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 invoke the
5971 @code{set target-charset} command with no argument, @value{GDBN} lists
5972 the 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 invoke the
5987 @code{set host-charset} command with no argument, @value{GDBN} lists the
5988 character sets it supports, placing an asterisk (@samp{*}) after those
5989 it can use as a host character set.
5991 @item set charset @var{charset}
5993 Set the current host and target character sets to @var{charset}. If you
5994 invoke the @code{set charset} command with no argument, it lists the
5995 character sets it supports. @value{GDBN} can only use certain character
5996 sets as its host character set; it marks those in the list with an
5997 asterisk (@samp{*}).
6000 @itemx show host-charset
6001 @itemx show target-charset
6002 @kindex show charset
6003 @kindex show host-charset
6004 @kindex show target-charset
6005 Show the current host and target charsets. The @code{show host-charset}
6006 and @code{show target-charset} commands are synonyms for @code{show
6011 @value{GDBN} currently includes support for the following character
6017 @cindex ASCII character set
6018 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6022 @cindex ISO 8859-1 character set
6023 @cindex ISO Latin 1 character set
6024 The ISO Latin 1 character set. This extends ASCII with accented
6025 characters needed for French, German, and Spanish. @value{GDBN} can use
6026 this as its host character set.
6030 @cindex EBCDIC character set
6031 @cindex IBM1047 character set
6032 Variants of the @sc{ebcdic} character set, used on some of IBM's
6033 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6034 @value{GDBN} cannot use these as its host character set.
6038 Note that these are all single-byte character sets. More work inside
6039 GDB is needed to support multi-byte or variable-width character
6040 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6042 Here is an example of @value{GDBN}'s character set support in action.
6043 Assume that the following source code has been placed in the file
6044 @file{charset-test.c}:
6050 = @{72, 101, 108, 108, 111, 44, 32, 119,
6051 111, 114, 108, 100, 33, 10, 0@};
6052 char ibm1047_hello[]
6053 = @{200, 133, 147, 147, 150, 107, 64, 166,
6054 150, 153, 147, 132, 90, 37, 0@};
6058 printf ("Hello, world!\n");
6062 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6063 containing the string @samp{Hello, world!} followed by a newline,
6064 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6066 We compile the program, and invoke the debugger on it:
6069 $ gcc -g charset-test.c -o charset-test
6070 $ gdb -nw charset-test
6071 GNU gdb 2001-12-19-cvs
6072 Copyright 2001 Free Software Foundation, Inc.
6077 We can use the @code{show charset} command to see what character sets
6078 @value{GDBN} is currently using to interpret and display characters and
6083 The current host and target character set is `iso-8859-1'.
6087 For the sake of printing this manual, let's use @sc{ascii} as our
6088 initial character set:
6090 (gdb) set charset ascii
6092 The current host and target character set is `ascii'.
6096 Let's assume that @sc{ascii} is indeed the correct character set for our
6097 host system --- in other words, let's assume that if @value{GDBN} prints
6098 characters using the @sc{ascii} character set, our terminal will display
6099 them properly. Since our current target character set is also
6100 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6103 (gdb) print ascii_hello
6104 $1 = 0x401698 "Hello, world!\n"
6105 (gdb) print ascii_hello[0]
6110 @value{GDBN} uses the target character set for character and string
6111 literals you use in expressions:
6119 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6122 @value{GDBN} relies on the user to tell it which character set the
6123 target program uses. If we print @code{ibm1047_hello} while our target
6124 character set is still @sc{ascii}, we get jibberish:
6127 (gdb) print ibm1047_hello
6128 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6129 (gdb) print ibm1047_hello[0]
6134 If we invoke the @code{set target-charset} command without an argument,
6135 @value{GDBN} tells us the character sets it supports:
6138 (gdb) set target-charset
6139 Valid character sets are:
6144 * - can be used as a host character set
6147 We can select @sc{ibm1047} as our target character set, and examine the
6148 program's strings again. Now the @sc{ascii} string is wrong, but
6149 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6150 target character set, @sc{ibm1047}, to the host character set,
6151 @sc{ascii}, and they display correctly:
6154 (gdb) set target-charset ibm1047
6156 The current host character set is `ascii'.
6157 The current target character set is `ibm1047'.
6158 (gdb) print ascii_hello
6159 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6160 (gdb) print ascii_hello[0]
6162 (gdb) print ibm1047_hello
6163 $8 = 0x4016a8 "Hello, world!\n"
6164 (gdb) print ibm1047_hello[0]
6169 As above, @value{GDBN} uses the target character set for character and
6170 string literals you use in expressions:
6178 The IBM1047 character set uses the number 78 to encode the @samp{+}
6183 @chapter C Preprocessor Macros
6185 Some languages, such as C and C++, provide a way to define and invoke
6186 ``preprocessor macros'' which expand into strings of tokens.
6187 @value{GDBN} can evaluate expressions containing macro invocations, show
6188 the result of macro expansion, and show a macro's definition, including
6189 where it was defined.
6191 You may need to compile your program specially to provide @value{GDBN}
6192 with information about preprocessor macros. Most compilers do not
6193 include macros in their debugging information, even when you compile
6194 with the @option{-g} flag. @xref{Compilation}.
6196 A program may define a macro at one point, remove that definition later,
6197 and then provide a different definition after that. Thus, at different
6198 points in the program, a macro may have different definitions, or have
6199 no definition at all. If there is a current stack frame, @value{GDBN}
6200 uses the macros in scope at that frame's source code line. Otherwise,
6201 @value{GDBN} uses the macros in scope at the current listing location;
6204 At the moment, @value{GDBN} does not support the @code{##}
6205 token-splicing operator, the @code{#} stringification operator, or
6206 variable-arity macros.
6208 Whenever @value{GDBN} evaluates an expression, it always expands any
6209 macro invocations present in the expression. @value{GDBN} also provides
6210 the following commands for working with macros explicitly.
6214 @kindex macro expand
6215 @cindex macro expansion, showing the results of preprocessor
6216 @cindex preprocessor macro expansion, showing the results of
6217 @cindex expanding preprocessor macros
6218 @item macro expand @var{expression}
6219 @itemx macro exp @var{expression}
6220 Show the results of expanding all preprocessor macro invocations in
6221 @var{expression}. Since @value{GDBN} simply expands macros, but does
6222 not parse the result, @var{expression} need not be a valid expression;
6223 it can be any string of tokens.
6225 @kindex macro expand-once
6226 @item macro expand-once @var{expression}
6227 @itemx macro exp1 @var{expression}
6228 @i{(This command is not yet implemented.)} Show the results of
6229 expanding those preprocessor macro invocations that appear explicitly in
6230 @var{expression}. Macro invocations appearing in that expansion are
6231 left unchanged. This command allows you to see the effect of a
6232 particular macro more clearly, without being confused by further
6233 expansions. Since @value{GDBN} simply expands macros, but does not
6234 parse the result, @var{expression} need not be a valid expression; it
6235 can be any string of tokens.
6238 @cindex macro definition, showing
6239 @cindex definition, showing a macro's
6240 @item info macro @var{macro}
6241 Show the definition of the macro named @var{macro}, and describe the
6242 source location where that definition was established.
6244 @kindex macro define
6245 @cindex user-defined macros
6246 @cindex defining macros interactively
6247 @cindex macros, user-defined
6248 @item macro define @var{macro} @var{replacement-list}
6249 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6250 @i{(This command is not yet implemented.)} Introduce a definition for a
6251 preprocessor macro named @var{macro}, invocations of which are replaced
6252 by the tokens given in @var{replacement-list}. The first form of this
6253 command defines an ``object-like'' macro, which takes no arguments; the
6254 second form defines a ``function-like'' macro, which takes the arguments
6255 given in @var{arglist}.
6257 A definition introduced by this command is in scope in every expression
6258 evaluated in @value{GDBN}, until it is removed with the @command{macro
6259 undef} command, described below. The definition overrides all
6260 definitions for @var{macro} present in the program being debugged, as
6261 well as any previous user-supplied definition.
6264 @item macro undef @var{macro}
6265 @i{(This command is not yet implemented.)} Remove any user-supplied
6266 definition for the macro named @var{macro}. This command only affects
6267 definitions provided with the @command{macro define} command, described
6268 above; it cannot remove definitions present in the program being
6273 @cindex macros, example of debugging with
6274 Here is a transcript showing the above commands in action. First, we
6275 show our source files:
6283 #define ADD(x) (M + x)
6288 printf ("Hello, world!\n");
6290 printf ("We're so creative.\n");
6292 printf ("Goodbye, world!\n");
6299 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6300 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6301 compiler includes information about preprocessor macros in the debugging
6305 $ gcc -gdwarf-2 -g3 sample.c -o sample
6309 Now, we start @value{GDBN} on our sample program:
6313 GNU gdb 2002-05-06-cvs
6314 Copyright 2002 Free Software Foundation, Inc.
6315 GDB is free software, @dots{}
6319 We can expand macros and examine their definitions, even when the
6320 program is not running. @value{GDBN} uses the current listing position
6321 to decide which macro definitions are in scope:
6327 5 #define ADD(x) (M + x)
6332 10 printf ("Hello, world!\n");
6334 12 printf ("We're so creative.\n");
6335 (gdb) info macro ADD
6336 Defined at /home/jimb/gdb/macros/play/sample.c:5
6337 #define ADD(x) (M + x)
6339 Defined at /home/jimb/gdb/macros/play/sample.h:1
6340 included at /home/jimb/gdb/macros/play/sample.c:2
6342 (gdb) macro expand ADD(1)
6343 expands to: (42 + 1)
6344 (gdb) macro expand-once ADD(1)
6345 expands to: once (M + 1)
6349 In the example above, note that @command{macro expand-once} expands only
6350 the macro invocation explicit in the original text --- the invocation of
6351 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6352 which was introduced by @code{ADD}.
6354 Once the program is running, GDB uses the macro definitions in force at
6355 the source line of the current stack frame:
6359 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6361 Starting program: /home/jimb/gdb/macros/play/sample
6363 Breakpoint 1, main () at sample.c:10
6364 10 printf ("Hello, world!\n");
6368 At line 10, the definition of the macro @code{N} at line 9 is in force:
6372 Defined at /home/jimb/gdb/macros/play/sample.c:9
6374 (gdb) macro expand N Q M
6381 As we step over directives that remove @code{N}'s definition, and then
6382 give it a new definition, @value{GDBN} finds the definition (or lack
6383 thereof) in force at each point:
6388 12 printf ("We're so creative.\n");
6390 The symbol `N' has no definition as a C/C++ preprocessor macro
6391 at /home/jimb/gdb/macros/play/sample.c:12
6394 14 printf ("Goodbye, world!\n");
6396 Defined at /home/jimb/gdb/macros/play/sample.c:13
6398 (gdb) macro expand N Q M
6399 expands to: 1729 < 42
6407 @chapter Tracepoints
6408 @c This chapter is based on the documentation written by Michael
6409 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6412 In some applications, it is not feasible for the debugger to interrupt
6413 the program's execution long enough for the developer to learn
6414 anything helpful about its behavior. If the program's correctness
6415 depends on its real-time behavior, delays introduced by a debugger
6416 might cause the program to change its behavior drastically, or perhaps
6417 fail, even when the code itself is correct. It is useful to be able
6418 to observe the program's behavior without interrupting it.
6420 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6421 specify locations in the program, called @dfn{tracepoints}, and
6422 arbitrary expressions to evaluate when those tracepoints are reached.
6423 Later, using the @code{tfind} command, you can examine the values
6424 those expressions had when the program hit the tracepoints. The
6425 expressions may also denote objects in memory---structures or arrays,
6426 for example---whose values @value{GDBN} should record; while visiting
6427 a particular tracepoint, you may inspect those objects as if they were
6428 in memory at that moment. However, because @value{GDBN} records these
6429 values without interacting with you, it can do so quickly and
6430 unobtrusively, hopefully not disturbing the program's behavior.
6432 The tracepoint facility is currently available only for remote
6433 targets. @xref{Targets}. In addition, your remote target must know how
6434 to collect trace data. This functionality is implemented in the remote
6435 stub; however, none of the stubs distributed with @value{GDBN} support
6436 tracepoints as of this writing.
6438 This chapter describes the tracepoint commands and features.
6442 * Analyze Collected Data::
6443 * Tracepoint Variables::
6446 @node Set Tracepoints
6447 @section Commands to Set Tracepoints
6449 Before running such a @dfn{trace experiment}, an arbitrary number of
6450 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6451 tracepoint has a number assigned to it by @value{GDBN}. Like with
6452 breakpoints, tracepoint numbers are successive integers starting from
6453 one. Many of the commands associated with tracepoints take the
6454 tracepoint number as their argument, to identify which tracepoint to
6457 For each tracepoint, you can specify, in advance, some arbitrary set
6458 of data that you want the target to collect in the trace buffer when
6459 it hits that tracepoint. The collected data can include registers,
6460 local variables, or global data. Later, you can use @value{GDBN}
6461 commands to examine the values these data had at the time the
6464 This section describes commands to set tracepoints and associated
6465 conditions and actions.
6468 * Create and Delete Tracepoints::
6469 * Enable and Disable Tracepoints::
6470 * Tracepoint Passcounts::
6471 * Tracepoint Actions::
6472 * Listing Tracepoints::
6473 * Starting and Stopping Trace Experiment::
6476 @node Create and Delete Tracepoints
6477 @subsection Create and Delete Tracepoints
6480 @cindex set tracepoint
6483 The @code{trace} command is very similar to the @code{break} command.
6484 Its argument can be a source line, a function name, or an address in
6485 the target program. @xref{Set Breaks}. The @code{trace} command
6486 defines a tracepoint, which is a point in the target program where the
6487 debugger will briefly stop, collect some data, and then allow the
6488 program to continue. Setting a tracepoint or changing its commands
6489 doesn't take effect until the next @code{tstart} command; thus, you
6490 cannot change the tracepoint attributes once a trace experiment is
6493 Here are some examples of using the @code{trace} command:
6496 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6498 (@value{GDBP}) @b{trace +2} // 2 lines forward
6500 (@value{GDBP}) @b{trace my_function} // first source line of function
6502 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6504 (@value{GDBP}) @b{trace *0x2117c4} // an address
6508 You can abbreviate @code{trace} as @code{tr}.
6511 @cindex last tracepoint number
6512 @cindex recent tracepoint number
6513 @cindex tracepoint number
6514 The convenience variable @code{$tpnum} records the tracepoint number
6515 of the most recently set tracepoint.
6517 @kindex delete tracepoint
6518 @cindex tracepoint deletion
6519 @item delete tracepoint @r{[}@var{num}@r{]}
6520 Permanently delete one or more tracepoints. With no argument, the
6521 default is to delete all tracepoints.
6526 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6528 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6532 You can abbreviate this command as @code{del tr}.
6535 @node Enable and Disable Tracepoints
6536 @subsection Enable and Disable Tracepoints
6539 @kindex disable tracepoint
6540 @item disable tracepoint @r{[}@var{num}@r{]}
6541 Disable tracepoint @var{num}, or all tracepoints if no argument
6542 @var{num} is given. A disabled tracepoint will have no effect during
6543 the next trace experiment, but it is not forgotten. You can re-enable
6544 a disabled tracepoint using the @code{enable tracepoint} command.
6546 @kindex enable tracepoint
6547 @item enable tracepoint @r{[}@var{num}@r{]}
6548 Enable tracepoint @var{num}, or all tracepoints. The enabled
6549 tracepoints will become effective the next time a trace experiment is
6553 @node Tracepoint Passcounts
6554 @subsection Tracepoint Passcounts
6558 @cindex tracepoint pass count
6559 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6560 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6561 automatically stop a trace experiment. If a tracepoint's passcount is
6562 @var{n}, then the trace experiment will be automatically stopped on
6563 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6564 @var{num} is not specified, the @code{passcount} command sets the
6565 passcount of the most recently defined tracepoint. If no passcount is
6566 given, the trace experiment will run until stopped explicitly by the
6572 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6573 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6575 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6576 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6577 (@value{GDBP}) @b{trace foo}
6578 (@value{GDBP}) @b{pass 3}
6579 (@value{GDBP}) @b{trace bar}
6580 (@value{GDBP}) @b{pass 2}
6581 (@value{GDBP}) @b{trace baz}
6582 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6583 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6584 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6585 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6589 @node Tracepoint Actions
6590 @subsection Tracepoint Action Lists
6594 @cindex tracepoint actions
6595 @item actions @r{[}@var{num}@r{]}
6596 This command will prompt for a list of actions to be taken when the
6597 tracepoint is hit. If the tracepoint number @var{num} is not
6598 specified, this command sets the actions for the one that was most
6599 recently defined (so that you can define a tracepoint and then say
6600 @code{actions} without bothering about its number). You specify the
6601 actions themselves on the following lines, one action at a time, and
6602 terminate the actions list with a line containing just @code{end}. So
6603 far, the only defined actions are @code{collect} and
6604 @code{while-stepping}.
6606 @cindex remove actions from a tracepoint
6607 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6608 and follow it immediately with @samp{end}.
6611 (@value{GDBP}) @b{collect @var{data}} // collect some data
6613 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6615 (@value{GDBP}) @b{end} // signals the end of actions.
6618 In the following example, the action list begins with @code{collect}
6619 commands indicating the things to be collected when the tracepoint is
6620 hit. Then, in order to single-step and collect additional data
6621 following the tracepoint, a @code{while-stepping} command is used,
6622 followed by the list of things to be collected while stepping. The
6623 @code{while-stepping} command is terminated by its own separate
6624 @code{end} command. Lastly, the action list is terminated by an
6628 (@value{GDBP}) @b{trace foo}
6629 (@value{GDBP}) @b{actions}
6630 Enter actions for tracepoint 1, one per line:
6639 @kindex collect @r{(tracepoints)}
6640 @item collect @var{expr1}, @var{expr2}, @dots{}
6641 Collect values of the given expressions when the tracepoint is hit.
6642 This command accepts a comma-separated list of any valid expressions.
6643 In addition to global, static, or local variables, the following
6644 special arguments are supported:
6648 collect all registers
6651 collect all function arguments
6654 collect all local variables.
6657 You can give several consecutive @code{collect} commands, each one
6658 with a single argument, or one @code{collect} command with several
6659 arguments separated by commas: the effect is the same.
6661 The command @code{info scope} (@pxref{Symbols, info scope}) is
6662 particularly useful for figuring out what data to collect.
6664 @kindex while-stepping @r{(tracepoints)}
6665 @item while-stepping @var{n}
6666 Perform @var{n} single-step traces after the tracepoint, collecting
6667 new data at each step. The @code{while-stepping} command is
6668 followed by the list of what to collect while stepping (followed by
6669 its own @code{end} command):
6673 > collect $regs, myglobal
6679 You may abbreviate @code{while-stepping} as @code{ws} or
6683 @node Listing Tracepoints
6684 @subsection Listing Tracepoints
6687 @kindex info tracepoints
6688 @cindex information about tracepoints
6689 @item info tracepoints @r{[}@var{num}@r{]}
6690 Display information about the tracepoint @var{num}. If you don't specify
6691 a tracepoint number, displays information about all the tracepoints
6692 defined so far. For each tracepoint, the following information is
6699 whether it is enabled or disabled
6703 its passcount as given by the @code{passcount @var{n}} command
6705 its step count as given by the @code{while-stepping @var{n}} command
6707 where in the source files is the tracepoint set
6709 its action list as given by the @code{actions} command
6713 (@value{GDBP}) @b{info trace}
6714 Num Enb Address PassC StepC What
6715 1 y 0x002117c4 0 0 <gdb_asm>
6716 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6717 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6722 This command can be abbreviated @code{info tp}.
6725 @node Starting and Stopping Trace Experiment
6726 @subsection Starting and Stopping Trace Experiment
6730 @cindex start a new trace experiment
6731 @cindex collected data discarded
6733 This command takes no arguments. It starts the trace experiment, and
6734 begins collecting data. This has the side effect of discarding all
6735 the data collected in the trace buffer during the previous trace
6739 @cindex stop a running trace experiment
6741 This command takes no arguments. It ends the trace experiment, and
6742 stops collecting data.
6744 @strong{Note:} a trace experiment and data collection may stop
6745 automatically if any tracepoint's passcount is reached
6746 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6749 @cindex status of trace data collection
6750 @cindex trace experiment, status of
6752 This command displays the status of the current trace data
6756 Here is an example of the commands we described so far:
6759 (@value{GDBP}) @b{trace gdb_c_test}
6760 (@value{GDBP}) @b{actions}
6761 Enter actions for tracepoint #1, one per line.
6762 > collect $regs,$locals,$args
6767 (@value{GDBP}) @b{tstart}
6768 [time passes @dots{}]
6769 (@value{GDBP}) @b{tstop}
6773 @node Analyze Collected Data
6774 @section Using the collected data
6776 After the tracepoint experiment ends, you use @value{GDBN} commands
6777 for examining the trace data. The basic idea is that each tracepoint
6778 collects a trace @dfn{snapshot} every time it is hit and another
6779 snapshot every time it single-steps. All these snapshots are
6780 consecutively numbered from zero and go into a buffer, and you can
6781 examine them later. The way you examine them is to @dfn{focus} on a
6782 specific trace snapshot. When the remote stub is focused on a trace
6783 snapshot, it will respond to all @value{GDBN} requests for memory and
6784 registers by reading from the buffer which belongs to that snapshot,
6785 rather than from @emph{real} memory or registers of the program being
6786 debugged. This means that @strong{all} @value{GDBN} commands
6787 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
6788 behave as if we were currently debugging the program state as it was
6789 when the tracepoint occurred. Any requests for data that are not in
6790 the buffer will fail.
6793 * tfind:: How to select a trace snapshot
6794 * tdump:: How to display all data for a snapshot
6795 * save-tracepoints:: How to save tracepoints for a future run
6799 @subsection @code{tfind @var{n}}
6802 @cindex select trace snapshot
6803 @cindex find trace snapshot
6804 The basic command for selecting a trace snapshot from the buffer is
6805 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
6806 counting from zero. If no argument @var{n} is given, the next
6807 snapshot is selected.
6809 Here are the various forms of using the @code{tfind} command.
6813 Find the first snapshot in the buffer. This is a synonym for
6814 @code{tfind 0} (since 0 is the number of the first snapshot).
6817 Stop debugging trace snapshots, resume @emph{live} debugging.
6820 Same as @samp{tfind none}.
6823 No argument means find the next trace snapshot.
6826 Find the previous trace snapshot before the current one. This permits
6827 retracing earlier steps.
6829 @item tfind tracepoint @var{num}
6830 Find the next snapshot associated with tracepoint @var{num}. Search
6831 proceeds forward from the last examined trace snapshot. If no
6832 argument @var{num} is given, it means find the next snapshot collected
6833 for the same tracepoint as the current snapshot.
6835 @item tfind pc @var{addr}
6836 Find the next snapshot associated with the value @var{addr} of the
6837 program counter. Search proceeds forward from the last examined trace
6838 snapshot. If no argument @var{addr} is given, it means find the next
6839 snapshot with the same value of PC as the current snapshot.
6841 @item tfind outside @var{addr1}, @var{addr2}
6842 Find the next snapshot whose PC is outside the given range of
6845 @item tfind range @var{addr1}, @var{addr2}
6846 Find the next snapshot whose PC is between @var{addr1} and
6847 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
6849 @item tfind line @r{[}@var{file}:@r{]}@var{n}
6850 Find the next snapshot associated with the source line @var{n}. If
6851 the optional argument @var{file} is given, refer to line @var{n} in
6852 that source file. Search proceeds forward from the last examined
6853 trace snapshot. If no argument @var{n} is given, it means find the
6854 next line other than the one currently being examined; thus saying
6855 @code{tfind line} repeatedly can appear to have the same effect as
6856 stepping from line to line in a @emph{live} debugging session.
6859 The default arguments for the @code{tfind} commands are specifically
6860 designed to make it easy to scan through the trace buffer. For
6861 instance, @code{tfind} with no argument selects the next trace
6862 snapshot, and @code{tfind -} with no argument selects the previous
6863 trace snapshot. So, by giving one @code{tfind} command, and then
6864 simply hitting @key{RET} repeatedly you can examine all the trace
6865 snapshots in order. Or, by saying @code{tfind -} and then hitting
6866 @key{RET} repeatedly you can examine the snapshots in reverse order.
6867 The @code{tfind line} command with no argument selects the snapshot
6868 for the next source line executed. The @code{tfind pc} command with
6869 no argument selects the next snapshot with the same program counter
6870 (PC) as the current frame. The @code{tfind tracepoint} command with
6871 no argument selects the next trace snapshot collected by the same
6872 tracepoint as the current one.
6874 In addition to letting you scan through the trace buffer manually,
6875 these commands make it easy to construct @value{GDBN} scripts that
6876 scan through the trace buffer and print out whatever collected data
6877 you are interested in. Thus, if we want to examine the PC, FP, and SP
6878 registers from each trace frame in the buffer, we can say this:
6881 (@value{GDBP}) @b{tfind start}
6882 (@value{GDBP}) @b{while ($trace_frame != -1)}
6883 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
6884 $trace_frame, $pc, $sp, $fp
6888 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
6889 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
6890 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
6891 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
6892 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
6893 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
6894 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
6895 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
6896 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
6897 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
6898 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
6901 Or, if we want to examine the variable @code{X} at each source line in
6905 (@value{GDBP}) @b{tfind start}
6906 (@value{GDBP}) @b{while ($trace_frame != -1)}
6907 > printf "Frame %d, X == %d\n", $trace_frame, X
6917 @subsection @code{tdump}
6919 @cindex dump all data collected at tracepoint
6920 @cindex tracepoint data, display
6922 This command takes no arguments. It prints all the data collected at
6923 the current trace snapshot.
6926 (@value{GDBP}) @b{trace 444}
6927 (@value{GDBP}) @b{actions}
6928 Enter actions for tracepoint #2, one per line:
6929 > collect $regs, $locals, $args, gdb_long_test
6932 (@value{GDBP}) @b{tstart}
6934 (@value{GDBP}) @b{tfind line 444}
6935 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
6937 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
6939 (@value{GDBP}) @b{tdump}
6940 Data collected at tracepoint 2, trace frame 1:
6941 d0 0xc4aa0085 -995491707
6945 d4 0x71aea3d 119204413
6950 a1 0x3000668 50333288
6953 a4 0x3000698 50333336
6955 fp 0x30bf3c 0x30bf3c
6956 sp 0x30bf34 0x30bf34
6958 pc 0x20b2c8 0x20b2c8
6962 p = 0x20e5b4 "gdb-test"
6969 gdb_long_test = 17 '\021'
6974 @node save-tracepoints
6975 @subsection @code{save-tracepoints @var{filename}}
6976 @kindex save-tracepoints
6977 @cindex save tracepoints for future sessions
6979 This command saves all current tracepoint definitions together with
6980 their actions and passcounts, into a file @file{@var{filename}}
6981 suitable for use in a later debugging session. To read the saved
6982 tracepoint definitions, use the @code{source} command (@pxref{Command
6985 @node Tracepoint Variables
6986 @section Convenience Variables for Tracepoints
6987 @cindex tracepoint variables
6988 @cindex convenience variables for tracepoints
6991 @vindex $trace_frame
6992 @item (int) $trace_frame
6993 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
6994 snapshot is selected.
6997 @item (int) $tracepoint
6998 The tracepoint for the current trace snapshot.
7001 @item (int) $trace_line
7002 The line number for the current trace snapshot.
7005 @item (char []) $trace_file
7006 The source file for the current trace snapshot.
7009 @item (char []) $trace_func
7010 The name of the function containing @code{$tracepoint}.
7013 Note: @code{$trace_file} is not suitable for use in @code{printf},
7014 use @code{output} instead.
7016 Here's a simple example of using these convenience variables for
7017 stepping through all the trace snapshots and printing some of their
7021 (@value{GDBP}) @b{tfind start}
7023 (@value{GDBP}) @b{while $trace_frame != -1}
7024 > output $trace_file
7025 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7031 @chapter Debugging Programs That Use Overlays
7034 If your program is too large to fit completely in your target system's
7035 memory, you can sometimes use @dfn{overlays} to work around this
7036 problem. @value{GDBN} provides some support for debugging programs that
7040 * How Overlays Work:: A general explanation of overlays.
7041 * Overlay Commands:: Managing overlays in @value{GDBN}.
7042 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7043 mapped by asking the inferior.
7044 * Overlay Sample Program:: A sample program using overlays.
7047 @node How Overlays Work
7048 @section How Overlays Work
7049 @cindex mapped overlays
7050 @cindex unmapped overlays
7051 @cindex load address, overlay's
7052 @cindex mapped address
7053 @cindex overlay area
7055 Suppose you have a computer whose instruction address space is only 64
7056 kilobytes long, but which has much more memory which can be accessed by
7057 other means: special instructions, segment registers, or memory
7058 management hardware, for example. Suppose further that you want to
7059 adapt a program which is larger than 64 kilobytes to run on this system.
7061 One solution is to identify modules of your program which are relatively
7062 independent, and need not call each other directly; call these modules
7063 @dfn{overlays}. Separate the overlays from the main program, and place
7064 their machine code in the larger memory. Place your main program in
7065 instruction memory, but leave at least enough space there to hold the
7066 largest overlay as well.
7068 Now, to call a function located in an overlay, you must first copy that
7069 overlay's machine code from the large memory into the space set aside
7070 for it in the instruction memory, and then jump to its entry point
7073 @c NB: In the below the mapped area's size is greater or equal to the
7074 @c size of all overlays. This is intentional to remind the developer
7075 @c that overlays don't necessarily need to be the same size.
7079 Data Instruction Larger
7080 Address Space Address Space Address Space
7081 +-----------+ +-----------+ +-----------+
7083 +-----------+ +-----------+ +-----------+<-- overlay 1
7084 | program | | main | .----| overlay 1 | load address
7085 | variables | | program | | +-----------+
7086 | and heap | | | | | |
7087 +-----------+ | | | +-----------+<-- overlay 2
7088 | | +-----------+ | | | load address
7089 +-----------+ | | | .-| overlay 2 |
7091 mapped --->+-----------+ | | +-----------+
7093 | overlay | <-' | | |
7094 | area | <---' +-----------+<-- overlay 3
7095 | | <---. | | load address
7096 +-----------+ `--| overlay 3 |
7103 @anchor{A code overlay}A code overlay
7107 The diagram (@pxref{A code overlay}) shows a system with separate data
7108 and instruction address spaces. To map an overlay, the program copies
7109 its code from the larger address space to the instruction address space.
7110 Since the overlays shown here all use the same mapped address, only one
7111 may be mapped at a time. For a system with a single address space for
7112 data and instructions, the diagram would be similar, except that the
7113 program variables and heap would share an address space with the main
7114 program and the overlay area.
7116 An overlay loaded into instruction memory and ready for use is called a
7117 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7118 instruction memory. An overlay not present (or only partially present)
7119 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7120 is its address in the larger memory. The mapped address is also called
7121 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7122 called the @dfn{load memory address}, or @dfn{LMA}.
7124 Unfortunately, overlays are not a completely transparent way to adapt a
7125 program to limited instruction memory. They introduce a new set of
7126 global constraints you must keep in mind as you design your program:
7131 Before calling or returning to a function in an overlay, your program
7132 must make sure that overlay is actually mapped. Otherwise, the call or
7133 return will transfer control to the right address, but in the wrong
7134 overlay, and your program will probably crash.
7137 If the process of mapping an overlay is expensive on your system, you
7138 will need to choose your overlays carefully to minimize their effect on
7139 your program's performance.
7142 The executable file you load onto your system must contain each
7143 overlay's instructions, appearing at the overlay's load address, not its
7144 mapped address. However, each overlay's instructions must be relocated
7145 and its symbols defined as if the overlay were at its mapped address.
7146 You can use GNU linker scripts to specify different load and relocation
7147 addresses for pieces of your program; see @ref{Overlay Description,,,
7148 ld.info, Using ld: the GNU linker}.
7151 The procedure for loading executable files onto your system must be able
7152 to load their contents into the larger address space as well as the
7153 instruction and data spaces.
7157 The overlay system described above is rather simple, and could be
7158 improved in many ways:
7163 If your system has suitable bank switch registers or memory management
7164 hardware, you could use those facilities to make an overlay's load area
7165 contents simply appear at their mapped address in instruction space.
7166 This would probably be faster than copying the overlay to its mapped
7167 area in the usual way.
7170 If your overlays are small enough, you could set aside more than one
7171 overlay area, and have more than one overlay mapped at a time.
7174 You can use overlays to manage data, as well as instructions. In
7175 general, data overlays are even less transparent to your design than
7176 code overlays: whereas code overlays only require care when you call or
7177 return to functions, data overlays require care every time you access
7178 the data. Also, if you change the contents of a data overlay, you
7179 must copy its contents back out to its load address before you can copy a
7180 different data overlay into the same mapped area.
7185 @node Overlay Commands
7186 @section Overlay Commands
7188 To use @value{GDBN}'s overlay support, each overlay in your program must
7189 correspond to a separate section of the executable file. The section's
7190 virtual memory address and load memory address must be the overlay's
7191 mapped and load addresses. Identifying overlays with sections allows
7192 @value{GDBN} to determine the appropriate address of a function or
7193 variable, depending on whether the overlay is mapped or not.
7195 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7196 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7201 Disable @value{GDBN}'s overlay support. When overlay support is
7202 disabled, @value{GDBN} assumes that all functions and variables are
7203 always present at their mapped addresses. By default, @value{GDBN}'s
7204 overlay support is disabled.
7206 @item overlay manual
7207 @kindex overlay manual
7208 @cindex manual overlay debugging
7209 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7210 relies on you to tell it which overlays are mapped, and which are not,
7211 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7212 commands described below.
7214 @item overlay map-overlay @var{overlay}
7215 @itemx overlay map @var{overlay}
7216 @kindex overlay map-overlay
7217 @cindex map an overlay
7218 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7219 be the name of the object file section containing the overlay. When an
7220 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7221 functions and variables at their mapped addresses. @value{GDBN} assumes
7222 that any other overlays whose mapped ranges overlap that of
7223 @var{overlay} are now unmapped.
7225 @item overlay unmap-overlay @var{overlay}
7226 @itemx overlay unmap @var{overlay}
7227 @kindex overlay unmap-overlay
7228 @cindex unmap an overlay
7229 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7230 must be the name of the object file section containing the overlay.
7231 When an overlay is unmapped, @value{GDBN} assumes it can find the
7232 overlay's functions and variables at their load addresses.
7235 @kindex overlay auto
7236 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7237 consults a data structure the overlay manager maintains in the inferior
7238 to see which overlays are mapped. For details, see @ref{Automatic
7241 @item overlay load-target
7243 @kindex overlay load-target
7244 @cindex reloading the overlay table
7245 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7246 re-reads the table @value{GDBN} automatically each time the inferior
7247 stops, so this command should only be necessary if you have changed the
7248 overlay mapping yourself using @value{GDBN}. This command is only
7249 useful when using automatic overlay debugging.
7251 @item overlay list-overlays
7253 @cindex listing mapped overlays
7254 Display a list of the overlays currently mapped, along with their mapped
7255 addresses, load addresses, and sizes.
7259 Normally, when @value{GDBN} prints a code address, it includes the name
7260 of the function the address falls in:
7264 $3 = @{int ()@} 0x11a0 <main>
7267 When overlay debugging is enabled, @value{GDBN} recognizes code in
7268 unmapped overlays, and prints the names of unmapped functions with
7269 asterisks around them. For example, if @code{foo} is a function in an
7270 unmapped overlay, @value{GDBN} prints it this way:
7274 No sections are mapped.
7276 $5 = @{int (int)@} 0x100000 <*foo*>
7279 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7284 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7285 mapped at 0x1016 - 0x104a
7287 $6 = @{int (int)@} 0x1016 <foo>
7290 When overlay debugging is enabled, @value{GDBN} can find the correct
7291 address for functions and variables in an overlay, whether or not the
7292 overlay is mapped. This allows most @value{GDBN} commands, like
7293 @code{break} and @code{disassemble}, to work normally, even on unmapped
7294 code. However, @value{GDBN}'s breakpoint support has some limitations:
7298 @cindex breakpoints in overlays
7299 @cindex overlays, setting breakpoints in
7300 You can set breakpoints in functions in unmapped overlays, as long as
7301 @value{GDBN} can write to the overlay at its load address.
7303 @value{GDBN} can not set hardware or simulator-based breakpoints in
7304 unmapped overlays. However, if you set a breakpoint at the end of your
7305 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7306 you are using manual overlay management), @value{GDBN} will re-set its
7307 breakpoints properly.
7311 @node Automatic Overlay Debugging
7312 @section Automatic Overlay Debugging
7313 @cindex automatic overlay debugging
7315 @value{GDBN} can automatically track which overlays are mapped and which
7316 are not, given some simple co-operation from the overlay manager in the
7317 inferior. If you enable automatic overlay debugging with the
7318 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7319 looks in the inferior's memory for certain variables describing the
7320 current state of the overlays.
7322 Here are the variables your overlay manager must define to support
7323 @value{GDBN}'s automatic overlay debugging:
7327 @item @code{_ovly_table}:
7328 This variable must be an array of the following structures:
7333 /* The overlay's mapped address. */
7336 /* The size of the overlay, in bytes. */
7339 /* The overlay's load address. */
7342 /* Non-zero if the overlay is currently mapped;
7344 unsigned long mapped;
7348 @item @code{_novlys}:
7349 This variable must be a four-byte signed integer, holding the total
7350 number of elements in @code{_ovly_table}.
7354 To decide whether a particular overlay is mapped or not, @value{GDBN}
7355 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7356 @code{lma} members equal the VMA and LMA of the overlay's section in the
7357 executable file. When @value{GDBN} finds a matching entry, it consults
7358 the entry's @code{mapped} member to determine whether the overlay is
7361 In addition, your overlay manager may define a function called
7362 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7363 will silently set a breakpoint there. If the overlay manager then
7364 calls this function whenever it has changed the overlay table, this
7365 will enable @value{GDBN} to accurately keep track of which overlays
7366 are in program memory, and update any breakpoints that may be set
7367 in overlays. This will allow breakpoints to work even if the
7368 overlays are kept in ROM or other non-writable memory while they
7369 are not being executed.
7371 @node Overlay Sample Program
7372 @section Overlay Sample Program
7373 @cindex overlay example program
7375 When linking a program which uses overlays, you must place the overlays
7376 at their load addresses, while relocating them to run at their mapped
7377 addresses. To do this, you must write a linker script (@pxref{Overlay
7378 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7379 since linker scripts are specific to a particular host system, target
7380 architecture, and target memory layout, this manual cannot provide
7381 portable sample code demonstrating @value{GDBN}'s overlay support.
7383 However, the @value{GDBN} source distribution does contain an overlaid
7384 program, with linker scripts for a few systems, as part of its test
7385 suite. The program consists of the following files from
7386 @file{gdb/testsuite/gdb.base}:
7390 The main program file.
7392 A simple overlay manager, used by @file{overlays.c}.
7397 Overlay modules, loaded and used by @file{overlays.c}.
7400 Linker scripts for linking the test program on the @code{d10v-elf}
7401 and @code{m32r-elf} targets.
7404 You can build the test program using the @code{d10v-elf} GCC
7405 cross-compiler like this:
7408 $ d10v-elf-gcc -g -c overlays.c
7409 $ d10v-elf-gcc -g -c ovlymgr.c
7410 $ d10v-elf-gcc -g -c foo.c
7411 $ d10v-elf-gcc -g -c bar.c
7412 $ d10v-elf-gcc -g -c baz.c
7413 $ d10v-elf-gcc -g -c grbx.c
7414 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7415 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7418 The build process is identical for any other architecture, except that
7419 you must substitute the appropriate compiler and linker script for the
7420 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7424 @chapter Using @value{GDBN} with Different Languages
7427 Although programming languages generally have common aspects, they are
7428 rarely expressed in the same manner. For instance, in ANSI C,
7429 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7430 Modula-2, it is accomplished by @code{p^}. Values can also be
7431 represented (and displayed) differently. Hex numbers in C appear as
7432 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7434 @cindex working language
7435 Language-specific information is built into @value{GDBN} for some languages,
7436 allowing you to express operations like the above in your program's
7437 native language, and allowing @value{GDBN} to output values in a manner
7438 consistent with the syntax of your program's native language. The
7439 language you use to build expressions is called the @dfn{working
7443 * Setting:: Switching between source languages
7444 * Show:: Displaying the language
7445 * Checks:: Type and range checks
7446 * Support:: Supported languages
7450 @section Switching between source languages
7452 There are two ways to control the working language---either have @value{GDBN}
7453 set it automatically, or select it manually yourself. You can use the
7454 @code{set language} command for either purpose. On startup, @value{GDBN}
7455 defaults to setting the language automatically. The working language is
7456 used to determine how expressions you type are interpreted, how values
7459 In addition to the working language, every source file that
7460 @value{GDBN} knows about has its own working language. For some object
7461 file formats, the compiler might indicate which language a particular
7462 source file is in. However, most of the time @value{GDBN} infers the
7463 language from the name of the file. The language of a source file
7464 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7465 show each frame appropriately for its own language. There is no way to
7466 set the language of a source file from within @value{GDBN}, but you can
7467 set the language associated with a filename extension. @xref{Show, ,
7468 Displaying the language}.
7470 This is most commonly a problem when you use a program, such
7471 as @code{cfront} or @code{f2c}, that generates C but is written in
7472 another language. In that case, make the
7473 program use @code{#line} directives in its C output; that way
7474 @value{GDBN} will know the correct language of the source code of the original
7475 program, and will display that source code, not the generated C code.
7478 * Filenames:: Filename extensions and languages.
7479 * Manually:: Setting the working language manually
7480 * Automatically:: Having @value{GDBN} infer the source language
7484 @subsection List of filename extensions and languages
7486 If a source file name ends in one of the following extensions, then
7487 @value{GDBN} infers that its language is the one indicated.
7507 Modula-2 source file
7511 Assembler source file. This actually behaves almost like C, but
7512 @value{GDBN} does not skip over function prologues when stepping.
7515 In addition, you may set the language associated with a filename
7516 extension. @xref{Show, , Displaying the language}.
7519 @subsection Setting the working language
7521 If you allow @value{GDBN} to set the language automatically,
7522 expressions are interpreted the same way in your debugging session and
7525 @kindex set language
7526 If you wish, you may set the language manually. To do this, issue the
7527 command @samp{set language @var{lang}}, where @var{lang} is the name of
7529 @code{c} or @code{modula-2}.
7530 For a list of the supported languages, type @samp{set language}.
7532 Setting the language manually prevents @value{GDBN} from updating the working
7533 language automatically. This can lead to confusion if you try
7534 to debug a program when the working language is not the same as the
7535 source language, when an expression is acceptable to both
7536 languages---but means different things. For instance, if the current
7537 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7545 might not have the effect you intended. In C, this means to add
7546 @code{b} and @code{c} and place the result in @code{a}. The result
7547 printed would be the value of @code{a}. In Modula-2, this means to compare
7548 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7551 @subsection Having @value{GDBN} infer the source language
7553 To have @value{GDBN} set the working language automatically, use
7554 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7555 then infers the working language. That is, when your program stops in a
7556 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7557 working language to the language recorded for the function in that
7558 frame. If the language for a frame is unknown (that is, if the function
7559 or block corresponding to the frame was defined in a source file that
7560 does not have a recognized extension), the current working language is
7561 not changed, and @value{GDBN} issues a warning.
7563 This may not seem necessary for most programs, which are written
7564 entirely in one source language. However, program modules and libraries
7565 written in one source language can be used by a main program written in
7566 a different source language. Using @samp{set language auto} in this
7567 case frees you from having to set the working language manually.
7570 @section Displaying the language
7572 The following commands help you find out which language is the
7573 working language, and also what language source files were written in.
7575 @kindex show language
7576 @kindex info frame@r{, show the source language}
7577 @kindex info source@r{, show the source language}
7580 Display the current working language. This is the
7581 language you can use with commands such as @code{print} to
7582 build and compute expressions that may involve variables in your program.
7585 Display the source language for this frame. This language becomes the
7586 working language if you use an identifier from this frame.
7587 @xref{Frame Info, ,Information about a frame}, to identify the other
7588 information listed here.
7591 Display the source language of this source file.
7592 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7593 information listed here.
7596 In unusual circumstances, you may have source files with extensions
7597 not in the standard list. You can then set the extension associated
7598 with a language explicitly:
7600 @kindex set extension-language
7601 @kindex info extensions
7603 @item set extension-language @var{.ext} @var{language}
7604 Set source files with extension @var{.ext} to be assumed to be in
7605 the source language @var{language}.
7607 @item info extensions
7608 List all the filename extensions and the associated languages.
7612 @section Type and range checking
7615 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7616 checking are included, but they do not yet have any effect. This
7617 section documents the intended facilities.
7619 @c FIXME remove warning when type/range code added
7621 Some languages are designed to guard you against making seemingly common
7622 errors through a series of compile- and run-time checks. These include
7623 checking the type of arguments to functions and operators, and making
7624 sure mathematical overflows are caught at run time. Checks such as
7625 these help to ensure a program's correctness once it has been compiled
7626 by eliminating type mismatches, and providing active checks for range
7627 errors when your program is running.
7629 @value{GDBN} can check for conditions like the above if you wish.
7630 Although @value{GDBN} does not check the statements in your program, it
7631 can check expressions entered directly into @value{GDBN} for evaluation via
7632 the @code{print} command, for example. As with the working language,
7633 @value{GDBN} can also decide whether or not to check automatically based on
7634 your program's source language. @xref{Support, ,Supported languages},
7635 for the default settings of supported languages.
7638 * Type Checking:: An overview of type checking
7639 * Range Checking:: An overview of range checking
7642 @cindex type checking
7643 @cindex checks, type
7645 @subsection An overview of type checking
7647 Some languages, such as Modula-2, are strongly typed, meaning that the
7648 arguments to operators and functions have to be of the correct type,
7649 otherwise an error occurs. These checks prevent type mismatch
7650 errors from ever causing any run-time problems. For example,
7658 The second example fails because the @code{CARDINAL} 1 is not
7659 type-compatible with the @code{REAL} 2.3.
7661 For the expressions you use in @value{GDBN} commands, you can tell the
7662 @value{GDBN} type checker to skip checking;
7663 to treat any mismatches as errors and abandon the expression;
7664 or to only issue warnings when type mismatches occur,
7665 but evaluate the expression anyway. When you choose the last of
7666 these, @value{GDBN} evaluates expressions like the second example above, but
7667 also issues a warning.
7669 Even if you turn type checking off, there may be other reasons
7670 related to type that prevent @value{GDBN} from evaluating an expression.
7671 For instance, @value{GDBN} does not know how to add an @code{int} and
7672 a @code{struct foo}. These particular type errors have nothing to do
7673 with the language in use, and usually arise from expressions, such as
7674 the one described above, which make little sense to evaluate anyway.
7676 Each language defines to what degree it is strict about type. For
7677 instance, both Modula-2 and C require the arguments to arithmetical
7678 operators to be numbers. In C, enumerated types and pointers can be
7679 represented as numbers, so that they are valid arguments to mathematical
7680 operators. @xref{Support, ,Supported languages}, for further
7681 details on specific languages.
7683 @value{GDBN} provides some additional commands for controlling the type checker:
7685 @kindex set check@r{, type}
7686 @kindex set check type
7687 @kindex show check type
7689 @item set check type auto
7690 Set type checking on or off based on the current working language.
7691 @xref{Support, ,Supported languages}, for the default settings for
7694 @item set check type on
7695 @itemx set check type off
7696 Set type checking on or off, overriding the default setting for the
7697 current working language. Issue a warning if the setting does not
7698 match the language default. If any type mismatches occur in
7699 evaluating an expression while type checking is on, @value{GDBN} prints a
7700 message and aborts evaluation of the expression.
7702 @item set check type warn
7703 Cause the type checker to issue warnings, but to always attempt to
7704 evaluate the expression. Evaluating the expression may still
7705 be impossible for other reasons. For example, @value{GDBN} cannot add
7706 numbers and structures.
7709 Show the current setting of the type checker, and whether or not @value{GDBN}
7710 is setting it automatically.
7713 @cindex range checking
7714 @cindex checks, range
7715 @node Range Checking
7716 @subsection An overview of range checking
7718 In some languages (such as Modula-2), it is an error to exceed the
7719 bounds of a type; this is enforced with run-time checks. Such range
7720 checking is meant to ensure program correctness by making sure
7721 computations do not overflow, or indices on an array element access do
7722 not exceed the bounds of the array.
7724 For expressions you use in @value{GDBN} commands, you can tell
7725 @value{GDBN} to treat range errors in one of three ways: ignore them,
7726 always treat them as errors and abandon the expression, or issue
7727 warnings but evaluate the expression anyway.
