cindex @code{--args}
1085 Change interpretation of command line so that arguments following the
1086 executable file are passed as command line arguments to the inferior.
1087 This option stops option processing.
1089 @item -baud @var{bps}
1091 @cindex @code{--baud}
1093 Set the line speed (baud rate or bits per second) of any serial
1094 interface used by @value{GDBN} for remote debugging.
1096 @item -tty @var{device}
1097 @itemx -t @var{device}
1098 @cindex @code{--tty}
1100 Run using @var{device} for your program's standard input and output.
1101 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1103 @c resolve the situation of these eventually
1105 @cindex @code{--tui}
1106 Activate the Terminal User Interface when starting.
1107 The Terminal User Interface manages several text windows on the terminal,
1108 showing source, assembly, registers and @value{GDBN} command outputs
1109 (@pxref{TUI, ,@value{GDBN} Text User Interface}).
1110 Do not use this option if you run @value{GDBN} from Emacs
1111 (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1114 @c @cindex @code{--xdb}
1115 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1116 @c For information, see the file @file{xdb_trans.html}, which is usually
1117 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1120 @item -interpreter @var{interp}
1121 @cindex @code{--interpreter}
1122 Use the interpreter @var{interp} for interface with the controlling
1123 program or device. This option is meant to be set by programs which
1124 communicate with @value{GDBN} using it as a back end.
1125 @xref{Interpreters, , Command Interpreters}.
1127 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1128 @value{GDBN} to use the current @dfn{@sc{gdb/mi} interface}
1129 (@pxref{GDB/MI, , The @sc{gdb/mi} Interface}). The previous @sc{gdb/mi}
1130 interface, included in @value{GDBN} version 5.3, can be selected with
1131 @samp{--interpreter=mi1}. Earlier @sc{gdb/mi} interfaces
1135 @cindex @code{--write}
1136 Open the executable and core files for both reading and writing. This
1137 is equivalent to the @samp{set write on} command inside @value{GDBN}
1141 @cindex @code{--statistics}
1142 This option causes @value{GDBN} to print statistics about time and
1143 memory usage after it completes each command and returns to the prompt.
1146 @cindex @code{--version}
1147 This option causes @value{GDBN} to print its version number and
1148 no-warranty blurb, and exit.
1153 @section Quitting @value{GDBN}
1154 @cindex exiting @value{GDBN}
1155 @cindex leaving @value{GDBN}
1158 @kindex quit @r{[}@var{expression}@r{]}
1159 @kindex q @r{(@code{quit})}
1160 @item quit @r{[}@var{expression}@r{]}
1162 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1163 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1164 do not supply @var{expression}, @value{GDBN} will terminate normally;
1165 otherwise it will terminate using the result of @var{expression} as the
1170 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1171 terminates the action of any @value{GDBN} command that is in progress and
1172 returns to @value{GDBN} command level. It is safe to type the interrupt
1173 character at any time because @value{GDBN} does not allow it to take effect
1174 until a time when it is safe.
1176 If you have been using @value{GDBN} to control an attached process or
1177 device, you can release it with the @code{detach} command
1178 (@pxref{Attach, ,Debugging an already-running process}).
1180 @node Shell Commands
1181 @section Shell commands
1183 If you need to execute occasional shell commands during your
1184 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1185 just use the @code{shell} command.
1189 @cindex shell escape
1190 @item shell @var{command string}
1191 Invoke a standard shell to execute @var{command string}.
1192 If it exists, the environment variable @code{SHELL} determines which
1193 shell to run. Otherwise @value{GDBN} uses the default shell
1194 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1197 The utility @code{make} is often needed in development environments.
1198 You do not have to use the @code{shell} command for this purpose in
1203 @cindex calling make
1204 @item make @var{make-args}
1205 Execute the @code{make} program with the specified
1206 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1210 @chapter @value{GDBN} Commands
1212 You can abbreviate a @value{GDBN} command to the first few letters of the command
1213 name, if that abbreviation is unambiguous; and you can repeat certain
1214 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1215 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1216 show you the alternatives available, if there is more than one possibility).
1219 * Command Syntax:: How to give commands to @value{GDBN}
1220 * Completion:: Command completion
1221 * Help:: How to ask @value{GDBN} for help
1224 @node Command Syntax
1225 @section Command syntax
1227 A @value{GDBN} command is a single line of input. There is no limit on
1228 how long it can be. It starts with a command name, which is followed by
1229 arguments whose meaning depends on the command name. For example, the
1230 command @code{step} accepts an argument which is the number of times to
1231 step, as in @samp{step 5}. You can also use the @code{step} command
1232 with no arguments. Some commands do not allow any arguments.
1234 @cindex abbreviation
1235 @value{GDBN} command names may always be truncated if that abbreviation is
1236 unambiguous. Other possible command abbreviations are listed in the
1237 documentation for individual commands. In some cases, even ambiguous
1238 abbreviations are allowed; for example, @code{s} is specially defined as
1239 equivalent to @code{step} even though there are other commands whose
1240 names start with @code{s}. You can test abbreviations by using them as
1241 arguments to the @code{help} command.
1243 @cindex repeating commands
1244 @kindex RET @r{(repeat last command)}
1245 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1246 repeat the previous command. Certain commands (for example, @code{run})
1247 will not repeat this way; these are commands whose unintentional
1248 repetition might cause trouble and which you are unlikely to want to
1251 The @code{list} and @code{x} commands, when you repeat them with
1252 @key{RET}, construct new arguments rather than repeating
1253 exactly as typed. This permits easy scanning of source or memory.
1255 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1256 output, in a way similar to the common utility @code{more}
1257 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1258 @key{RET} too many in this situation, @value{GDBN} disables command
1259 repetition after any command that generates this sort of display.
1261 @kindex # @r{(a comment)}
1263 Any text from a @kbd{#} to the end of the line is a comment; it does
1264 nothing. This is useful mainly in command files (@pxref{Command
1265 Files,,Command files}).
1267 @cindex repeating command sequences
1268 @kindex C-o @r{(operate-and-get-next)}
1269 The @kbd{C-o} binding is useful for repeating a complex sequence of
1270 commands. This command accepts the current line, like @kbd{RET}, and
1271 then fetches the next line relative to the current line from the history
1275 @section Command completion
1278 @cindex word completion
1279 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1280 only one possibility; it can also show you what the valid possibilities
1281 are for the next word in a command, at any time. This works for @value{GDBN}
1282 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1284 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1285 of a word. If there is only one possibility, @value{GDBN} fills in the
1286 word, and waits for you to finish the command (or press @key{RET} to
1287 enter it). For example, if you type
1289 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1290 @c complete accuracy in these examples; space introduced for clarity.
1291 @c If texinfo enhancements make it unnecessary, it would be nice to
1292 @c replace " @key" by "@key" in the following...
1294 (@value{GDBP}) info bre @key{TAB}
1298 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1299 the only @code{info} subcommand beginning with @samp{bre}:
1302 (@value{GDBP}) info breakpoints
1306 You can either press @key{RET} at this point, to run the @code{info
1307 breakpoints} command, or backspace and enter something else, if
1308 @samp{breakpoints} does not look like the command you expected. (If you
1309 were sure you wanted @code{info breakpoints} in the first place, you
1310 might as well just type @key{RET} immediately after @samp{info bre},
1311 to exploit command abbreviations rather than command completion).
1313 If there is more than one possibility for the next word when you press
1314 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1315 characters and try again, or just press @key{TAB} a second time;
1316 @value{GDBN} displays all the possible completions for that word. For
1317 example, you might want to set a breakpoint on a subroutine whose name
1318 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1319 just sounds the bell. Typing @key{TAB} again displays all the
1320 function names in your program that begin with those characters, for
1324 (@value{GDBP}) b make_ @key{TAB}
1325 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1326 make_a_section_from_file make_environ
1327 make_abs_section make_function_type
1328 make_blockvector make_pointer_type
1329 make_cleanup make_reference_type
1330 make_command make_symbol_completion_list
1331 (@value{GDBP}) b make_
1335 After displaying the available possibilities, @value{GDBN} copies your
1336 partial input (@samp{b make_} in the example) so you can finish the
1339 If you just want to see the list of alternatives in the first place, you
1340 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1341 means @kbd{@key{META} ?}. You can type this either by holding down a
1342 key designated as the @key{META} shift on your keyboard (if there is
1343 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1345 @cindex quotes in commands
1346 @cindex completion of quoted strings
1347 Sometimes the string you need, while logically a ``word'', may contain
1348 parentheses or other characters that @value{GDBN} normally excludes from
1349 its notion of a word. To permit word completion to work in this
1350 situation, you may enclose words in @code{'} (single quote marks) in
1351 @value{GDBN} commands.
1353 The most likely situation where you might need this is in typing the
1354 name of a C@t{++} function. This is because C@t{++} allows function
1355 overloading (multiple definitions of the same function, distinguished
1356 by argument type). For example, when you want to set a breakpoint you
1357 may need to distinguish whether you mean the version of @code{name}
1358 that takes an @code{int} parameter, @code{name(int)}, or the version
1359 that takes a @code{float} parameter, @code{name(float)}. To use the
1360 word-completion facilities in this situation, type a single quote
1361 @code{'} at the beginning of the function name. This alerts
1362 @value{GDBN} that it may need to consider more information than usual
1363 when you press @key{TAB} or @kbd{M-?} to request word completion:
1366 (@value{GDBP}) b 'bubble( @kbd{M-?}
1367 bubble(double,double) bubble(int,int)
1368 (@value{GDBP}) b 'bubble(
1371 In some cases, @value{GDBN} can tell that completing a name requires using
1372 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1373 completing as much as it can) if you do not type the quote in the first
1377 (@value{GDBP}) b bub @key{TAB}
1378 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1379 (@value{GDBP}) b 'bubble(
1383 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1384 you have not yet started typing the argument list when you ask for
1385 completion on an overloaded symbol.
1387 For more information about overloaded functions, see @ref{C plus plus
1388 expressions, ,C@t{++} expressions}. You can use the command @code{set
1389 overload-resolution off} to disable overload resolution;
1390 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1394 @section Getting help
1395 @cindex online documentation
1398 You can always ask @value{GDBN} itself for information on its commands,
1399 using the command @code{help}.
1402 @kindex h @r{(@code{help})}
1405 You can use @code{help} (abbreviated @code{h}) with no arguments to
1406 display a short list of named classes of commands:
1410 List of classes of commands:
1412 aliases -- Aliases of other commands
1413 breakpoints -- Making program stop at certain points
1414 data -- Examining data
1415 files -- Specifying and examining files
1416 internals -- Maintenance commands
1417 obscure -- Obscure features
1418 running -- Running the program
1419 stack -- Examining the stack
1420 status -- Status inquiries
1421 support -- Support facilities
1422 tracepoints -- Tracing of program execution without@*
1423 stopping the program
1424 user-defined -- User-defined commands
1426 Type "help" followed by a class name for a list of
1427 commands in that class.
1428 Type "help" followed by command name for full
1430 Command name abbreviations are allowed if unambiguous.
1433 @c the above line break eliminates huge line overfull...
1435 @item help @var{class}
1436 Using one of the general help classes as an argument, you can get a
1437 list of the individual commands in that class. For example, here is the
1438 help display for the class @code{status}:
1441 (@value{GDBP}) help status
1446 @c Line break in "show" line falsifies real output, but needed
1447 @c to fit in smallbook page size.
1448 info -- Generic command for showing things
1449 about the program being debugged
1450 show -- Generic command for showing things
1453 Type "help" followed by command name for full
1455 Command name abbreviations are allowed if unambiguous.
1459 @item help @var{command}
1460 With a command name as @code{help} argument, @value{GDBN} displays a
1461 short paragraph on how to use that command.
1464 @item apropos @var{args}
1465 The @code{apropos @var{args}} command searches through all of the @value{GDBN}
1466 commands, and their documentation, for the regular expression specified in
1467 @var{args}. It prints out all matches found. For example:
1478 set symbol-reloading -- Set dynamic symbol table reloading
1479 multiple times in one run
1480 show symbol-reloading -- Show dynamic symbol table reloading
1481 multiple times in one run
1486 @item complete @var{args}
1487 The @code{complete @var{args}} command lists all the possible completions
1488 for the beginning of a command. Use @var{args} to specify the beginning of the
1489 command you want completed. For example:
1495 @noindent results in:
1506 @noindent This is intended for use by @sc{gnu} Emacs.
1509 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1510 and @code{show} to inquire about the state of your program, or the state
1511 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1512 manual introduces each of them in the appropriate context. The listings
1513 under @code{info} and under @code{show} in the Index point to
1514 all the sub-commands. @xref{Index}.
1519 @kindex i @r{(@code{info})}
1521 This command (abbreviated @code{i}) is for describing the state of your
1522 program. For example, you can list the arguments given to your program
1523 with @code{info args}, list the registers currently in use with @code{info
1524 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1525 You can get a complete list of the @code{info} sub-commands with
1526 @w{@code{help info}}.
1530 You can assign the result of an expression to an environment variable with
1531 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1532 @code{set prompt $}.
1536 In contrast to @code{info}, @code{show} is for describing the state of
1537 @value{GDBN} itself.
1538 You can change most of the things you can @code{show}, by using the
1539 related command @code{set}; for example, you can control what number
1540 system is used for displays with @code{set radix}, or simply inquire
1541 which is currently in use with @code{show radix}.
1544 To display all the settable parameters and their current
1545 values, you can use @code{show} with no arguments; you may also use
1546 @code{info set}. Both commands produce the same display.
1547 @c FIXME: "info set" violates the rule that "info" is for state of
1548 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1549 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1553 Here are three miscellaneous @code{show} subcommands, all of which are
1554 exceptional in lacking corresponding @code{set} commands:
1557 @kindex show version
1558 @cindex version number
1560 Show what version of @value{GDBN} is running. You should include this
1561 information in @value{GDBN} bug-reports. If multiple versions of
1562 @value{GDBN} are in use at your site, you may need to determine which
1563 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1564 commands are introduced, and old ones may wither away. Also, many
1565 system vendors ship variant versions of @value{GDBN}, and there are
1566 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1567 The version number is the same as the one announced when you start
1570 @kindex show copying
1572 Display information about permission for copying @value{GDBN}.
1574 @kindex show warranty
1576 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1577 if your version of @value{GDBN} comes with one.
1582 @chapter Running Programs Under @value{GDBN}
1584 When you run a program under @value{GDBN}, you must first generate
1585 debugging information when you compile it.
1587 You may start @value{GDBN} with its arguments, if any, in an environment
1588 of your choice. If you are doing native debugging, you may redirect
1589 your program's input and output, debug an already running process, or
1590 kill a child process.
1593 * Compilation:: Compiling for debugging
1594 * Starting:: Starting your program
1595 * Arguments:: Your program's arguments
1596 * Environment:: Your program's environment
1598 * Working Directory:: Your program's working directory
1599 * Input/Output:: Your program's input and output
1600 * Attach:: Debugging an already-running process
1601 * Kill Process:: Killing the child process
1603 * Threads:: Debugging programs with multiple threads
1604 * Processes:: Debugging programs with multiple processes
1608 @section Compiling for debugging
1610 In order to debug a program effectively, you need to generate
1611 debugging information when you compile it. This debugging information
1612 is stored in the object file; it describes the data type of each
1613 variable or function and the correspondence between source line numbers
1614 and addresses in the executable code.
1616 To request debugging information, specify the @samp{-g} option when you run
1619 Most compilers do not include information about preprocessor macros in
1620 the debugging information if you specify the @option{-g} flag alone,
1621 because this information is rather large. Version 3.1 of @value{NGCC},
1622 the @sc{gnu} C compiler, provides macro information if you specify the
1623 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1624 debugging information in the Dwarf 2 format, and the latter requests
1625 ``extra information''. In the future, we hope to find more compact ways
1626 to represent macro information, so that it can be included with
1629 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1630 options together. Using those compilers, you cannot generate optimized
1631 executables containing debugging information.
1633 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1634 without @samp{-O}, making it possible to debug optimized code. We
1635 recommend that you @emph{always} use @samp{-g} whenever you compile a
1636 program. You may think your program is correct, but there is no sense
1637 in pushing your luck.
1639 @cindex optimized code, debugging
1640 @cindex debugging optimized code
1641 When you debug a program compiled with @samp{-g -O}, remember that the
1642 optimizer is rearranging your code; the debugger shows you what is
1643 really there. Do not be too surprised when the execution path does not
1644 exactly match your source file! An extreme example: if you define a
1645 variable, but never use it, @value{GDBN} never sees that
1646 variable---because the compiler optimizes it out of existence.
1648 Some things do not work as well with @samp{-g -O} as with just
1649 @samp{-g}, particularly on machines with instruction scheduling. If in
1650 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1651 please report it to us as a bug (including a test case!).
1653 Older versions of the @sc{gnu} C compiler permitted a variant option
1654 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1655 format; if your @sc{gnu} C compiler has this option, do not use it.
1659 @section Starting your program
1665 @kindex r @r{(@code{run})}
1668 Use the @code{run} command to start your program under @value{GDBN}.
1669 You must first specify the program name (except on VxWorks) with an
1670 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1671 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1672 (@pxref{Files, ,Commands to specify files}).
1676 If you are running your program in an execution environment that
1677 supports processes, @code{run} creates an inferior process and makes
1678 that process run your program. (In environments without processes,
1679 @code{run} jumps to the start of your program.)
1681 The execution of a program is affected by certain information it
1682 receives from its superior. @value{GDBN} provides ways to specify this
1683 information, which you must do @emph{before} starting your program. (You
1684 can change it after starting your program, but such changes only affect
1685 your program the next time you start it.) This information may be
1686 divided into four categories:
1689 @item The @emph{arguments.}
1690 Specify the arguments to give your program as the arguments of the
1691 @code{run} command. If a shell is available on your target, the shell
1692 is used to pass the arguments, so that you may use normal conventions
1693 (such as wildcard expansion or variable substitution) in describing
1695 In Unix systems, you can control which shell is used with the
1696 @code{SHELL} environment variable.
1697 @xref{Arguments, ,Your program's arguments}.
1699 @item The @emph{environment.}
1700 Your program normally inherits its environment from @value{GDBN}, but you can
1701 use the @value{GDBN} commands @code{set environment} and @code{unset
1702 environment} to change parts of the environment that affect
1703 your program. @xref{Environment, ,Your program's environment}.
1705 @item The @emph{working directory.}
1706 Your program inherits its working directory from @value{GDBN}. You can set
1707 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1708 @xref{Working Directory, ,Your program's working directory}.
1710 @item The @emph{standard input and output.}
1711 Your program normally uses the same device for standard input and
1712 standard output as @value{GDBN} is using. You can redirect input and output
1713 in the @code{run} command line, or you can use the @code{tty} command to
1714 set a different device for your program.
1715 @xref{Input/Output, ,Your program's input and output}.
1718 @emph{Warning:} While input and output redirection work, you cannot use
1719 pipes to pass the output of the program you are debugging to another
1720 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1724 When you issue the @code{run} command, your program begins to execute
1725 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1726 of how to arrange for your program to stop. Once your program has
1727 stopped, you may call functions in your program, using the @code{print}
1728 or @code{call} commands. @xref{Data, ,Examining Data}.
1730 If the modification time of your symbol file has changed since the last
1731 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1732 table, and reads it again. When it does this, @value{GDBN} tries to retain
1733 your current breakpoints.
1736 @section Your program's arguments
1738 @cindex arguments (to your program)
1739 The arguments to your program can be specified by the arguments of the
1741 They are passed to a shell, which expands wildcard characters and
1742 performs redirection of I/O, and thence to your program. Your
1743 @code{SHELL} environment variable (if it exists) specifies what shell
1744 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1745 the default shell (@file{/bin/sh} on Unix).
1747 On non-Unix systems, the program is usually invoked directly by
1748 @value{GDBN}, which emulates I/O redirection via the appropriate system
1749 calls, and the wildcard characters are expanded by the startup code of
1750 the program, not by the shell.
1752 @code{run} with no arguments uses the same arguments used by the previous
1753 @code{run}, or those set by the @code{set args} command.
1758 Specify the arguments to be used the next time your program is run. If
1759 @code{set args} has no arguments, @code{run} executes your program
1760 with no arguments. Once you have run your program with arguments,
1761 using @code{set args} before the next @code{run} is the only way to run
1762 it again without arguments.
1766 Show the arguments to give your program when it is started.
1770 @section Your program's environment
1772 @cindex environment (of your program)
1773 The @dfn{environment} consists of a set of environment variables and
1774 their values. Environment variables conventionally record such things as
1775 your user name, your home directory, your terminal type, and your search
1776 path for programs to run. Usually you set up environment variables with
1777 the shell and they are inherited by all the other programs you run. When
1778 debugging, it can be useful to try running your program with a modified
1779 environment without having to start @value{GDBN} over again.
1783 @item path @var{directory}
1784 Add @var{directory} to the front of the @code{PATH} environment variable
1785 (the search path for executables) that will be passed to your program.
1786 The value of @code{PATH} used by @value{GDBN} does not change.
1787 You may specify several directory names, separated by whitespace or by a
1788 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1789 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1790 is moved to the front, so it is searched sooner.
1792 You can use the string @samp{$cwd} to refer to whatever is the current
1793 working directory at the time @value{GDBN} searches the path. If you
1794 use @samp{.} instead, it refers to the directory where you executed the
1795 @code{path} command. @value{GDBN} replaces @samp{.} in the
1796 @var{directory} argument (with the current path) before adding
1797 @var{directory} to the search path.
1798 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1799 @c document that, since repeating it would be a no-op.
1803 Display the list of search paths for executables (the @code{PATH}
1804 environment variable).
1806 @kindex show environment
1807 @item show environment @r{[}@var{varname}@r{]}
1808 Print the value of environment variable @var{varname} to be given to
1809 your program when it starts. If you do not supply @var{varname},
1810 print the names and values of all environment variables to be given to
1811 your program. You can abbreviate @code{environment} as @code{env}.
1813 @kindex set environment
1814 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1815 Set environment variable @var{varname} to @var{value}. The value
1816 changes for your program only, not for @value{GDBN} itself. @var{value} may
1817 be any string; the values of environment variables are just strings, and
1818 any interpretation is supplied by your program itself. The @var{value}
1819 parameter is optional; if it is eliminated, the variable is set to a
1821 @c "any string" here does not include leading, trailing
1822 @c blanks. Gnu asks: does anyone care?
1824 For example, this command:
1831 tells the debugged program, when subsequently run, that its user is named
1832 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1833 are not actually required.)
1835 @kindex unset environment
1836 @item unset environment @var{varname}
1837 Remove variable @var{varname} from the environment to be passed to your
1838 program. This is different from @samp{set env @var{varname} =};
1839 @code{unset environment} removes the variable from the environment,
1840 rather than assigning it an empty value.
1843 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1845 by your @code{SHELL} environment variable if it exists (or
1846 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1847 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1848 @file{.bashrc} for BASH---any variables you set in that file affect
1849 your program. You may wish to move setting of environment variables to
1850 files that are only run when you sign on, such as @file{.login} or
1853 @node Working Directory
1854 @section Your program's working directory
1856 @cindex working directory (of your program)
1857 Each time you start your program with @code{run}, it inherits its
1858 working directory from the current working directory of @value{GDBN}.
1859 The @value{GDBN} working directory is initially whatever it inherited
1860 from its parent process (typically the shell), but you can specify a new
1861 working directory in @value{GDBN} with the @code{cd} command.
1863 The @value{GDBN} working directory also serves as a default for the commands
1864 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1869 @item cd @var{directory}
1870 Set the @value{GDBN} working directory to @var{directory}.
1874 Print the @value{GDBN} working directory.
1878 @section Your program's input and output
1883 By default, the program you run under @value{GDBN} does input and output to
1884 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1885 to its own terminal modes to interact with you, but it records the terminal
1886 modes your program was using and switches back to them when you continue
1887 running your program.
1890 @kindex info terminal
1892 Displays information recorded by @value{GDBN} about the terminal modes your
1896 You can redirect your program's input and/or output using shell
1897 redirection with the @code{run} command. For example,
1904 starts your program, diverting its output to the file @file{outfile}.
1907 @cindex controlling terminal
1908 Another way to specify where your program should do input and output is
1909 with the @code{tty} command. This command accepts a file name as
1910 argument, and causes this file to be the default for future @code{run}
1911 commands. It also resets the controlling terminal for the child
1912 process, for future @code{run} commands. For example,
1919 directs that processes started with subsequent @code{run} commands
1920 default to do input and output on the terminal @file{/dev/ttyb} and have
1921 that as their controlling terminal.
1923 An explicit redirection in @code{run} overrides the @code{tty} command's
1924 effect on the input/output device, but not its effect on the controlling
1927 When you use the @code{tty} command or redirect input in the @code{run}
1928 command, only the input @emph{for your program} is affected. The input
1929 for @value{GDBN} still comes from your terminal.
1932 @section Debugging an already-running process
1937 @item attach @var{process-id}
1938 This command attaches to a running process---one that was started
1939 outside @value{GDBN}. (@code{info files} shows your active
1940 targets.) The command takes as argument a process ID. The usual way to
1941 find out the process-id of a Unix process is with the @code{ps} utility,
1942 or with the @samp{jobs -l} shell command.
1944 @code{attach} does not repeat if you press @key{RET} a second time after
1945 executing the command.
1948 To use @code{attach}, your program must be running in an environment
1949 which supports processes; for example, @code{attach} does not work for
1950 programs on bare-board targets that lack an operating system. You must
1951 also have permission to send the process a signal.
1953 When you use @code{attach}, the debugger finds the program running in
1954 the process first by looking in the current working directory, then (if
1955 the program is not found) by using the source file search path
1956 (@pxref{Source Path, ,Specifying source directories}). You can also use
1957 the @code{file} command to load the program. @xref{Files, ,Commands to
1960 The first thing @value{GDBN} does after arranging to debug the specified
1961 process is to stop it. You can examine and modify an attached process
1962 with all the @value{GDBN} commands that are ordinarily available when
1963 you start processes with @code{run}. You can insert breakpoints; you
1964 can step and continue; you can modify storage. If you would rather the
1965 process continue running, you may use the @code{continue} command after
1966 attaching @value{GDBN} to the process.
1971 When you have finished debugging the attached process, you can use the
1972 @code{detach} command to release it from @value{GDBN} control. Detaching
1973 the process continues its execution. After the @code{detach} command,
1974 that process and @value{GDBN} become completely independent once more, and you
1975 are ready to @code{attach} another process or start one with @code{run}.
1976 @code{detach} does not repeat if you press @key{RET} again after
1977 executing the command.
1980 If you exit @value{GDBN} or use the @code{run} command while you have an
1981 attached process, you kill that process. By default, @value{GDBN} asks
1982 for confirmation if you try to do either of these things; you can
1983 control whether or not you need to confirm by using the @code{set
1984 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
1988 @section Killing the child process
1993 Kill the child process in which your program is running under @value{GDBN}.
1996 This command is useful if you wish to debug a core dump instead of a
1997 running process. @value{GDBN} ignores any core dump file while your program
2000 On some operating systems, a program cannot be executed outside @value{GDBN}
2001 while you have breakpoints set on it inside @value{GDBN}. You can use the
2002 @code{kill} command in this situation to permit running your program
2003 outside the debugger.
2005 The @code{kill} command is also useful if you wish to recompile and
2006 relink your program, since on many systems it is impossible to modify an
2007 executable file while it is running in a process. In this case, when you
2008 next type @code{run}, @value{GDBN} notices that the file has changed, and
2009 reads the symbol table again (while trying to preserve your current
2010 breakpoint settings).
2013 @section Debugging programs with multiple threads
2015 @cindex threads of execution
2016 @cindex multiple threads
2017 @cindex switching threads
2018 In some operating systems, such as HP-UX and Solaris, a single program
2019 may have more than one @dfn{thread} of execution. The precise semantics
2020 of threads differ from one operating system to another, but in general
2021 the threads of a single program are akin to multiple processes---except
2022 that they share one address space (that is, they can all examine and
2023 modify the same variables). On the other hand, each thread has its own
2024 registers and execution stack, and perhaps private memory.
2026 @value{GDBN} provides these facilities for debugging multi-thread
2030 @item automatic notification of new threads
2031 @item @samp{thread @var{threadno}}, a command to switch among threads
2032 @item @samp{info threads}, a command to inquire about existing threads
2033 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2034 a command to apply a command to a list of threads
2035 @item thread-specific breakpoints
2039 @emph{Warning:} These facilities are not yet available on every
2040 @value{GDBN} configuration where the operating system supports threads.
2041 If your @value{GDBN} does not support threads, these commands have no
2042 effect. For example, a system without thread support shows no output
2043 from @samp{info threads}, and always rejects the @code{thread} command,
2047 (@value{GDBP}) info threads
2048 (@value{GDBP}) thread 1
2049 Thread ID 1 not known. Use the "info threads" command to
2050 see the IDs of currently known threads.
2052 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2053 @c doesn't support threads"?
2056 @cindex focus of debugging
2057 @cindex current thread
2058 The @value{GDBN} thread debugging facility allows you to observe all
2059 threads while your program runs---but whenever @value{GDBN} takes
2060 control, one thread in particular is always the focus of debugging.
2061 This thread is called the @dfn{current thread}. Debugging commands show
2062 program information from the perspective of the current thread.
2064 @cindex @code{New} @var{systag} message
2065 @cindex thread identifier (system)
2066 @c FIXME-implementors!! It would be more helpful if the [New...] message
2067 @c included GDB's numeric thread handle, so you could just go to that
2068 @c thread without first checking `info threads'.
2069 Whenever @value{GDBN} detects a new thread in your program, it displays
2070 the target system's identification for the thread with a message in the
2071 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2072 whose form varies depending on the particular system. For example, on
2073 LynxOS, you might see
2076 [New process 35 thread 27]
2080 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2081 the @var{systag} is simply something like @samp{process 368}, with no
2084 @c FIXME!! (1) Does the [New...] message appear even for the very first
2085 @c thread of a program, or does it only appear for the
2086 @c second---i.e.@: when it becomes obvious we have a multithread
2088 @c (2) *Is* there necessarily a first thread always? Or do some
2089 @c multithread systems permit starting a program with multiple
2090 @c threads ab initio?
2092 @cindex thread number
2093 @cindex thread identifier (GDB)
2094 For debugging purposes, @value{GDBN} associates its own thread
2095 number---always a single integer---with each thread in your program.
2098 @kindex info threads
2100 Display a summary of all threads currently in your
2101 program. @value{GDBN} displays for each thread (in this order):
2104 @item the thread number assigned by @value{GDBN}
2106 @item the target system's thread identifier (@var{systag})
2108 @item the current stack frame summary for that thread
2112 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2113 indicates the current thread.
2117 @c end table here to get a little more width for example
2120 (@value{GDBP}) info threads
2121 3 process 35 thread 27 0x34e5 in sigpause ()
2122 2 process 35 thread 23 0x34e5 in sigpause ()
2123 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2129 @cindex thread number
2130 @cindex thread identifier (GDB)
2131 For debugging purposes, @value{GDBN} associates its own thread
2132 number---a small integer assigned in thread-creation order---with each
2133 thread in your program.
2135 @cindex @code{New} @var{systag} message, on HP-UX
2136 @cindex thread identifier (system), on HP-UX
2137 @c FIXME-implementors!! It would be more helpful if the [New...] message
2138 @c included GDB's numeric thread handle, so you could just go to that
2139 @c thread without first checking `info threads'.
2140 Whenever @value{GDBN} detects a new thread in your program, it displays
2141 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2142 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2143 whose form varies depending on the particular system. For example, on
2147 [New thread 2 (system thread 26594)]
2151 when @value{GDBN} notices a new thread.
2154 @kindex info threads
2156 Display a summary of all threads currently in your
2157 program. @value{GDBN} displays for each thread (in this order):
2160 @item the thread number assigned by @value{GDBN}
2162 @item the target system's thread identifier (@var{systag})
2164 @item the current stack frame summary for that thread
2168 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2169 indicates the current thread.
2173 @c end table here to get a little more width for example
2176 (@value{GDBP}) info threads
2177 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2179 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2180 from /usr/lib/libc.2
2181 1 system thread 27905 0x7b003498 in _brk () \@*
2182 from /usr/lib/libc.2
2186 @kindex thread @var{threadno}
2187 @item thread @var{threadno}
2188 Make thread number @var{threadno} the current thread. The command
2189 argument @var{threadno} is the internal @value{GDBN} thread number, as
2190 shown in the first field of the @samp{info threads} display.
2191 @value{GDBN} responds by displaying the system identifier of the thread
2192 you selected, and its current stack frame summary:
2195 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2196 (@value{GDBP}) thread 2
2197 [Switching to process 35 thread 23]
2198 0x34e5 in sigpause ()
2202 As with the @samp{[New @dots{}]} message, the form of the text after
2203 @samp{Switching to} depends on your system's conventions for identifying
2206 @kindex thread apply
2207 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2208 The @code{thread apply} command allows you to apply a command to one or
2209 more threads. Specify the numbers of the threads that you want affected
2210 with the command argument @var{threadno}. @var{threadno} is the internal
2211 @value{GDBN} thread number, as shown in the first field of the @samp{info
2212 threads} display. To apply a command to all threads, use
2213 @code{thread apply all} @var{args}.
2216 @cindex automatic thread selection
2217 @cindex switching threads automatically
2218 @cindex threads, automatic switching
2219 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2220 signal, it automatically selects the thread where that breakpoint or
2221 signal happened. @value{GDBN} alerts you to the context switch with a
2222 message of the form @samp{[Switching to @var{systag}]} to identify the
2225 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2226 more information about how @value{GDBN} behaves when you stop and start
2227 programs with multiple threads.
2229 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2230 watchpoints in programs with multiple threads.
2233 @section Debugging programs with multiple processes
2235 @cindex fork, debugging programs which call
2236 @cindex multiple processes
2237 @cindex processes, multiple
2238 On most systems, @value{GDBN} has no special support for debugging
2239 programs which create additional processes using the @code{fork}
2240 function. When a program forks, @value{GDBN} will continue to debug the
2241 parent process and the child process will run unimpeded. If you have
2242 set a breakpoint in any code which the child then executes, the child
2243 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2244 will cause it to terminate.
2246 However, if you want to debug the child process there is a workaround
2247 which isn't too painful. Put a call to @code{sleep} in the code which
2248 the child process executes after the fork. It may be useful to sleep
2249 only if a certain environment variable is set, or a certain file exists,
2250 so that the delay need not occur when you don't want to run @value{GDBN}
2251 on the child. While the child is sleeping, use the @code{ps} program to
2252 get its process ID. Then tell @value{GDBN} (a new invocation of
2253 @value{GDBN} if you are also debugging the parent process) to attach to
2254 the child process (@pxref{Attach}). From that point on you can debug
2255 the child process just like any other process which you attached to.
2257 On HP-UX (11.x and later only?), @value{GDBN} provides support for
2258 debugging programs that create additional processes using the
2259 @code{fork} or @code{vfork} function.
2261 By default, when a program forks, @value{GDBN} will continue to debug
2262 the parent process and the child process will run unimpeded.
2264 If you want to follow the child process instead of the parent process,
2265 use the command @w{@code{set follow-fork-mode}}.
2268 @kindex set follow-fork-mode
2269 @item set follow-fork-mode @var{mode}
2270 Set the debugger response to a program call of @code{fork} or
2271 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2272 process. The @var{mode} can be:
2276 The original process is debugged after a fork. The child process runs
2277 unimpeded. This is the default.
2280 The new process is debugged after a fork. The parent process runs
2284 The debugger will ask for one of the above choices.
2287 @item show follow-fork-mode
2288 Display the current debugger response to a @code{fork} or @code{vfork} call.
2291 If you ask to debug a child process and a @code{vfork} is followed by an
2292 @code{exec}, @value{GDBN} executes the new target up to the first
2293 breakpoint in the new target. If you have a breakpoint set on
2294 @code{main} in your original program, the breakpoint will also be set on
2295 the child process's @code{main}.
2297 When a child process is spawned by @code{vfork}, you cannot debug the
2298 child or parent until an @code{exec} call completes.
2300 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2301 call executes, the new target restarts. To restart the parent process,
2302 use the @code{file} command with the parent executable name as its
2305 You can use the @code{catch} command to make @value{GDBN} stop whenever
2306 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2307 Catchpoints, ,Setting catchpoints}.
2310 @chapter Stopping and Continuing
2312 The principal purposes of using a debugger are so that you can stop your
2313 program before it terminates; or so that, if your program runs into
2314 trouble, you can investigate and find out why.
2316 Inside @value{GDBN}, your program may stop for any of several reasons,
2317 such as a signal, a breakpoint, or reaching a new line after a
2318 @value{GDBN} command such as @code{step}. You may then examine and
2319 change variables, set new breakpoints or remove old ones, and then
2320 continue execution. Usually, the messages shown by @value{GDBN} provide
2321 ample explanation of the status of your program---but you can also
2322 explicitly request this information at any time.
2325 @kindex info program
2327 Display information about the status of your program: whether it is
2328 running or not, what process it is, and why it stopped.
2332 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2333 * Continuing and Stepping:: Resuming execution
2335 * Thread Stops:: Stopping and starting multi-thread programs
2339 @section Breakpoints, watchpoints, and catchpoints
2342 A @dfn{breakpoint} makes your program stop whenever a certain point in
2343 the program is reached. For each breakpoint, you can add conditions to
2344 control in finer detail whether your program stops. You can set
2345 breakpoints with the @code{break} command and its variants (@pxref{Set
2346 Breaks, ,Setting breakpoints}), to specify the place where your program
2347 should stop by line number, function name or exact address in the
2350 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2351 breakpoints in shared libraries before the executable is run. There is
2352 a minor limitation on HP-UX systems: you must wait until the executable
2353 is run in order to set breakpoints in shared library routines that are
2354 not called directly by the program (for example, routines that are
2355 arguments in a @code{pthread_create} call).
2358 @cindex memory tracing
2359 @cindex breakpoint on memory address
2360 @cindex breakpoint on variable modification
2361 A @dfn{watchpoint} is a special breakpoint that stops your program
2362 when the value of an expression changes. You must use a different
2363 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2364 watchpoints}), but aside from that, you can manage a watchpoint like
2365 any other breakpoint: you enable, disable, and delete both breakpoints
2366 and watchpoints using the same commands.
2368 You can arrange to have values from your program displayed automatically
2369 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2373 @cindex breakpoint on events
2374 A @dfn{catchpoint} is another special breakpoint that stops your program
2375 when a certain kind of event occurs, such as the throwing of a C@t{++}
2376 exception or the loading of a library. As with watchpoints, you use a
2377 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2378 catchpoints}), but aside from that, you can manage a catchpoint like any
2379 other breakpoint. (To stop when your program receives a signal, use the
2380 @code{handle} command; see @ref{Signals, ,Signals}.)
2382 @cindex breakpoint numbers
2383 @cindex numbers for breakpoints
2384 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2385 catchpoint when you create it; these numbers are successive integers
2386 starting with one. In many of the commands for controlling various
2387 features of breakpoints you use the breakpoint number to say which
2388 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2389 @dfn{disabled}; if disabled, it has no effect on your program until you
2392 @cindex breakpoint ranges
2393 @cindex ranges of breakpoints
2394 Some @value{GDBN} commands accept a range of breakpoints on which to
2395 operate. A breakpoint range is either a single breakpoint number, like
2396 @samp{5}, or two such numbers, in increasing order, separated by a
2397 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2398 all breakpoint in that range are operated on.
2401 * Set Breaks:: Setting breakpoints
2402 * Set Watchpoints:: Setting watchpoints
2403 * Set Catchpoints:: Setting catchpoints
2404 * Delete Breaks:: Deleting breakpoints
2405 * Disabling:: Disabling breakpoints
2406 * Conditions:: Break conditions
2407 * Break Commands:: Breakpoint command lists
2408 * Breakpoint Menus:: Breakpoint menus
2409 * Error in Breakpoints:: ``Cannot insert breakpoints''
2413 @subsection Setting breakpoints
2415 @c FIXME LMB what does GDB do if no code on line of breakpt?
2416 @c consider in particular declaration with/without initialization.
2418 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2421 @kindex b @r{(@code{break})}
2422 @vindex $bpnum@r{, convenience variable}
2423 @cindex latest breakpoint
2424 Breakpoints are set with the @code{break} command (abbreviated
2425 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2426 number of the breakpoint you've set most recently; see @ref{Convenience
2427 Vars,, Convenience variables}, for a discussion of what you can do with
2428 convenience variables.
2430 You have several ways to say where the breakpoint should go.
2433 @item break @var{function}
2434 Set a breakpoint at entry to function @var{function}.
2435 When using source languages that permit overloading of symbols, such as
2436 C@t{++}, @var{function} may refer to more than one possible place to break.
2437 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2439 @item break +@var{offset}
2440 @itemx break -@var{offset}
2441 Set a breakpoint some number of lines forward or back from the position
2442 at which execution stopped in the currently selected @dfn{stack frame}.
2443 (@xref{Frames, ,Frames}, for a description of stack frames.)
2445 @item break @var{linenum}
2446 Set a breakpoint at line @var{linenum} in the current source file.
2447 The current source file is the last file whose source text was printed.
2448 The breakpoint will stop your program just before it executes any of the
2451 @item break @var{filename}:@var{linenum}
2452 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2454 @item break @var{filename}:@var{function}
2455 Set a breakpoint at entry to function @var{function} found in file
2456 @var{filename}. Specifying a file name as well as a function name is
2457 superfluous except when multiple files contain similarly named
2460 @item break *@var{address}
2461 Set a breakpoint at address @var{address}. You can use this to set
2462 breakpoints in parts of your program which do not have debugging
2463 information or source files.
2466 When called without any arguments, @code{break} sets a breakpoint at
2467 the next instruction to be executed in the selected stack frame
2468 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2469 innermost, this makes your program stop as soon as control
2470 returns to that frame. This is similar to the effect of a
2471 @code{finish} command in the frame inside the selected frame---except
2472 that @code{finish} does not leave an active breakpoint. If you use
2473 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2474 the next time it reaches the current location; this may be useful
2477 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2478 least one instruction has been executed. If it did not do this, you
2479 would be unable to proceed past a breakpoint without first disabling the
2480 breakpoint. This rule applies whether or not the breakpoint already
2481 existed when your program stopped.
2483 @item break @dots{} if @var{cond}
2484 Set a breakpoint with condition @var{cond}; evaluate the expression
2485 @var{cond} each time the breakpoint is reached, and stop only if the
2486 value is nonzero---that is, if @var{cond} evaluates as true.
2487 @samp{@dots{}} stands for one of the possible arguments described
2488 above (or no argument) specifying where to break. @xref{Conditions,
2489 ,Break conditions}, for more information on breakpoint conditions.
2492 @item tbreak @var{args}
2493 Set a breakpoint enabled only for one stop. @var{args} are the
2494 same as for the @code{break} command, and the breakpoint is set in the same
2495 way, but the breakpoint is automatically deleted after the first time your
2496 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2499 @item hbreak @var{args}
2500 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2501 @code{break} command and the breakpoint is set in the same way, but the
2502 breakpoint requires hardware support and some target hardware may not
2503 have this support. The main purpose of this is EPROM/ROM code
2504 debugging, so you can set a breakpoint at an instruction without
2505 changing the instruction. This can be used with the new trap-generation
2506 provided by SPARClite DSU and some x86-based targets. These targets
2507 will generate traps when a program accesses some data or instruction
2508 address that is assigned to the debug registers. However the hardware
2509 breakpoint registers can take a limited number of breakpoints. For
2510 example, on the DSU, only two data breakpoints can be set at a time, and
2511 @value{GDBN} will reject this command if more than two are used. Delete
2512 or disable unused hardware breakpoints before setting new ones
2513 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2514 @xref{set remote hardware-breakpoint-limit}.
2518 @item thbreak @var{args}
2519 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2520 are the same as for the @code{hbreak} command and the breakpoint is set in
2521 the same way. However, like the @code{tbreak} command,
2522 the breakpoint is automatically deleted after the
2523 first time your program stops there. Also, like the @code{hbreak}
2524 command, the breakpoint requires hardware support and some target hardware
2525 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2526 See also @ref{Conditions, ,Break conditions}.
2529 @cindex regular expression
2530 @item rbreak @var{regex}
2531 Set breakpoints on all functions matching the regular expression
2532 @var{regex}. This command sets an unconditional breakpoint on all
2533 matches, printing a list of all breakpoints it set. Once these
2534 breakpoints are set, they are treated just like the breakpoints set with
2535 the @code{break} command. You can delete them, disable them, or make
2536 them conditional the same way as any other breakpoint.
2538 The syntax of the regular expression is the standard one used with tools
2539 like @file{grep}. Note that this is different from the syntax used by
2540 shells, so for instance @code{foo*} matches all functions that include
2541 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2542 @code{.*} leading and trailing the regular expression you supply, so to
2543 match only functions that begin with @code{foo}, use @code{^foo}.
2545 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2546 breakpoints on overloaded functions that are not members of any special
2549 @kindex info breakpoints
2550 @cindex @code{$_} and @code{info breakpoints}
2551 @item info breakpoints @r{[}@var{n}@r{]}
2552 @itemx info break @r{[}@var{n}@r{]}
2553 @itemx info watchpoints @r{[}@var{n}@r{]}
2554 Print a table of all breakpoints, watchpoints, and catchpoints set and
2555 not deleted, with the following columns for each breakpoint:
2558 @item Breakpoint Numbers
2560 Breakpoint, watchpoint, or catchpoint.
2562 Whether the breakpoint is marked to be disabled or deleted when hit.
2563 @item Enabled or Disabled
2564 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2565 that are not enabled.
2567 Where the breakpoint is in your program, as a memory address.
2569 Where the breakpoint is in the source for your program, as a file and
2574 If a breakpoint is conditional, @code{info break} shows the condition on
2575 the line following the affected breakpoint; breakpoint commands, if any,
2576 are listed after that.
2579 @code{info break} with a breakpoint
2580 number @var{n} as argument lists only that breakpoint. The
2581 convenience variable @code{$_} and the default examining-address for
2582 the @code{x} command are set to the address of the last breakpoint
2583 listed (@pxref{Memory, ,Examining memory}).
2586 @code{info break} displays a count of the number of times the breakpoint
2587 has been hit. This is especially useful in conjunction with the
2588 @code{ignore} command. You can ignore a large number of breakpoint
2589 hits, look at the breakpoint info to see how many times the breakpoint
2590 was hit, and then run again, ignoring one less than that number. This
2591 will get you quickly to the last hit of that breakpoint.
2594 @value{GDBN} allows you to set any number of breakpoints at the same place in
2595 your program. There is nothing silly or meaningless about this. When
2596 the breakpoints are conditional, this is even useful
2597 (@pxref{Conditions, ,Break conditions}).
2599 @cindex negative breakpoint numbers
2600 @cindex internal @value{GDBN} breakpoints
2601 @value{GDBN} itself sometimes sets breakpoints in your program for
2602 special purposes, such as proper handling of @code{longjmp} (in C
2603 programs). These internal breakpoints are assigned negative numbers,
2604 starting with @code{-1}; @samp{info breakpoints} does not display them.
2605 You can see these breakpoints with the @value{GDBN} maintenance command
2606 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2609 @node Set Watchpoints
2610 @subsection Setting watchpoints
2612 @cindex setting watchpoints
2613 @cindex software watchpoints
2614 @cindex hardware watchpoints
2615 You can use a watchpoint to stop execution whenever the value of an
2616 expression changes, without having to predict a particular place where
2619 Depending on your system, watchpoints may be implemented in software or
2620 hardware. @value{GDBN} does software watchpointing by single-stepping your
2621 program and testing the variable's value each time, which is hundreds of
2622 times slower than normal execution. (But this may still be worth it, to
2623 catch errors where you have no clue what part of your program is the
2626 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2627 @value{GDBN} includes support for
2628 hardware watchpoints, which do not slow down the running of your
2633 @item watch @var{expr}
2634 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2635 is written into by the program and its value changes.
2638 @item rwatch @var{expr}
2639 Set a watchpoint that will break when watch @var{expr} is read by the program.
2642 @item awatch @var{expr}
2643 Set a watchpoint that will break when @var{expr} is either read or written into
2646 @kindex info watchpoints
2647 @item info watchpoints
2648 This command prints a list of watchpoints, breakpoints, and catchpoints;
2649 it is the same as @code{info break}.
2652 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2653 watchpoints execute very quickly, and the debugger reports a change in
2654 value at the exact instruction where the change occurs. If @value{GDBN}
2655 cannot set a hardware watchpoint, it sets a software watchpoint, which
2656 executes more slowly and reports the change in value at the next
2657 statement, not the instruction, after the change occurs.
2659 When you issue the @code{watch} command, @value{GDBN} reports
2662 Hardware watchpoint @var{num}: @var{expr}
2666 if it was able to set a hardware watchpoint.
2668 Currently, the @code{awatch} and @code{rwatch} commands can only set
2669 hardware watchpoints, because accesses to data that don't change the
2670 value of the watched expression cannot be detected without examining
2671 every instruction as it is being executed, and @value{GDBN} does not do
2672 that currently. If @value{GDBN} finds that it is unable to set a
2673 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2674 will print a message like this:
2677 Expression cannot be implemented with read/access watchpoint.
2680 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2681 data type of the watched expression is wider than what a hardware
2682 watchpoint on the target machine can handle. For example, some systems
2683 can only watch regions that are up to 4 bytes wide; on such systems you
2684 cannot set hardware watchpoints for an expression that yields a
2685 double-precision floating-point number (which is typically 8 bytes
2686 wide). As a work-around, it might be possible to break the large region
2687 into a series of smaller ones and watch them with separate watchpoints.
2689 If you set too many hardware watchpoints, @value{GDBN} might be unable
2690 to insert all of them when you resume the execution of your program.
2691 Since the precise number of active watchpoints is unknown until such
2692 time as the program is about to be resumed, @value{GDBN} might not be
2693 able to warn you about this when you set the watchpoints, and the
2694 warning will be printed only when the program is resumed:
2697 Hardware watchpoint @var{num}: Could not insert watchpoint
2701 If this happens, delete or disable some of the watchpoints.
2703 The SPARClite DSU will generate traps when a program accesses some data
2704 or instruction address that is assigned to the debug registers. For the
2705 data addresses, DSU facilitates the @code{watch} command. However the
2706 hardware breakpoint registers can only take two data watchpoints, and
2707 both watchpoints must be the same kind. For example, you can set two
2708 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2709 @strong{or} two with @code{awatch} commands, but you cannot set one
2710 watchpoint with one command and the other with a different command.
2711 @value{GDBN} will reject the command if you try to mix watchpoints.
2712 Delete or disable unused watchpoint commands before setting new ones.
2714 If you call a function interactively using @code{print} or @code{call},
2715 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2716 kind of breakpoint or the call completes.
2718 @value{GDBN} automatically deletes watchpoints that watch local
2719 (automatic) variables, or expressions that involve such variables, when
2720 they go out of scope, that is, when the execution leaves the block in
2721 which these variables were defined. In particular, when the program
2722 being debugged terminates, @emph{all} local variables go out of scope,
2723 and so only watchpoints that watch global variables remain set. If you
2724 rerun the program, you will need to set all such watchpoints again. One
2725 way of doing that would be to set a code breakpoint at the entry to the
2726 @code{main} function and when it breaks, set all the watchpoints.
2729 @cindex watchpoints and threads
2730 @cindex threads and watchpoints
2731 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2732 usefulness. With the current watchpoint implementation, @value{GDBN}
2733 can only watch the value of an expression @emph{in a single thread}. If
2734 you are confident that the expression can only change due to the current
2735 thread's activity (and if you are also confident that no other thread
2736 can become current), then you can use watchpoints as usual. However,
2737 @value{GDBN} may not notice when a non-current thread's activity changes
2740 @c FIXME: this is almost identical to the previous paragraph.
2741 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2742 have only limited usefulness. If @value{GDBN} creates a software
2743 watchpoint, it can only watch the value of an expression @emph{in a
2744 single thread}. If you are confident that the expression can only
2745 change due to the current thread's activity (and if you are also
2746 confident that no other thread can become current), then you can use
2747 software watchpoints as usual. However, @value{GDBN} may not notice
2748 when a non-current thread's activity changes the expression. (Hardware
2749 watchpoints, in contrast, watch an expression in all threads.)
2752 @xref{set remote hardware-watchpoint-limit}.
2754 @node Set Catchpoints
2755 @subsection Setting catchpoints
2756 @cindex catchpoints, setting
2757 @cindex exception handlers
2758 @cindex event handling
2760 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2761 kinds of program events, such as C@t{++} exceptions or the loading of a
2762 shared library. Use the @code{catch} command to set a catchpoint.
2766 @item catch @var{event}
2767 Stop when @var{event} occurs. @var{event} can be any of the following:
2771 The throwing of a C@t{++} exception.
2775 The catching of a C@t{++} exception.
2779 A call to @code{exec}. This is currently only available for HP-UX.
2783 A call to @code{fork}. This is currently only available for HP-UX.
2787 A call to @code{vfork}. This is currently only available for HP-UX.
2790 @itemx load @var{libname}
2792 The dynamic loading of any shared library, or the loading of the library
2793 @var{libname}. This is currently only available for HP-UX.
2796 @itemx unload @var{libname}
2797 @kindex catch unload
2798 The unloading of any dynamically loaded shared library, or the unloading
2799 of the library @var{libname}. This is currently only available for HP-UX.
2802 @item tcatch @var{event}
2803 Set a catchpoint that is enabled only for one stop. The catchpoint is
2804 automatically deleted after the first time the event is caught.
2808 Use the @code{info break} command to list the current catchpoints.
2810 There are currently some limitations to C@t{++} exception handling
2811 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2815 If you call a function interactively, @value{GDBN} normally returns
2816 control to you when the function has finished executing. If the call
2817 raises an exception, however, the call may bypass the mechanism that
2818 returns control to you and cause your program either to abort or to
2819 simply continue running until it hits a breakpoint, catches a signal
2820 that @value{GDBN} is listening for, or exits. This is the case even if
2821 you set a catchpoint for the exception; catchpoints on exceptions are
2822 disabled within interactive calls.
2825 You cannot raise an exception interactively.
2828 You cannot install an exception handler interactively.
2831 @cindex raise exceptions
2832 Sometimes @code{catch} is not the best way to debug exception handling:
2833 if you need to know exactly where an exception is raised, it is better to
2834 stop @emph{before} the exception handler is called, since that way you
2835 can see the stack before any unwinding takes place. If you set a
2836 breakpoint in an exception handler instead, it may not be easy to find
2837 out where the exception was raised.
2839 To stop just before an exception handler is called, you need some
2840 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2841 raised by calling a library function named @code{__raise_exception}
2842 which has the following ANSI C interface:
2845 /* @var{addr} is where the exception identifier is stored.
2846 @var{id} is the exception identifier. */
2847 void __raise_exception (void **addr, void *id);
2851 To make the debugger catch all exceptions before any stack
2852 unwinding takes place, set a breakpoint on @code{__raise_exception}
2853 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2855 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2856 that depends on the value of @var{id}, you can stop your program when
2857 a specific exception is raised. You can use multiple conditional
2858 breakpoints to stop your program when any of a number of exceptions are
2863 @subsection Deleting breakpoints
2865 @cindex clearing breakpoints, watchpoints, catchpoints
2866 @cindex deleting breakpoints, watchpoints, catchpoints
2867 It is often necessary to eliminate a breakpoint, watchpoint, or
2868 catchpoint once it has done its job and you no longer want your program
2869 to stop there. This is called @dfn{deleting} the breakpoint. A
2870 breakpoint that has been deleted no longer exists; it is forgotten.
2872 With the @code{clear} command you can delete breakpoints according to
2873 where they are in your program. With the @code{delete} command you can
2874 delete individual breakpoints, watchpoints, or catchpoints by specifying
2875 their breakpoint numbers.
2877 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2878 automatically ignores breakpoints on the first instruction to be executed
2879 when you continue execution without changing the execution address.
2884 Delete any breakpoints at the next instruction to be executed in the
2885 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
2886 the innermost frame is selected, this is a good way to delete a
2887 breakpoint where your program just stopped.
2889 @item clear @var{function}
2890 @itemx clear @var{filename}:@var{function}
2891 Delete any breakpoints set at entry to the function @var{function}.
2893 @item clear @var{linenum}
2894 @itemx clear @var{filename}:@var{linenum}
2895 Delete any breakpoints set at or within the code of the specified line.
2897 @cindex delete breakpoints
2899 @kindex d @r{(@code{delete})}
2900 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2901 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
2902 ranges specified as arguments. If no argument is specified, delete all
2903 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
2904 confirm off}). You can abbreviate this command as @code{d}.
2908 @subsection Disabling breakpoints
2910 @kindex disable breakpoints
2911 @kindex enable breakpoints
2912 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
2913 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
2914 it had been deleted, but remembers the information on the breakpoint so
2915 that you can @dfn{enable} it again later.
2917 You disable and enable breakpoints, watchpoints, and catchpoints with
2918 the @code{enable} and @code{disable} commands, optionally specifying one
2919 or more breakpoint numbers as arguments. Use @code{info break} or
2920 @code{info watch} to print a list of breakpoints, watchpoints, and
2921 catchpoints if you do not know which numbers to use.
2923 A breakpoint, watchpoint, or catchpoint can have any of four different
2924 states of enablement:
2928 Enabled. The breakpoint stops your program. A breakpoint set
2929 with the @code{break} command starts out in this state.
2931 Disabled. The breakpoint has no effect on your program.
2933 Enabled once. The breakpoint stops your program, but then becomes
2936 Enabled for deletion. The breakpoint stops your program, but
2937 immediately after it does so it is deleted permanently. A breakpoint
2938 set with the @code{tbreak} command starts out in this state.
2941 You can use the following commands to enable or disable breakpoints,
2942 watchpoints, and catchpoints:
2945 @kindex disable breakpoints
2947 @kindex dis @r{(@code{disable})}
2948 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2949 Disable the specified breakpoints---or all breakpoints, if none are
2950 listed. A disabled breakpoint has no effect but is not forgotten. All
2951 options such as ignore-counts, conditions and commands are remembered in
2952 case the breakpoint is enabled again later. You may abbreviate
2953 @code{disable} as @code{dis}.
2955 @kindex enable breakpoints
2957 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2958 Enable the specified breakpoints (or all defined breakpoints). They
2959 become effective once again in stopping your program.
2961 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
2962 Enable the specified breakpoints temporarily. @value{GDBN} disables any
2963 of these breakpoints immediately after stopping your program.
2965 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
2966 Enable the specified breakpoints to work once, then die. @value{GDBN}
2967 deletes any of these breakpoints as soon as your program stops there.
2970 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
2971 @c confusing: tbreak is also initially enabled.
2972 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
2973 ,Setting breakpoints}), breakpoints that you set are initially enabled;
2974 subsequently, they become disabled or enabled only when you use one of
2975 the commands above. (The command @code{until} can set and delete a
2976 breakpoint of its own, but it does not change the state of your other
2977 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
2981 @subsection Break conditions
2982 @cindex conditional breakpoints
2983 @cindex breakpoint conditions
2985 @c FIXME what is scope of break condition expr? Context where wanted?
2986 @c in particular for a watchpoint?
2987 The simplest sort of breakpoint breaks every time your program reaches a
2988 specified place. You can also specify a @dfn{condition} for a
2989 breakpoint. A condition is just a Boolean expression in your
2990 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
2991 a condition evaluates the expression each time your program reaches it,
2992 and your program stops only if the condition is @emph{true}.
2994 This is the converse of using assertions for program validation; in that
2995 situation, you want to stop when the assertion is violated---that is,
2996 when the condition is false. In C, if you want to test an assertion expressed
2997 by the condition @var{assert}, you should set the condition
2998 @samp{! @var{assert}} on the appropriate breakpoint.
3000 Conditions are also accepted for watchpoints; you may not need them,
3001 since a watchpoint is inspecting the value of an expression anyhow---but
3002 it might be simpler, say, to just set a watchpoint on a variable name,
3003 and specify a condition that tests whether the new value is an interesting
3006 Break conditions can have side effects, and may even call functions in
3007 your program. This can be useful, for example, to activate functions
3008 that log program progress, or to use your own print functions to
3009 format special data structures. The effects are completely predictable
3010 unless there is another enabled breakpoint at the same address. (In
3011 that case, @value{GDBN} might see the other breakpoint first and stop your
3012 program without checking the condition of this one.) Note that
3013 breakpoint commands are usually more convenient and flexible than break
3015 purpose of performing side effects when a breakpoint is reached
3016 (@pxref{Break Commands, ,Breakpoint command lists}).
3018 Break conditions can be specified when a breakpoint is set, by using
3019 @samp{if} in the arguments to the @code{break} command. @xref{Set
3020 Breaks, ,Setting breakpoints}. They can also be changed at any time
3021 with the @code{condition} command.
3023 You can also use the @code{if} keyword with the @code{watch} command.
3024 The @code{catch} command does not recognize the @code{if} keyword;
3025 @code{condition} is the only way to impose a further condition on a
3030 @item condition @var{bnum} @var{expression}
3031 Specify @var{expression} as the break condition for breakpoint,
3032 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3033 breakpoint @var{bnum} stops your program only if the value of
3034 @var{expression} is true (nonzero, in C). When you use
3035 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3036 syntactic correctness, and to determine whether symbols in it have
3037 referents in the context of your breakpoint. If @var{expression} uses
3038 symbols not referenced in the context of the breakpoint, @value{GDBN}
3039 prints an error message:
3042 No symbol "foo" in current context.
3047 not actually evaluate @var{expression} at the time the @code{condition}
3048 command (or a command that sets a breakpoint with a condition, like
3049 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3051 @item condition @var{bnum}
3052 Remove the condition from breakpoint number @var{bnum}. It becomes
3053 an ordinary unconditional breakpoint.
3056 @cindex ignore count (of breakpoint)
3057 A special case of a breakpoint condition is to stop only when the
3058 breakpoint has been reached a certain number of times. This is so
3059 useful that there is a special way to do it, using the @dfn{ignore
3060 count} of the breakpoint. Every breakpoint has an ignore count, which
3061 is an integer. Most of the time, the ignore count is zero, and
3062 therefore has no effect. But if your program reaches a breakpoint whose
3063 ignore count is positive, then instead of stopping, it just decrements
3064 the ignore count by one and continues. As a result, if the ignore count
3065 value is @var{n}, the breakpoint does not stop the next @var{n} times
3066 your program reaches it.
3070 @item ignore @var{bnum} @var{count}
3071 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3072 The next @var{count} times the breakpoint is reached, your program's
3073 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3076 To make the breakpoint stop the next time it is reached, specify
3079 When you use @code{continue} to resume execution of your program from a
3080 breakpoint, you can specify an ignore count directly as an argument to
3081 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3082 Stepping,,Continuing and stepping}.
3084 If a breakpoint has a positive ignore count and a condition, the
3085 condition is not checked. Once the ignore count reaches zero,
3086 @value{GDBN} resumes checking the condition.
3088 You could achieve the effect of the ignore count with a condition such
3089 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3090 is decremented each time. @xref{Convenience Vars, ,Convenience
3094 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3097 @node Break Commands
3098 @subsection Breakpoint command lists
3100 @cindex breakpoint commands
3101 You can give any breakpoint (or watchpoint or catchpoint) a series of
3102 commands to execute when your program stops due to that breakpoint. For
3103 example, you might want to print the values of certain expressions, or
3104 enable other breakpoints.
3109 @item commands @r{[}@var{bnum}@r{]}
3110 @itemx @dots{} @var{command-list} @dots{}
3112 Specify a list of commands for breakpoint number @var{bnum}. The commands
3113 themselves appear on the following lines. Type a line containing just
3114 @code{end} to terminate the commands.
3116 To remove all commands from a breakpoint, type @code{commands} and
3117 follow it immediately with @code{end}; that is, give no commands.
3119 With no @var{bnum} argument, @code{commands} refers to the last
3120 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3121 recently encountered).
3124 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3125 disabled within a @var{command-list}.
3127 You can use breakpoint commands to start your program up again. Simply
3128 use the @code{continue} command, or @code{step}, or any other command
3129 that resumes execution.
3131 Any other commands in the command list, after a command that resumes
3132 execution, are ignored. This is because any time you resume execution
3133 (even with a simple @code{next} or @code{step}), you may encounter
3134 another breakpoint---which could have its own command list, leading to
3135 ambiguities about which list to execute.
3138 If the first command you specify in a command list is @code{silent}, the
3139 usual message about stopping at a breakpoint is not printed. This may
3140 be desirable for breakpoints that are to print a specific message and
3141 then continue. If none of the remaining commands print anything, you
3142 see no sign that the breakpoint was reached. @code{silent} is
3143 meaningful only at the beginning of a breakpoint command list.
3145 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3146 print precisely controlled output, and are often useful in silent
3147 breakpoints. @xref{Output, ,Commands for controlled output}.
3149 For example, here is how you could use breakpoint commands to print the
3150 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3156 printf "x is %d\n",x
3161 One application for breakpoint commands is to compensate for one bug so
3162 you can test for another. Put a breakpoint just after the erroneous line
3163 of code, give it a condition to detect the case in which something
3164 erroneous has been done, and give it commands to assign correct values
3165 to any variables that need them. End with the @code{continue} command
3166 so that your program does not stop, and start with the @code{silent}
3167 command so that no output is produced. Here is an example:
3178 @node Breakpoint Menus
3179 @subsection Breakpoint menus
3181 @cindex symbol overloading
3183 Some programming languages (notably C@t{++}) permit a single function name
3184 to be defined several times, for application in different contexts.
3185 This is called @dfn{overloading}. When a function name is overloaded,
3186 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3187 a breakpoint. If you realize this is a problem, you can use
3188 something like @samp{break @var{function}(@var{types})} to specify which
3189 particular version of the function you want. Otherwise, @value{GDBN} offers
3190 you a menu of numbered choices for different possible breakpoints, and
3191 waits for your selection with the prompt @samp{>}. The first two
3192 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3193 sets a breakpoint at each definition of @var{function}, and typing
3194 @kbd{0} aborts the @code{break} command without setting any new
3197 For example, the following session excerpt shows an attempt to set a
3198 breakpoint at the overloaded symbol @code{String::after}.
3199 We choose three particular definitions of that function name:
3201 @c FIXME! This is likely to change to show arg type lists, at least
3204 (@value{GDBP}) b String::after
3207 [2] file:String.cc; line number:867
3208 [3] file:String.cc; line number:860
3209 [4] file:String.cc; line number:875
3210 [5] file:String.cc; line number:853
3211 [6] file:String.cc; line number:846
3212 [7] file:String.cc; line number:735
3214 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3215 Breakpoint 2 at 0xb344: file String.cc, line 875.
3216 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3217 Multiple breakpoints were set.
3218 Use the "delete" command to delete unwanted
3224 @c @ifclear BARETARGET
3225 @node Error in Breakpoints
3226 @subsection ``Cannot insert breakpoints''
3228 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3230 Under some operating systems, breakpoints cannot be used in a program if
3231 any other process is running that program. In this situation,
3232 attempting to run or continue a program with a breakpoint causes
3233 @value{GDBN} to print an error message:
3236 Cannot insert breakpoints.
3237 The same program may be running in another process.
3240 When this happens, you have three ways to proceed:
3244 Remove or disable the breakpoints, then continue.
3247 Suspend @value{GDBN}, and copy the file containing your program to a new
3248 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3249 that @value{GDBN} should run your program under that name.
3250 Then start your program again.
3253 Relink your program so that the text segment is nonsharable, using the
3254 linker option @samp{-N}. The operating system limitation may not apply
3255 to nonsharable executables.