7729 A range error can result from numerical overflow, from exceeding an
7730 array index bound, or when you type a constant that is not a member
7731 of any type. Some languages, however, do not treat overflows as an
7732 error. In many implementations of C, mathematical overflow causes the
7733 result to ``wrap around'' to lower values---for example, if @var{m} is
7734 the largest integer value, and @var{s} is the smallest, then
7737 @var{m} + 1 @result{} @var{s}
7740 This, too, is specific to individual languages, and in some cases
7741 specific to individual compilers or machines. @xref{Support, ,
7742 Supported languages}, for further details on specific languages.
7744 @value{GDBN} provides some additional commands for controlling the range checker:
7746 @kindex set check@r{, range}
7747 @kindex set check range
7748 @kindex show check range
7750 @item set check range auto
7751 Set range checking on or off based on the current working language.
7752 @xref{Support, ,Supported languages}, for the default settings for
7755 @item set check range on
7756 @itemx set check range off
7757 Set range checking on or off, overriding the default setting for the
7758 current working language. A warning is issued if the setting does not
7759 match the language default. If a range error occurs and range checking is on,
7760 then a message is printed and evaluation of the expression is aborted.
7762 @item set check range warn
7763 Output messages when the @value{GDBN} range checker detects a range error,
7764 but attempt to evaluate the expression anyway. Evaluating the
7765 expression may still be impossible for other reasons, such as accessing
7766 memory that the process does not own (a typical example from many Unix
7770 Show the current setting of the range checker, and whether or not it is
7771 being set automatically by @value{GDBN}.
7775 @section Supported languages
7777 @value{GDBN} supports C, C@t{++}, Fortran, Java, assembly, and Modula-2.
7778 @c This is false ...
7779 Some @value{GDBN} features may be used in expressions regardless of the
7780 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
7781 and the @samp{@{type@}addr} construct (@pxref{Expressions,
7782 ,Expressions}) can be used with the constructs of any supported
7785 The following sections detail to what degree each source language is
7786 supported by @value{GDBN}. These sections are not meant to be language
7787 tutorials or references, but serve only as a reference guide to what the
7788 @value{GDBN} expression parser accepts, and what input and output
7789 formats should look like for different languages. There are many good
7790 books written on each of these languages; please look to these for a
7791 language reference or tutorial.
7795 * Modula-2:: Modula-2
7799 @subsection C and C@t{++}
7801 @cindex C and C@t{++}
7802 @cindex expressions in C or C@t{++}
7804 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
7805 to both languages. Whenever this is the case, we discuss those languages
7809 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
7810 @cindex @sc{gnu} C@t{++}
7811 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
7812 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
7813 effectively, you must compile your C@t{++} programs with a supported
7814 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
7815 compiler (@code{aCC}).
7817 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
7818 format; if it doesn't work on your system, try the stabs+ debugging
7819 format. You can select those formats explicitly with the @code{g++}
7820 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
7821 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
7822 CC, gcc.info, Using @sc{gnu} CC}.
7825 * C Operators:: C and C@t{++} operators
7826 * C Constants:: C and C@t{++} constants
7827 * C plus plus expressions:: C@t{++} expressions
7828 * C Defaults:: Default settings for C and C@t{++}
7829 * C Checks:: C and C@t{++} type and range checks
7830 * Debugging C:: @value{GDBN} and C
7831 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
7835 @subsubsection C and C@t{++} operators
7837 @cindex C and C@t{++} operators
7839 Operators must be defined on values of specific types. For instance,
7840 @code{+} is defined on numbers, but not on structures. Operators are
7841 often defined on groups of types.
7843 For the purposes of C and C@t{++}, the following definitions hold:
7848 @emph{Integral types} include @code{int} with any of its storage-class
7849 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
7852 @emph{Floating-point types} include @code{float}, @code{double}, and
7853 @code{long double} (if supported by the target platform).
7856 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
7859 @emph{Scalar types} include all of the above.
7864 The following operators are supported. They are listed here
7865 in order of increasing precedence:
7869 The comma or sequencing operator. Expressions in a comma-separated list
7870 are evaluated from left to right, with the result of the entire
7871 expression being the last expression evaluated.
7874 Assignment. The value of an assignment expression is the value
7875 assigned. Defined on scalar types.
7878 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
7879 and translated to @w{@code{@var{a} = @var{a op b}}}.
7880 @w{@code{@var{op}=}} and @code{=} have the same precedence.
7881 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
7882 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
7885 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
7886 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
7890 Logical @sc{or}. Defined on integral types.
7893 Logical @sc{and}. Defined on integral types.
7896 Bitwise @sc{or}. Defined on integral types.
7899 Bitwise exclusive-@sc{or}. Defined on integral types.
7902 Bitwise @sc{and}. Defined on integral types.
7905 Equality and inequality. Defined on scalar types. The value of these
7906 expressions is 0 for false and non-zero for true.
7908 @item <@r{, }>@r{, }<=@r{, }>=
7909 Less than, greater than, less than or equal, greater than or equal.
7910 Defined on scalar types. The value of these expressions is 0 for false
7911 and non-zero for true.
7914 left shift, and right shift. Defined on integral types.
7917 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
7920 Addition and subtraction. Defined on integral types, floating-point types and
7923 @item *@r{, }/@r{, }%
7924 Multiplication, division, and modulus. Multiplication and division are
7925 defined on integral and floating-point types. Modulus is defined on
7929 Increment and decrement. When appearing before a variable, the
7930 operation is performed before the variable is used in an expression;
7931 when appearing after it, the variable's value is used before the
7932 operation takes place.
7935 Pointer dereferencing. Defined on pointer types. Same precedence as
7939 Address operator. Defined on variables. Same precedence as @code{++}.
7941 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
7942 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
7943 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
7944 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
7948 Negative. Defined on integral and floating-point types. Same
7949 precedence as @code{++}.
7952 Logical negation. Defined on integral types. Same precedence as
7956 Bitwise complement operator. Defined on integral types. Same precedence as
7961 Structure member, and pointer-to-structure member. For convenience,
7962 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
7963 pointer based on the stored type information.
7964 Defined on @code{struct} and @code{union} data.
7967 Dereferences of pointers to members.
7970 Array indexing. @code{@var{a}[@var{i}]} is defined as
7971 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
7974 Function parameter list. Same precedence as @code{->}.
7977 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
7978 and @code{class} types.
7981 Doubled colons also represent the @value{GDBN} scope operator
7982 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
7986 If an operator is redefined in the user code, @value{GDBN} usually
7987 attempts to invoke the redefined version instead of using the operator's
7995 @subsubsection C and C@t{++} constants
7997 @cindex C and C@t{++} constants
7999 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8004 Integer constants are a sequence of digits. Octal constants are
8005 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8006 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8007 @samp{l}, specifying that the constant should be treated as a
8011 Floating point constants are a sequence of digits, followed by a decimal
8012 point, followed by a sequence of digits, and optionally followed by an
8013 exponent. An exponent is of the form:
8014 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8015 sequence of digits. The @samp{+} is optional for positive exponents.
8016 A floating-point constant may also end with a letter @samp{f} or
8017 @samp{F}, specifying that the constant should be treated as being of
8018 the @code{float} (as opposed to the default @code{double}) type; or with
8019 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8023 Enumerated constants consist of enumerated identifiers, or their
8024 integral equivalents.
8027 Character constants are a single character surrounded by single quotes
8028 (@code{'}), or a number---the ordinal value of the corresponding character
8029 (usually its @sc{ascii} value). Within quotes, the single character may
8030 be represented by a letter or by @dfn{escape sequences}, which are of
8031 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8032 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8033 @samp{@var{x}} is a predefined special character---for example,
8034 @samp{\n} for newline.
8037 String constants are a sequence of character constants surrounded by
8038 double quotes (@code{"}). Any valid character constant (as described
8039 above) may appear. Double quotes within the string must be preceded by
8040 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8044 Pointer constants are an integral value. You can also write pointers
8045 to constants using the C operator @samp{&}.
8048 Array constants are comma-separated lists surrounded by braces @samp{@{}
8049 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8050 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8051 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8055 * C plus plus expressions::
8062 @node C plus plus expressions
8063 @subsubsection C@t{++} expressions
8065 @cindex expressions in C@t{++}
8066 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8068 @cindex debugging C@t{++} programs
8069 @cindex C@t{++} compilers
8070 @cindex debug formats and C@t{++}
8071 @cindex @value{NGCC} and C@t{++}
8073 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8074 proper compiler and the proper debug format. Currently, @value{GDBN}
8075 works best when debugging C@t{++} code that is compiled with
8076 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8077 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8078 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8079 stabs+ as their default debug format, so you usually don't need to
8080 specify a debug format explicitly. Other compilers and/or debug formats
8081 are likely to work badly or not at all when using @value{GDBN} to debug
8087 @cindex member functions
8089 Member function calls are allowed; you can use expressions like
8092 count = aml->GetOriginal(x, y)
8095 @vindex this@r{, inside C@t{++} member functions}
8096 @cindex namespace in C@t{++}
8098 While a member function is active (in the selected stack frame), your
8099 expressions have the same namespace available as the member function;
8100 that is, @value{GDBN} allows implicit references to the class instance
8101 pointer @code{this} following the same rules as C@t{++}.
8103 @cindex call overloaded functions
8104 @cindex overloaded functions, calling
8105 @cindex type conversions in C@t{++}
8107 You can call overloaded functions; @value{GDBN} resolves the function
8108 call to the right definition, with some restrictions. @value{GDBN} does not
8109 perform overload resolution involving user-defined type conversions,
8110 calls to constructors, or instantiations of templates that do not exist
8111 in the program. It also cannot handle ellipsis argument lists or
8114 It does perform integral conversions and promotions, floating-point
8115 promotions, arithmetic conversions, pointer conversions, conversions of
8116 class objects to base classes, and standard conversions such as those of
8117 functions or arrays to pointers; it requires an exact match on the
8118 number of function arguments.
8120 Overload resolution is always performed, unless you have specified
8121 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8122 ,@value{GDBN} features for C@t{++}}.
8124 You must specify @code{set overload-resolution off} in order to use an
8125 explicit function signature to call an overloaded function, as in
8127 p 'foo(char,int)'('x', 13)
8130 The @value{GDBN} command-completion facility can simplify this;
8131 see @ref{Completion, ,Command completion}.
8133 @cindex reference declarations
8135 @value{GDBN} understands variables declared as C@t{++} references; you can use
8136 them in expressions just as you do in C@t{++} source---they are automatically
8139 In the parameter list shown when @value{GDBN} displays a frame, the values of
8140 reference variables are not displayed (unlike other variables); this
8141 avoids clutter, since references are often used for large structures.
8142 The @emph{address} of a reference variable is always shown, unless
8143 you have specified @samp{set print address off}.
8146 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8147 expressions can use it just as expressions in your program do. Since
8148 one scope may be defined in another, you can use @code{::} repeatedly if
8149 necessary, for example in an expression like
8150 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8151 resolving name scope by reference to source files, in both C and C@t{++}
8152 debugging (@pxref{Variables, ,Program variables}).
8155 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8156 calling virtual functions correctly, printing out virtual bases of
8157 objects, calling functions in a base subobject, casting objects, and
8158 invoking user-defined operators.
8161 @subsubsection C and C@t{++} defaults
8163 @cindex C and C@t{++} defaults
8165 If you allow @value{GDBN} to set type and range checking automatically, they
8166 both default to @code{off} whenever the working language changes to
8167 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8168 selects the working language.
8170 If you allow @value{GDBN} to set the language automatically, it
8171 recognizes source files whose names end with @file{.c}, @file{.C}, or
8172 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8173 these files, it sets the working language to C or C@t{++}.
8174 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8175 for further details.
8177 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8178 @c unimplemented. If (b) changes, it might make sense to let this node
8179 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8182 @subsubsection C and C@t{++} type and range checks
8184 @cindex C and C@t{++} checks
8186 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8187 is not used. However, if you turn type checking on, @value{GDBN}
8188 considers two variables type equivalent if:
8192 The two variables are structured and have the same structure, union, or
8196 The two variables have the same type name, or types that have been
8197 declared equivalent through @code{typedef}.
8200 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8203 The two @code{struct}, @code{union}, or @code{enum} variables are
8204 declared in the same declaration. (Note: this may not be true for all C
8209 Range checking, if turned on, is done on mathematical operations. Array
8210 indices are not checked, since they are often used to index a pointer
8211 that is not itself an array.
8214 @subsubsection @value{GDBN} and C
8216 The @code{set print union} and @code{show print union} commands apply to
8217 the @code{union} type. When set to @samp{on}, any @code{union} that is
8218 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8219 appears as @samp{@{...@}}.
8221 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8222 with pointers and a memory allocation function. @xref{Expressions,
8226 * Debugging C plus plus::
8229 @node Debugging C plus plus
8230 @subsubsection @value{GDBN} features for C@t{++}
8232 @cindex commands for C@t{++}
8234 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8235 designed specifically for use with C@t{++}. Here is a summary:
8238 @cindex break in overloaded functions
8239 @item @r{breakpoint menus}
8240 When you want a breakpoint in a function whose name is overloaded,
8241 @value{GDBN} breakpoint menus help you specify which function definition
8242 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8244 @cindex overloading in C@t{++}
8245 @item rbreak @var{regex}
8246 Setting breakpoints using regular expressions is helpful for setting
8247 breakpoints on overloaded functions that are not members of any special
8249 @xref{Set Breaks, ,Setting breakpoints}.
8251 @cindex C@t{++} exception handling
8254 Debug C@t{++} exception handling using these commands. @xref{Set
8255 Catchpoints, , Setting catchpoints}.
8258 @item ptype @var{typename}
8259 Print inheritance relationships as well as other information for type
8261 @xref{Symbols, ,Examining the Symbol Table}.
8263 @cindex C@t{++} symbol display
8264 @item set print demangle
8265 @itemx show print demangle
8266 @itemx set print asm-demangle
8267 @itemx show print asm-demangle
8268 Control whether C@t{++} symbols display in their source form, both when
8269 displaying code as C@t{++} source and when displaying disassemblies.
8270 @xref{Print Settings, ,Print settings}.
8272 @item set print object
8273 @itemx show print object
8274 Choose whether to print derived (actual) or declared types of objects.
8275 @xref{Print Settings, ,Print settings}.
8277 @item set print vtbl
8278 @itemx show print vtbl
8279 Control the format for printing virtual function tables.
8280 @xref{Print Settings, ,Print settings}.
8281 (The @code{vtbl} commands do not work on programs compiled with the HP
8282 ANSI C@t{++} compiler (@code{aCC}).)
8284 @kindex set overload-resolution
8285 @cindex overloaded functions, overload resolution
8286 @item set overload-resolution on
8287 Enable overload resolution for C@t{++} expression evaluation. The default
8288 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8289 and searches for a function whose signature matches the argument types,
8290 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8291 expressions}, for details). If it cannot find a match, it emits a
8294 @item set overload-resolution off
8295 Disable overload resolution for C@t{++} expression evaluation. For
8296 overloaded functions that are not class member functions, @value{GDBN}
8297 chooses the first function of the specified name that it finds in the
8298 symbol table, whether or not its arguments are of the correct type. For
8299 overloaded functions that are class member functions, @value{GDBN}
8300 searches for a function whose signature @emph{exactly} matches the
8303 @item @r{Overloaded symbol names}
8304 You can specify a particular definition of an overloaded symbol, using
8305 the same notation that is used to declare such symbols in C@t{++}: type
8306 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8307 also use the @value{GDBN} command-line word completion facilities to list the
8308 available choices, or to finish the type list for you.
8309 @xref{Completion,, Command completion}, for details on how to do this.
8313 @subsection Modula-2
8315 @cindex Modula-2, @value{GDBN} support
8317 The extensions made to @value{GDBN} to support Modula-2 only support
8318 output from the @sc{gnu} Modula-2 compiler (which is currently being
8319 developed). Other Modula-2 compilers are not currently supported, and
8320 attempting to debug executables produced by them is most likely
8321 to give an error as @value{GDBN} reads in the executable's symbol
8324 @cindex expressions in Modula-2
8326 * M2 Operators:: Built-in operators
8327 * Built-In Func/Proc:: Built-in functions and procedures
8328 * M2 Constants:: Modula-2 constants
8329 * M2 Defaults:: Default settings for Modula-2
8330 * Deviations:: Deviations from standard Modula-2
8331 * M2 Checks:: Modula-2 type and range checks
8332 * M2 Scope:: The scope operators @code{::} and @code{.}
8333 * GDB/M2:: @value{GDBN} and Modula-2
8337 @subsubsection Operators
8338 @cindex Modula-2 operators
8340 Operators must be defined on values of specific types. For instance,
8341 @code{+} is defined on numbers, but not on structures. Operators are
8342 often defined on groups of types. For the purposes of Modula-2, the
8343 following definitions hold:
8348 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8352 @emph{Character types} consist of @code{CHAR} and its subranges.
8355 @emph{Floating-point types} consist of @code{REAL}.
8358 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8362 @emph{Scalar types} consist of all of the above.
8365 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8368 @emph{Boolean types} consist of @code{BOOLEAN}.
8372 The following operators are supported, and appear in order of
8373 increasing precedence:
8377 Function argument or array index separator.
8380 Assignment. The value of @var{var} @code{:=} @var{value} is
8384 Less than, greater than on integral, floating-point, or enumerated
8388 Less than or equal to, greater than or equal to
8389 on integral, floating-point and enumerated types, or set inclusion on
8390 set types. Same precedence as @code{<}.
8392 @item =@r{, }<>@r{, }#
8393 Equality and two ways of expressing inequality, valid on scalar types.
8394 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8395 available for inequality, since @code{#} conflicts with the script
8399 Set membership. Defined on set types and the types of their members.
8400 Same precedence as @code{<}.
8403 Boolean disjunction. Defined on boolean types.
8406 Boolean conjunction. Defined on boolean types.
8409 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8412 Addition and subtraction on integral and floating-point types, or union
8413 and difference on set types.
8416 Multiplication on integral and floating-point types, or set intersection
8420 Division on floating-point types, or symmetric set difference on set
8421 types. Same precedence as @code{*}.
8424 Integer division and remainder. Defined on integral types. Same
8425 precedence as @code{*}.
8428 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8431 Pointer dereferencing. Defined on pointer types.
8434 Boolean negation. Defined on boolean types. Same precedence as
8438 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8439 precedence as @code{^}.
8442 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8445 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8449 @value{GDBN} and Modula-2 scope operators.
8453 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8454 treats the use of the operator @code{IN}, or the use of operators
8455 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8456 @code{<=}, and @code{>=} on sets as an error.
8460 @node Built-In Func/Proc
8461 @subsubsection Built-in functions and procedures
8462 @cindex Modula-2 built-ins
8464 Modula-2 also makes available several built-in procedures and functions.
8465 In describing these, the following metavariables are used:
8470 represents an @code{ARRAY} variable.
8473 represents a @code{CHAR} constant or variable.
8476 represents a variable or constant of integral type.
8479 represents an identifier that belongs to a set. Generally used in the
8480 same function with the metavariable @var{s}. The type of @var{s} should
8481 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8484 represents a variable or constant of integral or floating-point type.
8487 represents a variable or constant of floating-point type.
8493 represents a variable.
8496 represents a variable or constant of one of many types. See the
8497 explanation of the function for details.
8500 All Modula-2 built-in procedures also return a result, described below.
8504 Returns the absolute value of @var{n}.
8507 If @var{c} is a lower case letter, it returns its upper case
8508 equivalent, otherwise it returns its argument.
8511 Returns the character whose ordinal value is @var{i}.
8514 Decrements the value in the variable @var{v} by one. Returns the new value.
8516 @item DEC(@var{v},@var{i})
8517 Decrements the value in the variable @var{v} by @var{i}. Returns the
8520 @item EXCL(@var{m},@var{s})
8521 Removes the element @var{m} from the set @var{s}. Returns the new
8524 @item FLOAT(@var{i})
8525 Returns the floating point equivalent of the integer @var{i}.
8528 Returns the index of the last member of @var{a}.
8531 Increments the value in the variable @var{v} by one. Returns the new value.
8533 @item INC(@var{v},@var{i})
8534 Increments the value in the variable @var{v} by @var{i}. Returns the
8537 @item INCL(@var{m},@var{s})
8538 Adds the element @var{m} to the set @var{s} if it is not already
8539 there. Returns the new set.
8542 Returns the maximum value of the type @var{t}.
8545 Returns the minimum value of the type @var{t}.
8548 Returns boolean TRUE if @var{i} is an odd number.
8551 Returns the ordinal value of its argument. For example, the ordinal
8552 value of a character is its @sc{ascii} value (on machines supporting the
8553 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8554 integral, character and enumerated types.
8557 Returns the size of its argument. @var{x} can be a variable or a type.
8559 @item TRUNC(@var{r})
8560 Returns the integral part of @var{r}.
8562 @item VAL(@var{t},@var{i})
8563 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8567 @emph{Warning:} Sets and their operations are not yet supported, so
8568 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8572 @cindex Modula-2 constants
8574 @subsubsection Constants
8576 @value{GDBN} allows you to express the constants of Modula-2 in the following
8582 Integer constants are simply a sequence of digits. When used in an
8583 expression, a constant is interpreted to be type-compatible with the
8584 rest of the expression. Hexadecimal integers are specified by a
8585 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8588 Floating point constants appear as a sequence of digits, followed by a
8589 decimal point and another sequence of digits. An optional exponent can
8590 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8591 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8592 digits of the floating point constant must be valid decimal (base 10)
8596 Character constants consist of a single character enclosed by a pair of
8597 like quotes, either single (@code{'}) or double (@code{"}). They may
8598 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8599 followed by a @samp{C}.
8602 String constants consist of a sequence of characters enclosed by a
8603 pair of like quotes, either single (@code{'}) or double (@code{"}).
8604 Escape sequences in the style of C are also allowed. @xref{C
8605 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8609 Enumerated constants consist of an enumerated identifier.
8612 Boolean constants consist of the identifiers @code{TRUE} and
8616 Pointer constants consist of integral values only.
8619 Set constants are not yet supported.
8623 @subsubsection Modula-2 defaults
8624 @cindex Modula-2 defaults
8626 If type and range checking are set automatically by @value{GDBN}, they
8627 both default to @code{on} whenever the working language changes to
8628 Modula-2. This happens regardless of whether you or @value{GDBN}
8629 selected the working language.
8631 If you allow @value{GDBN} to set the language automatically, then entering
8632 code compiled from a file whose name ends with @file{.mod} sets the
8633 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
8634 the language automatically}, for further details.
8637 @subsubsection Deviations from standard Modula-2
8638 @cindex Modula-2, deviations from
8640 A few changes have been made to make Modula-2 programs easier to debug.
8641 This is done primarily via loosening its type strictness:
8645 Unlike in standard Modula-2, pointer constants can be formed by
8646 integers. This allows you to modify pointer variables during
8647 debugging. (In standard Modula-2, the actual address contained in a
8648 pointer variable is hidden from you; it can only be modified
8649 through direct assignment to another pointer variable or expression that
8650 returned a pointer.)
8653 C escape sequences can be used in strings and characters to represent
8654 non-printable characters. @value{GDBN} prints out strings with these
8655 escape sequences embedded. Single non-printable characters are
8656 printed using the @samp{CHR(@var{nnn})} format.
8659 The assignment operator (@code{:=}) returns the value of its right-hand
8663 All built-in procedures both modify @emph{and} return their argument.
8667 @subsubsection Modula-2 type and range checks
8668 @cindex Modula-2 checks
8671 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
8674 @c FIXME remove warning when type/range checks added
8676 @value{GDBN} considers two Modula-2 variables type equivalent if:
8680 They are of types that have been declared equivalent via a @code{TYPE
8681 @var{t1} = @var{t2}} statement
8684 They have been declared on the same line. (Note: This is true of the
8685 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
8688 As long as type checking is enabled, any attempt to combine variables
8689 whose types are not equivalent is an error.
8691 Range checking is done on all mathematical operations, assignment, array
8692 index bounds, and all built-in functions and procedures.
8695 @subsubsection The scope operators @code{::} and @code{.}
8697 @cindex @code{.}, Modula-2 scope operator
8698 @cindex colon, doubled as scope operator
8700 @vindex colon-colon@r{, in Modula-2}
8701 @c Info cannot handle :: but TeX can.
8704 @vindex ::@r{, in Modula-2}
8707 There are a few subtle differences between the Modula-2 scope operator
8708 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
8713 @var{module} . @var{id}
8714 @var{scope} :: @var{id}
8718 where @var{scope} is the name of a module or a procedure,
8719 @var{module} the name of a module, and @var{id} is any declared
8720 identifier within your program, except another module.
8722 Using the @code{::} operator makes @value{GDBN} search the scope
8723 specified by @var{scope} for the identifier @var{id}. If it is not
8724 found in the specified scope, then @value{GDBN} searches all scopes
8725 enclosing the one specified by @var{scope}.
8727 Using the @code{.} operator makes @value{GDBN} search the current scope for
8728 the identifier specified by @var{id} that was imported from the
8729 definition module specified by @var{module}. With this operator, it is
8730 an error if the identifier @var{id} was not imported from definition
8731 module @var{module}, or if @var{id} is not an identifier in
8735 @subsubsection @value{GDBN} and Modula-2
8737 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
8738 Five subcommands of @code{set print} and @code{show print} apply
8739 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
8740 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
8741 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
8742 analogue in Modula-2.
8744 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
8745 with any language, is not useful with Modula-2. Its
8746 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
8747 created in Modula-2 as they can in C or C@t{++}. However, because an
8748 address can be specified by an integral constant, the construct
8749 @samp{@{@var{type}@}@var{adrexp}} is still useful.
8751 @cindex @code{#} in Modula-2
8752 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
8753 interpreted as the beginning of a comment. Use @code{<>} instead.
8756 @chapter Examining the Symbol Table
8758 The commands described in this chapter allow you to inquire about the
8759 symbols (names of variables, functions and types) defined in your
8760 program. This information is inherent in the text of your program and
8761 does not change as your program executes. @value{GDBN} finds it in your
8762 program's symbol table, in the file indicated when you started @value{GDBN}
8763 (@pxref{File Options, ,Choosing files}), or by one of the
8764 file-management commands (@pxref{Files, ,Commands to specify files}).
8766 @cindex symbol names
8767 @cindex names of symbols
8768 @cindex quoting names
8769 Occasionally, you may need to refer to symbols that contain unusual
8770 characters, which @value{GDBN} ordinarily treats as word delimiters. The
8771 most frequent case is in referring to static variables in other
8772 source files (@pxref{Variables,,Program variables}). File names
8773 are recorded in object files as debugging symbols, but @value{GDBN} would
8774 ordinarily parse a typical file name, like @file{foo.c}, as the three words
8775 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
8776 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
8783 looks up the value of @code{x} in the scope of the file @file{foo.c}.
8786 @kindex info address
8787 @cindex address of a symbol
8788 @item info address @var{symbol}
8789 Describe where the data for @var{symbol} is stored. For a register
8790 variable, this says which register it is kept in. For a non-register
8791 local variable, this prints the stack-frame offset at which the variable
8794 Note the contrast with @samp{print &@var{symbol}}, which does not work
8795 at all for a register variable, and for a stack local variable prints
8796 the exact address of the current instantiation of the variable.
8799 @cindex symbol from address
8800 @item info symbol @var{addr}
8801 Print the name of a symbol which is stored at the address @var{addr}.
8802 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
8803 nearest symbol and an offset from it:
8806 (@value{GDBP}) info symbol 0x54320
8807 _initialize_vx + 396 in section .text
8811 This is the opposite of the @code{info address} command. You can use
8812 it to find out the name of a variable or a function given its address.
8815 @item whatis @var{expr}
8816 Print the data type of expression @var{expr}. @var{expr} is not
8817 actually evaluated, and any side-effecting operations (such as
8818 assignments or function calls) inside it do not take place.
8819 @xref{Expressions, ,Expressions}.
8822 Print the data type of @code{$}, the last value in the value history.
8825 @item ptype @var{typename}
8826 Print a description of data type @var{typename}. @var{typename} may be
8827 the name of a type, or for C code it may have the form @samp{class
8828 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
8829 @var{union-tag}} or @samp{enum @var{enum-tag}}.
8831 @item ptype @var{expr}
8833 Print a description of the type of expression @var{expr}. @code{ptype}
8834 differs from @code{whatis} by printing a detailed description, instead
8835 of just the name of the type.
8837 For example, for this variable declaration:
8840 struct complex @{double real; double imag;@} v;
8844 the two commands give this output:
8848 (@value{GDBP}) whatis v
8849 type = struct complex
8850 (@value{GDBP}) ptype v
8851 type = struct complex @{
8859 As with @code{whatis}, using @code{ptype} without an argument refers to
8860 the type of @code{$}, the last value in the value history.
8863 @item info types @var{regexp}
8865 Print a brief description of all types whose names match @var{regexp}
8866 (or all types in your program, if you supply no argument). Each
8867 complete typename is matched as though it were a complete line; thus,
8868 @samp{i type value} gives information on all types in your program whose
8869 names include the string @code{value}, but @samp{i type ^value$} gives
8870 information only on types whose complete name is @code{value}.
8872 This command differs from @code{ptype} in two ways: first, like
8873 @code{whatis}, it does not print a detailed description; second, it
8874 lists all source files where a type is defined.
8877 @cindex local variables
8878 @item info scope @var{addr}
8879 List all the variables local to a particular scope. This command
8880 accepts a location---a function name, a source line, or an address
8881 preceded by a @samp{*}, and prints all the variables local to the
8882 scope defined by that location. For example:
8885 (@value{GDBP}) @b{info scope command_line_handler}
8886 Scope for command_line_handler:
8887 Symbol rl is an argument at stack/frame offset 8, length 4.
8888 Symbol linebuffer is in static storage at address 0x150a18, length 4.
8889 Symbol linelength is in static storage at address 0x150a1c, length 4.
8890 Symbol p is a local variable in register $esi, length 4.
8891 Symbol p1 is a local variable in register $ebx, length 4.
8892 Symbol nline is a local variable in register $edx, length 4.
8893 Symbol repeat is a local variable at frame offset -8, length 4.
8897 This command is especially useful for determining what data to collect
8898 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
8903 Show information about the current source file---that is, the source file for
8904 the function containing the current point of execution:
8907 the name of the source file, and the directory containing it,
8909 the directory it was compiled in,
8911 its length, in lines,
8913 which programming language it is written in,
8915 whether the executable includes debugging information for that file, and
8916 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
8918 whether the debugging information includes information about
8919 preprocessor macros.
8923 @kindex info sources
8925 Print the names of all source files in your program for which there is
8926 debugging information, organized into two lists: files whose symbols
8927 have already been read, and files whose symbols will be read when needed.
8929 @kindex info functions
8930 @item info functions
8931 Print the names and data types of all defined functions.
8933 @item info functions @var{regexp}
8934 Print the names and data types of all defined functions
8935 whose names contain a match for regular expression @var{regexp}.
8936 Thus, @samp{info fun step} finds all functions whose names
8937 include @code{step}; @samp{info fun ^step} finds those whose names
8938 start with @code{step}. If a function name contains characters
8939 that conflict with the regular expression language (eg.
8940 @samp{operator*()}), they may be quoted with a backslash.
8942 @kindex info variables
8943 @item info variables
8944 Print the names and data types of all variables that are declared
8945 outside of functions (i.e.@: excluding local variables).
8947 @item info variables @var{regexp}
8948 Print the names and data types of all variables (except for local
8949 variables) whose names contain a match for regular expression
8953 This was never implemented.
8954 @kindex info methods
8956 @itemx info methods @var{regexp}
8957 The @code{info methods} command permits the user to examine all defined
8958 methods within C@t{++} program, or (with the @var{regexp} argument) a
8959 specific set of methods found in the various C@t{++} classes. Many
8960 C@t{++} classes provide a large number of methods. Thus, the output
8961 from the @code{ptype} command can be overwhelming and hard to use. The
8962 @code{info-methods} command filters the methods, printing only those
8963 which match the regular-expression @var{regexp}.
8966 @cindex reloading symbols
8967 Some systems allow individual object files that make up your program to
8968 be replaced without stopping and restarting your program. For example,
8969 in VxWorks you can simply recompile a defective object file and keep on
8970 running. If you are running on one of these systems, you can allow
8971 @value{GDBN} to reload the symbols for automatically relinked modules:
8974 @kindex set symbol-reloading
8975 @item set symbol-reloading on
8976 Replace symbol definitions for the corresponding source file when an
8977 object file with a particular name is seen again.
8979 @item set symbol-reloading off
8980 Do not replace symbol definitions when encountering object files of the
8981 same name more than once. This is the default state; if you are not
8982 running on a system that permits automatic relinking of modules, you
8983 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
8984 may discard symbols when linking large programs, that may contain
8985 several modules (from different directories or libraries) with the same
8988 @kindex show symbol-reloading
8989 @item show symbol-reloading
8990 Show the current @code{on} or @code{off} setting.
8993 @kindex set opaque-type-resolution
8994 @item set opaque-type-resolution on
8995 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
8996 declared as a pointer to a @code{struct}, @code{class}, or
8997 @code{union}---for example, @code{struct MyType *}---that is used in one
8998 source file although the full declaration of @code{struct MyType} is in
8999 another source file. The default is on.
9001 A change in the setting of this subcommand will not take effect until
9002 the next time symbols for a file are loaded.
9004 @item set opaque-type-resolution off
9005 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9006 is printed as follows:
9008 @{<no data fields>@}
9011 @kindex show opaque-type-resolution
9012 @item show opaque-type-resolution
9013 Show whether opaque types are resolved or not.
9015 @kindex maint print symbols
9017 @kindex maint print psymbols
9018 @cindex partial symbol dump
9019 @item maint print symbols @var{filename}
9020 @itemx maint print psymbols @var{filename}
9021 @itemx maint print msymbols @var{filename}
9022 Write a dump of debugging symbol data into the file @var{filename}.
9023 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9024 symbols with debugging data are included. If you use @samp{maint print
9025 symbols}, @value{GDBN} includes all the symbols for which it has already
9026 collected full details: that is, @var{filename} reflects symbols for
9027 only those files whose symbols @value{GDBN} has read. You can use the
9028 command @code{info sources} to find out which files these are. If you
9029 use @samp{maint print psymbols} instead, the dump shows information about
9030 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9031 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9032 @samp{maint print msymbols} dumps just the minimal symbol information
9033 required for each object file from which @value{GDBN} has read some symbols.
9034 @xref{Files, ,Commands to specify files}, for a discussion of how
9035 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9039 @chapter Altering Execution
9041 Once you think you have found an error in your program, you might want to
9042 find out for certain whether correcting the apparent error would lead to
9043 correct results in the rest of the run. You can find the answer by
9044 experiment, using the @value{GDBN} features for altering execution of the
9047 For example, you can store new values into variables or memory
9048 locations, give your program a signal, restart it at a different
9049 address, or even return prematurely from a function.
9052 * Assignment:: Assignment to variables
9053 * Jumping:: Continuing at a different address
9054 * Signaling:: Giving your program a signal
9055 * Returning:: Returning from a function
9056 * Calling:: Calling your program's functions
9057 * Patching:: Patching your program
9061 @section Assignment to variables
9064 @cindex setting variables
9065 To alter the value of a variable, evaluate an assignment expression.
9066 @xref{Expressions, ,Expressions}. For example,
9073 stores the value 4 into the variable @code{x}, and then prints the
9074 value of the assignment expression (which is 4).
9075 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9076 information on operators in supported languages.
9078 @kindex set variable
9079 @cindex variables, setting
9080 If you are not interested in seeing the value of the assignment, use the
9081 @code{set} command instead of the @code{print} command. @code{set} is
9082 really the same as @code{print} except that the expression's value is
9083 not printed and is not put in the value history (@pxref{Value History,
9084 ,Value history}). The expression is evaluated only for its effects.
9086 If the beginning of the argument string of the @code{set} command
9087 appears identical to a @code{set} subcommand, use the @code{set
9088 variable} command instead of just @code{set}. This command is identical
9089 to @code{set} except for its lack of subcommands. For example, if your
9090 program has a variable @code{width}, you get an error if you try to set
9091 a new value with just @samp{set width=13}, because @value{GDBN} has the
9092 command @code{set width}:
9095 (@value{GDBP}) whatis width
9097 (@value{GDBP}) p width
9099 (@value{GDBP}) set width=47
9100 Invalid syntax in expression.
9104 The invalid expression, of course, is @samp{=47}. In
9105 order to actually set the program's variable @code{width}, use
9108 (@value{GDBP}) set var width=47
9111 Because the @code{set} command has many subcommands that can conflict
9112 with the names of program variables, it is a good idea to use the
9113 @code{set variable} command instead of just @code{set}. For example, if
9114 your program has a variable @code{g}, you run into problems if you try
9115 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9116 the command @code{set gnutarget}, abbreviated @code{set g}:
9120 (@value{GDBP}) whatis g
9124 (@value{GDBP}) set g=4
9128 The program being debugged has been started already.
9129 Start it from the beginning? (y or n) y
9130 Starting program: /home/smith/cc_progs/a.out
9131 "/home/smith/cc_progs/a.out": can't open to read symbols:
9133 (@value{GDBP}) show g
9134 The current BFD target is "=4".
9139 The program variable @code{g} did not change, and you silently set the
9140 @code{gnutarget} to an invalid value. In order to set the variable
9144 (@value{GDBP}) set var g=4
9147 @value{GDBN} allows more implicit conversions in assignments than C; you can
9148 freely store an integer value into a pointer variable or vice versa,
9149 and you can convert any structure to any other structure that is the
9150 same length or shorter.
9151 @comment FIXME: how do structs align/pad in these conversions?
9152 @comment /doc@cygnus.com 18dec1990
9154 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9155 construct to generate a value of specified type at a specified address
9156 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9157 to memory location @code{0x83040} as an integer (which implies a certain size
9158 and representation in memory), and
9161 set @{int@}0x83040 = 4
9165 stores the value 4 into that memory location.
9168 @section Continuing at a different address
9170 Ordinarily, when you continue your program, you do so at the place where
9171 it stopped, with the @code{continue} command. You can instead continue at
9172 an address of your own choosing, with the following commands:
9176 @item jump @var{linespec}
9177 Resume execution at line @var{linespec}. Execution stops again
9178 immediately if there is a breakpoint there. @xref{List, ,Printing
9179 source lines}, for a description of the different forms of
9180 @var{linespec}. It is common practice to use the @code{tbreak} command
9181 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9184 The @code{jump} command does not change the current stack frame, or
9185 the stack pointer, or the contents of any memory location or any
9186 register other than the program counter. If line @var{linespec} is in
9187 a different function from the one currently executing, the results may
9188 be bizarre if the two functions expect different patterns of arguments or
9189 of local variables. For this reason, the @code{jump} command requests
9190 confirmation if the specified line is not in the function currently
9191 executing. However, even bizarre results are predictable if you are
9192 well acquainted with the machine-language code of your program.
9194 @item jump *@var{address}
9195 Resume execution at the instruction at address @var{address}.
9198 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9199 On many systems, you can get much the same effect as the @code{jump}
9200 command by storing a new value into the register @code{$pc}. The
9201 difference is that this does not start your program running; it only
9202 changes the address of where it @emph{will} run when you continue. For
9210 makes the next @code{continue} command or stepping command execute at
9211 address @code{0x485}, rather than at the address where your program stopped.
9212 @xref{Continuing and Stepping, ,Continuing and stepping}.
9214 The most common occasion to use the @code{jump} command is to back
9215 up---perhaps with more breakpoints set---over a portion of a program
9216 that has already executed, in order to examine its execution in more
9221 @section Giving your program a signal
9225 @item signal @var{signal}
9226 Resume execution where your program stopped, but immediately give it the
9227 signal @var{signal}. @var{signal} can be the name or the number of a
9228 signal. For example, on many systems @code{signal 2} and @code{signal
9229 SIGINT} are both ways of sending an interrupt signal.
9231 Alternatively, if @var{signal} is zero, continue execution without
9232 giving a signal. This is useful when your program stopped on account of
9233 a signal and would ordinary see the signal when resumed with the
9234 @code{continue} command; @samp{signal 0} causes it to resume without a
9237 @code{signal} does not repeat when you press @key{RET} a second time
9238 after executing the command.
9242 Invoking the @code{signal} command is not the same as invoking the
9243 @code{kill} utility from the shell. Sending a signal with @code{kill}
9244 causes @value{GDBN} to decide what to do with the signal depending on
9245 the signal handling tables (@pxref{Signals}). The @code{signal} command
9246 passes the signal directly to your program.
9250 @section Returning from a function
9253 @cindex returning from a function
9256 @itemx return @var{expression}
9257 You can cancel execution of a function call with the @code{return}
9258 command. If you give an
9259 @var{expression} argument, its value is used as the function's return
9263 When you use @code{return}, @value{GDBN} discards the selected stack frame
9264 (and all frames within it). You can think of this as making the
9265 discarded frame return prematurely. If you wish to specify a value to
9266 be returned, give that value as the argument to @code{return}.
9268 This pops the selected stack frame (@pxref{Selection, ,Selecting a
9269 frame}), and any other frames inside of it, leaving its caller as the
9270 innermost remaining frame. That frame becomes selected. The
9271 specified value is stored in the registers used for returning values
9274 The @code{return} command does not resume execution; it leaves the
9275 program stopped in the state that would exist if the function had just
9276 returned. In contrast, the @code{finish} command (@pxref{Continuing
9277 and Stepping, ,Continuing and stepping}) resumes execution until the
9278 selected stack frame returns naturally.
9281 @section Calling program functions
9283 @cindex calling functions
9286 @item call @var{expr}
9287 Evaluate the expression @var{expr} without displaying @code{void}
9291 You can use this variant of the @code{print} command if you want to
9292 execute a function from your program, but without cluttering the output
9293 with @code{void} returned values. If the result is not void, it
9294 is printed and saved in the value history.
9297 @section Patching programs
9299 @cindex patching binaries
9300 @cindex writing into executables
9301 @cindex writing into corefiles
9303 By default, @value{GDBN} opens the file containing your program's
9304 executable code (or the corefile) read-only. This prevents accidental
9305 alterations to machine code; but it also prevents you from intentionally
9306 patching your program's binary.
9308 If you'd like to be able to patch the binary, you can specify that
9309 explicitly with the @code{set write} command. For example, you might
9310 want to turn on internal debugging flags, or even to make emergency
9316 @itemx set write off
9317 If you specify @samp{set write on}, @value{GDBN} opens executable and
9318 core files for both reading and writing; if you specify @samp{set write
9319 off} (the default), @value{GDBN} opens them read-only.
9321 If you have already loaded a file, you must load it again (using the
9322 @code{exec-file} or @code{core-file} command) after changing @code{set
9323 write}, for your new setting to take effect.
9327 Display whether executable files and core files are opened for writing
9332 @chapter @value{GDBN} Files
9334 @value{GDBN} needs to know the file name of the program to be debugged,
9335 both in order to read its symbol table and in order to start your
9336 program. To debug a core dump of a previous run, you must also tell
9337 @value{GDBN} the name of the core dump file.
9340 * Files:: Commands to specify files
9341 * Separate Debug Files:: Debugging information in separate files
9342 * Symbol Errors:: Errors reading symbol files
9346 @section Commands to specify files
9348 @cindex symbol table
9349 @cindex core dump file
9351 You may want to specify executable and core dump file names. The usual
9352 way to do this is at start-up time, using the arguments to
9353 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
9354 Out of @value{GDBN}}).
9356 Occasionally it is necessary to change to a different file during a
9357 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
9358 a file you want to use. In these situations the @value{GDBN} commands
9359 to specify new files are useful.
9362 @cindex executable file
9364 @item file @var{filename}
9365 Use @var{filename} as the program to be debugged. It is read for its
9366 symbols and for the contents of pure memory. It is also the program
9367 executed when you use the @code{run} command. If you do not specify a
9368 directory and the file is not found in the @value{GDBN} working directory,
9369 @value{GDBN} uses the environment variable @code{PATH} as a list of
9370 directories to search, just as the shell does when looking for a program
9371 to run. You can change the value of this variable, for both @value{GDBN}
9372 and your program, using the @code{path} command.
9374 On systems with memory-mapped files, an auxiliary file named
9375 @file{@var{filename}.syms} may hold symbol table information for
9376 @var{filename}. If so, @value{GDBN} maps in the symbol table from
9377 @file{@var{filename}.syms}, starting up more quickly. See the
9378 descriptions of the file options @samp{-mapped} and @samp{-readnow}
9379 (available on the command line, and with the commands @code{file},
9380 @code{symbol-file}, or @code{add-symbol-file}, described below),
9381 for more information.
9384 @code{file} with no argument makes @value{GDBN} discard any information it
9385 has on both executable file and the symbol table.
9388 @item exec-file @r{[} @var{filename} @r{]}
9389 Specify that the program to be run (but not the symbol table) is found
9390 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
9391 if necessary to locate your program. Omitting @var{filename} means to
9392 discard information on the executable file.
9395 @item symbol-file @r{[} @var{filename} @r{]}
9396 Read symbol table information from file @var{filename}. @code{PATH} is
9397 searched when necessary. Use the @code{file} command to get both symbol
9398 table and program to run from the same file.
9400 @code{symbol-file} with no argument clears out @value{GDBN} information on your
9401 program's symbol table.
9403 The @code{symbol-file} command causes @value{GDBN} to forget the contents
9404 of its convenience variables, the value history, and all breakpoints and
9405 auto-display expressions. This is because they may contain pointers to
9406 the internal data recording symbols and data types, which are part of
9407 the old symbol table data being discarded inside @value{GDBN}.
9409 @code{symbol-file} does not repeat if you press @key{RET} again after
9412 When @value{GDBN} is configured for a particular environment, it
9413 understands debugging information in whatever format is the standard
9414 generated for that environment; you may use either a @sc{gnu} compiler, or
9415 other compilers that adhere to the local conventions.
9416 Best results are usually obtained from @sc{gnu} compilers; for example,
9417 using @code{@value{GCC}} you can generate debugging information for
9420 For most kinds of object files, with the exception of old SVR3 systems
9421 using COFF, the @code{symbol-file} command does not normally read the
9422 symbol table in full right away. Instead, it scans the symbol table
9423 quickly to find which source files and which symbols are present. The
9424 details are read later, one source file at a time, as they are needed.
9426 The purpose of this two-stage reading strategy is to make @value{GDBN}
9427 start up faster. For the most part, it is invisible except for
9428 occasional pauses while the symbol table details for a particular source
9429 file are being read. (The @code{set verbose} command can turn these
9430 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
9431 warnings and messages}.)
9433 We have not implemented the two-stage strategy for COFF yet. When the
9434 symbol table is stored in COFF format, @code{symbol-file} reads the
9435 symbol table data in full right away. Note that ``stabs-in-COFF''
9436 still does the two-stage strategy, since the debug info is actually
9440 @cindex reading symbols immediately
9441 @cindex symbols, reading immediately
9443 @cindex memory-mapped symbol file
9444 @cindex saving symbol table
9445 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9446 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9447 You can override the @value{GDBN} two-stage strategy for reading symbol
9448 tables by using the @samp{-readnow} option with any of the commands that
9449 load symbol table information, if you want to be sure @value{GDBN} has the
9450 entire symbol table available.
9452 If memory-mapped files are available on your system through the
9453 @code{mmap} system call, you can use another option, @samp{-mapped}, to
9454 cause @value{GDBN} to write the symbols for your program into a reusable
9455 file. Future @value{GDBN} debugging sessions map in symbol information
9456 from this auxiliary symbol file (if the program has not changed), rather
9457 than spending time reading the symbol table from the executable
9458 program. Using the @samp{-mapped} option has the same effect as
9459 starting @value{GDBN} with the @samp{-mapped} command-line option.
9461 You can use both options together, to make sure the auxiliary symbol
9462 file has all the symbol information for your program.
9464 The auxiliary symbol file for a program called @var{myprog} is called
9465 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
9466 than the corresponding executable), @value{GDBN} always attempts to use
9467 it when you debug @var{myprog}; no special options or commands are
9470 The @file{.syms} file is specific to the host machine where you run
9471 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
9472 symbol table. It cannot be shared across multiple host platforms.
9474 @c FIXME: for now no mention of directories, since this seems to be in
9475 @c flux. 13mar1992 status is that in theory GDB would look either in
9476 @c current dir or in same dir as myprog; but issues like competing
9477 @c GDB's, or clutter in system dirs, mean that in practice right now
9478 @c only current dir is used. FFish says maybe a special GDB hierarchy
9479 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
9484 @item core-file @r{[} @var{filename} @r{]}
9485 Specify the whereabouts of a core dump file to be used as the ``contents
9486 of memory''. Traditionally, core files contain only some parts of the
9487 address space of the process that generated them; @value{GDBN} can access the
9488 executable file itself for other parts.
9490 @code{core-file} with no argument specifies that no core file is
9493 Note that the core file is ignored when your program is actually running
9494 under @value{GDBN}. So, if you have been running your program and you
9495 wish to debug a core file instead, you must kill the subprocess in which
9496 the program is running. To do this, use the @code{kill} command
9497 (@pxref{Kill Process, ,Killing the child process}).
9499 @kindex add-symbol-file
9500 @cindex dynamic linking
9501 @item add-symbol-file @var{filename} @var{address}
9502 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9503 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
9504 The @code{add-symbol-file} command reads additional symbol table
9505 information from the file @var{filename}. You would use this command
9506 when @var{filename} has been dynamically loaded (by some other means)
9507 into the program that is running. @var{address} should be the memory
9508 address at which the file has been loaded; @value{GDBN} cannot figure
9509 this out for itself. You can additionally specify an arbitrary number
9510 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
9511 section name and base address for that section. You can specify any
9512 @var{address} as an expression.
9514 The symbol table of the file @var{filename} is added to the symbol table
9515 originally read with the @code{symbol-file} command. You can use the
9516 @code{add-symbol-file} command any number of times; the new symbol data
9517 thus read keeps adding to the old. To discard all old symbol data
9518 instead, use the @code{symbol-file} command without any arguments.
9520 @cindex relocatable object files, reading symbols from
9521 @cindex object files, relocatable, reading symbols from
9522 @cindex reading symbols from relocatable object files
9523 @cindex symbols, reading from relocatable object files
9524 @cindex @file{.o} files, reading symbols from
9525 Although @var{filename} is typically a shared library file, an
9526 executable file, or some other object file which has been fully
9527 relocated for loading into a process, you can also load symbolic
9528 information from relocatable @file{.o} files, as long as:
9532 the file's symbolic information refers only to linker symbols defined in
9533 that file, not to symbols defined by other object files,
9535 every section the file's symbolic information refers to has actually
9536 been loaded into the inferior, as it appears in the file, and
9538 you can determine the address at which every section was loaded, and
9539 provide these to the @code{add-symbol-file} command.
9543 Some embedded operating systems, like Sun Chorus and VxWorks, can load
9544 relocatable files into an already running program; such systems
9545 typically make the requirements above easy to meet. However, it's
9546 important to recognize that many native systems use complex link
9547 procedures (@code{.linkonce} section factoring and C++ constructor table
9548 assembly, for example) that make the requirements difficult to meet. In
9549 general, one cannot assume that using @code{add-symbol-file} to read a
9550 relocatable object file's symbolic information will have the same effect
9551 as linking the relocatable object file into the program in the normal
9554 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
9556 You can use the @samp{-mapped} and @samp{-readnow} options just as with
9557 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
9558 table information for @var{filename}.
9560 @kindex add-shared-symbol-file
9561 @item add-shared-symbol-file
9562 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
9563 operating system for the Motorola 88k. @value{GDBN} automatically looks for
9564 shared libraries, however if @value{GDBN} does not find yours, you can run
9565 @code{add-shared-symbol-file}. It takes no arguments.
9569 The @code{section} command changes the base address of section SECTION of
9570 the exec file to ADDR. This can be used if the exec file does not contain
9571 section addresses, (such as in the a.out format), or when the addresses
9572 specified in the file itself are wrong. Each section must be changed
9573 separately. The @code{info files} command, described below, lists all
9574 the sections and their addresses.
9580 @code{info files} and @code{info target} are synonymous; both print the
9581 current target (@pxref{Targets, ,Specifying a Debugging Target}),
9582 including the names of the executable and core dump files currently in
9583 use by @value{GDBN}, and the files from which symbols were loaded. The
9584 command @code{help target} lists all possible targets rather than
9587 @kindex maint info sections
9588 @item maint info sections
9589 Another command that can give you extra information about program sections
9590 is @code{maint info sections}. In addition to the section information
9591 displayed by @code{info files}, this command displays the flags and file
9592 offset of each section in the executable and core dump files. In addition,
9593 @code{maint info sections} provides the following command options (which
9594 may be arbitrarily combined):
9598 Display sections for all loaded object files, including shared libraries.
9599 @item @var{sections}
9600 Display info only for named @var{sections}.
9601 @item @var{section-flags}
9602 Display info only for sections for which @var{section-flags} are true.
9603 The section flags that @value{GDBN} currently knows about are:
9606 Section will have space allocated in the process when loaded.
9607 Set for all sections except those containing debug information.
9609 Section will be loaded from the file into the child process memory.
9610 Set for pre-initialized code and data, clear for @code{.bss} sections.
9612 Section needs to be relocated before loading.
9614 Section cannot be modified by the child process.
9616 Section contains executable code only.
9618 Section contains data only (no executable code).
9620 Section will reside in ROM.
9622 Section contains data for constructor/destructor lists.
9624 Section is not empty.
9626 An instruction to the linker to not output the section.
9627 @item COFF_SHARED_LIBRARY
9628 A notification to the linker that the section contains
9629 COFF shared library information.
9631 Section contains common symbols.
9634 @kindex set trust-readonly-sections
9635 @item set trust-readonly-sections on
9636 Tell @value{GDBN} that readonly sections in your object file
9637 really are read-only (i.e.@: that their contents will not change).
9638 In that case, @value{GDBN} can fetch values from these sections
9639 out of the object file, rather than from the target program.
9640 For some targets (notably embedded ones), this can be a significant
9641 enhancement to debugging performance.
9645 @item set trust-readonly-sections off
9646 Tell @value{GDBN} not to trust readonly sections. This means that
9647 the contents of the section might change while the program is running,
9648 and must therefore be fetched from the target when needed.
9651 All file-specifying commands allow both absolute and relative file names
9652 as arguments. @value{GDBN} always converts the file name to an absolute file
9653 name and remembers it that way.
9655 @cindex shared libraries
9656 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
9659 @value{GDBN} automatically loads symbol definitions from shared libraries
9660 when you use the @code{run} command, or when you examine a core file.
9661 (Before you issue the @code{run} command, @value{GDBN} does not understand
9662 references to a function in a shared library, however---unless you are
9663 debugging a core file).
9665 On HP-UX, if the program loads a library explicitly, @value{GDBN}
9666 automatically loads the symbols at the time of the @code{shl_load} call.
9668 @c FIXME: some @value{GDBN} release may permit some refs to undef
9669 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
9670 @c FIXME...lib; check this from time to time when updating manual
9672 There are times, however, when you may wish to not automatically load
9673 symbol definitions from shared libraries, such as when they are
9674 particularly large or there are many of them.
9676 To control the automatic loading of shared library symbols, use the
9680 @kindex set auto-solib-add
9681 @item set auto-solib-add @var{mode}
9682 If @var{mode} is @code{on}, symbols from all shared object libraries
9683 will be loaded automatically when the inferior begins execution, you
9684 attach to an independently started inferior, or when the dynamic linker
9685 informs @value{GDBN} that a new library has been loaded. If @var{mode}
9686 is @code{off}, symbols must be loaded manually, using the
9687 @code{sharedlibrary} command. The default value is @code{on}.
9689 @kindex show auto-solib-add
9690 @item show auto-solib-add
9691 Display the current autoloading mode.
9694 To explicitly load shared library symbols, use the @code{sharedlibrary}
9698 @kindex info sharedlibrary
9701 @itemx info sharedlibrary
9702 Print the names of the shared libraries which are currently loaded.
9704 @kindex sharedlibrary
9706 @item sharedlibrary @var{regex}
9707 @itemx share @var{regex}
9708 Load shared object library symbols for files matching a
9709 Unix regular expression.
9710 As with files loaded automatically, it only loads shared libraries
9711 required by your program for a core file or after typing @code{run}. If
9712 @var{regex} is omitted all shared libraries required by your program are
9716 On some systems, such as HP-UX systems, @value{GDBN} supports
9717 autoloading shared library symbols until a limiting threshold size is
9718 reached. This provides the benefit of allowing autoloading to remain on
9719 by default, but avoids autoloading excessively large shared libraries,
9720 up to a threshold that is initially set, but which you can modify if you
9723 Beyond that threshold, symbols from shared libraries must be explicitly
9724 loaded. To load these symbols, use the command @code{sharedlibrary
9725 @var{filename}}. The base address of the shared library is determined
9726 automatically by @value{GDBN} and need not be specified.
9728 To display or set the threshold, use the commands:
9731 @kindex set auto-solib-limit
9732 @item set auto-solib-limit @var{threshold}
9733 Set the autoloading size threshold, in an integral number of megabytes.
9734 If @var{threshold} is nonzero and shared library autoloading is enabled,
9735 symbols from all shared object libraries will be loaded until the total
9736 size of the loaded shared library symbols exceeds this threshold.
9737 Otherwise, symbols must be loaded manually, using the
9738 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
9741 @kindex show auto-solib-limit
9742 @item show auto-solib-limit
9743 Display the current autoloading size threshold, in megabytes.
9746 Shared libraries are also supported in many cross or remote debugging
9747 configurations. A copy of the target's libraries need to be present on the
9748 host system; they need to be the same as the target libraries, although the
9749 copies on the target can be stripped as long as the copies on the host are
9752 You need to tell @value{GDBN} where the target libraries are, so that it can
9753 load the correct copies---otherwise, it may try to load the host's libraries.
9754 @value{GDBN} has two variables to specify the search directories for target
9758 @kindex set solib-absolute-prefix
9759 @item set solib-absolute-prefix @var{path}
9760 If this variable is set, @var{path} will be used as a prefix for any
9761 absolute shared library paths; many runtime loaders store the absolute
9762 paths to the shared library in the target program's memory. If you use
9763 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
9764 out in the same way that they are on the target, with e.g.@: a
9765 @file{/usr/lib} hierarchy under @var{path}.
9767 You can set the default value of @samp{solib-absolute-prefix} by using the
9768 configure-time @samp{--with-sysroot} option.
9770 @kindex show solib-absolute-prefix
9771 @item show solib-absolute-prefix
9772 Display the current shared library prefix.
9774 @kindex set solib-search-path
9775 @item set solib-search-path @var{path}
9776 If this variable is set, @var{path} is a colon-separated list of directories
9777 to search for shared libraries. @samp{solib-search-path} is used after
9778 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
9779 the library is relative instead of absolute. If you want to use
9780 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
9781 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
9782 @value{GDBN} from finding your host's libraries.
9784 @kindex show solib-search-path
9785 @item show solib-search-path
9786 Display the current shared library search path.
9790 @node Separate Debug Files
9791 @section Debugging Information in Separate Files
9792 @cindex separate debugging information files
9793 @cindex debugging information in separate files
9794 @cindex @file{.debug} subdirectories
9795 @cindex debugging information directory, global
9796 @cindex global debugging information directory
9798 @value{GDBN} allows you to put a program's debugging information in a
9799 file separate from the executable itself, in a way that allows
9800 @value{GDBN} to find and load the debugging information automatically.
9801 Since debugging information can be very large --- sometimes larger
9802 than the executable code itself --- some systems distribute debugging
9803 information for their executables in separate files, which users can
9804 install only when they need to debug a problem.
9806 If an executable's debugging information has been extracted to a
9807 separate file, the executable should contain a @dfn{debug link} giving
9808 the name of the debugging information file (with no directory
9809 components), and a checksum of its contents. (The exact form of a
9810 debug link is described below.) If the full name of the directory
9811 containing the executable is @var{execdir}, and the executable has a
9812 debug link that specifies the name @var{debugfile}, then @value{GDBN}
9813 will automatically search for the debugging information file in three
9818 the directory containing the executable file (that is, it will look
9819 for a file named @file{@var{execdir}/@var{debugfile}},
9821 a subdirectory of that directory named @file{.debug} (that is, the
9822 file @file{@var{execdir}/.debug/@var{debugfile}}, and
9824 a subdirectory of the global debug file directory that includes the
9825 executable's full path, and the name from the link (that is, the file
9826 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
9827 @var{globaldebugdir} is the global debug file directory, and
9828 @var{execdir} has been turned into a relative path).
9831 @value{GDBN} checks under each of these names for a debugging
9832 information file whose checksum matches that given in the link, and
9833 reads the debugging information from the first one it finds.
9835 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
9836 which has a link containing the name @file{ls.debug}, and the global
9837 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
9838 for debug information in @file{/usr/bin/ls.debug},
9839 @file{/usr/bin/.debug/ls.debug}, and
9840 @file{/usr/lib/debug/usr/bin/ls.debug}.
9842 You can set the global debugging info directory's name, and view the
9843 name @value{GDBN} is currently using.
9847 @kindex set debug-file-directory
9848 @item set debug-file-directory @var{directory}
9849 Set the directory which @value{GDBN} searches for separate debugging
9850 information files to @var{directory}.
9852 @kindex show debug-file-directory
9853 @item show debug-file-directory
9854 Show the directory @value{GDBN} searches for separate debugging
9859 @cindex @code{.gnu_debuglink} sections
9861 A debug link is a special section of the executable file named
9862 @code{.gnu_debuglink}. The section must contain:
9866 A filename, with any leading directory components removed, followed by
9869 zero to three bytes of padding, as needed to reach the next four-byte
9870 boundary within the section, and
9872 a four-byte CRC checksum, stored in the same endianness used for the
9873 executable file itself. The checksum is computed on the debugging
9874 information file's full contents by the function given below, passing
9875 zero as the @var{crc} argument.
9878 Any executable file format can carry a debug link, as long as it can
9879 contain a section named @code{.gnu_debuglink} with the contents
9882 The debugging information file itself should be an ordinary
9883 executable, containing a full set of linker symbols, sections, and
9884 debugging information. The sections of the debugging information file
9885 should have the same names, addresses and sizes as the original file,
9886 but they need not contain any data --- much like a @code{.bss} section
9887 in an ordinary executable.
9889 As of December 2002, there is no standard GNU utility to produce
9890 separated executable / debugging information file pairs. Ulrich
9891 Drepper's @file{elfutils} package, starting with version 0.53,
9892 contains a version of the @code{strip} command such that the command
9893 @kbd{strip foo -f foo.debug} removes the debugging information from
9894 the executable file @file{foo}, places it in the file
9895 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
9897 Since there are many different ways to compute CRC's (different
9898 polynomials, reversals, byte ordering, etc.), the simplest way to
9899 describe the CRC used in @code{.gnu_debuglink} sections is to give the
9900 complete code for a function that computes it:
9902 @kindex @code{gnu_debuglink_crc32}
9905 gnu_debuglink_crc32 (unsigned long crc,
9906 unsigned char *buf, size_t len)
9908 static const unsigned long crc32_table[256] =
9910 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
9911 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
9912 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
9913 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
9914 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
9915 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
9916 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
9917 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
9918 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
9919 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
9920 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
9921 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
9922 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
9923 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
9924 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
9925 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
9926 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
9927 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
9928 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
9929 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
9930 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
9931 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
9932 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
9933 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
9934 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
9935 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
9936 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
9937 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
9938 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
9939 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
9940 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
9941 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
9942 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
9943 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
9944 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
9945 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
9946 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
9947 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
9948 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
9949 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
9950 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
9951 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
9952 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
9953 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
9954 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
9955 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
9956 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
9957 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
9958 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
9959 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
9960 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
9965 crc = ~crc & 0xffffffff;
9966 for (end = buf + len; buf < end; ++buf)
9967 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
9968 return ~crc & 0xffffffff;;
9974 @section Errors reading symbol files
9976 While reading a symbol file, @value{GDBN} occasionally encounters problems,
9977 such as symbol types it does not recognize, or known bugs in compiler
9978 output. By default, @value{GDBN} does not notify you of such problems, since
9979 they are relatively common and primarily of interest to people
9980 debugging compilers. If you are interested in seeing information
9981 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
9982 only one message about each such type of problem, no matter how many
9983 times the problem occurs; or you can ask @value{GDBN} to print more messages,
9984 to see how many times the problems occur, with the @code{set
9985 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
9988 The messages currently printed, and their meanings, include:
9991 @item inner block not inside outer block in @var{symbol}
9993 The symbol information shows where symbol scopes begin and end
9994 (such as at the start of a function or a block of statements). This
9995 error indicates that an inner scope block is not fully contained
9996 in its outer scope blocks.
9998 @value{GDBN} circumvents the problem by treating the inner block as if it had
9999 the same scope as the outer block. In the error message, @var{symbol}
10000 may be shown as ``@code{(don't know)}'' if the outer block is not a
10003 @item block at @var{address} out of order
10005 The symbol information for symbol scope blocks should occur in
10006 order of increasing addresses. This error indicates that it does not
10009 @value{GDBN} does not circumvent this problem, and has trouble
10010 locating symbols in the source file whose symbols it is reading. (You
10011 can often determine what source file is affected by specifying
10012 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10015 @item bad block start address patched
10017 The symbol information for a symbol scope block has a start address
10018 smaller than the address of the preceding source line. This is known
10019 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10021 @value{GDBN} circumvents the problem by treating the symbol scope block as
10022 starting on the previous source line.
10024 @item bad string table offset in symbol @var{n}
10027 Symbol number @var{n} contains a pointer into the string table which is
10028 larger than the size of the string table.
10030 @value{GDBN} circumvents the problem by considering the symbol to have the
10031 name @code{foo}, which may cause other problems if many symbols end up
10034 @item unknown symbol type @code{0x@var{nn}}
10036 The symbol information contains new data types that @value{GDBN} does
10037 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10038 uncomprehended information, in hexadecimal.
10040 @value{GDBN} circumvents the error by ignoring this symbol information.
10041 This usually allows you to debug your program, though certain symbols
10042 are not accessible. If you encounter such a problem and feel like
10043 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10044 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10045 and examine @code{*bufp} to see the symbol.
10047 @item stub type has NULL name
10049 @value{GDBN} could not find the full definition for a struct or class.
10051 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10052 The symbol information for a C@t{++} member function is missing some
10053 information that recent versions of the compiler should have output for
10056 @item info mismatch between compiler and debugger
10058 @value{GDBN} could not parse a type specification output by the compiler.
10063 @chapter Specifying a Debugging Target
10065 @cindex debugging target
10068 A @dfn{target} is the execution environment occupied by your program.
10070 Often, @value{GDBN} runs in the same host environment as your program;
10071 in that case, the debugging target is specified as a side effect when
10072 you use the @code{file} or @code{core} commands. When you need more
10073 flexibility---for example, running @value{GDBN} on a physically separate
10074 host, or controlling a standalone system over a serial port or a
10075 realtime system over a TCP/IP connection---you can use the @code{target}
10076 command to specify one of the target types configured for @value{GDBN}
10077 (@pxref{Target Commands, ,Commands for managing targets}).
10080 * Active Targets:: Active targets
10081 * Target Commands:: Commands for managing targets
10082 * Byte Order:: Choosing target byte order
10083 * Remote:: Remote debugging
10084 * KOD:: Kernel Object Display
10088 @node Active Targets
10089 @section Active targets
10091 @cindex stacking targets
10092 @cindex active targets
10093 @cindex multiple targets
10095 There are three classes of targets: processes, core files, and
10096 executable files. @value{GDBN} can work concurrently on up to three
10097 active targets, one in each class. This allows you to (for example)
10098 start a process and inspect its activity without abandoning your work on
10101 For example, if you execute @samp{gdb a.out}, then the executable file
10102 @code{a.out} is the only active target. If you designate a core file as
10103 well---presumably from a prior run that crashed and coredumped---then
10104 @value{GDBN} has two active targets and uses them in tandem, looking
10105 first in the corefile target, then in the executable file, to satisfy
10106 requests for memory addresses. (Typically, these two classes of target
10107 are complementary, since core files contain only a program's
10108 read-write memory---variables and so on---plus machine status, while
10109 executable files contain only the program text and initialized data.)
10111 When you type @code{run}, your executable file becomes an active process
10112 target as well. When a process target is active, all @value{GDBN}
10113 commands requesting memory addresses refer to that target; addresses in
10114 an active core file or executable file target are obscured while the
10115 process target is active.
10117 Use the @code{core-file} and @code{exec-file} commands to select a new
10118 core file or executable target (@pxref{Files, ,Commands to specify
10119 files}). To specify as a target a process that is already running, use
10120 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10123 @node Target Commands
10124 @section Commands for managing targets
10127 @item target @var{type} @var{parameters}
10128 Connects the @value{GDBN} host environment to a target machine or
10129 process. A target is typically a protocol for talking to debugging
10130 facilities. You use the argument @var{type} to specify the type or
10131 protocol of the target machine.
10133 Further @var{parameters} are interpreted by the target protocol, but
10134 typically include things like device names or host names to connect
10135 with, process numbers, and baud rates.
10137 The @code{target} command does not repeat if you press @key{RET} again
10138 after executing the command.
10140 @kindex help target
10142 Displays the names of all targets available. To display targets
10143 currently selected, use either @code{info target} or @code{info files}
10144 (@pxref{Files, ,Commands to specify files}).
10146 @item help target @var{name}
10147 Describe a particular target, including any parameters necessary to
10150 @kindex set gnutarget
10151 @item set gnutarget @var{args}
10152 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10153 knows whether it is reading an @dfn{executable},
10154 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10155 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10156 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10159 @emph{Warning:} To specify a file format with @code{set gnutarget},
10160 you must know the actual BFD name.
10164 @xref{Files, , Commands to specify files}.
10166 @kindex show gnutarget
10167 @item show gnutarget
10168 Use the @code{show gnutarget} command to display what file format
10169 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10170 @value{GDBN} will determine the file format for each file automatically,
10171 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10174 Here are some common targets (available, or not, depending on the GDB
10178 @kindex target exec
10179 @item target exec @var{program}
10180 An executable file. @samp{target exec @var{program}} is the same as
10181 @samp{exec-file @var{program}}.
10183 @kindex target core
10184 @item target core @var{filename}
10185 A core dump file. @samp{target core @var{filename}} is the same as
10186 @samp{core-file @var{filename}}.
10188 @kindex target remote
10189 @item target remote @var{dev}
10190 Remote serial target in GDB-specific protocol. The argument @var{dev}
10191 specifies what serial device to use for the connection (e.g.
10192 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
10193 supports the @code{load} command. This is only useful if you have
10194 some other way of getting the stub to the target system, and you can put
10195 it somewhere in memory where it won't get clobbered by the download.
10199 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
10207 works; however, you cannot assume that a specific memory map, device
10208 drivers, or even basic I/O is available, although some simulators do
10209 provide these. For info about any processor-specific simulator details,
10210 see the appropriate section in @ref{Embedded Processors, ,Embedded
10215 Some configurations may include these targets as well:
10219 @kindex target nrom
10220 @item target nrom @var{dev}
10221 NetROM ROM emulator. This target only supports downloading.
10225 Different targets are available on different configurations of @value{GDBN};
10226 your configuration may have more or fewer targets.
10228 Many remote targets require you to download the executable's code
10229 once you've successfully established a connection.
10233 @kindex load @var{filename}
10234 @item load @var{filename}
10235 Depending on what remote debugging facilities are configured into
10236 @value{GDBN}, the @code{load} command may be available. Where it exists, it
10237 is meant to make @var{filename} (an executable) available for debugging
10238 on the remote system---by downloading, or dynamic linking, for example.
10239 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
10240 the @code{add-symbol-file} command.
10242 If your @value{GDBN} does not have a @code{load} command, attempting to
10243 execute it gets the error message ``@code{You can't do that when your
10244 target is @dots{}}''
10246 The file is loaded at whatever address is specified in the executable.
10247 For some object file formats, you can specify the load address when you
10248 link the program; for other formats, like a.out, the object file format
10249 specifies a fixed address.
10250 @c FIXME! This would be a good place for an xref to the GNU linker doc.
10252 @code{load} does not repeat if you press @key{RET} again after using it.
10256 @section Choosing target byte order
10258 @cindex choosing target byte order
10259 @cindex target byte order
10261 Some types of processors, such as the MIPS, PowerPC, and Hitachi SH,
10262 offer the ability to run either big-endian or little-endian byte
10263 orders. Usually the executable or symbol will include a bit to
10264 designate the endian-ness, and you will not need to worry about
10265 which to use. However, you may still find it useful to adjust
10266 @value{GDBN}'s idea of processor endian-ness manually.
10269 @kindex set endian big
10270 @item set endian big
10271 Instruct @value{GDBN} to assume the target is big-endian.
10273 @kindex set endian little
10274 @item set endian little
10275 Instruct @value{GDBN} to assume the target is little-endian.
10277 @kindex set endian auto
10278 @item set endian auto
10279 Instruct @value{GDBN} to use the byte order associated with the
10283 Display @value{GDBN}'s current idea of the target byte order.
10287 Note that these commands merely adjust interpretation of symbolic
10288 data on the host, and that they have absolutely no effect on the
10292 @section Remote debugging
10293 @cindex remote debugging
10295 If you are trying to debug a program running on a machine that cannot run
10296 @value{GDBN} in the usual way, it is often useful to use remote debugging.
10297 For example, you might use remote debugging on an operating system kernel,
10298 or on a small system which does not have a general purpose operating system
10299 powerful enough to run a full-featured debugger.
10301 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
10302 to make this work with particular debugging targets. In addition,
10303 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
10304 but not specific to any particular target system) which you can use if you
10305 write the remote stubs---the code that runs on the remote system to
10306 communicate with @value{GDBN}.
10308 Other remote targets may be available in your
10309 configuration of @value{GDBN}; use @code{help target} to list them.
10312 @section Kernel Object Display
10314 @cindex kernel object display
10315 @cindex kernel object
10318 Some targets support kernel object display. Using this facility,
10319 @value{GDBN} communicates specially with the underlying operating system
10320 and can display information about operating system-level objects such as
10321 mutexes and other synchronization objects. Exactly which objects can be
10322 displayed is determined on a per-OS basis.
10324 Use the @code{set os} command to set the operating system. This tells
10325 @value{GDBN} which kernel object display module to initialize:
10328 (@value{GDBP}) set os cisco
10331 If @code{set os} succeeds, @value{GDBN} will display some information
10332 about the operating system, and will create a new @code{info} command
10333 which can be used to query the target. The @code{info} command is named
10334 after the operating system:
10337 (@value{GDBP}) info cisco
10338 List of Cisco Kernel Objects
10340 any Any and all objects
10343 Further subcommands can be used to query about particular objects known
10346 There is currently no way to determine whether a given operating system
10347 is supported other than to try it.
10350 @node Remote Debugging
10351 @chapter Debugging remote programs
10354 * Server:: Using the gdbserver program
10355 * NetWare:: Using the gdbserve.nlm program
10356 * Remote configuration:: Remote configuration
10357 * remote stub:: Implementing a remote stub
10361 @section Using the @code{gdbserver} program
10364 @cindex remote connection without stubs
10365 @code{gdbserver} is a control program for Unix-like systems, which
10366 allows you to connect your program with a remote @value{GDBN} via
10367 @code{target remote}---but without linking in the usual debugging stub.
10369 @code{gdbserver} is not a complete replacement for the debugging stubs,
10370 because it requires essentially the same operating-system facilities
10371 that @value{GDBN} itself does. In fact, a system that can run
10372 @code{gdbserver} to connect to a remote @value{GDBN} could also run
10373 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
10374 because it is a much smaller program than @value{GDBN} itself. It is
10375 also easier to port than all of @value{GDBN}, so you may be able to get
10376 started more quickly on a new system by using @code{gdbserver}.
10377 Finally, if you develop code for real-time systems, you may find that
10378 the tradeoffs involved in real-time operation make it more convenient to
10379 do as much development work as possible on another system, for example
10380 by cross-compiling. You can use @code{gdbserver} to make a similar
10381 choice for debugging.
10383 @value{GDBN} and @code{gdbserver} communicate via either a serial line
10384 or a TCP connection, using the standard @value{GDBN} remote serial
10388 @item On the target machine,
10389 you need to have a copy of the program you want to debug.
10390 @code{gdbserver} does not need your program's symbol table, so you can
10391 strip the program if necessary to save space. @value{GDBN} on the host
10392 system does all the symbol handling.
10394 To use the server, you must tell it how to communicate with @value{GDBN};
10395 the name of your program; and the arguments for your program. The usual
10399 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
10402 @var{comm} is either a device name (to use a serial line) or a TCP
10403 hostname and portnumber. For example, to debug Emacs with the argument
10404 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
10408 target> gdbserver /dev/com1 emacs foo.txt
10411 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
10414 To use a TCP connection instead of a serial line:
10417 target> gdbserver host:2345 emacs foo.txt
10420 The only difference from the previous example is the first argument,
10421 specifying that you are communicating with the host @value{GDBN} via
10422 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
10423 expect a TCP connection from machine @samp{host} to local TCP port 2345.
10424 (Currently, the @samp{host} part is ignored.) You can choose any number
10425 you want for the port number as long as it does not conflict with any
10426 TCP ports already in use on the target system (for example, @code{23} is
10427 reserved for @code{telnet}).@footnote{If you choose a port number that
10428 conflicts with another service, @code{gdbserver} prints an error message
10429 and exits.} You must use the same port number with the host @value{GDBN}
10430 @code{target remote} command.
10432 On some targets, @code{gdbserver} can also attach to running programs.
10433 This is accomplished via the @code{--attach} argument. The syntax is:
10436 target> gdbserver @var{comm} --attach @var{pid}
10439 @var{pid} is the process ID of a currently running process. It isn't necessary
10440 to point @code{gdbserver} at a binary for the running process.
10442 @item On the @value{GDBN} host machine,
10443 you need an unstripped copy of your program, since @value{GDBN} needs
10444 symbols and debugging information. Start up @value{GDBN} as usual,
10445 using the name of the local copy of your program as the first argument.
10446 (You may also need the @w{@samp{--baud}} option if the serial line is
10447 running at anything other than 9600@dmn{bps}.) After that, use @code{target
10448 remote} to establish communications with @code{gdbserver}. Its argument
10449 is either a device name (usually a serial device, like
10450 @file{/dev/ttyb}), or a TCP port descriptor in the form
10451 @code{@var{host}:@var{PORT}}. For example:
10454 (@value{GDBP}) target remote /dev/ttyb
10458 communicates with the server via serial line @file{/dev/ttyb}, and
10461 (@value{GDBP}) target remote the-target:2345
10465 communicates via a TCP connection to port 2345 on host @w{@file{the-target}}.
10466 For TCP connections, you must start up @code{gdbserver} prior to using
10467 the @code{target remote} command. Otherwise you may get an error whose
10468 text depends on the host system, but which usually looks something like
10469 @samp{Connection refused}.
10473 @section Using the @code{gdbserve.nlm} program
10475 @kindex gdbserve.nlm
10476 @code{gdbserve.nlm} is a control program for NetWare systems, which
10477 allows you to connect your program with a remote @value{GDBN} via
10478 @code{target remote}.
10480 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
10481 using the standard @value{GDBN} remote serial protocol.
10484 @item On the target machine,
10485 you need to have a copy of the program you want to debug.
10486 @code{gdbserve.nlm} does not need your program's symbol table, so you
10487 can strip the program if necessary to save space. @value{GDBN} on the
10488 host system does all the symbol handling.
10490 To use the server, you must tell it how to communicate with
10491 @value{GDBN}; the name of your program; and the arguments for your
10492 program. The syntax is:
10495 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
10496 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
10499 @var{board} and @var{port} specify the serial line; @var{baud} specifies
10500 the baud rate used by the connection. @var{port} and @var{node} default
10501 to 0, @var{baud} defaults to 9600@dmn{bps}.
10503 For example, to debug Emacs with the argument @samp{foo.txt}and
10504 communicate with @value{GDBN} over serial port number 2 or board 1
10505 using a 19200@dmn{bps} connection:
10508 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
10511 @item On the @value{GDBN} host machine,
10512 you need an unstripped copy of your program, since @value{GDBN} needs
10513 symbols and debugging information. Start up @value{GDBN} as usual,
10514 using the name of the local copy of your program as the first argument.
10515 (You may also need the @w{@samp{--baud}} option if the serial line is
10516 running at anything other than 9600@dmn{bps}. After that, use @code{target
10517 remote} to establish communications with @code{gdbserve.nlm}. Its
10518 argument is a device name (usually a serial device, like
10519 @file{/dev/ttyb}). For example:
10522 (@value{GDBP}) target remote /dev/ttyb
10526 communications with the server via serial line @file{/dev/ttyb}.
10529 @node Remote configuration
10530 @section Remote configuration
10532 The following configuration options are available when debugging remote
10536 @kindex set remote hardware-watchpoint-limit
10537 @kindex set remote hardware-breakpoint-limit
10538 @anchor{set remote hardware-watchpoint-limit}
10539 @anchor{set remote hardware-breakpoint-limit}
10540 @item set remote hardware-watchpoint-limit @var{limit}
10541 @itemx set remote hardware-breakpoint-limit @var{limit}
10542 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
10543 watchpoints. A limit of -1, the default, is treated as unlimited.
10547 @section Implementing a remote stub
10549 @cindex debugging stub, example
10550 @cindex remote stub, example
10551 @cindex stub example, remote debugging
10552 The stub files provided with @value{GDBN} implement the target side of the
10553 communication protocol, and the @value{GDBN} side is implemented in the
10554 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
10555 these subroutines to communicate, and ignore the details. (If you're
10556 implementing your own stub file, you can still ignore the details: start
10557 with one of the existing stub files. @file{sparc-stub.c} is the best
10558 organized, and therefore the easiest to read.)
10560 @cindex remote serial debugging, overview
10561 To debug a program running on another machine (the debugging
10562 @dfn{target} machine), you must first arrange for all the usual
10563 prerequisites for the program to run by itself. For example, for a C
10568 A startup routine to set up the C runtime environment; these usually
10569 have a name like @file{crt0}. The startup routine may be supplied by
10570 your hardware supplier, or you may have to write your own.
10573 A C subroutine library to support your program's
10574 subroutine calls, notably managing input and output.
10577 A way of getting your program to the other machine---for example, a
10578 download program. These are often supplied by the hardware
10579 manufacturer, but you may have to write your own from hardware
10583 The next step is to arrange for your program to use a serial port to
10584 communicate with the machine where @value{GDBN} is running (the @dfn{host}
10585 machine). In general terms, the scheme looks like this:
10589 @value{GDBN} already understands how to use this protocol; when everything
10590 else is set up, you can simply use the @samp{target remote} command
10591 (@pxref{Targets,,Specifying a Debugging Target}).
10593 @item On the target,
10594 you must link with your program a few special-purpose subroutines that
10595 implement the @value{GDBN} remote serial protocol. The file containing these
10596 subroutines is called a @dfn{debugging stub}.
10598 On certain remote targets, you can use an auxiliary program
10599 @code{gdbserver} instead of linking a stub into your program.
10600 @xref{Server,,Using the @code{gdbserver} program}, for details.
10603 The debugging stub is specific to the architecture of the remote
10604 machine; for example, use @file{sparc-stub.c} to debug programs on
10607 @cindex remote serial stub list
10608 These working remote stubs are distributed with @value{GDBN}:
10613 @cindex @file{i386-stub.c}
10616 For Intel 386 and compatible architectures.
10619 @cindex @file{m68k-stub.c}
10620 @cindex Motorola 680x0
10622 For Motorola 680x0 architectures.
10625 @cindex @file{sh-stub.c}
10628 For Hitachi SH architectures.
10631 @cindex @file{sparc-stub.c}
10633 For @sc{sparc} architectures.
10635 @item sparcl-stub.c
10636 @cindex @file{sparcl-stub.c}
10639 For Fujitsu @sc{sparclite} architectures.
10643 The @file{README} file in the @value{GDBN} distribution may list other
10644 recently added stubs.
10647 * Stub Contents:: What the stub can do for you
10648 * Bootstrapping:: What you must do for the stub
10649 * Debug Session:: Putting it all together
10652 @node Stub Contents
10653 @subsection What the stub can do for you
10655 @cindex remote serial stub
10656 The debugging stub for your architecture supplies these three
10660 @item set_debug_traps
10661 @kindex set_debug_traps
10662 @cindex remote serial stub, initialization
10663 This routine arranges for @code{handle_exception} to run when your
10664 program stops. You must call this subroutine explicitly near the
10665 beginning of your program.
10667 @item handle_exception
10668 @kindex handle_exception
10669 @cindex remote serial stub, main routine
10670 This is the central workhorse, but your program never calls it
10671 explicitly---the setup code arranges for @code{handle_exception} to
10672 run when a trap is triggered.
10674 @code{handle_exception} takes control when your program stops during
10675 execution (for example, on a breakpoint), and mediates communications
10676 with @value{GDBN} on the host machine. This is where the communications
10677 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
10678 representative on the target machine. It begins by sending summary
10679 information on the state of your program, then continues to execute,
10680 retrieving and transmitting any information @value{GDBN} needs, until you
10681 execute a @value{GDBN} command that makes your program resume; at that point,
10682 @code{handle_exception} returns control to your own code on the target
10686 @cindex @code{breakpoint} subroutine, remote
10687 Use this auxiliary subroutine to make your program contain a
10688 breakpoint. Depending on the particular situation, this may be the only
10689 way for @value{GDBN} to get control. For instance, if your target
10690 machine has some sort of interrupt button, you won't need to call this;
10691 pressing the interrupt button transfers control to
10692 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
10693 simply receiving characters on the serial port may also trigger a trap;
10694 again, in that situation, you don't need to call @code{breakpoint} from
10695 your own program---simply running @samp{target remote} from the host
10696 @value{GDBN} session gets control.
10698 Call @code{breakpoint} if none of these is true, or if you simply want
10699 to make certain your program stops at a predetermined point for the
10700 start of your debugging session.
10703 @node Bootstrapping
10704 @subsection What you must do for the stub
10706 @cindex remote stub, support routines
10707 The debugging stubs that come with @value{GDBN} are set up for a particular
10708 chip architecture, but they have no information about the rest of your
10709 debugging target machine.
10711 First of all you need to tell the stub how to communicate with the
10715 @item int getDebugChar()
10716 @kindex getDebugChar
10717 Write this subroutine to read a single character from the serial port.
10718 It may be identical to @code{getchar} for your target system; a
10719 different name is used to allow you to distinguish the two if you wish.
10721 @item void putDebugChar(int)
10722 @kindex putDebugChar
10723 Write this subroutine to write a single character to the serial port.
10724 It may be identical to @code{putchar} for your target system; a
10725 different name is used to allow you to distinguish the two if you wish.
10728 @cindex control C, and remote debugging
10729 @cindex interrupting remote targets
10730 If you want @value{GDBN} to be able to stop your program while it is
10731 running, you need to use an interrupt-driven serial driver, and arrange
10732 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
10733 character). That is the character which @value{GDBN} uses to tell the
10734 remote system to stop.
10736 Getting the debugging target to return the proper status to @value{GDBN}
10737 probably requires changes to the standard stub; one quick and dirty way
10738 is to just execute a breakpoint instruction (the ``dirty'' part is that
10739 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
10741 Other routines you need to supply are:
10744 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
10745 @kindex exceptionHandler
10746 Write this function to install @var{exception_address} in the exception
10747 handling tables. You need to do this because the stub does not have any
10748 way of knowing what the exception handling tables on your target system
10749 are like (for example, the processor's table might be in @sc{rom},
10750 containing entries which point to a table in @sc{ram}).
10751 @var{exception_number} is the exception number which should be changed;
10752 its meaning is architecture-dependent (for example, different numbers
10753 might represent divide by zero, misaligned access, etc). When this
10754 exception occurs, control should be transferred directly to
10755 @var{exception_address}, and the processor state (stack, registers,
10756 and so on) should be just as it is when a processor exception occurs. So if
10757 you want to use a jump instruction to reach @var{exception_address}, it
10758 should be a simple jump, not a jump to subroutine.
10760 For the 386, @var{exception_address} should be installed as an interrupt
10761 gate so that interrupts are masked while the handler runs. The gate
10762 should be at privilege level 0 (the most privileged level). The
10763 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
10764 help from @code{exceptionHandler}.
10766 @item void flush_i_cache()
10767 @kindex flush_i_cache
10768 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
10769 instruction cache, if any, on your target machine. If there is no
10770 instruction cache, this subroutine may be a no-op.
10772 On target machines that have instruction caches, @value{GDBN} requires this
10773 function to make certain that the state of your program is stable.
10777 You must also make sure this library routine is available:
10780 @item void *memset(void *, int, int)
10782 This is the standard library function @code{memset} that sets an area of
10783 memory to a known value. If you have one of the free versions of
10784 @code{libc.a}, @code{memset} can be found there; otherwise, you must
10785 either obtain it from your hardware manufacturer, or write your own.
10788 If you do not use the GNU C compiler, you may need other standard
10789 library subroutines as well; this varies from one stub to another,
10790 but in general the stubs are likely to use any of the common library
10791 subroutines which @code{@value{GCC}} generates as inline code.
10794 @node Debug Session
10795 @subsection Putting it all together
10797 @cindex remote serial debugging summary
10798 In summary, when your program is ready to debug, you must follow these
10803 Make sure you have defined the supporting low-level routines
10804 (@pxref{Bootstrapping,,What you must do for the stub}):
10806 @code{getDebugChar}, @code{putDebugChar},
10807 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
10811 Insert these lines near the top of your program:
10819 For the 680x0 stub only, you need to provide a variable called
10820 @code{exceptionHook}. Normally you just use:
10823 void (*exceptionHook)() = 0;
10827 but if before calling @code{set_debug_traps}, you set it to point to a
10828 function in your program, that function is called when
10829 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
10830 error). The function indicated by @code{exceptionHook} is called with
10831 one parameter: an @code{int} which is the exception number.
10834 Compile and link together: your program, the @value{GDBN} debugging stub for
10835 your target architecture, and the supporting subroutines.
10838 Make sure you have a serial connection between your target machine and
10839 the @value{GDBN} host, and identify the serial port on the host.
10842 @c The "remote" target now provides a `load' command, so we should
10843 @c document that. FIXME.
10844 Download your program to your target machine (or get it there by
10845 whatever means the manufacturer provides), and start it.
10848 To start remote debugging, run @value{GDBN} on the host machine, and specify
10849 as an executable file the program that is running in the remote machine.
10850 This tells @value{GDBN} how to find your program's symbols and the contents
10854 @cindex serial line, @code{target remote}
10855 Establish communication using the @code{target remote} command.
10856 Its argument specifies how to communicate with the target
10857 machine---either via a devicename attached to a direct serial line, or a
10858 TCP or UDP port (usually to a terminal server which in turn has a serial line
10859 to the target). For example, to use a serial line connected to the
10860 device named @file{/dev/ttyb}:
10863 target remote /dev/ttyb
10866 @cindex TCP port, @code{target remote}
10867 To use a TCP connection, use an argument of the form
10868 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
10869 For example, to connect to port 2828 on a
10870 terminal server named @code{manyfarms}:
10873 target remote manyfarms:2828
10876 If your remote target is actually running on the same machine as
10877 your debugger session (e.g.@: a simulator of your target running on
10878 the same host), you can omit the hostname. For example, to connect
10879 to port 1234 on your local machine:
10882 target remote :1234
10886 Note that the colon is still required here.
10888 @cindex UDP port, @code{target remote}
10889 To use a UDP connection, use an argument of the form
10890 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
10891 on a terminal server named @code{manyfarms}:
10894 target remote udp:manyfarms:2828
10897 When using a UDP connection for remote debugging, you should keep in mind
10898 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
10899 busy or unreliable networks, which will cause havoc with your debugging
10904 Now you can use all the usual commands to examine and change data and to
10905 step and continue the remote program.
10907 To resume the remote program and stop debugging it, use the @code{detach}
10910 @cindex interrupting remote programs
10911 @cindex remote programs, interrupting
10912 Whenever @value{GDBN} is waiting for the remote program, if you type the
10913 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
10914 program. This may or may not succeed, depending in part on the hardware
10915 and the serial drivers the remote system uses. If you type the
10916 interrupt character once again, @value{GDBN} displays this prompt:
10919 Interrupted while waiting for the program.
10920 Give up (and stop debugging it)? (y or n)
10923 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
10924 (If you decide you want to try again later, you can use @samp{target
10925 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
10926 goes back to waiting.
10929 @node Configurations
10930 @chapter Configuration-Specific Information
10932 While nearly all @value{GDBN} commands are available for all native and
10933 cross versions of the debugger, there are some exceptions. This chapter
10934 describes things that are only available in certain configurations.
10936 There are three major categories of configurations: native
10937 configurations, where the host and target are the same, embedded
10938 operating system configurations, which are usually the same for several
10939 different processor architectures, and bare embedded processors, which
10940 are quite different from each other.
10945 * Embedded Processors::
10952 This section describes details specific to particular native
10957 * SVR4 Process Information:: SVR4 process information
10958 * DJGPP Native:: Features specific to the DJGPP port
10959 * Cygwin Native:: Features specific to the Cygwin port
10965 On HP-UX systems, if you refer to a function or variable name that
10966 begins with a dollar sign, @value{GDBN} searches for a user or system
10967 name first, before it searches for a convenience variable.
10969 @node SVR4 Process Information
10970 @subsection SVR4 process information
10973 @cindex process image
10975 Many versions of SVR4 provide a facility called @samp{/proc} that can be
10976 used to examine the image of a running process using file-system
10977 subroutines. If @value{GDBN} is configured for an operating system with
10978 this facility, the command @code{info proc} is available to report on
10979 several kinds of information about the process running your program.
10980 @code{info proc} works only on SVR4 systems that include the
10981 @code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
10982 and Unixware, but not HP-UX or @sc{gnu}/Linux, for example.
10987 Summarize available information about the process.
10989 @kindex info proc mappings
10990 @item info proc mappings
10991 Report on the address ranges accessible in the program, with information
10992 on whether your program may read, write, or execute each range.
10994 @comment These sub-options of 'info proc' were not included when
10995 @comment procfs.c was re-written. Keep their descriptions around
10996 @comment against the day when someone finds the time to put them back in.
10997 @kindex info proc times
10998 @item info proc times
10999 Starting time, user CPU time, and system CPU time for your program and
11002 @kindex info proc id
11004 Report on the process IDs related to your program: its own process ID,
11005 the ID of its parent, the process group ID, and the session ID.
11007 @kindex info proc status
11008 @item info proc status
11009 General information on the state of the process. If the process is
11010 stopped, this report includes the reason for stopping, and any signal
11013 @item info proc all
11014 Show all the above information about the process.
11019 @subsection Features for Debugging @sc{djgpp} Programs
11020 @cindex @sc{djgpp} debugging
11021 @cindex native @sc{djgpp} debugging
11022 @cindex MS-DOS-specific commands
11024 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11025 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11026 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11027 top of real-mode DOS systems and their emulations.
11029 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11030 defines a few commands specific to the @sc{djgpp} port. This
11031 subsection describes those commands.
11036 This is a prefix of @sc{djgpp}-specific commands which print
11037 information about the target system and important OS structures.
11040 @cindex MS-DOS system info
11041 @cindex free memory information (MS-DOS)
11042 @item info dos sysinfo
11043 This command displays assorted information about the underlying
11044 platform: the CPU type and features, the OS version and flavor, the
11045 DPMI version, and the available conventional and DPMI memory.
11050 @cindex segment descriptor tables
11051 @cindex descriptor tables display
11053 @itemx info dos ldt
11054 @itemx info dos idt
11055 These 3 commands display entries from, respectively, Global, Local,
11056 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11057 tables are data structures which store a descriptor for each segment
11058 that is currently in use. The segment's selector is an index into a
11059 descriptor table; the table entry for that index holds the
11060 descriptor's base address and limit, and its attributes and access
11063 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11064 segment (used for both data and the stack), and a DOS segment (which
11065 allows access to DOS/BIOS data structures and absolute addresses in
11066 conventional memory). However, the DPMI host will usually define
11067 additional segments in order to support the DPMI environment.
11069 @cindex garbled pointers
11070 These commands allow to display entries from the descriptor tables.
11071 Without an argument, all entries from the specified table are
11072 displayed. An argument, which should be an integer expression, means
11073 display a single entry whose index is given by the argument. For
11074 example, here's a convenient way to display information about the
11075 debugged program's data segment:
11078 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11079 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11083 This comes in handy when you want to see whether a pointer is outside
11084 the data segment's limit (i.e.@: @dfn{garbled}).
11086 @cindex page tables display (MS-DOS)
11088 @itemx info dos pte
11089 These two commands display entries from, respectively, the Page
11090 Directory and the Page Tables. Page Directories and Page Tables are
11091 data structures which control how virtual memory addresses are mapped
11092 into physical addresses. A Page Table includes an entry for every
11093 page of memory that is mapped into the program's address space; there
11094 may be several Page Tables, each one holding up to 4096 entries. A
11095 Page Directory has up to 4096 entries, one each for every Page Table
11096 that is currently in use.
11098 Without an argument, @kbd{info dos pde} displays the entire Page
11099 Directory, and @kbd{info dos pte} displays all the entries in all of
11100 the Page Tables. An argument, an integer expression, given to the
11101 @kbd{info dos pde} command means display only that entry from the Page
11102 Directory table. An argument given to the @kbd{info dos pte} command
11103 means display entries from a single Page Table, the one pointed to by
11104 the specified entry in the Page Directory.