3259 A similar message can be printed if you request too many active
3260 hardware-assisted breakpoints and watchpoints:
3262 @c FIXME: the precise wording of this message may change; the relevant
3263 @c source change is not committed yet (Sep 3, 1999).
3265 Stopped; cannot insert breakpoints.
3266 You may have requested too many hardware breakpoints and watchpoints.
3270 This message is printed when you attempt to resume the program, since
3271 only then @value{GDBN} knows exactly how many hardware breakpoints and
3272 watchpoints it needs to insert.
3274 When this message is printed, you need to disable or remove some of the
3275 hardware-assisted breakpoints and watchpoints, and then continue.
3278 @node Continuing and Stepping
3279 @section Continuing and stepping
3283 @cindex resuming execution
3284 @dfn{Continuing} means resuming program execution until your program
3285 completes normally. In contrast, @dfn{stepping} means executing just
3286 one more ``step'' of your program, where ``step'' may mean either one
3287 line of source code, or one machine instruction (depending on what
3288 particular command you use). Either when continuing or when stepping,
3289 your program may stop even sooner, due to a breakpoint or a signal. (If
3290 it stops due to a signal, you may want to use @code{handle}, or use
3291 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3295 @kindex c @r{(@code{continue})}
3296 @kindex fg @r{(resume foreground execution)}
3297 @item continue @r{[}@var{ignore-count}@r{]}
3298 @itemx c @r{[}@var{ignore-count}@r{]}
3299 @itemx fg @r{[}@var{ignore-count}@r{]}
3300 Resume program execution, at the address where your program last stopped;
3301 any breakpoints set at that address are bypassed. The optional argument
3302 @var{ignore-count} allows you to specify a further number of times to
3303 ignore a breakpoint at this location; its effect is like that of
3304 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3306 The argument @var{ignore-count} is meaningful only when your program
3307 stopped due to a breakpoint. At other times, the argument to
3308 @code{continue} is ignored.
3310 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3311 debugged program is deemed to be the foreground program) are provided
3312 purely for convenience, and have exactly the same behavior as
3316 To resume execution at a different place, you can use @code{return}
3317 (@pxref{Returning, ,Returning from a function}) to go back to the
3318 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3319 different address}) to go to an arbitrary location in your program.
3321 A typical technique for using stepping is to set a breakpoint
3322 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3323 beginning of the function or the section of your program where a problem
3324 is believed to lie, run your program until it stops at that breakpoint,
3325 and then step through the suspect area, examining the variables that are
3326 interesting, until you see the problem happen.
3330 @kindex s @r{(@code{step})}
3332 Continue running your program until control reaches a different source
3333 line, then stop it and return control to @value{GDBN}. This command is
3334 abbreviated @code{s}.
3337 @c "without debugging information" is imprecise; actually "without line
3338 @c numbers in the debugging information". (gcc -g1 has debugging info but
3339 @c not line numbers). But it seems complex to try to make that
3340 @c distinction here.
3341 @emph{Warning:} If you use the @code{step} command while control is
3342 within a function that was compiled without debugging information,
3343 execution proceeds until control reaches a function that does have
3344 debugging information. Likewise, it will not step into a function which
3345 is compiled without debugging information. To step through functions
3346 without debugging information, use the @code{stepi} command, described
3350 The @code{step} command only stops at the first instruction of a source
3351 line. This prevents the multiple stops that could otherwise occur in
3352 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3353 to stop if a function that has debugging information is called within
3354 the line. In other words, @code{step} @emph{steps inside} any functions
3355 called within the line.
3357 Also, the @code{step} command only enters a function if there is line
3358 number information for the function. Otherwise it acts like the
3359 @code{next} command. This avoids problems when using @code{cc -gl}
3360 on MIPS machines. Previously, @code{step} entered subroutines if there
3361 was any debugging information about the routine.
3363 @item step @var{count}
3364 Continue running as in @code{step}, but do so @var{count} times. If a
3365 breakpoint is reached, or a signal not related to stepping occurs before
3366 @var{count} steps, stepping stops right away.
3369 @kindex n @r{(@code{next})}
3370 @item next @r{[}@var{count}@r{]}
3371 Continue to the next source line in the current (innermost) stack frame.
3372 This is similar to @code{step}, but function calls that appear within
3373 the line of code are executed without stopping. Execution stops when
3374 control reaches a different line of code at the original stack level
3375 that was executing when you gave the @code{next} command. This command
3376 is abbreviated @code{n}.
3378 An argument @var{count} is a repeat count, as for @code{step}.
3381 @c FIX ME!! Do we delete this, or is there a way it fits in with
3382 @c the following paragraph? --- Vctoria
3384 @c @code{next} within a function that lacks debugging information acts like
3385 @c @code{step}, but any function calls appearing within the code of the
3386 @c function are executed without stopping.
3388 The @code{next} command only stops at the first instruction of a
3389 source line. This prevents multiple stops that could otherwise occur in
3390 @code{switch} statements, @code{for} loops, etc.
3392 @kindex set step-mode
3394 @cindex functions without line info, and stepping
3395 @cindex stepping into functions with no line info
3396 @itemx set step-mode on
3397 The @code{set step-mode on} command causes the @code{step} command to
3398 stop at the first instruction of a function which contains no debug line
3399 information rather than stepping over it.
3401 This is useful in cases where you may be interested in inspecting the
3402 machine instructions of a function which has no symbolic info and do not
3403 want @value{GDBN} to automatically skip over this function.
3405 @item set step-mode off
3406 Causes the @code{step} command to step over any functions which contains no
3407 debug information. This is the default.
3411 Continue running until just after function in the selected stack frame
3412 returns. Print the returned value (if any).
3414 Contrast this with the @code{return} command (@pxref{Returning,
3415 ,Returning from a function}).
3418 @kindex u @r{(@code{until})}
3421 Continue running until a source line past the current line, in the
3422 current stack frame, is reached. This command is used to avoid single
3423 stepping through a loop more than once. It is like the @code{next}
3424 command, except that when @code{until} encounters a jump, it
3425 automatically continues execution until the program counter is greater
3426 than the address of the jump.
3428 This means that when you reach the end of a loop after single stepping
3429 though it, @code{until} makes your program continue execution until it
3430 exits the loop. In contrast, a @code{next} command at the end of a loop
3431 simply steps back to the beginning of the loop, which forces you to step
3432 through the next iteration.
3434 @code{until} always stops your program if it attempts to exit the current
3437 @code{until} may produce somewhat counterintuitive results if the order
3438 of machine code does not match the order of the source lines. For
3439 example, in the following excerpt from a debugging session, the @code{f}
3440 (@code{frame}) command shows that execution is stopped at line
3441 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3445 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3447 (@value{GDBP}) until
3448 195 for ( ; argc > 0; NEXTARG) @{
3451 This happened because, for execution efficiency, the compiler had
3452 generated code for the loop closure test at the end, rather than the
3453 start, of the loop---even though the test in a C @code{for}-loop is
3454 written before the body of the loop. The @code{until} command appeared
3455 to step back to the beginning of the loop when it advanced to this
3456 expression; however, it has not really gone to an earlier
3457 statement---not in terms of the actual machine code.
3459 @code{until} with no argument works by means of single
3460 instruction stepping, and hence is slower than @code{until} with an
3463 @item until @var{location}
3464 @itemx u @var{location}
3465 Continue running your program until either the specified location is
3466 reached, or the current stack frame returns. @var{location} is any of
3467 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3468 ,Setting breakpoints}). This form of the command uses breakpoints, and
3469 hence is quicker than @code{until} without an argument. The specified
3470 location is actually reached only if it is in the current frame. This
3471 implies that @code{until} can be used to skip over recursive function
3472 invocations. For instance in the code below, if the current location is
3473 line @code{96}, issuing @code{until 99} will execute the program up to
3474 line @code{99} in the same invocation of factorial, i.e. after the inner
3475 invocations have returned.
3478 94 int factorial (int value)
3480 96 if (value > 1) @{
3481 97 value *= factorial (value - 1);
3488 @kindex advance @var{location}
3489 @itemx advance @var{location}
3490 Continue running the program up to the given location. An argument is
3491 required, anything of the same form as arguments for the @code{break}
3492 command. Execution will also stop upon exit from the current stack
3493 frame. This command is similar to @code{until}, but @code{advance} will
3494 not skip over recursive function calls, and the target location doesn't
3495 have to be in the same frame as the current one.
3499 @kindex si @r{(@code{stepi})}
3501 @itemx stepi @var{arg}
3503 Execute one machine instruction, then stop and return to the debugger.
3505 It is often useful to do @samp{display/i $pc} when stepping by machine
3506 instructions. This makes @value{GDBN} automatically display the next
3507 instruction to be executed, each time your program stops. @xref{Auto
3508 Display,, Automatic display}.
3510 An argument is a repeat count, as in @code{step}.
3514 @kindex ni @r{(@code{nexti})}
3516 @itemx nexti @var{arg}
3518 Execute one machine instruction, but if it is a function call,
3519 proceed until the function returns.
3521 An argument is a repeat count, as in @code{next}.
3528 A signal is an asynchronous event that can happen in a program. The
3529 operating system defines the possible kinds of signals, and gives each
3530 kind a name and a number. For example, in Unix @code{SIGINT} is the
3531 signal a program gets when you type an interrupt character (often @kbd{C-c});
3532 @code{SIGSEGV} is the signal a program gets from referencing a place in
3533 memory far away from all the areas in use; @code{SIGALRM} occurs when
3534 the alarm clock timer goes off (which happens only if your program has
3535 requested an alarm).
3537 @cindex fatal signals
3538 Some signals, including @code{SIGALRM}, are a normal part of the
3539 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3540 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3541 program has not specified in advance some other way to handle the signal.
3542 @code{SIGINT} does not indicate an error in your program, but it is normally
3543 fatal so it can carry out the purpose of the interrupt: to kill the program.
3545 @value{GDBN} has the ability to detect any occurrence of a signal in your
3546 program. You can tell @value{GDBN} in advance what to do for each kind of
3549 @cindex handling signals
3550 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3551 @code{SIGALRM} be silently passed to your program
3552 (so as not to interfere with their role in the program's functioning)
3553 but to stop your program immediately whenever an error signal happens.
3554 You can change these settings with the @code{handle} command.
3557 @kindex info signals
3560 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3561 handle each one. You can use this to see the signal numbers of all
3562 the defined types of signals.
3564 @code{info handle} is an alias for @code{info signals}.
3567 @item handle @var{signal} @var{keywords}@dots{}
3568 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3569 can be the number of a signal or its name (with or without the
3570 @samp{SIG} at the beginning); a list of signal numbers of the form
3571 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3572 known signals. The @var{keywords} say what change to make.
3576 The keywords allowed by the @code{handle} command can be abbreviated.
3577 Their full names are:
3581 @value{GDBN} should not stop your program when this signal happens. It may
3582 still print a message telling you that the signal has come in.
3585 @value{GDBN} should stop your program when this signal happens. This implies
3586 the @code{print} keyword as well.
3589 @value{GDBN} should print a message when this signal happens.
3592 @value{GDBN} should not mention the occurrence of the signal at all. This
3593 implies the @code{nostop} keyword as well.
3597 @value{GDBN} should allow your program to see this signal; your program
3598 can handle the signal, or else it may terminate if the signal is fatal
3599 and not handled. @code{pass} and @code{noignore} are synonyms.
3603 @value{GDBN} should not allow your program to see this signal.
3604 @code{nopass} and @code{ignore} are synonyms.
3608 When a signal stops your program, the signal is not visible to the
3610 continue. Your program sees the signal then, if @code{pass} is in
3611 effect for the signal in question @emph{at that time}. In other words,
3612 after @value{GDBN} reports a signal, you can use the @code{handle}
3613 command with @code{pass} or @code{nopass} to control whether your
3614 program sees that signal when you continue.
3616 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3617 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3618 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3621 You can also use the @code{signal} command to prevent your program from
3622 seeing a signal, or cause it to see a signal it normally would not see,
3623 or to give it any signal at any time. For example, if your program stopped
3624 due to some sort of memory reference error, you might store correct
3625 values into the erroneous variables and continue, hoping to see more
3626 execution; but your program would probably terminate immediately as
3627 a result of the fatal signal once it saw the signal. To prevent this,
3628 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3632 @section Stopping and starting multi-thread programs
3634 When your program has multiple threads (@pxref{Threads,, Debugging
3635 programs with multiple threads}), you can choose whether to set
3636 breakpoints on all threads, or on a particular thread.
3639 @cindex breakpoints and threads
3640 @cindex thread breakpoints
3641 @kindex break @dots{} thread @var{threadno}
3642 @item break @var{linespec} thread @var{threadno}
3643 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3644 @var{linespec} specifies source lines; there are several ways of
3645 writing them, but the effect is always to specify some source line.
3647 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3648 to specify that you only want @value{GDBN} to stop the program when a
3649 particular thread reaches this breakpoint. @var{threadno} is one of the
3650 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3651 column of the @samp{info threads} display.
3653 If you do not specify @samp{thread @var{threadno}} when you set a
3654 breakpoint, the breakpoint applies to @emph{all} threads of your
3657 You can use the @code{thread} qualifier on conditional breakpoints as
3658 well; in this case, place @samp{thread @var{threadno}} before the
3659 breakpoint condition, like this:
3662 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3667 @cindex stopped threads
3668 @cindex threads, stopped
3669 Whenever your program stops under @value{GDBN} for any reason,
3670 @emph{all} threads of execution stop, not just the current thread. This
3671 allows you to examine the overall state of the program, including
3672 switching between threads, without worrying that things may change
3675 @cindex continuing threads
3676 @cindex threads, continuing
3677 Conversely, whenever you restart the program, @emph{all} threads start
3678 executing. @emph{This is true even when single-stepping} with commands
3679 like @code{step} or @code{next}.
3681 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3682 Since thread scheduling is up to your debugging target's operating
3683 system (not controlled by @value{GDBN}), other threads may
3684 execute more than one statement while the current thread completes a
3685 single step. Moreover, in general other threads stop in the middle of a
3686 statement, rather than at a clean statement boundary, when the program
3689 You might even find your program stopped in another thread after
3690 continuing or even single-stepping. This happens whenever some other
3691 thread runs into a breakpoint, a signal, or an exception before the
3692 first thread completes whatever you requested.
3694 On some OSes, you can lock the OS scheduler and thus allow only a single
3698 @item set scheduler-locking @var{mode}
3699 Set the scheduler locking mode. If it is @code{off}, then there is no
3700 locking and any thread may run at any time. If @code{on}, then only the
3701 current thread may run when the inferior is resumed. The @code{step}
3702 mode optimizes for single-stepping. It stops other threads from
3703 ``seizing the prompt'' by preempting the current thread while you are
3704 stepping. Other threads will only rarely (or never) get a chance to run
3705 when you step. They are more likely to run when you @samp{next} over a
3706 function call, and they are completely free to run when you use commands
3707 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3708 thread hits a breakpoint during its timeslice, they will never steal the
3709 @value{GDBN} prompt away from the thread that you are debugging.
3711 @item show scheduler-locking
3712 Display the current scheduler locking mode.
3717 @chapter Examining the Stack
3719 When your program has stopped, the first thing you need to know is where it
3720 stopped and how it got there.
3723 Each time your program performs a function call, information about the call
3725 That information includes the location of the call in your program,
3726 the arguments of the call,
3727 and the local variables of the function being called.
3728 The information is saved in a block of data called a @dfn{stack frame}.
3729 The stack frames are allocated in a region of memory called the @dfn{call
3732 When your program stops, the @value{GDBN} commands for examining the
3733 stack allow you to see all of this information.
3735 @cindex selected frame
3736 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3737 @value{GDBN} commands refer implicitly to the selected frame. In
3738 particular, whenever you ask @value{GDBN} for the value of a variable in
3739 your program, the value is found in the selected frame. There are
3740 special @value{GDBN} commands to select whichever frame you are
3741 interested in. @xref{Selection, ,Selecting a frame}.
3743 When your program stops, @value{GDBN} automatically selects the
3744 currently executing frame and describes it briefly, similar to the
3745 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3748 * Frames:: Stack frames
3749 * Backtrace:: Backtraces
3750 * Selection:: Selecting a frame
3751 * Frame Info:: Information on a frame
3756 @section Stack frames
3758 @cindex frame, definition
3760 The call stack is divided up into contiguous pieces called @dfn{stack
3761 frames}, or @dfn{frames} for short; each frame is the data associated
3762 with one call to one function. The frame contains the arguments given
3763 to the function, the function's local variables, and the address at
3764 which the function is executing.
3766 @cindex initial frame
3767 @cindex outermost frame
3768 @cindex innermost frame
3769 When your program is started, the stack has only one frame, that of the
3770 function @code{main}. This is called the @dfn{initial} frame or the
3771 @dfn{outermost} frame. Each time a function is called, a new frame is
3772 made. Each time a function returns, the frame for that function invocation
3773 is eliminated. If a function is recursive, there can be many frames for
3774 the same function. The frame for the function in which execution is
3775 actually occurring is called the @dfn{innermost} frame. This is the most
3776 recently created of all the stack frames that still exist.
3778 @cindex frame pointer
3779 Inside your program, stack frames are identified by their addresses. A
3780 stack frame consists of many bytes, each of which has its own address; each
3781 kind of computer has a convention for choosing one byte whose
3782 address serves as the address of the frame. Usually this address is kept
3783 in a register called the @dfn{frame pointer register} while execution is
3784 going on in that frame.
3786 @cindex frame number
3787 @value{GDBN} assigns numbers to all existing stack frames, starting with
3788 zero for the innermost frame, one for the frame that called it,
3789 and so on upward. These numbers do not really exist in your program;
3790 they are assigned by @value{GDBN} to give you a way of designating stack
3791 frames in @value{GDBN} commands.
3793 @c The -fomit-frame-pointer below perennially causes hbox overflow
3794 @c underflow problems.
3795 @cindex frameless execution
3796 Some compilers provide a way to compile functions so that they operate
3797 without stack frames. (For example, the @value{GCC} option
3799 @samp{-fomit-frame-pointer}
3801 generates functions without a frame.)
3802 This is occasionally done with heavily used library functions to save
3803 the frame setup time. @value{GDBN} has limited facilities for dealing
3804 with these function invocations. If the innermost function invocation
3805 has no stack frame, @value{GDBN} nevertheless regards it as though
3806 it had a separate frame, which is numbered zero as usual, allowing
3807 correct tracing of the function call chain. However, @value{GDBN} has
3808 no provision for frameless functions elsewhere in the stack.
3811 @kindex frame@r{, command}
3812 @cindex current stack frame
3813 @item frame @var{args}
3814 The @code{frame} command allows you to move from one stack frame to another,
3815 and to print the stack frame you select. @var{args} may be either the
3816 address of the frame or the stack frame number. Without an argument,
3817 @code{frame} prints the current stack frame.
3819 @kindex select-frame
3820 @cindex selecting frame silently
3822 The @code{select-frame} command allows you to move from one stack frame
3823 to another without printing the frame. This is the silent version of
3832 @cindex stack traces
3833 A backtrace is a summary of how your program got where it is. It shows one
3834 line per frame, for many frames, starting with the currently executing
3835 frame (frame zero), followed by its caller (frame one), and on up the
3840 @kindex bt @r{(@code{backtrace})}
3843 Print a backtrace of the entire stack: one line per frame for all
3844 frames in the stack.
3846 You can stop the backtrace at any time by typing the system interrupt
3847 character, normally @kbd{C-c}.
3849 @item backtrace @var{n}
3851 Similar, but print only the innermost @var{n} frames.
3853 @item backtrace -@var{n}
3855 Similar, but print only the outermost @var{n} frames.
3860 @kindex info s @r{(@code{info stack})}
3861 The names @code{where} and @code{info stack} (abbreviated @code{info s})
3862 are additional aliases for @code{backtrace}.
3864 Each line in the backtrace shows the frame number and the function name.
3865 The program counter value is also shown---unless you use @code{set
3866 print address off}. The backtrace also shows the source file name and
3867 line number, as well as the arguments to the function. The program
3868 counter value is omitted if it is at the beginning of the code for that
3871 Here is an example of a backtrace. It was made with the command
3872 @samp{bt 3}, so it shows the innermost three frames.
3876 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
3878 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
3879 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
3881 (More stack frames follow...)
3886 The display for frame zero does not begin with a program counter
3887 value, indicating that your program has stopped at the beginning of the
3888 code for line @code{993} of @code{builtin.c}.
3890 @kindex set backtrace-below-main
3891 @kindex show backtrace-below-main
3893 Most programs have a standard entry point---a place where system libraries
3894 and startup code transition into user code. For C this is @code{main}.
3895 When @value{GDBN} finds the entry function in a backtrace it will terminate
3896 the backtrace, to avoid tracing into highly system-specific (and generally
3897 uninteresting) code. If you need to examine the startup code, then you can
3898 change this behavior.
3901 @item set backtrace-below-main off
3902 Backtraces will stop when they encounter the user entry point. This is the
3905 @item set backtrace-below-main
3906 @itemx set backtrace-below-main on
3907 Backtraces will continue past the user entry point to the top of the stack.
3909 @item show backtrace-below-main
3910 Display the current backtrace policy.
3914 @section Selecting a frame
3916 Most commands for examining the stack and other data in your program work on
3917 whichever stack frame is selected at the moment. Here are the commands for
3918 selecting a stack frame; all of them finish by printing a brief description
3919 of the stack frame just selected.
3922 @kindex frame@r{, selecting}
3923 @kindex f @r{(@code{frame})}
3926 Select frame number @var{n}. Recall that frame zero is the innermost
3927 (currently executing) frame, frame one is the frame that called the
3928 innermost one, and so on. The highest-numbered frame is the one for
3931 @item frame @var{addr}
3933 Select the frame at address @var{addr}. This is useful mainly if the
3934 chaining of stack frames has been damaged by a bug, making it
3935 impossible for @value{GDBN} to assign numbers properly to all frames. In
3936 addition, this can be useful when your program has multiple stacks and
3937 switches between them.
3939 On the SPARC architecture, @code{frame} needs two addresses to
3940 select an arbitrary frame: a frame pointer and a stack pointer.
3942 On the MIPS and Alpha architecture, it needs two addresses: a stack
3943 pointer and a program counter.
3945 On the 29k architecture, it needs three addresses: a register stack
3946 pointer, a program counter, and a memory stack pointer.
3947 @c note to future updaters: this is conditioned on a flag
3948 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
3949 @c as of 27 Jan 1994.
3953 Move @var{n} frames up the stack. For positive numbers @var{n}, this
3954 advances toward the outermost frame, to higher frame numbers, to frames
3955 that have existed longer. @var{n} defaults to one.
3958 @kindex do @r{(@code{down})}
3960 Move @var{n} frames down the stack. For positive numbers @var{n}, this
3961 advances toward the innermost frame, to lower frame numbers, to frames
3962 that were created more recently. @var{n} defaults to one. You may
3963 abbreviate @code{down} as @code{do}.
3966 All of these commands end by printing two lines of output describing the
3967 frame. The first line shows the frame number, the function name, the
3968 arguments, and the source file and line number of execution in that
3969 frame. The second line shows the text of that source line.
3977 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
3979 10 read_input_file (argv[i]);
3983 After such a printout, the @code{list} command with no arguments
3984 prints ten lines centered on the point of execution in the frame.
3985 You can also edit the program at the point of execution with your favorite
3986 editing program by typing @code{edit}.
3987 @xref{List, ,Printing source lines},
3991 @kindex down-silently
3993 @item up-silently @var{n}
3994 @itemx down-silently @var{n}
3995 These two commands are variants of @code{up} and @code{down},
3996 respectively; they differ in that they do their work silently, without
3997 causing display of the new frame. They are intended primarily for use
3998 in @value{GDBN} command scripts, where the output might be unnecessary and
4003 @section Information about a frame
4005 There are several other commands to print information about the selected
4011 When used without any argument, this command does not change which
4012 frame is selected, but prints a brief description of the currently
4013 selected stack frame. It can be abbreviated @code{f}. With an
4014 argument, this command is used to select a stack frame.
4015 @xref{Selection, ,Selecting a frame}.
4018 @kindex info f @r{(@code{info frame})}
4021 This command prints a verbose description of the selected stack frame,
4026 the address of the frame
4028 the address of the next frame down (called by this frame)
4030 the address of the next frame up (caller of this frame)
4032 the language in which the source code corresponding to this frame is written
4034 the address of the frame's arguments
4036 the address of the frame's local variables
4038 the program counter saved in it (the address of execution in the caller frame)
4040 which registers were saved in the frame
4043 @noindent The verbose description is useful when
4044 something has gone wrong that has made the stack format fail to fit
4045 the usual conventions.
4047 @item info frame @var{addr}
4048 @itemx info f @var{addr}
4049 Print a verbose description of the frame at address @var{addr}, without
4050 selecting that frame. The selected frame remains unchanged by this
4051 command. This requires the same kind of address (more than one for some
4052 architectures) that you specify in the @code{frame} command.
4053 @xref{Selection, ,Selecting a frame}.
4057 Print the arguments of the selected frame, each on a separate line.
4061 Print the local variables of the selected frame, each on a separate
4062 line. These are all variables (declared either static or automatic)
4063 accessible at the point of execution of the selected frame.
4066 @cindex catch exceptions, list active handlers
4067 @cindex exception handlers, how to list
4069 Print a list of all the exception handlers that are active in the
4070 current stack frame at the current point of execution. To see other
4071 exception handlers, visit the associated frame (using the @code{up},
4072 @code{down}, or @code{frame} commands); then type @code{info catch}.
4073 @xref{Set Catchpoints, , Setting catchpoints}.
4079 @chapter Examining Source Files
4081 @value{GDBN} can print parts of your program's source, since the debugging
4082 information recorded in the program tells @value{GDBN} what source files were
4083 used to build it. When your program stops, @value{GDBN} spontaneously prints
4084 the line where it stopped. Likewise, when you select a stack frame
4085 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4086 execution in that frame has stopped. You can print other portions of
4087 source files by explicit command.
4089 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4090 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4091 @value{GDBN} under @sc{gnu} Emacs}.
4094 * List:: Printing source lines
4095 * Edit:: Editing source files
4096 * Search:: Searching source files
4097 * Source Path:: Specifying source directories
4098 * Machine Code:: Source and machine code
4102 @section Printing source lines
4105 @kindex l @r{(@code{list})}
4106 To print lines from a source file, use the @code{list} command
4107 (abbreviated @code{l}). By default, ten lines are printed.
4108 There are several ways to specify what part of the file you want to print.
4110 Here are the forms of the @code{list} command most commonly used:
4113 @item list @var{linenum}
4114 Print lines centered around line number @var{linenum} in the
4115 current source file.
4117 @item list @var{function}
4118 Print lines centered around the beginning of function
4122 Print more lines. If the last lines printed were printed with a
4123 @code{list} command, this prints lines following the last lines
4124 printed; however, if the last line printed was a solitary line printed
4125 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4126 Stack}), this prints lines centered around that line.
4129 Print lines just before the lines last printed.
4132 By default, @value{GDBN} prints ten source lines with any of these forms of
4133 the @code{list} command. You can change this using @code{set listsize}:
4136 @kindex set listsize
4137 @item set listsize @var{count}
4138 Make the @code{list} command display @var{count} source lines (unless
4139 the @code{list} argument explicitly specifies some other number).
4141 @kindex show listsize
4143 Display the number of lines that @code{list} prints.
4146 Repeating a @code{list} command with @key{RET} discards the argument,
4147 so it is equivalent to typing just @code{list}. This is more useful
4148 than listing the same lines again. An exception is made for an
4149 argument of @samp{-}; that argument is preserved in repetition so that
4150 each repetition moves up in the source file.
4153 In general, the @code{list} command expects you to supply zero, one or two
4154 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4155 of writing them, but the effect is always to specify some source line.
4156 Here is a complete description of the possible arguments for @code{list}:
4159 @item list @var{linespec}
4160 Print lines centered around the line specified by @var{linespec}.
4162 @item list @var{first},@var{last}
4163 Print lines from @var{first} to @var{last}. Both arguments are
4166 @item list ,@var{last}
4167 Print lines ending with @var{last}.
4169 @item list @var{first},
4170 Print lines starting with @var{first}.
4173 Print lines just after the lines last printed.
4176 Print lines just before the lines last printed.
4179 As described in the preceding table.
4182 Here are the ways of specifying a single source line---all the
4187 Specifies line @var{number} of the current source file.
4188 When a @code{list} command has two linespecs, this refers to
4189 the same source file as the first linespec.
4192 Specifies the line @var{offset} lines after the last line printed.
4193 When used as the second linespec in a @code{list} command that has
4194 two, this specifies the line @var{offset} lines down from the
4198 Specifies the line @var{offset} lines before the last line printed.
4200 @item @var{filename}:@var{number}
4201 Specifies line @var{number} in the source file @var{filename}.
4203 @item @var{function}
4204 Specifies the line that begins the body of the function @var{function}.
4205 For example: in C, this is the line with the open brace.
4207 @item @var{filename}:@var{function}
4208 Specifies the line of the open-brace that begins the body of the
4209 function @var{function} in the file @var{filename}. You only need the
4210 file name with a function name to avoid ambiguity when there are
4211 identically named functions in different source files.
4213 @item *@var{address}
4214 Specifies the line containing the program address @var{address}.
4215 @var{address} may be any expression.
4219 @section Editing source files
4220 @cindex editing source files
4223 @kindex e @r{(@code{edit})}
4224 To edit the lines in a source file, use the @code{edit} command.
4225 The editing program of your choice
4226 is invoked with the current line set to
4227 the active line in the program.
4228 Alternatively, there are several ways to specify what part of the file you
4229 want to print if you want to see other parts of the program.
4231 Here are the forms of the @code{edit} command most commonly used:
4235 Edit the current source file at the active line number in the program.
4237 @item edit @var{number}
4238 Edit the current source file with @var{number} as the active line number.
4240 @item edit @var{function}
4241 Edit the file containing @var{function} at the beginning of its definition.
4243 @item edit @var{filename}:@var{number}
4244 Specifies line @var{number} in the source file @var{filename}.
4246 @item edit @var{filename}:@var{function}
4247 Specifies the line that begins the body of the
4248 function @var{function} in the file @var{filename}. You only need the
4249 file name with a function name to avoid ambiguity when there are
4250 identically named functions in different source files.
4252 @item edit *@var{address}
4253 Specifies the line containing the program address @var{address}.
4254 @var{address} may be any expression.
4257 @subsection Choosing your editor
4258 You can customize @value{GDBN} to use any editor you want
4260 The only restriction is that your editor (say @code{ex}), recognizes the
4261 following command-line syntax:
4263 ex +@var{number} file
4265 The optional numeric value +@var{number} designates the active line in
4266 the file.}. By default, it is @value{EDITOR}, but you can change this
4267 by setting the environment variable @code{EDITOR} before using
4268 @value{GDBN}. For example, to configure @value{GDBN} to use the
4269 @code{vi} editor, you could use these commands with the @code{sh} shell:
4275 or in the @code{csh} shell,
4277 setenv EDITOR /usr/bin/vi
4282 @section Searching source files
4284 @kindex reverse-search
4286 There are two commands for searching through the current source file for a
4291 @kindex forward-search
4292 @item forward-search @var{regexp}
4293 @itemx search @var{regexp}
4294 The command @samp{forward-search @var{regexp}} checks each line,
4295 starting with the one following the last line listed, for a match for
4296 @var{regexp}. It lists the line that is found. You can use the
4297 synonym @samp{search @var{regexp}} or abbreviate the command name as
4300 @item reverse-search @var{regexp}
4301 The command @samp{reverse-search @var{regexp}} checks each line, starting
4302 with the one before the last line listed and going backward, for a match
4303 for @var{regexp}. It lists the line that is found. You can abbreviate
4304 this command as @code{rev}.
4308 @section Specifying source directories
4311 @cindex directories for source files
4312 Executable programs sometimes do not record the directories of the source
4313 files from which they were compiled, just the names. Even when they do,
4314 the directories could be moved between the compilation and your debugging
4315 session. @value{GDBN} has a list of directories to search for source files;
4316 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4317 it tries all the directories in the list, in the order they are present
4318 in the list, until it finds a file with the desired name. Note that
4319 the executable search path is @emph{not} used for this purpose. Neither is
4320 the current working directory, unless it happens to be in the source
4323 If @value{GDBN} cannot find a source file in the source path, and the
4324 object program records a directory, @value{GDBN} tries that directory
4325 too. If the source path is empty, and there is no record of the
4326 compilation directory, @value{GDBN} looks in the current directory as a
4329 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4330 any information it has cached about where source files are found and where
4331 each line is in the file.
4335 When you start @value{GDBN}, its source path includes only @samp{cdir}
4336 and @samp{cwd}, in that order.
4337 To add other directories, use the @code{directory} command.
4340 @item directory @var{dirname} @dots{}
4341 @item dir @var{dirname} @dots{}
4342 Add directory @var{dirname} to the front of the source path. Several
4343 directory names may be given to this command, separated by @samp{:}
4344 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4345 part of absolute file names) or
4346 whitespace. You may specify a directory that is already in the source
4347 path; this moves it forward, so @value{GDBN} searches it sooner.
4351 @vindex $cdir@r{, convenience variable}
4352 @vindex $cwdr@r{, convenience variable}
4353 @cindex compilation directory
4354 @cindex current directory
4355 @cindex working directory
4356 @cindex directory, current
4357 @cindex directory, compilation
4358 You can use the string @samp{$cdir} to refer to the compilation
4359 directory (if one is recorded), and @samp{$cwd} to refer to the current
4360 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4361 tracks the current working directory as it changes during your @value{GDBN}
4362 session, while the latter is immediately expanded to the current
4363 directory at the time you add an entry to the source path.
4366 Reset the source path to empty again. This requires confirmation.
4368 @c RET-repeat for @code{directory} is explicitly disabled, but since
4369 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4371 @item show directories
4372 @kindex show directories
4373 Print the source path: show which directories it contains.
4376 If your source path is cluttered with directories that are no longer of
4377 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4378 versions of source. You can correct the situation as follows:
4382 Use @code{directory} with no argument to reset the source path to empty.
4385 Use @code{directory} with suitable arguments to reinstall the
4386 directories you want in the source path. You can add all the
4387 directories in one command.
4391 @section Source and machine code
4393 You can use the command @code{info line} to map source lines to program
4394 addresses (and vice versa), and the command @code{disassemble} to display
4395 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4396 mode, the @code{info line} command causes the arrow to point to the
4397 line specified. Also, @code{info line} prints addresses in symbolic form as
4402 @item info line @var{linespec}
4403 Print the starting and ending addresses of the compiled code for
4404 source line @var{linespec}. You can specify source lines in any of
4405 the ways understood by the @code{list} command (@pxref{List, ,Printing
4409 For example, we can use @code{info line} to discover the location of
4410 the object code for the first line of function
4411 @code{m4_changequote}:
4413 @c FIXME: I think this example should also show the addresses in
4414 @c symbolic form, as they usually would be displayed.
4416 (@value{GDBP}) info line m4_changequote
4417 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4421 We can also inquire (using @code{*@var{addr}} as the form for
4422 @var{linespec}) what source line covers a particular address:
4424 (@value{GDBP}) info line *0x63ff
4425 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4428 @cindex @code{$_} and @code{info line}
4429 @kindex x@r{(examine), and} info line
4430 After @code{info line}, the default address for the @code{x} command
4431 is changed to the starting address of the line, so that @samp{x/i} is
4432 sufficient to begin examining the machine code (@pxref{Memory,
4433 ,Examining memory}). Also, this address is saved as the value of the
4434 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4439 @cindex assembly instructions
4440 @cindex instructions, assembly
4441 @cindex machine instructions
4442 @cindex listing machine instructions
4444 This specialized command dumps a range of memory as machine
4445 instructions. The default memory range is the function surrounding the
4446 program counter of the selected frame. A single argument to this
4447 command is a program counter value; @value{GDBN} dumps the function
4448 surrounding this value. Two arguments specify a range of addresses
4449 (first inclusive, second exclusive) to dump.
4452 The following example shows the disassembly of a range of addresses of
4453 HP PA-RISC 2.0 code:
4456 (@value{GDBP}) disas 0x32c4 0x32e4
4457 Dump of assembler code from 0x32c4 to 0x32e4:
4458 0x32c4 <main+204>: addil 0,dp
4459 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4460 0x32cc <main+212>: ldil 0x3000,r31
4461 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4462 0x32d4 <main+220>: ldo 0(r31),rp
4463 0x32d8 <main+224>: addil -0x800,dp
4464 0x32dc <main+228>: ldo 0x588(r1),r26
4465 0x32e0 <main+232>: ldil 0x3000,r31
4466 End of assembler dump.
4469 Some architectures have more than one commonly-used set of instruction
4470 mnemonics or other syntax.
4473 @kindex set disassembly-flavor
4474 @cindex assembly instructions
4475 @cindex instructions, assembly
4476 @cindex machine instructions
4477 @cindex listing machine instructions
4478 @cindex Intel disassembly flavor
4479 @cindex AT&T disassembly flavor
4480 @item set disassembly-flavor @var{instruction-set}
4481 Select the instruction set to use when disassembling the
4482 program via the @code{disassemble} or @code{x/i} commands.
4484 Currently this command is only defined for the Intel x86 family. You
4485 can set @var{instruction-set} to either @code{intel} or @code{att}.
4486 The default is @code{att}, the AT&T flavor used by default by Unix
4487 assemblers for x86-based targets.
4492 @chapter Examining Data
4494 @cindex printing data
4495 @cindex examining data
4498 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4499 @c document because it is nonstandard... Under Epoch it displays in a
4500 @c different window or something like that.
4501 The usual way to examine data in your program is with the @code{print}
4502 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4503 evaluates and prints the value of an expression of the language your
4504 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4505 Different Languages}).
4508 @item print @var{expr}
4509 @itemx print /@var{f} @var{expr}
4510 @var{expr} is an expression (in the source language). By default the
4511 value of @var{expr} is printed in a format appropriate to its data type;
4512 you can choose a different format by specifying @samp{/@var{f}}, where
4513 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4517 @itemx print /@var{f}
4518 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4519 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4520 conveniently inspect the same value in an alternative format.
4523 A more low-level way of examining data is with the @code{x} command.
4524 It examines data in memory at a specified address and prints it in a
4525 specified format. @xref{Memory, ,Examining memory}.
4527 If you are interested in information about types, or about how the
4528 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4529 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4533 * Expressions:: Expressions
4534 * Variables:: Program variables
4535 * Arrays:: Artificial arrays
4536 * Output Formats:: Output formats
4537 * Memory:: Examining memory
4538 * Auto Display:: Automatic display
4539 * Print Settings:: Print settings
4540 * Value History:: Value history
4541 * Convenience Vars:: Convenience variables
4542 * Registers:: Registers
4543 * Floating Point Hardware:: Floating point hardware
4544 * Vector Unit:: Vector Unit
4545 * Memory Region Attributes:: Memory region attributes
4546 * Dump/Restore Files:: Copy between memory and a file
4547 * Character Sets:: Debugging programs that use a different
4548 character set than GDB does
4552 @section Expressions
4555 @code{print} and many other @value{GDBN} commands accept an expression and
4556 compute its value. Any kind of constant, variable or operator defined
4557 by the programming language you are using is valid in an expression in
4558 @value{GDBN}. This includes conditional expressions, function calls,
4559 casts, and string constants. It also includes preprocessor macros, if
4560 you compiled your program to include this information; see
4563 @value{GDBN} supports array constants in expressions input by
4564 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4565 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4566 memory that is @code{malloc}ed in the target program.
4568 Because C is so widespread, most of the expressions shown in examples in
4569 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4570 Languages}, for information on how to use expressions in other
4573 In this section, we discuss operators that you can use in @value{GDBN}
4574 expressions regardless of your programming language.
4576 Casts are supported in all languages, not just in C, because it is so
4577 useful to cast a number into a pointer in order to examine a structure
4578 at that address in memory.
4579 @c FIXME: casts supported---Mod2 true?
4581 @value{GDBN} supports these operators, in addition to those common
4582 to programming languages:
4586 @samp{@@} is a binary operator for treating parts of memory as arrays.
4587 @xref{Arrays, ,Artificial arrays}, for more information.
4590 @samp{::} allows you to specify a variable in terms of the file or
4591 function where it is defined. @xref{Variables, ,Program variables}.
4593 @cindex @{@var{type}@}
4594 @cindex type casting memory
4595 @cindex memory, viewing as typed object
4596 @cindex casts, to view memory
4597 @item @{@var{type}@} @var{addr}
4598 Refers to an object of type @var{type} stored at address @var{addr} in
4599 memory. @var{addr} may be any expression whose value is an integer or
4600 pointer (but parentheses are required around binary operators, just as in
4601 a cast). This construct is allowed regardless of what kind of data is
4602 normally supposed to reside at @var{addr}.
4606 @section Program variables
4608 The most common kind of expression to use is the name of a variable
4611 Variables in expressions are understood in the selected stack frame
4612 (@pxref{Selection, ,Selecting a frame}); they must be either:
4616 global (or file-static)
4623 visible according to the scope rules of the
4624 programming language from the point of execution in that frame
4627 @noindent This means that in the function
4642 you can examine and use the variable @code{a} whenever your program is
4643 executing within the function @code{foo}, but you can only use or
4644 examine the variable @code{b} while your program is executing inside
4645 the block where @code{b} is declared.
4647 @cindex variable name conflict
4648 There is an exception: you can refer to a variable or function whose
4649 scope is a single source file even if the current execution point is not
4650 in this file. But it is possible to have more than one such variable or
4651 function with the same name (in different source files). If that
4652 happens, referring to that name has unpredictable effects. If you wish,
4653 you can specify a static variable in a particular function or file,
4654 using the colon-colon notation:
4656 @cindex colon-colon, context for variables/functions
4658 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4659 @cindex @code{::}, context for variables/functions
4662 @var{file}::@var{variable}
4663 @var{function}::@var{variable}
4667 Here @var{file} or @var{function} is the name of the context for the
4668 static @var{variable}. In the case of file names, you can use quotes to
4669 make sure @value{GDBN} parses the file name as a single word---for example,
4670 to print a global value of @code{x} defined in @file{f2.c}:
4673 (@value{GDBP}) p 'f2.c'::x
4676 @cindex C@t{++} scope resolution
4677 This use of @samp{::} is very rarely in conflict with the very similar
4678 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4679 scope resolution operator in @value{GDBN} expressions.
4680 @c FIXME: Um, so what happens in one of those rare cases where it's in
4683 @cindex wrong values
4684 @cindex variable values, wrong
4686 @emph{Warning:} Occasionally, a local variable may appear to have the
4687 wrong value at certain points in a function---just after entry to a new
4688 scope, and just before exit.
4690 You may see this problem when you are stepping by machine instructions.
4691 This is because, on most machines, it takes more than one instruction to
4692 set up a stack frame (including local variable definitions); if you are
4693 stepping by machine instructions, variables may appear to have the wrong
4694 values until the stack frame is completely built. On exit, it usually
4695 also takes more than one machine instruction to destroy a stack frame;
4696 after you begin stepping through that group of instructions, local
4697 variable definitions may be gone.
4699 This may also happen when the compiler does significant optimizations.
4700 To be sure of always seeing accurate values, turn off all optimization
4703 @cindex ``No symbol "foo" in current context''
4704 Another possible effect of compiler optimizations is to optimize
4705 unused variables out of existence, or assign variables to registers (as
4706 opposed to memory addresses). Depending on the support for such cases
4707 offered by the debug info format used by the compiler, @value{GDBN}
4708 might not be able to display values for such local variables. If that
4709 happens, @value{GDBN} will print a message like this:
4712 No symbol "foo" in current context.
4715 To solve such problems, either recompile without optimizations, or use a
4716 different debug info format, if the compiler supports several such
4717 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler
4718 usually supports the @option{-gstabs+} option. @option{-gstabs+}
4719 produces debug info in a format that is superior to formats such as
4720 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
4721 an effective form for debug info. @xref{Debugging Options,,Options
4722 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
4726 @section Artificial arrays
4728 @cindex artificial array
4729 @kindex @@@r{, referencing memory as an array}
4730 It is often useful to print out several successive objects of the
4731 same type in memory; a section of an array, or an array of
4732 dynamically determined size for which only a pointer exists in the
4735 You can do this by referring to a contiguous span of memory as an
4736 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4737 operand of @samp{@@} should be the first element of the desired array
4738 and be an individual object. The right operand should be the desired length
4739 of the array. The result is an array value whose elements are all of
4740 the type of the left argument. The first element is actually the left
4741 argument; the second element comes from bytes of memory immediately
4742 following those that hold the first element, and so on. Here is an
4743 example. If a program says
4746 int *array = (int *) malloc (len * sizeof (int));
4750 you can print the contents of @code{array} with
4756 The left operand of @samp{@@} must reside in memory. Array values made
4757 with @samp{@@} in this way behave just like other arrays in terms of
4758 subscripting, and are coerced to pointers when used in expressions.
4759 Artificial arrays most often appear in expressions via the value history
4760 (@pxref{Value History, ,Value history}), after printing one out.
4762 Another way to create an artificial array is to use a cast.
4763 This re-interprets a value as if it were an array.
4764 The value need not be in memory:
4766 (@value{GDBP}) p/x (short[2])0x12345678
4767 $1 = @{0x1234, 0x5678@}
4770 As a convenience, if you leave the array length out (as in
4771 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
4772 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
4774 (@value{GDBP}) p/x (short[])0x12345678
4775 $2 = @{0x1234, 0x5678@}
4778 Sometimes the artificial array mechanism is not quite enough; in
4779 moderately complex data structures, the elements of interest may not
4780 actually be adjacent---for example, if you are interested in the values
4781 of pointers in an array. One useful work-around in this situation is
4782 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
4783 variables}) as a counter in an expression that prints the first
4784 interesting value, and then repeat that expression via @key{RET}. For
4785 instance, suppose you have an array @code{dtab} of pointers to
4786 structures, and you are interested in the values of a field @code{fv}
4787 in each structure. Here is an example of what you might type:
4797 @node Output Formats
4798 @section Output formats
4800 @cindex formatted output
4801 @cindex output formats
4802 By default, @value{GDBN} prints a value according to its data type. Sometimes
4803 this is not what you want. For example, you might want to print a number
4804 in hex, or a pointer in decimal. Or you might want to view data in memory
4805 at a certain address as a character string or as an instruction. To do
4806 these things, specify an @dfn{output format} when you print a value.
4808 The simplest use of output formats is to say how to print a value
4809 already computed. This is done by starting the arguments of the
4810 @code{print} command with a slash and a format letter. The format
4811 letters supported are:
4815 Regard the bits of the value as an integer, and print the integer in
4819 Print as integer in signed decimal.
4822 Print as integer in unsigned decimal.
4825 Print as integer in octal.
4828 Print as integer in binary. The letter @samp{t} stands for ``two''.
4829 @footnote{@samp{b} cannot be used because these format letters are also
4830 used with the @code{x} command, where @samp{b} stands for ``byte'';
4831 see @ref{Memory,,Examining memory}.}
4834 @cindex unknown address, locating
4835 @cindex locate address
4836 Print as an address, both absolute in hexadecimal and as an offset from
4837 the nearest preceding symbol. You can use this format used to discover
4838 where (in what function) an unknown address is located:
4841 (@value{GDBP}) p/a 0x54320
4842 $3 = 0x54320 <_initialize_vx+396>
4846 The command @code{info symbol 0x54320} yields similar results.
4847 @xref{Symbols, info symbol}.
4850 Regard as an integer and print it as a character constant.
4853 Regard the bits of the value as a floating point number and print
4854 using typical floating point syntax.
4857 For example, to print the program counter in hex (@pxref{Registers}), type
4864 Note that no space is required before the slash; this is because command
4865 names in @value{GDBN} cannot contain a slash.
4867 To reprint the last value in the value history with a different format,
4868 you can use the @code{print} command with just a format and no
4869 expression. For example, @samp{p/x} reprints the last value in hex.
4872 @section Examining memory
4874 You can use the command @code{x} (for ``examine'') to examine memory in
4875 any of several formats, independently of your program's data types.
4877 @cindex examining memory
4879 @kindex x @r{(examine memory)}
4880 @item x/@var{nfu} @var{addr}
4883 Use the @code{x} command to examine memory.
4886 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
4887 much memory to display and how to format it; @var{addr} is an
4888 expression giving the address where you want to start displaying memory.
4889 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
4890 Several commands set convenient defaults for @var{addr}.
4893 @item @var{n}, the repeat count
4894 The repeat count is a decimal integer; the default is 1. It specifies
4895 how much memory (counting by units @var{u}) to display.
4896 @c This really is **decimal**; unaffected by 'set radix' as of GDB
4899 @item @var{f}, the display format
4900 The display format is one of the formats used by @code{print},
4901 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
4902 The default is @samp{x} (hexadecimal) initially.
4903 The default changes each time you use either @code{x} or @code{print}.
4905 @item @var{u}, the unit size
4906 The unit size is any of
4912 Halfwords (two bytes).
4914 Words (four bytes). This is the initial default.
4916 Giant words (eight bytes).
4919 Each time you specify a unit size with @code{x}, that size becomes the
4920 default unit the next time you use @code{x}. (For the @samp{s} and
4921 @samp{i} formats, the unit size is ignored and is normally not written.)
4923 @item @var{addr}, starting display address
4924 @var{addr} is the address where you want @value{GDBN} to begin displaying
4925 memory. The expression need not have a pointer value (though it may);
4926 it is always interpreted as an integer address of a byte of memory.
4927 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
4928 @var{addr} is usually just after the last address examined---but several
4929 other commands also set the default address: @code{info breakpoints} (to
4930 the address of the last breakpoint listed), @code{info line} (to the
4931 starting address of a line), and @code{print} (if you use it to display
4932 a value from memory).
4935 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
4936 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
4937 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
4938 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
4939 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
4941 Since the letters indicating unit sizes are all distinct from the
4942 letters specifying output formats, you do not have to remember whether
4943 unit size or format comes first; either order works. The output
4944 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
4945 (However, the count @var{n} must come first; @samp{wx4} does not work.)
4947 Even though the unit size @var{u} is ignored for the formats @samp{s}
4948 and @samp{i}, you might still want to use a count @var{n}; for example,
4949 @samp{3i} specifies that you want to see three machine instructions,
4950 including any operands. The command @code{disassemble} gives an
4951 alternative way of inspecting machine instructions; see @ref{Machine
4952 Code,,Source and machine code}.
4954 All the defaults for the arguments to @code{x} are designed to make it
4955 easy to continue scanning memory with minimal specifications each time
4956 you use @code{x}. For example, after you have inspected three machine
4957 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
4958 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
4959 the repeat count @var{n} is used again; the other arguments default as
4960 for successive uses of @code{x}.
4962 @cindex @code{$_}, @code{$__}, and value history
4963 The addresses and contents printed by the @code{x} command are not saved
4964 in the value history because there is often too much of them and they
4965 would get in the way. Instead, @value{GDBN} makes these values available for
4966 subsequent use in expressions as values of the convenience variables
4967 @code{$_} and @code{$__}. After an @code{x} command, the last address
4968 examined is available for use in expressions in the convenience variable
4969 @code{$_}. The contents of that address, as examined, are available in
4970 the convenience variable @code{$__}.
4972 If the @code{x} command has a repeat count, the address and contents saved
4973 are from the last memory unit printed; this is not the same as the last
4974 address printed if several units were printed on the last line of output.
4977 @section Automatic display
4978 @cindex automatic display
4979 @cindex display of expressions
4981 If you find that you want to print the value of an expression frequently
4982 (to see how it changes), you might want to add it to the @dfn{automatic
4983 display list} so that @value{GDBN} prints its value each time your program stops.
4984 Each expression added to the list is given a number to identify it;
4985 to remove an expression from the list, you specify that number.
4986 The automatic display looks like this:
4990 3: bar[5] = (struct hack *) 0x3804
4994 This display shows item numbers, expressions and their current values. As with
4995 displays you request manually using @code{x} or @code{print}, you can
4996 specify the output format you prefer; in fact, @code{display} decides
4997 whether to use @code{print} or @code{x} depending on how elaborate your
4998 format specification is---it uses @code{x} if you specify a unit size,
4999 or one of the two formats (@samp{i} and @samp{s}) that are only
5000 supported by @code{x}; otherwise it uses @code{print}.
5004 @item display @var{expr}
5005 Add the expression @var{expr} to the list of expressions to display
5006 each time your program stops. @xref{Expressions, ,Expressions}.
5008 @code{display} does not repeat if you press @key{RET} again after using it.
5010 @item display/@var{fmt} @var{expr}
5011 For @var{fmt} specifying only a display format and not a size or
5012 count, add the expression @var{expr} to the auto-display list but
5013 arrange to display it each time in the specified format @var{fmt}.
5014 @xref{Output Formats,,Output formats}.
5016 @item display/@var{fmt} @var{addr}
5017 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5018 number of units, add the expression @var{addr} as a memory address to
5019 be examined each time your program stops. Examining means in effect
5020 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5023 For example, @samp{display/i $pc} can be helpful, to see the machine
5024 instruction about to be executed each time execution stops (@samp{$pc}
5025 is a common name for the program counter; @pxref{Registers, ,Registers}).
5028 @kindex delete display
5030 @item undisplay @var{dnums}@dots{}
5031 @itemx delete display @var{dnums}@dots{}
5032 Remove item numbers @var{dnums} from the list of expressions to display.
5034 @code{undisplay} does not repeat if you press @key{RET} after using it.
5035 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5037 @kindex disable display
5038 @item disable display @var{dnums}@dots{}
5039 Disable the display of item numbers @var{dnums}. A disabled display
5040 item is not printed automatically, but is not forgotten. It may be
5041 enabled again later.
5043 @kindex enable display
5044 @item enable display @var{dnums}@dots{}
5045 Enable display of item numbers @var{dnums}. It becomes effective once
5046 again in auto display of its expression, until you specify otherwise.
5049 Display the current values of the expressions on the list, just as is
5050 done when your program stops.
5052 @kindex info display
5054 Print the list of expressions previously set up to display
5055 automatically, each one with its item number, but without showing the
5056 values. This includes disabled expressions, which are marked as such.
5057 It also includes expressions which would not be displayed right now
5058 because they refer to automatic variables not currently available.
5061 If a display expression refers to local variables, then it does not make
5062 sense outside the lexical context for which it was set up. Such an
5063 expression is disabled when execution enters a context where one of its
5064 variables is not defined. For example, if you give the command
5065 @code{display last_char} while inside a function with an argument
5066 @code{last_char}, @value{GDBN} displays this argument while your program
5067 continues to stop inside that function. When it stops elsewhere---where
5068 there is no variable @code{last_char}---the display is disabled
5069 automatically. The next time your program stops where @code{last_char}
5070 is meaningful, you can enable the display expression once again.
5072 @node Print Settings
5073 @section Print settings
5075 @cindex format options
5076 @cindex print settings
5077 @value{GDBN} provides the following ways to control how arrays, structures,
5078 and symbols are printed.
5081 These settings are useful for debugging programs in any language:
5084 @kindex set print address
5085 @item set print address
5086 @itemx set print address on
5087 @value{GDBN} prints memory addresses showing the location of stack
5088 traces, structure values, pointer values, breakpoints, and so forth,
5089 even when it also displays the contents of those addresses. The default
5090 is @code{on}. For example, this is what a stack frame display looks like with
5091 @code{set print address on}:
5096 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5098 530 if (lquote != def_lquote)
5102 @item set print address off
5103 Do not print addresses when displaying their contents. For example,
5104 this is the same stack frame displayed with @code{set print address off}:
5108 (@value{GDBP}) set print addr off
5110 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5111 530 if (lquote != def_lquote)
5115 You can use @samp{set print address off} to eliminate all machine
5116 dependent displays from the @value{GDBN} interface. For example, with
5117 @code{print address off}, you should get the same text for backtraces on
5118 all machines---whether or not they involve pointer arguments.
5120 @kindex show print address
5121 @item show print address
5122 Show whether or not addresses are to be printed.
5125 When @value{GDBN} prints a symbolic address, it normally prints the
5126 closest earlier symbol plus an offset. If that symbol does not uniquely
5127 identify the address (for example, it is a name whose scope is a single
5128 source file), you may need to clarify. One way to do this is with
5129 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5130 you can set @value{GDBN} to print the source file and line number when
5131 it prints a symbolic address:
5134 @kindex set print symbol-filename
5135 @item set print symbol-filename on
5136 Tell @value{GDBN} to print the source file name and line number of a
5137 symbol in the symbolic form of an address.
5139 @item set print symbol-filename off
5140 Do not print source file name and line number of a symbol. This is the
5143 @kindex show print symbol-filename
5144 @item show print symbol-filename
5145 Show whether or not @value{GDBN} will print the source file name and
5146 line number of a symbol in the symbolic form of an address.
5149 Another situation where it is helpful to show symbol filenames and line
5150 numbers is when disassembling code; @value{GDBN} shows you the line
5151 number and source file that corresponds to each instruction.
5153 Also, you may wish to see the symbolic form only if the address being
5154 printed is reasonably close to the closest earlier symbol:
5157 @kindex set print max-symbolic-offset
5158 @item set print max-symbolic-offset @var{max-offset}
5159 Tell @value{GDBN} to only display the symbolic form of an address if the
5160 offset between the closest earlier symbol and the address is less than
5161 @var{max-offset}. The default is 0, which tells @value{GDBN}
5162 to always print the symbolic form of an address if any symbol precedes it.
5164 @kindex show print max-symbolic-offset
5165 @item show print max-symbolic-offset
5166 Ask how large the maximum offset is that @value{GDBN} prints in a
5170 @cindex wild pointer, interpreting
5171 @cindex pointer, finding referent
5172 If you have a pointer and you are not sure where it points, try
5173 @samp{set print symbol-filename on}. Then you can determine the name
5174 and source file location of the variable where it points, using
5175 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5176 For example, here @value{GDBN} shows that a variable @code{ptt} points
5177 at another variable @code{t}, defined in @file{hi2.c}:
5180 (@value{GDBP}) set print symbol-filename on
5181 (@value{GDBP}) p/a ptt
5182 $4 = 0xe008 <t in hi2.c>
5186 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5187 does not show the symbol name and filename of the referent, even with
5188 the appropriate @code{set print} options turned on.
5191 Other settings control how different kinds of objects are printed:
5194 @kindex set print array
5195 @item set print array
5196 @itemx set print array on
5197 Pretty print arrays. This format is more convenient to read,
5198 but uses more space. The default is off.
5200 @item set print array off
5201 Return to compressed format for arrays.
5203 @kindex show print array
5204 @item show print array
5205 Show whether compressed or pretty format is selected for displaying
5208 @kindex set print elements
5209 @item set print elements @var{number-of-elements}
5210 Set a limit on how many elements of an array @value{GDBN} will print.
5211 If @value{GDBN} is printing a large array, it stops printing after it has
5212 printed the number of elements set by the @code{set print elements} command.
5213 This limit also applies to the display of strings.
5214 When @value{GDBN} starts, this limit is set to 200.
5215 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5217 @kindex show print elements
5218 @item show print elements
5219 Display the number of elements of a large array that @value{GDBN} will print.
5220 If the number is 0, then the printing is unlimited.
5222 @kindex set print null-stop
5223 @item set print null-stop
5224 Cause @value{GDBN} to stop printing the characters of an array when the first
5225 @sc{null} is encountered. This is useful when large arrays actually
5226 contain only short strings.
5229 @kindex set print pretty
5230 @item set print pretty on
5231 Cause @value{GDBN} to print structures in an indented format with one member
5232 per line, like this:
5247 @item set print pretty off
5248 Cause @value{GDBN} to print structures in a compact format, like this:
5252 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5253 meat = 0x54 "Pork"@}
5258 This is the default format.
5260 @kindex show print pretty
5261 @item show print pretty
5262 Show which format @value{GDBN} is using to print structures.
5264 @kindex set print sevenbit-strings
5265 @item set print sevenbit-strings on
5266 Print using only seven-bit characters; if this option is set,
5267 @value{GDBN} displays any eight-bit characters (in strings or
5268 character values) using the notation @code{\}@var{nnn}. This setting is
5269 best if you are working in English (@sc{ascii}) and you use the
5270 high-order bit of characters as a marker or ``meta'' bit.
5272 @item set print sevenbit-strings off
5273 Print full eight-bit characters. This allows the use of more
5274 international character sets, and is the default.
5276 @kindex show print sevenbit-strings
5277 @item show print sevenbit-strings
5278 Show whether or not @value{GDBN} is printing only seven-bit characters.
5280 @kindex set print union
5281 @item set print union on
5282 Tell @value{GDBN} to print unions which are contained in structures. This
5283 is the default setting.
5285 @item set print union off
5286 Tell @value{GDBN} not to print unions which are contained in structures.
5288 @kindex show print union
5289 @item show print union
5290 Ask @value{GDBN} whether or not it will print unions which are contained in
5293 For example, given the declarations
5296 typedef enum @{Tree, Bug@} Species;
5297 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5298 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5309 struct thing foo = @{Tree, @{Acorn@}@};
5313 with @code{set print union on} in effect @samp{p foo} would print
5316 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5320 and with @code{set print union off} in effect it would print
5323 $1 = @{it = Tree, form = @{...@}@}
5329 These settings are of interest when debugging C@t{++} programs:
5333 @kindex set print demangle
5334 @item set print demangle
5335 @itemx set print demangle on
5336 Print C@t{++} names in their source form rather than in the encoded
5337 (``mangled'') form passed to the assembler and linker for type-safe
5338 linkage. The default is on.
5340 @kindex show print demangle
5341 @item show print demangle
5342 Show whether C@t{++} names are printed in mangled or demangled form.
5344 @kindex set print asm-demangle
5345 @item set print asm-demangle
5346 @itemx set print asm-demangle on
5347 Print C@t{++} names in their source form rather than their mangled form, even
5348 in assembler code printouts such as instruction disassemblies.
5351 @kindex show print asm-demangle
5352 @item show print asm-demangle
5353 Show whether C@t{++} names in assembly listings are printed in mangled
5356 @kindex set demangle-style
5357 @cindex C@t{++} symbol decoding style
5358 @cindex symbol decoding style, C@t{++}
5359 @item set demangle-style @var{style}
5360 Choose among several encoding schemes used by different compilers to
5361 represent C@t{++} names. The choices for @var{style} are currently:
5365 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5368 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5369 This is the default.
5372 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5375 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5378 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5379 @strong{Warning:} this setting alone is not sufficient to allow
5380 debugging @code{cfront}-generated executables. @value{GDBN} would
5381 require further enhancement to permit that.
5384 If you omit @var{style}, you will see a list of possible formats.
5386 @kindex show demangle-style
5387 @item show demangle-style
5388 Display the encoding style currently in use for decoding C@t{++} symbols.
5390 @kindex set print object
5391 @item set print object
5392 @itemx set print object on
5393 When displaying a pointer to an object, identify the @emph{actual}
5394 (derived) type of the object rather than the @emph{declared} type, using
5395 the virtual function table.
5397 @item set print object off
5398 Display only the declared type of objects, without reference to the
5399 virtual function table. This is the default setting.
5401 @kindex show print object
5402 @item show print object
5403 Show whether actual, or declared, object types are displayed.
5405 @kindex set print static-members
5406 @item set print static-members
5407 @itemx set print static-members on
5408 Print static members when displaying a C@t{++} object. The default is on.
5410 @item set print static-members off
5411 Do not print static members when displaying a C@t{++} object.
5413 @kindex show print static-members
5414 @item show print static-members
5415 Show whether C@t{++} static members are printed, or not.
5417 @c These don't work with HP ANSI C++ yet.
5418 @kindex set print vtbl
5419 @item set print vtbl
5420 @itemx set print vtbl on
5421 Pretty print C@t{++} virtual function tables. The default is off.
5422 (The @code{vtbl} commands do not work on programs compiled with the HP
5423 ANSI C@t{++} compiler (@code{aCC}).)
5425 @item set print vtbl off
5426 Do not pretty print C@t{++} virtual function tables.
5428 @kindex show print vtbl
5429 @item show print vtbl
5430 Show whether C@t{++} virtual function tables are pretty printed, or not.
5434 @section Value history
5436 @cindex value history
5437 Values printed by the @code{print} command are saved in the @value{GDBN}
5438 @dfn{value history}. This allows you to refer to them in other expressions.
5439 Values are kept until the symbol table is re-read or discarded
5440 (for example with the @code{file} or @code{symbol-file} commands).
5441 When the symbol table changes, the value history is discarded,
5442 since the values may contain pointers back to the types defined in the
5447 @cindex history number
5448 The values printed are given @dfn{history numbers} by which you can
5449 refer to them. These are successive integers starting with one.
5450 @code{print} shows you the history number assigned to a value by
5451 printing @samp{$@var{num} = } before the value; here @var{num} is the
5454 To refer to any previous value, use @samp{$} followed by the value's
5455 history number. The way @code{print} labels its output is designed to
5456 remind you of this. Just @code{$} refers to the most recent value in
5457 the history, and @code{$$} refers to the value before that.
5458 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5459 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5460 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5462 For example, suppose you have just printed a pointer to a structure and
5463 want to see the contents of the structure. It suffices to type
5469 If you have a chain of structures where the component @code{next} points
5470 to the next one, you can print the contents of the next one with this:
5477 You can print successive links in the chain by repeating this
5478 command---which you can do by just typing @key{RET}.
5480 Note that the history records values, not expressions. If the value of
5481 @code{x} is 4 and you type these commands:
5489 then the value recorded in the value history by the @code{print} command
5490 remains 4 even though the value of @code{x} has changed.
5495 Print the last ten values in the value history, with their item numbers.
5496 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5497 values} does not change the history.
5499 @item show values @var{n}
5500 Print ten history values centered on history item number @var{n}.
5503 Print ten history values just after the values last printed. If no more
5504 values are available, @code{show values +} produces no display.
5507 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5508 same effect as @samp{show values +}.
5510 @node Convenience Vars
5511 @section Convenience variables
5513 @cindex convenience variables
5514 @value{GDBN} provides @dfn{convenience variables} that you can use within
5515 @value{GDBN} to hold on to a value and refer to it later. These variables
5516 exist entirely within @value{GDBN}; they are not part of your program, and
5517 setting a convenience variable has no direct effect on further execution
5518 of your program. That is why you can use them freely.
5520 Convenience variables are prefixed with @samp{$}. Any name preceded by
5521 @samp{$} can be used for a convenience variable, unless it is one of
5522 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5523 (Value history references, in contrast, are @emph{numbers} preceded
5524 by @samp{$}. @xref{Value History, ,Value history}.)
5526 You can save a value in a convenience variable with an assignment
5527 expression, just as you would set a variable in your program.
5531 set $foo = *object_ptr
5535 would save in @code{$foo} the value contained in the object pointed to by
5538 Using a convenience variable for the first time creates it, but its
5539 value is @code{void} until you assign a new value. You can alter the
5540 value with another assignment at any time.
5542 Convenience variables have no fixed types. You can assign a convenience
5543 variable any type of value, including structures and arrays, even if
5544 that variable already has a value of a different type. The convenience
5545 variable, when used as an expression, has the type of its current value.
5548 @kindex show convenience
5549 @item show convenience
5550 Print a list of convenience variables used so far, and their values.
5551 Abbreviated @code{show conv}.
5554 One of the ways to use a convenience variable is as a counter to be
5555 incremented or a pointer to be advanced. For example, to print
5556 a field from successive elements of an array of structures:
5560 print bar[$i++]->contents
5564 Repeat that command by typing @key{RET}.
5566 Some convenience variables are created automatically by @value{GDBN} and given
5567 values likely to be useful.