11106 @cindex direct memory access (DMA) on MS-DOS
11107 These commands are useful when your program uses @dfn{DMA} (Direct
11108 Memory Access), which needs physical addresses to program the DMA
11111 These commands are supported only with some DPMI servers.
11113 @cindex physical address from linear address
11114 @item info dos address-pte @var{addr}
11115 This command displays the Page Table entry for a specified linear
11116 address. The argument linear address @var{addr} should already have the
11117 appropriate segment's base address added to it, because this command
11118 accepts addresses which may belong to @emph{any} segment. For
11119 example, here's how to display the Page Table entry for the page where
11120 the variable @code{i} is stored:
11123 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
11124 @exdent @code{Page Table entry for address 0x11a00d30:}
11125 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
11129 This says that @code{i} is stored at offset @code{0xd30} from the page
11130 whose physical base address is @code{0x02698000}, and prints all the
11131 attributes of that page.
11133 Note that you must cast the addresses of variables to a @code{char *},
11134 since otherwise the value of @code{__djgpp_base_address}, the base
11135 address of all variables and functions in a @sc{djgpp} program, will
11136 be added using the rules of C pointer arithmetics: if @code{i} is
11137 declared an @code{int}, @value{GDBN} will add 4 times the value of
11138 @code{__djgpp_base_address} to the address of @code{i}.
11140 Here's another example, it displays the Page Table entry for the
11144 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
11145 @exdent @code{Page Table entry for address 0x29110:}
11146 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
11150 (The @code{+ 3} offset is because the transfer buffer's address is the
11151 3rd member of the @code{_go32_info_block} structure.) The output of
11152 this command clearly shows that addresses in conventional memory are
11153 mapped 1:1, i.e.@: the physical and linear addresses are identical.
11155 This command is supported only with some DPMI servers.
11158 @node Cygwin Native
11159 @subsection Features for Debugging MS Windows PE executables
11160 @cindex MS Windows debugging
11161 @cindex native Cygwin debugging
11162 @cindex Cygwin-specific commands
11164 @value{GDBN} supports native debugging of MS Windows programs, including
11165 DLLs with and without symbolic debugging information. There are various
11166 additional Cygwin-specific commands, described in this subsection. The
11167 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
11168 that have no debugging symbols.
11174 This is a prefix of MS Windows specific commands which print
11175 information about the target system and important OS structures.
11177 @item info w32 selector
11178 This command displays information returned by
11179 the Win32 API @code{GetThreadSelectorEntry} function.
11180 It takes an optional argument that is evaluated to
11181 a long value to give the information about this given selector.
11182 Without argument, this command displays information
11183 about the the six segment registers.
11187 This is a Cygwin specific alias of info shared.
11189 @kindex dll-symbols
11191 This command loads symbols from a dll similarly to
11192 add-sym command but without the need to specify a base address.
11194 @kindex set new-console
11195 @item set new-console @var{mode}
11196 If @var{mode} is @code{on} the debuggee will
11197 be started in a new console on next start.
11198 If @var{mode} is @code{off}i, the debuggee will
11199 be started in the same console as the debugger.
11201 @kindex show new-console
11202 @item show new-console
11203 Displays whether a new console is used
11204 when the debuggee is started.
11206 @kindex set new-group
11207 @item set new-group @var{mode}
11208 This boolean value controls whether the debuggee should
11209 start a new group or stay in the same group as the debugger.
11210 This affects the way the Windows OS handles
11213 @kindex show new-group
11214 @item show new-group
11215 Displays current value of new-group boolean.
11217 @kindex set debugevents
11218 @item set debugevents
11219 This boolean value adds debug output concerning events seen by the debugger.
11221 @kindex set debugexec
11222 @item set debugexec
11223 This boolean value adds debug output concerning execute events
11224 seen by the debugger.
11226 @kindex set debugexceptions
11227 @item set debugexceptions
11228 This boolean value adds debug ouptut concerning exception events
11229 seen by the debugger.
11231 @kindex set debugmemory
11232 @item set debugmemory
11233 This boolean value adds debug ouptut concerning memory events
11234 seen by the debugger.
11238 This boolean values specifies whether the debuggee is called
11239 via a shell or directly (default value is on).
11243 Displays if the debuggee will be started with a shell.
11248 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
11251 @node Non-debug DLL symbols
11252 @subsubsection Support for DLLs without debugging symbols
11253 @cindex DLLs with no debugging symbols
11254 @cindex Minimal symbols and DLLs
11256 Very often on windows, some of the DLLs that your program relies on do
11257 not include symbolic debugging information (for example,
11258 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
11259 symbols in a DLL, it relies on the minimal amount of symbolic
11260 information contained in the DLL's export table. This subsubsection
11261 describes working with such symbols, known internally to @value{GDBN} as
11262 ``minimal symbols''.
11264 Note that before the debugged program has started execution, no DLLs
11265 will have been loaded. The easiest way around this problem is simply to
11266 start the program --- either by setting a breakpoint or letting the
11267 program run once to completion. It is also possible to force
11268 @value{GDBN} to load a particular DLL before starting the executable ---
11269 see the shared library information in @pxref{Files} or the
11270 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
11271 explicitly loading symbols from a DLL with no debugging information will
11272 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
11273 which may adversely affect symbol lookup performance.
11275 @subsubsection DLL name prefixes
11277 In keeping with the naming conventions used by the Microsoft debugging
11278 tools, DLL export symbols are made available with a prefix based on the
11279 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
11280 also entered into the symbol table, so @code{CreateFileA} is often
11281 sufficient. In some cases there will be name clashes within a program
11282 (particularly if the executable itself includes full debugging symbols)
11283 necessitating the use of the fully qualified name when referring to the
11284 contents of the DLL. Use single-quotes around the name to avoid the
11285 exclamation mark (``!'') being interpreted as a language operator.
11287 Note that the internal name of the DLL may be all upper-case, even
11288 though the file name of the DLL is lower-case, or vice-versa. Since
11289 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
11290 some confusion. If in doubt, try the @code{info functions} and
11291 @code{info variables} commands or even @code{maint print msymbols} (see
11292 @pxref{Symbols}). Here's an example:
11295 (gdb) info function CreateFileA
11296 All functions matching regular expression "CreateFileA":
11298 Non-debugging symbols:
11299 0x77e885f4 CreateFileA
11300 0x77e885f4 KERNEL32!CreateFileA
11304 (gdb) info function !
11305 All functions matching regular expression "!":
11307 Non-debugging symbols:
11308 0x6100114c cygwin1!__assert
11309 0x61004034 cygwin1!_dll_crt0@@0
11310 0x61004240 cygwin1!dll_crt0(per_process *)
11314 @subsubsection Working with minimal symbols
11316 Symbols extracted from a DLL's export table do not contain very much
11317 type information. All that @value{GDBN} can do is guess whether a symbol
11318 refers to a function or variable depending on the linker section that
11319 contains the symbol. Also note that the actual contents of the memory
11320 contained in a DLL are not available unless the program is running. This
11321 means that you cannot examine the contents of a variable or disassemble
11322 a function within a DLL without a running program.
11324 Variables are generally treated as pointers and dereferenced
11325 automatically. For this reason, it is often necessary to prefix a
11326 variable name with the address-of operator (``&'') and provide explicit
11327 type information in the command. Here's an example of the type of
11331 (gdb) print 'cygwin1!__argv'
11336 (gdb) x 'cygwin1!__argv'
11337 0x10021610: "\230y\""
11340 And two possible solutions:
11343 (gdb) print ((char **)'cygwin1!__argv')[0]
11344 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
11348 (gdb) x/2x &'cygwin1!__argv'
11349 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
11350 (gdb) x/x 0x10021608
11351 0x10021608: 0x0022fd98
11352 (gdb) x/s 0x0022fd98
11353 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
11356 Setting a break point within a DLL is possible even before the program
11357 starts execution. However, under these circumstances, @value{GDBN} can't
11358 examine the initial instructions of the function in order to skip the
11359 function's frame set-up code. You can work around this by using ``*&''
11360 to set the breakpoint at a raw memory address:
11363 (gdb) break *&'python22!PyOS_Readline'
11364 Breakpoint 1 at 0x1e04eff0
11367 The author of these extensions is not entirely convinced that setting a
11368 break point within a shared DLL like @file{kernel32.dll} is completely
11372 @section Embedded Operating Systems
11374 This section describes configurations involving the debugging of
11375 embedded operating systems that are available for several different
11379 * VxWorks:: Using @value{GDBN} with VxWorks
11382 @value{GDBN} includes the ability to debug programs running on
11383 various real-time operating systems.
11386 @subsection Using @value{GDBN} with VxWorks
11392 @kindex target vxworks
11393 @item target vxworks @var{machinename}
11394 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
11395 is the target system's machine name or IP address.
11399 On VxWorks, @code{load} links @var{filename} dynamically on the
11400 current target system as well as adding its symbols in @value{GDBN}.
11402 @value{GDBN} enables developers to spawn and debug tasks running on networked
11403 VxWorks targets from a Unix host. Already-running tasks spawned from
11404 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
11405 both the Unix host and on the VxWorks target. The program
11406 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
11407 installed with the name @code{vxgdb}, to distinguish it from a
11408 @value{GDBN} for debugging programs on the host itself.)
11411 @item VxWorks-timeout @var{args}
11412 @kindex vxworks-timeout
11413 All VxWorks-based targets now support the option @code{vxworks-timeout}.
11414 This option is set by the user, and @var{args} represents the number of
11415 seconds @value{GDBN} waits for responses to rpc's. You might use this if
11416 your VxWorks target is a slow software simulator or is on the far side
11417 of a thin network line.
11420 The following information on connecting to VxWorks was current when
11421 this manual was produced; newer releases of VxWorks may use revised
11424 @kindex INCLUDE_RDB
11425 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
11426 to include the remote debugging interface routines in the VxWorks
11427 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
11428 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
11429 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
11430 source debugging task @code{tRdbTask} when VxWorks is booted. For more
11431 information on configuring and remaking VxWorks, see the manufacturer's
11433 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
11435 Once you have included @file{rdb.a} in your VxWorks system image and set
11436 your Unix execution search path to find @value{GDBN}, you are ready to
11437 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
11438 @code{vxgdb}, depending on your installation).
11440 @value{GDBN} comes up showing the prompt:
11447 * VxWorks Connection:: Connecting to VxWorks
11448 * VxWorks Download:: VxWorks download
11449 * VxWorks Attach:: Running tasks
11452 @node VxWorks Connection
11453 @subsubsection Connecting to VxWorks
11455 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
11456 network. To connect to a target whose host name is ``@code{tt}'', type:
11459 (vxgdb) target vxworks tt
11463 @value{GDBN} displays messages like these:
11466 Attaching remote machine across net...
11471 @value{GDBN} then attempts to read the symbol tables of any object modules
11472 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
11473 these files by searching the directories listed in the command search
11474 path (@pxref{Environment, ,Your program's environment}); if it fails
11475 to find an object file, it displays a message such as:
11478 prog.o: No such file or directory.
11481 When this happens, add the appropriate directory to the search path with
11482 the @value{GDBN} command @code{path}, and execute the @code{target}
11485 @node VxWorks Download
11486 @subsubsection VxWorks download
11488 @cindex download to VxWorks
11489 If you have connected to the VxWorks target and you want to debug an
11490 object that has not yet been loaded, you can use the @value{GDBN}
11491 @code{load} command to download a file from Unix to VxWorks
11492 incrementally. The object file given as an argument to the @code{load}
11493 command is actually opened twice: first by the VxWorks target in order
11494 to download the code, then by @value{GDBN} in order to read the symbol
11495 table. This can lead to problems if the current working directories on
11496 the two systems differ. If both systems have NFS mounted the same
11497 filesystems, you can avoid these problems by using absolute paths.
11498 Otherwise, it is simplest to set the working directory on both systems
11499 to the directory in which the object file resides, and then to reference
11500 the file by its name, without any path. For instance, a program
11501 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
11502 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
11503 program, type this on VxWorks:
11506 -> cd "@var{vxpath}/vw/demo/rdb"
11510 Then, in @value{GDBN}, type:
11513 (vxgdb) cd @var{hostpath}/vw/demo/rdb
11514 (vxgdb) load prog.o
11517 @value{GDBN} displays a response similar to this:
11520 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
11523 You can also use the @code{load} command to reload an object module
11524 after editing and recompiling the corresponding source file. Note that
11525 this makes @value{GDBN} delete all currently-defined breakpoints,
11526 auto-displays, and convenience variables, and to clear the value
11527 history. (This is necessary in order to preserve the integrity of
11528 debugger's data structures that reference the target system's symbol
11531 @node VxWorks Attach
11532 @subsubsection Running tasks
11534 @cindex running VxWorks tasks
11535 You can also attach to an existing task using the @code{attach} command as
11539 (vxgdb) attach @var{task}
11543 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
11544 or suspended when you attach to it. Running tasks are suspended at
11545 the time of attachment.
11547 @node Embedded Processors
11548 @section Embedded Processors
11550 This section goes into details specific to particular embedded
11556 * H8/300:: Hitachi H8/300
11557 * H8/500:: Hitachi H8/500
11558 * M32R/D:: Mitsubishi M32R/D
11559 * M68K:: Motorola M68K
11560 * MIPS Embedded:: MIPS Embedded
11561 * OpenRISC 1000:: OpenRisc 1000
11562 * PA:: HP PA Embedded
11565 * Sparclet:: Tsqware Sparclet
11566 * Sparclite:: Fujitsu Sparclite
11567 * ST2000:: Tandem ST2000
11568 * Z8000:: Zilog Z8000
11577 @item target rdi @var{dev}
11578 ARM Angel monitor, via RDI library interface to ADP protocol. You may
11579 use this target to communicate with both boards running the Angel
11580 monitor, or with the EmbeddedICE JTAG debug device.
11583 @item target rdp @var{dev}
11589 @subsection Hitachi H8/300
11593 @kindex target hms@r{, with H8/300}
11594 @item target hms @var{dev}
11595 A Hitachi SH, H8/300, or H8/500 board, attached via serial line to your host.
11596 Use special commands @code{device} and @code{speed} to control the serial
11597 line and the communications speed used.
11599 @kindex target e7000@r{, with H8/300}
11600 @item target e7000 @var{dev}
11601 E7000 emulator for Hitachi H8 and SH.
11603 @kindex target sh3@r{, with H8/300}
11604 @kindex target sh3e@r{, with H8/300}
11605 @item target sh3 @var{dev}
11606 @itemx target sh3e @var{dev}
11607 Hitachi SH-3 and SH-3E target systems.
11611 @cindex download to H8/300 or H8/500
11612 @cindex H8/300 or H8/500 download
11613 @cindex download to Hitachi SH
11614 @cindex Hitachi SH download
11615 When you select remote debugging to a Hitachi SH, H8/300, or H8/500
11616 board, the @code{load} command downloads your program to the Hitachi
11617 board and also opens it as the current executable target for
11618 @value{GDBN} on your host (like the @code{file} command).
11620 @value{GDBN} needs to know these things to talk to your
11621 Hitachi SH, H8/300, or H8/500:
11625 that you want to use @samp{target hms}, the remote debugging interface
11626 for Hitachi microprocessors, or @samp{target e7000}, the in-circuit
11627 emulator for the Hitachi SH and the Hitachi 300H. (@samp{target hms} is
11628 the default when @value{GDBN} is configured specifically for the Hitachi SH,
11629 H8/300, or H8/500.)
11632 what serial device connects your host to your Hitachi board (the first
11633 serial device available on your host is the default).
11636 what speed to use over the serial device.
11640 * Hitachi Boards:: Connecting to Hitachi boards.
11641 * Hitachi ICE:: Using the E7000 In-Circuit Emulator.
11642 * Hitachi Special:: Special @value{GDBN} commands for Hitachi micros.
11645 @node Hitachi Boards
11646 @subsubsection Connecting to Hitachi boards
11648 @c only for Unix hosts
11650 @cindex serial device, Hitachi micros
11651 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
11652 need to explicitly set the serial device. The default @var{port} is the
11653 first available port on your host. This is only necessary on Unix
11654 hosts, where it is typically something like @file{/dev/ttya}.
11657 @cindex serial line speed, Hitachi micros
11658 @code{@value{GDBN}} has another special command to set the communications
11659 speed: @samp{speed @var{bps}}. This command also is only used from Unix
11660 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
11661 the DOS @code{mode} command (for instance,
11662 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
11664 The @samp{device} and @samp{speed} commands are available only when you
11665 use a Unix host to debug your Hitachi microprocessor programs. If you
11667 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
11668 called @code{asynctsr} to communicate with the development board
11669 through a PC serial port. You must also use the DOS @code{mode} command
11670 to set up the serial port on the DOS side.
11672 The following sample session illustrates the steps needed to start a
11673 program under @value{GDBN} control on an H8/300. The example uses a
11674 sample H8/300 program called @file{t.x}. The procedure is the same for
11675 the Hitachi SH and the H8/500.
11677 First hook up your development board. In this example, we use a
11678 board attached to serial port @code{COM2}; if you use a different serial
11679 port, substitute its name in the argument of the @code{mode} command.
11680 When you call @code{asynctsr}, the auxiliary comms program used by the
11681 debugger, you give it just the numeric part of the serial port's name;
11682 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
11686 C:\H8300\TEST> asynctsr 2
11687 C:\H8300\TEST> mode com2:9600,n,8,1,p
11689 Resident portion of MODE loaded
11691 COM2: 9600, n, 8, 1, p
11696 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
11697 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
11698 disable it, or even boot without it, to use @code{asynctsr} to control
11699 your development board.
11702 @kindex target hms@r{, and serial protocol}
11703 Now that serial communications are set up, and the development board is
11704 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
11705 the name of your program as the argument. @code{@value{GDBN}} prompts
11706 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
11707 commands to begin your debugging session: @samp{target hms} to specify
11708 cross-debugging to the Hitachi board, and the @code{load} command to
11709 download your program to the board. @code{load} displays the names of
11710 the program's sections, and a @samp{*} for each 2K of data downloaded.
11711 (If you want to refresh @value{GDBN} data on symbols or on the
11712 executable file without downloading, use the @value{GDBN} commands
11713 @code{file} or @code{symbol-file}. These commands, and @code{load}
11714 itself, are described in @ref{Files,,Commands to specify files}.)
11717 (eg-C:\H8300\TEST) @value{GDBP} t.x
11718 @value{GDBN} is free software and you are welcome to distribute copies
11719 of it under certain conditions; type "show copying" to see
11721 There is absolutely no warranty for @value{GDBN}; type "show warranty"
11723 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
11724 (@value{GDBP}) target hms
11725 Connected to remote H8/300 HMS system.
11726 (@value{GDBP}) load t.x
11727 .text : 0x8000 .. 0xabde ***********
11728 .data : 0xabde .. 0xad30 *
11729 .stack : 0xf000 .. 0xf014 *
11732 At this point, you're ready to run or debug your program. From here on,
11733 you can use all the usual @value{GDBN} commands. The @code{break} command
11734 sets breakpoints; the @code{run} command starts your program;
11735 @code{print} or @code{x} display data; the @code{continue} command
11736 resumes execution after stopping at a breakpoint. You can use the
11737 @code{help} command at any time to find out more about @value{GDBN} commands.
11739 Remember, however, that @emph{operating system} facilities aren't
11740 available on your development board; for example, if your program hangs,
11741 you can't send an interrupt---but you can press the @sc{reset} switch!
11743 Use the @sc{reset} button on the development board
11746 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
11747 no way to pass an interrupt signal to the development board); and
11750 to return to the @value{GDBN} command prompt after your program finishes
11751 normally. The communications protocol provides no other way for @value{GDBN}
11752 to detect program completion.
11755 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
11756 development board as a ``normal exit'' of your program.
11759 @subsubsection Using the E7000 in-circuit emulator
11761 @kindex target e7000@r{, with Hitachi ICE}
11762 You can use the E7000 in-circuit emulator to develop code for either the
11763 Hitachi SH or the H8/300H. Use one of these forms of the @samp{target
11764 e7000} command to connect @value{GDBN} to your E7000:
11767 @item target e7000 @var{port} @var{speed}
11768 Use this form if your E7000 is connected to a serial port. The
11769 @var{port} argument identifies what serial port to use (for example,
11770 @samp{com2}). The third argument is the line speed in bits per second
11771 (for example, @samp{9600}).
11773 @item target e7000 @var{hostname}
11774 If your E7000 is installed as a host on a TCP/IP network, you can just
11775 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
11778 @node Hitachi Special
11779 @subsubsection Special @value{GDBN} commands for Hitachi micros
11781 Some @value{GDBN} commands are available only for the H8/300:
11785 @kindex set machine
11786 @kindex show machine
11787 @item set machine h8300
11788 @itemx set machine h8300h
11789 Condition @value{GDBN} for one of the two variants of the H8/300
11790 architecture with @samp{set machine}. You can use @samp{show machine}
11791 to check which variant is currently in effect.
11800 @kindex set memory @var{mod}
11801 @cindex memory models, H8/500
11802 @item set memory @var{mod}
11804 Specify which H8/500 memory model (@var{mod}) you are using with
11805 @samp{set memory}; check which memory model is in effect with @samp{show
11806 memory}. The accepted values for @var{mod} are @code{small},
11807 @code{big}, @code{medium}, and @code{compact}.
11812 @subsection Mitsubishi M32R/D
11816 @kindex target m32r
11817 @item target m32r @var{dev}
11818 Mitsubishi M32R/D ROM monitor.
11825 The Motorola m68k configuration includes ColdFire support, and
11826 target command for the following ROM monitors.
11830 @kindex target abug
11831 @item target abug @var{dev}
11832 ABug ROM monitor for M68K.
11834 @kindex target cpu32bug
11835 @item target cpu32bug @var{dev}
11836 CPU32BUG monitor, running on a CPU32 (M68K) board.
11838 @kindex target dbug
11839 @item target dbug @var{dev}
11840 dBUG ROM monitor for Motorola ColdFire.
11843 @item target est @var{dev}
11844 EST-300 ICE monitor, running on a CPU32 (M68K) board.
11846 @kindex target rom68k
11847 @item target rom68k @var{dev}
11848 ROM 68K monitor, running on an M68K IDP board.
11854 @kindex target rombug
11855 @item target rombug @var{dev}
11856 ROMBUG ROM monitor for OS/9000.
11860 @node MIPS Embedded
11861 @subsection MIPS Embedded
11863 @cindex MIPS boards
11864 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
11865 MIPS board attached to a serial line. This is available when
11866 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
11869 Use these @value{GDBN} commands to specify the connection to your target board:
11872 @item target mips @var{port}
11873 @kindex target mips @var{port}
11874 To run a program on the board, start up @code{@value{GDBP}} with the
11875 name of your program as the argument. To connect to the board, use the
11876 command @samp{target mips @var{port}}, where @var{port} is the name of
11877 the serial port connected to the board. If the program has not already
11878 been downloaded to the board, you may use the @code{load} command to
11879 download it. You can then use all the usual @value{GDBN} commands.
11881 For example, this sequence connects to the target board through a serial
11882 port, and loads and runs a program called @var{prog} through the
11886 host$ @value{GDBP} @var{prog}
11887 @value{GDBN} is free software and @dots{}
11888 (@value{GDBP}) target mips /dev/ttyb
11889 (@value{GDBP}) load @var{prog}
11893 @item target mips @var{hostname}:@var{portnumber}
11894 On some @value{GDBN} host configurations, you can specify a TCP
11895 connection (for instance, to a serial line managed by a terminal
11896 concentrator) instead of a serial port, using the syntax
11897 @samp{@var{hostname}:@var{portnumber}}.
11899 @item target pmon @var{port}
11900 @kindex target pmon @var{port}
11903 @item target ddb @var{port}
11904 @kindex target ddb @var{port}
11905 NEC's DDB variant of PMON for Vr4300.
11907 @item target lsi @var{port}
11908 @kindex target lsi @var{port}
11909 LSI variant of PMON.
11911 @kindex target r3900
11912 @item target r3900 @var{dev}
11913 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
11915 @kindex target array
11916 @item target array @var{dev}
11917 Array Tech LSI33K RAID controller board.
11923 @value{GDBN} also supports these special commands for MIPS targets:
11926 @item set processor @var{args}
11927 @itemx show processor
11928 @kindex set processor @var{args}
11929 @kindex show processor
11930 Use the @code{set processor} command to set the type of MIPS
11931 processor when you want to access processor-type-specific registers.
11932 For example, @code{set processor @var{r3041}} tells @value{GDBN}
11933 to use the CPU registers appropriate for the 3041 chip.
11934 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
11935 is using. Use the @code{info reg} command to see what registers
11936 @value{GDBN} is using.
11938 @item set mipsfpu double
11939 @itemx set mipsfpu single
11940 @itemx set mipsfpu none
11941 @itemx show mipsfpu
11942 @kindex set mipsfpu
11943 @kindex show mipsfpu
11944 @cindex MIPS remote floating point
11945 @cindex floating point, MIPS remote
11946 If your target board does not support the MIPS floating point
11947 coprocessor, you should use the command @samp{set mipsfpu none} (if you
11948 need this, you may wish to put the command in your @value{GDBN} init
11949 file). This tells @value{GDBN} how to find the return value of
11950 functions which return floating point values. It also allows
11951 @value{GDBN} to avoid saving the floating point registers when calling
11952 functions on the board. If you are using a floating point coprocessor
11953 with only single precision floating point support, as on the @sc{r4650}
11954 processor, use the command @samp{set mipsfpu single}. The default
11955 double precision floating point coprocessor may be selected using
11956 @samp{set mipsfpu double}.
11958 In previous versions the only choices were double precision or no
11959 floating point, so @samp{set mipsfpu on} will select double precision
11960 and @samp{set mipsfpu off} will select no floating point.
11962 As usual, you can inquire about the @code{mipsfpu} variable with
11963 @samp{show mipsfpu}.
11965 @item set remotedebug @var{n}
11966 @itemx show remotedebug
11967 @kindex set remotedebug@r{, MIPS protocol}
11968 @kindex show remotedebug@r{, MIPS protocol}
11969 @cindex @code{remotedebug}, MIPS protocol
11970 @cindex MIPS @code{remotedebug} protocol
11971 @c FIXME! For this to be useful, you must know something about the MIPS
11972 @c FIXME...protocol. Where is it described?
11973 You can see some debugging information about communications with the board
11974 by setting the @code{remotedebug} variable. If you set it to @code{1} using
11975 @samp{set remotedebug 1}, every packet is displayed. If you set it
11976 to @code{2}, every character is displayed. You can check the current value
11977 at any time with the command @samp{show remotedebug}.
11979 @item set timeout @var{seconds}
11980 @itemx set retransmit-timeout @var{seconds}
11981 @itemx show timeout
11982 @itemx show retransmit-timeout
11983 @cindex @code{timeout}, MIPS protocol
11984 @cindex @code{retransmit-timeout}, MIPS protocol
11985 @kindex set timeout
11986 @kindex show timeout
11987 @kindex set retransmit-timeout
11988 @kindex show retransmit-timeout
11989 You can control the timeout used while waiting for a packet, in the MIPS
11990 remote protocol, with the @code{set timeout @var{seconds}} command. The
11991 default is 5 seconds. Similarly, you can control the timeout used while
11992 waiting for an acknowledgement of a packet with the @code{set
11993 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
11994 You can inspect both values with @code{show timeout} and @code{show
11995 retransmit-timeout}. (These commands are @emph{only} available when
11996 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
11998 The timeout set by @code{set timeout} does not apply when @value{GDBN}
11999 is waiting for your program to stop. In that case, @value{GDBN} waits
12000 forever because it has no way of knowing how long the program is going
12001 to run before stopping.
12004 @node OpenRISC 1000
12005 @subsection OpenRISC 1000
12006 @cindex OpenRISC 1000
12008 @cindex or1k boards
12009 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12010 about platform and commands.
12014 @kindex target jtag
12015 @item target jtag jtag://@var{host}:@var{port}
12017 Connects to remote JTAG server.
12018 JTAG remote server can be either an or1ksim or JTAG server,
12019 connected via parallel port to the board.
12021 Example: @code{target jtag jtag://localhost:9999}
12024 @item or1ksim @var{command}
12025 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12026 Simulator, proprietary commands can be executed.
12028 @kindex info or1k spr
12029 @item info or1k spr
12030 Displays spr groups.
12032 @item info or1k spr @var{group}
12033 @itemx info or1k spr @var{groupno}
12034 Displays register names in selected group.
12036 @item info or1k spr @var{group} @var{register}
12037 @itemx info or1k spr @var{register}
12038 @itemx info or1k spr @var{groupno} @var{registerno}
12039 @itemx info or1k spr @var{registerno}
12040 Shows information about specified spr register.
12043 @item spr @var{group} @var{register} @var{value}
12044 @itemx spr @var{register @var{value}}
12045 @itemx spr @var{groupno} @var{registerno @var{value}}
12046 @itemx spr @var{registerno @var{value}}
12047 Writes @var{value} to specified spr register.
12050 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12051 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12052 program execution and is thus much faster. Hardware breakpoints/watchpoint
12053 triggers can be set using:
12056 Load effective address/data
12058 Store effective address/data
12060 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12065 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12066 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12068 @code{htrace} commands:
12069 @cindex OpenRISC 1000 htrace
12072 @item hwatch @var{conditional}
12073 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
12074 or Data. For example:
12076 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12078 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12080 @kindex htrace info
12082 Display information about current HW trace configuration.
12084 @kindex htrace trigger
12085 @item htrace trigger @var{conditional}
12086 Set starting criteria for HW trace.
12088 @kindex htrace qualifier
12089 @item htrace qualifier @var{conditional}
12090 Set acquisition qualifier for HW trace.
12092 @kindex htrace stop
12093 @item htrace stop @var{conditional}
12094 Set HW trace stopping criteria.
12096 @kindex htrace record
12097 @item htrace record [@var{data}]*
12098 Selects the data to be recorded, when qualifier is met and HW trace was
12101 @kindex htrace enable
12102 @item htrace enable
12103 @kindex htrace disable
12104 @itemx htrace disable
12105 Enables/disables the HW trace.
12107 @kindex htrace rewind
12108 @item htrace rewind [@var{filename}]
12109 Clears currently recorded trace data.
12111 If filename is specified, new trace file is made and any newly collected data
12112 will be written there.
12114 @kindex htrace print
12115 @item htrace print [@var{start} [@var{len}]]
12116 Prints trace buffer, using current record configuration.
12118 @kindex htrace mode continuous
12119 @item htrace mode continuous
12120 Set continuous trace mode.
12122 @kindex htrace mode suspend
12123 @item htrace mode suspend
12124 Set suspend trace mode.
12129 @subsection PowerPC
12133 @kindex target dink32
12134 @item target dink32 @var{dev}
12135 DINK32 ROM monitor.
12137 @kindex target ppcbug
12138 @item target ppcbug @var{dev}
12139 @kindex target ppcbug1
12140 @item target ppcbug1 @var{dev}
12141 PPCBUG ROM monitor for PowerPC.
12144 @item target sds @var{dev}
12145 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
12150 @subsection HP PA Embedded
12154 @kindex target op50n
12155 @item target op50n @var{dev}
12156 OP50N monitor, running on an OKI HPPA board.
12158 @kindex target w89k
12159 @item target w89k @var{dev}
12160 W89K monitor, running on a Winbond HPPA board.
12165 @subsection Hitachi SH
12169 @kindex target hms@r{, with Hitachi SH}
12170 @item target hms @var{dev}
12171 A Hitachi SH board attached via serial line to your host. Use special
12172 commands @code{device} and @code{speed} to control the serial line and
12173 the communications speed used.
12175 @kindex target e7000@r{, with Hitachi SH}
12176 @item target e7000 @var{dev}
12177 E7000 emulator for Hitachi SH.
12179 @kindex target sh3@r{, with SH}
12180 @kindex target sh3e@r{, with SH}
12181 @item target sh3 @var{dev}
12182 @item target sh3e @var{dev}
12183 Hitachi SH-3 and SH-3E target systems.
12188 @subsection Tsqware Sparclet
12192 @value{GDBN} enables developers to debug tasks running on
12193 Sparclet targets from a Unix host.
12194 @value{GDBN} uses code that runs on
12195 both the Unix host and on the Sparclet target. The program
12196 @code{@value{GDBP}} is installed and executed on the Unix host.
12199 @item remotetimeout @var{args}
12200 @kindex remotetimeout
12201 @value{GDBN} supports the option @code{remotetimeout}.
12202 This option is set by the user, and @var{args} represents the number of
12203 seconds @value{GDBN} waits for responses.
12206 @cindex compiling, on Sparclet
12207 When compiling for debugging, include the options @samp{-g} to get debug
12208 information and @samp{-Ttext} to relocate the program to where you wish to
12209 load it on the target. You may also want to add the options @samp{-n} or
12210 @samp{-N} in order to reduce the size of the sections. Example:
12213 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
12216 You can use @code{objdump} to verify that the addresses are what you intended:
12219 sparclet-aout-objdump --headers --syms prog
12222 @cindex running, on Sparclet
12224 your Unix execution search path to find @value{GDBN}, you are ready to
12225 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
12226 (or @code{sparclet-aout-gdb}, depending on your installation).
12228 @value{GDBN} comes up showing the prompt:
12235 * Sparclet File:: Setting the file to debug
12236 * Sparclet Connection:: Connecting to Sparclet
12237 * Sparclet Download:: Sparclet download
12238 * Sparclet Execution:: Running and debugging
12241 @node Sparclet File
12242 @subsubsection Setting file to debug
12244 The @value{GDBN} command @code{file} lets you choose with program to debug.
12247 (gdbslet) file prog
12251 @value{GDBN} then attempts to read the symbol table of @file{prog}.
12252 @value{GDBN} locates
12253 the file by searching the directories listed in the command search
12255 If the file was compiled with debug information (option "-g"), source
12256 files will be searched as well.
12257 @value{GDBN} locates
12258 the source files by searching the directories listed in the directory search
12259 path (@pxref{Environment, ,Your program's environment}).
12261 to find a file, it displays a message such as:
12264 prog: No such file or directory.
12267 When this happens, add the appropriate directories to the search paths with
12268 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
12269 @code{target} command again.
12271 @node Sparclet Connection
12272 @subsubsection Connecting to Sparclet
12274 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
12275 To connect to a target on serial port ``@code{ttya}'', type:
12278 (gdbslet) target sparclet /dev/ttya
12279 Remote target sparclet connected to /dev/ttya
12280 main () at ../prog.c:3
12284 @value{GDBN} displays messages like these:
12290 @node Sparclet Download
12291 @subsubsection Sparclet download
12293 @cindex download to Sparclet
12294 Once connected to the Sparclet target,
12295 you can use the @value{GDBN}
12296 @code{load} command to download the file from the host to the target.
12297 The file name and load offset should be given as arguments to the @code{load}
12299 Since the file format is aout, the program must be loaded to the starting
12300 address. You can use @code{objdump} to find out what this value is. The load
12301 offset is an offset which is added to the VMA (virtual memory address)
12302 of each of the file's sections.
12303 For instance, if the program
12304 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
12305 and bss at 0x12010170, in @value{GDBN}, type:
12308 (gdbslet) load prog 0x12010000
12309 Loading section .text, size 0xdb0 vma 0x12010000
12312 If the code is loaded at a different address then what the program was linked
12313 to, you may need to use the @code{section} and @code{add-symbol-file} commands
12314 to tell @value{GDBN} where to map the symbol table.
12316 @node Sparclet Execution
12317 @subsubsection Running and debugging
12319 @cindex running and debugging Sparclet programs
12320 You can now begin debugging the task using @value{GDBN}'s execution control
12321 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
12322 manual for the list of commands.
12326 Breakpoint 1 at 0x12010000: file prog.c, line 3.
12328 Starting program: prog
12329 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
12330 3 char *symarg = 0;
12332 4 char *execarg = "hello!";
12337 @subsection Fujitsu Sparclite
12341 @kindex target sparclite
12342 @item target sparclite @var{dev}
12343 Fujitsu sparclite boards, used only for the purpose of loading.
12344 You must use an additional command to debug the program.
12345 For example: target remote @var{dev} using @value{GDBN} standard
12351 @subsection Tandem ST2000
12353 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
12356 To connect your ST2000 to the host system, see the manufacturer's
12357 manual. Once the ST2000 is physically attached, you can run:
12360 target st2000 @var{dev} @var{speed}
12364 to establish it as your debugging environment. @var{dev} is normally
12365 the name of a serial device, such as @file{/dev/ttya}, connected to the
12366 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
12367 connection (for example, to a serial line attached via a terminal
12368 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
12370 The @code{load} and @code{attach} commands are @emph{not} defined for
12371 this target; you must load your program into the ST2000 as you normally
12372 would for standalone operation. @value{GDBN} reads debugging information
12373 (such as symbols) from a separate, debugging version of the program
12374 available on your host computer.
12375 @c FIXME!! This is terribly vague; what little content is here is
12376 @c basically hearsay.
12378 @cindex ST2000 auxiliary commands
12379 These auxiliary @value{GDBN} commands are available to help you with the ST2000
12383 @item st2000 @var{command}
12384 @kindex st2000 @var{cmd}
12385 @cindex STDBUG commands (ST2000)
12386 @cindex commands to STDBUG (ST2000)
12387 Send a @var{command} to the STDBUG monitor. See the manufacturer's
12388 manual for available commands.
12391 @cindex connect (to STDBUG)
12392 Connect the controlling terminal to the STDBUG command monitor. When
12393 you are done interacting with STDBUG, typing either of two character
12394 sequences gets you back to the @value{GDBN} command prompt:
12395 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
12396 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
12400 @subsection Zilog Z8000
12403 @cindex simulator, Z8000
12404 @cindex Zilog Z8000 simulator
12406 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
12409 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
12410 unsegmented variant of the Z8000 architecture) or the Z8001 (the
12411 segmented variant). The simulator recognizes which architecture is
12412 appropriate by inspecting the object code.
12415 @item target sim @var{args}
12417 @kindex target sim@r{, with Z8000}
12418 Debug programs on a simulated CPU. If the simulator supports setup
12419 options, specify them via @var{args}.
12423 After specifying this target, you can debug programs for the simulated
12424 CPU in the same style as programs for your host computer; use the
12425 @code{file} command to load a new program image, the @code{run} command
12426 to run your program, and so on.
12428 As well as making available all the usual machine registers
12429 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
12430 additional items of information as specially named registers:
12435 Counts clock-ticks in the simulator.
12438 Counts instructions run in the simulator.
12441 Execution time in 60ths of a second.
12445 You can refer to these values in @value{GDBN} expressions with the usual
12446 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
12447 conditional breakpoint that suspends only after at least 5000
12448 simulated clock ticks.
12450 @node Architectures
12451 @section Architectures
12453 This section describes characteristics of architectures that affect
12454 all uses of @value{GDBN} with the architecture, both native and cross.
12467 @kindex set rstack_high_address
12468 @cindex AMD 29K register stack
12469 @cindex register stack, AMD29K
12470 @item set rstack_high_address @var{address}
12471 On AMD 29000 family processors, registers are saved in a separate
12472 @dfn{register stack}. There is no way for @value{GDBN} to determine the
12473 extent of this stack. Normally, @value{GDBN} just assumes that the
12474 stack is ``large enough''. This may result in @value{GDBN} referencing
12475 memory locations that do not exist. If necessary, you can get around
12476 this problem by specifying the ending address of the register stack with
12477 the @code{set rstack_high_address} command. The argument should be an
12478 address, which you probably want to precede with @samp{0x} to specify in
12481 @kindex show rstack_high_address
12482 @item show rstack_high_address
12483 Display the current limit of the register stack, on AMD 29000 family
12491 See the following section.
12496 @cindex stack on Alpha
12497 @cindex stack on MIPS
12498 @cindex Alpha stack
12500 Alpha- and MIPS-based computers use an unusual stack frame, which
12501 sometimes requires @value{GDBN} to search backward in the object code to
12502 find the beginning of a function.
12504 @cindex response time, MIPS debugging
12505 To improve response time (especially for embedded applications, where
12506 @value{GDBN} may be restricted to a slow serial line for this search)
12507 you may want to limit the size of this search, using one of these
12511 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
12512 @item set heuristic-fence-post @var{limit}
12513 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
12514 search for the beginning of a function. A value of @var{0} (the
12515 default) means there is no limit. However, except for @var{0}, the
12516 larger the limit the more bytes @code{heuristic-fence-post} must search
12517 and therefore the longer it takes to run.
12519 @item show heuristic-fence-post
12520 Display the current limit.
12524 These commands are available @emph{only} when @value{GDBN} is configured
12525 for debugging programs on Alpha or MIPS processors.
12528 @node Controlling GDB
12529 @chapter Controlling @value{GDBN}
12531 You can alter the way @value{GDBN} interacts with you by using the
12532 @code{set} command. For commands controlling how @value{GDBN} displays
12533 data, see @ref{Print Settings, ,Print settings}. Other settings are
12538 * Editing:: Command editing
12539 * History:: Command history
12540 * Screen Size:: Screen size
12541 * Numbers:: Numbers
12542 * ABI:: Configuring the current ABI
12543 * Messages/Warnings:: Optional warnings and messages
12544 * Debugging Output:: Optional messages about internal happenings
12552 @value{GDBN} indicates its readiness to read a command by printing a string
12553 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
12554 can change the prompt string with the @code{set prompt} command. For
12555 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
12556 the prompt in one of the @value{GDBN} sessions so that you can always tell
12557 which one you are talking to.
12559 @emph{Note:} @code{set prompt} does not add a space for you after the
12560 prompt you set. This allows you to set a prompt which ends in a space
12561 or a prompt that does not.
12565 @item set prompt @var{newprompt}
12566 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
12568 @kindex show prompt
12570 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
12574 @section Command editing
12576 @cindex command line editing
12578 @value{GDBN} reads its input commands via the @dfn{readline} interface. This
12579 @sc{gnu} library provides consistent behavior for programs which provide a
12580 command line interface to the user. Advantages are @sc{gnu} Emacs-style
12581 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
12582 substitution, and a storage and recall of command history across
12583 debugging sessions.
12585 You may control the behavior of command line editing in @value{GDBN} with the
12586 command @code{set}.
12589 @kindex set editing
12592 @itemx set editing on
12593 Enable command line editing (enabled by default).
12595 @item set editing off
12596 Disable command line editing.
12598 @kindex show editing
12600 Show whether command line editing is enabled.
12604 @section Command history
12606 @value{GDBN} can keep track of the commands you type during your
12607 debugging sessions, so that you can be certain of precisely what
12608 happened. Use these commands to manage the @value{GDBN} command
12612 @cindex history substitution
12613 @cindex history file
12614 @kindex set history filename
12615 @kindex GDBHISTFILE
12616 @item set history filename @var{fname}
12617 Set the name of the @value{GDBN} command history file to @var{fname}.
12618 This is the file where @value{GDBN} reads an initial command history
12619 list, and where it writes the command history from this session when it
12620 exits. You can access this list through history expansion or through
12621 the history command editing characters listed below. This file defaults
12622 to the value of the environment variable @code{GDBHISTFILE}, or to
12623 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
12626 @cindex history save
12627 @kindex set history save
12628 @item set history save
12629 @itemx set history save on
12630 Record command history in a file, whose name may be specified with the
12631 @code{set history filename} command. By default, this option is disabled.
12633 @item set history save off
12634 Stop recording command history in a file.
12636 @cindex history size
12637 @kindex set history size
12638 @item set history size @var{size}
12639 Set the number of commands which @value{GDBN} keeps in its history list.
12640 This defaults to the value of the environment variable
12641 @code{HISTSIZE}, or to 256 if this variable is not set.
12644 @cindex history expansion
12645 History expansion assigns special meaning to the character @kbd{!}.
12646 @ifset have-readline-appendices
12647 @xref{Event Designators}.
12650 Since @kbd{!} is also the logical not operator in C, history expansion
12651 is off by default. If you decide to enable history expansion with the
12652 @code{set history expansion on} command, you may sometimes need to
12653 follow @kbd{!} (when it is used as logical not, in an expression) with
12654 a space or a tab to prevent it from being expanded. The readline
12655 history facilities do not attempt substitution on the strings
12656 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
12658 The commands to control history expansion are:
12661 @kindex set history expansion
12662 @item set history expansion on
12663 @itemx set history expansion
12664 Enable history expansion. History expansion is off by default.
12666 @item set history expansion off
12667 Disable history expansion.
12669 The readline code comes with more complete documentation of
12670 editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs
12671 or @code{vi} may wish to read it.
12672 @ifset have-readline-appendices
12673 @xref{Command Line Editing}.
12677 @kindex show history
12679 @itemx show history filename
12680 @itemx show history save
12681 @itemx show history size
12682 @itemx show history expansion
12683 These commands display the state of the @value{GDBN} history parameters.
12684 @code{show history} by itself displays all four states.
12690 @item show commands
12691 Display the last ten commands in the command history.
12693 @item show commands @var{n}
12694 Print ten commands centered on command number @var{n}.
12696 @item show commands +
12697 Print ten commands just after the commands last printed.
12701 @section Screen size
12702 @cindex size of screen
12703 @cindex pauses in output
12705 Certain commands to @value{GDBN} may produce large amounts of
12706 information output to the screen. To help you read all of it,
12707 @value{GDBN} pauses and asks you for input at the end of each page of
12708 output. Type @key{RET} when you want to continue the output, or @kbd{q}
12709 to discard the remaining output. Also, the screen width setting
12710 determines when to wrap lines of output. Depending on what is being
12711 printed, @value{GDBN} tries to break the line at a readable place,
12712 rather than simply letting it overflow onto the following line.
12714 Normally @value{GDBN} knows the size of the screen from the terminal
12715 driver software. For example, on Unix @value{GDBN} uses the termcap data base
12716 together with the value of the @code{TERM} environment variable and the
12717 @code{stty rows} and @code{stty cols} settings. If this is not correct,
12718 you can override it with the @code{set height} and @code{set
12725 @kindex show height
12726 @item set height @var{lpp}
12728 @itemx set width @var{cpl}
12730 These @code{set} commands specify a screen height of @var{lpp} lines and
12731 a screen width of @var{cpl} characters. The associated @code{show}
12732 commands display the current settings.
12734 If you specify a height of zero lines, @value{GDBN} does not pause during
12735 output no matter how long the output is. This is useful if output is to a
12736 file or to an editor buffer.
12738 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
12739 from wrapping its output.
12744 @cindex number representation
12745 @cindex entering numbers
12747 You can always enter numbers in octal, decimal, or hexadecimal in
12748 @value{GDBN} by the usual conventions: octal numbers begin with
12749 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
12750 begin with @samp{0x}. Numbers that begin with none of these are, by
12751 default, entered in base 10; likewise, the default display for
12752 numbers---when no particular format is specified---is base 10. You can
12753 change the default base for both input and output with the @code{set
12757 @kindex set input-radix
12758 @item set input-radix @var{base}
12759 Set the default base for numeric input. Supported choices
12760 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12761 specified either unambiguously or using the current default radix; for
12771 sets the base to decimal. On the other hand, @samp{set radix 10}
12772 leaves the radix unchanged no matter what it was.
12774 @kindex set output-radix
12775 @item set output-radix @var{base}
12776 Set the default base for numeric display. Supported choices
12777 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12778 specified either unambiguously or using the current default radix.
12780 @kindex show input-radix
12781 @item show input-radix
12782 Display the current default base for numeric input.
12784 @kindex show output-radix
12785 @item show output-radix
12786 Display the current default base for numeric display.
12790 @section Configuring the current ABI
12792 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
12793 application automatically. However, sometimes you need to override its
12794 conclusions. Use these commands to manage @value{GDBN}'s view of the
12801 One @value{GDBN} configuration can debug binaries for multiple operating
12802 system targets, either via remote debugging or native emulation.
12803 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
12804 but you can override its conclusion using the @code{set osabi} command.
12805 One example where this is useful is in debugging of binaries which use
12806 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
12807 not have the same identifying marks that the standard C library for your
12812 Show the OS ABI currently in use.
12815 With no argument, show the list of registered available OS ABI's.
12817 @item set osabi @var{abi}
12818 Set the current OS ABI to @var{abi}.
12821 @cindex float promotion
12822 @kindex set coerce-float-to-double
12824 Generally, the way that an argument of type @code{float} is passed to a
12825 function depends on whether the function is prototyped. For a prototyped
12826 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
12827 according to the architecture's convention for @code{float}. For unprototyped
12828 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
12829 @code{double} and then passed.
12831 Unfortunately, some forms of debug information do not reliably indicate whether
12832 a function is prototyped. If @value{GDBN} calls a function that is not marked
12833 as prototyped, it consults @kbd{set coerce-float-to-double}.
12836 @item set coerce-float-to-double
12837 @itemx set coerce-float-to-double on
12838 Arguments of type @code{float} will be promoted to @code{double} when passed
12839 to an unprototyped function. This is the default setting.
12841 @item set coerce-float-to-double off
12842 Arguments of type @code{float} will be passed directly to unprototyped
12847 @kindex show cp-abi
12848 @value{GDBN} needs to know the ABI used for your program's C@t{++}
12849 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
12850 used to build your application. @value{GDBN} only fully supports
12851 programs with a single C@t{++} ABI; if your program contains code using
12852 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
12853 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
12854 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
12855 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
12856 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
12857 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
12862 Show the C@t{++} ABI currently in use.
12865 With no argument, show the list of supported C@t{++} ABI's.
12867 @item set cp-abi @var{abi}
12868 @itemx set cp-abi auto
12869 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
12872 @node Messages/Warnings
12873 @section Optional warnings and messages
12875 By default, @value{GDBN} is silent about its inner workings. If you are
12876 running on a slow machine, you may want to use the @code{set verbose}
12877 command. This makes @value{GDBN} tell you when it does a lengthy
12878 internal operation, so you will not think it has crashed.
12880 Currently, the messages controlled by @code{set verbose} are those
12881 which announce that the symbol table for a source file is being read;
12882 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
12885 @kindex set verbose
12886 @item set verbose on
12887 Enables @value{GDBN} output of certain informational messages.
12889 @item set verbose off
12890 Disables @value{GDBN} output of certain informational messages.
12892 @kindex show verbose
12894 Displays whether @code{set verbose} is on or off.
12897 By default, if @value{GDBN} encounters bugs in the symbol table of an
12898 object file, it is silent; but if you are debugging a compiler, you may
12899 find this information useful (@pxref{Symbol Errors, ,Errors reading
12904 @kindex set complaints
12905 @item set complaints @var{limit}
12906 Permits @value{GDBN} to output @var{limit} complaints about each type of
12907 unusual symbols before becoming silent about the problem. Set
12908 @var{limit} to zero to suppress all complaints; set it to a large number
12909 to prevent complaints from being suppressed.
12911 @kindex show complaints
12912 @item show complaints
12913 Displays how many symbol complaints @value{GDBN} is permitted to produce.
12917 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
12918 lot of stupid questions to confirm certain commands. For example, if
12919 you try to run a program which is already running:
12923 The program being debugged has been started already.
12924 Start it from the beginning? (y or n)
12927 If you are willing to unflinchingly face the consequences of your own
12928 commands, you can disable this ``feature'':
12932 @kindex set confirm
12934 @cindex confirmation
12935 @cindex stupid questions
12936 @item set confirm off
12937 Disables confirmation requests.
12939 @item set confirm on
12940 Enables confirmation requests (the default).
12942 @kindex show confirm
12944 Displays state of confirmation requests.
12948 @node Debugging Output
12949 @section Optional messages about internal happenings
12951 @kindex set debug arch
12952 @item set debug arch
12953 Turns on or off display of gdbarch debugging info. The default is off
12954 @kindex show debug arch
12955 @item show debug arch
12956 Displays the current state of displaying gdbarch debugging info.
12957 @kindex set debug event
12958 @item set debug event
12959 Turns on or off display of @value{GDBN} event debugging info. The
12961 @kindex show debug event
12962 @item show debug event
12963 Displays the current state of displaying @value{GDBN} event debugging
12965 @kindex set debug expression
12966 @item set debug expression
12967 Turns on or off display of @value{GDBN} expression debugging info. The
12969 @kindex show debug expression
12970 @item show debug expression
12971 Displays the current state of displaying @value{GDBN} expression
12973 @kindex set debug frame
12974 @item set debug frame
12975 Turns on or off display of @value{GDBN} frame debugging info. The
12977 @kindex show debug frame
12978 @item show debug frame
12979 Displays the current state of displaying @value{GDBN} frame debugging
12981 @kindex set debug overload
12982 @item set debug overload
12983 Turns on or off display of @value{GDBN} C@t{++} overload debugging
12984 info. This includes info such as ranking of functions, etc. The default
12986 @kindex show debug overload
12987 @item show debug overload
12988 Displays the current state of displaying @value{GDBN} C@t{++} overload
12990 @kindex set debug remote
12991 @cindex packets, reporting on stdout
12992 @cindex serial connections, debugging
12993 @item set debug remote
12994 Turns on or off display of reports on all packets sent back and forth across
12995 the serial line to the remote machine. The info is printed on the
12996 @value{GDBN} standard output stream. The default is off.
12997 @kindex show debug remote
12998 @item show debug remote
12999 Displays the state of display of remote packets.
13000 @kindex set debug serial
13001 @item set debug serial
13002 Turns on or off display of @value{GDBN} serial debugging info. The
13004 @kindex show debug serial
13005 @item show debug serial
13006 Displays the current state of displaying @value{GDBN} serial debugging
13008 @kindex set debug target
13009 @item set debug target
13010 Turns on or off display of @value{GDBN} target debugging info. This info
13011 includes what is going on at the target level of GDB, as it happens. The
13013 @kindex show debug target
13014 @item show debug target
13015 Displays the current state of displaying @value{GDBN} target debugging
13017 @kindex set debug varobj
13018 @item set debug varobj
13019 Turns on or off display of @value{GDBN} variable object debugging
13020 info. The default is off.
13021 @kindex show debug varobj
13022 @item show debug varobj
13023 Displays the current state of displaying @value{GDBN} variable object
13028 @chapter Canned Sequences of Commands
13030 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13031 command lists}), @value{GDBN} provides two ways to store sequences of
13032 commands for execution as a unit: user-defined commands and command
13036 * Define:: User-defined commands
13037 * Hooks:: User-defined command hooks
13038 * Command Files:: Command files
13039 * Output:: Commands for controlled output
13043 @section User-defined commands
13045 @cindex user-defined command
13046 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13047 which you assign a new name as a command. This is done with the
13048 @code{define} command. User commands may accept up to 10 arguments
13049 separated by whitespace. Arguments are accessed within the user command
13050 via @var{$arg0@dots{}$arg9}. A trivial example:
13054 print $arg0 + $arg1 + $arg2
13058 To execute the command use:
13065 This defines the command @code{adder}, which prints the sum of
13066 its three arguments. Note the arguments are text substitutions, so they may
13067 reference variables, use complex expressions, or even perform inferior
13073 @item define @var{commandname}
13074 Define a command named @var{commandname}. If there is already a command
13075 by that name, you are asked to confirm that you want to redefine it.
13077 The definition of the command is made up of other @value{GDBN} command lines,
13078 which are given following the @code{define} command. The end of these
13079 commands is marked by a line containing @code{end}.
13084 Takes a single argument, which is an expression to evaluate.
13085 It is followed by a series of commands that are executed
13086 only if the expression is true (nonzero).
13087 There can then optionally be a line @code{else}, followed
13088 by a series of commands that are only executed if the expression
13089 was false. The end of the list is marked by a line containing @code{end}.
13093 The syntax is similar to @code{if}: the command takes a single argument,
13094 which is an expression to evaluate, and must be followed by the commands to
13095 execute, one per line, terminated by an @code{end}.
13096 The commands are executed repeatedly as long as the expression
13100 @item document @var{commandname}
13101 Document the user-defined command @var{commandname}, so that it can be
13102 accessed by @code{help}. The command @var{commandname} must already be
13103 defined. This command reads lines of documentation just as @code{define}
13104 reads the lines of the command definition, ending with @code{end}.
13105 After the @code{document} command is finished, @code{help} on command
13106 @var{commandname} displays the documentation you have written.
13108 You may use the @code{document} command again to change the
13109 documentation of a command. Redefining the command with @code{define}
13110 does not change the documentation.
13112 @kindex help user-defined
13113 @item help user-defined
13114 List all user-defined commands, with the first line of the documentation
13119 @itemx show user @var{commandname}
13120 Display the @value{GDBN} commands used to define @var{commandname} (but
13121 not its documentation). If no @var{commandname} is given, display the
13122 definitions for all user-defined commands.
13124 @kindex show max-user-call-depth
13125 @kindex set max-user-call-depth
13126 @item show max-user-call-depth
13127 @itemx set max-user-call-depth
13128 The value of @code{max-user-call-depth} controls how many recursion
13129 levels are allowed in user-defined commands before GDB suspects an
13130 infinite recursion and aborts the command.
13134 When user-defined commands are executed, the
13135 commands of the definition are not printed. An error in any command
13136 stops execution of the user-defined command.
13138 If used interactively, commands that would ask for confirmation proceed
13139 without asking when used inside a user-defined command. Many @value{GDBN}
13140 commands that normally print messages to say what they are doing omit the
13141 messages when used in a user-defined command.
13144 @section User-defined command hooks
13145 @cindex command hooks
13146 @cindex hooks, for commands
13147 @cindex hooks, pre-command
13151 You may define @dfn{hooks}, which are a special kind of user-defined
13152 command. Whenever you run the command @samp{foo}, if the user-defined
13153 command @samp{hook-foo} exists, it is executed (with no arguments)
13154 before that command.
13156 @cindex hooks, post-command
13159 A hook may also be defined which is run after the command you executed.
13160 Whenever you run the command @samp{foo}, if the user-defined command
13161 @samp{hookpost-foo} exists, it is executed (with no arguments) after
13162 that command. Post-execution hooks may exist simultaneously with
13163 pre-execution hooks, for the same command.
13165 It is valid for a hook to call the command which it hooks. If this
13166 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
13168 @c It would be nice if hookpost could be passed a parameter indicating
13169 @c if the command it hooks executed properly or not. FIXME!
13171 @kindex stop@r{, a pseudo-command}
13172 In addition, a pseudo-command, @samp{stop} exists. Defining
13173 (@samp{hook-stop}) makes the associated commands execute every time
13174 execution stops in your program: before breakpoint commands are run,
13175 displays are printed, or the stack frame is printed.
13177 For example, to ignore @code{SIGALRM} signals while
13178 single-stepping, but treat them normally during normal execution,
13183 handle SIGALRM nopass
13187 handle SIGALRM pass
13190 define hook-continue
13191 handle SIGLARM pass
13195 As a further example, to hook at the begining and end of the @code{echo}
13196 command, and to add extra text to the beginning and end of the message,
13204 define hookpost-echo
13208 (@value{GDBP}) echo Hello World
13209 <<<---Hello World--->>>
13214 You can define a hook for any single-word command in @value{GDBN}, but
13215 not for command aliases; you should define a hook for the basic command
13216 name, e.g. @code{backtrace} rather than @code{bt}.
13217 @c FIXME! So how does Joe User discover whether a command is an alias
13219 If an error occurs during the execution of your hook, execution of
13220 @value{GDBN} commands stops and @value{GDBN} issues a prompt
13221 (before the command that you actually typed had a chance to run).
13223 If you try to define a hook which does not match any known command, you
13224 get a warning from the @code{define} command.
13226 @node Command Files
13227 @section Command files
13229 @cindex command files
13230 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
13231 commands. Comments (lines starting with @kbd{#}) may also be included.
13232 An empty line in a command file does nothing; it does not mean to repeat
13233 the last command, as it would from the terminal.
13236 @cindex @file{.gdbinit}
13237 @cindex @file{gdb.ini}
13238 When you start @value{GDBN}, it automatically executes commands from its
13239 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
13240 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
13241 limitations of file names imposed by DOS filesystems.}.
13242 During startup, @value{GDBN} does the following:
13246 Reads the init file (if any) in your home directory@footnote{On
13247 DOS/Windows systems, the home directory is the one pointed to by the
13248 @code{HOME} environment variable.}.
13251 Processes command line options and operands.
13254 Reads the init file (if any) in the current working directory.
13257 Reads command files specified by the @samp{-x} option.
13260 The init file in your home directory can set options (such as @samp{set
13261 complaints}) that affect subsequent processing of command line options
13262 and operands. Init files are not executed if you use the @samp{-nx}
13263 option (@pxref{Mode Options, ,Choosing modes}).
13265 @cindex init file name
13266 On some configurations of @value{GDBN}, the init file is known by a
13267 different name (these are typically environments where a specialized
13268 form of @value{GDBN} may need to coexist with other forms, hence a
13269 different name for the specialized version's init file). These are the
13270 environments with special init file names:
13272 @cindex @file{.vxgdbinit}
13275 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
13277 @cindex @file{.os68gdbinit}
13279 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
13281 @cindex @file{.esgdbinit}
13283 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
13286 You can also request the execution of a command file with the
13287 @code{source} command:
13291 @item source @var{filename}
13292 Execute the command file @var{filename}.
13295 The lines in a command file are executed sequentially. They are not
13296 printed as they are executed. An error in any command terminates
13297 execution of the command file and control is returned to the console.
13299 Commands that would ask for confirmation if used interactively proceed
13300 without asking when used in a command file. Many @value{GDBN} commands that
13301 normally print messages to say what they are doing omit the messages
13302 when called from command files.
13304 @value{GDBN} also accepts command input from standard input. In this
13305 mode, normal output goes to standard output and error output goes to
13306 standard error. Errors in a command file supplied on standard input do
13307 not terminate execution of the command file --- execution continues with
13311 gdb < cmds > log 2>&1
13314 (The syntax above will vary depending on the shell used.) This example
13315 will execute commands from the file @file{cmds}. All output and errors
13316 would be directed to @file{log}.
13319 @section Commands for controlled output
13321 During the execution of a command file or a user-defined command, normal
13322 @value{GDBN} output is suppressed; the only output that appears is what is
13323 explicitly printed by the commands in the definition. This section
13324 describes three commands useful for generating exactly the output you
13329 @item echo @var{text}
13330 @c I do not consider backslash-space a standard C escape sequence
13331 @c because it is not in ANSI.
13332 Print @var{text}. Nonprinting characters can be included in
13333 @var{text} using C escape sequences, such as @samp{\n} to print a
13334 newline. @strong{No newline is printed unless you specify one.}
13335 In addition to the standard C escape sequences, a backslash followed
13336 by a space stands for a space. This is useful for displaying a
13337 string with spaces at the beginning or the end, since leading and
13338 trailing spaces are otherwise trimmed from all arguments.
13339 To print @samp{@w{ }and foo =@w{ }}, use the command
13340 @samp{echo \@w{ }and foo = \@w{ }}.
13342 A backslash at the end of @var{text} can be used, as in C, to continue
13343 the command onto subsequent lines. For example,
13346 echo This is some text\n\
13347 which is continued\n\
13348 onto several lines.\n
13351 produces the same output as
13354 echo This is some text\n
13355 echo which is continued\n
13356 echo onto several lines.\n
13360 @item output @var{expression}
13361 Print the value of @var{expression} and nothing but that value: no
13362 newlines, no @samp{$@var{nn} = }. The value is not entered in the
13363 value history either. @xref{Expressions, ,Expressions}, for more information
13366 @item output/@var{fmt} @var{expression}
13367 Print the value of @var{expression} in format @var{fmt}. You can use
13368 the same formats as for @code{print}. @xref{Output Formats,,Output
13369 formats}, for more information.
13372 @item printf @var{string}, @var{expressions}@dots{}
13373 Print the values of the @var{expressions} under the control of
13374 @var{string}. The @var{expressions} are separated by commas and may be
13375 either numbers or pointers. Their values are printed as specified by
13376 @var{string}, exactly as if your program were to execute the C
13378 @c FIXME: the above implies that at least all ANSI C formats are
13379 @c supported, but it isn't true: %E and %G don't work (or so it seems).
13380 @c Either this is a bug, or the manual should document what formats are
13384 printf (@var{string}, @var{expressions}@dots{});
13387 For example, you can print two values in hex like this:
13390 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
13393 The only backslash-escape sequences that you can use in the format
13394 string are the simple ones that consist of backslash followed by a
13399 @chapter Command Interpreters
13400 @cindex command interpreters
13402 @value{GDBN} supports multiple command interpreters, and some command
13403 infrastructure to allow users or user interface writers to switch
13404 between interpreters or run commands in other interpreters.
13406 @value{GDBN} currently supports two command interpreters, the console
13407 interpreter (sometimes called the command-line interpreter or @sc{cli})
13408 and the machine interface interpreter (or @sc{gdb/mi}). This manual
13409 describes both of these interfaces in great detail.
13411 By default, @value{GDBN} will start with the console interpreter.
13412 However, the user may choose to start @value{GDBN} with another
13413 interpreter by specifying the @option{-i} or @option{--interpreter}
13414 startup options. Defined interpreters include:
13418 @cindex console interpreter
13419 The traditional console or command-line interpreter. This is the most often
13420 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
13421 @value{GDBN} will use this interpreter.
13424 @cindex mi interpreter
13425 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
13426 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
13427 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
13431 @cindex mi2 interpreter
13432 The current @sc{gdb/mi} interface.
13435 @cindex mi1 interpreter
13436 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
13440 @cindex invoke another interpreter
13441 The interpreter being used by @value{GDBN} may not be dynamically
13442 switched at runtime. Although possible, this could lead to a very
13443 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
13444 enters the command "interpreter-set console" in a console view,
13445 @value{GDBN} would switch to using the console interpreter, rendering
13446 the IDE inoperable!
13448 @kindex interpreter-exec
13449 Although you may only choose a single interpreter at startup, you may execute
13450 commands in any interpreter from the current interpreter using the appropriate
13451 command. If you are running the console interpreter, simply use the
13452 @code{interpreter-exec} command:
13455 interpreter-exec mi "-data-list-register-names"
13458 @sc{gdb/mi} has a similar command, although it is only available in versions of
13459 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
13462 @chapter @value{GDBN} Text User Interface
13466 * TUI Overview:: TUI overview
13467 * TUI Keys:: TUI key bindings
13468 * TUI Single Key Mode:: TUI single key mode
13469 * TUI Commands:: TUI specific commands
13470 * TUI Configuration:: TUI configuration variables
13473 The @value{GDBN} Text User Interface, TUI in short,
13474 is a terminal interface which uses the @code{curses} library
13475 to show the source file, the assembly output, the program registers
13476 and @value{GDBN} commands in separate text windows.
13477 The TUI is available only when @value{GDBN} is configured
13478 with the @code{--enable-tui} configure option (@pxref{Configure Options}).
13481 @section TUI overview
13483 The TUI has two display modes that can be switched while
13488 A curses (or TUI) mode in which it displays several text
13489 windows on the terminal.
13492 A standard mode which corresponds to the @value{GDBN} configured without
13496 In the TUI mode, @value{GDBN} can display several text window
13501 This window is the @value{GDBN} command window with the @value{GDBN}
13502 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
13503 managed using readline but through the TUI. The @emph{command}
13504 window is always visible.
13507 The source window shows the source file of the program. The current
13508 line as well as active breakpoints are displayed in this window.
13511 The assembly window shows the disassembly output of the program.
13514 This window shows the processor registers. It detects when
13515 a register is changed and when this is the case, registers that have
13516 changed are highlighted.
13520 The source and assembly windows show the current program position
13521 by highlighting the current line and marking them with the @samp{>} marker.
13522 Breakpoints are also indicated with two markers. A first one
13523 indicates the breakpoint type:
13527 Breakpoint which was hit at least once.
13530 Breakpoint which was never hit.
13533 Hardware breakpoint which was hit at least once.
13536 Hardware breakpoint which was never hit.
13540 The second marker indicates whether the breakpoint is enabled or not:
13544 Breakpoint is enabled.
13547 Breakpoint is disabled.
13551 The source, assembly and register windows are attached to the thread
13552 and the frame position. They are updated when the current thread
13553 changes, when the frame changes or when the program counter changes.
13554 These three windows are arranged by the TUI according to several
13555 layouts. The layout defines which of these three windows are visible.
13556 The following layouts are available:
13566 source and assembly
13569 source and registers
13572 assembly and registers
13576 On top of the command window a status line gives various information
13577 concerning the current process begin debugged. The status line is
13578 updated when the information it shows changes. The following fields
13583 Indicates the current gdb target
13584 (@pxref{Targets, ,Specifying a Debugging Target}).
13587 Gives information about the current process or thread number.
13588 When no process is being debugged, this field is set to @code{No process}.
13591 Gives the current function name for the selected frame.
13592 The name is demangled if demangling is turned on (@pxref{Print Settings}).
13593 When there is no symbol corresponding to the current program counter
13594 the string @code{??} is displayed.
13597 Indicates the current line number for the selected frame.
13598 When the current line number is not known the string @code{??} is displayed.
13601 Indicates the current program counter address.
13606 @section TUI Key Bindings
13607 @cindex TUI key bindings
13609 The TUI installs several key bindings in the readline keymaps
13610 (@pxref{Command Line Editing}).
13611 They allow to leave or enter in the TUI mode or they operate
13612 directly on the TUI layout and windows. The TUI also provides
13613 a @emph{SingleKey} keymap which binds several keys directly to
13614 @value{GDBN} commands. The following key bindings
13615 are installed for both TUI mode and the @value{GDBN} standard mode.
13624 Enter or leave the TUI mode. When the TUI mode is left,
13625 the curses window management is left and @value{GDBN} operates using
13626 its standard mode writing on the terminal directly. When the TUI
13627 mode is entered, the control is given back to the curses windows.
13628 The screen is then refreshed.
13632 Use a TUI layout with only one window. The layout will
13633 either be @samp{source} or @samp{assembly}. When the TUI mode
13634 is not active, it will switch to the TUI mode.
13636 Think of this key binding as the Emacs @kbd{C-x 1} binding.
13640 Use a TUI layout with at least two windows. When the current
13641 layout shows already two windows, a next layout with two windows is used.
13642 When a new layout is chosen, one window will always be common to the
13643 previous layout and the new one.
13645 Think of it as the Emacs @kbd{C-x 2} binding.
13649 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
13650 (@pxref{TUI Single Key Mode}).
13654 The following key bindings are handled only by the TUI mode:
13659 Scroll the active window one page up.
13663 Scroll the active window one page down.
13667 Scroll the active window one line up.
13671 Scroll the active window one line down.
13675 Scroll the active window one column left.
13679 Scroll the active window one column right.
13683 Refresh the screen.
13687 In the TUI mode, the arrow keys are used by the active window
13688 for scrolling. This means they are not available for readline. It is
13689 necessary to use other readline key bindings such as @key{C-p}, @key{C-n},
13690 @key{C-b} and @key{C-f}.
13692 @node TUI Single Key Mode
13693 @section TUI Single Key Mode
13694 @cindex TUI single key mode
13696 The TUI provides a @emph{SingleKey} mode in which it installs a particular
13697 key binding in the readline keymaps to connect single keys to
13701 @kindex c @r{(SingleKey TUI key)}
13705 @kindex d @r{(SingleKey TUI key)}
13709 @kindex f @r{(SingleKey TUI key)}
13713 @kindex n @r{(SingleKey TUI key)}
13717 @kindex q @r{(SingleKey TUI key)}
13719 exit the @emph{SingleKey} mode.
13721 @kindex r @r{(SingleKey TUI key)}
13725 @kindex s @r{(SingleKey TUI key)}
13729 @kindex u @r{(SingleKey TUI key)}
13733 @kindex v @r{(SingleKey TUI key)}
13737 @kindex w @r{(SingleKey TUI key)}
13743 Other keys temporarily switch to the @value{GDBN} command prompt.
13744 The key that was pressed is inserted in the editing buffer so that
13745 it is possible to type most @value{GDBN} commands without interaction
13746 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
13747 @emph{SingleKey} mode is restored. The only way to permanently leave
13748 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
13752 @section TUI specific commands
13753 @cindex TUI commands
13755 The TUI has specific commands to control the text windows.
13756 These commands are always available, that is they do not depend on
13757 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
13758 is in the standard mode, using these commands will automatically switch
13764 List and give the size of all displayed windows.
13767 @kindex layout next
13768 Display the next layout.
13771 @kindex layout prev
13772 Display the previous layout.
13776 Display the source window only.
13780 Display the assembly window only.
13783 @kindex layout split
13784 Display the source and assembly window.
13787 @kindex layout regs
13788 Display the register window together with the source or assembly window.
13790 @item focus next | prev | src | asm | regs | split
13792 Set the focus to the named window.
13793 This command allows to change the active window so that scrolling keys
13794 can be affected to another window.
13798 Refresh the screen. This is similar to using @key{C-L} key.
13802 Update the source window and the current execution point.
13804 @item winheight @var{name} +@var{count}
13805 @itemx winheight @var{name} -@var{count}
13807 Change the height of the window @var{name} by @var{count}
13808 lines. Positive counts increase the height, while negative counts
13813 @node TUI Configuration
13814 @section TUI configuration variables
13815 @cindex TUI configuration variables
13817 The TUI has several configuration variables that control the
13818 appearance of windows on the terminal.
13821 @item set tui border-kind @var{kind}
13822 @kindex set tui border-kind
13823 Select the border appearance for the source, assembly and register windows.
13824 The possible values are the following:
13827 Use a space character to draw the border.
13830 Use ascii characters + - and | to draw the border.
13833 Use the Alternate Character Set to draw the border. The border is
13834 drawn using character line graphics if the terminal supports them.
13838 @item set tui active-border-mode @var{mode}
13839 @kindex set tui active-border-mode
13840 Select the attributes to display the border of the active window.
13841 The possible values are @code{normal}, @code{standout}, @code{reverse},
13842 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
13844 @item set tui border-mode @var{mode}
13845 @kindex set tui border-mode
13846 Select the attributes to display the border of other windows.
13847 The @var{mode} can be one of the following:
13850 Use normal attributes to display the border.
13856 Use reverse video mode.
13859 Use half bright mode.
13861 @item half-standout
13862 Use half bright and standout mode.
13865 Use extra bright or bold mode.
13867 @item bold-standout
13868 Use extra bright or bold and standout mode.
13875 @chapter Using @value{GDBN} under @sc{gnu} Emacs
13878 @cindex @sc{gnu} Emacs
13879 A special interface allows you to use @sc{gnu} Emacs to view (and
13880 edit) the source files for the program you are debugging with
13883 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
13884 executable file you want to debug as an argument. This command starts
13885 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
13886 created Emacs buffer.
13887 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
13889 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
13894 All ``terminal'' input and output goes through the Emacs buffer.
13897 This applies both to @value{GDBN} commands and their output, and to the input
13898 and output done by the program you are debugging.
13900 This is useful because it means that you can copy the text of previous
13901 commands and input them again; you can even use parts of the output
13904 All the facilities of Emacs' Shell mode are available for interacting
13905 with your program. In particular, you can send signals the usual
13906 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
13911 @value{GDBN} displays source code through Emacs.
13914 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
13915 source file for that frame and puts an arrow (@samp{=>}) at the
13916 left margin of the current line. Emacs uses a separate buffer for
13917 source display, and splits the screen to show both your @value{GDBN} session
13920 Explicit @value{GDBN} @code{list} or search commands still produce output as
13921 usual, but you probably have no reason to use them from Emacs.
13924 @emph{Warning:} If the directory where your program resides is not your
13925 current directory, it can be easy to confuse Emacs about the location of
13926 the source files, in which case the auxiliary display buffer does not
13927 appear to show your source. @value{GDBN} can find programs by searching your
13928 environment's @code{PATH} variable, so the @value{GDBN} input and output
13929 session proceeds normally; but Emacs does not get enough information
13930 back from @value{GDBN} to locate the source files in this situation. To
13931 avoid this problem, either start @value{GDBN} mode from the directory where
13932 your program resides, or specify an absolute file name when prompted for the
13933 @kbd{M-x gdb} argument.
13935 A similar confusion can result if you use the @value{GDBN} @code{file} command to
13936 switch to debugging a program in some other location, from an existing
13937 @value{GDBN} buffer in Emacs.
13940 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If
13941 you need to call @value{GDBN} by a different name (for example, if you keep
13942 several configurations around, with different names) you can set the
13943 Emacs variable @code{gdb-command-name}; for example,
13946 (setq gdb-command-name "mygdb")
13950 (preceded by @kbd{M-:} or @kbd{ESC :}, or typed in the @code{*scratch*} buffer, or
13951 in your @file{.emacs} file) makes Emacs call the program named
13952 ``@code{mygdb}'' instead.
13954 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
13955 addition to the standard Shell mode commands:
13959 Describe the features of Emacs' @value{GDBN} Mode.
13962 Execute to another source line, like the @value{GDBN} @code{step} command; also
13963 update the display window to show the current file and location.
13966 Execute to next source line in this function, skipping all function
13967 calls, like the @value{GDBN} @code{next} command. Then update the display window
13968 to show the current file and location.
13971 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
13972 display window accordingly.
13974 @item M-x gdb-nexti
13975 Execute to next instruction, using the @value{GDBN} @code{nexti} command; update
13976 display window accordingly.
13979 Execute until exit from the selected stack frame, like the @value{GDBN}
13980 @code{finish} command.
13983 Continue execution of your program, like the @value{GDBN} @code{continue}
13986 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}.
13989 Go up the number of frames indicated by the numeric argument
13990 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
13991 like the @value{GDBN} @code{up} command.
13993 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-u}.
13996 Go down the number of frames indicated by the numeric argument, like the
13997 @value{GDBN} @code{down} command.
13999 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-d}.
14002 Read the number where the cursor is positioned, and insert it at the end
14003 of the @value{GDBN} I/O buffer. For example, if you wish to disassemble code
14004 around an address that was displayed earlier, type @kbd{disassemble};
14005 then move the cursor to the address display, and pick up the
14006 argument for @code{disassemble} by typing @kbd{C-x &}.
14008 You can customize this further by defining elements of the list
14009 @code{gdb-print-command}; once it is defined, you can format or
14010 otherwise process numbers picked up by @kbd{C-x &} before they are
14011 inserted. A numeric argument to @kbd{C-x &} indicates that you
14012 wish special formatting, and also acts as an index to pick an element of the
14013 list. If the list element is a string, the number to be inserted is
14014 formatted using the Emacs function @code{format}; otherwise the number
14015 is passed as an argument to the corresponding list element.
14018 In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break})
14019 tells @value{GDBN} to set a breakpoint on the source line point is on.
14021 If you accidentally delete the source-display buffer, an easy way to get
14022 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14023 request a frame display; when you run under Emacs, this recreates
14024 the source buffer if necessary to show you the context of the current
14027 The source files displayed in Emacs are in ordinary Emacs buffers
14028 which are visiting the source files in the usual way. You can edit
14029 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14030 communicates with Emacs in terms of line numbers. If you add or
14031 delete lines from the text, the line numbers that @value{GDBN} knows cease
14032 to correspond properly with the code.
14034 @c The following dropped because Epoch is nonstandard. Reactivate
14035 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14037 @kindex Emacs Epoch environment
14041 Version 18 of @sc{gnu} Emacs has a built-in window system
14042 called the @code{epoch}
14043 environment. Users of this environment can use a new command,
14044 @code{inspect} which performs identically to @code{print} except that
14045 each value is printed in its own window.
14050 @chapter The @sc{gdb/mi} Interface
14052 @unnumberedsec Function and Purpose
14054 @cindex @sc{gdb/mi}, its purpose
14055 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
14056 specifically intended to support the development of systems which use
14057 the debugger as just one small component of a larger system.
14059 This chapter is a specification of the @sc{gdb/mi} interface. It is written
14060 in the form of a reference manual.
14062 Note that @sc{gdb/mi} is still under construction, so some of the
14063 features described below are incomplete and subject to change.
14065 @unnumberedsec Notation and Terminology
14067 @cindex notational conventions, for @sc{gdb/mi}
14068 This chapter uses the following notation:
14072 @code{|} separates two alternatives.
14075 @code{[ @var{something} ]} indicates that @var{something} is optional:
14076 it may or may not be given.
14079 @code{( @var{group} )*} means that @var{group} inside the parentheses
14080 may repeat zero or more times.
14083 @code{( @var{group} )+} means that @var{group} inside the parentheses
14084 may repeat one or more times.
14087 @code{"@var{string}"} means a literal @var{string}.
14091 @heading Dependencies
14094 @heading Acknowledgments
14096 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
14100 * GDB/MI Command Syntax::
14101 * GDB/MI Compatibility with CLI::
14102 * GDB/MI Output Records::
14103 * GDB/MI Command Description Format::
14104 * GDB/MI Breakpoint Table Commands::
14105 * GDB/MI Data Manipulation::
14106 * GDB/MI Program Control::
14107 * GDB/MI Miscellaneous Commands::
14109 * GDB/MI Kod Commands::
14110 * GDB/MI Memory Overlay Commands::
14111 * GDB/MI Signal Handling Commands::
14113 * GDB/MI Stack Manipulation::
14114 * GDB/MI Symbol Query::
14115 * GDB/MI Target Manipulation::
14116 * GDB/MI Thread Commands::
14117 * GDB/MI Tracepoint Commands::
14118 * GDB/MI Variable Objects::
14121 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14122 @node GDB/MI Command Syntax
14123 @section @sc{gdb/mi} Command Syntax
14126 * GDB/MI Input Syntax::
14127 * GDB/MI Output Syntax::
14128 * GDB/MI Simple Examples::
14131 @node GDB/MI Input Syntax
14132 @subsection @sc{gdb/mi} Input Syntax
14134 @cindex input syntax for @sc{gdb/mi}
14135 @cindex @sc{gdb/mi}, input syntax
14137 @item @var{command} @expansion{}
14138 @code{@var{cli-command} | @var{mi-command}}
14140 @item @var{cli-command} @expansion{}
14141 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
14142 @var{cli-command} is any existing @value{GDBN} CLI command.
14144 @item @var{mi-command} @expansion{}
14145 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
14146 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
14148 @item @var{token} @expansion{}
14149 "any sequence of digits"
14151 @item @var{option} @expansion{}
14152 @code{"-" @var{parameter} [ " " @var{parameter} ]}
14154 @item @var{parameter} @expansion{}
14155 @code{@var{non-blank-sequence} | @var{c-string}}
14157 @item @var{operation} @expansion{}
14158 @emph{any of the operations described in this chapter}
14160 @item @var{non-blank-sequence} @expansion{}
14161 @emph{anything, provided it doesn't contain special characters such as
14162 "-", @var{nl}, """ and of course " "}
14164 @item @var{c-string} @expansion{}
14165 @code{""" @var{seven-bit-iso-c-string-content} """}
14167 @item @var{nl} @expansion{}
14176 The CLI commands are still handled by the @sc{mi} interpreter; their
14177 output is described below.
14180 The @code{@var{token}}, when present, is passed back when the command
14184 Some @sc{mi} commands accept optional arguments as part of the parameter
14185 list. Each option is identified by a leading @samp{-} (dash) and may be
14186 followed by an optional argument parameter. Options occur first in the
14187 parameter list and can be delimited from normal parameters using
14188 @samp{--} (this is useful when some parameters begin with a dash).
14195 We want easy access to the existing CLI syntax (for debugging).
14198 We want it to be easy to spot a @sc{mi} operation.
14201 @node GDB/MI Output Syntax
14202 @subsection @sc{gdb/mi} Output Syntax
14204 @cindex output syntax of @sc{gdb/mi}
14205 @cindex @sc{gdb/mi}, output syntax
14206 The output from @sc{gdb/mi} consists of zero or more out-of-band records
14207 followed, optionally, by a single result record. This result record
14208 is for the most recent command. The sequence of output records is
14209 terminated by @samp{(@value{GDBP})}.
14211 If an input command was prefixed with a @code{@var{token}} then the
14212 corresponding output for that command will also be prefixed by that same
14216 @item @var{output} @expansion{}
14217 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
14219 @item @var{result-record} @expansion{}
14220 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
14222 @item @var{out-of-band-record} @expansion{}
14223 @code{@var{async-record} | @var{stream-record}}
14225 @item @var{async-record} @expansion{}
14226 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
14228 @item @var{exec-async-output} @expansion{}
14229 @code{[ @var{token} ] "*" @var{async-output}}
14231 @item @var{status-async-output} @expansion{}
14232 @code{[ @var{token} ] "+" @var{async-output}}
14234 @item @var{notify-async-output} @expansion{}
14235 @code{[ @var{token} ] "=" @var{async-output}}
14237 @item @var{async-output} @expansion{}
14238 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
14240 @item @var{result-class} @expansion{}
14241 @code{"done" | "running" | "connected" | "error" | "exit"}
14243 @item @var{async-class} @expansion{}
14244 @code{"stopped" | @var{others}} (where @var{others} will be added
14245 depending on the needs---this is still in development).
14247 @item @var{result} @expansion{}
14248 @code{ @var{variable} "=" @var{value}}
14250 @item @var{variable} @expansion{}
14251 @code{ @var{string} }
14253 @item @var{value} @expansion{}
14254 @code{ @var{const} | @var{tuple} | @var{list} }
14256 @item @var{const} @expansion{}
14257 @code{@var{c-string}}
14259 @item @var{tuple} @expansion{}
14260 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
14262 @item @var{list} @expansion{}
14263 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
14264 @var{result} ( "," @var{result} )* "]" }
14266 @item @var{stream-record} @expansion{}
14267 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
14269 @item @var{console-stream-output} @expansion{}
14270 @code{"~" @var{c-string}}
14272 @item @var{target-stream-output} @expansion{}
14273 @code{"@@" @var{c-string}}
14275 @item @var{log-stream-output} @expansion{}
14276 @code{"&" @var{c-string}}
14278 @item @var{nl} @expansion{}
14281 @item @var{token} @expansion{}
14282 @emph{any sequence of digits}.
14290 All output sequences end in a single line containing a period.
14293 The @code{@var{token}} is from the corresponding request. If an execution
14294 command is interrupted by the @samp{-exec-interrupt} command, the
14295 @var{token} associated with the @samp{*stopped} message is the one of the
14296 original execution command, not the one of the interrupt command.
14299 @cindex status output in @sc{gdb/mi}
14300 @var{status-async-output} contains on-going status information about the
14301 progress of a slow operation. It can be discarded. All status output is
14302 prefixed by @samp{+}.
14305 @cindex async output in @sc{gdb/mi}
14306 @var{exec-async-output} contains asynchronous state change on the target
14307 (stopped, started, disappeared). All async output is prefixed by
14311 @cindex notify output in @sc{gdb/mi}
14312 @var{notify-async-output} contains supplementary information that the
14313 client should handle (e.g., a new breakpoint information). All notify
14314 output is prefixed by @samp{=}.
14317 @cindex console output in @sc{gdb/mi}
14318 @var{console-stream-output} is output that should be displayed as is in the
14319 console. It is the textual response to a CLI command. All the console
14320 output is prefixed by @samp{~}.
14323 @cindex target output in @sc{gdb/mi}
14324 @var{target-stream-output} is the output produced by the target program.
14325 All the target output is prefixed by @samp{@@}.
14328 @cindex log output in @sc{gdb/mi}
14329 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
14330 instance messages that should be displayed as part of an error log. All
14331 the log output is prefixed by @samp{&}.
14334 @cindex list output in @sc{gdb/mi}
14335 New @sc{gdb/mi} commands should only output @var{lists} containing
14341 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
14342 details about the various output records.
14344 @node GDB/MI Simple Examples
14345 @subsection Simple Examples of @sc{gdb/mi} Interaction
14346 @cindex @sc{gdb/mi}, simple examples
14348 This subsection presents several simple examples of interaction using
14349 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
14350 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
14351 the output received from @sc{gdb/mi}.
14353 @subsubheading Target Stop
14354 @c Ummm... There is no "-stop" command. This assumes async, no?
14355 Here's an example of stopping the inferior process:
14366 <- *stop,reason="stop",address="0x123",source="a.c:123"
14370 @subsubheading Simple CLI Command
14372 Here's an example of a simple CLI command being passed through
14373 @sc{gdb/mi} and on to the CLI.
14383 @subsubheading Command With Side Effects
14386 -> -symbol-file xyz.exe
14387 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
14391 @subsubheading A Bad Command
14393 Here's what happens if you pass a non-existent command:
14397 <- ^error,msg="Undefined MI command: rubbish"
14401 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14402 @node GDB/MI Compatibility with CLI
14403 @section @sc{gdb/mi} Compatibility with CLI
14405 @cindex compatibility, @sc{gdb/mi} and CLI
14406 @cindex @sc{gdb/mi}, compatibility with CLI
14407 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
14408 accepts existing CLI commands. As specified by the syntax, such
14409 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
14412 This mechanism is provided as an aid to developers of @sc{gdb/mi}
14413 clients and not as a reliable interface into the CLI. Since the command
14414 is being interpreteted in an environment that assumes @sc{gdb/mi}
14415 behaviour, the exact output of such commands is likely to end up being
14416 an un-supported hybrid of @sc{gdb/mi} and CLI output.
14418 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14419 @node GDB/MI Output Records
14420 @section @sc{gdb/mi} Output Records
14423 * GDB/MI Result Records::
14424 * GDB/MI Stream Records::
14425 * GDB/MI Out-of-band Records::
14428 @node GDB/MI Result Records
14429 @subsection @sc{gdb/mi} Result Records
14431 @cindex result records in @sc{gdb/mi}
14432 @cindex @sc{gdb/mi}, result records
14433 In addition to a number of out-of-band notifications, the response to a
14434 @sc{gdb/mi} command includes one of the following result indications:
14438 @item "^done" [ "," @var{results} ]
14439 The synchronous operation was successful, @code{@var{results}} are the return
14444 @c Is this one correct? Should it be an out-of-band notification?
14445 The asynchronous operation was successfully started. The target is
14448 @item "^error" "," @var{c-string}
14450 The operation failed. The @code{@var{c-string}} contains the corresponding
14454 @node GDB/MI Stream Records
14455 @subsection @sc{gdb/mi} Stream Records
14457 @cindex @sc{gdb/mi}, stream records
14458 @cindex stream records in @sc{gdb/mi}
14459 @value{GDBN} internally maintains a number of output streams: the console, the
14460 target, and the log. The output intended for each of these streams is
14461 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
14463 Each stream record begins with a unique @dfn{prefix character} which
14464 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
14465 Syntax}). In addition to the prefix, each stream record contains a
14466 @code{@var{string-output}}. This is either raw text (with an implicit new
14467 line) or a quoted C string (which does not contain an implicit newline).
14470 @item "~" @var{string-output}
14471 The console output stream contains text that should be displayed in the
14472 CLI console window. It contains the textual responses to CLI commands.
14474 @item "@@" @var{string-output}
14475 The target output stream contains any textual output from the running
14478 @item "&" @var{string-output}
14479 The log stream contains debugging messages being produced by @value{GDBN}'s
14483 @node GDB/MI Out-of-band Records
14484 @subsection @sc{gdb/mi} Out-of-band Records
14486 @cindex out-of-band records in @sc{gdb/mi}
14487 @cindex @sc{gdb/mi}, out-of-band records
14488 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
14489 additional changes that have occurred. Those changes can either be a
14490 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
14491 target activity (e.g., target stopped).
14493 The following is a preliminary list of possible out-of-band records.
14500 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14501 @node GDB/MI Command Description Format
14502 @section @sc{gdb/mi} Command Description Format
14504 The remaining sections describe blocks of commands. Each block of
14505 commands is laid out in a fashion similar to this section.
14507 Note the the line breaks shown in the examples are here only for
14508 readability. They don't appear in the real output.
14509 Also note that the commands with a non-available example (N.A.@:) are
14510 not yet implemented.
14512 @subheading Motivation
14514 The motivation for this collection of commands.
14516 @subheading Introduction
14518 A brief introduction to this collection of commands as a whole.
14520 @subheading Commands
14522 For each command in the block, the following is described:
14524 @subsubheading Synopsis
14527 -command @var{args}@dots{}
14530 @subsubheading @value{GDBN} Command
14532 The corresponding @value{GDBN} CLI command.
14534 @subsubheading Result
14536 @subsubheading Out-of-band
14538 @subsubheading Notes
14540 @subsubheading Example
14543 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14544 @node GDB/MI Breakpoint Table Commands
14545 @section @sc{gdb/mi} Breakpoint table commands
14547 @cindex breakpoint commands for @sc{gdb/mi}
14548 @cindex @sc{gdb/mi}, breakpoint commands
14549 This section documents @sc{gdb/mi} commands for manipulating
14552 @subheading The @code{-break-after} Command
14553 @findex -break-after
14555 @subsubheading Synopsis
14558 -break-after @var{number} @var{count}
14561 The breakpoint number @var{number} is not in effect until it has been
14562 hit @var{count} times. To see how this is reflected in the output of
14563 the @samp{-break-list} command, see the description of the
14564 @samp{-break-list} command below.
14566 @subsubheading @value{GDBN} Command
14568 The corresponding @value{GDBN} command is @samp{ignore}.
14570 @subsubheading Example
14575 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
14582 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14583 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14584 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14585 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14586 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14587 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14588 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14589 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14590 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
14596 @subheading The @code{-break-catch} Command
14597 @findex -break-catch
14599 @subheading The @code{-break-commands} Command
14600 @findex -break-commands
14604 @subheading The @code{-break-condition} Command
14605 @findex -break-condition
14607 @subsubheading Synopsis
14610 -break-condition @var{number} @var{expr}
14613 Breakpoint @var{number} will stop the program only if the condition in
14614 @var{expr} is true. The condition becomes part of the
14615 @samp{-break-list} output (see the description of the @samp{-break-list}
14618 @subsubheading @value{GDBN} Command
14620 The corresponding @value{GDBN} command is @samp{condition}.
14622 @subsubheading Example
14626 -break-condition 1 1
14630 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14631 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14632 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14633 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14634 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14635 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14636 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14637 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14638 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
14639 times="0",ignore="3"@}]@}
14643 @subheading The @code{-break-delete} Command
14644 @findex -break-delete
14646 @subsubheading Synopsis
14649 -break-delete ( @var{breakpoint} )+
14652 Delete the breakpoint(s) whose number(s) are specified in the argument
14653 list. This is obviously reflected in the breakpoint list.
14655 @subsubheading @value{GDBN} command
14657 The corresponding @value{GDBN} command is @samp{delete}.
14659 @subsubheading Example
14667 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
14668 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14669 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14670 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14671 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14672 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14673 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14678 @subheading The @code{-break-disable} Command
14679 @findex -break-disable
14681 @subsubheading Synopsis
14684 -break-disable ( @var{breakpoint} )+
14687 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
14688 break list is now set to @samp{n} for the named @var{breakpoint}(s).
14690 @subsubheading @value{GDBN} Command
14692 The corresponding @value{GDBN} command is @samp{disable}.
14694 @subsubheading Example
14702 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14703 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14704 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14705 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14706 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14707 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14708 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14709 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
14710 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
14714 @subheading The @code{-break-enable} Command
14715 @findex -break-enable
14717 @subsubheading Synopsis
14720 -break-enable ( @var{breakpoint} )+
14723 Enable (previously disabled) @var{breakpoint}(s).
14725 @subsubheading @value{GDBN} Command
14727 The corresponding @value{GDBN} command is @samp{enable}.
14729 @subsubheading Example
14737 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14738 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14739 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14740 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14741 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14742 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14743 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14744 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
14745 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
14749 @subheading The @code{-break-info} Command
14750 @findex -break-info
14752 @subsubheading Synopsis
14755 -break-info @var{breakpoint}
14759 Get information about a single breakpoint.
14761 @subsubheading @value{GDBN} command
14763 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
14765 @subsubheading Example
14768 @subheading The @code{-break-insert} Command
14769 @findex -break-insert
14771 @subsubheading Synopsis
14774 -break-insert [ -t ] [ -h ] [ -r ]
14775 [ -c @var{condition} ] [ -i @var{ignore-count} ]
14776 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
14780 If specified, @var{line}, can be one of:
14787 @item filename:linenum
14788 @item filename:function
14792 The possible optional parameters of this command are:
14796 Insert a tempoary breakpoint.
14798 Insert a hardware breakpoint.
14799 @item -c @var{condition}
14800 Make the breakpoint conditional on @var{condition}.
14801 @item -i @var{ignore-count}
14802 Initialize the @var{ignore-count}.
14804 Insert a regular breakpoint in all the functions whose names match the
14805 given regular expression. Other flags are not applicable to regular
14809 @subsubheading Result
14811 The result is in the form:
14814 ^done,bkptno="@var{number}",func="@var{funcname}",
14815 file="@var{filename}",line="@var{lineno}"
14819 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
14820 is the name of the function where the breakpoint was inserted,
14821 @var{filename} is the name of the source file which contains this
14822 function, and @var{lineno} is the source line number within that file.
14824 Note: this format is open to change.
14825 @c An out-of-band breakpoint instead of part of the result?
14827 @subsubheading @value{GDBN} Command
14829 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
14830 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
14832 @subsubheading Example
14837 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
14839 -break-insert -t foo
14840 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
14843 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
14844 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14845 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14846 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14847 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14848 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14849 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14850 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14851 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
14852 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
14853 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
14855 -break-insert -r foo.*
14856 ~int foo(int, int);
14857 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
14861 @subheading The @code{-break-list} Command
14862 @findex -break-list
14864 @subsubheading Synopsis
14870 Displays the list of inserted breakpoints, showing the following fields:
14874 number of the breakpoint
14876 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
14878 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
14881 is the breakpoint enabled or no: @samp{y} or @samp{n}
14883 memory location at which the breakpoint is set
14885 logical location of the breakpoint, expressed by function name, file
14888 number of times the breakpoint has been hit
14891 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
14892 @code{body} field is an empty list.