5570 @vindex $_@r{, convenience variable}
5572 The variable @code{$_} is automatically set by the @code{x} command to
5573 the last address examined (@pxref{Memory, ,Examining memory}). Other
5574 commands which provide a default address for @code{x} to examine also
5575 set @code{$_} to that address; these commands include @code{info line}
5576 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5577 except when set by the @code{x} command, in which case it is a pointer
5578 to the type of @code{$__}.
5580 @vindex $__@r{, convenience variable}
5582 The variable @code{$__} is automatically set by the @code{x} command
5583 to the value found in the last address examined. Its type is chosen
5584 to match the format in which the data was printed.
5587 @vindex $_exitcode@r{, convenience variable}
5588 The variable @code{$_exitcode} is automatically set to the exit code when
5589 the program being debugged terminates.
5592 On HP-UX systems, if you refer to a function or variable name that
5593 begins with a dollar sign, @value{GDBN} searches for a user or system
5594 name first, before it searches for a convenience variable.
5600 You can refer to machine register contents, in expressions, as variables
5601 with names starting with @samp{$}. The names of registers are different
5602 for each machine; use @code{info registers} to see the names used on
5606 @kindex info registers
5607 @item info registers
5608 Print the names and values of all registers except floating-point
5609 and vector registers (in the selected stack frame).
5611 @kindex info all-registers
5612 @cindex floating point registers
5613 @item info all-registers
5614 Print the names and values of all registers, including floating-point
5615 and vector registers (in the selected stack frame).
5617 @item info registers @var{regname} @dots{}
5618 Print the @dfn{relativized} value of each specified register @var{regname}.
5619 As discussed in detail below, register values are normally relative to
5620 the selected stack frame. @var{regname} may be any register name valid on
5621 the machine you are using, with or without the initial @samp{$}.
5624 @value{GDBN} has four ``standard'' register names that are available (in
5625 expressions) on most machines---whenever they do not conflict with an
5626 architecture's canonical mnemonics for registers. The register names
5627 @code{$pc} and @code{$sp} are used for the program counter register and
5628 the stack pointer. @code{$fp} is used for a register that contains a
5629 pointer to the current stack frame, and @code{$ps} is used for a
5630 register that contains the processor status. For example,
5631 you could print the program counter in hex with
5638 or print the instruction to be executed next with
5645 or add four to the stack pointer@footnote{This is a way of removing
5646 one word from the stack, on machines where stacks grow downward in
5647 memory (most machines, nowadays). This assumes that the innermost
5648 stack frame is selected; setting @code{$sp} is not allowed when other
5649 stack frames are selected. To pop entire frames off the stack,
5650 regardless of machine architecture, use @code{return};
5651 see @ref{Returning, ,Returning from a function}.} with
5657 Whenever possible, these four standard register names are available on
5658 your machine even though the machine has different canonical mnemonics,
5659 so long as there is no conflict. The @code{info registers} command
5660 shows the canonical names. For example, on the SPARC, @code{info
5661 registers} displays the processor status register as @code{$psr} but you
5662 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5663 is an alias for the @sc{eflags} register.
5665 @value{GDBN} always considers the contents of an ordinary register as an
5666 integer when the register is examined in this way. Some machines have
5667 special registers which can hold nothing but floating point; these
5668 registers are considered to have floating point values. There is no way
5669 to refer to the contents of an ordinary register as floating point value
5670 (although you can @emph{print} it as a floating point value with
5671 @samp{print/f $@var{regname}}).
5673 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5674 means that the data format in which the register contents are saved by
5675 the operating system is not the same one that your program normally
5676 sees. For example, the registers of the 68881 floating point
5677 coprocessor are always saved in ``extended'' (raw) format, but all C
5678 programs expect to work with ``double'' (virtual) format. In such
5679 cases, @value{GDBN} normally works with the virtual format only (the format
5680 that makes sense for your program), but the @code{info registers} command
5681 prints the data in both formats.
5683 Normally, register values are relative to the selected stack frame
5684 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5685 value that the register would contain if all stack frames farther in
5686 were exited and their saved registers restored. In order to see the
5687 true contents of hardware registers, you must select the innermost
5688 frame (with @samp{frame 0}).
5690 However, @value{GDBN} must deduce where registers are saved, from the machine
5691 code generated by your compiler. If some registers are not saved, or if
5692 @value{GDBN} is unable to locate the saved registers, the selected stack
5693 frame makes no difference.
5695 @node Floating Point Hardware
5696 @section Floating point hardware
5697 @cindex floating point
5699 Depending on the configuration, @value{GDBN} may be able to give
5700 you more information about the status of the floating point hardware.
5705 Display hardware-dependent information about the floating
5706 point unit. The exact contents and layout vary depending on the
5707 floating point chip. Currently, @samp{info float} is supported on
5708 the ARM and x86 machines.
5712 @section Vector Unit
5715 Depending on the configuration, @value{GDBN} may be able to give you
5716 more information about the status of the vector unit.
5721 Display information about the vector unit. The exact contents and
5722 layout vary depending on the hardware.
5725 @node Memory Region Attributes
5726 @section Memory region attributes
5727 @cindex memory region attributes
5729 @dfn{Memory region attributes} allow you to describe special handling
5730 required by regions of your target's memory. @value{GDBN} uses attributes
5731 to determine whether to allow certain types of memory accesses; whether to
5732 use specific width accesses; and whether to cache target memory.
5734 Defined memory regions can be individually enabled and disabled. When a
5735 memory region is disabled, @value{GDBN} uses the default attributes when
5736 accessing memory in that region. Similarly, if no memory regions have
5737 been defined, @value{GDBN} uses the default attributes when accessing
5740 When a memory region is defined, it is given a number to identify it;
5741 to enable, disable, or remove a memory region, you specify that number.
5745 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
5746 Define memory region bounded by @var{lower} and @var{upper} with
5747 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
5748 special case: it is treated as the the target's maximum memory address.
5749 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
5752 @item delete mem @var{nums}@dots{}
5753 Remove memory regions @var{nums}@dots{}.
5756 @item disable mem @var{nums}@dots{}
5757 Disable memory regions @var{nums}@dots{}.
5758 A disabled memory region is not forgotten.
5759 It may be enabled again later.
5762 @item enable mem @var{nums}@dots{}
5763 Enable memory regions @var{nums}@dots{}.
5767 Print a table of all defined memory regions, with the following columns
5771 @item Memory Region Number
5772 @item Enabled or Disabled.
5773 Enabled memory regions are marked with @samp{y}.
5774 Disabled memory regions are marked with @samp{n}.
5777 The address defining the inclusive lower bound of the memory region.
5780 The address defining the exclusive upper bound of the memory region.
5783 The list of attributes set for this memory region.
5788 @subsection Attributes
5790 @subsubsection Memory Access Mode
5791 The access mode attributes set whether @value{GDBN} may make read or
5792 write accesses to a memory region.
5794 While these attributes prevent @value{GDBN} from performing invalid
5795 memory accesses, they do nothing to prevent the target system, I/O DMA,
5796 etc. from accessing memory.
5800 Memory is read only.
5802 Memory is write only.
5804 Memory is read/write. This is the default.
5807 @subsubsection Memory Access Size
5808 The acccess size attributes tells @value{GDBN} to use specific sized
5809 accesses in the memory region. Often memory mapped device registers
5810 require specific sized accesses. If no access size attribute is
5811 specified, @value{GDBN} may use accesses of any size.
5815 Use 8 bit memory accesses.
5817 Use 16 bit memory accesses.
5819 Use 32 bit memory accesses.
5821 Use 64 bit memory accesses.
5824 @c @subsubsection Hardware/Software Breakpoints
5825 @c The hardware/software breakpoint attributes set whether @value{GDBN}
5826 @c will use hardware or software breakpoints for the internal breakpoints
5827 @c used by the step, next, finish, until, etc. commands.
5831 @c Always use hardware breakpoints
5832 @c @item swbreak (default)
5835 @subsubsection Data Cache
5836 The data cache attributes set whether @value{GDBN} will cache target
5837 memory. While this generally improves performance by reducing debug
5838 protocol overhead, it can lead to incorrect results because @value{GDBN}
5839 does not know about volatile variables or memory mapped device
5844 Enable @value{GDBN} to cache target memory.
5846 Disable @value{GDBN} from caching target memory. This is the default.
5849 @c @subsubsection Memory Write Verification
5850 @c The memory write verification attributes set whether @value{GDBN}
5851 @c will re-reads data after each write to verify the write was successful.
5855 @c @item noverify (default)
5858 @node Dump/Restore Files
5859 @section Copy between memory and a file
5860 @cindex dump/restore files
5861 @cindex append data to a file
5862 @cindex dump data to a file
5863 @cindex restore data from a file
5868 The commands @code{dump}, @code{append}, and @code{restore} are used
5869 for copying data between target memory and a file. Data is written
5870 into a file using @code{dump} or @code{append}, and restored from a
5871 file into memory by using @code{restore}. Files may be binary, srec,
5872 intel hex, or tekhex (but only binary files can be appended).
5876 @kindex append binary
5877 @item dump binary memory @var{filename} @var{start_addr} @var{end_addr}
5878 Dump contents of memory from @var{start_addr} to @var{end_addr} into
5879 raw binary format file @var{filename}.
5881 @item append binary memory @var{filename} @var{start_addr} @var{end_addr}
5882 Append contents of memory from @var{start_addr} to @var{end_addr} to
5883 raw binary format file @var{filename}.
5885 @item dump binary value @var{filename} @var{expression}
5886 Dump value of @var{expression} into raw binary format file @var{filename}.
5888 @item append binary memory @var{filename} @var{expression}
5889 Append value of @var{expression} to raw binary format file @var{filename}.
5892 @item dump ihex memory @var{filename} @var{start_addr} @var{end_addr}
5893 Dump contents of memory from @var{start_addr} to @var{end_addr} into
5894 intel hex format file @var{filename}.
5896 @item dump ihex value @var{filename} @var{expression}
5897 Dump value of @var{expression} into intel hex format file @var{filename}.
5900 @item dump srec memory @var{filename} @var{start_addr} @var{end_addr}
5901 Dump contents of memory from @var{start_addr} to @var{end_addr} into
5902 srec format file @var{filename}.
5904 @item dump srec value @var{filename} @var{expression}
5905 Dump value of @var{expression} into srec format file @var{filename}.
5908 @item dump tekhex memory @var{filename} @var{start_addr} @var{end_addr}
5909 Dump contents of memory from @var{start_addr} to @var{end_addr} into
5910 tekhex format file @var{filename}.
5912 @item dump tekhex value @var{filename} @var{expression}
5913 Dump value of @var{expression} into tekhex format file @var{filename}.
5915 @item restore @var{filename} [@var{binary}] @var{bias} @var{start} @var{end}
5916 Restore the contents of file @var{filename} into memory. The @code{restore}
5917 command can automatically recognize any known bfd file format, except for
5918 raw binary. To restore a raw binary file you must use the optional argument
5919 @var{binary} after the filename.
5921 If @var{bias} is non-zero, its value will be added to the addresses
5922 contained in the file. Binary files always start at address zero, so
5923 they will be restored at address @var{bias}. Other bfd files have
5924 a built-in location; they will be restored at offset @var{bias}
5927 If @var{start} and/or @var{end} are non-zero, then only data between
5928 file offset @var{start} and file offset @var{end} will be restored.
5929 These offsets are relative to the addresses in the file, before
5930 the @var{bias} argument is applied.
5934 @node Character Sets
5935 @section Character Sets
5936 @cindex character sets
5938 @cindex translating between character sets
5939 @cindex host character set
5940 @cindex target character set
5942 If the program you are debugging uses a different character set to
5943 represent characters and strings than the one @value{GDBN} uses itself,
5944 @value{GDBN} can automatically translate between the character sets for
5945 you. The character set @value{GDBN} uses we call the @dfn{host
5946 character set}; the one the inferior program uses we call the
5947 @dfn{target character set}.
5949 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
5950 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
5951 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
5952 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
5953 then the host character set is Latin-1, and the target character set is
5954 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
5955 target-charset EBCDIC-US}, then @value{GDBN} translates between
5956 @sc{ebcdic} and Latin 1 as you print character or string values, or use
5957 character and string literals in expressions.
5959 @value{GDBN} has no way to automatically recognize which character set
5960 the inferior program uses; you must tell it, using the @code{set
5961 target-charset} command, described below.
5963 Here are the commands for controlling @value{GDBN}'s character set
5967 @item set target-charset @var{charset}
5968 @kindex set target-charset
5969 Set the current target character set to @var{charset}. We list the
5970 character set names @value{GDBN} recognizes below, but if you type
5971 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
5972 list the target character sets it supports.
5976 @item set host-charset @var{charset}
5977 @kindex set host-charset
5978 Set the current host character set to @var{charset}.
5980 By default, @value{GDBN} uses a host character set appropriate to the
5981 system it is running on; you can override that default using the
5982 @code{set host-charset} command.
5984 @value{GDBN} can only use certain character sets as its host character
5985 set. We list the character set names @value{GDBN} recognizes below, and
5986 indicate which can be host character sets, but if you type
5987 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
5988 list the host character sets it supports.
5990 @item set charset @var{charset}
5992 Set the current host and target character sets to @var{charset}. As
5993 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
5994 @value{GDBN} will list the name of the character sets that can be used
5995 for both host and target.
5999 @kindex show charset
6000 Show the names of the current host and target charsets.
6002 @itemx show host-charset
6003 @kindex show host-charset
6004 Show the name of the current host charset.
6006 @itemx show target-charset
6007 @kindex show target-charset
6008 Show the name of the current target charset.
6012 @value{GDBN} currently includes support for the following character
6018 @cindex ASCII character set
6019 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6023 @cindex ISO 8859-1 character set
6024 @cindex ISO Latin 1 character set
6025 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6026 characters needed for French, German, and Spanish. @value{GDBN} can use
6027 this as its host character set.
6031 @cindex EBCDIC character set
6032 @cindex IBM1047 character set
6033 Variants of the @sc{ebcdic} character set, used on some of IBM's
6034 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6035 @value{GDBN} cannot use these as its host character set.
6039 Note that these are all single-byte character sets. More work inside
6040 GDB is needed to support multi-byte or variable-width character
6041 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6043 Here is an example of @value{GDBN}'s character set support in action.
6044 Assume that the following source code has been placed in the file
6045 @file{charset-test.c}:
6051 = @{72, 101, 108, 108, 111, 44, 32, 119,
6052 111, 114, 108, 100, 33, 10, 0@};
6053 char ibm1047_hello[]
6054 = @{200, 133, 147, 147, 150, 107, 64, 166,
6055 150, 153, 147, 132, 90, 37, 0@};
6059 printf ("Hello, world!\n");
6063 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6064 containing the string @samp{Hello, world!} followed by a newline,
6065 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6067 We compile the program, and invoke the debugger on it:
6070 $ gcc -g charset-test.c -o charset-test
6071 $ gdb -nw charset-test
6072 GNU gdb 2001-12-19-cvs
6073 Copyright 2001 Free Software Foundation, Inc.
6078 We can use the @code{show charset} command to see what character sets
6079 @value{GDBN} is currently using to interpret and display characters and
6084 The current host and target character set is `ISO-8859-1'.
6088 For the sake of printing this manual, let's use @sc{ascii} as our
6089 initial character set:
6091 (gdb) set charset ASCII
6093 The current host and target character set is `ASCII'.
6097 Let's assume that @sc{ascii} is indeed the correct character set for our
6098 host system --- in other words, let's assume that if @value{GDBN} prints
6099 characters using the @sc{ascii} character set, our terminal will display
6100 them properly. Since our current target character set is also
6101 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6104 (gdb) print ascii_hello
6105 $1 = 0x401698 "Hello, world!\n"
6106 (gdb) print ascii_hello[0]
6111 @value{GDBN} uses the target character set for character and string
6112 literals you use in expressions:
6120 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6123 @value{GDBN} relies on the user to tell it which character set the
6124 target program uses. If we print @code{ibm1047_hello} while our target
6125 character set is still @sc{ascii}, we get jibberish:
6128 (gdb) print ibm1047_hello
6129 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6130 (gdb) print ibm1047_hello[0]
6135 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6136 @value{GDBN} tells us the character sets it supports:
6139 (gdb) set target-charset
6140 ASCII EBCDIC-US IBM1047 ISO-8859-1
6141 (gdb) set target-charset
6144 We can select @sc{ibm1047} as our target character set, and examine the
6145 program's strings again. Now the @sc{ascii} string is wrong, but
6146 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6147 target character set, @sc{ibm1047}, to the host character set,
6148 @sc{ascii}, and they display correctly:
6151 (gdb) set target-charset IBM1047
6153 The current host character set is `ASCII'.
6154 The current target character set is `IBM1047'.
6155 (gdb) print ascii_hello
6156 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6157 (gdb) print ascii_hello[0]
6159 (gdb) print ibm1047_hello
6160 $8 = 0x4016a8 "Hello, world!\n"
6161 (gdb) print ibm1047_hello[0]
6166 As above, @value{GDBN} uses the target character set for character and
6167 string literals you use in expressions:
6175 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6180 @chapter C Preprocessor Macros
6182 Some languages, such as C and C++, provide a way to define and invoke
6183 ``preprocessor macros'' which expand into strings of tokens.
6184 @value{GDBN} can evaluate expressions containing macro invocations, show
6185 the result of macro expansion, and show a macro's definition, including
6186 where it was defined.
6188 You may need to compile your program specially to provide @value{GDBN}
6189 with information about preprocessor macros. Most compilers do not
6190 include macros in their debugging information, even when you compile
6191 with the @option{-g} flag. @xref{Compilation}.
6193 A program may define a macro at one point, remove that definition later,
6194 and then provide a different definition after that. Thus, at different
6195 points in the program, a macro may have different definitions, or have
6196 no definition at all. If there is a current stack frame, @value{GDBN}
6197 uses the macros in scope at that frame's source code line. Otherwise,
6198 @value{GDBN} uses the macros in scope at the current listing location;
6201 At the moment, @value{GDBN} does not support the @code{##}
6202 token-splicing operator, the @code{#} stringification operator, or
6203 variable-arity macros.
6205 Whenever @value{GDBN} evaluates an expression, it always expands any
6206 macro invocations present in the expression. @value{GDBN} also provides
6207 the following commands for working with macros explicitly.
6211 @kindex macro expand
6212 @cindex macro expansion, showing the results of preprocessor
6213 @cindex preprocessor macro expansion, showing the results of
6214 @cindex expanding preprocessor macros
6215 @item macro expand @var{expression}
6216 @itemx macro exp @var{expression}
6217 Show the results of expanding all preprocessor macro invocations in
6218 @var{expression}. Since @value{GDBN} simply expands macros, but does
6219 not parse the result, @var{expression} need not be a valid expression;
6220 it can be any string of tokens.
6222 @kindex macro expand-once
6223 @item macro expand-once @var{expression}
6224 @itemx macro exp1 @var{expression}
6225 @i{(This command is not yet implemented.)} Show the results of
6226 expanding those preprocessor macro invocations that appear explicitly in
6227 @var{expression}. Macro invocations appearing in that expansion are
6228 left unchanged. This command allows you to see the effect of a
6229 particular macro more clearly, without being confused by further
6230 expansions. Since @value{GDBN} simply expands macros, but does not
6231 parse the result, @var{expression} need not be a valid expression; it
6232 can be any string of tokens.
6235 @cindex macro definition, showing
6236 @cindex definition, showing a macro's
6237 @item info macro @var{macro}
6238 Show the definition of the macro named @var{macro}, and describe the
6239 source location where that definition was established.
6241 @kindex macro define
6242 @cindex user-defined macros
6243 @cindex defining macros interactively
6244 @cindex macros, user-defined
6245 @item macro define @var{macro} @var{replacement-list}
6246 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6247 @i{(This command is not yet implemented.)} Introduce a definition for a
6248 preprocessor macro named @var{macro}, invocations of which are replaced
6249 by the tokens given in @var{replacement-list}. The first form of this
6250 command defines an ``object-like'' macro, which takes no arguments; the
6251 second form defines a ``function-like'' macro, which takes the arguments
6252 given in @var{arglist}.
6254 A definition introduced by this command is in scope in every expression
6255 evaluated in @value{GDBN}, until it is removed with the @command{macro
6256 undef} command, described below. The definition overrides all
6257 definitions for @var{macro} present in the program being debugged, as
6258 well as any previous user-supplied definition.
6261 @item macro undef @var{macro}
6262 @i{(This command is not yet implemented.)} Remove any user-supplied
6263 definition for the macro named @var{macro}. This command only affects
6264 definitions provided with the @command{macro define} command, described
6265 above; it cannot remove definitions present in the program being
6270 @cindex macros, example of debugging with
6271 Here is a transcript showing the above commands in action. First, we
6272 show our source files:
6280 #define ADD(x) (M + x)
6285 printf ("Hello, world!\n");
6287 printf ("We're so creative.\n");
6289 printf ("Goodbye, world!\n");
6296 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6297 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6298 compiler includes information about preprocessor macros in the debugging
6302 $ gcc -gdwarf-2 -g3 sample.c -o sample
6306 Now, we start @value{GDBN} on our sample program:
6310 GNU gdb 2002-05-06-cvs
6311 Copyright 2002 Free Software Foundation, Inc.
6312 GDB is free software, @dots{}
6316 We can expand macros and examine their definitions, even when the
6317 program is not running. @value{GDBN} uses the current listing position
6318 to decide which macro definitions are in scope:
6324 5 #define ADD(x) (M + x)
6329 10 printf ("Hello, world!\n");
6331 12 printf ("We're so creative.\n");
6332 (gdb) info macro ADD
6333 Defined at /home/jimb/gdb/macros/play/sample.c:5
6334 #define ADD(x) (M + x)
6336 Defined at /home/jimb/gdb/macros/play/sample.h:1
6337 included at /home/jimb/gdb/macros/play/sample.c:2
6339 (gdb) macro expand ADD(1)
6340 expands to: (42 + 1)
6341 (gdb) macro expand-once ADD(1)
6342 expands to: once (M + 1)
6346 In the example above, note that @command{macro expand-once} expands only
6347 the macro invocation explicit in the original text --- the invocation of
6348 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6349 which was introduced by @code{ADD}.
6351 Once the program is running, GDB uses the macro definitions in force at
6352 the source line of the current stack frame:
6356 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6358 Starting program: /home/jimb/gdb/macros/play/sample
6360 Breakpoint 1, main () at sample.c:10
6361 10 printf ("Hello, world!\n");
6365 At line 10, the definition of the macro @code{N} at line 9 is in force:
6369 Defined at /home/jimb/gdb/macros/play/sample.c:9
6371 (gdb) macro expand N Q M
6378 As we step over directives that remove @code{N}'s definition, and then
6379 give it a new definition, @value{GDBN} finds the definition (or lack
6380 thereof) in force at each point:
6385 12 printf ("We're so creative.\n");
6387 The symbol `N' has no definition as a C/C++ preprocessor macro
6388 at /home/jimb/gdb/macros/play/sample.c:12
6391 14 printf ("Goodbye, world!\n");
6393 Defined at /home/jimb/gdb/macros/play/sample.c:13
6395 (gdb) macro expand N Q M
6396 expands to: 1729 < 42
6404 @chapter Tracepoints
6405 @c This chapter is based on the documentation written by Michael
6406 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6409 In some applications, it is not feasible for the debugger to interrupt
6410 the program's execution long enough for the developer to learn
6411 anything helpful about its behavior. If the program's correctness
6412 depends on its real-time behavior, delays introduced by a debugger
6413 might cause the program to change its behavior drastically, or perhaps
6414 fail, even when the code itself is correct. It is useful to be able
6415 to observe the program's behavior without interrupting it.
6417 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6418 specify locations in the program, called @dfn{tracepoints}, and
6419 arbitrary expressions to evaluate when those tracepoints are reached.
6420 Later, using the @code{tfind} command, you can examine the values
6421 those expressions had when the program hit the tracepoints. The
6422 expressions may also denote objects in memory---structures or arrays,
6423 for example---whose values @value{GDBN} should record; while visiting
6424 a particular tracepoint, you may inspect those objects as if they were
6425 in memory at that moment. However, because @value{GDBN} records these
6426 values without interacting with you, it can do so quickly and
6427 unobtrusively, hopefully not disturbing the program's behavior.
6429 The tracepoint facility is currently available only for remote
6430 targets. @xref{Targets}. In addition, your remote target must know how
6431 to collect trace data. This functionality is implemented in the remote
6432 stub; however, none of the stubs distributed with @value{GDBN} support
6433 tracepoints as of this writing.
6435 This chapter describes the tracepoint commands and features.
6439 * Analyze Collected Data::
6440 * Tracepoint Variables::
6443 @node Set Tracepoints
6444 @section Commands to Set Tracepoints
6446 Before running such a @dfn{trace experiment}, an arbitrary number of
6447 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6448 tracepoint has a number assigned to it by @value{GDBN}. Like with
6449 breakpoints, tracepoint numbers are successive integers starting from
6450 one. Many of the commands associated with tracepoints take the
6451 tracepoint number as their argument, to identify which tracepoint to
6454 For each tracepoint, you can specify, in advance, some arbitrary set
6455 of data that you want the target to collect in the trace buffer when
6456 it hits that tracepoint. The collected data can include registers,
6457 local variables, or global data. Later, you can use @value{GDBN}
6458 commands to examine the values these data had at the time the
6461 This section describes commands to set tracepoints and associated
6462 conditions and actions.
6465 * Create and Delete Tracepoints::
6466 * Enable and Disable Tracepoints::
6467 * Tracepoint Passcounts::
6468 * Tracepoint Actions::
6469 * Listing Tracepoints::
6470 * Starting and Stopping Trace Experiment::
6473 @node Create and Delete Tracepoints
6474 @subsection Create and Delete Tracepoints
6477 @cindex set tracepoint
6480 The @code{trace} command is very similar to the @code{break} command.
6481 Its argument can be a source line, a function name, or an address in
6482 the target program. @xref{Set Breaks}. The @code{trace} command
6483 defines a tracepoint, which is a point in the target program where the
6484 debugger will briefly stop, collect some data, and then allow the
6485 program to continue. Setting a tracepoint or changing its commands
6486 doesn't take effect until the next @code{tstart} command; thus, you
6487 cannot change the tracepoint attributes once a trace experiment is
6490 Here are some examples of using the @code{trace} command:
6493 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6495 (@value{GDBP}) @b{trace +2} // 2 lines forward
6497 (@value{GDBP}) @b{trace my_function} // first source line of function
6499 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6501 (@value{GDBP}) @b{trace *0x2117c4} // an address
6505 You can abbreviate @code{trace} as @code{tr}.
6508 @cindex last tracepoint number
6509 @cindex recent tracepoint number
6510 @cindex tracepoint number
6511 The convenience variable @code{$tpnum} records the tracepoint number
6512 of the most recently set tracepoint.
6514 @kindex delete tracepoint
6515 @cindex tracepoint deletion
6516 @item delete tracepoint @r{[}@var{num}@r{]}
6517 Permanently delete one or more tracepoints. With no argument, the
6518 default is to delete all tracepoints.
6523 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6525 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6529 You can abbreviate this command as @code{del tr}.
6532 @node Enable and Disable Tracepoints
6533 @subsection Enable and Disable Tracepoints
6536 @kindex disable tracepoint
6537 @item disable tracepoint @r{[}@var{num}@r{]}
6538 Disable tracepoint @var{num}, or all tracepoints if no argument
6539 @var{num} is given. A disabled tracepoint will have no effect during
6540 the next trace experiment, but it is not forgotten. You can re-enable
6541 a disabled tracepoint using the @code{enable tracepoint} command.
6543 @kindex enable tracepoint
6544 @item enable tracepoint @r{[}@var{num}@r{]}
6545 Enable tracepoint @var{num}, or all tracepoints. The enabled
6546 tracepoints will become effective the next time a trace experiment is
6550 @node Tracepoint Passcounts
6551 @subsection Tracepoint Passcounts
6555 @cindex tracepoint pass count
6556 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6557 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6558 automatically stop a trace experiment. If a tracepoint's passcount is
6559 @var{n}, then the trace experiment will be automatically stopped on
6560 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6561 @var{num} is not specified, the @code{passcount} command sets the
6562 passcount of the most recently defined tracepoint. If no passcount is
6563 given, the trace experiment will run until stopped explicitly by the
6569 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6570 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6572 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6573 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6574 (@value{GDBP}) @b{trace foo}
6575 (@value{GDBP}) @b{pass 3}
6576 (@value{GDBP}) @b{trace bar}
6577 (@value{GDBP}) @b{pass 2}
6578 (@value{GDBP}) @b{trace baz}
6579 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6580 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6581 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6582 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6586 @node Tracepoint Actions
6587 @subsection Tracepoint Action Lists
6591 @cindex tracepoint actions
6592 @item actions @r{[}@var{num}@r{]}
6593 This command will prompt for a list of actions to be taken when the
6594 tracepoint is hit. If the tracepoint number @var{num} is not
6595 specified, this command sets the actions for the one that was most
6596 recently defined (so that you can define a tracepoint and then say
6597 @code{actions} without bothering about its number). You specify the
6598 actions themselves on the following lines, one action at a time, and
6599 terminate the actions list with a line containing just @code{end}. So
6600 far, the only defined actions are @code{collect} and
6601 @code{while-stepping}.
6603 @cindex remove actions from a tracepoint
6604 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6605 and follow it immediately with @samp{end}.
6608 (@value{GDBP}) @b{collect @var{data}} // collect some data
6610 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6612 (@value{GDBP}) @b{end} // signals the end of actions.
6615 In the following example, the action list begins with @code{collect}
6616 commands indicating the things to be collected when the tracepoint is
6617 hit. Then, in order to single-step and collect additional data
6618 following the tracepoint, a @code{while-stepping} command is used,
6619 followed by the list of things to be collected while stepping. The
6620 @code{while-stepping} command is terminated by its own separate
6621 @code{end} command. Lastly, the action list is terminated by an
6625 (@value{GDBP}) @b{trace foo}
6626 (@value{GDBP}) @b{actions}
6627 Enter actions for tracepoint 1, one per line:
6636 @kindex collect @r{(tracepoints)}
6637 @item collect @var{expr1}, @var{expr2}, @dots{}
6638 Collect values of the given expressions when the tracepoint is hit.
6639 This command accepts a comma-separated list of any valid expressions.
6640 In addition to global, static, or local variables, the following
6641 special arguments are supported:
6645 collect all registers
6648 collect all function arguments
6651 collect all local variables.
6654 You can give several consecutive @code{collect} commands, each one
6655 with a single argument, or one @code{collect} command with several
6656 arguments separated by commas: the effect is the same.
6658 The command @code{info scope} (@pxref{Symbols, info scope}) is
6659 particularly useful for figuring out what data to collect.
6661 @kindex while-stepping @r{(tracepoints)}
6662 @item while-stepping @var{n}
6663 Perform @var{n} single-step traces after the tracepoint, collecting
6664 new data at each step. The @code{while-stepping} command is
6665 followed by the list of what to collect while stepping (followed by
6666 its own @code{end} command):
6670 > collect $regs, myglobal
6676 You may abbreviate @code{while-stepping} as @code{ws} or
6680 @node Listing Tracepoints
6681 @subsection Listing Tracepoints
6684 @kindex info tracepoints
6685 @cindex information about tracepoints
6686 @item info tracepoints @r{[}@var{num}@r{]}
6687 Display information about the tracepoint @var{num}. If you don't specify
6688 a tracepoint number, displays information about all the tracepoints
6689 defined so far. For each tracepoint, the following information is
6696 whether it is enabled or disabled
6700 its passcount as given by the @code{passcount @var{n}} command
6702 its step count as given by the @code{while-stepping @var{n}} command
6704 where in the source files is the tracepoint set
6706 its action list as given by the @code{actions} command
6710 (@value{GDBP}) @b{info trace}
6711 Num Enb Address PassC StepC What
6712 1 y 0x002117c4 0 0 <gdb_asm>
6713 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6714 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6719 This command can be abbreviated @code{info tp}.
6722 @node Starting and Stopping Trace Experiment
6723 @subsection Starting and Stopping Trace Experiment
6727 @cindex start a new trace experiment
6728 @cindex collected data discarded
6730 This command takes no arguments. It starts the trace experiment, and
6731 begins collecting data. This has the side effect of discarding all
6732 the data collected in the trace buffer during the previous trace
6736 @cindex stop a running trace experiment
6738 This command takes no arguments. It ends the trace experiment, and
6739 stops collecting data.
6741 @strong{Note:} a trace experiment and data collection may stop
6742 automatically if any tracepoint's passcount is reached
6743 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6746 @cindex status of trace data collection
6747 @cindex trace experiment, status of
6749 This command displays the status of the current trace data
6753 Here is an example of the commands we described so far:
6756 (@value{GDBP}) @b{trace gdb_c_test}
6757 (@value{GDBP}) @b{actions}
6758 Enter actions for tracepoint #1, one per line.
6759 > collect $regs,$locals,$args
6764 (@value{GDBP}) @b{tstart}
6765 [time passes @dots{}]
6766 (@value{GDBP}) @b{tstop}
6770 @node Analyze Collected Data
6771 @section Using the collected data
6773 After the tracepoint experiment ends, you use @value{GDBN} commands
6774 for examining the trace data. The basic idea is that each tracepoint
6775 collects a trace @dfn{snapshot} every time it is hit and another
6776 snapshot every time it single-steps. All these snapshots are
6777 consecutively numbered from zero and go into a buffer, and you can
6778 examine them later. The way you examine them is to @dfn{focus} on a
6779 specific trace snapshot. When the remote stub is focused on a trace
6780 snapshot, it will respond to all @value{GDBN} requests for memory and
6781 registers by reading from the buffer which belongs to that snapshot,
6782 rather than from @emph{real} memory or registers of the program being
6783 debugged. This means that @strong{all} @value{GDBN} commands
6784 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
6785 behave as if we were currently debugging the program state as it was
6786 when the tracepoint occurred. Any requests for data that are not in
6787 the buffer will fail.
6790 * tfind:: How to select a trace snapshot
6791 * tdump:: How to display all data for a snapshot
6792 * save-tracepoints:: How to save tracepoints for a future run
6796 @subsection @code{tfind @var{n}}
6799 @cindex select trace snapshot
6800 @cindex find trace snapshot
6801 The basic command for selecting a trace snapshot from the buffer is
6802 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
6803 counting from zero. If no argument @var{n} is given, the next
6804 snapshot is selected.
6806 Here are the various forms of using the @code{tfind} command.
6810 Find the first snapshot in the buffer. This is a synonym for
6811 @code{tfind 0} (since 0 is the number of the first snapshot).
6814 Stop debugging trace snapshots, resume @emph{live} debugging.
6817 Same as @samp{tfind none}.
6820 No argument means find the next trace snapshot.
6823 Find the previous trace snapshot before the current one. This permits
6824 retracing earlier steps.
6826 @item tfind tracepoint @var{num}
6827 Find the next snapshot associated with tracepoint @var{num}. Search
6828 proceeds forward from the last examined trace snapshot. If no
6829 argument @var{num} is given, it means find the next snapshot collected
6830 for the same tracepoint as the current snapshot.
6832 @item tfind pc @var{addr}
6833 Find the next snapshot associated with the value @var{addr} of the
6834 program counter. Search proceeds forward from the last examined trace
6835 snapshot. If no argument @var{addr} is given, it means find the next
6836 snapshot with the same value of PC as the current snapshot.
6838 @item tfind outside @var{addr1}, @var{addr2}
6839 Find the next snapshot whose PC is outside the given range of
6842 @item tfind range @var{addr1}, @var{addr2}
6843 Find the next snapshot whose PC is between @var{addr1} and
6844 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
6846 @item tfind line @r{[}@var{file}:@r{]}@var{n}
6847 Find the next snapshot associated with the source line @var{n}. If
6848 the optional argument @var{file} is given, refer to line @var{n} in
6849 that source file. Search proceeds forward from the last examined
6850 trace snapshot. If no argument @var{n} is given, it means find the
6851 next line other than the one currently being examined; thus saying
6852 @code{tfind line} repeatedly can appear to have the same effect as
6853 stepping from line to line in a @emph{live} debugging session.
6856 The default arguments for the @code{tfind} commands are specifically
6857 designed to make it easy to scan through the trace buffer. For
6858 instance, @code{tfind} with no argument selects the next trace
6859 snapshot, and @code{tfind -} with no argument selects the previous
6860 trace snapshot. So, by giving one @code{tfind} command, and then
6861 simply hitting @key{RET} repeatedly you can examine all the trace
6862 snapshots in order. Or, by saying @code{tfind -} and then hitting
6863 @key{RET} repeatedly you can examine the snapshots in reverse order.
6864 The @code{tfind line} command with no argument selects the snapshot
6865 for the next source line executed. The @code{tfind pc} command with
6866 no argument selects the next snapshot with the same program counter
6867 (PC) as the current frame. The @code{tfind tracepoint} command with
6868 no argument selects the next trace snapshot collected by the same
6869 tracepoint as the current one.
6871 In addition to letting you scan through the trace buffer manually,
6872 these commands make it easy to construct @value{GDBN} scripts that
6873 scan through the trace buffer and print out whatever collected data
6874 you are interested in. Thus, if we want to examine the PC, FP, and SP
6875 registers from each trace frame in the buffer, we can say this:
6878 (@value{GDBP}) @b{tfind start}
6879 (@value{GDBP}) @b{while ($trace_frame != -1)}
6880 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
6881 $trace_frame, $pc, $sp, $fp
6885 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
6886 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
6887 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
6888 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
6889 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
6890 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
6891 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
6892 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
6893 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
6894 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
6895 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
6898 Or, if we want to examine the variable @code{X} at each source line in
6902 (@value{GDBP}) @b{tfind start}
6903 (@value{GDBP}) @b{while ($trace_frame != -1)}
6904 > printf "Frame %d, X == %d\n", $trace_frame, X
6914 @subsection @code{tdump}
6916 @cindex dump all data collected at tracepoint
6917 @cindex tracepoint data, display
6919 This command takes no arguments. It prints all the data collected at
6920 the current trace snapshot.
6923 (@value{GDBP}) @b{trace 444}
6924 (@value{GDBP}) @b{actions}
6925 Enter actions for tracepoint #2, one per line:
6926 > collect $regs, $locals, $args, gdb_long_test
6929 (@value{GDBP}) @b{tstart}
6931 (@value{GDBP}) @b{tfind line 444}
6932 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
6934 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
6936 (@value{GDBP}) @b{tdump}
6937 Data collected at tracepoint 2, trace frame 1:
6938 d0 0xc4aa0085 -995491707
6942 d4 0x71aea3d 119204413
6947 a1 0x3000668 50333288
6950 a4 0x3000698 50333336
6952 fp 0x30bf3c 0x30bf3c
6953 sp 0x30bf34 0x30bf34
6955 pc 0x20b2c8 0x20b2c8
6959 p = 0x20e5b4 "gdb-test"
6966 gdb_long_test = 17 '\021'
6971 @node save-tracepoints
6972 @subsection @code{save-tracepoints @var{filename}}
6973 @kindex save-tracepoints
6974 @cindex save tracepoints for future sessions
6976 This command saves all current tracepoint definitions together with
6977 their actions and passcounts, into a file @file{@var{filename}}
6978 suitable for use in a later debugging session. To read the saved
6979 tracepoint definitions, use the @code{source} command (@pxref{Command
6982 @node Tracepoint Variables
6983 @section Convenience Variables for Tracepoints
6984 @cindex tracepoint variables
6985 @cindex convenience variables for tracepoints
6988 @vindex $trace_frame
6989 @item (int) $trace_frame
6990 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
6991 snapshot is selected.
6994 @item (int) $tracepoint
6995 The tracepoint for the current trace snapshot.
6998 @item (int) $trace_line
6999 The line number for the current trace snapshot.
7002 @item (char []) $trace_file
7003 The source file for the current trace snapshot.
7006 @item (char []) $trace_func
7007 The name of the function containing @code{$tracepoint}.
7010 Note: @code{$trace_file} is not suitable for use in @code{printf},
7011 use @code{output} instead.
7013 Here's a simple example of using these convenience variables for
7014 stepping through all the trace snapshots and printing some of their
7018 (@value{GDBP}) @b{tfind start}
7020 (@value{GDBP}) @b{while $trace_frame != -1}
7021 > output $trace_file
7022 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7028 @chapter Debugging Programs That Use Overlays
7031 If your program is too large to fit completely in your target system's
7032 memory, you can sometimes use @dfn{overlays} to work around this
7033 problem. @value{GDBN} provides some support for debugging programs that
7037 * How Overlays Work:: A general explanation of overlays.
7038 * Overlay Commands:: Managing overlays in @value{GDBN}.
7039 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7040 mapped by asking the inferior.
7041 * Overlay Sample Program:: A sample program using overlays.
7044 @node How Overlays Work
7045 @section How Overlays Work
7046 @cindex mapped overlays
7047 @cindex unmapped overlays
7048 @cindex load address, overlay's
7049 @cindex mapped address
7050 @cindex overlay area
7052 Suppose you have a computer whose instruction address space is only 64
7053 kilobytes long, but which has much more memory which can be accessed by
7054 other means: special instructions, segment registers, or memory
7055 management hardware, for example. Suppose further that you want to
7056 adapt a program which is larger than 64 kilobytes to run on this system.
7058 One solution is to identify modules of your program which are relatively
7059 independent, and need not call each other directly; call these modules
7060 @dfn{overlays}. Separate the overlays from the main program, and place
7061 their machine code in the larger memory. Place your main program in
7062 instruction memory, but leave at least enough space there to hold the
7063 largest overlay as well.
7065 Now, to call a function located in an overlay, you must first copy that
7066 overlay's machine code from the large memory into the space set aside
7067 for it in the instruction memory, and then jump to its entry point
7070 @c NB: In the below the mapped area's size is greater or equal to the
7071 @c size of all overlays. This is intentional to remind the developer
7072 @c that overlays don't necessarily need to be the same size.
7076 Data Instruction Larger
7077 Address Space Address Space Address Space
7078 +-----------+ +-----------+ +-----------+
7080 +-----------+ +-----------+ +-----------+<-- overlay 1
7081 | program | | main | .----| overlay 1 | load address
7082 | variables | | program | | +-----------+
7083 | and heap | | | | | |
7084 +-----------+ | | | +-----------+<-- overlay 2
7085 | | +-----------+ | | | load address
7086 +-----------+ | | | .-| overlay 2 |
7088 mapped --->+-----------+ | | +-----------+
7090 | overlay | <-' | | |
7091 | area | <---' +-----------+<-- overlay 3
7092 | | <---. | | load address
7093 +-----------+ `--| overlay 3 |
7100 @anchor{A code overlay}A code overlay
7104 The diagram (@pxref{A code overlay}) shows a system with separate data
7105 and instruction address spaces. To map an overlay, the program copies
7106 its code from the larger address space to the instruction address space.
7107 Since the overlays shown here all use the same mapped address, only one
7108 may be mapped at a time. For a system with a single address space for
7109 data and instructions, the diagram would be similar, except that the
7110 program variables and heap would share an address space with the main
7111 program and the overlay area.
7113 An overlay loaded into instruction memory and ready for use is called a
7114 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7115 instruction memory. An overlay not present (or only partially present)
7116 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7117 is its address in the larger memory. The mapped address is also called
7118 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7119 called the @dfn{load memory address}, or @dfn{LMA}.
7121 Unfortunately, overlays are not a completely transparent way to adapt a
7122 program to limited instruction memory. They introduce a new set of
7123 global constraints you must keep in mind as you design your program:
7128 Before calling or returning to a function in an overlay, your program
7129 must make sure that overlay is actually mapped. Otherwise, the call or
7130 return will transfer control to the right address, but in the wrong
7131 overlay, and your program will probably crash.
7134 If the process of mapping an overlay is expensive on your system, you
7135 will need to choose your overlays carefully to minimize their effect on
7136 your program's performance.
7139 The executable file you load onto your system must contain each
7140 overlay's instructions, appearing at the overlay's load address, not its
7141 mapped address. However, each overlay's instructions must be relocated
7142 and its symbols defined as if the overlay were at its mapped address.
7143 You can use GNU linker scripts to specify different load and relocation
7144 addresses for pieces of your program; see @ref{Overlay Description,,,
7145 ld.info, Using ld: the GNU linker}.
7148 The procedure for loading executable files onto your system must be able
7149 to load their contents into the larger address space as well as the
7150 instruction and data spaces.
7154 The overlay system described above is rather simple, and could be
7155 improved in many ways:
7160 If your system has suitable bank switch registers or memory management
7161 hardware, you could use those facilities to make an overlay's load area
7162 contents simply appear at their mapped address in instruction space.
7163 This would probably be faster than copying the overlay to its mapped
7164 area in the usual way.
7167 If your overlays are small enough, you could set aside more than one
7168 overlay area, and have more than one overlay mapped at a time.
7171 You can use overlays to manage data, as well as instructions. In
7172 general, data overlays are even less transparent to your design than
7173 code overlays: whereas code overlays only require care when you call or
7174 return to functions, data overlays require care every time you access
7175 the data. Also, if you change the contents of a data overlay, you
7176 must copy its contents back out to its load address before you can copy a
7177 different data overlay into the same mapped area.
7182 @node Overlay Commands
7183 @section Overlay Commands
7185 To use @value{GDBN}'s overlay support, each overlay in your program must
7186 correspond to a separate section of the executable file. The section's
7187 virtual memory address and load memory address must be the overlay's
7188 mapped and load addresses. Identifying overlays with sections allows
7189 @value{GDBN} to determine the appropriate address of a function or
7190 variable, depending on whether the overlay is mapped or not.
7192 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7193 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7198 Disable @value{GDBN}'s overlay support. When overlay support is
7199 disabled, @value{GDBN} assumes that all functions and variables are
7200 always present at their mapped addresses. By default, @value{GDBN}'s
7201 overlay support is disabled.
7203 @item overlay manual
7204 @kindex overlay manual
7205 @cindex manual overlay debugging
7206 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7207 relies on you to tell it which overlays are mapped, and which are not,
7208 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7209 commands described below.
7211 @item overlay map-overlay @var{overlay}
7212 @itemx overlay map @var{overlay}
7213 @kindex overlay map-overlay
7214 @cindex map an overlay
7215 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7216 be the name of the object file section containing the overlay. When an
7217 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7218 functions and variables at their mapped addresses. @value{GDBN} assumes
7219 that any other overlays whose mapped ranges overlap that of
7220 @var{overlay} are now unmapped.
7222 @item overlay unmap-overlay @var{overlay}
7223 @itemx overlay unmap @var{overlay}
7224 @kindex overlay unmap-overlay
7225 @cindex unmap an overlay
7226 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7227 must be the name of the object file section containing the overlay.
7228 When an overlay is unmapped, @value{GDBN} assumes it can find the
7229 overlay's functions and variables at their load addresses.
7232 @kindex overlay auto
7233 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7234 consults a data structure the overlay manager maintains in the inferior
7235 to see which overlays are mapped. For details, see @ref{Automatic
7238 @item overlay load-target
7240 @kindex overlay load-target
7241 @cindex reloading the overlay table
7242 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7243 re-reads the table @value{GDBN} automatically each time the inferior
7244 stops, so this command should only be necessary if you have changed the
7245 overlay mapping yourself using @value{GDBN}. This command is only
7246 useful when using automatic overlay debugging.
7248 @item overlay list-overlays
7250 @cindex listing mapped overlays
7251 Display a list of the overlays currently mapped, along with their mapped
7252 addresses, load addresses, and sizes.
7256 Normally, when @value{GDBN} prints a code address, it includes the name
7257 of the function the address falls in:
7261 $3 = @{int ()@} 0x11a0 <main>
7264 When overlay debugging is enabled, @value{GDBN} recognizes code in
7265 unmapped overlays, and prints the names of unmapped functions with
7266 asterisks around them. For example, if @code{foo} is a function in an
7267 unmapped overlay, @value{GDBN} prints it this way:
7271 No sections are mapped.
7273 $5 = @{int (int)@} 0x100000 <*foo*>
7276 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7281 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7282 mapped at 0x1016 - 0x104a
7284 $6 = @{int (int)@} 0x1016 <foo>
7287 When overlay debugging is enabled, @value{GDBN} can find the correct
7288 address for functions and variables in an overlay, whether or not the
7289 overlay is mapped. This allows most @value{GDBN} commands, like
7290 @code{break} and @code{disassemble}, to work normally, even on unmapped
7291 code. However, @value{GDBN}'s breakpoint support has some limitations:
7295 @cindex breakpoints in overlays
7296 @cindex overlays, setting breakpoints in
7297 You can set breakpoints in functions in unmapped overlays, as long as
7298 @value{GDBN} can write to the overlay at its load address.
7300 @value{GDBN} can not set hardware or simulator-based breakpoints in
7301 unmapped overlays. However, if you set a breakpoint at the end of your
7302 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7303 you are using manual overlay management), @value{GDBN} will re-set its
7304 breakpoints properly.
7308 @node Automatic Overlay Debugging
7309 @section Automatic Overlay Debugging
7310 @cindex automatic overlay debugging
7312 @value{GDBN} can automatically track which overlays are mapped and which
7313 are not, given some simple co-operation from the overlay manager in the
7314 inferior. If you enable automatic overlay debugging with the
7315 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7316 looks in the inferior's memory for certain variables describing the
7317 current state of the overlays.
7319 Here are the variables your overlay manager must define to support
7320 @value{GDBN}'s automatic overlay debugging:
7324 @item @code{_ovly_table}:
7325 This variable must be an array of the following structures:
7330 /* The overlay's mapped address. */
7333 /* The size of the overlay, in bytes. */
7336 /* The overlay's load address. */
7339 /* Non-zero if the overlay is currently mapped;
7341 unsigned long mapped;
7345 @item @code{_novlys}:
7346 This variable must be a four-byte signed integer, holding the total
7347 number of elements in @code{_ovly_table}.
7351 To decide whether a particular overlay is mapped or not, @value{GDBN}
7352 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7353 @code{lma} members equal the VMA and LMA of the overlay's section in the
7354 executable file. When @value{GDBN} finds a matching entry, it consults
7355 the entry's @code{mapped} member to determine whether the overlay is
7358 In addition, your overlay manager may define a function called
7359 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7360 will silently set a breakpoint there. If the overlay manager then
7361 calls this function whenever it has changed the overlay table, this
7362 will enable @value{GDBN} to accurately keep track of which overlays
7363 are in program memory, and update any breakpoints that may be set
7364 in overlays. This will allow breakpoints to work even if the
7365 overlays are kept in ROM or other non-writable memory while they
7366 are not being executed.
7368 @node Overlay Sample Program
7369 @section Overlay Sample Program
7370 @cindex overlay example program
7372 When linking a program which uses overlays, you must place the overlays
7373 at their load addresses, while relocating them to run at their mapped
7374 addresses. To do this, you must write a linker script (@pxref{Overlay
7375 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7376 since linker scripts are specific to a particular host system, target
7377 architecture, and target memory layout, this manual cannot provide
7378 portable sample code demonstrating @value{GDBN}'s overlay support.
7380 However, the @value{GDBN} source distribution does contain an overlaid
7381 program, with linker scripts for a few systems, as part of its test
7382 suite. The program consists of the following files from
7383 @file{gdb/testsuite/gdb.base}:
7387 The main program file.
7389 A simple overlay manager, used by @file{overlays.c}.
7394 Overlay modules, loaded and used by @file{overlays.c}.
7397 Linker scripts for linking the test program on the @code{d10v-elf}
7398 and @code{m32r-elf} targets.
7401 You can build the test program using the @code{d10v-elf} GCC
7402 cross-compiler like this:
7405 $ d10v-elf-gcc -g -c overlays.c
7406 $ d10v-elf-gcc -g -c ovlymgr.c
7407 $ d10v-elf-gcc -g -c foo.c
7408 $ d10v-elf-gcc -g -c bar.c
7409 $ d10v-elf-gcc -g -c baz.c
7410 $ d10v-elf-gcc -g -c grbx.c
7411 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7412 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7415 The build process is identical for any other architecture, except that
7416 you must substitute the appropriate compiler and linker script for the
7417 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7421 @chapter Using @value{GDBN} with Different Languages
7424 Although programming languages generally have common aspects, they are
7425 rarely expressed in the same manner. For instance, in ANSI C,
7426 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7427 Modula-2, it is accomplished by @code{p^}. Values can also be
7428 represented (and displayed) differently. Hex numbers in C appear as
7429 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7431 @cindex working language
7432 Language-specific information is built into @value{GDBN} for some languages,
7433 allowing you to express operations like the above in your program's
7434 native language, and allowing @value{GDBN} to output values in a manner
7435 consistent with the syntax of your program's native language. The
7436 language you use to build expressions is called the @dfn{working
7440 * Setting:: Switching between source languages
7441 * Show:: Displaying the language
7442 * Checks:: Type and range checks
7443 * Support:: Supported languages
7447 @section Switching between source languages
7449 There are two ways to control the working language---either have @value{GDBN}
7450 set it automatically, or select it manually yourself. You can use the
7451 @code{set language} command for either purpose. On startup, @value{GDBN}
7452 defaults to setting the language automatically. The working language is
7453 used to determine how expressions you type are interpreted, how values
7456 In addition to the working language, every source file that
7457 @value{GDBN} knows about has its own working language. For some object
7458 file formats, the compiler might indicate which language a particular
7459 source file is in. However, most of the time @value{GDBN} infers the
7460 language from the name of the file. The language of a source file
7461 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7462 show each frame appropriately for its own language. There is no way to
7463 set the language of a source file from within @value{GDBN}, but you can
7464 set the language associated with a filename extension. @xref{Show, ,
7465 Displaying the language}.
7467 This is most commonly a problem when you use a program, such
7468 as @code{cfront} or @code{f2c}, that generates C but is written in
7469 another language. In that case, make the
7470 program use @code{#line} directives in its C output; that way
7471 @value{GDBN} will know the correct language of the source code of the original
7472 program, and will display that source code, not the generated C code.
7475 * Filenames:: Filename extensions and languages.
7476 * Manually:: Setting the working language manually
7477 * Automatically:: Having @value{GDBN} infer the source language
7481 @subsection List of filename extensions and languages
7483 If a source file name ends in one of the following extensions, then
7484 @value{GDBN} infers that its language is the one indicated.
7504 Modula-2 source file
7508 Assembler source file. This actually behaves almost like C, but
7509 @value{GDBN} does not skip over function prologues when stepping.
7512 In addition, you may set the language associated with a filename
7513 extension. @xref{Show, , Displaying the language}.
7516 @subsection Setting the working language
7518 If you allow @value{GDBN} to set the language automatically,
7519 expressions are interpreted the same way in your debugging session and
7522 @kindex set language
7523 If you wish, you may set the language manually. To do this, issue the
7524 command @samp{set language @var{lang}}, where @var{lang} is the name of
7526 @code{c} or @code{modula-2}.
7527 For a list of the supported languages, type @samp{set language}.
7529 Setting the language manually prevents @value{GDBN} from updating the working
7530 language automatically. This can lead to confusion if you try
7531 to debug a program when the working language is not the same as the
7532 source language, when an expression is acceptable to both
7533 languages---but means different things. For instance, if the current
7534 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7542 might not have the effect you intended. In C, this means to add
7543 @code{b} and @code{c} and place the result in @code{a}. The result
7544 printed would be the value of @code{a}. In Modula-2, this means to compare
7545 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7548 @subsection Having @value{GDBN} infer the source language
7550 To have @value{GDBN} set the working language automatically, use
7551 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7552 then infers the working language. That is, when your program stops in a
7553 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7554 working language to the language recorded for the function in that
7555 frame. If the language for a frame is unknown (that is, if the function
7556 or block corresponding to the frame was defined in a source file that
7557 does not have a recognized extension), the current working language is
7558 not changed, and @value{GDBN} issues a warning.
7560 This may not seem necessary for most programs, which are written
7561 entirely in one source language. However, program modules and libraries
7562 written in one source language can be used by a main program written in
7563 a different source language. Using @samp{set language auto} in this
7564 case frees you from having to set the working language manually.
7567 @section Displaying the language
7569 The following commands help you find out which language is the
7570 working language, and also what language source files were written in.
7572 @kindex show language
7573 @kindex info frame@r{, show the source language}
7574 @kindex info source@r{, show the source language}
7577 Display the current working language. This is the
7578 language you can use with commands such as @code{print} to
7579 build and compute expressions that may involve variables in your program.
7582 Display the source language for this frame. This language becomes the
7583 working language if you use an identifier from this frame.
7584 @xref{Frame Info, ,Information about a frame}, to identify the other
7585 information listed here.
7588 Display the source language of this source file.
7589 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7590 information listed here.
7593 In unusual circumstances, you may have source files with extensions
7594 not in the standard list. You can then set the extension associated
7595 with a language explicitly:
7597 @kindex set extension-language
7598 @kindex info extensions
7600 @item set extension-language @var{.ext} @var{language}
7601 Set source files with extension @var{.ext} to be assumed to be in
7602 the source language @var{language}.
7604 @item info extensions
7605 List all the filename extensions and the associated languages.
7609 @section Type and range checking
7612 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7613 checking are included, but they do not yet have any effect. This
7614 section documents the intended facilities.
7616 @c FIXME remove warning when type/range code added
7618 Some languages are designed to guard you against making seemingly common
7619 errors through a series of compile- and run-time checks. These include
7620 checking the type of arguments to functions and operators, and making
7621 sure mathematical overflows are caught at run time. Checks such as
7622 these help to ensure a program's correctness once it has been compiled
7623 by eliminating type mismatches, and providing active checks for range
7624 errors when your program is running.
7626 @value{GDBN} can check for conditions like the above if you wish.
7627 Although @value{GDBN} does not check the statements in your program, it
7628 can check expressions entered directly into @value{GDBN} for evaluation via
7629 the @code{print} command, for example. As with the working language,
7630 @value{GDBN} can also decide whether or not to check automatically based on
7631 your program's source language. @xref{Support, ,Supported languages},
7632 for the default settings of supported languages.
7635 * Type Checking:: An overview of type checking
7636 * Range Checking:: An overview of range checking
7639 @cindex type checking
7640 @cindex checks, type
7642 @subsection An overview of type checking
7644 Some languages, such as Modula-2, are strongly typed, meaning that the
7645 arguments to operators and functions have to be of the correct type,
7646 otherwise an error occurs. These checks prevent type mismatch
7647 errors from ever causing any run-time problems. For example,
7655 The second example fails because the @code{CARDINAL} 1 is not
7656 type-compatible with the @code{REAL} 2.3.
7658 For the expressions you use in @value{GDBN} commands, you can tell the
7659 @value{GDBN} type checker to skip checking;
7660 to treat any mismatches as errors and abandon the expression;
7661 or to only issue warnings when type mismatches occur,
7662 but evaluate the expression anyway. When you choose the last of
7663 these, @value{GDBN} evaluates expressions like the second example above, but
7664 also issues a warning.
7666 Even if you turn type checking off, there may be other reasons
7667 related to type that prevent @value{GDBN} from evaluating an expression.
7668 For instance, @value{GDBN} does not know how to add an @code{int} and
7669 a @code{struct foo}. These particular type errors have nothing to do
7670 with the language in use, and usually arise from expressions, such as
7671 the one described above, which make little sense to evaluate anyway.
7673 Each language defines to what degree it is strict about type. For
7674 instance, both Modula-2 and C require the arguments to arithmetical
7675 operators to be numbers. In C, enumerated types and pointers can be
7676 represented as numbers, so that they are valid arguments to mathematical
7677 operators. @xref{Support, ,Supported languages}, for further
7678 details on specific languages.
7680 @value{GDBN} provides some additional commands for controlling the type checker:
7682 @kindex set check@r{, type}
7683 @kindex set check type
7684 @kindex show check type
7686 @item set check type auto
7687 Set type checking on or off based on the current working language.
7688 @xref{Support, ,Supported languages}, for the default settings for
7691 @item set check type on
7692 @itemx set check type off
7693 Set type checking on or off, overriding the default setting for the
7694 current working language. Issue a warning if the setting does not
7695 match the language default. If any type mismatches occur in
7696 evaluating an expression while type checking is on, @value{GDBN} prints a
7697 message and aborts evaluation of the expression.
7699 @item set check type warn
7700 Cause the type checker to issue warnings, but to always attempt to
7701 evaluate the expression. Evaluating the expression may still
7702 be impossible for other reasons. For example, @value{GDBN} cannot add
7703 numbers and structures.
7706 Show the current setting of the type checker, and whether or not @value{GDBN}
7707 is setting it automatically.
7710 @cindex range checking
7711 @cindex checks, range
7712 @node Range Checking
7713 @subsection An overview of range checking
7715 In some languages (such as Modula-2), it is an error to exceed the
7716 bounds of a type; this is enforced with run-time checks. Such range
7717 checking is meant to ensure program correctness by making sure
7718 computations do not overflow, or indices on an array element access do
7719 not exceed the bounds of the array.
7721 For expressions you use in @value{GDBN} commands, you can tell
7722 @value{GDBN} to treat range errors in one of three ways: ignore them,
7723 always treat them as errors and abandon the expression, or issue
7724 warnings but evaluate the expression anyway.
7726 A range error can result from numerical overflow, from exceeding an
7727 array index bound, or when you type a constant that is not a member
7728 of any type. Some languages, however, do not treat overflows as an
7729 error. In many implementations of C, mathematical overflow causes the
7730 result to ``wrap around'' to lower values---for example, if @var{m} is
7731 the largest integer value, and @var{s} is the smallest, then
7734 @var{m} + 1 @result{} @var{s}
7737 This, too, is specific to individual languages, and in some cases
7738 specific to individual compilers or machines. @xref{Support, ,
7739 Supported languages}, for further details on specific languages.
7741 @value{GDBN} provides some additional commands for controlling the range checker:
7743 @kindex set check@r{, range}
7744 @kindex set check range
7745 @kindex show check range
7747 @item set check range auto
7748 Set range checking on or off based on the current working language.
7749 @xref{Support, ,Supported languages}, for the default settings for
7752 @item set check range on
7753 @itemx set check range off
7754 Set range checking on or off, overriding the default setting for the
7755 current working language. A warning is issued if the setting does not
7756 match the language default. If a range error occurs and range checking is on,
7757 then a message is printed and evaluation of the expression is aborted.
7759 @item set check range warn
7760 Output messages when the @value{GDBN} range checker detects a range error,
7761 but attempt to evaluate the expression anyway. Evaluating the
7762 expression may still be impossible for other reasons, such as accessing
7763 memory that the process does not own (a typical example from many Unix
7767 Show the current setting of the range checker, and whether or not it is
7768 being set automatically by @value{GDBN}.
7772 @section Supported languages
7774 @value{GDBN} supports C, C@t{++}, Fortran, Java, assembly, and Modula-2.
7775 @c This is false ...
7776 Some @value{GDBN} features may be used in expressions regardless of the
7777 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
7778 and the @samp{@{type@}addr} construct (@pxref{Expressions,
7779 ,Expressions}) can be used with the constructs of any supported
7782 The following sections detail to what degree each source language is
7783 supported by @value{GDBN}. These sections are not meant to be language
7784 tutorials or references, but serve only as a reference guide to what the
7785 @value{GDBN} expression parser accepts, and what input and output
7786 formats should look like for different languages. There are many good
7787 books written on each of these languages; please look to these for a
7788 language reference or tutorial.
7792 * Modula-2:: Modula-2
7796 @subsection C and C@t{++}
7798 @cindex C and C@t{++}
7799 @cindex expressions in C or C@t{++}
7801 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
7802 to both languages. Whenever this is the case, we discuss those languages
7806 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
7807 @cindex @sc{gnu} C@t{++}
7808 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
7809 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
7810 effectively, you must compile your C@t{++} programs with a supported
7811 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
7812 compiler (@code{aCC}).
7814 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
7815 format; if it doesn't work on your system, try the stabs+ debugging
7816 format. You can select those formats explicitly with the @code{g++}
7817 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
7818 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
7819 CC, gcc.info, Using @sc{gnu} CC}.
7822 * C Operators:: C and C@t{++} operators
7823 * C Constants:: C and C@t{++} constants
7824 * C plus plus expressions:: C@t{++} expressions
7825 * C Defaults:: Default settings for C and C@t{++}
7826 * C Checks:: C and C@t{++} type and range checks
7827 * Debugging C:: @value{GDBN} and C
7828 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
7832 @subsubsection C and C@t{++} operators
7834 @cindex C and C@t{++} operators
7836 Operators must be defined on values of specific types. For instance,
7837 @code{+} is defined on numbers, but not on structures. Operators are
7838 often defined on groups of types.
7840 For the purposes of C and C@t{++}, the following definitions hold:
7845 @emph{Integral types} include @code{int} with any of its storage-class
7846 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
7849 @emph{Floating-point types} include @code{float}, @code{double}, and
7850 @code{long double} (if supported by the target platform).
7853 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
7856 @emph{Scalar types} include all of the above.
7861 The following operators are supported. They are listed here
7862 in order of increasing precedence:
7866 The comma or sequencing operator. Expressions in a comma-separated list
7867 are evaluated from left to right, with the result of the entire
7868 expression being the last expression evaluated.
7871 Assignment. The value of an assignment expression is the value
7872 assigned. Defined on scalar types.
7875 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
7876 and translated to @w{@code{@var{a} = @var{a op b}}}.
7877 @w{@code{@var{op}=}} and @code{=} have the same precedence.
7878 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
7879 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
7882 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
7883 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
7887 Logical @sc{or}. Defined on integral types.
7890 Logical @sc{and}. Defined on integral types.
7893 Bitwise @sc{or}. Defined on integral types.
7896 Bitwise exclusive-@sc{or}. Defined on integral types.
7899 Bitwise @sc{and}. Defined on integral types.
7902 Equality and inequality. Defined on scalar types. The value of these
7903 expressions is 0 for false and non-zero for true.
7905 @item <@r{, }>@r{, }<=@r{, }>=
7906 Less than, greater than, less than or equal, greater than or equal.
7907 Defined on scalar types. The value of these expressions is 0 for false
7908 and non-zero for true.
7911 left shift, and right shift. Defined on integral types.
7914 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
7917 Addition and subtraction. Defined on integral types, floating-point types and
7920 @item *@r{, }/@r{, }%
7921 Multiplication, division, and modulus. Multiplication and division are
7922 defined on integral and floating-point types. Modulus is defined on
7926 Increment and decrement. When appearing before a variable, the
7927 operation is performed before the variable is used in an expression;
7928 when appearing after it, the variable's value is used before the
7929 operation takes place.
7932 Pointer dereferencing. Defined on pointer types. Same precedence as
7936 Address operator. Defined on variables. Same precedence as @code{++}.
7938 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
7939 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
7940 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
7941 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
7945 Negative. Defined on integral and floating-point types. Same
7946 precedence as @code{++}.
7949 Logical negation. Defined on integral types. Same precedence as
7953 Bitwise complement operator. Defined on integral types. Same precedence as
7958 Structure member, and pointer-to-structure member. For convenience,
7959 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
7960 pointer based on the stored type information.
7961 Defined on @code{struct} and @code{union} data.
7964 Dereferences of pointers to members.
7967 Array indexing. @code{@var{a}[@var{i}]} is defined as
7968 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
7971 Function parameter list. Same precedence as @code{->}.
7974 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
7975 and @code{class} types.