14894 @subsubheading @value{GDBN} Command
14896 The corresponding @value{GDBN} command is @samp{info break}.
14898 @subsubheading Example
14903 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
14904 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14905 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14906 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14907 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14908 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14909 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14910 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14911 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
14912 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
14913 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
14917 Here's an example of the result when there are no breakpoints:
14922 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
14923 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14924 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14925 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14926 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14927 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14928 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14933 @subheading The @code{-break-watch} Command
14934 @findex -break-watch
14936 @subsubheading Synopsis
14939 -break-watch [ -a | -r ]
14942 Create a watchpoint. With the @samp{-a} option it will create an
14943 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
14944 read from or on a write to the memory location. With the @samp{-r}
14945 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
14946 trigger only when the memory location is accessed for reading. Without
14947 either of the options, the watchpoint created is a regular watchpoint,
14948 i.e. it will trigger when the memory location is accessed for writing.
14949 @xref{Set Watchpoints, , Setting watchpoints}.
14951 Note that @samp{-break-list} will report a single list of watchpoints and
14952 breakpoints inserted.
14954 @subsubheading @value{GDBN} Command
14956 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
14959 @subsubheading Example
14961 Setting a watchpoint on a variable in the @code{main} function:
14966 ^done,wpt=@{number="2",exp="x"@}
14970 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
14971 value=@{old="-268439212",new="55"@},
14972 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
14976 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
14977 the program execution twice: first for the variable changing value, then
14978 for the watchpoint going out of scope.
14983 ^done,wpt=@{number="5",exp="C"@}
14987 ^done,reason="watchpoint-trigger",
14988 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
14989 frame=@{func="callee4",args=[],
14990 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
14994 ^done,reason="watchpoint-scope",wpnum="5",
14995 frame=@{func="callee3",args=[@{name="strarg",
14996 value="0x11940 \"A string argument.\""@}],
14997 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15001 Listing breakpoints and watchpoints, at different points in the program
15002 execution. Note that once the watchpoint goes out of scope, it is
15008 ^done,wpt=@{number="2",exp="C"@}
15011 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15012 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15013 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15014 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15015 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15016 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15017 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15018 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15019 addr="0x00010734",func="callee4",
15020 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15021 bkpt=@{number="2",type="watchpoint",disp="keep",
15022 enabled="y",addr="",what="C",times="0"@}]@}
15026 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
15027 value=@{old="-276895068",new="3"@},
15028 frame=@{func="callee4",args=[],
15029 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15032 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15033 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15034 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15035 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15036 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15037 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15038 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15039 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15040 addr="0x00010734",func="callee4",
15041 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15042 bkpt=@{number="2",type="watchpoint",disp="keep",
15043 enabled="y",addr="",what="C",times="-5"@}]@}
15047 ^done,reason="watchpoint-scope",wpnum="2",
15048 frame=@{func="callee3",args=[@{name="strarg",
15049 value="0x11940 \"A string argument.\""@}],
15050 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15053 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15054 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15055 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15056 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15057 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15058 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15059 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15060 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15061 addr="0x00010734",func="callee4",
15062 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
15066 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15067 @node GDB/MI Data Manipulation
15068 @section @sc{gdb/mi} Data Manipulation
15070 @cindex data manipulation, in @sc{gdb/mi}
15071 @cindex @sc{gdb/mi}, data manipulation
15072 This section describes the @sc{gdb/mi} commands that manipulate data:
15073 examine memory and registers, evaluate expressions, etc.
15075 @c REMOVED FROM THE INTERFACE.
15076 @c @subheading -data-assign
15077 @c Change the value of a program variable. Plenty of side effects.
15078 @c @subsubheading GDB command
15080 @c @subsubheading Example
15083 @subheading The @code{-data-disassemble} Command
15084 @findex -data-disassemble
15086 @subsubheading Synopsis
15090 [ -s @var{start-addr} -e @var{end-addr} ]
15091 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
15099 @item @var{start-addr}
15100 is the beginning address (or @code{$pc})
15101 @item @var{end-addr}
15103 @item @var{filename}
15104 is the name of the file to disassemble
15105 @item @var{linenum}
15106 is the line number to disassemble around
15108 is the the number of disassembly lines to be produced. If it is -1,
15109 the whole function will be disassembled, in case no @var{end-addr} is
15110 specified. If @var{end-addr} is specified as a non-zero value, and
15111 @var{lines} is lower than the number of disassembly lines between
15112 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
15113 displayed; if @var{lines} is higher than the number of lines between
15114 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
15117 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
15121 @subsubheading Result
15123 The output for each instruction is composed of four fields:
15132 Note that whatever included in the instruction field, is not manipulated
15133 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
15135 @subsubheading @value{GDBN} Command
15137 There's no direct mapping from this command to the CLI.
15139 @subsubheading Example
15141 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
15145 -data-disassemble -s $pc -e "$pc + 20" -- 0
15148 @{address="0x000107c0",func-name="main",offset="4",
15149 inst="mov 2, %o0"@},
15150 @{address="0x000107c4",func-name="main",offset="8",
15151 inst="sethi %hi(0x11800), %o2"@},
15152 @{address="0x000107c8",func-name="main",offset="12",
15153 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
15154 @{address="0x000107cc",func-name="main",offset="16",
15155 inst="sethi %hi(0x11800), %o2"@},
15156 @{address="0x000107d0",func-name="main",offset="20",
15157 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
15161 Disassemble the whole @code{main} function. Line 32 is part of
15165 -data-disassemble -f basics.c -l 32 -- 0
15167 @{address="0x000107bc",func-name="main",offset="0",
15168 inst="save %sp, -112, %sp"@},
15169 @{address="0x000107c0",func-name="main",offset="4",
15170 inst="mov 2, %o0"@},
15171 @{address="0x000107c4",func-name="main",offset="8",
15172 inst="sethi %hi(0x11800), %o2"@},
15174 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
15175 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
15179 Disassemble 3 instructions from the start of @code{main}:
15183 -data-disassemble -f basics.c -l 32 -n 3 -- 0
15185 @{address="0x000107bc",func-name="main",offset="0",
15186 inst="save %sp, -112, %sp"@},
15187 @{address="0x000107c0",func-name="main",offset="4",
15188 inst="mov 2, %o0"@},
15189 @{address="0x000107c4",func-name="main",offset="8",
15190 inst="sethi %hi(0x11800), %o2"@}]
15194 Disassemble 3 instructions from the start of @code{main} in mixed mode:
15198 -data-disassemble -f basics.c -l 32 -n 3 -- 1
15200 src_and_asm_line=@{line="31",
15201 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15202 testsuite/gdb.mi/basics.c",line_asm_insn=[
15203 @{address="0x000107bc",func-name="main",offset="0",
15204 inst="save %sp, -112, %sp"@}]@},
15205 src_and_asm_line=@{line="32",
15206 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15207 testsuite/gdb.mi/basics.c",line_asm_insn=[
15208 @{address="0x000107c0",func-name="main",offset="4",
15209 inst="mov 2, %o0"@},
15210 @{address="0x000107c4",func-name="main",offset="8",
15211 inst="sethi %hi(0x11800), %o2"@}]@}]
15216 @subheading The @code{-data-evaluate-expression} Command
15217 @findex -data-evaluate-expression
15219 @subsubheading Synopsis
15222 -data-evaluate-expression @var{expr}
15225 Evaluate @var{expr} as an expression. The expression could contain an
15226 inferior function call. The function call will execute synchronously.
15227 If the expression contains spaces, it must be enclosed in double quotes.
15229 @subsubheading @value{GDBN} Command
15231 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
15232 @samp{call}. In @code{gdbtk} only, there's a corresponding
15233 @samp{gdb_eval} command.
15235 @subsubheading Example
15237 In the following example, the numbers that precede the commands are the
15238 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
15239 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
15243 211-data-evaluate-expression A
15246 311-data-evaluate-expression &A
15247 311^done,value="0xefffeb7c"
15249 411-data-evaluate-expression A+3
15252 511-data-evaluate-expression "A + 3"
15258 @subheading The @code{-data-list-changed-registers} Command
15259 @findex -data-list-changed-registers
15261 @subsubheading Synopsis
15264 -data-list-changed-registers
15267 Display a list of the registers that have changed.
15269 @subsubheading @value{GDBN} Command
15271 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
15272 has the corresponding command @samp{gdb_changed_register_list}.
15274 @subsubheading Example
15276 On a PPC MBX board:
15284 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
15285 args=[],file="try.c",line="5"@}
15287 -data-list-changed-registers
15288 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
15289 "10","11","13","14","15","16","17","18","19","20","21","22","23",
15290 "24","25","26","27","28","30","31","64","65","66","67","69"]
15295 @subheading The @code{-data-list-register-names} Command
15296 @findex -data-list-register-names
15298 @subsubheading Synopsis
15301 -data-list-register-names [ ( @var{regno} )+ ]
15304 Show a list of register names for the current target. If no arguments
15305 are given, it shows a list of the names of all the registers. If
15306 integer numbers are given as arguments, it will print a list of the
15307 names of the registers corresponding to the arguments. To ensure
15308 consistency between a register name and its number, the output list may
15309 include empty register names.
15311 @subsubheading @value{GDBN} Command
15313 @value{GDBN} does not have a command which corresponds to
15314 @samp{-data-list-register-names}. In @code{gdbtk} there is a
15315 corresponding command @samp{gdb_regnames}.
15317 @subsubheading Example
15319 For the PPC MBX board:
15322 -data-list-register-names
15323 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
15324 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
15325 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
15326 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
15327 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
15328 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
15329 "", "pc","ps","cr","lr","ctr","xer"]
15331 -data-list-register-names 1 2 3
15332 ^done,register-names=["r1","r2","r3"]
15336 @subheading The @code{-data-list-register-values} Command
15337 @findex -data-list-register-values
15339 @subsubheading Synopsis
15342 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
15345 Display the registers' contents. @var{fmt} is the format according to
15346 which the registers' contents are to be returned, followed by an optional
15347 list of numbers specifying the registers to display. A missing list of
15348 numbers indicates that the contents of all the registers must be returned.
15350 Allowed formats for @var{fmt} are:
15367 @subsubheading @value{GDBN} Command
15369 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
15370 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
15372 @subsubheading Example
15374 For a PPC MBX board (note: line breaks are for readability only, they
15375 don't appear in the actual output):
15379 -data-list-register-values r 64 65
15380 ^done,register-values=[@{number="64",value="0xfe00a300"@},
15381 @{number="65",value="0x00029002"@}]
15383 -data-list-register-values x
15384 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
15385 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
15386 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
15387 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
15388 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
15389 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
15390 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
15391 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
15392 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
15393 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
15394 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
15395 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
15396 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
15397 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
15398 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
15399 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
15400 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
15401 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
15402 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
15403 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
15404 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
15405 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
15406 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
15407 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
15408 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
15409 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
15410 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
15411 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
15412 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
15413 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
15414 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
15415 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
15416 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
15417 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
15418 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
15419 @{number="69",value="0x20002b03"@}]
15424 @subheading The @code{-data-read-memory} Command
15425 @findex -data-read-memory
15427 @subsubheading Synopsis
15430 -data-read-memory [ -o @var{byte-offset} ]
15431 @var{address} @var{word-format} @var{word-size}
15432 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
15439 @item @var{address}
15440 An expression specifying the address of the first memory word to be
15441 read. Complex expressions containing embedded white space should be
15442 quoted using the C convention.
15444 @item @var{word-format}
15445 The format to be used to print the memory words. The notation is the
15446 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
15449 @item @var{word-size}
15450 The size of each memory word in bytes.
15452 @item @var{nr-rows}
15453 The number of rows in the output table.
15455 @item @var{nr-cols}
15456 The number of columns in the output table.
15459 If present, indicates that each row should include an @sc{ascii} dump. The
15460 value of @var{aschar} is used as a padding character when a byte is not a
15461 member of the printable @sc{ascii} character set (printable @sc{ascii}
15462 characters are those whose code is between 32 and 126, inclusively).
15464 @item @var{byte-offset}
15465 An offset to add to the @var{address} before fetching memory.
15468 This command displays memory contents as a table of @var{nr-rows} by
15469 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
15470 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
15471 (returned as @samp{total-bytes}). Should less than the requested number
15472 of bytes be returned by the target, the missing words are identified
15473 using @samp{N/A}. The number of bytes read from the target is returned
15474 in @samp{nr-bytes} and the starting address used to read memory in
15477 The address of the next/previous row or page is available in
15478 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
15481 @subsubheading @value{GDBN} Command
15483 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
15484 @samp{gdb_get_mem} memory read command.
15486 @subsubheading Example
15488 Read six bytes of memory starting at @code{bytes+6} but then offset by
15489 @code{-6} bytes. Format as three rows of two columns. One byte per
15490 word. Display each word in hex.
15494 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
15495 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
15496 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
15497 prev-page="0x0000138a",memory=[
15498 @{addr="0x00001390",data=["0x00","0x01"]@},
15499 @{addr="0x00001392",data=["0x02","0x03"]@},
15500 @{addr="0x00001394",data=["0x04","0x05"]@}]
15504 Read two bytes of memory starting at address @code{shorts + 64} and
15505 display as a single word formatted in decimal.
15509 5-data-read-memory shorts+64 d 2 1 1
15510 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
15511 next-row="0x00001512",prev-row="0x0000150e",
15512 next-page="0x00001512",prev-page="0x0000150e",memory=[
15513 @{addr="0x00001510",data=["128"]@}]
15517 Read thirty two bytes of memory starting at @code{bytes+16} and format
15518 as eight rows of four columns. Include a string encoding with @samp{x}
15519 used as the non-printable character.
15523 4-data-read-memory bytes+16 x 1 8 4 x
15524 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
15525 next-row="0x000013c0",prev-row="0x0000139c",
15526 next-page="0x000013c0",prev-page="0x00001380",memory=[
15527 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
15528 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
15529 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
15530 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
15531 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
15532 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
15533 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
15534 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
15538 @subheading The @code{-display-delete} Command
15539 @findex -display-delete
15541 @subsubheading Synopsis
15544 -display-delete @var{number}
15547 Delete the display @var{number}.
15549 @subsubheading @value{GDBN} Command
15551 The corresponding @value{GDBN} command is @samp{delete display}.
15553 @subsubheading Example
15557 @subheading The @code{-display-disable} Command
15558 @findex -display-disable
15560 @subsubheading Synopsis
15563 -display-disable @var{number}
15566 Disable display @var{number}.
15568 @subsubheading @value{GDBN} Command
15570 The corresponding @value{GDBN} command is @samp{disable display}.
15572 @subsubheading Example
15576 @subheading The @code{-display-enable} Command
15577 @findex -display-enable
15579 @subsubheading Synopsis
15582 -display-enable @var{number}
15585 Enable display @var{number}.
15587 @subsubheading @value{GDBN} Command
15589 The corresponding @value{GDBN} command is @samp{enable display}.
15591 @subsubheading Example
15595 @subheading The @code{-display-insert} Command
15596 @findex -display-insert
15598 @subsubheading Synopsis
15601 -display-insert @var{expression}
15604 Display @var{expression} every time the program stops.
15606 @subsubheading @value{GDBN} Command
15608 The corresponding @value{GDBN} command is @samp{display}.
15610 @subsubheading Example
15614 @subheading The @code{-display-list} Command
15615 @findex -display-list
15617 @subsubheading Synopsis
15623 List the displays. Do not show the current values.
15625 @subsubheading @value{GDBN} Command
15627 The corresponding @value{GDBN} command is @samp{info display}.
15629 @subsubheading Example
15633 @subheading The @code{-environment-cd} Command
15634 @findex -environment-cd
15636 @subsubheading Synopsis
15639 -environment-cd @var{pathdir}
15642 Set @value{GDBN}'s working directory.
15644 @subsubheading @value{GDBN} Command
15646 The corresponding @value{GDBN} command is @samp{cd}.
15648 @subsubheading Example
15652 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
15658 @subheading The @code{-environment-directory} Command
15659 @findex -environment-directory
15661 @subsubheading Synopsis
15664 -environment-directory [ -r ] [ @var{pathdir} ]+
15667 Add directories @var{pathdir} to beginning of search path for source files.
15668 If the @samp{-r} option is used, the search path is reset to the default
15669 search path. If directories @var{pathdir} are supplied in addition to the
15670 @samp{-r} option, the search path is first reset and then addition
15672 Multiple directories may be specified, separated by blanks. Specifying
15673 multiple directories in a single command
15674 results in the directories added to the beginning of the
15675 search path in the same order they were presented in the command.
15676 If blanks are needed as
15677 part of a directory name, double-quotes should be used around
15678 the name. In the command output, the path will show up separated
15679 by the system directory-separator character. The directory-seperator
15680 character must not be used
15681 in any directory name.
15682 If no directories are specified, the current search path is displayed.
15684 @subsubheading @value{GDBN} Command
15686 The corresponding @value{GDBN} command is @samp{dir}.
15688 @subsubheading Example
15692 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
15693 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
15695 -environment-directory ""
15696 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
15698 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
15699 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
15701 -environment-directory -r
15702 ^done,source-path="$cdir:$cwd"
15707 @subheading The @code{-environment-path} Command
15708 @findex -environment-path
15710 @subsubheading Synopsis
15713 -environment-path [ -r ] [ @var{pathdir} ]+
15716 Add directories @var{pathdir} to beginning of search path for object files.
15717 If the @samp{-r} option is used, the search path is reset to the original
15718 search path that existed at gdb start-up. If directories @var{pathdir} are
15719 supplied in addition to the
15720 @samp{-r} option, the search path is first reset and then addition
15722 Multiple directories may be specified, separated by blanks. Specifying
15723 multiple directories in a single command
15724 results in the directories added to the beginning of the
15725 search path in the same order they were presented in the command.
15726 If blanks are needed as
15727 part of a directory name, double-quotes should be used around
15728 the name. In the command output, the path will show up separated
15729 by the system directory-separator character. The directory-seperator
15730 character must not be used
15731 in any directory name.
15732 If no directories are specified, the current path is displayed.
15735 @subsubheading @value{GDBN} Command
15737 The corresponding @value{GDBN} command is @samp{path}.
15739 @subsubheading Example
15744 ^done,path="/usr/bin"
15746 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
15747 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
15749 -environment-path -r /usr/local/bin
15750 ^done,path="/usr/local/bin:/usr/bin"
15755 @subheading The @code{-environment-pwd} Command
15756 @findex -environment-pwd
15758 @subsubheading Synopsis
15764 Show the current working directory.
15766 @subsubheading @value{GDBN} command
15768 The corresponding @value{GDBN} command is @samp{pwd}.
15770 @subsubheading Example
15775 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
15779 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15780 @node GDB/MI Program Control
15781 @section @sc{gdb/mi} Program control
15783 @subsubheading Program termination
15785 As a result of execution, the inferior program can run to completion, if
15786 it doesn't encounter any breakpoints. In this case the output will
15787 include an exit code, if the program has exited exceptionally.
15789 @subsubheading Examples
15792 Program exited normally:
15800 *stopped,reason="exited-normally"
15805 Program exited exceptionally:
15813 *stopped,reason="exited",exit-code="01"
15817 Another way the program can terminate is if it receives a signal such as
15818 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
15822 *stopped,reason="exited-signalled",signal-name="SIGINT",
15823 signal-meaning="Interrupt"
15827 @subheading The @code{-exec-abort} Command
15828 @findex -exec-abort
15830 @subsubheading Synopsis
15836 Kill the inferior running program.
15838 @subsubheading @value{GDBN} Command
15840 The corresponding @value{GDBN} command is @samp{kill}.
15842 @subsubheading Example
15846 @subheading The @code{-exec-arguments} Command
15847 @findex -exec-arguments
15849 @subsubheading Synopsis
15852 -exec-arguments @var{args}
15855 Set the inferior program arguments, to be used in the next
15858 @subsubheading @value{GDBN} Command
15860 The corresponding @value{GDBN} command is @samp{set args}.
15862 @subsubheading Example
15865 Don't have one around.
15868 @subheading The @code{-exec-continue} Command
15869 @findex -exec-continue
15871 @subsubheading Synopsis
15877 Asynchronous command. Resumes the execution of the inferior program
15878 until a breakpoint is encountered, or until the inferior exits.
15880 @subsubheading @value{GDBN} Command
15882 The corresponding @value{GDBN} corresponding is @samp{continue}.
15884 @subsubheading Example
15891 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
15892 file="hello.c",line="13"@}
15897 @subheading The @code{-exec-finish} Command
15898 @findex -exec-finish
15900 @subsubheading Synopsis
15906 Asynchronous command. Resumes the execution of the inferior program
15907 until the current function is exited. Displays the results returned by
15910 @subsubheading @value{GDBN} Command
15912 The corresponding @value{GDBN} command is @samp{finish}.
15914 @subsubheading Example
15916 Function returning @code{void}.
15923 *stopped,reason="function-finished",frame=@{func="main",args=[],
15924 file="hello.c",line="7"@}
15928 Function returning other than @code{void}. The name of the internal
15929 @value{GDBN} variable storing the result is printed, together with the
15936 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
15937 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
15938 file="recursive2.c",line="14"@},
15939 gdb-result-var="$1",return-value="0"
15944 @subheading The @code{-exec-interrupt} Command
15945 @findex -exec-interrupt
15947 @subsubheading Synopsis
15953 Asynchronous command. Interrupts the background execution of the target.
15954 Note how the token associated with the stop message is the one for the
15955 execution command that has been interrupted. The token for the interrupt
15956 itself only appears in the @samp{^done} output. If the user is trying to
15957 interrupt a non-running program, an error message will be printed.
15959 @subsubheading @value{GDBN} Command
15961 The corresponding @value{GDBN} command is @samp{interrupt}.
15963 @subsubheading Example
15974 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
15975 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
15980 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
15985 @subheading The @code{-exec-next} Command
15988 @subsubheading Synopsis
15994 Asynchronous command. Resumes execution of the inferior program, stopping
15995 when the beginning of the next source line is reached.
15997 @subsubheading @value{GDBN} Command
15999 The corresponding @value{GDBN} command is @samp{next}.
16001 @subsubheading Example
16007 *stopped,reason="end-stepping-range",line="8",file="hello.c"
16012 @subheading The @code{-exec-next-instruction} Command
16013 @findex -exec-next-instruction
16015 @subsubheading Synopsis
16018 -exec-next-instruction
16021 Asynchronous command. Executes one machine instruction. If the
16022 instruction is a function call continues until the function returns. If
16023 the program stops at an instruction in the middle of a source line, the
16024 address will be printed as well.
16026 @subsubheading @value{GDBN} Command
16028 The corresponding @value{GDBN} command is @samp{nexti}.
16030 @subsubheading Example
16034 -exec-next-instruction
16038 *stopped,reason="end-stepping-range",
16039 addr="0x000100d4",line="5",file="hello.c"
16044 @subheading The @code{-exec-return} Command
16045 @findex -exec-return
16047 @subsubheading Synopsis
16053 Makes current function return immediately. Doesn't execute the inferior.
16054 Displays the new current frame.
16056 @subsubheading @value{GDBN} Command
16058 The corresponding @value{GDBN} command is @samp{return}.
16060 @subsubheading Example
16064 200-break-insert callee4
16065 200^done,bkpt=@{number="1",addr="0x00010734",
16066 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16071 000*stopped,reason="breakpoint-hit",bkptno="1",
16072 frame=@{func="callee4",args=[],
16073 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16079 111^done,frame=@{level="0",func="callee3",
16080 args=[@{name="strarg",
16081 value="0x11940 \"A string argument.\""@}],
16082 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16087 @subheading The @code{-exec-run} Command
16090 @subsubheading Synopsis
16096 Asynchronous command. Starts execution of the inferior from the
16097 beginning. The inferior executes until either a breakpoint is
16098 encountered or the program exits.
16100 @subsubheading @value{GDBN} Command
16102 The corresponding @value{GDBN} command is @samp{run}.
16104 @subsubheading Example
16109 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
16114 *stopped,reason="breakpoint-hit",bkptno="1",
16115 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
16120 @subheading The @code{-exec-show-arguments} Command
16121 @findex -exec-show-arguments
16123 @subsubheading Synopsis
16126 -exec-show-arguments
16129 Print the arguments of the program.
16131 @subsubheading @value{GDBN} Command
16133 The corresponding @value{GDBN} command is @samp{show args}.
16135 @subsubheading Example
16138 @c @subheading -exec-signal
16140 @subheading The @code{-exec-step} Command
16143 @subsubheading Synopsis
16149 Asynchronous command. Resumes execution of the inferior program, stopping
16150 when the beginning of the next source line is reached, if the next
16151 source line is not a function call. If it is, stop at the first
16152 instruction of the called function.
16154 @subsubheading @value{GDBN} Command
16156 The corresponding @value{GDBN} command is @samp{step}.
16158 @subsubheading Example
16160 Stepping into a function:
16166 *stopped,reason="end-stepping-range",
16167 frame=@{func="foo",args=[@{name="a",value="10"@},
16168 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
16178 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
16183 @subheading The @code{-exec-step-instruction} Command
16184 @findex -exec-step-instruction
16186 @subsubheading Synopsis
16189 -exec-step-instruction
16192 Asynchronous command. Resumes the inferior which executes one machine
16193 instruction. The output, once @value{GDBN} has stopped, will vary depending on
16194 whether we have stopped in the middle of a source line or not. In the
16195 former case, the address at which the program stopped will be printed as
16198 @subsubheading @value{GDBN} Command
16200 The corresponding @value{GDBN} command is @samp{stepi}.
16202 @subsubheading Example
16206 -exec-step-instruction
16210 *stopped,reason="end-stepping-range",
16211 frame=@{func="foo",args=[],file="try.c",line="10"@}
16213 -exec-step-instruction
16217 *stopped,reason="end-stepping-range",
16218 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
16223 @subheading The @code{-exec-until} Command
16224 @findex -exec-until
16226 @subsubheading Synopsis
16229 -exec-until [ @var{location} ]
16232 Asynchronous command. Executes the inferior until the @var{location}
16233 specified in the argument is reached. If there is no argument, the inferior
16234 executes until a source line greater than the current one is reached.
16235 The reason for stopping in this case will be @samp{location-reached}.
16237 @subsubheading @value{GDBN} Command
16239 The corresponding @value{GDBN} command is @samp{until}.
16241 @subsubheading Example
16245 -exec-until recursive2.c:6
16249 *stopped,reason="location-reached",frame=@{func="main",args=[],
16250 file="recursive2.c",line="6"@}
16255 @subheading -file-clear
16256 Is this going away????
16260 @subheading The @code{-file-exec-and-symbols} Command
16261 @findex -file-exec-and-symbols
16263 @subsubheading Synopsis
16266 -file-exec-and-symbols @var{file}
16269 Specify the executable file to be debugged. This file is the one from
16270 which the symbol table is also read. If no file is specified, the
16271 command clears the executable and symbol information. If breakpoints
16272 are set when using this command with no arguments, @value{GDBN} will produce
16273 error messages. Otherwise, no output is produced, except a completion
16276 @subsubheading @value{GDBN} Command
16278 The corresponding @value{GDBN} command is @samp{file}.
16280 @subsubheading Example
16284 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16290 @subheading The @code{-file-exec-file} Command
16291 @findex -file-exec-file
16293 @subsubheading Synopsis
16296 -file-exec-file @var{file}
16299 Specify the executable file to be debugged. Unlike
16300 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
16301 from this file. If used without argument, @value{GDBN} clears the information
16302 about the executable file. No output is produced, except a completion
16305 @subsubheading @value{GDBN} Command
16307 The corresponding @value{GDBN} command is @samp{exec-file}.
16309 @subsubheading Example
16313 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16319 @subheading The @code{-file-list-exec-sections} Command
16320 @findex -file-list-exec-sections
16322 @subsubheading Synopsis
16325 -file-list-exec-sections
16328 List the sections of the current executable file.
16330 @subsubheading @value{GDBN} Command
16332 The @value{GDBN} command @samp{info file} shows, among the rest, the same
16333 information as this command. @code{gdbtk} has a corresponding command
16334 @samp{gdb_load_info}.
16336 @subsubheading Example
16340 @subheading The @code{-file-list-exec-source-files} Command
16341 @findex -file-list-exec-source-files
16343 @subsubheading Synopsis
16346 -file-list-exec-source-files
16349 List the source files for the current executable.
16351 @subsubheading @value{GDBN} Command
16353 There's no @value{GDBN} command which directly corresponds to this one.
16354 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
16356 @subsubheading Example
16360 @subheading The @code{-file-list-shared-libraries} Command
16361 @findex -file-list-shared-libraries
16363 @subsubheading Synopsis
16366 -file-list-shared-libraries
16369 List the shared libraries in the program.
16371 @subsubheading @value{GDBN} Command
16373 The corresponding @value{GDBN} command is @samp{info shared}.
16375 @subsubheading Example
16379 @subheading The @code{-file-list-symbol-files} Command
16380 @findex -file-list-symbol-files
16382 @subsubheading Synopsis
16385 -file-list-symbol-files
16390 @subsubheading @value{GDBN} Command
16392 The corresponding @value{GDBN} command is @samp{info file} (part of it).
16394 @subsubheading Example
16398 @subheading The @code{-file-symbol-file} Command
16399 @findex -file-symbol-file
16401 @subsubheading Synopsis
16404 -file-symbol-file @var{file}
16407 Read symbol table info from the specified @var{file} argument. When
16408 used without arguments, clears @value{GDBN}'s symbol table info. No output is
16409 produced, except for a completion notification.
16411 @subsubheading @value{GDBN} Command
16413 The corresponding @value{GDBN} command is @samp{symbol-file}.
16415 @subsubheading Example
16419 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16424 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16425 @node GDB/MI Miscellaneous Commands
16426 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
16428 @c @subheading -gdb-complete
16430 @subheading The @code{-gdb-exit} Command
16433 @subsubheading Synopsis
16439 Exit @value{GDBN} immediately.
16441 @subsubheading @value{GDBN} Command
16443 Approximately corresponds to @samp{quit}.
16445 @subsubheading Example
16452 @subheading The @code{-gdb-set} Command
16455 @subsubheading Synopsis
16461 Set an internal @value{GDBN} variable.
16462 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
16464 @subsubheading @value{GDBN} Command
16466 The corresponding @value{GDBN} command is @samp{set}.
16468 @subsubheading Example
16478 @subheading The @code{-gdb-show} Command
16481 @subsubheading Synopsis
16487 Show the current value of a @value{GDBN} variable.
16489 @subsubheading @value{GDBN} command
16491 The corresponding @value{GDBN} command is @samp{show}.
16493 @subsubheading Example
16502 @c @subheading -gdb-source
16505 @subheading The @code{-gdb-version} Command
16506 @findex -gdb-version
16508 @subsubheading Synopsis
16514 Show version information for @value{GDBN}. Used mostly in testing.
16516 @subsubheading @value{GDBN} Command
16518 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
16519 information when you start an interactive session.
16521 @subsubheading Example
16523 @c This example modifies the actual output from GDB to avoid overfull
16529 ~Copyright 2000 Free Software Foundation, Inc.
16530 ~GDB is free software, covered by the GNU General Public License, and
16531 ~you are welcome to change it and/or distribute copies of it under
16532 ~ certain conditions.
16533 ~Type "show copying" to see the conditions.
16534 ~There is absolutely no warranty for GDB. Type "show warranty" for
16536 ~This GDB was configured as
16537 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
16542 @subheading The @code{-interpreter-exec} Command
16543 @findex -interpreter-exec
16545 @subheading Synopsis
16548 -interpreter-exec @var{interpreter} @var{command}
16551 Execute the specified @var{command} in the given @var{interpreter}.
16553 @subheading @value{GDBN} Command
16555 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
16557 @subheading Example
16561 -interpreter-exec console "break main"
16562 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
16563 &"During symbol reading, bad structure-type format.\n"
16564 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
16570 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16571 @node GDB/MI Kod Commands
16572 @section @sc{gdb/mi} Kod Commands
16574 The Kod commands are not implemented.
16576 @c @subheading -kod-info
16578 @c @subheading -kod-list
16580 @c @subheading -kod-list-object-types
16582 @c @subheading -kod-show
16584 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16585 @node GDB/MI Memory Overlay Commands
16586 @section @sc{gdb/mi} Memory Overlay Commands
16588 The memory overlay commands are not implemented.
16590 @c @subheading -overlay-auto
16592 @c @subheading -overlay-list-mapping-state
16594 @c @subheading -overlay-list-overlays
16596 @c @subheading -overlay-map
16598 @c @subheading -overlay-off
16600 @c @subheading -overlay-on
16602 @c @subheading -overlay-unmap
16604 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16605 @node GDB/MI Signal Handling Commands
16606 @section @sc{gdb/mi} Signal Handling Commands
16608 Signal handling commands are not implemented.
16610 @c @subheading -signal-handle
16612 @c @subheading -signal-list-handle-actions
16614 @c @subheading -signal-list-signal-types
16618 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16619 @node GDB/MI Stack Manipulation
16620 @section @sc{gdb/mi} Stack Manipulation Commands
16623 @subheading The @code{-stack-info-frame} Command
16624 @findex -stack-info-frame
16626 @subsubheading Synopsis
16632 Get info on the current frame.
16634 @subsubheading @value{GDBN} Command
16636 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
16637 (without arguments).
16639 @subsubheading Example
16642 @subheading The @code{-stack-info-depth} Command
16643 @findex -stack-info-depth
16645 @subsubheading Synopsis
16648 -stack-info-depth [ @var{max-depth} ]
16651 Return the depth of the stack. If the integer argument @var{max-depth}
16652 is specified, do not count beyond @var{max-depth} frames.
16654 @subsubheading @value{GDBN} Command
16656 There's no equivalent @value{GDBN} command.
16658 @subsubheading Example
16660 For a stack with frame levels 0 through 11:
16667 -stack-info-depth 4
16670 -stack-info-depth 12
16673 -stack-info-depth 11
16676 -stack-info-depth 13
16681 @subheading The @code{-stack-list-arguments} Command
16682 @findex -stack-list-arguments
16684 @subsubheading Synopsis
16687 -stack-list-arguments @var{show-values}
16688 [ @var{low-frame} @var{high-frame} ]
16691 Display a list of the arguments for the frames between @var{low-frame}
16692 and @var{high-frame} (inclusive). If @var{low-frame} and
16693 @var{high-frame} are not provided, list the arguments for the whole call
16696 The @var{show-values} argument must have a value of 0 or 1. A value of
16697 0 means that only the names of the arguments are listed, a value of 1
16698 means that both names and values of the arguments are printed.
16700 @subsubheading @value{GDBN} Command
16702 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
16703 @samp{gdb_get_args} command which partially overlaps with the
16704 functionality of @samp{-stack-list-arguments}.
16706 @subsubheading Example
16713 frame=@{level="0",addr="0x00010734",func="callee4",
16714 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
16715 frame=@{level="1",addr="0x0001076c",func="callee3",
16716 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
16717 frame=@{level="2",addr="0x0001078c",func="callee2",
16718 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
16719 frame=@{level="3",addr="0x000107b4",func="callee1",
16720 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
16721 frame=@{level="4",addr="0x000107e0",func="main",
16722 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
16724 -stack-list-arguments 0
16727 frame=@{level="0",args=[]@},
16728 frame=@{level="1",args=[name="strarg"]@},
16729 frame=@{level="2",args=[name="intarg",name="strarg"]@},
16730 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
16731 frame=@{level="4",args=[]@}]
16733 -stack-list-arguments 1
16736 frame=@{level="0",args=[]@},
16738 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
16739 frame=@{level="2",args=[
16740 @{name="intarg",value="2"@},
16741 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
16742 @{frame=@{level="3",args=[
16743 @{name="intarg",value="2"@},
16744 @{name="strarg",value="0x11940 \"A string argument.\""@},
16745 @{name="fltarg",value="3.5"@}]@},
16746 frame=@{level="4",args=[]@}]
16748 -stack-list-arguments 0 2 2
16749 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
16751 -stack-list-arguments 1 2 2
16752 ^done,stack-args=[frame=@{level="2",
16753 args=[@{name="intarg",value="2"@},
16754 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
16758 @c @subheading -stack-list-exception-handlers
16761 @subheading The @code{-stack-list-frames} Command
16762 @findex -stack-list-frames
16764 @subsubheading Synopsis
16767 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
16770 List the frames currently on the stack. For each frame it displays the
16775 The frame number, 0 being the topmost frame, i.e. the innermost function.
16777 The @code{$pc} value for that frame.
16781 File name of the source file where the function lives.
16783 Line number corresponding to the @code{$pc}.
16786 If invoked without arguments, this command prints a backtrace for the
16787 whole stack. If given two integer arguments, it shows the frames whose
16788 levels are between the two arguments (inclusive). If the two arguments
16789 are equal, it shows the single frame at the corresponding level.
16791 @subsubheading @value{GDBN} Command
16793 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
16795 @subsubheading Example
16797 Full stack backtrace:
16803 [frame=@{level="0",addr="0x0001076c",func="foo",
16804 file="recursive2.c",line="11"@},
16805 frame=@{level="1",addr="0x000107a4",func="foo",
16806 file="recursive2.c",line="14"@},
16807 frame=@{level="2",addr="0x000107a4",func="foo",
16808 file="recursive2.c",line="14"@},
16809 frame=@{level="3",addr="0x000107a4",func="foo",
16810 file="recursive2.c",line="14"@},
16811 frame=@{level="4",addr="0x000107a4",func="foo",
16812 file="recursive2.c",line="14"@},
16813 frame=@{level="5",addr="0x000107a4",func="foo",
16814 file="recursive2.c",line="14"@},
16815 frame=@{level="6",addr="0x000107a4",func="foo",
16816 file="recursive2.c",line="14"@},
16817 frame=@{level="7",addr="0x000107a4",func="foo",
16818 file="recursive2.c",line="14"@},
16819 frame=@{level="8",addr="0x000107a4",func="foo",
16820 file="recursive2.c",line="14"@},
16821 frame=@{level="9",addr="0x000107a4",func="foo",
16822 file="recursive2.c",line="14"@},
16823 frame=@{level="10",addr="0x000107a4",func="foo",
16824 file="recursive2.c",line="14"@},
16825 frame=@{level="11",addr="0x00010738",func="main",
16826 file="recursive2.c",line="4"@}]
16830 Show frames between @var{low_frame} and @var{high_frame}:
16834 -stack-list-frames 3 5
16836 [frame=@{level="3",addr="0x000107a4",func="foo",
16837 file="recursive2.c",line="14"@},
16838 frame=@{level="4",addr="0x000107a4",func="foo",
16839 file="recursive2.c",line="14"@},
16840 frame=@{level="5",addr="0x000107a4",func="foo",
16841 file="recursive2.c",line="14"@}]
16845 Show a single frame:
16849 -stack-list-frames 3 3
16851 [frame=@{level="3",addr="0x000107a4",func="foo",
16852 file="recursive2.c",line="14"@}]
16857 @subheading The @code{-stack-list-locals} Command
16858 @findex -stack-list-locals
16860 @subsubheading Synopsis
16863 -stack-list-locals @var{print-values}
16866 Display the local variable names for the current frame. With an
16867 argument of 0 prints only the names of the variables, with argument of 1
16868 prints also their values.
16870 @subsubheading @value{GDBN} Command
16872 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
16874 @subsubheading Example
16878 -stack-list-locals 0
16879 ^done,locals=[name="A",name="B",name="C"]
16881 -stack-list-locals 1
16882 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
16883 @{name="C",value="3"@}]
16888 @subheading The @code{-stack-select-frame} Command
16889 @findex -stack-select-frame
16891 @subsubheading Synopsis
16894 -stack-select-frame @var{framenum}
16897 Change the current frame. Select a different frame @var{framenum} on
16900 @subsubheading @value{GDBN} Command
16902 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
16903 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
16905 @subsubheading Example
16909 -stack-select-frame 2
16914 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16915 @node GDB/MI Symbol Query
16916 @section @sc{gdb/mi} Symbol Query Commands
16919 @subheading The @code{-symbol-info-address} Command
16920 @findex -symbol-info-address
16922 @subsubheading Synopsis
16925 -symbol-info-address @var{symbol}
16928 Describe where @var{symbol} is stored.
16930 @subsubheading @value{GDBN} Command
16932 The corresponding @value{GDBN} command is @samp{info address}.
16934 @subsubheading Example
16938 @subheading The @code{-symbol-info-file} Command
16939 @findex -symbol-info-file
16941 @subsubheading Synopsis
16947 Show the file for the symbol.
16949 @subsubheading @value{GDBN} Command
16951 There's no equivalent @value{GDBN} command. @code{gdbtk} has
16952 @samp{gdb_find_file}.
16954 @subsubheading Example
16958 @subheading The @code{-symbol-info-function} Command
16959 @findex -symbol-info-function
16961 @subsubheading Synopsis
16964 -symbol-info-function
16967 Show which function the symbol lives in.
16969 @subsubheading @value{GDBN} Command
16971 @samp{gdb_get_function} in @code{gdbtk}.
16973 @subsubheading Example
16977 @subheading The @code{-symbol-info-line} Command
16978 @findex -symbol-info-line
16980 @subsubheading Synopsis
16986 Show the core addresses of the code for a source line.
16988 @subsubheading @value{GDBN} Command
16990 The corresponding @value{GDBN} comamnd is @samp{info line}.
16991 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
16993 @subsubheading Example
16997 @subheading The @code{-symbol-info-symbol} Command
16998 @findex -symbol-info-symbol
17000 @subsubheading Synopsis
17003 -symbol-info-symbol @var{addr}
17006 Describe what symbol is at location @var{addr}.
17008 @subsubheading @value{GDBN} Command
17010 The corresponding @value{GDBN} command is @samp{info symbol}.
17012 @subsubheading Example
17016 @subheading The @code{-symbol-list-functions} Command
17017 @findex -symbol-list-functions
17019 @subsubheading Synopsis
17022 -symbol-list-functions
17025 List the functions in the executable.
17027 @subsubheading @value{GDBN} Command
17029 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
17030 @samp{gdb_search} in @code{gdbtk}.
17032 @subsubheading Example
17036 @subheading The @code{-symbol-list-types} Command
17037 @findex -symbol-list-types
17039 @subsubheading Synopsis
17045 List all the type names.
17047 @subsubheading @value{GDBN} Command
17049 The corresponding commands are @samp{info types} in @value{GDBN},
17050 @samp{gdb_search} in @code{gdbtk}.
17052 @subsubheading Example
17056 @subheading The @code{-symbol-list-variables} Command
17057 @findex -symbol-list-variables
17059 @subsubheading Synopsis
17062 -symbol-list-variables
17065 List all the global and static variable names.
17067 @subsubheading @value{GDBN} Command
17069 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
17071 @subsubheading Example
17075 @subheading The @code{-symbol-locate} Command
17076 @findex -symbol-locate
17078 @subsubheading Synopsis
17084 @subsubheading @value{GDBN} Command
17086 @samp{gdb_loc} in @code{gdbtk}.
17088 @subsubheading Example
17092 @subheading The @code{-symbol-type} Command
17093 @findex -symbol-type
17095 @subsubheading Synopsis
17098 -symbol-type @var{variable}
17101 Show type of @var{variable}.
17103 @subsubheading @value{GDBN} Command
17105 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
17106 @samp{gdb_obj_variable}.
17108 @subsubheading Example
17112 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17113 @node GDB/MI Target Manipulation
17114 @section @sc{gdb/mi} Target Manipulation Commands
17117 @subheading The @code{-target-attach} Command
17118 @findex -target-attach
17120 @subsubheading Synopsis
17123 -target-attach @var{pid} | @var{file}
17126 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
17128 @subsubheading @value{GDBN} command
17130 The corresponding @value{GDBN} command is @samp{attach}.
17132 @subsubheading Example
17136 @subheading The @code{-target-compare-sections} Command
17137 @findex -target-compare-sections
17139 @subsubheading Synopsis
17142 -target-compare-sections [ @var{section} ]
17145 Compare data of section @var{section} on target to the exec file.
17146 Without the argument, all sections are compared.
17148 @subsubheading @value{GDBN} Command
17150 The @value{GDBN} equivalent is @samp{compare-sections}.
17152 @subsubheading Example
17156 @subheading The @code{-target-detach} Command
17157 @findex -target-detach
17159 @subsubheading Synopsis
17165 Disconnect from the remote target. There's no output.
17167 @subsubheading @value{GDBN} command
17169 The corresponding @value{GDBN} command is @samp{detach}.
17171 @subsubheading Example
17181 @subheading The @code{-target-download} Command
17182 @findex -target-download
17184 @subsubheading Synopsis
17190 Loads the executable onto the remote target.
17191 It prints out an update message every half second, which includes the fields:
17195 The name of the section.
17197 The size of what has been sent so far for that section.
17199 The size of the section.
17201 The total size of what was sent so far (the current and the previous sections).
17203 The size of the overall executable to download.
17207 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
17208 @sc{gdb/mi} Output Syntax}).
17210 In addition, it prints the name and size of the sections, as they are
17211 downloaded. These messages include the following fields:
17215 The name of the section.
17217 The size of the section.
17219 The size of the overall executable to download.
17223 At the end, a summary is printed.
17225 @subsubheading @value{GDBN} Command
17227 The corresponding @value{GDBN} command is @samp{load}.
17229 @subsubheading Example
17231 Note: each status message appears on a single line. Here the messages
17232 have been broken down so that they can fit onto a page.
17237 +download,@{section=".text",section-size="6668",total-size="9880"@}
17238 +download,@{section=".text",section-sent="512",section-size="6668",
17239 total-sent="512",total-size="9880"@}
17240 +download,@{section=".text",section-sent="1024",section-size="6668",
17241 total-sent="1024",total-size="9880"@}
17242 +download,@{section=".text",section-sent="1536",section-size="6668",
17243 total-sent="1536",total-size="9880"@}
17244 +download,@{section=".text",section-sent="2048",section-size="6668",
17245 total-sent="2048",total-size="9880"@}
17246 +download,@{section=".text",section-sent="2560",section-size="6668",
17247 total-sent="2560",total-size="9880"@}
17248 +download,@{section=".text",section-sent="3072",section-size="6668",
17249 total-sent="3072",total-size="9880"@}
17250 +download,@{section=".text",section-sent="3584",section-size="6668",
17251 total-sent="3584",total-size="9880"@}
17252 +download,@{section=".text",section-sent="4096",section-size="6668",
17253 total-sent="4096",total-size="9880"@}
17254 +download,@{section=".text",section-sent="4608",section-size="6668",
17255 total-sent="4608",total-size="9880"@}
17256 +download,@{section=".text",section-sent="5120",section-size="6668",
17257 total-sent="5120",total-size="9880"@}
17258 +download,@{section=".text",section-sent="5632",section-size="6668",
17259 total-sent="5632",total-size="9880"@}
17260 +download,@{section=".text",section-sent="6144",section-size="6668",
17261 total-sent="6144",total-size="9880"@}
17262 +download,@{section=".text",section-sent="6656",section-size="6668",
17263 total-sent="6656",total-size="9880"@}
17264 +download,@{section=".init",section-size="28",total-size="9880"@}
17265 +download,@{section=".fini",section-size="28",total-size="9880"@}
17266 +download,@{section=".data",section-size="3156",total-size="9880"@}
17267 +download,@{section=".data",section-sent="512",section-size="3156",
17268 total-sent="7236",total-size="9880"@}
17269 +download,@{section=".data",section-sent="1024",section-size="3156",
17270 total-sent="7748",total-size="9880"@}
17271 +download,@{section=".data",section-sent="1536",section-size="3156",
17272 total-sent="8260",total-size="9880"@}
17273 +download,@{section=".data",section-sent="2048",section-size="3156",
17274 total-sent="8772",total-size="9880"@}
17275 +download,@{section=".data",section-sent="2560",section-size="3156",
17276 total-sent="9284",total-size="9880"@}
17277 +download,@{section=".data",section-sent="3072",section-size="3156",
17278 total-sent="9796",total-size="9880"@}
17279 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
17285 @subheading The @code{-target-exec-status} Command
17286 @findex -target-exec-status
17288 @subsubheading Synopsis
17291 -target-exec-status
17294 Provide information on the state of the target (whether it is running or
17295 not, for instance).