7978 Doubled colons also represent the @value{GDBN} scope operator
7979 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
7983 If an operator is redefined in the user code, @value{GDBN} usually
7984 attempts to invoke the redefined version instead of using the operator's
7992 @subsubsection C and C@t{++} constants
7994 @cindex C and C@t{++} constants
7996 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8001 Integer constants are a sequence of digits. Octal constants are
8002 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8003 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8004 @samp{l}, specifying that the constant should be treated as a
8008 Floating point constants are a sequence of digits, followed by a decimal
8009 point, followed by a sequence of digits, and optionally followed by an
8010 exponent. An exponent is of the form:
8011 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8012 sequence of digits. The @samp{+} is optional for positive exponents.
8013 A floating-point constant may also end with a letter @samp{f} or
8014 @samp{F}, specifying that the constant should be treated as being of
8015 the @code{float} (as opposed to the default @code{double}) type; or with
8016 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8020 Enumerated constants consist of enumerated identifiers, or their
8021 integral equivalents.
8024 Character constants are a single character surrounded by single quotes
8025 (@code{'}), or a number---the ordinal value of the corresponding character
8026 (usually its @sc{ascii} value). Within quotes, the single character may
8027 be represented by a letter or by @dfn{escape sequences}, which are of
8028 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8029 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8030 @samp{@var{x}} is a predefined special character---for example,
8031 @samp{\n} for newline.
8034 String constants are a sequence of character constants surrounded by
8035 double quotes (@code{"}). Any valid character constant (as described
8036 above) may appear. Double quotes within the string must be preceded by
8037 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8041 Pointer constants are an integral value. You can also write pointers
8042 to constants using the C operator @samp{&}.
8045 Array constants are comma-separated lists surrounded by braces @samp{@{}
8046 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8047 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8048 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8052 * C plus plus expressions::
8059 @node C plus plus expressions
8060 @subsubsection C@t{++} expressions
8062 @cindex expressions in C@t{++}
8063 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8065 @cindex debugging C@t{++} programs
8066 @cindex C@t{++} compilers
8067 @cindex debug formats and C@t{++}
8068 @cindex @value{NGCC} and C@t{++}
8070 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8071 proper compiler and the proper debug format. Currently, @value{GDBN}
8072 works best when debugging C@t{++} code that is compiled with
8073 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8074 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8075 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8076 stabs+ as their default debug format, so you usually don't need to
8077 specify a debug format explicitly. Other compilers and/or debug formats
8078 are likely to work badly or not at all when using @value{GDBN} to debug
8084 @cindex member functions
8086 Member function calls are allowed; you can use expressions like
8089 count = aml->GetOriginal(x, y)
8092 @vindex this@r{, inside C@t{++} member functions}
8093 @cindex namespace in C@t{++}
8095 While a member function is active (in the selected stack frame), your
8096 expressions have the same namespace available as the member function;
8097 that is, @value{GDBN} allows implicit references to the class instance
8098 pointer @code{this} following the same rules as C@t{++}.
8100 @cindex call overloaded functions
8101 @cindex overloaded functions, calling
8102 @cindex type conversions in C@t{++}
8104 You can call overloaded functions; @value{GDBN} resolves the function
8105 call to the right definition, with some restrictions. @value{GDBN} does not
8106 perform overload resolution involving user-defined type conversions,
8107 calls to constructors, or instantiations of templates that do not exist
8108 in the program. It also cannot handle ellipsis argument lists or
8111 It does perform integral conversions and promotions, floating-point
8112 promotions, arithmetic conversions, pointer conversions, conversions of
8113 class objects to base classes, and standard conversions such as those of
8114 functions or arrays to pointers; it requires an exact match on the
8115 number of function arguments.
8117 Overload resolution is always performed, unless you have specified
8118 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8119 ,@value{GDBN} features for C@t{++}}.
8121 You must specify @code{set overload-resolution off} in order to use an
8122 explicit function signature to call an overloaded function, as in
8124 p 'foo(char,int)'('x', 13)
8127 The @value{GDBN} command-completion facility can simplify this;
8128 see @ref{Completion, ,Command completion}.
8130 @cindex reference declarations
8132 @value{GDBN} understands variables declared as C@t{++} references; you can use
8133 them in expressions just as you do in C@t{++} source---they are automatically
8136 In the parameter list shown when @value{GDBN} displays a frame, the values of
8137 reference variables are not displayed (unlike other variables); this
8138 avoids clutter, since references are often used for large structures.
8139 The @emph{address} of a reference variable is always shown, unless
8140 you have specified @samp{set print address off}.
8143 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8144 expressions can use it just as expressions in your program do. Since
8145 one scope may be defined in another, you can use @code{::} repeatedly if
8146 necessary, for example in an expression like
8147 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8148 resolving name scope by reference to source files, in both C and C@t{++}
8149 debugging (@pxref{Variables, ,Program variables}).
8152 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8153 calling virtual functions correctly, printing out virtual bases of
8154 objects, calling functions in a base subobject, casting objects, and
8155 invoking user-defined operators.
8158 @subsubsection C and C@t{++} defaults
8160 @cindex C and C@t{++} defaults
8162 If you allow @value{GDBN} to set type and range checking automatically, they
8163 both default to @code{off} whenever the working language changes to
8164 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8165 selects the working language.
8167 If you allow @value{GDBN} to set the language automatically, it
8168 recognizes source files whose names end with @file{.c}, @file{.C}, or
8169 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8170 these files, it sets the working language to C or C@t{++}.
8171 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8172 for further details.
8174 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8175 @c unimplemented. If (b) changes, it might make sense to let this node
8176 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8179 @subsubsection C and C@t{++} type and range checks
8181 @cindex C and C@t{++} checks
8183 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8184 is not used. However, if you turn type checking on, @value{GDBN}
8185 considers two variables type equivalent if:
8189 The two variables are structured and have the same structure, union, or
8193 The two variables have the same type name, or types that have been
8194 declared equivalent through @code{typedef}.
8197 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8200 The two @code{struct}, @code{union}, or @code{enum} variables are
8201 declared in the same declaration. (Note: this may not be true for all C
8206 Range checking, if turned on, is done on mathematical operations. Array
8207 indices are not checked, since they are often used to index a pointer
8208 that is not itself an array.
8211 @subsubsection @value{GDBN} and C
8213 The @code{set print union} and @code{show print union} commands apply to
8214 the @code{union} type. When set to @samp{on}, any @code{union} that is
8215 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8216 appears as @samp{@{...@}}.
8218 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8219 with pointers and a memory allocation function. @xref{Expressions,
8223 * Debugging C plus plus::
8226 @node Debugging C plus plus
8227 @subsubsection @value{GDBN} features for C@t{++}
8229 @cindex commands for C@t{++}
8231 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8232 designed specifically for use with C@t{++}. Here is a summary:
8235 @cindex break in overloaded functions
8236 @item @r{breakpoint menus}
8237 When you want a breakpoint in a function whose name is overloaded,
8238 @value{GDBN} breakpoint menus help you specify which function definition
8239 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8241 @cindex overloading in C@t{++}
8242 @item rbreak @var{regex}
8243 Setting breakpoints using regular expressions is helpful for setting
8244 breakpoints on overloaded functions that are not members of any special
8246 @xref{Set Breaks, ,Setting breakpoints}.
8248 @cindex C@t{++} exception handling
8251 Debug C@t{++} exception handling using these commands. @xref{Set
8252 Catchpoints, , Setting catchpoints}.
8255 @item ptype @var{typename}
8256 Print inheritance relationships as well as other information for type
8258 @xref{Symbols, ,Examining the Symbol Table}.
8260 @cindex C@t{++} symbol display
8261 @item set print demangle
8262 @itemx show print demangle
8263 @itemx set print asm-demangle
8264 @itemx show print asm-demangle
8265 Control whether C@t{++} symbols display in their source form, both when
8266 displaying code as C@t{++} source and when displaying disassemblies.
8267 @xref{Print Settings, ,Print settings}.
8269 @item set print object
8270 @itemx show print object
8271 Choose whether to print derived (actual) or declared types of objects.
8272 @xref{Print Settings, ,Print settings}.
8274 @item set print vtbl
8275 @itemx show print vtbl
8276 Control the format for printing virtual function tables.
8277 @xref{Print Settings, ,Print settings}.
8278 (The @code{vtbl} commands do not work on programs compiled with the HP
8279 ANSI C@t{++} compiler (@code{aCC}).)
8281 @kindex set overload-resolution
8282 @cindex overloaded functions, overload resolution
8283 @item set overload-resolution on
8284 Enable overload resolution for C@t{++} expression evaluation. The default
8285 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8286 and searches for a function whose signature matches the argument types,
8287 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8288 expressions}, for details). If it cannot find a match, it emits a
8291 @item set overload-resolution off
8292 Disable overload resolution for C@t{++} expression evaluation. For
8293 overloaded functions that are not class member functions, @value{GDBN}
8294 chooses the first function of the specified name that it finds in the
8295 symbol table, whether or not its arguments are of the correct type. For
8296 overloaded functions that are class member functions, @value{GDBN}
8297 searches for a function whose signature @emph{exactly} matches the
8300 @item @r{Overloaded symbol names}
8301 You can specify a particular definition of an overloaded symbol, using
8302 the same notation that is used to declare such symbols in C@t{++}: type
8303 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8304 also use the @value{GDBN} command-line word completion facilities to list the
8305 available choices, or to finish the type list for you.
8306 @xref{Completion,, Command completion}, for details on how to do this.
8310 @subsection Modula-2
8312 @cindex Modula-2, @value{GDBN} support
8314 The extensions made to @value{GDBN} to support Modula-2 only support
8315 output from the @sc{gnu} Modula-2 compiler (which is currently being
8316 developed). Other Modula-2 compilers are not currently supported, and
8317 attempting to debug executables produced by them is most likely
8318 to give an error as @value{GDBN} reads in the executable's symbol
8321 @cindex expressions in Modula-2
8323 * M2 Operators:: Built-in operators
8324 * Built-In Func/Proc:: Built-in functions and procedures
8325 * M2 Constants:: Modula-2 constants
8326 * M2 Defaults:: Default settings for Modula-2
8327 * Deviations:: Deviations from standard Modula-2
8328 * M2 Checks:: Modula-2 type and range checks
8329 * M2 Scope:: The scope operators @code{::} and @code{.}
8330 * GDB/M2:: @value{GDBN} and Modula-2
8334 @subsubsection Operators
8335 @cindex Modula-2 operators
8337 Operators must be defined on values of specific types. For instance,
8338 @code{+} is defined on numbers, but not on structures. Operators are
8339 often defined on groups of types. For the purposes of Modula-2, the
8340 following definitions hold:
8345 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8349 @emph{Character types} consist of @code{CHAR} and its subranges.
8352 @emph{Floating-point types} consist of @code{REAL}.
8355 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8359 @emph{Scalar types} consist of all of the above.
8362 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8365 @emph{Boolean types} consist of @code{BOOLEAN}.
8369 The following operators are supported, and appear in order of
8370 increasing precedence:
8374 Function argument or array index separator.
8377 Assignment. The value of @var{var} @code{:=} @var{value} is
8381 Less than, greater than on integral, floating-point, or enumerated
8385 Less than or equal to, greater than or equal to
8386 on integral, floating-point and enumerated types, or set inclusion on
8387 set types. Same precedence as @code{<}.
8389 @item =@r{, }<>@r{, }#
8390 Equality and two ways of expressing inequality, valid on scalar types.
8391 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8392 available for inequality, since @code{#} conflicts with the script
8396 Set membership. Defined on set types and the types of their members.
8397 Same precedence as @code{<}.
8400 Boolean disjunction. Defined on boolean types.
8403 Boolean conjunction. Defined on boolean types.
8406 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8409 Addition and subtraction on integral and floating-point types, or union
8410 and difference on set types.
8413 Multiplication on integral and floating-point types, or set intersection
8417 Division on floating-point types, or symmetric set difference on set
8418 types. Same precedence as @code{*}.
8421 Integer division and remainder. Defined on integral types. Same
8422 precedence as @code{*}.
8425 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8428 Pointer dereferencing. Defined on pointer types.
8431 Boolean negation. Defined on boolean types. Same precedence as
8435 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8436 precedence as @code{^}.
8439 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8442 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8446 @value{GDBN} and Modula-2 scope operators.
8450 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8451 treats the use of the operator @code{IN}, or the use of operators
8452 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8453 @code{<=}, and @code{>=} on sets as an error.
8457 @node Built-In Func/Proc
8458 @subsubsection Built-in functions and procedures
8459 @cindex Modula-2 built-ins
8461 Modula-2 also makes available several built-in procedures and functions.
8462 In describing these, the following metavariables are used:
8467 represents an @code{ARRAY} variable.
8470 represents a @code{CHAR} constant or variable.
8473 represents a variable or constant of integral type.
8476 represents an identifier that belongs to a set. Generally used in the
8477 same function with the metavariable @var{s}. The type of @var{s} should
8478 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8481 represents a variable or constant of integral or floating-point type.
8484 represents a variable or constant of floating-point type.
8490 represents a variable.
8493 represents a variable or constant of one of many types. See the
8494 explanation of the function for details.
8497 All Modula-2 built-in procedures also return a result, described below.
8501 Returns the absolute value of @var{n}.
8504 If @var{c} is a lower case letter, it returns its upper case
8505 equivalent, otherwise it returns its argument.
8508 Returns the character whose ordinal value is @var{i}.
8511 Decrements the value in the variable @var{v} by one. Returns the new value.
8513 @item DEC(@var{v},@var{i})
8514 Decrements the value in the variable @var{v} by @var{i}. Returns the
8517 @item EXCL(@var{m},@var{s})
8518 Removes the element @var{m} from the set @var{s}. Returns the new
8521 @item FLOAT(@var{i})
8522 Returns the floating point equivalent of the integer @var{i}.
8525 Returns the index of the last member of @var{a}.
8528 Increments the value in the variable @var{v} by one. Returns the new value.
8530 @item INC(@var{v},@var{i})
8531 Increments the value in the variable @var{v} by @var{i}. Returns the
8534 @item INCL(@var{m},@var{s})
8535 Adds the element @var{m} to the set @var{s} if it is not already
8536 there. Returns the new set.
8539 Returns the maximum value of the type @var{t}.
8542 Returns the minimum value of the type @var{t}.
8545 Returns boolean TRUE if @var{i} is an odd number.
8548 Returns the ordinal value of its argument. For example, the ordinal
8549 value of a character is its @sc{ascii} value (on machines supporting the
8550 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8551 integral, character and enumerated types.
8554 Returns the size of its argument. @var{x} can be a variable or a type.
8556 @item TRUNC(@var{r})
8557 Returns the integral part of @var{r}.
8559 @item VAL(@var{t},@var{i})
8560 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8564 @emph{Warning:} Sets and their operations are not yet supported, so
8565 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8569 @cindex Modula-2 constants
8571 @subsubsection Constants
8573 @value{GDBN} allows you to express the constants of Modula-2 in the following
8579 Integer constants are simply a sequence of digits. When used in an
8580 expression, a constant is interpreted to be type-compatible with the
8581 rest of the expression. Hexadecimal integers are specified by a
8582 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8585 Floating point constants appear as a sequence of digits, followed by a
8586 decimal point and another sequence of digits. An optional exponent can
8587 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8588 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8589 digits of the floating point constant must be valid decimal (base 10)
8593 Character constants consist of a single character enclosed by a pair of
8594 like quotes, either single (@code{'}) or double (@code{"}). They may
8595 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8596 followed by a @samp{C}.
8599 String constants consist of a sequence of characters enclosed by a
8600 pair of like quotes, either single (@code{'}) or double (@code{"}).
8601 Escape sequences in the style of C are also allowed. @xref{C
8602 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8606 Enumerated constants consist of an enumerated identifier.
8609 Boolean constants consist of the identifiers @code{TRUE} and
8613 Pointer constants consist of integral values only.
8616 Set constants are not yet supported.
8620 @subsubsection Modula-2 defaults
8621 @cindex Modula-2 defaults
8623 If type and range checking are set automatically by @value{GDBN}, they
8624 both default to @code{on} whenever the working language changes to
8625 Modula-2. This happens regardless of whether you or @value{GDBN}
8626 selected the working language.
8628 If you allow @value{GDBN} to set the language automatically, then entering
8629 code compiled from a file whose name ends with @file{.mod} sets the
8630 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
8631 the language automatically}, for further details.
8634 @subsubsection Deviations from standard Modula-2
8635 @cindex Modula-2, deviations from
8637 A few changes have been made to make Modula-2 programs easier to debug.
8638 This is done primarily via loosening its type strictness:
8642 Unlike in standard Modula-2, pointer constants can be formed by
8643 integers. This allows you to modify pointer variables during
8644 debugging. (In standard Modula-2, the actual address contained in a
8645 pointer variable is hidden from you; it can only be modified
8646 through direct assignment to another pointer variable or expression that
8647 returned a pointer.)
8650 C escape sequences can be used in strings and characters to represent
8651 non-printable characters. @value{GDBN} prints out strings with these
8652 escape sequences embedded. Single non-printable characters are
8653 printed using the @samp{CHR(@var{nnn})} format.
8656 The assignment operator (@code{:=}) returns the value of its right-hand
8660 All built-in procedures both modify @emph{and} return their argument.
8664 @subsubsection Modula-2 type and range checks
8665 @cindex Modula-2 checks
8668 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
8671 @c FIXME remove warning when type/range checks added
8673 @value{GDBN} considers two Modula-2 variables type equivalent if:
8677 They are of types that have been declared equivalent via a @code{TYPE
8678 @var{t1} = @var{t2}} statement
8681 They have been declared on the same line. (Note: This is true of the
8682 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
8685 As long as type checking is enabled, any attempt to combine variables
8686 whose types are not equivalent is an error.
8688 Range checking is done on all mathematical operations, assignment, array
8689 index bounds, and all built-in functions and procedures.
8692 @subsubsection The scope operators @code{::} and @code{.}
8694 @cindex @code{.}, Modula-2 scope operator
8695 @cindex colon, doubled as scope operator
8697 @vindex colon-colon@r{, in Modula-2}
8698 @c Info cannot handle :: but TeX can.
8701 @vindex ::@r{, in Modula-2}
8704 There are a few subtle differences between the Modula-2 scope operator
8705 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
8710 @var{module} . @var{id}
8711 @var{scope} :: @var{id}
8715 where @var{scope} is the name of a module or a procedure,
8716 @var{module} the name of a module, and @var{id} is any declared
8717 identifier within your program, except another module.
8719 Using the @code{::} operator makes @value{GDBN} search the scope
8720 specified by @var{scope} for the identifier @var{id}. If it is not
8721 found in the specified scope, then @value{GDBN} searches all scopes
8722 enclosing the one specified by @var{scope}.
8724 Using the @code{.} operator makes @value{GDBN} search the current scope for
8725 the identifier specified by @var{id} that was imported from the
8726 definition module specified by @var{module}. With this operator, it is
8727 an error if the identifier @var{id} was not imported from definition
8728 module @var{module}, or if @var{id} is not an identifier in
8732 @subsubsection @value{GDBN} and Modula-2
8734 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
8735 Five subcommands of @code{set print} and @code{show print} apply
8736 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
8737 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
8738 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
8739 analogue in Modula-2.
8741 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
8742 with any language, is not useful with Modula-2. Its
8743 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
8744 created in Modula-2 as they can in C or C@t{++}. However, because an
8745 address can be specified by an integral constant, the construct
8746 @samp{@{@var{type}@}@var{adrexp}} is still useful.
8748 @cindex @code{#} in Modula-2
8749 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
8750 interpreted as the beginning of a comment. Use @code{<>} instead.
8753 @chapter Examining the Symbol Table
8755 The commands described in this chapter allow you to inquire about the
8756 symbols (names of variables, functions and types) defined in your
8757 program. This information is inherent in the text of your program and
8758 does not change as your program executes. @value{GDBN} finds it in your
8759 program's symbol table, in the file indicated when you started @value{GDBN}
8760 (@pxref{File Options, ,Choosing files}), or by one of the
8761 file-management commands (@pxref{Files, ,Commands to specify files}).
8763 @cindex symbol names
8764 @cindex names of symbols
8765 @cindex quoting names
8766 Occasionally, you may need to refer to symbols that contain unusual
8767 characters, which @value{GDBN} ordinarily treats as word delimiters. The
8768 most frequent case is in referring to static variables in other
8769 source files (@pxref{Variables,,Program variables}). File names
8770 are recorded in object files as debugging symbols, but @value{GDBN} would
8771 ordinarily parse a typical file name, like @file{foo.c}, as the three words
8772 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
8773 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
8780 looks up the value of @code{x} in the scope of the file @file{foo.c}.
8783 @kindex info address
8784 @cindex address of a symbol
8785 @item info address @var{symbol}
8786 Describe where the data for @var{symbol} is stored. For a register
8787 variable, this says which register it is kept in. For a non-register
8788 local variable, this prints the stack-frame offset at which the variable
8791 Note the contrast with @samp{print &@var{symbol}}, which does not work
8792 at all for a register variable, and for a stack local variable prints
8793 the exact address of the current instantiation of the variable.
8796 @cindex symbol from address
8797 @item info symbol @var{addr}
8798 Print the name of a symbol which is stored at the address @var{addr}.
8799 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
8800 nearest symbol and an offset from it:
8803 (@value{GDBP}) info symbol 0x54320
8804 _initialize_vx + 396 in section .text
8808 This is the opposite of the @code{info address} command. You can use
8809 it to find out the name of a variable or a function given its address.
8812 @item whatis @var{expr}
8813 Print the data type of expression @var{expr}. @var{expr} is not
8814 actually evaluated, and any side-effecting operations (such as
8815 assignments or function calls) inside it do not take place.
8816 @xref{Expressions, ,Expressions}.
8819 Print the data type of @code{$}, the last value in the value history.
8822 @item ptype @var{typename}
8823 Print a description of data type @var{typename}. @var{typename} may be
8824 the name of a type, or for C code it may have the form @samp{class
8825 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
8826 @var{union-tag}} or @samp{enum @var{enum-tag}}.
8828 @item ptype @var{expr}
8830 Print a description of the type of expression @var{expr}. @code{ptype}
8831 differs from @code{whatis} by printing a detailed description, instead
8832 of just the name of the type.
8834 For example, for this variable declaration:
8837 struct complex @{double real; double imag;@} v;
8841 the two commands give this output:
8845 (@value{GDBP}) whatis v
8846 type = struct complex
8847 (@value{GDBP}) ptype v
8848 type = struct complex @{
8856 As with @code{whatis}, using @code{ptype} without an argument refers to
8857 the type of @code{$}, the last value in the value history.
8860 @item info types @var{regexp}
8862 Print a brief description of all types whose names match @var{regexp}
8863 (or all types in your program, if you supply no argument). Each
8864 complete typename is matched as though it were a complete line; thus,
8865 @samp{i type value} gives information on all types in your program whose
8866 names include the string @code{value}, but @samp{i type ^value$} gives
8867 information only on types whose complete name is @code{value}.
8869 This command differs from @code{ptype} in two ways: first, like
8870 @code{whatis}, it does not print a detailed description; second, it
8871 lists all source files where a type is defined.
8874 @cindex local variables
8875 @item info scope @var{addr}
8876 List all the variables local to a particular scope. This command
8877 accepts a location---a function name, a source line, or an address
8878 preceded by a @samp{*}, and prints all the variables local to the
8879 scope defined by that location. For example:
8882 (@value{GDBP}) @b{info scope command_line_handler}
8883 Scope for command_line_handler:
8884 Symbol rl is an argument at stack/frame offset 8, length 4.
8885 Symbol linebuffer is in static storage at address 0x150a18, length 4.
8886 Symbol linelength is in static storage at address 0x150a1c, length 4.
8887 Symbol p is a local variable in register $esi, length 4.
8888 Symbol p1 is a local variable in register $ebx, length 4.
8889 Symbol nline is a local variable in register $edx, length 4.
8890 Symbol repeat is a local variable at frame offset -8, length 4.
8894 This command is especially useful for determining what data to collect
8895 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
8900 Show information about the current source file---that is, the source file for
8901 the function containing the current point of execution:
8904 the name of the source file, and the directory containing it,
8906 the directory it was compiled in,
8908 its length, in lines,
8910 which programming language it is written in,
8912 whether the executable includes debugging information for that file, and
8913 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
8915 whether the debugging information includes information about
8916 preprocessor macros.
8920 @kindex info sources
8922 Print the names of all source files in your program for which there is
8923 debugging information, organized into two lists: files whose symbols
8924 have already been read, and files whose symbols will be read when needed.
8926 @kindex info functions
8927 @item info functions
8928 Print the names and data types of all defined functions.
8930 @item info functions @var{regexp}
8931 Print the names and data types of all defined functions
8932 whose names contain a match for regular expression @var{regexp}.
8933 Thus, @samp{info fun step} finds all functions whose names
8934 include @code{step}; @samp{info fun ^step} finds those whose names
8935 start with @code{step}. If a function name contains characters
8936 that conflict with the regular expression language (eg.
8937 @samp{operator*()}), they may be quoted with a backslash.
8939 @kindex info variables
8940 @item info variables
8941 Print the names and data types of all variables that are declared
8942 outside of functions (i.e.@: excluding local variables).
8944 @item info variables @var{regexp}
8945 Print the names and data types of all variables (except for local
8946 variables) whose names contain a match for regular expression
8950 This was never implemented.
8951 @kindex info methods
8953 @itemx info methods @var{regexp}
8954 The @code{info methods} command permits the user to examine all defined
8955 methods within C@t{++} program, or (with the @var{regexp} argument) a
8956 specific set of methods found in the various C@t{++} classes. Many
8957 C@t{++} classes provide a large number of methods. Thus, the output
8958 from the @code{ptype} command can be overwhelming and hard to use. The
8959 @code{info-methods} command filters the methods, printing only those
8960 which match the regular-expression @var{regexp}.
8963 @cindex reloading symbols
8964 Some systems allow individual object files that make up your program to
8965 be replaced without stopping and restarting your program. For example,
8966 in VxWorks you can simply recompile a defective object file and keep on
8967 running. If you are running on one of these systems, you can allow
8968 @value{GDBN} to reload the symbols for automatically relinked modules:
8971 @kindex set symbol-reloading
8972 @item set symbol-reloading on
8973 Replace symbol definitions for the corresponding source file when an
8974 object file with a particular name is seen again.
8976 @item set symbol-reloading off
8977 Do not replace symbol definitions when encountering object files of the
8978 same name more than once. This is the default state; if you are not
8979 running on a system that permits automatic relinking of modules, you
8980 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
8981 may discard symbols when linking large programs, that may contain
8982 several modules (from different directories or libraries) with the same
8985 @kindex show symbol-reloading
8986 @item show symbol-reloading
8987 Show the current @code{on} or @code{off} setting.
8990 @kindex set opaque-type-resolution
8991 @item set opaque-type-resolution on
8992 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
8993 declared as a pointer to a @code{struct}, @code{class}, or
8994 @code{union}---for example, @code{struct MyType *}---that is used in one
8995 source file although the full declaration of @code{struct MyType} is in
8996 another source file. The default is on.
8998 A change in the setting of this subcommand will not take effect until
8999 the next time symbols for a file are loaded.
9001 @item set opaque-type-resolution off
9002 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9003 is printed as follows:
9005 @{<no data fields>@}
9008 @kindex show opaque-type-resolution
9009 @item show opaque-type-resolution
9010 Show whether opaque types are resolved or not.
9012 @kindex maint print symbols
9014 @kindex maint print psymbols
9015 @cindex partial symbol dump
9016 @item maint print symbols @var{filename}
9017 @itemx maint print psymbols @var{filename}
9018 @itemx maint print msymbols @var{filename}
9019 Write a dump of debugging symbol data into the file @var{filename}.
9020 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9021 symbols with debugging data are included. If you use @samp{maint print
9022 symbols}, @value{GDBN} includes all the symbols for which it has already
9023 collected full details: that is, @var{filename} reflects symbols for
9024 only those files whose symbols @value{GDBN} has read. You can use the
9025 command @code{info sources} to find out which files these are. If you
9026 use @samp{maint print psymbols} instead, the dump shows information about
9027 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9028 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9029 @samp{maint print msymbols} dumps just the minimal symbol information
9030 required for each object file from which @value{GDBN} has read some symbols.
9031 @xref{Files, ,Commands to specify files}, for a discussion of how
9032 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9034 @kindex maint list symtabs
9035 @kindex maint list psymtabs
9036 @cindex listing @value{GDBN}'s internal symbol tables
9037 @cindex symbol tables, listing @value{GDBN}'s internal
9038 @cindex full symbol tables, listing @value{GDBN}'s internal
9039 @cindex partial symbol tables, listing @value{GDBN}'s internal
9040 @item maint list symtabs @r{[} @var{regexp} @r{]}
9041 @itemx maint list psymtabs @r{[} @var{regexp} @r{]}
9043 List the @code{struct symtab} or @code{struct partial_symtab}
9044 structures whose names match @var{regexp}. If @var{regexp} is not
9045 given, list them all. The output includes expressions which you can
9046 copy into a @value{GDBN} debugging this one to examine a particular
9047 structure in more detail. For example:
9050 (@value{GDBP}) maint list psymtabs dwarf2read
9051 @{ objfile /home/gnu/build/gdb/gdb
9052 ((struct objfile *) 0x82e69d0)
9053 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
9054 ((struct partial_symtab *) 0x8474b10)
9057 text addresses 0x814d3c8 -- 0x8158074
9058 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
9059 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
9063 (@value{GDBP}) maint list symtabs
9067 We see that there is one partial symbol table whose filename contains
9068 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
9069 and we see that @value{GDBN} has not read in any symtabs yet at all.
9070 If we set a breakpoint on a function, that will cause @value{GDBN} to
9071 read the symtab for the compilation unit containing that function:
9074 (@value{GDBP}) break dwarf2_psymtab_to_symtab
9075 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
9077 (@value{GDBP}) maint list symtabs
9078 @{ objfile /home/gnu/build/gdb/gdb
9079 ((struct objfile *) 0x82e69d0)
9080 @{ symtab /home/gnu/src/gdb/dwarf2read.c
9081 ((struct symtab *) 0x86c1f38)
9084 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
9094 @chapter Altering Execution
9096 Once you think you have found an error in your program, you might want to
9097 find out for certain whether correcting the apparent error would lead to
9098 correct results in the rest of the run. You can find the answer by
9099 experiment, using the @value{GDBN} features for altering execution of the
9102 For example, you can store new values into variables or memory
9103 locations, give your program a signal, restart it at a different
9104 address, or even return prematurely from a function.
9107 * Assignment:: Assignment to variables
9108 * Jumping:: Continuing at a different address
9109 * Signaling:: Giving your program a signal
9110 * Returning:: Returning from a function
9111 * Calling:: Calling your program's functions
9112 * Patching:: Patching your program
9116 @section Assignment to variables
9119 @cindex setting variables
9120 To alter the value of a variable, evaluate an assignment expression.
9121 @xref{Expressions, ,Expressions}. For example,
9128 stores the value 4 into the variable @code{x}, and then prints the
9129 value of the assignment expression (which is 4).
9130 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9131 information on operators in supported languages.
9133 @kindex set variable
9134 @cindex variables, setting
9135 If you are not interested in seeing the value of the assignment, use the
9136 @code{set} command instead of the @code{print} command. @code{set} is
9137 really the same as @code{print} except that the expression's value is
9138 not printed and is not put in the value history (@pxref{Value History,
9139 ,Value history}). The expression is evaluated only for its effects.
9141 If the beginning of the argument string of the @code{set} command
9142 appears identical to a @code{set} subcommand, use the @code{set
9143 variable} command instead of just @code{set}. This command is identical
9144 to @code{set} except for its lack of subcommands. For example, if your
9145 program has a variable @code{width}, you get an error if you try to set
9146 a new value with just @samp{set width=13}, because @value{GDBN} has the
9147 command @code{set width}:
9150 (@value{GDBP}) whatis width
9152 (@value{GDBP}) p width
9154 (@value{GDBP}) set width=47
9155 Invalid syntax in expression.
9159 The invalid expression, of course, is @samp{=47}. In
9160 order to actually set the program's variable @code{width}, use
9163 (@value{GDBP}) set var width=47
9166 Because the @code{set} command has many subcommands that can conflict
9167 with the names of program variables, it is a good idea to use the
9168 @code{set variable} command instead of just @code{set}. For example, if
9169 your program has a variable @code{g}, you run into problems if you try
9170 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9171 the command @code{set gnutarget}, abbreviated @code{set g}:
9175 (@value{GDBP}) whatis g
9179 (@value{GDBP}) set g=4
9183 The program being debugged has been started already.
9184 Start it from the beginning? (y or n) y
9185 Starting program: /home/smith/cc_progs/a.out
9186 "/home/smith/cc_progs/a.out": can't open to read symbols:
9188 (@value{GDBP}) show g
9189 The current BFD target is "=4".
9194 The program variable @code{g} did not change, and you silently set the
9195 @code{gnutarget} to an invalid value. In order to set the variable
9199 (@value{GDBP}) set var g=4
9202 @value{GDBN} allows more implicit conversions in assignments than C; you can
9203 freely store an integer value into a pointer variable or vice versa,
9204 and you can convert any structure to any other structure that is the
9205 same length or shorter.
9206 @comment FIXME: how do structs align/pad in these conversions?
9207 @comment /doc@cygnus.com 18dec1990
9209 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9210 construct to generate a value of specified type at a specified address
9211 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9212 to memory location @code{0x83040} as an integer (which implies a certain size
9213 and representation in memory), and
9216 set @{int@}0x83040 = 4
9220 stores the value 4 into that memory location.
9223 @section Continuing at a different address
9225 Ordinarily, when you continue your program, you do so at the place where
9226 it stopped, with the @code{continue} command. You can instead continue at
9227 an address of your own choosing, with the following commands:
9231 @item jump @var{linespec}
9232 Resume execution at line @var{linespec}. Execution stops again
9233 immediately if there is a breakpoint there. @xref{List, ,Printing
9234 source lines}, for a description of the different forms of
9235 @var{linespec}. It is common practice to use the @code{tbreak} command
9236 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9239 The @code{jump} command does not change the current stack frame, or
9240 the stack pointer, or the contents of any memory location or any
9241 register other than the program counter. If line @var{linespec} is in
9242 a different function from the one currently executing, the results may
9243 be bizarre if the two functions expect different patterns of arguments or
9244 of local variables. For this reason, the @code{jump} command requests
9245 confirmation if the specified line is not in the function currently
9246 executing. However, even bizarre results are predictable if you are
9247 well acquainted with the machine-language code of your program.
9249 @item jump *@var{address}
9250 Resume execution at the instruction at address @var{address}.
9253 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9254 On many systems, you can get much the same effect as the @code{jump}
9255 command by storing a new value into the register @code{$pc}. The
9256 difference is that this does not start your program running; it only
9257 changes the address of where it @emph{will} run when you continue. For
9265 makes the next @code{continue} command or stepping command execute at
9266 address @code{0x485}, rather than at the address where your program stopped.
9267 @xref{Continuing and Stepping, ,Continuing and stepping}.
9269 The most common occasion to use the @code{jump} command is to back
9270 up---perhaps with more breakpoints set---over a portion of a program
9271 that has already executed, in order to examine its execution in more
9276 @section Giving your program a signal
9280 @item signal @var{signal}
9281 Resume execution where your program stopped, but immediately give it the
9282 signal @var{signal}. @var{signal} can be the name or the number of a
9283 signal. For example, on many systems @code{signal 2} and @code{signal
9284 SIGINT} are both ways of sending an interrupt signal.
9286 Alternatively, if @var{signal} is zero, continue execution without
9287 giving a signal. This is useful when your program stopped on account of
9288 a signal and would ordinary see the signal when resumed with the
9289 @code{continue} command; @samp{signal 0} causes it to resume without a
9292 @code{signal} does not repeat when you press @key{RET} a second time
9293 after executing the command.
9297 Invoking the @code{signal} command is not the same as invoking the
9298 @code{kill} utility from the shell. Sending a signal with @code{kill}
9299 causes @value{GDBN} to decide what to do with the signal depending on
9300 the signal handling tables (@pxref{Signals}). The @code{signal} command
9301 passes the signal directly to your program.
9305 @section Returning from a function
9308 @cindex returning from a function
9311 @itemx return @var{expression}
9312 You can cancel execution of a function call with the @code{return}
9313 command. If you give an
9314 @var{expression} argument, its value is used as the function's return
9318 When you use @code{return}, @value{GDBN} discards the selected stack frame
9319 (and all frames within it). You can think of this as making the
9320 discarded frame return prematurely. If you wish to specify a value to
9321 be returned, give that value as the argument to @code{return}.
9323 This pops the selected stack frame (@pxref{Selection, ,Selecting a
9324 frame}), and any other frames inside of it, leaving its caller as the
9325 innermost remaining frame. That frame becomes selected. The
9326 specified value is stored in the registers used for returning values
9329 The @code{return} command does not resume execution; it leaves the
9330 program stopped in the state that would exist if the function had just
9331 returned. In contrast, the @code{finish} command (@pxref{Continuing
9332 and Stepping, ,Continuing and stepping}) resumes execution until the
9333 selected stack frame returns naturally.
9336 @section Calling program functions
9338 @cindex calling functions
9341 @item call @var{expr}
9342 Evaluate the expression @var{expr} without displaying @code{void}
9346 You can use this variant of the @code{print} command if you want to
9347 execute a function from your program, but without cluttering the output
9348 with @code{void} returned values. If the result is not void, it
9349 is printed and saved in the value history.
9352 @section Patching programs
9354 @cindex patching binaries
9355 @cindex writing into executables
9356 @cindex writing into corefiles
9358 By default, @value{GDBN} opens the file containing your program's
9359 executable code (or the corefile) read-only. This prevents accidental
9360 alterations to machine code; but it also prevents you from intentionally
9361 patching your program's binary.
9363 If you'd like to be able to patch the binary, you can specify that
9364 explicitly with the @code{set write} command. For example, you might
9365 want to turn on internal debugging flags, or even to make emergency
9371 @itemx set write off
9372 If you specify @samp{set write on}, @value{GDBN} opens executable and
9373 core files for both reading and writing; if you specify @samp{set write
9374 off} (the default), @value{GDBN} opens them read-only.
9376 If you have already loaded a file, you must load it again (using the
9377 @code{exec-file} or @code{core-file} command) after changing @code{set
9378 write}, for your new setting to take effect.
9382 Display whether executable files and core files are opened for writing
9387 @chapter @value{GDBN} Files
9389 @value{GDBN} needs to know the file name of the program to be debugged,
9390 both in order to read its symbol table and in order to start your
9391 program. To debug a core dump of a previous run, you must also tell
9392 @value{GDBN} the name of the core dump file.
9395 * Files:: Commands to specify files
9396 * Separate Debug Files:: Debugging information in separate files
9397 * Symbol Errors:: Errors reading symbol files
9401 @section Commands to specify files
9403 @cindex symbol table
9404 @cindex core dump file
9406 You may want to specify executable and core dump file names. The usual
9407 way to do this is at start-up time, using the arguments to
9408 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
9409 Out of @value{GDBN}}).
9411 Occasionally it is necessary to change to a different file during a
9412 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
9413 a file you want to use. In these situations the @value{GDBN} commands
9414 to specify new files are useful.
9417 @cindex executable file
9419 @item file @var{filename}
9420 Use @var{filename} as the program to be debugged. It is read for its
9421 symbols and for the contents of pure memory. It is also the program
9422 executed when you use the @code{run} command. If you do not specify a
9423 directory and the file is not found in the @value{GDBN} working directory,
9424 @value{GDBN} uses the environment variable @code{PATH} as a list of
9425 directories to search, just as the shell does when looking for a program
9426 to run. You can change the value of this variable, for both @value{GDBN}
9427 and your program, using the @code{path} command.
9429 On systems with memory-mapped files, an auxiliary file named
9430 @file{@var{filename}.syms} may hold symbol table information for
9431 @var{filename}. If so, @value{GDBN} maps in the symbol table from
9432 @file{@var{filename}.syms}, starting up more quickly. See the
9433 descriptions of the file options @samp{-mapped} and @samp{-readnow}
9434 (available on the command line, and with the commands @code{file},
9435 @code{symbol-file}, or @code{add-symbol-file}, described below),
9436 for more information.
9439 @code{file} with no argument makes @value{GDBN} discard any information it
9440 has on both executable file and the symbol table.
9443 @item exec-file @r{[} @var{filename} @r{]}
9444 Specify that the program to be run (but not the symbol table) is found
9445 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
9446 if necessary to locate your program. Omitting @var{filename} means to
9447 discard information on the executable file.
9450 @item symbol-file @r{[} @var{filename} @r{]}
9451 Read symbol table information from file @var{filename}. @code{PATH} is
9452 searched when necessary. Use the @code{file} command to get both symbol
9453 table and program to run from the same file.
9455 @code{symbol-file} with no argument clears out @value{GDBN} information on your
9456 program's symbol table.
9458 The @code{symbol-file} command causes @value{GDBN} to forget the contents
9459 of its convenience variables, the value history, and all breakpoints and
9460 auto-display expressions. This is because they may contain pointers to
9461 the internal data recording symbols and data types, which are part of
9462 the old symbol table data being discarded inside @value{GDBN}.
9464 @code{symbol-file} does not repeat if you press @key{RET} again after
9467 When @value{GDBN} is configured for a particular environment, it
9468 understands debugging information in whatever format is the standard
9469 generated for that environment; you may use either a @sc{gnu} compiler, or
9470 other compilers that adhere to the local conventions.
9471 Best results are usually obtained from @sc{gnu} compilers; for example,
9472 using @code{@value{GCC}} you can generate debugging information for
9475 For most kinds of object files, with the exception of old SVR3 systems
9476 using COFF, the @code{symbol-file} command does not normally read the
9477 symbol table in full right away. Instead, it scans the symbol table
9478 quickly to find which source files and which symbols are present. The
9479 details are read later, one source file at a time, as they are needed.
9481 The purpose of this two-stage reading strategy is to make @value{GDBN}
9482 start up faster. For the most part, it is invisible except for
9483 occasional pauses while the symbol table details for a particular source
9484 file are being read. (The @code{set verbose} command can turn these
9485 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
9486 warnings and messages}.)
9488 We have not implemented the two-stage strategy for COFF yet. When the
9489 symbol table is stored in COFF format, @code{symbol-file} reads the
9490 symbol table data in full right away. Note that ``stabs-in-COFF''
9491 still does the two-stage strategy, since the debug info is actually
9495 @cindex reading symbols immediately
9496 @cindex symbols, reading immediately
9498 @cindex memory-mapped symbol file
9499 @cindex saving symbol table
9500 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9501 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9502 You can override the @value{GDBN} two-stage strategy for reading symbol
9503 tables by using the @samp{-readnow} option with any of the commands that
9504 load symbol table information, if you want to be sure @value{GDBN} has the
9505 entire symbol table available.
9507 If memory-mapped files are available on your system through the
9508 @code{mmap} system call, you can use another option, @samp{-mapped}, to
9509 cause @value{GDBN} to write the symbols for your program into a reusable
9510 file. Future @value{GDBN} debugging sessions map in symbol information
9511 from this auxiliary symbol file (if the program has not changed), rather
9512 than spending time reading the symbol table from the executable
9513 program. Using the @samp{-mapped} option has the same effect as
9514 starting @value{GDBN} with the @samp{-mapped} command-line option.
9516 You can use both options together, to make sure the auxiliary symbol
9517 file has all the symbol information for your program.
9519 The auxiliary symbol file for a program called @var{myprog} is called
9520 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
9521 than the corresponding executable), @value{GDBN} always attempts to use
9522 it when you debug @var{myprog}; no special options or commands are
9525 The @file{.syms} file is specific to the host machine where you run
9526 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
9527 symbol table. It cannot be shared across multiple host platforms.
9529 @c FIXME: for now no mention of directories, since this seems to be in
9530 @c flux. 13mar1992 status is that in theory GDB would look either in
9531 @c current dir or in same dir as myprog; but issues like competing
9532 @c GDB's, or clutter in system dirs, mean that in practice right now
9533 @c only current dir is used. FFish says maybe a special GDB hierarchy
9534 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
9539 @item core-file @r{[} @var{filename} @r{]}
9540 Specify the whereabouts of a core dump file to be used as the ``contents
9541 of memory''. Traditionally, core files contain only some parts of the
9542 address space of the process that generated them; @value{GDBN} can access the
9543 executable file itself for other parts.
9545 @code{core-file} with no argument specifies that no core file is
9548 Note that the core file is ignored when your program is actually running
9549 under @value{GDBN}. So, if you have been running your program and you
9550 wish to debug a core file instead, you must kill the subprocess in which
9551 the program is running. To do this, use the @code{kill} command
9552 (@pxref{Kill Process, ,Killing the child process}).
9554 @kindex add-symbol-file
9555 @cindex dynamic linking
9556 @item add-symbol-file @var{filename} @var{address}
9557 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9558 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
9559 The @code{add-symbol-file} command reads additional symbol table
9560 information from the file @var{filename}. You would use this command
9561 when @var{filename} has been dynamically loaded (by some other means)
9562 into the program that is running. @var{address} should be the memory
9563 address at which the file has been loaded; @value{GDBN} cannot figure
9564 this out for itself. You can additionally specify an arbitrary number
9565 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
9566 section name and base address for that section. You can specify any
9567 @var{address} as an expression.
9569 The symbol table of the file @var{filename} is added to the symbol table
9570 originally read with the @code{symbol-file} command. You can use the
9571 @code{add-symbol-file} command any number of times; the new symbol data
9572 thus read keeps adding to the old. To discard all old symbol data
9573 instead, use the @code{symbol-file} command without any arguments.
9575 @cindex relocatable object files, reading symbols from
9576 @cindex object files, relocatable, reading symbols from
9577 @cindex reading symbols from relocatable object files
9578 @cindex symbols, reading from relocatable object files
9579 @cindex @file{.o} files, reading symbols from
9580 Although @var{filename} is typically a shared library file, an
9581 executable file, or some other object file which has been fully
9582 relocated for loading into a process, you can also load symbolic
9583 information from relocatable @file{.o} files, as long as:
9587 the file's symbolic information refers only to linker symbols defined in
9588 that file, not to symbols defined by other object files,
9590 every section the file's symbolic information refers to has actually
9591 been loaded into the inferior, as it appears in the file, and
9593 you can determine the address at which every section was loaded, and
9594 provide these to the @code{add-symbol-file} command.
9598 Some embedded operating systems, like Sun Chorus and VxWorks, can load
9599 relocatable files into an already running program; such systems
9600 typically make the requirements above easy to meet. However, it's
9601 important to recognize that many native systems use complex link
9602 procedures (@code{.linkonce} section factoring and C++ constructor table
9603 assembly, for example) that make the requirements difficult to meet. In
9604 general, one cannot assume that using @code{add-symbol-file} to read a
9605 relocatable object file's symbolic information will have the same effect
9606 as linking the relocatable object file into the program in the normal
9609 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
9611 You can use the @samp{-mapped} and @samp{-readnow} options just as with
9612 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
9613 table information for @var{filename}.
9615 @kindex add-shared-symbol-file
9616 @item add-shared-symbol-file
9617 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
9618 operating system for the Motorola 88k. @value{GDBN} automatically looks for
9619 shared libraries, however if @value{GDBN} does not find yours, you can run
9620 @code{add-shared-symbol-file}. It takes no arguments.
9624 The @code{section} command changes the base address of section SECTION of
9625 the exec file to ADDR. This can be used if the exec file does not contain
9626 section addresses, (such as in the a.out format), or when the addresses
9627 specified in the file itself are wrong. Each section must be changed
9628 separately. The @code{info files} command, described below, lists all
9629 the sections and their addresses.
9635 @code{info files} and @code{info target} are synonymous; both print the
9636 current target (@pxref{Targets, ,Specifying a Debugging Target}),
9637 including the names of the executable and core dump files currently in
9638 use by @value{GDBN}, and the files from which symbols were loaded. The
9639 command @code{help target} lists all possible targets rather than
9642 @kindex maint info sections
9643 @item maint info sections
9644 Another command that can give you extra information about program sections
9645 is @code{maint info sections}. In addition to the section information
9646 displayed by @code{info files}, this command displays the flags and file
9647 offset of each section in the executable and core dump files. In addition,
9648 @code{maint info sections} provides the following command options (which
9649 may be arbitrarily combined):
9653 Display sections for all loaded object files, including shared libraries.
9654 @item @var{sections}
9655 Display info only for named @var{sections}.
9656 @item @var{section-flags}
9657 Display info only for sections for which @var{section-flags} are true.
9658 The section flags that @value{GDBN} currently knows about are:
9661 Section will have space allocated in the process when loaded.
9662 Set for all sections except those containing debug information.
9664 Section will be loaded from the file into the child process memory.
9665 Set for pre-initialized code and data, clear for @code{.bss} sections.
9667 Section needs to be relocated before loading.
9669 Section cannot be modified by the child process.
9671 Section contains executable code only.
9673 Section contains data only (no executable code).
9675 Section will reside in ROM.
9677 Section contains data for constructor/destructor lists.
9679 Section is not empty.
9681 An instruction to the linker to not output the section.
9682 @item COFF_SHARED_LIBRARY
9683 A notification to the linker that the section contains
9684 COFF shared library information.
9686 Section contains common symbols.
9689 @kindex set trust-readonly-sections
9690 @item set trust-readonly-sections on
9691 Tell @value{GDBN} that readonly sections in your object file
9692 really are read-only (i.e.@: that their contents will not change).
9693 In that case, @value{GDBN} can fetch values from these sections
9694 out of the object file, rather than from the target program.
9695 For some targets (notably embedded ones), this can be a significant
9696 enhancement to debugging performance.
9700 @item set trust-readonly-sections off
9701 Tell @value{GDBN} not to trust readonly sections. This means that
9702 the contents of the section might change while the program is running,
9703 and must therefore be fetched from the target when needed.
9706 All file-specifying commands allow both absolute and relative file names
9707 as arguments. @value{GDBN} always converts the file name to an absolute file
9708 name and remembers it that way.
9710 @cindex shared libraries
9711 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
9714 @value{GDBN} automatically loads symbol definitions from shared libraries
9715 when you use the @code{run} command, or when you examine a core file.
9716 (Before you issue the @code{run} command, @value{GDBN} does not understand
9717 references to a function in a shared library, however---unless you are
9718 debugging a core file).
9720 On HP-UX, if the program loads a library explicitly, @value{GDBN}
9721 automatically loads the symbols at the time of the @code{shl_load} call.
9723 @c FIXME: some @value{GDBN} release may permit some refs to undef
9724 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
9725 @c FIXME...lib; check this from time to time when updating manual
9727 There are times, however, when you may wish to not automatically load
9728 symbol definitions from shared libraries, such as when they are
9729 particularly large or there are many of them.
9731 To control the automatic loading of shared library symbols, use the
9735 @kindex set auto-solib-add
9736 @item set auto-solib-add @var{mode}
9737 If @var{mode} is @code{on}, symbols from all shared object libraries
9738 will be loaded automatically when the inferior begins execution, you
9739 attach to an independently started inferior, or when the dynamic linker
9740 informs @value{GDBN} that a new library has been loaded. If @var{mode}
9741 is @code{off}, symbols must be loaded manually, using the
9742 @code{sharedlibrary} command. The default value is @code{on}.
9744 @kindex show auto-solib-add
9745 @item show auto-solib-add
9746 Display the current autoloading mode.
9749 To explicitly load shared library symbols, use the @code{sharedlibrary}
9753 @kindex info sharedlibrary
9756 @itemx info sharedlibrary
9757 Print the names of the shared libraries which are currently loaded.
9759 @kindex sharedlibrary
9761 @item sharedlibrary @var{regex}
9762 @itemx share @var{regex}
9763 Load shared object library symbols for files matching a
9764 Unix regular expression.
9765 As with files loaded automatically, it only loads shared libraries
9766 required by your program for a core file or after typing @code{run}. If
9767 @var{regex} is omitted all shared libraries required by your program are
9771 On some systems, such as HP-UX systems, @value{GDBN} supports
9772 autoloading shared library symbols until a limiting threshold size is
9773 reached. This provides the benefit of allowing autoloading to remain on
9774 by default, but avoids autoloading excessively large shared libraries,
9775 up to a threshold that is initially set, but which you can modify if you
9778 Beyond that threshold, symbols from shared libraries must be explicitly
9779 loaded. To load these symbols, use the command @code{sharedlibrary
9780 @var{filename}}. The base address of the shared library is determined
9781 automatically by @value{GDBN} and need not be specified.
9783 To display or set the threshold, use the commands:
9786 @kindex set auto-solib-limit
9787 @item set auto-solib-limit @var{threshold}
9788 Set the autoloading size threshold, in an integral number of megabytes.
9789 If @var{threshold} is nonzero and shared library autoloading is enabled,
9790 symbols from all shared object libraries will be loaded until the total
9791 size of the loaded shared library symbols exceeds this threshold.
9792 Otherwise, symbols must be loaded manually, using the
9793 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
9796 @kindex show auto-solib-limit
9797 @item show auto-solib-limit
9798 Display the current autoloading size threshold, in megabytes.
9801 Shared libraries are also supported in many cross or remote debugging
9802 configurations. A copy of the target's libraries need to be present on the
9803 host system; they need to be the same as the target libraries, although the
9804 copies on the target can be stripped as long as the copies on the host are
9807 You need to tell @value{GDBN} where the target libraries are, so that it can
9808 load the correct copies---otherwise, it may try to load the host's libraries.
9809 @value{GDBN} has two variables to specify the search directories for target
9813 @kindex set solib-absolute-prefix
9814 @item set solib-absolute-prefix @var{path}
9815 If this variable is set, @var{path} will be used as a prefix for any
9816 absolute shared library paths; many runtime loaders store the absolute
9817 paths to the shared library in the target program's memory. If you use
9818 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
9819 out in the same way that they are on the target, with e.g.@: a
9820 @file{/usr/lib} hierarchy under @var{path}.
9822 You can set the default value of @samp{solib-absolute-prefix} by using the
9823 configure-time @samp{--with-sysroot} option.
9825 @kindex show solib-absolute-prefix
9826 @item show solib-absolute-prefix
9827 Display the current shared library prefix.
9829 @kindex set solib-search-path
9830 @item set solib-search-path @var{path}
9831 If this variable is set, @var{path} is a colon-separated list of directories
9832 to search for shared libraries. @samp{solib-search-path} is used after
9833 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
9834 the library is relative instead of absolute. If you want to use
9835 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
9836 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
9837 @value{GDBN} from finding your host's libraries.
9839 @kindex show solib-search-path
9840 @item show solib-search-path
9841 Display the current shared library search path.
9845 @node Separate Debug Files
9846 @section Debugging Information in Separate Files
9847 @cindex separate debugging information files
9848 @cindex debugging information in separate files
9849 @cindex @file{.debug} subdirectories
9850 @cindex debugging information directory, global
9851 @cindex global debugging information directory
9853 @value{GDBN} allows you to put a program's debugging information in a
9854 file separate from the executable itself, in a way that allows
9855 @value{GDBN} to find and load the debugging information automatically.
9856 Since debugging information can be very large --- sometimes larger
9857 than the executable code itself --- some systems distribute debugging
9858 information for their executables in separate files, which users can
9859 install only when they need to debug a problem.
9861 If an executable's debugging information has been extracted to a
9862 separate file, the executable should contain a @dfn{debug link} giving
9863 the name of the debugging information file (with no directory
9864 components), and a checksum of its contents. (The exact form of a
9865 debug link is described below.) If the full name of the directory
9866 containing the executable is @var{execdir}, and the executable has a
9867 debug link that specifies the name @var{debugfile}, then @value{GDBN}
9868 will automatically search for the debugging information file in three
9873 the directory containing the executable file (that is, it will look
9874 for a file named @file{@var{execdir}/@var{debugfile}},
9876 a subdirectory of that directory named @file{.debug} (that is, the
9877 file @file{@var{execdir}/.debug/@var{debugfile}}, and
9879 a subdirectory of the global debug file directory that includes the
9880 executable's full path, and the name from the link (that is, the file
9881 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
9882 @var{globaldebugdir} is the global debug file directory, and
9883 @var{execdir} has been turned into a relative path).
9886 @value{GDBN} checks under each of these names for a debugging
9887 information file whose checksum matches that given in the link, and
9888 reads the debugging information from the first one it finds.
9890 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
9891 which has a link containing the name @file{ls.debug}, and the global
9892 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
9893 for debug information in @file{/usr/bin/ls.debug},
9894 @file{/usr/bin/.debug/ls.debug}, and
9895 @file{/usr/lib/debug/usr/bin/ls.debug}.
9897 You can set the global debugging info directory's name, and view the
9898 name @value{GDBN} is currently using.
9902 @kindex set debug-file-directory
9903 @item set debug-file-directory @var{directory}
9904 Set the directory which @value{GDBN} searches for separate debugging
9905 information files to @var{directory}.
9907 @kindex show debug-file-directory
9908 @item show debug-file-directory
9909 Show the directory @value{GDBN} searches for separate debugging
9914 @cindex @code{.gnu_debuglink} sections
9916 A debug link is a special section of the executable file named
9917 @code{.gnu_debuglink}. The section must contain:
9921 A filename, with any leading directory components removed, followed by
9924 zero to three bytes of padding, as needed to reach the next four-byte
9925 boundary within the section, and
9927 a four-byte CRC checksum, stored in the same endianness used for the
9928 executable file itself. The checksum is computed on the debugging
9929 information file's full contents by the function given below, passing
9930 zero as the @var{crc} argument.
9933 Any executable file format can carry a debug link, as long as it can
9934 contain a section named @code{.gnu_debuglink} with the contents
9937 The debugging information file itself should be an ordinary
9938 executable, containing a full set of linker symbols, sections, and
9939 debugging information. The sections of the debugging information file
9940 should have the same names, addresses and sizes as the original file,
9941 but they need not contain any data --- much like a @code{.bss} section
9942 in an ordinary executable.
9944 As of December 2002, there is no standard GNU utility to produce
9945 separated executable / debugging information file pairs. Ulrich
9946 Drepper's @file{elfutils} package, starting with version 0.53,
9947 contains a version of the @code{strip} command such that the command
9948 @kbd{strip foo -f foo.debug} removes the debugging information from
9949 the executable file @file{foo}, places it in the file
9950 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
9952 Since there are many different ways to compute CRC's (different
9953 polynomials, reversals, byte ordering, etc.), the simplest way to
9954 describe the CRC used in @code{.gnu_debuglink} sections is to give the
9955 complete code for a function that computes it:
9957 @kindex @code{gnu_debuglink_crc32}
9960 gnu_debuglink_crc32 (unsigned long crc,
9961 unsigned char *buf, size_t len)
9963 static const unsigned long crc32_table[256] =
9965 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
9966 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
9967 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
9968 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
9969 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
9970 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
9971 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
9972 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
9973 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
9974 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
9975 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
9976 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
9977 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
9978 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
9979 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
9980 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
9981 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
9982 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
9983 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
9984 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
9985 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
9986 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
9987 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
9988 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
9989 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
9990 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
9991 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
9992 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
9993 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
9994 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
9995 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
9996 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
9997 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
9998 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
9999 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
10000 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
10001 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
10002 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
10003 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
10004 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
10005 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
10006 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
10007 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
10008 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
10009 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
10010 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
10011 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
10012 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
10013 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
10014 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
10015 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
10018 unsigned char *end;
10020 crc = ~crc & 0xffffffff;
10021 for (end = buf + len; buf < end; ++buf)
10022 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
10023 return ~crc & 0xffffffff;;
10028 @node Symbol Errors
10029 @section Errors reading symbol files
10031 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10032 such as symbol types it does not recognize, or known bugs in compiler
10033 output. By default, @value{GDBN} does not notify you of such problems, since
10034 they are relatively common and primarily of interest to people
10035 debugging compilers. If you are interested in seeing information
10036 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10037 only one message about each such type of problem, no matter how many
10038 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10039 to see how many times the problems occur, with the @code{set
10040 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10043 The messages currently printed, and their meanings, include:
10046 @item inner block not inside outer block in @var{symbol}
10048 The symbol information shows where symbol scopes begin and end
10049 (such as at the start of a function or a block of statements). This
10050 error indicates that an inner scope block is not fully contained
10051 in its outer scope blocks.
10053 @value{GDBN} circumvents the problem by treating the inner block as if it had
10054 the same scope as the outer block. In the error message, @var{symbol}
10055 may be shown as ``@code{(don't know)}'' if the outer block is not a
10058 @item block at @var{address} out of order
10060 The symbol information for symbol scope blocks should occur in
10061 order of increasing addresses. This error indicates that it does not
10064 @value{GDBN} does not circumvent this problem, and has trouble
10065 locating symbols in the source file whose symbols it is reading. (You
10066 can often determine what source file is affected by specifying
10067 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10070 @item bad block start address patched
10072 The symbol information for a symbol scope block has a start address
10073 smaller than the address of the preceding source line. This is known
10074 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10076 @value{GDBN} circumvents the problem by treating the symbol scope block as
10077 starting on the previous source line.
10079 @item bad string table offset in symbol @var{n}
10082 Symbol number @var{n} contains a pointer into the string table which is
10083 larger than the size of the string table.
10085 @value{GDBN} circumvents the problem by considering the symbol to have the
10086 name @code{foo}, which may cause other problems if many symbols end up
10089 @item unknown symbol type @code{0x@var{nn}}
10091 The symbol information contains new data types that @value{GDBN} does
10092 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10093 uncomprehended information, in hexadecimal.
10095 @value{GDBN} circumvents the error by ignoring this symbol information.
10096 This usually allows you to debug your program, though certain symbols
10097 are not accessible. If you encounter such a problem and feel like
10098 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10099 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10100 and examine @code{*bufp} to see the symbol.
10102 @item stub type has NULL name
10104 @value{GDBN} could not find the full definition for a struct or class.
10106 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10107 The symbol information for a C@t{++} member function is missing some
10108 information that recent versions of the compiler should have output for
10111 @item info mismatch between compiler and debugger
10113 @value{GDBN} could not parse a type specification output by the compiler.
10118 @chapter Specifying a Debugging Target
10120 @cindex debugging target
10123 A @dfn{target} is the execution environment occupied by your program.
10125 Often, @value{GDBN} runs in the same host environment as your program;
10126 in that case, the debugging target is specified as a side effect when
10127 you use the @code{file} or @code{core} commands. When you need more
10128 flexibility---for example, running @value{GDBN} on a physically separate
10129 host, or controlling a standalone system over a serial port or a
10130 realtime system over a TCP/IP connection---you can use the @code{target}
10131 command to specify one of the target types configured for @value{GDBN}
10132 (@pxref{Target Commands, ,Commands for managing targets}).
10135 * Active Targets:: Active targets
10136 * Target Commands:: Commands for managing targets
10137 * Byte Order:: Choosing target byte order
10138 * Remote:: Remote debugging
10139 * KOD:: Kernel Object Display
10143 @node Active Targets
10144 @section Active targets
10146 @cindex stacking targets
10147 @cindex active targets
10148 @cindex multiple targets
10150 There are three classes of targets: processes, core files, and
10151 executable files. @value{GDBN} can work concurrently on up to three
10152 active targets, one in each class. This allows you to (for example)
10153 start a process and inspect its activity without abandoning your work on
10156 For example, if you execute @samp{gdb a.out}, then the executable file
10157 @code{a.out} is the only active target. If you designate a core file as
10158 well---presumably from a prior run that crashed and coredumped---then
10159 @value{GDBN} has two active targets and uses them in tandem, looking
10160 first in the corefile target, then in the executable file, to satisfy
10161 requests for memory addresses. (Typically, these two classes of target
10162 are complementary, since core files contain only a program's
10163 read-write memory---variables and so on---plus machine status, while
10164 executable files contain only the program text and initialized data.)
10166 When you type @code{run}, your executable file becomes an active process
10167 target as well. When a process target is active, all @value{GDBN}
10168 commands requesting memory addresses refer to that target; addresses in
10169 an active core file or executable file target are obscured while the
10170 process target is active.
10172 Use the @code{core-file} and @code{exec-file} commands to select a new
10173 core file or executable target (@pxref{Files, ,Commands to specify
10174 files}). To specify as a target a process that is already running, use
10175 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10178 @node Target Commands
10179 @section Commands for managing targets
10182 @item target @var{type} @var{parameters}
10183 Connects the @value{GDBN} host environment to a target machine or
10184 process. A target is typically a protocol for talking to debugging
10185 facilities. You use the argument @var{type} to specify the type or
10186 protocol of the target machine.
10188 Further @var{parameters} are interpreted by the target protocol, but
10189 typically include things like device names or host names to connect
10190 with, process numbers, and baud rates.
10192 The @code{target} command does not repeat if you press @key{RET} again
10193 after executing the command.
10195 @kindex help target
10197 Displays the names of all targets available. To display targets
10198 currently selected, use either @code{info target} or @code{info files}
10199 (@pxref{Files, ,Commands to specify files}).
10201 @item help target @var{name}
10202 Describe a particular target, including any parameters necessary to
10205 @kindex set gnutarget
10206 @item set gnutarget @var{args}
10207 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10208 knows whether it is reading an @dfn{executable},
10209 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10210 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10211 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10214 @emph{Warning:} To specify a file format with @code{set gnutarget},
10215 you must know the actual BFD name.
10219 @xref{Files, , Commands to specify files}.
10221 @kindex show gnutarget
10222 @item show gnutarget
10223 Use the @code{show gnutarget} command to display what file format
10224 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10225 @value{GDBN} will determine the file format for each file automatically,
10226 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10229 Here are some common targets (available, or not, depending on the GDB
10233 @kindex target exec
10234 @item target exec @var{program}
10235 An executable file. @samp{target exec @var{program}} is the same as
10236 @samp{exec-file @var{program}}.
10238 @kindex target core
10239 @item target core @var{filename}
10240 A core dump file. @samp{target core @var{filename}} is the same as
10241 @samp{core-file @var{filename}}.
10243 @kindex target remote
10244 @item target remote @var{dev}
10245 Remote serial target in GDB-specific protocol. The argument @var{dev}
10246 specifies what serial device to use for the connection (e.g.
10247 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
10248 supports the @code{load} command. This is only useful if you have
10249 some other way of getting the stub to the target system, and you can put
10250 it somewhere in memory where it won't get clobbered by the download.
10254 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
10262 works; however, you cannot assume that a specific memory map, device
10263 drivers, or even basic I/O is available, although some simulators do
10264 provide these. For info about any processor-specific simulator details,
10265 see the appropriate section in @ref{Embedded Processors, ,Embedded
10270 Some configurations may include these targets as well:
10274 @kindex target nrom
10275 @item target nrom @var{dev}
10276 NetROM ROM emulator. This target only supports downloading.
10280 Different targets are available on different configurations of @value{GDBN};
10281 your configuration may have more or fewer targets.
10283 Many remote targets require you to download the executable's code
10284 once you've successfully established a connection.
10288 @kindex load @var{filename}
10289 @item load @var{filename}
10290 Depending on what remote debugging facilities are configured into
10291 @value{GDBN}, the @code{load} command may be available. Where it exists, it
10292 is meant to make @var{filename} (an executable) available for debugging
10293 on the remote system---by downloading, or dynamic linking, for example.
10294 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
10295 the @code{add-symbol-file} command.
10297 If your @value{GDBN} does not have a @code{load} command, attempting to
10298 execute it gets the error message ``@code{You can't do that when your
10299 target is @dots{}}''
10301 The file is loaded at whatever address is specified in the executable.
10302 For some object file formats, you can specify the load address when you
10303 link the program; for other formats, like a.out, the object file format
10304 specifies a fixed address.