17297 @subsubheading @value{GDBN} Command
17299 There's no equivalent @value{GDBN} command.
17301 @subsubheading Example
17305 @subheading The @code{-target-list-available-targets} Command
17306 @findex -target-list-available-targets
17308 @subsubheading Synopsis
17311 -target-list-available-targets
17314 List the possible targets to connect to.
17316 @subsubheading @value{GDBN} Command
17318 The corresponding @value{GDBN} command is @samp{help target}.
17320 @subsubheading Example
17324 @subheading The @code{-target-list-current-targets} Command
17325 @findex -target-list-current-targets
17327 @subsubheading Synopsis
17330 -target-list-current-targets
17333 Describe the current target.
17335 @subsubheading @value{GDBN} Command
17337 The corresponding information is printed by @samp{info file} (among
17340 @subsubheading Example
17344 @subheading The @code{-target-list-parameters} Command
17345 @findex -target-list-parameters
17347 @subsubheading Synopsis
17350 -target-list-parameters
17355 @subsubheading @value{GDBN} Command
17359 @subsubheading Example
17363 @subheading The @code{-target-select} Command
17364 @findex -target-select
17366 @subsubheading Synopsis
17369 -target-select @var{type} @var{parameters @dots{}}
17372 Connect @value{GDBN} to the remote target. This command takes two args:
17376 The type of target, for instance @samp{async}, @samp{remote}, etc.
17377 @item @var{parameters}
17378 Device names, host names and the like. @xref{Target Commands, ,
17379 Commands for managing targets}, for more details.
17382 The output is a connection notification, followed by the address at
17383 which the target program is, in the following form:
17386 ^connected,addr="@var{address}",func="@var{function name}",
17387 args=[@var{arg list}]
17390 @subsubheading @value{GDBN} Command
17392 The corresponding @value{GDBN} command is @samp{target}.
17394 @subsubheading Example
17398 -target-select async /dev/ttya
17399 ^connected,addr="0xfe00a300",func="??",args=[]
17403 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17404 @node GDB/MI Thread Commands
17405 @section @sc{gdb/mi} Thread Commands
17408 @subheading The @code{-thread-info} Command
17409 @findex -thread-info
17411 @subsubheading Synopsis
17417 @subsubheading @value{GDBN} command
17421 @subsubheading Example
17425 @subheading The @code{-thread-list-all-threads} Command
17426 @findex -thread-list-all-threads
17428 @subsubheading Synopsis
17431 -thread-list-all-threads
17434 @subsubheading @value{GDBN} Command
17436 The equivalent @value{GDBN} command is @samp{info threads}.
17438 @subsubheading Example
17442 @subheading The @code{-thread-list-ids} Command
17443 @findex -thread-list-ids
17445 @subsubheading Synopsis
17451 Produces a list of the currently known @value{GDBN} thread ids. At the
17452 end of the list it also prints the total number of such threads.
17454 @subsubheading @value{GDBN} Command
17456 Part of @samp{info threads} supplies the same information.
17458 @subsubheading Example
17460 No threads present, besides the main process:
17465 ^done,thread-ids=@{@},number-of-threads="0"
17475 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17476 number-of-threads="3"
17481 @subheading The @code{-thread-select} Command
17482 @findex -thread-select
17484 @subsubheading Synopsis
17487 -thread-select @var{threadnum}
17490 Make @var{threadnum} the current thread. It prints the number of the new
17491 current thread, and the topmost frame for that thread.
17493 @subsubheading @value{GDBN} Command
17495 The corresponding @value{GDBN} command is @samp{thread}.
17497 @subsubheading Example
17504 *stopped,reason="end-stepping-range",thread-id="2",line="187",
17505 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
17509 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17510 number-of-threads="3"
17513 ^done,new-thread-id="3",
17514 frame=@{level="0",func="vprintf",
17515 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
17516 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
17520 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17521 @node GDB/MI Tracepoint Commands
17522 @section @sc{gdb/mi} Tracepoint Commands
17524 The tracepoint commands are not yet implemented.
17526 @c @subheading -trace-actions
17528 @c @subheading -trace-delete
17530 @c @subheading -trace-disable
17532 @c @subheading -trace-dump
17534 @c @subheading -trace-enable
17536 @c @subheading -trace-exists
17538 @c @subheading -trace-find
17540 @c @subheading -trace-frame-number
17542 @c @subheading -trace-info
17544 @c @subheading -trace-insert
17546 @c @subheading -trace-list
17548 @c @subheading -trace-pass-count
17550 @c @subheading -trace-save
17552 @c @subheading -trace-start
17554 @c @subheading -trace-stop
17557 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17558 @node GDB/MI Variable Objects
17559 @section @sc{gdb/mi} Variable Objects
17562 @subheading Motivation for Variable Objects in @sc{gdb/mi}
17564 For the implementation of a variable debugger window (locals, watched
17565 expressions, etc.), we are proposing the adaptation of the existing code
17566 used by @code{Insight}.
17568 The two main reasons for that are:
17572 It has been proven in practice (it is already on its second generation).
17575 It will shorten development time (needless to say how important it is
17579 The original interface was designed to be used by Tcl code, so it was
17580 slightly changed so it could be used through @sc{gdb/mi}. This section
17581 describes the @sc{gdb/mi} operations that will be available and gives some
17582 hints about their use.
17584 @emph{Note}: In addition to the set of operations described here, we
17585 expect the @sc{gui} implementation of a variable window to require, at
17586 least, the following operations:
17589 @item @code{-gdb-show} @code{output-radix}
17590 @item @code{-stack-list-arguments}
17591 @item @code{-stack-list-locals}
17592 @item @code{-stack-select-frame}
17595 @subheading Introduction to Variable Objects in @sc{gdb/mi}
17597 @cindex variable objects in @sc{gdb/mi}
17598 The basic idea behind variable objects is the creation of a named object
17599 to represent a variable, an expression, a memory location or even a CPU
17600 register. For each object created, a set of operations is available for
17601 examining or changing its properties.
17603 Furthermore, complex data types, such as C structures, are represented
17604 in a tree format. For instance, the @code{struct} type variable is the
17605 root and the children will represent the struct members. If a child
17606 is itself of a complex type, it will also have children of its own.
17607 Appropriate language differences are handled for C, C@t{++} and Java.
17609 When returning the actual values of the objects, this facility allows
17610 for the individual selection of the display format used in the result
17611 creation. It can be chosen among: binary, decimal, hexadecimal, octal
17612 and natural. Natural refers to a default format automatically
17613 chosen based on the variable type (like decimal for an @code{int}, hex
17614 for pointers, etc.).
17616 The following is the complete set of @sc{gdb/mi} operations defined to
17617 access this functionality:
17619 @multitable @columnfractions .4 .6
17620 @item @strong{Operation}
17621 @tab @strong{Description}
17623 @item @code{-var-create}
17624 @tab create a variable object
17625 @item @code{-var-delete}
17626 @tab delete the variable object and its children
17627 @item @code{-var-set-format}
17628 @tab set the display format of this variable
17629 @item @code{-var-show-format}
17630 @tab show the display format of this variable
17631 @item @code{-var-info-num-children}
17632 @tab tells how many children this object has
17633 @item @code{-var-list-children}
17634 @tab return a list of the object's children
17635 @item @code{-var-info-type}
17636 @tab show the type of this variable object
17637 @item @code{-var-info-expression}
17638 @tab print what this variable object represents
17639 @item @code{-var-show-attributes}
17640 @tab is this variable editable? does it exist here?
17641 @item @code{-var-evaluate-expression}
17642 @tab get the value of this variable
17643 @item @code{-var-assign}
17644 @tab set the value of this variable
17645 @item @code{-var-update}
17646 @tab update the variable and its children
17649 In the next subsection we describe each operation in detail and suggest
17650 how it can be used.
17652 @subheading Description And Use of Operations on Variable Objects
17654 @subheading The @code{-var-create} Command
17655 @findex -var-create
17657 @subsubheading Synopsis
17660 -var-create @{@var{name} | "-"@}
17661 @{@var{frame-addr} | "*"@} @var{expression}
17664 This operation creates a variable object, which allows the monitoring of
17665 a variable, the result of an expression, a memory cell or a CPU
17668 The @var{name} parameter is the string by which the object can be
17669 referenced. It must be unique. If @samp{-} is specified, the varobj
17670 system will generate a string ``varNNNNNN'' automatically. It will be
17671 unique provided that one does not specify @var{name} on that format.
17672 The command fails if a duplicate name is found.
17674 The frame under which the expression should be evaluated can be
17675 specified by @var{frame-addr}. A @samp{*} indicates that the current
17676 frame should be used.
17678 @var{expression} is any expression valid on the current language set (must not
17679 begin with a @samp{*}), or one of the following:
17683 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
17686 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
17689 @samp{$@var{regname}} --- a CPU register name
17692 @subsubheading Result
17694 This operation returns the name, number of children and the type of the
17695 object created. Type is returned as a string as the ones generated by
17696 the @value{GDBN} CLI:
17699 name="@var{name}",numchild="N",type="@var{type}"
17703 @subheading The @code{-var-delete} Command
17704 @findex -var-delete
17706 @subsubheading Synopsis
17709 -var-delete @var{name}
17712 Deletes a previously created variable object and all of its children.
17714 Returns an error if the object @var{name} is not found.
17717 @subheading The @code{-var-set-format} Command
17718 @findex -var-set-format
17720 @subsubheading Synopsis
17723 -var-set-format @var{name} @var{format-spec}
17726 Sets the output format for the value of the object @var{name} to be
17729 The syntax for the @var{format-spec} is as follows:
17732 @var{format-spec} @expansion{}
17733 @{binary | decimal | hexadecimal | octal | natural@}
17737 @subheading The @code{-var-show-format} Command
17738 @findex -var-show-format
17740 @subsubheading Synopsis
17743 -var-show-format @var{name}
17746 Returns the format used to display the value of the object @var{name}.
17749 @var{format} @expansion{}
17754 @subheading The @code{-var-info-num-children} Command
17755 @findex -var-info-num-children
17757 @subsubheading Synopsis
17760 -var-info-num-children @var{name}
17763 Returns the number of children of a variable object @var{name}:
17770 @subheading The @code{-var-list-children} Command
17771 @findex -var-list-children
17773 @subsubheading Synopsis
17776 -var-list-children @var{name}
17779 Returns a list of the children of the specified variable object:
17782 numchild=@var{n},children=[@{name=@var{name},
17783 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
17787 @subheading The @code{-var-info-type} Command
17788 @findex -var-info-type
17790 @subsubheading Synopsis
17793 -var-info-type @var{name}
17796 Returns the type of the specified variable @var{name}. The type is
17797 returned as a string in the same format as it is output by the
17801 type=@var{typename}
17805 @subheading The @code{-var-info-expression} Command
17806 @findex -var-info-expression
17808 @subsubheading Synopsis
17811 -var-info-expression @var{name}
17814 Returns what is represented by the variable object @var{name}:
17817 lang=@var{lang-spec},exp=@var{expression}
17821 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
17823 @subheading The @code{-var-show-attributes} Command
17824 @findex -var-show-attributes
17826 @subsubheading Synopsis
17829 -var-show-attributes @var{name}
17832 List attributes of the specified variable object @var{name}:
17835 status=@var{attr} [ ( ,@var{attr} )* ]
17839 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
17841 @subheading The @code{-var-evaluate-expression} Command
17842 @findex -var-evaluate-expression
17844 @subsubheading Synopsis
17847 -var-evaluate-expression @var{name}
17850 Evaluates the expression that is represented by the specified variable
17851 object and returns its value as a string in the current format specified
17858 Note that one must invoke @code{-var-list-children} for a variable
17859 before the value of a child variable can be evaluated.
17861 @subheading The @code{-var-assign} Command
17862 @findex -var-assign
17864 @subsubheading Synopsis
17867 -var-assign @var{name} @var{expression}
17870 Assigns the value of @var{expression} to the variable object specified
17871 by @var{name}. The object must be @samp{editable}. If the variable's
17872 value is altered by the assign, the variable will show up in any
17873 subsequent @code{-var-update} list.
17875 @subsubheading Example
17883 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
17887 @subheading The @code{-var-update} Command
17888 @findex -var-update
17890 @subsubheading Synopsis
17893 -var-update @{@var{name} | "*"@}
17896 Update the value of the variable object @var{name} by evaluating its
17897 expression after fetching all the new values from memory or registers.
17898 A @samp{*} causes all existing variable objects to be updated.
17902 @chapter @value{GDBN} Annotations
17904 This chapter describes annotations in @value{GDBN}. Annotations are
17905 designed to interface @value{GDBN} to graphical user interfaces or
17906 other similar programs which want to interact with @value{GDBN} at a
17907 relatively high level.
17910 This is Edition @value{EDITION}, @value{DATE}.
17914 * Annotations Overview:: What annotations are; the general syntax.
17915 * Server Prefix:: Issuing a command without affecting user state.
17916 * Value Annotations:: Values are marked as such.
17917 * Frame Annotations:: Stack frames are annotated.
17918 * Displays:: @value{GDBN} can be told to display something periodically.
17919 * Prompting:: Annotations marking @value{GDBN}'s need for input.
17920 * Errors:: Annotations for error messages.
17921 * Breakpoint Info:: Information on breakpoints.
17922 * Invalidation:: Some annotations describe things now invalid.
17923 * Annotations for Running::
17924 Whether the program is running, how it stopped, etc.
17925 * Source Annotations:: Annotations describing source code.
17926 * TODO:: Annotations which might be added in the future.
17929 @node Annotations Overview
17930 @section What is an Annotation?
17931 @cindex annotations
17933 To produce annotations, start @value{GDBN} with the @code{--annotate=2} option.
17935 Annotations start with a newline character, two @samp{control-z}
17936 characters, and the name of the annotation. If there is no additional
17937 information associated with this annotation, the name of the annotation
17938 is followed immediately by a newline. If there is additional
17939 information, the name of the annotation is followed by a space, the
17940 additional information, and a newline. The additional information
17941 cannot contain newline characters.
17943 Any output not beginning with a newline and two @samp{control-z}
17944 characters denotes literal output from @value{GDBN}. Currently there is
17945 no need for @value{GDBN} to output a newline followed by two
17946 @samp{control-z} characters, but if there was such a need, the
17947 annotations could be extended with an @samp{escape} annotation which
17948 means those three characters as output.
17950 A simple example of starting up @value{GDBN} with annotations is:
17955 Copyright 2000 Free Software Foundation, Inc.
17956 GDB is free software, covered by the GNU General Public License,
17957 and you are welcome to change it and/or distribute copies of it
17958 under certain conditions.
17959 Type "show copying" to see the conditions.
17960 There is absolutely no warranty for GDB. Type "show warranty"
17962 This GDB was configured as "sparc-sun-sunos4.1.3"
17973 Here @samp{quit} is input to @value{GDBN}; the rest is output from
17974 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
17975 denotes a @samp{control-z} character) are annotations; the rest is
17976 output from @value{GDBN}.
17978 @node Server Prefix
17979 @section The Server Prefix
17980 @cindex server prefix for annotations
17982 To issue a command to @value{GDBN} without affecting certain aspects of
17983 the state which is seen by users, prefix it with @samp{server }. This
17984 means that this command will not affect the command history, nor will it
17985 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
17986 pressed on a line by itself.
17988 The server prefix does not affect the recording of values into the value
17989 history; to print a value without recording it into the value history,
17990 use the @code{output} command instead of the @code{print} command.
17992 @node Value Annotations
17995 @cindex annotations for values
17996 When a value is printed in various contexts, @value{GDBN} uses
17997 annotations to delimit the value from the surrounding text.
17999 @findex value-history-begin
18000 @findex value-history-value
18001 @findex value-history-end
18002 If a value is printed using @code{print} and added to the value history,
18003 the annotation looks like
18006 ^Z^Zvalue-history-begin @var{history-number} @var{value-flags}
18007 @var{history-string}
18008 ^Z^Zvalue-history-value
18010 ^Z^Zvalue-history-end
18014 where @var{history-number} is the number it is getting in the value
18015 history, @var{history-string} is a string, such as @samp{$5 = }, which
18016 introduces the value to the user, @var{the-value} is the output
18017 corresponding to the value itself, and @var{value-flags} is @samp{*} for
18018 a value which can be dereferenced and @samp{-} for a value which cannot.
18020 @findex value-begin
18022 If the value is not added to the value history (it is an invalid float
18023 or it is printed with the @code{output} command), the annotation is similar:
18026 ^Z^Zvalue-begin @var{value-flags}
18032 @findex arg-name-end
18035 When @value{GDBN} prints an argument to a function (for example, in the output
18036 from the @code{backtrace} command), it annotates it as follows:
18040 @var{argument-name}
18042 @var{separator-string}
18043 ^Z^Zarg-value @var{value-flags}
18049 where @var{argument-name} is the name of the argument,
18050 @var{separator-string} is text which separates the name from the value
18051 for the user's benefit (such as @samp{=}), and @var{value-flags} and
18052 @var{the-value} have the same meanings as in a
18053 @code{value-history-begin} annotation.
18055 @findex field-begin
18056 @findex field-name-end
18057 @findex field-value
18059 When printing a structure, @value{GDBN} annotates it as follows:
18062 ^Z^Zfield-begin @var{value-flags}
18065 @var{separator-string}
18072 where @var{field-name} is the name of the field, @var{separator-string}
18073 is text which separates the name from the value for the user's benefit
18074 (such as @samp{=}), and @var{value-flags} and @var{the-value} have the
18075 same meanings as in a @code{value-history-begin} annotation.
18077 When printing an array, @value{GDBN} annotates it as follows:
18080 ^Z^Zarray-section-begin @var{array-index} @var{value-flags}
18084 where @var{array-index} is the index of the first element being
18085 annotated and @var{value-flags} has the same meaning as in a
18086 @code{value-history-begin} annotation. This is followed by any number
18087 of elements, where is element can be either a single element:
18091 @samp{,} @var{whitespace} ; @r{omitted for the first element}
18096 or a repeated element
18099 @findex elt-rep-end
18101 @samp{,} @var{whitespace} ; @r{omitted for the first element}
18103 ^Z^Zelt-rep @var{number-of-repetitions}
18104 @var{repetition-string}
18108 In both cases, @var{the-value} is the output for the value of the
18109 element and @var{whitespace} can contain spaces, tabs, and newlines. In
18110 the repeated case, @var{number-of-repetitions} is the number of
18111 consecutive array elements which contain that value, and
18112 @var{repetition-string} is a string which is designed to convey to the
18113 user that repetition is being depicted.
18115 @findex array-section-end
18116 Once all the array elements have been output, the array annotation is
18120 ^Z^Zarray-section-end
18123 @node Frame Annotations
18126 @cindex annotations for frames
18127 Whenever @value{GDBN} prints a frame, it annotates it. For example, this applies
18128 to frames printed when @value{GDBN} stops, output from commands such as
18129 @code{backtrace} or @code{up}, etc.
18131 @findex frame-begin
18132 The frame annotation begins with
18135 ^Z^Zframe-begin @var{level} @var{address}
18140 where @var{level} is the number of the frame (0 is the innermost frame,
18141 and other frames have positive numbers), @var{address} is the address of
18142 the code executing in that frame, and @var{level-string} is a string
18143 designed to convey the level to the user. @var{address} is in the form
18144 @samp{0x} followed by one or more lowercase hex digits (note that this
18145 does not depend on the language). The frame ends with
18152 Between these annotations is the main body of the frame, which can
18157 @findex function-call
18160 @var{function-call-string}
18163 where @var{function-call-string} is text designed to convey to the user
18164 that this frame is associated with a function call made by @value{GDBN} to a
18165 function in the program being debugged.
18168 @findex signal-handler-caller
18170 ^Z^Zsignal-handler-caller
18171 @var{signal-handler-caller-string}
18174 where @var{signal-handler-caller-string} is text designed to convey to
18175 the user that this frame is associated with whatever mechanism is used
18176 by this operating system to call a signal handler (it is the frame which
18177 calls the signal handler, not the frame for the signal handler itself).
18182 @findex frame-address
18183 @findex frame-address-end
18184 This can optionally (depending on whether this is thought of as
18185 interesting information for the user to see) begin with
18190 ^Z^Zframe-address-end
18191 @var{separator-string}
18194 where @var{address} is the address executing in the frame (the same
18195 address as in the @code{frame-begin} annotation, but printed in a form
18196 which is intended for user consumption---in particular, the syntax varies
18197 depending on the language), and @var{separator-string} is a string
18198 intended to separate this address from what follows for the user's
18201 @findex frame-function-name
18206 ^Z^Zframe-function-name
18207 @var{function-name}
18212 where @var{function-name} is the name of the function executing in the
18213 frame, or @samp{??} if not known, and @var{arguments} are the arguments
18214 to the frame, with parentheses around them (each argument is annotated
18215 individually as well, @pxref{Value Annotations}).
18217 @findex frame-source-begin
18218 @findex frame-source-file
18219 @findex frame-source-file-end
18220 @findex frame-source-line
18221 @findex frame-source-end
18222 If source information is available, a reference to it is then printed:
18225 ^Z^Zframe-source-begin
18226 @var{source-intro-string}
18227 ^Z^Zframe-source-file
18229 ^Z^Zframe-source-file-end
18231 ^Z^Zframe-source-line
18233 ^Z^Zframe-source-end
18236 where @var{source-intro-string} separates for the user's benefit the
18237 reference from the text which precedes it, @var{filename} is the name of
18238 the source file, and @var{line-number} is the line number within that
18239 file (the first line is line 1).
18241 @findex frame-where
18242 If @value{GDBN} prints some information about where the frame is from (which
18243 library, which load segment, etc.; currently only done on the RS/6000),
18244 it is annotated with
18251 Then, if source is to actually be displayed for this frame (for example,
18252 this is not true for output from the @code{backtrace} command), then a
18253 @code{source} annotation (@pxref{Source Annotations}) is displayed. Unlike
18254 most annotations, this is output instead of the normal text which would be
18255 output, not in addition.
18261 @findex display-begin
18262 @findex display-number-end
18263 @findex display-format
18264 @findex display-expression
18265 @findex display-expression-end
18266 @findex display-value
18267 @findex display-end
18268 @cindex annotations for display
18269 When @value{GDBN} is told to display something using the @code{display} command,
18270 the results of the display are annotated:
18275 ^Z^Zdisplay-number-end
18276 @var{number-separator}
18279 ^Z^Zdisplay-expression
18281 ^Z^Zdisplay-expression-end
18282 @var{expression-separator}
18289 where @var{number} is the number of the display, @var{number-separator}
18290 is intended to separate the number from what follows for the user,
18291 @var{format} includes information such as the size, format, or other
18292 information about how the value is being displayed, @var{expression} is
18293 the expression being displayed, @var{expression-separator} is intended
18294 to separate the expression from the text that follows for the user,
18295 and @var{value} is the actual value being displayed.
18298 @section Annotation for @value{GDBN} Input
18300 @cindex annotations for prompts
18301 When @value{GDBN} prompts for input, it annotates this fact so it is possible
18302 to know when to send output, when the output from a given command is
18305 Different kinds of input each have a different @dfn{input type}. Each
18306 input type has three annotations: a @code{pre-} annotation, which
18307 denotes the beginning of any prompt which is being output, a plain
18308 annotation, which denotes the end of the prompt, and then a @code{post-}
18309 annotation which denotes the end of any echo which may (or may not) be
18310 associated with the input. For example, the @code{prompt} input type
18311 features the following annotations:
18319 The input types are
18324 @findex post-prompt
18326 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
18328 @findex pre-commands
18330 @findex post-commands
18332 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
18333 command. The annotations are repeated for each command which is input.
18335 @findex pre-overload-choice
18336 @findex overload-choice
18337 @findex post-overload-choice
18338 @item overload-choice
18339 When @value{GDBN} wants the user to select between various overloaded functions.
18345 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
18347 @findex pre-prompt-for-continue
18348 @findex prompt-for-continue
18349 @findex post-prompt-for-continue
18350 @item prompt-for-continue
18351 When @value{GDBN} is asking the user to press return to continue. Note: Don't
18352 expect this to work well; instead use @code{set height 0} to disable
18353 prompting. This is because the counting of lines is buggy in the
18354 presence of annotations.
18359 @cindex annotations for errors, warnings and interrupts
18366 This annotation occurs right before @value{GDBN} responds to an interrupt.
18373 This annotation occurs right before @value{GDBN} responds to an error.
18375 Quit and error annotations indicate that any annotations which @value{GDBN} was
18376 in the middle of may end abruptly. For example, if a
18377 @code{value-history-begin} annotation is followed by a @code{error}, one
18378 cannot expect to receive the matching @code{value-history-end}. One
18379 cannot expect not to receive it either, however; an error annotation
18380 does not necessarily mean that @value{GDBN} is immediately returning all the way
18383 @findex error-begin
18384 A quit or error annotation may be preceded by
18390 Any output between that and the quit or error annotation is the error
18393 Warning messages are not yet annotated.
18394 @c If we want to change that, need to fix warning(), type_error(),
18395 @c range_error(), and possibly other places.
18397 @node Breakpoint Info
18398 @section Information on Breakpoints
18400 @cindex annotations for breakpoints
18401 The output from the @code{info breakpoints} command is annotated as follows:
18403 @findex breakpoints-headers
18404 @findex breakpoints-table
18406 ^Z^Zbreakpoints-headers
18408 ^Z^Zbreakpoints-table
18412 where @var{header-entry} has the same syntax as an entry (see below) but
18413 instead of containing data, it contains strings which are intended to
18414 convey the meaning of each field to the user. This is followed by any
18415 number of entries. If a field does not apply for this entry, it is
18416 omitted. Fields may contain trailing whitespace. Each entry consists
18445 Note that @var{address} is intended for user consumption---the syntax
18446 varies depending on the language.
18448 The output ends with
18450 @findex breakpoints-table-end
18452 ^Z^Zbreakpoints-table-end
18456 @section Invalidation Notices
18458 @cindex annotations for invalidation messages
18459 The following annotations say that certain pieces of state may have
18463 @findex frames-invalid
18464 @item ^Z^Zframes-invalid
18466 The frames (for example, output from the @code{backtrace} command) may
18469 @findex breakpoints-invalid
18470 @item ^Z^Zbreakpoints-invalid
18472 The breakpoints may have changed. For example, the user just added or
18473 deleted a breakpoint.
18476 @node Annotations for Running
18477 @section Running the Program
18478 @cindex annotations for running programs
18482 When the program starts executing due to a @value{GDBN} command such as
18483 @code{step} or @code{continue},
18489 is output. When the program stops,
18495 is output. Before the @code{stopped} annotation, a variety of
18496 annotations describe how the program stopped.
18500 @item ^Z^Zexited @var{exit-status}
18501 The program exited, and @var{exit-status} is the exit status (zero for
18502 successful exit, otherwise nonzero).
18505 @findex signal-name
18506 @findex signal-name-end
18507 @findex signal-string
18508 @findex signal-string-end
18509 @item ^Z^Zsignalled
18510 The program exited with a signal. After the @code{^Z^Zsignalled}, the
18511 annotation continues:
18517 ^Z^Zsignal-name-end
18521 ^Z^Zsignal-string-end
18526 where @var{name} is the name of the signal, such as @code{SIGILL} or
18527 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
18528 as @code{Illegal Instruction} or @code{Segmentation fault}.
18529 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
18530 user's benefit and have no particular format.
18534 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
18535 just saying that the program received the signal, not that it was
18536 terminated with it.
18539 @item ^Z^Zbreakpoint @var{number}
18540 The program hit breakpoint number @var{number}.
18543 @item ^Z^Zwatchpoint @var{number}
18544 The program hit watchpoint number @var{number}.
18547 @node Source Annotations
18548 @section Displaying Source
18549 @cindex annotations for source display
18552 The following annotation is used instead of displaying source code:
18555 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
18558 where @var{filename} is an absolute file name indicating which source
18559 file, @var{line} is the line number within that file (where 1 is the
18560 first line in the file), @var{character} is the character position
18561 within the file (where 0 is the first character in the file) (for most
18562 debug formats this will necessarily point to the beginning of a line),
18563 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
18564 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
18565 @var{addr} is the address in the target program associated with the
18566 source which is being displayed. @var{addr} is in the form @samp{0x}
18567 followed by one or more lowercase hex digits (note that this does not
18568 depend on the language).
18571 @section Annotations We Might Want in the Future
18575 the target might have changed (registers, heap contents, or
18576 execution status). For performance, we might eventually want
18577 to hit `registers-invalid' and `all-registers-invalid' with
18580 - systematic annotation for set/show parameters (including
18581 invalidation notices).
18583 - similarly, `info' returns a list of candidates for invalidation
18588 @chapter Reporting Bugs in @value{GDBN}
18589 @cindex bugs in @value{GDBN}
18590 @cindex reporting bugs in @value{GDBN}
18592 Your bug reports play an essential role in making @value{GDBN} reliable.
18594 Reporting a bug may help you by bringing a solution to your problem, or it
18595 may not. But in any case the principal function of a bug report is to help
18596 the entire community by making the next version of @value{GDBN} work better. Bug
18597 reports are your contribution to the maintenance of @value{GDBN}.
18599 In order for a bug report to serve its purpose, you must include the
18600 information that enables us to fix the bug.
18603 * Bug Criteria:: Have you found a bug?
18604 * Bug Reporting:: How to report bugs
18608 @section Have you found a bug?
18609 @cindex bug criteria
18611 If you are not sure whether you have found a bug, here are some guidelines:
18614 @cindex fatal signal
18615 @cindex debugger crash
18616 @cindex crash of debugger
18618 If the debugger gets a fatal signal, for any input whatever, that is a
18619 @value{GDBN} bug. Reliable debuggers never crash.
18621 @cindex error on valid input
18623 If @value{GDBN} produces an error message for valid input, that is a
18624 bug. (Note that if you're cross debugging, the problem may also be
18625 somewhere in the connection to the target.)
18627 @cindex invalid input
18629 If @value{GDBN} does not produce an error message for invalid input,
18630 that is a bug. However, you should note that your idea of
18631 ``invalid input'' might be our idea of ``an extension'' or ``support
18632 for traditional practice''.
18635 If you are an experienced user of debugging tools, your suggestions
18636 for improvement of @value{GDBN} are welcome in any case.
18639 @node Bug Reporting
18640 @section How to report bugs
18641 @cindex bug reports
18642 @cindex @value{GDBN} bugs, reporting
18644 A number of companies and individuals offer support for @sc{gnu} products.
18645 If you obtained @value{GDBN} from a support organization, we recommend you
18646 contact that organization first.
18648 You can find contact information for many support companies and
18649 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
18651 @c should add a web page ref...
18653 In any event, we also recommend that you submit bug reports for
18654 @value{GDBN}. The prefered method is to submit them directly using
18655 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
18656 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
18659 @strong{Do not send bug reports to @samp{info-gdb}, or to
18660 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
18661 not want to receive bug reports. Those that do have arranged to receive
18664 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
18665 serves as a repeater. The mailing list and the newsgroup carry exactly
18666 the same messages. Often people think of posting bug reports to the
18667 newsgroup instead of mailing them. This appears to work, but it has one
18668 problem which can be crucial: a newsgroup posting often lacks a mail
18669 path back to the sender. Thus, if we need to ask for more information,
18670 we may be unable to reach you. For this reason, it is better to send
18671 bug reports to the mailing list.
18673 The fundamental principle of reporting bugs usefully is this:
18674 @strong{report all the facts}. If you are not sure whether to state a
18675 fact or leave it out, state it!
18677 Often people omit facts because they think they know what causes the
18678 problem and assume that some details do not matter. Thus, you might
18679 assume that the name of the variable you use in an example does not matter.
18680 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
18681 stray memory reference which happens to fetch from the location where that
18682 name is stored in memory; perhaps, if the name were different, the contents
18683 of that location would fool the debugger into doing the right thing despite
18684 the bug. Play it safe and give a specific, complete example. That is the
18685 easiest thing for you to do, and the most helpful.
18687 Keep in mind that the purpose of a bug report is to enable us to fix the
18688 bug. It may be that the bug has been reported previously, but neither
18689 you nor we can know that unless your bug report is complete and
18692 Sometimes people give a few sketchy facts and ask, ``Does this ring a
18693 bell?'' Those bug reports are useless, and we urge everyone to
18694 @emph{refuse to respond to them} except to chide the sender to report
18697 To enable us to fix the bug, you should include all these things:
18701 The version of @value{GDBN}. @value{GDBN} announces it if you start
18702 with no arguments; you can also print it at any time using @code{show
18705 Without this, we will not know whether there is any point in looking for
18706 the bug in the current version of @value{GDBN}.
18709 The type of machine you are using, and the operating system name and
18713 What compiler (and its version) was used to compile @value{GDBN}---e.g.
18714 ``@value{GCC}--2.8.1''.
18717 What compiler (and its version) was used to compile the program you are
18718 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
18719 C Compiler''. For GCC, you can say @code{gcc --version} to get this
18720 information; for other compilers, see the documentation for those
18724 The command arguments you gave the compiler to compile your example and
18725 observe the bug. For example, did you use @samp{-O}? To guarantee
18726 you will not omit something important, list them all. A copy of the
18727 Makefile (or the output from make) is sufficient.
18729 If we were to try to guess the arguments, we would probably guess wrong
18730 and then we might not encounter the bug.
18733 A complete input script, and all necessary source files, that will
18737 A description of what behavior you observe that you believe is
18738 incorrect. For example, ``It gets a fatal signal.''
18740 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
18741 will certainly notice it. But if the bug is incorrect output, we might
18742 not notice unless it is glaringly wrong. You might as well not give us
18743 a chance to make a mistake.
18745 Even if the problem you experience is a fatal signal, you should still
18746 say so explicitly. Suppose something strange is going on, such as, your
18747 copy of @value{GDBN} is out of synch, or you have encountered a bug in
18748 the C library on your system. (This has happened!) Your copy might
18749 crash and ours would not. If you told us to expect a crash, then when
18750 ours fails to crash, we would know that the bug was not happening for
18751 us. If you had not told us to expect a crash, then we would not be able
18752 to draw any conclusion from our observations.
18755 If you wish to suggest changes to the @value{GDBN} source, send us context
18756 diffs. If you even discuss something in the @value{GDBN} source, refer to
18757 it by context, not by line number.
18759 The line numbers in our development sources will not match those in your
18760 sources. Your line numbers would convey no useful information to us.
18764 Here are some things that are not necessary:
18768 A description of the envelope of the bug.
18770 Often people who encounter a bug spend a lot of time investigating
18771 which changes to the input file will make the bug go away and which
18772 changes will not affect it.
18774 This is often time consuming and not very useful, because the way we
18775 will find the bug is by running a single example under the debugger
18776 with breakpoints, not by pure deduction from a series of examples.
18777 We recommend that you save your time for something else.
18779 Of course, if you can find a simpler example to report @emph{instead}
18780 of the original one, that is a convenience for us. Errors in the
18781 output will be easier to spot, running under the debugger will take
18782 less time, and so on.
18784 However, simplification is not vital; if you do not want to do this,
18785 report the bug anyway and send us the entire test case you used.
18788 A patch for the bug.
18790 A patch for the bug does help us if it is a good one. But do not omit
18791 the necessary information, such as the test case, on the assumption that
18792 a patch is all we need. We might see problems with your patch and decide
18793 to fix the problem another way, or we might not understand it at all.
18795 Sometimes with a program as complicated as @value{GDBN} it is very hard to
18796 construct an example that will make the program follow a certain path
18797 through the code. If you do not send us the example, we will not be able
18798 to construct one, so we will not be able to verify that the bug is fixed.
18800 And if we cannot understand what bug you are trying to fix, or why your
18801 patch should be an improvement, we will not install it. A test case will
18802 help us to understand.
18805 A guess about what the bug is or what it depends on.
18807 Such guesses are usually wrong. Even we cannot guess right about such
18808 things without first using the debugger to find the facts.
18811 @c The readline documentation is distributed with the readline code
18812 @c and consists of the two following files:
18814 @c inc-hist.texinfo
18815 @c Use -I with makeinfo to point to the appropriate directory,
18816 @c environment var TEXINPUTS with TeX.
18817 @include rluser.texinfo
18818 @include inc-hist.texinfo
18821 @node Formatting Documentation
18822 @appendix Formatting Documentation
18824 @cindex @value{GDBN} reference card
18825 @cindex reference card
18826 The @value{GDBN} 4 release includes an already-formatted reference card, ready
18827 for printing with PostScript or Ghostscript, in the @file{gdb}
18828 subdirectory of the main source directory@footnote{In
18829 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
18830 release.}. If you can use PostScript or Ghostscript with your printer,
18831 you can print the reference card immediately with @file{refcard.ps}.
18833 The release also includes the source for the reference card. You
18834 can format it, using @TeX{}, by typing:
18840 The @value{GDBN} reference card is designed to print in @dfn{landscape}
18841 mode on US ``letter'' size paper;
18842 that is, on a sheet 11 inches wide by 8.5 inches
18843 high. You will need to specify this form of printing as an option to
18844 your @sc{dvi} output program.
18846 @cindex documentation
18848 All the documentation for @value{GDBN} comes as part of the machine-readable
18849 distribution. The documentation is written in Texinfo format, which is
18850 a documentation system that uses a single source file to produce both
18851 on-line information and a printed manual. You can use one of the Info
18852 formatting commands to create the on-line version of the documentation
18853 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
18855 @value{GDBN} includes an already formatted copy of the on-line Info
18856 version of this manual in the @file{gdb} subdirectory. The main Info
18857 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
18858 subordinate files matching @samp{gdb.info*} in the same directory. If
18859 necessary, you can print out these files, or read them with any editor;
18860 but they are easier to read using the @code{info} subsystem in @sc{gnu}
18861 Emacs or the standalone @code{info} program, available as part of the
18862 @sc{gnu} Texinfo distribution.
18864 If you want to format these Info files yourself, you need one of the
18865 Info formatting programs, such as @code{texinfo-format-buffer} or
18868 If you have @code{makeinfo} installed, and are in the top level
18869 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
18870 version @value{GDBVN}), you can make the Info file by typing:
18877 If you want to typeset and print copies of this manual, you need @TeX{},
18878 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
18879 Texinfo definitions file.
18881 @TeX{} is a typesetting program; it does not print files directly, but
18882 produces output files called @sc{dvi} files. To print a typeset
18883 document, you need a program to print @sc{dvi} files. If your system
18884 has @TeX{} installed, chances are it has such a program. The precise
18885 command to use depends on your system; @kbd{lpr -d} is common; another
18886 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
18887 require a file name without any extension or a @samp{.dvi} extension.
18889 @TeX{} also requires a macro definitions file called
18890 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
18891 written in Texinfo format. On its own, @TeX{} cannot either read or
18892 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
18893 and is located in the @file{gdb-@var{version-number}/texinfo}
18896 If you have @TeX{} and a @sc{dvi} printer program installed, you can
18897 typeset and print this manual. First switch to the the @file{gdb}
18898 subdirectory of the main source directory (for example, to
18899 @file{gdb-@value{GDBVN}/gdb}) and type:
18905 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
18907 @node Installing GDB
18908 @appendix Installing @value{GDBN}
18909 @cindex configuring @value{GDBN}
18910 @cindex installation
18911 @cindex configuring @value{GDBN}, and source tree subdirectories
18913 @value{GDBN} comes with a @code{configure} script that automates the process
18914 of preparing @value{GDBN} for installation; you can then use @code{make} to
18915 build the @code{gdb} program.
18917 @c irrelevant in info file; it's as current as the code it lives with.
18918 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
18919 look at the @file{README} file in the sources; we may have improved the
18920 installation procedures since publishing this manual.}
18923 The @value{GDBN} distribution includes all the source code you need for
18924 @value{GDBN} in a single directory, whose name is usually composed by
18925 appending the version number to @samp{gdb}.
18927 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
18928 @file{gdb-@value{GDBVN}} directory. That directory contains:
18931 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
18932 script for configuring @value{GDBN} and all its supporting libraries
18934 @item gdb-@value{GDBVN}/gdb
18935 the source specific to @value{GDBN} itself
18937 @item gdb-@value{GDBVN}/bfd
18938 source for the Binary File Descriptor library
18940 @item gdb-@value{GDBVN}/include
18941 @sc{gnu} include files
18943 @item gdb-@value{GDBVN}/libiberty
18944 source for the @samp{-liberty} free software library
18946 @item gdb-@value{GDBVN}/opcodes
18947 source for the library of opcode tables and disassemblers
18949 @item gdb-@value{GDBVN}/readline
18950 source for the @sc{gnu} command-line interface
18952 @item gdb-@value{GDBVN}/glob
18953 source for the @sc{gnu} filename pattern-matching subroutine
18955 @item gdb-@value{GDBVN}/mmalloc
18956 source for the @sc{gnu} memory-mapped malloc package
18959 The simplest way to configure and build @value{GDBN} is to run @code{configure}
18960 from the @file{gdb-@var{version-number}} source directory, which in
18961 this example is the @file{gdb-@value{GDBVN}} directory.
18963 First switch to the @file{gdb-@var{version-number}} source directory
18964 if you are not already in it; then run @code{configure}. Pass the
18965 identifier for the platform on which @value{GDBN} will run as an
18971 cd gdb-@value{GDBVN}
18972 ./configure @var{host}
18977 where @var{host} is an identifier such as @samp{sun4} or
18978 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
18979 (You can often leave off @var{host}; @code{configure} tries to guess the
18980 correct value by examining your system.)
18982 Running @samp{configure @var{host}} and then running @code{make} builds the
18983 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
18984 libraries, then @code{gdb} itself. The configured source files, and the
18985 binaries, are left in the corresponding source directories.
18988 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
18989 system does not recognize this automatically when you run a different
18990 shell, you may need to run @code{sh} on it explicitly:
18993 sh configure @var{host}
18996 If you run @code{configure} from a directory that contains source
18997 directories for multiple libraries or programs, such as the
18998 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
18999 creates configuration files for every directory level underneath (unless
19000 you tell it not to, with the @samp{--norecursion} option).
19002 You should run the @code{configure} script from the top directory in the
19003 source tree, the @file{gdb-@var{version-number}} directory. If you run
19004 @code{configure} from one of the subdirectories, you will configure only
19005 that subdirectory. That is usually not what you want. In particular,
19006 if you run the first @code{configure} from the @file{gdb} subdirectory
19007 of the @file{gdb-@var{version-number}} directory, you will omit the
19008 configuration of @file{bfd}, @file{readline}, and other sibling
19009 directories of the @file{gdb} subdirectory. This leads to build errors
19010 about missing include files such as @file{bfd/bfd.h}.
19012 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
19013 However, you should make sure that the shell on your path (named by
19014 the @samp{SHELL} environment variable) is publicly readable. Remember
19015 that @value{GDBN} uses the shell to start your program---some systems refuse to
19016 let @value{GDBN} debug child processes whose programs are not readable.
19019 * Separate Objdir:: Compiling @value{GDBN} in another directory
19020 * Config Names:: Specifying names for hosts and targets
19021 * Configure Options:: Summary of options for configure
19024 @node Separate Objdir
19025 @section Compiling @value{GDBN} in another directory
19027 If you want to run @value{GDBN} versions for several host or target machines,
19028 you need a different @code{gdb} compiled for each combination of
19029 host and target. @code{configure} is designed to make this easy by
19030 allowing you to generate each configuration in a separate subdirectory,
19031 rather than in the source directory. If your @code{make} program
19032 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
19033 @code{make} in each of these directories builds the @code{gdb}
19034 program specified there.
19036 To build @code{gdb} in a separate directory, run @code{configure}
19037 with the @samp{--srcdir} option to specify where to find the source.
19038 (You also need to specify a path to find @code{configure}
19039 itself from your working directory. If the path to @code{configure}
19040 would be the same as the argument to @samp{--srcdir}, you can leave out
19041 the @samp{--srcdir} option; it is assumed.)
19043 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
19044 separate directory for a Sun 4 like this:
19048 cd gdb-@value{GDBVN}
19051 ../gdb-@value{GDBVN}/configure sun4
19056 When @code{configure} builds a configuration using a remote source
19057 directory, it creates a tree for the binaries with the same structure
19058 (and using the same names) as the tree under the source directory. In
19059 the example, you'd find the Sun 4 library @file{libiberty.a} in the
19060 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
19061 @file{gdb-sun4/gdb}.
19063 Make sure that your path to the @file{configure} script has just one
19064 instance of @file{gdb} in it. If your path to @file{configure} looks
19065 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
19066 one subdirectory of @value{GDBN}, not the whole package. This leads to
19067 build errors about missing include files such as @file{bfd/bfd.h}.
19069 One popular reason to build several @value{GDBN} configurations in separate
19070 directories is to configure @value{GDBN} for cross-compiling (where
19071 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
19072 programs that run on another machine---the @dfn{target}).
19073 You specify a cross-debugging target by
19074 giving the @samp{--target=@var{target}} option to @code{configure}.
19076 When you run @code{make} to build a program or library, you must run
19077 it in a configured directory---whatever directory you were in when you
19078 called @code{configure} (or one of its subdirectories).
19080 The @code{Makefile} that @code{configure} generates in each source
19081 directory also runs recursively. If you type @code{make} in a source
19082 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19083 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19084 will build all the required libraries, and then build GDB.
19086 When you have multiple hosts or targets configured in separate
19087 directories, you can run @code{make} on them in parallel (for example,
19088 if they are NFS-mounted on each of the hosts); they will not interfere
19092 @section Specifying names for hosts and targets
19094 The specifications used for hosts and targets in the @code{configure}
19095 script are based on a three-part naming scheme, but some short predefined
19096 aliases are also supported. The full naming scheme encodes three pieces
19097 of information in the following pattern:
19100 @var{architecture}-@var{vendor}-@var{os}
19103 For example, you can use the alias @code{sun4} as a @var{host} argument,
19104 or as the value for @var{target} in a @code{--target=@var{target}}
19105 option. The equivalent full name is @samp{sparc-sun-sunos4}.
19107 The @code{configure} script accompanying @value{GDBN} does not provide
19108 any query facility to list all supported host and target names or
19109 aliases. @code{configure} calls the Bourne shell script
19110 @code{config.sub} to map abbreviations to full names; you can read the
19111 script, if you wish, or you can use it to test your guesses on
19112 abbreviations---for example:
19115 % sh config.sub i386-linux
19117 % sh config.sub alpha-linux
19118 alpha-unknown-linux-gnu
19119 % sh config.sub hp9k700
19121 % sh config.sub sun4
19122 sparc-sun-sunos4.1.1
19123 % sh config.sub sun3
19124 m68k-sun-sunos4.1.1
19125 % sh config.sub i986v
19126 Invalid configuration `i986v': machine `i986v' not recognized
19130 @code{config.sub} is also distributed in the @value{GDBN} source
19131 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
19133 @node Configure Options
19134 @section @code{configure} options
19136 Here is a summary of the @code{configure} options and arguments that
19137 are most often useful for building @value{GDBN}. @code{configure} also has
19138 several other options not listed here. @inforef{What Configure
19139 Does,,configure.info}, for a full explanation of @code{configure}.
19142 configure @r{[}--help@r{]}
19143 @r{[}--prefix=@var{dir}@r{]}
19144 @r{[}--exec-prefix=@var{dir}@r{]}
19145 @r{[}--srcdir=@var{dirname}@r{]}
19146 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
19147 @r{[}--target=@var{target}@r{]}
19152 You may introduce options with a single @samp{-} rather than
19153 @samp{--} if you prefer; but you may abbreviate option names if you use
19158 Display a quick summary of how to invoke @code{configure}.
19160 @item --prefix=@var{dir}
19161 Configure the source to install programs and files under directory
19164 @item --exec-prefix=@var{dir}
19165 Configure the source to install programs under directory
19168 @c avoid splitting the warning from the explanation:
19170 @item --srcdir=@var{dirname}
19171 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
19172 @code{make} that implements the @code{VPATH} feature.}@*
19173 Use this option to make configurations in directories separate from the
19174 @value{GDBN} source directories. Among other things, you can use this to
19175 build (or maintain) several configurations simultaneously, in separate
19176 directories. @code{configure} writes configuration specific files in
19177 the current directory, but arranges for them to use the source in the
19178 directory @var{dirname}. @code{configure} creates directories under
19179 the working directory in parallel to the source directories below
19182 @item --norecursion
19183 Configure only the directory level where @code{configure} is executed; do not
19184 propagate configuration to subdirectories.
19186 @item --target=@var{target}
19187 Configure @value{GDBN} for cross-debugging programs running on the specified
19188 @var{target}. Without this option, @value{GDBN} is configured to debug
19189 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
19191 There is no convenient way to generate a list of all available targets.
19193 @item @var{host} @dots{}
19194 Configure @value{GDBN} to run on the specified @var{host}.
19196 There is no convenient way to generate a list of all available hosts.
19199 There are many other options available as well, but they are generally
19200 needed for special purposes only.
19202 @node Maintenance Commands
19203 @appendix Maintenance Commands
19204 @cindex maintenance commands
19205 @cindex internal commands
19207 In addition to commands intended for @value{GDBN} users, @value{GDBN}
19208 includes a number of commands intended for @value{GDBN} developers.