10305 @c FIXME! This would be a good place for an xref to the GNU linker doc.
10307 @code{load} does not repeat if you press @key{RET} again after using it.
10311 @section Choosing target byte order
10313 @cindex choosing target byte order
10314 @cindex target byte order
10316 Some types of processors, such as the MIPS, PowerPC, and Hitachi SH,
10317 offer the ability to run either big-endian or little-endian byte
10318 orders. Usually the executable or symbol will include a bit to
10319 designate the endian-ness, and you will not need to worry about
10320 which to use. However, you may still find it useful to adjust
10321 @value{GDBN}'s idea of processor endian-ness manually.
10324 @kindex set endian big
10325 @item set endian big
10326 Instruct @value{GDBN} to assume the target is big-endian.
10328 @kindex set endian little
10329 @item set endian little
10330 Instruct @value{GDBN} to assume the target is little-endian.
10332 @kindex set endian auto
10333 @item set endian auto
10334 Instruct @value{GDBN} to use the byte order associated with the
10338 Display @value{GDBN}'s current idea of the target byte order.
10342 Note that these commands merely adjust interpretation of symbolic
10343 data on the host, and that they have absolutely no effect on the
10347 @section Remote debugging
10348 @cindex remote debugging
10350 If you are trying to debug a program running on a machine that cannot run
10351 @value{GDBN} in the usual way, it is often useful to use remote debugging.
10352 For example, you might use remote debugging on an operating system kernel,
10353 or on a small system which does not have a general purpose operating system
10354 powerful enough to run a full-featured debugger.
10356 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
10357 to make this work with particular debugging targets. In addition,
10358 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
10359 but not specific to any particular target system) which you can use if you
10360 write the remote stubs---the code that runs on the remote system to
10361 communicate with @value{GDBN}.
10363 Other remote targets may be available in your
10364 configuration of @value{GDBN}; use @code{help target} to list them.
10367 @section Kernel Object Display
10369 @cindex kernel object display
10370 @cindex kernel object
10373 Some targets support kernel object display. Using this facility,
10374 @value{GDBN} communicates specially with the underlying operating system
10375 and can display information about operating system-level objects such as
10376 mutexes and other synchronization objects. Exactly which objects can be
10377 displayed is determined on a per-OS basis.
10379 Use the @code{set os} command to set the operating system. This tells
10380 @value{GDBN} which kernel object display module to initialize:
10383 (@value{GDBP}) set os cisco
10386 If @code{set os} succeeds, @value{GDBN} will display some information
10387 about the operating system, and will create a new @code{info} command
10388 which can be used to query the target. The @code{info} command is named
10389 after the operating system:
10392 (@value{GDBP}) info cisco
10393 List of Cisco Kernel Objects
10395 any Any and all objects
10398 Further subcommands can be used to query about particular objects known
10401 There is currently no way to determine whether a given operating system
10402 is supported other than to try it.
10405 @node Remote Debugging
10406 @chapter Debugging remote programs
10409 * Server:: Using the gdbserver program
10410 * NetWare:: Using the gdbserve.nlm program
10411 * Remote configuration:: Remote configuration
10412 * remote stub:: Implementing a remote stub
10416 @section Using the @code{gdbserver} program
10419 @cindex remote connection without stubs
10420 @code{gdbserver} is a control program for Unix-like systems, which
10421 allows you to connect your program with a remote @value{GDBN} via
10422 @code{target remote}---but without linking in the usual debugging stub.
10424 @code{gdbserver} is not a complete replacement for the debugging stubs,
10425 because it requires essentially the same operating-system facilities
10426 that @value{GDBN} itself does. In fact, a system that can run
10427 @code{gdbserver} to connect to a remote @value{GDBN} could also run
10428 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
10429 because it is a much smaller program than @value{GDBN} itself. It is
10430 also easier to port than all of @value{GDBN}, so you may be able to get
10431 started more quickly on a new system by using @code{gdbserver}.
10432 Finally, if you develop code for real-time systems, you may find that
10433 the tradeoffs involved in real-time operation make it more convenient to
10434 do as much development work as possible on another system, for example
10435 by cross-compiling. You can use @code{gdbserver} to make a similar
10436 choice for debugging.
10438 @value{GDBN} and @code{gdbserver} communicate via either a serial line
10439 or a TCP connection, using the standard @value{GDBN} remote serial
10443 @item On the target machine,
10444 you need to have a copy of the program you want to debug.
10445 @code{gdbserver} does not need your program's symbol table, so you can
10446 strip the program if necessary to save space. @value{GDBN} on the host
10447 system does all the symbol handling.
10449 To use the server, you must tell it how to communicate with @value{GDBN};
10450 the name of your program; and the arguments for your program. The usual
10454 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
10457 @var{comm} is either a device name (to use a serial line) or a TCP
10458 hostname and portnumber. For example, to debug Emacs with the argument
10459 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
10463 target> gdbserver /dev/com1 emacs foo.txt
10466 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
10469 To use a TCP connection instead of a serial line:
10472 target> gdbserver host:2345 emacs foo.txt
10475 The only difference from the previous example is the first argument,
10476 specifying that you are communicating with the host @value{GDBN} via
10477 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
10478 expect a TCP connection from machine @samp{host} to local TCP port 2345.
10479 (Currently, the @samp{host} part is ignored.) You can choose any number
10480 you want for the port number as long as it does not conflict with any
10481 TCP ports already in use on the target system (for example, @code{23} is
10482 reserved for @code{telnet}).@footnote{If you choose a port number that
10483 conflicts with another service, @code{gdbserver} prints an error message
10484 and exits.} You must use the same port number with the host @value{GDBN}
10485 @code{target remote} command.
10487 On some targets, @code{gdbserver} can also attach to running programs.
10488 This is accomplished via the @code{--attach} argument. The syntax is:
10491 target> gdbserver @var{comm} --attach @var{pid}
10494 @var{pid} is the process ID of a currently running process. It isn't necessary
10495 to point @code{gdbserver} at a binary for the running process.
10497 @item On the @value{GDBN} host machine,
10498 you need an unstripped copy of your program, since @value{GDBN} needs
10499 symbols and debugging information. Start up @value{GDBN} as usual,
10500 using the name of the local copy of your program as the first argument.
10501 (You may also need the @w{@samp{--baud}} option if the serial line is
10502 running at anything other than 9600@dmn{bps}.) After that, use @code{target
10503 remote} to establish communications with @code{gdbserver}. Its argument
10504 is either a device name (usually a serial device, like
10505 @file{/dev/ttyb}), or a TCP port descriptor in the form
10506 @code{@var{host}:@var{PORT}}. For example:
10509 (@value{GDBP}) target remote /dev/ttyb
10513 communicates with the server via serial line @file{/dev/ttyb}, and
10516 (@value{GDBP}) target remote the-target:2345
10520 communicates via a TCP connection to port 2345 on host @w{@file{the-target}}.
10521 For TCP connections, you must start up @code{gdbserver} prior to using
10522 the @code{target remote} command. Otherwise you may get an error whose
10523 text depends on the host system, but which usually looks something like
10524 @samp{Connection refused}.
10528 @section Using the @code{gdbserve.nlm} program
10530 @kindex gdbserve.nlm
10531 @code{gdbserve.nlm} is a control program for NetWare systems, which
10532 allows you to connect your program with a remote @value{GDBN} via
10533 @code{target remote}.
10535 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
10536 using the standard @value{GDBN} remote serial protocol.
10539 @item On the target machine,
10540 you need to have a copy of the program you want to debug.
10541 @code{gdbserve.nlm} does not need your program's symbol table, so you
10542 can strip the program if necessary to save space. @value{GDBN} on the
10543 host system does all the symbol handling.
10545 To use the server, you must tell it how to communicate with
10546 @value{GDBN}; the name of your program; and the arguments for your
10547 program. The syntax is:
10550 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
10551 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
10554 @var{board} and @var{port} specify the serial line; @var{baud} specifies
10555 the baud rate used by the connection. @var{port} and @var{node} default
10556 to 0, @var{baud} defaults to 9600@dmn{bps}.
10558 For example, to debug Emacs with the argument @samp{foo.txt}and
10559 communicate with @value{GDBN} over serial port number 2 or board 1
10560 using a 19200@dmn{bps} connection:
10563 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
10566 @item On the @value{GDBN} host machine,
10567 you need an unstripped copy of your program, since @value{GDBN} needs
10568 symbols and debugging information. Start up @value{GDBN} as usual,
10569 using the name of the local copy of your program as the first argument.
10570 (You may also need the @w{@samp{--baud}} option if the serial line is
10571 running at anything other than 9600@dmn{bps}. After that, use @code{target
10572 remote} to establish communications with @code{gdbserve.nlm}. Its
10573 argument is a device name (usually a serial device, like
10574 @file{/dev/ttyb}). For example:
10577 (@value{GDBP}) target remote /dev/ttyb
10581 communications with the server via serial line @file{/dev/ttyb}.
10584 @node Remote configuration
10585 @section Remote configuration
10587 The following configuration options are available when debugging remote
10591 @kindex set remote hardware-watchpoint-limit
10592 @kindex set remote hardware-breakpoint-limit
10593 @anchor{set remote hardware-watchpoint-limit}
10594 @anchor{set remote hardware-breakpoint-limit}
10595 @item set remote hardware-watchpoint-limit @var{limit}
10596 @itemx set remote hardware-breakpoint-limit @var{limit}
10597 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
10598 watchpoints. A limit of -1, the default, is treated as unlimited.
10602 @section Implementing a remote stub
10604 @cindex debugging stub, example
10605 @cindex remote stub, example
10606 @cindex stub example, remote debugging
10607 The stub files provided with @value{GDBN} implement the target side of the
10608 communication protocol, and the @value{GDBN} side is implemented in the
10609 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
10610 these subroutines to communicate, and ignore the details. (If you're
10611 implementing your own stub file, you can still ignore the details: start
10612 with one of the existing stub files. @file{sparc-stub.c} is the best
10613 organized, and therefore the easiest to read.)
10615 @cindex remote serial debugging, overview
10616 To debug a program running on another machine (the debugging
10617 @dfn{target} machine), you must first arrange for all the usual
10618 prerequisites for the program to run by itself. For example, for a C
10623 A startup routine to set up the C runtime environment; these usually
10624 have a name like @file{crt0}. The startup routine may be supplied by
10625 your hardware supplier, or you may have to write your own.
10628 A C subroutine library to support your program's
10629 subroutine calls, notably managing input and output.
10632 A way of getting your program to the other machine---for example, a
10633 download program. These are often supplied by the hardware
10634 manufacturer, but you may have to write your own from hardware
10638 The next step is to arrange for your program to use a serial port to
10639 communicate with the machine where @value{GDBN} is running (the @dfn{host}
10640 machine). In general terms, the scheme looks like this:
10644 @value{GDBN} already understands how to use this protocol; when everything
10645 else is set up, you can simply use the @samp{target remote} command
10646 (@pxref{Targets,,Specifying a Debugging Target}).
10648 @item On the target,
10649 you must link with your program a few special-purpose subroutines that
10650 implement the @value{GDBN} remote serial protocol. The file containing these
10651 subroutines is called a @dfn{debugging stub}.
10653 On certain remote targets, you can use an auxiliary program
10654 @code{gdbserver} instead of linking a stub into your program.
10655 @xref{Server,,Using the @code{gdbserver} program}, for details.
10658 The debugging stub is specific to the architecture of the remote
10659 machine; for example, use @file{sparc-stub.c} to debug programs on
10662 @cindex remote serial stub list
10663 These working remote stubs are distributed with @value{GDBN}:
10668 @cindex @file{i386-stub.c}
10671 For Intel 386 and compatible architectures.
10674 @cindex @file{m68k-stub.c}
10675 @cindex Motorola 680x0
10677 For Motorola 680x0 architectures.
10680 @cindex @file{sh-stub.c}
10683 For Hitachi SH architectures.
10686 @cindex @file{sparc-stub.c}
10688 For @sc{sparc} architectures.
10690 @item sparcl-stub.c
10691 @cindex @file{sparcl-stub.c}
10694 For Fujitsu @sc{sparclite} architectures.
10698 The @file{README} file in the @value{GDBN} distribution may list other
10699 recently added stubs.
10702 * Stub Contents:: What the stub can do for you
10703 * Bootstrapping:: What you must do for the stub
10704 * Debug Session:: Putting it all together
10707 @node Stub Contents
10708 @subsection What the stub can do for you
10710 @cindex remote serial stub
10711 The debugging stub for your architecture supplies these three
10715 @item set_debug_traps
10716 @kindex set_debug_traps
10717 @cindex remote serial stub, initialization
10718 This routine arranges for @code{handle_exception} to run when your
10719 program stops. You must call this subroutine explicitly near the
10720 beginning of your program.
10722 @item handle_exception
10723 @kindex handle_exception
10724 @cindex remote serial stub, main routine
10725 This is the central workhorse, but your program never calls it
10726 explicitly---the setup code arranges for @code{handle_exception} to
10727 run when a trap is triggered.
10729 @code{handle_exception} takes control when your program stops during
10730 execution (for example, on a breakpoint), and mediates communications
10731 with @value{GDBN} on the host machine. This is where the communications
10732 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
10733 representative on the target machine. It begins by sending summary
10734 information on the state of your program, then continues to execute,
10735 retrieving and transmitting any information @value{GDBN} needs, until you
10736 execute a @value{GDBN} command that makes your program resume; at that point,
10737 @code{handle_exception} returns control to your own code on the target
10741 @cindex @code{breakpoint} subroutine, remote
10742 Use this auxiliary subroutine to make your program contain a
10743 breakpoint. Depending on the particular situation, this may be the only
10744 way for @value{GDBN} to get control. For instance, if your target
10745 machine has some sort of interrupt button, you won't need to call this;
10746 pressing the interrupt button transfers control to
10747 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
10748 simply receiving characters on the serial port may also trigger a trap;
10749 again, in that situation, you don't need to call @code{breakpoint} from
10750 your own program---simply running @samp{target remote} from the host
10751 @value{GDBN} session gets control.
10753 Call @code{breakpoint} if none of these is true, or if you simply want
10754 to make certain your program stops at a predetermined point for the
10755 start of your debugging session.
10758 @node Bootstrapping
10759 @subsection What you must do for the stub
10761 @cindex remote stub, support routines
10762 The debugging stubs that come with @value{GDBN} are set up for a particular
10763 chip architecture, but they have no information about the rest of your
10764 debugging target machine.
10766 First of all you need to tell the stub how to communicate with the
10770 @item int getDebugChar()
10771 @kindex getDebugChar
10772 Write this subroutine to read a single character from the serial port.
10773 It may be identical to @code{getchar} for your target system; a
10774 different name is used to allow you to distinguish the two if you wish.
10776 @item void putDebugChar(int)
10777 @kindex putDebugChar
10778 Write this subroutine to write a single character to the serial port.
10779 It may be identical to @code{putchar} for your target system; a
10780 different name is used to allow you to distinguish the two if you wish.
10783 @cindex control C, and remote debugging
10784 @cindex interrupting remote targets
10785 If you want @value{GDBN} to be able to stop your program while it is
10786 running, you need to use an interrupt-driven serial driver, and arrange
10787 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
10788 character). That is the character which @value{GDBN} uses to tell the
10789 remote system to stop.
10791 Getting the debugging target to return the proper status to @value{GDBN}
10792 probably requires changes to the standard stub; one quick and dirty way
10793 is to just execute a breakpoint instruction (the ``dirty'' part is that
10794 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
10796 Other routines you need to supply are:
10799 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
10800 @kindex exceptionHandler
10801 Write this function to install @var{exception_address} in the exception
10802 handling tables. You need to do this because the stub does not have any
10803 way of knowing what the exception handling tables on your target system
10804 are like (for example, the processor's table might be in @sc{rom},
10805 containing entries which point to a table in @sc{ram}).
10806 @var{exception_number} is the exception number which should be changed;
10807 its meaning is architecture-dependent (for example, different numbers
10808 might represent divide by zero, misaligned access, etc). When this
10809 exception occurs, control should be transferred directly to
10810 @var{exception_address}, and the processor state (stack, registers,
10811 and so on) should be just as it is when a processor exception occurs. So if
10812 you want to use a jump instruction to reach @var{exception_address}, it
10813 should be a simple jump, not a jump to subroutine.
10815 For the 386, @var{exception_address} should be installed as an interrupt
10816 gate so that interrupts are masked while the handler runs. The gate
10817 should be at privilege level 0 (the most privileged level). The
10818 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
10819 help from @code{exceptionHandler}.
10821 @item void flush_i_cache()
10822 @kindex flush_i_cache
10823 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
10824 instruction cache, if any, on your target machine. If there is no
10825 instruction cache, this subroutine may be a no-op.
10827 On target machines that have instruction caches, @value{GDBN} requires this
10828 function to make certain that the state of your program is stable.
10832 You must also make sure this library routine is available:
10835 @item void *memset(void *, int, int)
10837 This is the standard library function @code{memset} that sets an area of
10838 memory to a known value. If you have one of the free versions of
10839 @code{libc.a}, @code{memset} can be found there; otherwise, you must
10840 either obtain it from your hardware manufacturer, or write your own.
10843 If you do not use the GNU C compiler, you may need other standard
10844 library subroutines as well; this varies from one stub to another,
10845 but in general the stubs are likely to use any of the common library
10846 subroutines which @code{@value{GCC}} generates as inline code.
10849 @node Debug Session
10850 @subsection Putting it all together
10852 @cindex remote serial debugging summary
10853 In summary, when your program is ready to debug, you must follow these
10858 Make sure you have defined the supporting low-level routines
10859 (@pxref{Bootstrapping,,What you must do for the stub}):
10861 @code{getDebugChar}, @code{putDebugChar},
10862 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
10866 Insert these lines near the top of your program:
10874 For the 680x0 stub only, you need to provide a variable called
10875 @code{exceptionHook}. Normally you just use:
10878 void (*exceptionHook)() = 0;
10882 but if before calling @code{set_debug_traps}, you set it to point to a
10883 function in your program, that function is called when
10884 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
10885 error). The function indicated by @code{exceptionHook} is called with
10886 one parameter: an @code{int} which is the exception number.
10889 Compile and link together: your program, the @value{GDBN} debugging stub for
10890 your target architecture, and the supporting subroutines.
10893 Make sure you have a serial connection between your target machine and
10894 the @value{GDBN} host, and identify the serial port on the host.
10897 @c The "remote" target now provides a `load' command, so we should
10898 @c document that. FIXME.
10899 Download your program to your target machine (or get it there by
10900 whatever means the manufacturer provides), and start it.
10903 To start remote debugging, run @value{GDBN} on the host machine, and specify
10904 as an executable file the program that is running in the remote machine.
10905 This tells @value{GDBN} how to find your program's symbols and the contents
10909 @cindex serial line, @code{target remote}
10910 Establish communication using the @code{target remote} command.
10911 Its argument specifies how to communicate with the target
10912 machine---either via a devicename attached to a direct serial line, or a
10913 TCP or UDP port (usually to a terminal server which in turn has a serial line
10914 to the target). For example, to use a serial line connected to the
10915 device named @file{/dev/ttyb}:
10918 target remote /dev/ttyb
10921 @cindex TCP port, @code{target remote}
10922 To use a TCP connection, use an argument of the form
10923 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
10924 For example, to connect to port 2828 on a
10925 terminal server named @code{manyfarms}:
10928 target remote manyfarms:2828
10931 If your remote target is actually running on the same machine as
10932 your debugger session (e.g.@: a simulator of your target running on
10933 the same host), you can omit the hostname. For example, to connect
10934 to port 1234 on your local machine:
10937 target remote :1234
10941 Note that the colon is still required here.
10943 @cindex UDP port, @code{target remote}
10944 To use a UDP connection, use an argument of the form
10945 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
10946 on a terminal server named @code{manyfarms}:
10949 target remote udp:manyfarms:2828
10952 When using a UDP connection for remote debugging, you should keep in mind
10953 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
10954 busy or unreliable networks, which will cause havoc with your debugging
10959 Now you can use all the usual commands to examine and change data and to
10960 step and continue the remote program.
10962 To resume the remote program and stop debugging it, use the @code{detach}
10965 @cindex interrupting remote programs
10966 @cindex remote programs, interrupting
10967 Whenever @value{GDBN} is waiting for the remote program, if you type the
10968 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
10969 program. This may or may not succeed, depending in part on the hardware
10970 and the serial drivers the remote system uses. If you type the
10971 interrupt character once again, @value{GDBN} displays this prompt:
10974 Interrupted while waiting for the program.
10975 Give up (and stop debugging it)? (y or n)
10978 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
10979 (If you decide you want to try again later, you can use @samp{target
10980 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
10981 goes back to waiting.
10984 @node Configurations
10985 @chapter Configuration-Specific Information
10987 While nearly all @value{GDBN} commands are available for all native and
10988 cross versions of the debugger, there are some exceptions. This chapter
10989 describes things that are only available in certain configurations.
10991 There are three major categories of configurations: native
10992 configurations, where the host and target are the same, embedded
10993 operating system configurations, which are usually the same for several
10994 different processor architectures, and bare embedded processors, which
10995 are quite different from each other.
11000 * Embedded Processors::
11007 This section describes details specific to particular native
11012 * SVR4 Process Information:: SVR4 process information
11013 * DJGPP Native:: Features specific to the DJGPP port
11014 * Cygwin Native:: Features specific to the Cygwin port
11020 On HP-UX systems, if you refer to a function or variable name that
11021 begins with a dollar sign, @value{GDBN} searches for a user or system
11022 name first, before it searches for a convenience variable.
11024 @node SVR4 Process Information
11025 @subsection SVR4 process information
11028 @cindex process image
11030 Many versions of SVR4 provide a facility called @samp{/proc} that can be
11031 used to examine the image of a running process using file-system
11032 subroutines. If @value{GDBN} is configured for an operating system with
11033 this facility, the command @code{info proc} is available to report on
11034 several kinds of information about the process running your program.
11035 @code{info proc} works only on SVR4 systems that include the
11036 @code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
11037 and Unixware, but not HP-UX or @sc{gnu}/Linux, for example.
11042 Summarize available information about the process.
11044 @kindex info proc mappings
11045 @item info proc mappings
11046 Report on the address ranges accessible in the program, with information
11047 on whether your program may read, write, or execute each range.
11049 @comment These sub-options of 'info proc' were not included when
11050 @comment procfs.c was re-written. Keep their descriptions around
11051 @comment against the day when someone finds the time to put them back in.
11052 @kindex info proc times
11053 @item info proc times
11054 Starting time, user CPU time, and system CPU time for your program and
11057 @kindex info proc id
11059 Report on the process IDs related to your program: its own process ID,
11060 the ID of its parent, the process group ID, and the session ID.
11062 @kindex info proc status
11063 @item info proc status
11064 General information on the state of the process. If the process is
11065 stopped, this report includes the reason for stopping, and any signal
11068 @item info proc all
11069 Show all the above information about the process.
11074 @subsection Features for Debugging @sc{djgpp} Programs
11075 @cindex @sc{djgpp} debugging
11076 @cindex native @sc{djgpp} debugging
11077 @cindex MS-DOS-specific commands
11079 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11080 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11081 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11082 top of real-mode DOS systems and their emulations.
11084 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11085 defines a few commands specific to the @sc{djgpp} port. This
11086 subsection describes those commands.
11091 This is a prefix of @sc{djgpp}-specific commands which print
11092 information about the target system and important OS structures.
11095 @cindex MS-DOS system info
11096 @cindex free memory information (MS-DOS)
11097 @item info dos sysinfo
11098 This command displays assorted information about the underlying
11099 platform: the CPU type and features, the OS version and flavor, the
11100 DPMI version, and the available conventional and DPMI memory.
11105 @cindex segment descriptor tables
11106 @cindex descriptor tables display
11108 @itemx info dos ldt
11109 @itemx info dos idt
11110 These 3 commands display entries from, respectively, Global, Local,
11111 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11112 tables are data structures which store a descriptor for each segment
11113 that is currently in use. The segment's selector is an index into a
11114 descriptor table; the table entry for that index holds the
11115 descriptor's base address and limit, and its attributes and access
11118 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11119 segment (used for both data and the stack), and a DOS segment (which
11120 allows access to DOS/BIOS data structures and absolute addresses in
11121 conventional memory). However, the DPMI host will usually define
11122 additional segments in order to support the DPMI environment.
11124 @cindex garbled pointers
11125 These commands allow to display entries from the descriptor tables.
11126 Without an argument, all entries from the specified table are
11127 displayed. An argument, which should be an integer expression, means
11128 display a single entry whose index is given by the argument. For
11129 example, here's a convenient way to display information about the
11130 debugged program's data segment:
11133 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11134 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11138 This comes in handy when you want to see whether a pointer is outside
11139 the data segment's limit (i.e.@: @dfn{garbled}).
11141 @cindex page tables display (MS-DOS)
11143 @itemx info dos pte
11144 These two commands display entries from, respectively, the Page
11145 Directory and the Page Tables. Page Directories and Page Tables are
11146 data structures which control how virtual memory addresses are mapped
11147 into physical addresses. A Page Table includes an entry for every
11148 page of memory that is mapped into the program's address space; there
11149 may be several Page Tables, each one holding up to 4096 entries. A
11150 Page Directory has up to 4096 entries, one each for every Page Table
11151 that is currently in use.
11153 Without an argument, @kbd{info dos pde} displays the entire Page
11154 Directory, and @kbd{info dos pte} displays all the entries in all of
11155 the Page Tables. An argument, an integer expression, given to the
11156 @kbd{info dos pde} command means display only that entry from the Page
11157 Directory table. An argument given to the @kbd{info dos pte} command
11158 means display entries from a single Page Table, the one pointed to by
11159 the specified entry in the Page Directory.
11161 @cindex direct memory access (DMA) on MS-DOS
11162 These commands are useful when your program uses @dfn{DMA} (Direct
11163 Memory Access), which needs physical addresses to program the DMA
11166 These commands are supported only with some DPMI servers.
11168 @cindex physical address from linear address
11169 @item info dos address-pte @var{addr}
11170 This command displays the Page Table entry for a specified linear
11171 address. The argument linear address @var{addr} should already have the
11172 appropriate segment's base address added to it, because this command
11173 accepts addresses which may belong to @emph{any} segment. For
11174 example, here's how to display the Page Table entry for the page where
11175 the variable @code{i} is stored:
11178 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
11179 @exdent @code{Page Table entry for address 0x11a00d30:}
11180 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
11184 This says that @code{i} is stored at offset @code{0xd30} from the page
11185 whose physical base address is @code{0x02698000}, and prints all the
11186 attributes of that page.
11188 Note that you must cast the addresses of variables to a @code{char *},
11189 since otherwise the value of @code{__djgpp_base_address}, the base
11190 address of all variables and functions in a @sc{djgpp} program, will
11191 be added using the rules of C pointer arithmetics: if @code{i} is
11192 declared an @code{int}, @value{GDBN} will add 4 times the value of
11193 @code{__djgpp_base_address} to the address of @code{i}.
11195 Here's another example, it displays the Page Table entry for the
11199 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
11200 @exdent @code{Page Table entry for address 0x29110:}
11201 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
11205 (The @code{+ 3} offset is because the transfer buffer's address is the
11206 3rd member of the @code{_go32_info_block} structure.) The output of
11207 this command clearly shows that addresses in conventional memory are
11208 mapped 1:1, i.e.@: the physical and linear addresses are identical.
11210 This command is supported only with some DPMI servers.
11213 @node Cygwin Native
11214 @subsection Features for Debugging MS Windows PE executables
11215 @cindex MS Windows debugging
11216 @cindex native Cygwin debugging
11217 @cindex Cygwin-specific commands
11219 @value{GDBN} supports native debugging of MS Windows programs, including
11220 DLLs with and without symbolic debugging information. There are various
11221 additional Cygwin-specific commands, described in this subsection. The
11222 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
11223 that have no debugging symbols.
11229 This is a prefix of MS Windows specific commands which print
11230 information about the target system and important OS structures.
11232 @item info w32 selector
11233 This command displays information returned by
11234 the Win32 API @code{GetThreadSelectorEntry} function.
11235 It takes an optional argument that is evaluated to
11236 a long value to give the information about this given selector.
11237 Without argument, this command displays information
11238 about the the six segment registers.
11242 This is a Cygwin specific alias of info shared.
11244 @kindex dll-symbols
11246 This command loads symbols from a dll similarly to
11247 add-sym command but without the need to specify a base address.
11249 @kindex set new-console
11250 @item set new-console @var{mode}
11251 If @var{mode} is @code{on} the debuggee will
11252 be started in a new console on next start.
11253 If @var{mode} is @code{off}i, the debuggee will
11254 be started in the same console as the debugger.
11256 @kindex show new-console
11257 @item show new-console
11258 Displays whether a new console is used
11259 when the debuggee is started.
11261 @kindex set new-group
11262 @item set new-group @var{mode}
11263 This boolean value controls whether the debuggee should
11264 start a new group or stay in the same group as the debugger.
11265 This affects the way the Windows OS handles
11268 @kindex show new-group
11269 @item show new-group
11270 Displays current value of new-group boolean.
11272 @kindex set debugevents
11273 @item set debugevents
11274 This boolean value adds debug output concerning events seen by the debugger.
11276 @kindex set debugexec
11277 @item set debugexec
11278 This boolean value adds debug output concerning execute events
11279 seen by the debugger.
11281 @kindex set debugexceptions
11282 @item set debugexceptions
11283 This boolean value adds debug ouptut concerning exception events
11284 seen by the debugger.
11286 @kindex set debugmemory
11287 @item set debugmemory
11288 This boolean value adds debug ouptut concerning memory events
11289 seen by the debugger.
11293 This boolean values specifies whether the debuggee is called
11294 via a shell or directly (default value is on).
11298 Displays if the debuggee will be started with a shell.
11303 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
11306 @node Non-debug DLL symbols
11307 @subsubsection Support for DLLs without debugging symbols
11308 @cindex DLLs with no debugging symbols
11309 @cindex Minimal symbols and DLLs
11311 Very often on windows, some of the DLLs that your program relies on do
11312 not include symbolic debugging information (for example,
11313 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
11314 symbols in a DLL, it relies on the minimal amount of symbolic
11315 information contained in the DLL's export table. This subsubsection
11316 describes working with such symbols, known internally to @value{GDBN} as
11317 ``minimal symbols''.
11319 Note that before the debugged program has started execution, no DLLs
11320 will have been loaded. The easiest way around this problem is simply to
11321 start the program --- either by setting a breakpoint or letting the
11322 program run once to completion. It is also possible to force
11323 @value{GDBN} to load a particular DLL before starting the executable ---
11324 see the shared library information in @pxref{Files} or the
11325 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
11326 explicitly loading symbols from a DLL with no debugging information will
11327 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
11328 which may adversely affect symbol lookup performance.
11330 @subsubsection DLL name prefixes
11332 In keeping with the naming conventions used by the Microsoft debugging
11333 tools, DLL export symbols are made available with a prefix based on the
11334 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
11335 also entered into the symbol table, so @code{CreateFileA} is often
11336 sufficient. In some cases there will be name clashes within a program
11337 (particularly if the executable itself includes full debugging symbols)
11338 necessitating the use of the fully qualified name when referring to the
11339 contents of the DLL. Use single-quotes around the name to avoid the
11340 exclamation mark (``!'') being interpreted as a language operator.
11342 Note that the internal name of the DLL may be all upper-case, even
11343 though the file name of the DLL is lower-case, or vice-versa. Since
11344 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
11345 some confusion. If in doubt, try the @code{info functions} and
11346 @code{info variables} commands or even @code{maint print msymbols} (see
11347 @pxref{Symbols}). Here's an example:
11350 (gdb) info function CreateFileA
11351 All functions matching regular expression "CreateFileA":
11353 Non-debugging symbols:
11354 0x77e885f4 CreateFileA
11355 0x77e885f4 KERNEL32!CreateFileA
11359 (gdb) info function !
11360 All functions matching regular expression "!":
11362 Non-debugging symbols:
11363 0x6100114c cygwin1!__assert
11364 0x61004034 cygwin1!_dll_crt0@@0
11365 0x61004240 cygwin1!dll_crt0(per_process *)
11369 @subsubsection Working with minimal symbols
11371 Symbols extracted from a DLL's export table do not contain very much
11372 type information. All that @value{GDBN} can do is guess whether a symbol
11373 refers to a function or variable depending on the linker section that
11374 contains the symbol. Also note that the actual contents of the memory
11375 contained in a DLL are not available unless the program is running. This
11376 means that you cannot examine the contents of a variable or disassemble
11377 a function within a DLL without a running program.
11379 Variables are generally treated as pointers and dereferenced
11380 automatically. For this reason, it is often necessary to prefix a
11381 variable name with the address-of operator (``&'') and provide explicit
11382 type information in the command. Here's an example of the type of
11386 (gdb) print 'cygwin1!__argv'
11391 (gdb) x 'cygwin1!__argv'
11392 0x10021610: "\230y\""
11395 And two possible solutions:
11398 (gdb) print ((char **)'cygwin1!__argv')[0]
11399 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
11403 (gdb) x/2x &'cygwin1!__argv'
11404 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
11405 (gdb) x/x 0x10021608
11406 0x10021608: 0x0022fd98
11407 (gdb) x/s 0x0022fd98
11408 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
11411 Setting a break point within a DLL is possible even before the program
11412 starts execution. However, under these circumstances, @value{GDBN} can't
11413 examine the initial instructions of the function in order to skip the
11414 function's frame set-up code. You can work around this by using ``*&''
11415 to set the breakpoint at a raw memory address:
11418 (gdb) break *&'python22!PyOS_Readline'
11419 Breakpoint 1 at 0x1e04eff0
11422 The author of these extensions is not entirely convinced that setting a
11423 break point within a shared DLL like @file{kernel32.dll} is completely
11427 @section Embedded Operating Systems
11429 This section describes configurations involving the debugging of
11430 embedded operating systems that are available for several different
11434 * VxWorks:: Using @value{GDBN} with VxWorks
11437 @value{GDBN} includes the ability to debug programs running on
11438 various real-time operating systems.
11441 @subsection Using @value{GDBN} with VxWorks
11447 @kindex target vxworks
11448 @item target vxworks @var{machinename}
11449 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
11450 is the target system's machine name or IP address.
11454 On VxWorks, @code{load} links @var{filename} dynamically on the
11455 current target system as well as adding its symbols in @value{GDBN}.
11457 @value{GDBN} enables developers to spawn and debug tasks running on networked
11458 VxWorks targets from a Unix host. Already-running tasks spawned from
11459 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
11460 both the Unix host and on the VxWorks target. The program
11461 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
11462 installed with the name @code{vxgdb}, to distinguish it from a
11463 @value{GDBN} for debugging programs on the host itself.)
11466 @item VxWorks-timeout @var{args}
11467 @kindex vxworks-timeout
11468 All VxWorks-based targets now support the option @code{vxworks-timeout}.
11469 This option is set by the user, and @var{args} represents the number of
11470 seconds @value{GDBN} waits for responses to rpc's. You might use this if
11471 your VxWorks target is a slow software simulator or is on the far side
11472 of a thin network line.
11475 The following information on connecting to VxWorks was current when
11476 this manual was produced; newer releases of VxWorks may use revised
11479 @kindex INCLUDE_RDB
11480 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
11481 to include the remote debugging interface routines in the VxWorks
11482 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
11483 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
11484 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
11485 source debugging task @code{tRdbTask} when VxWorks is booted. For more
11486 information on configuring and remaking VxWorks, see the manufacturer's
11488 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
11490 Once you have included @file{rdb.a} in your VxWorks system image and set
11491 your Unix execution search path to find @value{GDBN}, you are ready to
11492 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
11493 @code{vxgdb}, depending on your installation).
11495 @value{GDBN} comes up showing the prompt:
11502 * VxWorks Connection:: Connecting to VxWorks
11503 * VxWorks Download:: VxWorks download
11504 * VxWorks Attach:: Running tasks
11507 @node VxWorks Connection
11508 @subsubsection Connecting to VxWorks
11510 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
11511 network. To connect to a target whose host name is ``@code{tt}'', type:
11514 (vxgdb) target vxworks tt
11518 @value{GDBN} displays messages like these:
11521 Attaching remote machine across net...
11526 @value{GDBN} then attempts to read the symbol tables of any object modules
11527 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
11528 these files by searching the directories listed in the command search
11529 path (@pxref{Environment, ,Your program's environment}); if it fails
11530 to find an object file, it displays a message such as:
11533 prog.o: No such file or directory.
11536 When this happens, add the appropriate directory to the search path with
11537 the @value{GDBN} command @code{path}, and execute the @code{target}
11540 @node VxWorks Download
11541 @subsubsection VxWorks download
11543 @cindex download to VxWorks
11544 If you have connected to the VxWorks target and you want to debug an
11545 object that has not yet been loaded, you can use the @value{GDBN}
11546 @code{load} command to download a file from Unix to VxWorks
11547 incrementally. The object file given as an argument to the @code{load}
11548 command is actually opened twice: first by the VxWorks target in order
11549 to download the code, then by @value{GDBN} in order to read the symbol
11550 table. This can lead to problems if the current working directories on
11551 the two systems differ. If both systems have NFS mounted the same
11552 filesystems, you can avoid these problems by using absolute paths.
11553 Otherwise, it is simplest to set the working directory on both systems
11554 to the directory in which the object file resides, and then to reference
11555 the file by its name, without any path. For instance, a program
11556 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
11557 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
11558 program, type this on VxWorks:
11561 -> cd "@var{vxpath}/vw/demo/rdb"
11565 Then, in @value{GDBN}, type:
11568 (vxgdb) cd @var{hostpath}/vw/demo/rdb
11569 (vxgdb) load prog.o
11572 @value{GDBN} displays a response similar to this:
11575 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
11578 You can also use the @code{load} command to reload an object module
11579 after editing and recompiling the corresponding source file. Note that
11580 this makes @value{GDBN} delete all currently-defined breakpoints,
11581 auto-displays, and convenience variables, and to clear the value
11582 history. (This is necessary in order to preserve the integrity of
11583 debugger's data structures that reference the target system's symbol
11586 @node VxWorks Attach
11587 @subsubsection Running tasks
11589 @cindex running VxWorks tasks
11590 You can also attach to an existing task using the @code{attach} command as
11594 (vxgdb) attach @var{task}
11598 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
11599 or suspended when you attach to it. Running tasks are suspended at
11600 the time of attachment.
11602 @node Embedded Processors
11603 @section Embedded Processors
11605 This section goes into details specific to particular embedded
11611 * H8/300:: Hitachi H8/300
11612 * H8/500:: Hitachi H8/500
11613 * M32R/D:: Mitsubishi M32R/D
11614 * M68K:: Motorola M68K
11615 * MIPS Embedded:: MIPS Embedded
11616 * OpenRISC 1000:: OpenRisc 1000
11617 * PA:: HP PA Embedded
11620 * Sparclet:: Tsqware Sparclet
11621 * Sparclite:: Fujitsu Sparclite
11622 * ST2000:: Tandem ST2000
11623 * Z8000:: Zilog Z8000
11632 @item target rdi @var{dev}
11633 ARM Angel monitor, via RDI library interface to ADP protocol. You may
11634 use this target to communicate with both boards running the Angel
11635 monitor, or with the EmbeddedICE JTAG debug device.
11638 @item target rdp @var{dev}
11644 @subsection Hitachi H8/300
11648 @kindex target hms@r{, with H8/300}
11649 @item target hms @var{dev}
11650 A Hitachi SH, H8/300, or H8/500 board, attached via serial line to your host.
11651 Use special commands @code{device} and @code{speed} to control the serial
11652 line and the communications speed used.
11654 @kindex target e7000@r{, with H8/300}
11655 @item target e7000 @var{dev}
11656 E7000 emulator for Hitachi H8 and SH.
11658 @kindex target sh3@r{, with H8/300}
11659 @kindex target sh3e@r{, with H8/300}
11660 @item target sh3 @var{dev}
11661 @itemx target sh3e @var{dev}
11662 Hitachi SH-3 and SH-3E target systems.
11666 @cindex download to H8/300 or H8/500
11667 @cindex H8/300 or H8/500 download
11668 @cindex download to Hitachi SH
11669 @cindex Hitachi SH download
11670 When you select remote debugging to a Hitachi SH, H8/300, or H8/500
11671 board, the @code{load} command downloads your program to the Hitachi
11672 board and also opens it as the current executable target for
11673 @value{GDBN} on your host (like the @code{file} command).
11675 @value{GDBN} needs to know these things to talk to your
11676 Hitachi SH, H8/300, or H8/500:
11680 that you want to use @samp{target hms}, the remote debugging interface
11681 for Hitachi microprocessors, or @samp{target e7000}, the in-circuit
11682 emulator for the Hitachi SH and the Hitachi 300H. (@samp{target hms} is
11683 the default when @value{GDBN} is configured specifically for the Hitachi SH,
11684 H8/300, or H8/500.)
11687 what serial device connects your host to your Hitachi board (the first
11688 serial device available on your host is the default).
11691 what speed to use over the serial device.
11695 * Hitachi Boards:: Connecting to Hitachi boards.
11696 * Hitachi ICE:: Using the E7000 In-Circuit Emulator.
11697 * Hitachi Special:: Special @value{GDBN} commands for Hitachi micros.
11700 @node Hitachi Boards
11701 @subsubsection Connecting to Hitachi boards
11703 @c only for Unix hosts
11705 @cindex serial device, Hitachi micros
11706 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
11707 need to explicitly set the serial device. The default @var{port} is the
11708 first available port on your host. This is only necessary on Unix
11709 hosts, where it is typically something like @file{/dev/ttya}.
11712 @cindex serial line speed, Hitachi micros
11713 @code{@value{GDBN}} has another special command to set the communications
11714 speed: @samp{speed @var{bps}}. This command also is only used from Unix
11715 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
11716 the DOS @code{mode} command (for instance,
11717 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
11719 The @samp{device} and @samp{speed} commands are available only when you
11720 use a Unix host to debug your Hitachi microprocessor programs. If you
11722 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
11723 called @code{asynctsr} to communicate with the development board
11724 through a PC serial port. You must also use the DOS @code{mode} command
11725 to set up the serial port on the DOS side.
11727 The following sample session illustrates the steps needed to start a
11728 program under @value{GDBN} control on an H8/300. The example uses a
11729 sample H8/300 program called @file{t.x}. The procedure is the same for
11730 the Hitachi SH and the H8/500.
11732 First hook up your development board. In this example, we use a
11733 board attached to serial port @code{COM2}; if you use a different serial
11734 port, substitute its name in the argument of the @code{mode} command.
11735 When you call @code{asynctsr}, the auxiliary comms program used by the
11736 debugger, you give it just the numeric part of the serial port's name;
11737 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
11741 C:\H8300\TEST> asynctsr 2
11742 C:\H8300\TEST> mode com2:9600,n,8,1,p
11744 Resident portion of MODE loaded
11746 COM2: 9600, n, 8, 1, p
11751 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
11752 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
11753 disable it, or even boot without it, to use @code{asynctsr} to control
11754 your development board.
11757 @kindex target hms@r{, and serial protocol}
11758 Now that serial communications are set up, and the development board is
11759 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
11760 the name of your program as the argument. @code{@value{GDBN}} prompts
11761 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
11762 commands to begin your debugging session: @samp{target hms} to specify
11763 cross-debugging to the Hitachi board, and the @code{load} command to
11764 download your program to the board. @code{load} displays the names of
11765 the program's sections, and a @samp{*} for each 2K of data downloaded.
11766 (If you want to refresh @value{GDBN} data on symbols or on the
11767 executable file without downloading, use the @value{GDBN} commands
11768 @code{file} or @code{symbol-file}. These commands, and @code{load}
11769 itself, are described in @ref{Files,,Commands to specify files}.)
11772 (eg-C:\H8300\TEST) @value{GDBP} t.x
11773 @value{GDBN} is free software and you are welcome to distribute copies
11774 of it under certain conditions; type "show copying" to see
11776 There is absolutely no warranty for @value{GDBN}; type "show warranty"
11778 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
11779 (@value{GDBP}) target hms
11780 Connected to remote H8/300 HMS system.
11781 (@value{GDBP}) load t.x
11782 .text : 0x8000 .. 0xabde ***********
11783 .data : 0xabde .. 0xad30 *
11784 .stack : 0xf000 .. 0xf014 *
11787 At this point, you're ready to run or debug your program. From here on,
11788 you can use all the usual @value{GDBN} commands. The @code{break} command
11789 sets breakpoints; the @code{run} command starts your program;
11790 @code{print} or @code{x} display data; the @code{continue} command
11791 resumes execution after stopping at a breakpoint. You can use the
11792 @code{help} command at any time to find out more about @value{GDBN} commands.
11794 Remember, however, that @emph{operating system} facilities aren't
11795 available on your development board; for example, if your program hangs,
11796 you can't send an interrupt---but you can press the @sc{reset} switch!
11798 Use the @sc{reset} button on the development board
11801 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
11802 no way to pass an interrupt signal to the development board); and
11805 to return to the @value{GDBN} command prompt after your program finishes
11806 normally. The communications protocol provides no other way for @value{GDBN}
11807 to detect program completion.
11810 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
11811 development board as a ``normal exit'' of your program.
11814 @subsubsection Using the E7000 in-circuit emulator
11816 @kindex target e7000@r{, with Hitachi ICE}
11817 You can use the E7000 in-circuit emulator to develop code for either the
11818 Hitachi SH or the H8/300H. Use one of these forms of the @samp{target
11819 e7000} command to connect @value{GDBN} to your E7000:
11822 @item target e7000 @var{port} @var{speed}
11823 Use this form if your E7000 is connected to a serial port. The
11824 @var{port} argument identifies what serial port to use (for example,
11825 @samp{com2}). The third argument is the line speed in bits per second
11826 (for example, @samp{9600}).
11828 @item target e7000 @var{hostname}
11829 If your E7000 is installed as a host on a TCP/IP network, you can just
11830 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
11833 @node Hitachi Special
11834 @subsubsection Special @value{GDBN} commands for Hitachi micros
11836 Some @value{GDBN} commands are available only for the H8/300:
11840 @kindex set machine
11841 @kindex show machine
11842 @item set machine h8300
11843 @itemx set machine h8300h
11844 Condition @value{GDBN} for one of the two variants of the H8/300
11845 architecture with @samp{set machine}. You can use @samp{show machine}
11846 to check which variant is currently in effect.
11855 @kindex set memory @var{mod}
11856 @cindex memory models, H8/500
11857 @item set memory @var{mod}
11859 Specify which H8/500 memory model (@var{mod}) you are using with
11860 @samp{set memory}; check which memory model is in effect with @samp{show
11861 memory}. The accepted values for @var{mod} are @code{small},
11862 @code{big}, @code{medium}, and @code{compact}.
11867 @subsection Mitsubishi M32R/D
11871 @kindex target m32r
11872 @item target m32r @var{dev}
11873 Mitsubishi M32R/D ROM monitor.
11880 The Motorola m68k configuration includes ColdFire support, and
11881 target command for the following ROM monitors.
11885 @kindex target abug
11886 @item target abug @var{dev}
11887 ABug ROM monitor for M68K.
11889 @kindex target cpu32bug
11890 @item target cpu32bug @var{dev}
11891 CPU32BUG monitor, running on a CPU32 (M68K) board.
11893 @kindex target dbug
11894 @item target dbug @var{dev}
11895 dBUG ROM monitor for Motorola ColdFire.
11898 @item target est @var{dev}
11899 EST-300 ICE monitor, running on a CPU32 (M68K) board.
11901 @kindex target rom68k
11902 @item target rom68k @var{dev}
11903 ROM 68K monitor, running on an M68K IDP board.
11909 @kindex target rombug
11910 @item target rombug @var{dev}
11911 ROMBUG ROM monitor for OS/9000.
11915 @node MIPS Embedded
11916 @subsection MIPS Embedded
11918 @cindex MIPS boards
11919 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
11920 MIPS board attached to a serial line. This is available when
11921 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
11924 Use these @value{GDBN} commands to specify the connection to your target board:
11927 @item target mips @var{port}
11928 @kindex target mips @var{port}
11929 To run a program on the board, start up @code{@value{GDBP}} with the
11930 name of your program as the argument. To connect to the board, use the
11931 command @samp{target mips @var{port}}, where @var{port} is the name of
11932 the serial port connected to the board. If the program has not already
11933 been downloaded to the board, you may use the @code{load} command to
11934 download it. You can then use all the usual @value{GDBN} commands.
11936 For example, this sequence connects to the target board through a serial
11937 port, and loads and runs a program called @var{prog} through the
11941 host$ @value{GDBP} @var{prog}
11942 @value{GDBN} is free software and @dots{}
11943 (@value{GDBP}) target mips /dev/ttyb
11944 (@value{GDBP}) load @var{prog}
11948 @item target mips @var{hostname}:@var{portnumber}
11949 On some @value{GDBN} host configurations, you can specify a TCP
11950 connection (for instance, to a serial line managed by a terminal
11951 concentrator) instead of a serial port, using the syntax
11952 @samp{@var{hostname}:@var{portnumber}}.
11954 @item target pmon @var{port}
11955 @kindex target pmon @var{port}
11958 @item target ddb @var{port}
11959 @kindex target ddb @var{port}
11960 NEC's DDB variant of PMON for Vr4300.
11962 @item target lsi @var{port}
11963 @kindex target lsi @var{port}
11964 LSI variant of PMON.
11966 @kindex target r3900
11967 @item target r3900 @var{dev}
11968 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
11970 @kindex target array
11971 @item target array @var{dev}
11972 Array Tech LSI33K RAID controller board.
11978 @value{GDBN} also supports these special commands for MIPS targets:
11981 @item set processor @var{args}
11982 @itemx show processor
11983 @kindex set processor @var{args}
11984 @kindex show processor
11985 Use the @code{set processor} command to set the type of MIPS
11986 processor when you want to access processor-type-specific registers.
11987 For example, @code{set processor @var{r3041}} tells @value{GDBN}
11988 to use the CPU registers appropriate for the 3041 chip.
11989 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
11990 is using. Use the @code{info reg} command to see what registers
11991 @value{GDBN} is using.
11993 @item set mipsfpu double
11994 @itemx set mipsfpu single
11995 @itemx set mipsfpu none
11996 @itemx show mipsfpu
11997 @kindex set mipsfpu
11998 @kindex show mipsfpu
11999 @cindex MIPS remote floating point
12000 @cindex floating point, MIPS remote
12001 If your target board does not support the MIPS floating point
12002 coprocessor, you should use the command @samp{set mipsfpu none} (if you
12003 need this, you may wish to put the command in your @value{GDBN} init
12004 file). This tells @value{GDBN} how to find the return value of
12005 functions which return floating point values. It also allows
12006 @value{GDBN} to avoid saving the floating point registers when calling
12007 functions on the board. If you are using a floating point coprocessor
12008 with only single precision floating point support, as on the @sc{r4650}
12009 processor, use the command @samp{set mipsfpu single}. The default
12010 double precision floating point coprocessor may be selected using
12011 @samp{set mipsfpu double}.
12013 In previous versions the only choices were double precision or no
12014 floating point, so @samp{set mipsfpu on} will select double precision
12015 and @samp{set mipsfpu off} will select no floating point.
12017 As usual, you can inquire about the @code{mipsfpu} variable with
12018 @samp{show mipsfpu}.
12020 @item set remotedebug @var{n}
12021 @itemx show remotedebug
12022 @kindex set remotedebug@r{, MIPS protocol}
12023 @kindex show remotedebug@r{, MIPS protocol}
12024 @cindex @code{remotedebug}, MIPS protocol
12025 @cindex MIPS @code{remotedebug} protocol
12026 @c FIXME! For this to be useful, you must know something about the MIPS
12027 @c FIXME...protocol. Where is it described?
12028 You can see some debugging information about communications with the board
12029 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12030 @samp{set remotedebug 1}, every packet is displayed. If you set it
12031 to @code{2}, every character is displayed. You can check the current value
12032 at any time with the command @samp{show remotedebug}.
12034 @item set timeout @var{seconds}
12035 @itemx set retransmit-timeout @var{seconds}
12036 @itemx show timeout
12037 @itemx show retransmit-timeout
12038 @cindex @code{timeout}, MIPS protocol
12039 @cindex @code{retransmit-timeout}, MIPS protocol
12040 @kindex set timeout
12041 @kindex show timeout
12042 @kindex set retransmit-timeout
12043 @kindex show retransmit-timeout
12044 You can control the timeout used while waiting for a packet, in the MIPS
12045 remote protocol, with the @code{set timeout @var{seconds}} command. The
12046 default is 5 seconds. Similarly, you can control the timeout used while
12047 waiting for an acknowledgement of a packet with the @code{set
12048 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12049 You can inspect both values with @code{show timeout} and @code{show
12050 retransmit-timeout}. (These commands are @emph{only} available when
12051 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12053 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12054 is waiting for your program to stop. In that case, @value{GDBN} waits
12055 forever because it has no way of knowing how long the program is going
12056 to run before stopping.
12059 @node OpenRISC 1000
12060 @subsection OpenRISC 1000
12061 @cindex OpenRISC 1000
12063 @cindex or1k boards
12064 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12065 about platform and commands.
12069 @kindex target jtag
12070 @item target jtag jtag://@var{host}:@var{port}
12072 Connects to remote JTAG server.
12073 JTAG remote server can be either an or1ksim or JTAG server,
12074 connected via parallel port to the board.
12076 Example: @code{target jtag jtag://localhost:9999}
12079 @item or1ksim @var{command}
12080 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12081 Simulator, proprietary commands can be executed.
12083 @kindex info or1k spr
12084 @item info or1k spr
12085 Displays spr groups.
12087 @item info or1k spr @var{group}
12088 @itemx info or1k spr @var{groupno}
12089 Displays register names in selected group.
12091 @item info or1k spr @var{group} @var{register}
12092 @itemx info or1k spr @var{register}
12093 @itemx info or1k spr @var{groupno} @var{registerno}
12094 @itemx info or1k spr @var{registerno}
12095 Shows information about specified spr register.
12098 @item spr @var{group} @var{register} @var{value}
12099 @itemx spr @var{register @var{value}}
12100 @itemx spr @var{groupno} @var{registerno @var{value}}
12101 @itemx spr @var{registerno @var{value}}
12102 Writes @var{value} to specified spr register.
12105 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12106 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12107 program execution and is thus much faster. Hardware breakpoints/watchpoint
12108 triggers can be set using:
12111 Load effective address/data
12113 Store effective address/data
12115 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12120 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12121 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12123 @code{htrace} commands:
12124 @cindex OpenRISC 1000 htrace
12127 @item hwatch @var{conditional}
12128 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
12129 or Data. For example:
12131 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12133 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12135 @kindex htrace info
12137 Display information about current HW trace configuration.
12139 @kindex htrace trigger
12140 @item htrace trigger @var{conditional}
12141 Set starting criteria for HW trace.
12143 @kindex htrace qualifier
12144 @item htrace qualifier @var{conditional}
12145 Set acquisition qualifier for HW trace.
12147 @kindex htrace stop
12148 @item htrace stop @var{conditional}
12149 Set HW trace stopping criteria.
12151 @kindex htrace record
12152 @item htrace record [@var{data}]*
12153 Selects the data to be recorded, when qualifier is met and HW trace was
12156 @kindex htrace enable
12157 @item htrace enable
12158 @kindex htrace disable
12159 @itemx htrace disable
12160 Enables/disables the HW trace.
12162 @kindex htrace rewind
12163 @item htrace rewind [@var{filename}]
12164 Clears currently recorded trace data.
12166 If filename is specified, new trace file is made and any newly collected data
12167 will be written there.
12169 @kindex htrace print
12170 @item htrace print [@var{start} [@var{len}]]
12171 Prints trace buffer, using current record configuration.
12173 @kindex htrace mode continuous
12174 @item htrace mode continuous
12175 Set continuous trace mode.
12177 @kindex htrace mode suspend
12178 @item htrace mode suspend
12179 Set suspend trace mode.
12184 @subsection PowerPC
12188 @kindex target dink32
12189 @item target dink32 @var{dev}
12190 DINK32 ROM monitor.
12192 @kindex target ppcbug
12193 @item target ppcbug @var{dev}
12194 @kindex target ppcbug1
12195 @item target ppcbug1 @var{dev}
12196 PPCBUG ROM monitor for PowerPC.
12199 @item target sds @var{dev}
12200 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
12205 @subsection HP PA Embedded
12209 @kindex target op50n
12210 @item target op50n @var{dev}
12211 OP50N monitor, running on an OKI HPPA board.
12213 @kindex target w89k
12214 @item target w89k @var{dev}
12215 W89K monitor, running on a Winbond HPPA board.
12220 @subsection Hitachi SH
12224 @kindex target hms@r{, with Hitachi SH}
12225 @item target hms @var{dev}
12226 A Hitachi SH board attached via serial line to your host. Use special
12227 commands @code{device} and @code{speed} to control the serial line and
12228 the communications speed used.
12230 @kindex target e7000@r{, with Hitachi SH}
12231 @item target e7000 @var{dev}
12232 E7000 emulator for Hitachi SH.
12234 @kindex target sh3@r{, with SH}
12235 @kindex target sh3e@r{, with SH}
12236 @item target sh3 @var{dev}
12237 @item target sh3e @var{dev}
12238 Hitachi SH-3 and SH-3E target systems.
12243 @subsection Tsqware Sparclet
12247 @value{GDBN} enables developers to debug tasks running on
12248 Sparclet targets from a Unix host.
12249 @value{GDBN} uses code that runs on
12250 both the Unix host and on the Sparclet target. The program
12251 @code{@value{GDBP}} is installed and executed on the Unix host.
12254 @item remotetimeout @var{args}
12255 @kindex remotetimeout
12256 @value{GDBN} supports the option @code{remotetimeout}.
12257 This option is set by the user, and @var{args} represents the number of
12258 seconds @value{GDBN} waits for responses.
12261 @cindex compiling, on Sparclet
12262 When compiling for debugging, include the options @samp{-g} to get debug
12263 information and @samp{-Ttext} to relocate the program to where you wish to
12264 load it on the target. You may also want to add the options @samp{-n} or
12265 @samp{-N} in order to reduce the size of the sections. Example:
12268 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
12271 You can use @code{objdump} to verify that the addresses are what you intended:
12274 sparclet-aout-objdump --headers --syms prog
12277 @cindex running, on Sparclet
12279 your Unix execution search path to find @value{GDBN}, you are ready to
12280 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
12281 (or @code{sparclet-aout-gdb}, depending on your installation).
12283 @value{GDBN} comes up showing the prompt:
12290 * Sparclet File:: Setting the file to debug
12291 * Sparclet Connection:: Connecting to Sparclet
12292 * Sparclet Download:: Sparclet download
12293 * Sparclet Execution:: Running and debugging
12296 @node Sparclet File
12297 @subsubsection Setting file to debug
12299 The @value{GDBN} command @code{file} lets you choose with program to debug.
12302 (gdbslet) file prog
12306 @value{GDBN} then attempts to read the symbol table of @file{prog}.
12307 @value{GDBN} locates
12308 the file by searching the directories listed in the command search
12310 If the file was compiled with debug information (option "-g"), source
12311 files will be searched as well.
12312 @value{GDBN} locates
12313 the source files by searching the directories listed in the directory search
12314 path (@pxref{Environment, ,Your program's environment}).
12316 to find a file, it displays a message such as:
12319 prog: No such file or directory.
12322 When this happens, add the appropriate directories to the search paths with
12323 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
12324 @code{target} command again.
12326 @node Sparclet Connection
12327 @subsubsection Connecting to Sparclet
12329 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
12330 To connect to a target on serial port ``@code{ttya}'', type:
12333 (gdbslet) target sparclet /dev/ttya
12334 Remote target sparclet connected to /dev/ttya
12335 main () at ../prog.c:3
12339 @value{GDBN} displays messages like these:
12345 @node Sparclet Download
12346 @subsubsection Sparclet download
12348 @cindex download to Sparclet
12349 Once connected to the Sparclet target,
12350 you can use the @value{GDBN}
12351 @code{load} command to download the file from the host to the target.
12352 The file name and load offset should be given as arguments to the @code{load}
12354 Since the file format is aout, the program must be loaded to the starting
12355 address. You can use @code{objdump} to find out what this value is. The load
12356 offset is an offset which is added to the VMA (virtual memory address)
12357 of each of the file's sections.
12358 For instance, if the program
12359 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
12360 and bss at 0x12010170, in @value{GDBN}, type:
12363 (gdbslet) load prog 0x12010000
12364 Loading section .text, size 0xdb0 vma 0x12010000
12367 If the code is loaded at a different address then what the program was linked
12368 to, you may need to use the @code{section} and @code{add-symbol-file} commands
12369 to tell @value{GDBN} where to map the symbol table.
12371 @node Sparclet Execution
12372 @subsubsection Running and debugging
12374 @cindex running and debugging Sparclet programs
12375 You can now begin debugging the task using @value{GDBN}'s execution control
12376 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
12377 manual for the list of commands.
12381 Breakpoint 1 at 0x12010000: file prog.c, line 3.
12383 Starting program: prog
12384 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
12385 3 char *symarg = 0;
12387 4 char *execarg = "hello!";
12392 @subsection Fujitsu Sparclite
12396 @kindex target sparclite
12397 @item target sparclite @var{dev}
12398 Fujitsu sparclite boards, used only for the purpose of loading.
12399 You must use an additional command to debug the program.
12400 For example: target remote @var{dev} using @value{GDBN} standard
12406 @subsection Tandem ST2000
12408 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
12411 To connect your ST2000 to the host system, see the manufacturer's
12412 manual. Once the ST2000 is physically attached, you can run:
12415 target st2000 @var{dev} @var{speed}
12419 to establish it as your debugging environment. @var{dev} is normally
12420 the name of a serial device, such as @file{/dev/ttya}, connected to the
12421 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
12422 connection (for example, to a serial line attached via a terminal
12423 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
12425 The @code{load} and @code{attach} commands are @emph{not} defined for
12426 this target; you must load your program into the ST2000 as you normally
12427 would for standalone operation. @value{GDBN} reads debugging information
12428 (such as symbols) from a separate, debugging version of the program
12429 available on your host computer.
12430 @c FIXME!! This is terribly vague; what little content is here is
12431 @c basically hearsay.
12433 @cindex ST2000 auxiliary commands
12434 These auxiliary @value{GDBN} commands are available to help you with the ST2000
12438 @item st2000 @var{command}
12439 @kindex st2000 @var{cmd}
12440 @cindex STDBUG commands (ST2000)
12441 @cindex commands to STDBUG (ST2000)
12442 Send a @var{command} to the STDBUG monitor. See the manufacturer's
12443 manual for available commands.
12446 @cindex connect (to STDBUG)
12447 Connect the controlling terminal to the STDBUG command monitor. When
12448 you are done interacting with STDBUG, typing either of two character
12449 sequences gets you back to the @value{GDBN} command prompt:
12450 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
12451 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
12455 @subsection Zilog Z8000
12458 @cindex simulator, Z8000
12459 @cindex Zilog Z8000 simulator
12461 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
12464 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
12465 unsegmented variant of the Z8000 architecture) or the Z8001 (the
12466 segmented variant). The simulator recognizes which architecture is
12467 appropriate by inspecting the object code.
12470 @item target sim @var{args}
12472 @kindex target sim@r{, with Z8000}
12473 Debug programs on a simulated CPU. If the simulator supports setup
12474 options, specify them via @var{args}.
12478 After specifying this target, you can debug programs for the simulated
12479 CPU in the same style as programs for your host computer; use the
12480 @code{file} command to load a new program image, the @code{run} command
12481 to run your program, and so on.
12483 As well as making available all the usual machine registers
12484 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
12485 additional items of information as specially named registers:
12490 Counts clock-ticks in the simulator.
12493 Counts instructions run in the simulator.
12496 Execution time in 60ths of a second.
12500 You can refer to these values in @value{GDBN} expressions with the usual
12501 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
12502 conditional breakpoint that suspends only after at least 5000
12503 simulated clock ticks.
12505 @node Architectures
12506 @section Architectures
12508 This section describes characteristics of architectures that affect
12509 all uses of @value{GDBN} with the architecture, both native and cross.
12522 @kindex set rstack_high_address
12523 @cindex AMD 29K register stack
12524 @cindex register stack, AMD29K
12525 @item set rstack_high_address @var{address}
12526 On AMD 29000 family processors, registers are saved in a separate
12527 @dfn{register stack}. There is no way for @value{GDBN} to determine the
12528 extent of this stack. Normally, @value{GDBN} just assumes that the
12529 stack is ``large enough''. This may result in @value{GDBN} referencing
12530 memory locations that do not exist. If necessary, you can get around
12531 this problem by specifying the ending address of the register stack with
12532 the @code{set rstack_high_address} command. The argument should be an
12533 address, which you probably want to precede with @samp{0x} to specify in
12536 @kindex show rstack_high_address
12537 @item show rstack_high_address
12538 Display the current limit of the register stack, on AMD 29000 family
12546 See the following section.
12551 @cindex stack on Alpha
12552 @cindex stack on MIPS
12553 @cindex Alpha stack
12555 Alpha- and MIPS-based computers use an unusual stack frame, which
12556 sometimes requires @value{GDBN} to search backward in the object code to
12557 find the beginning of a function.
12559 @cindex response time, MIPS debugging
12560 To improve response time (especially for embedded applications, where
12561 @value{GDBN} may be restricted to a slow serial line for this search)
12562 you may want to limit the size of this search, using one of these
12566 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
12567 @item set heuristic-fence-post @var{limit}
12568 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
12569 search for the beginning of a function. A value of @var{0} (the
12570 default) means there is no limit. However, except for @var{0}, the
12571 larger the limit the more bytes @code{heuristic-fence-post} must search
12572 and therefore the longer it takes to run.
12574 @item show heuristic-fence-post
12575 Display the current limit.
12579 These commands are available @emph{only} when @value{GDBN} is configured
12580 for debugging programs on Alpha or MIPS processors.
12583 @node Controlling GDB
12584 @chapter Controlling @value{GDBN}
12586 You can alter the way @value{GDBN} interacts with you by using the
12587 @code{set} command. For commands controlling how @value{GDBN} displays
12588 data, see @ref{Print Settings, ,Print settings}. Other settings are
12593 * Editing:: Command editing
12594 * History:: Command history
12595 * Screen Size:: Screen size
12596 * Numbers:: Numbers
12597 * ABI:: Configuring the current ABI
12598 * Messages/Warnings:: Optional warnings and messages
12599 * Debugging Output:: Optional messages about internal happenings
12607 @value{GDBN} indicates its readiness to read a command by printing a string
12608 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
12609 can change the prompt string with the @code{set prompt} command. For
12610 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
12611 the prompt in one of the @value{GDBN} sessions so that you can always tell
12612 which one you are talking to.
12614 @emph{Note:} @code{set prompt} does not add a space for you after the
12615 prompt you set. This allows you to set a prompt which ends in a space
12616 or a prompt that does not.
12620 @item set prompt @var{newprompt}
12621 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
12623 @kindex show prompt
12625 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
12629 @section Command editing
12631 @cindex command line editing
12633 @value{GDBN} reads its input commands via the @dfn{readline} interface. This
12634 @sc{gnu} library provides consistent behavior for programs which provide a
12635 command line interface to the user. Advantages are @sc{gnu} Emacs-style
12636 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
12637 substitution, and a storage and recall of command history across
12638 debugging sessions.
12640 You may control the behavior of command line editing in @value{GDBN} with the
12641 command @code{set}.
12644 @kindex set editing
12647 @itemx set editing on
12648 Enable command line editing (enabled by default).
12650 @item set editing off
12651 Disable command line editing.
12653 @kindex show editing
12655 Show whether command line editing is enabled.
12659 @section Command history
12661 @value{GDBN} can keep track of the commands you type during your
12662 debugging sessions, so that you can be certain of precisely what
12663 happened. Use these commands to manage the @value{GDBN} command
12667 @cindex history substitution
12668 @cindex history file
12669 @kindex set history filename
12670 @kindex GDBHISTFILE
12671 @item set history filename @var{fname}
12672 Set the name of the @value{GDBN} command history file to @var{fname}.
12673 This is the file where @value{GDBN} reads an initial command history
12674 list, and where it writes the command history from this session when it
12675 exits. You can access this list through history expansion or through
12676 the history command editing characters listed below. This file defaults
12677 to the value of the environment variable @code{GDBHISTFILE}, or to
12678 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
12681 @cindex history save
12682 @kindex set history save
12683 @item set history save
12684 @itemx set history save on
12685 Record command history in a file, whose name may be specified with the
12686 @code{set history filename} command. By default, this option is disabled.
12688 @item set history save off
12689 Stop recording command history in a file.
12691 @cindex history size
12692 @kindex set history size
12693 @item set history size @var{size}
12694 Set the number of commands which @value{GDBN} keeps in its history list.
12695 This defaults to the value of the environment variable
12696 @code{HISTSIZE}, or to 256 if this variable is not set.
12699 @cindex history expansion
12700 History expansion assigns special meaning to the character @kbd{!}.
12701 @ifset have-readline-appendices
12702 @xref{Event Designators}.
12705 Since @kbd{!} is also the logical not operator in C, history expansion
12706 is off by default. If you decide to enable history expansion with the
12707 @code{set history expansion on} command, you may sometimes need to
12708 follow @kbd{!} (when it is used as logical not, in an expression) with
12709 a space or a tab to prevent it from being expanded. The readline
12710 history facilities do not attempt substitution on the strings
12711 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
12713 The commands to control history expansion are:
12716 @kindex set history expansion
12717 @item set history expansion on
12718 @itemx set history expansion
12719 Enable history expansion. History expansion is off by default.
12721 @item set history expansion off
12722 Disable history expansion.
12724 The readline code comes with more complete documentation of
12725 editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs
12726 or @code{vi} may wish to read it.
12727 @ifset have-readline-appendices
12728 @xref{Command Line Editing}.
12732 @kindex show history
12734 @itemx show history filename
12735 @itemx show history save
12736 @itemx show history size
12737 @itemx show history expansion
12738 These commands display the state of the @value{GDBN} history parameters.
12739 @code{show history} by itself displays all four states.
12745 @item show commands
12746 Display the last ten commands in the command history.
12748 @item show commands @var{n}
12749 Print ten commands centered on command number @var{n}.
12751 @item show commands +
12752 Print ten commands just after the commands last printed.
12756 @section Screen size
12757 @cindex size of screen
12758 @cindex pauses in output
12760 Certain commands to @value{GDBN} may produce large amounts of
12761 information output to the screen. To help you read all of it,
12762 @value{GDBN} pauses and asks you for input at the end of each page of
12763 output. Type @key{RET} when you want to continue the output, or @kbd{q}
12764 to discard the remaining output. Also, the screen width setting
12765 determines when to wrap lines of output. Depending on what is being
12766 printed, @value{GDBN} tries to break the line at a readable place,
12767 rather than simply letting it overflow onto the following line.
12769 Normally @value{GDBN} knows the size of the screen from the terminal
12770 driver software. For example, on Unix @value{GDBN} uses the termcap data base
12771 together with the value of the @code{TERM} environment variable and the
12772 @code{stty rows} and @code{stty cols} settings. If this is not correct,
12773 you can override it with the @code{set height} and @code{set
12780 @kindex show height
12781 @item set height @var{lpp}
12783 @itemx set width @var{cpl}
12785 These @code{set} commands specify a screen height of @var{lpp} lines and
12786 a screen width of @var{cpl} characters. The associated @code{show}
12787 commands display the current settings.
12789 If you specify a height of zero lines, @value{GDBN} does not pause during
12790 output no matter how long the output is. This is useful if output is to a
12791 file or to an editor buffer.
12793 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
12794 from wrapping its output.
12799 @cindex number representation
12800 @cindex entering numbers
12802 You can always enter numbers in octal, decimal, or hexadecimal in
12803 @value{GDBN} by the usual conventions: octal numbers begin with
12804 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
12805 begin with @samp{0x}. Numbers that begin with none of these are, by
12806 default, entered in base 10; likewise, the default display for
12807 numbers---when no particular format is specified---is base 10. You can
12808 change the default base for both input and output with the @code{set
12812 @kindex set input-radix
12813 @item set input-radix @var{base}
12814 Set the default base for numeric input. Supported choices
12815 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12816 specified either unambiguously or using the current default radix; for
12826 sets the base to decimal. On the other hand, @samp{set radix 10}
12827 leaves the radix unchanged no matter what it was.
12829 @kindex set output-radix
12830 @item set output-radix @var{base}
12831 Set the default base for numeric display. Supported choices
12832 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12833 specified either unambiguously or using the current default radix.
12835 @kindex show input-radix
12836 @item show input-radix
12837 Display the current default base for numeric input.
12839 @kindex show output-radix
12840 @item show output-radix
12841 Display the current default base for numeric display.
12845 @section Configuring the current ABI
12847 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
12848 application automatically. However, sometimes you need to override its
12849 conclusions. Use these commands to manage @value{GDBN}'s view of the
12856 One @value{GDBN} configuration can debug binaries for multiple operating
12857 system targets, either via remote debugging or native emulation.
12858 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
12859 but you can override its conclusion using the @code{set osabi} command.
12860 One example where this is useful is in debugging of binaries which use
12861 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
12862 not have the same identifying marks that the standard C library for your
12867 Show the OS ABI currently in use.
12870 With no argument, show the list of registered available OS ABI's.
12872 @item set osabi @var{abi}
12873 Set the current OS ABI to @var{abi}.
12876 @cindex float promotion
12877 @kindex set coerce-float-to-double
12879 Generally, the way that an argument of type @code{float} is passed to a
12880 function depends on whether the function is prototyped. For a prototyped
12881 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
12882 according to the architecture's convention for @code{float}. For unprototyped
12883 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
12884 @code{double} and then passed.
12886 Unfortunately, some forms of debug information do not reliably indicate whether
12887 a function is prototyped. If @value{GDBN} calls a function that is not marked
12888 as prototyped, it consults @kbd{set coerce-float-to-double}.
12891 @item set coerce-float-to-double
12892 @itemx set coerce-float-to-double on
12893 Arguments of type @code{float} will be promoted to @code{double} when passed
12894 to an unprototyped function. This is the default setting.
12896 @item set coerce-float-to-double off
12897 Arguments of type @code{float} will be passed directly to unprototyped
12902 @kindex show cp-abi
12903 @value{GDBN} needs to know the ABI used for your program's C@t{++}
12904 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
12905 used to build your application. @value{GDBN} only fully supports
12906 programs with a single C@t{++} ABI; if your program contains code using
12907 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
12908 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
12909 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
12910 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
12911 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
12912 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
12917 Show the C@t{++} ABI currently in use.
12920 With no argument, show the list of supported C@t{++} ABI's.
12922 @item set cp-abi @var{abi}
12923 @itemx set cp-abi auto
12924 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
12927 @node Messages/Warnings
12928 @section Optional warnings and messages
12930 By default, @value{GDBN} is silent about its inner workings. If you are
12931 running on a slow machine, you may want to use the @code{set verbose}
12932 command. This makes @value{GDBN} tell you when it does a lengthy
12933 internal operation, so you will not think it has crashed.
12935 Currently, the messages controlled by @code{set verbose} are those
12936 which announce that the symbol table for a source file is being read;
12937 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
12940 @kindex set verbose
12941 @item set verbose on
12942 Enables @value{GDBN} output of certain informational messages.
12944 @item set verbose off
12945 Disables @value{GDBN} output of certain informational messages.
12947 @kindex show verbose
12949 Displays whether @code{set verbose} is on or off.
12952 By default, if @value{GDBN} encounters bugs in the symbol table of an
12953 object file, it is silent; but if you are debugging a compiler, you may
12954 find this information useful (@pxref{Symbol Errors, ,Errors reading
12959 @kindex set complaints
12960 @item set complaints @var{limit}
12961 Permits @value{GDBN} to output @var{limit} complaints about each type of
12962 unusual symbols before becoming silent about the problem. Set
12963 @var{limit} to zero to suppress all complaints; set it to a large number
12964 to prevent complaints from being suppressed.
12966 @kindex show complaints
12967 @item show complaints
12968 Displays how many symbol complaints @value{GDBN} is permitted to produce.
12972 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
12973 lot of stupid questions to confirm certain commands. For example, if
12974 you try to run a program which is already running:
12978 The program being debugged has been started already.
12979 Start it from the beginning? (y or n)
12982 If you are willing to unflinchingly face the consequences of your own
12983 commands, you can disable this ``feature'':
12987 @kindex set confirm
12989 @cindex confirmation
12990 @cindex stupid questions
12991 @item set confirm off
12992 Disables confirmation requests.
12994 @item set confirm on
12995 Enables confirmation requests (the default).
12997 @kindex show confirm
12999 Displays state of confirmation requests.
13003 @node Debugging Output
13004 @section Optional messages about internal happenings
13006 @kindex set debug arch
13007 @item set debug arch
13008 Turns on or off display of gdbarch debugging info. The default is off
13009 @kindex show debug arch
13010 @item show debug arch
13011 Displays the current state of displaying gdbarch debugging info.
13012 @kindex set debug event
13013 @item set debug event
13014 Turns on or off display of @value{GDBN} event debugging info. The
13016 @kindex show debug event
13017 @item show debug event
13018 Displays the current state of displaying @value{GDBN} event debugging
13020 @kindex set debug expression
13021 @item set debug expression
13022 Turns on or off display of @value{GDBN} expression debugging info. The
13024 @kindex show debug expression
13025 @item show debug expression
13026 Displays the current state of displaying @value{GDBN} expression
13028 @kindex set debug frame
13029 @item set debug frame
13030 Turns on or off display of @value{GDBN} frame debugging info. The
13032 @kindex show debug frame
13033 @item show debug frame
13034 Displays the current state of displaying @value{GDBN} frame debugging
13036 @kindex set debug overload
13037 @item set debug overload
13038 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13039 info. This includes info such as ranking of functions, etc. The default
13041 @kindex show debug overload
13042 @item show debug overload
13043 Displays the current state of displaying @value{GDBN} C@t{++} overload
13045 @kindex set debug remote
13046 @cindex packets, reporting on stdout
13047 @cindex serial connections, debugging
13048 @item set debug remote
13049 Turns on or off display of reports on all packets sent back and forth across
13050 the serial line to the remote machine. The info is printed on the
13051 @value{GDBN} standard output stream. The default is off.
13052 @kindex show debug remote
13053 @item show debug remote
13054 Displays the state of display of remote packets.
13055 @kindex set debug serial
13056 @item set debug serial
13057 Turns on or off display of @value{GDBN} serial debugging info. The
13059 @kindex show debug serial
13060 @item show debug serial
13061 Displays the current state of displaying @value{GDBN} serial debugging
13063 @kindex set debug target
13064 @item set debug target
13065 Turns on or off display of @value{GDBN} target debugging info. This info
13066 includes what is going on at the target level of GDB, as it happens. The
13068 @kindex show debug target
13069 @item show debug target
13070 Displays the current state of displaying @value{GDBN} target debugging
13072 @kindex set debug varobj
13073 @item set debug varobj
13074 Turns on or off display of @value{GDBN} variable object debugging
13075 info. The default is off.
13076 @kindex show debug varobj
13077 @item show debug varobj
13078 Displays the current state of displaying @value{GDBN} variable object
13083 @chapter Canned Sequences of Commands
13085 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13086 command lists}), @value{GDBN} provides two ways to store sequences of
13087 commands for execution as a unit: user-defined commands and command
13091 * Define:: User-defined commands
13092 * Hooks:: User-defined command hooks
13093 * Command Files:: Command files
13094 * Output:: Commands for controlled output
13098 @section User-defined commands
13100 @cindex user-defined command
13101 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13102 which you assign a new name as a command. This is done with the
13103 @code{define} command. User commands may accept up to 10 arguments
13104 separated by whitespace. Arguments are accessed within the user command
13105 via @var{$arg0@dots{}$arg9}. A trivial example:
13109 print $arg0 + $arg1 + $arg2
13113 To execute the command use:
13120 This defines the command @code{adder}, which prints the sum of
13121 its three arguments. Note the arguments are text substitutions, so they may
13122 reference variables, use complex expressions, or even perform inferior
13128 @item define @var{commandname}
13129 Define a command named @var{commandname}. If there is already a command
13130 by that name, you are asked to confirm that you want to redefine it.
13132 The definition of the command is made up of other @value{GDBN} command lines,
13133 which are given following the @code{define} command. The end of these
13134 commands is marked by a line containing @code{end}.
13139 Takes a single argument, which is an expression to evaluate.
13140 It is followed by a series of commands that are executed
13141 only if the expression is true (nonzero).
13142 There can then optionally be a line @code{else}, followed
13143 by a series of commands that are only executed if the expression
13144 was false. The end of the list is marked by a line containing @code{end}.
13148 The syntax is similar to @code{if}: the command takes a single argument,
13149 which is an expression to evaluate, and must be followed by the commands to
13150 execute, one per line, terminated by an @code{end}.
13151 The commands are executed repeatedly as long as the expression
13155 @item document @var{commandname}
13156 Document the user-defined command @var{commandname}, so that it can be
13157 accessed by @code{help}. The command @var{commandname} must already be
13158 defined. This command reads lines of documentation just as @code{define}
13159 reads the lines of the command definition, ending with @code{end}.
13160 After the @code{document} command is finished, @code{help} on command
13161 @var{commandname} displays the documentation you have written.
13163 You may use the @code{document} command again to change the
13164 documentation of a command. Redefining the command with @code{define}
13165 does not change the documentation.
13167 @kindex help user-defined
13168 @item help user-defined
13169 List all user-defined commands, with the first line of the documentation
13174 @itemx show user @var{commandname}
13175 Display the @value{GDBN} commands used to define @var{commandname} (but
13176 not its documentation). If no @var{commandname} is given, display the
13177 definitions for all user-defined commands.
13179 @kindex show max-user-call-depth
13180 @kindex set max-user-call-depth
13181 @item show max-user-call-depth
13182 @itemx set max-user-call-depth
13183 The value of @code{max-user-call-depth} controls how many recursion
13184 levels are allowed in user-defined commands before GDB suspects an
13185 infinite recursion and aborts the command.
13189 When user-defined commands are executed, the
13190 commands of the definition are not printed. An error in any command
13191 stops execution of the user-defined command.
13193 If used interactively, commands that would ask for confirmation proceed
13194 without asking when used inside a user-defined command. Many @value{GDBN}
13195 commands that normally print messages to say what they are doing omit the
13196 messages when used in a user-defined command.
13199 @section User-defined command hooks
13200 @cindex command hooks
13201 @cindex hooks, for commands
13202 @cindex hooks, pre-command
13206 You may define @dfn{hooks}, which are a special kind of user-defined
13207 command. Whenever you run the command @samp{foo}, if the user-defined
13208 command @samp{hook-foo} exists, it is executed (with no arguments)
13209 before that command.
13211 @cindex hooks, post-command
13214 A hook may also be defined which is run after the command you executed.
13215 Whenever you run the command @samp{foo}, if the user-defined command
13216 @samp{hookpost-foo} exists, it is executed (with no arguments) after
13217 that command. Post-execution hooks may exist simultaneously with
13218 pre-execution hooks, for the same command.
13220 It is valid for a hook to call the command which it hooks. If this
13221 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
13223 @c It would be nice if hookpost could be passed a parameter indicating
13224 @c if the command it hooks executed properly or not. FIXME!
13226 @kindex stop@r{, a pseudo-command}
13227 In addition, a pseudo-command, @samp{stop} exists. Defining
13228 (@samp{hook-stop}) makes the associated commands execute every time
13229 execution stops in your program: before breakpoint commands are run,
13230 displays are printed, or the stack frame is printed.
13232 For example, to ignore @code{SIGALRM} signals while
13233 single-stepping, but treat them normally during normal execution,
13238 handle SIGALRM nopass
13242 handle SIGALRM pass
13245 define hook-continue
13246 handle SIGLARM pass
13250 As a further example, to hook at the begining and end of the @code{echo}
13251 command, and to add extra text to the beginning and end of the message,
13259 define hookpost-echo
13263 (@value{GDBP}) echo Hello World
13264 <<<---Hello World--->>>
13269 You can define a hook for any single-word command in @value{GDBN}, but
13270 not for command aliases; you should define a hook for the basic command
13271 name, e.g. @code{backtrace} rather than @code{bt}.
13272 @c FIXME! So how does Joe User discover whether a command is an alias
13274 If an error occurs during the execution of your hook, execution of
13275 @value{GDBN} commands stops and @value{GDBN} issues a prompt
13276 (before the command that you actually typed had a chance to run).
13278 If you try to define a hook which does not match any known command, you
13279 get a warning from the @code{define} command.
13281 @node Command Files
13282 @section Command files
13284 @cindex command files
13285 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
13286 commands. Comments (lines starting with @kbd{#}) may also be included.
13287 An empty line in a command file does nothing; it does not mean to repeat
13288 the last command, as it would from the terminal.
13291 @cindex @file{.gdbinit}
13292 @cindex @file{gdb.ini}
13293 When you start @value{GDBN}, it automatically executes commands from its
13294 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
13295 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
13296 limitations of file names imposed by DOS filesystems.}.
13297 During startup, @value{GDBN} does the following:
13301 Reads the init file (if any) in your home directory@footnote{On
13302 DOS/Windows systems, the home directory is the one pointed to by the
13303 @code{HOME} environment variable.}.
13306 Processes command line options and operands.
13309 Reads the init file (if any) in the current working directory.
13312 Reads command files specified by the @samp{-x} option.
13315 The init file in your home directory can set options (such as @samp{set
13316 complaints}) that affect subsequent processing of command line options
13317 and operands. Init files are not executed if you use the @samp{-nx}
13318 option (@pxref{Mode Options, ,Choosing modes}).
13320 @cindex init file name
13321 On some configurations of @value{GDBN}, the init file is known by a
13322 different name (these are typically environments where a specialized
13323 form of @value{GDBN} may need to coexist with other forms, hence a
13324 different name for the specialized version's init file). These are the
13325 environments with special init file names:
13327 @cindex @file{.vxgdbinit}
13330 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
13332 @cindex @file{.os68gdbinit}
13334 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
13336 @cindex @file{.esgdbinit}
13338 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
13341 You can also request the execution of a command file with the
13342 @code{source} command:
13346 @item source @var{filename}
13347 Execute the command file @var{filename}.
13350 The lines in a command file are executed sequentially. They are not
13351 printed as they are executed. An error in any command terminates
13352 execution of the command file and control is returned to the console.
13354 Commands that would ask for confirmation if used interactively proceed
13355 without asking when used in a command file. Many @value{GDBN} commands that
13356 normally print messages to say what they are doing omit the messages
13357 when called from command files.
13359 @value{GDBN} also accepts command input from standard input. In this
13360 mode, normal output goes to standard output and error output goes to
13361 standard error. Errors in a command file supplied on standard input do
13362 not terminate execution of the command file --- execution continues with
13366 gdb < cmds > log 2>&1
13369 (The syntax above will vary depending on the shell used.) This example
13370 will execute commands from the file @file{cmds}. All output and errors
13371 would be directed to @file{log}.
13374 @section Commands for controlled output
13376 During the execution of a command file or a user-defined command, normal
13377 @value{GDBN} output is suppressed; the only output that appears is what is
13378 explicitly printed by the commands in the definition. This section
13379 describes three commands useful for generating exactly the output you
13384 @item echo @var{text}
13385 @c I do not consider backslash-space a standard C escape sequence
13386 @c because it is not in ANSI.
13387 Print @var{text}. Nonprinting characters can be included in
13388 @var{text} using C escape sequences, such as @samp{\n} to print a
13389 newline. @strong{No newline is printed unless you specify one.}
13390 In addition to the standard C escape sequences, a backslash followed
13391 by a space stands for a space. This is useful for displaying a
13392 string with spaces at the beginning or the end, since leading and
13393 trailing spaces are otherwise trimmed from all arguments.
13394 To print @samp{@w{ }and foo =@w{ }}, use the command
13395 @samp{echo \@w{ }and foo = \@w{ }}.
13397 A backslash at the end of @var{text} can be used, as in C, to continue
13398 the command onto subsequent lines. For example,
13401 echo This is some text\n\
13402 which is continued\n\
13403 onto several lines.\n
13406 produces the same output as
13409 echo This is some text\n
13410 echo which is continued\n
13411 echo onto several lines.\n
13415 @item output @var{expression}
13416 Print the value of @var{expression} and nothing but that value: no
13417 newlines, no @samp{$@var{nn} = }. The value is not entered in the
13418 value history either. @xref{Expressions, ,Expressions}, for more information
13421 @item output/@var{fmt} @var{expression}
13422 Print the value of @var{expression} in format @var{fmt}. You can use
13423 the same formats as for @code{print}. @xref{Output Formats,,Output
13424 formats}, for more information.
13427 @item printf @var{string}, @var{expressions}@dots{}
13428 Print the values of the @var{expressions} under the control of
13429 @var{string}. The @var{expressions} are separated by commas and may be
13430 either numbers or pointers. Their values are printed as specified by
13431 @var{string}, exactly as if your program were to execute the C
13433 @c FIXME: the above implies that at least all ANSI C formats are
13434 @c supported, but it isn't true: %E and %G don't work (or so it seems).
13435 @c Either this is a bug, or the manual should document what formats are
13439 printf (@var{string}, @var{expressions}@dots{});
13442 For example, you can print two values in hex like this:
13445 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
13448 The only backslash-escape sequences that you can use in the format
13449 string are the simple ones that consist of backslash followed by a
13454 @chapter Command Interpreters
13455 @cindex command interpreters
13457 @value{GDBN} supports multiple command interpreters, and some command
13458 infrastructure to allow users or user interface writers to switch
13459 between interpreters or run commands in other interpreters.
13461 @value{GDBN} currently supports two command interpreters, the console
13462 interpreter (sometimes called the command-line interpreter or @sc{cli})
13463 and the machine interface interpreter (or @sc{gdb/mi}). This manual
13464 describes both of these interfaces in great detail.
13466 By default, @value{GDBN} will start with the console interpreter.
13467 However, the user may choose to start @value{GDBN} with another
13468 interpreter by specifying the @option{-i} or @option{--interpreter}
13469 startup options. Defined interpreters include:
13473 @cindex console interpreter
13474 The traditional console or command-line interpreter. This is the most often
13475 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
13476 @value{GDBN} will use this interpreter.
13479 @cindex mi interpreter
13480 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
13481 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
13482 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
13486 @cindex mi2 interpreter
13487 The current @sc{gdb/mi} interface.
13490 @cindex mi1 interpreter
13491 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
13495 @cindex invoke another interpreter
13496 The interpreter being used by @value{GDBN} may not be dynamically
13497 switched at runtime. Although possible, this could lead to a very
13498 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
13499 enters the command "interpreter-set console" in a console view,
13500 @value{GDBN} would switch to using the console interpreter, rendering
13501 the IDE inoperable!
13503 @kindex interpreter-exec
13504 Although you may only choose a single interpreter at startup, you may execute
13505 commands in any interpreter from the current interpreter using the appropriate
13506 command. If you are running the console interpreter, simply use the
13507 @code{interpreter-exec} command:
13510 interpreter-exec mi "-data-list-register-names"
13513 @sc{gdb/mi} has a similar command, although it is only available in versions of
13514 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
13517 @chapter @value{GDBN} Text User Interface
13521 * TUI Overview:: TUI overview
13522 * TUI Keys:: TUI key bindings
13523 * TUI Single Key Mode:: TUI single key mode
13524 * TUI Commands:: TUI specific commands
13525 * TUI Configuration:: TUI configuration variables
13528 The @value{GDBN} Text User Interface, TUI in short,
13529 is a terminal interface which uses the @code{curses} library
13530 to show the source file, the assembly output, the program registers
13531 and @value{GDBN} commands in separate text windows.
13532 The TUI is available only when @value{GDBN} is configured
13533 with the @code{--enable-tui} configure option (@pxref{Configure Options}).
13536 @section TUI overview
13538 The TUI has two display modes that can be switched while
13543 A curses (or TUI) mode in which it displays several text
13544 windows on the terminal.
13547 A standard mode which corresponds to the @value{GDBN} configured without
13551 In the TUI mode, @value{GDBN} can display several text window
13556 This window is the @value{GDBN} command window with the @value{GDBN}
13557 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
13558 managed using readline but through the TUI. The @emph{command}
13559 window is always visible.
13562 The source window shows the source file of the program. The current
13563 line as well as active breakpoints are displayed in this window.
13566 The assembly window shows the disassembly output of the program.
13569 This window shows the processor registers. It detects when
13570 a register is changed and when this is the case, registers that have
13571 changed are highlighted.
13575 The source and assembly windows show the current program position
13576 by highlighting the current line and marking them with the @samp{>} marker.
13577 Breakpoints are also indicated with two markers. A first one
13578 indicates the breakpoint type:
13582 Breakpoint which was hit at least once.
13585 Breakpoint which was never hit.
13588 Hardware breakpoint which was hit at least once.
13591 Hardware breakpoint which was never hit.
13595 The second marker indicates whether the breakpoint is enabled or not:
13599 Breakpoint is enabled.
13602 Breakpoint is disabled.
13606 The source, assembly and register windows are attached to the thread
13607 and the frame position. They are updated when the current thread
13608 changes, when the frame changes or when the program counter changes.
13609 These three windows are arranged by the TUI according to several
13610 layouts. The layout defines which of these three windows are visible.
13611 The following layouts are available:
13621 source and assembly
13624 source and registers
13627 assembly and registers
13631 On top of the command window a status line gives various information
13632 concerning the current process begin debugged. The status line is
13633 updated when the information it shows changes. The following fields
13638 Indicates the current gdb target
13639 (@pxref{Targets, ,Specifying a Debugging Target}).
13642 Gives information about the current process or thread number.
13643 When no process is being debugged, this field is set to @code{No process}.
13646 Gives the current function name for the selected frame.
13647 The name is demangled if demangling is turned on (@pxref{Print Settings}).
13648 When there is no symbol corresponding to the current program counter
13649 the string @code{??} is displayed.
13652 Indicates the current line number for the selected frame.
13653 When the current line number is not known the string @code{??} is displayed.
13656 Indicates the current program counter address.
13661 @section TUI Key Bindings
13662 @cindex TUI key bindings
13664 The TUI installs several key bindings in the readline keymaps
13665 (@pxref{Command Line Editing}).
13666 They allow to leave or enter in the TUI mode or they operate
13667 directly on the TUI layout and windows. The TUI also provides
13668 a @emph{SingleKey} keymap which binds several keys directly to
13669 @value{GDBN} commands. The following key bindings
13670 are installed for both TUI mode and the @value{GDBN} standard mode.
13679 Enter or leave the TUI mode. When the TUI mode is left,
13680 the curses window management is left and @value{GDBN} operates using
13681 its standard mode writing on the terminal directly. When the TUI
13682 mode is entered, the control is given back to the curses windows.
13683 The screen is then refreshed.
13687 Use a TUI layout with only one window. The layout will
13688 either be @samp{source} or @samp{assembly}. When the TUI mode
13689 is not active, it will switch to the TUI mode.
13691 Think of this key binding as the Emacs @kbd{C-x 1} binding.
13695 Use a TUI layout with at least two windows. When the current
13696 layout shows already two windows, a next layout with two windows is used.
13697 When a new layout is chosen, one window will always be common to the
13698 previous layout and the new one.
13700 Think of it as the Emacs @kbd{C-x 2} binding.
13704 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
13705 (@pxref{TUI Single Key Mode}).
13709 The following key bindings are handled only by the TUI mode:
13714 Scroll the active window one page up.
13718 Scroll the active window one page down.
13722 Scroll the active window one line up.
13726 Scroll the active window one line down.
13730 Scroll the active window one column left.
13734 Scroll the active window one column right.
13738 Refresh the screen.
13742 In the TUI mode, the arrow keys are used by the active window
13743 for scrolling. This means they are not available for readline. It is
13744 necessary to use other readline key bindings such as @key{C-p}, @key{C-n},
13745 @key{C-b} and @key{C-f}.
13747 @node TUI Single Key Mode
13748 @section TUI Single Key Mode
13749 @cindex TUI single key mode
13751 The TUI provides a @emph{SingleKey} mode in which it installs a particular
13752 key binding in the readline keymaps to connect single keys to
13756 @kindex c @r{(SingleKey TUI key)}
13760 @kindex d @r{(SingleKey TUI key)}
13764 @kindex f @r{(SingleKey TUI key)}
13768 @kindex n @r{(SingleKey TUI key)}
13772 @kindex q @r{(SingleKey TUI key)}
13774 exit the @emph{SingleKey} mode.
13776 @kindex r @r{(SingleKey TUI key)}
13780 @kindex s @r{(SingleKey TUI key)}
13784 @kindex u @r{(SingleKey TUI key)}
13788 @kindex v @r{(SingleKey TUI key)}
13792 @kindex w @r{(SingleKey TUI key)}
13798 Other keys temporarily switch to the @value{GDBN} command prompt.
13799 The key that was pressed is inserted in the editing buffer so that
13800 it is possible to type most @value{GDBN} commands without interaction
13801 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
13802 @emph{SingleKey} mode is restored. The only way to permanently leave
13803 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
13807 @section TUI specific commands
13808 @cindex TUI commands
13810 The TUI has specific commands to control the text windows.
13811 These commands are always available, that is they do not depend on
13812 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
13813 is in the standard mode, using these commands will automatically switch
13819 List and give the size of all displayed windows.
13822 @kindex layout next
13823 Display the next layout.
13826 @kindex layout prev
13827 Display the previous layout.
13831 Display the source window only.
13835 Display the assembly window only.
13838 @kindex layout split
13839 Display the source and assembly window.
13842 @kindex layout regs
13843 Display the register window together with the source or assembly window.
13845 @item focus next | prev | src | asm | regs | split
13847 Set the focus to the named window.
13848 This command allows to change the active window so that scrolling keys
13849 can be affected to another window.
13853 Refresh the screen. This is similar to using @key{C-L} key.
13857 Update the source window and the current execution point.
13859 @item winheight @var{name} +@var{count}
13860 @itemx winheight @var{name} -@var{count}
13862 Change the height of the window @var{name} by @var{count}
13863 lines. Positive counts increase the height, while negative counts
13868 @node TUI Configuration
13869 @section TUI configuration variables
13870 @cindex TUI configuration variables
13872 The TUI has several configuration variables that control the
13873 appearance of windows on the terminal.
13876 @item set tui border-kind @var{kind}
13877 @kindex set tui border-kind
13878 Select the border appearance for the source, assembly and register windows.
13879 The possible values are the following:
13882 Use a space character to draw the border.
13885 Use ascii characters + - and | to draw the border.
13888 Use the Alternate Character Set to draw the border. The border is
13889 drawn using character line graphics if the terminal supports them.
13893 @item set tui active-border-mode @var{mode}
13894 @kindex set tui active-border-mode
13895 Select the attributes to display the border of the active window.
13896 The possible values are @code{normal}, @code{standout}, @code{reverse},
13897 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
13899 @item set tui border-mode @var{mode}
13900 @kindex set tui border-mode
13901 Select the attributes to display the border of other windows.
13902 The @var{mode} can be one of the following:
13905 Use normal attributes to display the border.
13911 Use reverse video mode.
13914 Use half bright mode.
13916 @item half-standout
13917 Use half bright and standout mode.
13920 Use extra bright or bold mode.
13922 @item bold-standout
13923 Use extra bright or bold and standout mode.
13930 @chapter Using @value{GDBN} under @sc{gnu} Emacs
13933 @cindex @sc{gnu} Emacs
13934 A special interface allows you to use @sc{gnu} Emacs to view (and
13935 edit) the source files for the program you are debugging with
13938 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
13939 executable file you want to debug as an argument. This command starts
13940 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
13941 created Emacs buffer.
13942 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
13944 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
13949 All ``terminal'' input and output goes through the Emacs buffer.
13952 This applies both to @value{GDBN} commands and their output, and to the input
13953 and output done by the program you are debugging.
13955 This is useful because it means that you can copy the text of previous
13956 commands and input them again; you can even use parts of the output
13959 All the facilities of Emacs' Shell mode are available for interacting
13960 with your program. In particular, you can send signals the usual
13961 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
13966 @value{GDBN} displays source code through Emacs.
13969 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
13970 source file for that frame and puts an arrow (@samp{=>}) at the
13971 left margin of the current line. Emacs uses a separate buffer for
13972 source display, and splits the screen to show both your @value{GDBN} session
13975 Explicit @value{GDBN} @code{list} or search commands still produce output as
13976 usual, but you probably have no reason to use them from Emacs.
13979 @emph{Warning:} If the directory where your program resides is not your
13980 current directory, it can be easy to confuse Emacs about the location of
13981 the source files, in which case the auxiliary display buffer does not
13982 appear to show your source. @value{GDBN} can find programs by searching your
13983 environment's @code{PATH} variable, so the @value{GDBN} input and output
13984 session proceeds normally; but Emacs does not get enough information
13985 back from @value{GDBN} to locate the source files in this situation. To
13986 avoid this problem, either start @value{GDBN} mode from the directory where
13987 your program resides, or specify an absolute file name when prompted for the
13988 @kbd{M-x gdb} argument.
13990 A similar confusion can result if you use the @value{GDBN} @code{file} command to
13991 switch to debugging a program in some other location, from an existing
13992 @value{GDBN} buffer in Emacs.
13995 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If
13996 you need to call @value{GDBN} by a different name (for example, if you keep
13997 several configurations around, with different names) you can set the
13998 Emacs variable @code{gdb-command-name}; for example,
14001 (setq gdb-command-name "mygdb")
14005 (preceded by @kbd{M-:} or @kbd{ESC :}, or typed in the @code{*scratch*} buffer, or
14006 in your @file{.emacs} file) makes Emacs call the program named
14007 ``@code{mygdb}'' instead.
14009 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
14010 addition to the standard Shell mode commands:
14014 Describe the features of Emacs' @value{GDBN} Mode.
14017 Execute to another source line, like the @value{GDBN} @code{step} command; also
14018 update the display window to show the current file and location.
14021 Execute to next source line in this function, skipping all function
14022 calls, like the @value{GDBN} @code{next} command. Then update the display window
14023 to show the current file and location.
14026 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
14027 display window accordingly.
14029 @item M-x gdb-nexti
14030 Execute to next instruction, using the @value{GDBN} @code{nexti} command; update
14031 display window accordingly.
14034 Execute until exit from the selected stack frame, like the @value{GDBN}
14035 @code{finish} command.
14038 Continue execution of your program, like the @value{GDBN} @code{continue}
14041 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}.
14044 Go up the number of frames indicated by the numeric argument
14045 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
14046 like the @value{GDBN} @code{up} command.
14048 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-u}.
14051 Go down the number of frames indicated by the numeric argument, like the
14052 @value{GDBN} @code{down} command.
14054 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-d}.
14057 Read the number where the cursor is positioned, and insert it at the end
14058 of the @value{GDBN} I/O buffer. For example, if you wish to disassemble code
14059 around an address that was displayed earlier, type @kbd{disassemble};
14060 then move the cursor to the address display, and pick up the
14061 argument for @code{disassemble} by typing @kbd{C-x &}.
14063 You can customize this further by defining elements of the list
14064 @code{gdb-print-command}; once it is defined, you can format or
14065 otherwise process numbers picked up by @kbd{C-x &} before they are
14066 inserted. A numeric argument to @kbd{C-x &} indicates that you
14067 wish special formatting, and also acts as an index to pick an element of the
14068 list. If the list element is a string, the number to be inserted is
14069 formatted using the Emacs function @code{format}; otherwise the number
14070 is passed as an argument to the corresponding list element.
14073 In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break})
14074 tells @value{GDBN} to set a breakpoint on the source line point is on.
14076 If you accidentally delete the source-display buffer, an easy way to get
14077 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14078 request a frame display; when you run under Emacs, this recreates
14079 the source buffer if necessary to show you the context of the current
14082 The source files displayed in Emacs are in ordinary Emacs buffers
14083 which are visiting the source files in the usual way. You can edit
14084 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14085 communicates with Emacs in terms of line numbers. If you add or
14086 delete lines from the text, the line numbers that @value{GDBN} knows cease
14087 to correspond properly with the code.
14089 @c The following dropped because Epoch is nonstandard. Reactivate
14090 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14092 @kindex Emacs Epoch environment
14096 Version 18 of @sc{gnu} Emacs has a built-in window system
14097 called the @code{epoch}
14098 environment. Users of this environment can use a new command,
14099 @code{inspect} which performs identically to @code{print} except that
14100 each value is printed in its own window.
14105 @chapter The @sc{gdb/mi} Interface
14107 @unnumberedsec Function and Purpose
14109 @cindex @sc{gdb/mi}, its purpose
14110 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
14111 specifically intended to support the development of systems which use
14112 the debugger as just one small component of a larger system.
14114 This chapter is a specification of the @sc{gdb/mi} interface. It is written
14115 in the form of a reference manual.
14117 Note that @sc{gdb/mi} is still under construction, so some of the
14118 features described below are incomplete and subject to change.
14120 @unnumberedsec Notation and Terminology
14122 @cindex notational conventions, for @sc{gdb/mi}
14123 This chapter uses the following notation:
14127 @code{|} separates two alternatives.
14130 @code{[ @var{something} ]} indicates that @var{something} is optional:
14131 it may or may not be given.
14134 @code{( @var{group} )*} means that @var{group} inside the parentheses
14135 may repeat zero or more times.
14138 @code{( @var{group} )+} means that @var{group} inside the parentheses
14139 may repeat one or more times.
14142 @code{"@var{string}"} means a literal @var{string}.
14146 @heading Dependencies
14149 @heading Acknowledgments
14151 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
14155 * GDB/MI Command Syntax::
14156 * GDB/MI Compatibility with CLI::
14157 * GDB/MI Output Records::
14158 * GDB/MI Command Description Format::
14159 * GDB/MI Breakpoint Table Commands::
14160 * GDB/MI Data Manipulation::
14161 * GDB/MI Program Control::
14162 * GDB/MI Miscellaneous Commands::
14164 * GDB/MI Kod Commands::
14165 * GDB/MI Memory Overlay Commands::
14166 * GDB/MI Signal Handling Commands::
14168 * GDB/MI Stack Manipulation::
14169 * GDB/MI Symbol Query::
14170 * GDB/MI Target Manipulation::
14171 * GDB/MI Thread Commands::
14172 * GDB/MI Tracepoint Commands::
14173 * GDB/MI Variable Objects::
14176 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14177 @node GDB/MI Command Syntax
14178 @section @sc{gdb/mi} Command Syntax
14181 * GDB/MI Input Syntax::
14182 * GDB/MI Output Syntax::
14183 * GDB/MI Simple Examples::
14186 @node GDB/MI Input Syntax
14187 @subsection @sc{gdb/mi} Input Syntax
14189 @cindex input syntax for @sc{gdb/mi}
14190 @cindex @sc{gdb/mi}, input syntax
14192 @item @var{command} @expansion{}
14193 @code{@var{cli-command} | @var{mi-command}}
14195 @item @var{cli-command} @expansion{}
14196 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
14197 @var{cli-command} is any existing @value{GDBN} CLI command.
14199 @item @var{mi-command} @expansion{}
14200 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
14201 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
14203 @item @var{token} @expansion{}
14204 "any sequence of digits"
14206 @item @var{option} @expansion{}
14207 @code{"-" @var{parameter} [ " " @var{parameter} ]}
14209 @item @var{parameter} @expansion{}
14210 @code{@var{non-blank-sequence} | @var{c-string}}
14212 @item @var{operation} @expansion{}
14213 @emph{any of the operations described in this chapter}
14215 @item @var{non-blank-sequence} @expansion{}
14216 @emph{anything, provided it doesn't contain special characters such as
14217 "-", @var{nl}, """ and of course " "}
14219 @item @var{c-string} @expansion{}
14220 @code{""" @var{seven-bit-iso-c-string-content} """}
14222 @item @var{nl} @expansion{}
14231 The CLI commands are still handled by the @sc{mi} interpreter; their
14232 output is described below.
14235 The @code{@var{token}}, when present, is passed back when the command
14239 Some @sc{mi} commands accept optional arguments as part of the parameter
14240 list. Each option is identified by a leading @samp{-} (dash) and may be
14241 followed by an optional argument parameter. Options occur first in the
14242 parameter list and can be delimited from normal parameters using
14243 @samp{--} (this is useful when some parameters begin with a dash).
14250 We want easy access to the existing CLI syntax (for debugging).
14253 We want it to be easy to spot a @sc{mi} operation.
14256 @node GDB/MI Output Syntax
14257 @subsection @sc{gdb/mi} Output Syntax
14259 @cindex output syntax of @sc{gdb/mi}
14260 @cindex @sc{gdb/mi}, output syntax
14261 The output from @sc{gdb/mi} consists of zero or more out-of-band records
14262 followed, optionally, by a single result record. This result record
14263 is for the most recent command. The sequence of output records is
14264 terminated by @samp{(@value{GDBP})}.
14266 If an input command was prefixed with a @code{@var{token}} then the
14267 corresponding output for that command will also be prefixed by that same
14271 @item @var{output} @expansion{}
14272 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
14274 @item @var{result-record} @expansion{}
14275 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
14277 @item @var{out-of-band-record} @expansion{}
14278 @code{@var{async-record} | @var{stream-record}}
14280 @item @var{async-record} @expansion{}
14281 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
14283 @item @var{exec-async-output} @expansion{}
14284 @code{[ @var{token} ] "*" @var{async-output}}
14286 @item @var{status-async-output} @expansion{}
14287 @code{[ @var{token} ] "+" @var{async-output}}
14289 @item @var{notify-async-output} @expansion{}
14290 @code{[ @var{token} ] "=" @var{async-output}}
14292 @item @var{async-output} @expansion{}
14293 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
14295 @item @var{result-class} @expansion{}
14296 @code{"done" | "running" | "connected" | "error" | "exit"}
14298 @item @var{async-class} @expansion{}
14299 @code{"stopped" | @var{others}} (where @var{others} will be added
14300 depending on the needs---this is still in development).
14302 @item @var{result} @expansion{}
14303 @code{ @var{variable} "=" @var{value}}
14305 @item @var{variable} @expansion{}
14306 @code{ @var{string} }
14308 @item @var{value} @expansion{}
14309 @code{ @var{const} | @var{tuple} | @var{list} }
14311 @item @var{const} @expansion{}
14312 @code{@var{c-string}}
14314 @item @var{tuple} @expansion{}
14315 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
14317 @item @var{list} @expansion{}
14318 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
14319 @var{result} ( "," @var{result} )* "]" }
14321 @item @var{stream-record} @expansion{}
14322 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
14324 @item @var{console-stream-output} @expansion{}
14325 @code{"~" @var{c-string}}
14327 @item @var{target-stream-output} @expansion{}
14328 @code{"@@" @var{c-string}}
14330 @item @var{log-stream-output} @expansion{}
14331 @code{"&" @var{c-string}}
14333 @item @var{nl} @expansion{}
14336 @item @var{token} @expansion{}
14337 @emph{any sequence of digits}.
14345 All output sequences end in a single line containing a period.
14348 The @code{@var{token}} is from the corresponding request. If an execution
14349 command is interrupted by the @samp{-exec-interrupt} command, the
14350 @var{token} associated with the @samp{*stopped} message is the one of the
14351 original execution command, not the one of the interrupt command.
14354 @cindex status output in @sc{gdb/mi}
14355 @var{status-async-output} contains on-going status information about the
14356 progress of a slow operation. It can be discarded. All status output is
14357 prefixed by @samp{+}.
14360 @cindex async output in @sc{gdb/mi}
14361 @var{exec-async-output} contains asynchronous state change on the target
14362 (stopped, started, disappeared). All async output is prefixed by
14366 @cindex notify output in @sc{gdb/mi}
14367 @var{notify-async-output} contains supplementary information that the
14368 client should handle (e.g., a new breakpoint information). All notify
14369 output is prefixed by @samp{=}.
14372 @cindex console output in @sc{gdb/mi}
14373 @var{console-stream-output} is output that should be displayed as is in the
14374 console. It is the textual response to a CLI command. All the console
14375 output is prefixed by @samp{~}.
14378 @cindex target output in @sc{gdb/mi}
14379 @var{target-stream-output} is the output produced by the target program.
14380 All the target output is prefixed by @samp{@@}.
14383 @cindex log output in @sc{gdb/mi}
14384 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
14385 instance messages that should be displayed as part of an error log. All
14386 the log output is prefixed by @samp{&}.
14389 @cindex list output in @sc{gdb/mi}
14390 New @sc{gdb/mi} commands should only output @var{lists} containing
14396 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
14397 details about the various output records.
14399 @node GDB/MI Simple Examples
14400 @subsection Simple Examples of @sc{gdb/mi} Interaction
14401 @cindex @sc{gdb/mi}, simple examples
14403 This subsection presents several simple examples of interaction using
14404 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
14405 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
14406 the output received from @sc{gdb/mi}.
14408 @subsubheading Target Stop
14409 @c Ummm... There is no "-stop" command. This assumes async, no?
14410 Here's an example of stopping the inferior process:
14421 <- *stop,reason="stop",address="0x123",source="a.c:123"
14425 @subsubheading Simple CLI Command
14427 Here's an example of a simple CLI command being passed through
14428 @sc{gdb/mi} and on to the CLI.
14438 @subsubheading Command With Side Effects
14441 -> -symbol-file xyz.exe
14442 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
14446 @subsubheading A Bad Command
14448 Here's what happens if you pass a non-existent command:
14452 <- ^error,msg="Undefined MI command: rubbish"
14456 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14457 @node GDB/MI Compatibility with CLI
14458 @section @sc{gdb/mi} Compatibility with CLI
14460 @cindex compatibility, @sc{gdb/mi} and CLI
14461 @cindex @sc{gdb/mi}, compatibility with CLI
14462 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
14463 accepts existing CLI commands. As specified by the syntax, such
14464 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
14467 This mechanism is provided as an aid to developers of @sc{gdb/mi}
14468 clients and not as a reliable interface into the CLI. Since the command
14469 is being interpreteted in an environment that assumes @sc{gdb/mi}
14470 behaviour, the exact output of such commands is likely to end up being
14471 an un-supported hybrid of @sc{gdb/mi} and CLI output.
14473 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14474 @node GDB/MI Output Records
14475 @section @sc{gdb/mi} Output Records
14478 * GDB/MI Result Records::
14479 * GDB/MI Stream Records::
14480 * GDB/MI Out-of-band Records::
14483 @node GDB/MI Result Records
14484 @subsection @sc{gdb/mi} Result Records
14486 @cindex result records in @sc{gdb/mi}
14487 @cindex @sc{gdb/mi}, result records
14488 In addition to a number of out-of-band notifications, the response to a
14489 @sc{gdb/mi} command includes one of the following result indications:
14493 @item "^done" [ "," @var{results} ]
14494 The synchronous operation was successful, @code{@var{results}} are the return
14499 @c Is this one correct? Should it be an out-of-band notification?
14500 The asynchronous operation was successfully started. The target is
14503 @item "^error" "," @var{c-string}
14505 The operation failed. The @code{@var{c-string}} contains the corresponding
14509 @node GDB/MI Stream Records
14510 @subsection @sc{gdb/mi} Stream Records
14512 @cindex @sc{gdb/mi}, stream records
14513 @cindex stream records in @sc{gdb/mi}
14514 @value{GDBN} internally maintains a number of output streams: the console, the
14515 target, and the log. The output intended for each of these streams is
14516 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
14518 Each stream record begins with a unique @dfn{prefix character} which
14519 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
14520 Syntax}). In addition to the prefix, each stream record contains a
14521 @code{@var{string-output}}. This is either raw text (with an implicit new
14522 line) or a quoted C string (which does not contain an implicit newline).
14525 @item "~" @var{string-output}
14526 The console output stream contains text that should be displayed in the
14527 CLI console window. It contains the textual responses to CLI commands.
14529 @item "@@" @var{string-output}
14530 The target output stream contains any textual output from the running
14533 @item "&" @var{string-output}
14534 The log stream contains debugging messages being produced by @value{GDBN}'s
14538 @node GDB/MI Out-of-band Records
14539 @subsection @sc{gdb/mi} Out-of-band Records
14541 @cindex out-of-band records in @sc{gdb/mi}
14542 @cindex @sc{gdb/mi}, out-of-band records
14543 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
14544 additional changes that have occurred. Those changes can either be a
14545 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
14546 target activity (e.g., target stopped).
14548 The following is a preliminary list of possible out-of-band records.
14555 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14556 @node GDB/MI Command Description Format
14557 @section @sc{gdb/mi} Command Description Format
14559 The remaining sections describe blocks of commands. Each block of
14560 commands is laid out in a fashion similar to this section.
14562 Note the the line breaks shown in the examples are here only for
14563 readability. They don't appear in the real output.
14564 Also note that the commands with a non-available example (N.A.@:) are
14565 not yet implemented.
14567 @subheading Motivation
14569 The motivation for this collection of commands.
14571 @subheading Introduction
14573 A brief introduction to this collection of commands as a whole.
14575 @subheading Commands
14577 For each command in the block, the following is described:
14579 @subsubheading Synopsis
14582 -command @var{args}@dots{}
14585 @subsubheading @value{GDBN} Command
14587 The corresponding @value{GDBN} CLI command.
14589 @subsubheading Result
14591 @subsubheading Out-of-band
14593 @subsubheading Notes
14595 @subsubheading Example
14598 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14599 @node GDB/MI Breakpoint Table Commands
14600 @section @sc{gdb/mi} Breakpoint table commands
14602 @cindex breakpoint commands for @sc{gdb/mi}
14603 @cindex @sc{gdb/mi}, breakpoint commands
14604 This section documents @sc{gdb/mi} commands for manipulating
14607 @subheading The @code{-break-after} Command
14608 @findex -break-after
14610 @subsubheading Synopsis
14613 -break-after @var{number} @var{count}
14616 The breakpoint number @var{number} is not in effect until it has been
14617 hit @var{count} times. To see how this is reflected in the output of
14618 the @samp{-break-list} command, see the description of the
14619 @samp{-break-list} command below.
14621 @subsubheading @value{GDBN} Command
14623 The corresponding @value{GDBN} command is @samp{ignore}.
14625 @subsubheading Example
14630 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
14637 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14638 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14639 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14640 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14641 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14642 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14643 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14644 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14645 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
14651 @subheading The @code{-break-catch} Command
14652 @findex -break-catch
14654 @subheading The @code{-break-commands} Command
14655 @findex -break-commands
14659 @subheading The @code{-break-condition} Command
14660 @findex -break-condition
14662 @subsubheading Synopsis
14665 -break-condition @var{number} @var{expr}
14668 Breakpoint @var{number} will stop the program only if the condition in
14669 @var{expr} is true. The condition becomes part of the
14670 @samp{-break-list} output (see the description of the @samp{-break-list}
14673 @subsubheading @value{GDBN} Command
14675 The corresponding @value{GDBN} command is @samp{condition}.
14677 @subsubheading Example
14681 -break-condition 1 1
14685 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14686 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14687 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14688 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14689 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14690 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14691 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14692 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14693 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
14694 times="0",ignore="3"@}]@}
14698 @subheading The @code{-break-delete} Command
14699 @findex -break-delete
14701 @subsubheading Synopsis
14704 -break-delete ( @var{breakpoint} )+
14707 Delete the breakpoint(s) whose number(s) are specified in the argument
14708 list. This is obviously reflected in the breakpoint list.
14710 @subsubheading @value{GDBN} command
14712 The corresponding @value{GDBN} command is @samp{delete}.
14714 @subsubheading Example
14722 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
14723 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14724 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14725 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14726 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14727 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14728 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14733 @subheading The @code{-break-disable} Command
14734 @findex -break-disable
14736 @subsubheading Synopsis
14739 -break-disable ( @var{breakpoint} )+
14742 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
14743 break list is now set to @samp{n} for the named @var{breakpoint}(s).
14745 @subsubheading @value{GDBN} Command
14747 The corresponding @value{GDBN} command is @samp{disable}.
14749 @subsubheading Example
14757 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14758 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14759 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14760 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14761 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14762 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14763 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14764 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
14765 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
14769 @subheading The @code{-break-enable} Command
14770 @findex -break-enable
14772 @subsubheading Synopsis
14775 -break-enable ( @var{breakpoint} )+
14778 Enable (previously disabled) @var{breakpoint}(s).
14780 @subsubheading @value{GDBN} Command
14782 The corresponding @value{GDBN} command is @samp{enable}.
14784 @subsubheading Example
14792 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14793 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14794 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14795 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14796 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14797 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14798 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14799 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
14800 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
14804 @subheading The @code{-break-info} Command
14805 @findex -break-info
14807 @subsubheading Synopsis
14810 -break-info @var{breakpoint}
14814 Get information about a single breakpoint.
14816 @subsubheading @value{GDBN} command
14818 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
14820 @subsubheading Example
14823 @subheading The @code{-break-insert} Command
14824 @findex -break-insert
14826 @subsubheading Synopsis
14829 -break-insert [ -t ] [ -h ] [ -r ]
14830 [ -c @var{condition} ] [ -i @var{ignore-count} ]
14831 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
14835 If specified, @var{line}, can be one of:
14842 @item filename:linenum
14843 @item filename:function
14847 The possible optional parameters of this command are:
14851 Insert a tempoary breakpoint.
14853 Insert a hardware breakpoint.
14854 @item -c @var{condition}
14855 Make the breakpoint conditional on @var{condition}.
14856 @item -i @var{ignore-count}
14857 Initialize the @var{ignore-count}.
14859 Insert a regular breakpoint in all the functions whose names match the
14860 given regular expression. Other flags are not applicable to regular
14864 @subsubheading Result
14866 The result is in the form:
14869 ^done,bkptno="@var{number}",func="@var{funcname}",
14870 file="@var{filename}",line="@var{lineno}"
14874 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
14875 is the name of the function where the breakpoint was inserted,
14876 @var{filename} is the name of the source file which contains this
14877 function, and @var{lineno} is the source line number within that file.
14879 Note: this format is open to change.
14880 @c An out-of-band breakpoint instead of part of the result?
14882 @subsubheading @value{GDBN} Command
14884 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
14885 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
14887 @subsubheading Example
14892 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
14894 -break-insert -t foo
14895 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
14898 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
14899 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14900 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14901 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14902 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14903 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14904 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14905 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14906 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
14907 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
14908 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
14910 -break-insert -r foo.*
14911 ~int foo(int, int);
14912 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
14916 @subheading The @code{-break-list} Command
14917 @findex -break-list
14919 @subsubheading Synopsis
14925 Displays the list of inserted breakpoints, showing the following fields:
14929 number of the breakpoint
14931 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
14933 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
14936 is the breakpoint enabled or no: @samp{y} or @samp{n}
14938 memory location at which the breakpoint is set
14940 logical location of the breakpoint, expressed by function name, file
14943 number of times the breakpoint has been hit
14946 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
14947 @code{body} field is an empty list.
14949 @subsubheading @value{GDBN} Command
14951 The corresponding @value{GDBN} command is @samp{info break}.
14953 @subsubheading Example
14958 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
14959 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14960 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14961 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14962 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14963 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14964 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14965 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14966 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
14967 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
14968 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
14972 Here's an example of the result when there are no breakpoints:
14977 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
14978 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14979 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14980 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14981 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14982 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14983 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14988 @subheading The @code{-break-watch} Command
14989 @findex -break-watch
14991 @subsubheading Synopsis
14994 -break-watch [ -a | -r ]
14997 Create a watchpoint. With the @samp{-a} option it will create an
14998 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
14999 read from or on a write to the memory location. With the @samp{-r}
15000 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
15001 trigger only when the memory location is accessed for reading. Without
15002 either of the options, the watchpoint created is a regular watchpoint,
15003 i.e. it will trigger when the memory location is accessed for writing.
15004 @xref{Set Watchpoints, , Setting watchpoints}.
15006 Note that @samp{-break-list} will report a single list of watchpoints and
15007 breakpoints inserted.
15009 @subsubheading @value{GDBN} Command
15011 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
15014 @subsubheading Example
15016 Setting a watchpoint on a variable in the @code{main} function:
15021 ^done,wpt=@{number="2",exp="x"@}
15025 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
15026 value=@{old="-268439212",new="55"@},
15027 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
15031 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
15032 the program execution twice: first for the variable changing value, then
15033 for the watchpoint going out of scope.
15038 ^done,wpt=@{number="5",exp="C"@}
15042 ^done,reason="watchpoint-trigger",
15043 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
15044 frame=@{func="callee4",args=[],
15045 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15049 ^done,reason="watchpoint-scope",wpnum="5",
15050 frame=@{func="callee3",args=[@{name="strarg",
15051 value="0x11940 \"A string argument.\""@}],
15052 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15056 Listing breakpoints and watchpoints, at different points in the program
15057 execution. Note that once the watchpoint goes out of scope, it is
15063 ^done,wpt=@{number="2",exp="C"@}
15066 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15067 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15068 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15069 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15070 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15071 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15072 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15073 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15074 addr="0x00010734",func="callee4",
15075 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15076 bkpt=@{number="2",type="watchpoint",disp="keep",
15077 enabled="y",addr="",what="C",times="0"@}]@}
15081 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
15082 value=@{old="-276895068",new="3"@},
15083 frame=@{func="callee4",args=[],
15084 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15087 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15088 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15089 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15090 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15091 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15092 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15093 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15094 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15095 addr="0x00010734",func="callee4",
15096 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15097 bkpt=@{number="2",type="watchpoint",disp="keep",
15098 enabled="y",addr="",what="C",times="-5"@}]@}
15102 ^done,reason="watchpoint-scope",wpnum="2",
15103 frame=@{func="callee3",args=[@{name="strarg",
15104 value="0x11940 \"A string argument.\""@}],
15105 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15108 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15109 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15110 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15111 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15112 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15113 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15114 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15115 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15116 addr="0x00010734",func="callee4",
15117 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
15121 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15122 @node GDB/MI Data Manipulation
15123 @section @sc{gdb/mi} Data Manipulation
15125 @cindex data manipulation, in @sc{gdb/mi}
15126 @cindex @sc{gdb/mi}, data manipulation
15127 This section describes the @sc{gdb/mi} commands that manipulate data:
15128 examine memory and registers, evaluate expressions, etc.
15130 @c REMOVED FROM THE INTERFACE.
15131 @c @subheading -data-assign
15132 @c Change the value of a program variable. Plenty of side effects.
15133 @c @subsubheading GDB command
15135 @c @subsubheading Example
15138 @subheading The @code{-data-disassemble} Command
15139 @findex -data-disassemble
15141 @subsubheading Synopsis
15145 [ -s @var{start-addr} -e @var{end-addr} ]
15146 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
15154 @item @var{start-addr}
15155 is the beginning address (or @code{$pc})
15156 @item @var{end-addr}
15158 @item @var{filename}
15159 is the name of the file to disassemble
15160 @item @var{linenum}
15161 is the line number to disassemble around
15163 is the the number of disassembly lines to be produced. If it is -1,
15164 the whole function will be disassembled, in case no @var{end-addr} is
15165 specified. If @var{end-addr} is specified as a non-zero value, and
15166 @var{lines} is lower than the number of disassembly lines between
15167 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
15168 displayed; if @var{lines} is higher than the number of lines between
15169 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
15172 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
15176 @subsubheading Result
15178 The output for each instruction is composed of four fields:
15187 Note that whatever included in the instruction field, is not manipulated
15188 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
15190 @subsubheading @value{GDBN} Command
15192 There's no direct mapping from this command to the CLI.
15194 @subsubheading Example
15196 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
15200 -data-disassemble -s $pc -e "$pc + 20" -- 0
15203 @{address="0x000107c0",func-name="main",offset="4",
15204 inst="mov 2, %o0"@},
15205 @{address="0x000107c4",func-name="main",offset="8",
15206 inst="sethi %hi(0x11800), %o2"@},
15207 @{address="0x000107c8",func-name="main",offset="12",
15208 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
15209 @{address="0x000107cc",func-name="main",offset="16",
15210 inst="sethi %hi(0x11800), %o2"@},
15211 @{address="0x000107d0",func-name="main",offset="20",
15212 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
15216 Disassemble the whole @code{main} function. Line 32 is part of
15220 -data-disassemble -f basics.c -l 32 -- 0
15222 @{address="0x000107bc",func-name="main",offset="0",
15223 inst="save %sp, -112, %sp"@},
15224 @{address="0x000107c0",func-name="main",offset="4",
15225 inst="mov 2, %o0"@},
15226 @{address="0x000107c4",func-name="main",offset="8",
15227 inst="sethi %hi(0x11800), %o2"@},
15229 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
15230 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
15234 Disassemble 3 instructions from the start of @code{main}:
15238 -data-disassemble -f basics.c -l 32 -n 3 -- 0
15240 @{address="0x000107bc",func-name="main",offset="0",
15241 inst="save %sp, -112, %sp"@},
15242 @{address="0x000107c0",func-name="main",offset="4",
15243 inst="mov 2, %o0"@},
15244 @{address="0x000107c4",func-name="main",offset="8",
15245 inst="sethi %hi(0x11800), %o2"@}]
15249 Disassemble 3 instructions from the start of @code{main} in mixed mode:
15253 -data-disassemble -f basics.c -l 32 -n 3 -- 1
15255 src_and_asm_line=@{line="31",
15256 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15257 testsuite/gdb.mi/basics.c",line_asm_insn=[
15258 @{address="0x000107bc",func-name="main",offset="0",
15259 inst="save %sp, -112, %sp"@}]@},
15260 src_and_asm_line=@{line="32",
15261 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15262 testsuite/gdb.mi/basics.c",line_asm_insn=[
15263 @{address="0x000107c0",func-name="main",offset="4",
15264 inst="mov 2, %o0"@},
15265 @{address="0x000107c4",func-name="main",offset="8",
15266 inst="sethi %hi(0x11800), %o2"@}]@}]
15271 @subheading The @code{-data-evaluate-expression} Command
15272 @findex -data-evaluate-expression
15274 @subsubheading Synopsis
15277 -data-evaluate-expression @var{expr}
15280 Evaluate @var{expr} as an expression. The expression could contain an
15281 inferior function call. The function call will execute synchronously.
15282 If the expression contains spaces, it must be enclosed in double quotes.
15284 @subsubheading @value{GDBN} Command
15286 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
15287 @samp{call}. In @code{gdbtk} only, there's a corresponding
15288 @samp{gdb_eval} command.
15290 @subsubheading Example
15292 In the following example, the numbers that precede the commands are the
15293 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
15294 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
15298 211-data-evaluate-expression A
15301 311-data-evaluate-expression &A
15302 311^done,value="0xefffeb7c"
15304 411-data-evaluate-expression A+3
15307 511-data-evaluate-expression "A + 3"
15313 @subheading The @code{-data-list-changed-registers} Command
15314 @findex -data-list-changed-registers
15316 @subsubheading Synopsis
15319 -data-list-changed-registers
15322 Display a list of the registers that have changed.
15324 @subsubheading @value{GDBN} Command
15326 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
15327 has the corresponding command @samp{gdb_changed_register_list}.
15329 @subsubheading Example
15331 On a PPC MBX board:
15339 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
15340 args=[],file="try.c",line="5"@}
15342 -data-list-changed-registers
15343 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
15344 "10","11","13","14","15","16","17","18","19","20","21","22","23",
15345 "24","25","26","27","28","30","31","64","65","66","67","69"]
15350 @subheading The @code{-data-list-register-names} Command
15351 @findex -data-list-register-names
15353 @subsubheading Synopsis
15356 -data-list-register-names [ ( @var{regno} )+ ]
15359 Show a list of register names for the current target. If no arguments
15360 are given, it shows a list of the names of all the registers. If
15361 integer numbers are given as arguments, it will print a list of the
15362 names of the registers corresponding to the arguments. To ensure
15363 consistency between a register name and its number, the output list may
15364 include empty register names.
15366 @subsubheading @value{GDBN} Command
15368 @value{GDBN} does not have a command which corresponds to
15369 @samp{-data-list-register-names}. In @code{gdbtk} there is a
15370 corresponding command @samp{gdb_regnames}.
15372 @subsubheading Example
15374 For the PPC MBX board:
15377 -data-list-register-names
15378 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
15379 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
15380 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
15381 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
15382 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
15383 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
15384 "", "pc","ps","cr","lr","ctr","xer"]
15386 -data-list-register-names 1 2 3
15387 ^done,register-names=["r1","r2","r3"]
15391 @subheading The @code{-data-list-register-values} Command
15392 @findex -data-list-register-values
15394 @subsubheading Synopsis
15397 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
15400 Display the registers' contents. @var{fmt} is the format according to
15401 which the registers' contents are to be returned, followed by an optional
15402 list of numbers specifying the registers to display. A missing list of
15403 numbers indicates that the contents of all the registers must be returned.
15405 Allowed formats for @var{fmt} are:
15422 @subsubheading @value{GDBN} Command
15424 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
15425 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
15427 @subsubheading Example
15429 For a PPC MBX board (note: line breaks are for readability only, they
15430 don't appear in the actual output):
15434 -data-list-register-values r 64 65
15435 ^done,register-values=[@{number="64",value="0xfe00a300"@},
15436 @{number="65",value="0x00029002"@}]
15438 -data-list-register-values x
15439 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
15440 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
15441 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
15442 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
15443 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
15444 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
15445 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
15446 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
15447 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
15448 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
15449 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
15450 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
15451 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
15452 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
15453 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
15454 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
15455 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
15456 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
15457 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
15458 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
15459 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
15460 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
15461 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
15462 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
15463 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
15464 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
15465 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
15466 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
15467 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
15468 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
15469 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
15470 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
15471 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
15472 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
15473 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
15474 @{number="69",value="0x20002b03"@}]
15479 @subheading The @code{-data-read-memory} Command
15480 @findex -data-read-memory
15482 @subsubheading Synopsis
15485 -data-read-memory [ -o @var{byte-offset} ]
15486 @var{address} @var{word-format} @var{word-size}
15487 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
15494 @item @var{address}
15495 An expression specifying the address of the first memory word to be
15496 read. Complex expressions containing embedded white space should be
15497 quoted using the C convention.
15499 @item @var{word-format}
15500 The format to be used to print the memory words. The notation is the
15501 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
15504 @item @var{word-size}
15505 The size of each memory word in bytes.
15507 @item @var{nr-rows}
15508 The number of rows in the output table.
15510 @item @var{nr-cols}
15511 The number of columns in the output table.
15514 If present, indicates that each row should include an @sc{ascii} dump. The
15515 value of @var{aschar} is used as a padding character when a byte is not a
15516 member of the printable @sc{ascii} character set (printable @sc{ascii}
15517 characters are those whose code is between 32 and 126, inclusively).