19209 These commands are provided here for reference.
19212 @kindex maint info breakpoints
19213 @item @anchor{maint info breakpoints}maint info breakpoints
19214 Using the same format as @samp{info breakpoints}, display both the
19215 breakpoints you've set explicitly, and those @value{GDBN} is using for
19216 internal purposes. Internal breakpoints are shown with negative
19217 breakpoint numbers. The type column identifies what kind of breakpoint
19222 Normal, explicitly set breakpoint.
19225 Normal, explicitly set watchpoint.
19228 Internal breakpoint, used to handle correctly stepping through
19229 @code{longjmp} calls.
19231 @item longjmp resume
19232 Internal breakpoint at the target of a @code{longjmp}.
19235 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
19238 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
19241 Shared library events.
19245 @kindex maint internal-error
19246 @kindex maint internal-warning
19247 @item maint internal-error
19248 @itemx maint internal-warning
19249 Cause @value{GDBN} to call the internal function @code{internal_error}
19250 or @code{internal_warning} and hence behave as though an internal error
19251 or internal warning has been detected. In addition to reporting the
19252 internal problem, these functions give the user the opportunity to
19253 either quit @value{GDBN} or create a core file of the current
19254 @value{GDBN} session.
19257 (gdb) @kbd{maint internal-error testing, 1, 2}
19258 @dots{}/maint.c:121: internal-error: testing, 1, 2
19259 A problem internal to GDB has been detected. Further
19260 debugging may prove unreliable.
19261 Quit this debugging session? (y or n) @kbd{n}
19262 Create a core file? (y or n) @kbd{n}
19266 Takes an optional parameter that is used as the text of the error or
19269 @kindex maint print registers
19270 @kindex maint print raw-registers
19271 @kindex maint print cooked-registers
19272 @kindex maint print register-groups
19273 @item maint print registers
19274 @itemx maint print raw-registers
19275 @itemx maint print cooked-registers
19276 @itemx maint print register-groups
19277 Print @value{GDBN}'s internal register data structures.
19279 The command @code{maint print raw-registers} includes the contents of
19280 the raw register cache; the command @code{maint print cooked-registers}
19281 includes the (cooked) value of all registers; and the command
19282 @code{maint print register-groups} includes the groups that each
19283 register is a member of. @xref{Registers,, Registers, gdbint,
19284 @value{GDBN} Internals}.
19286 Takes an optional file parameter.
19288 @kindex maint print reggroups
19289 @item maint print reggroups
19290 Print @value{GDBN}'s internal register group data structures.
19292 Takes an optional file parameter.
19295 (gdb) @kbd{maint print reggroups}
19306 @kindex maint set profile
19307 @kindex maint show profile
19308 @cindex profiling GDB
19309 @item maint set profile
19310 @itemx maint show profile
19311 Control profiling of @value{GDBN}.
19313 Profiling will be disabled until you use the @samp{maint set profile}
19314 command to enable it. When you enable profiling, the system will begin
19315 collecting timing and execution count data; when you disable profiling or
19316 exit @value{GDBN}, the results will be written to a log file. Remember that
19317 if you use profiling, @value{GDBN} will overwrite the profiling log file
19318 (often called @file{gmon.out}). If you have a record of important profiling
19319 data in a @file{gmon.out} file, be sure to move it to a safe location.
19321 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
19322 compiled with the @samp{-pg} compiler option.
19327 @node Remote Protocol
19328 @appendix @value{GDBN} Remote Serial Protocol
19333 * Stop Reply Packets::
19334 * General Query Packets::
19335 * Register Packet Format::
19337 * File-I/O remote protocol extension::
19343 There may be occasions when you need to know something about the
19344 protocol---for example, if there is only one serial port to your target
19345 machine, you might want your program to do something special if it
19346 recognizes a packet meant for @value{GDBN}.
19348 In the examples below, @samp{->} and @samp{<-} are used to indicate
19349 transmitted and received data respectfully.
19351 @cindex protocol, @value{GDBN} remote serial
19352 @cindex serial protocol, @value{GDBN} remote
19353 @cindex remote serial protocol
19354 All @value{GDBN} commands and responses (other than acknowledgments) are
19355 sent as a @var{packet}. A @var{packet} is introduced with the character
19356 @samp{$}, the actual @var{packet-data}, and the terminating character
19357 @samp{#} followed by a two-digit @var{checksum}:
19360 @code{$}@var{packet-data}@code{#}@var{checksum}
19364 @cindex checksum, for @value{GDBN} remote
19366 The two-digit @var{checksum} is computed as the modulo 256 sum of all
19367 characters between the leading @samp{$} and the trailing @samp{#} (an
19368 eight bit unsigned checksum).
19370 Implementors should note that prior to @value{GDBN} 5.0 the protocol
19371 specification also included an optional two-digit @var{sequence-id}:
19374 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
19377 @cindex sequence-id, for @value{GDBN} remote
19379 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
19380 has never output @var{sequence-id}s. Stubs that handle packets added
19381 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
19383 @cindex acknowledgment, for @value{GDBN} remote
19384 When either the host or the target machine receives a packet, the first
19385 response expected is an acknowledgment: either @samp{+} (to indicate
19386 the package was received correctly) or @samp{-} (to request
19390 -> @code{$}@var{packet-data}@code{#}@var{checksum}
19395 The host (@value{GDBN}) sends @var{command}s, and the target (the
19396 debugging stub incorporated in your program) sends a @var{response}. In
19397 the case of step and continue @var{command}s, the response is only sent
19398 when the operation has completed (the target has again stopped).
19400 @var{packet-data} consists of a sequence of characters with the
19401 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
19404 Fields within the packet should be separated using @samp{,} @samp{;} or
19405 @cindex remote protocol, field separator
19406 @samp{:}. Except where otherwise noted all numbers are represented in
19407 @sc{hex} with leading zeros suppressed.
19409 Implementors should note that prior to @value{GDBN} 5.0, the character
19410 @samp{:} could not appear as the third character in a packet (as it
19411 would potentially conflict with the @var{sequence-id}).
19413 Response @var{data} can be run-length encoded to save space. A @samp{*}
19414 means that the next character is an @sc{ascii} encoding giving a repeat count
19415 which stands for that many repetitions of the character preceding the
19416 @samp{*}. The encoding is @code{n+29}, yielding a printable character
19417 where @code{n >=3} (which is where rle starts to win). The printable
19418 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
19419 value greater than 126 should not be used.
19421 Some remote systems have used a different run-length encoding mechanism
19422 loosely refered to as the cisco encoding. Following the @samp{*}
19423 character are two hex digits that indicate the size of the packet.
19430 means the same as "0000".
19432 The error response returned for some packets includes a two character
19433 error number. That number is not well defined.
19435 For any @var{command} not supported by the stub, an empty response
19436 (@samp{$#00}) should be returned. That way it is possible to extend the
19437 protocol. A newer @value{GDBN} can tell if a packet is supported based
19440 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
19441 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
19447 The following table provides a complete list of all currently defined
19448 @var{command}s and their corresponding response @var{data}.
19452 @item @code{!} --- extended mode
19453 @cindex @code{!} packet
19455 Enable extended mode. In extended mode, the remote server is made
19456 persistent. The @samp{R} packet is used to restart the program being
19462 The remote target both supports and has enabled extended mode.
19465 @item @code{?} --- last signal
19466 @cindex @code{?} packet
19468 Indicate the reason the target halted. The reply is the same as for
19472 @xref{Stop Reply Packets}, for the reply specifications.
19474 @item @code{a} --- reserved
19476 Reserved for future use.
19478 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
19479 @cindex @code{A} packet
19481 Initialized @samp{argv[]} array passed into program. @var{arglen}
19482 specifies the number of bytes in the hex encoded byte stream @var{arg}.
19483 See @code{gdbserver} for more details.
19491 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
19492 @cindex @code{b} packet
19494 Change the serial line speed to @var{baud}.
19496 JTC: @emph{When does the transport layer state change? When it's
19497 received, or after the ACK is transmitted. In either case, there are
19498 problems if the command or the acknowledgment packet is dropped.}
19500 Stan: @emph{If people really wanted to add something like this, and get
19501 it working for the first time, they ought to modify ser-unix.c to send
19502 some kind of out-of-band message to a specially-setup stub and have the
19503 switch happen "in between" packets, so that from remote protocol's point
19504 of view, nothing actually happened.}
19506 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
19507 @cindex @code{B} packet
19509 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
19510 breakpoint at @var{addr}.
19512 This packet has been replaced by the @samp{Z} and @samp{z} packets
19513 (@pxref{insert breakpoint or watchpoint packet}).
19515 @item @code{c}@var{addr} --- continue
19516 @cindex @code{c} packet
19518 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19522 @xref{Stop Reply Packets}, for the reply specifications.
19524 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
19525 @cindex @code{C} packet
19527 Continue with signal @var{sig} (hex signal number). If
19528 @code{;}@var{addr} is omitted, resume at same address.
19531 @xref{Stop Reply Packets}, for the reply specifications.
19533 @item @code{d} --- toggle debug @strong{(deprecated)}
19534 @cindex @code{d} packet
19538 @item @code{D} --- detach
19539 @cindex @code{D} packet
19541 Detach @value{GDBN} from the remote system. Sent to the remote target
19542 before @value{GDBN} disconnects.
19546 @item @emph{no response}
19547 @value{GDBN} does not check for any response after sending this packet.
19550 @item @code{e} --- reserved
19552 Reserved for future use.
19554 @item @code{E} --- reserved
19556 Reserved for future use.
19558 @item @code{f} --- reserved
19560 Reserved for future use.
19562 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
19563 @cindex @code{F} packet
19565 This packet is send by @value{GDBN} as reply to a @code{F} request packet
19566 sent by the target. This is part of the File-I/O protocol extension.
19567 @xref{File-I/O remote protocol extension}, for the specification.
19569 @item @code{g} --- read registers
19570 @anchor{read registers packet}
19571 @cindex @code{g} packet
19573 Read general registers.
19577 @item @var{XX@dots{}}
19578 Each byte of register data is described by two hex digits. The bytes
19579 with the register are transmitted in target byte order. The size of
19580 each register and their position within the @samp{g} @var{packet} are
19581 determined by the @value{GDBN} internal macros @var{REGISTER_RAW_SIZE}
19582 and @var{REGISTER_NAME} macros. The specification of several standard
19583 @code{g} packets is specified below.
19588 @item @code{G}@var{XX@dots{}} --- write regs
19589 @cindex @code{G} packet
19591 @xref{read registers packet}, for a description of the @var{XX@dots{}}
19602 @item @code{h} --- reserved
19604 Reserved for future use.
19606 @item @code{H}@var{c}@var{t@dots{}} --- set thread
19607 @cindex @code{H} packet
19609 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
19610 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
19611 should be @samp{c} for step and continue operations, @samp{g} for other
19612 operations. The thread designator @var{t@dots{}} may be -1, meaning all
19613 the threads, a thread number, or zero which means pick any thread.
19624 @c 'H': How restrictive (or permissive) is the thread model. If a
19625 @c thread is selected and stopped, are other threads allowed
19626 @c to continue to execute? As I mentioned above, I think the
19627 @c semantics of each command when a thread is selected must be
19628 @c described. For example:
19630 @c 'g': If the stub supports threads and a specific thread is
19631 @c selected, returns the register block from that thread;
19632 @c otherwise returns current registers.
19634 @c 'G' If the stub supports threads and a specific thread is
19635 @c selected, sets the registers of the register block of
19636 @c that thread; otherwise sets current registers.
19638 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
19639 @anchor{cycle step packet}
19640 @cindex @code{i} packet
19642 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
19643 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
19644 step starting at that address.
19646 @item @code{I} --- signal then cycle step @strong{(reserved)}
19647 @cindex @code{I} packet
19649 @xref{step with signal packet}. @xref{cycle step packet}.
19651 @item @code{j} --- reserved
19653 Reserved for future use.
19655 @item @code{J} --- reserved
19657 Reserved for future use.
19659 @item @code{k} --- kill request
19660 @cindex @code{k} packet
19662 FIXME: @emph{There is no description of how to operate when a specific
19663 thread context has been selected (i.e.@: does 'k' kill only that
19666 @item @code{K} --- reserved
19668 Reserved for future use.
19670 @item @code{l} --- reserved
19672 Reserved for future use.
19674 @item @code{L} --- reserved
19676 Reserved for future use.
19678 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
19679 @cindex @code{m} packet
19681 Read @var{length} bytes of memory starting at address @var{addr}.
19682 Neither @value{GDBN} nor the stub assume that sized memory transfers are
19683 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
19684 transfer mechanism is needed.}
19688 @item @var{XX@dots{}}
19689 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
19690 to read only part of the data. Neither @value{GDBN} nor the stub assume
19691 that sized memory transfers are assumed using word aligned
19692 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
19698 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
19699 @cindex @code{M} packet
19701 Write @var{length} bytes of memory starting at address @var{addr}.
19702 @var{XX@dots{}} is the data.
19709 for an error (this includes the case where only part of the data was
19713 @item @code{n} --- reserved
19715 Reserved for future use.
19717 @item @code{N} --- reserved
19719 Reserved for future use.
19721 @item @code{o} --- reserved
19723 Reserved for future use.
19725 @item @code{O} --- reserved
19727 Reserved for future use.
19729 @item @code{p}@var{n@dots{}} --- read reg @strong{(reserved)}
19730 @cindex @code{p} packet
19732 @xref{write register packet}.
19736 @item @var{r@dots{}.}
19737 The hex encoded value of the register in target byte order.
19740 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
19741 @anchor{write register packet}
19742 @cindex @code{P} packet
19744 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
19745 digits for each byte in the register (target byte order).
19755 @item @code{q}@var{query} --- general query
19756 @anchor{general query packet}
19757 @cindex @code{q} packet
19759 Request info about @var{query}. In general @value{GDBN} queries have a
19760 leading upper case letter. Custom vendor queries should use a company
19761 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
19762 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
19763 that they match the full @var{query} name.
19767 @item @var{XX@dots{}}
19768 Hex encoded data from query. The reply can not be empty.
19772 Indicating an unrecognized @var{query}.
19775 @item @code{Q}@var{var}@code{=}@var{val} --- general set
19776 @cindex @code{Q} packet
19778 Set value of @var{var} to @var{val}.
19780 @xref{general query packet}, for a discussion of naming conventions.
19782 @item @code{r} --- reset @strong{(deprecated)}
19783 @cindex @code{r} packet
19785 Reset the entire system.
19787 @item @code{R}@var{XX} --- remote restart
19788 @cindex @code{R} packet
19790 Restart the program being debugged. @var{XX}, while needed, is ignored.
19791 This packet is only available in extended mode.
19795 @item @emph{no reply}
19796 The @samp{R} packet has no reply.
19799 @item @code{s}@var{addr} --- step
19800 @cindex @code{s} packet
19802 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19806 @xref{Stop Reply Packets}, for the reply specifications.
19808 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
19809 @anchor{step with signal packet}
19810 @cindex @code{S} packet
19812 Like @samp{C} but step not continue.
19815 @xref{Stop Reply Packets}, for the reply specifications.
19817 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
19818 @cindex @code{t} packet
19820 Search backwards starting at address @var{addr} for a match with pattern
19821 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
19822 @var{addr} must be at least 3 digits.
19824 @item @code{T}@var{XX} --- thread alive
19825 @cindex @code{T} packet
19827 Find out if the thread XX is alive.
19832 thread is still alive
19837 @item @code{u} --- reserved
19839 Reserved for future use.
19841 @item @code{U} --- reserved
19843 Reserved for future use.
19845 @item @code{v} --- reserved
19847 Reserved for future use.
19849 @item @code{V} --- reserved
19851 Reserved for future use.
19853 @item @code{w} --- reserved
19855 Reserved for future use.
19857 @item @code{W} --- reserved
19859 Reserved for future use.
19861 @item @code{x} --- reserved
19863 Reserved for future use.
19865 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
19866 @cindex @code{X} packet
19868 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
19869 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
19870 escaped using @code{0x7d}.
19880 @item @code{y} --- reserved
19882 Reserved for future use.
19884 @item @code{Y} reserved
19886 Reserved for future use.
19888 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
19889 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
19890 @anchor{insert breakpoint or watchpoint packet}
19891 @cindex @code{z} packet
19892 @cindex @code{Z} packets
19894 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
19895 watchpoint starting at address @var{address} and covering the next
19896 @var{length} bytes.
19898 Each breakpoint and watchpoint packet @var{type} is documented
19901 @emph{Implementation notes: A remote target shall return an empty string
19902 for an unrecognized breakpoint or watchpoint packet @var{type}. A
19903 remote target shall support either both or neither of a given
19904 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
19905 avoid potential problems with duplicate packets, the operations should
19906 be implemented in an idempotent way.}
19908 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
19909 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
19910 @cindex @code{z0} packet
19911 @cindex @code{Z0} packet
19913 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
19914 @code{addr} of size @code{length}.
19916 A memory breakpoint is implemented by replacing the instruction at
19917 @var{addr} with a software breakpoint or trap instruction. The
19918 @code{length} is used by targets that indicates the size of the
19919 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
19920 @sc{mips} can insert either a 2 or 4 byte breakpoint).
19922 @emph{Implementation note: It is possible for a target to copy or move
19923 code that contains memory breakpoints (e.g., when implementing
19924 overlays). The behavior of this packet, in the presence of such a
19925 target, is not defined.}
19937 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
19938 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
19939 @cindex @code{z1} packet
19940 @cindex @code{Z1} packet
19942 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
19943 address @code{addr} of size @code{length}.
19945 A hardware breakpoint is implemented using a mechanism that is not
19946 dependant on being able to modify the target's memory.
19948 @emph{Implementation note: A hardware breakpoint is not affected by code
19961 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
19962 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
19963 @cindex @code{z2} packet
19964 @cindex @code{Z2} packet
19966 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
19978 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
19979 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
19980 @cindex @code{z3} packet
19981 @cindex @code{Z3} packet
19983 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
19995 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
19996 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
19997 @cindex @code{z4} packet
19998 @cindex @code{Z4} packet
20000 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
20014 @node Stop Reply Packets
20015 @section Stop Reply Packets
20016 @cindex stop reply packets
20018 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
20019 receive any of the below as a reply. In the case of the @samp{C},
20020 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
20021 when the target halts. In the below the exact meaning of @samp{signal
20022 number} is poorly defined. In general one of the UNIX signal numbering
20023 conventions is used.
20028 @var{AA} is the signal number
20030 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
20031 @cindex @code{T} packet reply
20033 @var{AA} = two hex digit signal number; @var{n...} = register number
20034 (hex), @var{r...} = target byte ordered register contents, size defined
20035 by @code{REGISTER_RAW_SIZE}; @var{n...} = @samp{thread}, @var{r...} =
20036 thread process ID, this is a hex integer; @var{n...} = (@samp{watch} |
20037 @samp{rwatch} | @samp{awatch}, @var{r...} = data address, this is a hex
20038 integer; @var{n...} = other string not starting with valid hex digit.
20039 @value{GDBN} should ignore this @var{n...}, @var{r...} pair and go on
20040 to the next. This way we can extend the protocol.
20044 The process exited, and @var{AA} is the exit status. This is only
20045 applicable to certain targets.
20049 The process terminated with signal @var{AA}.
20051 @item N@var{AA};@var{t@dots{}};@var{d@dots{}};@var{b@dots{}} @strong{(obsolete)}
20053 @var{AA} = signal number; @var{t@dots{}} = address of symbol
20054 @code{_start}; @var{d@dots{}} = base of data section; @var{b@dots{}} =
20055 base of bss section. @emph{Note: only used by Cisco Systems targets.
20056 The difference between this reply and the @samp{qOffsets} query is that
20057 the @samp{N} packet may arrive spontaneously whereas the @samp{qOffsets}
20058 is a query initiated by the host debugger.}
20060 @item O@var{XX@dots{}}
20062 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
20063 any time while the program is running and the debugger should continue
20064 to wait for @samp{W}, @samp{T}, etc.
20066 @item F@var{call-id}@code{,}@var{parameter@dots{}}
20068 @var{call-id} is the identifier which says which host system call should
20069 be called. This is just the name of the function. Translation into the
20070 correct system call is only applicable as it's defined in @value{GDBN}.
20071 @xref{File-I/O remote protocol extension}, for a list of implemented
20074 @var{parameter@dots{}} is a list of parameters as defined for this very
20077 The target replies with this packet when it expects @value{GDBN} to call
20078 a host system call on behalf of the target. @value{GDBN} replies with
20079 an appropriate @code{F} packet and keeps up waiting for the next reply
20080 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
20081 @samp{s} action is expected to be continued.
20082 @xref{File-I/O remote protocol extension}, for more details.
20086 @node General Query Packets
20087 @section General Query Packets
20089 The following set and query packets have already been defined.
20093 @item @code{q}@code{C} --- current thread
20095 Return the current thread id.
20099 @item @code{QC}@var{pid}
20100 Where @var{pid} is a HEX encoded 16 bit process id.
20102 Any other reply implies the old pid.
20105 @item @code{q}@code{fThreadInfo} -- all thread ids
20107 @code{q}@code{sThreadInfo}
20109 Obtain a list of active thread ids from the target (OS). Since there
20110 may be too many active threads to fit into one reply packet, this query
20111 works iteratively: it may require more than one query/reply sequence to
20112 obtain the entire list of threads. The first query of the sequence will
20113 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
20114 sequence will be the @code{qs}@code{ThreadInfo} query.
20116 NOTE: replaces the @code{qL} query (see below).
20120 @item @code{m}@var{id}
20122 @item @code{m}@var{id},@var{id}@dots{}
20123 a comma-separated list of thread ids
20125 (lower case 'el') denotes end of list.
20128 In response to each query, the target will reply with a list of one or
20129 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
20130 will respond to each reply with a request for more thread ids (using the
20131 @code{qs} form of the query), until the target responds with @code{l}
20132 (lower-case el, for @code{'last'}).
20134 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
20136 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
20137 string description of a thread's attributes from the target OS. This
20138 string may contain anything that the target OS thinks is interesting for
20139 @value{GDBN} to tell the user about the thread. The string is displayed
20140 in @value{GDBN}'s @samp{info threads} display. Some examples of
20141 possible thread extra info strings are ``Runnable'', or ``Blocked on
20146 @item @var{XX@dots{}}
20147 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
20148 the printable string containing the extra information about the thread's
20152 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
20154 Obtain thread information from RTOS. Where: @var{startflag} (one hex
20155 digit) is one to indicate the first query and zero to indicate a
20156 subsequent query; @var{threadcount} (two hex digits) is the maximum
20157 number of threads the response packet can contain; and @var{nextthread}
20158 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
20159 returned in the response as @var{argthread}.
20161 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
20166 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
20167 Where: @var{count} (two hex digits) is the number of threads being
20168 returned; @var{done} (one hex digit) is zero to indicate more threads
20169 and one indicates no further threads; @var{argthreadid} (eight hex
20170 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
20171 is a sequence of thread IDs from the target. @var{threadid} (eight hex
20172 digits). See @code{remote.c:parse_threadlist_response()}.
20175 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
20179 @item @code{E}@var{NN}
20180 An error (such as memory fault)
20181 @item @code{C}@var{CRC32}
20182 A 32 bit cyclic redundancy check of the specified memory region.
20185 @item @code{q}@code{Offsets} --- query sect offs
20187 Get section offsets that the target used when re-locating the downloaded
20188 image. @emph{Note: while a @code{Bss} offset is included in the
20189 response, @value{GDBN} ignores this and instead applies the @code{Data}
20190 offset to the @code{Bss} section.}
20194 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
20197 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
20199 Returns information on @var{threadid}. Where: @var{mode} is a hex
20200 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
20207 See @code{remote.c:remote_unpack_thread_info_response()}.
20209 @item @code{q}@code{Rcmd,}@var{command} --- remote command
20211 @var{command} (hex encoded) is passed to the local interpreter for
20212 execution. Invalid commands should be reported using the output string.
20213 Before the final result packet, the target may also respond with a
20214 number of intermediate @code{O}@var{output} console output packets.
20215 @emph{Implementors should note that providing access to a stubs's
20216 interpreter may have security implications}.
20221 A command response with no output.
20223 A command response with the hex encoded output string @var{OUTPUT}.
20224 @item @code{E}@var{NN}
20225 Indicate a badly formed request.
20227 When @samp{q}@samp{Rcmd} is not recognized.
20230 @item @code{qSymbol::} --- symbol lookup
20232 Notify the target that @value{GDBN} is prepared to serve symbol lookup
20233 requests. Accept requests from the target for the values of symbols.
20238 The target does not need to look up any (more) symbols.
20239 @item @code{qSymbol:}@var{sym_name}
20240 The target requests the value of symbol @var{sym_name} (hex encoded).
20241 @value{GDBN} may provide the value by using the
20242 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
20245 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
20247 Set the value of @var{sym_name} to @var{sym_value}.
20249 @var{sym_name} (hex encoded) is the name of a symbol whose value the
20250 target has previously requested.
20252 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
20253 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
20259 The target does not need to look up any (more) symbols.
20260 @item @code{qSymbol:}@var{sym_name}
20261 The target requests the value of a new symbol @var{sym_name} (hex
20262 encoded). @value{GDBN} will continue to supply the values of symbols
20263 (if available), until the target ceases to request them.
20268 @node Register Packet Format
20269 @section Register Packet Format
20271 The following @samp{g}/@samp{G} packets have previously been defined.
20272 In the below, some thirty-two bit registers are transferred as
20273 sixty-four bits. Those registers should be zero/sign extended (which?)
20274 to fill the space allocated. Register bytes are transfered in target
20275 byte order. The two nibbles within a register byte are transfered
20276 most-significant - least-significant.
20282 All registers are transfered as thirty-two bit quantities in the order:
20283 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
20284 registers; fsr; fir; fp.
20288 All registers are transfered as sixty-four bit quantities (including
20289 thirty-two bit registers such as @code{sr}). The ordering is the same
20297 Example sequence of a target being re-started. Notice how the restart
20298 does not get any direct output:
20303 @emph{target restarts}
20306 <- @code{T001:1234123412341234}
20310 Example sequence of a target being stepped by a single instruction:
20313 -> @code{G1445@dots{}}
20318 <- @code{T001:1234123412341234}
20322 <- @code{1455@dots{}}
20326 @node File-I/O remote protocol extension
20327 @section File-I/O remote protocol extension
20328 @cindex File-I/O remote protocol extension
20331 * File-I/O Overview::
20332 * Protocol basics::
20333 * The `F' request packet::
20334 * The `F' reply packet::
20335 * Memory transfer::
20336 * The Ctrl-C message::
20338 * The isatty call::
20339 * The system call::
20340 * List of supported calls::
20341 * Protocol specific representation of datatypes::
20343 * File-I/O Examples::
20346 @node File-I/O Overview
20347 @subsection File-I/O Overview
20348 @cindex file-i/o overview
20350 The File I/O remote protocol extension (short: File-I/O) allows the
20351 target to use the hosts file system and console I/O when calling various
20352 system calls. System calls on the target system are translated into a
20353 remote protocol packet to the host system which then performs the needed
20354 actions and returns with an adequate response packet to the target system.
20355 This simulates file system operations even on targets that lack file systems.
20357 The protocol is defined host- and target-system independent. It uses
20358 it's own independent representation of datatypes and values. Both,
20359 @value{GDBN} and the target's @value{GDBN} stub are responsible for
20360 translating the system dependent values into the unified protocol values
20361 when data is transmitted.
20363 The communication is synchronous. A system call is possible only
20364 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
20365 packets. While @value{GDBN} handles the request for a system call,
20366 the target is stopped to allow deterministic access to the target's
20367 memory. Therefore File-I/O is not interuptible by target signals. It
20368 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
20370 The target's request to perform a host system call does not finish
20371 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
20372 after finishing the system call, the target returns to continuing the
20373 previous activity (continue, step). No additional continue or step
20374 request from @value{GDBN} is required.
20378 <- target requests 'system call X'
20379 target is stopped, @value{GDBN} executes system call
20380 -> GDB returns result
20381 ... target continues, GDB returns to wait for the target
20382 <- target hits breakpoint and sends a Txx packet
20385 The protocol is only used for files on the host file system and
20386 for I/O on the console. Character or block special devices, pipes,
20387 named pipes or sockets or any other communication method on the host
20388 system are not supported by this protocol.
20390 @node Protocol basics
20391 @subsection Protocol basics
20392 @cindex protocol basics, file-i/o
20394 The File-I/O protocol uses the @code{F} packet, as request as well
20395 as as reply packet. Since a File-I/O system call can only occur when
20396 @value{GDBN} is waiting for the continuing or stepping target, the
20397 File-I/O request is a reply that @value{GDBN} has to expect as a result
20398 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
20399 This @code{F} packet contains all information needed to allow @value{GDBN}
20400 to call the appropriate host system call:
20404 A unique identifier for the requested system call.
20407 All parameters to the system call. Pointers are given as addresses
20408 in the target memory address space. Pointers to strings are given as
20409 pointer/length pair. Numerical values are given as they are.
20410 Numerical control values are given in a protocol specific representation.
20414 At that point @value{GDBN} has to perform the following actions.
20418 If parameter pointer values are given, which point to data needed as input
20419 to a system call, @value{GDBN} requests this data from the target with a
20420 standard @code{m} packet request. This additional communication has to be
20421 expected by the target implementation and is handled as any other @code{m}
20425 @value{GDBN} translates all value from protocol representation to host
20426 representation as needed. Datatypes are coerced into the host types.
20429 @value{GDBN} calls the system call
20432 It then coerces datatypes back to protocol representation.
20435 If pointer parameters in the request packet point to buffer space in which
20436 a system call is expected to copy data to, the data is transmitted to the
20437 target using a @code{M} or @code{X} packet. This packet has to be expected
20438 by the target implementation and is handled as any other @code{M} or @code{X}
20443 Eventually @value{GDBN} replies with another @code{F} packet which contains all
20444 necessary information for the target to continue. This at least contains
20451 @code{errno}, if has been changed by the system call.
20458 After having done the needed type and value coercion, the target continues
20459 the latest continue or step action.
20461 @node The `F' request packet
20462 @subsection The @code{F} request packet
20463 @cindex file-i/o request packet
20464 @cindex @code{F} request packet
20466 The @code{F} request packet has the following format:
20471 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
20474 @var{call-id} is the identifier to indicate the host system call to be called.
20475 This is just the name of the function.
20477 @var{parameter@dots{}} are the parameters to the system call.
20481 Parameters are hexadecimal integer values, either the real values in case
20482 of scalar datatypes, as pointers to target buffer space in case of compound
20483 datatypes and unspecified memory areas or as pointer/length pairs in case
20484 of string parameters. These are appended to the call-id, each separated
20485 from its predecessor by a comma. All values are transmitted in ASCII
20486 string representation, pointer/length pairs separated by a slash.
20488 @node The `F' reply packet
20489 @subsection The @code{F} reply packet
20490 @cindex file-i/o reply packet
20491 @cindex @code{F} reply packet
20493 The @code{F} reply packet has the following format:
20498 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
20501 @var{retcode} is the return code of the system call as hexadecimal value.
20503 @var{errno} is the errno set by the call, in protocol specific representation.
20504 This parameter can be omitted if the call was successful.
20506 @var{Ctrl-C flag} is only send if the user requested a break. In this
20507 case, @var{errno} must be send as well, even if the call was successful.
20508 The @var{Ctrl-C flag} itself consists of the character 'C':
20515 or, if the call was interupted before the host call has been performed:
20522 assuming 4 is the protocol specific representation of @code{EINTR}.
20526 @node Memory transfer
20527 @subsection Memory transfer
20528 @cindex memory transfer, in file-i/o protocol
20530 Structured data which is transferred using a memory read or write as e.g.@:
20531 a @code{struct stat} is expected to be in a protocol specific format with
20532 all scalar multibyte datatypes being big endian. This should be done by
20533 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
20534 it transfers memory to the target. Transferred pointers to structured
20535 data should point to the already coerced data at any time.
20537 @node The Ctrl-C message
20538 @subsection The Ctrl-C message
20539 @cindex ctrl-c message, in file-i/o protocol
20541 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
20542 reply packet. In this case the target should behave, as if it had
20543 gotten a break message. The meaning for the target is ``system call
20544 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
20545 (as with a break message) and return to @value{GDBN} with a @code{T02}
20546 packet. In this case, it's important for the target to know, in which
20547 state the system call was interrupted. Since this action is by design
20548 not an atomic operation, we have to differ between two cases:
20552 The system call hasn't been performed on the host yet.
20555 The system call on the host has been finished.
20559 These two states can be distinguished by the target by the value of the
20560 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
20561 call hasn't been performed. This is equivalent to the @code{EINTR} handling
20562 on POSIX systems. In any other case, the target may presume that the
20563 system call has been finished --- successful or not --- and should behave
20564 as if the break message arrived right after the system call.
20566 @value{GDBN} must behave reliable. If the system call has not been called
20567 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
20568 @code{errno} in the packet. If the system call on the host has been finished
20569 before the user requests a break, the full action must be finshed by
20570 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
20571 The @code{F} packet may only be send when either nothing has happened
20572 or the full action has been completed.
20575 @subsection Console I/O
20576 @cindex console i/o as part of file-i/o
20578 By default and if not explicitely closed by the target system, the file
20579 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
20580 on the @value{GDBN} console is handled as any other file output operation
20581 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
20582 by @value{GDBN} so that after the target read request from file descriptor
20583 0 all following typing is buffered until either one of the following
20588 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
20590 system call is treated as finished.
20593 The user presses @kbd{Enter}. This is treated as end of input with a trailing
20597 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
20598 character, especially no Ctrl-D is appended to the input.
20602 If the user has typed more characters as fit in the buffer given to
20603 the read call, the trailing characters are buffered in @value{GDBN} until
20604 either another @code{read(0, @dots{})} is requested by the target or debugging
20605 is stopped on users request.
20607 @node The isatty call
20608 @subsection The isatty(3) call
20609 @cindex isatty call, file-i/o protocol
20611 A special case in this protocol is the library call @code{isatty} which
20612 is implemented as it's own call inside of this protocol. It returns
20613 1 to the target if the file descriptor given as parameter is attached
20614 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
20615 would require implementing @code{ioctl} and would be more complex than
20618 @node The system call
20619 @subsection The system(3) call
20620 @cindex system call, file-i/o protocol
20622 The other special case in this protocol is the @code{system} call which
20623 is implemented as it's own call, too. @value{GDBN} is taking over the full
20624 task of calling the necessary host calls to perform the @code{system}
20625 call. The return value of @code{system} is simplified before it's returned
20626 to the target. Basically, the only signal transmitted back is @code{EINTR}
20627 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
20628 entirely of the exit status of the called command.
20630 Due to security concerns, the @code{system} call is refused to be called
20631 by @value{GDBN} by default. The user has to allow this call explicitly by
20635 @kindex set remote system-call-allowed 1
20636 @item @code{set remote system-call-allowed 1}
20639 Disabling the @code{system} call is done by
20642 @kindex set remote system-call-allowed 0
20643 @item @code{set remote system-call-allowed 0}
20646 The current setting is shown by typing
20649 @kindex show remote system-call-allowed
20650 @item @code{show remote system-call-allowed}
20653 @node List of supported calls
20654 @subsection List of supported calls
20655 @cindex list of supported file-i/o calls
20672 @unnumberedsubsubsec open
20673 @cindex open, file-i/o system call
20677 int open(const char *pathname, int flags);
20678 int open(const char *pathname, int flags, mode_t mode);
20681 Fopen,pathptr/len,flags,mode
20685 @code{flags} is the bitwise or of the following values:
20689 If the file does not exist it will be created. The host
20690 rules apply as far as file ownership and time stamps
20694 When used with O_CREAT, if the file already exists it is
20695 an error and open() fails.
20698 If the file already exists and the open mode allows
20699 writing (O_RDWR or O_WRONLY is given) it will be
20700 truncated to length 0.
20703 The file is opened in append mode.
20706 The file is opened for reading only.
20709 The file is opened for writing only.
20712 The file is opened for reading and writing.
20715 Each other bit is silently ignored.
20720 @code{mode} is the bitwise or of the following values:
20724 User has read permission.
20727 User has write permission.
20730 Group has read permission.
20733 Group has write permission.
20736 Others have read permission.
20739 Others have write permission.
20742 Each other bit is silently ignored.
20747 @exdent Return value:
20748 open returns the new file descriptor or -1 if an error
20756 pathname already exists and O_CREAT and O_EXCL were used.
20759 pathname refers to a directory.
20762 The requested access is not allowed.
20765 pathname was too long.
20768 A directory component in pathname does not exist.
20771 pathname refers to a device, pipe, named pipe or socket.
20774 pathname refers to a file on a read-only filesystem and
20775 write access was requested.
20778 pathname is an invalid pointer value.
20781 No space on device to create the file.
20784 The process already has the maximum number of files open.
20787 The limit on the total number of files open on the system
20791 The call was interrupted by the user.
20795 @unnumberedsubsubsec close
20796 @cindex close, file-i/o system call
20805 @exdent Return value:
20806 close returns zero on success, or -1 if an error occurred.
20813 fd isn't a valid open file descriptor.
20816 The call was interrupted by the user.
20820 @unnumberedsubsubsec read
20821 @cindex read, file-i/o system call
20825 int read(int fd, void *buf, unsigned int count);
20828 Fread,fd,bufptr,count
20830 @exdent Return value:
20831 On success, the number of bytes read is returned.
20832 Zero indicates end of file. If count is zero, read
20833 returns zero as well. On error, -1 is returned.
20840 fd is not a valid file descriptor or is not open for
20844 buf is an invalid pointer value.
20847 The call was interrupted by the user.
20851 @unnumberedsubsubsec write
20852 @cindex write, file-i/o system call
20856 int write(int fd, const void *buf, unsigned int count);
20859 Fwrite,fd,bufptr,count
20861 @exdent Return value:
20862 On success, the number of bytes written are returned.
20863 Zero indicates nothing was written. On error, -1
20871 fd is not a valid file descriptor or is not open for
20875 buf is an invalid pointer value.
20878 An attempt was made to write a file that exceeds the
20879 host specific maximum file size allowed.
20882 No space on device to write the data.
20885 The call was interrupted by the user.
20889 @unnumberedsubsubsec lseek
20890 @cindex lseek, file-i/o system call
20894 long lseek (int fd, long offset, int flag);
20897 Flseek,fd,offset,flag
20900 @code{flag} is one of:
20904 The offset is set to offset bytes.
20907 The offset is set to its current location plus offset
20911 The offset is set to the size of the file plus offset
20916 @exdent Return value:
20917 On success, the resulting unsigned offset in bytes from
20918 the beginning of the file is returned. Otherwise, a
20919 value of -1 is returned.
20926 fd is not a valid open file descriptor.
20929 fd is associated with the @value{GDBN} console.
20932 flag is not a proper value.
20935 The call was interrupted by the user.
20939 @unnumberedsubsubsec rename
20940 @cindex rename, file-i/o system call
20944 int rename(const char *oldpath, const char *newpath);
20947 Frename,oldpathptr/len,newpathptr/len
20949 @exdent Return value:
20950 On success, zero is returned. On error, -1 is returned.
20957 newpath is an existing directory, but oldpath is not a
20961 newpath is a non-empty directory.
20964 oldpath or newpath is a directory that is in use by some
20968 An attempt was made to make a directory a subdirectory
20972 A component used as a directory in oldpath or new
20973 path is not a directory. Or oldpath is a directory
20974 and newpath exists but is not a directory.
20977 oldpathptr or newpathptr are invalid pointer values.
20980 No access to the file or the path of the file.
20984 oldpath or newpath was too long.
20987 A directory component in oldpath or newpath does not exist.
20990 The file is on a read-only filesystem.
20993 The device containing the file has no room for the new
20997 The call was interrupted by the user.
21001 @unnumberedsubsubsec unlink
21002 @cindex unlink, file-i/o system call
21006 int unlink(const char *pathname);
21009 Funlink,pathnameptr/len
21011 @exdent Return value:
21012 On success, zero is returned. On error, -1 is returned.
21019 No access to the file or the path of the file.
21022 The system does not allow unlinking of directories.
21025 The file pathname cannot be unlinked because it's
21026 being used by another process.
21029 pathnameptr is an invalid pointer value.
21032 pathname was too long.
21035 A directory component in pathname does not exist.
21038 A component of the path is not a directory.
21041 The file is on a read-only filesystem.
21044 The call was interrupted by the user.
21048 @unnumberedsubsubsec stat/fstat
21049 @cindex fstat, file-i/o system call
21050 @cindex stat, file-i/o system call
21054 int stat(const char *pathname, struct stat *buf);
21055 int fstat(int fd, struct stat *buf);
21058 Fstat,pathnameptr/len,bufptr
21061 @exdent Return value:
21062 On success, zero is returned. On error, -1 is returned.
21069 fd is not a valid open file.
21072 A directory component in pathname does not exist or the
21073 path is an empty string.
21076 A component of the path is not a directory.
21079 pathnameptr is an invalid pointer value.
21082 No access to the file or the path of the file.
21085 pathname was too long.
21088 The call was interrupted by the user.
21092 @unnumberedsubsubsec gettimeofday
21093 @cindex gettimeofday, file-i/o system call
21097 int gettimeofday(struct timeval *tv, void *tz);
21100 Fgettimeofday,tvptr,tzptr
21102 @exdent Return value:
21103 On success, 0 is returned, -1 otherwise.
21110 tz is a non-NULL pointer.
21113 tvptr and/or tzptr is an invalid pointer value.
21117 @unnumberedsubsubsec isatty
21118 @cindex isatty, file-i/o system call
21122 int isatty(int fd);
21127 @exdent Return value:
21128 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
21135 The call was interrupted by the user.
21139 @unnumberedsubsubsec system
21140 @cindex system, file-i/o system call
21144 int system(const char *command);
21147 Fsystem,commandptr/len
21149 @exdent Return value:
21150 The value returned is -1 on error and the return status
21151 of the command otherwise. Only the exit status of the
21152 command is returned, which is extracted from the hosts
21153 system return value by calling WEXITSTATUS(retval).
21154 In case /bin/sh could not be executed, 127 is returned.
21161 The call was interrupted by the user.
21164 @node Protocol specific representation of datatypes
21165 @subsection Protocol specific representation of datatypes
21166 @cindex protocol specific representation of datatypes, in file-i/o protocol
21169 * Integral datatypes::
21175 @node Integral datatypes
21176 @unnumberedsubsubsec Integral datatypes
21177 @cindex integral datatypes, in file-i/o protocol
21179 The integral datatypes used in the system calls are
21182 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
21185 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
21186 implemented as 32 bit values in this protocol.
21188 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
21190 @xref{Limits}, for corresponding MIN and MAX values (similar to those
21191 in @file{limits.h}) to allow range checking on host and target.
21193 @code{time_t} datatypes are defined as seconds since the Epoch.
21195 All integral datatypes transferred as part of a memory read or write of a
21196 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
21199 @node Pointer values
21200 @unnumberedsubsubsec Pointer values
21201 @cindex pointer values, in file-i/o protocol
21203 Pointers to target data are transmitted as they are. An exception
21204 is made for pointers to buffers for which the length isn't
21205 transmitted as part of the function call, namely strings. Strings
21206 are transmitted as a pointer/length pair, both as hex values, e.g.@:
21213 which is a pointer to data of length 18 bytes at position 0x1aaf.
21214 The length is defined as the full string length in bytes, including
21215 the trailing null byte. Example:
21218 ``hello, world'' at address 0x123456
21229 @unnumberedsubsubsec struct stat
21230 @cindex struct stat, in file-i/o protocol
21232 The buffer of type struct stat used by the target and @value{GDBN} is defined
21237 unsigned int st_dev; /* device */
21238 unsigned int st_ino; /* inode */
21239 mode_t st_mode; /* protection */
21240 unsigned int st_nlink; /* number of hard links */
21241 unsigned int st_uid; /* user ID of owner */
21242 unsigned int st_gid; /* group ID of owner */
21243 unsigned int st_rdev; /* device type (if inode device) */
21244 unsigned long st_size; /* total size, in bytes */
21245 unsigned long st_blksize; /* blocksize for filesystem I/O */
21246 unsigned long st_blocks; /* number of blocks allocated */
21247 time_t st_atime; /* time of last access */
21248 time_t st_mtime; /* time of last modification */
21249 time_t st_ctime; /* time of last change */
21253 The integral datatypes are conforming to the definitions given in the
21254 approriate section (see @ref{Integral datatypes}, for details) so this
21255 structure is of size 64 bytes.
21257 The values of several fields have a restricted meaning and/or
21264 st_ino: No valid meaning for the target. Transmitted unchanged.
21266 st_mode: Valid mode bits are described in Appendix C. Any other
21267 bits have currently no meaning for the target.
21269 st_uid: No valid meaning for the target. Transmitted unchanged.
21271 st_gid: No valid meaning for the target. Transmitted unchanged.
21273 st_rdev: No valid meaning for the target. Transmitted unchanged.
21275 st_atime, st_mtime, st_ctime:
21276 These values have a host and file system dependent
21277 accuracy. Especially on Windows hosts the file systems
21278 don't support exact timing values.
21281 The target gets a struct stat of the above representation and is
21282 responsible to coerce it to the target representation before
21285 Note that due to size differences between the host and target
21286 representation of stat members, these members could eventually
21287 get truncated on the target.
21289 @node struct timeval
21290 @unnumberedsubsubsec struct timeval
21291 @cindex struct timeval, in file-i/o protocol
21293 The buffer of type struct timeval used by the target and @value{GDBN}
21294 is defined as follows:
21298 time_t tv_sec; /* second */
21299 long tv_usec; /* microsecond */
21303 The integral datatypes are conforming to the definitions given in the
21304 approriate section (see @ref{Integral datatypes}, for details) so this
21305 structure is of size 8 bytes.
21308 @subsection Constants
21309 @cindex constants, in file-i/o protocol
21311 The following values are used for the constants inside of the
21312 protocol. @value{GDBN} and target are resposible to translate these
21313 values before and after the call as needed.
21324 @unnumberedsubsubsec Open flags
21325 @cindex open flags, in file-i/o protocol
21327 All values are given in hexadecimal representation.
21339 @node mode_t values
21340 @unnumberedsubsubsec mode_t values
21341 @cindex mode_t values, in file-i/o protocol
21343 All values are given in octal representation.
21360 @unnumberedsubsubsec Errno values
21361 @cindex errno values, in file-i/o protocol
21363 All values are given in decimal representation.
21388 EUNKNOWN is used as a fallback error value if a host system returns
21389 any error value not in the list of supported error numbers.
21392 @unnumberedsubsubsec Lseek flags
21393 @cindex lseek flags, in file-i/o protocol
21402 @unnumberedsubsubsec Limits
21403 @cindex limits, in file-i/o protocol
21405 All values are given in decimal representation.
21408 INT_MIN -2147483648
21410 UINT_MAX 4294967295
21411 LONG_MIN -9223372036854775808
21412 LONG_MAX 9223372036854775807
21413 ULONG_MAX 18446744073709551615
21416 @node File-I/O Examples
21417 @subsection File-I/O Examples
21418 @cindex file-i/o examples
21420 Example sequence of a write call, file descriptor 3, buffer is at target
21421 address 0x1234, 6 bytes should be written:
21424 <- @code{Fwrite,3,1234,6}
21425 @emph{request memory read from target}
21428 @emph{return "6 bytes written"}
21432 Example sequence of a read call, file descriptor 3, buffer is at target
21433 address 0x1234, 6 bytes should be read:
21436 <- @code{Fread,3,1234,6}
21437 @emph{request memory write to target}
21438 -> @code{X1234,6:XXXXXX}
21439 @emph{return "6 bytes read"}
21443 Example sequence of a read call, call fails on the host due to invalid
21444 file descriptor (EBADF):
21447 <- @code{Fread,3,1234,6}
21451 Example sequence of a read call, user presses Ctrl-C before syscall on
21455 <- @code{Fread,3,1234,6}
21460 Example sequence of a read call, user presses Ctrl-C after syscall on
21464 <- @code{Fread,3,1234,6}
21465 -> @code{X1234,6:XXXXXX}
21479 % I think something like @colophon should be in texinfo. In the
21481 \long\def\colophon{\hbox to0pt{}\vfill
21482 \centerline{The body of this manual is set in}
21483 \centerline{\fontname\tenrm,}
21484 \centerline{with headings in {\bf\fontname\tenbf}}
21485 \centerline{and examples in {\tt\fontname\tentt}.}
21486 \centerline{{\it\fontname\tenit\/},}
21487 \centerline{{\bf\fontname\tenbf}, and}
21488 \centerline{{\sl\fontname\tensl\/}}
21489 \centerline{are used for emphasis.}\vfill}
21491 % Blame: doc@cygnus.com, 1991.