15519 @item @var{byte-offset}
15520 An offset to add to the @var{address} before fetching memory.
15523 This command displays memory contents as a table of @var{nr-rows} by
15524 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
15525 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
15526 (returned as @samp{total-bytes}). Should less than the requested number
15527 of bytes be returned by the target, the missing words are identified
15528 using @samp{N/A}. The number of bytes read from the target is returned
15529 in @samp{nr-bytes} and the starting address used to read memory in
15532 The address of the next/previous row or page is available in
15533 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
15536 @subsubheading @value{GDBN} Command
15538 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
15539 @samp{gdb_get_mem} memory read command.
15541 @subsubheading Example
15543 Read six bytes of memory starting at @code{bytes+6} but then offset by
15544 @code{-6} bytes. Format as three rows of two columns. One byte per
15545 word. Display each word in hex.
15549 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
15550 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
15551 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
15552 prev-page="0x0000138a",memory=[
15553 @{addr="0x00001390",data=["0x00","0x01"]@},
15554 @{addr="0x00001392",data=["0x02","0x03"]@},
15555 @{addr="0x00001394",data=["0x04","0x05"]@}]
15559 Read two bytes of memory starting at address @code{shorts + 64} and
15560 display as a single word formatted in decimal.
15564 5-data-read-memory shorts+64 d 2 1 1
15565 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
15566 next-row="0x00001512",prev-row="0x0000150e",
15567 next-page="0x00001512",prev-page="0x0000150e",memory=[
15568 @{addr="0x00001510",data=["128"]@}]
15572 Read thirty two bytes of memory starting at @code{bytes+16} and format
15573 as eight rows of four columns. Include a string encoding with @samp{x}
15574 used as the non-printable character.
15578 4-data-read-memory bytes+16 x 1 8 4 x
15579 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
15580 next-row="0x000013c0",prev-row="0x0000139c",
15581 next-page="0x000013c0",prev-page="0x00001380",memory=[
15582 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
15583 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
15584 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
15585 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
15586 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
15587 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
15588 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
15589 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
15593 @subheading The @code{-display-delete} Command
15594 @findex -display-delete
15596 @subsubheading Synopsis
15599 -display-delete @var{number}
15602 Delete the display @var{number}.
15604 @subsubheading @value{GDBN} Command
15606 The corresponding @value{GDBN} command is @samp{delete display}.
15608 @subsubheading Example
15612 @subheading The @code{-display-disable} Command
15613 @findex -display-disable
15615 @subsubheading Synopsis
15618 -display-disable @var{number}
15621 Disable display @var{number}.
15623 @subsubheading @value{GDBN} Command
15625 The corresponding @value{GDBN} command is @samp{disable display}.
15627 @subsubheading Example
15631 @subheading The @code{-display-enable} Command
15632 @findex -display-enable
15634 @subsubheading Synopsis
15637 -display-enable @var{number}
15640 Enable display @var{number}.
15642 @subsubheading @value{GDBN} Command
15644 The corresponding @value{GDBN} command is @samp{enable display}.
15646 @subsubheading Example
15650 @subheading The @code{-display-insert} Command
15651 @findex -display-insert
15653 @subsubheading Synopsis
15656 -display-insert @var{expression}
15659 Display @var{expression} every time the program stops.
15661 @subsubheading @value{GDBN} Command
15663 The corresponding @value{GDBN} command is @samp{display}.
15665 @subsubheading Example
15669 @subheading The @code{-display-list} Command
15670 @findex -display-list
15672 @subsubheading Synopsis
15678 List the displays. Do not show the current values.
15680 @subsubheading @value{GDBN} Command
15682 The corresponding @value{GDBN} command is @samp{info display}.
15684 @subsubheading Example
15688 @subheading The @code{-environment-cd} Command
15689 @findex -environment-cd
15691 @subsubheading Synopsis
15694 -environment-cd @var{pathdir}
15697 Set @value{GDBN}'s working directory.
15699 @subsubheading @value{GDBN} Command
15701 The corresponding @value{GDBN} command is @samp{cd}.
15703 @subsubheading Example
15707 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
15713 @subheading The @code{-environment-directory} Command
15714 @findex -environment-directory
15716 @subsubheading Synopsis
15719 -environment-directory [ -r ] [ @var{pathdir} ]+
15722 Add directories @var{pathdir} to beginning of search path for source files.
15723 If the @samp{-r} option is used, the search path is reset to the default
15724 search path. If directories @var{pathdir} are supplied in addition to the
15725 @samp{-r} option, the search path is first reset and then addition
15727 Multiple directories may be specified, separated by blanks. Specifying
15728 multiple directories in a single command
15729 results in the directories added to the beginning of the
15730 search path in the same order they were presented in the command.
15731 If blanks are needed as
15732 part of a directory name, double-quotes should be used around
15733 the name. In the command output, the path will show up separated
15734 by the system directory-separator character. The directory-seperator
15735 character must not be used
15736 in any directory name.
15737 If no directories are specified, the current search path is displayed.
15739 @subsubheading @value{GDBN} Command
15741 The corresponding @value{GDBN} command is @samp{dir}.
15743 @subsubheading Example
15747 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
15748 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
15750 -environment-directory ""
15751 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
15753 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
15754 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
15756 -environment-directory -r
15757 ^done,source-path="$cdir:$cwd"
15762 @subheading The @code{-environment-path} Command
15763 @findex -environment-path
15765 @subsubheading Synopsis
15768 -environment-path [ -r ] [ @var{pathdir} ]+
15771 Add directories @var{pathdir} to beginning of search path for object files.
15772 If the @samp{-r} option is used, the search path is reset to the original
15773 search path that existed at gdb start-up. If directories @var{pathdir} are
15774 supplied in addition to the
15775 @samp{-r} option, the search path is first reset and then addition
15777 Multiple directories may be specified, separated by blanks. Specifying
15778 multiple directories in a single command
15779 results in the directories added to the beginning of the
15780 search path in the same order they were presented in the command.
15781 If blanks are needed as
15782 part of a directory name, double-quotes should be used around
15783 the name. In the command output, the path will show up separated
15784 by the system directory-separator character. The directory-seperator
15785 character must not be used
15786 in any directory name.
15787 If no directories are specified, the current path is displayed.
15790 @subsubheading @value{GDBN} Command
15792 The corresponding @value{GDBN} command is @samp{path}.
15794 @subsubheading Example
15799 ^done,path="/usr/bin"
15801 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
15802 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
15804 -environment-path -r /usr/local/bin
15805 ^done,path="/usr/local/bin:/usr/bin"
15810 @subheading The @code{-environment-pwd} Command
15811 @findex -environment-pwd
15813 @subsubheading Synopsis
15819 Show the current working directory.
15821 @subsubheading @value{GDBN} command
15823 The corresponding @value{GDBN} command is @samp{pwd}.
15825 @subsubheading Example
15830 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
15834 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15835 @node GDB/MI Program Control
15836 @section @sc{gdb/mi} Program control
15838 @subsubheading Program termination
15840 As a result of execution, the inferior program can run to completion, if
15841 it doesn't encounter any breakpoints. In this case the output will
15842 include an exit code, if the program has exited exceptionally.
15844 @subsubheading Examples
15847 Program exited normally:
15855 *stopped,reason="exited-normally"
15860 Program exited exceptionally:
15868 *stopped,reason="exited",exit-code="01"
15872 Another way the program can terminate is if it receives a signal such as
15873 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
15877 *stopped,reason="exited-signalled",signal-name="SIGINT",
15878 signal-meaning="Interrupt"
15882 @subheading The @code{-exec-abort} Command
15883 @findex -exec-abort
15885 @subsubheading Synopsis
15891 Kill the inferior running program.
15893 @subsubheading @value{GDBN} Command
15895 The corresponding @value{GDBN} command is @samp{kill}.
15897 @subsubheading Example
15901 @subheading The @code{-exec-arguments} Command
15902 @findex -exec-arguments
15904 @subsubheading Synopsis
15907 -exec-arguments @var{args}
15910 Set the inferior program arguments, to be used in the next
15913 @subsubheading @value{GDBN} Command
15915 The corresponding @value{GDBN} command is @samp{set args}.
15917 @subsubheading Example
15920 Don't have one around.
15923 @subheading The @code{-exec-continue} Command
15924 @findex -exec-continue
15926 @subsubheading Synopsis
15932 Asynchronous command. Resumes the execution of the inferior program
15933 until a breakpoint is encountered, or until the inferior exits.
15935 @subsubheading @value{GDBN} Command
15937 The corresponding @value{GDBN} corresponding is @samp{continue}.
15939 @subsubheading Example
15946 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
15947 file="hello.c",line="13"@}
15952 @subheading The @code{-exec-finish} Command
15953 @findex -exec-finish
15955 @subsubheading Synopsis
15961 Asynchronous command. Resumes the execution of the inferior program
15962 until the current function is exited. Displays the results returned by
15965 @subsubheading @value{GDBN} Command
15967 The corresponding @value{GDBN} command is @samp{finish}.
15969 @subsubheading Example
15971 Function returning @code{void}.
15978 *stopped,reason="function-finished",frame=@{func="main",args=[],
15979 file="hello.c",line="7"@}
15983 Function returning other than @code{void}. The name of the internal
15984 @value{GDBN} variable storing the result is printed, together with the
15991 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
15992 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
15993 file="recursive2.c",line="14"@},
15994 gdb-result-var="$1",return-value="0"
15999 @subheading The @code{-exec-interrupt} Command
16000 @findex -exec-interrupt
16002 @subsubheading Synopsis
16008 Asynchronous command. Interrupts the background execution of the target.
16009 Note how the token associated with the stop message is the one for the
16010 execution command that has been interrupted. The token for the interrupt
16011 itself only appears in the @samp{^done} output. If the user is trying to
16012 interrupt a non-running program, an error message will be printed.
16014 @subsubheading @value{GDBN} Command
16016 The corresponding @value{GDBN} command is @samp{interrupt}.
16018 @subsubheading Example
16029 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
16030 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
16035 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
16040 @subheading The @code{-exec-next} Command
16043 @subsubheading Synopsis
16049 Asynchronous command. Resumes execution of the inferior program, stopping
16050 when the beginning of the next source line is reached.
16052 @subsubheading @value{GDBN} Command
16054 The corresponding @value{GDBN} command is @samp{next}.
16056 @subsubheading Example
16062 *stopped,reason="end-stepping-range",line="8",file="hello.c"
16067 @subheading The @code{-exec-next-instruction} Command
16068 @findex -exec-next-instruction
16070 @subsubheading Synopsis
16073 -exec-next-instruction
16076 Asynchronous command. Executes one machine instruction. If the
16077 instruction is a function call continues until the function returns. If
16078 the program stops at an instruction in the middle of a source line, the
16079 address will be printed as well.
16081 @subsubheading @value{GDBN} Command
16083 The corresponding @value{GDBN} command is @samp{nexti}.
16085 @subsubheading Example
16089 -exec-next-instruction
16093 *stopped,reason="end-stepping-range",
16094 addr="0x000100d4",line="5",file="hello.c"
16099 @subheading The @code{-exec-return} Command
16100 @findex -exec-return
16102 @subsubheading Synopsis
16108 Makes current function return immediately. Doesn't execute the inferior.
16109 Displays the new current frame.
16111 @subsubheading @value{GDBN} Command
16113 The corresponding @value{GDBN} command is @samp{return}.
16115 @subsubheading Example
16119 200-break-insert callee4
16120 200^done,bkpt=@{number="1",addr="0x00010734",
16121 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16126 000*stopped,reason="breakpoint-hit",bkptno="1",
16127 frame=@{func="callee4",args=[],
16128 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16134 111^done,frame=@{level="0",func="callee3",
16135 args=[@{name="strarg",
16136 value="0x11940 \"A string argument.\""@}],
16137 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16142 @subheading The @code{-exec-run} Command
16145 @subsubheading Synopsis
16151 Asynchronous command. Starts execution of the inferior from the
16152 beginning. The inferior executes until either a breakpoint is
16153 encountered or the program exits.
16155 @subsubheading @value{GDBN} Command
16157 The corresponding @value{GDBN} command is @samp{run}.
16159 @subsubheading Example
16164 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
16169 *stopped,reason="breakpoint-hit",bkptno="1",
16170 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
16175 @subheading The @code{-exec-show-arguments} Command
16176 @findex -exec-show-arguments
16178 @subsubheading Synopsis
16181 -exec-show-arguments
16184 Print the arguments of the program.
16186 @subsubheading @value{GDBN} Command
16188 The corresponding @value{GDBN} command is @samp{show args}.
16190 @subsubheading Example
16193 @c @subheading -exec-signal
16195 @subheading The @code{-exec-step} Command
16198 @subsubheading Synopsis
16204 Asynchronous command. Resumes execution of the inferior program, stopping
16205 when the beginning of the next source line is reached, if the next
16206 source line is not a function call. If it is, stop at the first
16207 instruction of the called function.
16209 @subsubheading @value{GDBN} Command
16211 The corresponding @value{GDBN} command is @samp{step}.
16213 @subsubheading Example
16215 Stepping into a function:
16221 *stopped,reason="end-stepping-range",
16222 frame=@{func="foo",args=[@{name="a",value="10"@},
16223 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
16233 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
16238 @subheading The @code{-exec-step-instruction} Command
16239 @findex -exec-step-instruction
16241 @subsubheading Synopsis
16244 -exec-step-instruction
16247 Asynchronous command. Resumes the inferior which executes one machine
16248 instruction. The output, once @value{GDBN} has stopped, will vary depending on
16249 whether we have stopped in the middle of a source line or not. In the
16250 former case, the address at which the program stopped will be printed as
16253 @subsubheading @value{GDBN} Command
16255 The corresponding @value{GDBN} command is @samp{stepi}.
16257 @subsubheading Example
16261 -exec-step-instruction
16265 *stopped,reason="end-stepping-range",
16266 frame=@{func="foo",args=[],file="try.c",line="10"@}
16268 -exec-step-instruction
16272 *stopped,reason="end-stepping-range",
16273 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
16278 @subheading The @code{-exec-until} Command
16279 @findex -exec-until
16281 @subsubheading Synopsis
16284 -exec-until [ @var{location} ]
16287 Asynchronous command. Executes the inferior until the @var{location}
16288 specified in the argument is reached. If there is no argument, the inferior
16289 executes until a source line greater than the current one is reached.
16290 The reason for stopping in this case will be @samp{location-reached}.
16292 @subsubheading @value{GDBN} Command
16294 The corresponding @value{GDBN} command is @samp{until}.
16296 @subsubheading Example
16300 -exec-until recursive2.c:6
16304 *stopped,reason="location-reached",frame=@{func="main",args=[],
16305 file="recursive2.c",line="6"@}
16310 @subheading -file-clear
16311 Is this going away????
16315 @subheading The @code{-file-exec-and-symbols} Command
16316 @findex -file-exec-and-symbols
16318 @subsubheading Synopsis
16321 -file-exec-and-symbols @var{file}
16324 Specify the executable file to be debugged. This file is the one from
16325 which the symbol table is also read. If no file is specified, the
16326 command clears the executable and symbol information. If breakpoints
16327 are set when using this command with no arguments, @value{GDBN} will produce
16328 error messages. Otherwise, no output is produced, except a completion
16331 @subsubheading @value{GDBN} Command
16333 The corresponding @value{GDBN} command is @samp{file}.
16335 @subsubheading Example
16339 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16345 @subheading The @code{-file-exec-file} Command
16346 @findex -file-exec-file
16348 @subsubheading Synopsis
16351 -file-exec-file @var{file}
16354 Specify the executable file to be debugged. Unlike
16355 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
16356 from this file. If used without argument, @value{GDBN} clears the information
16357 about the executable file. No output is produced, except a completion
16360 @subsubheading @value{GDBN} Command
16362 The corresponding @value{GDBN} command is @samp{exec-file}.
16364 @subsubheading Example
16368 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16374 @subheading The @code{-file-list-exec-sections} Command
16375 @findex -file-list-exec-sections
16377 @subsubheading Synopsis
16380 -file-list-exec-sections
16383 List the sections of the current executable file.
16385 @subsubheading @value{GDBN} Command
16387 The @value{GDBN} command @samp{info file} shows, among the rest, the same
16388 information as this command. @code{gdbtk} has a corresponding command
16389 @samp{gdb_load_info}.
16391 @subsubheading Example
16395 @subheading The @code{-file-list-exec-source-file} Command
16396 @findex -file-list-exec-source-file
16398 @subsubheading Synopsis
16401 -file-list-exec-source-file
16404 List the line number, the current source file, and the absolute path
16405 to the current source file for the current executable.
16407 @subsubheading @value{GDBN} Command
16409 There's no @value{GDBN} command which directly corresponds to this one.
16411 @subsubheading Example
16415 123-file-list-exec-source-file
16416 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
16421 @subheading The @code{-file-list-exec-source-files} Command
16422 @findex -file-list-exec-source-files
16424 @subsubheading Synopsis
16427 -file-list-exec-source-files
16430 List the source files for the current executable.
16432 @subsubheading @value{GDBN} Command
16434 There's no @value{GDBN} command which directly corresponds to this one.
16435 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
16437 @subsubheading Example
16441 @subheading The @code{-file-list-shared-libraries} Command
16442 @findex -file-list-shared-libraries
16444 @subsubheading Synopsis
16447 -file-list-shared-libraries
16450 List the shared libraries in the program.
16452 @subsubheading @value{GDBN} Command
16454 The corresponding @value{GDBN} command is @samp{info shared}.
16456 @subsubheading Example
16460 @subheading The @code{-file-list-symbol-files} Command
16461 @findex -file-list-symbol-files
16463 @subsubheading Synopsis
16466 -file-list-symbol-files
16471 @subsubheading @value{GDBN} Command
16473 The corresponding @value{GDBN} command is @samp{info file} (part of it).
16475 @subsubheading Example
16479 @subheading The @code{-file-symbol-file} Command
16480 @findex -file-symbol-file
16482 @subsubheading Synopsis
16485 -file-symbol-file @var{file}
16488 Read symbol table info from the specified @var{file} argument. When
16489 used without arguments, clears @value{GDBN}'s symbol table info. No output is
16490 produced, except for a completion notification.
16492 @subsubheading @value{GDBN} Command
16494 The corresponding @value{GDBN} command is @samp{symbol-file}.
16496 @subsubheading Example
16500 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16505 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16506 @node GDB/MI Miscellaneous Commands
16507 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
16509 @c @subheading -gdb-complete
16511 @subheading The @code{-gdb-exit} Command
16514 @subsubheading Synopsis
16520 Exit @value{GDBN} immediately.
16522 @subsubheading @value{GDBN} Command
16524 Approximately corresponds to @samp{quit}.
16526 @subsubheading Example
16533 @subheading The @code{-gdb-set} Command
16536 @subsubheading Synopsis
16542 Set an internal @value{GDBN} variable.
16543 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
16545 @subsubheading @value{GDBN} Command
16547 The corresponding @value{GDBN} command is @samp{set}.
16549 @subsubheading Example
16559 @subheading The @code{-gdb-show} Command
16562 @subsubheading Synopsis
16568 Show the current value of a @value{GDBN} variable.
16570 @subsubheading @value{GDBN} command
16572 The corresponding @value{GDBN} command is @samp{show}.
16574 @subsubheading Example
16583 @c @subheading -gdb-source
16586 @subheading The @code{-gdb-version} Command
16587 @findex -gdb-version
16589 @subsubheading Synopsis
16595 Show version information for @value{GDBN}. Used mostly in testing.
16597 @subsubheading @value{GDBN} Command
16599 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
16600 information when you start an interactive session.
16602 @subsubheading Example
16604 @c This example modifies the actual output from GDB to avoid overfull
16610 ~Copyright 2000 Free Software Foundation, Inc.
16611 ~GDB is free software, covered by the GNU General Public License, and
16612 ~you are welcome to change it and/or distribute copies of it under
16613 ~ certain conditions.
16614 ~Type "show copying" to see the conditions.
16615 ~There is absolutely no warranty for GDB. Type "show warranty" for
16617 ~This GDB was configured as
16618 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
16623 @subheading The @code{-interpreter-exec} Command
16624 @findex -interpreter-exec
16626 @subheading Synopsis
16629 -interpreter-exec @var{interpreter} @var{command}
16632 Execute the specified @var{command} in the given @var{interpreter}.
16634 @subheading @value{GDBN} Command
16636 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
16638 @subheading Example
16642 -interpreter-exec console "break main"
16643 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
16644 &"During symbol reading, bad structure-type format.\n"
16645 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
16651 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16652 @node GDB/MI Kod Commands
16653 @section @sc{gdb/mi} Kod Commands
16655 The Kod commands are not implemented.
16657 @c @subheading -kod-info
16659 @c @subheading -kod-list
16661 @c @subheading -kod-list-object-types
16663 @c @subheading -kod-show
16665 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16666 @node GDB/MI Memory Overlay Commands
16667 @section @sc{gdb/mi} Memory Overlay Commands
16669 The memory overlay commands are not implemented.
16671 @c @subheading -overlay-auto
16673 @c @subheading -overlay-list-mapping-state
16675 @c @subheading -overlay-list-overlays
16677 @c @subheading -overlay-map
16679 @c @subheading -overlay-off
16681 @c @subheading -overlay-on
16683 @c @subheading -overlay-unmap
16685 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16686 @node GDB/MI Signal Handling Commands
16687 @section @sc{gdb/mi} Signal Handling Commands
16689 Signal handling commands are not implemented.
16691 @c @subheading -signal-handle
16693 @c @subheading -signal-list-handle-actions
16695 @c @subheading -signal-list-signal-types
16699 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16700 @node GDB/MI Stack Manipulation
16701 @section @sc{gdb/mi} Stack Manipulation Commands
16704 @subheading The @code{-stack-info-frame} Command
16705 @findex -stack-info-frame
16707 @subsubheading Synopsis
16713 Get info on the current frame.
16715 @subsubheading @value{GDBN} Command
16717 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
16718 (without arguments).
16720 @subsubheading Example
16723 @subheading The @code{-stack-info-depth} Command
16724 @findex -stack-info-depth
16726 @subsubheading Synopsis
16729 -stack-info-depth [ @var{max-depth} ]
16732 Return the depth of the stack. If the integer argument @var{max-depth}
16733 is specified, do not count beyond @var{max-depth} frames.
16735 @subsubheading @value{GDBN} Command
16737 There's no equivalent @value{GDBN} command.
16739 @subsubheading Example
16741 For a stack with frame levels 0 through 11:
16748 -stack-info-depth 4
16751 -stack-info-depth 12
16754 -stack-info-depth 11
16757 -stack-info-depth 13
16762 @subheading The @code{-stack-list-arguments} Command
16763 @findex -stack-list-arguments
16765 @subsubheading Synopsis
16768 -stack-list-arguments @var{show-values}
16769 [ @var{low-frame} @var{high-frame} ]
16772 Display a list of the arguments for the frames between @var{low-frame}
16773 and @var{high-frame} (inclusive). If @var{low-frame} and
16774 @var{high-frame} are not provided, list the arguments for the whole call
16777 The @var{show-values} argument must have a value of 0 or 1. A value of
16778 0 means that only the names of the arguments are listed, a value of 1
16779 means that both names and values of the arguments are printed.
16781 @subsubheading @value{GDBN} Command
16783 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
16784 @samp{gdb_get_args} command which partially overlaps with the
16785 functionality of @samp{-stack-list-arguments}.
16787 @subsubheading Example
16794 frame=@{level="0",addr="0x00010734",func="callee4",
16795 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
16796 frame=@{level="1",addr="0x0001076c",func="callee3",
16797 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
16798 frame=@{level="2",addr="0x0001078c",func="callee2",
16799 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
16800 frame=@{level="3",addr="0x000107b4",func="callee1",
16801 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
16802 frame=@{level="4",addr="0x000107e0",func="main",
16803 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
16805 -stack-list-arguments 0
16808 frame=@{level="0",args=[]@},
16809 frame=@{level="1",args=[name="strarg"]@},
16810 frame=@{level="2",args=[name="intarg",name="strarg"]@},
16811 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
16812 frame=@{level="4",args=[]@}]
16814 -stack-list-arguments 1
16817 frame=@{level="0",args=[]@},
16819 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
16820 frame=@{level="2",args=[
16821 @{name="intarg",value="2"@},
16822 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
16823 @{frame=@{level="3",args=[
16824 @{name="intarg",value="2"@},
16825 @{name="strarg",value="0x11940 \"A string argument.\""@},
16826 @{name="fltarg",value="3.5"@}]@},
16827 frame=@{level="4",args=[]@}]
16829 -stack-list-arguments 0 2 2
16830 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
16832 -stack-list-arguments 1 2 2
16833 ^done,stack-args=[frame=@{level="2",
16834 args=[@{name="intarg",value="2"@},
16835 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
16839 @c @subheading -stack-list-exception-handlers
16842 @subheading The @code{-stack-list-frames} Command
16843 @findex -stack-list-frames
16845 @subsubheading Synopsis
16848 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
16851 List the frames currently on the stack. For each frame it displays the
16856 The frame number, 0 being the topmost frame, i.e. the innermost function.
16858 The @code{$pc} value for that frame.
16862 File name of the source file where the function lives.
16864 Line number corresponding to the @code{$pc}.
16867 If invoked without arguments, this command prints a backtrace for the
16868 whole stack. If given two integer arguments, it shows the frames whose
16869 levels are between the two arguments (inclusive). If the two arguments
16870 are equal, it shows the single frame at the corresponding level.
16872 @subsubheading @value{GDBN} Command
16874 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
16876 @subsubheading Example
16878 Full stack backtrace:
16884 [frame=@{level="0",addr="0x0001076c",func="foo",
16885 file="recursive2.c",line="11"@},
16886 frame=@{level="1",addr="0x000107a4",func="foo",
16887 file="recursive2.c",line="14"@},
16888 frame=@{level="2",addr="0x000107a4",func="foo",
16889 file="recursive2.c",line="14"@},
16890 frame=@{level="3",addr="0x000107a4",func="foo",
16891 file="recursive2.c",line="14"@},
16892 frame=@{level="4",addr="0x000107a4",func="foo",
16893 file="recursive2.c",line="14"@},
16894 frame=@{level="5",addr="0x000107a4",func="foo",
16895 file="recursive2.c",line="14"@},
16896 frame=@{level="6",addr="0x000107a4",func="foo",
16897 file="recursive2.c",line="14"@},
16898 frame=@{level="7",addr="0x000107a4",func="foo",
16899 file="recursive2.c",line="14"@},
16900 frame=@{level="8",addr="0x000107a4",func="foo",
16901 file="recursive2.c",line="14"@},
16902 frame=@{level="9",addr="0x000107a4",func="foo",
16903 file="recursive2.c",line="14"@},
16904 frame=@{level="10",addr="0x000107a4",func="foo",
16905 file="recursive2.c",line="14"@},
16906 frame=@{level="11",addr="0x00010738",func="main",
16907 file="recursive2.c",line="4"@}]
16911 Show frames between @var{low_frame} and @var{high_frame}:
16915 -stack-list-frames 3 5
16917 [frame=@{level="3",addr="0x000107a4",func="foo",
16918 file="recursive2.c",line="14"@},
16919 frame=@{level="4",addr="0x000107a4",func="foo",
16920 file="recursive2.c",line="14"@},
16921 frame=@{level="5",addr="0x000107a4",func="foo",
16922 file="recursive2.c",line="14"@}]
16926 Show a single frame:
16930 -stack-list-frames 3 3
16932 [frame=@{level="3",addr="0x000107a4",func="foo",
16933 file="recursive2.c",line="14"@}]
16938 @subheading The @code{-stack-list-locals} Command
16939 @findex -stack-list-locals
16941 @subsubheading Synopsis
16944 -stack-list-locals @var{print-values}
16947 Display the local variable names for the current frame. With an
16948 argument of 0 prints only the names of the variables, with argument of 1
16949 prints also their values.
16951 @subsubheading @value{GDBN} Command
16953 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
16955 @subsubheading Example
16959 -stack-list-locals 0
16960 ^done,locals=[name="A",name="B",name="C"]
16962 -stack-list-locals 1
16963 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
16964 @{name="C",value="3"@}]
16969 @subheading The @code{-stack-select-frame} Command
16970 @findex -stack-select-frame
16972 @subsubheading Synopsis
16975 -stack-select-frame @var{framenum}
16978 Change the current frame. Select a different frame @var{framenum} on
16981 @subsubheading @value{GDBN} Command
16983 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
16984 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
16986 @subsubheading Example
16990 -stack-select-frame 2
16995 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16996 @node GDB/MI Symbol Query
16997 @section @sc{gdb/mi} Symbol Query Commands
17000 @subheading The @code{-symbol-info-address} Command
17001 @findex -symbol-info-address
17003 @subsubheading Synopsis
17006 -symbol-info-address @var{symbol}
17009 Describe where @var{symbol} is stored.
17011 @subsubheading @value{GDBN} Command
17013 The corresponding @value{GDBN} command is @samp{info address}.
17015 @subsubheading Example
17019 @subheading The @code{-symbol-info-file} Command
17020 @findex -symbol-info-file
17022 @subsubheading Synopsis
17028 Show the file for the symbol.
17030 @subsubheading @value{GDBN} Command
17032 There's no equivalent @value{GDBN} command. @code{gdbtk} has
17033 @samp{gdb_find_file}.
17035 @subsubheading Example
17039 @subheading The @code{-symbol-info-function} Command
17040 @findex -symbol-info-function
17042 @subsubheading Synopsis
17045 -symbol-info-function
17048 Show which function the symbol lives in.
17050 @subsubheading @value{GDBN} Command
17052 @samp{gdb_get_function} in @code{gdbtk}.
17054 @subsubheading Example
17058 @subheading The @code{-symbol-info-line} Command
17059 @findex -symbol-info-line
17061 @subsubheading Synopsis
17067 Show the core addresses of the code for a source line.
17069 @subsubheading @value{GDBN} Command
17071 The corresponding @value{GDBN} comamnd is @samp{info line}.
17072 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
17074 @subsubheading Example
17078 @subheading The @code{-symbol-info-symbol} Command
17079 @findex -symbol-info-symbol
17081 @subsubheading Synopsis
17084 -symbol-info-symbol @var{addr}
17087 Describe what symbol is at location @var{addr}.
17089 @subsubheading @value{GDBN} Command
17091 The corresponding @value{GDBN} command is @samp{info symbol}.
17093 @subsubheading Example
17097 @subheading The @code{-symbol-list-functions} Command
17098 @findex -symbol-list-functions
17100 @subsubheading Synopsis
17103 -symbol-list-functions
17106 List the functions in the executable.
17108 @subsubheading @value{GDBN} Command
17110 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
17111 @samp{gdb_search} in @code{gdbtk}.
17113 @subsubheading Example
17117 @subheading The @code{-symbol-list-lines} Command
17118 @findex -symbol-list-lines
17120 @subsubheading Synopsis
17123 -symbol-list-lines @var{filename}
17126 Print the list of lines that contain code and their associated program
17127 addresses for the given source filename. The entries are sorted in
17128 ascending PC order.
17130 @subsubheading @value{GDBN} Command
17132 There is no corresponding @value{GDBN} command.
17134 @subsubheading Example
17137 -symbol-list-lines basics.c
17138 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
17143 @subheading The @code{-symbol-list-types} Command
17144 @findex -symbol-list-types
17146 @subsubheading Synopsis
17152 List all the type names.
17154 @subsubheading @value{GDBN} Command
17156 The corresponding commands are @samp{info types} in @value{GDBN},
17157 @samp{gdb_search} in @code{gdbtk}.
17159 @subsubheading Example
17163 @subheading The @code{-symbol-list-variables} Command
17164 @findex -symbol-list-variables
17166 @subsubheading Synopsis
17169 -symbol-list-variables
17172 List all the global and static variable names.
17174 @subsubheading @value{GDBN} Command
17176 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
17178 @subsubheading Example
17182 @subheading The @code{-symbol-locate} Command
17183 @findex -symbol-locate
17185 @subsubheading Synopsis
17191 @subsubheading @value{GDBN} Command
17193 @samp{gdb_loc} in @code{gdbtk}.
17195 @subsubheading Example
17199 @subheading The @code{-symbol-type} Command
17200 @findex -symbol-type
17202 @subsubheading Synopsis
17205 -symbol-type @var{variable}
17208 Show type of @var{variable}.
17210 @subsubheading @value{GDBN} Command
17212 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
17213 @samp{gdb_obj_variable}.
17215 @subsubheading Example
17219 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17220 @node GDB/MI Target Manipulation
17221 @section @sc{gdb/mi} Target Manipulation Commands
17224 @subheading The @code{-target-attach} Command
17225 @findex -target-attach
17227 @subsubheading Synopsis
17230 -target-attach @var{pid} | @var{file}
17233 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
17235 @subsubheading @value{GDBN} command
17237 The corresponding @value{GDBN} command is @samp{attach}.
17239 @subsubheading Example
17243 @subheading The @code{-target-compare-sections} Command
17244 @findex -target-compare-sections
17246 @subsubheading Synopsis
17249 -target-compare-sections [ @var{section} ]
17252 Compare data of section @var{section} on target to the exec file.
17253 Without the argument, all sections are compared.
17255 @subsubheading @value{GDBN} Command
17257 The @value{GDBN} equivalent is @samp{compare-sections}.
17259 @subsubheading Example
17263 @subheading The @code{-target-detach} Command
17264 @findex -target-detach
17266 @subsubheading Synopsis
17272 Disconnect from the remote target. There's no output.
17274 @subsubheading @value{GDBN} command
17276 The corresponding @value{GDBN} command is @samp{detach}.
17278 @subsubheading Example
17288 @subheading The @code{-target-download} Command
17289 @findex -target-download
17291 @subsubheading Synopsis
17297 Loads the executable onto the remote target.
17298 It prints out an update message every half second, which includes the fields:
17302 The name of the section.
17304 The size of what has been sent so far for that section.
17306 The size of the section.
17308 The total size of what was sent so far (the current and the previous sections).
17310 The size of the overall executable to download.
17314 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
17315 @sc{gdb/mi} Output Syntax}).
17317 In addition, it prints the name and size of the sections, as they are
17318 downloaded. These messages include the following fields:
17322 The name of the section.
17324 The size of the section.
17326 The size of the overall executable to download.
17330 At the end, a summary is printed.
17332 @subsubheading @value{GDBN} Command
17334 The corresponding @value{GDBN} command is @samp{load}.
17336 @subsubheading Example
17338 Note: each status message appears on a single line. Here the messages
17339 have been broken down so that they can fit onto a page.
17344 +download,@{section=".text",section-size="6668",total-size="9880"@}
17345 +download,@{section=".text",section-sent="512",section-size="6668",
17346 total-sent="512",total-size="9880"@}
17347 +download,@{section=".text",section-sent="1024",section-size="6668",
17348 total-sent="1024",total-size="9880"@}
17349 +download,@{section=".text",section-sent="1536",section-size="6668",
17350 total-sent="1536",total-size="9880"@}
17351 +download,@{section=".text",section-sent="2048",section-size="6668",
17352 total-sent="2048",total-size="9880"@}
17353 +download,@{section=".text",section-sent="2560",section-size="6668",
17354 total-sent="2560",total-size="9880"@}
17355 +download,@{section=".text",section-sent="3072",section-size="6668",
17356 total-sent="3072",total-size="9880"@}
17357 +download,@{section=".text",section-sent="3584",section-size="6668",
17358 total-sent="3584",total-size="9880"@}
17359 +download,@{section=".text",section-sent="4096",section-size="6668",
17360 total-sent="4096",total-size="9880"@}
17361 +download,@{section=".text",section-sent="4608",section-size="6668",
17362 total-sent="4608",total-size="9880"@}
17363 +download,@{section=".text",section-sent="5120",section-size="6668",
17364 total-sent="5120",total-size="9880"@}
17365 +download,@{section=".text",section-sent="5632",section-size="6668",
17366 total-sent="5632",total-size="9880"@}
17367 +download,@{section=".text",section-sent="6144",section-size="6668",
17368 total-sent="6144",total-size="9880"@}
17369 +download,@{section=".text",section-sent="6656",section-size="6668",
17370 total-sent="6656",total-size="9880"@}
17371 +download,@{section=".init",section-size="28",total-size="9880"@}
17372 +download,@{section=".fini",section-size="28",total-size="9880"@}
17373 +download,@{section=".data",section-size="3156",total-size="9880"@}
17374 +download,@{section=".data",section-sent="512",section-size="3156",
17375 total-sent="7236",total-size="9880"@}
17376 +download,@{section=".data",section-sent="1024",section-size="3156",
17377 total-sent="7748",total-size="9880"@}
17378 +download,@{section=".data",section-sent="1536",section-size="3156",
17379 total-sent="8260",total-size="9880"@}
17380 +download,@{section=".data",section-sent="2048",section-size="3156",
17381 total-sent="8772",total-size="9880"@}
17382 +download,@{section=".data",section-sent="2560",section-size="3156",
17383 total-sent="9284",total-size="9880"@}
17384 +download,@{section=".data",section-sent="3072",section-size="3156",
17385 total-sent="9796",total-size="9880"@}
17386 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
17392 @subheading The @code{-target-exec-status} Command
17393 @findex -target-exec-status
17395 @subsubheading Synopsis
17398 -target-exec-status
17401 Provide information on the state of the target (whether it is running or
17402 not, for instance).
17404 @subsubheading @value{GDBN} Command
17406 There's no equivalent @value{GDBN} command.
17408 @subsubheading Example
17412 @subheading The @code{-target-list-available-targets} Command
17413 @findex -target-list-available-targets
17415 @subsubheading Synopsis
17418 -target-list-available-targets
17421 List the possible targets to connect to.
17423 @subsubheading @value{GDBN} Command
17425 The corresponding @value{GDBN} command is @samp{help target}.
17427 @subsubheading Example
17431 @subheading The @code{-target-list-current-targets} Command
17432 @findex -target-list-current-targets
17434 @subsubheading Synopsis
17437 -target-list-current-targets
17440 Describe the current target.
17442 @subsubheading @value{GDBN} Command
17444 The corresponding information is printed by @samp{info file} (among
17447 @subsubheading Example
17451 @subheading The @code{-target-list-parameters} Command
17452 @findex -target-list-parameters
17454 @subsubheading Synopsis
17457 -target-list-parameters
17462 @subsubheading @value{GDBN} Command
17466 @subsubheading Example
17470 @subheading The @code{-target-select} Command
17471 @findex -target-select
17473 @subsubheading Synopsis
17476 -target-select @var{type} @var{parameters @dots{}}
17479 Connect @value{GDBN} to the remote target. This command takes two args:
17483 The type of target, for instance @samp{async}, @samp{remote}, etc.
17484 @item @var{parameters}
17485 Device names, host names and the like. @xref{Target Commands, ,
17486 Commands for managing targets}, for more details.
17489 The output is a connection notification, followed by the address at
17490 which the target program is, in the following form:
17493 ^connected,addr="@var{address}",func="@var{function name}",
17494 args=[@var{arg list}]
17497 @subsubheading @value{GDBN} Command
17499 The corresponding @value{GDBN} command is @samp{target}.
17501 @subsubheading Example
17505 -target-select async /dev/ttya
17506 ^connected,addr="0xfe00a300",func="??",args=[]
17510 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17511 @node GDB/MI Thread Commands
17512 @section @sc{gdb/mi} Thread Commands
17515 @subheading The @code{-thread-info} Command
17516 @findex -thread-info
17518 @subsubheading Synopsis
17524 @subsubheading @value{GDBN} command
17528 @subsubheading Example
17532 @subheading The @code{-thread-list-all-threads} Command
17533 @findex -thread-list-all-threads
17535 @subsubheading Synopsis
17538 -thread-list-all-threads
17541 @subsubheading @value{GDBN} Command
17543 The equivalent @value{GDBN} command is @samp{info threads}.
17545 @subsubheading Example
17549 @subheading The @code{-thread-list-ids} Command
17550 @findex -thread-list-ids
17552 @subsubheading Synopsis
17558 Produces a list of the currently known @value{GDBN} thread ids. At the
17559 end of the list it also prints the total number of such threads.
17561 @subsubheading @value{GDBN} Command
17563 Part of @samp{info threads} supplies the same information.
17565 @subsubheading Example
17567 No threads present, besides the main process:
17572 ^done,thread-ids=@{@},number-of-threads="0"
17582 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17583 number-of-threads="3"
17588 @subheading The @code{-thread-select} Command
17589 @findex -thread-select
17591 @subsubheading Synopsis
17594 -thread-select @var{threadnum}
17597 Make @var{threadnum} the current thread. It prints the number of the new
17598 current thread, and the topmost frame for that thread.
17600 @subsubheading @value{GDBN} Command
17602 The corresponding @value{GDBN} command is @samp{thread}.
17604 @subsubheading Example
17611 *stopped,reason="end-stepping-range",thread-id="2",line="187",
17612 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
17616 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17617 number-of-threads="3"
17620 ^done,new-thread-id="3",
17621 frame=@{level="0",func="vprintf",
17622 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
17623 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
17627 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17628 @node GDB/MI Tracepoint Commands
17629 @section @sc{gdb/mi} Tracepoint Commands
17631 The tracepoint commands are not yet implemented.
17633 @c @subheading -trace-actions
17635 @c @subheading -trace-delete
17637 @c @subheading -trace-disable
17639 @c @subheading -trace-dump
17641 @c @subheading -trace-enable
17643 @c @subheading -trace-exists
17645 @c @subheading -trace-find
17647 @c @subheading -trace-frame-number
17649 @c @subheading -trace-info
17651 @c @subheading -trace-insert
17653 @c @subheading -trace-list
17655 @c @subheading -trace-pass-count
17657 @c @subheading -trace-save
17659 @c @subheading -trace-start
17661 @c @subheading -trace-stop
17664 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17665 @node GDB/MI Variable Objects
17666 @section @sc{gdb/mi} Variable Objects
17669 @subheading Motivation for Variable Objects in @sc{gdb/mi}
17671 For the implementation of a variable debugger window (locals, watched
17672 expressions, etc.), we are proposing the adaptation of the existing code
17673 used by @code{Insight}.
17675 The two main reasons for that are:
17679 It has been proven in practice (it is already on its second generation).
17682 It will shorten development time (needless to say how important it is
17686 The original interface was designed to be used by Tcl code, so it was
17687 slightly changed so it could be used through @sc{gdb/mi}. This section
17688 describes the @sc{gdb/mi} operations that will be available and gives some
17689 hints about their use.
17691 @emph{Note}: In addition to the set of operations described here, we
17692 expect the @sc{gui} implementation of a variable window to require, at
17693 least, the following operations:
17696 @item @code{-gdb-show} @code{output-radix}
17697 @item @code{-stack-list-arguments}
17698 @item @code{-stack-list-locals}
17699 @item @code{-stack-select-frame}
17702 @subheading Introduction to Variable Objects in @sc{gdb/mi}
17704 @cindex variable objects in @sc{gdb/mi}
17705 The basic idea behind variable objects is the creation of a named object
17706 to represent a variable, an expression, a memory location or even a CPU
17707 register. For each object created, a set of operations is available for
17708 examining or changing its properties.
17710 Furthermore, complex data types, such as C structures, are represented
17711 in a tree format. For instance, the @code{struct} type variable is the
17712 root and the children will represent the struct members. If a child
17713 is itself of a complex type, it will also have children of its own.
17714 Appropriate language differences are handled for C, C@t{++} and Java.
17716 When returning the actual values of the objects, this facility allows
17717 for the individual selection of the display format used in the result
17718 creation. It can be chosen among: binary, decimal, hexadecimal, octal
17719 and natural. Natural refers to a default format automatically
17720 chosen based on the variable type (like decimal for an @code{int}, hex
17721 for pointers, etc.).
17723 The following is the complete set of @sc{gdb/mi} operations defined to
17724 access this functionality:
17726 @multitable @columnfractions .4 .6
17727 @item @strong{Operation}
17728 @tab @strong{Description}
17730 @item @code{-var-create}
17731 @tab create a variable object
17732 @item @code{-var-delete}
17733 @tab delete the variable object and its children
17734 @item @code{-var-set-format}
17735 @tab set the display format of this variable
17736 @item @code{-var-show-format}
17737 @tab show the display format of this variable
17738 @item @code{-var-info-num-children}
17739 @tab tells how many children this object has
17740 @item @code{-var-list-children}
17741 @tab return a list of the object's children
17742 @item @code{-var-info-type}
17743 @tab show the type of this variable object
17744 @item @code{-var-info-expression}
17745 @tab print what this variable object represents
17746 @item @code{-var-show-attributes}
17747 @tab is this variable editable? does it exist here?
17748 @item @code{-var-evaluate-expression}
17749 @tab get the value of this variable
17750 @item @code{-var-assign}
17751 @tab set the value of this variable
17752 @item @code{-var-update}
17753 @tab update the variable and its children
17756 In the next subsection we describe each operation in detail and suggest
17757 how it can be used.
17759 @subheading Description And Use of Operations on Variable Objects
17761 @subheading The @code{-var-create} Command
17762 @findex -var-create
17764 @subsubheading Synopsis
17767 -var-create @{@var{name} | "-"@}
17768 @{@var{frame-addr} | "*"@} @var{expression}
17771 This operation creates a variable object, which allows the monitoring of
17772 a variable, the result of an expression, a memory cell or a CPU
17775 The @var{name} parameter is the string by which the object can be
17776 referenced. It must be unique. If @samp{-} is specified, the varobj
17777 system will generate a string ``varNNNNNN'' automatically. It will be
17778 unique provided that one does not specify @var{name} on that format.
17779 The command fails if a duplicate name is found.
17781 The frame under which the expression should be evaluated can be
17782 specified by @var{frame-addr}. A @samp{*} indicates that the current
17783 frame should be used.
17785 @var{expression} is any expression valid on the current language set (must not
17786 begin with a @samp{*}), or one of the following:
17790 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
17793 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
17796 @samp{$@var{regname}} --- a CPU register name
17799 @subsubheading Result
17801 This operation returns the name, number of children and the type of the
17802 object created. Type is returned as a string as the ones generated by
17803 the @value{GDBN} CLI:
17806 name="@var{name}",numchild="N",type="@var{type}"
17810 @subheading The @code{-var-delete} Command
17811 @findex -var-delete
17813 @subsubheading Synopsis
17816 -var-delete @var{name}
17819 Deletes a previously created variable object and all of its children.
17821 Returns an error if the object @var{name} is not found.
17824 @subheading The @code{-var-set-format} Command
17825 @findex -var-set-format
17827 @subsubheading Synopsis
17830 -var-set-format @var{name} @var{format-spec}
17833 Sets the output format for the value of the object @var{name} to be
17836 The syntax for the @var{format-spec} is as follows:
17839 @var{format-spec} @expansion{}
17840 @{binary | decimal | hexadecimal | octal | natural@}
17844 @subheading The @code{-var-show-format} Command
17845 @findex -var-show-format
17847 @subsubheading Synopsis
17850 -var-show-format @var{name}
17853 Returns the format used to display the value of the object @var{name}.
17856 @var{format} @expansion{}
17861 @subheading The @code{-var-info-num-children} Command
17862 @findex -var-info-num-children
17864 @subsubheading Synopsis
17867 -var-info-num-children @var{name}
17870 Returns the number of children of a variable object @var{name}:
17877 @subheading The @code{-var-list-children} Command
17878 @findex -var-list-children
17880 @subsubheading Synopsis
17883 -var-list-children @var{name}
17886 Returns a list of the children of the specified variable object:
17889 numchild=@var{n},children=[@{name=@var{name},
17890 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
17894 @subheading The @code{-var-info-type} Command
17895 @findex -var-info-type
17897 @subsubheading Synopsis
17900 -var-info-type @var{name}
17903 Returns the type of the specified variable @var{name}. The type is
17904 returned as a string in the same format as it is output by the
17908 type=@var{typename}
17912 @subheading The @code{-var-info-expression} Command
17913 @findex -var-info-expression
17915 @subsubheading Synopsis
17918 -var-info-expression @var{name}
17921 Returns what is represented by the variable object @var{name}:
17924 lang=@var{lang-spec},exp=@var{expression}
17928 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
17930 @subheading The @code{-var-show-attributes} Command
17931 @findex -var-show-attributes
17933 @subsubheading Synopsis
17936 -var-show-attributes @var{name}
17939 List attributes of the specified variable object @var{name}:
17942 status=@var{attr} [ ( ,@var{attr} )* ]
17946 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
17948 @subheading The @code{-var-evaluate-expression} Command
17949 @findex -var-evaluate-expression
17951 @subsubheading Synopsis
17954 -var-evaluate-expression @var{name}
17957 Evaluates the expression that is represented by the specified variable
17958 object and returns its value as a string in the current format specified
17965 Note that one must invoke @code{-var-list-children} for a variable
17966 before the value of a child variable can be evaluated.
17968 @subheading The @code{-var-assign} Command
17969 @findex -var-assign
17971 @subsubheading Synopsis
17974 -var-assign @var{name} @var{expression}
17977 Assigns the value of @var{expression} to the variable object specified
17978 by @var{name}. The object must be @samp{editable}. If the variable's
17979 value is altered by the assign, the variable will show up in any
17980 subsequent @code{-var-update} list.
17982 @subsubheading Example
17990 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
17994 @subheading The @code{-var-update} Command
17995 @findex -var-update
17997 @subsubheading Synopsis
18000 -var-update @{@var{name} | "*"@}
18003 Update the value of the variable object @var{name} by evaluating its
18004 expression after fetching all the new values from memory or registers.
18005 A @samp{*} causes all existing variable objects to be updated.
18009 @chapter @value{GDBN} Annotations
18011 This chapter describes annotations in @value{GDBN}. Annotations are
18012 designed to interface @value{GDBN} to graphical user interfaces or
18013 other similar programs which want to interact with @value{GDBN} at a
18014 relatively high level.
18017 This is Edition @value{EDITION}, @value{DATE}.
18021 * Annotations Overview:: What annotations are; the general syntax.
18022 * Server Prefix:: Issuing a command without affecting user state.
18023 * Value Annotations:: Values are marked as such.
18024 * Frame Annotations:: Stack frames are annotated.
18025 * Displays:: @value{GDBN} can be told to display something periodically.
18026 * Prompting:: Annotations marking @value{GDBN}'s need for input.
18027 * Errors:: Annotations for error messages.
18028 * Breakpoint Info:: Information on breakpoints.
18029 * Invalidation:: Some annotations describe things now invalid.
18030 * Annotations for Running::
18031 Whether the program is running, how it stopped, etc.
18032 * Source Annotations:: Annotations describing source code.
18033 * TODO:: Annotations which might be added in the future.
18036 @node Annotations Overview
18037 @section What is an Annotation?
18038 @cindex annotations
18040 To produce annotations, start @value{GDBN} with the @code{--annotate=2} option.
18042 Annotations start with a newline character, two @samp{control-z}
18043 characters, and the name of the annotation. If there is no additional
18044 information associated with this annotation, the name of the annotation
18045 is followed immediately by a newline. If there is additional
18046 information, the name of the annotation is followed by a space, the
18047 additional information, and a newline. The additional information
18048 cannot contain newline characters.
18050 Any output not beginning with a newline and two @samp{control-z}
18051 characters denotes literal output from @value{GDBN}. Currently there is
18052 no need for @value{GDBN} to output a newline followed by two
18053 @samp{control-z} characters, but if there was such a need, the
18054 annotations could be extended with an @samp{escape} annotation which
18055 means those three characters as output.
18057 A simple example of starting up @value{GDBN} with annotations is:
18062 Copyright 2000 Free Software Foundation, Inc.
18063 GDB is free software, covered by the GNU General Public License,
18064 and you are welcome to change it and/or distribute copies of it
18065 under certain conditions.
18066 Type "show copying" to see the conditions.
18067 There is absolutely no warranty for GDB. Type "show warranty"
18069 This GDB was configured as "sparc-sun-sunos4.1.3"
18080 Here @samp{quit} is input to @value{GDBN}; the rest is output from
18081 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
18082 denotes a @samp{control-z} character) are annotations; the rest is
18083 output from @value{GDBN}.
18085 @node Server Prefix
18086 @section The Server Prefix
18087 @cindex server prefix for annotations
18089 To issue a command to @value{GDBN} without affecting certain aspects of
18090 the state which is seen by users, prefix it with @samp{server }. This
18091 means that this command will not affect the command history, nor will it
18092 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18093 pressed on a line by itself.
18095 The server prefix does not affect the recording of values into the value
18096 history; to print a value without recording it into the value history,
18097 use the @code{output} command instead of the @code{print} command.
18099 @node Value Annotations
18102 @cindex annotations for values
18103 When a value is printed in various contexts, @value{GDBN} uses
18104 annotations to delimit the value from the surrounding text.
18106 @findex value-history-begin
18107 @findex value-history-value
18108 @findex value-history-end
18109 If a value is printed using @code{print} and added to the value history,
18110 the annotation looks like
18113 ^Z^Zvalue-history-begin @var{history-number} @var{value-flags}
18114 @var{history-string}
18115 ^Z^Zvalue-history-value
18117 ^Z^Zvalue-history-end
18121 where @var{history-number} is the number it is getting in the value
18122 history, @var{history-string} is a string, such as @samp{$5 = }, which
18123 introduces the value to the user, @var{the-value} is the output
18124 corresponding to the value itself, and @var{value-flags} is @samp{*} for
18125 a value which can be dereferenced and @samp{-} for a value which cannot.
18127 @findex value-begin
18129 If the value is not added to the value history (it is an invalid float
18130 or it is printed with the @code{output} command), the annotation is similar:
18133 ^Z^Zvalue-begin @var{value-flags}
18139 @findex arg-name-end
18142 When @value{GDBN} prints an argument to a function (for example, in the output
18143 from the @code{backtrace} command), it annotates it as follows:
18147 @var{argument-name}
18149 @var{separator-string}
18150 ^Z^Zarg-value @var{value-flags}
18156 where @var{argument-name} is the name of the argument,
18157 @var{separator-string} is text which separates the name from the value
18158 for the user's benefit (such as @samp{=}), and @var{value-flags} and
18159 @var{the-value} have the same meanings as in a
18160 @code{value-history-begin} annotation.
18162 @findex field-begin
18163 @findex field-name-end
18164 @findex field-value
18166 When printing a structure, @value{GDBN} annotates it as follows:
18169 ^Z^Zfield-begin @var{value-flags}
18172 @var{separator-string}
18179 where @var{field-name} is the name of the field, @var{separator-string}
18180 is text which separates the name from the value for the user's benefit
18181 (such as @samp{=}), and @var{value-flags} and @var{the-value} have the
18182 same meanings as in a @code{value-history-begin} annotation.
18184 When printing an array, @value{GDBN} annotates it as follows:
18187 ^Z^Zarray-section-begin @var{array-index} @var{value-flags}
18191 where @var{array-index} is the index of the first element being
18192 annotated and @var{value-flags} has the same meaning as in a
18193 @code{value-history-begin} annotation. This is followed by any number
18194 of elements, where is element can be either a single element:
18198 @samp{,} @var{whitespace} ; @r{omitted for the first element}
18203 or a repeated element
18206 @findex elt-rep-end
18208 @samp{,} @var{whitespace} ; @r{omitted for the first element}
18210 ^Z^Zelt-rep @var{number-of-repetitions}
18211 @var{repetition-string}
18215 In both cases, @var{the-value} is the output for the value of the
18216 element and @var{whitespace} can contain spaces, tabs, and newlines. In
18217 the repeated case, @var{number-of-repetitions} is the number of
18218 consecutive array elements which contain that value, and
18219 @var{repetition-string} is a string which is designed to convey to the
18220 user that repetition is being depicted.
18222 @findex array-section-end
18223 Once all the array elements have been output, the array annotation is
18227 ^Z^Zarray-section-end
18230 @node Frame Annotations
18233 @cindex annotations for frames
18234 Whenever @value{GDBN} prints a frame, it annotates it. For example, this applies
18235 to frames printed when @value{GDBN} stops, output from commands such as
18236 @code{backtrace} or @code{up}, etc.
18238 @findex frame-begin
18239 The frame annotation begins with
18242 ^Z^Zframe-begin @var{level} @var{address}
18247 where @var{level} is the number of the frame (0 is the innermost frame,
18248 and other frames have positive numbers), @var{address} is the address of
18249 the code executing in that frame, and @var{level-string} is a string
18250 designed to convey the level to the user. @var{address} is in the form
18251 @samp{0x} followed by one or more lowercase hex digits (note that this
18252 does not depend on the language). The frame ends with
18259 Between these annotations is the main body of the frame, which can
18264 @findex function-call
18267 @var{function-call-string}
18270 where @var{function-call-string} is text designed to convey to the user
18271 that this frame is associated with a function call made by @value{GDBN} to a
18272 function in the program being debugged.
18275 @findex signal-handler-caller
18277 ^Z^Zsignal-handler-caller
18278 @var{signal-handler-caller-string}
18281 where @var{signal-handler-caller-string} is text designed to convey to
18282 the user that this frame is associated with whatever mechanism is used
18283 by this operating system to call a signal handler (it is the frame which
18284 calls the signal handler, not the frame for the signal handler itself).
18289 @findex frame-address
18290 @findex frame-address-end
18291 This can optionally (depending on whether this is thought of as
18292 interesting information for the user to see) begin with
18297 ^Z^Zframe-address-end
18298 @var{separator-string}
18301 where @var{address} is the address executing in the frame (the same
18302 address as in the @code{frame-begin} annotation, but printed in a form
18303 which is intended for user consumption---in particular, the syntax varies
18304 depending on the language), and @var{separator-string} is a string
18305 intended to separate this address from what follows for the user's
18308 @findex frame-function-name
18313 ^Z^Zframe-function-name
18314 @var{function-name}
18319 where @var{function-name} is the name of the function executing in the
18320 frame, or @samp{??} if not known, and @var{arguments} are the arguments
18321 to the frame, with parentheses around them (each argument is annotated
18322 individually as well, @pxref{Value Annotations}).
18324 @findex frame-source-begin
18325 @findex frame-source-file
18326 @findex frame-source-file-end
18327 @findex frame-source-line
18328 @findex frame-source-end
18329 If source information is available, a reference to it is then printed:
18332 ^Z^Zframe-source-begin
18333 @var{source-intro-string}
18334 ^Z^Zframe-source-file
18336 ^Z^Zframe-source-file-end
18338 ^Z^Zframe-source-line
18340 ^Z^Zframe-source-end
18343 where @var{source-intro-string} separates for the user's benefit the
18344 reference from the text which precedes it, @var{filename} is the name of
18345 the source file, and @var{line-number} is the line number within that
18346 file (the first line is line 1).
18348 @findex frame-where
18349 If @value{GDBN} prints some information about where the frame is from (which
18350 library, which load segment, etc.; currently only done on the RS/6000),
18351 it is annotated with
18358 Then, if source is to actually be displayed for this frame (for example,
18359 this is not true for output from the @code{backtrace} command), then a
18360 @code{source} annotation (@pxref{Source Annotations}) is displayed. Unlike
18361 most annotations, this is output instead of the normal text which would be
18362 output, not in addition.
18368 @findex display-begin
18369 @findex display-number-end
18370 @findex display-format
18371 @findex display-expression
18372 @findex display-expression-end
18373 @findex display-value
18374 @findex display-end
18375 @cindex annotations for display
18376 When @value{GDBN} is told to display something using the @code{display} command,
18377 the results of the display are annotated:
18382 ^Z^Zdisplay-number-end
18383 @var{number-separator}
18386 ^Z^Zdisplay-expression
18388 ^Z^Zdisplay-expression-end
18389 @var{expression-separator}
18396 where @var{number} is the number of the display, @var{number-separator}
18397 is intended to separate the number from what follows for the user,
18398 @var{format} includes information such as the size, format, or other
18399 information about how the value is being displayed, @var{expression} is
18400 the expression being displayed, @var{expression-separator} is intended
18401 to separate the expression from the text that follows for the user,
18402 and @var{value} is the actual value being displayed.
18405 @section Annotation for @value{GDBN} Input
18407 @cindex annotations for prompts
18408 When @value{GDBN} prompts for input, it annotates this fact so it is possible
18409 to know when to send output, when the output from a given command is
18412 Different kinds of input each have a different @dfn{input type}. Each
18413 input type has three annotations: a @code{pre-} annotation, which
18414 denotes the beginning of any prompt which is being output, a plain
18415 annotation, which denotes the end of the prompt, and then a @code{post-}
18416 annotation which denotes the end of any echo which may (or may not) be
18417 associated with the input. For example, the @code{prompt} input type
18418 features the following annotations:
18426 The input types are
18431 @findex post-prompt
18433 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
18435 @findex pre-commands
18437 @findex post-commands
18439 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
18440 command. The annotations are repeated for each command which is input.
18442 @findex pre-overload-choice
18443 @findex overload-choice
18444 @findex post-overload-choice
18445 @item overload-choice
18446 When @value{GDBN} wants the user to select between various overloaded functions.
18452 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
18454 @findex pre-prompt-for-continue
18455 @findex prompt-for-continue
18456 @findex post-prompt-for-continue
18457 @item prompt-for-continue
18458 When @value{GDBN} is asking the user to press return to continue. Note: Don't
18459 expect this to work well; instead use @code{set height 0} to disable
18460 prompting. This is because the counting of lines is buggy in the
18461 presence of annotations.
18466 @cindex annotations for errors, warnings and interrupts
18473 This annotation occurs right before @value{GDBN} responds to an interrupt.
18480 This annotation occurs right before @value{GDBN} responds to an error.
18482 Quit and error annotations indicate that any annotations which @value{GDBN} was
18483 in the middle of may end abruptly. For example, if a
18484 @code{value-history-begin} annotation is followed by a @code{error}, one
18485 cannot expect to receive the matching @code{value-history-end}. One
18486 cannot expect not to receive it either, however; an error annotation
18487 does not necessarily mean that @value{GDBN} is immediately returning all the way
18490 @findex error-begin
18491 A quit or error annotation may be preceded by
18497 Any output between that and the quit or error annotation is the error
18500 Warning messages are not yet annotated.
18501 @c If we want to change that, need to fix warning(), type_error(),
18502 @c range_error(), and possibly other places.
18504 @node Breakpoint Info
18505 @section Information on Breakpoints
18507 @cindex annotations for breakpoints
18508 The output from the @code{info breakpoints} command is annotated as follows:
18510 @findex breakpoints-headers
18511 @findex breakpoints-table
18513 ^Z^Zbreakpoints-headers
18515 ^Z^Zbreakpoints-table
18519 where @var{header-entry} has the same syntax as an entry (see below) but
18520 instead of containing data, it contains strings which are intended to
18521 convey the meaning of each field to the user. This is followed by any
18522 number of entries. If a field does not apply for this entry, it is
18523 omitted. Fields may contain trailing whitespace. Each entry consists
18552 Note that @var{address} is intended for user consumption---the syntax
18553 varies depending on the language.
18555 The output ends with
18557 @findex breakpoints-table-end
18559 ^Z^Zbreakpoints-table-end
18563 @section Invalidation Notices
18565 @cindex annotations for invalidation messages
18566 The following annotations say that certain pieces of state may have
18570 @findex frames-invalid
18571 @item ^Z^Zframes-invalid
18573 The frames (for example, output from the @code{backtrace} command) may
18576 @findex breakpoints-invalid
18577 @item ^Z^Zbreakpoints-invalid
18579 The breakpoints may have changed. For example, the user just added or
18580 deleted a breakpoint.
18583 @node Annotations for Running
18584 @section Running the Program
18585 @cindex annotations for running programs
18589 When the program starts executing due to a @value{GDBN} command such as
18590 @code{step} or @code{continue},
18596 is output. When the program stops,
18602 is output. Before the @code{stopped} annotation, a variety of
18603 annotations describe how the program stopped.
18607 @item ^Z^Zexited @var{exit-status}
18608 The program exited, and @var{exit-status} is the exit status (zero for
18609 successful exit, otherwise nonzero).
18612 @findex signal-name
18613 @findex signal-name-end
18614 @findex signal-string
18615 @findex signal-string-end
18616 @item ^Z^Zsignalled
18617 The program exited with a signal. After the @code{^Z^Zsignalled}, the
18618 annotation continues:
18624 ^Z^Zsignal-name-end
18628 ^Z^Zsignal-string-end
18633 where @var{name} is the name of the signal, such as @code{SIGILL} or
18634 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
18635 as @code{Illegal Instruction} or @code{Segmentation fault}.
18636 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
18637 user's benefit and have no particular format.
18641 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
18642 just saying that the program received the signal, not that it was
18643 terminated with it.
18646 @item ^Z^Zbreakpoint @var{number}
18647 The program hit breakpoint number @var{number}.
18650 @item ^Z^Zwatchpoint @var{number}
18651 The program hit watchpoint number @var{number}.
18654 @node Source Annotations
18655 @section Displaying Source
18656 @cindex annotations for source display
18659 The following annotation is used instead of displaying source code:
18662 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
18665 where @var{filename} is an absolute file name indicating which source
18666 file, @var{line} is the line number within that file (where 1 is the
18667 first line in the file), @var{character} is the character position
18668 within the file (where 0 is the first character in the file) (for most
18669 debug formats this will necessarily point to the beginning of a line),
18670 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
18671 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
18672 @var{addr} is the address in the target program associated with the
18673 source which is being displayed. @var{addr} is in the form @samp{0x}
18674 followed by one or more lowercase hex digits (note that this does not
18675 depend on the language).
18678 @section Annotations We Might Want in the Future
18682 the target might have changed (registers, heap contents, or
18683 execution status). For performance, we might eventually want
18684 to hit `registers-invalid' and `all-registers-invalid' with
18687 - systematic annotation for set/show parameters (including
18688 invalidation notices).
18690 - similarly, `info' returns a list of candidates for invalidation
18695 @chapter Reporting Bugs in @value{GDBN}
18696 @cindex bugs in @value{GDBN}
18697 @cindex reporting bugs in @value{GDBN}
18699 Your bug reports play an essential role in making @value{GDBN} reliable.
18701 Reporting a bug may help you by bringing a solution to your problem, or it
18702 may not. But in any case the principal function of a bug report is to help
18703 the entire community by making the next version of @value{GDBN} work better. Bug
18704 reports are your contribution to the maintenance of @value{GDBN}.
18706 In order for a bug report to serve its purpose, you must include the
18707 information that enables us to fix the bug.
18710 * Bug Criteria:: Have you found a bug?
18711 * Bug Reporting:: How to report bugs
18715 @section Have you found a bug?
18716 @cindex bug criteria
18718 If you are not sure whether you have found a bug, here are some guidelines:
18721 @cindex fatal signal
18722 @cindex debugger crash
18723 @cindex crash of debugger
18725 If the debugger gets a fatal signal, for any input whatever, that is a
18726 @value{GDBN} bug. Reliable debuggers never crash.
18728 @cindex error on valid input
18730 If @value{GDBN} produces an error message for valid input, that is a
18731 bug. (Note that if you're cross debugging, the problem may also be
18732 somewhere in the connection to the target.)
18734 @cindex invalid input
18736 If @value{GDBN} does not produce an error message for invalid input,
18737 that is a bug. However, you should note that your idea of
18738 ``invalid input'' might be our idea of ``an extension'' or ``support
18739 for traditional practice''.
18742 If you are an experienced user of debugging tools, your suggestions
18743 for improvement of @value{GDBN} are welcome in any case.
18746 @node Bug Reporting
18747 @section How to report bugs
18748 @cindex bug reports
18749 @cindex @value{GDBN} bugs, reporting
18751 A number of companies and individuals offer support for @sc{gnu} products.
18752 If you obtained @value{GDBN} from a support organization, we recommend you
18753 contact that organization first.
18755 You can find contact information for many support companies and
18756 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
18758 @c should add a web page ref...
18760 In any event, we also recommend that you submit bug reports for
18761 @value{GDBN}. The prefered method is to submit them directly using
18762 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
18763 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
18766 @strong{Do not send bug reports to @samp{info-gdb}, or to
18767 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
18768 not want to receive bug reports. Those that do have arranged to receive
18771 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
18772 serves as a repeater. The mailing list and the newsgroup carry exactly
18773 the same messages. Often people think of posting bug reports to the
18774 newsgroup instead of mailing them. This appears to work, but it has one
18775 problem which can be crucial: a newsgroup posting often lacks a mail
18776 path back to the sender. Thus, if we need to ask for more information,
18777 we may be unable to reach you. For this reason, it is better to send
18778 bug reports to the mailing list.
18780 The fundamental principle of reporting bugs usefully is this:
18781 @strong{report all the facts}. If you are not sure whether to state a
18782 fact or leave it out, state it!
18784 Often people omit facts because they think they know what causes the
18785 problem and assume that some details do not matter. Thus, you might
18786 assume that the name of the variable you use in an example does not matter.
18787 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
18788 stray memory reference which happens to fetch from the location where that
18789 name is stored in memory; perhaps, if the name were different, the contents
18790 of that location would fool the debugger into doing the right thing despite
18791 the bug. Play it safe and give a specific, complete example. That is the
18792 easiest thing for you to do, and the most helpful.
18794 Keep in mind that the purpose of a bug report is to enable us to fix the
18795 bug. It may be that the bug has been reported previously, but neither
18796 you nor we can know that unless your bug report is complete and
18799 Sometimes people give a few sketchy facts and ask, ``Does this ring a
18800 bell?'' Those bug reports are useless, and we urge everyone to
18801 @emph{refuse to respond to them} except to chide the sender to report
18804 To enable us to fix the bug, you should include all these things:
18808 The version of @value{GDBN}. @value{GDBN} announces it if you start
18809 with no arguments; you can also print it at any time using @code{show
18812 Without this, we will not know whether there is any point in looking for
18813 the bug in the current version of @value{GDBN}.
18816 The type of machine you are using, and the operating system name and
18820 What compiler (and its version) was used to compile @value{GDBN}---e.g.
18821 ``@value{GCC}--2.8.1''.
18824 What compiler (and its version) was used to compile the program you are
18825 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
18826 C Compiler''. For GCC, you can say @code{gcc --version} to get this
18827 information; for other compilers, see the documentation for those
18831 The command arguments you gave the compiler to compile your example and
18832 observe the bug. For example, did you use @samp{-O}? To guarantee
18833 you will not omit something important, list them all. A copy of the
18834 Makefile (or the output from make) is sufficient.
18836 If we were to try to guess the arguments, we would probably guess wrong
18837 and then we might not encounter the bug.
18840 A complete input script, and all necessary source files, that will
18844 A description of what behavior you observe that you believe is
18845 incorrect. For example, ``It gets a fatal signal.''
18847 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
18848 will certainly notice it. But if the bug is incorrect output, we might
18849 not notice unless it is glaringly wrong. You might as well not give us
18850 a chance to make a mistake.
18852 Even if the problem you experience is a fatal signal, you should still
18853 say so explicitly. Suppose something strange is going on, such as, your
18854 copy of @value{GDBN} is out of synch, or you have encountered a bug in
18855 the C library on your system. (This has happened!) Your copy might
18856 crash and ours would not. If you told us to expect a crash, then when
18857 ours fails to crash, we would know that the bug was not happening for
18858 us. If you had not told us to expect a crash, then we would not be able
18859 to draw any conclusion from our observations.
18862 If you wish to suggest changes to the @value{GDBN} source, send us context
18863 diffs. If you even discuss something in the @value{GDBN} source, refer to
18864 it by context, not by line number.
18866 The line numbers in our development sources will not match those in your
18867 sources. Your line numbers would convey no useful information to us.
18871 Here are some things that are not necessary:
18875 A description of the envelope of the bug.
18877 Often people who encounter a bug spend a lot of time investigating
18878 which changes to the input file will make the bug go away and which
18879 changes will not affect it.
18881 This is often time consuming and not very useful, because the way we
18882 will find the bug is by running a single example under the debugger
18883 with breakpoints, not by pure deduction from a series of examples.
18884 We recommend that you save your time for something else.
18886 Of course, if you can find a simpler example to report @emph{instead}
18887 of the original one, that is a convenience for us. Errors in the
18888 output will be easier to spot, running under the debugger will take
18889 less time, and so on.
18891 However, simplification is not vital; if you do not want to do this,
18892 report the bug anyway and send us the entire test case you used.
18895 A patch for the bug.
18897 A patch for the bug does help us if it is a good one. But do not omit
18898 the necessary information, such as the test case, on the assumption that
18899 a patch is all we need. We might see problems with your patch and decide
18900 to fix the problem another way, or we might not understand it at all.
18902 Sometimes with a program as complicated as @value{GDBN} it is very hard to
18903 construct an example that will make the program follow a certain path
18904 through the code. If you do not send us the example, we will not be able
18905 to construct one, so we will not be able to verify that the bug is fixed.
18907 And if we cannot understand what bug you are trying to fix, or why your
18908 patch should be an improvement, we will not install it. A test case will
18909 help us to understand.
18912 A guess about what the bug is or what it depends on.
18914 Such guesses are usually wrong. Even we cannot guess right about such
18915 things without first using the debugger to find the facts.
18918 @c The readline documentation is distributed with the readline code
18919 @c and consists of the two following files:
18921 @c inc-hist.texinfo
18922 @c Use -I with makeinfo to point to the appropriate directory,
18923 @c environment var TEXINPUTS with TeX.
18924 @include rluser.texinfo
18925 @include inc-hist.texinfo
18928 @node Formatting Documentation
18929 @appendix Formatting Documentation
18931 @cindex @value{GDBN} reference card
18932 @cindex reference card
18933 The @value{GDBN} 4 release includes an already-formatted reference card, ready
18934 for printing with PostScript or Ghostscript, in the @file{gdb}
18935 subdirectory of the main source directory@footnote{In
18936 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
18937 release.}. If you can use PostScript or Ghostscript with your printer,
18938 you can print the reference card immediately with @file{refcard.ps}.
18940 The release also includes the source for the reference card. You
18941 can format it, using @TeX{}, by typing:
18947 The @value{GDBN} reference card is designed to print in @dfn{landscape}
18948 mode on US ``letter'' size paper;
18949 that is, on a sheet 11 inches wide by 8.5 inches
18950 high. You will need to specify this form of printing as an option to
18951 your @sc{dvi} output program.
18953 @cindex documentation
18955 All the documentation for @value{GDBN} comes as part of the machine-readable
18956 distribution. The documentation is written in Texinfo format, which is
18957 a documentation system that uses a single source file to produce both
18958 on-line information and a printed manual. You can use one of the Info
18959 formatting commands to create the on-line version of the documentation
18960 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
18962 @value{GDBN} includes an already formatted copy of the on-line Info
18963 version of this manual in the @file{gdb} subdirectory. The main Info
18964 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
18965 subordinate files matching @samp{gdb.info*} in the same directory. If
18966 necessary, you can print out these files, or read them with any editor;
18967 but they are easier to read using the @code{info} subsystem in @sc{gnu}
18968 Emacs or the standalone @code{info} program, available as part of the
18969 @sc{gnu} Texinfo distribution.
18971 If you want to format these Info files yourself, you need one of the
18972 Info formatting programs, such as @code{texinfo-format-buffer} or
18975 If you have @code{makeinfo} installed, and are in the top level
18976 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
18977 version @value{GDBVN}), you can make the Info file by typing:
18984 If you want to typeset and print copies of this manual, you need @TeX{},
18985 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
18986 Texinfo definitions file.
18988 @TeX{} is a typesetting program; it does not print files directly, but
18989 produces output files called @sc{dvi} files. To print a typeset
18990 document, you need a program to print @sc{dvi} files. If your system
18991 has @TeX{} installed, chances are it has such a program. The precise
18992 command to use depends on your system; @kbd{lpr -d} is common; another
18993 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
18994 require a file name without any extension or a @samp{.dvi} extension.
18996 @TeX{} also requires a macro definitions file called
18997 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
18998 written in Texinfo format. On its own, @TeX{} cannot either read or
18999 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
19000 and is located in the @file{gdb-@var{version-number}/texinfo}
19003 If you have @TeX{} and a @sc{dvi} printer program installed, you can
19004 typeset and print this manual. First switch to the the @file{gdb}
19005 subdirectory of the main source directory (for example, to
19006 @file{gdb-@value{GDBVN}/gdb}) and type:
19012 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
19014 @node Installing GDB
19015 @appendix Installing @value{GDBN}
19016 @cindex configuring @value{GDBN}
19017 @cindex installation
19018 @cindex configuring @value{GDBN}, and source tree subdirectories
19020 @value{GDBN} comes with a @code{configure} script that automates the process
19021 of preparing @value{GDBN} for installation; you can then use @code{make} to
19022 build the @code{gdb} program.
19024 @c irrelevant in info file; it's as current as the code it lives with.
19025 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
19026 look at the @file{README} file in the sources; we may have improved the
19027 installation procedures since publishing this manual.}
19030 The @value{GDBN} distribution includes all the source code you need for
19031 @value{GDBN} in a single directory, whose name is usually composed by
19032 appending the version number to @samp{gdb}.
19034 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
19035 @file{gdb-@value{GDBVN}} directory. That directory contains:
19038 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
19039 script for configuring @value{GDBN} and all its supporting libraries
19041 @item gdb-@value{GDBVN}/gdb
19042 the source specific to @value{GDBN} itself
19044 @item gdb-@value{GDBVN}/bfd
19045 source for the Binary File Descriptor library
19047 @item gdb-@value{GDBVN}/include
19048 @sc{gnu} include files
19050 @item gdb-@value{GDBVN}/libiberty
19051 source for the @samp{-liberty} free software library
19053 @item gdb-@value{GDBVN}/opcodes
19054 source for the library of opcode tables and disassemblers
19056 @item gdb-@value{GDBVN}/readline
19057 source for the @sc{gnu} command-line interface
19059 @item gdb-@value{GDBVN}/glob
19060 source for the @sc{gnu} filename pattern-matching subroutine
19062 @item gdb-@value{GDBVN}/mmalloc
19063 source for the @sc{gnu} memory-mapped malloc package
19066 The simplest way to configure and build @value{GDBN} is to run @code{configure}
19067 from the @file{gdb-@var{version-number}} source directory, which in
19068 this example is the @file{gdb-@value{GDBVN}} directory.
19070 First switch to the @file{gdb-@var{version-number}} source directory
19071 if you are not already in it; then run @code{configure}. Pass the
19072 identifier for the platform on which @value{GDBN} will run as an
19078 cd gdb-@value{GDBVN}
19079 ./configure @var{host}
19084 where @var{host} is an identifier such as @samp{sun4} or
19085 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
19086 (You can often leave off @var{host}; @code{configure} tries to guess the
19087 correct value by examining your system.)
19089 Running @samp{configure @var{host}} and then running @code{make} builds the
19090 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
19091 libraries, then @code{gdb} itself. The configured source files, and the
19092 binaries, are left in the corresponding source directories.
19095 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
19096 system does not recognize this automatically when you run a different
19097 shell, you may need to run @code{sh} on it explicitly:
19100 sh configure @var{host}
19103 If you run @code{configure} from a directory that contains source
19104 directories for multiple libraries or programs, such as the
19105 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
19106 creates configuration files for every directory level underneath (unless
19107 you tell it not to, with the @samp{--norecursion} option).
19109 You should run the @code{configure} script from the top directory in the
19110 source tree, the @file{gdb-@var{version-number}} directory. If you run
19111 @code{configure} from one of the subdirectories, you will configure only
19112 that subdirectory. That is usually not what you want. In particular,
19113 if you run the first @code{configure} from the @file{gdb} subdirectory
19114 of the @file{gdb-@var{version-number}} directory, you will omit the
19115 configuration of @file{bfd}, @file{readline}, and other sibling
19116 directories of the @file{gdb} subdirectory. This leads to build errors
19117 about missing include files such as @file{bfd/bfd.h}.
19119 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
19120 However, you should make sure that the shell on your path (named by
19121 the @samp{SHELL} environment variable) is publicly readable. Remember
19122 that @value{GDBN} uses the shell to start your program---some systems refuse to
19123 let @value{GDBN} debug child processes whose programs are not readable.
19126 * Separate Objdir:: Compiling @value{GDBN} in another directory
19127 * Config Names:: Specifying names for hosts and targets
19128 * Configure Options:: Summary of options for configure
19131 @node Separate Objdir
19132 @section Compiling @value{GDBN} in another directory
19134 If you want to run @value{GDBN} versions for several host or target machines,
19135 you need a different @code{gdb} compiled for each combination of
19136 host and target. @code{configure} is designed to make this easy by
19137 allowing you to generate each configuration in a separate subdirectory,
19138 rather than in the source directory. If your @code{make} program
19139 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
19140 @code{make} in each of these directories builds the @code{gdb}
19141 program specified there.
19143 To build @code{gdb} in a separate directory, run @code{configure}
19144 with the @samp{--srcdir} option to specify where to find the source.
19145 (You also need to specify a path to find @code{configure}
19146 itself from your working directory. If the path to @code{configure}
19147 would be the same as the argument to @samp{--srcdir}, you can leave out
19148 the @samp{--srcdir} option; it is assumed.)
19150 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
19151 separate directory for a Sun 4 like this:
19155 cd gdb-@value{GDBVN}
19158 ../gdb-@value{GDBVN}/configure sun4
19163 When @code{configure} builds a configuration using a remote source
19164 directory, it creates a tree for the binaries with the same structure
19165 (and using the same names) as the tree under the source directory. In
19166 the example, you'd find the Sun 4 library @file{libiberty.a} in the
19167 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
19168 @file{gdb-sun4/gdb}.
19170 Make sure that your path to the @file{configure} script has just one
19171 instance of @file{gdb} in it. If your path to @file{configure} looks
19172 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
19173 one subdirectory of @value{GDBN}, not the whole package. This leads to
19174 build errors about missing include files such as @file{bfd/bfd.h}.
19176 One popular reason to build several @value{GDBN} configurations in separate
19177 directories is to configure @value{GDBN} for cross-compiling (where
19178 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
19179 programs that run on another machine---the @dfn{target}).
19180 You specify a cross-debugging target by
19181 giving the @samp{--target=@var{target}} option to @code{configure}.
19183 When you run @code{make} to build a program or library, you must run
19184 it in a configured directory---whatever directory you were in when you
19185 called @code{configure} (or one of its subdirectories).
19187 The @code{Makefile} that @code{configure} generates in each source
19188 directory also runs recursively. If you type @code{make} in a source
19189 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19190 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19191 will build all the required libraries, and then build GDB.
19193 When you have multiple hosts or targets configured in separate
19194 directories, you can run @code{make} on them in parallel (for example,
19195 if they are NFS-mounted on each of the hosts); they will not interfere
19199 @section Specifying names for hosts and targets
19201 The specifications used for hosts and targets in the @code{configure}
19202 script are based on a three-part naming scheme, but some short predefined
19203 aliases are also supported. The full naming scheme encodes three pieces
19204 of information in the following pattern:
19207 @var{architecture}-@var{vendor}-@var{os}
19210 For example, you can use the alias @code{sun4} as a @var{host} argument,
19211 or as the value for @var{target} in a @code{--target=@var{target}}
19212 option. The equivalent full name is @samp{sparc-sun-sunos4}.
19214 The @code{configure} script accompanying @value{GDBN} does not provide
19215 any query facility to list all supported host and target names or
19216 aliases. @code{configure} calls the Bourne shell script
19217 @code{config.sub} to map abbreviations to full names; you can read the
19218 script, if you wish, or you can use it to test your guesses on
19219 abbreviations---for example:
19222 % sh config.sub i386-linux
19224 % sh config.sub alpha-linux
19225 alpha-unknown-linux-gnu
19226 % sh config.sub hp9k700
19228 % sh config.sub sun4
19229 sparc-sun-sunos4.1.1
19230 % sh config.sub sun3
19231 m68k-sun-sunos4.1.1
19232 % sh config.sub i986v
19233 Invalid configuration `i986v': machine `i986v' not recognized
19237 @code{config.sub} is also distributed in the @value{GDBN} source
19238 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
19240 @node Configure Options
19241 @section @code{configure} options
19243 Here is a summary of the @code{configure} options and arguments that
19244 are most often useful for building @value{GDBN}. @code{configure} also has
19245 several other options not listed here. @inforef{What Configure
19246 Does,,configure.info}, for a full explanation of @code{configure}.
19249 configure @r{[}--help@r{]}
19250 @r{[}--prefix=@var{dir}@r{]}
19251 @r{[}--exec-prefix=@var{dir}@r{]}
19252 @r{[}--srcdir=@var{dirname}@r{]}
19253 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
19254 @r{[}--target=@var{target}@r{]}
19259 You may introduce options with a single @samp{-} rather than
19260 @samp{--} if you prefer; but you may abbreviate option names if you use
19265 Display a quick summary of how to invoke @code{configure}.
19267 @item --prefix=@var{dir}
19268 Configure the source to install programs and files under directory
19271 @item --exec-prefix=@var{dir}
19272 Configure the source to install programs under directory
19275 @c avoid splitting the warning from the explanation:
19277 @item --srcdir=@var{dirname}
19278 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
19279 @code{make} that implements the @code{VPATH} feature.}@*
19280 Use this option to make configurations in directories separate from the
19281 @value{GDBN} source directories. Among other things, you can use this to
19282 build (or maintain) several configurations simultaneously, in separate
19283 directories. @code{configure} writes configuration specific files in
19284 the current directory, but arranges for them to use the source in the
19285 directory @var{dirname}. @code{configure} creates directories under
19286 the working directory in parallel to the source directories below
19289 @item --norecursion
19290 Configure only the directory level where @code{configure} is executed; do not
19291 propagate configuration to subdirectories.
19293 @item --target=@var{target}
19294 Configure @value{GDBN} for cross-debugging programs running on the specified
19295 @var{target}. Without this option, @value{GDBN} is configured to debug
19296 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
19298 There is no convenient way to generate a list of all available targets.
19300 @item @var{host} @dots{}
19301 Configure @value{GDBN} to run on the specified @var{host}.
19303 There is no convenient way to generate a list of all available hosts.
19306 There are many other options available as well, but they are generally
19307 needed for special purposes only.
19309 @node Maintenance Commands
19310 @appendix Maintenance Commands
19311 @cindex maintenance commands
19312 @cindex internal commands
19314 In addition to commands intended for @value{GDBN} users, @value{GDBN}
19315 includes a number of commands intended for @value{GDBN} developers.
19316 These commands are provided here for reference.
19319 @kindex maint info breakpoints
19320 @item @anchor{maint info breakpoints}maint info breakpoints
19321 Using the same format as @samp{info breakpoints}, display both the
19322 breakpoints you've set explicitly, and those @value{GDBN} is using for
19323 internal purposes. Internal breakpoints are shown with negative
19324 breakpoint numbers. The type column identifies what kind of breakpoint
19329 Normal, explicitly set breakpoint.
19332 Normal, explicitly set watchpoint.
19335 Internal breakpoint, used to handle correctly stepping through
19336 @code{longjmp} calls.
19338 @item longjmp resume
19339 Internal breakpoint at the target of a @code{longjmp}.
19342 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
19345 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
19348 Shared library events.
19352 @kindex maint internal-error
19353 @kindex maint internal-warning
19354 @item maint internal-error
19355 @itemx maint internal-warning
19356 Cause @value{GDBN} to call the internal function @code{internal_error}
19357 or @code{internal_warning} and hence behave as though an internal error
19358 or internal warning has been detected. In addition to reporting the
19359 internal problem, these functions give the user the opportunity to
19360 either quit @value{GDBN} or create a core file of the current
19361 @value{GDBN} session.
19364 (gdb) @kbd{maint internal-error testing, 1, 2}
19365 @dots{}/maint.c:121: internal-error: testing, 1, 2
19366 A problem internal to GDB has been detected. Further
19367 debugging may prove unreliable.
19368 Quit this debugging session? (y or n) @kbd{n}
19369 Create a core file? (y or n) @kbd{n}
19373 Takes an optional parameter that is used as the text of the error or
19376 @kindex maint print dummy-frames
19377 @item maint print dummy-frames
19379 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
19384 (gdb) @kbd{print add(2,3)}
19385 Breakpoint 2, add (a=2, b=3) at @dots{}
19387 The program being debugged stopped while in a function called from GDB.
19389 (gdb) @kbd{maint print dummy-frames}
19390 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
19391 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
19392 call_lo=0x01014000 call_hi=0x01014001
19396 Takes an optional file parameter.
19398 @kindex maint print registers
19399 @kindex maint print raw-registers
19400 @kindex maint print cooked-registers
19401 @kindex maint print register-groups
19402 @item maint print registers
19403 @itemx maint print raw-registers
19404 @itemx maint print cooked-registers
19405 @itemx maint print register-groups
19406 Print @value{GDBN}'s internal register data structures.
19408 The command @code{maint print raw-registers} includes the contents of
19409 the raw register cache; the command @code{maint print cooked-registers}
19410 includes the (cooked) value of all registers; and the command
19411 @code{maint print register-groups} includes the groups that each
19412 register is a member of. @xref{Registers,, Registers, gdbint,
19413 @value{GDBN} Internals}.
19415 Takes an optional file parameter.
19417 @kindex maint print reggroups
19418 @item maint print reggroups
19419 Print @value{GDBN}'s internal register group data structures.
19421 Takes an optional file parameter.
19424 (gdb) @kbd{maint print reggroups}
19435 @kindex maint set profile
19436 @kindex maint show profile
19437 @cindex profiling GDB
19438 @item maint set profile
19439 @itemx maint show profile
19440 Control profiling of @value{GDBN}.
19442 Profiling will be disabled until you use the @samp{maint set profile}
19443 command to enable it. When you enable profiling, the system will begin
19444 collecting timing and execution count data; when you disable profiling or
19445 exit @value{GDBN}, the results will be written to a log file. Remember that
19446 if you use profiling, @value{GDBN} will overwrite the profiling log file
19447 (often called @file{gmon.out}). If you have a record of important profiling
19448 data in a @file{gmon.out} file, be sure to move it to a safe location.
19450 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
19451 compiled with the @samp{-pg} compiler option.
19456 @node Remote Protocol
19457 @appendix @value{GDBN} Remote Serial Protocol
19462 * Stop Reply Packets::
19463 * General Query Packets::
19464 * Register Packet Format::
19466 * File-I/O remote protocol extension::
19472 There may be occasions when you need to know something about the
19473 protocol---for example, if there is only one serial port to your target
19474 machine, you might want your program to do something special if it
19475 recognizes a packet meant for @value{GDBN}.
19477 In the examples below, @samp{->} and @samp{<-} are used to indicate
19478 transmitted and received data respectfully.
19480 @cindex protocol, @value{GDBN} remote serial
19481 @cindex serial protocol, @value{GDBN} remote
19482 @cindex remote serial protocol
19483 All @value{GDBN} commands and responses (other than acknowledgments) are
19484 sent as a @var{packet}. A @var{packet} is introduced with the character
19485 @samp{$}, the actual @var{packet-data}, and the terminating character
19486 @samp{#} followed by a two-digit @var{checksum}:
19489 @code{$}@var{packet-data}@code{#}@var{checksum}
19493 @cindex checksum, for @value{GDBN} remote
19495 The two-digit @var{checksum} is computed as the modulo 256 sum of all
19496 characters between the leading @samp{$} and the trailing @samp{#} (an
19497 eight bit unsigned checksum).
19499 Implementors should note that prior to @value{GDBN} 5.0 the protocol
19500 specification also included an optional two-digit @var{sequence-id}:
19503 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
19506 @cindex sequence-id, for @value{GDBN} remote
19508 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
19509 has never output @var{sequence-id}s. Stubs that handle packets added
19510 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
19512 @cindex acknowledgment, for @value{GDBN} remote
19513 When either the host or the target machine receives a packet, the first
19514 response expected is an acknowledgment: either @samp{+} (to indicate
19515 the package was received correctly) or @samp{-} (to request
19519 -> @code{$}@var{packet-data}@code{#}@var{checksum}
19524 The host (@value{GDBN}) sends @var{command}s, and the target (the
19525 debugging stub incorporated in your program) sends a @var{response}. In
19526 the case of step and continue @var{command}s, the response is only sent
19527 when the operation has completed (the target has again stopped).
19529 @var{packet-data} consists of a sequence of characters with the
19530 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
19533 Fields within the packet should be separated using @samp{,} @samp{;} or
19534 @cindex remote protocol, field separator
19535 @samp{:}. Except where otherwise noted all numbers are represented in
19536 @sc{hex} with leading zeros suppressed.
19538 Implementors should note that prior to @value{GDBN} 5.0, the character
19539 @samp{:} could not appear as the third character in a packet (as it
19540 would potentially conflict with the @var{sequence-id}).
19542 Response @var{data} can be run-length encoded to save space. A @samp{*}
19543 means that the next character is an @sc{ascii} encoding giving a repeat count
19544 which stands for that many repetitions of the character preceding the
19545 @samp{*}. The encoding is @code{n+29}, yielding a printable character
19546 where @code{n >=3} (which is where rle starts to win). The printable
19547 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
19548 value greater than 126 should not be used.
19550 Some remote systems have used a different run-length encoding mechanism
19551 loosely refered to as the cisco encoding. Following the @samp{*}
19552 character are two hex digits that indicate the size of the packet.
19559 means the same as "0000".
19561 The error response returned for some packets includes a two character
19562 error number. That number is not well defined.
19564 For any @var{command} not supported by the stub, an empty response
19565 (@samp{$#00}) should be returned. That way it is possible to extend the
19566 protocol. A newer @value{GDBN} can tell if a packet is supported based
19569 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
19570 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
19576 The following table provides a complete list of all currently defined
19577 @var{command}s and their corresponding response @var{data}.
19581 @item @code{!} --- extended mode
19582 @cindex @code{!} packet
19584 Enable extended mode. In extended mode, the remote server is made
19585 persistent. The @samp{R} packet is used to restart the program being
19591 The remote target both supports and has enabled extended mode.
19594 @item @code{?} --- last signal
19595 @cindex @code{?} packet
19597 Indicate the reason the target halted. The reply is the same as for
19601 @xref{Stop Reply Packets}, for the reply specifications.
19603 @item @code{a} --- reserved
19605 Reserved for future use.
19607 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
19608 @cindex @code{A} packet
19610 Initialized @samp{argv[]} array passed into program. @var{arglen}
19611 specifies the number of bytes in the hex encoded byte stream @var{arg}.
19612 See @code{gdbserver} for more details.
19620 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
19621 @cindex @code{b} packet
19623 Change the serial line speed to @var{baud}.
19625 JTC: @emph{When does the transport layer state change? When it's
19626 received, or after the ACK is transmitted. In either case, there are
19627 problems if the command or the acknowledgment packet is dropped.}
19629 Stan: @emph{If people really wanted to add something like this, and get
19630 it working for the first time, they ought to modify ser-unix.c to send
19631 some kind of out-of-band message to a specially-setup stub and have the
19632 switch happen "in between" packets, so that from remote protocol's point
19633 of view, nothing actually happened.}
19635 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
19636 @cindex @code{B} packet
19638 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
19639 breakpoint at @var{addr}.
19641 This packet has been replaced by the @samp{Z} and @samp{z} packets
19642 (@pxref{insert breakpoint or watchpoint packet}).
19644 @item @code{c}@var{addr} --- continue
19645 @cindex @code{c} packet
19647 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19651 @xref{Stop Reply Packets}, for the reply specifications.
19653 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
19654 @cindex @code{C} packet
19656 Continue with signal @var{sig} (hex signal number). If
19657 @code{;}@var{addr} is omitted, resume at same address.
19660 @xref{Stop Reply Packets}, for the reply specifications.
19662 @item @code{d} --- toggle debug @strong{(deprecated)}
19663 @cindex @code{d} packet
19667 @item @code{D} --- detach
19668 @cindex @code{D} packet
19670 Detach @value{GDBN} from the remote system. Sent to the remote target
19671 before @value{GDBN} disconnects.
19675 @item @emph{no response}
19676 @value{GDBN} does not check for any response after sending this packet.
19679 @item @code{e} --- reserved
19681 Reserved for future use.
19683 @item @code{E} --- reserved
19685 Reserved for future use.
19687 @item @code{f} --- reserved
19689 Reserved for future use.
19691 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
19692 @cindex @code{F} packet
19694 This packet is send by @value{GDBN} as reply to a @code{F} request packet
19695 sent by the target. This is part of the File-I/O protocol extension.
19696 @xref{File-I/O remote protocol extension}, for the specification.
19698 @item @code{g} --- read registers
19699 @anchor{read registers packet}
19700 @cindex @code{g} packet
19702 Read general registers.
19706 @item @var{XX@dots{}}
19707 Each byte of register data is described by two hex digits. The bytes
19708 with the register are transmitted in target byte order. The size of
19709 each register and their position within the @samp{g} @var{packet} are
19710 determined by the @value{GDBN} internal macros @var{REGISTER_RAW_SIZE}
19711 and @var{REGISTER_NAME} macros. The specification of several standard
19712 @code{g} packets is specified below.
19717 @item @code{G}@var{XX@dots{}} --- write regs
19718 @cindex @code{G} packet
19720 @xref{read registers packet}, for a description of the @var{XX@dots{}}
19731 @item @code{h} --- reserved
19733 Reserved for future use.
19735 @item @code{H}@var{c}@var{t@dots{}} --- set thread
19736 @cindex @code{H} packet
19738 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
19739 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
19740 should be @samp{c} for step and continue operations, @samp{g} for other
19741 operations. The thread designator @var{t@dots{}} may be -1, meaning all
19742 the threads, a thread number, or zero which means pick any thread.
19753 @c 'H': How restrictive (or permissive) is the thread model. If a
19754 @c thread is selected and stopped, are other threads allowed
19755 @c to continue to execute? As I mentioned above, I think the
19756 @c semantics of each command when a thread is selected must be
19757 @c described. For example:
19759 @c 'g': If the stub supports threads and a specific thread is
19760 @c selected, returns the register block from that thread;
19761 @c otherwise returns current registers.
19763 @c 'G' If the stub supports threads and a specific thread is
19764 @c selected, sets the registers of the register block of
19765 @c that thread; otherwise sets current registers.
19767 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
19768 @anchor{cycle step packet}
19769 @cindex @code{i} packet
19771 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
19772 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
19773 step starting at that address.
19775 @item @code{I} --- signal then cycle step @strong{(reserved)}
19776 @cindex @code{I} packet
19778 @xref{step with signal packet}. @xref{cycle step packet}.
19780 @item @code{j} --- reserved
19782 Reserved for future use.
19784 @item @code{J} --- reserved
19786 Reserved for future use.
19788 @item @code{k} --- kill request
19789 @cindex @code{k} packet
19791 FIXME: @emph{There is no description of how to operate when a specific
19792 thread context has been selected (i.e.@: does 'k' kill only that
19795 @item @code{K} --- reserved
19797 Reserved for future use.
19799 @item @code{l} --- reserved
19801 Reserved for future use.
19803 @item @code{L} --- reserved
19805 Reserved for future use.
19807 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
19808 @cindex @code{m} packet
19810 Read @var{length} bytes of memory starting at address @var{addr}.
19811 Neither @value{GDBN} nor the stub assume that sized memory transfers are
19812 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
19813 transfer mechanism is needed.}
19817 @item @var{XX@dots{}}
19818 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
19819 to read only part of the data. Neither @value{GDBN} nor the stub assume
19820 that sized memory transfers are assumed using word aligned
19821 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
19827 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
19828 @cindex @code{M} packet
19830 Write @var{length} bytes of memory starting at address @var{addr}.
19831 @var{XX@dots{}} is the data.
19838 for an error (this includes the case where only part of the data was
19842 @item @code{n} --- reserved
19844 Reserved for future use.
19846 @item @code{N} --- reserved
19848 Reserved for future use.
19850 @item @code{o} --- reserved
19852 Reserved for future use.
19854 @item @code{O} --- reserved
19856 Reserved for future use.
19858 @item @code{p}@var{n@dots{}} --- read reg @strong{(reserved)}
19859 @cindex @code{p} packet
19861 @xref{write register packet}.
19865 @item @var{r@dots{}.}
19866 The hex encoded value of the register in target byte order.
19869 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
19870 @anchor{write register packet}
19871 @cindex @code{P} packet
19873 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
19874 digits for each byte in the register (target byte order).
19884 @item @code{q}@var{query} --- general query
19885 @anchor{general query packet}
19886 @cindex @code{q} packet
19888 Request info about @var{query}. In general @value{GDBN} queries have a
19889 leading upper case letter. Custom vendor queries should use a company
19890 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
19891 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
19892 that they match the full @var{query} name.
19896 @item @var{XX@dots{}}
19897 Hex encoded data from query. The reply can not be empty.
19901 Indicating an unrecognized @var{query}.
19904 @item @code{Q}@var{var}@code{=}@var{val} --- general set
19905 @cindex @code{Q} packet
19907 Set value of @var{var} to @var{val}.
19909 @xref{general query packet}, for a discussion of naming conventions.
19911 @item @code{r} --- reset @strong{(deprecated)}
19912 @cindex @code{r} packet
19914 Reset the entire system.
19916 @item @code{R}@var{XX} --- remote restart
19917 @cindex @code{R} packet
19919 Restart the program being debugged. @var{XX}, while needed, is ignored.
19920 This packet is only available in extended mode.
19924 @item @emph{no reply}
19925 The @samp{R} packet has no reply.
19928 @item @code{s}@var{addr} --- step
19929 @cindex @code{s} packet
19931 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19935 @xref{Stop Reply Packets}, for the reply specifications.
19937 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
19938 @anchor{step with signal packet}
19939 @cindex @code{S} packet
19941 Like @samp{C} but step not continue.
19944 @xref{Stop Reply Packets}, for the reply specifications.
19946 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
19947 @cindex @code{t} packet
19949 Search backwards starting at address @var{addr} for a match with pattern
19950 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
19951 @var{addr} must be at least 3 digits.
19953 @item @code{T}@var{XX} --- thread alive
19954 @cindex @code{T} packet
19956 Find out if the thread XX is alive.
19961 thread is still alive
19966 @item @code{u} --- reserved
19968 Reserved for future use.
19970 @item @code{U} --- reserved
19972 Reserved for future use.
19974 @item @code{v} --- reserved
19976 Reserved for future use.
19978 @item @code{V} --- reserved
19980 Reserved for future use.
19982 @item @code{w} --- reserved
19984 Reserved for future use.
19986 @item @code{W} --- reserved
19988 Reserved for future use.
19990 @item @code{x} --- reserved
19992 Reserved for future use.
19994 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
19995 @cindex @code{X} packet
19997 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
19998 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
19999 escaped using @code{0x7d}.
20009 @item @code{y} --- reserved
20011 Reserved for future use.
20013 @item @code{Y} reserved
20015 Reserved for future use.
20017 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
20018 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
20019 @anchor{insert breakpoint or watchpoint packet}
20020 @cindex @code{z} packet
20021 @cindex @code{Z} packets
20023 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
20024 watchpoint starting at address @var{address} and covering the next
20025 @var{length} bytes.
20027 Each breakpoint and watchpoint packet @var{type} is documented
20030 @emph{Implementation notes: A remote target shall return an empty string
20031 for an unrecognized breakpoint or watchpoint packet @var{type}. A
20032 remote target shall support either both or neither of a given
20033 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
20034 avoid potential problems with duplicate packets, the operations should
20035 be implemented in an idempotent way.}
20037 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
20038 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
20039 @cindex @code{z0} packet
20040 @cindex @code{Z0} packet
20042 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
20043 @code{addr} of size @code{length}.
20045 A memory breakpoint is implemented by replacing the instruction at
20046 @var{addr} with a software breakpoint or trap instruction. The
20047 @code{length} is used by targets that indicates the size of the
20048 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
20049 @sc{mips} can insert either a 2 or 4 byte breakpoint).
20051 @emph{Implementation note: It is possible for a target to copy or move
20052 code that contains memory breakpoints (e.g., when implementing
20053 overlays). The behavior of this packet, in the presence of such a
20054 target, is not defined.}
20066 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
20067 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
20068 @cindex @code{z1} packet
20069 @cindex @code{Z1} packet
20071 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
20072 address @code{addr} of size @code{length}.
20074 A hardware breakpoint is implemented using a mechanism that is not
20075 dependant on being able to modify the target's memory.
20077 @emph{Implementation note: A hardware breakpoint is not affected by code
20090 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
20091 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
20092 @cindex @code{z2} packet
20093 @cindex @code{Z2} packet
20095 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
20107 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
20108 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
20109 @cindex @code{z3} packet
20110 @cindex @code{Z3} packet
20112 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
20124 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
20125 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
20126 @cindex @code{z4} packet
20127 @cindex @code{Z4} packet
20129 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
20143 @node Stop Reply Packets
20144 @section Stop Reply Packets
20145 @cindex stop reply packets
20147 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
20148 receive any of the below as a reply. In the case of the @samp{C},
20149 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
20150 when the target halts. In the below the exact meaning of @samp{signal
20151 number} is poorly defined. In general one of the UNIX signal numbering
20152 conventions is used.
20157 @var{AA} is the signal number
20159 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
20160 @cindex @code{T} packet reply
20162 @var{AA} = two hex digit signal number; @var{n...} = register number
20163 (hex), @var{r...} = target byte ordered register contents, size defined
20164 by @code{REGISTER_RAW_SIZE}; @var{n...} = @samp{thread}, @var{r...} =
20165 thread process ID, this is a hex integer; @var{n...} = (@samp{watch} |
20166 @samp{rwatch} | @samp{awatch}, @var{r...} = data address, this is a hex
20167 integer; @var{n...} = other string not starting with valid hex digit.
20168 @value{GDBN} should ignore this @var{n...}, @var{r...} pair and go on
20169 to the next. This way we can extend the protocol.
20173 The process exited, and @var{AA} is the exit status. This is only
20174 applicable to certain targets.
20178 The process terminated with signal @var{AA}.
20180 @item N@var{AA};@var{t@dots{}};@var{d@dots{}};@var{b@dots{}} @strong{(obsolete)}
20182 @var{AA} = signal number; @var{t@dots{}} = address of symbol
20183 @code{_start}; @var{d@dots{}} = base of data section; @var{b@dots{}} =
20184 base of bss section. @emph{Note: only used by Cisco Systems targets.
20185 The difference between this reply and the @samp{qOffsets} query is that
20186 the @samp{N} packet may arrive spontaneously whereas the @samp{qOffsets}
20187 is a query initiated by the host debugger.}
20189 @item O@var{XX@dots{}}
20191 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
20192 any time while the program is running and the debugger should continue
20193 to wait for @samp{W}, @samp{T}, etc.
20195 @item F@var{call-id}@code{,}@var{parameter@dots{}}
20197 @var{call-id} is the identifier which says which host system call should
20198 be called. This is just the name of the function. Translation into the
20199 correct system call is only applicable as it's defined in @value{GDBN}.
20200 @xref{File-I/O remote protocol extension}, for a list of implemented
20203 @var{parameter@dots{}} is a list of parameters as defined for this very
20206 The target replies with this packet when it expects @value{GDBN} to call
20207 a host system call on behalf of the target. @value{GDBN} replies with
20208 an appropriate @code{F} packet and keeps up waiting for the next reply
20209 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
20210 @samp{s} action is expected to be continued.
20211 @xref{File-I/O remote protocol extension}, for more details.
20215 @node General Query Packets
20216 @section General Query Packets
20218 The following set and query packets have already been defined.
20222 @item @code{q}@code{C} --- current thread
20224 Return the current thread id.
20228 @item @code{QC}@var{pid}
20229 Where @var{pid} is a HEX encoded 16 bit process id.
20231 Any other reply implies the old pid.
20234 @item @code{q}@code{fThreadInfo} -- all thread ids
20236 @code{q}@code{sThreadInfo}
20238 Obtain a list of active thread ids from the target (OS). Since there
20239 may be too many active threads to fit into one reply packet, this query
20240 works iteratively: it may require more than one query/reply sequence to
20241 obtain the entire list of threads. The first query of the sequence will
20242 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
20243 sequence will be the @code{qs}@code{ThreadInfo} query.
20245 NOTE: replaces the @code{qL} query (see below).
20249 @item @code{m}@var{id}
20251 @item @code{m}@var{id},@var{id}@dots{}
20252 a comma-separated list of thread ids
20254 (lower case 'el') denotes end of list.
20257 In response to each query, the target will reply with a list of one or
20258 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
20259 will respond to each reply with a request for more thread ids (using the
20260 @code{qs} form of the query), until the target responds with @code{l}
20261 (lower-case el, for @code{'last'}).
20263 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
20265 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
20266 string description of a thread's attributes from the target OS. This
20267 string may contain anything that the target OS thinks is interesting for
20268 @value{GDBN} to tell the user about the thread. The string is displayed
20269 in @value{GDBN}'s @samp{info threads} display. Some examples of
20270 possible thread extra info strings are ``Runnable'', or ``Blocked on
20275 @item @var{XX@dots{}}
20276 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
20277 the printable string containing the extra information about the thread's
20281 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
20283 Obtain thread information from RTOS. Where: @var{startflag} (one hex
20284 digit) is one to indicate the first query and zero to indicate a
20285 subsequent query; @var{threadcount} (two hex digits) is the maximum
20286 number of threads the response packet can contain; and @var{nextthread}
20287 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
20288 returned in the response as @var{argthread}.
20290 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
20295 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
20296 Where: @var{count} (two hex digits) is the number of threads being
20297 returned; @var{done} (one hex digit) is zero to indicate more threads
20298 and one indicates no further threads; @var{argthreadid} (eight hex
20299 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
20300 is a sequence of thread IDs from the target. @var{threadid} (eight hex
20301 digits). See @code{remote.c:parse_threadlist_response()}.
20304 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
20308 @item @code{E}@var{NN}
20309 An error (such as memory fault)
20310 @item @code{C}@var{CRC32}
20311 A 32 bit cyclic redundancy check of the specified memory region.
20314 @item @code{q}@code{Offsets} --- query sect offs
20316 Get section offsets that the target used when re-locating the downloaded
20317 image. @emph{Note: while a @code{Bss} offset is included in the
20318 response, @value{GDBN} ignores this and instead applies the @code{Data}
20319 offset to the @code{Bss} section.}
20323 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
20326 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
20328 Returns information on @var{threadid}. Where: @var{mode} is a hex
20329 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
20336 See @code{remote.c:remote_unpack_thread_info_response()}.
20338 @item @code{q}@code{Rcmd,}@var{command} --- remote command
20340 @var{command} (hex encoded) is passed to the local interpreter for
20341 execution. Invalid commands should be reported using the output string.
20342 Before the final result packet, the target may also respond with a
20343 number of intermediate @code{O}@var{output} console output packets.
20344 @emph{Implementors should note that providing access to a stubs's
20345 interpreter may have security implications}.
20350 A command response with no output.
20352 A command response with the hex encoded output string @var{OUTPUT}.
20353 @item @code{E}@var{NN}
20354 Indicate a badly formed request.
20356 When @samp{q}@samp{Rcmd} is not recognized.
20359 @item @code{qSymbol::} --- symbol lookup
20361 Notify the target that @value{GDBN} is prepared to serve symbol lookup
20362 requests. Accept requests from the target for the values of symbols.
20367 The target does not need to look up any (more) symbols.
20368 @item @code{qSymbol:}@var{sym_name}
20369 The target requests the value of symbol @var{sym_name} (hex encoded).
20370 @value{GDBN} may provide the value by using the
20371 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
20374 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
20376 Set the value of @var{sym_name} to @var{sym_value}.
20378 @var{sym_name} (hex encoded) is the name of a symbol whose value the
20379 target has previously requested.
20381 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
20382 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
20388 The target does not need to look up any (more) symbols.
20389 @item @code{qSymbol:}@var{sym_name}
20390 The target requests the value of a new symbol @var{sym_name} (hex
20391 encoded). @value{GDBN} will continue to supply the values of symbols
20392 (if available), until the target ceases to request them.
20397 @node Register Packet Format
20398 @section Register Packet Format
20400 The following @samp{g}/@samp{G} packets have previously been defined.
20401 In the below, some thirty-two bit registers are transferred as
20402 sixty-four bits. Those registers should be zero/sign extended (which?)
20403 to fill the space allocated. Register bytes are transfered in target
20404 byte order. The two nibbles within a register byte are transfered
20405 most-significant - least-significant.
20411 All registers are transfered as thirty-two bit quantities in the order:
20412 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
20413 registers; fsr; fir; fp.
20417 All registers are transfered as sixty-four bit quantities (including
20418 thirty-two bit registers such as @code{sr}). The ordering is the same
20426 Example sequence of a target being re-started. Notice how the restart
20427 does not get any direct output:
20432 @emph{target restarts}
20435 <- @code{T001:1234123412341234}
20439 Example sequence of a target being stepped by a single instruction:
20442 -> @code{G1445@dots{}}
20447 <- @code{T001:1234123412341234}
20451 <- @code{1455@dots{}}
20455 @node File-I/O remote protocol extension
20456 @section File-I/O remote protocol extension
20457 @cindex File-I/O remote protocol extension
20460 * File-I/O Overview::
20461 * Protocol basics::
20462 * The `F' request packet::
20463 * The `F' reply packet::
20464 * Memory transfer::
20465 * The Ctrl-C message::
20467 * The isatty call::
20468 * The system call::
20469 * List of supported calls::
20470 * Protocol specific representation of datatypes::
20472 * File-I/O Examples::
20475 @node File-I/O Overview
20476 @subsection File-I/O Overview
20477 @cindex file-i/o overview
20479 The File I/O remote protocol extension (short: File-I/O) allows the
20480 target to use the hosts file system and console I/O when calling various
20481 system calls. System calls on the target system are translated into a
20482 remote protocol packet to the host system which then performs the needed
20483 actions and returns with an adequate response packet to the target system.
20484 This simulates file system operations even on targets that lack file systems.
20486 The protocol is defined host- and target-system independent. It uses
20487 it's own independent representation of datatypes and values. Both,
20488 @value{GDBN} and the target's @value{GDBN} stub are responsible for
20489 translating the system dependent values into the unified protocol values
20490 when data is transmitted.
20492 The communication is synchronous. A system call is possible only
20493 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
20494 packets. While @value{GDBN} handles the request for a system call,
20495 the target is stopped to allow deterministic access to the target's
20496 memory. Therefore File-I/O is not interuptible by target signals. It
20497 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
20499 The target's request to perform a host system call does not finish
20500 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
20501 after finishing the system call, the target returns to continuing the
20502 previous activity (continue, step). No additional continue or step
20503 request from @value{GDBN} is required.
20507 <- target requests 'system call X'
20508 target is stopped, @value{GDBN} executes system call
20509 -> GDB returns result
20510 ... target continues, GDB returns to wait for the target
20511 <- target hits breakpoint and sends a Txx packet
20514 The protocol is only used for files on the host file system and
20515 for I/O on the console. Character or block special devices, pipes,
20516 named pipes or sockets or any other communication method on the host
20517 system are not supported by this protocol.
20519 @node Protocol basics
20520 @subsection Protocol basics
20521 @cindex protocol basics, file-i/o
20523 The File-I/O protocol uses the @code{F} packet, as request as well
20524 as as reply packet. Since a File-I/O system call can only occur when
20525 @value{GDBN} is waiting for the continuing or stepping target, the
20526 File-I/O request is a reply that @value{GDBN} has to expect as a result
20527 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
20528 This @code{F} packet contains all information needed to allow @value{GDBN}
20529 to call the appropriate host system call:
20533 A unique identifier for the requested system call.
20536 All parameters to the system call. Pointers are given as addresses
20537 in the target memory address space. Pointers to strings are given as
20538 pointer/length pair. Numerical values are given as they are.
20539 Numerical control values are given in a protocol specific representation.
20543 At that point @value{GDBN} has to perform the following actions.
20547 If parameter pointer values are given, which point to data needed as input
20548 to a system call, @value{GDBN} requests this data from the target with a
20549 standard @code{m} packet request. This additional communication has to be
20550 expected by the target implementation and is handled as any other @code{m}
20554 @value{GDBN} translates all value from protocol representation to host
20555 representation as needed. Datatypes are coerced into the host types.
20558 @value{GDBN} calls the system call
20561 It then coerces datatypes back to protocol representation.
20564 If pointer parameters in the request packet point to buffer space in which
20565 a system call is expected to copy data to, the data is transmitted to the
20566 target using a @code{M} or @code{X} packet. This packet has to be expected
20567 by the target implementation and is handled as any other @code{M} or @code{X}
20572 Eventually @value{GDBN} replies with another @code{F} packet which contains all
20573 necessary information for the target to continue. This at least contains
20580 @code{errno}, if has been changed by the system call.
20587 After having done the needed type and value coercion, the target continues
20588 the latest continue or step action.
20590 @node The `F' request packet
20591 @subsection The @code{F} request packet
20592 @cindex file-i/o request packet
20593 @cindex @code{F} request packet
20595 The @code{F} request packet has the following format:
20600 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
20603 @var{call-id} is the identifier to indicate the host system call to be called.
20604 This is just the name of the function.
20606 @var{parameter@dots{}} are the parameters to the system call.
20610 Parameters are hexadecimal integer values, either the real values in case
20611 of scalar datatypes, as pointers to target buffer space in case of compound
20612 datatypes and unspecified memory areas or as pointer/length pairs in case
20613 of string parameters. These are appended to the call-id, each separated
20614 from its predecessor by a comma. All values are transmitted in ASCII
20615 string representation, pointer/length pairs separated by a slash.
20617 @node The `F' reply packet
20618 @subsection The @code{F} reply packet
20619 @cindex file-i/o reply packet
20620 @cindex @code{F} reply packet
20622 The @code{F} reply packet has the following format:
20627 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
20630 @var{retcode} is the return code of the system call as hexadecimal value.
20632 @var{errno} is the errno set by the call, in protocol specific representation.
20633 This parameter can be omitted if the call was successful.
20635 @var{Ctrl-C flag} is only send if the user requested a break. In this
20636 case, @var{errno} must be send as well, even if the call was successful.
20637 The @var{Ctrl-C flag} itself consists of the character 'C':
20644 or, if the call was interupted before the host call has been performed:
20651 assuming 4 is the protocol specific representation of @code{EINTR}.
20655 @node Memory transfer
20656 @subsection Memory transfer
20657 @cindex memory transfer, in file-i/o protocol
20659 Structured data which is transferred using a memory read or write as e.g.@:
20660 a @code{struct stat} is expected to be in a protocol specific format with
20661 all scalar multibyte datatypes being big endian. This should be done by
20662 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
20663 it transfers memory to the target. Transferred pointers to structured
20664 data should point to the already coerced data at any time.
20666 @node The Ctrl-C message
20667 @subsection The Ctrl-C message
20668 @cindex ctrl-c message, in file-i/o protocol
20670 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
20671 reply packet. In this case the target should behave, as if it had
20672 gotten a break message. The meaning for the target is ``system call
20673 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
20674 (as with a break message) and return to @value{GDBN} with a @code{T02}
20675 packet. In this case, it's important for the target to know, in which
20676 state the system call was interrupted. Since this action is by design
20677 not an atomic operation, we have to differ between two cases:
20681 The system call hasn't been performed on the host yet.
20684 The system call on the host has been finished.
20688 These two states can be distinguished by the target by the value of the
20689 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
20690 call hasn't been performed. This is equivalent to the @code{EINTR} handling
20691 on POSIX systems. In any other case, the target may presume that the
20692 system call has been finished --- successful or not --- and should behave
20693 as if the break message arrived right after the system call.
20695 @value{GDBN} must behave reliable. If the system call has not been called
20696 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
20697 @code{errno} in the packet. If the system call on the host has been finished
20698 before the user requests a break, the full action must be finshed by
20699 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
20700 The @code{F} packet may only be send when either nothing has happened
20701 or the full action has been completed.
20704 @subsection Console I/O
20705 @cindex console i/o as part of file-i/o
20707 By default and if not explicitely closed by the target system, the file
20708 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
20709 on the @value{GDBN} console is handled as any other file output operation
20710 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
20711 by @value{GDBN} so that after the target read request from file descriptor
20712 0 all following typing is buffered until either one of the following
20717 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
20719 system call is treated as finished.
20722 The user presses @kbd{Enter}. This is treated as end of input with a trailing
20726 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
20727 character, especially no Ctrl-D is appended to the input.
20731 If the user has typed more characters as fit in the buffer given to
20732 the read call, the trailing characters are buffered in @value{GDBN} until
20733 either another @code{read(0, @dots{})} is requested by the target or debugging
20734 is stopped on users request.
20736 @node The isatty call
20737 @subsection The isatty(3) call
20738 @cindex isatty call, file-i/o protocol
20740 A special case in this protocol is the library call @code{isatty} which
20741 is implemented as it's own call inside of this protocol. It returns
20742 1 to the target if the file descriptor given as parameter is attached
20743 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
20744 would require implementing @code{ioctl} and would be more complex than
20747 @node The system call
20748 @subsection The system(3) call
20749 @cindex system call, file-i/o protocol
20751 The other special case in this protocol is the @code{system} call which
20752 is implemented as it's own call, too. @value{GDBN} is taking over the full
20753 task of calling the necessary host calls to perform the @code{system}
20754 call. The return value of @code{system} is simplified before it's returned
20755 to the target. Basically, the only signal transmitted back is @code{EINTR}
20756 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
20757 entirely of the exit status of the called command.
20759 Due to security concerns, the @code{system} call is refused to be called
20760 by @value{GDBN} by default. The user has to allow this call explicitly by
20764 @kindex set remote system-call-allowed 1
20765 @item @code{set remote system-call-allowed 1}
20768 Disabling the @code{system} call is done by
20771 @kindex set remote system-call-allowed 0
20772 @item @code{set remote system-call-allowed 0}
20775 The current setting is shown by typing
20778 @kindex show remote system-call-allowed
20779 @item @code{show remote system-call-allowed}
20782 @node List of supported calls
20783 @subsection List of supported calls
20784 @cindex list of supported file-i/o calls
20801 @unnumberedsubsubsec open
20802 @cindex open, file-i/o system call
20806 int open(const char *pathname, int flags);
20807 int open(const char *pathname, int flags, mode_t mode);
20810 Fopen,pathptr/len,flags,mode
20814 @code{flags} is the bitwise or of the following values:
20818 If the file does not exist it will be created. The host
20819 rules apply as far as file ownership and time stamps
20823 When used with O_CREAT, if the file already exists it is
20824 an error and open() fails.
20827 If the file already exists and the open mode allows
20828 writing (O_RDWR or O_WRONLY is given) it will be
20829 truncated to length 0.
20832 The file is opened in append mode.
20835 The file is opened for reading only.
20838 The file is opened for writing only.
20841 The file is opened for reading and writing.
20844 Each other bit is silently ignored.
20849 @code{mode} is the bitwise or of the following values:
20853 User has read permission.
20856 User has write permission.
20859 Group has read permission.
20862 Group has write permission.
20865 Others have read permission.
20868 Others have write permission.
20871 Each other bit is silently ignored.
20876 @exdent Return value:
20877 open returns the new file descriptor or -1 if an error
20885 pathname already exists and O_CREAT and O_EXCL were used.
20888 pathname refers to a directory.
20891 The requested access is not allowed.
20894 pathname was too long.
20897 A directory component in pathname does not exist.
20900 pathname refers to a device, pipe, named pipe or socket.
20903 pathname refers to a file on a read-only filesystem and
20904 write access was requested.
20907 pathname is an invalid pointer value.
20910 No space on device to create the file.
20913 The process already has the maximum number of files open.
20916 The limit on the total number of files open on the system
20920 The call was interrupted by the user.
20924 @unnumberedsubsubsec close
20925 @cindex close, file-i/o system call
20934 @exdent Return value:
20935 close returns zero on success, or -1 if an error occurred.
20942 fd isn't a valid open file descriptor.
20945 The call was interrupted by the user.
20949 @unnumberedsubsubsec read
20950 @cindex read, file-i/o system call
20954 int read(int fd, void *buf, unsigned int count);
20957 Fread,fd,bufptr,count
20959 @exdent Return value:
20960 On success, the number of bytes read is returned.
20961 Zero indicates end of file. If count is zero, read
20962 returns zero as well. On error, -1 is returned.
20969 fd is not a valid file descriptor or is not open for
20973 buf is an invalid pointer value.
20976 The call was interrupted by the user.
20980 @unnumberedsubsubsec write
20981 @cindex write, file-i/o system call
20985 int write(int fd, const void *buf, unsigned int count);
20988 Fwrite,fd,bufptr,count
20990 @exdent Return value:
20991 On success, the number of bytes written are returned.
20992 Zero indicates nothing was written. On error, -1
21000 fd is not a valid file descriptor or is not open for
21004 buf is an invalid pointer value.
21007 An attempt was made to write a file that exceeds the
21008 host specific maximum file size allowed.
21011 No space on device to write the data.
21014 The call was interrupted by the user.
21018 @unnumberedsubsubsec lseek
21019 @cindex lseek, file-i/o system call
21023 long lseek (int fd, long offset, int flag);
21026 Flseek,fd,offset,flag
21029 @code{flag} is one of:
21033 The offset is set to offset bytes.
21036 The offset is set to its current location plus offset
21040 The offset is set to the size of the file plus offset
21045 @exdent Return value:
21046 On success, the resulting unsigned offset in bytes from
21047 the beginning of the file is returned. Otherwise, a
21048 value of -1 is returned.
21055 fd is not a valid open file descriptor.
21058 fd is associated with the @value{GDBN} console.
21061 flag is not a proper value.
21064 The call was interrupted by the user.
21068 @unnumberedsubsubsec rename
21069 @cindex rename, file-i/o system call
21073 int rename(const char *oldpath, const char *newpath);
21076 Frename,oldpathptr/len,newpathptr/len
21078 @exdent Return value:
21079 On success, zero is returned. On error, -1 is returned.
21086 newpath is an existing directory, but oldpath is not a
21090 newpath is a non-empty directory.
21093 oldpath or newpath is a directory that is in use by some
21097 An attempt was made to make a directory a subdirectory
21101 A component used as a directory in oldpath or new
21102 path is not a directory. Or oldpath is a directory
21103 and newpath exists but is not a directory.
21106 oldpathptr or newpathptr are invalid pointer values.
21109 No access to the file or the path of the file.
21113 oldpath or newpath was too long.
21116 A directory component in oldpath or newpath does not exist.
21119 The file is on a read-only filesystem.
21122 The device containing the file has no room for the new
21126 The call was interrupted by the user.
21130 @unnumberedsubsubsec unlink
21131 @cindex unlink, file-i/o system call
21135 int unlink(const char *pathname);
21138 Funlink,pathnameptr/len
21140 @exdent Return value:
21141 On success, zero is returned. On error, -1 is returned.
21148 No access to the file or the path of the file.
21151 The system does not allow unlinking of directories.
21154 The file pathname cannot be unlinked because it's
21155 being used by another process.
21158 pathnameptr is an invalid pointer value.
21161 pathname was too long.
21164 A directory component in pathname does not exist.
21167 A component of the path is not a directory.
21170 The file is on a read-only filesystem.
21173 The call was interrupted by the user.
21177 @unnumberedsubsubsec stat/fstat
21178 @cindex fstat, file-i/o system call
21179 @cindex stat, file-i/o system call
21183 int stat(const char *pathname, struct stat *buf);
21184 int fstat(int fd, struct stat *buf);
21187 Fstat,pathnameptr/len,bufptr
21190 @exdent Return value:
21191 On success, zero is returned. On error, -1 is returned.
21198 fd is not a valid open file.
21201 A directory component in pathname does not exist or the
21202 path is an empty string.
21205 A component of the path is not a directory.
21208 pathnameptr is an invalid pointer value.
21211 No access to the file or the path of the file.
21214 pathname was too long.
21217 The call was interrupted by the user.
21221 @unnumberedsubsubsec gettimeofday
21222 @cindex gettimeofday, file-i/o system call
21226 int gettimeofday(struct timeval *tv, void *tz);
21229 Fgettimeofday,tvptr,tzptr
21231 @exdent Return value:
21232 On success, 0 is returned, -1 otherwise.
21239 tz is a non-NULL pointer.
21242 tvptr and/or tzptr is an invalid pointer value.
21246 @unnumberedsubsubsec isatty
21247 @cindex isatty, file-i/o system call
21251 int isatty(int fd);
21256 @exdent Return value:
21257 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
21264 The call was interrupted by the user.
21268 @unnumberedsubsubsec system
21269 @cindex system, file-i/o system call
21273 int system(const char *command);
21276 Fsystem,commandptr/len
21278 @exdent Return value:
21279 The value returned is -1 on error and the return status
21280 of the command otherwise. Only the exit status of the
21281 command is returned, which is extracted from the hosts
21282 system return value by calling WEXITSTATUS(retval).
21283 In case /bin/sh could not be executed, 127 is returned.
21290 The call was interrupted by the user.
21293 @node Protocol specific representation of datatypes
21294 @subsection Protocol specific representation of datatypes
21295 @cindex protocol specific representation of datatypes, in file-i/o protocol
21298 * Integral datatypes::
21304 @node Integral datatypes
21305 @unnumberedsubsubsec Integral datatypes
21306 @cindex integral datatypes, in file-i/o protocol
21308 The integral datatypes used in the system calls are
21311 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
21314 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
21315 implemented as 32 bit values in this protocol.
21317 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
21319 @xref{Limits}, for corresponding MIN and MAX values (similar to those
21320 in @file{limits.h}) to allow range checking on host and target.
21322 @code{time_t} datatypes are defined as seconds since the Epoch.
21324 All integral datatypes transferred as part of a memory read or write of a
21325 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
21328 @node Pointer values
21329 @unnumberedsubsubsec Pointer values
21330 @cindex pointer values, in file-i/o protocol
21332 Pointers to target data are transmitted as they are. An exception
21333 is made for pointers to buffers for which the length isn't
21334 transmitted as part of the function call, namely strings. Strings
21335 are transmitted as a pointer/length pair, both as hex values, e.g.@:
21342 which is a pointer to data of length 18 bytes at position 0x1aaf.
21343 The length is defined as the full string length in bytes, including
21344 the trailing null byte. Example:
21347 ``hello, world'' at address 0x123456
21358 @unnumberedsubsubsec struct stat
21359 @cindex struct stat, in file-i/o protocol
21361 The buffer of type struct stat used by the target and @value{GDBN} is defined
21366 unsigned int st_dev; /* device */
21367 unsigned int st_ino; /* inode */
21368 mode_t st_mode; /* protection */
21369 unsigned int st_nlink; /* number of hard links */
21370 unsigned int st_uid; /* user ID of owner */
21371 unsigned int st_gid; /* group ID of owner */
21372 unsigned int st_rdev; /* device type (if inode device) */
21373 unsigned long st_size; /* total size, in bytes */
21374 unsigned long st_blksize; /* blocksize for filesystem I/O */
21375 unsigned long st_blocks; /* number of blocks allocated */
21376 time_t st_atime; /* time of last access */
21377 time_t st_mtime; /* time of last modification */
21378 time_t st_ctime; /* time of last change */
21382 The integral datatypes are conforming to the definitions given in the
21383 approriate section (see @ref{Integral datatypes}, for details) so this
21384 structure is of size 64 bytes.
21386 The values of several fields have a restricted meaning and/or
21393 st_ino: No valid meaning for the target. Transmitted unchanged.
21395 st_mode: Valid mode bits are described in Appendix C. Any other
21396 bits have currently no meaning for the target.
21398 st_uid: No valid meaning for the target. Transmitted unchanged.
21400 st_gid: No valid meaning for the target. Transmitted unchanged.
21402 st_rdev: No valid meaning for the target. Transmitted unchanged.
21404 st_atime, st_mtime, st_ctime:
21405 These values have a host and file system dependent
21406 accuracy. Especially on Windows hosts the file systems
21407 don't support exact timing values.
21410 The target gets a struct stat of the above representation and is
21411 responsible to coerce it to the target representation before
21414 Note that due to size differences between the host and target
21415 representation of stat members, these members could eventually
21416 get truncated on the target.
21418 @node struct timeval
21419 @unnumberedsubsubsec struct timeval
21420 @cindex struct timeval, in file-i/o protocol
21422 The buffer of type struct timeval used by the target and @value{GDBN}
21423 is defined as follows:
21427 time_t tv_sec; /* second */
21428 long tv_usec; /* microsecond */
21432 The integral datatypes are conforming to the definitions given in the
21433 approriate section (see @ref{Integral datatypes}, for details) so this
21434 structure is of size 8 bytes.
21437 @subsection Constants
21438 @cindex constants, in file-i/o protocol
21440 The following values are used for the constants inside of the
21441 protocol. @value{GDBN} and target are resposible to translate these
21442 values before and after the call as needed.
21453 @unnumberedsubsubsec Open flags
21454 @cindex open flags, in file-i/o protocol
21456 All values are given in hexadecimal representation.
21468 @node mode_t values
21469 @unnumberedsubsubsec mode_t values
21470 @cindex mode_t values, in file-i/o protocol
21472 All values are given in octal representation.
21489 @unnumberedsubsubsec Errno values
21490 @cindex errno values, in file-i/o protocol
21492 All values are given in decimal representation.
21517 EUNKNOWN is used as a fallback error value if a host system returns
21518 any error value not in the list of supported error numbers.
21521 @unnumberedsubsubsec Lseek flags
21522 @cindex lseek flags, in file-i/o protocol
21531 @unnumberedsubsubsec Limits
21532 @cindex limits, in file-i/o protocol
21534 All values are given in decimal representation.
21537 INT_MIN -2147483648
21539 UINT_MAX 4294967295
21540 LONG_MIN -9223372036854775808
21541 LONG_MAX 9223372036854775807
21542 ULONG_MAX 18446744073709551615
21545 @node File-I/O Examples
21546 @subsection File-I/O Examples
21547 @cindex file-i/o examples
21549 Example sequence of a write call, file descriptor 3, buffer is at target
21550 address 0x1234, 6 bytes should be written:
21553 <- @code{Fwrite,3,1234,6}
21554 @emph{request memory read from target}
21557 @emph{return "6 bytes written"}
21561 Example sequence of a read call, file descriptor 3, buffer is at target
21562 address 0x1234, 6 bytes should be read:
21565 <- @code{Fread,3,1234,6}
21566 @emph{request memory write to target}
21567 -> @code{X1234,6:XXXXXX}
21568 @emph{return "6 bytes read"}
21572 Example sequence of a read call, call fails on the host due to invalid
21573 file descriptor (EBADF):
21576 <- @code{Fread,3,1234,6}
21580 Example sequence of a read call, user presses Ctrl-C before syscall on
21584 <- @code{Fread,3,1234,6}
21589 Example sequence of a read call, user presses Ctrl-C after syscall on
21593 <- @code{Fread,3,1234,6}
21594 -> @code{X1234,6:XXXXXX}
21608 % I think something like @colophon should be in texinfo. In the
21610 \long\def\colophon{\hbox to0pt{}\vfill
21611 \centerline{The body of this manual is set in}
21612 \centerline{\fontname\tenrm,}
21613 \centerline{with headings in {\bf\fontname\tenbf}}
21614 \centerline{and examples in {\tt\fontname\tentt}.}
21615 \centerline{{\it\fontname\tenit\/},}
21616 \centerline{{\bf\fontname\tenbf}, and}
21617 \centerline{{\sl\fontname\tensl\/}}
21618 \centerline{are used for emphasis.}\vfill}
21620 % Blame: doc@cygnus.com, 1991.